DOORNVALLEI EXT 5 & 6

Transcription

1 DOORNVALLEI EXT 5 & 6 Proposed township establishment on portion 107 the farm Doornkloof 391 JR Sewer Pipe Crossings - Sesmylspruit Construction Method Statement April 2016 Revision 3 PREPARED FOR: PREPARED BY: M&T DEVELOPMENT (PTY) LTD ECO COURT (FIRST FLOOR) 340 WITCH-HAZEL STREET CENTURION 0169 TEL: (012) FAX: (012) LV & PARTNERS OFFICE 10, 3 rd FLOOR 476 KINGS HIGHWAY LYNNWOOD 0081 TEL: (012) FAX: (012) Prepared by LV & Partners 7 April 2016 Page 1

2 TABLE OF CONTENTS 1. INTRODUCTION BACKGROUND DESCRIPTION OF THE PROJECT;;;;;;;...;;;;;;;;;;;;;;; PURPOSE OF THE METHOD STATEMENT ROLES AND RESPONSIBILITIES CONSULTANTS RESPONSIBILITIES CONTRACTOR RESPONSIBILITIES TYPICAL STREAM CROSSING CONSTRUCTION METHOD TO BE EMPLOYED GENERAL SESMYLSPRUIT STREAM GENERAL CONDUCT AND SITE MANAGEMENT STREAM CROSSING QUALITY MANAGEMENT MANAGEMENT OF CONSTRUCTION CAMPSITES AT RIVER CROSSINGS REHABILITATION MONITORING AND AUDITING Prepared by LV & Partners 7 April 2016 Page 2

3 1. INTRODUCTION 1.1 BACKGROUND LV & Partners was appointed by M-T Development (Pty) Ltd on 25 February 2008 to investigate bulk water and sanitation infrastructure options for a new development known as Doornvallei X 5 & 6 on land known as portion 107 of the farm Doornkloof 391 JR. Preliminary investigations and discussions with the City of Tshwane revealed that 2 sewer connections across the existing Sesmylspruit will be required. The topography of the area includes a watershed line running in a north-south direction dividing the land in 2 halves. The western half (Extension 6) drains in a north-western direction and the eastern half (Extension 5) in a north-eastern direction. A sewer connection across the Sesmylspruit is required on the western side, and another on the eastern side. An existing sewer pipe crossing the Sesmylspruit on the western side is currently not operational due to lack of maintenance and neglect. In order to avoid environmental damage, it is recommended that the new proposed sewer connection on the western side be installed as a matter of urgency. The existing sewer pipe connection may then be removed and/or blocked off. 1.2 DESCRIPTION OF THE PROJECT Following discussions with the Department of Water and Sanitation, and after considering various options, it was decided to cross the Sesmylspruit by means of a weir structure in both locations east and west. A sleeve at the required slope inside the weir structure facilitates the sewer pipe crossing and allows the sewer pipe to be installed via the sleeve. Refer to drawing number 15-DOORN-X5&6-CIV-SEW PURPOSE OF THE METHOD STATEMENT The Department of Water and Sanitation (DWS) requires a method statement / management plan for the crossing of the Sesmylspruit Stream for dispensing of the water use license application in terms of section 22(3) of the Water Act. Due to the ecological importance and sensitivity of all natural water courses and their flood plains, it is essential that minimal damage is incurred through construction activities. It is therefore essential that construction activities are undertaken in such a manner that minimal impact results on the water resource. Prepared by LV & Partners 7 April 2016 Page 3

4 The purpose of this method statement is to guide construction activities at the stream crossing to achieve this objective, to set environmental standards for the construction of the weir and to minimize the risk of damaging and impairing natural ecosystems and environmental quality. This method statement should become part of the tender specifications to ensure that provision is made and incorporated at the start of construction activities. The contractor should be legally required to comply with the standards set out in the Stream Crossing Construction Method Statement. 2. ROLES AND RESPONSIBILITIES 2.1 CONSULTANTS RESPONSIBILITIES Construction supervision by the consultant is undertaken on a part time bases for this project and therefore the day to day responsibility of effective environmental management will be directed to the Contractor. 2.2 CONTRACTOR RESPONSIBILITIES The contractor is responsible for all environmental management of the construction phase of the project. The contractor must define responsibilities, lines of communication and qualifications of staff responsible for environmental management on the project and the implementation of this method statement. 3. TYPICAL STREAM CROSSING CONSTRUCTION METHODS The construction methodologies listed below are guidelines for the contractor to enable him to construct the weir in an environmentally responsible manner. 3.1 GENERAL Various construction methods may be considered by the contractor, depending on the following factors: - Constraints by authorities and property owners, - Constraints based on the conditions set out in the Environmental Management Plan, - Constraints of this method statement, - Flow velocities and flow depths during construction and at peak flow conditions, - Prevailing geology, - Accessibility, and - Available technology Prepared by LV & Partners 7 April 2016 Page 4

