The East Troy Contaminated Aquifer (ETCA) Site is an area on the eastern side of Troy, Ohio, that includes a volatile organic compound (VOC) plume(s) underlying a mix of residential, public, and commercial properties. The ETCA Site, is bordered by the Great Miami River, to the north; Race Drive, to the South; Williams Street, to the east, and South Market to the west. The Site’s meridian coordinates (recorded at the intersection of Union and Franklin Streets) are 40.03635° north and 84.19897° west. The Ohio Environmental Protection Agency (OEPA) indicated to U.S. EPA that two or more sources are contributing to two groundwater contamination plumes within the Site. Unidentified source(s) created a Tetrachloroethylene (PCE) groundwater contamination plume 0.5 mile to the east of downtown Troy between Walnut Street and the City of Troy municipal well field along the Great Miami River. U.S. EPA, OEPA, and the City of Troy are concerned that vapor intrusion into structures is occurring due to the groundwater contamination. Vapor Intrusion is the migration of volatile organic compounds such as PCE from contaminated groundwater to soil gas to indoor air.
On September 23, 2002, the OEPA completed an Expanded Site Inspection (ESI) Report for U.S. EPA Region V. The ESI noted that the City of Troy operates two well fields located along a 1.25 mile segment of the Great Miami River. Five wells are located in the west well field, and five wells are located in the east well field. The wells are screened in sand and gravel, and individual wells produce as much as 1,500 gallons per minute. The current production of the well fields is 5.4 million gallons per day.
The ESI was conducted from June 11 through July 9, 2002. OEPA collected groundwater samples from boreholes and installed and sampled monitoring wells to identify contaminant source areas and to delineate the pathways by which VOCs are entering the east well field. The ESI confirmed that the aquifer is contaminated with VOCs, and surmises based on available information that VOCs have emanated from multiple sources.
PCE is the primary contaminant at the Site and has historically been used in the dry cleaning industry as a cleaning solvent and in the automotive industry as a degreaser. OEPA has been conducting a multi-year groundwater monitoring effort in both plume areas and has identified PCE concentrations greater than 40 parts per billion (ppb) in the Plume 1 area and at concentrations greater than 800 ppb in the Plume 2 area.
In 2006, the OEPA completed soil gas monitoring and groundwater monitoring well sampling in the City of Troy’s residential east side along Franklin Street and Main Street. Groundwater sample results indicated PCE levels as high as 801 ppb under residential yards along Franklin Street. Soil gas monitoring indicated PCE levels as high as 58 ppb in residential yards along Franklin Street. Elevated levels of PCE in groundwater and soil gas were detected in a three block residential area between Franklin Street and Main Street.
LJB, Inc. (Consultant hired by the City of Troy)conducted two rounds of air sampling in Troy, Ohio, in 2006. LJB completed indoor ambient air sampling at 15 locations, including the Troy Police Station, St. Patrick Church, St. Patrick Elementary School, Forest Elementary School, and Total Team Sports store. Elevated levels of PCE were detected by LJB in indoor air at the following locations: Troy Police Station, St. Patrick Elementary School, Forest Elementary School, and Total Team Sports Store. LJB’s “Inhalation Air Sampling Data Report” dated June 13, 2006, summarized the two air monitoring events and concluded that inhabitants of structures within and around the two plume areas are at risk of inhaling a potential carcinogenic compound.
In a letter dated June 30, 2006, the OEPA requested U.S. EPA assistance in conducting a time-critical removal action at the ETCA Site. OEPA noted that groundwater is contaminated with VOCs from two or more sources, and wells within the Troy east well field have been impacted with VOCs above the federal MCLs. PCE has been detected in indoor air samples collected by the City of Troy from several occupied structures including the Troy Police Station, two elementary schools and a commercial business. OEPA noted that residences and other occupied structures above and adjacent to the ground water plumes are at risk for exposure to VOCs through vapor intrusion as the chemicals travel from the groundwater, into the soil gas, through the basement and then into the indoor air. OEPA requested that U.S. EPA conduct a removal action assessment to determine the extent of vapor intrusion contamination and to mitigate levels of VOCs in indoor air that exceed screening levels established by ATSDR and ODH.
From July 2006 through September 2006, the U.S. EPA collected Phase 1 sub-slab and indoor air samples from the east Troy residential area near Franklin Street in order to determine if there was a threat presented by vapor intrusion. A total of 19 locations were sampled, including 14 residential locations, 3 schools, a church and the City of Troy Police Station.
Air samples were collected in accordance with the U.S. EPA Environmental Response Team (ERT) standard operating procedures for the construction and installation of permanent sub-slab soil gas wells (vapor probes). The purpose of the sub-slab vapor probe sampling is to determine if VOCs are migrating from groundwater to surrounding soil gas to the foundation of a structure. Sub-slab vapor probe sampling is conducted prior to indoor air sampling. If sub-slab sampling results are less than the ATSDR sub-slab screening level (12 ppb for PCE) then no further action is taken. If sub-slab sampling results are greater than the ATSDR sub-slab screening level, then indoor air sampling is conducted. If indoor air samples are greater than the ATSDR indoor air screening level a completed exposure pathway is documented.
