Environmental
Updated 4-18-2022
How is a Site Investigated for VOCs?
Environmental investigation of a site with volatile organic compounds (VOCs) involves the following approach:
- Define the source area – the area with the highest concentration of chemicals, usually where the spill or leak occurred historically
- Define if and where chemicals have moved away from the source (nature and extent of contaminant presence)
- Requires an understanding of detailed site geology – soil, bedrock underlying soil, and groundwater in soil or bedrock fractures.
- Some chemicals sink down through the soil and groundwater until reaching an impermeable layer (e.g., clay) or bedrock and form a concentrated area of dense non-aqueous phase liquid (DNAPL).
- Some dissolved chemicals mix with and move with groundwater, forming a groundwater plume. Chemical migration in groundwater is slower than the movement of groundwater. Therefore, the ability of a chemical plume to move is limited. Groundwater can also upwell into surface water through streams and springs.
- VOCs can evaporate from soil or groundwater and be carried to the surface through the soil in vapors. These vapors can enter a building through cracks in foundations or other preferential pathways such as sump pumps or sewer lines (known as “vapor intrusion”).
How is a Site Cleaned Up Under the Massachusetts Continency Plan (MCP)?
The Massachusetts Contingency Plan (MCP) is the process defined by state regulations that governs site cleanup in Massachusetts. The MCP outlines a phased approach to site investigation and cleanup.
Generalized Massachusetts Contingency Plan (MCP) Public Involvement Process
Phase I: Initial Investigation
• Initial investigations
• Implement preliminary response actions where needed
Phase II: Comprehensive Site Assessment
• Determine nature and extent of contamination
• Evaluate potential risk to determine if cleanup plan is needed
Phase III: Remedial Action Plan
• Evaluate cleanup options based on defined criteria
(e.g., effectiveness, feasibility, comparative benefits, etc.)
Phase IV: Remedy Implementation
• Complete cleanup design and plans
• Begin treatment
Phase V: Operation
and Maintenance
• Verify that cleanup continues to operate as planned
• Monitor remedy effectiveness
Permanent or Temporary Solution
• Determination that a site has been cleaned up to background levels, if feasible, or, if not, to levels of no significant risk.
Under the MCP, the need for cleanup is dictated by potential health and environmental risk.
- Risk (the chances that a person exposed to a contaminant will become sick) is based on:
- Exposure (can a person come into contact with a contaminant and, if so, how much)
- Toxicity (how dangerous is the contaminant)
- Without exposure, there is no risk.
The MCP requires that a site must be cleaned up to background levels if “feasible” or, if not, to levels of “no significant risk.”
- Background levels – the levels of contaminants that would exist without the site
- No significant risk – a regulatory term describing when a contaminant is either not detected or is below a level that would cause a defined level of increased risk to human health or the environment
- Feasible – when existing technology (or modification of existing technology) can treat contaminants to the extent necessary to achieve background levels
More information about Massachusetts’ Waste Site Cleanup Program can be found on the Massachusetts Department of Environmental Protection website.
History of Environmental Investigation and Treatment
Varian Site Investigation and the Cleanup Public Involvement Process
Phase I: Initial Investigation
• Initial investigations in the late 1980s; before the MCP
• Conducted groundwater pump & treat to contain contamination
Phase II: Comprehensive Site Assessment
• Completed in 2000; no significant risk in downgradient areas
• Treatment needed to address source areas
Phase III: Remedial Action Plan
• Completed in 2001, 2012; included pilot tests of pump & treat, chemical oxidation, and soil vapor extraction (SVE)
• Multiple treatment alternatives analyzed; chemical oxidation and SVEselected
Phase IV: Remedy Implementation
• Detailed plans completed in 2002 and 2012
• Cleanup using chemical oxidation and SVEinitiated; supplemented with bioremediation
Phase V: Operation
and Maintenance
• Periodic modifications to treatment with regular reporting to MassDEP; ongoing groundwater monitoring
Permanent or Temporary Solution
• Determination that a site has been cleaned up to background levels, if feasible, or, if not, to levels of no significant risk.
Since 1992, environmental investigations and ongoing operation of treatment systems have been conducted for addressing contaminants present in site subsurface soils and groundwater.
Groundwater: Results of environmental sampling and analysis, conducted under the regulatory oversight of the MassDEP, have indicated that there is not a “significant risk” to the offsite community. Groundwater containing contaminants at 150 Sohier Road was pumped and treated from 1992 to 2002 to limit or contain further movement of the groundwater. Offsite groundwater has been continually sampled and monitored since the 1990s, with reports submitted to MassDEP.
Source Areas: Results of environmental investigations indicated that there is a potential health risk onsite, in the locations where the releases occurred, also known as the source areas. Therefore, ongoing treatment has focused primarily on these onsite source areas. Treatment of source areas reduces potential risk onsite, while also limiting movement of contaminants offsite. Several source treatment technologies have been implemented since 2002 and continue to operate, with sampling and modifications and reports submitted to MassDEP.
Links to a series of Community Guides on types of source area treatment technologies, published by the U.S. Environmental Protection Agency, can be found on our More Information page.
All site reports associated with the MCP process, including inspection and monitoring reports, can be found in MassDEP’s online document portal.
Conceptual Site Model
Site investigators develop conceptual site models based on site data to portray contaminant sources, migration and exposure pathways, and receptors – the people and animals who are potentially exposed to contaminants. Conceptual site models evolve as new data are collected.
MassDEP Evaluation 2020-2021
In response to community concerns, in 2020-2021, MassDEP evaluated remedial investigations, treatment, and potential exposure at the site. MassDEP issued a report in January 2021 and held a public meeting in February 2021.
In the report, Mass DEP:
Found no evidence that workers or residents are being exposed to significant levels of site-related contaminants.
Acknowledged that extensive investigatory and remedial work has been conducted, but data gaps justify further investigative work and remedial refinements.
Additional work identified included:
- Additional indoor air (vapor intrusion) sampling
- Additional wells and sampling in several locations (onsite and downgradient)
- Sampling of stream water, sediment, and spring
- An evaluation of techniques to better delineate dense nonaqueous phase liquid (DNAPL) in source areas
In February 2022, MassDEP ended the site’s “remedy operation status” and required that additional investigation and cleanup efforts be conducted.