Opportunistic approaches to incorporating multi-functioning SuDS into housing redevelopments Making Sustainable Drainage Schemes (SuDS) work for everyone 28th February 2018 Roger Nowell SuDS Lead Officer Sheffield City Council
Sheffield and SuDS SuDS Design Statement SuDS guidance Surface water management for new development SuDS typologies
Typologies- urban extensive Typical development Larger supermarkets, retail, extensive office, factories, operational, schools, leisure Management Privately managed, Yorkshire Water may adopt tanks, may include offsite Council managed features Criteria 30% reduction for brownfield, greenfield for greenfield sites or redevelopment where to different discharge route. Potential for discharge to surface water sewer and possibly watercourse Typical SuDS solutions Concrete block permeable paving for car parks lined for storage where contamination or discharge to sewer, non-lined for infiltration or partial infiltration where direct discharge to watercourse. Can act to store roof water through horizontal diffuser pipes in sub-base or surface inflow removing need for other storage. Landscape requirements - potential to be integrated and enhanced through SuDS function, e.g. linear green verges / planting designed to intercept lateral run-off from impermeable surfaces. Larger open spaces and peripheral landscapes within or external to the site for detention basins /ponds Pre application Application Benefit in ensuring optimum site layout to accommodate SuDS inclusion. Establishing likely discharge rates SuDS design statement should demonstrate SuDS approach /options analysis. Drainage solution should show approximate volumes from development, methods of collection, movement, treatment and storage. Confirmed discharge routes. The
Typologies- urban intensive Typical development Block development - City centre and immediate peripheral valley bottom uses, outer commercial centres Flats, offices, shops, leisure Management Criteria Typical SUDS solutions Privately managed infrastructure Typically 30 % reduction for discharge rates to be applied to the 1 in 1 return period event. Likely discharge to the combined sewer. Possible discharge to surface water sewer or watercourse if economically proportionate when greenfield discharge may be required. Treatment a high priority where discharge to surface water system Green/blue roofs and podiums can provide a considerable proportion, if not all, of a site s attenuation requirements through the inclusion of fit for purpose shallow storage, for example geocellular layer. Permeable paving in courtyards and parking areas can be adapted to store surrounding roof water through modifications of sub-base depths. Courtyard planters can be designed to receive surface and roofwater before passing flows to underground storage. Extreme events can be managed on the surface of sunken external areas. Pre application Whilst options for surface water management are less complex with these tight sites, pre application discussions are always encouraged. Application Concise SUDS design statement to outline drainage solution Green roof Planting areas playing their role in water management Conditions Detailed calculations Detailed design Confirmation of management arrangements, e.g. management company, schedule of maintenance
Manor Fields - Sheffield Retrofit SUDS Offsite system 300 dwelling housing estate 1in 100 year aspiration Local Authority adoption 05/03/2018 Roger Nowell Sheffield City Council
Existing valley connecting to main stream Lowflow channel Basin 3 Overflow channels Basin 1 Volume control device Storm basin aspiring to manage 100 year storm Overflow channel Lowflow channel Basin 2 Lowflow channel Inlet from housing
Roger Nowell, Ian Stanyon Sheffield City Council
05/03/2018 Roger Nowell Sheffield City Council
SHEFFIELD HOUSING COMPANY A Joint Venture Housing and Regeneration Company
Why Sheffield Housing Company? Undesirable neighbourhoods leading to housing market failure.
What is Sheffield Housing Company? Delivery Mechanism: SCC LAND KGP CASH Repayment of Land Value Land is matched by EQUITY Repayment of Equity Division of Surplus SHC 50:50 SCC : KGP Borrows development finance Division of Surplus KEY SHC Sheffield Housing Company KGP Keepmoat Great Places NEW HOMES
Progress to Date Phase 1 : 3 sites, 293 homes in total, 80% Open Market Sale, 20% Social and Affordable Rent. Complete. Phase 2 : 5 sites, 478 homes, 85% Open Market Sale, 5% Affordable Rent, 5% Shared Ownership, 5% Private Rent. All sites under construction. Phase 3: 2 sites, 333 homes, 35% Open Market Sale, 65% Private Rented. All sites under construction. Phase 4: 5 sites, 455 homes, 90% Open Market Sale, 10% Shared Ownership. 1 site submitted for Planning approval, remaining sites due for submission early 2018.
Sheffield south
The case for Improving viability Land management resources More sustainable approach to w ater quantity and quality management Biodiversity Open space SuDS Play/recreation Reducing flows to combined sew er Landscape investment
Shallow profiles Maximum storage depths appropriate to setting Pre-treatment basins for 1 in 1 with short-circuit wetland to allow tolerance on sediment accumulation Wider storage wet /dry return period definition Natural construction in soil and stone Stone /gabion protection to inlets and outlets Design
Sheffield Council adoption Annual income from households as part of management company charge Annual maintenance Staff management costsoperations, inspections Financial management Intermittant requiring long-term financial allocation from income - desilting, allowances for repair, replacement Transparency - reviews Generally informal maintenance mown frameworks flail/strim sufficiently often to check any unwanted incoming woody growth
Progress to date Parson Cross 150 homes, OMS/AH scheme complete 100 homes, OMS/AH scheme under const. 250 homes, OMS/AH scheme 2019 50 homes, OMS scheme 2021 65M retail development complete/ongoing 5M school investment complete 0.6M investment in parks - 2018 Initial Sales Price Latest Sales Price Percentage Increase 2 Beds 103,000 (Jan 13) 131,000 (Oct 17) 27.2% 3 Beds 118,500 (Feb 13) 151,000 (Sep 17) 28.0%
Wider site may get wet in the most extreme weather when the basin is full Wet grassy channel to carry the rainfall run-off from the inlet to wetland to help clean the flow of any di rt off the roads and to provide long habitat for animals and plants Meadow with central lawns for play Hollow that will fill with water when it rains very ha rd Everyda y s hallow wetland with gentle sides for safe access. To be planted with wetland plants to encourage wildlife. Outlet to Bagley Dyke watercourse which is below ground. All the water held within the pocket park will slowly be released through here within a day leaving the site to dry out. Central grass space that will occasionally be covered in water when it rains hard Rocky inlet to slow the flow and provide place for amphibians Inlet pipe from drainpipes and road gulleys in new housing area
Woodthorpe ravine
Pipworth Regional SuDS Development Numbers of units draining to offsite SuDS %age proportion Manor 10/11 181 43 Manor 8 82 19.5 Manor 12 130 31 Manor 13 28 6.5 Total 421
500K scheme efficiently storing over 5000m3
Success factors Past experience allays fears SHC as a partnership allowed trust to be developed and to feel confident of future revenue based resourcing Use of open space economic benefit Close working between LLFA and SHC SuDS demonstrated to bring other benefits Thank you roger.nowell@sheffield.gov.uk