The Department of Environmental Protection (DEP) has conducted an investigation in the Town of Wilmington at the request of local officials and area residents, to evaluate a number of areas where contamination was found to be present. The primary objective of this investigation was to determine if people were being exposed to unacceptable levels of chemical contaminants, and to identify any sources or potential sources where releases of chemical contaminants to the environment may have occurred. The areas discussed in this report include the residential neighborhoods near Kelly Hill and the commercial and industrial properties located along Main Street from Rte. 62 to Silver Lake. Recent activities conducted at the McDonald Road site in North Wilmington (Release Tracking Number 3-19231) and the Olin Chemical site in South Wilmington (Release Tracking Number 3-0471) are not discussed in this report.

Executive Summary

The Massachusetts Department of Environmental Protection has conducted an evaluation of contamination problems in central Wilmington, focussing on drinking water well contamination in the Kelly Hill area, and soil and groundwater pollution along Main Street. This evaluation consisted of a review of information and data available in agency files for contaminated sites within this area, and a limited field investigative effort to obtain and analyze soil, groundwater, and drinking water samples.

The findings of this effort are summarized below:

• The bedrock aquifer beneath the Kelly Hill area is contaminated by low to moderate levels of tetrachloroethylene (PCE) and methyl tertiary butyl ether (MtBE). Given the complexities associated with contaminant movement in bedrock fractures, it is not possible to conclusively identify the origin(s) of this contamination, although available lines of evidence implicate septic system discharges (PCE) and residential use and spillage of gasoline (MtBE) as the most likely sources. Additional investigation is necessary, however, to rule out any possible connections between this contaminated aquifer and groundwater contamination along Main Street.

• Although most homes on Kelly Hill are connected to the municipal water supply system, up to 30 homes reportedly obtain their drinking water from on-property drinking water wells. Of 13 private wells tested, 8 were found to contain levels of PCE or MtBE. As a result of this testing effort, three homes have abandoned their wells and have been connected to the municipal water supply system. Given the nature and extent of contamination in this area, it is recommended that all homes using private wells be tested regularly, be equipped with treatment devices, and/or be tied into the municipal water supply system.

• A number of facilities along Main Street have historically stored, spilled, or disposed of petroleum products and/or industrial solvents. As a result of these practices, the underlying groundwater is now contaminated with moderate to high concentrations of a number of chemical compounds and hydrocarbons. The most significant problem identified to date is in the area of 315 to 319 Main Street, where up to 420 mg/L of trichloroethylene (TCE) has been detected in the deep overburden aquifer. (Note that TCE has only been detected at trace levels in the Kelly Hill area. Its presence at such levels is likely to be a result of the degradation of tetrachloroethylene.)

• Although significant levels of oil and hazardous materials are present in the subsurface along the Main Street study area, investigations conducted to date by DEP have ruled out any current impacts to nearby populations. There are no known private drinking water wells within this area of town (other than the Kelly Hill wells, which are likely not being impacted by groundwater contaminants from this area). Moreover, because the most highly contaminated groundwater is in the deepest portions of the aquifer, it is unlikely to directly or significantly impact human activities, including de-watering activities associated with building/roadway construction and basement sump pumps. However, DEP will continue to monitor concerns in this regard, and will obtain sump-water and indoor air samples from homes and buildings in potentially impacted areas near Middlesex Avenue during high-groundwater conditions of March and/or April.

Detailed Discussion:

• Kelly Hill - Private Wells
  • Discussion

  • Recommendations

• Main Street Area
  • DEP 21E Sites
  • DEP Subsurface Investigations
  • Discussion

  • Recommendations

• Silver Lake Area
  • Discussion

  • Recommendations

• Maps
  • Wilmington, Private Well Sampling, Kelly Hill
  • Wilmington Surface Water Flow
  • 21E Sites
  • Wilmington, Main Street 21E Sites with MtBE
  • Wilmington, 21E Sites with PCE Contamination
  • Subsurface Investigations

The information on this web page is based on a February 25, 2000 memorandum [updated March 15, 2000] from Paul Giddings, NERO BWSC to Richard Chalpin, Regional Engineer, BWSC NERO and John Fitzgerald, Regional Engineer, BWSC NERO. Additional review of the memorandum was provided by Valerie Thompson, BWSC NERO and Stephen Johnson, Section Chief, BWSC NERO.