The Louisville District completed the Remedial Investigation/Feasibility Study ahead of schedule for the former Nike C-47 launch and control areas and obtained project closeout at the nearby control area.
“We had a good understanding of the geological conditions leading to selection of the appropriate bioremediation technology for an effective treatment at the launch area,” said Corey Knox, Louisville District chemist.
In 1956, the Department of Defense acquired Nike C-47 missile base in Hobart, Indiana. The control and launch areas consisted of 20.46 acres and 14.16 acres, respectively.
It was used as a missile battery base until its deactivation in 1972. Under the Formerly Used Defense Sites program, the U.S. Army Corps of Engineers Louisville District manages the site cleanup for DoD.
The former Nike C-47 was a unique situation, where the team was able to perform a pilot study at the launch area early on within the RI phase of the Comprehensive Environmental Response, Compensation and Liability Act process.
According to Clayton Hayes, district project manager, the project wasn’t overly complex. There was known trichloroethene contamination at the launch area, which was located relatively shallow in the groundwater and confined within a small defined area.
“To add, there was a single contract in place covering both the launch and control projects, which helped the project move forward more efficiently and contributed to saving time and money – finishing earlier than planned,” Hayes said. “Leading up to the Decision Document, we investigated areas of concern, analyzed it, tested and determined what needed to be done. Also, we re-evaluated human health risks and any mitigation efforts that may be needed following the CERCLA process.”
According to Knox, given that this bioremediation technology proved to be effective in other locations with similar conditions, it seemed to be a good candidate for the pilot study at the launch area.
Within a few months following injection into the groundwater wells, the initial results showed that the microbes had effectively reduced TCE concentrations in the groundwater; however, vinyl chloride (breakdown of TCE) did become present. To mitigate this effect, a second microbial treatment had to be employed specifically designed to target vinyl chloride, which later also proved to be effective, Knox said.
As a result of the positive results achieved from the pilot study, “We achieved a signed DD, Aug. 27, 2019, allowing the completion of the RI phase of work following the CERCLA process,” Hayes said. “Therefore, we are now moving into the next CERCLA phase (Remedial Action – Operations) to monitor the groundwater at the launch area for at least another six quarters.”
Quarterly groundwater sampling is slated to continue at the launch area as required by the Indiana Department of Environmental Management to demonstrate that the groundwater continues to remain free of contamination, according to Knox.
The former Nike C-47 control area obtained project closeout based on the no further action DD. This resulted from conducting a re-evaluation of the risk assessment by comparison of soil data to updated U.S. Environmental Protection Agency regional screening levels, thus, showing no significant risk to human health and the environment.
“We are fairly confident that the results will be favorable, and the launch area project can potentially be closed,” Hayes said.
According to Hayes and Knox, having technically proficient team members, timely reviews, the right resources, implementing a pilot study early on in the CERCLA process, and having an effective treatment all played a significant role in the timely closure of the RI/FS phase at the launch and control area projects.
The team is now focused on taking the right steps and actions aimed toward the close out of the launch area project.