LITTLE VALLEY, NY
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The Little Valley Superfund site is comprised of a trichloroethylene (TCE)-contaminated groundwater plume that extends approximately eight miles southeastward from the Village of Little Valley to the northern edge of the City of Salamanca, which is part of the Allegheny Indian Reservation, in Cattauragus County, New York. The site is located in a rural, agricultural area with a number of small, active and inactive industries and more than 200 residential properties situated along Route 353, the main transportation route between Little Valley and the City of the Salamanca.
In 1982, the Cattaraugus County Health Department (CCHD) and the New York State Department of Environmental Conservation (NYSDEC), while investigating TCE contamination in the vicinity of a small manufacturing facility on Route 353, detected TCE in nearby private wells. NYSDEC installed a number of monitoring wells in the area to investigate possible sources of the contamination, including a former drum storage area, a private disposal site next to the former drum storage area, an inactive municipal landfill which accepted industrial wastes, and industrial facilities.
Following the installation of treatment systems on private wells, EPA put the site’s long-term remedy in place, which consisted of soil remediation, a long-term groundwater monitoring program, institutional controls, and an evaluation of the potential for soil vapor intrusion into structures within the study area and mitigation, if necessary.
What Has Been Done to Clean Up the Site?
EPA placed the site on the Superfund program’s National Priorities List (NPL) in June 1996.
The site is being addressed in two phases--an interim groundwater remedy consisting of point-of-entry treatment units (POETs) (Operable Unit One [OU1]) and a final groundwater remedy, including the control of the sources of groundwater contamination (OU2).
Immediate Action: Following the listing of the Site on the NPL, EPA evaluated the residential well sample results and concluded that contaminant levels at the site did not warrant immediate action while a focused feasibility study (FFS) was prepared to develop, screen and evaluate various alternatives for an alternative water supply system for the affected and potentially affected residences at the site. Some residents elected to install treatment units on their wells. Others bought bottled water. Based upon the findings of the FFS, EPA issued a ROD in 1996, providing for the installation of air stripper treatment units on all affected and potentially affected private wells to ensure that drinking water standards are met. Installation of the air stripper treatment units was completed in 1997. Subsequently, granular activated carbon units were installed in conjunction with the air strippers to enhance performance.
In 2002, it was determined that the existing air strippers were reaching the end of their useful life and were replaced with granular activated carbon treatment units alone. The activated carbon treatment units will continue to provide potable water until drinking water standards are met at the site. Maintenance of the treatment units and monitoring of the private wells is being performed by NYSDEC.
Long-Term Cleanup: Based on the FFS, EPA issued a ROD in 1996, providing for an alternate water supply. The ROD called for the installation of point-of-use air stripper treatment units on all affected and potentially affected private wells.
Installation of the air stripper treatment units on over 90 private wells with TCE concentrations above the MCL finished in 1997. Granular activated carbon units were later installed in addition to the air strippers to improve overall contaminant removal efficiency. Since the air strippers were reaching the end of their useful life, and because of the significant reduction in contaminant concentrations in the private wells, EPA determined that granular activated carbon units alone would effectively remove the contamination. EPA’s five-year reviews in 2002, 2007, and 2012, and 2017 concluded that the remedy is functioning as intended. Samples indicate that TCE concentrations are decreasing in nearly all the wells. The filters will remain in use until the pre-filtered TCE levels drop below the state drinking water standard.
A remedial investigation (RI), conducted from 1997 through 2005, identified five areas as either current or likely past sources of TCE—Bush Industries Ares (BIA); Cattaraugus Cutlery Area (CCA); Great Triangle Area (Drum Storage Area); Luminite Area; and Ninth Street Landfill Area.
Based upon the soil data collected during the RI, the CCA was determined to be a localized source of groundwater contamination at the site. In addition, TCE concentrations in the groundwater underlying this area were found to exceed the Maximum Contaminant Levels (MCL) and did not appear to be decreasing over time in specific monitoring wells. Based upon the TCE concentrations that were detected in the soil and the TCE concentrations which exceeded MCLs in the groundwater, the RI concluded that the BIA also appeared to be a current localized source of groundwater contamination. The RI also concluded that the TCE levels in this area appeared to be decreasing due to natural attenuation.
Based upon the results of a June 2005 RI/feasibility study report, a ROD was signed in 2005 that called for the excavation and off-site treatment/disposal of an estimated 220 cubic yards of contaminated soils located on the CCA and monitored natural attenuation (MNA) for the site-wide groundwater. Annual MNA monitoring is being performed by EPA as a long-term response action.
