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1.1.1 Incident Category
CERCLA incident category: Inactive Production Facility
1.1.2 Site Description
1.1.2.1 Site Location
The Site is located at, and in the area of, 1205 East 7th Street, Atlantic, Cass County, Iowa. The approximate coordinates of the Site are latitude 41.403718° North and longitude 94.995763° West. The Site is a former dry cleaning facility, which has since been turned into a parking lot for an adjacent commercial building.
The City of Atlantic has a population of 7,008 (U.S. Census Bureau 2012) and is located in Cass County, Iowa, approximately 45 miles northeast of Council Bluffs and 75 miles west of Des Moines. Land use in the area of the Site is a mixture of commercial and residential. The City of Atlantic Municipal Utility well field is located adjacent to Troublesome Creek.
1.1.2.2 Description of Threat
Analytical results from samples collected by the Iowa Department of Natural Resources (IDNR) indicate that hazardous substances have been released into the environment at the Site. Tetrachloroethene (PCE) and its degradation products, including trichloroethene (TCE), are hazardous substances as defined in CERCLA section 101(14), 42 U.S.C. § 9601(14), and as designated in 40 CFR § 302.4. PCE has been detected in one city municipal well at concentration levels that exceed the EPA’s Maximum Contaminant Levels (MCL) of 5 micrograms per liter (µg/L). Concentrations of PCE as high as 170 µg/L have been found in one city municipal well.
1.1.3 Removal Preliminary Assessment/Removal Site Inspection Results
Preliminary assessment site activities from August 1982 to February 2, 2012 are taken from written reports.
August 1982
During a water quality survey conducted by IDNR in August of 1982, PCE was detected in municipal well AMU-7 at concentrations as high as 170 µg/L. Subsequent sampling in August 1984 by IDNR showed an increase in PCE concentrations at AMU-7, with levels as high as 260 µg/L. As a result, AMU-7 was disconnected from the municipal water supply system and has been continuously pumped to provide hydraulic control to the remaining municipal wells.
August 1982 to November 1987
Groundwater from AMU-7 was pumped into Buttermilk Creek in an attempt to restrict migration of the PCE to other municipal wells. In December 1987, the discharge from AMU-7 to Buttermilk Creek was rerouted to the 3rd street sanitary sewer line for treatment at the city’s public owned treatment works (POTW).
August 1987
The EPA conducted a soil gas survey to delineate the approximate extent of PCE contamination. Analytical results suggested the source area was just south of East 7th Street, about 250 feet east of the former dry cleaner and Iowa Department of Transportation (IDOT) materials testing lab (Table 1). The report stated that a release of PCE likely occurred at the Site and migrated through surface runoff and groundwater flow to this topographic low. In addition, the migration from the Site may have followed the storm sewer system along the southern side of East 7th Street.
1988
The EPA assessed the Site using the Hazardous Ranking Score (HRS) model. Two pathways were scored (groundwater and surface water). The overall site score was 26.14.
In August 1988, IDNR conducted follow-up investigations of PCE contamination to better define the source. Thirty-four soil gas samples and ten soil samples were collected for analysis. The sampling focused on the area of the Site and the source area identified during the 1987 EPA investigation. The investigation confirmed the level of PCE contamination originally detected 250 feet east of the Site. However, significantly higher PCE levels were detected in soil gas near the Site (greater than 10,000 parts per million (ppm). Based on these findings, IDNR concluded that the silty, clayey soil beneath the Site is the predominant source of PCE contamination impacting the groundwater. The soils appear to be contaminated to at least 20 feet below grade (fbg). IDNR recommended installing groundwater monitoring wells to better define the extent of the PCE contamination near the suspected source.
October 2002
In October 2002, EPA field activities included 13 soil borings to depths ranging from 23 to 36 fbg, and the installation of three groundwater monitoring wells. The soil borings were advanced around the previously identified source area. PCE was identified in soil from two Geoprobe borings and soil from one monitoring well boring. Groundwater samples were collected from the three monitoring wells. Analytical results can be found in Table 3. Monitoring wells locations can be found in document section.
May 2003
On May 13, 2003, the EPA collected water samples from Monitoring Wells (MW) MW-1, MW-2 and MW-3 and Atlantic Municipal Utility wells (AMU) AMU 6 & 7. The monitoring wells were sampled using a standard bailer and passive diffusion bags (PDBs). Analytical results as high as 4,300 µg/L for PCE was found in MW-2. Analytical results can be found in Table 3.
July 2003
The EPA collected water samples from MW-1, MW-2 and MW-3 and AMU 6 & 7 on July 29, 2003. Samples were collected using bailers and with PDBs. Analytical results show PCE concentrations as high as 5,300 µg/L in MW-2 (Table 3).
June 2005
The EPA and the Environmental Response Team (ERT), with support from the Response Engineering and Analytical Contract (REAC), performed a hydrogeologic investigation of the Site. The primary purpose of this investigation was to define the nature and extent of groundwater contamination, upgradient of the AMU-7 well, for assessing the applicability of installing a permeable reactive barrier (PRB) for groundwater treatment and protection. As part of the investigation, six boreholes were installed about 150 feet upgradient of AMU-7.
PCE was reported in water samples from all six borings, with the highest concentration of 446 µg/L in the boring farthest east. Also, the breakdown product TCE was detected in groundwater samples from each boring. The eastern extent of the plume near the well field was not delineated in this investigation and remains undefined. Following the investigation, preliminary cost estimates to install a PRB were calculated. The total costs for this remedial technology were prohibitive to implement under the removal program.
December 2011
The EPA collected groundwater samples and performed a HRS evaluation in December 2011. In addition, groundwater samples were collected from nine active municipal wells and from AMU-7 that is now off line and pumped to the POTW.
Analytical results for PCE as high as 2,500 µg/L were found in MW-2 and in AMU-7 PCE results were 87 µg/L (Table 3).
The results of the HRS showed a site score of 50 on the groundwater pathway.
February 2012 to July 2012
OSC Susan Fisher became the OSC of record for the Site on February 3, 2012.
OSC Fisher met with Jon Martens , AMU, and Keith Wilken, Iowa Department of Natural Resources (IDNR) - Atlantic field office, to discuss the history of the Site on July 11, 2015.
OSC Fisher also met with Rolling Hills Bank & Trust in Atlantic, Iowa on July 11, 2015 to discuss access to the commercial building parking lot to collect future soil and groundwater samples.
OSC Fisher talked to property owners to obtain access to their properties to collect groundwater samples in October 2012.
September – October 2012
On October 1, 2012, the Geoprobe Membrane Interface Probe (MIP) was used to better delineate the vertical and horizontal extent of contamination at the Site. A Geoprobe was used at each location to advance a MIP tool through the subsurface soil to obtain a continuous log of chlorinated volatile organic compounds (VOCs) in soil, and to collect electrical conductivity (EC) results as well. (MIP and EC logs can be found in the document section.)
February 2013
On February 6, 2013, the EPA met with Rolling Hills Bank & Trust. The meeting was held to discuss vapor intrusion sampling at the bank and commercial building, and collection of additions soil and groundwater samples at the commercial building property. Rolling Hills Bank & Trust gave access to collect vapor intrusion samples. Access to collect vapor intrusion samples was also given by 10 other properties in Atlantic in the vicinity of the commercial building parking lot.
On February 12, 2013, the EPA collected 7 indoor air samples and 9 subslab samples.
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