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ENV= <br /> A M f N 1 C A <br /> Mr. Duane White <br /> California Department of Toxic Substances Control <br /> September 24, 2004 <br /> Page 5 of 6 <br /> These 10 wells are proposed to be sampled once a year to monitor the continuing <br /> progress of natural attenuation of the COCs in groundwater at the Site. BTEX and TPHg <br /> analyses are proposed to be eliminated from 5 of the 10 wells because they have not been <br /> detected or have been detected at concentrations near or less than the RAOs in recent <br /> groundwater monitoring events. Groundwater monitoring data will be provided in an <br /> annual report to be submitted to the DTSC by November 15. The groundwater monitoring <br /> program will be evaluated once a year, and modifications to the program, if appropriate, <br /> will be proposed in the annual report. <br /> The other 16 monitoring wells are proposed to be eliminated from the groundwater <br /> monitoring program for one or more of the following reasons: <br /> A. They do not provide additional groundwater information for the monitoring of <br /> remediation progress at the Site. <br /> B. COCs have not been detected (ND) in the groundwater samples collected from <br /> these wells in the recent groundwater monitoring events. <br /> C. The concentrations of CDCs detected in the groundwater samples collected <br /> from these wells in the recent groundwater monitoring events have been near or <br /> less than the RAOs. <br /> The specific reason(s) for eliminating each one of these 16 monitoring wells are <br /> summarized in the following table: <br /> Zone Well <br /> A MW1 R This is a cross-gradient well and COC concentrations have been NDs, near the <br /> RAOs, and/or less than the RAOs for more than four consecutive rounds. <br /> A MW2 This is an up-or cross-gradient well and COC concentrations have been NDs, <br /> near the RAOs, and/or less than the RAOs for more than four consecutive rounds. <br /> A MW3 This is a cross-gradient well and COC concentrations have been NDs, near the <br /> RAOs, and/or less than the RAOs for more than four consecutive rounds. <br /> A --M—W7 This is an in-plume well and COC concentrations have been NDs, near the RAOs, <br /> and/or less than the RAOs for more than four consecutive rounds. In addition, <br /> MW8 (which is included in the proposed revised groundwater monitoring program), <br /> located less than 80 feet upgradient of MW7, will provide better information for <br /> remediation progress evaluation, <br /> A MW 11 This is an offsite downgradient well and COC concentrations have been NDs, near <br /> the RAOs, and/or less than the RAOs for more than four consecutive rounds. <br /> A MW12 This is an up-gradient well and COC concentrations have been NDs for more than <br /> four consecutive rounds. <br /> A MW20 This is a downgradient well and COC concentrations have been NDs, near the <br /> RAOs, and/or less than the RAOs for more than four consecutive rounds. <br /> CADocuments and SettingsVniavier\Local Settings\Temporary Internet FIles1OLKWDTSC response Itr Sep2004_revised.doc <br />