Engineering Services Report for. Proposed Student Housing Development. Westwood Hotel Site. Dangan, Upper Newcastle. Galway City

Transcription

1 Engineering Services Report for Proposed Student Housing Development Westwood Hotel Site Dangan, Upper Newcastle Galway City Client: NTM ROI Seed Capital LP Job No. A079 May 2018

2 Engineering Services Report For Proposed Student Housing Development Westwood Hotel Site, Dangan, Upper Newcastle, Galway City CONTENTS: 1.0 INTRODUCTION SCOPE OF WORKS SITE CONTEXT FOUL DRAINAGE STORM DRAINAGE FLOOD RISK ASSESSMENT POTABLE WATER SUPPLY 13 Appendix A Existing Drainage Records from Galway City Council Appendix B Pre-Development Enquiry to Irish Water Appendix C Irish Water Response to Pre-Development Enquiry Appendix D Attenuation Calculation Appendix E OPW Floodmaps Report This Report was prepared by CS Consulting Engineers for the benefit of its Client only. The contents of this Report are shared with interested parties for information only and without any warranty or guarantee, express or implied, as to the accuracy, reliability or completeness of its content. This Report cannot be relied on by any party other than the party who commissioned it. File Location: J:\A_JOBS\Job-A079\B_Documents\Reports\ESR Job Ref: Author Reviewed By Authorised Issue Date Rev No. A079 GL NB OS A Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report

3 Engineering Services Report For Proposed Student Housing Development Westwood Hotel Site, Dangan, Upper Newcastle, Galway City 1.0 INTRODUCTION Cronin & Sutton Consulting were commissioned by NTM ROI Seed Capital LP, in conjunction with a multi-disciplinary design team, to develop an Engineering Services Report (ESR) to accompany a planning application for the development will comprising of 63 apartments with 394 number student bedrooms to be constructed on the site of the existing Westwood House Hotel. It is proposed to demolish the existing hotel and construct the student accommodation together with a reception area, social spaces, storage areas, all ancillary facilities associated with student accommodation and a commercial retail/café space with 24 number car spaces, (10 permanent and 14 temporary for summer use), an access road, hard and soft landscaping areas etc. The purpose of this Engineering Services Report is to review the potential services available to develop the proposed subject lands. This report addresses drainage (both foul & storm), potable water and flood risk assessment items for the site. The development site is located within the curtilage of Galway City Council (GCC) and is located to the west of the junction of the Upper Newcastle Road and the Thomas Hynes Road (N59), see Figure 1 for site location map. The remainder of the site is bounded to the Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 1

4 south and east by the Tudor Lawn and Dun Daingean residential estates respectively. The total site area of the development is approximately 8,797 sqm (0.88 Ha) and is predominately hardstanding in the form of the existing hotel structure and 97 car parking spaces and access roads. Approximately 2,000m 2 of a greenfield area exists on the site and is predominately situated to the southern quarter of the site. Figure 1 Location of the Proposed Development Site (map data & imagery: Google) A full description of the scheme is outlined in the Planning Report prepared by McCarthy Keville O'Sullivan Ltd. and this report should be read in conjunction with all other documents and drawings submitted with this planning application. Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 2

5 2.0 SCOPE OF WORKS Cronin & Sutton Consulting were commissioned by NTM ROI Seed Capital LP to prepare the following Engineering Services Report to accompany a planning application for the site at the Westwood House Hotel, Galway City. In compiling this report CS Consulting liaised with a number of third parties, namely: Galway City Council, Irish Water, Clients representatives & Design Team. In preparing this report the site was visited and assessed. No intrusive on site testing was carried out and all conclusions indicated in this report were based solely on desk top information. 3.0 SITE CONTEXT 3.1 Site Description The total site area of the development is approximately 8,797 sqm (0.88 Ha) The status of the is existing site is predominately hardstanding in the form of the existing hotel structure and car parking spaces and access roads, however approximately 2,000m 2 is greenfield situated to the southern quarter of the site. The topography of the existing site is relatively flat with a small fall southward with ground levels along the northern boundary at 15.9m OD, falling to 15.25m OD on the southern boundary (Note all levels to Malin Head Datum). Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 3

