GeoInsighter Spring 2003 Newsletter

New Remediation Criteria In Connecticut

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The Connecticut Department of Environmental Protection (CTDEP) issued in March 2003 proposed revisions to its Remediation Standard Regulations Volatilization Criteria. The proposed changes include revisions, mostly downward, in allowable concentrations of volatile organic substances in ground water, soil vapor, and target indoor air; new applicability requirements for the criteria; and the addition of several new regulated compounds.

These proposals may create significant issues in Connecticut, as many properties contaminated by common volatile organic compounds may not meet the new criteria. Also, the broadened applicability of the criteria will mean that the vast majority of sites studied will now be subject to these standards. Any ongoing evaluations of sites subject to the Remedial Standard Regulations will be affected by these revisions.

The purpose of the volatilization criteria is to assess situations where constituents in soil or ground water can travel as a vapor into nearby structures and create an unacceptable risk to people breathing the indoor air. Because these situations are created from the interaction of a variety of factors, the department utilized refinements in vapor transport models, toxicity data, exposure assumptions, and quantification limits in developing the proposed revisions. In general, these refinements include a greater rate of vapor transport into structures, increased exposure and susceptibility of children to carcinogens, lowered toxicity values, and lowered quantification limits. These refinements result in a lower criterion for most substances.

Revisions to Existing Criteria

The criteria are subdivided into two classes: Ground Water Volatilization Criteria and Soil Vapor Volatilization Criteria (GWVC/SVVC). In each class, a Residential and Industrial/Commercial standard is defined, depending on the type of land use at the site. The proposed revisions update the original 1996 criteria by lowering standards for 24 of the GWVC and 28 of the SVVC, while maintaining or raising standards for several others. The table below illustrates the changes in industrial/commercial criteria for several common compounds.

 
New Criteria

The proposed revisions include standards for 13 new compounds: trichlorofluoromethane, cis-1,2-dichloroethene, 1,2,4-trimethylbenzene, chloroethane, trans-1,2-dichloroethene, 1,3,5-trimethylbenzene, chloromethane, bromodichloromethane, 4-isopropyltoluene, dichlorodifluoromethane, n- butylbenzene, isopropylbenzene, and sec-butylbenzene.

Revised Applicability

The proposed revisions make the volatilization criteria applicable in any situation where polluted ground water is found within 30 feet of the ground surface or a building. The existing regulations use a 15-foot separation value that is provided by natural geologic conditions in many areas of the state. With the proposed 30-foot separation distance, sites will rarely be exempt from the criteria due to the relatively high water table found throughout Connecticut.

The CTDEP is advising that the proposed revisions be incorporated into all current assessments subject to the Remediation Standard Regulations. The CTDEP does not anticipate applying the proposed revisions to sites previously remediated and certified as compliant with the regulations.

The CTDEP is proposing these revisions as part of its application to the United States Environmental Protection Agency for authorization under the Resource Conservation and Recovery Act Corrective Action Program. The intended effect of these revisions will make the Connecticut regulations more consistent with the most recent federal guidance on evaluating indoor air impacts from contaminated soil and ground water.

A complete copy of the proposed revisions can be found at the CTDEP website: http://dep.state.ct.us/wtr/regs/remediationregs.htm.

The CTDEP is accepting comments on these proposed changes through June 30, 2003. Comments may be sent to: Ruth Lepley Parks, Permitting, Enforcement and Remediation Division, Connecticut Department of Environmental Protection, 79 Elm Street, Hartford, CT 06106. Email: ruth.lepley@po.state.ct.us.

James W. Dziuba, L.E.P.
jwdziuba@geoinc.com

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