The sub-slab vapor probes were installed in residences or commercial buildings with basements having concrete slab floors or where the main floor was a concrete slab. Air samples were collected from the crawl space areas of structures that did not have concrete basements. All samples were collected using pre-cleaned, laboratory-supplied SUMMA canisters. The SUMMA canisters were fitted with regulators to allow for sample collection over a 24-hour period.
In a letter dated September 11, 2006, ATSDR and ODH provided U.S. EPA health-based guidance to evaluate the results of indoor and subsurface air sampling for PCE and TCE in Troy, Ohio. In the letter, ATSDR and ODH identified residential indoor air and sub-slab screening levels (including residences and schools) as well as non-residential building indoor air and sub-slab screening levels (police station, church, and commercial structures).
In the letter dated September 11, 2006, ATSDR and ODH concluded that several residential and school locations exceed the screening criteria and made the following recommendations upon the review of U.S. EPA air sample data at the Site:
“This groundwater plume may have been impacting these properties for an extended period of time. The implementation of a long-term remedy to remove the source is unlikely to occur in the near future. Therefore, we recommend that interim measures be taken at these properties to disrupt the vapor intrusion pathway into homes, which may include the installation of a sub-slab depressurization system, sealing cracks in walls and floors of the basement, and sealing or fixing drains that could be a pathway. These interim measures should be implemented as soon as feasible, while the long-term solution, such as source removal at the Site, is being executed.”
To further define the extent of contamination, the U.S. EPA conducted additional residential sampling in a Phase 2 investigation in 2006 and 2007. U.S. EPA conducted a public meeting in Troy, Ohio, on October 25, 2006, and invited residents to sign-up for sub-slab and indoor air sampling. In addition, U.S. EPA sent letters in December 2006, to 400 residences in the plume area, requesting access to conduct sub-slab and indoor air sampling. Approximately 60 additional residents agreed to provide access for the sub-slab and indoor air sampling.
From October 2006 through April 2007, the U.S. EPA collected sub-slab and indoor air samples from residential locations bounded by South Market Street to the west, Race Drive to the south, Williams Street to the east, and the Great Miami River to the north. A total of 60 sub-slab and 61 indoor air samples were collected.
In summary from July 2006 through April 2007, the U.S. EPA collected sub-slab and indoor air samples from a total of 85 locations, which included 78 residences, 2 churches, 4 schools and the Troy Police Station during Phase 1 and Phase 2 air sampling activities. U.S. EPA has contacted all property owners with elevated indoor air levels and conducted a meeting with owners and the Ohio Department of Health to explain the sample results, health issues, and proposed vapor abatement system. Property owners with indoor air levels less than the ATSDR and ODH screening levels have received a summary letter and sample results from U.S. EPA.
U.S. EPA has documented a total of 16 residential locations and one elementary school which show indoor air PCE and/or TCE vapor concentrations exceeding the ATSDR screening level of 1.2 ppb or 0.4 ppb, respectively.
May 31: Meeting held with property owners of residences exceeding ATSDR indoor air screening levels and representatives from St. Patrick’s School (School). City of Troy representatives were also in attendance. U.S. EPA provided property owners and School representatives the proposed plan for a vapor abatement system (VAS) to be designed and installed at each location with follow up sampling to confirm mitigation. Ohio Department of Health Bob Frey answered health questions from owners. Property owners and School representative signed the Operation and Maintenance Letter agreement with U.S. EPA for VAS installation and set up appointments for U.S. EPA’s Superfund Technical Assessment and Response Team (START) contractor, Emergency and Rapid Response Services (ERRS) contractor, System installation contractor, and environmental engineer/consultant to visit each location for VAS design.
June 5-7 START, ERRS, System installation contractor and environmental engineer visited all 16 residences to design specific VAS, begin photo documentation, and schedule installation. VAS scheduled to be installed June 19 – July 24.
16 residential VAS installations will occur between June 19 and July 24, with post-installation sampling 30 days and 90 days after VAS installation.
Design of school VAS on-going. School VAS installation is scheduled for July 2007.
16 residential VAS installations will occur between June 19 and July 24, with post-installation sampling 30 days and 90 days after VAS installation.
Design of school VAS on-going. School VAS is scheduled for July 2007.
Indoor air levels of PCE and/or TCE above ATSDR and ODH screening levels identified at 16 residential and one school location.
Vapor Abatement Systems (VAS) will be installed at 17 locations in June-July 2007. VAS will be designed to vent volatile organice compounds from below the structure slab to above the roof line. EPA will conduct post-installation sampling at all 17 locations to confirm that indoor air is below ATSDR and ODH indoor air screening levels.
|