5 3.2 SESMYLSPRUIT STREAM The proposed new sewer pipe crossings in the Sesmylspruit is located in the upper reaches of the Hartbeespoort Dam catchment area. The Sesmylspruit is a perennial stream and has a definite defined channel. Discharge volumes are controlled at the Rietvlei Dam. Construction should however preferably be done in the dry season when low flow is expected. The sewer pipe crossings can be reached either via Irene Glen Estate in the south, or via Cornwall Hill Estate in the north. It is recommended that the construction of both weirs be conducted from the south via Irene Glen Estate. The area south of the western weir and east of the eastern weir are open areas. The contractor will negotiate a suitable area for a camp site at each weir and the temporary stockpiling of excavated material with Irene Glen Estate. The location of each of the two concrete weirs should be isolated by diverting current flow patterns of the water in the river around the specific locations. This can be achieved by means of sandbags utilizing material from the site so as not to introduce foreign material to the site. The isolated areas should then be de-watered. This can be achieved by means of well pointing. Sufficient working space should be allowed for around each of the proposed structures. Remove debris, concrete elements, brick elements and clay deposits up to 500mm below the stream bed level and to the approved plan dimensions as shown on the approved construction drawings and stockpile the spoil material in the designated area. This material can also be spoiled at an approved site to be identified by the contractor. Excavation equipment and trucks will not be allowed to operate outside the designated areas as negotiated with Irene Glen Estate at the stream crossing. The in-situ material will then be trimmed and compacted with impact compaction equipment to the specified densities. The excavation should then be lined with a heavy duty Bidim layer and filled with 500mm dump rock up to the founding level. The grading of the dump rock is to be pre-approved, the Bidim material should be wide enough to be folded back over the dump rock and firmly stitched in position as shown on drawing number 15-DOORN-X5&6-CIV-SEW-300. The foundations shall be excavated, and the holes be kept clean of debris and water until the foundations have been cast and the concrete hardened. Prepared by LV & Partners 7 April 2016 Page 5

6 Once the foundations are in place, each of the new weirs can be built and backfilling and compaction of stockpiled in-situ material (from the foundation excavations) will commence. This backfilling will be done up to the natural stream bed levels. The contractor shall take satisfactory precautions to ensure that the shuttering and scaffolding required for construction will not result in pollution of the site. Should any flow in the system occur, it is not to be reduced at any time to ensure that the downstream riverine system functionality is maintained. After the sewer pipe crossings have been constructed, all material shall be disposed of at an approved dumping area and the stream, in the construction area, shall be restored to its natural condition. In this regard special mention is made of ensuring the following: - Ensure that no upstream ponding occurs, - Ensure that turbulent flow creation is limited to prevent erosion, - Ensure that all sediment in the system due to construction activities is removed, - Ensure that all unnatural rock, concrete spoil and other rough surface material are removed from the stream bed. Prepared by LV & Partners 7 April 2016 Page 6

7 4. GENERAL CONDUCT AND SITE MANAGEMENT 4.1 STREAM CROSSING The contractor is responsible for controlling riparian and instream damage to the stream that will be crossed. Construction shall be halted in the event of aquatic organism stress caused by the works, until adequate controls are put in place The contractor must prepare a detailed method statement that will include, but not be limited to: - a biophysical description of the site, - timing and duration of stream crossing construction, - an itemized list of the equipment to be used for the stream crossing, - measures to maintain flow in the system throughout the construction period should any occur, - A description of the design and methods for the creation of any stream diversions, - measures that will be used control sediment and turbidity, spillage of fuel and cement; and a monitoring programme to provide rapid feedback on the effectiveness of controls, - measures that will be used to minimise the impact of blasting (if any) on aquatic species During construction the contractor must make provision to maintain the natural flow of any drainage line affected by construction In excavating the bed of the water body, the contractor must backfill the excavation with material which was originally removed from the stream bed. Further care must be taken to minimize the amount of material used for backfill which have abrasive surfaces Where isolating the location of a works, the following measures, amongst others, may be considered by the contractor in order to minimize the risk of increased suspended sediment in the water column downstream of the works: - Elimination of surface flow through the construction site, Prepared by LV & Partners 7 April 2016 Page 7

