Vapor Intrusion

While not formally a part of the MassDEP Reg Reform initiative, the Bureau of Waste Site Cleanup is developing revisions to the Massachusetts Contingency Plan (310 CMR 40.0000) related to the vapor intrusion pathway. This work is being conducted in consultation with the existing Indoor Air/VI Workgroup and documented on the Indoor Air Project blog at

Next Meeting:

  • There will be a Waste Site Cleanup Advisory Committee meeting on Thursday, June 27th from 9:30 am to noon at MassDEP’s Boston Office, One Winter Street, 2nd floor conference rooms A & B.  The first ½ hour of the meeting will provide general program updates.  From 10 am to noon we will hold a discussion on the public comment we’ve received on the Active Pathway Elimination Measure proposal (the proposed changes that provide for a Permanent Solution with Conditions where a subslab depressurization system is operated as to prevent vapor intrusion impacts to a building as part of a permanent solution).  This portion of the meeting is intended to assist MassDEP in developing the final amendments for this closure option through more focused discussion of the different procedural and technical requirements proposed in the public hearing draft.  A list of topics to be covered by this discussion will be sent ahead of the meeting.

Supplemental Material:


One Response

  1. Suggestion for addressing issue of how to have a Class A-2 Response Action Outcome (RAO) (no AUL) with an operating Sub-Slab

    Depressurization System:
    (Matt Hackman/LSP)

    Currently, one of the issues with sites where volatile contaminants might pose a risk of vapor intrusion, where an active physical/mechanical

    vapor intrusion mitigation system, such as a sub-slab depressurization system (SSDS) is in place, is that there is no satisfactory way to achieve

    a permanent solution without an Activity and Use Limitation (AUL) being recorded on the property deed.

    This seems to be problematic on at least two points:

    1. MADEP is concerned about the effectiveness of the AUL process, because there appear to have been numerous cases where the

    AUL recorded on a property deed/title was not transferred when the deed/title was transferred to the new owner. There apparently is not a

    process in place under the real estate laws or registry procedures to notify MADEP every time the property is transferred.

    2. There is apparently considerable resistance to property owners to accepting an AUL on their property, particularly with residential

    properties, both single-family and multiple famiily, such as apartments and condominiums, due to requirements for notice in all leases and some

    form of incorporation in condominium titles. This is an additional problem when the Responsible Party is not the property owner, for example

    when volatile contaminants may potentially or actually impact off-site properties, or when the release site was sold but the RP retains liability for


    I think the MADEP should consider issuing operating permits for remediation systems, including, but not limited to, SSDS, and allow the

    presence of a valid operating permit to be relied on by the LSP and RP when submitting a RAO.

    I believe an operating permit is superior to an AUL for the following reasons:

    1. An operating permit is administered directly by the MADEP, and does not involve other entities such as registries or other statutes or

    regulations, such as those governing real estate.

    2. Operating permits are issued for fixed terms, which allows MADEP to re-visit permits at regular intervals if MADEP determines that

    the permit conditions require changing. This avoids the more complex regulatory change process, as it is administered by MADEP. This also

    provides a regular check on the identity and contact information of the permittee.

    3. Operating permits are typically transferable, allowing for more flexibility to the RP, property owner and/or permittee, for example when

    a commercial building changes management companies or owners. The permit transfer process would require that the new permittee notify

    MADEP with all required information.

    4. MADEP has extensive experience with operating permits in their air and wastewater pollution control programs, as just two examples.

    5. Operating permits are well understood by commercial and industrial property managers and are accepted as normal practice, unlike

    the potential stignma of an AUL. Most large buildings have at least an operating permit for their heating system boilers, and operating permits

    are issued by other state agencies for systems such as elevators.

    6. Operating permits offer flexibility. Typically such permits fall into two categories: general permits and individual permits.