6 4.0 FOUL DRAINAGE 4.1 Existing Foul Drainage Infrastructure Records obtained from Galway City Council (Appendix A) indicate an existing 225mm public foul sewer running eastwards along the northern boundary of the development site, on the Upper Newcastle Road. From a topographical survey taken of the site the existing foul effluent of the hotel outfalls to this sewer. 4.2 Proposed Foul Drainage Infrastructure The proposed development is to consist of 394 number student accommodation rooms, an office, launderette (for the student use only) and a retail unit. Due to the proposed layout of the new buildings, the existing foul outfall is deemed unfeasible to re-use and therefore a new foul network and outfall will be constructed to cater for the foul effluent generated. All foul effluent generated from the proposed development will be collected in pipes of 100mm, 150mm and 225mm in diameter and flow under gravity to the existing 225mm foul sewers on the Upper Newcastle Road a new manhole. The drainage network for the development will be in accordance with Part H of the Building Regulations and the connection manhole to the requirements and specifications of Irish Water. The proposed foul effluent generated by the subject lands will be completely separated from all surface water flows, including post-attenuation storm flows so here will be a minimal impact on the receiving drainage infrastructure. Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 4

7 A pre-development enquiry was issued to Irish Water Ltd (Ref: ) in respect to the proposed development and the response received from Irish Water confirmed that there was adequate capacity in the public network to cater for the peak foul discharge of 6.21 l/s from proposed development. A copy of the pre-development enquiry is included in Appendix B, with the respective response letter in Appendix C and the proposed foul water drainage infrastructure and routing plan is shown on drawings A included with this submission. CS confirm, following the grant of permission, the development will be constructed in one phase, with occupation of the development due in September Therefore, a connection to the Irish Water sewer network on the Upper Newcastle will be required before this date. There are no existing Irish Water assets traversing the development site, so there is no requirement for diversions or protection measures to be introduced. The existing 225mm foul sewer on the Upper Newcastle Road is also deep enough to withstand construction traffic loadings and we confirm no protection measures will be required. Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 5

8 5.0 STORMWATER DRAINAGE 5.1 Existing Stormwater Drainage Infrastructure Records obtained from Galway City Council (Appendix A) indicate a 375mm diameter public storm drain running eastwards along the northern boundary of the development site, on the Upper Newcastle Road. From a topographical survey taken of the site the existing surface water runoff of the hotel grounds outfall to this drain unattenuated. 5.2 Proposed Storm Water Infrastructure and SuDs CS consulting had preliminary discussions with Mr. Joe McGuire of the drainage department of Galway City Council and stated the existing development site discharged to the public network unattenuated. Mr McGuire confirmed he would no objections to the development if the existing discharge rate from the site could be reduced by 50%. Analysis carried out based on the topographical survey of the site, indicates a flow of 30 l/s currently discharging from the site for a 2-year return rainfall event. Based on the above, it is proposed to limit the surface water flow from the proposed development to 15 l/s (reducing the current flow by 50%). The total site area of the development site subject to re-development is approximately 8,797 sqm (0.88 Ha) with an internal hardstanding area of 5,100 m2 for the external roads, footpaths and roof areas. Based on these parameters the attenuation required for this development is 120 m 3 of storage for the 1 in 100 year storm event plus climate change (see Appendix D for calculations). Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 6

9 It is proposed to retain the storm water volumes in underground tanks (Aquacell Ltd or similar approved), 14.0 x 6.0 x 1.45m deep (120m 3 ) and to release the restricted storm water into the public 375mm diameter surface water drainage system on the Upper Newcastle Road. The last public manhole is to be constructed in accordance with Local Authority s requirements and the storm water flow will be restricted to 15.0 l/s by the use of a flow control i.e. a hydrobrake or similar approved. Additional SuDS features such as a swale to roadway, permeable paving to parking bays, gravel drains to footpaths and waterbutts will be provided to reduce the volume of surface water runoff entering the drainage network. The drainage network for the development will be in accordance with Part H of the Building Regulations and to best practices. The proposed surface water network will be completely separated from all foul water flows, including post-attenuation so there will be a minimal impact on the receiving drainage infrastructure. The proposed surface water drainage infrastructure and routing plan is shown on drawing A included with this submission. Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 7

10 6.0 FLOOD RISK ASSESSMENT 6.1 Level of Service There is an existing inherent risk of any flood event occurring during any given year. Typically, this likelihood of occurrence was traditionally expressed as a 1-in-100 chance of a 100-year storm event happening in any given year. A less ambiguous expression of probability is the Annual Exceedance Probability (AEP), which may be defined as the probability of a flood event being exceeded in any given year. Therefore, a 1 in 100 year storm event has a return period of 1% AEP flood event, similarly a 100% AEP can be expressed as a 1-in-1-year event. 6.2 The Planning System and Flood Risk Management, Guidelines for Planning Authorities set out the best practice standards for flood risk assessment in Ireland. These standards are summarised in Table 1.0 (extract from Guidelines document). Under these guidelines a proposed development site has first to be assessed to determine the flood zone category it falls under. Flooding Source Drainage River Tidal/Coastal Residential 1% AEP 0.1% AEP 0.1% AEP Commercial 1% AEP 1% AEP 0.5% AEP Water-compatible - >1% AEP >0.5% AEP (docks, marinas) Table 1.0 Summary of Level of Service Flooding Source. Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 8

