LNAPL

Revisions related to issues involving Light Non-Aqueous Phase Liquids under the MCP.

Agenda for the February 16, 2012 meeting.

2 Responses

  1. A dedicated group of LSP’s, risk assessors, and other stakeholders met for several years to develop recommended changes for LNAPL regulations, practice standard improvement, and LNAPL risk characterization issues. Results were published as a White Paper in 2008.

    Regulatory reform recommendations were limited to four items only:

    1. Eliminate the 1/2″ UCL.

    2. Change the definition of LNAPL to be consistent with multiphase flow theory.

    3. Simplify the reporting conditions for LNAPL in a monitoring well. A 72-hour reporting condition for LNAPL at any thickness greater than 0.01-ft is recommended.

    4. Clarify source definitions in the MCP to recognize that residual LNAPL can act as a potential ongoing source for intermedia transfer of contaminants, and to differentiate these “secondary sources” from primary release sources such as tanks and pipelines.

    Mobility evaluation was recommended as the logical method of evaluating future site risk (or “source control”). Various methods are available to evaluate mobility, including bail down tests and direct calculation from measurable soil properties. These methods are generally complimentary. Regulatory change does not require details on mobility analysis, as this can be addressed in future modification of the EPH/VPH guidance. A demonstration of effective immobility should be sufficient to satisfy source control requirements.

    Changes to LNAPL provision in the MCP have been discussed for years by MassDEP, LSPs and PRPs. The 1/2-inch LNAPL UCL is recognized as a standard that is not based on valid science, and is frequently the only issue preventing closure at Sites with no significant risk. Given the short amount of time available for MassDEP to issue a Public Comment Draft for MCP changes (April of 2012), the recommendations developed by the dedicated LSP Association’s Technical Practice Committee should form the basis of regulatory change related to LNAPL. Future LNAPL Workgroup meetings can be used as the vehicle to further develop detailed technical guidance.

  2. LNAPL regulation changes are needed to foster the implementation of appropriate technologies to advance the assessment and cleanup of numerous LNAPL sites in Massachusetts that are stuck in the system. Similar to the original implementation of the privatized program, these further changes are needed to move these sites forward. In addition to the many private-sector sites, there are numerous state-funded sites in the current program which are relying on the current regulations that don’t provide a meaningful end-point and have goals that aren’t attainable or simply don’t provide a commensurate return on the investments that continue to be made. Changes to the LNAPL regulations would foster efforts to work toward closure of these sites.

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