An Bord Pleanála
Surface water disposal, drainage and cumulative impacts
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- First party evidence
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Surface water disposal, drainage and cumulative impacts(27/04/2007) While the module was related to surface water drainage and disposal (except solid waste) it was outlined by the inspector that following on from the module on the natural heritage, the indirect impact on the natural heritage arising from the surface water disposal and drainage would also be examined in this module. The module would also examine the cumulative impacts. Dr. Eaken (DoEH&LG), Ecologist, also attended the session. Mr. Manahan stated that Ryanair team would not be making any contribution to the hearing. First party evidenceMr. Paul Couchlan for the DAA was, a chartered civil engineer. He was the lead infrastructure engineer for the T2 project. He said his brief of evidence would primarily relate to surface water drainage, and in particular attenuation to address the issue of flooding and pollution control. Reading from a written document (AN 27/04/07) he said the surface water drainage for T2 project has been designed to comply in all respects with the relevant LAP surface water objectives and complied with the recommendations of the Greater Dublin Strategic Drainage Study (GDSDS) in respect of new development and redevelopment of brownfield areas, so as to attenuate to pre-development green field run off rates. The GDSDS required no flooding on site up to 1:30 year storm event, with protection of buildings up to 1:100 year storm event, and allowance of 10% for effects of climate change. DAA had specifically required attenuation at 1:100 on site to prevent flooding and mitigation of risk to aircraft from birds attracted to ponded water. He stated therefore the surface water attenuation system was designed whereby the surface water is channelled to underground storage tanks and where the flow is restricted to a controlled run off rate of 2 litres /second / hectare (onerous rate in accordance with GDSDS) The surface water run off from paved areas, roads and hard standing areas would be collected through trapped road gullies or through drainage channels and discharged through precast concrete spigot and socket pipes. The scheme drained to two different catchments. Cuckoo stream collected the runoff from the airside areas, while Kealy’s stream collected landside run-off. At the request of the Eastern Regional Fisheries Board, some of the areas previously included in the Kealy’s stream catchment were redirected to Cuckoo Stream catchment. This would not have any negative impact as all the areas were attenuated at greenfield rates and attenuation measures would more than compensate for the small increase in volumes. He described the details of the system and concluded that this in conjunction with similar levels of compliance as part of the Northern Parallel Runway scheme will result in overall positive cumulative impact at the campus. The pollution control of surface water run-off was addressed in two parts. On the airside run off would be intercepted on apron slabs through a network of continuous drainage channels discharging into underground surface water system. Online monitoring within a downstream manhole would be provided to detect the presence of contaminants including de-icing agents.
In the event of on-line monitoring detecting contaminants, a shut-off valve would close and direct the contaminated water to a separate holding tank which will then be diverted to the foul sewer system, so that de-icing run off did not compromise the requirement to maintain salmonid water. To address the hydrocarbons in hardstanding areas and roads petrol interceptors would be placed at source, prior to discharge to the water course or to surface water drains. He referred to two drawings to indicate the proposed surface drainage network. These were also included in the EIS. They show drainage proposals in the new road layout on the landside and around proposed pier E on the airside. The aquifer in the area was a bedrock aquifer. In the location of T2 there was a covering of between 10m –20m depth of highly impermeable boulder clay which effectively protected the bedrock aquifer from any potential surface water pollution. Planning authority’s evidenceMr. Flanagan for the planning authority drew attention to the significant number of objectives in the LAP contained in pages 27-29, and in particular SW4. Mr. Patrick Finn, senior executive engineer for the water works department read from a written evidence (AP-27/04/07). He said the application was assessed having regard to the objectives of LAP and in particular sections 7.1,- 7.4. the water services department had sought clarification on a number of points but following liaison with the planning department the requirements of the water services department were incorporated as conditions. They were satisfied that surface water issues could be adequately addressed by way of conditions and recommended that condition number 21 be re-worded (details provided). He referred to document ‘Control of water Pollution from Construction Sites Guidance for Consultants and Contractors- 2001. They were satisfied that the ground water issues could be adequately addressed by conditions numbers 22 and 23, (again recommending re-wording). The water services department had undertaken to extend the 900mm sewer to Colistown Cross by Sept 2009, and they were satisfied that there would be adequate capacity in the public sewer to cater for the proposed development. they were satisfied that foul drainage issues would be adequately addressed by way of condition numbers 17, 19 and 20. They were also satisfied that the existing public water mains in the charge of the County Council were adequate to cater for the proposed development and an adequate water supply would be available. They had no objection to the internal water supply network detailed design being finalised at a later stage subject to adequate storage and pressure boosting being incorporated in the design and to details being agreed prior to commencement of work. They were satisfied the water supply issues could be adequately addressed by conditions 5, 24, and 25. Directory: news news -> Nonprofit grant application news -> Bulletin 4 Monday July 8, 2002 Backgammon news -> Last year four of the best Afrikaans Christian singers joined forces to tour Down Under with the production ‘Manne wat Glo’ news -> Management and Marketing news -> World Computer-Chess Championship news -> World Computer-Chess Championship news -> World Computer-Chess Championship Download 0.92 Mb. Share with your friends:
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