FIELD DOCUMENTS FILE 2 - Laserfiche WebLink

Home Browse Search

Chevron #9-4054 May 2014 2103 Country Club Boulevard, Stockton Claim No: 12729 Site by the Stockton East Water District and the California Water Service. The affected groundwater is not currently being used as a source of drinking water, and it is highly unlikely that the affected groundwater will be used as a source of drinking water in the foreseeable future. Other designated beneficial uses of impacted groundwater are not threatened, and it is highly unlikely that they will be, considering these factors in the context of the site setting. Rationale for Closure under the Policy • General Criteria: The case meets all eight Policy general criteria. • Groundwater Specific Criteria: The case does not meet Policy criteria because the contaminant plume that exceeds water quality objectives is not defined. • Vapor Intrusion to Indoor Air: The case does not meet Policy criteria because the maximum benzene concentration in groundwater is greater than 1,000 micrograms per liter (Ng/L) and the minimum depth to groundwater is less than 30 feet. • Direct Contact and Outdoor Air Exposure: The case meets Policy Criterion 3a. Maximum concentrations in soil are less than those in Policy Table 1 for Commercial/Industrial use, and the concentration limits for a Utility Worker are not exceeded. There are no soil sample results in the case record for naphthalene. However, the relative concentration of naphthalene in soil can be conservatively estimated using the published relative concentrations of naphthalene and benzene in gasoline. Taken from Potter and Simmons (1998), gasoline mixtures contain approximately 2 percent benzene and 0.25 percent naphthalene. Therefore, benzene can be used as a surrogate for naphthalene concentrations with a safety factor of eight. Benzene concentrations from the Site are below the naphthalene thresholds in Policy Table 1. Therefore, the estimated naphthalene concentrations meet the thresholds in Table 1 and the Policy criteria for direct contact by a factor of eight. It is highly unlikely that naphthalene concentrations in the soil, if any, exceed the threshold. Objections to Closure and Responses According to the Path to Closure page in GeoTracker, final on November 22, 2013, the County opposes closure because: • Conceptual site model is inadequate. RESPONSE: Adequate data is available in GeoTracker to prepare a conceptual site model consistent with the Policy. • Secondary source remains. RESPONSE: Secondary source as defined by the Policy has been removed by excavation and active remediation. • The case does not meet Policy groundwater criteria. RESPONSE: We concur. Recommendation The Fund concurs with the County that the Responsible Party should resume active remediation to achieve water quality objectives in a timely manner and should define the extent of groundwater contamination. - �i✓f �L �.3/6%i y" Kirk Lharson, P.G. Date Robeft Trommer, C.H.G. Date Engineering Geologist Senior Engineering Geologist Technical Review Unit Chief, Technical Review Unit (916) 341-5663 (916) 341-5684 Page 2 of 15