The Mottolo Superfund Site (Site) encompasses a portion of 50-acre wooded property located off Blueberry Hill Road in Raymond, New Hampshire. The Site, formerly used as a pig farm, is approximately three miles south of the town’s center and is surrounded by rural residential property.
From 1975 to 1979 over 1,600 drums and pails of chemical manufacturing wastes from two companies were disposed in a quarter-acre pit at the Site. In 1979, State inspections indicated that soil and groundwater beneath the Site were contaminated with volatile organic compounds (VOCs) and arsenic, and that the contaminants were seeping into a brook (Brook A) that empties into the Exeter River, one half mile to the north. Between November 1980 and January 1982, the Environmental Protection Agency (EPA) excavated and removed the drums and pails found at the Site, along with 160 tons of contaminated soil. In July 1987, the Site was subsequently added to the National Priorities List of sites eligible for cleanup under the Superfund program.
In 1991 EPA selected groundwater, surface water, and soil cleanup remedies which included installing a groundwater interceptor trench; installing and operating a vacuum extraction system to remove VOCs from the soils; installing a security fence to limit access to contaminated areas, continued monitoring of groundwater and surface water, and; institutional controls, which restrict the use of contaminated groundwater and prevent disturbance of cleanup activities. Construction of the vacuum extraction system was completed in 1993 and operated until December 1996, when soil cleanup levels were attained.
In 2000, EPA removed the chain link fence surrounding a portion of the Site and installed a new entry gate and modified the remaining wells. In September of 2003, the responsibility for operating and maintaining the remedy was officially transferred from EPA to the New Hampshire Department of Environmental Services (NHDES).
In 2003 NHDES instituted a residential well sampling program to monitor the residential wells directly abutting the southern border of the Site. Residential well sampling in this area has been on-going since 2003 with analysis showing no exceedances of drinking water quality standards.
EPA completed the Third Five-Year Review (EPA Review) for this Site in August 2008, which called into question the protectiveness of the remedy because of the persistent and slightly increasing concentrations of several contaminants in groundwater in a number of monitoring wells since the last five-year review in 2004 and increasing residential development pressure west of the Site. The Review also analyzed the natural attenuation component of the remedy and found it not to be occurring uniformly across the Site and that the estimated cleanup times had not been achieved. Residential development around the site continues with increasing pressures on the groundwater resources that may present opportunity for exposure. The Third Five-Year Review recommended: improving on-site monitoring; expanding off-site monitoring of residential wells; investigating on-site subsurface soils for residual contamination; and finalizing site institutional controls to fully assess and ensure protectiveness.
To begin addressing the issues identified in EPA’s Review, DES implemented a site-wide groundwater sampling event during the summer of 2009 and expanded the residential sampling program to include all residences in the immediate vicinity of the Site. In June 2009, analyses for VOCs and arsenic were performed on 27 water supply wells in the immediate vicinity of the site.
Sampling results revealed that many of the residential wells (located mostly west of the site) had elevated concentrations of arsenic and four residential wells had detectable concentrations of VOCs. One of the affected residential wells had a concentration of trichloroethylene (a volatile organic compound) slightly above the drinking water standard of 5 micrograms per liter. A second home had a concentration of trichloroethylene just below the drinking water standard.
The owners of these two residences were immediately informed of the discovery and bottled water was delivered to the homes the same day. Follow-on confirmation sampling provided sufficient data to initiate the design and installation of point-of-entry water treatment systems to remove VOCs from the water at these two homes.
Based on the results of the June sampling event, the water supplies for seven additional homes (located further west of the Site) were analyzed for VOCs and arsenic. Arsenic is a naturally occurring metal that exceeds the drinking water quality standard of 10 micrograms per liter in approximately 20 percent of the bedrock wells in New Hampshire. However, review of the data from these seven wells showed that the elevated concentrations of arsenic in these homes could not be disassociated from site-related impacts. Consequently, DES provided bottled water to nine additional homes where arsenic exceeded the drinking water standard. DES also began an extended effort to assemble a technical team that could assist in planning investigative activities and associated data interpretation that would assist NHDES and EPA in evaluating the full extent of site-related impacts.
On September 15, 2009, DES held a public meeting in Raymond to present a brief site history, an update of recent and planned on-site and off-site sampling and a discussion of possible future actions at the Site. Additional response actions that occurred over the fall and winter of 2009-2010 included conducting a subsurface investigation to identify possible on-site residual sources of arsenic and VOCs, installing three new on-site deep bedrock wells followed by geophysical testing and water sampling, and conducting additional sampling of 65 area residential wells.
In early 2010, DES’s contractor, GZA GeoEnvironmental Inc., prepared a 2009 Data Report, which provided a summary, analysis, interpretation, and findings of the extensive residential sampling programs, on-site subsurface investigation, and overburden and deep bedrock groundwater sampling events. In general, the report findings concluded that the combined presence of the site contaminant trichloroethylene (TCE) and associated site-related chemistry impacts on groundwater has likely mobilized arsenic, resulting in concentrations above background levels in the area adjacent to the western boundary of the Mottolo Site. Key findings of the report, areas impacted, next steps and schedule were presented at a March 24 public meeting.
In general, the 2009 Data Report identified homes located west and south of the Site where supplied alternate water options would be considered in a focused feasibility study (FFS), the next phase of evaluating an appropriate long-term solution to the Site impacts previously discussed. The options to be evaluated in the FFS include: (1) extending the municipal water system; (2) constructing a localized community water supply and distribution system, and; (3) providing point-of-entry or point-of-use treatment systems for each impacted household. The FFS is scheduled for completion in summer 2010 followed by EPA’s preparation and release of a selected remedy in a Proposed Plan. The Proposed Plan will be presented at a subsequent public meeting followed by a 30-day public comment period. Upon EPA responding to public comments received, the agencies will proceed with formalizing the final remedy in an Amended Record of Decision (AROD), which will provide the essential elements of the remedy and the basis for EPA’s monetary contribution to the final remedy. The AROD is anticipated to be final in September 2010.
Mottolo Site – Current Activity