ARCHIVED REPORTS_XR0004246 - Laserfiche WebLink

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Chevron Products Company 2 Chevron Servrce Station#9.6258 2409 East Mai S CA July 29,`1999 In June 1996, NorCal Geophysical Consultants, Inc (NorCal) performed a geophysical 40 survey at the site NorCal identified five anomalies associated with the waste-oil tank, sump drain lune, two corners of the former building where utilities entered the building, one location adjacent to the former pump islands, and one location where the former product lines and utility lines crossed Subsequent excavation in these areas revealed debris within approximately 2 feet of the surface, including asphalt, both clay and metal piping, and wires In September and October 1996,Pacific Environmental Group, Inc (Pacific) observed excavation of the waste-oil tank and former product lines, excavation of debris from the former gasoline UST pit, and limited over-excavation of the former gasoline UST pit No detectable concentrations of hydrocarbons were reported in soil samples collected in the areas of the former waste-oil UST and product lines Gasoline hydrocarbon concentrations of up to 4,000 parts per million (ppm) were reported in the southeast corner of the former UST pit After limited over-excavation of approximately 380 cubic yards of impacted soil and 200 cubic yards of concrete debris from the former gasoline UST pit, perimeter soil samples collected from the excavation were reported nondetectable to 2,300 ppm TPH-g In May 1997, one boring(B-7) was drilled within the southeast portion of the footprint of the former gasoline UST pit Analytical soil results reported nondetectable levels of benzene throughout the total depth explored TPH-g reported in soil samples collected .1 from boring B-7 ranged 1,700 ppm at approximately 26 feet bgs to nondetectable levels at approximately 46 feet bgs Groundwater was encountered in boring B-7 at a depth of approximately 58 feet bgs A groundwater"grab" sample collected from B-7 was reported to contain 32,000 parts per billion (ppb) TPH-g and nondetectable concentrations of benzene ASSESSMENT ACTIVITIES AND FINDINGS On April 6 and 7, 1999, three soil borings were dnlled and continuously cored by West Hazmat Drilling of Sacramento, California The three soil borings were converted into groundwater momtonng wells (MW-1 through MW-3) Boring logs are included as Attachment B Field and laboratory procedures are presented as Attachment C Certified analytical reports and chain-of-custody documentation are presented as Attachment D The findings of this assessment are discussed below • Subsurface Conditions. The site is underlain by layers of fine- grained sediments (sandy silts and silty clays), and coarse-grained sediments (silty sands, and sands) Groundwater was initially encountered between approximately 48 and 54 feet bgs at the site Groundwater stabilized at approximately 48 feet bgs Groundwater floc. direction was meas,ired to be to the east at an appruxin�,iI e-