SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

• JM Equipment Company 1245 West Charter Way, Stockton Claim No: 12607 shallow groundwater is not currently being used as a source of drinking water, and it is highly unlikely that the affected shallow 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 Specific Criteria: The case does not meet Policy criteria because contaminant plume that exceeds water quality objectives is greater than 100 feet in length and the dissolved concentration of benzene is greater than 3,000 micrograms per liter(Ng/L). • Vapor Intrusion to Indoor Air: The case meets Policy Criterion 2b. Although no document titled 'Risk Assessment'was found in the files reviewed, a professional assessment of site- specific risk from exposure through the vapor intrusion pathway was performed by Fund staff.The assessment found that there is no significant risk of petroleum vapors adversely affecting human health. The onsite building is a covered equipment storage shed which has ample ventilation that would prevent the accumulation of soil vapors in the building. • 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, finalized on June 4, 2015, the County staff objects to UST case closure because: • Secondary source remains. RESPONSE: Secondary source as defined by the Policy was removed by excavation and active remediation. • The case does not meet Policy groundwater criteria. RESPONSE: We concur; the case does not meet Policy criteria because contaminant plume that exceeds water quality objectives is greater than 100 feet in length and the dissolved concentration of benzene is greater than 3,000 Ng/L. • The case does not meet Policy vapor criteria. RESPONSE: The case meets Policy Criterion 2b. Although no document titled 'Risk Assessment'was found in the files reviewed, a professional assessment of site-specific risk from exposure through the vapor intrusion pathway was performed by Fund staff. The assessment found that there is no significant risk of petroleum vapors adversely affecting human health. The onsite building is a covered equipment storage shed which has ample ventilation that would prevent the accumulation of soil vapors in the building. Page 2 of 3