8 - In cases where the entire flow of water of a water body is diverted around the water crossing site, it must be returned to the water body immediately downstream of the crossing site, - The use of silt fences or hay bales to isolate the construction area from the water body in situations where the flow velocities and volumes are low, - The treatment of any water removed from the isolation area, prior to discharge into the downstream water course, to remove suspended sediment The contractor must monitor the effect of construction on downstream, sediment loads when flow is occurring. The monitoring program shall include sampling in the water upstream and downstream of the works during the period when construction in the stream is taking place. The details of the sampling program shall include, as a minimum, a provision of two samples per day (1 upstream, 1 downstream at a distance of 50m from the construction works) for the duration of the stream crossing works. The samples shall be analyzed by a reputable water laboratory for total suspended solids and turbidity, using recognized methods of determination, and the results shall be presented on the same day as the sample was taken. Sampling times shall be selected to correspond with any periods of higher sediment load The contractor must not remove any vegetation within the flood plain area, other than that which is absolutely necessary along the construction route The construction area is to be defined and any areas beyond the construction area are to be cordoned off with danger tape and designated as no go areas for personnel and construction vehicles The contractor must manage all temporary construction roads in or adjacent to flood plain area so as to disperse run-off and avoid concentrating water flows Prepared by LV & Partners 7 April 2016 Page 8

9 4.2 QUALITY MANAGEMENT The contractor must employ such up to date techniques, practices and methods of construction that will ensure compliance with this standard and, in general, minimise environmental damage, control waste, avoid pollution, and prevent loss or damage to natural resources The contractor must prevent or minimize the occurrence of accidents which may cause damage to the water environment, prevent or minimize the effects of such incidents The ultimate responsibility for non-compliance with the standards in this method statement lies solely with the contractor. 4.3 MANAGEMENT OF CONSTRUCTION CAMPSITES AT STREAM CROSSINGS The contractor must comply with all relevant laws and regulations concerning water provision, sanitation, wastewater discharge and solid waste disposal The contractor may not establish any campsite within 100m of any water course The contractor must prepare documentation that specifies details pertaining to site layout, topsoil management, sewage treatment, solid waste disposal, erosion control, litter management, provision for vehicle and plant servicing, water supply, and rehabilitation The contractor must classify all hazardous material to be used on site according to recognized Codes of Practice such as SABS Code 0228 for the Identification and Classification of Dangerous Substances and Goods and the Department of Water Affairs and Forestry s Minimum Requirements for the Handling, Classification and Disposal of Hazardous Waste, and must ensure that the handling, storage, transport and disposal of these materials meets the requirements of these Codes At the stream crossing, the contractor must place on-site tools and equipment, such as pumps, compressors and generators on bermed impermeable sheeting to prevent Prepared by LV & Partners 7 April 2016 Page 9

10 hydraulic fluid or fuel leaks from contaminating soil or ground water or entering any water course or wetland The contractor must ensure that all equipment which is required to work in the stream is cleaned of oil, grease and other contaminants damaging to aquatic life The contractor must ensure that there is sufficient absorbent material available onsite to manage accidental spills. 4.4 REHABILITATION The stream embankment must be stabilized using re-vegetation to ensure that the embankments are protected against erosion Measures using indigenous grasses to permanently stabilize disturbed areas must be fully effective by the end of one growing season Debris disposal and clean up shall be carried out to return the water course to its pre- existing condition prior to construction. 5. MONITORING AND AUDITING Monitoring and auditing will be as per the Environmental Management Plan to the project. The Client, M-T Development (Pty) Ltd, must audit the contractors compliance through the appointment of an Environmental Control Officer (ECO) to monitor the impact of the project on the water environment. The responsibilities will include: - Monitoring the impact of the project on the water environment, - Audit compliance by the contractor with this method statement, - Prepare water environmental audit reports - Weekly inspections culminating into a monthly audit and report must be undertaken. - These reports will be forwarded to the DWS Regional Office. Prepared by LV & Partners 7 April 2016 Page 10

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