Soil & Groundwater Investigations
Underground Storage Tanks
MDEQ contracted ERG to conduct a remedial investigation and feasibility studya to determine the presence of soil and groundwater contamination and LNAPL, and define the vertical and horizontal extent of contamination, with the overall cleanup goal for soil and groundwater will be to reduce contaminant concentrations to within residential criteria.
The Memphis Shell Site is a former LUST facility located in the rural town of Memphis, in northern Macomb County, Michigan. The Site is a former service station that operated from the early 1970’s to approximately 2001. Three confirmed releases from the UST system had been reported from 1998 to 1999, which resulted in LNAPL and dissolved petroleum contaminants migrating approximately 250 feet from the former USTs the east-southeast direction, under a State highway and beneath residential homes on the east side of the road.
Additional remedial investigation was conducted, which included an LIF study and the installation of several monitoring wells. Based on the investigation, the estimated area of the LNAPL plume was approximately 17,000 square feet, and is located in the upper portion of a sandy aquifer approximately 40 to 45 feet below grade.
As part of the remedial actions, existing USTs and grossly contaminated soil, that acted as the source of groundwater contamination, were removed. After UST removal, a feasibility study was performed to determine the best way to reduce the mass of the LNAPL plume. Based on the feasibility analysis, in-situ chemical oxidation (ISCO) with sodium persulfate and sodium hydroxide, was selected as the most suitable and cost effective remedial option for the site. A successful pilot test was conducted in August 2015 and full scale ISCO was conducted in March 2016 and again in August 2016. Post-injection monitoring has indicated a major decrease in LNAPL mass.