LNAPL Meeting Agenda

LNAPL Reg Reform Discussion
February 16, 2012
1:00  – 3:00 am
MassDEP, One Winter Street, Boston, 2nd Floor


 1:00        Welcome and Introductions
1:10        Background on LNAPL MCP issues and regulatory/policy discussions to date
1:30        The definition, meaning and purpose of an Upper Concentration Limit (UCL)
2:00        Discussion of Regulatory provisions which better address LNAPL UCL concerns?


Under the provisions of 310 CMR 40.0996, “the presence of non-aqueous phase liquids (NAPL) having a thickness equal to or greater than ½ inch in any environmental medium is considered to be a level which exceeds Upper Concentration Limits (UCLs)” and hence which prohibits the attainment of a Permanent Solution.  In addition, 310 CMR 40.0006 states this thickness is “as a continuous separate phase as measured in a groundwater monitoring well or otherwise observed in the environment.”

As articulated in earlier MassDEP guidance, (Characterizing Risks Posed by Petroleum Contaminated Sites: Implementation of the MADEP VPH/EPH Approach; 2002):

The occurrence, detection and migration of non-aqueous phase liquids in the subsurface are a complex phenomenon.  Many investigators have attempted to develop theoretical and/or empirical methods to correlate the apparent thickness of NAPL, as measured in a monitoring well, to the actual thickness of that NAPL in the surrounding formation……..Unfortunately, none of the methods or approaches presented to date appears to be sufficiently reliable or reproducible at field sites, especially when significant fluctuations occur in the elevation of the groundwater table

Since 2002, improved LNAPL assessment techniques based on the fundamental principles of multi-phase fluid flow in porous media (FFPM, used for decades in the oil industry) have been developed and applied over the last several years to environmental applications.  A number of states and regulatory authorities, including MassDEP, have formed workgroups and are developing guidelines based on FFPM concepts to more accurately describe the nature, extent and behavior of LNAPL in the subsurface formation.  These efforts have considered similar works from Texas, Alaska, British Columbia, API, ITRC, U.S.EPA, and ASTM, among others.

Integrating these improved LNAPL assessment techniques into the overall MCP regulatory framework has proven to be a challenging task involving disparate and often conflicting opinions and approaches from among MassDEP’s LNAPL Workgroup.  However, consensus has emerged around the following:

  • The current MCP criterion of ½ inch of LNAPL is not an ideal metric for assessing compliance with a UCL and, in some cases, may be a barrier for sites’ otherwise meeting the requirements for a Permanent Solution.
  • The application of the fundamental principles of multi-phase fluid flow in porous media (FFPM) has been overwhelmingly accepted by the scientific and regulatory communities throughout north America, and it is clearly consistent with the Response Action Performance Standard 310 CMR 40.0191(2)(b) “use of accurate and up-to-date methods, standards and practices, equipment and technologies which are appropriate, available and generally accepted by the professional and trade communities conducting response actions…”

Questions?:  Ken Marra, kendall.marra@state.ma.us, (617) 292-5966