25F - AGMT HAZARDOUS MATERIALS SURVEYS

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b. Free product has been removed to the Free product has not been a concent at the site, and Is not known to maximum extent practicable, may still be present Yes currently exist beneath the site. below the site where the release originated, but does not extend off-site. c. The plume has been stable or decreasing for a Monitoring data from the past five years Indicates the dissolved - minimum of five years. Yes phase plume Is stable. TPHg concentrations In wells BH -2, BH -3, and BH -16 remain high, however. d. The nearest existing water supply well or The nearest groundwaterproduction well is greater than 2,600 feet surface water body is greater than 1,000 feet from Yes from the site. the defined plume boundary. e. The property owner Is willing to accept a landIf necessary, this Issue will have to be discussed with Tesoro's legal use restriction if the regulatory agency requires a Unknown department. land use restriction as a condition of closure. Class a a. The regulatory agency determines, based on The plume meets most of the conditions for closure under Class 3, an analysis of site specific conditions that under Including not posing a threat to human heath and safety under current current and masonablyanddpated near-term and reasonably anticipated near -tern future scenarios, future scenarios, the contaminenl plume poses e low threat to human heath and safety and to the Yes environment and water quality objectives will be achieved within a reasonable Umeframe. 2, Vapor Intrusion to Indoor Air To evaluate If the madla-specific criteria for petroloum vapor Intrusion to Indoor alram considered a low -threat forthe vapor-Intrusion- to-Indoorair pathway at the alto, a site specific soil vapor surveywlll need to be conducted and the date compared to Scenario 1: Unweathered LNAPL In Groundwater of the LTCCP document. The required characteristics are as follows: The elle is a retail gasoline service station and will remain as a gasoline service station for the foreseeable future. It Is not anticipeted that the site will house residential buildings. A soll vapor survey and health risk assessment conducted In 2013 determine Insignificant Impacts to workers at the site or nearby residences. 1. The bloatenuaton zone shall be a continuous The groundwater table Is approximately 10 feel below ground surface zone that provides a separation of at least 30 feet at the site. LNAPL has not been encountered in groundwater vertically between the LNAPL In groundwater and monitodng wells In recent sampling events. TPHg Is dissolved In the foundation of exisUng or potential buildings. As groundwater up to 3,200 pgA, based on data collected in April 2017. used In this context unweathered LNAPL is generally understood to mean petroleum product that has not been subjected to significantYes volatilization or solubilisation, and therefore has not lost a significant portion of Its volatile or soluble constituents (e.g., comparable to recently dispensed fuel). 2. Total TPH (TPH-g and TPH-d combined) are In confirnatlon borings advanced in March 2012, residual TPHg In loll less than 100 mg/kg throughout the entre depth of No urea detected up to 2,600 mglkg at 10 feet logs In boring CSB -1. the bicattenuaton zone. 3. Direct Contact and Outdoor Air Exposure The maximum concentrations of petroleum The maximum concentrations reported for benzene, ethylbenzene, constituents In soil should be compered to the naphthalene, and PAHs in the 6 and 10 That samples ere below the RWOCB's commercial and utility worker RWOCB's commercial and utility worker thresholds, as Indicated in thresholds, as Indicated In Chart 1 , taken from the Table 1 below, taken from the LTCCP. The reported maximum LTCCP to Indicate soil will have no signlflcant dsk concentrations from soil evaluations atter remedlal action are: of adversely affecting human health. • The maximum benzene concentration detected in soil was 9.0 mg/kg in soil boring CSB -1-10 collected from 10 feet bgs on 3116/12 Yes - The maximum ethylbenzane concentration detected in soil was 69 mglkg In soil boring CSB -1.10 collected from 10 feet bgs on 316/12 - Naphthalene concentrations have not been reportedrdetected at the site - PolyaromaUc hydrocarbons (PAHs) concentrations have not been reported/detected al the site 25F-55