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. MEMORANDUM CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD • CENTRAL VALLEY REGION 3443 Routier Road, Suite A Sacramento, CA 95827-3098 Phone: (916) 255-3000 CALNET: 8-494-3000 TO: 1905 N. Broadway file FROM: Wendy Wyels 'Agricultural Unit DATE: 5 March 1997 SIGNATURE: SUBJECT: REVIEW OF THE GROUNDWATER CLEANUP REMEDIAL ALTERNATIVES DOCUMENT Per staff's request, Unocal has submitted a document titled "Evaluation of Alternatives for Remediation of I,2-Dichloropropane in Groundwater" for the former PureGro/Brea Ag facility at 1905 N. Broadway, Stockton. The document was submitted in August 1996, but was not reviewed until recently. The delay occurred because staff could not review this document without knowing the fate of the State Board's Containment Zone Policy (formally known as "Amended Resolution No. 92- 49 [amended October 1996]). The policy was adopted by the State Board on 2 October 1996, but not approved by the Office of Administrative Law until January 1997. The report has been reviewed in the context of the policies for groundwater investigation and remediation as set forth in the State Board Amended Resolution No. 92-49 and the Regional Board Basin Plan. My general comments are as follows: 1. The authors of the document conclude that there is no practical way to remediate the 1,2-DCP in the groundwater, and recommend that no action be taken to remediate the groundwater. State policy will not allow staff to approve this recommendation. The discharger has not shown that it is technically or economically infeasible to remediate this site. If technical or economic infeasibility is shown, then the Board may consider adopting a "Containment Zone" designation for this site. However, Amended Resolution No. 92-49 (enclosed) states that containment zones are more appropriate for sites which have a strong sorption of pollutants to soils, pollutant entrapment (as in the case of dense non-aqueous phase liquids [DNAPLs]), or complex geology. None of those cases appear to apply here. The discharger needs to complete a full feasibility study, as described in the Basin Plan. An excerpt from the Basin Plan regarding groundwater remediation is enclosed). 2. The document only addresses the chemical 1,2-dichloropropane (1,2-DCP). As shown in the table below, nine additional chemicals have been found in the groundwater at concentrations exceeding their regulatory level of concern. The feasibility study must cover the remediation of all ten chemicals. 3. In order to determine groundwater cleanup levels that are protective of human health, as well as of beneficial uses, a human health risk assessment is necessary. The risk assessment is to follow Board guidance (enclosed), and must be approved by toxicologists from either DTSC or OEHHA.