EPA proposes interim cleanup plan for Rhode Island’s David Liquid Waste Superfund site

The U.S. Environmental Protection Agency (EPA) has released a proposed plan for an interim remedy for the cleanup of groundwater at the Davis Liquid Waste Superfund site located in Smithfield, Rhode Island.

EPA has considered several alternative methods to address groundwater contamination at the site and is seeking public comments on the preferred remedy until July 15. After the public has had an opportunity to review and provide comment, EPA will formalize selection of the interim remedy in a “Record of Decision (ROD) Amendment 2 (Interim Remedy)" expected in September. This decision document will amend the groundwater remedy selected in the 1987 ROD that was amended again with the 2010 ROD Amendment.

EPA's preferred alternative for the interim remedy in the proposed plan is designed to prevent current and future human health and ecological exposure to, and risk from, hazardous materials until a final remedy is selected for groundwater at the site. The proposed plan includes:

• On-site treatment of groundwater contaminants, which will be evaluated at regular intervals to determine efficacy.
• Filling an existing manmade ditch to maintain groundwater flow in the overburden aquifer.
• Monitoring of the dissolved groundwater contaminant plume.
• Adopting institutional controls to prevent contact with contaminated groundwater and exposure to vapor intrusion from contaminated groundwater into structures.
• Continued monitoring and assessment as well as 5-year reviews to assess the performance of the interim remedy and ensure the site remains protective of human health and the environment.

The interim action that EPA proposes defers the selection of a final groundwater remedy for the site pending an evaluation of the effectiveness of on-site treatment to reduce the presence of dense non-aqueous phase liquid (DNAPL). During the first 5-year review of the site's remediation efforts, EPA will assess the need for changes to the interim remedy. During the second 5-year review, EPA will evaluate progress in reducing the DNAPL mass and attaining cleanup levels in groundwater.

The estimated total present value of this proposed cleanup approach, including construction, operation and maintenance, and long-term monitoring is approximately $6.7 million.

During the mid-1970s, local officials received complaints from nearby residents about chemical odors in their private water supply around the site. The drinking water wells were found to have been contaminated by a variety of chemicals. The major contaminants of concern in the overburden and bedrock groundwater that exceed federal and state standards are: volatile organic compounds (VOCs), such as tetrachloroethene, trichloroethene, vinyl chloride and benzene; semi-volatile organic compounds (SVOCs), including bis(2-chloroethyl) ether; pesticides, such as aldrin and dieldrin; and metals, including arsenic and manganese.

Exposure risks to residents from contaminated groundwater has already been minimized by prior cleanup activities at the site, including:

• Extension of the municipal waterline.
• Approximately 100,000 cubic yards of contaminated soil and debris were excavated and either disposed off-site or treated and backfilled at the site.
• Removal of buried hazardous waste drums.
• Removal of over 6 million discarded tires.