Bridgwater landfill blight set for redevelopment
Planning permission has been submitted for a 2.5 hectare extension to the existing Bridgwater Retail Park, to be constructed primarily on the site of a former cellophane factory landfill in the heart of a commercial and retail area in Bridgwater.
The site has never been developed because of considerable issues relating to the historic use of the site, formerly a clay pit and then a landfill for the disposal of waste from one of Bridgwater’s cellophane factories. Historically it had been planned that the site be put to public use as a skateboard park by covering it, but even that never progressed. A much smaller area south of the landfill forms the remaining 25% of the redevelopment area, and although currently wasteland, it has housed a cotton mill, outboard engine business and also car repairs/servicing.
Clarkebond was appointed by Chelverton, on behalf of LaSalle, to investigate the site for geotechnical and Ground Engineering aspects, leading to an options appraisal for any remediation and risk reduction measures. The landfill waste extended to 6m depth. Shallow groundwater and potential pollution pathways to the nearby River Parrett presented significant pollution concerns. Despite some previous investigation of the site finding diesel- and petrol-range hydrocarbons, as well as PAHs, associated sporadic free-product and ammonia, Clarkebond’s careful design of further investigation work and subsequent detailed assessment proved that most risks were now not significant. Methane concentrations of up to 60% have been recorded on site, but Clarkebond was able to demonstrate that generation rates were low enough to avoid significant gas protection measures being required to new buildings.
A traditional gas cut-off trench would be the usual approach to the new development causing migration of gas to neighbouring land, but such would have caused significant disposal costs for a considerable volume of arisings from the landfill. Clarkebond has proposed an alternative solution which avoids this issue. Pesticides had also migrated into the site from a nearby former historic timber treatment works, but concentrations were proven low enough to avoid mitigation.
A remediation and risk reduction strategy has been produced by Clarkebond that deals with issues of soil contamination, groundwater quality, landfill gas, and Japanese Knotweed.
As with most structures in the area the new buildings will be piled. Clarkebond will be advising on measures to lessen the impacts of settlements in surrounding non-piled areas and are also undertaking a detailed flood risk assessment.
“This site presented a lot of challenges’, comments Clarkebond’s Ground Engineering Associate Director, André Gilleard, ‘but all these issues can be tackled – our skill lies in finding commercial solutions to them!"
Client’s Agent: LaSalle Investment Management
Development Manager: Chelverton
Planning Consultant: NJL Planning
Structural, Civil and Ground Engineering Consultant: Clarkebond
Flood Risk Assessment: Clarkebond
Quantity Surveyor: Sweett Group