NASSAU – The U.S. Environmental Protection Agency (EPA) has announced that an additional treatment technology will be added to the existing treatment plant at the Dewey Loeffel Landfill Superfund site in the Rensselaer County Town of Nassau. The plant, which began operating in January 2014, is treating liquids seeping from the landfill, called leachate, and contaminated groundwater. The new treatment system is being added to further address the long-term treatment of the chemical 1,4-dioxane. The new system will be in place by November 2014.
Since the treatment plant began operating, the EPA has required that the treated water be stored in a series of three on-site storage tanks and tested before each individual tank is discharged to the Valatie Kill. This tank-by-tank process will continue until 7 to 10 days prior to delivery of the new treatment system, expected in late October. In order for the new system to be installed, the storage tanks at the site will need to be removed.
The EPA will approve direct discharge from the plant to the Valatie Kill at that time, provided the sampling data continue to meet the stringent discharge limits set by the New York State Department of Environmental Conservation (DEC). It is anticipated that the EPA will have sampling data from about 40 individual tanks by the time it allows any direct discharges from the treatment plant.
The rate of groundwater and leachate coming into the plant for treatment, called the flow rate, will be reduced to as low as possible while the additional treatment technology is being installed. The plant needs to be kept running during the two to three week installation period to ensure that one of the treatment technologies in the plant that relies on microorganisms to treat the wastewater can continue to operate effectively. The wastewater and leachate coming into the plant provide the nutrients these microorganisms need to survive. After the new treatment system is installed the flow rate will be increased. Surface water will be sampled at least three times after direct discharge is approved.
The slow startup phase was intended to gradually bring the plant up to capacity to ensure that it is working effectively and is capable of meeting the discharge limits set by the DEC. Over 25 tanks have been sampled, analyzed and individually discharged to the Valatie Kill. The majority of compounds tested for in the tanks that were discharged have not been detected in the treated water and all have been below the requirements set by the DEC. The carbon filtration system, which is a component of the existing treatment plant, has been removing 1,4-dioxane and will continue to be the primary treatment method for 1,4-dioxane until the new treatment technology is in place this fall.
From 1952 until 1968, the Dewey Loeffel Landfill was used for the disposal of an estimated 46,000 tons of waste materials generated by several Capital District companies including General Electric, Honeywell International, Inc. and SI Group, Inc. The waste included industrial solvents, waste oils, polychlorinated biphenyls (PCBs), scrap materials, sludge and solids. Volatile organic compounds and other hazardous substances have seeped out of the landfill and contaminated the groundwater. PCBs have also moved downstream, causing contamination of sediment and several species of fish in and near Nassau Lake.
The treatment plant was built and is being operated GE and the SI group, under a 2012 agreement with the EPA. The added treatment is being installed because the EPA and the companies have agreed that adding the specialized treatment is the best long-term treatment option for 1,4-dioxane.The construction of the treatment plant was an action that was taken to address potential risks to human health and the environment, but does not represent the final cleanup decision for the site. A comprehensive long-term investigation is now under way which will identify permanent cleanup options for the contaminated groundwater, surface water, soil, and sediment associated with the site.
In November 2013 GE and SI Group agreed to conduct comprehensive studies of the contamination at the site. After these comprehensive studies are completed, the EPA will evaluate cleanup options. These options will be presented to the public and the public will have an opportunity to comment on the proposed cleanup plan. The final cleanup plan selected for the groundwater may include changes to the treatment plant.
The EPA has a webpage about the site at www.epa.gov/region2/superfund/npl/dewey.