E256 V9 TIEU DU AN DA NANG (GIAI DOAN 1) August 2003

Transcription

1 Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized Public Disclosure Authorized C6NG H6A XA H6I CHU' NGHIA VIfT NAM CONG TY MOI TRUONG DO THI TP. DA NANG DU` AN Vt SINH BA THANH PH6 VIlT NAM SOCIALIST REPUBLIC OF VIETNAM DANANG URBAN ENVIRONMENT COMPANY E256 V9 TIEU DU AN DA NANG (GIAI DOAN 1) August 2003 VIETNAM THREE CrTIES SANITATION PROJECT DANANG SUB-PROJECT (PHASE 1) ADDITIONAL WORKS ADDITIONAL WORKS PROJECT VOLUME 1: DETAILED DESIGN REPORT DDR AUGUST 2003 CONSTRUCTION MANAGEMENT CONSULTANTS ~ r DHV Consultants Camp Dresser & McKee VIWASE

2 CONG HOA XA HOI CHUJ NGHiA VIfT NAM CONG TY MOI TRUfONG DO THI TP. DA NANG SOCIALIST REPUBLIC OF VIETNAM DANANG URBAN ENVIRONMENT COMPANY DIY AN VP, SINH BA THANH PH6 VItT NAM TIEU DII' AN DA NANG (GIAI DOAN 1) VIETNAM THREE CITIES SANITATION PROJECT DANANG SUB-PROJECT (PHASE 1) ADDITIONAL WORKS ADDITIONAL WORKS PROJECT VOLUME 1: DETAILED DESIGN REPORT DDR Camp Dresser & McKee VIWASE

3 Vietnam Three Cities Sanitation Projcct ADDITIONAL WORKS PROGRAMME REPORTS 1. DETAILED DESIGN REPORT (DDR) 2. RESETTLEMENT ACTION PLAN (RAP) 3. ENVIRONMENTAL IMIPACT ASSESSMENT (EIA) 4. ENVIRONMENTAL MANGEMENT PLAN (EMP) 5. TENDER DOCUMENTS FOR CONTRACT 020 Construction Management Consultants Page 5 DHV, CDNI and VIWASE

4 Abbreviations BoQ CDM CMC DHV dia dwf GID HDPE ICB NS mln PAP PC RM QA SEMP Urenco USD VIWASE VND WB Bill of Quantities CDM International, a subsidiary of Camp, Dresser & McKee Inc. Contract Management Consultants DHV Consultants, leading firm of the CMC diameter dry weather flow Gravity Interceptor Drain High Density Polyethylene International Competitive Bidding National Shopping million Project Affected Person People's Committee Rising Mains Quality Assurance Site Environmental Management Plan Danang Urban Environment Company US dollar Vietnam Consultant on Water Supply, Sanitation and Environment Vietnamese Dong (currency unit) World Bank Construction Management Consultants Page 6

5 Table of Contents Summary 10 I Introduction Background On Going Phase 1 Project This report and related reports (DDR, RAP, EIA, ENP, TDO20) DRAINAGE - GENERAL Introduction Existing system Scope of Drainage Works Design criteria Meteorology Return periods ,,, Flow estimation Shape and gradients of drains Wastewater and drains, interception of wastewater Side Entry Pits (kerb inlets) Inlets for maintenance (manholes) Siltation and trash collection Structural 34 3 DRAINAGE - DETAILED DESIGNS....., Le Dinh Tham drain Location and justification Catchment area and design flows Alignment and longitudinal profile Cross section Connections to other drains Interception of wastewater flows from the drain Special issues Le Do drain Location, options and justification Catchment area and design flows Alignment and longitudinal profile Cross section Connections to other drains ,, Interception of wastewater flows from the drain Special issues Xuan Hoa drain...,,...,,, Location, options and justification......_ Catchment area and design flows Alignment and longitudinal profile ,,,,,,,,,, Cross section...,,,, Connections to other drains Interception of wastewater flows from the drain Special issues Geotechnical considerations Construction Management Consultants Page 7

6 3.4 An Khe drain Location and justification Catchment area and design flows Alignment and longitudinal profile Cross section Connections to other drains Interception of wastewater flows from the drain Special issues Geotechnical considerations My Khe drain Location options considered Catchment area and design flows Alignment and longitudinal profile Cross section Connections to other drains Interception of wastewater flows from the drain Special issues Geotechnical considerations.53 4 WASTEWATER COLLECTION - GENERAL Introduction Existing situation Construction of wastewater collection system under WB (IDA) project Wastewater systems in additional works programme Design criteria Basic concept of GEDs, Pumping stations and Rising Mains Design peak factor Implications of the adopted design criteria Domestic wastewater flows Non-domestic flows Interception of wastewater from drains Pipe sizes and slopes Pipe types, bedding Maximum depth GID manholes GID connection points Vent poles Pumping station designs, control features Rising mains.69 5 WASTEWATER COLLECTION - DETAILED DESIGNS Introduction Hoa Cuong catchment Existing design Description of additional area and integration with existing design/options Design flows Alignment, SPS locations and longitudinal profile Special issues Son Tra catchment Existing design Description of additional area and integration with existing design/options. 74 Construction Management Consultants Page 8 DHV, CDNI and VIWASE

7 5.3.3 Design flows Alignment, SPS locations and longitudinal profile Special issues Ngu Hanh Son catchment Original designs and changes foreseen Description of additional area and integration with existing design/options Design flows Alignment, SPS locations and longitudinal profile Special issues PROCUREMENT PLAN FOR ADDITIONAL WORKS..., Introduction Details on procurement proposals....., Drainage Additional Wastewater collection systems Floating covers for the Son Tra and Ngu Hanh Son wastewater treatment plants Beach Cleaning Equipment.....,, Detailed Engineering...,.,, Overview of the proposed Procurement Plan COSTS RESETTLEMENT..., Introduction Im pacts of the Project., 87...,.,,.,.,,,,.., Loss of Agricultural Land Loss of Residential Land Im pacts on Structures Loss of other Fixed Assets Loss of Incomes and Businesses Impacts on Public Infrastructure and Utilities Temporary Impacts Relocation Requirements....., Resettlement Cost......,,....., 89 9 ENVIRONMENTAL CONSIDERATIONS Introduction Alternatives Impacts Environmental Management Plan Conclusion APPENDICES A. I Drainage Hydraulics - Le Dinh Tham Drain...,,., 93 A.2 Drainage Hydraulics - Le Do Drain A.3 Drainage Hydraulics - Xuan Hoa Drain A.4 Drainage Hydraulics - An Khe Drain A.5 Drainage Hydraulics - My Khe Drain B. Wastewater flow calculations C. I Cost comparison 2/9 Street C.2 Cost comparison Son Tra Beach area D. Geotechnical investigations Construction Management Consultants Page 9

8 Summary 1. Introduction The construction of Phase I of Danang Drainage and Sanitation Project covering Danang's five urban districts is currently underway and is expected to bring substantial net benefits to Danang city. Due to the savings generated through Phase I's bidding process, about 11 USD million of additional drainage and wastewater works (hereafter known as the Additional Works Project) have been approved both by World Bank (in Aide Memoire of April 2, 2002) and Danang Peoples' Committee (in Decision No 1450/VP of April 11, 2002). 2. Scope The majority of Additional Works Project funds will be used to support drainage works. Wastewater works are the Project's second budgetary priority, and beach cleaning is a tertiary priority. Detailed engineering and supervision of the additional works construction are included in the scope of the Additional Works. The table below shows the main features of the Additional Works scope, including their estimated base costs. Component Item [km USD'OOO Drainage Le Dinh Tham Le Do ,046 Xuan Hoa An Khe My Khe ,634 Wastewater Hoa Cuong - rerouting Son Tra - additions 488 Ngu Hanh Son - complete 1,622 Floating covers Son Tr WWTP 231 Ngu Hanh Son WWTP 1421 Beach Cleaiiing eq uipment 2 pc 82 Detailed Engineering I Drainage All drains consist of simple box culverts. In most cases, as they drains are large, they consist of double or triple box culverts, to avoid too large a span. To concentrate dry weather flows, one section of each culvert is provided with a V-shaped floor. Foundation of the culverts on Danang soils is generally no problem. However, the Xuan Hoa drain and the An Khe drain are mostly located in existing river beds while a small part of the My Khe drain is located in a swamp. Geotechnical investigations have revealed that in some locations, mud deposits have to be removed and the Bills of Quantities provide for this. 4. Additions to the Wastewater collection systems The city administration has seen the need for wastewater removal and treatment and has earmarked some residential areas in the Hoa Cuong, Son Tra and Ngu Hanh Son catchment areas to be provided with wastewater systems. In the Hoa Cuong area, the replacement of a long rising main to the WWTP by a combination of Gravity Interceptor Drains (GID) and shorter rising mains, as well as a rerouting along the river provided for the required additional system, at negligible costs. In the Son Tra area, the city had planned to add an independent wastewater system to serve the additional areas. It turned out that integrating the added system with the system planned before would lead to cost savings and a higher flexibility. Construction Management Consultants Page 10 DHV, CDMI and VIWASE

9 The wastewater system for Ngu Hanh Son is closely related to the My Khe drain to be constructed as part of the Additional Works program. A completely new system was required, therefore, in comparison to the system design for the ongoing Phase I project. It was decided to remove the complete system from the ongoing contract 013 and ad it to a new package Floating covers Floating covers will be provided for the two large treatment plants (at Hoa Cuong and Phu Loc), presently under construction. To minimize the costs, it was previously decided to omit such floating covers for the two smaller plants at Son Tra and Ngu Hanh Son. However, they were always desired and, with the budget not yet exhausted, they were now added to the Additional Works. The best is to have floating covers installed while lagoons are empty and it is recommended to procure the covers as soon as possible, through a variation to contract Beach cleaning equipment Two small self-propelled beach cleaners were delivered in April EIA and RAP As part of the detailed engineering study, an EIA, EMP and RAP were prepared and submitted to the World Bank for approval. Most of the project components are hardly affected by resettlement, except the Le Do drain, where over a section of 250m, out of its total length of 1200m, considerable resettlement will be required. 8. Procurement Plan The procurement plan for the Additional Works is complicated and simple at the same time. It is complicated as a. large number of Additional Works project components are shifted to ongoing contracts througlh addendum or variation orders, while parts of the Phase 1 defined project will be shifted to a new civil works package, 020. It is simple as only two new contract packages are proposed. Most of the Additional Works should be procured under new package 020. This applies to all drainage works, except the Le Do drain. Its construction is urgent and it is proposed to ad this work to existing contract 013. For the additional wastewater systems the situation is more diverse. The Hoa Cuong system hardly includes new items and works should be executed under the existing contract 013. The additions to the Son Tra wastewater system are very much integrated with the already contracted works and are best procured through a variation to contract 013. However, the complete Ngu Hanh Son system will be lifted from contract 013 and moved to contract 020. This compensates somewhat the variations made to this contract for the Le Do drain and the Son Tra wastewater system additions. Floating covers for the two small treatment plants are best procured under variation to ongoing contract 012. Two self-propelled beach cleaners were procured already under a small (national Shopping) contract 016, while detailed engineering was procured under an Addendum to ongoing contract 011 (for Construction Management Services). Construction Management Consultants Page 11

10 The resulting procurement proposal is presented in the table below. Contracts 011, 012 and 0 13 are ongoing contracts, contract 016 was prepared especially for the beach cleaners and has been concluded already, while package 020 will contain the bulk of the Additional Works. Tender documents for package 020 were prepared as part of the detailed engineering study. Component Item Proposed procurement.. O l Drainage Le Dinh Tham 0 Le Do. = = Xuan Hoa _ An Khe _ My Khe = Wastewater Hoa Cuong additions Son Tra additions Ngu Hanh Son (from 012) _ Ngu Hanh Son additions Floating covers Son Tra WWTP e I.Ngu Hanh Son WWTP. Beach Cleaning equipment *) [ _ l Detailed Engineering *) 1 * l l *) already procured 9. Costs Costs were calculated as base costs and as total costs. The difference is largest for the work items to be procured under package 020, as additions are made for costs of general and preliminary items, physical and price contingencies. An overview is shown in the table below. Contract Base costs Total costs (USD'ooo) (USD'ooo) 011 (already procured) (variation) (variation) (already procured) (new package) 7,091 9,109 Land acquisition Total 9,842 11,937 The additional works will have a significant impact on the contributions to the project by the World Bank and by the project owner URENCO. As, apart from the additional works, there had been already many alterations to contract scope of 012 and 013, a complete new cost estimate for the project was made. The table below shows the most important details. Construction Management Consultants Page 12

11 Olil Construction Management *) 2,772 2,386 2, ,824 ioo% 2, Landfill, 4 Treatrnent Plants *) 9,445 7,164 6,675 1,291 7,966 8o% 6,373 1, Sewerage/Dmainage/Transf st* 19,677 14,924 11,364 2,330 13,694 80% 10,955-2, Equipm/vehicles )2,012 2,012 2, Beach cleaning equipment *) 3,555 2, % Small equipment/tools ) _ _ TA A - Institutional 1,965 1,754 1,224 1, % 1, TA B - Institutional (AusAid) 1,240 1,240 1,240 1, Auditing Additional constr. works ) 9,109 9,109 80% 7,288 1,822 Revolving Fund 1,000 1,000 1,000 1, % 1,000 Land acquisition 1,397 1,397 1,397 1,397 1,397 Land acq Additional. Works *) Management, miscellaneous Taxes *) 2,777 2, ,232 3,232 Grand tatab. 41,05 35,874 3,7 t i ,912 1_ 2,230. ~ ~ ~ ~ I. i '" 1*, ni01'. Surplus or Shortfall.(-) 0 l. l_ -4, ,009 *) Contracts/items that include Additional Works It may be noted that, while the total budget increases to well above the original budget of USD mln referred to in the project Appraisal report, the World Bank share is expected to remain below the original budget of USD mln. The Urenco share increases sharply, from the original USD 7.22 mln to USD min. Construction Management Consultants Page 13

12 1 INTRODUCTION 1.1 Background Danang is Vietnam's fourth largest city and is located along the coast mid way between Hanoi in the north and Ho Chi Minh City in the south. The city covers an area of 6,671 hectares and its 1999 population was estimated at 684,000 (a figure which is expected to grow to 904,000 by the year 2010). The population density is high: in some areas near to 600 persons per hectare. Increased industrial development and tourism are targeted for the city's economic growth and both require effective and efficient urban infrastructure. The existing sanitary facilities, however, are totally inadequate. Regular flooding hampers the economic development and contributes to poor health conditions in the town. Also untreated wastewater of the city discharges directly to the Han River, the Danang Bay or the sea in the east. The City of Danang has embarked on an ambitious program to improve the living condition of its citizens. Through funding by of the Australian Government a number of studies were prepared with respect to the improvement of water supply and sanitation. Following the completion of these master planning and feasibility studies, GHD-Kinhill from Australia in co-operation with VIWASE from Hanoi prepared detailed designs and tender documents for Sanitation works. 1.2 On Going Phase 1 Project Following the planning and study stage, a credit towvards the cost of rehabilitation and expansion of the sanitation systems in urban districts of- amongst others - Danang City was received from the International Development Association (IDA) by the Government of Vietnam. Phase 1 of the resulting sanitation project comprises: * Upgrading of the stormwater system * Collection and treatment of domestic and industrial wastewater Improvement of the solid waste collection and disposal system * Institutional strengthening * A community education and awareness campaign At the moment the construction works are ongoing under the supervision of CMC - Construction Management Consultants, a joint venture of DHV Consultants from the Netherlands, CDM International from the USA and VIWASE from Hanoi. The construction project takes place in five urban districts of Danang city (see Figure 1-1 and Figure 1-2 for the revised scope of works). The total investment of the project was estimated at USD 41M. However, after having awarded all contracts, the total value of the contracts of the Danang Sanitation Project was USD 30M, about USD 1 IM lower than estimated. Construction Management Consultants Page 14

13 DA NANG SUBPROJECT - PHASE 1: WASTEWATER WORKS TIeU Df ANDA NANG - GW DOM 1: CACC CNG vec THoAT NLrCC THk, ,...-= :/ A :~~~~ t-- :::- :,:::,,~ ~ ~ ~ ~ ~~~~~ ,-- :----:N NGM A...O /C<= = == < z ~~~~~~--:--- /--::f GHICHO - u ~ ~~ LEGEND ^-- C6SiO1{rOOM n------= V H A ONO NAN O R t1 t3 H Figure 1-1 Revised Scope of Main wastewater works for Phase 1 Danang Sanitation Project Construction Management Consultants Page 15

14 DA NANG SU9PROCT P-HASE 1: MAIN DRAINGE WORKS MTU ovandangi -GWWMN 1:cCcCOWVISCTHOATNLCMtLA A~ ~~~~ :- x, LEGEND ~ ~ ~ ~~ uto~~~t~~?1r ~~~~RAN4 ~~~~A -AN A 1 LEGEND me3thoatpu^:n".alo aau(t 1) GHI CHt g -1 Figure 1-2 Revised Scope of Main drainage works for Phase 1 Danang Sanitation Project Construction Management Consultants Page 16

15 1.3 In a meeting in April 2002, the World Bank agreed that the savings from the ongoing Phase I project could be used for expanding the scope of the Danang Sanitation project. Under the direction of the Danang People Committee, the Danang Construction Planning Institution prepared the Feasibility Study "Danang Extended Sanitation Project Using Saving After Bidding" outlining how the finds should be used. The identified items are: 1. Flood mitigation works in a. Hai Chau and Thanh Khe Districts (drainage catchment A) b. Son Tra and Ngu Hanh Son Districts (drainage catchment B) 2. Extension of the wastewater collection system in a. Hoa Cuong wastewater catchment b. Son Tra wastewater catchment c. Ngu Hanh Son wastewater catchment 3. Floating covers for Son Tra and Ngu Hanh Son Wastewater Treatment Plants 4. Procurement of Beach Cleaning Machines 5. Extension of Contract Management Services After approval of this feasibility study by the World Bank and the Prime Minister's Office, an Addendum for Detailed Designs & Construction Management Consultancy was signed between the Danang Urban Environment Company and the Consortium of DHV Consultants, CDM International and VIWASE in January The Addendum covers * Preparation of detailed designs and cost estimates * Preparation of tender documents and bid evaluation criteria * Preparation of environmental impact assessment and resettlement action plan Bidding, pre-bid meetings and evaluation of bids * Additional construction management * Services during defects liability period 1.4 This report and related reports (DDR, RAP, EIA, EMP, TDO20) In the framework of the the following reports have been produced: * (DDR) * Resettlement Action Plan (RAP) * Environmental Impact Assessment (EIA) * Environmental Management Plan (EMP) * Tender Documents for contract 020 (TDO20), including design drawings The purpose of this detailed design report is to document the basis of the detailed designs and cost estimates of the additional wastewater and drainage works of the Danang Sanitation project. This report has been prepared on the basis of a number of other documents: * Master Plan Report of Socio-Economic Development of Danang city in the period of Construction Master Plan of Danang city prepared by Rural and Urban Planning Institution in the year of 1993 Construction Management Consultants Page 17

16 * General Planning Adjustment Report of Danang city to the year 2020 prepared by Rural And Urban Planning Institution - Ministry of Construction in the year of 2000 * Feasibility Study Danang Extended Sanitation Project Using Saving after Bidding (Danang, November 2002) * Final Feasibility Study of Danang Sanitation project * Feasibility Study of Danang Water Supply project in the period of prepared by Viet Nam Water supply and Environment Consultant Company (VIWASE) - Ministry of Construction a Recent survey data of the existing drainage system * GHD-Kinhill Drainage Design Report / Wastewater Design Report G 013 Contract Documents Construction Management Consultants Page 18

17 2 DRAINAGE - GENERAL 2.1 Introduction Existing system Danang is a coastal city, with a land elevation of between 2-6m. Due to its proximity to the coast, drainage of the city has generally been expedient. At present, Danang drainage system has a combined stormwater and sewerage system; for stormwater, domestic wastewater and industrial effluent. The total length of the drainage network is about 120 km; most drains are made of pitched stone and concrete covers. Some recently constructed drains are reinforced concrete pipes or concrete box culverts. The drainage network is mainly located in the Hai Chau and Thanh Khe districts. Son Tra, Ngu Hanh Son and Lien Chieu districts hardly have any drainage system except in some newly developed residential areas. Drainage in these latter districts is generally by means of soakage and infiltration into the soil, or as overland flows to nearby lakes, rivers, and the sea. Most drains constructed before 1995 are inadequate; they are intended for local drainage only and not for conveyance of stormwater from the hinterland. This lack of primary drainage network is the cause of much local flooding. In addition, side entry pits have inadequate capacity because of bad design/construction or blockage. Also, the drains themselves are often blocked by sand and trash. Flooding occurs in a number of city streets whenever there is heavy rain. Some areas are 1.5m deep in floodwater for several days. Adverse impacts of flooding include traffic congestion; property and construction work damage; loss of business and trading; environmental pollution; as well as ocher social and health problems. Wastewater flows from households and, industries, which are often discharged untreated, are also a serious threat to the health of the general public and to the sea and river environment. In particular Danang Bay which has a beautiful beach close to the city is so heavily polluted that it should not be used for recreation anymore. In phase I of the Danang sanitation subproject, the drainage system is being upgraded and enlarged to mitigate the risk of flooding in priority areas. At the same time gravity interceptor drains, pump stations and wastewater treatment plants are being constructed to reduce the discharge of untreated wastewater and improve the effluent quality discharged into the environment. Based on drainage flow directions, land topography, and available spot level survey information, the study area can broadly be divided into 14 main catchments as follows (see Figure 2-0): Catchment I: Dam Rong This catchment is bounded by Danang Bay to the north, Ong Ich Khiem Street to the west, Le Loi Street to the east and Con market to the south. The size of the catchment is 210 Ha. The population is approximately 61,000 in 2000 and 71,000 in Major trunk drains in the catchment are the Ong Ich Khiem Street drain and the Dam Rong Lake and channel system. In phase 1 of Danang sanitation subproject, a new stormwater drain of 3.5-2x2.4m wide and 1.5m deep has been constructed in Ong Ich Khiem Street to Danang Bay. The former drainage system has been rehabilitated for wastewater drainage. In phase I of the Danang sanitation subproject, wastewater discharging to Dam Rong-Lake I is to be collected and transferred to the Phu Loc WWTP by SPS 18 to reduce pollution in this area. Construction Management Consultants Page 19

18 Figure 2-0 Drainage Catchment Areas of Danang Catch ment II: Le Loi - Le Duan - Han River This catchment is bounded to the North by Dong Da Street, to the West by Le Loi Street, to the South by Le Duan Street and to the East by the Han River. The size of the catchment is 70 Ha. The population is approximately 20,000 in 2000 and 23,000 in Most of drains in this catchment follow the direction from West to East to the Han River. These drains are on either side of the road, each about mm wide x mrn deep. Construction Management Consultants Page 20

19 In this catchment, the drains in Nguyen Du, Ly Tu Trong streets are being upgraded to mitigate flood risk in these areas. Wastewater will be collected by GID and transferred by SPS12 in Bach Dang Street to Hoa Cuong WWTP. Catchment III: Hai Chau - Le Dinh Duong - Han River This catchment is bounded to the North by Le Duan Street, to the West by Ong Ich Khiem Street, to the South by Trung Nu Vuong Street and to the East by the Han River. The size of the catchment is 169 Ha. The population is approximately 57,000 in 2000 and 67,000 in Most of drains in this catchment follow the direction from West to East to the Han River. Among the outfalls, the recently constructed one in Le Dinh Duong Street is the largest with a size of 3.0m wide x 1.5m deep. In this catchment, the drains in Phan Dinh Phung, Hung Vuong, Tran Quoc Toan and Le Dinh Duong streets are being upgraded to mitigate flood risk in these areas. Wastewater will be collected by GID and transferred by SPS 13 in Bach Dang Street to Hoa Cuong WWTP. Catchment IV: Binh Thuan - Nguyen Van Troi - Han River This catchment is bordered by Hoang Dieu Street to the East, Nguyen Tri Phuong Street to the West, Nguyen Van Linh Street to the North and Nguyen Van Troi Street to the South. It has an area of 162 ha. The population is 29,000 in 2000 and 35,000 in The main trunk drain is Me Linh drain running in a southerly direction starting from the southern end of old Thac Gian lake, through the middle of the catchment to Nguyen Van Troi Street and discharging to the Han River. The Thac Gian lakes have progressively been filled over the years to cater for residential developments; as a result flooding has become a serious problem in this area. In phase 1, the Danang sanitation subproject is upgrading only the existing downstream drain in Nguyen Van Troi Street discharging to Han River. In the additional works programme also the upstream section is to be upgraded. Catchment V. Thac Gian - Vinh Trung - Danang Bay This catchment is bordered by Ong Ich Khiem Street to the east, Danang Bay to the north, Phan Thanh-Le Do Street to the west, and Nguyen Van Linh Street to the south. It has an area of 174 Ha. The population is 68,000 in 2000 and 80,000 in This catchment has two main trunk drains: Bac Dau drain and Thac Gian lake-tan Chinh lake-danang Bay drain. The starting point of the Bac Dau drain is Danang railway station at the end of Hoang Hoa Tham street. The section crossing the railway station comprises two DN1000 drains to Tran Cao Van Street, continuing with a drain of 2.Om wide and m deep. De-sludging this section along the railway station proves to be very difficult and construction in recent years has left much of these two drains damaged causing their drainage capacity to be reduced. Thac Gian - Tan Chinh Lake - Danang Bay drain: This drain starts from the outlet drain in the north of Thac Gian Lake then goes across Tan Chinh Lake and ends at Danang Bay. Size of the drain is m wide and 1.4m deep. The section from Thac Gian Lake to Tan Chinh Lake is covered by reinforced concrete slabs. The remaining section across Tam Thuan ward is open. Thac Gian Lake used to be quite large but in recent years the lake is being gradually filled up for the development of residential area's; the remaining lake area is presently about 3.8ha, the remaining lake volume is small, about 80,000m 3. Tan Chinh Lake has progressively been encroached on by surrounding households; the remaining lake area is about 0.5ha. This lake has not been under the management of any agency. It has become desolate and is currently overgrown with water hyacinth. Depth is approximately only 1m. According to City planning, this lake will be filled for construction of the Tan Chinh market. Construction Management Consultants Page 21

20 Wastewater in the catchment will be collected by GID along Lien Chieu-Thuan Phuoc road and transferred by SPS 19, SPS20 and SPS21 to Phu Loc WWTP. Catchment VI. Airport - 29/3 Lake - Phu Loc River This catchment stretches from Nguyen Van Linh Street across Danang Airport to National Highway 1A in the south. It is bordered by Phan Thanh-Le Do Street to the east, Danang Bay to the north and National Highway IA to the west. It has an area of 905 Ha (including 400 ha of the airport. The population is 91,000 in 2000 and 112,000 in The trunk drainage system consists of (i) Drain from 29/3 Lake to Phu Loc River: a 3.8km long drain starting at Lake 29/3 with a 2.4m wide x 2m deep culvert and a 5.4m wide x 2.Om deep drain from the Airport to Dien Bien Phu Street, continuing with a m wide x 1.7m deep drain from Dien Bien Phu street to Ha Huy Tap street and a 4.2 wide x 1.7m deep drain from Ha Huy Tap street to Tran Cao Van street. The middle section - being smaller than the upstream drain - has insufficient capacity and causes serious flooding in the low lying area to the south of Dien Bien Phu Street. This is addressed in the additional works program. (ii) Drain from Xuan Hoa A pond to Phu Loc River: This drain presently discharges by gravity along irrigation canals. The 3.Om wide x Om deep up-stream section with length of 400m from Xuan Ha A pond to Dien Bien Phu Street and the 4.2m wide x 1.7m deep down-stream section in Thanh Loc Dan residential area are box culverts with reinforced concrete covers. The earth channel in the middle section between Dien Bien Phu Street and Tran Cao Van Street overflows on open land because the channel size is small and culvert crossing the railway has a diameter of only 1.5m. This is addressed in the additional works program. r, (iii) Drain from An Khe pond to Phu Loc river: This drain discharges wastewater from two outfalls in the north-west of Danang Airport. The drain from Huynh Ngoc Hue residential area (east of Huynh Ngoc Hue Street) to the pond with size of 3.2m wide x 1.2m deep is being constructed. There is an unused earth channel across low land. Along this channel, there are two large drains: one across Dien Bien Phu Street and a drain across the railway with a size of 6.Om wide x 2.5m deep. In this catchment, there are a number of lakes and ponds used for stormwater regulation, such as 29/3 lake, Airport lake, An Khe pond. 29/3 lake: Apart from the function of stormwater drainage, this lake also serves as a recreation park. Therefore, the water level must be kept at a certain level (+3.00m). The present area of the lake is 10.3 ha. It is 2.Om deep and has a volume of 200,000m 3. Airport lake: This lake is inside the Danang Airport area. The surface area is about 6.8ha with a volume of 150,000m 3. An Khe pond: This lake receives a large amount of stormwater run-off Its purpose is merely for stormwater regulation. The city is planning to build the An Khe cultural park in a part of An Khe pond in next years. About 12 hectare of the pond will be retained. Catchment VII: Hoa Cuong - Han River The Hoa Cuong catchment extends from Nguyen Van Troi Street to the North, Danang airport to the West, and the Han River to the South and East. This catchment receives a large volume of wastewater from Danang airport. The area of the catchment is 522 Ha. The population is 29,000 in 2000 and 47,000 in Construction Management Consultants Page 22

