One of the first UK stormwater treatment solutions using Hydro International’s innovative Up-Flo™ filtration technology has enabled developer Fairview New Homes to incorporate SuDS with two levels of treatment into the surface water drainage for a new access road.

Situation

Developers Fairview New Homes needed to build a new access road for commercial and light retail in Faversham, Kent, UK.

The access road was needed to service retail and light commercial units as part of the mixed-use redevelopment of the Eurocentre wholesale distribution centre, on the site which is bounded by the London to Dover main railway line.  

Problem

To meet Environment Agency planning requirements they needed to provide two levels of treatment for the surface water runoff from the road, but using completely natural features wasn't possible.  While much of the access road offers natural flow to a swale for treatment, around 100 metres of the road was below surrounding land.

“We needed to provide polishing treatment to remove finely dispersed pollutants, as it was adjacent to a source protection area. To create sufficient fall for a swale, we would have had to try and install it some three metres below ground level, which was not possible," said Phil Tomes, Infrastructure Design engineering consultants, "Kent Highways specified maintenance requirements before agreeing to adoption of the installation. They preferred to avoid their crews having to physically enter the chamber through a manhole cover in order to change the filter medium bags in the Up-Flo™ unit.

Solution

Developers Fairview New Homes and consultants Infrastructure Design Ltd worked with Hydro International to develop a unique solution for the site which combined a custom-modified Up-Flo™ Filter unit with Stormbloc® modular storage and infiltration blocks.

Outcome

Hydro International's design team adapted the Up-Flo™ Filter design by mounting the modules containing the filter bags on a platform that could be raised and lowered with a screw-operated penstock gate mechanism. The design enables the filter bags to be exchanged at approximately ground level.  Maintenance intervals are currently estimated as yearly or longer.

To meet the surface water discharge constraints for the site, the final discharge from the filtration unit has to be infiltrated into the ground. Without room for a separate soakaway, Hydro International's Stormbloc® storage infiltration tank was used. Because it is load-bearing, it could be easily sited under public space in a shallow excavation and landscaped over. This provides around 180 m³ (47,500 gallons) of storage attenuation and infiltration, without occupying valuable surface area.