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t <br /> Corrective Action Plan—Tosco (76) Service Station No 11192,Stockton, California <br /> March 13,2002 <br /> 33 Cleanup Levels <br /> Cleanup levels for ground or surface waters, affected or threatened by the unauthorized release, shall <br /> meet the following requirements <br /> (a) For waters with current or potential beneficial uses for which numerical objectives <br /> have been designated in water quality control plans, the responsible party shall <br /> propose at least two alternatives to achieve these numerical objectives. <br /> (it) For waters with current or potential beneficial uses for which no numerical <br /> objectives have been designated in water quality control plans, the responsible <br /> party shall recommend target cleanup levels for long-term corrective actions to the <br /> regulatory agency for concurrence <br /> Final cleanup level goals for MtBE and BTEX constituents will be the California Department of <br /> Health Services Maximum Contaminant Levels (MCLS), which are 13 ppb for MtBE, 1 0 ppb for <br /> benzene, 150 ppb for toluene, 700 ppb for ethylbenzene and 1,750 ppb for xylenes <br /> If the above MCL cleanup levels cannot be attained, then remediation will cease when asymptotic <br /> concentrations are reached Concentrations will be declared to be asymptotic when no statistically <br /> significant changes are observed <br /> If it appears that the cleanup goals cannot be attained, an evaluation of risk to human health and <br /> environment (Risk-Based Corrective Action or RBCA) may be proposed The RBCA would <br /> determine site specific Risk Based Screening Levels, which could then be implemented for the site <br /> 34 Remedial Action Plan <br /> Based on the information provided and the various remedial alternatives evaluated in this CAP, GR <br /> recommends the installation of an ozone rnicrosparge system, presented as Option #5 in the <br /> Feasibility Study above Proposed rnicrosparge point locations are shown on Figure 3 The sparge <br /> points will target the shallow and deeper groundwater zones, and be placed at depths of <br /> approximately 30 and 80 feet bgs, as described below <br /> Once the remedial system is installed and operating for as period of six months, a system status <br /> report will be issued, which will include progress monitoring results Further status reports will be <br /> prepared and submitted on a semi-annual basis <br /> 14024508 12 <br />