SITE INFORMATION AND CORRESPONDENCE FILE 1

Home Browse Search

West Clay Properties January 2015 639 West Clay Street Claim No: 8542 groundwater will be used as a source of drinking water in the foreseeable future. Other designated beneficial uses of the affected shallow 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 Risk from Residual Petroleum Hydrocarbons: The case does not meet Policy criteria because the extent of the groundwater plume is not defined. • Indoor Vapor Risk from Residual Petroleum Hydrocarbons: The case meets the Policy Exclusion for Active Station. Soil vapor evaluation is not required because the Site is an active commercial petroleum fueling facility and the release characteristics do not pose an unacceptable health risk. • Direct Contact Risk from Residual Petroleum Hydrocarbons: 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 a February 26, 2014 letter, 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. <<��, ,. - ' '<d caw, • Secondary source remains. RESPONSE: Secondary source as defined by the Policy was removed by excavation to the extent practical in 2003. J-' �r � • The case does not meet Policy groundwater criteria. RESPONSE: We concur. Recommendation The Fund recommends that the County direct the Responsible Party to define the extent of groundwater contamination north (downgradient) of the Site. Kit< Larson, P.G. Date Robert 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 2