Summary of Fifth WR Grace Five-Year Review


The Environmental Protection Agency has released a new Five-Year Review (FYR) Report on the WR Grace (WRG) Superfund site, a former industrial site that straddles the town line between Acton and Concord. The purpose of a five-year review is to evaluate how well a clean up plan (“remedy”) is working to be protective of human health and the environment. 

If any issues are found during the review, they are documented and recommendations to address them are put forward. This is the 5th FYR for the WR Grace Superfund site; links to the previous FYRs can be found here.

Potential sources of contamination are spread across a wide area, on both the north and south side of the MBTA train line, as shown below:

from the 5th Five-Year Review Report for the WRG site

The WR Grace site cleanup effort encompasses two different types of contaminated materials:

  • Surface materials (soil and sludge), also known as OU-1 or “Operating Unit 1”: The remedy for this material was to excavate the contaminated soil and either ship it off site or place it in a landfill within the WRG property. The landfill was then closed with an impermeable cap. This all happened prior to the last FYR. The sole recommendation concerning OU-1 coming out of the current FYR is to enact a NAUL (Notice of Activity and Use Limitation) that would prevent disturbance of the landfill by future owners or users of the land.
  • Groundwater contamination, also known as OU-3 or “Operating Unit 3”: The OU-3 cleanup is ongoing. Most of the new information in the 2019 FYR is about OU-3.

Operating Unit 3 (groundwater and wetlands):

The stated goals of the OU-3 cleanup are to restore the drinking water aquifer and to eliminate the threats posed by direct contact with or ingestion of contaminants in sediment in two areas: the North Lagoon Wetland and Sinking Pond. The locations of these and other features are shown on a site map, here

The OU-3 effort has been underway since a Record of Decision (ROD) was signed in 2005. The ROD sets quantitative cleanup levels for arsenic and manganese in the two wetland areas, and for 17 different contaminants in the groundwater. Among these are benzene, VC (vinyl chloride), VDC (vinylidene chloride), MTBE (methyl tert-butyl ether), TCE (trichloroethylene), arsenic, and lead. 1,4-dioxane is not among them.

Multiple kinds of actions have been underway under OU-3:

  • The upper layer of sediment was removed from the North Lagoon Wetland and from Sinking Pond, and replaced with clean soil. This activity met its goals and concluded in 2011.
  • Various groundwater extraction and treatment systems have operated in disparate parts of the site over differing time intervals. More detail below.
  •  “Institutional controls” (ICs) refer to administrative and legal controls that help minimize potential for human exposure to contamination; zoning restrictions are one example. One IC is currently in place: the Acton Board of Health has an administrative hold (also known as a “moratorium”) on the installation of private irrigation wells around the WR Grace site. Discussions are ongoing about what kinds of ICs would be appropriate for the site in the longer term.
  • “Monitored Natural Attenuation (MNA)” means letting natural processes decrease the concentration or the mobility of contaminants, while continuing to collect and analyze soil and water samples. For example, microbial action can break down contaminants, or they can stick to soil particles. MNA is the remedy being used for most of the WRG site.

Groundwater Monitoring, Extraction, and Treatment:

Each year, the contractor working on the WR Grace site collects multiple water samples from a network of monitoring wells, and analyzes them for one or more of the following: volatile organic compounds (VOCs), inorganic compounds such as arsenic, geochemical parameters such as pH, and 1,4-dioxane. The Green Acton website covered the findings reported in the 2018 annual monitoring report with respect to VOCs (levels of which have generally been getting better) and 1,4-dioxane (whose levels have not been improving.)

There are two areas of the WR Grace site where groundwater has been proactively extracted and treated in recent years.

From April 2010 through September 2013, a temporary groundwater extraction and treatment system operated in the Northeast Area (see location map here). Its goal was to intersect a VDC plume in the bedrock that was migrating toward the Acton Water District School Street public water supply wells. Water was pulled up out of the bedrock at 20 gallons per minute, treated for VDCs, arsenic, and odor, and then re-injected into the overburden aquifer. Shutting down this treatment system was controversial in Acton, but the federal Environmental Protection Agency (EPA) and MassDEP (Massachusetts Department of Environmental Protection) determined that the system had achieved its goals. The goals and history of the Northeast Area treatment system are covered in detail in the previous FYR and mentioned only briefly in the current FYR. 

