Mr Harvey Emms Newcastle City Council Strategic Housing
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Mr Harvey Emms Newcastle City Council Strategic Housing, Planning and Transportation,Environment and Regeneration Civic Centre Newcastle upon Tyne Tyne and Wear NE1 8PD 20 February 2013 Dear Mr Emms NewcastleGateshead Local Development Framework. Consultation on proposed major changes to One Core Strategy. Further to the above consultation and your meeting with Richard Warneford and Mike Madine on 19 December 2012 I am now able to provide Northumbrian Water’s (NWL) overall response to the document as well as a detailed breakdown of the potential impact of each site upon our water supply and sewerage network. Methodology for assessing the impact of the proposals We have used the GIS shape files and associated spreadsheet provided by Theo van Looij on 21 December 2012 and as agreed with Theo we have not considered sites which are identified as complete or discounted. As a consequence of this, of the 500 sites identified on the original spreadsheet only 247 required an impact assessment. We sought clarification from Theo on the timescales for development and agreed the following criteria: 1. Short term (up to 2018) 2. Medium term (2018 – 2023) 3. Long term (2023 – 2030) 4. Ultra Long term (post 2030) We then carried out an assessment of each of the 247 sites which considered the following key issues which could affect the development. 1. The presence of existing NWL water mains and sewerage infrastructure within the site boundaries which could restrict the developable area or require diversion. 2. The presence of existing water mains within vicinity of the development and any issues over our capacity to supply water. 3. The presence of existing sewers within vicinity of the development and any issues over their capacity to drain the site. 4. As part of (3) above, an assessment of current and future surface water management with particular regard to surface water separation and reduction in run-off. The results of our site by site assessment are included in the attached excel spreadsheet which we will also e mail to you as we believe it will be useful for you to have this electronically. Having completed the individual site assessments we then carried out a further exercise to look at the cumulative impact of some of the major strategic development areas to identify the need for further work, such as the need for a drainage master planning exercise. We have taken the opportunity to consider what our analysis means in terms of emerging policies and later in this letter we will make some recommendations particularly with regard to surface water management. Finally at your meeting with Richard and Mike you raised concerns regarding Howdon Sewage Treatment Works (STW) and its ability to support all of the development within Newcastle, Gateshead and neighbouring council areas. Our estimate is that the total number of net additional homes across the Howdon catchment is in excess of 40,000 across the plan period to 2030 and we will update you on our proposals to provide capacity for this housing. NWL water mains and sewerage infrastructure within the site boundaries We have identified that 126 of the 247 sites we have assessed have water mains, sewers or both crossing the sites. In some instances on previously developed land these are relics of the former development and can in all probability be abandoned, however on many of the sites the water and sewerage assets serve a wider area and need to be maintained. We have also identified a number of sites where there are existing sewage pumping stations and in accordance with the nationally agreed “Sewers for Adoption” - 7th edition we would require a minimum distance of 15 metres from any habitable rooms. This is to limit the potential impact on future residents from noise and odour from these assets. In many cases developers would prefer to start from a clear site to maximise housing yield and Section 185 of the Water Industry Act 1991 contains provision for the diversion of water mains and sewers, including pumping stations at the developer’s cost. In terms of site viability we recognise that it would assist you if you had an early indication of the potential limitations of development so we are providing a PDF copy of our GIS sewer or water map for each site. Our GIS team will have this ready in the next day or so and we will send it out to you under separate cover. We also considered that you would need to understand the potential restrictions of the NWL assets remaining insitu and the following tables set out our standard easement widths upon which no buildings could be constructed as this could be a limiting factor in terms of the layout and scale of the development. Our standard easement widths are as follows: For Sewers (measurements given are either side of sewer) Sewer Depth to Not 226mm 476mm 725mm 1125mm Dia. / 925mm to 1400 or For Box Culverts, the Invert of Exceeding to to to to size 1124mm Greater greater of; Sewer (m) 225mm 475mm 724mm 924mm 1399mm (mm) 4.0m from centreline less than 3.0 3.0m 3.0m 3.5m 4.0m 5.0m 5.0m 5.0m or 2.0m from the outside edge 5.0m from centreline 3.0 to 4.0 3.0m 3.0m 4.0m 5.0m 5.0m 5.0m 5.0m or 2.0m from the outside edge 6.0m from centreline 4.0 to 5.0 4.0m 4.0m 5.0m 5.0m 6.0m 6.5m 6.5m or 2.5m from the outside edge 6.0m from centreline 5.0 to 6.0 5.0m 5.0m 6.0m 6.5m 6.5m 6.5m 6.5m or 2.5m from the outside edge 6.0m from centreline 6.0 to 7.5 6.0m 6.0m 6.0m 6.5m 6.5m 6.5m 6.5m or 2.5m from the outside edge 6.0m from centreline 7.5 of greater 4.0m 4.0m 4.0m 5.0m 5.0m 5.0m 6.0m or 2.5m from the outside edge For Water Mains Internal Diameter of pipe Easement width, each side of the Approximate easement width in total extreme edge of the pipe Greater than 600mm 6.0m 13.0m Greater than 300mm, up to and 4.5m 9.5m including 600mm Up to and including 300mm 3.0m 6.0m The tables above give general guidance of our easement requirements simply for the purposes of your viability testing but I have also enclosed the current version of the full easement guidance documents for water mains and sewers for your information. There will be some sewerage assets which because of their depth may be able to remain in place and be built over subject to some detailed negotiations and engineering assessment of foundation details. Typically this is where sewers have greater than nine metres of cover. It is vital that developers consult us at the pre-development enquiry stage to agree details before designing their site layout to enable us to agree the necessary levels of protection. Water Supply You will note from the spreadsheet that in all cases we are able to provide a water supply to the site at present and it is our statutory duty to provide a water supply for domestic purposes. Developers of these sites can requisition a water main from us or elect to follow the “self lay” process where they lay the mains themselves. There will be occasions where the development of some of the sites will require some degree of reinforcement in our wider water supply network but there is a mechanism in both the requisition and self lay processes to facilitate this. These costs are built into the cost of providing the water main and funded by developers. In general most of the brownfield sites are unlikely to require such network reinforcement but certainly some of the larger greenfield sites will and this is particularly so in two areas within your plan. They are the areas at: The A696 corridor between the A1 and the airport Brunton Park/Woolsington Dinnington For these sites it is recommended that the requirement to consider an overall water supply strategy for the cumulative impact of all of these sites is built into the scope of a master planning exercise. Sewerage Capacity Newcastle City Council’s area is covered by 12 drainage areas of which we have good hydraulic model coverage. Five of the drainage areas have been modelled as part of the Tyneside Sustainable Sewerage Study and a further four have been modelled as part of our Drainage Area Study programme during 2012. This leaves three drainage areas in Walker, Byker and Moore Croft, Newburn where we do not have model coverage which limits our ability to give a detailed response for 43 of the sites within the overall 247. To assist you with the immediate consideration of the short term sites within these drainage areas, of which there are 14 identified up to 2018, we have provided a desk top assessment of likely drainage discharge points within the spreadsheet. Where we have model coverage, the models provide an overview of the performance of the public sewerage system and have been used to assess the impacts of proposed developments within those areas. For our Drainage Area Studies models we considered development up to 2020 and for our Tyneside Study we considered development proposals up to 2050. Each length of public sewer has been assessed and assigned a capacity factor that reflects hydraulic performance and the likelihood of flow escaping during storm events with a return period of once in 20 years (this equates to an annual probability of 5%).