    A. General Permits are issued to MADEP, and contain standardized requirements for operation, monitoring and reporting.

    Then parties wishing to be covered under the General Permit register with MADEP. They are most often used for systems which are relatively

    simple and which do not have site-specific conditions or requirements. A concept for a SSDS General Permit might include monitoring and

    recording the pressure differential between the sub-slab and the indoor air immediately above, in order to demonstrate that depressurization was

    actually occurring. The general permit could specify design requirements, such as designed and stamped by a professional engineer.

    The principle here is that, if the system is properly designed, then the relevant operating parameter to insure effectiveness is achieving a design

    minimum pressure differential. The permit would specify the minimum pressure differential required, the frequency of monitoring, and would

    require reporting to MADEP and appropriate actions to take if the pressure differential fell below the minimum value. This simple monitoring

    concept was used by EPA for fiber-bed scrubbers to control hexavalent chromium emissions, for example. For simple systems, monitoring

    records might be maintained at the permittee’s site, and no regular reporting to MADEP required, or perhaps annual summary reporting.

    B. Individual Permits are issued by MADEP when there are site-specific conditions that exceed the standardized requirements

    for operation, monitoring and reporting. These might include recording more operating parameters, such as concentrations of volatile

    compounds in the sub-slab portion to make sure that these are within the design parameters, increased and/or more frequent reporting,

    site-specific contingency plans for addressing system failure, etc. A Title V permit for major sources of air pollution is an example of such an

    individual permit. Individual permits are similarly used for larger or more complex wastewater discharges.

    7. Operating permits could be issued to a wider number of parties, and managed by standard contracts, without involving changes to the

    deed. In a commercial building, the permit might be issued to the management company. A RP responsible for maintaining SSDS at off-site

    single-family residential properties might be the permittee for all those properties, allowing the residents to have less perception of impairment of

    their property.

    8. Because of the problems involved in recording AULs, particularly when the RP is not the property owner and the stigma of AULs on a

    property title/deed, RPs and property owners are often reluctant to install and maintain SSDS and other remedial systems. This means that, in

    some cases, lesser protection is afforded to building occupants, when an operating system might be more protective.

    I think the biggest advantage is to MADEP. By issuing operating permits, MADEP remains firmly in control. These permits would include the

    right of inspection, all reporting would go direct to MADEP and MADEP would automatically be notified if such permits were not renewed, as well

    as having the enforcement authority such permits convey. MADEP BWSC already has experience managing Remedial Monitoring Reports, and

    these could be used as the reporting mechanism for operating permits as well. Again, if, for example, the operating permit was issued to a

    property management company which had a SSDS under a day-care facility in a commercial property, MADEP might specify monthly reporting

    for basic parameters, such as pressure differential, and annual operation and maintenance reports. Given the rapid advancement and quickly

    dropping costs of real-time monitoring and remote alarm notification by internet or cellular or land-line telephone, MADEP might even specify that

    system alarms be reported automatically to MADEP and that MADEP staff have the ability to query the system remotely using a web browser.

    These features are superior to the existing AUL process and give MADEP better control and notification.

    Again, the advantage to property owners and RPs would be that the cumbersome processes required to record, modify and transfer AULs would

    not be needed, the potential stigma of an AUL on the property deed/title would not exist, and thus there would be a greater willingness to install

    and utilize these systems, providing better protection of human health.

    For example NYDOH requires that all new buildings in brownfield areas incorporate the sub-slab components of a SSDS (typically a

    low-permeability membrane barrier, a permeable zone of crushed stone, sand or manufactured material, and the piping or other vapor

    withdrawal mechanism), regardless of whether it is currently required by site conditions. I think this is good public policy because the cost on

    installing such components is small at the time of construction, and, in case of a future release, allows the effective (both cost- and operational-)

    implementation of a SSDS without requiring major alteration of the building.

    For all of the above reasons, MADEP can have a higher degree of confidence that systems, such as SSDS are being properly operated and

    maintained, and thus could allow LSPs and RPs to achieve a Class A-2 RAO, which would be a major improvement over the current approach.

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