11 6.3 Climate Change It is a requirement of Galway City Council and the Department of the Environment, Community & Local Government (DoECLG) flooding guidelines (The Planning System and Flood Risk Management, Guidelines for Planning Authorities) that the predicted effects of climate change are incorporated into any proposed design, see Table 2.0. Design Category Drainage Fluvial (River flows) Mean Sea Level Rise Predicted Impact of Climate Change 20% Increase in extreme rainfall depths 20% Increase in flood flows +500mm Table 2.0 The predicted climate change variations based on MRFS 1 (OPW) 6.4 Flood Zones The flooding guidelines categorise the risks associated with flooding into three areas, Zone A, B & C. This categorisation is indicated as follows; Zone A High Probability of Flooding. Where the average probability of flooding from rivers and sea is highest (greater than 1% annually or 1 in 100 for river flooding or 0.5% annually or 1 in 200 for coastal flooding). Zone B Moderate Probability of Flooding. Where the average probability of flooding from rivers and sea is moderate (risk between 0.1% annually or 1 in 1000 years and 1% annually or 1 in 100 years for river flooding, and between 0.1% or 1 in 1000 years and 0.5% annually or 1 in 200 for coastal flooding). 1 Mid-Range Future Scenario, OPW Assessment of Potential Future Scenarios, Flood Risk Management Draft Guidance, Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 9

12 Zone C Low Probability of Flooding. Where the probability of flooding from rivers and sea is moderate (risk is less than 0.1% annually or 1 in 1000 years for both rivers and coastal flooding). In accordance with DoECLG flooding guidelines (the Planning Systems and Flood Risk Management Guidelines for Planning Authorities), residential dwellings are classified as highly vulnerable developments. 6.5 Flood Zone of Proposed Development From a review of the OPW floodmaps website the proposed development is located within the Zone C designation. Figure.1.0 Source-pathway-receptor model from Flood Risk Management Guidelines. 6.6 Fluvial Flooding The site is located approximately 550m from the Corrib River to the north east of the development site and is deemed to be located in Zone C due to the local topography of the development site to the river. A review of the Office of Public Works flood maps database, the area does not indicate any historical fluvial flooding within close vicinity of the site. See Appendix E for the OPW Floodmaps Report. Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 10

13 6.7 Tidal Flooding The sites location and elevation is such that it is not effected by tidal water bodies and as such tidal flooding is negligible. 6.8 Pluvial Flooding Pluvial flooding is flooding which has originated from overland flow resulting from high intensity rain fall. There are no records of flood events due to high rainfall events in the area but due the local topography we understand the risk of fluvial flooding to the site is negligible. See Appendix E for OPW Floodmaps Report, following a review of these maps the potential flooding the development site is deemed not to be at risk from pluvial flooding. The development itself will be designed to cater for a 100 year storm event in accordance with requirements of Galway City Council to minimise the risk of pluvial flooding. 6.9 Potential for Site to Contribute to Off-Site Flooding The existing site currently discharges surface water runoff to the public network unrestricted. The proposed development will reduce the runoff entering the public system by 50% provide attenuation sized for a 1 in 100 year storm event (120m 3 ) including climate change By restricting the flow to a reduced rate, the likelihood of the proposed development adversely affecting the public drainage system or contributing to downstream flooding is mitigated. Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 11

14 6.10 Existing Off-Site Drainage There is no evidence of hydraulic issues with the local drainage infrastructure. Notwithstanding, the proposed entrances to the development will be slightly raised above the adjoining highway to ensure the egress of flood water from the Upper Newcastle Road, Thomas Hynes Road and Tudor Lawn does not occur Groundwater Flooding No records of groundwater flooding have been found in proximity to the development site and no basement construction is proposed, therefore groundwater flooding of the development site is deemed negligible. Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 12