21 Additional Works. Program The catchment is currently drained by two irrigation canals, which discharge into two main watercourses running parallel in the middle of the catchment (running north to south) and discharge to the Han River at Do Xu Bridge. During heavy rain, the above irrigation canals can not meet the required drainage capacity causing flooding in the whole area. In recent years, the southwest area of the city is being urbanized rapidly. Catchment VIII: Airport West - Han River This catchment comprises 1/4 of Airport West. Irrigation canals on the fields of the Hoa Cam commune drain to Cau Do River in the south. Catchment IX. West Son Tra district - Han River This catchment comprises the westem half of Son Tra district. The catchment is bordered by the dividing line along the old railway to the east, Nguyen Van Thoai Street to the south, Son Tra peninsula to the north and Han River to the west. Catchment area is 767ha. The population is 57,000 in 2000 and 69,000 in Flow direction in this catchment is western, along roads. Catchment X. East Son Tra district - China Beach This catchment comprises the eastern half of Son Tra district. The catchment is bordered by the dividing line along the old railway to the west, Nguyen Van Thoai Street to the south, Son Tra peninsula to the north and the East Sea to the east. The catchment area is 813ha. The population is 44,000 in 2000 and 54,000 in Flow direction in this catchment is easterly, along the watercourses at the My Khe Beach Hotel, An Don export processing zone and roads. Catchment XI. East Ngu Hanh Son district - China Beach This catchment comprises of the eastern half of Ngu Hanh Son district. The catchment is bordered by Ngu Hanh Son Street to the west, Nguyen Van Thoai Street to the north, Non Nuoc resort to the south and the East Sea to the east. The catchment area is 541ha. The population is 21,000 in 2000 and 32,000 in Drainage system in this catchment is not completed. Drainage is generally by means of soakage and infiltration into the soil, or as overland flows to nearby watercourses and subsequently to the East Sea. Catchment XII: West Ngu Hanh Son district - Han river This catchment comprises of the western half of Ngu Hanh Son district. The catchment is bordered by Ngu Hanh Son Street to the east, Nguyen Van Thoai Street to the north, Hoa Hai ward to the south and Han River to the west. The catchment area is 440ha. The population is 16,000 in 2000 and 22,000 in No drainage system currently exists in this catchment because population is small and is concentrated along Ngu Hanh Son Street. Presently the area between the Tran Thi Ly Bridge and the Tuyen Son Bridge is being back filled and will be developed into a residential area similarly to the areas to the north. Catchment XIII: Lien Chieu South - Danang Bay The Phu Loc River drains this catchment and discharges to the Danang Bay. Catchment area is 1,170ha. Catchment XIV: Lien Chieu Center - Danang Bay This catchment drains to the Cu De River and Dai'ang Bay. The catchment has an area of about 825 ha. Construction Management Consultants Page 23

22 Catchment XV: Lien Chieu North - Danang Bay This catchment drains to the Cu De River and Danang Bay. The catchment has an area of about 460 ha Scope of Drainage Works The feasibility study identified a number of drains which were removed from the ongoing Phase I project because of budget concerns. Among the removed works were drains for areas regularly suffering from serious flooding. On account of the additional available budget these works can now be implemented after all. In addition, priority areas for drainage improvement were identified. For the resulting list of drains detailed designs have been prepared (see Figure 2-1): 1. Drain from Le Dinh Tham to Duy Tan Road. This drain will be referred to as the Le Dinh Tham Drain 2. Drain from Dien Bien Phu Street to Danang Bay through Le Do Street. This drain will be referred to as the Le Do Drain 3. Drain from Dien Bien Phu Street (Xuan Hoa pond) to Tran Cao Van Street (Phu Loc River). This drain will be referred to as the Xuan Hoa Drain 4. Drain from An Khe pond to Phu Loc River. This drain will be referred to as the An Khe Drain 5. Drain from My Khe to Bac Me An. This drain will be referred to as the My Khe Drain Where the ongoing Phase 1 works mainly address the drainage in the catchments I, II, III & V, the above drains will particularly improve the drainage capacity of catchmnent IV (Drain #1) and catchment VI (Drains #2, #3 & #4). The ongoing Phase 1 project also includes a number of drains in catchments X & Xl. These drains, however, do not have a proper outlet out of the area. Drain #5, the My Khe Drain, will integrate with those drains and provide the necessary primary infrastructure to discharge stormwater run-off to the sea. Construction Managcment Consultants Page 24

23 DA NANG SUBPROJECT- PiAE 1: ADDITI WORKS - MAIN DRAINAGE WORKS TIfU DAN t NANG - GLAIDOMN 1: C6NG TRhH 86S SG - C4 C6NG VIeC TOAT NUJC MuA S WHB^l~ ~~ ~ ~~~~ g t }SX L S~~~~~~~~~~~~~~~~~~~~ J~~~~~~~~~~~~ O LEGEND I~~~~WS1VWJWAThRORAI [ibend ~ ~ ~ ~~~... IAE Ni 1111RC... ^N _ E DH, CDM an.wws DHV, CDM and ~ VIWASE ~ ~ ~ ~ ~~~~~~~~O V

24 2.2 Design criteria During the engineering study for the ongoing Phase I project, GHD-Kinhill developed a number of design criteria. Based on these design criteria, detailed designs for the stormwater drains were made. The Ministry of Construction and the World Bank approved the designed system. As it is not desirable to alter the design criteria at this stage, especially where they were approved by all, and since the additional works program is a supplement to the ongoing Phase I works, also here in principle the same design criteria have been applied Meteorology The climate of Danang city is sunny and hot during the dry season (from February to August) and rainy and wet during the rainy season (from September to January). The annual average temperature is C and the annual average precipitation is 2,066 mm. Danang city is much affected by major storms from the middle of September to January. Data of rainfall in Danang city starting from the year 1963 is still archived in the hydrometeorological centre of the Middle Province of Vietnam. About 70% of annual rainfall falls during the rainy season of which October and November are the wettest months, with about 1,000mm of precipitation (equivalent to 50% of annual average rainfall). February, March and April are the driest months, with about mm of precipitation (see Table 2-1). l January Februarg March April May June July August September October November ,312.8 December Year 2, , , ,239.5 Table 2-1 Rainfall in months of year (mm) Total annual evaporation in Danang city is about 1,120mm. The highest evaporation is from May to August and lowest in December. The Danang drainage system directly discharges to Han River, Danang Bay and the East Sea; it is therefore directly affected by tide. Tidal patterns are mainly semi-diurnal in nature. High tide and low tide last for 5.5 hours on average. However, sometimes the tide pattern is diurnal; as a result high tide and low tide last longer. In that case the duration of low tide and high tide is on average Construction Management Consultants Page 26

25 11.5 and 13 hours respectively. Typical high tide levels are between O.Om and +0.6m; highest recorded tidal level is +1.35m (see Table 2-2). These levels are relative to Danang datum level. Danang datum level [m] Mean sea level Highest recorded tide level 1.35 Lowest recorded tide level Typical high tide level 0.0 to 0.6 Typical low tide level -0.6 to -0.2 Table 2-2 Danang Tidal levels All outfall drains, which have been provided with dry weather flow interceptors as part of the wastewater collection system, have been provided with a weir with an overflow level of +0.6m to minimise high tide swamping of that system Return periods As with other natural phenomena, occurrence of flooding is governed by chance. The chance of flooding is described by a statistical analysis of flooding history in the subject watershed or in similar watersheds. Because it is not economically feasible to design a structure for the maximum possible runoff from a watershed, the designer must choose a design frequency appropriate for the structure. The expected frequency for a given flood is the reciprocal of the probability or chance that the flood will be equalled or exceeded in a given year. For example, if a flood has a 20 percent chance of being equalled or exceeded each year, over a long period of time the flood will be equalled or exceeded on an average of once every five years. This is called the return period or recurrence interval (RI). A five-year flood is not one that will necessarily be equalled or exceeded every five years. There is a 20 percent chance that the flood will be equalled or exceeded in any year; therefore, the five-year flood could conceivably occur in several consecutive years. The same reasoning applies to floods with other return periods. In determining the required dimensions of a drain a distinction is made between smaller collector drains with a total catchment size of no more than 30ha., medium size trunk drains with a total catchment size of between 30ha. and 100ha., and large size end drains with a total catchment size of more than looha. (see Table 2-3). Drainage Area Return Period Smaller collector drains < 30 ha. 2 years Medium size trunk drains ha. 5 years Large size end drains > 100 ha. 10 years Table 2-3 Design return periods Flow estimation The flow estimations on which the drains were designed have been carried out using the Rational Method. Construction Management Consultants Page 27

26 The Rational fornula estimates the peak rate of runoff at any location in a watershed as a function of the drainage area, runoff coefficient, and mean rainfall intensity for a duration equal to the time of concentration (the time required for water to flow from the most remote point of the basin to the location being analyzed). The rational formula is expressed as Q=C x I x A where: Q = maximum rate of runoff (m 3 /s) C = runoff coefficient I= average rainfall intensity (Us.ha) A = drainage area (ha) Calculation of the flow at the various inlets and junctions along the drain line is carried out from the top of the system progressively downstream. The runoff coefficient indicates the fraction of stormnwater originating from the catchment that actually reaches the drain. Generally, larger areas with permeable soils, flat slopes and dense vegetation should have the lowest "C" values. Smaller areas with dense or impermeable soils, moderate to steep slopes, and sparse vegetation should be assigned the highest "C" values. A run-off coefficient of between 0.5 and 0.8 has been adopted for all residential areas depending on the extent of development. For some areas, even though at present they are not extensively developed, a high "C" value of 0.8 is assigned because of the planned development of the area. Because the drainage works will need to meet the drainage requirements of Danang for a design horizon of approximately 20 years, relatively high values for "C" have been adopted. The total peak flow at any point is dependent on the Timc of Concentration (ta) at that point, the actual flow being the result of the sum of the CXA values of the contributing sub-catchments, multiplied by I appropriate for t, at that point. The time of concentration is the time at which the entire watershed begins to contribute to runoff, this is calculated as the time taken for runoff to flow from the most hydraulically remote point of the drainage area to the point under investigation. Use of the rational formula requires the time of concentration for each design point within the drainage basin. The duration of rainfall is then set equal to the time of concentration and is used to estimate the design average rainfall intensity (I). The time of concentration is calculated as the sum of the catchment's overland flow time and channel flow times. Pipe flow times are calculated as the time of travel through the pipe at its average flow velocity when flowing full multiplied by a factor of 2 for flat gradients of less than 1%. The average rainfall intensity (I) has been determined according to the formula of Dr. Tran Huu Uyen': I = [(20 + b)y 120 (1 + C LogP)]/(l + t)n where: I = average rainfall intensity (U/s.ha) n, b, C depend on the geographical area ' Hanoi Construction Institute Study for Determination of Stormwater Flow Rates for Urban Vietnamese Areas (Published Hanoi 1996) Construction Management Consultants Page 28

27 Danang Sub-project (Phase I) I20 = rainfall intensity at 20'" minute P = design flooding frequency t = the calculated time of an event (minutes) For Danang city the coefficient are as follows: n = b = 2.64 C = I20 = Shape and gradients of drains The Manning Equation for Uniform Flow has been used as the basis for determining the size and grades of the drains: Q = I/n x A R% SV where: Q = discharge (m 3 /s) n = Manning's roughness coefficient (a coefficient for quantifying the roughness characteristics of the channel) A = cross-sectional area of flow (m 2 ) R = hydraulic radius (m) = A / WP WP = wetted perimeter of flow (the length of the channel boundary in direct contact with the water) (m) S = slope of the energy grade line (m/m) (For uniform, steady flow, S = channel slope) Drains are laid with uniform slope between manholes. The minimum slope applied is 0.1%. Hydrauiic energy profiles have been accepted as closely following the tops of the channels. Drains are laid with straight alignment between manholes except where street or road layouts are such that straight alignment between manholes is impractical, drains may be curved to conform to their curvature. When a smaller drain joins a larger one, the invert of the larger sewer is lowered sufficiently to maintain the same energy gradient. An appropriate method for securing this result is to place the soffit of both drains at the same level. Generally, drains do not decrease in size in downstream direction unless the gradient of the downstream section is much larger than upstream. The forrn of the drainage conduits depends on a variety of factors, including: * Construction cost * Flow capacity required * Width of land available for drainage works * Degree of disruption which might be caused by construction of the drain Traditionally, drainage in Danang has been constructed using box channel sections as compared to pipe sections. The use of box channel sections is attractive especially for larger size drains because they can be constructed using local labour at lower unit costs than equivalent flow capacity pipe sections. Box channel sections have therefore been adopted as the standard section for new and upgrade channel type drainage works for the ongoing Phase I works. The designs for the stormwater drains of the additional works program also use the box channel as standard section. Construction Management Consultants Page 29

28 Danang Sub-project (Phase I) Since all the drains in the additional works programme are in the middle or at the end or catchments there is no need to set a minimum size for box channel sections. A major issue for drainage design in the Danang area, because of its predominately flat gradients, is the consideration of the required self scouring of the drainage channels. Lack of self scouring ability increases maintenance requirements for drain desludging and reduces public and occupational health and safety. Box channel sections traditionally have flat bottoms that are not effective in their self scouring ability, especially with the inevitable flat gradients. As a result they suffer from siltation and debris accumulation. A method to increase self scouring ability, box channel drains can be constructed with a low flow circular shaped invert with battered benches. The size of the circular invert is adequate to carry the peak dry weather flow. However, application of battered benches increases the amount of concrete needed to construct the drain - and thus the cost - considerably. Especially for drains with a width of more than 1.5meter, the amount of extra concrete necessary to construct the battered benches is substantial; although it must be said that the concrete used for the battered benches is of a low grade. For example, a circular shaped invert with battered benches will add around 20% of concrete volume to a drain of 2m by 2m. A low flow circular shaped invert with battered benches is appropriate for small drains of say less than 1.5m wide. For larger drains, however, to concentrate the flow in the centre of the drain and thus increase the self scouring ability without adding to the volurthe of concrete, the bottoms of the drains are constructed in a V-shape. Although this is slightly less effective than the circular shaped invert with battered benclves it is a less costly compromise that will still reduce maintenance requirenients for drain desludging and improve public and occupational health and safety. In cases where two or more channel sections are needed because of the required large flow width, only one channel shall have a V-shaped invert. The invert of the other channel(s) shall slope towards the V-shaped invert with a minimum slope of 2%. The dividing wall between the channels shall have connection pipes (diameter 150mm) every 25m allowing the small flow to cross over into the section with the V-shaped invert. Typical cross-sections are shown in Figure 2-2, Figure 2-3 and Figure 2-4. Construction Management Consultants Page 30

29 a- = 15"< g~~~~~~ =0 mu I?<efO // Y' z y), /' K/ Figure 2-2 Typical section of (2.Oxl.5) & (2.2x1.5) box culvert 3M_ mm Figure 2-3 Typical section of (2.x1.)&(2.2xl.5) box culvert a~~~~~~~~~~~~~cw1 Figure 2-4 Typical section of 3x(2.7x2) box culvert Construction Management Consultants Page 31

30 Due to the characteristics of storm events (relatively short and heavy, only during a certain time of year), box channel section that carry stormwater only shall not have the V-shaped invert Wastewater and drains, interception of wastewater In general drains in Danang carry both wastewater and stormwater; i.e. the drainage system is a combined system. Wastewater from residences, hotels, restaurants, factories, etc. flows either overland to the nearest drain inlet or through a connection pipe between the premises and the drain directly into the drain. Stormwater flows overland to the nearest inlet - usually a kerb inlet along the road. The design of the drainage network of Danang is such that water (be it wastewater or stormwater) is transported from the drain inlet to the nearest body of open water where it is discharged. Under the ongoing Phase I project, a wastewater collection system is being constructed in each of four wastewater catchments in Danang (also see paragraph 4.1.2). Each wastewater catchment will thus be provided with a wastewater collection system, generally located near outfalls where dry weather flows of wastewater will be intercepted and diverted from the combined drains. Except for the Le Do Drain (2) all drains in the additional works program carry both stormwater and wastewater. Even though the Le Do drain only carries stormwater run-off, a facility for diversion of wastewater has been included in the design of the outfall. In case it turns out that a considerable amount of wastewater enters the drain after all, diversion of wastewater can be easily achieved. This is also the case should it be decided that the Le Do drain is to carry both stormwater and wastewater flows. The two drains Le Dinh Tham and Xuan Hoa form an intermediate section. Their outfalls do not form part of the additional works program. The downstream section of Le Dinh Tham drain has already been upgraded under the ongoing Phase 1 project; its outfall has been fitted with a wastewater interceptor. The downstream section of Xuan Hoa drain is not part of any ongoing or planned upgrading; however, interception of wastewater at its outfall was planned under the Phase 1 project. Due to a change of alignment of a rising main, interception of wastewater at this point has been removed from the scope of that project. The An Khe drain forms the outlet for a number of retention ponds; wastewater should not be allowed to enter these ponds in the first place. Wastewater generated upstream from the ponds should be intercepted and diverted to a treatment plant before it enters the ponds. The choice of diverting wastewater upstream from the An Khe drain or at its outfall can be made at a later stage. Although no wastewater will be intercepted under the additional works program, a facility for diversion of wastewater has been included in the design of the outfall. At the outfalls of the My Khe drain wastewater will actually be intercepted. To that end design of each of its outfalls has been fitted with a diversion structure and a pumping station Side Entry Pits (kerb inlets) The ability of a drainage system to capture and carry away stormwater is limited by the effectiveness of its inlet structures. The standard Vietnamese practice in Danang of placing grates, or trash collection bars, across inlet openings is very restrictive on the inlet's capacity because of the marked reduction in inlet area as Construction Management Consultants Page 32

31 a result of the collection of trash behind the grate bars. Even though Danang's streets are regularly swept, the situation is often reached in heavy downpours where inlets are partially or even totally blocked by the collection of trash, leaves and fallen tree branches behind grate bars. To address to above mentioned limitations a new side entry pit design was made by GHD-Kinhill. This side entry pit has no grate bars and a much larger opening. The design, however, met with objections from URENCO and the general public due to the large and unprotected opening. A revised design with a number of modifications was made by CMC in conjunction with URENCO, as shown in Figure 2-5. TO LEEL (A) I SE DErAlL A cm DINH 4,4- ROA LEM eal4 DErAIL A -TYPE 2 S.MI. 1/10 h, w hs il r Figure 2-5 Typical section of a Side Entry Pit The spacing of the side entry pits is related to the capacity of the roadway to carry flow without excessive inconvenience by flooding to road users. In places with known local flooding problems and/or major overland flow from side streets, an inlet spacing of approximately 25m is set to achieve sufficient road-flow capture. In other places an inlet spacing of approximately 50m is sufficient Inlets for maintenance (manholes) In order to be able to carry out maintenance on the drain, inlets are provided at regular intervals for a person and/or equipment to enter the drain. These manholes are installed at the end of each line; at all changes in grade, size, or alignment; at all intersections; and at distances not greater than 50 meters. The minimum size of the manhole is 1.2m x 0.75m (rectangular), or 1.2m (circular diameter). The minimum opening dimensions of manhole covers are 600mm x 600mm (rectangular), or 600mm (circular diameter). In those cases where the drain consists of two (or more) channels, the manholes are consecutively located on alternate channels. Access between channels is provided by openings in the dividing wall. Construction Management Consultants Page 33

32 Danang Sub-project (Phase I) Siltation and trash collection As mentioned in paragraph 2.2.4, the design of the cross-section of the drain is meant to reduce maintenance requirements for drain desludging. However, due to the predominately flat gradients in Danang, siltation of the drains can never be fully avoided and can become a major problem. Also the sandy nature of the area's soils, stormwater litter, wastewater sludge, lack of erosion and sediment control measures at constructions sites and rubbish disposal into drains by residents contribute to the problem. Therefore, even with the measures in place to improve the self scouring ability drains need to be inspected regularly for blockages and siltation. To reduce the inflow of silt and sand, silt traps are provided on all side entry pits. These need to be desilted (either manually or by suction truck) on a regular basis. During heavy storm events trash can be dragged along and enter the drain through side entry pits. Also at overflows from stormwater regulation lakes trash can enter the drains. In order to avoid trash from be discharged from the outfalls to the Phu Loc River (An Khe Drain), Danang Bay (Le Do Drain) or East Sea (My Khe Drain) trash capture devices are installed at the outfall of each drain. Raking out the trash and its collection should be done on a regular basis - with a higher frequency during the rainy season and a lower frequency during the dry season. Material collected is to be carted to the new solid waste landfill area Structural 1. Design backgrounds a. Current construction standards o Design standards of "Reinforcement concrete structure" TCVN o Design standard of "Loading capacity and impacts" TCVN o Bridge and drainage design process to the ultimate state 22 TCN b. Other sources of reference o Reinforcement concrete structure (of basic components). The Publisher of Science - Technique, year o Soil pressure and retaining wall - The Publisher of Construction of o Technical standards of works of road conrmunications - Volume II (Survey and Design) - Ministry of Communication and Transport, c. Geologicalfeatures of the works Most of the earth layers along the drainage works are sandy soil but it is not excluded that some locations where the drains cross were farming fields or river beds in the past, pockets of mud may be found. If the drainage foundation is of sand, it can bear the loads of the drain and of the traffic above. However, a 0.2 m-thick layer of stone should be used to be able to drain away groundwater easily form the trench. If mud is found, the mud area can be either replaced with sand or the foundation can be strengthened using bamboo piles. Concrete piles are not preferred, as they are expensive and connection to drains with a shallow foundation is problematic. Construction Management Consultants Page 34

33 Preliminarily selected geological parameters of soil, assumed for drain calculation were: - Internal friction angle (p= 200 -Density y= 1.85 T/m 3 - Cohesion c= 0.2 T/m 2 2. Principles of design All loading levels, used for structural designs, are taken in accordance with the TCVN Loading and safety factor Safety factor Loads With reference to With reference to Note intensity and stability changes in form and location Frequent load: e Loads from the structure itself TCVN Long-term temporarv load e Loads from internal wastewater TCVN and stormwater * Loads from underground water pressure TCVN Short-term temporara load e By people and small vehicles TCVN * By to traffic TCVN Furthermore, a vibration factor must be taken into account that represents the extra forces on the drain caused by vehicle movement on the drain. A vibration factor of 1.3 is used. The weight loading on the drain include: - The load of the reinforced concrete drain itself - The load of soil cover over the drain (including road base and soil on top of the drain) - The water inside the drain - The loads by people and vehicles during road traffic - Other loads that interact to the drain foundation (as mentioned above) 3. Structural solution As the completed structures have to function in aggressive environments (salt water, wastewater), reinforcement may more easily be affected. To avoid early corrosion of reinforcements, concrete cover on each reinforcement bar is selected as 50 mm. The concrete design strength used for drain works is 25 MPa. Reinforced steel used for drainage works is the C-II steel, with design tensile stress 2600 kg/cm2 (260 N/mm2). Any C-I steel used will be calculated with design tensile stress of 2100 kg/cm2 (210 N/mm2). Construction Management Consultants Page 3 5

34 3 DRAINAGE - DETAILED DESIGNS 3.1 Le Dinh Tham drain Location and justification The existing drains in Binh Thuan ward, connecting the old Thac Gian Lake to the Han River, have insufficient capacity to meet the current drainage needs. The area suffers from frequent flooding. Originally almost the entire drain from the old Thac Gian Lake to the Han River was to be upgraded as part of the ongoing Phase 1 Sub-project. Due to budget constraints it was decided that only the downstream section in Duy Tan Street from Le Dinh Tham T-junction to the Han River was to be upgraded. In order to solve the drainage problem in this area as well as make full use of the new drain in Duy Tan Street, part of the upstream stretch from Thac Gian Lake to Duy Tan Street is added to the scope of the additional works programme. The section upstream from Le Dinh Thanh Street (Binh Tuan ward) is characterized by a densely built-up area and narrow alleys (no more than 2-2.5m wide). Most alleys already have a drain along it. Options for increasing the drainage capacity of the area are limited. There are two parallel alleys running north of Le Dinh Thanh Street. The one on the east has a drain 2.4m wide x 1.3m high. The one on the west has no drain and can be used to increase the drainage capacity. Upgrading further upstream would require widening of alleys and consequently demolishing a great number of houses necessitating considerable relocation. Under the additional works programme a.section of around 350m upstream from Le Dinh Thanh Street will be added along the alley that has no drain yet. To this section a 260m long drain along Le Dinh Thanh Street is added until the T-junction with Duy Tan Street. The new drain will be connected to the - under phase 1 project upgraded - drain in Duy Tan Street Catchment area and design flows The catchment area of the Le Dinh Thanh drain consists of the western part of Binh Thuan ward and most of Hoa Thuan ward. The total drainage area is around 123 ha. The upstream section of the drain along Le Dinh Thanh Street and the upstream alley drains around 77 ha. The design flow increases from 9.8 m 3 /s for the section in the alley to 12 m 3 /s for the section in Le Dinh Thanh Street Alignment and longitudinal profile As mentioned above the new drain will run for about 350m along an alley north of Le Dinh Thanh Street and connect to the existing drain at the upstream end. The complete width of the alley will be required. At the downstream end the drain will connect to the drains (old and new) along Le Dinh Thanh Street. Along Le Dinh Thanh Street - from Trung Nu Vuong Street to the T-junction with Duy Tan Street - a new drain will be laid under the pavement on the western side. For a Plan and Profile see Drawing DG-A-DT Construction Management Consultants Page 36

35 3.1.4 Cross section The cross section of the drain along the alley in Binh Tuan ward consists of 1 channel of 2.2m wide and 1.5m high; the drain along Le Dinh Thanh Street is 2.7m wide and 1.5m high (see Drawing DG-A-DT ?). See Appendix A. 1 for a detailed hydraulic calculation. Special attention has been paid to the self scouring ability of the drain during low flow. The floor of the middle channel has been set at angle so that a V-shape is formed. The cross section in this part is smaller, thus increasing the depth of flow and velocity under low flow conditions Connections to other drains The new drain in the alley will have to connect at the upstream end with the existing drains at an invert level of 2.30m. On exiting the alley the drain is to be connected with the existing drains along Trung Nu Vuong Street as well as the existing drain in Le Dinh Thanh Street at invert level 1.95m. The new drain along Le Dinh Thanh Street will also start at this level and connect to the new drains in Duy Tan Street at invert level 1.69m Interception of wastewater flows from the drain The concerning drain forms the middle part of the Thac Gian Lake - Han River drainage system. The drain will serve for both wastewater and stormwater flow combined. The wastewater will be intercepted 940m downstream of the new drain near the outfall at Nguyen Van Troi Street. From there the wastewater will flow through GID14 to SPS14 and ultimately to Hoa Cuong WWTP Special issues The upper reaches of the drainage system of Binh Thuan ward will still not have enough capacity after the above mentioned additions. Tackling that problem at this point in time does not seem feasible, but it should be addressed in due course. The upstream end of the new alley drain is the lowest point in the area. Any stormwater that can not be conveyed through the upstream drainage system will flow overland to this point. It is therefore essential to make a proper facility for any overland stormwater flow to easily enter the drain at this point; this will reduce any inconvenience due to the limited upstream drainage capacity considerably. A long entry structure is therefore included in the design at this point. 3.2 Le Do drain Location, options and justification Thanh Khe district is developing rapidly. Recent surveys and capacity calculations have revealed that the district's drainage system needs to be upgraded to be more suitable with the development of the District. At the moment, the run-off from the Airport and 29/3 Lake catchment areas flows along a watercourse/drain north of Dien Bien Phu Street (on the border between An Khe and Xuan Ha wards) through a low lying area towards the Phu Loc River. This low lying area is prone to frequent flooding. Now that these low lying areas are being developed into residential areas the stormwater coming from the Airport and 29/3 Lake catchment areas needs to be diverted. Construction Management Consultants Page 37

