Although banned from agricultural use for more than forty years, carbon tetrachloride (CT) has been a “gift” that has kept on giving for decades in barns, silos and farm businesses across the United States. Left untreated, as has usually been the case, CT breaks down into byproducts such as chloroform, dichloromethane and methyl chloride. Although CT has been a regulated Contaminant of Concern (COC) for many years, USEPA has recently put CT on a list of chemicals to be further evaluated under the revised TSCA (Toxic Substances Control Act).
The pending sale of a Sheridan, Oregon, parcel that formerly was the home of a farm Co-op facility triggered Phase I and Phase II Environmental Site Assessments in 2015. CT contamination in groundwater was detected in several temporary borings/monitoring wells, with one groundwater sample measuring 65,500 ppb for CT, 3,190 ppb for Chloroform, and 8,850 ppb for 1,2-dichloroethane (aka 1,2 DCA or EDC).
BB&A Environmental, an RPI Group Approved Installer, was contracted to conduct an RDC (Remediation Design Characterization) to precisely determine the locations and BOS 100® dosage for injections. This effort included 90 soil and 11 groundwater samples. All of the RDC samples were analyzed using Method 8260B at the RPI Group Project Support Laboratory in Golden, Colorado. As with all RPI Group Trap & Treat® projects, the RDC analytical work was provided at no cost to the project. Compliance analyses were provided by a third party certified laboratory in Oregon.
After three quarterly monitoring events, contamination has been significantly reduced or eliminated at the four wells located in the treatment areas. At the most seriously impacted well (see above), third quarter measurements were 91.6 ppb for CT, 392 ppb for Chloroform and 115 ppb for 1,2 DCA. The other wells are either ND or significantly below applicable RBCs (Risk-Based Concentrations). One more monitoring event is planned at which time it is assumed that a request for site closure will be submitted to the Oregon Department of Environmental Quality.
A case study for this project will be published after closure has been achieved. Until then, additional details can be viewed by clicking here or you can simply contact Randy Boese rjboese@bbaenv.com.