15 7.0 POTABLE WATER SUPPLY 7.1 Existing Potable Water Supply Records obtained from Galway City Council indicate a 100mm PVC public watermain entering the development site from Tudor Lawn that currently supplies the existing hotel. 7.2 Proposed Potable Water Supply It is proposed to re-use the existing water connection from the Tudor Lawn, to serve the new development. The connection will be 110mm diameter PE pipework to Irish Water Ltd standards and will be looped around the proposed development to supply each block as well as for firefighting purposes. 24-hour water storage will be provided at roof level to each block via a pump system which will in turn feed the student units below under gravity. Dual flush toilets and aeration taps to sinks will also be provided to each unit to help reduce the demand of potable water. A pre-development enquiry was issued to Irish Water Ltd (Ref: ) in respect to the proposed development and the response received from Irish Water confirmed that there was adequate capacity in the public network to cater for the peak water demand of 3.1 l/s from proposed development. Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 13

16 However, it was confirmed in the pre-development enquiry response that there is insufficient pressure to serve the higher floors of the development with potable water for fire-fighting purposes. To cater for fire-fighting it is proposed to provide additional breaker tanks and booster pump sets adjacent to each hydrant to ensure sufficient flow to the higher floors. A copy of the pre-development enquiry is included in Appendix B, with the respective response letter in Appendix C and the proposed watermain infrastructure and routing plan is shown on drawing A included with this submission. CS confirm, following the grant of permission, the development will be constructed in one phase, with occupation of the development due in September Therefore, a connection to the Irish Water sewer network on the Upper Newcastle will be required before this date. There are no existing Irish Water assets traversing the development site, so there is no requirement for diversions or protection measures to be introduced. On behalf of Cronin & Sutton Consulting: Gary Lindsay Associate BE, CEng, MIEI Student Housing, Westwood Hotel Site, Galway City - Engineering Services Report 14

17 Appendix A Existing Drainage Records from Galway City Council Student Accommodation, Westwood, Galway City - Engineering Services Report 15

18 Galway City Council Water Department September 5, :1,000 Flow Control Valves Part Closed Reservoir Potable Water mi Non-return Hydro Air Control Valves Water Stop Valves Potable Raw Water Water Mains(Non Irish Water Owned) Untreated km Orifice Plate Non Boundary Meter Pump Stations Potable Water PRV PSV Other Boundary Valves Meter Group Scheme Source Boundary Meter Water Network Structures Abstraction Point Kisok Water Fittings Water Lateral Lines Irish Water Non IW Water Abandoned Lines Open District (Boundary Meter) Cap Water Casings Closed Water Hydrants Other Fitting Part Closed Fire Hydrant Water Distribution Chambers Non Boundary Valves Open Fire Hydrant/Washout Washout Pressure Monitoring Point Water Mains(Irish Water Owned) osi Closed Treatment Plant Untreated For Non-SLA Local Authority staff use only. "Copyright Ordnance Survey Ireland. All rights reserved.2017/14/ccma/galwaycitycouncil."

19 Galway City Council Water Department September 5, 2017 Gravity Main (Irish Water Owned) Surface Gravity Main (Non-Irish Water Owned) Surface Storm Manholes Cascade Catchpit Hatchbox Lamphole Standard Other; Unknown Storm Inlets Gully Standard Other; Unknown Storm Fittings Vent/Col Other; Unknown Storm Discharge Points Outfall Overflow Soakaway Other; Unknown Storm Culverts Storm Clean Outs Stormwater Pressure Mains Surface osi 1:1, mi km For Non-SLA Local Authority staff use only. "Copyright Ordnance Survey Ireland. All rights reserved.2017/14/ccma/galwaycitycouncil."

20 Galway City Council Water Department September 5, :1,000 Sewer Discharge Points Gully Foul mi Outfall Overflow Standard Other; Unknown Overflow Unknown km Soakaway Sewer Manholes Sewer Gravity Mains (Non-Irish Water owned) Standard Outlet Cascade Combined Other; Unknown Catchpit Foul Sewer Clean Outs Hatchbox Overflow Rodding Eye Flushing Structure Other; Unknown Lamphole Standard Other; Unknown Unknown Sewer Pressurized Mains Combined Sewer Flow Control Valves Treatment plant Sewer Fittings Vent/Col Foul Overflow osi Pump station Other; Unknown Unknown Sewer Inlets Sewer Gravity Mains (Irish Water owned) Catchpit Combined For Non-SLA Local Authority staff use only. "Copyright Ordnance Survey Ireland. All rights reserved.2017/14/ccma/galwaycitycouncil."