The other extraction and treatment system is the Landfill Area Treatment System (see map). This system includes 3 extraction wells on the Acton side of the town line, 2 wells in Concord, and a treatment system right in the center of the WRG site. This system began operating in May 2011, and is still going. It treats for arsenic, iron, manganese, phosphorous, and VOCs. The treated effluent is discharged into Sinking Pond, and the levels in the effluent are as low as they are supposed to be under the ROD. An attempt has been made to treat for 1,4-dioxane, but that has not been effective, according to the report. 

By far the majority of the acreage of the WRG undergoes “monitored natural attenuation” (MNA) as the designated groundwater remedy. The report is quite upbeat about the areas “treated” with this remedy, with one exception. That exception is in the area of the Former Primary Lagoon, where one cluster of monitoring wells (OSA-13) has been showing rising levels of VC and VDC. The report calls for further investigation of this area. 


Appendix D includes a report on habitat restoration from Roberts Environmental Consulting, Inc. The team reported on areas around Sinking Pond and the North Lagoon Wetland, where trees and shrubs had been planted around the pond and wetland, noting that very few of them had survived. The report is documented with numerous photos, such as the one below:

Sinking Pond, from the 2019 WR Grace Five-Year Review, Appendix D

Interviews with Stakeholders:

As part of the FYR process, EPA interviewed Acton stakeholders, including the Town of Acton Health Department, Acton Water District officials, and representatives of Green Acton (Co-President Jim Snyder-Grant and Water Committee Chair Kim Kastens). Acton interviewees expressed a desire for more-frequent and -informative communication with local officials and residents, and for 1,4-dioxane in the groundwater to be better studied and remediated. An interview with the MassDEP project manager yielded a similar recommendation: that an evaluation should be conducted to determine if further action is warranted to address residual 1,4-dioxane contamination.

EPA also interviewed a WR Grace representative, who stated that the groundwater remediation is proceeding well. WR Grace would like to discontinue withdrawals from two extraction wells, which are yielding little water. In addition, the corporation would like to discontinue use of the photocatalytic oxidation portion of the Landfill Area Treatment System; this was intended to remediate for 1,4-dioxane, but is not working, according to the company. 

EPA’s Conclusions:

The gist of a Five-Year Review is contained in a statement called the Protectiveness Determination. 

For OU-1 (surface materials), the 2019 Protectiveness Statement says that “The remedy for OU-1 is protective of human health and the environment in the short-term.” The contaminated soil has been excavated and either taken off site or placed in the on-site Industrial Landfill, which has been capped. To become “protective . . . in the long run,” there needs to be a binding restriction (NAUL) that would keep future owners from disturbing the landfill.

For OU-3 (groundwater), the 2019 Protectiveness Statement says that “The remedy is protective in the short-term, because there is no current exposure to contamination in groundwater or sediment.” The reasons given for there being “no current exposure to contamination” are: (a) the groundwater in the vicinity of the Industrial Landfill is being extracted and treated, (b) the Acton Health Department maintains an administrative hold on private wells for irrigation within 500 feet of the groundwater contamination plume, and (c) The Acton Water District (AWD) provides treatment of groundwater from the five public water supply wells in the vicinity of the site. 

All three of these lines of reasoning have been criticized, as follows: The extraction and treatment program has been criticized because it does not treat for 1,4-dioxane. The line of reasoning based on the administrative hold on private irrigation wells has been criticized because the hold was intended as a temporary measure until the remedy had cleaned up the aquifer — not as a substitute for cleaning up. With respect to the third line of reasoning, a 2005 press release from the Acton Board of Selectmen, the Acton Board of Water Commissioners, and ACES (Acton Citizens for Environmental Safety) stated that if the remedy relies on the logic that the groundwater presents no danger because the Acton Water District successfully treats the water, then “EPA has . . . turned upside down both the ‘environmental protection’ mandate and the ‘polluter pays’ principle[s] of federal Superfund law.”


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