PCE Remediation at Helena Solvent Site


HydroSolutions has been involved with investigation and remediation activities at the Helena Solvent Site since 2008, beginning with an environmental site review for the owner of The Hustad Center in response to a DEQ enforcement action. Following this site review, the property owner responded to DEQ requirements and contracted with HydroSolutions to initiate a focused source investigation, soil and groundwater sampling, indoor air sampling, installation of an indoor air mitigation system, groundwater monitoring, sub-slab air monitoring, and indoor air monitoring. HydroSolutions oversaw the installation of the sub-slab depressurization system to mitigate the effects of contaminated vapor intrusion from the sub-slab into the office space.

DEQ and the property owner entered into an administrative settlement agreement in 2016, settling the owner's liability for the Helena Solvent Site. HydroSolutions provided technical assistance to the settlement negotiations. Pursuant to the administrative settlement agreement, DEQ took over site investigation and remediation activities and contracted with HydroSolutions to conduct interim remedial actions.

Over the past year, HydroSolutions completed a remedial investigation of soil and groundwater contaminated with tetrachloroethene (PCE) and other chlorinated solvents. A focused source area investigation included push-probe and membrane interface probe (MIP) technology, groundwater and soil sampling, as well as indoor air and soil vapor point sampling. Horizontal drilling techniques were implemented to install a soil vapor extraction (SVE) system beneath the dry cleaning building to remediate the PCE contamination. HydroSolutions is currently evaluating SVE performance, performing operation and maintenance on the SVE system, monitoring indoor air and groundwater, and evaluating abiotic and anaerobic degradation processes of contaminants for natural attenuation conditions. Contact Dave Donohue at 406-443-6169 x 103 or davidd@hydrosi.com for more detailed project information. Click here for information from DEQ about the Helena Solvent Site.