21 Appendix B Pre-Development Enquiry to Irish Water Student Accommodation, Westwood, Galway City - Engineering Services Report 16

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31 Appendix C Irish Water Response to Pre-Development Enquiry Student Accommodation, Westwood, Galway City - Engineering Services Report 17

32 Biggurat Westwood Ireland Lt c/o Gary Lindsay CS Group, Dame Street Dublin 2 Letter Ref: CDSCOF1 3rd November 2017 Dear Sir/Madam, Re: pre-connection enquiry - Subject to contract Contract denied Connections for 427 Room Student Accomodation Development at Westwood House Hotel, Dangan, Upper Newcastle Road, Galway Irish Water has reviewed your pre-connection enquiry in relation to water and wastewater connections at Dangan, Upper Newcastle Road, Galway Based upon the details you have provided with your pre-connection enquiry and on the capacity currently available as assessed by Irish Water, we wish to advise you that, subject to a valid connection agreement being put in place, your proposed connection to the Irish Water network can be facilitated. The existing Westwood House Hotel has an existing connection to the Irish Water network and it is proposed to utilise the existing connection point for the proposed development. The existing Irish Water water supply network can facilitate the proposed additional demand asscociated with the proposed student accomodation development. The confirmation of feasibility to connect to the Irish Water infrastructure does not extend to your fire flow requirements. To guarantee a flow to meet the Fire Authority requirements you should provide adequate fire storage capacity within your development. The existing Westwood House Hotel has an existing connection to the Irish Water 225mm diameter wastewater network which runs along the N59 Moycullen Road. The existing Irish Water wastewater network can facilitate the proposed additional loading asscociated with the proposed student accomodation development. It is noted that should a trade type effluent be proposed as part of the proposed development then a Trade Effluent to Sewer Discharge Licence may require to be in place prior to a connection being made. The applicant is advised to visit in this regard. The water and wastewater infrastructure should be designed and constructed in accordance with the IW Codes of Practice and Standard Details. You are advised that this correspondence does not constitute an offer in whole or in part to provide a connection to any Irish Water infrastructure and is provided subject to a connection agreement being signed at a later date.

33 A connection agreement can be applied for by completing the connection application form available at Irish Water s current charges for water and wastewater connections are set out in the Water Charges Plan as approved by the Commission for Energy Regulation. If you have any further questions, please contact James O Malley from the design team at jomalley@water.ie. For further information, visit Yours sincerely, Maria O Dwyer Connections and Developer Services

34 Appendix D Attenuation Calculation Student Accommodation, Westwood, Galway City - Engineering Services Report 18

35 JOB NAME:Westwood Galway JOB NO: A079 Oct-17 TITLE: Preliminary Attenuation Calculations CALCS BY: CHECK'D: GL RFM RCD. 48 ISSUE. 1 REV. 1 Design Storm Return Period: Nearest Rainfall Gauge: 100 years Sligo Total Site Area: 0.80 ha Roof Area: 0.00 ha.@ 100% Impervious Hard Surface: 0.51 ha.@ 95% Impervious Open Area: 0.29 ha.@ 5% Impervious Effective Impermeable Area: 0.50 ha Allowable Outflow Calculate IH124: QBAR = x AREA 0.89 x SAAR 1.17 x SOIL 2.17 SAAR: 919 mm Soil Type: 3 SOIL: 0.37 QBAR/ha 3.95 l/s/ha Specified Allowable Outflow Allowable Outflow l/s/ha l/s Duration Rainfall Intensity Discharge Proposed Contiguous Total Allowable Storage 100 Q Runoff Land Runoff Outflow Req'd Year (= 2.71Ai) Runoff (min) (mm) (mm/hr) (l/s) (m 3 ) (m 3 ) (m 3 ) (m 3 ) (m 3 ) Storage required = 120 m 3

36 Appendix E OPW Floodmaps Report Student Accommodation, Westwood, Galway City - Engineering Services Report 19

37 Summary Local Area Report This Flood Report summarises all flood events within 2.5 kilometres of the map centre. The map centre is in: County: Galway NGR: M This Flood Report has been downloaded from the Web site The users should take account of the restrictions and limitations relating to the content and use of this Web site that are explained in the Disclaimer box when entering the site. It is a condition of use of the Web site that you accept the User Declaration and the Disclaimer. Map Legend Flood Points Multiple / Recurring Flood Points Areas Flooded Hydrometric Stations Rivers Lakes River Catchment Areas Land Commission * Drainage Districts * Benefiting Lands * 1 Result Map Scale 1:5,229 * Important: These maps do not indicate flood hazard or flood extent. Thier purpose and scope is explained in the Glossary. 1. Quay Street Galway Jan 1995 Start Date: 17/Jan/1995 County: Galway Flood Quality Code: 3 Additional Information: Reports (1) More Mapped Information Report Produced: 12-Jan :29