Client: Earth Tech - MDEQ Project Management Firm
Site Location: 109 East Munising Avenue, Munising, Michigan
Project Dates: 05/01 - Present
Sagasser & Associates, Inc. was subcontracted by a State of Michigan Contract Management firm to complete RI, FAR, FFS, Interim Response Design and Oversight for a known contaminated facility. The Site consisted of a former gas station facility with several historical leaking UST systems. Sagasser & Associates, Inc. conducted an extensive RI that included soil characterization (14 soil probe borings), groundwater characterization (12 probe wells and 46 permanent wells), domestic well sampling (geothermal heating/cooling system), free product assessment, and petroleum vapor assessment.
The soil types generally consisted of fine to coarse sand to depths on the order of 24 to 34 feet below ground surface (bgs), underlain by alternating silt/clay/sand layers to 47 feet bgs. Soil contamination was identified in the immediate vicinity of the former UST basin and dispenser island. Groundwater was encountered at the Site at depths on the order of 2.5 to 19 feet bgs, dependent upon location relative to Lake Superior (450 feet downgradient of the Site). The groundwater contaminant plume was shown to spread laterally as it migrated to Lake Superior, and was also shown to be influenced by adjacent property activities (geothermal well and discharge system).
The RI activities identified several acute hazards to include: Soil contamination exceeded drinking water protection and GSI criteria; and groundwater contamination exceeded the drinking water and GSI criteria from the Site to Lake Superior and volatilization to indoor air criteria on-Site.
A focused feasibility study was conducted for the site to address the acute hazards concurrently by developing a remedial approach that incorporates each of the acute hazards to be mitigated. The evaluation of remedial technologies indicated that no one technology would fully eliminate the acute hazards. Based on an evaluation of the existing immediate threats identified at the Site, the technologies available to remediate the Site, and the relative costs for those remedial technologies, a remedial approach was recommended for the Site. The remedial approach included long-term monitoring, natural attenuation, periodic dual-phase extraction, and risk assessment.
Sagasser & Associates, Inc. developed an interim response plan that included free product/vapor recovery utilizing a vacuum truck. Six recovery wells were installed at the Site and free product/vapor recovery events are progressing for a period of 12 months. In addition, vapor monitoring around the subsurface and interior of potentially impacted buildings and an ongoing evaluation for the need of a mixing zone determination are also being performed.