Client: Oil Company, Gaylord, Michigan 49734
Site Location: 917 US-2 West, St. Ignace, Mackinac County, Michigan
Project Dates: 5/97 - Present
The Site is an active truck stop/gas station. A release of gasoline was identified at the Site subsequent to water entering one of the 7 existing USTs. The leaking UST, situated between two other USTs, was removed and replaced. Sagasser & Associates, Inc. assisted in the closure and documentation of the leaking UST, performed the RI, designed remedial system specifications, oversaw remedial system installation, and O&M.
Site investigation activities have included free product discovery, free product delineation/assessment, immediate abatement/removal of free product and periodic monitoring for recurrence of free product. Field investigation activities have included completion of hand auger borings, direct push borings (Geoprobe©) for soil contaminant delineation; soil sampling utilizing EPA 5035 methanol preservation techniques; hollow-stem augering, mud rotary augering and rock coring. In addition, 18 monitor wells have been installed for delineation of groundwater impact in the confined aquifer of a fractured/weathered limestone bedrock formation. Monitor wells include horizontal and vertical delineation wells and 4 recovery wells.
The project also included evaluation of migration and exposure pathways, comparison to Tier I RBSLs and preliminary assessment of Tier I/II SSTLs. Subsequently, Sagasser & Associates, Inc. completed the RI, pilot testing and feasibility study, which identified high vacuum dual phase extraction (HVDPE) as the most practical interim remedial alternative. The remedial system installation activities included preparation of bid specifications, requests for bids, bid review and recommendations, contractor negotiations and contracting, permitting and construction oversight. Sagasser & Associates, Inc. designed/maintains an HVDPE remedial system which mitigated free product and significant soil and groundwater contaminants. Source area impact has been decreased from 3,900,000 ug/L to 1,200 ug/L. In addition, excavation activities were conducted that included source area unconsolidated soils and weathered bedrock with limited dewatering.
Numerous reports have been prepared for this project including IAR, RI, FFS, Interim Response Action Design, Excavation Oversight, System O&M, Free Product Monitoring and Quarterly Monitoring Reports.