BOZEMAN SOLVENT SITE
The Bozeman Solvent Site (BSS) is a Montana Superfund site located in the western portion of Bozeman, Montana. The City of Bozeman and Jewel Companies were named as Potentially Responsible Parties. The main issue of concern is a chlorinated solvent plume consisting predominately of perchloroethylene (PCE) in alluvial/fluvial valley aquifer. The PCE was first discovered in 1989 at concentrations up to 714 parts per billion in a public water supply serving a trailer court. Subsequent investigations revealed that the source of PCE was a dry cleaner located in the Buttrey Shopping Center (BSC). A majority of the plume likely commenced in a time frame between 1977 to 1983. The relatively complex nature of the alluvial/fluvial aquifer led to a shallow plume and a deeper plume. The following activities were performed by WET personnel to address the solvent contamination:
- Remedial Investigation (RI)
- Fate and Transport Groundwater Model (F&T model)
- Interim Remediation Activities
- Feasibility Study (FS)
Two accelerated interim remedial actions were implemented before completion of the RI. The first action included replacement of the original leaking sewer line that terminated an ongoing source to the plume. During the sewer line replacement soil remediation action, key areas of soil contamination were identified. Impacted soils were excavated and treated and disposed of. A soil vapor extraction system was then installed and operated to remediate remaining impacted soils.
The two interim remedial actions resulted in relatively rapid improvements in groundwater quality at the site. PCE levels in adjacent site wells had decreased by 80 percent or more at about the time of SVE operation shutdown. A three-dimensional, seven-layer, fate and transport (F&T) groundwater model was successfully developed to represent PCE transport in both the shallow and deeper strata. The FS developed a full range of remedial alternatives addressing the remaining residual on-site sources and the extensive PCE plume. Onsite alternatives evaluated included SVE to in-situ biological treatment to hydraulic containment to address residual sources, and vapor venting options to control indoor air exposure. The plume alternatives included monitored natural attenuation, plume control and plume remediation pump and treat along with alternatives to provide replacement drinking water to groundwater users at and in the vicinity of the plume. The F&T model was a key element for the development and evaluation of plume remedial alternatives.