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San Joaquin County Record Center - 4 - 6 May 2022 630 North California Street Stockton, San Joaquin County hydrocarbons were not detected in shallow soil during the July 2019 shallow soil investigation and benzene concentrations in groundwater are less than 100 ug/L. Current Site conditions meet screening levels outlined in Appendix 3, Scenarios 3a of the LTCP. GENERAL SITE CONDITIONS Soil beneath the Site consists primarily of lean clay from ground surface to approximately 25 ft bgs, poorly graded sand from approximately 25 to 35 ft bgs, and lean clay from approximately 35 to 41 ft bgs. Depth to groundwater beneath the Site in well MW-1 ranged from 18.34 to 29.77 feet below top of casing. The southern adjacent property (602 North California Street) is the location of the Stallworth Auto Detail environmental case. The groundwater gradient directions measured at the Stallworth Auto case have historically been northeasterly to easterly. Petroleum constituent remaining in groundwater beneath the Site consist of 4,900 ug/L TPH-G, 1,700 ug/L TPH-D, 1.5 ug/L benzene, 32 ug/L toluene, 160 ug/L ethylbenzene, 750 ug/L total xylenes, and 180 ug/L naphthalene. Stable to decreasing petroleum hydrocarbon concentrations have been observed in the Site well. Active remediation was not performed at the Site. On 4 June 2021, Condor destroyed the one monitoring well, MW-1. LOW-THREAT UST CLOSURE POLICY EVALUATION Condor concluded that the Site meets the criteria necessary for closure as outlined in the LTCP. Central Valley Water Board staff concurs with this conclusion, as discussed in the following: General Criteria - This Site meets the eight General Criteria for closure as outlined in the LTCP. Media Specific Criteria - This Site meets the three Media Specific Criteria as outlined in items 1 through 3 below for case closure under the LTCP. Groundwater - Condor concluded that the Site's residual petroleum plume in groundwater is adequately defined, and that the petroleum hydrocarbon groundwater plume is stable to shrinking. Condor reported that the closest water supply well is an inactive well located approximately 1,730 feet east from the Site property and that the closest surface water body is McCleod Lake approximately 2,450 feet southwest of the Site property. Condor estimated that the groundwater plume that exceeds water quality objectives is less than 100 feet in length. Based on a stable to shrinking plume, an estimated petroleum hydrocarbon plume length of less than 100 feet, and the distance to the closest water supply well and surface water, the Site meets Groundwater-Specific Criteria Class (1) of the LTCP. Petroleum Vapor Intrusion to Indoor Air — Condor concluded that the Site meets Petroleum Vapor Intrusion to Indoor Air Criteria Class 3. Petroleum