36 The following options (of which number 2 and 3 are discussed in the Feasibility study) have been considered: Option 1: Upgrade the drain along the existing route The first option is to increase the capacity of the existing watercourse/drain. Advantages: The middle stretch of the route runs through an open area requiring no cutting of roads or relocation of affected persons. Limitations: Due to the distance between Dien Bien Phu Street and the Phu Loc River (>3km) the length of drain needing to be upgraded is considerable. The limited available hydraulic slope would require the width of the drain to be substantially more than that of the existing drains/watercourse. As a result of the density of the built-up area along particularly the up- and down-stream ends of this route, this option would require a significant amount of relocation. Option 2: Partially upgrade the existing drain and construct a new drain through Chinh Gian and Tam Thuan residential areas to Danang Bay The second option goes through Chinh Gian residential area, a concrete enterprise, Lane 256 Tran Cao Van and Tam Thuan residential area. This is a drain of around 950m long connecting Dien Bien Phu Street with Danang Bay. Advantages: The length of drain is relatively short and traffic will not be obstructed much during construction. Also, the access road to the houses along the drain will be improved. Limitations: The available area for construction is very limited; the route runs along narrow alleys. Due to the limited space heavy machinery cannot be used resulting in an increased time'of construction and an increased cost of construction. Also the number of people affected by the construction and the people to be relocated is substantial. Excavation and construction depth is large due to low invert level of the existing drain in Xuan Ha ward; the resulting low invert level at the outfall reduces the capacity of the drain because of tidal influence. Operation and maintenance costs are also expected to be high. Option 3: Construct a completely new drain along Le Do Street to Danang Bay The third option has a drain running along Le Do Street. This is a drain of around I 100m long connecting Dien Bien Phu Street with Danang Bay. Advantages: The benefits lie in the less costly construction because of the accessibility for heavy equipment and resulting shorter construction period; also the depth of construction is less than for the other options. Required resettlement is very limited because the upstream 800m can be constructed in the existing Le Do Street. Only the remaining 250m downstream section crossing an existing neighbourhood needs resettlement. Also operation and maintenance costs are expected to be lower. Limitations: Construction along the Le Do Street will cause inconvenience for local residents and obstruct traffic, albeit temporary. The length of drain is slightly longer than option 2, but considerably shorter than option 1. Recommendation: Based on the above advantages and limitations option 3 to construct a drain along Le Do Street is chosen. Construction Management Consultants Page 38

37 Danang Sub-project (Phase l) The Le Do Drain has been included in the ongoing Phase I works (contract 013). Because of the impending construction of the road linking Tran Cao Van Street and Nguyen Tat Thanh Street it is necessary to construct the drain - which lies along this new section of road - as soon as possible. If the drain is not constructed soonest, either the construction of the road has to be delayed or the road will need to be cut only a short time after it has been constructed Catchment area and design flows As mentioned.above, the main function with the drain is to divert stormwater from the Airport and 29/3 catchment areas away from the low lying area between An Khe and Xuan Ha wards and towards Danang Bay. The catchment area of 29/3 Lake is around 63 ha. The catchment area of the Airport Lake is around 205 ha. Both lakes have a stormwater regulation function and reduce the peak flow considerably. The area drained by 29/3 Lake is densely populated and built up; a run-off coefficient of 0.8 has been adopted for this area. The area drained by the Airport Lake is mainly unpaved; a run-off coefficient of 0.5 has been adopted for this area. The following tables (Table 3-1 and Table 3-2) show the hydraulic behaviour of the lakes. The level of both lakes is normally kept at 3.00m. As stormwater run-off starts flowing into the lakes the level is raised; with the rising level, water starts to flow out off the lake. The higher the level of the lake, the larger the outflow from the lake. As long as the inflow to the lake is larger than the outflow, the level is being raised. For a 10 year return period the inflow to the lakes has been determined. Also for each 0.1 Om of raised lake level the outflow has been determined. The level of 29/3 Lake is raised to a maximum of 3.55m before the outflow becomes larger than the inflow; the maximum stormwater outflow at that moment is 2.89 m 3 /s 29/3 Lake: Lake area 10.3 ha. Lake depth 2.5 m Catchment area 63.2 ha. Max. Inflow m 3 /s Water-level Capacity Retention Cap. Outflow [ml [m3] [m3] [m3ls] ,900 _ ,200 10, ,500 20, ,800 30, ,100 41, ,400 51, Outfall at 29/3 Lake: B x H = 2.4 x 2.Om Table 3-1 Hydraulic behaviour 29/3 Lake Similarly, the level of the Airport Lake is raised to a maximum of 3.49m before the outflow becomes larger than the inflow; the maximum stormwater outflow at that moment is m 3 /s. Construction Management Consultants Page 39

38 Airport Lake: Lake area Lake depth Catchment area 6.8 ha. 2.5 m ha. Max. Inflow m 3 /s Water-level Capacity Retention Cap. Outflow [ml 1m3] Im3] [m3ls] , ,200 6, ,000 13, ,800 20, ,600 27, Outfall at Airport Lake: B x H = 3.0 x 2.0m Table 3-2 Hydraulic behaviour Airport Lake (San Bay) See Appendix A.2 for a detailed flood routing calculation. Along Le Do Street a number of existing drains will be connected to the new drain. The contributing area is around 44 ha. The flow towards Xuan Ha ward needs to be limited in order to reduce the flood risk in that area. At the upstream entry to the existing drain (Dien Bien Phu Street) a slot of 5m wide x 0.3m high will allow the dry weather flow as well as a limited stormwater flow (max 3.5 m 3 /s) to continue through the existing drain. The new drain through Le Do Street will be used strictly for excess stormwater discharge. All upstream dry weather flow (wastewater) will continue to flow through the existing drain. The design flow for the drain in Le Do Street at the upstream entry point is =9.74 m 3 /s gradually increasing to m 3 /s at the downstream end Alignment and longitudinal profile The drain will start at the crossing of the existing drain (5.4m wide x 2.Om deep) in Dien Bien Phu Street near the bus station. The starting invert level is 1.80m. The drain will run eastward in Dien Bien Phu Street along the northern side of the road. At the corner of Dien Bien Phu Street and Le Do Street the drain will turn northward into Le Do Street. From here until Danang Bay the drain will continue along the western side of Le Do Street. A connecting road is being built from the T-junction of Le Do Street with Tran Cao Van Street to the road along Danang Bay. Saving can be achieved by first putting in the drain and then surface the road. The drain will lie in the road along the entire route since the sidewalks are occupied by existing roadside drains. For a Plan and Profile see Drawing DG-A-LD Cross section The cross section of the drain is 2 x 2m wide and 1.5m high for the first 489m and 2 x 2m wide and 1. 7m high for the remaining 55 5m (see Drawing DG-A-LD2-01-0?). See Appendix A.2 for a detailed hydraulic calculation. Construction Management Consultants Page 40

39 n Connections to other drains At five locations the new drain will cross an existing drain. Drainage capacity of the area is improved by making a connection between the existing drains and the new drain so that excess stormwater can overflow into the new drain. Special attention needs to be given to preventing wastewater from entering the new drain from the connection to existing (combined) drains. To that end the invert of the new drain at the up-stream connection will be 300mm higher (1.80m) than the invert level of the existing drain (1.50m) crossing Dien Bien Phu Street. The wastewater will continue flowing along the existing drain, towards Phu Loc River. In addition, every connection to other drains along Le Do Street has a small weir Interception of wastewater flows from the drain Dry weather flow from upstream as well as along the route of the new drain will not be allowed to enter. At present, wastewater either flows through the existing drain on the border between An Khe and Xuan Ha wards (from the area of 29/3 Lake and the Airport Lake) towards Phu Loc River; or through existing drains in the Xuan Ha, Tam Huan and Chinh Gian wards towards Danang Bay where it is intercepted by the newly built GlDs along the boulevard. No additional wastewater discharge capacity is required. By not allowing wastewater to enter the drain no interceptor structure will be required at the outfall to the Danang Bay. This will reduce cost (construction and O&M) Special issues As mentioned in paragraph 3.2.2, the flow towards Xuan Ha ward through the existing drain needs to be limited in order to reduce the flood risk in that area. At the upstream entry to the existing drain (Dien Bien Phu Street) a slot of 5m wide x 0.3m high will allow the dry weather flow as well as a limited stormwater flow (max 3.5 m 3 /s) to continue through the existing drain. This can be achieved by installing runners on each side of the drain into which partitions can be slotted. A stopper of 300mm high at the bottom of the runners prevents the bottom partition to slide all the way down leaving a slot for the dry weather flow as well as a limited stormwater flow to continue through the existing drain. Each partition is around 300mm high; six partitions would be necessary to close the top section of the existing drain. A gap of at least 300mm needs to be left open at the top to be able to slide the partitions into the runners. Because of the high build-up of sand along this section of Danang Bay, 3.3 Xuan Hoa drain Location, options and justification The catchment of this drain includes northwest of Danang Airport and the northern part of An Khe ward. At the northwestern side of the airport a stormwater management lake is situated: Xuan Hoa pond. Formerly this pond was relatively small; however, as part of the redevelopment of the area a much larger body of water has been created (according to the most recent master plan approximately 4.7 ha.). A number of (new) drains from the area discharge into this lake. At the northwest corner of the lake there is an outlet to a new drain (3.0m wide, 1.5m high); this drain connects northwards, to Dien Bien Phu Street. Construction Management Consultants Page 41

40 North of Dien Bien Phu Street the drain continues as an open earth channel, at places very narrow and shallow. During rainfall the open channel overflows into the surrounding low lying area causing flooding. According to the city's plans, the low lying area is to be backfilled up to a level of 3m and further developed as a residential area. To protect this redeveloped area against flood risks the flow needs to be contained. The following options have been considered: Option 1: Upgrade the drain along the e-xisting route The first option is to increase the capacity of the existing watercourse/drain. This would mean that the open earth channel is to be upgraded to a box channel section with sufficient capacity to discharge the incoming upstream flow as well as the local drainage. Advantages: Almost the entire length of the drain runs through an open area requiring very limited cutting of roads or relocation of affected persons. Access to the area for heavy equipment is good except for the first two hundred meters. The area the drain runs through will be developed into a residential area and can take advantage of the drainage capacity of the drain. Limitations: The length of drain is longer than the second option by around 300m. Although the slope along the first 70 meters is considerable, along most of the route the available (hydraulic) slope is limited. Option 2: Drain along Ha Huy Tap Street An alternative route considered is similar to the one for the drainage of San Bay and 29/3 Lakes to the east (Le Do drain, see paragraph 3.2). From the crossing with Dien Bien Phu Street the drain runs eastward in Dien Bien Phu Street. At the corner of Dien Bien Phu Street and Ha Huy Tap Street the drain turns northward. From there until Danang Bay the drain continues along Ha Huy Tap Street. Advantages: This route is shorter (around 900m instead of around 1200m) than the existing route. Required resettlement is very limited because the downstream section crossing an existing neighbourhood is combined with the construction of a new road between Tran Cao Van Street and Danang Bay for which resettlement is already required. The rest of the route is along existing roads. Limitations: The route is almost entirely along existing roads increasing the cost because of road reconstruction. Construction along Ha Huy Tap Street will cause inconvenience for local residents and obstruct traffic. This route will require crossing an existing drain going east to west just south of the railway (connecting the low lying area between Xuan Ha and An Khe wards with the Phu Loc River). This drain has a very low invert level and special arrangements would have to be made in order to prevent the inflow of seawater during high tide. Also, this route does not address the drainage of the area itself between Dien Bien Phu Street and Tran Cao Van Street west of Ha Huy Tap Street. Recommendation: Based on the above advantages and limitations option I to construct a drain along the existing route is chosen Catchment area and design flows The catchmnent area of Xuan Hoa pond is around 100 ha. and covers the northwestern side of the airport and the middle of An Khe ward. Since the area is being gradually redeveloped and Construction Management Consultants Page 42

41 increasingly built-up, a run-off coefficient of 0.8 has been adopted. The pond has a stormwater regulation function and reduces the peak flow considerably. Xuan Hoa pond: Lake area 4.7 ha. Lake depth 1 m Catchment area 99.8 ha. Max. Inflow m 3 /s Water-level Capacity Effective cap. Outflow [l [m3] [m31 [m/s] , ,700 4, ,400 9, ,100 14, ,800 18, ,500 23, ,200 28, ,900 32, ,600 37, Outfall at Xuan Hoa pond: B x H = 3.0 x 1.5m Table 3-3 Hydraulic behaviour Xuan Hoa pond The level the lake is normally kept at 2.00m.; this is the invert level of the outgoing -drain. As stormwater run-off starts flowing into the lake the level rises; with the rising level, water starts to flow out off the lake. The higher the level of the lake, the larger the outflow from the lake. As long as the inflow to the lake is larger than the outflow, the level continues to rise. For a 10 year return period the inflow to the lakes has been determined. Also for each 0.1 Om of raised -lake level the outflow has been determined. The level of Xuan Hoa pond rises to a maximum of 2.81m before the outflow becomes larger than the inflow; the maximum stormwater outflow at that moment is 7.79 m 3 /s. See Appendix A.3 for a detailed flood routing calculation. The design flow for the drain at the upstream entry point (Dien Bien Phu Street) is 8.07 m 3 /s (being the design stormwater run-off increased with 0.28 m 3 /s wastewater flow from the upstream area) gradually increasing to m 3 /s at the downstream end (Tran Cao Van Street) Alignment and longitudinal profile The drain will start by crossing Dien Bien Phu Street 150m west of Ha Huy Tap Street, connecting to the existing (new) drain (3.Om wide x 1.5m high). The starting invert level is 1.80m. The drain will run northward with a steep gradient (1.5%) between a number of houses up to a small pathway crossing. In some places this section is quite narrow. After crossing the pathway, the gradient becomes quite flat (0.1%) necessitating a wide drain (4.2m wide). Following the railway crossing, the drain turns westward and runs (with a gradient of 0.1%) along the fence of the Hospital. This and the more westward lying area will be backfilled up to a level of 3m and developed as a residential area. The drain will follow planned road alignments. For the last Construction Management Consultants Page 43

42 IOOm again the drain runs between a number of houses and a school up to Tran Cao Van Street. Here it connects to an existing drain (invert level -0.25m) to Phu Loc River. Except for about 150m, the drain will lie.in open terrain. At a later stage, a road will be built over the drain. Of the 150m not in open terrain, the drain will lie for about loom in the sidewalk and for about 50m in an asphalt road. For a Plan and Profile see Drawing DG-A-XH Cross section The cross section of the drain is I channel of 2m wide and 1.5m high (see Drawing DG-A-XH3-01-0?) for the first 70m between a narrow part with two rows of houses and I channel of 2.2m wide and 1.5m high for the next 140m (Dien Bien Phu - railway); for the remaining 895m (railway - Tran Cao Van Street) the cross section consists of 2 channels of which 160m each 2m wide and 1.5m high and 735 each 2.2m wide and 1.5m high (see Drawing DG-A-XH3-01-0?). See Appendix A.3 for a detailed hydraulic calculation Connections to other drains At the upstream and downstream ends the drain connects to existing drains. Upstream in Dien Bien Phu Street at an invert level of 1.80m; downstream across the Tran Cao Van Street at an invert level of-0.25m. At present, run-off and wastewater from the area between Dien Bien Phu Street and the railway runs through a collection of small drains and open channels to the culvert under the railway. The new drain will block this flow. A pipe (diameter 500mm) is laid alongside the drain crossing-the railway; this pipe creates a (temporary) open connection across the railway. In future, a road is planned along each side of the railway. The run-off and wastewater from the area along the railway will be collected by the drain along these future roads; these drains are subsequently connected to the Xuan Hoa drain. The area downstream from the railway crossing is to be backfilled and developed as a residential area. As soon as the built-up area is expanded new drains will be connected. Between chainage 880m and 980m the drain runs parallel to a major drain coming from Chinh Gian and Xuan Ha wards. This is also the section where the drain runs under the southern side walk; the other drain runs under the northern side walk. A connection between the two drains will be made across the road Interception of wastewater flows from the drain The Xuan Ha drain forns the middle part of the Xuan Hoa - Phu Loc drainage system. The drain will carry both wastewater and stormwater run-off. No diversion of wastewater from this section of drain is foreseen. However, at the point where water is discharged into Phu Loc River (150m west of Tran Cao Van Street) a diversion structure and pumping station were foreseen. Because of a change in the routing of the wastewater pipeline, these were deleted from the ongoing Phase I project, but will be built in the future. In the calculation of the cross section the influence on the flow capacity of the diversion structure (weir) has been taken into account. Construction Management Consultants Page 44

43 3.3.7 Special issues The drainage of the area along route of the new drain is presently provided by an open channel. Construction of the new box drain in the bedding of the open drain will prevent wastewater and run-off from this area to be properly evacuated. It is not recommended to add entry pits for water from this unpaved area to enter the drain because of the risk of sand and dirt entering the drain. The drain will be easily blocked creating a flooding risk for the upstream areas. This situation is temporary since the area north of the railway will be back filled and developed into a residential area in the near future; the local drainage system will be connected to the new box drain. The area between Dien Bien Phu Street and the railway will be connected to the roadside drains of the planned road along the railway; these drains are subsequently connected to the Xuan Hoa drain Geotechnical considerations Soil in Danang, with soils of (fine) sand, is generally good or very good for the construction of drains. The additional loads imposed by the new drains on the sub soils are generally very minimal as in almost all cases the drains replace outcoming soil with similar or higher weights. However, there are exceptions. Recently, the ongoing project has had to deal with pockets of very muddy soil that were unsuitable for foundation of drains. These were found in locations where there have traditionally been rivers or swamps. It was found that roads were constructed over such mud layers with a sub-base of about 2 m of good soil. During the construction of drains, the good top layer would be removed and mud started exactly at the base level of the drain. The Xuan Hoa drain will be almost totally constru'cted in a former river bed and it was suspected that soft soil conditions might exist. Geotechnical investigations were carried out, therefore, along the drain alignment. In total 10 SPT tests were made and, for confirmation of the soil types, 5 boreholes were made. The SPT give the best indications regarding bearing capacity of the soil and they show clearly the thickness of the poor soil layers. Mud was indeed found, with a thickness generally varying between 0.3 and 1.5 m. At one location the SPT values increase near the 0.7 level, but then decreased again sharply between m below groundlevel. Taking into account foundation levels of the drain, the drain base would be founded on soil with sufficient bearing capacity. Occasionally, it may be necessary to remove some additional mud and replace it with good soil. At the one location with poor sub-soil, some more mud may have to be replaced with sand. The bill of Quantities made for this drain allows for mud replacement. It is indicated that the quantities shown in the Bill are provisional and may be changed subject to approval of the Engineer. The amounts involved in mud replacement are estimated to be only a few percent of the drain construction costs. 3.4 An Khe drain Location and justification The An Khe drain is a large natural channel originating from the western side of the Airport; it crosses the low lying areas on the western side of An Khe ward and the marsh area in Thanh Loc Dan ward. The channel terminates at Phu Loc River, behind the Taiwan Textile Factory. In the near future the City is planning to construct the An Khe cultural park zone in the southwestern part of An Khe ward, thus filling up the natural channel itself and the surrounding low lying area. Also a large part of the area will be developed as a residential area. Construction Management Consultants Page 45

44 Danang Sub-project (Phase I) Three interconnected ponds with a total surface area of around 12 ha. will be retained for stormwater management purposes. The reduction of retention capacity necessitates the increase in discharge capacity of the downstream channel. The northern most pond is connected through two culverts crossing the railway to the channel on the other side. The only available route for the new drain is along the existing channel around the Taiwan Textile Factory to the Phu Loc River Catchment area and design flows The catchment area of An Khe ponds is around 3 10 ha. and covers the western side of the airport, the western side of An Khe ward and the southern side of Thanh Loc Dan ward. Since the area is being gradually redeveloped and increasingly built-up, a run-off coefficient of 0.8 has been adopted. The ponds have a stormwater regulation function and reduce the peak flow considerably. An Khe ponds: Lake area 12 ha. Lake depth 1.5 m Catchment area ha. Max. Inflow m 3 /s Water-level Capacity Retention Cap. Outflow [m] [m3] [m 3 ] [m 3 /s] ,000 _ ,000 12, ,000 24, ,000 36, ,000 48, ,000 60, ,000 72, ,000 84, ,000 96, , , Outfall at An Khe pond: B x H = 8.0 x 2.Om Table 3-4 Hydraulic behaviour An Khe ponds The water level of the lake is kept at 1.00m by a weir at the upstream end of the drain. As stormwater run-off starts flowing into the lake the water level rises; with the rising level, water starts to flow out off the lake. The higher the level of the lake, the larger the outflow from the lake. As long as the inflow to the lake is larger than the outflow, the level continues to rise. For a 10 year return period the inflow to the lakes has been determined. Also for each 0.1Dm of raised lake level the outflow has been determined (see Table 3-4). The level of An Khe pond rises to a maximum of 1.98m before the outflow becomes larger than the inflow; the maximum stormwater outflow at that moment is m 3 /s See Appendix A.4 for a detailed flood routing calculation. Construction Management Consultants Page 46

45 The design flow for the drain at the upstream entry point (railway) is m 3 /s (being the design stormwater run-off increased with 0.35 m 3 /s wastewater flow from the upstream area) gradually increasing to m 3 /s at the downstream end (Phu Loc River) Alignment and longitudinal profile The drain connects the stormwater regulation pond south of the railway with the Phu Loc River in the north. The railway at this point consist of two tracks, one going to Hanoi and one going to Ho Chi Minh City. Both tracks have two culverts/bridges each where the open stream crosses under the railway. The eastern culvert is 8m wide; the western culvert is 4m wide. The outlet from the pond and the connection to the culverts under the southern railway track is the responsibility of the local PC constructing the pond. The drain as designed under the additional works program starts at the north side of the Ho Chi Minh railway track (the southern of the two tracks). Both culverts of the southem track are connected to the culverts of the northern (Hanoi) track by a short section of drain; each section is as wide as the culvert (8m respectively 4m). At the northern side of the Hanoi track the drain runs in an easterly direction along the railway from the larger culvert to where the smaller culvert joins with the drain. From here the drain turns northward and then runs along the property boundary of the Taiwan Garment Factory until it reaches the Phu Loc River For the entire length the drain lies in open terrain at a slope of 0.1%. Although at present no master plan for the area exists, at a later stage the area might be developed and a road could be built over the drain. For a Plan and Profile see Drawing DG-A-AK Cross section The cross section the drain between the eastern 2 culverts is 8m wide and 2m high, while the cross section the drain between the western 2 culverts is 4m wide and 2m high. The cross section of the drain from the railway to Phu Loc River consists of one section of 3 x 2.67m wide and 2m high (see Drawing DG-A-AK4-01-0?). Special attention has been paid to the self scouring ability of the drain during low flow. The floor of the middle channel has been set at angle so that a V-shape is formed. The cross section in this part is smaller, thus increasing the depth of flow and velocity under low flow conditions. See Appendix A.4 for a detailed hydraulic calculation Connections to other drains At the upstream end the drain connects to the culverts under the southern track of the railway. The invert levels of the culverts are 0.28m for the eastern (8m wide) culvert and 0.30m for the western (4m wide) culvert. The short sections between the two railway tracks connecting each of the two culverts continue from these invert levels under a slope of approximately 0.1%. The invert levels of the culverts under the northern track of the railway are 0.26m for the eastern (8m wide) culvert and 0.22m for the western (4m wide) culvert. At the north side of the Hanoi track, the drain will start from the eastern (8m wide) culvert at an invert level of 0.26m. A lower invert level would result in a too deep invert level at the Construction Management Consultants Page 47

46 downstream end and - because the outflow invert level is below the outside water level - reduce the flow capacity of the drain; a higher invert level would result in the top of the drain to be above the surface level of the surrounding area and in effect reduce the flow capacity of the drain. After running west for approximately I OOm the western (4m wide) culvert connects to the drain. The invert level at the outflow to the Phu Loc River - approximately 600m downstream - is -0.34m. In between the drain does not cross other drains. The outfall to the Phu Loc River consists of a two channel sluice gate which has fallen into disrepair. This gate is replaced by a proper outfall structure with a trash rack and tidal weir, Interception of wastewater flows from the drain The new box drain forms the final section of the An Khe - Phu Loc drainage system. For the foreseeable future the drain will carry both wastewater and stormwater run-off. However, since the drain forms the outlet for a number of retention ponds, wastewater should not be allowed to enter these ponds in the first place. Wastewater generated upstream from the ponds should be intercepted and diverted to a treatment plant before it enters the ponds. Not knowing at which point wastewater flows will be intercepted, a diversion structure and pumping station have been reckoned with at the point where water is discharged into Phu Loc River. In the calculation of the cross section the influence on the flow capacity of such a diversion structure (weir) has been taken into account. At this point in time, however, no diversion structure will be constructed and no wastewater will be intercepted Special issues Special attention should be paid to the outflow structures of the pond i.e. the inflow structure to the drain. Since considerable amounts of water have to pass over the weir the length should be sufficient for the water surface of the pond not rise too much. At the time of writing this report the outfall structures of the pond had not yet been constructed. The level of the outfall weir was subsequently not known. Therefore a weir has been integrated into the design at the upstream entrance to the drain; i.e. at the north side of the railway where the culverts connect to the drain. The width of the weir is set at 12m; this is the width of both culverts together. The height of the weir is set at +1.OOm. With a weir of these dimensions the water level will not exceed 2m for an event with a return period of 10 years. With a level of the surrounding area of between 2.5m and 4.5m this leaves enough freeboard. Should, at the time of construction of the drain, the outfalls of the pond already be constructed and should the level of that weir be not lower than +1.OOm while the width is not less than 12m the weir at the entrance to the drain can be dispensed with. At the moment, low-income residences and home-businesses along the drain discharge their wastewater directly to the low lying area through which the existing open channel flows; also local stormwater run-off flows through the open channel to the Phu Loc River. Construction of the new box drain in the bedding of the open drain will prevent wastewater and run-off from this area to be properly evacuated. Construction Management Consultants Page 48

47 n It is not recommended to add entry pits for water from this unpaved area to enter the drain because of the risk of sand and dirt entering the drain. The drain will be easily blocked creating a flooding risk for the upstream areas. It is not clear if or when the area north of the railway will be back filled and developed into a residential or industrial area. Considering the development of other areas in Danang, it seems highly likely that this area will at some point be back filled and further developed. In the mean time, water from the area will collect around the new drain and soak into the sandy soil. Although this is not an optimal situation, the risk of damage is negligible since there are no structures in the low lying area and the amounts of water are small. Another point of attention is the bamboo bridge crossing the open stream. The top level of the box drain is around 0.5m higher than the present level of the bridge. The access ramp should be raised and the top of the drain should be made suitable for crossing with motorbikes. On either side of the drain the access ramps should be fitted with a small culvert (diameter 500mm) for local drainage to be able to pass Geotechnical considerations Soil in Danang, with soils of (fine) sand, is generally good or very good for the construction of drains. The additional loads imposed by the new drains on the sub soils are generally very minimal as in almost all cases the drains replace outcoming soil with similar or higher weights. The An Khe drain will be almost totally constructed in a former river bed and it was suspected that soft soil conditions rnight exist. Geotechnical investigations were carried out, therefore, along the drain alignment. In total 6 SPT tests were made and 2 boreholes. The SPT give the best indications regarding bearing capacity of the soil and they show clearly the thickness of any poor soil layers. It was found that SPT values were generally high and no soil improvement would be required. However, at one location, representing approx m of the drain alignment, mud was-found up to 3.6 m below ground level. As at this location, the drain will be built with a base at approx the same as the existing groundlevel, up to 5,300 m3 of mud may have to be replaced. The bill of Quantities made for this drain allows for mud replacement. 3.5 My Khe drain Location options considered The drainage system in Son Tra and Ngu Hanh Son districts is not clearly established. In the districts' area there are only few drains, located mainly in new residential areas. Waste- and stormwater from residential areas along East Bach Dang Street discharges directly to the Han River through drains from Ngo Quyen Street connecting to East Bach Bang Street. Similarly waste- and stormwater from the area west of Ngu Hanh Son Street is discharged directly to the Han River. All waste- and stormwater from residential areas east of Ngo Quyen/Ngu Hanh Son Streets is discharged to the natural low land of the catchment; this low land is situated between the elevated area just behind the beach (dunes) and the raised carriageway of Ngo Quyen/Ngu Hanh Son Streets. Construction Management Consultants Page 49

