Triangle Gas Station Remediation
A release of approximately 4,000 gallons of gasoline was identified in April 2000. Monitoring indicated free product at a thickness of greater than four feet in two locations. A pilot test was conducted to evaluate soil vapor extraction and dual phase extraction (DPE). This was done to assess corrective action alternatives and to determine design parameters. Based on the results of the pilot test, a Corrective Action Design report, recommending dual phase extraction, was prepared and subsequently approved by the MPCA.
We designed the DPE system and performed oversight during installation. The station remained active during the entire system installation. The water discharge to sanitary sewer required secondary treatment with activated carbon to meet the requirements of the water treatment facility. The air discharge was treated with a thermal oxidizer.
The dual phase system operated for six months recovering 3,000 gallons of gasoline. This system also treated and discharged 180,000 gallons of water. We performed all operation and maintenance of the system and the leak site was closed after one year of post remediation groundwater monitoring.