Engineers at the U.S. Army Corps of Engineers Engineer Research and Development Center’s (ERDC) Cold Regions Research and Engineering Laboratory (CRREL) have used an innovative technology to chemically cleanup an on-site groundwater contaminant, trichloroethylene (TCE). This new cleanup practice uses potassium permanganate to oxidize the TCE and has readily gained acceptance by regulatory agencies. CRREL has an ongoing effort to cleanup groundwater contamination discovered in 1990.
From the inception of CRREL in the early 1960’s until the late 1980’s, much of the extensive refrigeration system within the laboratory complex used TCE as a refrigerant and groundwater as a coolant. Since the late 1980’s, all of the TCE has been replaced by ethylene glycol and there is no ongoing TCE use at CRREL. However, during the time that TCE was in use, some undetermined quantity of TCE was released to the environment. This was due to commonly accepted practices of the time, as well as accidental releases.
The Agency for Toxic Substances and Disease Registry characterizes TCE as, “A colorless liquid which is used as a solvent for cleaning metal parts…and is an ingredient in adhesives, paint removers, typewriter correction fluids and spot removers. Drinking or breathing high levels of trichloroethylene may cause nervous system effects, liver and lung damage, abnormal heartbeat, coma, and possibly death.”
Since 1993, groundwater has been processed through the onsite groundwater treatment plant. The groundwater is “cleaned” through a process that incorporates air-stripping towers that capture the TCE on granular activated carbon. The processed water is then used in the cooling systems throughout the CRREL facility and discharged to the Connecticut River at less than five parts per billion. TCE levels in onsite well water is continually monitored and regularly reported to New Hampshire Department of Environmental Services (NHDES).
While several decontamination options exist, potassium permanganate, the chemical neutralization compound currently employed at CRREL, has emerged as a safe and appropriate treatment for TCE-contaminated groundwater and soils. Among its wide-ranging uses, potassium permanganate has a long history of safe application to drinking water for oxidizing minerals and controlling taste and odor. Aqueous solutions of potassium permanganate range in color from light pink to dark purple, depending on the concentration.
In 1999, a model for the groundwater flow and pumping scheme at CRREL was completed and showed that the pumping of water created an effective hydraulic barrier that prevented off-site migration of any groundwater contamination. However, residual TCE in subsurface soils may contribute to groundwater contamination and the current focus of restoration work is the reduction of TCE in these soils.
“The remedial action plan combines an aggressive soil treatment strategy with normal groundwater extraction operations. It enables us to contain and reduce the groundwater contamination with a minimization of impact to the aquifer system,” said Dr. Daniel McKay, CRREL’s Environmental Engineer.
CRREL used a potassium permanganate solution concentration range of 0.6 to 3%. This solution was applied to contaminated soils beneath the ground surface by both low and high-velocity injection at depths generally between 8 to 32 ft., or over 100 ft. above the water table. This soil treatment should mitigate TCE migration to groundwater.
“We appreciate how CRREL has worked hard to address their problems,” said Robert Minicucci, NHDES’s Project Manager.
As per New Hampshire State Law, CRREL has submitted its remedial action plan to NHDES and held a public meeting on April 30 to address community concerns.
“We’re pleased that we had the opportunity to test new technology while still progressing toward our ultimate goal of cleanup. The cooperation of the Army Environmental Center and the New Hampshire Department of Environmental Services made this effort possible and is much appreciated. The remedial action plan is the culmination of those efforts and the final chapter in the overall cleanup effort at CRREL. There will be ongoing activity related to continued operation of our groundwater treatment plant and groundwater monitoring, but most of the hard remediation work is now behind us,” said Robert Sletten, CRREL’s Remedial Program Manager.
POC is Robert Sletten, (603) 646-4443, e-mail: email@example.com.
Marie Darling is a public affairs specialist with ERDC-CRREL.
Public Works Digest • July/August 2003