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The Millsboro TCE Site included a probable source area, a TCE-contaminated ground water plume, and the public drinking water supply system operated by the Town of Millsboro. A Removal Action was conducted at the Site to assure safe drinking water to the public until the EPA Remedial Program could take over. The probable TCE source area is located at the intersection of Wharton Street and South Dupont Highway. The facility included an underground tank suspected to be the probable source of the TCE contamination to the public water supply wells. The Site additionally includes a plume of TCE-contaminated groundwater migrating from the probable source area towards and into public drinking water supply wells serving the Town of Millsboro. There are two supply wells known to be contaminated by TCE and these 2 wells have carbon filtration units which remove contamination before delivering the treated water to the community of Millsboro. See previous POLREPs for additional Site background information.
An Action Memorandum was signed on July 14, 2009, and included funding in the amount of $420,000 to conduct weekly sampling of drinking water and drinking water sources (ground water) and to change carbon filtration units in which contaminated ground water is treated before delivery to the community of Millsboro. The required sampling was initiated in September 2009 and the EPA response contractor was mobilized to the Site September 9, 2009 in order to initiate activities enabling EPA to be ready to change the carbons when needed. The sampling continued through the week of April 19, 2010, and was conducted by the EPA Superfund Technical Assistance and Response Team (START) contractor (Tetra Tech). Sampling was continued beyond the week of April 19th by contractors funded by Potentially Responsible Parties (PRPs). Samples collected by EPA were analyzed throughout the project by laboratories participating in the EPA Contract Laboratory Program (CLP). The analytical results were reviewed by the Environmental Services Assistance Team (ESAT). The weekly samples were analyzed for the volatile organic compounds TCE and its breakdown products.
During the Removal Action, samples were collected from 2 public wells and from 2 points in the distribution system, At each public well, a sample was collected before the 2 carbon units at each well ("lead" sample), from between the 2 units present at each well site ("middle" sample), and from a point after the carbon units at each well ("lag" sample). The highest concentration found at well #1 was 230 ug/L detected on 2/22/10. The highest concentration detected at well #2 was 280 ug/L on 9/9/09. Concentrations after the carbon units did not exceed 0.5 ug/L..
Over the course of the response action, the analytical results were routinely reviewed by EPA and the Town of Millsboro. The analytical results were also sent to the Delaware Department of Natural Resources and Environmental Control (DNREC). The responsibility for determining the need for a carbon change in order to assure the protection of the residents of the Town of Millsboro was, by agreement, that of the Town of Millsboro.
The carbon units attached to the 2 contaminated wells were changed one time by EPA over a 3 day period in November and December 2009. The change out was conducted by Siemens under subcontract to the EPA ERRS contractor (Guardian Environmental). The spent carbon was shipped off-Site to Siemens Water Technologies for regeneration/re-use. Overall, 18,000 pounds of spent carbon was transported from the Site to Siemens to be regenerated and re-used.
The Site was proposed to the National Priorities List in September 2009 during the timeframe of the Removal Action. A Remedial Project Manager was assigned and initiated the process of identifying potentially responsible parties (PRPs) and seeking to get those parties to assume responsibility for the activities conducted under the Removal Action. An Order requiring response actions from PRPs was signed by the Region on May 10, 2010. The PRPs (e.g., Mallinckrodt Veterinary, Inc. and Merck & Co., Inc.) initiated routine sampling during the week of April 26, 2010 and continue that sampling at this time while the SIte progresses through the EPA Remedial Process. At this time the EPA Remedial Project Manager (RPM) and the EPA Remedial Program are conducting actions at the Site and the Removal Action is concluded. Now that the PRPs are assuming the activities of the EPA Removal Action, the scope and intent of the Removal Action as selected in the July 2009 Action Memorandum are completed.
All current activities are performed by the EPA RPM and Remedial Program.
There are no future planned Removal Actions and the Removal Action at this Site is concluded.
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