Resilient Cities SuDS Audit Pilots Aim of the Audit To help schools - PowerPoint PPT Presentation

Resilient Cities SuDS Audit Pilots

Aim of the Audit To help schools achieve a reduction in their chargeable area for surface water drainage through the application of the Business in the Community’s Ready- Reckoner’ and SuDS Audit Guide

Surface / Highway Drainage Charge Surface Water Drainage Charge This charge is based on the impermeable area from which rainwater drains into the sewer system . Highway Water Drainage Charge This charge covers the cost of draining the impermeable roads and footpaths in the Northwest from which rainwater runs off into the sewer system. The customer’s original site area is used as a proxy for site size and therefore indicative of the volume of traffic travelling to and from the site using the roads and pavements of the Northwest.

SuDS Audit Guide

United Utilities Band Charging for Surface Water Drainage

Road Test Pilots The Ready-Reckoner and SuDS Audit Gide were trialled at; Burnage Academy for Boys Chorlton High School

Burnage Academy for Boys The ‘Academy’ located in south east Manchester has 953 pupils and over 148 teaching and support staff. In 2010 a £17m redevelopment of the school under the Government's Building Schools for the Future programme was undertaken which saw the original 1930s and 1950s buildings demolished and replaced with a new building.

Surface Water Charge Status Chargeable surface area is 28,120m2 Charge Banding 10 Prior to 2015 the School was classified as band 9 based on an aerial photo analysis. The Academy requested of United Utilities a review of the site area with a view to dropping down to band 8. UU sent their contractors to physically review the site drainage and they found that the field drains from the sports pitch are connected to the public sewer. Subsequently the sports pitch was then added to the site area and as a consequence the surface drainage area was recalculated as 29,261 m2 which resulted in the banding change from 9 to 10, a difference of nearly £10,000.

Site Drainage

Site Layout

SuDS Opportunities Sports Pitch – infiltration via a swale

SuDS Opportunities Sloped pedestrian entrance – infiltration via a permeable surface Main building flat roof – interception via a green roof

SuDS Opportunities Existing Service Road with Cellular Grassed Paving System – potential for extending system Internal courtyard - further green space or permeable paving material to allow water to infiltrate

Findings If the water falling onto the grass sports pitch was able to infiltrate then a band change from 10 to 8 could be achieved. This would result in an annual cost saving of £15,594.49

Constraints / Opportunities Constraint Infiltration – borehole data provided by the school demonstrated that the dominant subsoil is clay which would impede infiltration Green roofs – structural tests would be required to determine loading capacity Opportunities Sink boreholes to a depth below the clay subsoil to allow rainwater via a surface SuDS feature into the aquifer below. Pipe water off site and discharge to the exposed Shawbrook which is found 200m to the north next to St Bernard’s Church.

Chorlton High School Chorlton High School located in south Manchester was designated a specialist Arts College in 2002 and benefited from a £17 million rebuild. The school now boasts state-of- the-art facilities, including specialist drama and music rooms, a 300 seater theatre, an all- weather pitch for sports and a gymnasium. CHS became an academy on 1 January 2013 and is one of the biggest in Manchester hosting nearly 1500 pupils.

Surface Water Charge Status • The chargeable surface area is 30,785m2 • Charge Banding 10 – this was for the Highway Water Drainage Charge only

Drainage into the Chorlton Brook The drainage plan demonstrated that the majority of the site surface water runoff was discharged into the nearby Chorlton Brook and so it would not be possible to achieve a band change for the Surface Water Drainage Charge. However, it was agreed that the audit should still be carried out as although ‘hypothetical’ it would provide a valuable ‘field’ opportunity for testing the tool kits.

Site Layout

SuDS Opportunities Grassed area adjacent to astro turf sports pitch – storage via a detention basin

SuDS Opportunities Low lying area at edge of playground – conveyance to Chorlton Brook via a filter strip Plant room – interception via extensive green roof system

SuDS Opportunities Atrium next to canteen – infiltration / conveyance via a rain garden Main entrance – interception via downpipe connection to rain trough planter

SuDS Opportunities End to end parking strips – Infiltration / conveyance via narrow filter drain between the opposing parking bays

Constraints / Opportunities Opportunities Although the majority of the surface water is taken to the Chorlton Brook and so a band change is not realistic there is still the scope for; • reducing the volume of water that goes to the Brook • cleaning surface water runoff before it enters the Brook • reducing and cleaning the highway runoff into the surface water drain Constraints • an assessment would be needed of subsoil conditions to determine the feasibility of infiltration • structural tests would be required to determine loading capacity of roofs to support green roof installations

Getting the Message Across to Schools Flooding What Can We Do About It?

Getting the Message Across to Schools A lesson plan has been devised for Key Stage 2 / Key Stage 3 students The lesson focuses on; • The hydrological cycle • What happens to our waste water • What are the cause of flooding • How can SuDs help manage surface water runoff and reduce flood risk • How to carry out a SuDS audit of the school grounds / buildings

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