48 An outfall connecting the low lying area with the sea is situated between Nguyen Van Thoai Street and the My Khe Beach Hotels. The invert level of this drain, however, lies considerably higher than the area it is supposed to drain. The result is that during the rainy season the low area turns into a series of small lakes; during the dry season the area is returned to a sewage filled swamp. In the northeast of Ngu Hanh Son district a natural watercourse originates from Nguyen Van Thoai Street and runs to the back of the Furama resort where it empties to the sea. This watercourse, however, suffers from heavy siltation and clogging resulting in a high invert level and small crosssection, and thus limited drainage capacity. As a result of the limited and poor opportunities for discharging waste- and stormwater out of the area, new residential areas - although they have a local drainage system - are regularly affected by flooding. To address drainage problems in the southeast of Son Tra and the northeast of Ngu Hanh Son several options have been explored. The areas in Son Tra and Ngu Hanh Son are discussed in conjunction because - even though they lie in different districts - hydraulically they form one area. This area will be backfilled to a minimum level of +2.50m and developed into a residential area. The natural orientation of the drainage is towards the lowest points in the area, about 500m inland from the beach. Along the centre of this low lying area - in north-south direction - a major drain will be constructed. The drain starts at Nguyen Cong Tru Street and runs all the way down to Ho Xuan Huong Street past the Furama Resort along the planned road designated by the temporary name of Number 4 Street. The drainage options for the area differ in the way the water is discharged to the surface water: to the sea in the east or to the river in the west. Option 1: Discharge to My Khe Beach. Wastewater from main drain is discharged to My Khe Beach by three outlets. Outlet 1 is the same as the existing one between Nguyen Van Thoai Street and the My Khe Beach Hotels; however, the invert of the drain is lowered and the cross-section of the drain is enlarged to 7.5m wide by 2m high. The outfall will receive most of the waste- and stormwater of the catchment east of Ngo Quyen Street between Nguyen Cuong Tru Street and south of Nguyen Van Thoai Street. Outlet 2 is new and runs along the north boundary of the Sao Paolo Monastery. The dimension of the outlet drain is 7.5m wide and 2.Om high. The outfall will receive most of the waste- and stormwater of the catchment east of Ngu Hanh Son Street between south of Nguyen Van Thoai Street and north of Ho Xuan Huong Street. Outlet 3 runs along the same route as the existing natural watercourse to the south of the Furama Resort. The dimension of the outlet drain is 5.0m wide and 2.Om high. The outfall will receive most of the waste- and stormwater of the catchment east of Ngu Hanh Son Street between north of Ho Xuan Huong Street and the Furama Resort. Advantages: Two of the three outlets follow the route of existing drains. All the outlet drains follow the shortest route to the surface water. Consequently the invert levels and cross-sections of the drains remain within limits. Disadvantages: My Khe beach already attracts many local and international tourists and is to be further developed into a high class tourist attraction. Construction of outfalls at these locations will cause pollution of the beach area. Debris will give the beach an unattractive sight; wastewater overflows will create unsafe swimming water due to pathogens. Construction Management Consultants Page 50

49 Option 2: Discharge to the Han River. In this option, waste- and stormwater from the main drain is evacuated in westerly direction towards the Han River. The collected water from the north end of the drain is discharged through a drain (8.Om wide by 2.Om high) along Nguyen Cong Tru Street; discharge through the Le Huu Trac Street is no longer an option since the recent construction of a large drain with a slope towards the beach away from the river. Water from the middle part of the drain is discharged along the Phan Tu Street by a lo.om wide by 2.Om high drain. A 7.5m wide by 2.Om wide drain along the Ho Xuan Huong Street discharges the water from the south end of the main drain. Advantages: No waste- or stormwater will be discharged along My Khe beach reducing the risk of pollution of the prized tourist area. Disadvantages: The construction cost is considerably higher than Option I due to the greater length of drains as well as the large construction depth necessary to cross the relative high level of the Ngo Quyen/Ngu Hanh Son Streets carriageway. Also, the water level of the river is higher than that of the sea resulting in flatter hydraulic gradients and thus requiring bigger drains. Moreover, although the Han River is not used for swimming, debris will reduce the attractiveness of the boulevard being constructed all along the river. Recommendation: Based on the above advantages and limitations, specifically the high construction cost of Option 2, Option 1 - to construct the outfalls towards the beach - is chosen. The negative impacts of Option 1 on the environment can mostly be mitigated by constructing trash capture devices upstream of outfalls as well as wastewater interceptors (also see paragraph 5.4). The beach cleaning machines purchased in the framework of this project will deal with any debris passing the trash capture devices and inadvertently cast from the outfalls. Finally, pathogens can survive in salt water for only a very short time, much shorter than in fresh water Catchment area and design flows The catchment area of the My Khe drain is bounded in the north by Pham Van Dong Street and in the south by the old military airfield. The western boundary is formed by the raised carriageway of Ngo Quyen/Ngu Hanh Son Streets and the eastern boundary is formed by the East Sea. The total drainage area amounts to about 330ha. Around 120ha. is drained through the My Khe Beach Hotel outfall, 123ha. through the Sao Paolo Monastery outfall, and 88ha. through the Furama Resort outfall. The design flow of the north section of the main drain between Nguyen Cong Tru Street and the beginning of the My Khe Outfall increases from 6 m 3 /s to a maximum of 12 m 3 /s. The design flow for south section of the drain to the My Khe Outfall varies between 4 m 3 /s to a maximum of 11 m 3 /s. The My Khe Beach outlet drain is designed for a flow of around 23 m 3 /s. For the north section connecting to the St. Paolo Monastery the design flow increases from 6 m 3 /s to a maximum of 13 m 3 /s, with the flow from the south section varies from 5 m 3 /s to a maximum of 11 m 3 /s. The St. Paolo Monastery outlet drain itself is designed for a flow of around 24 m 3 /s. Finally, the Furama section of the main drain is designed for a flow of 5 m 3 /s up to 15 m 3 /s. Construction Management Consultants Page 51

50 3.5.3 Alignment and longitudinal profile In the past, development of the area was more or less unstructured. At the present a master plan is being implemented. This master plan implies a new road grid; also a number of additional roads are being built. Implementing a new road grid in an already developed area results in the relocation of a considerable number of people. The construction of the main drainage system should not add to these numbers. Therefore the My Khe drain will in principle follow the new road grid of the current master plan for the area. At the north end of the drain - between Nguyen Cong Tru Street and the My Khe Beach Hotel outfall, the planned road goes through a built-up area. An alternative route for the drain is suggested to minirnise the number of affected people. This route goes along an existing pathway and through the low lying swampy area, and lies approximately 80m to the west of the planned road. Since the resettlement process for the people affected by the new road alignment has not started yet the designed alignment for the drain in this section is along the path that requires the least resettlement and affects the least number of people. The middle section of the drain - between the My Khe Beach Hotel outfall and the Sao Paolo Monastery outfall - goes through a more or less empty area; no or very little resettlement for the new road grid is foreseen. The drain will follow the planned road along this section. At the south end of the drain - south of the Sao Paolo Monastery outfall - population densities are relatively high. 'The newly planned roads in the area between Ba Huyen Thanh Quan Strerst and Ho Xuan Huong Street are designed through this densely built-up area. Because of relocation issues, the World Bank could not agree with this alignment and therefore this section of the drain has been removed from the additional works program. The section south of Ba Huyen Thanh Quan Street to the Furama Resort outfall could still be built at a later stage under the direction of and funding by the City Cross section Table 3-5 shows the dimensions of the cross-sections for the My Khe drain. The box drain consists of 2 or 3 flow-channels each varying in width between 2 and 3 meter (total widths varying between 4m and 9m). The height of the drain is kept at 1.5 meter over the complete length because this will keep the invert of the outfall above the level of +0.60m; thus a tidal weir is not necessary. A higher invert level of the outfalls also improves the evacuation of stormwater run-off over the beach to the sea. The feasibility study calculated a drain height for the outfalls of 2m; the lower height of 1. 5m requires the drain to be around 20% wider than originally calculated. Section No. of Width [ml Heignr Channels channel Total [ml My Khe Beach Outfall St. Paolo Outfall Furama Outfall Nguyen Cuong Tru Street to I My Khe Beach Outfall My Khe Beach Outfall to St. Paolo Outfall St. Paolo Outfall to Furama Outfall Construction Management Consultants Page 52

51 Table 3-5 Cross sections of My Khe box drain For a detailed hydraulic calculation see Appendix A Connections to other drains At the north end the My Khe drain connects to the drain along Nguyen Cuong Tru Street and the drain coming from the north. At the south end it connects to the drain along Ba Huyen Thanh Quan Street. At a later stage the extended southward section will connect to the drain along Ho Xuan Huong Street. In between, all drains running west-east will be connected since it is the main drain for the entire area i.e. the drains in Le Huu Trac Street, Nguyen Duy Hieu Street, Nguyen Van Thoai Street and Phan Tu Street. All drains along the new coastal road to be constructed between Nguyen Cuong Tru Street and Ho Xuan Huong Street are to discharge towards one of the outfalls and not directly to sea Interception of wastewater flows from the drain The drain has only two outlets to the sea. At a later stage another outlet will be added south of the Furama Resort. There are no other outlets along this stretch of coastline. At these outlets the wastewater will be intercepted and pumped to the Ngu Hanh Son wastewater treatment plant (see paragraph 5.4) Special issues Resettlement issues have played an important part in the alignment and extend of the My Khe drain. At the north end of the drain an alignment has been chosen which minimises the number of project affected people. However, it should be noted that, if the alignment of the planned road remains unaltered and the drain is laid along the here proposed alignment more people will be affected than if the drain is laid along the same alignment as the proposed road. Both alignments should be in tune with each other and this should be co-ordinated by the relevant authorities notably the Danang People's Committee Geotechnical considerations Soil in Danang, with soils of (fine) sand, is generally good or very good for the construction of drains. The additional loads imposed by the new drains on the sub soils are generally very minimal as in almost all cases the drains replace outcoming soil with similar or higher weights. The My Khe drain will be partly constructed in a swamp and, although the soil conditions in the area are known to be good, geotechnical investigations were carried out in the swamp area. In total 4 SPT tests were made and 2 boreholes. The SPT give the best indications regarding bearing capacity of the soil and they show clearly the thickness of any poor soil layers. It was found that SPT values were generally high with less than 0.5 m of mud. At one location, the mud layer was a little higher, but sub-soils below the initial mud was found to be very good. Some mud will have to removed, however, and the Bill of Quantities allows for this. Construction Management Consultants Page 53

52 n 4 WASTEWATER COLLECTION - GENERAL 4.1 Introduction Existing situation At present all wastewater is discharged into the surface water untreated. Under the Danang Sanitation subproject funded by the IDA, wastewater of four districts: Hai Chau, Thanh Khe, Son Tra and Ngu Hanh Son will be collected and transferred to four WWTPs: Hoa Cuong, Phu Loc, Son Tra and Ngu Hanh Son. In the following paragraph a brief description of the ongoing works in each catchment area is given Construction of wastewater collection system under WB (IDA) project Hoa Cuong WWTPcatchment All wastewater of catchments II, III, IV and part of VII (see paragraph 2.1. I for a description of these catclunents) will be treated at Hoa Cuong WWTP. Wastewater is to be collected by GID and pumped by SPS12, SPS13, SPS14 and SPS15 on Bach Dang - 2/9 Street to the WWTP. In the future, wastewater of the entire catchment VII and catchment VIII will be treated in this WWTP. Hoa Cuong WWTP is constructed in Hoa Cuong area in the south-west of the city. The treatment consists of two anaerobic lagoons with floating covers to enhance the treatment process, and to collect gas in order to prevent the spread of bad smell. Phu Loc WWTP catchment Phu Loc WWTP will treat wastewater of catchments I, V and VI. A GID system and pumps SPS 18 in Dam Rong Lake I, SPS19 and SPS20 on Lien Chieu - Thuan Phuoc road, SPS31 in 29/3 Lake park and SPS21 in Phu Loc river will collect and transfer wastewater to the WWTP. In phase II, the WWTP will be upgraded to include the catchment XIII of Lien Chieu district. Phu Loc WWTP is constructed in Hoa Minh ward, Lien Chieu district. The treatment consists of two anaerobic lagoons as well, also with floating covers. Son Tra WWTP catchment Wastewater in catchment IX and X of Son Tra district will be treated in Son Tra WWTP. GIDs are constructed along East Bach Dang Street and along the coast in Man Thai and Phuoc My wards. A system of pumps and rising mains (SPS1, SPS2, SPS8, and SPS9) conveys the wastewater to the treatment plant. The WWTP is constructed in Tho Quang ward, Son Tra district. Wastewater is treated in two anaerobic lagoons. Floating covers are provided in the framework of the additional works program. Ngu Hanh Son WWTP catchment Ngu Hanh Son WWTP will treat wastewater from catchments XI and XII of Ngu Hanh Son district. Wastewater will be collected along the Han River and along the beach from My Khe to the Furama resort, and transferred to Ngu Hanh Son treatment plant by pumps and rising mains. The WWTP will be constructed in Hoa Hai commune, Ngu Hanh Son district. Wastewater is treated by two anaerobic lagoons. Here as well, floating covers are provided in the framework of the additional works program. Construction Management Consultants Page 54 DHV, CDM and VlWASE

53 Figure 4-0 Wastewater Catchment Areas of Danang Construction Management Consultants Page 55

54 4.1.3 Wastewater systems in additional works programme After the completion of the ongoing Phase I project, most of the crowded residential areas will have at their disposal a wastewater collection system. As is mentioned in the feasibility study, however, due to rapid city development in the years since the inception of the Phase 1 project, expansion of the systems described above is necessary to protect the Han River and My Khe Beach areas for further environmental degradation. Because of the development as an entertainment and recreational area of 2/9 street and the urbanisation of the area around Pham Van Dong Street and south of Tran Ly Bridge, extensions of the wastewater collection system have been identified for Hoa Cuong, Son Tra and Ngu Hanh Son catchment areas. In addition to the works identified in the feasibility study, a number of works from the ongoing Phase 1 project have been redesigned and included in this report. Partly due to budget constraint in the ongoing contract 013 and partly due to design issues and opportunities to save costs, a number of works have been exchanged between ongoing contract 013 and the additional works contract 020 (also see Chapter 6). Hoa Cuong WWTP catchment The feasibility study has identified a gravity interceptor drain along the south end of 2/9 Street (between Duy Tan Street and Tuyen Son Bridge), including a pumping station and a rising main to the Hoa Cuong treatment plant. Although the concept of GID and SPS remained, the detailed design presented in this report deviates from the design presented in the feasibility study. Integrating the wastewater collection system for this area with the ongoing Phase 1 project proved to produce both a technica.ly and a financially much more attractive solution. All additional works along 2/9 Street have been included in the ongoing contract 013. Son Tra WWTP catchment The feasibility study has identified a gravity interceptor drain along the middle coastal stretch of Phuoc My ward (between Nguyen Cong Tru Street and Man Thai ward), including a pumping station and a rising main to the Son Tra treatment plant. In addition to the wastewater collection systems identified in the feasibility study for the Son Tra WWTP catchment area, this report also discusses the wastewater collection system along Man Thai fishing village included in the ongoing Phase 1 works. The situation along this fishing village has changed since the time of the original design. At the moment a coastal road is being constructed along the eastern seaboard. Construction has started several kilometres north of the village. Within a year the road is expected to pass the village. This creates better possibilities for a GID system - which was originally rejected - since a wide area is being cleared along the beach for this road. The wastewater collection system has been redesigned and integrated with the wastewater collection system of the additional works area between Nguyen Cong Tru Street and Man Thai ward. Construction Management Consultants Page 56 DHV, CDM ond VIWASE

55 DA NANG SUBPROJECT - PHASE 1: ADDIONAL WORKS - WASTEWATER WORKS TIeU DVAN DA NANG - GLA ON 1: CAC CNG vi$c THoAT NUOCT J 8 isung AHICHO f h J51 S T- =~ Y LEG END -'<-- CeNoTHUsOwn,rCz GHI~ ~ ~ ~ ~ ~~~- 7HO o = irw~~~~down W' OiA Figure 4-1 Main wastewater works for Construction Management Consultants Page 57

56 The wastewater collection system along Man Thai fishing village remains part of ongoing contract 013 while the wastewater collection system between Nguyen Cong Tru Street and Man Thai ward is part of the additional works contract 020. Ngu Hanh Son WWTP catchment The feasibility study has identified a gravity interceptor drain along the Han River embankment of northwest Bac My An ward (between Tran Thi Ly bridge and Tuyen Son bridge), including a pumping station and a rising main to the Ngu Hanh Son treatment plant. In addition to the wastewater collection systems identified in the feasibility study for the Ngu Hanh Son WWTP catchment area this report also covers the interception of wastewater along the southern coastal stretch of Phuoc My ward and the northern coastal stretch of Bac My An ward (from Nguyen Cong Tru Street to the Furama Resort). This latter system was originally part of the ongoing Phase 1 works and consisted of a number of GIDs along the coast. However, due to the inclusion of the large main drain of the area in the additional works program (see paragraph 3.5) the possibility arose to develop a technically and a financially more attractive alternative. The wastewater collection system between Nguyen Cong Tru Street to the Furama Resort is removed from the ongoing contract 013 and will be part of the additional works contract 020, as is the wastewater collection system between Tran Thi Ly bridge and Tuyen Son bridge 4.2 Design criteria As for the (combined) stormwater drains, GHD -Kinhill developed a number of design criteria during the engineering study for the ongoing Phase, I project, for the wastewater collection system. The Ministry of Construction and the World Bank approved the designed system based on these design criteria. Since the additional works program is a supplement to the ongoing Phase 1 works, also here in principle the same design criteria have been applied Basic concept of GIDs, Pumping stations and Rising Mains The first step in introducing a wastewater collection system to an already developed area is to intercept the dry weather flow (dwf) before it has a chance to enter the surface water. During the engineering study for the ongoing Phase I project, GHD-Kinhill designed a wastewater collection system consisting of gravity interceptor drains (GID), sewage pumping stations (SPS) and rising mains (RM). Although this system intercepts most of the wastewater, it still allows overflows of a mixture of wastewater and stormwater run-off during precipitation; it is, however the least-cost solution with the highest initial impact. The Ministry of Construction and the World Bank approved the designed system. The design foresees in a basic first stage system, with wastewater pipelines (GIDs and RMs) in principle only along the Bay of Danang, the Han River and China Beach (My Khe Beach). Wastewater (and stormwater) flows in the direction of the nearest surface waters through existing and/or new drains. Just upstream of the outfalls to the. surface water, special diversion structures are built that intercept a minimal flow from these drains and transport them through a combination of small and relatively steep graded GIDs, submersible type SPSs and RMs to the wastewater treatment plants. Construction Management Consultants Page 58

57 Danang Sub-project (Phase I) In principle this wastewater collection system is designed such that during dry periods, the complete flow in the drains, supposed to be wastewater, will be intercepted and diverted to the wastewater treatment plants. The wastewater collection system cannot handle very large flows, so during storms, the excess flows in the drains will discharge into the surface waters Design peak factor It is common practice to design wastewater collection systems by taking into account estimated average wastewater flows and then applying a certain peak factor. The peak factor allows for the system to cope with variations in the flow during the day, as most of the daily wastewater flows are produced during peak hours, usually around and h each day. By applying the peak factor, the wastewater collection system will be able to cope with peak flows during "rush hours", as well as of the unavoidable errors in the estimation of wastewater flows. However, applying a large peak factor means also that during "off peak" periods the system has a large unused capacity. GHD-Kinhill, in its designs, has used a peak factor of 1.2, much lower than the usual typical design factor of 2.5 to 5. The lower peak factor was selected based on measured average and peak dry weather flows in 13 existing major drains in Danang. It arises from a combination of the flow buffering in septic tanks and the extremely flat low-lying topography and hence flat graded drains in Danang. In addition, it was assumed that any higher than expected peaks could be buffered in the large storage created by the tidal weirs. The direct result of the lowered peak factor is a fuller utilization of the unused "off-peak" capacity in the system. Pipelines and pump stations are now 83% (100/1.2) utilised compared to 20% to 40% in conventionally designed systems. That is, with the selected system, more than double the population can be served by this system, compared to a conventionally designed system of the same cost. This approach created a wastewater system that allowed the service area to include most of all four wastewater catchments in the project with relative limited funding Implications of the adopted design criteria As it is not desirable to alter the design criteria at this stage, especially where they were approved by all and have led to an affordable cost effective system, CMC, in adjusting the design calculations of the ongoing works to the new field conditions, have also applied the design criteria (and notably the very small peak factor) listed above. Since the additional works program is a supplement to the ongoing Phase 1 works, also here the same design criteria have been applied. However, the implications of these design criteria should be well understood by all parties, to avoid disappointment with the system once it is completed (with chances that actual conditions vary adversely from design assumptions). Some implications are: 1. The wastewater collection system is designed using the year 2010 as a design horizon. That is very short for a system that will not be completed until about the year Using the low peak factor could imply that, at outfalls connected to drains with less buffer capacity, there is a higher risk that wastewater is discharged during peak hours, say during a number of hours per day. 3. Similarly at outfalls in drains serving areas with rapid population growth there is a higher risk that a permanent overflow of wastewater from the diversion structures will occur Construction Management Consultants Page 59 DHV, CDM and VTWASE

58 prematurely, as the system can only cope with an average excess flow of 20% above the estimated flows. 4. As precise estimation of wastewater flows (and groundwater flows infiltrating into the drains), is difficult, it is possible that average flows could be either smaller or larger than estimated. If they are significantly larger there is risk of premature overflow occurrences at some outfalls. If premature overflow occurs for whatever reason and it is deemed unacceptable, additional wastewater collection capacity will have to be installed, and this could be relatively soon after completion of the project. The overflow from a relatively new system may cause disappointment, but is a direct result of budget limitations and the chosen strategy. If it occurs, it should not be forgotten that the system was very cost effective and that early stage development of the system was implied. 5. If average flows are estimated precisely (which is impossible), the pumping stations, designed with peak factor 1.2, would have to pump out wastewater on average during 100/1.2 = 83% of the time. If wastewater flows are higher than estimated, the SPS will soon operate 100% of the time. Although this is efficient, it decreases the technical lifetime of the pump due to increased wear and tear. It should be noted that, because of standby pumps, actual pump running hours would be less. For example, an SPS with I pump will be equipped with one standby pump and a, say 100% SPS running time, would be equally shared by the two pumps, so pump running hours would not exceed 50% (12 hours per day). On the other hand, the pumps of an SPS with 3 duty pumps and I standby would be running 75% of the time (i.e. 18 hours) Domestic wastewater flows Domestic wastewater flows are calculated based on a combination of per capita consumption for either population connected to the existing water supply or those not connected to the water supply, a percentage of the water supply being discharged as wastewater and a peak factor (see Table 4-1). Year I/cap.d W/S: w w-factor: I/cap.d non W/S: w w-factor: peak factor Table 4-1 Domestic wastewater criteria The wastewater factor accounts for the fact that not all water supplied ends up as wastewater. The peak factor accounts for the fact that wastewater is not produced evenly over the day; this is fuirther discussed in paragraph Non-domestic flows The non-domestic wastewater flows are taken as a percentage of the domestic wastewater flow. Distinction is made between wastewater from industries and wastewater from services such as hotels and restaurants. These percentages have been assessed for each sub-catchment area. Table 4-2 shows the weighted average for all catchment areas. Construction Management Consultants Page 60

59 Year Industry as % of domestic 28% 33% 33% Service as % of domestic 14% 19% 19% Total 42% 52% 52% Table 4-2 Non-domestic wastewater criteria Interception of wastewater from drains As mentioned in paragraph drains in Danang carry both wastewater and stormwater. At each point where a GID crosses a drain, a wastewater interceptor is constructed which diverts the wastewater from the drain to the GID. The aim of the flow diversion structures is to: * Collect all the DWF from major stormwater channels, culverts and drains * Exclude trash and floatables without blockage * Pass grit and sediment without blockage * Avoid overflows from GIDs The exclusion of trash and floatables will minimise blockage risks to both pumping stations and pipelines. In addition it will minimise occupational health and safety risks. All trash clearing and any necessary blockage clearing can be carried out in relatively open and shallow pits. The need for access to enclosed spaces, particularly deep enclosed spaces will be subsequently reduced and only be required for relatively infrequent maintenance purposes. Grit accumulation in the system, especially during storm events, will be unavoidable and the structures have been designed to continuously transfer grit to a centralised collection point at the wastewater treatment plant; this is deemed as the most effective handling means. However, if large grit quantities prove troublesome in operation, intermediate grit traps can be constructed later as necessary. These traps can be located in the stormwater drains immediately upstream of the intake diversion structure and/or at rising main discharge point s and will reduce (but not completely eliminate) the problem, albeit at additional operational costs. The diversion structures comprise a grated collection pit and a special arrangement at either a manhole or pumping station in the GID system. * The diversion structures are positioned in the floor of the major stormwater channels or drains. Interception of DWF at any other points, say from pits in side drains, will have a low capture efficiency and present major operational blockage risks * The grates are recessed 200mm below the drain invert level to ensure maximum capture efficiency, and provide operating buffer storage for pump operation and trash collection. * Where existing stormwater drain invert levels are below +0.6m at the diversion point weirs are provided to a level of +0.6m. This "tidal barrier" prevents back flow from river or sea in all but high tide and flood situations. The weir length is set so that the maximum depth of water over the weir is 0.5m; this to minimise the impact on the normal hydraulic performance of the drain at maximum design flow. * Hinged grated cover, with grates to a "toothed comb" design, are provide for ease of maintenance. This is a standardised 20Us modular size and can be economically fabricated in Vietnam. Construction Management Consultants Page 61

60 * The grating has a spacing of 40mm. This is to minimise blockage risks to all pipeworks and pumps. * Grating is permanently submerged and has very low flow through velocity to ensure trash and floatables remain floating above the grate. This reduces tendencies for debris to accumulate on the grate, be partially sucked through it or wrap around it. In this way blockage risks are minimised and the easily rakeable floating debris will allow quicker cleaning with reduced difficulty. * In the base of the collection pit a carefully shaped concrete shaped bench throat to the outlet pipe is applied to limit large objects getting into the outlet pipe and the pumping station. * A maximum 5 metre long outlet pipe between the diversion and the pumping station without bends or fittings is applied and sized to achieve high scouring velocities on pump operation so that pipe blockage risks are very small. The integration of the DWF diversion structure with the stormwater drain trash removal structure requires daily manual cleaning of accumulated trash. The trash removal should be an extension of the existing solid waste, street sweeping and garbage collection service Pipe sizes and slopes The Vietnamese MOC minimum pipe diameter for a storm water system is 300mmn. However, for the GID system a minimum diameter of 200mm is adopted. Unlike stormwater drains or combined drain systems, the GIDs will be totally enclosed with entry only via house connections that have a maximum diameter of 100mm or via diversion structures that have 40mm gratings to prevent larger objects from entering. While blockage risks from large objects decreases with larger diameters, for given flows the blockage risks from siltation increases with oversized pipes. For new dry weather flow diversion works and GIDs, siltation problems must be avoided by ensuring self cleansing velocities and grades. This is essential because: * Environmental, aesthetic and public health consequences of GID blockage are generally more severe than stormwater drain blockages, * Difficulty and cost of unblocking GEDs is much higher than for stormwater drains; * Occupational health and safety risks to maintenance personnel are increased with increased risk of blockages. To preserve the condition and capacity of the pipelines wherever practicable, minimum grades at or steeper than the self cleansing grade should be adopted. The grades must be sufficient to prevent sediment build-up and, if possible, also prevent slime growth on pipe walls. Self cleansing flow conditions must be attained at least daily during dry weather at all points within the wastewater collection system. Additional flushing capacity is not available in wet weather conditions as GIDs are not meant to carry stormwater. Pipe diameter selection in the wastewater system for self cleansing must be achieved under dry weather flow conditions only. The criteria for minimum grades have a direct impact on the excavation depth of the pipeline and thus the cost of construction. The system is designed for the year 2010; flows in the initial years Construction Management Consultants Page 62

