Brief History/Current Status of WR Grace Superfund Site (December 2010), Acton, MA

ACES, (Acton Citizens for Environmental Safety), has been a strong and persistent advocate for the most thorough investigation and protective cleanup of the WR Grace Site possible, ever since contamination was discovered in the late 1970’s.

Brief Background:
In 1978 two of Acton’s Town wells (40% of the Town’s water supply), were found to be contaminated with organic chemicals. Contamination was later determined to have come from a nearby industrial site, designated by EPA in 1983 as the WR Grace Superfund Site. The major groundwater contaminants currently at the site are in two categories: volatile organic compounds (VOCs) and inorganics (metals). The three major VOC contaminants at the site are benzene, vinyl chloride and vinylidene chloride or VDC (also known as 1,1-dichloroethene or DCE). There has been longstanding treatment via an air-stripping tower to remove these contaminants from groundwater on the southern portion of the site. The treated water is then discharged into Sinking Pond, an onsite kettle pond. The major inorganic contaminants at the site include arsenic and manganese. Unlike treatment prior to 2010, future groundwater treatment will include metals removal. Since the 2005 EPA Record of Decision, an additional contaminant, 1,4-dioxane, has been identified as a concern. Prior to 2005 there was no testing for this contaminant which has since been found at elevated concentrations in the landfill area.

Cleanup Activities 2010/2011
This fall (2010), WR Grace is in the process of putting in foundations etc. for a new water treatment plant in the Landfill Area part of the site near Sinking Pond. The current Landfill Area treatment does not remove metals from the water before dumping it into Sinking Pond. Therefore there has been an ongoing discharge of arsenic, iron, manganese, etc. into the Pond for the last 25+ years. The result is that the pond sediment is contaminated with high levels of arsenic, etc.

The current phase of cleanup at the WR Grace Superfund Site that is being undertaken per the 2005 Record of Decision by EPA, has three components. Status as of fall 2010:

1. Northeast Area Groundwater:
The new Northeast Area Groundwater Treatment System on the north side of the MBTA tracks has been operational since spring 2010. It removes volatile organic compounds and arsenic from the water and then discharges the treated water directly into the ground via “recharge wells”. This is the first time there has been active treatment by WR Grace on this part of the site.

2. Landfill Area Groundwater:
WR Grace hopes to complete the new Landfill Area Treatment Plant near Sinking Pond by spring/summer 2011, to replace the existing plant on this part of the site, (south of the MBTA tracks). They have already installed new additional extraction wells in this area. The new plant will remove metals—including arsenic, iron and manganese, as well as volatile organic compounds, and also treat for 1,4-dioxane before discharging the treated water into Sinking Pond.

3. Sinking Pond Sediments, and North Lagoon Wetland Area Sediments:
After the Landfill Area Treatment Plant is up and running the sediments around the perimeter of Sinking Pond will be excavated, dewatered and trucked and disposed of offsite. Sediments in the North Lagoon Wetland Area, (located adjacent to Fort Pond Brook, north of the MBTA tracks) will also be removed, etc. The disturbed areas will be restored and replanted.

Additional Background Information: In 1978 two Acton town wells were found to be contaminated with organic compounds. These public wells, Assabet 1 and Assabet 2, had been in operation since the early 1970’s, and in 1978 supplied 40% of the town’s drinking water. Contaminants included : Ethylbenzene, 1,1-Dichloroethylene (also known as DCE or VDC), Benzene, 1,1,1-Trichloroethane (TCA), Trichloroethylene (TCE), Methylene Chloride, Toluene, and Chlorobenzene.

At its Acton facility, which it purchased in the 1950’s, WR Grace produced latex and rubber based products and cellulose battery separators. WR Grace disposed of industrial wastes, including VDC, onsite in unlined impoundments. Onsite waste disposal was ceased in 1980. In 1980 the US Environmental Protection Agency and WR Grace entered into a consent decree. The WR Grace Site was added to the EPA National Priority List, as a Superfund Site in 1983. Removal and treatment of contaminated soil and sludge was completed in 1997. The final step at the site was to fully characterize and delineate the groundwater contamination, (and associated sediment and surface water contamination), and to remediate the site as appropriate.

The Northeast Area of the site has only recently been delineated by WR Grace. The groundwater contamination in this area is in bedrock under residential areas, and is at shallower depths near Fort Pond Brook and as the plume is drawn into three public water supply wells. The well water is treated by the Acton Water District with a stripping tower to meet federal drinking water standards before distribution as public drinking water. In the spring of 2010 WR Grace installed a groundwater treatment system to treat the most concentrated portion of the plume in the Northeast Area.

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