SITE INFORMATION AND CORRESPONDENCE 2011-2015

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Weldon Church Residence- December 2013 104 West Beverly Place, Tracy Claim No: 8502 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. 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.w 1 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 meets Policy Criterion 2a by Scenario 3a. The maximum benzene concentration in groundwater is less than 100 pg/L. The minimum depth to groundwater is greater than 5 feet, overlain by soil containing less than 100 mg/kg -- .4/0 of TPH. in addition, a vapor survey investigation was conducted in August 2013, which ,? G _concluded the calculated cancer risk was 4.8 x 10-7 and the hazard index was less than 1 -Tf (0.000001). .2,q • Direct Contact and Outdoor Air Exposure: This case meets Policy Criterion 3b. Although PA no document titled "Risk Assessment" was found in the files reviewed, a professional assessment of site-specific risk from potential exposure to residual soil contamination was performed by Fund staff. The assessment found that maximum concentrations of petroleum constituents remaining in soil will have no significant risk of adversely affecting human health. Excavation was conducted to a depth of 12 feet. Residual hydrocarbons are limited to a thin zone between 6 and 10 feet and accidental exposure to site soils is highly unlikely. Residual hydrocarbons present in along the excavation walls in 1995 are not confirmed in recent samplings conducted in 2003. 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, according to the Policy, was removed by excavation in 1995. • The Case does not meet the Policy vapor pathway criteria. RESPONSE: The case meets Policy Criterion 2a by Scenario 3a and Criteria 2b. • The case does not meet the Policy direct contact pathway criteria. RESPONSE: This case meets Policy Criterion 3b. Determination The Fund Manager has notified the tank owners or operators and reviewed the case history of their tank case. The Fund Manager determines that closure of the tank case is appropriate based upon that review. The Fund Manager has prepared this review summary report summarizing the reasons for this determination, provided the Review Summary Report to the applicable regional board and local agency, as appropriate, with an opportunity for comment on the Review Summary Report. Pursuant to Health and Safety Code as of the date of the signature of the Fund Manager below, the regional board or local agency shall not issue a corrective action directive or enforce an existing corrective action directive for the tank case until the board issues a decision on the closure of the tank case, unless one of the following applies: Page 2 of 12