Unleaded Gasoline Spill Remediation

During the delivery of product to a 6,000-gallon unleaded gasoline underground storage tank (UST) at Westtown School in Chester County, Pennsylvania, a hose ruptured resulting in a release of gasoline to the ground surface. The gasoline flowed across a paved area and into a stormwater drain pipe, which discharged into a grass swale. A spring-fed stream is present downgradient of the swale and flows into the East Branch Chester Creek.

Initial remedial actions included the over-excavation of 250 tons of gasoline-impacted soils and the removal of 600 gallons of mixed gasoline and water  from the swale. Subsequent remedial efforts included the removal and disposal of additional impacted soils and a high vacuum extraction event that removed 2,900 gallons of contaminated water from the  swale.

Nine groundwater monitoring wells were installed to assess the condition of groundwater in the spill area. Quarterly groundwater monitoring and sampling occurred over a 10-month period. A Remedial Action Completion Report was submitted to PADEP and Westtown School received a Release of Liability under residential Statewide Health Standards for soil and groundwater.

Following the completion of the remediation activities, the site was evaluated by a Professional Engineer to determine restoration options, and a detailed survey of the site conditions was performed. A geomorphic assessment of the stream channel was conducted to characterize the substrate material and to provide data needed to develop a stream channel design with stable dimensions. Consultations with the Chester County Conservation District and PADEP Bureau of Watershed Management resulted in an approved stream channel design to effect the restoration of the impacted watercourses.