61 after construction will be much lower than the design flows. Requiring self cleansing grades at these low flows will result in extremely steep grades. No grading advantage to reduce pipeline depths is possible by selecting larger diameters. A practical compromise is a grade where the minimum shear stress required for self cleansing is achieved assuming full pipe flow. The standard Vietnamese MOC formula for self cleansing grade of 1 in D (pipe diameter in millimetre) reasonably achieves this sheer stress. Table 4-3 shows the pipe size used in the detailed design and the minimum grade at which they are to be laid. Pipe Size Minimum Grade [mm] [I n..i 1 _ Table 4-3 Pipe sizes and minimum grades Pipe types, bedding There is a range of pipe materials available for GlDs. Suitable materials include reinforced concrete, ductile iron, vitrified clay, and a range of plastic materials such as upvc, HDPE and ABS. Neither reinforced concrete nor vitrified clay GID pipelines are recommended because there is unlikely to significant cost advantage; and adequate "in-ground" construction quality can not be guaranteed (in particular the water tightness of the in-ground pipelines) in Vietnamese conditions. Ductile iron is not recommended because of the likely higher costs and increased susceptibility to corrosion. Plastic materials are the preferred materials because of lower costs, resistance to corrosion, product quality control and smooth bores (which are a major advantage in reducing grades and blockage risks). Of the available plastic materials upvc could be used for GIDs up to a diameter of 315mm. For GIDs with a diameter of mm the material of choice is HDPE since upvc is generally not available in large diameter. As more recently, the price differences between HDPE and PVC have become much smaller, HDPE is the preferred material for all pipe sizes, in the Additional works. Reasons are its flexibility, better UV-resistance, better capability to withstand mishandling and less problems with joints (once they are made). The maximum diameter applied in this project 800mm. This pipe is made of a special ribbed HDPE. HPDE is also the material of choice for rising mains of all diameters on the grounds of continuity (avoiding the need for thrust blocks), ability to flex around curves (reducing the need and cost of fittings) and lower friction losses. It is essential that when the pipe is laid in the ground that it is properly "cradled" or "bedded" in uniform compacted granular material (usually coarse sand) and carefully backfilled and Construction Management Consultants Page 63

62 compacted. This is to ensure the integrity of the pipe shape and structure is maintained for the operational life time of the pipeline Maximum depth With the flat terrain of Danang and the location of the GIDs parallel to the shore or river embankment, the interceptor drains have the potential to become very deep very quickly. This necessity for deep construction is an unavoidable characteristic of wastewater pipe systems in flat areas and is a distinguishing feature from other pipeline and cable utility systems which are invariably constructed as shallow as possible. With depth the cost of the pipeline increases greatly. For example there is typically 'about a threefold increase in unit pipeline costs from a pipeline at minimum depth to one about 5 meters depth. In addition, construction difficulties increase exponentially with depth, particularly when the excavation depth is in soft ground and below the permanent water table. This situation is common in Danang. The typical characteristics of deep excavation are: * Requirement of continuous trench support including the need for piling; * Requirement for continuous pumping; * Collapsed ground behind trench supports; * Risks to existing services (e.g. exposed water main); * Unstable ground conditions at the base of excavation; * Extent of excavation, spoil heaps and construction area requirements. The unavoidable consequences during construction of deep pipelines are major social disruption, dislocation and consequential community costs. The advantage of having pipelines go to a greater depth is that fewer pumps are required. However the cost advantage of having fewer pumps does not countervail against the extra cost associated with the deeper excavation depth; for example, with a maximum depth of about 7 to 8 meters it is possible to halve the number of pumping stations but the overall capital costs are doubled. Also, hardly any power cost economics are to be gained since the same volume of wastewater is pumped the same net distance against the same net lift. The maximum excavation depth for GIDs is consequently set at 5m GIED manholes In order to be able to carry out maintenance on the drain, inlets are provided at regular intervals of 0oom for a person and/or equipment to enter the drain. These manholes comprise a pit of minimum 1,000mm diameter for person access, provide for inspection and emergency cleaning and blockage clearing. Another major function of manholes is to provide house connection points of entry since no connections should be made directly to the GID; this to reduce the risk of damage to the GID. Covers are to be sealed to prevent entry of stormwater and egress of odours. Covers are also fitted with a locking device to prevent unauthorised entry. Construction Management Consultants Page 64

63 GID manholes are carefully benched and channelled at the base, at dropper pipes and base bends on incoming connections, and at branch drains. This is to minimise turbulence in the flows and build-up of sediment in "dead zones"; it will also minimise odour generation and asset deterioration from evolved gasses. No climbing steps will be provided. Entry is strictly limited to specialised personnel only, that will use special equipment to enter any manholes, if it cannot be avoided GIID connection points Since the GIDs are deep and mostly at or below the permanent ground water table, the retrofitting of property connection points will be very costly and lead to risk of damage and permanent groundwater leaks into the pipeline. In a wastewater collection system it is essential that the water tightness of the pipeline system is maintained at all times. This to avoid prejudicing system capacity and reduces the running cost of unnecessary pumping and treatment. Accordingly, all property connection points are constructed as an integral part of the initial pipeline construction. All new or redeveloped properties should be required to connect to only these connection points. Connection points are located at a maximum of loom intervals. With an interval of GID manholes of loom and an interval of GID connection points of loom the maximum distance from properties to a point of connection to the GID is 25m Vent poles Vent poles from GID manholes are positioned at the head of every GID and from manholes that receive rising main discharge. These vent poles allow air movement to and from the pipeline when the system "swamps" during storms, empties after storm flow and when pumps start and stop. This avoids either discharge of air through water seals to private properties creating major health, odour and noise problems or blowing of street manhole covers creating public safety and operational problems. During dry weather it will also allow venting of the GID system. This will reduce occupation health and safety risks, reduce overall system odour risks and minimise premature asset deterioration from hydrogen sulphide attack of concrete and fixtures Pumping station designs, control features Pumping station designs are based on the adoption of submersible sewage pumps. These pumps have been developed in the last 40 years, and are proven and universally adopted worldwide for wastewater pumping. Submersible pumps suit a wide variety of operating conditions. In most sewerage systems, pump, motor and impeller sizes are individually tailored for each pumping station in the system. Construction Management Consultants Page 65

64 Danang Sub-project (Phase l) Given that these types of pumps have not been previously universally adopted in Vietnam and considering the standards of available maintenance, in principle a two 2 level standardised pump selection has been adopted. This reduces capital and maintenance costs as well as spare part inventories and allows maintenance skill requirements to focus on a restricted range of equipment. It should also minimise the risks of mal-operation resulting from replacement with incorrect spares or complete units. Pump capacities are dependent on operating head. The "large" pumps have a nominal design capacity in the range of 100 to 200 I/s each and the "medium" pumps have a nominal capacity in the range of 20 to 40 I/s each at a head ranging between 10 and 15 meter. Depending on the required flow and the resulting head up to a maximum of three duty pumps are required. Each pump station is equipped with a pedestal mounted switchboard which is located adjacent to a nearby fence or building wall and which is elevated above flood level if necessary. All other structures are entirely underground. Pumping stations are located within the public land without requiring large site acquisition. The visual, social and environmental impact of operating pumping stations are kept to a minimum. Pumps are equipped with 3 phase power at permanent station sites. The duty pumps are to start progressively to limit start power requirements. Hour run meters are provide at each station, but no flow meters. The submersible pumps are easily demountable on specially designed guide rails. No specialised mechanical equipment or expertise is required for pump removal. Pump maintenance and repair is therefore economically and safely carried out in a specialised central workshop. Pumping stations are totally sealed and ventilated using a small constantly running fan located in the switchboard. This fan is of a standard design readily available in Danang. The fan slightly pressurises the interior of the pumping station to dispel air via the incoming GIDs to vent poles at the head of each GID. This avoids dangerous build-up of hydrogen sulphide gas within the system and minimises condensation and corrosion conditions; the contra flow air movement within the GIDs increases oxygen transfer to the wastewater thereby reducing odour risks. Each pumping station has several control arrangements: * Primary pump control * Secondary overriding pump control * Tertiary overriding pump control * PC based operator interface system Primary pump control - Normal dry weather operation The primary set of pump level controls is located in the pumping station wet well and control operations under normal dry weather conditions. Primary pump start level control: * Pump GID Centreline * Pump GIl) Centreline +100mm 2 under contracto 13 a three level standardised pump selection was adopted; however, in the additional works program there is no need for the smallest size (temporary) pumps Construction Management Consultants Page 66

65 * Pump GID Centreline +200mm In case of multiple GIDs entering the wet well, the centreline of the lowest incoming GID is taken; this should also be the GID with the largest diameter. Primary pump stop level control: * Pump Minimum pump submergence +200mm * Pump Minimum pump submergence +100mm * Pump Minimum pump submergence The GID centreline to minimum pump submergence is set to give a maximum of 10 starts per hour. Controls are set to automatically cycle pump starts to give even wear on all pumps and to avoid sediment build-up if a standby pump is left idle for any length of time. Secondary overriding pump control - Wet weather and tidal swamping operation During wet weather and spring tides, the GID system and the pumping station will all be "swamped". It is also expected that, during wet weather, flows in stormwater drains will be so diluted that there will be no net benefit in pumping to the treatment plant for significant part of times. Therefore during stormwater overflow conditions, pumps can be shut down. This will also reduce power costs. To shut down pumps, a secondary "wet weather" pump start level control is located in an adjacent stormwater diversion structure upstream of the tidal barrier. This secondary pump start level control is set at the tidal barrier level of (0.6m) +100mm (in operations this level can be varied to suit likely flow conditions) and overrides the primary pump start level controls to shut all pumps down. All pumps will be automatically shut down during significant wet weather flows as well as during major tidal inflows. This will save power and minimise saltwater contamination of the treatment process. Timers will first progressively restart all pumps after a pre-set period, and then stop them progressively after a pre-set period. Variable timer settings will be possible between 15 rninutes and 24 hours but initial settings of 1/2 hour run and 2 hours stops are set as initial settings. This frequent restarting with all duty pumps running simultaneously is essential during wet weather storms to: * Minimise accumulation in diversion structures and prevent accumulation of grit in pump wells. Excessive grit accumulation can block or damage pumps, can block diversion structures and GIDs, and overload grit removal capabilities at the WWTPs. * Keep grit and sludge moving as much as possible and avoid solidification or calcification which often occurs to sludge held immobile even for relatively short periods and which can partially or wholly block rising mains and GIDs. * Retain sewage from direct connections within the GID/pumping station system, pass it to the treatment plant and minimise overflow of raw sewage to the environment. * Maintain bacterial processes at the treatment plant by maintaining some load - albeit low pollution loads due to the dilution of wastewater flows with storm flows. * Maintain flows at the WWTP outfalls to limit outfall blockage risks by sand movement along the river bed during floods. * Maximise removal of pollutants - particularly from the more highly polluted first flush flows - which would otherwise go to the environment. Construction Management Consultants Page 67

66 For the above reasons it is essential that the pump systems are not shut down during rainy periods or during the wet season. When the storm flows subside, the secondary control level is no longer activated (i.e. the water level in the drain upstream of the tidal barrier has fallen below 0.6m +O.Om). The controls revert to normal (primary pump control) operation and the duty pumps will run until pump stop control levels are reached in the wet well. Tertiary overriding pump control - Wet weather and tidal svamping operation During wet weather or by tidal inflow it is possible under some conditions that overflow at the rising main discharge point occurs. This can happen where a rising main discharges into an adjacent catchment GID which is swamped. Similar conditions might result if an extended power outage occurs at a downstream pumping station or the downstream pumping station has completely failed for some other reason. Therefore at each discharge manhole a tertiary overriding pump level control is provided which will shut down the pumps in all upstream pumping stations in case the receiving GID is swamped; the discharge manhole is also provide with an overflow. The upstream pumping station will change to the same variable timer starting and stopping regime as is required under the Secondary pump level control system until all the downstream pumping stations are operating in the Primary pump level control mode. Restarting of the upstream pumping station pumps in Primary pump level control mode shall be programmed to progressively occur from the downstream catchment pumping stations lowest to the upstream pumping station in the system. PC based operator interface system As well as normal override controls, at each pumping station a PC based operator interface system is to be provided. This system - through a remote telemetry connection between each pumping station and a central PC based operator - allows full remote monitoring, control and recording of the system operation, such as: * Each pump's operational status, e Each pump's current draw; Pumping station operational mode; * Pumping station alarm status based on level detectors; Pumping rate based on wet well volume and level detectors. The PC based operator interface system for the additional works is to be integrated into the control system for the ongoing Phase I works. The already implemented PC based operator interface system is to be reprogrammed to accommodate the controls for the additional works program. The location of the base station(s) is still under discussion. The recommended location of the base station for this control system is one at each of the treatment plants. In this way the operator can control the rising main/pumping system that discharged to the WWTP under its own control. The result of any control action taken by the operator can immediately be observed at the treatment plant. This is not possible in case the control system is located in a central office building in Danang. Construction Management Consultants Page 68

67 These control arrangements, combined with the diversion structures and overflow arrangements, ensure that first pumping priority is given to sewage from direct connections, second pumping priority is given to dry weather flows and third pumping priority is given to wet weather stormwater flows Rising mains Rising mains from pumping stations are similar in design and operation to water mains. However, they can present major operational and maintenance problems specifically relating to the pumping of wastewater. The design must take into carefiul consideration: * Minimnising the length of the rising main to reduce detention times and potential for odour generation. Unlike gravity drains there is no air/water interface within pressure mains and therefore no opportunity for oxygen transfer to keep the wastewater turning anaerobic and generating sulphide. Minimising the length also reduces friction head and therefore pump size and operating costs. * Minirnising the diameter again to minimise detention times, but also to improve the self cleansing ability and the slime shearing ability of the pipe. Wall slimes are a major source of dangerous and odour producing gases and should therefore be minimised. A smaller diameter, however, does increase frictional head and thus pump size and operating costs. * Pumping to adjacent GIDs in adjacent catchments resulting in higher capacity flows in those GIDs. This allows larger diameter drains with flatter self cleansing grades to be installed. This reduces the number of pumping stations required and allows more aeration of flows to occur reducing potential for odour generation. * Avoiding odour gcneration by making arrangements to avoid drops and to minimise turbulence by controlled grades. High Density Polyethylene (HDPE) is adopted as pipe material because of its operational advantages including reduced power consumption, breakage risks and odour generation potential. This is achieved through the materials: * High corrosion and abrasion resistance. * Smooth bore and low joints requirement reducing the blockage risks and slime build-up, and increasing velocities (i.e. higher self cleansing ability). * Continuity of pipeline eliminating the need for thrust blocks. * Flexibility i.e. ability to lay around curves and to withstand deformation without loosing operating integrity. * Ability to colour the pipe material for easy identification purposes thus reducing risks of mistaken tapping of the main as a water main. Construction Management Consultants Page 69

68 Additional Works Prograrn 5 WASTEWATER COLLECTION - DETAILED DESIGNS 5.1 Introduction The following section discusses for each wastewater catchment area in the additional works program the final designs for the wastewater collection systems. Since most works either have an impact on or are impacted by the ongoing Phase 1 works, necessitating a change from the feasibility study, the existing designs and their integration with the additional works are discussed first. Subsequently the design flows, chosen diameters and alignment of pipes are discussed. 5.2 Hoa Cuong catchment Existing design All wastewater of catchment II, III, IV and VII along the shore of the Han River will be treated at Hoa Cuong WWTP. The WWTP is located in the southwest of Hoa Cuong ward. In the original design, wastewater from catchments II and III is collected by GID and pumped by SPS12, SPS13 and SPS14 on Bach Dang - 2/9 Street to the WWTP. Wastewater from the two main drains of catchment IV is intercepted at SPS 14 and directly pumped to the WWTP. The southern stretch of 2/9 Street - from Duy Tan Street to T-crossing with Nui Thanh Street is not included Description of additional area and integration with existing design/options An entertainment centre is being developed on the east side of 2/9 road comprising the Danang water park - which is in operation - and a sport centre and park area - which are being finalized. In addition, a considerable volume of wastewater generated along Nui Thanh and 2/9 Streets is being discharged directly to this area causing serious pollution. In the additional works programme it is therefore proposed to construct GIDs along the south end of 2/9 Street and pump the collected wastewater to the Hoa Cuong treatment plant. As mentioned above, in the original Phase I plans wastewater construction works (GIDs) in 2/9 street end approximately at the Duy Tan Street. From there, wastewater is to be pumped by a long rising main to the Hoa Cuong WWTP. In the designs only one rising main (630 mm) is foreseen. However, due to the length of the rising main, the static head and the amount of waste water to be pumped, two rising mains (630 mm) as well as two large pumping stations would be required. The feasibility study for the additional works program proposed a small GID (#15) to be constructed along the south-end of 2/9 street; and a new SPS (#15) to pump the wastewater through a rising main (RM15) to Hoa Cuong WWTP (see Figure 5-1). For 2/9 Street it is more efficient and cost effective to continue the GID being constructed north of Duy Tan Street in southward direction, all the way to Tuyen Son Bridge as part of the ongoing Phase I works. Construction Management Consultants Page 70

69 In that case, the GID coming from the north of Duy Duy Tan Street 4 TranThi Ly Tan Street/Tran Thi Ly bridge is continued for another GI Bridge 550m to the south of Duy Tan Street/Tran Thi Ly r SP14 - bridge; from here the wastewater is pumped (SPS 14) to _ - a large diameter GIlD further (600m) down the road. - =.q ="_ 2j This GID is continued until the end of 2/9 Street from i JIJRNl 4 I where a large pumping station (SPS 15) pumps the G wastewater to the Hoa Cuong treatment plant (see LJ= Figure 5-2). Figure 5-2)~~~~~~~~~~~~~~~~~~~ _n ID14A The positive impact of this option is that RM14 is much shorter (600 m instead of 2,433 m), reducing both Z. SPS15 investment and operational cost. Also, instead of needing two large-diameter rising mains, only one RMI (630 mm) is needed. In addition, the construction in the X A area would be limited to one time period and one W location, reducing both cost and nuisance. The negative impact is that part of GID15 needs to be / much bigger (800mm instead of 200mm) to accommodate the wastewater flow from SPS14; also <', the capacity of SPS15 and RM15 need to be much \ GID5 : >" -. Figure 5-1 Feasibility Option bigger. Both former and latter would increase the investment cost, the latter would also increase the operational cost for SPS1 5. D as TranThiLy.s Duy Tan Street l TahiL However the cost increase of enlarging B GID15/SPS15/RM15 would be offset by the reduction. GID14 :>"_ in cost for SPS14/RM14. JL SPS14. The total investment cost for the 2/9 road area would be:\ reduced by almost 5 0% (see Appendix C. 1). L_J}w}l.-D... Also total operational cost would be less since the uw 14 GID14A wastewater from SPS 14 will flow partly under gravity instead of being pumped all the way to Hoa Cuong WWTP. }!f In consultation with URENCO and the World Bank it was decided to integrate the wastewater collection \ ' 1 system of 2/9 Street south of Duy Tan Street of the i cjl ^o Jl additional works program into the design for the WWrP r -V -c-l wastewater collection system north of Duy Tan Street of the ongoing Phase 1 works and thus achieve RM15 Bndge-i additional cost savings. S Design flows A "' ; The dimensions of the GIDs is based on the size of the flow it intercepts from drains it crosses (usually at outfalls or road crossings) plus the size of the flow it " u Figure 5-2 Detailed design Option Construction Management Consultants Page 71 e on

70 receives from upstream GIDs and/or pumping stations. The system along the south end of 2/9 street is divided into a continuation of GID 14 from north of Duy Tan Street for about 450m until the 29/3 Square and GID 15 from the 29/3 Square until the T- crossing with Nui Thanh Street (I 530m). At each outfall along the road the GID will intercept the wastewater coming fom the main- and side streets. At this point in the calculation a node is set. The continuation of GID14 has 5 nodes just as GID15. Table 5-1 shows for each section the length from one node to another, the catchment area that drains to the section from side streets, the upstream (peak) inflow, the total peak flow upon which the size of the drain is based and finally the diameter of that section of GID (or rising main). Node I Node 2 LarNth Catch Area Lateral Upstream Design Diameter mentinftw tinflow f low [ml [ha] [I/SI [I/Si [I/si Innm ] 14/1 14/9 453 IV /9 14/ IV /15 SPS VIla A/1 14A/6 238 VIIa A/2 SPS14 68 VIIa SPS14 15/ * 15/1 15/2 45 VIIa /2 15/8 339 Vlla /8 15/ VIla /14 SPS VIIa A/I SPS VIIa ** SPS15 WWTP * Table 5-1 Design nows 2/9 Street (* Rising main; ** Future extension) A large pumping station (SPS 14) with 3 duty pumps (1 standby) transfers the wastewater through a 502m long rising main (630mm) to the starting point of GID15 at the south end of 29/3 Square. The combination of pump characteristics and rising main characteristics results in a maximum pump capacity of 545 I/s. Another large pumping station (SPS15) with 3 duty pumps (1 standby) transfers the wastewater through a 710m long rising main (630mm) to the Hoa Cuong treatment plant. The combination of pump characteristics and rising main characteristics results in a maximum pump capacity of 582 I/s Alignment, SPS locations and longitudinal profile The alignment of the GID is on the eastern side of 2/9 Street. However, a 900mm water main already runs under that side of the pavement right next to the carriageway. The trench for the GID should be far enough away from this water main so as not to disturb its bedding. Next to the pavement, which is 5m wide, runs a patch of grass 6m wide. The alignment of the GD is therefore right on the border between the pavement and the patch of grass. Construction Management Consultants Page 72 DHV, CDM and VIWASF

71 The alignment of the rising main from SPS 14 to the start of GID 15 is along the eastern side of the 2/9 Street, in the pavement. The rising main from SPS15 to the Hoa Cuong runs straight west along the pavement to the south side of the new road coming from the Tuyen Son Bridge Special issues The alignment of the rising main from SPS15 to Hoa Cuong treatment plant is along a newly planned road running east-west from 2/9 Street. Presently this road has not been built yet. At the moment of construction of the rising main, there is a possibility that the road is still not built. An alternative route for the rising main is along an alley between 2/9 Street and Nui Thanh Street, continuing on the other side of Nui Thanh Street along the access way to a factory and between a couple of houses. Drawback of this alternative is that the length of pipe required is larger and that the pipeline crosses private property. Rising main 15 has to cross Nui Thanh Street which lies considerably higher than 2/9 Street. Because of the sharp vertical bend, an air-valve is required here to release trapped air that could block the flow of water. Near the treatment plant, the rising main crosses an open drainage channel. This crossing is achieved with a steel casing pipe. However, the open drain might in the near future be replaced by a large concrete box drain. Crossing straight through the box drain is undesirable since it would involve a major reconstruction (and widening) of the drain. It is recommended to cross under the drain and continue at the same depth to the discharge point at the nearby WWTP. In that case also here an air-valve is required because of the sharp vertical bend. Since there is a high point in the rising main around Nui Thanh Street, a scour valve is required at each end of the pipeline in order to be able to empty the entire conduit. The scour valve at the treatment plant discharges to the wet well of the treatment plant pumping station. The scour valve at 2/9 Street discharges to the wet well, which has an overflow to a nearby roadside drain. 5.3 Son Tra catchment Existing design Under the ongoing works of Phase 1 the wastewater of part of An Hai Bac ward is collected along the Han River embankment north of the Han River Bridge by a series of GIDs and pumped to the Son Tra treatment plant in the north. Also the wastewater from the fishing village on the eastern seaboard in Man Thai ward is to be collected and pumped to the Son Tra treatment plant. This latter system, however, consists of a number of (temporary) pumping stations at existing outlets to the sea and small bore rising mains. The reason for not using gravity interceptors is that the construction of GIDs to serve these areas would have involved major community disruption. Resettlement of around 150 houses per kilometre of GID would have been unavoidable due to the construction width necessary. Construction along the beach would substantially reduce resettlement but not enough; it would also add to the cost and require additional pumping stations due to the difficulties and risks of construction along the water front. The above situation along the fishing village of Man Thai ward has changed since the time of the original design. At the moment a coastal road is being constructed along the eastern seaboard. Construction Management Consultants Page 73

72 Construction has started several kilometres north of the village. Within a year the road is expected to pass the village. This creates better possibilities for a GID system since a wide area is being cleared along the beach for this road. For that reason the system has been redesigned and integrated with the additional works program Description of additional area and integration with existing design/options With the finalization of the Pham Van Dong Street (between the Son Hang Bridge and the beach), it is expected that new residential areas will quickly develop along this road. A much larger volume of wastewater than present will be discharged to sea if no counter measures are taken. In addition, a large drain originating from the industries along Ngo Quyen Street flows into the sea 600m to the north of Pham Van Dong Street. In the additional works program a wastewater collection system will intercept the wastewater between Pham Van Dong Street and the fishing village covered in the Phase I works. This will greatly reduce the levels of pollution along this part of the Son Tra beach area. Since the system along the fishing village is redesigned it makes great sense (both from a technical as well as a financial point of view) to make an integrated design for the wastewater collection system along the Son Tra coast line. In that case the total investment cost for the Son Tra coastal area would be reduced by almost 15% (see Appendix C.2). In the integrated design a GID starts from Pham Van Dong Street northward (GID2) and another from an existing outfall southward (GID2A) As at,present, not much wastewater is expected form the area around Pham Van Dong Street, the first section of GID 2 will not be installed, at present. Pumping station (SPS2) pumps the intercepted wastewater from GID2 and GID2A to GIDI. This GID continues northward along the fishing village until SPS1. From the North side, the system starts with a small pumping station that pumps intercepted wastewater from another fishing village towards GID 1 A. GID 1 A transports the pumped wastewater towards SPS 1, while collecting further wastewater along the way. Finally the wastewater is pumped by SPS 1 to the Son Tra treatment plant Design flows The dimensions of the GIDs is based on the size of the flow it intercepts from drains it crosses (usually at outfalls or road crossings) plus the size of the flow it receives from upstream GIDs and/or pumping stations. The system along the Son Tra coastline is divided into 2 sections of GIDs and pumping stations: The first section includes 573m of GID2 from Pham Van Dong Street that will be constructed in the future, followed by 200m that will be constructed as part of the additional works. GID2A is about 560 m long. The second section includes GIDI (776m) and GIDla (220m). Table 5-2 shows for each section the length from one node to another, the catchment area that drains to the section from side streets, the upstream inflow, the total flow upon which the size of the drain is based and finally the diameter of that section of GID (or rising main). Construction Management Consultants Page 74

73 Node 1 Nde 2 Lent Catch Area Lateral upstream Design Diameter..., _ tmr [ha) [I/S [I/u] fi/s] [MM] -2/3-2/2 157 Xa ** -2/2-2/1 210 Xa ** -2/1 2/1 206 Xa ** 2/1 SPS2 200 Xa A/1 2A/7 296 Xb A/7 2A/ Xb A/11 SPS2 91 Xa SPS2 1/ * 1/l 1/9 432 Xb /9 1/ Xb /15 1/16 60 Xb /16 SPS1 271 Xb A/1 SPS1 377 Xb SPS1 WWTP * Table 5-2 Design flows Son Tra beach area (* Rising main; ** Future extension) A medium size pumping station (SPS2) with 2 duty pumps (1 standby) transfers the wastewater through a 877m long rising main (315mm) to the starting point of GID1. The combination of pump characteristics and rising main characteristics results in a maximum pump capacity of 120 V/s. A small size pumping station (TPS1.01) with 1 duty pump (1 standby) transfers the wastewater through a 407m long rising main (160mm) to GID1A. The combination of pump characteristics and rising main characteristics results in a maximum pump capacity of 10 I/s. Finally a medium-large size pumping station (SPS1) with 2 duty pumps (1 standby) transfers the wastewater through a 1290m long rising main (400mm) to the Son Tra treatment plant. The combination of pump characteristics and rising main characteristics results in a maximum pump capacity of 146 1/s Alignment, SPS locations and longitudinal profile The alignment of the GIDs is on the eastern side of the new coastal road, in the pavement. Of the three pumping stations, the first (SPS2) is located almost 800 m north of Pham Van Dong Street; TPS1.01 is located on the south bank of a stream/open drain at the south end of the fishing village; the third pumping station (SPSI) located at the end of a small unpaved road between the houses of the fishing village leading towards Phan Ba Phien Street. The road is just wide enough to install the 400 mm RM1 that, via Phan Ba Phien Street and after crossing Ngo Quyen road, ultimately goes to the Son Tra WWTP. The alignment of the rising main from SPS2 to the start of GIDI is along the new coastal road, in the pavement, as is the alignment of the rising main from TPS 1.01 to the start of GID I A. The rising main from SPS 1 to the Son Tra treatment plant first runs west towards Ngo Quyen road. It runs parallel to this road and then turns west towards the treatment plant. Construction Management Consultants Page 75

74 5.3.5 Special issues In Son Tra wastewater catchment area, part of GIDI, SPSI, RM1 and TPS 1.01 are part of Contract 013 of the ongoing Phase I works; GID2, SPS2 and RM2 are part of the additional works program. GID1, SPSI and RM1 have been redesigned in such a way that they can accommodate the future flows from the additional areas to the south. Originally a number (4) of temporary wastewater pumps and a small SPS along the fishing village of Man Thai were foreseen. A small bore rising main was to pump the limited wastewater amounts to Son Tra WWTP. In the redesign, a GID is foreseen along the new coastal road. The pumping station SPSI is enlarged as well as the diameter of the rising main. The alignment of the rising main, however, remains almost unaltered. 5.4 Ngu Hanh Son catchment Original designs and changes foreseen The original design for the Ngu Hanh Son wastewater catchment area of the ongoing Phase I works envisioned GIDs along My Khe Beach (in the south of Phuoc My ward) and Bac Me An Beach covering roughly the area between the My Khe Beach Hotel and the Furama Resort (or between Nguyen Cong Tru and Ho Xuan Huong roads). However, part of Phuoc My ward and An Hai Tay ward drain towards a low lying area inland from the My Khe Beach Hotel; due to its elevation, this area cannot discharge its water by gravity towards the beach. To protect the ponds formed in the low lying area from wastewater discharge, a number of additional temporary pumping stations were to pump the water to the GIDs located along the beach. From the GIDs, pumping stations were to transport the wastewater to the Ngu Hanh Son treatment plant. Due to the delays in project implementation and the rapid development of the area the wastewater collection system has been reconsidered. In the additional works program a large stormwater drain is constructed along the low lying areas in the south of Phuoc My ward to the middle of Bac My An ward (see paragraph 3.5). All wastewater and stormwater run-off from the area south of Nguyen Cong Tru Street and east of Ngu Hanh Son Street will flow to this drain. The area presently has two outfalls: one south of My Khe Beach Hotel, one south of Furama Resort; both discharging wastewater as well as stormwater run-off. Under the additional works program the outfall south of My Khe Beach Hotel is upgraded and another outfall is added between the two existing outfalls, north of St. Paulo Monastery. The upgraded outfall south of My Khe Beach Hotel and the new outfall north of St. Paulo Monastery are utilised to discharge storm water from the new drain; in a later stage the drain will be extended south towards the Furama Resort, and the Furama outfall will be upgraded. Construction Management Consultants Page 76 DHV, CDM and VIWASF.

