Presentation: VI Guidance Update

On Tuesday, January 11, 2011, Gerard Martin (MassDEP) was the guest speaker at the Licensed Site Professional Association (LSPA) monthly membership meeting. The presentation was titled, “Vapor Intrusion Guidance Update”, and was intended to provide a summary of what’s in the draft guidance document to facilitate the LSPA members’ review and comment.

The PowerPoint slides from the presentation are now available for download below, in both PDF and PowerPoint formats.

PDF version: 1-11-11_LSPA_FINAL_G-Martin (781 KB, pdf)
PowerPoint version:  1-11-11_LSPA_FINAL_G-Martin (1.6 MB, pptx)


3 Responses

  1. SEE ALSO: Comments posted on the Public Review Draft thread:

  2. CDM Inc. would like to offer the following comments:

    1) Page 6, Figure 1-1: For the question “Is LNAPL/DNAPL present?”—does depth to groundwater matter? Can it be deeper than 15 feet?
    2) Page 16, Table 2-1: For the comparison of subslab soil gas concentrations to threshold values, may average values be used or is it restricted to a point-by-point comparison?
    3) Page 16, Table 2-1: It would be helpful to have an explanation of how 2X groundwater concentrations were selected as a screening criterion.
    4) Page 16, Table 2-2: If you screen against commercial/industrial soil gas screening levels and determine a VI pathway is incomplete, would you need an AUL?
    5) Page 21, Section 2.3.4: The use of passive samplers is not discussed at all in this section. It would be instructive if MassDEP could state the department’s position regarding the use of passive samplers.

  3. Thank you for allowing us the opportunity to review the December 2010 Interim Draft Vapor Intrusion Guidance. The workgroup is to be commended for compiling such an informative document. I offer the following comments:

    1. Page 14. Paragraph 2. I suggest you provide a reference to the recommendations for sample spacing provided in Section 2.3.3 at the end of the paragraph.
    2. Page 16. Table 2-1. The referenced table utilizes a figure of two times the GW-2 standard as a decision point for identifying lines of evidence. Because the GW-2 standards were conservatively set to be protective of indoor air, an exceedence of GW-2 implies that a potential indoor air quality problem may be present. For this reason, I believe the current standard of care for undertaking a vapor intrusion pathway (VIP) evaluation is any concentration greater than a GW-2 standard. At this stage of investigation, to suggest that the concentrations must be greater than twice the standard to warrant identification as a line of evidence appears to be inconsistent, and not prudent.
    3. Page 20. Paragraph 5. I suggest the minimum duration of 4 hours sample time be deleted. While I understand the reasoning for using a longer sampling duration to gain a representative sample, under some circumstances, shorter intervals are just as satisfactory. I note that at present, there are Tier 1A sites which utilize a two-hour sampling interval (RTN-3-0386).
    4. Page 27. Paragraph 2. The use of an AUL to restrict future exposures under a new construction scenario is recommended. Why not allow an AUL to restrict all future exposure scenarios-new or existing buildings?
    5. Page 32. Section 3.3. The use of “crawlspace ventilation” systems are also effective in mitigating VIPs, and may be applicable for consideration as an alternative to traditional SSD systems.
    6. Page 47. Paragraph 4. & Page 59, Paragraph 2. Closure monitoring for over a period of two years is excessive and not likely to be practical. The emphasis should be placed on collecting representative samples over variable conditions likely to exist at the site.
    7. Page 68. Paragraph 2. Use of a Class C-1 RAO for any site that relies on the operation and maintenance of an active remedial system is risky given the perceived regulatory end-point most PRP’s have of the outcome. It is advisable to have reference in the section to the Post Class C Outcome requirements at 40.0897.
    8. Page 69. Paragraph 1. The comparison to Point-of-Entry Treatment systems for private wells needs clarification. Closure with an existing Critical Exposure Pathway (CEP) can only be attained when it is determined to be infeasible to mitigate or eliminate. The infeasibility of continuing to maintain a POET system is difficult to demonstrate. Where the operation of a SSD would is less costly than a POET, infeasibility would be even more difficult to justify.
    9. Appendix III, page 5, paragraph 4. The re-use of Tedlar® bags is acceptable if the lab demonstrates effective purging and cleaning with an inert gas in-between sampling.
    10. Appendix III, page 10. The IAQ survey form contains information that some individuals may not want to become public information. I suggest some consideration be paid to altering the language, such as stating that “a car was parked in the garage”, instead of a car is “typically parked in the garage”.
    11. Appendix III, page 16. The use of Tedlar® bags is an appropriate option for collecting grab soil gas samples.

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