The 2005 ROD also called for an evaluation of the potential for soil vapor intrusion into structures within the study area and mitigation, if necessary. In addition, the ROD included institutional controls in the form of informational devices (e.g., notifications). Lastly, the ROD made the interim alternate water supply remedy called for in the 1996 ROD the final remedy for the water supply.
In fall 2005, in accordance with the selected remedy for the soil, EPA undertook pre-excavation soil sampling to define the boundaries of the soil contamination at the CCA. The results from this sampling effort indicated that the volume of contaminated soil was substantially greater than originally estimated in the 2005 ROD (it increased from approximately 220 cubic yards to approximately 3,000 cubic yards).
In 2006, a ROD amendment was approved, changing the soil remedy selected in the 2005 ROD to in-situ soil vapor extraction (ISVE). The 2006 ROD amendment also called for excavation and off-site treatment/disposal as a contingency remedy should operational data indicate that ISVE would not address all the contaminated soils.
The ISVE system operated at the CCA from 2006 through 2013, reducing the volume of TCE-contaminated soil to an estimated 20 cubic yards. At that time, it became apparent that the ISVE system was no longer effective in extracting TCE from the soil. In 2014, approximately 25 cubic yards of TCE-contaminated soil was excavated at the CCA and disposed of off-site. EPA subsequently released an Explanation of Significant Differences (ESD) to document this change to the remedy.
Volatile organic compounds (VOCs) in groundwater, even at low levels, can migrate as vapors through the soil and into buildings. This process, which is called soil vapor intrusion (SVI), can result in unacceptable human exposures to VOCs inside occupied buildings. To evaluate the possibility of SVI at the site, in 2005, EPA tested under the slabs of 23 houses and a manufacturing facility as a representative sample of the more than 300 residences and businesses overlying the contaminant plume. In 2006, EPA revisited 12 of the houses tested in 2005 to sample the indoor air and also tested under the foundations of an additional four houses. Based upon these results, EPA collect subslab soil gas samples from an additional 84 houses and indoor air samples were collected from 36 houses. Based upon the results of these sampling efforts, subslab mitigation systems were installed beneath two residences in fall 2006. In 2012, based upon the results of continued annual soil vapor intrusion sampling, subslab mitigation systems were installed at two additional homes.
Review of the residential well sampling results indicates that there are decreasing levels of contaminants in all but a few drinking water wells. There is no current unacceptable risk associated with exposure to the contaminated groundwater, because point-of-use treatment systems have been installed on all affected drinking water wells.
Cattaraugus County Health Department (CCHD) issues an annual notice to local governmental agencies, including the building code enforcement officers, stating that if any unimproved parcel where the underlying groundwater is contaminated with TCE above the MCL is developed, the groundwater should not be used without appropriate treatment. In addition, EPA notified the BIA and CCA property owners that the underlying groundwater is contaminated and should not be used without treatment. As part of the annual natural attenuation monitoring event at the BIA and CCA, the properties are inspected to verify that wells without treatment systems have not been installed. An annual report summarizing the results of the groundwater monitoring and the findings of such inspections is prepared.
EPA determined that an institutional control to prevent exposure to potential SVI at parcels that are developed in the future was needed to ensure protectiveness. This was documented in a 2014 ESD. CCHD’s annual notice to the local governmental agencies also advises that if new structures are constructed over the TCE plume (including at the CCA and Bush Industries properties), vapor mitigation measures should be implemented as part of the new construction or a property-specific evaluation should be performed to demonstrate that vapor intrusion will not be a concern at the property.
All of the property owners/renters with drinking water wells that are protected with POETs are aware of the fact that the groundwater they use is contaminated and should not be used without treatment. They are reminded of this on a periodic basis when NYSDEC collects samples from their wells and/or provides maintenance related to their individual treatment units.
What Is the Current Site Status?
In September 2017, an agreement was signed between EPA and NYSDEC transferring the responsibilities from the EPAlead remedial action to New York State's State-lead operation and maintenance ("O&M) of the groundwater portion of the remedy selected in the August 19, 2005 ROD.
NYSDEC is performing site-wide groundwater monitoring; site-wide SVIsampling; operation, maintenance and monitoring associated with the vapor intrusion mitigation systems; and institutional controls verification inspections at the BIA and CCA at the Site.