75 n Since there are only three points at which water is discharged to the sea and these points lie too far apart (1400m) to connect by one gravity pipe, the wastewater will be intercepted at these three points and directly pumped away Description of additional area and integration with existing design/options River Presently the area between the Tran Thi Ly Bridge and the Tuyen Son Bridge is being back filled and will be developed into a residential area similarly to the areas to the north along the river. The drainage system of the area will discharge towards the Han River. In order to protect the river environment a GID along the embankment will intercept the untreated wastewater and transport it to pumping stations which in turn pumps it to the Ngu Hanh Son treatment plant. The length of road along the river between the two bridges is around 1.5km. This length is too long to cover by one GID without intermediate pumping station; the excavation depth would otherwise be too deep. Therefore this section of GID has two pumping stations: one relatively small one to lift the wastewater to the nearby continuing GID and one to pump the wastewater to the Ngu Hanh Son treatment plant. Beach As mentioned in paragraph 5.4.1, the wastewater from the area east of Ngu Hanh Son Street is to be intercepted at the three outfalls along the beach. Since the distance between the outfalls is too large to bridge with one GID without intermediate pumping stations, the intercepted wastewater is therefore pumped directly from the outfalls. Since it does not make sense to pump the water from { D :c. each outfall to the treatment plant by separate rising,:j 9i mains it is first conveyed to one point i.e. the pumping j station/outfall closest to the treatment plant, which is '). N the Furama outfall (N.B. Even if at some stage it were SPS3 decided to delete the Furama section of the My Khe j -i,x. ; N 0 drain, the wastewater at the existing Furama Outfall can.. z still be intercepted at this location and wastewater from.. My Khe Drain the northern and middle outfalls, resp. My Khe Beach - and St. Paulo Monastery, can be conveyed to the GIDS j. SPS4 Furama outfall. Paulo For the conveyance of the wastewater from the Furama.. ' Resort Outfall to the treatment plant there are several : l\ 'RM33 R options. a.ss3^,r4*\... Option 1 (Figure 5-3) j) GID Pump directly to the Ngu Hanh Son treatment plant. r-#.>;' '9>L \ \' Advantage: d between t \ * No interference or dependency between the beach system and the river system. Limitation: :-'s N~ * This would mean two long rising mains to the I \\ Ngu Hanh Son treatment plant: one from the /.. beach area and one from the river area. Figurc 5-3 Option 1 Construction Management Consultants Page 77

76 Option 2 (Figure 5-4) g i,.t Pump to the south of the Hu Xuan Huong/Ngu Hanh Son intersection where it is joined with the rising main from jn.s the Han River section. At this point either both the rising ;if LX4 main from SPS34 (beach) and the rising main from M.. Khe Co SPS33 (river) discharge to a new pumping station --.*-t, -U (SPS35) which subsequently pumps both combined flows > MyKheDrain i to the treatment plant; or both rising mains join into one GID5 ' \ \ PS; combined rising main requiring both SPS34 and SPS33 to '' \\ \ SPS4 be able to pump against each other. -,Palo Advantage:. I SPS33 RM 3 3 RM4 *\ a * Only one long rising main along Le Van Hien t IFurama Street to the treatment plant. ;::igid33- - Lirnitation: ~<<t..'-3 > >,tp3 * Extra pumping station south of Hu Xuan Huong/Ngu Hanh Son intersection or larger.' ' pumping stations at SPS34 and SPS33. * More complex operation and maintenance - Option 3 (Figure 5-5). - Pump to the beginning of GED33 on the other side of the.: i>. 8, peninsula along the Han River In this case the wastewater from the Furama Resort Outfall would be pumped to the Figure 54 Option 2 St. Paulo Monastery Outfall; from there all wastewater - from the beach area would be pumped from SPS4 along h 1 ' l Phan Tu Street to GID33. Advantage: :--- l'si: * The rising main coming from the beach area can : be shorter by about 2,600m as compared to option I I t * The pump in SPS34 can be much smaller. My Khe Drain * Flatter gradient of GID33 because of increased > GIDS flow; this means the final pumping station can be x SPS5 located further south, closer to the treatment plant. l : o S u10 Limitation: - :.i * Larger pumping station at SPS33 j IGD33 \ t Furama * Larger diameter for GID33 :SPS33 * Wastewater from the beach area has to be pumped ) \ -- 0; 'S SPS34 PS; up to the relatively high level of Ngu Hanh Son v- \ ' RM3i" Street twice; the first time by SPS 4 and the -- s second time by SPS33...:. o * The rising main from SPS4 has to cross the newly 3". "... constructed Ngu Hanh Son Street. - Option 1 has a substantial higher cost for the extra rising, main and, although Option 3 has some clear advantages, it has a highly undesirable crossing of the newly Figure 5-5 Option 3 It N Construction Management Consultants Page 78

77 constructed Ngu Hanh Son Street. Since the difference in cost between options 2 and 3 is very small, Option 2 is chosen Design flows The dimensions of the GIDs is based on the size of the flow it intercepts from drains it crosses (usually at road crossings) plus the size of the flow it receives from upstream GIDs and/or pumping stations. The wastewater collection system in the Ngu Hanh Son catchment is divided into a western section along the river and an eastern section along the beach. River The section along the Han River - consisting of 2 lengths of GIDs and 2 pumping stations - collects the wastewater from the area between Ngu Hanh Son Street and the river. Beach The eastern section of the catchment only has three outfalls to the sea at which points the wastewater is intercepted. Table 5-3 shows for each section the length from one node to another, the catchment area that drains to the section from side streets, the upstream inflow, the total flow upon which the size of the drain(or rising main) is based and finally the diameter of that section of GID (or rising main). catch Lateral upstream Dimse Node I Node 2 Lenrgth t 1 r ea inflow Design tml rh ial [/sj [Is] [mm] Eastern section, along the Beach: SPS3 SPS Xa * SPS4 SPS Xa/XIa * SPS34 SPS Xia/XIb * Western section, along the Han River: 5/1 5/2 160 XlIa /2 SPS5 56 XIIa A/1 5A/2 210 XIIa A/2 SPS5 176 XIIa SPS5 33/1 662 XIIa * 33/1 33/2 180 XIIa /2 33/3 216 XIIa /3 SPS33 80 XlIa A/1 33A/2 88 XIIa A/2 SPS33 88 XIIa SPS33 SPS * Combined section, to the Ngu Hanh Son WWTP: SPS35 GID [ * GID35 WWTP Table S-3 Design flows Ngu Hanh Son area (* Rising main) Construction Management Consultants Page 79

78 Vietnam Three Cities Sanitation Projcct Alignment, SPS locations and longitudinal profile River The alignment of the GIDs along the river is on the western side of the new embankment road, in the pavement. The two pumping stations in the western catchment of Ngu Hanh Son are located in such a way that excavations do not become deeper than necessary, whereby it was ensured that the larger diameter upstream GID would be slightly deeper than the smaller drain. The operation of the pumping station will thus be based on the larger GID with the larger flow. The pumping stations of the eastern catchment of Ngu Hanh Son are located directly next to each of the sea outfalls, where the wastewater is intercepted from the combined drain. The alignment of the rising main from SPS5 to the start of GID33 is along the river on the western side of the new embankment road, in the pavement. The rising main from SPS33 to SPS35 first runs parallel to the Han River, towards the Tuyen Son bridge, then crosses the new road, makes a bend and then goes east up towards Ngu Hanh Son Street, towards SPS35. Beach The rising main from SPS3 follows the alignment of a new beach road, to be constructed in the near future, and leads directly to SPS4. An alternative option would be to lay the rising main from SPS3 in a westward direction, parallel to the My Khe outfall drain and then - at the drain's T-junction - turn it south for about 630m until the (northern) upstream start of the Bac My An section of the drain. There, the wastewater would then be injected again into the drain and would flow under gravity towards the Bac My An outfall where it would be intercepted again. The drain and rising main could be constructed at the same time, in the same trench and would not result in additional land requirements. It is considered best to keep wastewater, once it is already intercepted, inside the wastewater collection system and not relate it again to a large combined drain. However, if at some stage, construction along the road meets technical or political obstacles, it could be decided to select the altemative option described here. However, it would require a revision of the interceptor at the Bac My An outfall which would have to cope with larger wastewater flows. Similar to RM3, the rising main from SPS4 towards SPS34 follows the alignment of the new beach road until it reaches SPS 34. An alternative option as described above for RM3, with injection of intercepted wastewater back into the next section of the drain, would also be possible here. However, it is as yet uncertain if the complete drain will be built. A section requiring much resettlement may well be dropped (without seriously hampering the overall functioning of the My Khe drain), which would complicate the alternative option. The rising main from SPS34 runs straight west from the beach to Le Van Hien Street. The alignment follows as much as possible the planned road alignment. Since the Hu Xuan Huong Street has been recently reconstructed by the time the rising main is built, it is not recommended to follow that street; going through Hu Xuan Huong Street would also result in a longer pipeline. The location where RM33 and RM34 come together - at SPS35 - lies approx. 60m south of the Hu Xuan Huong/Ngu Hanh Son Street intersection. Construction Management Consultants Page 80

79 The rising main from SPS35 to the Ngu Hanh Son treatment plant follows the Eastern side of Le Van Hien Street south until the turn-off and then uphill towards the treatment plant. The last 300m the area slopes down towards the treatment plant. Near the high point, the rising main discharges into a manhole from where the wastewater flows towards the treatment plant by gravity Special issues As mentioned in paragraph 5.4.1, originally GlDs were foreseen for the beach area of the Ngu Hanh Son wastewater catchment area. These GIDs have been removed from the Contract 013 ongoing Phase I works and the design and construction for the wastewater collection of the area added to Additional Works package 020. Wastewater is intercepted at each of the three outfalls: the reconstructed My Khe Beach Outfall, the new St. Paulo Monastery Outfall, and the existing Furama Outfall. At the outfalls, the shape of the drain is such (V-form of the middle drain) that a relatively small interceptor at the end of the rmiddle of the three channels of the drain suffices. Construction Management Consultants Page 81

80 6 PROCUREMENT PLAN FOR ADDITIONAL WORKS 6.1 Introduction The procurement plan for the Additional Works is complicated and simple at the same time. It is complicated as a large number of Additional Works project components are shifted to ongoing contracts through addendum or variation orders, while parts of the Phase I defined project will be shifted to a new civil works package, 020. The additional works consist of: 1. Drainage 2. Wastewater collection systems 3. Floating covers for Son Tra and Ngu Hanh Son wastewater treatment plants 4. Beach Cleaning Equipment 5. Detailed Engineering Details on procurement for each of these components are presented below. 6.2 Details on procurement proposals Drainage Except for the Dinh Tham drain, all Additional Works drains are considerably larger than those constructed under the ongoing Phase 1 works and they are not connected to any of the drains in the present program. Moreover, there have been several large variation orders already to contract 013 and there is no strong reason to include drainage works in the ongoing contract 013. However, there is a strong desire to construct the Le Do drain as early as possible. Most of the drain will be constructed under an existing road, while upon completion of the drain, the road will be extended immediately and connected to the new Lien Chieu road along the Danang Bay. A request was made by the Danang People's Committee to include the Le Do drain in the ongoing.3 contract 013, as then an early start could be made with the drain construction3. It is proposed, therefore, to include all drains (except Le Do drain) into a new package (020) and construct Le Do drain under a variation order to ongoing contract Additional Wastewater collection systems The Additional Works contain additions to the wastewater collection systems of Hoa Cuong, Son Tra and Ngu Hanh Son. The additions to the Hoa Cuong system are very minimal and the new design has integrated the additions with the original system. The logical way to construct it is through a (minimal) variation to the ongoing contract 013. Similarly, most of the Son Tra wastewater system remains unchanged. Only along the East coast of the catchment area, a system with temporary pumping stations is replaced by a (slightly) more elaborate wastewater collection system along the new coastal road, presently under construction. Also here, a variation to ongoing contract 013 is the best. The Ngu Hanh Son wastewater collection system has changed completely. The changes are caused by the new My Khe drain, with three sea outfalls, that will be constructed under future package 3The World Bank has agreed with the request, provided the RAP will be approved first. Construction Managcment Consultants Page 82

81 020. The wastewater collection system must be constructed together with the new drains. In case something changes (which occurs frequently), the wastewater system can be adjusted at the same time. Constructing the Ngu Hanh Son wastewater system now, as a variation to contract 013, does not make sense. It would result in a completed wastewater system, while most of the related drainage infrastructure would not be in place. It is proposed, therefore, to remove the complete Ngu Hanh Son wastewater system from contract 013 and procure the new design of the wastewater system, including the additions, under package 020. This proposal also compensates to a large extent the extra costs to contract 013 for the construction of the Le Do drain (see Section 6.2.1) Floating covers for the Son Tra and Ngu Hanh Son wastewater treatment plants The costs of HDPE floating covers for the two smaller treatment plants at Son Tra and Ngu Hanh Son (that are presently constructed under contract 012) are quite substantial. As contract 012 already faces cost overruns, ideally, procurement of floating covers would be made under package 020 (or a separate small package). However, for reasons presented below, it is proposed to procure the two floating covers under a variation to ongoing contract 012. Floating covers must be made while the treatment lagoons are empty. Although it is not impossible to construct the covers over lagoons filled with wastewater, it is difficult, the quality often suffers and it adds to their costs. Therefore, it is much preferred to construct floating covers at the same time as the treatment plants, when lagoons are still empty. Keeping the lagoons at Son Tra empty until a floating cover is installed under future package 020 would delay the start of operations of the otherwise completed Son Tra wastewater system. Another aspect to consider is that the (minimally reinforced) concrete lining of the lagoons may suffer if the lagoons are kept empty and under the blazing sun for prolonged periods of time. Adding the floating cover under a variation to 012 is proposed, therefore. A later start of operations does not matter for the Ngu Hanh Son treatment plant, which will only become operational after the construction of the My Khe drain and the Ngu Hanh Son wastewater system, both proposed for procurement under future package 020. Nevertheless, when already 3 out of 4 covers will be procured under contract 012 it seems odd to move the last cover for the small Ngu Hanh Son plant to package Beach Cleaning Equipment Two self-propelled beach cleaners were procured already under a small (national Shopping) contract 016. Delivery of the equipment took place in April Detailed Engineering Detailed Engineering was procured under an Addendum to ongoing contract 011 (for Construction Management Services). The addendum was signed in January 2003 and includes detailed engineering and preparation of Resettlement Action Plan (RAP), Environmental Impact Assessment (EIA), Environmental Management Plan (EMP) and Tender Documents for package 020. Construction Management Consultants Page 83

82 6.3 Overview of the proposed Procurement Plan Based on the above considerations, the resulting procurement proposal is presented in the table below. Contracts 011, 012 and 013 are ongoing contracts, contract 016 was prepared especially for the beach cleaners and has been concluded already, while package 020 will contain the bulk of the Additional Works. Component Item Proposed procurement a Oil Drainage Le Dinh Tham Le Do _ Xuan Hoa An Khc My Khe Wastewater Hoa Cuong additions Son Tra additions Ngu Hanh Son (from 012) Ngu Hanh Son additions =_=_=_ Floating covers Son Tra WWTP _ I. ~~Ngu Hanh Son WWTP.l Beach Cleaning equipment *) Detailed Engineering *) C * Table 6-1 Proposed procurement plan for the Additional Works *) already procured Construction Management Consultants Page 84

83 7 COSTS Upon completion of the detailed engineering, cost estimates have changed a little in comparison to those presented in the feasibility study for the Additional Works. Because of the proposed packaging, costs are also presented in a slightly different way. Furthermore, costs of land acquisition/compensation, are now presented separately. Component Item = Estimated costs (USD'01O) Drainage Le Dinh Tham _ = 379 Le Do 1,046 Xuan Hoa 762 An Khe _ 694 My Khe 3,634 Wastewater Hoa Cuong additions Son Tra additions 488 Ngu Hanh Son (complete) ,622 Floating covers Son Tra WWTP 231. Ngu Hanh Son WWTP 142 Beach Cleaning equipment I I 82 Detailed Engineering 637 Total i ,091 *) By rerouting and re-designing ongoing works, the additional costs became negligible Table 7-1 Estimated Base costs of Additional works Costs for land acquisition and compensation are estimated at USD 996,000 (incl. contingencies). It should be noted that the amounts shown in the table are net, without costs for general and preliminary items, physical and price contingencies, etc. To reach at a genuine total cost of the additional work, additions must be made which are specific for each contract or package. An overview is shown in the table below. Contract Base costs Total costs (USD'000) (USD'OOO) 011 (already procured) (variation) (variation) (already procured) (new package) 7,091 9,109 Land acquisition Total 9,842 11,937 Table 7-2 Estimated total costs of Additional works The additional works will have a significant impact on the contributions to the project by the World Bank and by the project owner URENCO. As, apart from the additional works, there had been already many alterations to contract scope of 012 and 013, a complete new cost estimate for the project was made. The table below shows the most important details. Construction Management Consultants Page 85

84 Ol 11 construction Managemnent * 2,772 2,386 2, ioo 0% 2, Landfill, 4 Treatinent Plants *) 9,445 7, ,291 7,966 S0% , Sewerage/DrainagerTransf st *) 19X677 14,924 11,364 2,330 13,694 80% 10,955 2, Equipm/vehicles )2,012 2,012 2, Beach cleaning equipment ) 3,555 2, % Small equipment/tools ) TA A - Institutional 1,965 1,754 1,224 1, % 1, TA B - Institutional (AusAid) t,240 1,240 1,240 1, Auditing Additional constr. works ')9,109 9,109 80% 7,288 1,822 Revolving Fund 1,000 1,000 1,000 1, % 1,000 Land acquisition 1,397 1,397 1,397 1,397 1,397 Land acq Additional. Works ) Management, miscellaneous Taxes 2,777 2, ,232. _ 3,232 Grand to1ais , ,-5 4S, I= 35 C Tntibud.c.4 = 1 H(:, ~ z 5th 7.22f;' Surplus or Shortfall- (-). :.-., *) Contracts/items that include Additional Works Table 7-3 Overview of project costs and distribution over World Bank and URENCO. It may be noted that, while the total budget increases to well above the original budget of USD mln referred to in the project Appraisal report, the World Bank share is expected to remain below the original budget of USD mln. The Urenco share increases sharply, from the original USD 7.22 mln to USD mln. Construction Management Consultants Page 86

85 8 RESETTLEMENT 8.1 Introduction The drainage component of the project will cause some adverse impacts on peoples' assets. The wastewater works and beach cleaning components will not result in adverse impacts on peoples' assets nor will they cause any loss of businesses or incomes. A resettlement Action Plan (RAP) was prepared that covers: a) project components and impacts; b) compensation entitlement policy; c) costs and budgets; and d) implementation arrangements. Details are presented in Volume 2: Resettlement Action Plan (RAP). A summary of the findings is presented in this chapter. For the RAP preparation census, inventory and socio-economic surveys were conducted covering 143 PAPs. The socio-economic characteristics of the PAPs indicate that: * Average household size of the PAPs in the four sub-project areas is 5.8. * Most of the households are either salaried persons working in government departments (42.1%) or in business and commerce (3 7.8%). A small number of households also earn their living by fishing (9.8%) or through agricultural activities (9.8%). * Majority (50.3%) of the surveyed households have an average monthly household income ranging between one to 2 million VND. The percentage of those earning below one million VND is 32.2%. 25 households or 17.5%, have an average monthly household income of more than 2 million VND. Most of these come from the Le Do area. 8.2 Impacts of the Project The Additional Works Project will affect a total of 187 PAPs. Except for the Le Do area, other components will result in only marginal impacts on the PAPs. In Le Do the major impact is due to the proposed road and a 23 m (20 m for plots and 3 m for a lane) wide adjoining areas on both sides of the road designated for redevelopment. The urban redevelopment of the area, including the road, will affect a total of 102 households, 90 of them severely Loss of Agricultural Land The project will impact a total of 40 PAPs due to the loss of agricultural land. Most of these PAPs (32 Households) are in the An Khe area. Only four of the 32 PAPs affected in An Khe area own the affected land. The remaining 28 PAPs have the affected land on lease from the commune. Total land that will need to be acquired totals 588 m2. Additionally, 2,526 m2 of commune land that is on lease will need to be repossessed for the project Loss of Residential Land A total of 134 PAPs would be affected due to the loss of 11,978.5 m2 of residential land of which 102 PAPs (10,364.5 m2) are affected due to the urban redevelopment project in Le Do area. Of these 90 PAPs would be affected due to the loss of their entire land holdings (8,428.7 m2) while 12 PAPs will be affected due to the partial loss of residential land. In Le Dinh Tham, 13 PAPs (69.5 m2) will be affected by partial loss of residential land. The corresponding number in My Khe is 19 PAPs with 1,544.5 m2. Construction Management Consultants Page 87

86 Danang Sub-project (Phase I) Impacts on Structures The project will impact a total of 110 PAPs due to the loss of structures. The total area of the affected structures is 7,312.9 m2, taking into account all the floors. Majority of the affected structures are category 3 and Loss of other Fixed Assets A total of 75 PAPs, most of them in the Le Do area, will be affected by the loss of boundary walls. 29 PAPs will be affected by the loss of fences. Additionally, the loss of paved yards will impact a total of 78 PAPs, again most of them in the Le Do area. 4 PAPs in An Khe area would be affected by the loss of fish-ponds (214 m2) and would be entitled to compensation for the same. A total of 24 PAPs would be affected due to the loss of trees, most of them in the Le Do area Loss of Incomes and Businesses A total of 43 PAPs would be affected due to the loss of incomes from cultivation of agricultural land. Additionally, a total of 12 PAPs will be affected by loss of business incomes. All these businesses are managed from affected houses. Only 6 of the affected businesses will be displaced by the project Impacts on Public Infrastructure and Utilities The proposed drainage and associated road development will cause extensive impact on existing public utilities such as: electric poles, power distribution lines, road side pavements, existing drains etc. In accordance with the policy, all impacted public facilities and utilities will be made good and the DNPC will ensure repairs and rehabilitation of all affected infrastructure. 8.3 Temporary Impacts Construction works implementation of extended project will have temporary impacts on a large number of road side businesses, houses and other establishments. The impacts would be mainly the restricted access and inconvenience during the project implementation. There may some minor impacts on the boundary walls, fences and other fixed assets during the construction phase. 8.4 Relocation Requirements Out of the 187 PAPs affected by the project, only 90 PAPs will be displaced requiring relocation. All these PAPs are affected by the proposed road and redevelopment of Le Do area. In addition to the 90 PAPs requiring relocation, another 12 PAPs would be marginally affected due to the loss of residential land, houses and other fixed assets, trees, businesses and incomes. The Da Nang Peoples' Committee (DNPC) proposes to develop the vacated area and provide plots of regular size (4.5x20m) and sell them to people, with priority given to the PAPs. The selling price is tentatively fixed at VND 3.0 million/m2 whereas the current compensation rate for residential land in the area varies between 0.5 for land behind the main road, to VND 3.6 million/m2 for plots facing he main road. Further, after the redevelopment only a maximum of 68 plots can be planned in the area. Therefore, the remaining 22 PAPs are to be relocated at a newly developed area in Thanh Loc Dan. At Thanh Loc Dan the selling price of the plots of similar size is between VND million per m2. Construction Management Consultants Page 88

87 Danang Sub-project (Phase I) Since the developed plots at Le Do and Thanh Loc Dan area are to be sold to people, the PAPs have the choice to either buy the developed plots from DNPC from the compensation entitlements or settle themselves anywhere at their choice of location. The Entitlement Matrix summarizing the entitlements for each category of PAPs is included in the RAP. 8.5 Resettlement Cost The resettlement cost for the project will be part of the project cost. They will be covered out of the funds provided by DNPC and a necessary budget has been allocated for the purpose. The resettlement cost of the Additional Works Project, estimated using the compensation rates and allowances established by the DNPC, amount to VND 14,444 million. This includes contingencies of 10%, external monitoring cost of VND 150 million, and administration cost of VND 550 million. In the case of any over-runs, URENCO will be responsible to provide any additional funds as necessary to ensure that resettlement implementation is carried out in a timely manner. Construction Management Consultants Page 89

88 9 ENVIRONMENTAL CONSIDERATIONS 9.1 Introduction An assessment of the Additional Works Project's potential environmental impacts was conducted for Pre-construction, Construction, and Operation phases. The assessment evaluated a range of potential impacts that could occur as a result of the Additional Works Project. Alternative options of project design were considered to minimize negative impacts of the project. Details are presented in Volume 3: Environmental Impact Assessment (EIA). Mitigation of negative impacts are described in great detail and are mostly based on experiences from the ongoing sanitation project. Details are presented in Volume 4: Environmental Management Plan (EMP). A summary of the findings of the environmental studies is presented in this chapter. 9.2 Alternatives Numerous alternatives are being considered within the Additional Works Project. However, the practical scope of options are limited, as the project needs to integrate with Phase I works - both in location and operational design. The "No Project" alternative would likely mean that: 1. flooding in the Additional Works Project area will continue which would continue to impact public health, economic development, and transport, 2. wastewater will continue to drain into nearby rivers and beaches, which will negatively affect public health and tourism; and 3. solid waste will continue to be dumped on popular beaches, which will negatively affect public health and tourism. 9.3 Impacts An assessment of the Additional Works Project's potential environmental impacts was conducted for Pre-construction, Construction, and Operation phases. The assessment evaluated a range of potential impacts that could occur as a result of the Additional Works Project. The selection of potential impacts for evaluation was based on site visits, discussions with Phase I project staff, URENCO, DoSTE and others; and through review of relevant documents such as World Bank's Environmental Assessment Sourcebook, Phase I environmental assessment reports, the Additional Works Project's Feasibility Study and others. The below provides a summary impact evaluation of potential impacts that could be created by the Additional Works Project. Table 1: Summary of impacts. Impact Title Pre-Construction Phase Resettlement and Relocation of Cultural Property Land Acquisition Health Risks Related to Mines, Explosives & Toxic Substances Construction Phase Generation of Dust Generation of Noise Generation of Air Pollution Traffic Congestion Impact Evaluation Mitigable Mitigable Mitigable Minor Negative Mitigable Mitigable Mitigable Construction Management Consultants Page 90

