BCI Engineers and Scientists

BCI coordinated remedial activities designed to remove petroleum hydrocarbons from groundwater resulting from a release of unleaded gasoline from a former leaking underground storage tank (UST) site in Williamston, Michigan.

A release from the former UST system was reported in August 1996 and subsequently investigated to delineate the extent of soil and groundwater contamination. Soil and groundwater contamination was limited to a small on-site area between the former USTs and dispensers.

However, cleanup of the remaining contamination was complicated by the small size of the site and existing infrastructure which included a new, operating unleaded gasoline UST and associated piping and dispensers in the area of the release.

The remediation technique utilized to meet cleanup objectives was vacuum enhanced recovery (VER) from several wells installed in the area of the highest reported groundwater contamination. VER is a remediation technique which utilizes a vac truck to apply a high vacuum, or negative pressure, on a recovery well and geologic formation in order to enhance the mobility and recovery of contaminants.

During 1998 and 1999, nine VER events, lasting approximately eight hours each, were completed at the site with a total of approximately 9,200 gallons of groundwater recovered and properly disposed. After theremedial actions were completed, benzene concentrations at the recovery well were reduced by approximately 75 percent. After completion of the VER, natural attenuation/biodegradation of the remaining groundwater contamination was demonstrated through periodic groundwater monitoring.

After groundwater monitoring confirmed that the groundwater contamination plume was stable and not advancing, BCI assisted the client in preparing a Restrictive Covenant and Notice to Local Unit(s) of Government of Land Use Restrictions filed in support ofthis closure. Activities restricted on the site included the use of groundwater for any potable or non-potable use, the off-site transport of soils without adequate analytical characterization, and maintenance of an impermeable barrier (for example, pavement) on-site in the area of impacts.