Remediation in the works for Millsboro Superfund site
Story Location:
Millsboro, DE
United States
More than a decade after state officials found elevated levels of trichloroethylene-contaminated ground water in Millsboro, experts with the U.S. Environmental Protection Agency have unveiled a plan for removing the remaining contamination.
“Your water is perfectly fine and perfectly good to drink. I've personally been drinking it all day,” said EPA remedial program manager Christian Matta, taking a sip of Millsboro tap water to prove his point. “The TCE is removed at the filters and does not affect the distribution system.”
When contamination was first detected in the town's water supply by the state Office of Drinking water in 2005, levels of trichloroethylene, or TCE, were alarmingly higher than the national safe drinking water standards, which have current limits of no more than 5 parts per billion, or 0.005 milligrams per liter. Some areas of TCE concentrations reached more than 1,000 parts per billion, according to EPA studies.
Public comment period open through May 4
A public comment period on the proposed action is open through Wednesday, May 4. Comments may be submitted in writing to Christian Matta, U.S. Environmental Protection Agency, Region 3 Office, 1650 Arch Street (Mailcode 3HS22), Philadelphia, PA 19103, or by email to matta.christian@epa.gov or deitzel.carrie@epa.gov.
An investigation launched by the state Department of Natural Resources and Environmental Control found the source of the contamination was a former poultry vaccine-manufacturing plant at 225 W. DuPont Hwy. The plant, in operation from 1952 to 1999, was demolished in 2000.
Millsboro TCE Superfund site timeline
1952-1999: Site at 225 W. DuPont Hwy. in Millsboro operated as a poultry vaccine manufacturing plant, where TCE was used as a refrigerant
2000: Facility demolished
2005: Elevated levels of TCE found in Millsboro's drinking water supply system
November 2005: Granular activated carbon filtration units installed to remove TCE
December 2005: DNREC investigation underway to find source; officials locate a TCE plume moving from 225 W. DuPont Hwy. toward Millsboro Pond
July 2006: 209 tons of contaminated waste are removed and underground tanks removed
2008: DNREC begins an in-situ chemical oxidation pilot study to break-down TCE
September 2009: EPA proposes listing the site on the National Priorities List, which is withdrawn when the agency and the responsible parties, Intervet Inc. and Mallinckrodt Veterinary, enter into a voluntary clean-up agreement
May 2010: The responsible parties enter into a voluntary administrative order on consent, requiring weekly testing, studies, carbon filters, assessments and other remediation work
February 2011: The responsible parties enter into a second administrative order on consent for engineering evaluation and cost analysis
April 2015: Mallinckrodt Veterinary enters into a $2.75 million settlement with DNREC to reimburse the state agency for clean-up efforts
April 2016: EPA officials update Millsboro residents on findings of engineering evaluation and cost analysis
TCE, which is commonly used in vapor degreasing of metal parts, can also be found in paint removers/strippers, adhesives and refrigerants. The pollutant is moderately water soluble, can move through soils, and is the most frequently reported organic contaminant in groundwater, the EPA says. The EPA also states people who drink TCE-contaminated water over extended periods may experience liver problems and may have an increased cancer risk.
Since TCE was found in Millsboro's drinking water supply in 2005, contaminated surface soils have been removed, affected drinking water supply wells were taken offline and several pilot projects by both DNREC and EPA experts have maintained control of the TCE plume and treated groundwater with carbon filters and other measures.
Former manufacturer Mallinckrodt Veterinary, identified as one of the responsible parties by Delaware's Hazardous Substance Cleanup Act program, entered into a settlement agreement in April 2015 to repay DNREC $2.75 million for testing and cleanup of the site from 2006 to 2009.
“Since DNREC began the initial remediation back in 2006 and 2008, the TCE concentrations have dropped 10 to 100 times from what they were,” said Darren Scillieri, a representative with ARCADIS, a design, consulting and engineering firm that helped prepare the report.
Scillieri said no health risks have been identified from the current soil contamination, because of the low levels of TCE and the depth of the pollutant. The groundwater plume, which flows to the northeast and dives deeper as it moves, is under control, he said, and there have been no concerning levels of TCE vapors detected at the site, he said.
The 2,500-foot-long plume, which Matta said has been reduced by about 80 percent since site work began, extends beyond the half-acre source site, and is 550 feet at its widest point.
But there is still a lot more work to be done.
TCE contamination of soil and groundwater remains at the site and within a plume being controlled by pumping stations. Most of the contamination is found 10 to 14 feet below ground surface, Matta said. No private wells are permitted in the area, he said.
A detailed engineering evaluation and cost analysis review provided several options for complete cleanup. EPA officials plan to first treat contaminated groundwater and soil by chemical oxidation, which uses hydrogen peroxide to break down the TCE. Second, contaminated ground water will be extracted, treated in a carbon filtration system and then injected back into the aquifer. The third step of the plan requires long-term monitoring of the site.
Millsboro resident Patricia Hawkins said she had no idea about the pollution until after she moved to town about five years ago.
“I love it here, but it's really a disappointment,” she said. “We need action and assurance that it's being taken care of and done the proper way.”
The proposed remediation plan is expected to cost about $4 million and take 20 years to complete. The responsible parties, Intervet Inc. and Mallinckrodt Veterinary will pay for the work, Matta said. If the proposed plan is approved, work may begin as early as the end of 2016.
A public comment period on the proposed action is open through Wednesday, May 4. Comments may be submitted in writing to Christian Matta, U.S. Environmental Protection Agency, Region 3 Office, 1650 Arch Street (Mailcode 3HS22), Philadelphia, PA 19103, or by email to matta.christian@epa.gov or deitzel.carrie@epa.gov.