89 Impact Title Odour Generation and Occupational Hygiene Damage to Access Roads Damage to Adjacent Property Soil Erosion and Sediment Transport Impacts on Vegetation Water Quality/Quantity Impacts on residential wells Drainage Construction Impacts on Public and Worker Health Oil spills near the construction site Electricity management near the construction site Damage to underground utilities in the Construction area Operation Phase Solid Waste Accumulation at Drainage Outlets Impacts on Dengue Fever Flushing of residual wastewater during rainy periods Water Quality/Quantity Impacts on residential wells Changes to Wastewater Services in the Project Area Changes to Flood Control in the Project Area Odours at Wastewater Treatment Plants Land Utility Values/Development Options Solid Waste at Beaches Impact Evaluation Mitigable Minor Negative Mitigable Mitigable Mitigable Minor Negative Mitigable Mitigable Mitigable Mitigable Minor Negative Minor Positive Minor Negative Minor Negative Major Positive Major Positive Minor Positive Major Positive Minor Positive 9.4 Environmental Management Plan An Environmental Management Plan (EMP) has been produced for this Additional Works Project. (Volume 4 of the detailed engineering study reports). The EMP: 1) identifies potential adverse impacts and suggests measures to mitigate adverse impacts; 2) suggests programmes to monitor both the effectiveness of the mitigation measures; and the numerous positive impacts created by Additional Works Project; and 3) provides guidance on the institutional responsibilities for Pre-Construction, Construction, and Operation Phases. 9.5 Conclusion This project's purpose is to mitigate priority urban environmental issues - namely, sewage and sanitation services in areas that could not be supported by the Phase I project. The construction of these services will create some short-term negative impacts. However, the Additional Works Project's long-term positive impacts during operation outweigh its negative impacts by far. Construction Management Consultants Page 91

90 APPENDICES Construction Management Consultants Page 92

91 Vietnam ThTrF e ities Sanitation Project A.1 Drainage Hydraulics - Le Dinh Tham Drain Table 1: Catchment A -Stormwater Flowrate Calculation of Binh Thuan Ward -Nguyen Van Troi Street Froml To L(m) Lcum (m) v (mis) t (min) T(min) I (m/s.ha) C I A (ha) Qst(m3/s) WF(m'/s) Qcomb I I I J p1.59 Lag time to drain 17 min _4 V S flood freq. 5 years , O S ' Ex. coyv 0.20 m new cos 0.25 m Table 2: Catchment A - Hydraulic Calculation of New design From To L(m) Hyd.Slop 8 (m) I-H(m) WH(m) A (m2) R RN(213) Qst(m3/s) V (m/s) Ototal %Qde/pre Remark Slope of Dr. Surface level Invert level Top level Depth of cover I Water level a100% C od % E)isiungDrain % 23j 43.' a a5 -. O jd a10o0% 22C % E)isttngDr3in tl01% 'C % % E6lsing. rain a 300%. 10 O, _? M 41A) ('i ' 0(IF, a100% Exie.ng Dain 010i Cr % % Additional Po g X % Exstcng Drain M Q05. C9s % % Additional Prog % h4ml - h.ght of drain; WH(mnl. tgn ofwtwo In drain Construction Management Consultants Page 93

92 Vietnam Three Cities Sanitation Proj'ect A.2 Drainage Hydraulics - Le Do Drain Table 1: Catchment A -Stormwater Flowrate Calculation of Chlnh Glan Ward - Le Do Street From To L m cm v(rl)t(mn (i)('sh A (ha) Qst(m Is) DWF(m s)qcomb , Lagtrime todrain 90min oa flood freq. 10Oyears upstream rnflow 9.74 mnais , oooo Le Do street -Da Nang Blay I , , , OM _ _ a a _ * & Chainag. (ml , I 0.00, Surface level-invert level -Top level -Water level Construction Management Consultants Page 94

93 Vietnam Three uities Sanitation Proj'ect Additional works Programn Table 2: Catchment A - Hydraulic Calculation of Chinh Glan Ward - Le Do Street From To L(m) By.lp 8(m)-) H(m m) 2) R IRI2/3)_ Qst(m3/s) V (mis) # Chan. Ototal %Qdr/des Remark Slope of Dr. surfac level Inivert level Top leel Dphof cover Water level HdSoi I50% % 0.150% % % /. _ % 0.150% % % % 0.150% i % i5o% % 0.150% % i50% % 0.150% % I50% , % 0.150% % % , % 0.150% 3.95, % % % 0.150% , % D% % 0.150% % % % 0.150% % o. 150%' 2 1.~ % 0.150% S4% _ % , % 0.150% % a. 15o% % 0.150% T % % ~ , % 0.150% % % % O h % % % %A % 17 17e 7.5 a. 15% % 0.150% M5% 17a % % 0.150% 300O % 18a % % 0.150% % % % 0.150% % %/ `1% A % % % 0.150% % % OS-% 0.150% % 23 2 _50 0~226% % 0 15D%/ ( % , 0.235%, , 7.22, % 0.150% % % % % I.r % HoCal heswu. ad ara WVWp)Cai * ht of waterin drain Constructi'on Management Consultants Page 95 DliV, CDM and VIWASE

94 Airport Lake : > / ca ' 3.20 * Time [min) Inflow Outflow -i Water level] 3.00 Construction Management Consultants Page 96

95 2913 Lake S \ ~ _ 8~ a) o8 o 7I 4 ~~~~~~~~~~~~~~~ 2 ~~~~~~~~~~~~~~~ 0 ~~~~~~~~~~~~~~~ Time [min] Inflow - Outflow Waterlevel Construction Management Consultants Page 97

96 Detailed Design, Report Hydraulic behaviour Airport Lake (San Bay) 10 Year return period Time intensity Area Inflow rate Outflow rate Regulation Water level (min) (mm/h) (ha) (m3/s) (m3/s) (m3) (m) i Construction Management Consultants Page 98

97 Hydraulic behaviour 29/3 Lake 10 Year return period Time Rain Area Inflow Outflow Regulation Lake water intensity level (min) (m3/s) (ha) (m3/s) (m3/s) (m3) (m) , , Construction Management Consultants Page 99 DHV, CDM and %IWASE

98 Hydraulic behaviour 29/3 Lake 10 Year return period Time Rain intensity Area Inflow Outflow Regulation lever level (min) (m3ls) (ha) (m3/s) (m3/s) (m3) (m, Construction Management Consultants Page 100

99 A.3 Drainage Hydraulics - Xuan Hoa Drain Table 1: Catchrnent A -Stornwvater Flowrate Calculation of Dien Bien Phu - Tran Cao Van Lag time to drain 2S min upstream inflow 7.80 m3's From To I Lcum (m) v (mis in) T(min) (m/s ha C A (ha) Qst(Ms) DWF(m'/s) Qcomb flood freq. 10 years _ Dien Bien Phu -Tran Cao Van EXuan Hoa Drain] a a , _\ _ _ \s _~~~~~~~~~ ' U , Chainage m g [mi Surface level -Invert level -Top level -Water level Construction Management Consultants Page 101

100 Table 2: Catchment A - Hydraulic Calculation of Dien Blen Phu -Tran Cao Van (Xuan Hoa) Fromn To L-) Hyd.Slop (m) IH(m) WH(m) I A (m2) R RA(2 QSt(m3/s) V (fms) Qchan Qtotal % de/pre Remark Slope of Dr. Surface level Invert level Tp level Dept ho er Water level Hyd.Slope % B% 1.500% % 2 3 _ % % 0.1o o.o U% o% % 0.100% , % 4 4a 7.5 o.100% % 0.100% U% 4a o.1oo% % 0.100% U h% D %. 100% % 6 I % 0.1A00% % o.10%oo % _ 0.100% 2.3t o44 28: U2% % 0.100% t % t% % 0.100% t02 t U% _65 o.100% % 0.100% % _ o% % 0.100% % % % 0.100% % o00% % 0.100% % o% % 0.100% , 1.34, % % % 0.070% % _ % % 0.070%, % _ % % 0.070% % % % 0.070% % % % _ 0,070% % 20 1 T 10, 0.070%, ) % 07% , Htt oit f ^; wid4(o HdiW of twg. h- dr Construction Management Consultants Page 102

101 Xuan Hoa E e / 2.60 X 0 o~~~~~~~~~~~~~~~~~~~~~~~~~~ L 0 Ca / (U 5.00 = 2.20 #~~~~ of Time [min] Inflow - Outflow - Water level Construction Management Consultants Page 103

102 Hydraulic behaviour Xuan Ha pond 10 Year return period -nme Rains Area Inflow rate Outflow rate Regulation Water level (min) (mm/h) (ha) (m3/s) (m3/s) (m3) ( Construction Management Consultants Page 104

103 , AA4 Drainage Hydraulics - An Khe Drain able I: Catchment A -Stormwater Flowrate Calculation of An Khe Lakes -Pho Loc River Lag time to drain 50 min upstream infliow 18.00m3eVs ro L_ Lu i) ms ~n T(min) (m/rha c A(a) i) J( s cm flood f req. 10 years _ An Khe Lakes - Pho Loc River _ _ _ , _ l , Cluainage (mln ~Surface level -invert level -Top level -Water lievel rable 2: Catchment A - Hydraulic Calculation of An Khe Lakes -Pho Loc River -ro To [(m) Hyd.Slope B (in) H4(m) WH(m) A (m2) R R-(2l3) Qst)m3!s) V (mis) it Chan. Ototal %Qde/pre Remark Slope of Dr. Surface level Invert level Top level Depth of cover Water level Hyd.Slope 1 2 _ % % 0.100%/ , % iOO% % 0.100% %A 3 4 _60 0.1i00% % 0.100% % 4 5 _60 0.1i00% % % % 5 6 _ % , % 0.100% , % % % % _ % % , ii0% _ % A R I3%.0% % ?.1% Construction Management Consultants Page 105

104 An Khe Lake E / > o > -J / t o~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~c ca , / e _ L Time [min] Inflow - Outflow -Water level Construction Management Consultants Page 106

105 Hydraulic behaviour An Khe Lake 10 Year return period Time intensity Area Inflow rate Outflow rate Regulation Water level (min) (mm/h) (ha) (m3/s) (m3/s) (m3) (m) Construction Management Consultants Page 107

106 A.5 Drainage Hydraulics - My Khe Drain ible 1: Catchnient B - Stormwater Flowiate Calculation of My Khte I Bac My An -Sea outfall Lag time to drain 20 min upstreamn inflow From To IL (m Lcum (m) v (m/s mn)a _Tmin) (m a Ira C A (ha) Qst(m Is) DWF(m Is) Qcomb flood freq. 10 years Run-off area Halm MK6 jmk ] 26 0, I 1K My Khe I Bac My An -Sea outfall M1<4 IMK AK401J MK MK13 14K MK2 MK ~ MK1< BA-MK A-MK BAl , G BAl BA BA2 BA BA3 BA j BA4 BA J BA401 BA j BA4 BAS _ BA5 IA B-A6 BA BA? FRi [ B _FRI1 FR O0D FR2 FR3 j Chalnage[lml I -Surfa ce leveli - Top level - Water level -Invert level 'able 2: Catchtment B -Hydraulic Calculation of New design From To d(slo B m H-Im) WH(m) A (m2) R R-(213) Q(m3is) V ns 8channel Ctotal %Odefpre Remarke Slope of Dr. Surfac level Invert level Top leel fo fcvrwater level tidso MK6 MK % ~ / 0.190% l0% MK5 MK % J % 0.100%A % MK4 MK %A ~ J % 01100%/ % 14K401 MK % % 0_10 33_ % MK4 MK I2120% % %, ~ f0% 14K3 MK ~ %.0400% ~.0% 14K2 MK % [ % 1-0i20%l % 1411 IBA-MK %l [ % I 0120% % I BA-MK GAI %A % 0,120% % BAl BA i20% % 0.120% _ % BA2 BA % % 0.250% i % BA3 BAA % j~148.8b 0.250% i % BA4 8A % J % 0.100%/ % BA401 8A % % 0.100% f5% BA4 GAS %/ % -0,100%, CM2% BA5 BA % [ % % BA6 BA % %.0100% % BA7 FRi : % % FRI FR % 0.120% ~ FR2 FR3 J 5.0% ] I _ I 0100%I. 3.00J % 110.)- tail i.fn d WP. dnnl I Hig 01 a.i, in ".ii Construction Management Consultants Page mn3/s

107 B. Wastewater flow calculations Y ear 2000 District # Ward Area Population Density Pop. WS Conn. hh w ST [hal I#; [pen/hal [%l IN1 [%] Hai Chau District I Hai Chau I 85 21, % 16,281 90% 2 Hai Chau II 51 18, % 17,555 90% 3 Thach Thang 68 20, % 15, /0 4 Thanh Binh 99 22, % 21,265 45% _ 5 Thuan _ Phuoc 46 12, % 9,231 60% 6 Phuoc Ninh 37 15, % 15,112 90% 7 Nam Duong 26 12, % 11,465 90% 8 Binh Hien 31 12, % 11,519 90% 9 Binh Thuan 86 15, % 14,261 90% 10 Hoa Thuan , % 13,117 75% I I Khue Trung , % 7,576 25% 12 Hoa Cuong , % 13,518 40% Thanh Khe District 13 An Khe , % 14,683 60% 14 ThanhLocDan , % 14,199 55% 1_5 Xuan Ha 67 20, % 19,188 65% 16 Tam Thuan 48 20, % 19,629 60% 17 Chinh Gian 63 16, % 16,105 90% 18 Vinh Trung 38 20, % 19,374 90% 19 Tan Chinh 36, 17, % 16,873 90% 20 Thac Gian 68 17, % 13,288 90% Son 1.L District 21 Tho Quang , % 11,730 45% 22 Man Thai , % 7,537 50% 23 Nai Hien Dong , % 9,869 55% 24 An Hai Bac , % 11,011 65% 25 An Hai Tay , % 11,249 65% 26 Phuoc My , % 7,313 40% 27 An Hai Dong , % 11,079 65% Ngu hanh Son District 28 Bac My An , % 17,188 55% 29 Hoa Quy , % 5,637 30% 30 Hoa Hai 337 9, % 4,974 30% Pop. WS Conn.: percentage and number of people having a water supply connection hh w ST: Households having a Septic Tank Construction Management Consultants Page 109 DHV, CDM and VTWASE

108 = Year 2010 District # Ward Growth Population Density Pop. WS Conn. hh w ST _ [%/yearl l#] [pers/hal [%/ [#l l%/ Hai Chau District I Hai Chau I 1.60% 25, % 25, % 2 Hai Chau n 1.60% 21, % 21, % 3 Thach Thang 1.60% 24, % 24, % 4 Thanh Binh 1.60% 26, % 26,235 80% 5 Thuan Phuoc 1.60% 14, % 14,426 90% 6 Phuoc Ninh 1.60% 18, % 18, % 7 Nam Duong 1.60% 14, % 14, % 8 Binh Fiecn 1.60% 14, % 14, % 9 Binh Thuan 1.60% 17, % 17, % 10 Hoa Thuan 1.60% 21, % % 1 Khue Trung 5.00% 17, % 17,630 60% 12 Hoa Cuong 5.00% 31, % 31,456 70% Thanh Khe District 13 An Khe 3.00% 28, % 28,190 80% 14 Thanh Loc Dan 2.50% 25, % 25,966 70% 15 Xuan Ha 1.60% 23, % 23,672 70% 16 Tan Thuan 1.60% 24, % 24,217 70% 17 Chinh Gian 1.60% 19, % 19, % 18 Vinh Trung 1.60% 23, % 23, % 19 Tan Chinh 1.60% 20, % 20, % 20 Thac Gian 1.60% 20, % 20, % Son Tra District 21 Tho Quang 2.00% 20, % 20,427 80% 22 Man Thai 2.00% 13, % 13,125 80% 23 Nai Hien Dong 2.00% 17, % 17,186 80% 24 An Hai Bac 2.00% 19, % 19,175 80% 25 An Hai Tay 2.00% 19, % 19,589 80% 26 Phuoc My 2.00% 12, % 12,735 80% 27 An Hai Dong 2.00% 19, % 19,293 80% Ngu hanh Son District 28 Bac My An 5.00% 39, % 39,996 80% 29 Hoa Quy 2.00% 13, % 10,994 60% 30 Hoa Hai 2.00% 12, % 9,700 60% Pop. WS Conn.: percentage and number of people having a water supply connection hh w ST: Households having a Septic Tank Construction Management Consultants Page 110

109 = Y ear 2020 District # Ward Growth Population Density Pop. WS Conn. hh w ST [oi%/yearl [#1 [pers/hal 1%[ 1 IN] 1% Hai Chau Distnct I Hai Chau I 0.90% 27, % 27, /% 2 Hai Chau II 0.90% 23, % 23, % 3 ThachThang 0.90% 26, % 26, % 4 Thanh Buih 0.90% 28, % 28, % 5 Thuan Phuoc 0.90% 15, % % 6 Phuoc Ninh 0.90% 20, % 20, % 7 NamrDuong 0.90% 15, % 15, % 8 Binh Hien 0.90% 15, % 15, % 9 Binh Thuan 0.90% 19, % 19, % 10 Hoa Thuan 0.90% 24, % 24, % 11 Khue Trung 3.00% 23, % 23, % 12 Hoa Cuong 3.00% 42, % 42, % Thanh Khe District 13 An Khe 1.50% 32, % 32, % 14 Thanh Loc Dan 1.10% 28, % 28, % 15 Xuan Ha 1.10% 26, % 26, % 16 Tam Thuan 0.90% 26, % 26, % 17 Chinh Gian 0.90% 21, % 1 21, % 18 Vinh Trung 0.90% 26, % 26, % 19 Tan Chinh 0.90% 22, % 22, % 20 Thac Gian 0.90% 22, % 22, % Son Tra District 21 Tho Quang 2.00% 24, % 24, % 22 Man Thai 2.00% 15, % 15, % 23 Nai Hien Dong 2.00% 20, % 20, % 24 An Hai Bac 2.00% 23, % 23, % 25 AnHai Tay 2.00% 23, % 23, % 26 Phuoc My 2.00% 15, % 15, % 27 An Hai Dong 2.00% 23, % 23, % Ngu hanh Son District 28 Bac My An 2.50% 51, % 51, % 29 Hoa Quy 2.00% 16, % 16, % 30 Hoa Hai 2.00% 14, % 14, % Pop. WS Conn.: percentage and number of people having a water supply connection hh w ST: Households having a Septic Tank Construction Management Consultants Page 111

110 I Hai Chau I 16 Tam Thuan 2 Hai Chau Chinh Gian 3 Thach Thang 18 Vinh Trung 4 ThanhBinh 19 Tan Chirnh 5 Thuan Phuoc 20 Thac Gian 6 Phuoc Ninh 21 Tho Quang 7 Nam Duong 22 Man Thai, 8 Binh Hien 23 Nai Hien Dong 9 Binh Thuan 24 An Hai Bac 10 Hoa Thuan 25 An Hai Tay 11 Khue Trung 26 Phuoc My 'i.i 12 Hoa Cuong 27 An Hai Dong RANHGIdTI-IANHP116 HAICHAUI 113 ANK 21 Khe Tn 28 Bac My An 14 12anh Loc Dan 29 Hoa Quv '.NH Gid PHIJONG ~ *{~ ~j~pjj~ ~ XUAN HA15 Xuan Ha 30 Hoa Hai 5IN THICHUANHANGC 17 THAN 25 ANHANTAY 7 NAMIAHAIN 19 THANCHLNH 27 ANTHAlI 2 HA 11~~~~~~~~~~U TQN oirisan I THN PH 1 HALCHA NI 18 VNH TRUN 26 NHU THOUAG 28BC M? A RANH HANH PH612 GIC Cosrcto sant angmn HOAI CHU I 13A KN2GHOUN 8 A?A Page V,CDMaSa Construction~~~~ ~~~~ Manaemen Consutant 17g CHN G1N 212 AA OLHON sat an 1HVRNG PHVO IN 8 2 PUOEM H SHN

111 n District # Ward Area Catchment VI lhal I II m IV V VIa Vlb Hai Chau District I Hai Chau % 39% 48% 2 Hai Chau n 51 58% 42% 3 Thach Thang 68 46% 54% 4 Thanh Binh 99 74% 26% 5 Thuan Phuoc % 6 Phuoc Ninh % 7 Nam Duong 26 48% 15% 37% 8 Binh Hien % 9 Binh Thuan 86 30% 70% 10 HoaThuan % 36% I1I Khue Trung 340 2% 12 Hoa Cuong 199 5% 1 Thanh Khe District 13 An Khe % 90% 14 Thanh Loc Dan % 1 5 Xuan Ha 67 6% 94%. 16 Tam Thuan 48 7% 90% 3% 17 Chinh Gian 63 28% 12% 60% 18 Vinh Tmng 38 6% _ 2% 10% 82% 19 Tan Chinh 36 36% 64% 20 Thac Gian 68 9% 29% 62% Son Tra District 21 Tho Quang Man Thai Nai Hien Dong An Hai Bac An Hai Tay Phuoc My 168 _27 An Hai Dong 178 Ngu hanh Son District 28 _Bac My An 605 _ 29 Hoa Quy Hoa Hai 337 _ Catchmnent area ral Catchmnent Pop ,906 19,536 56,917 29,128 68,068 23,118 67, ,384 22,896 66,709 34,678 79,777 27,455 84, ,075 25,043 72,961 38,411 87,285 30,704 94,973 Density [pers/hal Construction Management Consultants Page 113

112 District # Ward Area VII TX. fhal Vlla Vlb VIII IXa lxb IXc Hai Chau District I Hai Chau I 85 2 Hai Chau II 51 3 Thach Thang 68 4 Thanh Binh 99 5 Thuan Phuoc 46 6 Phuoc Ninh 37 7 Nam Duong 26 8 Binh Hien 31 9 Binh Thuan HoaThuan Khue Trung 340 0% 98% 12 Hoa Cuong I199 50% 45% Thanh Khe District 13 An Khe Thanh Loc Dan Xuan Ha Tam Thuan Chinh Gian Vinh Trung Tan Chinh Thac Gian 68 Son Tra District 21 Tho Quang 528 _10% 23% 22 Man Thai 145 9% 23 Nai Hien Dong % 90% _ 24 An Hai Bac % 10% r 25 An Hai Tay % 26 Phuoc My An Hai Dong % Ngu hanh Son District 28 Bac My An Hoa Quy 357 _ 30 Hoa Hai 337 Catchment area [hal Catchment Pop ,656 19,296-35,913 16,907 3, ,728 31,433-43,777 20,609 4, ,138 42,243 53,364 25,122 5,727 Density [pers/hal Construction Management Consultants Page 114

113 Diitrict # Ward Area X Xi XII rhal Xa Xb Xc Xla Xlb XIla XIlb Hai Chau District I Hai Chau I 85 2 Hai Chau n 51 3 Thach Thang 68 4 Thanh Binh 99 5 Thuan Phuoc 46 _ 6 Phuoc Ninh 37 _ 7 Nam Duong 26 8 Binh Hien 31 9 Binh Thuan Hoa Thuan Khue Trung Hoa Cuong 199 Thanh Khe District 13 An Khe Thanh Loc Dan Xuan Ha Tam Thuan Chinh Gian Vinh Trung Tan Chinh Thac Gian 68 Son Tra District 21 Tho Quang 528 _ 15% 52% 22 Man Thai % 23 Nai Hien Dong An Hai Bac % 25 An Hai Tay 120 3% 26 Phuoc My % 27 An Hai Dong % Ngu hanh Son District 28 Bac My An 605 3% 25% 41% 10% 21% 29 Hoa Quy 357 _33% 67% 30 Hoa Hai 337-7% 4% Catchment area [ha] Catchment _ Pop ,735 12,312 8,714 17,529 3,093 11,748 3, ,016 15,008 10,622 25,425 6,356 13,354 8, ,225 18,294 12,948 30,265 10,088 13,949 13,949 Density [pers/hal Construction Management Consultants Page 115

114 Catchment Population WS conn. Population WS conn. Population non-ws conn. Nr Area (ha) I % 100% 100% 52,949 71,384 78,075 7,957 U 70 75% 100% 100% 14,652 22,896 25,043 4,884 m % 100% 100% 51,987 66,709 72,961 4,930 IV % 100% 100% 24,058 34,678 38,411 5,069 V % 100% 100% 63,637 79,777 87,285 4,431 VIa 90 93% 100% 100% 21,438 27,455 30,704 1,680 VIb % 100% 100% 62,765 67,685 94,973 4,920 17,081 VIIa % 100% 100% 6,759 15,728 21,138 2,897 - VUb % 100% 100% 13,508 31,433 42,243 5,789 VIE txa % 100% 100% 25,139 43,777 53,364 10,774 - IXb % 100% 100% 11,835 20,609 25,122 5,072 cxc % 100% 100% 2,698 4,698 5,727 1,156 - Xa % 100% 100% 15,914 28,016 34,225 6,820 - Xb % 100% 100% 8,618 15,008 18,294 3,693 - Xc % 100% 100% 6,100 10,622 12,948 2,614 XIa % 100% 100% 12,270 25,425 30,265 5,259 - XIb % 95% 100% 1,977 6,042 10,088 1, XIIa 63 70% 100% 100% 8,224 13,354 13,949 3,524 XI[b % 89% 100% 2,266 7,949 13,949 1, Population WS-conn. percentage and number of people having a water supply connection Population non WS-conn.: number of people having NO water supply connection Catchment Industry (% of domestic) Service (% of domestic). Nr Area (ha) % 35% 35% 10% 15% 15% H 70 25% 30% 30% 15% 20% 20% mi % 30% 30% 15% 20% 20% rv % 35% 35% 15% 20% 20% V % 40% 40% 15% 20% 20% VIa 90 35% 40% 40% 15% 20% 20% Vlb % 40% 40% 15% 20% 20% VIIa % 30% 30% 20% 25% 25% VIlb % 35% 35% 10% 15% 15% VIm LXa % 35% 35% 15% 20% 20% IXb % 35% 35% 15% 20% 20% Dcc % 25% 25% 10% 15% 15% Xa % 40% 40% 20% 25% 25% Xb % 30% 30% 20% 25% 25% Xc % 25% 25% 10% 15% 15% Xla % 35% 35% 20% 25% 25% XIb % 25% 25% 10% 15% 15% Xlla 63 30% 35% 35% 15% 20% 20% XUb % 25% 25% 10% 1% 15% Construction Management Consultants Page 116

115 _ IUcap.d W/S: w w-factor I/cap.d non W/S: w w-factor: Catchment Domestic wastewater [I/sl Non-dom. wastewater [I/si Total wastewater [1/si Nr Area (ha) l II III IV V VIa VIb VlIa VIIb viii IXa lxb D(c Xa Xb Xc XIa XIb XlIa XIlb Construction Management Consultants Page 117

116 vietnam I hree Cities Sanitation Project Danang Sub-project (Phase I) From To Length Catchment Area Total av. Wastewater Contributing WWTP Street Nodel Node2 [ml [ha] yi/si Area [hal Hoa Cuong Ng thien Thuat 14/1 14/9 453 IV Duy Tan A /9 40 IV /9 14/9 14/ Vlla /15 SPS VIla A/ A/I Vlila A/6 ISPS14 68 VIla SPS14 15/ /1 15/2 45 Vlla /2 15/8 339 VIla /8 15/ Vlla /1 4 S VIla Future ext. 15A/1 SPS VIla SPS15 WWTP 710. From To Av. WW Node I Upstream WW Node 1 Total WW Node 1 WWTP Street Nodel Node2 [I/sus- [-s] ji/sj Hoa Cuong Ng thien Thuat 14/1 14/ Duy Tan A / /9 14/9 14/ /15 SPSI A/1 14A/ _ A/6 SPS SPS14 15/1 _. 15/1 15/ /2 15/ /8 15/ Construction Management Consultants Page 1 18

