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ENVIRONMENTAL SUSTAINABLE SOLUTIONS LTDProject:Westfield Community SchoolLocation:Wigan CouncilType of System:Rainwater Harvesting / Attenuation SystemSize: Attenuation – 38 m 3 / RWH Tank – 147 m 3Depth of Cover:500 to 700 mmDate of Installation: 2004Discharged to:Restricted flow to main sewerProblem:The design for the Westfield Community School development in Wigan Councilrequired that stormwater runoff from the site be attenuated to 10 lts/secdischarge to main sewer system.Original Solution:The original design was to collect the runoff from the field and roof area usingtraditional drains introducing flow into a conventional concrete attenuation tankwith an orifice plate fitted at the outlet pipe.Engineers Requirements:The engineering requirements for managing the stormwater were assessed asfollows.∗ Restricted discharge from the site.∗ A high tank storage requirement in a highly restricted limited spaceESS Solution:ESS provided solution using ESS Geocell modules ®having a void ratio of 95% and high load bearingcapacity of more than 450 kN/m 2 , ESS 52 mmdrainage cells, ESS Tuflex geomembrane having adensity of 0.9 g/cm 3 and a tensile resistance of 26N/mm 2 , ESS Rainmanager C-Class (RainwaterHarvesting System) and ESS Hydrobrake flow controlsystem.Case Study – Westfield Community School - 1 -

ESS proposed rainwater harvesting system and a separate attenuation tank. Halfof the roof area stormwater is collected in the ESS rainwater harvesting tankdesigned. The water to be reused in the school is pumped back using therainmanager inside the rainwater harvesting tank after filtration usingrainmanager. The school also has an ESS educational panel (typical panel shown)below showing the schematics of RWH system for the students, enabling them tocalculate water.Fig 1. ESS Rainwater Harvesting Educational PanelStormwater from the remaining roof area and the site is collected in the ESSattenuation tank. ESS Hydrobrake limiting the flow to 10 lts/sec discharge to themain sewer system is connected at the outlet of the attenuation tank.Attenuation Tank – 38 m 3The attenuation tank is constructed using ESS treble Geocell modules wrappedwith Tuflex impermeable geomembrane. Outlet from the attenuation tank isconnected to ESS Hydrobrake flow control system in the nearby outlet chamber(typical installation drawings below). The attenuation tank has a 225 mm inletpipe and also a 100 mm inlet pipe from the rainwater harvesting tank (overflowpipe from the RWH tank). The outlet pipe of 125 mm dia from the attenuationtank is fitted with a Hydrobrake is connected to the main sewer.Case Study – Westfield Community School - 2 -

Rainwater Harvesting Tank – 147 m 3The rainwater harvesting tank (RWH) is constructed using ESS triple Geocellmodules wrapped with Tuflex impermeable geomembrane having therainmanager fixed into the attenuation tank using 52 mm drainage cells (typicalinstallation drawings below). The RWH tank has a 225 mm inlet pipe and a 100mm overflow pipe connected to the attenuation tank. The rainmanager is acircular tank with an outlet pipe with a filter chamber inside and a pump forpumping the required filtered water for the school. The filtered water is used forflushing toilets, cleaning school areas and irrigation of landscape areas.Case Study – Westfield Community School - 3 -

Benefits:∗ Flexible ideal site solutions (High void ratio and High load bearingcapacity)∗ More efficient design∗ Less excavation required compared to traditional tanking system∗ Innovative and Economical solutions∗ Effective source control systemsCase Study – Westfield Community School - 4 -