Contaminated Land - former garage site

  • Groundwater hydrocarbon remediation

Contaminated Land

Contaminated Land - former garage site

Delta-Simons was asked by Caffyns to undertake preliminary Phase I and intrusive Phase II site investigation works at their former garage site in Goring-by-Sea, and subsequently carry out groundwater hydrocarbon remediation.

Purpose

Delta-Simons has provided environmental consultancy services to Caffyns plc for a number of years, and was asked to undertake preliminary Phase I and intrusive Phase II site investigation works at their former garage site in Goring-by-Sea, following planning conditions for contaminated land associated with the proposed residential/commercial redevelopment of the site. During these works, hydrocarbon impact was identified within the underlying groundwater in the area of a former underground fuel storage tank, which had previously been removed under Delta-Simons guidance.

Outline / Scope of Works

Delta-Simons subsequently undertook a Detailed Quantitative Risk Assessment in order to determine whether remedial works to address the hydrocarbon contamination would be required. The assessment established that the contamination would be unlikely to migrate significantly off-site, but given the environmental sensitivity of the site area (which included the underlying Principal Aquifer) a ‘passive' ongoing remediation system, as well as long term groundwater quality monitoring in order to demonstrate betterment of groundwater quality, would likely be sufficient to address the contaminative impact. For commercial reasons, it was decided to undertake a more intensive method of remediation, involving chemical injection, in order to remove the need for a long-term monitoring programme.

Outcome / Client Benefits

The injection works were completed over a period of two weeks in April 2015, after which Delta-Simons completed three return groundwater monitoring periods (monthly) in order to retrieve samples to determine the effectiveness of the remedial works. On completion of the monitoring an overall reduction in contaminant mass was demonstrated within groundwater, which was detailed within a Remediation Validation Report to the satisfaction of the Environment Agency who recommended discharge of relevant planning conditions.