117 Vietnam I hree Cities Sanitatioinroject From To Av. WW Node I Upstream WW Node 1 Total WW Node I WWTP Street Nodel Node2 Il/sI [I/sI II/sI Hoa Cuong /14 SPS Future ext. 15A/1I SPS SPS15 WWTP I From To Peak WW Node I Flow from Upstream SPS Design WW Node 1 WWTP Street Nodel Node2 [l/s] [l/sl [UsI Hoa Cuong Ng thien Thuat 14/1 14/ Duy Tan A / /9 14/9 14/ /15 SPS A/1 14A/ A/6 SPS SPS14 15/ /1 15/ /2 15/ /8 15/ /14 SPS Future ext. 15A/1 SPS SPS15 WWTP Construction Management Consultants Page 119

118 v riornam 1 ce ities a-nitation -roject From To Length Catchment Area Total av. Wastewater Contributing WWTP Street Nodel Node2 [ml [hal [I/s] Area [ha] Son Tra Son Tra -2/3-2/2 157 Xa /2-2/1 210 Xa /1 2/1 206 Xa /1 SPS2 200 Xa A/1 2A/7 296 Xb A/7 2A/ Xb A/I1I SPS2 91 Xa SPS2 1/1 806 ManThai 1/1 1/9 432 Xb /9 1/ Xb /15 1/16 60 Xb /16 SPSI 271 Xb IA/I SPSI 377 Xb SPSI WWV/TP From To Av. WW Node I Upstream WW Node I Total WW Node I WWTP Street Nodel Node2 [I/s] [u/s] lus] Son Tra Son Tra -2/3-2/ /2-2/ /1 2/ /1 SPS A/1 2A/ A/7 2AJ W2A11I SPS SPS2 1/1 _ Construction Management Consultants Page 120

119 Vnrnmin TI hre itiessanitation Froject From To Av. WW Node 1 Upstream WW Node 1 Total WW Node WWTP I Street Nodel Node2 Il/sI Il/sI [Ils] Son Tra ManThai 1/1 1/ /9 1/ /15 1/ /16 SPSI IA/ SPSI SPSI WWTP From To Peak WW Node 1 Flow from Upstream SPS Design WW Node I WWTP Street Nodel Node2 [us] Il/s]. _sl Son Tra Son Tra -2/3-2/ /2-2/ /1 2/ _ = /1 SPS _ A/l 2A A/7 2A/ A/J I SPS SPS2 1/ ManThai 1/1 I1/ /9 1/ /15 1/ /16 SPSI IA/I SPSI SPS I WWVTP Construction Management Consultants Page 121

120 VlLnanM ThJee tities Nanitation Project From To Length Catchment Area Total av. Wastewater Contributing WWTP I Area Nodel Node2 Im] [ha] Ills] Area [ha] Ngu Hanh Son _ =- Han River 5/1 5/2 160 Xfla /2 SPS5 56 XHa A/I SA/2 210 Xlla A/2 SPS5 176 Xlla SPS5 33/ /1 33/2 180 Xlla /2 33/3 216 Xffa /3 SPS33 80 Xlla A/1 33A/ XHa A/1-1 SPS33 88 Xfla SPS33 SPS WW Pumps My Khe Xa SPS3 SPS Xa Bac My An Xla SPS4 SPS Furama Xla SPS34 SPS Xlb SPS35 G1D GID35 WWTP 298 Construction Management Consultants DHV, CDM and VRWASE Page 122

121 Vrieam Thlree Cities sanitation F'roject Additional Works Progran I From To Av. WW Node 1 Upstream WW Node I Total WW Node 1 WWTP I Area Nodel Node2 [u/s] Uls] _sl Ngu Hanh Son Han River 5/1 5/ /2 SPS AJI 5A/ A/2 SPS SPS5 33/1 33/1 33/ /2 33/ /3 SPS A/I 33A/ WW Purnps 33A/2 SPS SPS33 SPS35 MyKhe SPS3 SPS _ _ Bac MyAn SPS4 SPS34 Furama SPS34 SPS35 GID35 SPS35 GID35 WWTP Construction Management Consultants DHV, CDM and VlWASE Page 123

122 Vietnam Three CitiesS-nitationi Project Danang Sub-project (Phase I) From To Av. WW Node 1 Upstream WW Node I Total WW Node I WWTP I Area Nodel Node2 [l/sl _l/si lus] Ngu Hanh Son Han River 5/1 5/ /2 SPS AII 5A/ A12 SPS SPS / / / /2 33/ /3 SPS ( A/1 33A/ A/ SPS SPS33 SPS WW Pumps MyKhe SPS SPS Bac My An SPS SPS Furama SPS34 SPS35 _ SPS35 GID GID WWTP Construction Management Consultants Page 124

123 Detailed Design Rcport C.1 Cost comparison 2/9 Street A comparison has been made for the wastewater collection system of 2/9 Street between the investment cost of the original design - where the proposed system is separate and independent of the ongoing Phase I works - and an alternative - where the proposed system is integrated into the ongoing Phase 1 works. Table C. 1 shows the cost of the original design, where small diameter GIDs (14A, 15 and 15A) collect wastewater along 2/9 Street south of Tran Thi Ly bridge. Two large pumping stations (SPS14) and two long rising mains pump the wastewater collected from the area north of Duy Tan Street/Tran Thi Ly Bridge to Hoa Cuong treatment plant. A small pumping station (SPS 15) pumps the wastewater collected along the south end of 2/9 street to the Hoa Cuong treatment plant. Option Nr of HC.A Oia/pumnps unit Length/Nr Rate USD Total USD GID14A 200 mm m ,672 SPS14 large, 560 I/s 4 Nr 2 108, ,303 RM14 2x630 mm m ,093,822 GID mm m ,505 GID15A 200 mm m ,836 SPS15 medium, 19 I/s 2 Nr 1 25,247 25,247 RM mm m ,508 Total 1,498,892 Table C.1 Cost estimate of original design for wastewater system 2/9 street Table C.2 shows the cost of the integrated design, where the GID coming from the north of Duy Tan Street/Tran Thi Ly bridge is continued for another 558m to the south of Duy Tan Street/Tran Thi Ly bridge; from here the wastewater is pumped (SPS 14) to a large diameter GID further down the road. This GID is continued till the end of 2/9 Street from where a large pumping station (SPS 15) pumps the wastewater to the Hoa Cuong treatment plant. OpHon Dia/pumps prpof unit Length/Nr Rate USD Total USD GID mm m ,744 GID14A 200 mm m ,912 SPS14 large, 540 I/s 4 Nr 1 108, ,651 RM mm m ,500 GID mm m ,488 GID15A 200 mm m ,360 SPS15 large, 600 I/s 4 Nr 1 108, ,651 RM mm m ,850 Total 766,156 Table C.2 Cost estimate of integrated design for wastewater system 2/9 street The unit rates used in the cost estimate were derived from the cost items submitted by the contractor for the ongoing Phase 1 works. They were "normalized" to compensate inconsistencies in the bid prices, like higher costs for smaller pipes. Construction Management Consultants Page 125

124 C.2 Cost comparison Son Tra Beach area A comparison has been made for the wastewater collection system of the Son Tra beach area between the investment cost of the original design - where the proposed system is separate and independent of the ongoing Phase I works - and an alternative - where the proposed system is integrated with the ongoing Phase I works. Table C.3 shows the cost of the original design, where the redesigned Phase I wastewater construction works include a GID (#1) along the beach at the north-east side of Son Tra. Collected wastewater is to be pumped (by SPSU/RM1) to WWTP Son Tra. The additional works program includes a GID (#2) to the south side of GID1. Collected wastewater is to be pumped over great distance (by SPSl/RM1) to WWTP Son Tra. Opthi Dia/pumps Nrof unit Length/Nr Rate USO Total USO Northern System GID mm m ,600 GID 1A 200 mm m ,604 SPS 1 Medium, 40 I/s 2 Nr 1 25,247 25,247 RM mm m ,018 Added system GID 1X 200 mm m ,040 GIDlAX 200 mm m SPSlX Medium, 30 I/s 2 Nr 1 25,247 25,247 RM1X 200 mm m ,000 GID2 u/s 315 mm m ,132 GID 2 d/s 400 mm m ,600 GID 2A 315 mm m ,956 SPS2 Medium, 90 I/s 3 Nr 1 40,531 40,531 RM2 to WWTP 400 mm m ,600 Total 738,575 Table C.3 Cost estimate of original (re-)design for wastewater system Son Tra beach area Table C.4 shows the cost of the integrated design, where for the North-east Son Tra area it would be more efficient to have the wastewater from GID2 pumped (by SPS2/RM2) to GIDI where it flows under gravity to SPS1, from there the wastewater from GID I/GID2 is pumped to WWTP. Option option Nr of Dia/pumps pumps unit Length/Nr Rate USD Total USD GID mm m ,347 GID 1A 200 mm m ,604 SPS 1 large, 146 I/s 3 Nr 1 70,417 70,417 RM mm m ,214 GID 2 u/s 315 mm m ,132 GID 2 d/s 400 mm m ,600 GID 2A/2 315 mm m ,956 SPS2 medium, 90 I/s 3 Nr 1 40,531 40,531 RM2 315 mm m ,316 Total 632,117 Table C.4 Cost estimate of integrated design for wastewater system Son Tra beach area Construction Management Consultants Page 126

125 D. Geotechnical investigations Construction Management Consultants Page 128

126 LOCATION OF BORE HOLE & SPT POINT - VI TRI LO KHOAN VA DIEM XUYEN XUAN HOA DRAIN - TUYEN C6NG THOAT NU'OC MJA XUAN HOA XH10 'XH8 XH7 N- XH6 XH5 KH4XH4 -a -. a~xh3 NOTE - GHI CHO * BORE HOLE - LO KHOAN - H2 * SPT POINT - DIEM XUYEN DONG -XH1 XH 1

127 BIEU DO THI NGHIEM XUYE,N DONG Cong trinh: Tuyen cong thoat nucrc Xuan Hoi (Dien Bien Phu' - Tran Cao Van) NgAy thifc hien:0 1/08/2003 Ddn vi thgc hien:vien Quy hoach XMy dung thanh Pho Da Nang Vi tri va so hieu:xhi Th6ng so k' thuat: Khoi lttong bua: 4.5 Kg Chieu d ai can: 120 cm Khoi ludng dau n6i: 0.1 Kg Chieu cao bua rdi: 30 cm Khoi lucng can: 1.5 Kg DO6ng kinh can: 0.12 cm Khoi ludng de, can tri1ot Kg Dien tich mui xuyen: 3.86 cm- 0 So bua(n) , I -350 '~~~~~~~~~~~~: == 1 ' T j _-; == X - cr ~~rt I =r : i _-.

128 BIEU DO THI NGHIEM XUYEN DONG C6ng trinh: Tuyen cc5ng tho6it nttdc Xudn Hoa (Dien Bi&n Phu' - Tran Cao Vin) Ngay thtuc hien:0 1/08/2003) Don vi thl!c hi~n:vidn Quy hoach Xdy dtung thainh Pho6 Di Nd5ng Vi tri v~i so' hieu:xh2 Th6ng so' k~ thuat: Kho6i Iiuong bda: 4.5 Kg Chieu daii c-an: 120 cm Kh-oi ILtdng d'au n6i: 0. I Kg Chieu cao biia roi: 30 cm Kho6i hfdng can: 1.5 Kg Duding k-inh can: cm Khoi hlung de, can truiot Kg Di~n tich mei xu.v&n: 3.86 cm- 0'' So btia(n) i **-750 _i ~-800

129 BIEU DO THI NGHIEM XUYEN DONG CBng trinh: Tuyen cong thoat niudc Xuan Hoa (Dien Bien Phu - Tran Cao V3n) Ngay thtuc hien:01/08/2003 Ddn vi thurc hien:vi&n Quy hoach Xay dttng tharnh Pho5 Da Nang Vi tri va so hieu:xh3 Th6ng so ky thuat: Khoi ltung bua: 4.5 Kg Chieu dai can: 120 cm Khoi luong dau n6i: 0. 1 Kg Chieu cao bua rdi: 30 cm Khoi ludng can: 1.5 Kg Dut6ng k-inh can: 0.12 cm Khoi hlfong de, can trudt Kg Dien tich mui xuyen: 3.86 cm S6 bua(n) ~ ~ ~ ~~~~~R _ _, I: ,.., ! ~-800

130 BIEU DO THi NGHIEM XUYEN DONG Cong trinh: Tuyen cong thoat nudc Xuan Hoa (Di8n Bien Phu - Tran Cao Van) Ngay thic hien:01/08/2003 Ddn vi thilc hien:vien Quy hoach Xay dung thanh Pho Da Ning Vi tri va so hieu:xh4 Th6ng so ky thuat: Khoi ltdng bda: 4.5 Kg Chieu dai ca-n: 120 cm Khoi lucdng dau n6i: 0. 1 Kg Chieu cao bua rdi: 30 cm Kh6i ILcsng can: 1.5 Kg Du6ng kfnh can: 0.12 cm Khoi ludng de, can trucdt 1.16 Kg Dien tich mui xuyen: 3.86 cm EE s6 bua(n) so- I ~~~t.t,a I S _ t i -400 I = I: r I I f II, j._ f f, I I I } 1~~ t ~ 4 i f 1 '-- 1 i- l---e-s----3-; I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ --- L -=--r i L----I,E

131 BIEU DO THI NGHIEM XUYEN DONG Cong trinh: Tuyen cong thoat nudc Xuan Hoa (Di?n Bidn Phu' - Tran Cao Van) Ngay thifc hien:01/08/2003 Don vi thuc hien:vi6n Quy hoach Xay dung thanh Pho Di Nang Vi tri va so hieu:xh5 Th6ng so ky thuat: Khoi kldng bua: 4.5 Kg Chieu dai can: 120 cm Khoi lufcng dau noi: 0.1 Kg Chieu cao bua rdi: 30 cm Kh6i ILdng can: 1.5 Kg Du6ng kinh can: 0.12 cm Khoi ludng de, can trijdt 1.16 Kg Dien tich mdi xuyen: 3.86 cm' S6 biia(n) ,~~~~~~~~ ~~~~~~~~~~~~~~ =3 T- -T-- j -- '3-- ;i I I I i > f +i ;-4-i i t-t ;- L' = - -H ~~~~~~~~~ _, I t: i s I _R_; r r= < = : f: 4 -i -3: I-I

132 BIEU DO THI NGHIEM XUYtN D6NG Cong trinh: Tuy6n cong thoat nudc Xuan Hoa (Di?n Bien Phu' - Tran Cao Van) NgAy thgc hidn:02/08/2003 Don vi thic hi8n:vi8n Quy hoach Xay dtung thanh Pho6 Di Nang Vi tri va s6 hiedu:xh6 Th6ng so ky thuat: Kh6i liong bua: 4.5 Kg Chieu dai c-an: 120 cm Khoi liong dau n 6 i: 0.1 Kg Chieu cao bua rdi: 30 cm Khoi luiing can: 1.5 Kg DItl6ng kinh can: 0.12 cm Kholi ludng de, can trudt 1.16 Kg Dien tich mdi xuyen: 3.86 cm 0-50 S6 bua(n) E T =I IT -I - I I _ttei= _ =F ~~~~~~I= - +- I -=--L:t t i : =i3 50T -. I j ---- I I F I ~ ~ ~ ~ ~~~~~~~~~~ I :=0 II -600 I L *,: f _- --:-- wi r8...

133 BItU DO THI NGHItM XUYtN DONG Cong trinh: Tuyen cong thoat nudc Xuan Hoa (Dien Bien Phu - Tran Cao Van) Ngay thic hien:02/08/2003 Dan vi thuc hien:vidn Quy hoach Xay dutng thanh Pho Di NLng Vi tri va so hieu:xh7 Th6ng so' ky thuat: Kh6i lhidng bua: 4.5 Kg Chieu dai can: 120 cm.kho'i lfong dau noi: 0.1 Kg Chieu cao bua rdi: 30 cm Khoi Iludng can: 1.5 Kg D)Udng kinh can: 0.12 cm Khoi Wldng de, can trntdt 1.16 Kg Dien tich mdi xuven: 3.86 cmz So blia(n) o 0I -50*..- i..;..-- i, 1---{-l- -100* I _ i-,f--l..x _ = -700-,,

134 BIEU DO THI NGHItM XUYtN D6NG Cong trinh: Tuyen cong thoat nurdc Xuan Hoa (Dien Bien Phu' - Tran Cao Van) Ngay thilc hien:02/08/2003 Ddn vi thiic hien:vien Quy hoach Xay dutng thanh Pho Da Nang Vi tri va so hieu:xh8 Th6ng so ky thuat: Khoi lhdng bua: 4.5 Kg Chieu dai c-an: 120 cm Khoi ludng dau n6i: 0.1 Kg Chieu cao bua rdi: 30 cm Khoi lidng can: 1.5 Kg Dtu8ng kinh can: 0.12 cm Khoi lidng de, can trdft 1.16 Kg Dien tich mui xuyen: 3.86 cm 2 So bua(n) i = =t= 0.. L 4 I i f = ~ _- + = i i _T

135 BIEU DO THI NGHItM XUYPN DONG Cong trinh: Tuyen cong thoat nu'dc Xuan Hoa (Dien Bien Phu' - Tran Cao Van) Ngay thuc hien:02/08/2003 Ddn vi thiuc hien:vien Quy hoach Xay dupng thanh PhOa DA Nang Vi tri va so hieu:xh9 Thong so ky thuat: Khoi lucong bua: 4.5 Kg Chieu dai can: 120 cm Khoi ludng dau n 6 i: 0.1 Kg Chieu cao bua rdi: 30 cm Khoi ludng can: 1.5 Kg Du6ng kinh can: 0.12 cm Kh0i ludng de, can trudt 1.16 Kg Dien tich mui xuyen: 3.86 cm So bda(n) =>=~I; i; j _ 3 I ~~~~~~~~~I I!, F r - T 1-T -1=_C!!0I = i: {' ; ~~~~~~~~- -T - I I- fl};i r I J -700 *~

136 BIEU DO THI NGHIEM XUYtN DONG Cong trinh: Tuy6n cong thoat nudc Xuan Hoa (Di8n Bi8n Phbu - Tran Cao Van) Ngay thuc hien:02/08/2003 Dcin vi thuc hi6n:vi8n Quy hoach Xay dtrng thanh Ph0 Oa Nang Vi tri va so hieu:xh10 Th6ng so k9 thuat: Khoi ltqng biia: 4.5 Kg Chi6u dai can: 120 cm Khoi lcing dau n6i: 0.1 Kg Chi6u cao bua roi: 30 cm Khoi lidng can: 1.5 Kg Du6ng kinh can: 0.12 cm Khoilacrng de,cantracit 1.16 Kg Di6ntichmiiixuyen: 3.86 cm 2 So bua(n) I I I #'t' O t -I = i _It! f I _H:_

137 n o C>> - 0 A 0, O H o :< O L 64 n X F9 0 0:- _ 1- X o { ~~DoE.l S umi D - r CO W, DOsS cb" - p-x00 o. l t.* o c auz DO sfu 8 X (in) ~ ~ ~ O 0~~~~~~ _ h~... Dia chi o 0~~~--

138 HINH TRU LO KHOAN SO H.tU: LK2(XH5) CONG TRINH TUYgN C6NG TmOAT NIJCC xuan HA CAO D0 M!JC NUdC NGAM: M CAO DQ L6 KHOAN GIA DiNH:0.00 M DUONG KINH L6 KHOAN: I 10 MM DO SAU L6 KHOAN: 5.0 M TY L : 1/50 STANDARD PENETRATION TEST MO TA DAC DIM LOAIDT NtN o E N N.ddSPTthcoebidu u Dat hbru ca, r cay muc, xac thiic vat o.ootrang thmi chay Cat min mau xam, xam sam, xim trang nau vang, trang thai bao hoa k6t ca'u reii rac : 017Ot 1 C ; 8: E t170 Cat bui,cat pha loang 1o nau vang, nau d, v&t xam lici, xdm trang, xam nhat Trang thai bao hoa I I I I ket c^au rdi rac den chat vcra ~ ~5.0C l l 1l l t {

139 HINH TRU LO KHOAN SO HItU: LK3(XH6) CONG TRINH TUYgN C6NG THOAT NJ(dC XUAN HA CAO D0 M1VC NTJOC NGAM: M CAO DO L6 KHOAN GIA DuNH :0. oom DUNG KfNH L6 KHOAN: 10 MM DO SAU L6 KH4OAN :5.0 M TY' L: 1/50 STANDARD PENETRAnON TEST MO TA DAC Dlf M LOAI DAT NtN O E u E N N.d6SPTtco.j GC7. cd t min xam den(idp b mat hoa MA u) trang thadi am tr6t 04 ~ 0,4 - to -.-: _ Cdt mm mau xdm, Xdm tring trang thai bao ho: ket cau rdi rac cho den chat via OC

140 HINH TRU LO KHOAN s6 HI2U: LK4 (XH7-vi trf tr&n m6p luy mucdng dat do hien tai) CONG TRINH : TUY N C6NG THOAT NUI1C XUAN HA CAO D0 MVC NTJdC NGAM: M CAO DO L6 KHOAN GIA DTNH: 0.00 M DUdNG KtNH L6 KHOAN: I1o MM DO SAU L6 KROAN :5.0 M TY L4-1/50 STANDARD PENETRATION TEST MO TA DAC DIM LOAI DAT NN o 0 E u N N.d6SPTtbeocbdusAu ma U _ I _ ~~~~~ Da't dd, thanh phan :cat min, A cat xen Ian gach vun, da dam mau nau Da't h0u cci, t.hanh phan gan mcat min... xam den, xac re cay huu cd. k6m chat (ldp ber mlt mircrng nu'dc ngqp hien tai c cat min, c t vira mau xam, xam sam, xam trlng, xam den trang th i bao hoa. ket ca'u k~~tc ur~~iirac rdi rac3.0-30; *: f r cat rmin, cat vlfa mau x m, xam sam, xam crang,trang thai bao hoa ke't c au rdi rac cho den chat vira S 11_',, I

141 0~~~~~~~~~~~~~~~ 0 ~~~:. wlt iipi cr Ct~~~o. 0 r ( O', >4 ~0 0LA Z( C =7- C~~~ - :3-0 r) :-3(i) 0 < '- uq ~ ~ ~ D~* _ I ~~~~~~ z C>C) C) 0~~~~~~~~~z DO -U C)> L0 m u d Do Hsu 0.~ ~ ~

142 CONG TRIN:T WVI TR & M XUYEN DONG VI TRI LO KHOAN NC COTHOAT NLC ANKHE \ > - 7 ; z~~~~~~~~~v TRf XUYtN D6NZ CHU GIAI O DIEM DIgM XUYftN DONG

143 Cong trinh: TuyLn thoit nudc AnKhe Ngay thtc hien:30/07/2003 BIEU DO THI NGHIEM XUYtN DONG Ddd vi thuc bi8n:vien Quy hoach Xay duong thanh Ph6: Da Nang Vi tri va so hieu:ak I Th6ng so ky thuat: Khoi luidng bua: 4.5 Kg Chieu dai can: 120 cm Kh6i ludng dau noi: 0. 1 Kg Chieu cao bua rdi: 30 cm Khoi lutdng can: 1.5 Kg Duidng kinh can: 0.12 cm Khoi Iludng de, can trtdt Kg Dien tich mui xuyen: 3.86 cm: 0 S6 bua(n) I oo L i l 18 ~~~~~I t I I I400- I M I t, f -r ' SI -j;- j'0 'i -_ 4 r - j J F z ; } :-t- -' ===; -~~~~~~~~~~~I f -700 '_: - * T ;'13-~1f. i, i, i5ii S! : =],, + 4 p fi 4. t E 1---~8 -

144 BItU DO THI NGHIPM XUYtN D6NG Cong trinh: Tuyen thoat nifdc An Kh8 Ngay thuc hien:3 1/07/2003 Ddn vi thutc hien:vien Quy hoach Xay dnsng thanh Pho Di Nang Vi tri va so hieu:ak2 Thong so ky thuat: Khoi lhdng bua: 4.5 Kg Chieu dai can: 120 cm Khoi ltrdng dau noi: 0. 1 Kg Chieu cao bua rdi: 30 cm Khoi lhfdng can: 1.5 Kg DL[6ng kinh can: 0.12 cm Khoi ludng de, can trtudt 1.16 Kg Dien tich mui xuyen: 3.86 cm' S6 btia(n) i=: 1- > = - ; - --i t ; $ i --! I - i_ JVJ =t = 1 =~~~~I j ft I j7 I -100I I == i i i -350 i- ; *4 S f 0r ~I f -50- === ~~~~~~~~~I F\ = I >

145 BIEU DO THI NGHIEM XUYE'N DONG Cong trinh: Tuyen thoat nitfc An Khe Ngay thgc hien:3 1/07/2003 DcIn vi thuc hi8n:vien Quy hoach Xay dung thanh Pho DO Nang Vi tri va so' hieu:ak3 Th6ng so ki thuat: Khgi litdng bua: 4.5 Kg Chieu dai can: 120 cm Khoi ludng dau noi: 0.1 Kg Chieu cao biia rdi: 30 cm Khoi Iidng can: 1.5 Kg DtI8ng kinh can: 0.12 cm Khoi ILudng de, can trudt 1.16 Kg Dien tich mdi xuyen: 3.86 cm 2 S6 bia(n) O~~~~~~~~~~,I I f -I t I g_w t i t ' j i ' t == i -550 _ ~- -65 =F

146 BItU DO THI NGHItM XUYtN DONG C6ng trinh: Tuyen thoat nudc An Kh8 Ngay thi4c hien:3 1/07/2003 Don vi thuc hien:vien Quy hoach Xay dung thanh Pho Da Nang Vi tri va so hieu:ak4 Th6ng so ky7 thuat: Khoi Ithdng bua: 4.5 Kg Chieu dai can: 120 cm Kh6i lutdng dau noi: 0. 1 Kg Chieu cao bua rdi: 30 cm Khoi Itrdng can: 1.5 Kg Dtf6ng kinh can: 0.12 cm Khoi lttdng de, can trtdt 1.16 Kg Dien tich mui xuyen: 3.86 cm2 S6 bua(n) I ; r I I T ~~~~I I. I =-_ I ~~~4=== == = -00i i 30 _, f -f I I I I g;1 t l I I ~ ~~~I 4. i l I i j _ I l t i t t i I i leif if i[t [;j -400-

147 Cong trinh: Tuyen thoat ntldc An Khe Ngay thttc hien:3 1/07/2003 BItU DO THI NGHItM XUYPN DONG Ddn vi thfc hiien:vien Quy hoach Xay dttng thanh Pho Di Ning Vi tri va so hieu:ak5 Th6ng so ky thuat: Khoi LuOng bua: 4.5 Kg Chieu dai c-an: 120 cm Khoi Iiodng dau noi: 0. 1 Kg Chieu cao bua rdi: 30 cm Kh6i ludng can: 1.5 Kg Dudng kinh can: 0.12 cm Khoi ludng de, can tlfdt 1.16 Kg Dien tich mdi xuyen: 3.86 cm S6 btia(n) i t- ~~~~~~~~~~~~~I =et I "- t :- - it -300 I II H t E _g -800 I1 txtwxm -it T-WtW

148 BItU DO THI NGHIEM XUYftN DONG Cong trinh: Tuyen th6at nut6c An Khe Ngay thutc hien:3 1/07/2003 Odn vi thulc hien:vien Quy hoach Xay ditng thanh Pho Da Ning Vi tri va so hieu:ak6 Th6ng so ki thuat: Khoi lutdng bua: 4.5 Kg Chieu dai can: 120 cm Kh6i litdng dau noi: 0.1 Kg Chi6u cao bua roi: 30 cm Khoi Ildng can: 1.5 Kg Du6ng kinh can: 0.12 cm Khoi lutong de, ca-n truiot 1.16 Kg Di8n tich miixuyen: 3.86 cm So bua(n) T I. * I T I. I. -50, I _ I I I I -300.~~ ~~~ I t I j l i I: I i I -i -1 - i-i - i i- _ tr;v -i i i---. I!_--,:i- l, ji= = : m ---- S l-t- - t i : = ~~~rr -- I i -I-8J}t00