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M Civic Center Square 2444 Main Street, Suite 215 Fresno, California 93721-2734 (5591 264-2535 • FAX (559) 264-7431 GEOMATRIX January 30, 2002 Project No. 005352 Ms. Amy Terrell California Regional Water Quality Control Board Central Valley Region 3443 Routier Road, Suite A Sacramento, California 95827-3003 Subject: Proposed Long-Term Groundwater Monitoring System 1904 Charter Way, Stockton, California Glenn Springs Holdings, Inc. Dear Ms. Terrell: On February 7, 1996, the Regional Board issued Revised Monitoring and Reporting Program No. 96-817 (MRP) for the 1904 Charter Way property to Occidental Chemical Corporation, J. R. Simplot Company, UNOCAL, and Volpi Ranch. Glenn Springs Holdings, Inc. (GSHI) is managing site assessment and remediation on behalf of Occidental Chemical Corporation. The MRP required groundwater monitoring from specified monitoring wells on a three-times- yearly(trimesterly) frequency. On behalf of GSHI, Geomatrix has been providing trimester groundwater monitoring reports to the Regional Board since that time. In July 2001, Geomatrix submitted a"Limited Additional Groundwater Assessment, Bridgeport Trials Development—Unit 5"to the Regional Board on behalf of GSHI. The work plan proposed installation of 7 temporary wells on the Bridgeport property to be used to develop a groundwater monitoring network that would replace three of the existing monitoring wells (MW-12, MW-13, and MW-14). The three existing groundwater monitoring wells are located within lots proposed for the Bridgeport development. The Regional Board conditionally approved the work plan in a June 2001 letter to GSHI- The 7 temporary wells (TW_A through TW-G) were installed in July 2001 and were sampled on July 24 and 25, 2001. The analytical results of these samples were documented in the "Limited Additional Groundwater Assessment, Bridgeport Trails Development" that was transmitted by Geomatrix to the Regional Board on October 18, 2001. Since that time, Geomatrix has had discussions withrepresentatives of the Bridgeport Trails Development about locating the long-term monitoring well network. Following those' discussions, Geomatrix and GSHI developed the proposal described below for the long-term groundwater monitoring network on the Bridgeport development property. The locations of existing monitoring and temporary wells are shown on Figure 1. The existing and proposed monitoring well networks are compared on the following table: Geomatrix Consultants, Inc. Engineers. Geologists, and Environmental Scientists 1:,PROJEC R5352.000\document5352-43.doc