SITE INFORMATION AND CORRESPONDENCE

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N N ' Guardino — Crawford Company September 2013 517 West Fremont Street, Stockton Claim No: 14349 and it is highly unlikely that they will be, considering these factors in the context of the site setting . Remaining petroleum hydrocarbon constituents are limited and stable, and concentrations are decreasing . Corrective actions have been implemented and additional corrective actions are not _ necessary. Any remaining_petroleum hydrocarbon constituents do not pose a significant risk to human health , safety or the environment. _ Rationale for Closure under the Policy + General Criteria: The case meets all eight Policy general criteria. • Groundwater Specific Criteria : The case meets Policy Criterion 1 by Class 1 . The contaminant plume that exceeds water quality objectives is less than 100 feet in length There is no free product.-"The nearest water supply well or surface water body is greater than 250 feet from the defined plume boundary. — • Vapor Intrusion to Indoor Air: The case does not meet Policy criteria 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/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 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 . Recommendation The Fund concurs with the County that the Responsible Party should begin active remediation to achieve water quality objectives in a timely manner. ' Kirk 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 12