Client: Randy Rothe [MDEQ] - (989) 705-3416
Site Location: 102 South Bridge Street, Bellaire, Michigan
Project Dates: 10/99 - Present
Sagasser & Associates, Inc. was subcontracted by a State of Michigan Contract Management firm to complete Acute Risk Abatement (ARA), Site Investigation (SI) and Focused Feasibility Study (FFS) of a known contaminated facility. The project involved identification of potentially contributing sources to the LUST site contamination, assessing the impact to residential wells, vapor monitoring of indoor air and substructures, free product and soil and groundwater contaminant delineation.
The Site consisted of a former gas station facility with four separate UST basins. Sagasser & Associates, Inc. conducted an extensive SI that identified several acute hazards to include impacted soil within each former UST basin, a free product plume within the source area, impacted groundwater approximately 600 feet down gradient affecting drinking water, and a down gradient river basin and associated river. The groundwater aquifer characteristics vary from an unconfined condition at the Site and confined conditions within the down gradient river basin (including some artesian conditions).
Based on the results of the SI, ARA and FFS, Sagasser & Associates, Inc. concluded that remediation of the acute hazards be accomplished utilizing a combination of remedial technologies. Utilizing a mixing zone determination, SSTLs were recommended for addressing the groundwater contaminant plume venting to the river. For abating free product, soil and source area groundwater contamination, high vacuum dual phase extraction (HVDPE) was recommended. Enhanced biodegradation utilizing air sparge (AS) and soil vapor extraction (SVE) was determined to be the most appropriate remedial alternative for the confined portion of the aquifer.
Sagasser & Associates, Inc. conducted Pilot Testing, Remedial Design, Specifications and Remedial Construction Oversight at the Site. The pilot testing consisted of a 24-hour HVDPE aquifer characterization test, an AS/SVE test, infiltration/aquifer capacity test, and slug tests. Sagasser & Associates, Inc. designed the remediation system and developed the specifications for construction of the remediation system for the Site.
The project included installation of additional monitor wells, 19 recovery wells (7 DPE and 12 SVE, two SVE wells are utilized also as injection wells for treated water), 35 AS wells, 6 vapor monitoring points to monitor volatiles at adjacent residential basements, approximately 1500 feet of trenching and associated underground piping, remedial system housing, dual-phase / soil vapor extraction / rotary vane compressor remediation equipment, O/W separator, carbon filtration, catalytic oxidation, electrical system and controls, HVAC system, telemetry, Site restoration, system startup and operation & maintenance (O&M) oversight activities. The bulk of construction activities were completed in approximately 120 days. The project is currently in the O&M phase. The strategy employed for remediation is to mitigate free product utilizing HVDPE and subsequently convert the existing system components to AS/SVE to abate remaining acute hazards.
The system operations, during the first 1.75 years of the 3 year projected timeframe, have resulted in the mitigation of benzene levels from 8,000 ug/L to <5 ug/L throughout the source area. See the benzene isopleths on the back of this sheet. Similarly, total VOCs have been significantly abated throughout the area being remediated (e.g., highest total VOCs were reduced from 74,000 ug/L to <500 ug/l [MW-21]).
Numerous reports have been prepared for this project including ARA, SI, FFS, Remedial Design, Construction Specifications, Construction Oversight Report, System O&M Oversight, Free Product Monitoring and Quarterly Monitoring Reports.