Groundwater Remediation

Client / Britannia Construction
Site / Tesco, Cheltenham
Value / £335k
Timescale / 15 Months

Summary

Sanctus, working in conjunction with White Young Green Environmental and Britannia Construction, were involved in the extension and redevelopment of a Tesco store on Tewkesbury Road, Cheltenham. Sanctus produced an environmental management plan addressing numerous environmental issues associated with the site’s historical use as a gasworks.

Sanctus designed and installed a bespoke groundwater pump and treat system to remediate a heavily contaminated zone of soil and groundwater at the site. The Tesco store remained open during the remedial and extension works. Where necessary, critical work was carried out overnight.

Conceptual and design models were produced based on geophysical analysis of the strata beneath the car park and chemical analysis of groundwater obtained during site investigations.

Groundwater abstraction wells and pipework were installed during the night within the carpark area of the Tesco store. This caused minimal disruption to the Tesco retail operation.

Heavy oils and tars, both dense non-aqueous phase liquids (DNAPL’s) and light non-aqueous phase liquids (LNAPL’s), had impacted the groundwater and overlying soils in an area where historic gasholders had been located.

A total of 42,250 litres of DNAPL was recovered and recycled at a suitably licensed offsite facility, and 2,079,000 litres of contaminated water was successfully treated and discharged to a foul sewer. With close liaison with the Environment Agency and Cheltenham Borough Council, Sanctus implemented a groundwater monitoring programme, which verified the success of the remediation works and continued throughout the construction works phase, ensuring that the development did not have adverse effects on the wider water environment.

The treatment system was installed in a discreet location onsite using minimal ground footprint. The enclosure and apparatus utilised ensured minimal visual impact and acoustic disturbance to the Tesco customers and surrounding local residents.

In addition to the remedial works, Sanctus carried out characterisation and classification of all construction waste and contaminated soils emanating from the redevelopment works at the site. This ensured reuse of materials was maximised and significantly reduced offsite disposal to landfill. The works also included the requirements under duty of care legislation.