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H — I SOIL AND GROUNDWATER SAMPLING Former Parts Depot, Stockton, CA October 2009; Page 2 of 3 The borings contained unconsolidated deposits that consisted of clay and silt. Boring logs are shown in Attachment B. Soil samples were collected from each boring at an approximate depth of 6 feet,just below the estimated bottom of the septic field. The samples were analyzed for volatile organic compounds(VOCs)and semivolatile organic compounds (SVOCs). No compounds were detected. Laboratory reports are summarized in Table 1. The reports are presented in Attachment C. WESTERN PROPERTY BOUNDARY Three borings were drilled near the western property boundary,based on observations made during the Phase I ESA.The borings were drilled in areas with distressed/dead vegetation and stained soil.The adjacent property west of the John Deere property is currently occupied by a company(Siena Chemical)that is believed to manufacture chemicals for the swimming pool and cleaning industries.The borings were drilled within a few feet of a fence separating the properties. Boring locations are depicted on Figure 1. Soil samples were collected from the surface and at an approximate depth of 3 feet Boring logs are shown in Attachment B. The samples were analyzed for volatile organic compounds VOCs, SVOCs, Resource Conservation and Recovery Act(RCRA) metals,and indicator parameters including alkalinity, chloride,nitrogen, sulfate, and pH (Table 1). Laboratory reports are provided in Attachment C. The borings contained unconsolidated deposits that consisted of clay. Chloroform exceeded the U.S. EPA RSL for the protection of groundwater. Acetone was detected in three samples at levels that did not exceed the RSLs. It is likely that both compounds are the result of spills from the neighboring property. Based on observations made during the Phase I assessment, sodium hypochlorite solution(chlorine bleach)was stored by Sierra Chemical Co. in totes along the property boundary. When sodium hypochlorite is mixed with common industrial solvents such as acetone,it can produce chloroform. This may be the case at this site,as acetone and chloroform were the only VOCs detected along the western property boundary. SVOCs were not detected in any of the six soil samples from the western property boundary. Arsenic was detected at levels from 5.6 mg/kg to 13 mg/kg,while U.S. EPA's lowest RSL for arsenic is 0.0013 mg/kg. Barium was detected from 230 mg/kg to 450 mg/kg,versus the lowest RSL of 82 mg/kg. Therefore,both arsenic and barium exceeded the U.S. EPA RSLs. Lead and chromium were also detected,but did not exceed their respective RSLs. It is not clear whether the metal concentrations are naturally occurring or the result of anthropogenic sources. Sulfate was identified at concentrations ranging from 39 to 180 mg/kg,but there is no RSL for sulfate in soil.Nitrate(as N)ranged from 8 to 43 mg/kg. U.S. EPA does not have an RSL for the leaching-to-groundwater scenario, but the state of California enforces a provisional standard of 100 mg/kg nitrate. Chloride ranged from 55 mg/kg to 1300 mg/kg, with the highest concentrations being observed in soil samples collected near where tank cars containing chlorine were stored on sidings. (Photo 4).