Project: Lane’s Garage, Tolleshunt Major
Client: Developer
Value: £4,630

Knight Environmental Limited provided technical environmental services that included site investigation, risk assessment, remedial design and liaison with the Regulatory Authorities at a former petrol service station and garage services site in Tolleshunt Major, Essex. Underground storage tanks (USTs) were identified on the site.

The site investigation identified localised areas with elevated levels of hydrocarbons with one locality where the groundwater was found to contain approximately 50% free phase product, primarily petrol.

A remediation strategy was designed which would remove any potential pathway between the identified contaminant source and the receptor, namely the future end-user of the site, thus reducing any significant pollutant linkages associated with a risk to human health.

The remediation strategy comprised the removal of the UST and the excavation of localised areas with elevated concentrations of identified contaminants and backfilling of excavation with chemically acceptable and certified materials.

Following the removal of the UST, the identified localised area of impaction surrounding the UST was excavated around and beneath the UST by at least 1.0 metre. The remedial strategy combined the removal of the source with the creation of a protective barrier appropriate to reduce the possibility of contact through excavation in open space and landscaped areas.

Approximately 30 tonnes of hazardous non-special waste were excavated contaminant hotspots and removed from site under “Duty of Care” protocols. The excavated material was removed to a suitably licensed facility. Any water collected within the excavation after the removal of the UST, was removed and disposed of to a licensed facility.

On completion of excavation of contaminated material the site, the excavations were backfilled with imported chemically acceptable to a specified level. In order to avoid foundation problems, concrete was poured above the backfilled material to original ground level. A minimum thickness of 1.8 metres if concrete was poured into the hole.