The Department of Energy and two companies have agreed to carry out “remedial design” for the cleanup approach selected by the Environmental Protection Agency for the radioactively contaminated area of the West Lake Landfill in Bridgeton, Mo.
The Energy Department, Bridgeton Landfill LLC, and Cotter Corp. are the potentially responsible parties for the EPA Superfund site. They committed to remedial design under an amendment to the standing remedial investigation/feasibility study administrative settlement agreement and order on consent for West Lake, the EPA said in a press release Wednesday.
“This Administrative Settlement and Order on Consent is an enforceable agreement with the PRPs who will perform the work under EPA oversight,” Jim Guilford, administrator for EPA Region 7, in the release. “The design work includes additional site testing, modeling, and engineering design that are required to ensure the remedy can be implemented in the most expedient and safe manner.”
Last September, the EPA laid out a remediation approach that encompasses partial excavation and off-site disposal of contaminated material, with the impacted area then capped with an engineered cover. The EPA expects the potentially responsible parties to conduct that work.
The three parties are required to provide the agency with a remedial design work plan that will provide a broad look at the process, details of the design, and a schedule for the preliminary design.
Remedial design will cover soil boring and other data gathering, preparation of a 3-D model for the excavation approach, and readying a construction schedule, among other work. It is expected to take two-and-a-half to three years – compared to a previous estimate of 18 months.
“While this is longer than previously anticipated, we believe that a carefully designed remedy based on sound science and engineering is the best way to ensure worker safety and public safety during construction,” the EPA said in a separate update this week.
Two sections of the 200-acre Superfund site, now formally known as Operable Unit 1, were contaminated in 1973 by 39,000 tons of surface soil dating to the Manhattan Project that had been combined with 8,700 tons of radioactive leached barium sulfite residues before being used as trash coverage.
West Lake’s groundwater was found to have unsafe levels of radioactive uranium, radium, and thorium-230 during tests from 2012 to 2014. The majority of the radioactive material is thorium-230, which is a decay product of uranium, which was processed at St. Louis’ Mallinckrodt Chemical Works facility during World War II.
Concerns about the landfill have been exacerbated by an underground fire at the adjoining Bridgeton Landfill.
The remediation approach replaces a plan laid out in a 2008 EPA record of decision that involved placing an engineered cover over the radiologically impacted areas, along with monitoring wells.
In an amended record of decision last September, the EPA set out a remediation approach that calls for excavating radiologically impacted material as far down as 20 feet in West Lake’s contaminated sections. In most cases, material contaminated at levels above 52.9 picocuries per gram would be removed to a depth of 12 feet. In certain sections material with concentrations above 52.9 picocuries per gram will not be removed at depths of 8 to 12 feet.
An off-site disposal facility for the waste has not been selected.
The project has been estimated to cost $205 million, with excavation lasting three years. Both projections could be updated following the design phase, EPA spokeswoman Emily Albano said by email Thursday.
Bridgeton Landfill, a subsidiary of waste disposal company Republic Services that owns the landfill, in September said it objected to the new remediation approach over the prior “cap and monitor” plan. It did not respond to a request for comment this week.
A subsequent agreement will be necessary for actual implementation of the remedy. The agency is in talks with the three entities on an enforceable agreement, Albano said.
