Two Up-Flo™ Filters and one Downstream Defender® advanced vortex separator were installed together to meet the required Total Suspended Solids (TSS) and metals removals.

Situation

The Eastways project in Witham, Essex, was an existing industrial unit that was being upgraded to include the construction of a new food production facility with internal offices, a new site entrance, and a new vehicle turning area.  This project needed a drainage strategy suitable for an industrial site, to control surface water runoff and remove pollution.

Problem

The stormwater runoff from the roofs, roads, car parks and ground area could not be infiltrated so needed to be stored within the development site for storms up to a 1 in 100-year event, with an additional allowance for climate change. With no nearby watercourse, the stored runoff will then flow off the site into a public sewer.

The first drainage design put forward for the site was rejected by Essex County Council because the surface water treatment only included one petrol interceptor which did not address the requirements for Total Suspended Solids (TSS) and metals removal.

A higher level of treatment was required for the site, and the solution was needed quickly to keep the project on track.

Solution

Bell Munro Consulting worked with Hydro International to find a solution. It was agreed that all site runoff was to be via conventional drainage to a public service water sewer and would include Sustainable Drainage Systems (SuDs) in underground storage with limited flows into the public sewer, and in-line control measures to remove pollution from the runoff.

Working together they developed an effective and advanced stormwater treatment solution that was tailored to meet site requirements, by combining two 1.2 m (4 ft) Up-Flo™ Filter systems and one 1.8 m (6 ft) Downstream Defender®.

To meet the tight delivery deadline and to keep the project on schedule, the Up-Flo™ Filters and Downstream Defender® separator were supplied in twin wall plastic chambers. The strength of the twin wall chambers meant that there was no need to back fill with concrete and it also made them lighter and easier to move around on site.

Working with Hydro International’s technical team, we were able to provide an advanced treatment solution that met not only the hydrocarbon pollutant removal, but also removed Total Suspended Solids and metals," said Alan Morris, Associate Civil/Structural Engineer at Bell Munro Consulting, "The flexibility of material choice for the chamber enabled us to keep to our project schedule.