SITE INFORMATION AND CORRESPONDENCE FILE 2

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i Nomellini Property December 2013 1045 West Charter Way, Stockton Claim No: 552 Rationale for Closure under the Policy • General Criteria : The case meets all eight Policy general criteria . • Groundwater Specific Criteria : The case does not meet the Policy criteria because the extent of groundwater contamination is not defined-and dissolved concentration of benzene is greater than 1 , 000 micrograms per liter (Ng/L). • Vapor Intrusion to Indoor Air: This case does not meet the vapor intrusion criteria of the Policy because the maximum benzene concentration in groundwater is greater than 1 , 000 lag/L, while 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 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 directly substituted 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, the County opposes closure because: • Secondary source remains. RESPONSE: Secondary source as defined by the Policy was removed by excavation in 1988. • The case does not meet Policy indoor vapor criteria. RESPONSE : We concur, based on existing data . Recommendation The current groundwater quality is unknown. The Fund recommends that the County direct that Responsible Party to conduct a complete round of groundwater monitoring including all monitoring and remediation wells to establish current groundwater conditions. Ramesh Sundareswaran Date Robert Trommer, C. H . G . Date Water Resource Control Engineer Senior Engineering Geologist Technical Review Unit Chief, Technical Review Unit (916) 341 -5670 (916) 341 -5684 Page 2 of 14