Remediation Status: In groundwater monitoring

Why the technology was selected:
Based on bench scale testing, in-situ chemical oxidation was selected.

Date implemented:
1999 (1 event), 2001 (1 event), 2009 (2 events)

Final remediation design:
In 1999, there were two five-day injection events utilizing hydrogen peroxide, in three injection wells. The volume of treated groundwater was estimated to be approximately 17,000 gallons. Initially, an aqueous solution of ferrous sulfate and hydrochloric acid and finally by a 35% solution of hydrogen peroxide (495 gallons in the first event and 605 gallons in the second injection event). In August and September of 2001, a total of 135 gallons of a 5.5% solution of potassium permanganate was injected at the site. In May and July of 2009, 2 events occurred where 360 pounds (lbs) of RegenOX oxidant was mixed with 500 gallon of potable water to form a 5 % solution and then injected into the ground during each event. The injection target goal was 20 feet below ground surface.

Other technologies used:
N/A

Results to date:
*The 1999-2001 In-situ chemical oxidation events resulted in only minor reductions in chlorinated solvent concentrations. Since those events, the source area and plume have been better characterized. The size and concentration of the plume are greater than was thought when the remediation events were conducted. Groundwater analytical results in 2007 indicated concentrations of PCE and its daughter products exceeding Tier 1 PCLs in the samples collected from wells MW-1 and MW-6. Daughter products exceeding their Tier 1 PCLs included TCE, cis- and trans-1,2-DCE, 1,1-dichloroethene (1,1-DCE), and vinyl chloride. The highest concentration of PCE (8.1 mg/L) and its daughter products were reported in well MW-6. *Groundwater analytical results in 2008 continue to indicate concentrations of PCE and its daughter products exceeding Tier 1 PCLs. PCE, TCE, Cis-1,2-DCE, Trans-1,2-DCE, and 1,1-DCE have shown an increase in concentrations since last sampled in December, 2007, with vinyl chloride showing the only decrease in concentration. The increase in daughter products indicates that reductive dechlorination continues to occur at the site. *2012: None of the treatments have been sucessful in the long term. The likely causes of the failed remedial actions include site hydrogeology and the design of the Chemical oxidation injection events was not dense enough.

Next Steps:
* In 2006, this site transfered from an RP-lead program to a state lead program. * Continue Monitoring of existing monitor wells to obtain additional groundwater data and evaluate any trends. * Investigation of second groundwater unit is ongoing. *In 2009, a pilot study will evaluate the applicability and/or effectiveness of in-situ chemical oxidation (ISCO) with regards to the site s geologic conditions and in terms of the reduction of chlorinated solvent contaminant concentrations currently above TRRP Tier 1 PCLs in the shallow groundwater bearing unit. As part of the study, a sodium percarbonate based chemical oxidant will be injected into the subsurface to treat COCs. This oxidant will be utilized in the study because it will exist in the subsurface over a longer period than the previously injected oxidant. *There was a FY10 Biotrap feasibility study to conduct if a particular type of bioremediation will be more feasible on site. The recommendations from this study concluded the biostimulation and bioaugmenation together is a suitable treatment for the containment source area ("hot spot"). There has been no further remedial actions or studies on this site beyond groundwater mointoring and further assessments of the contaminent source.