Guest post by Adam J. Last, PE, LSP of Corporate Environmental Advisors, Inc.

As we reported earlier here, the Massachusetts Department of Environmental Protection (MassDEP) has proposed significant amendments to the Massachusetts Contingency Plan (MCP), the regulations governing the assessment and remediation of oil and hazardous material releases.  The proposed changes are part of Governor Deval Patrick’s Regulatory Reform Initiative intended to streamline small business regulations and improve government efficiencies.

In Part I of this two-part series, we outlined the proposed amendments for streamlining site classification, simplifying site closure options, and streamlining Notice of Activity and Use Limitation (AUL) requirements.  Part II provides an overview of the proposed amendments updating the assessment and closure requirements for sites where non-aqueous phase liquid (NAPL) is present, presenting a new definition of “Background” affecting sites with historic fill material, and creating a new regulatory endpoint for sites where vapor intrusion is being mitigated.

NAPL Assessment and Closure Requirements

A number of common contaminants, such as oil, are liquids that do not dissolve readily in water. These are known as non-aqueous phase liquids (NAPLs).  There are two classes of NAPLs: light NAPLs (LNAPLs), such as gasoline, which are less dense than water; and dense NAPLs (DNAPLs), such as the common solvent trichloroethylene, which are more dense than water. MassDEP’s proposed amendments revise definitions, notification requirements, assessment and closure requirements related to NAPLs to reflect a more accurate understanding of the behavior of NAPL in the subsurface environment.  These changes include:

• Revising the current definition of NAPL and creating new definitions for DNAPL, LNAPL, Non-Stable NAPL, and Stable NAPL;
• Establishing 1/8 inch of NAPL in a monitoring well or excavation as a 72 hour reporting condition and the trigger for further assessment of NAPL;
• Incorporating an LNAPL Conceptual Site Model and NAPL assessment activities into the Phase I and Phase II site characterization requirements;
• Eliminating the ½ inch NAPL Upper Concentration Limit (UCL) criterion that has prevented some disposal sites from achieving a Permanent Solution; and 
• Making a Permanent Solution achievable with an AUL when NAPL is limited to Stable NAPL.

Definition of Anthropogenic Background

One of the more interesting proposed definition changes in the MCP amendments is the definition of “Background” which would consider both natural and man-made (anthropogenic) conditions to each qualify as “Background”.  Natural Background are those levels of oil and/or hazardous material that are attributable to naturally occurring geologic or ecological conditions.  Anthropogenic Background means those levels of oil and/or hazardous material that are attributable to man-made sources.

Of particular note is that Historic Fill is included in the definition of Anthropogenic Background.  By defining Historic Fill and including it in the definition of Anthropogenic Background, many properties with historic fill material, which would be recognized as disposal sites under the current MCP, would not be recognized as disposal sites under the amended MCP.  Anthropogenic Background conditions would not be regulated under M.G.L. Chapter 21E and would not require remediation.

Vapor Intrusion

A new type of MCP permit for the operation of Active Exposure Pathway Elimination Measures is proposed as part of the amendments related to vapor intrusion.  New closure provisions are also proposed for sites where Active Exposure Pathway Elimination Measures are operating.  At some disposal sites where sub-slab depressurization systems are operating to mitigate vapor intrusion, the operation of the sub-slab depressurization system has prevented a Permanent Solution.  With the creation of the definition for Active Exposure Pathway Elimination Measures and associated permitting requirements, sites with operating sub-slab depressurization systems may soon be eligible for a Permanent Solution with Conditions.

The proposed MCP changes, when made effective, are intended to reduce regulatory compliance costs and provide some sites that have been in regulatory limbo options to help meet a regulatory endpoint.  MassDEP is seeking comments to the proposed regulatory changes through May 17, 2013 when the comment period closes.  Additional information and the proposed amendments are available for review at MassDEP’s website here.

For questions regarding MCP compliance and the proposed amendments to the MCP, please contact Adam Last, a Professional Engineer and Licensed Site Professional in the environmental engineering group of Corporate Environmental Advisors, at (508) 835-8822 or via email at alast@cea-inc.com.  For questions regarding environmental liability concerns or disputes, contact David McCay, a Massachusetts environmental attorney at Mirick O’Connell at (508) 791-8500 or via email at dmccay@mirickoconnell.com.