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AINVest Subsurface Investigation <br /> Former Diesel Tank and Spray Rack Site <br /> RMC Lonestar Kerlinger Plant <br /> 30350 South Tracy Boulevard, Tracy, California <br /> I. EXECUTIVE SUMMARY <br /> AllWest conducted a subsurface investigation program of the former diesel tank and spray rack <br /> site at RMC Lonestar's Kerlinger Plant located at 30350 South Tracy Boulevard in Tracy, <br /> California on February 9 and 10, 1994. The program included the advancement of eight soil <br /> boreholes, the collection of soil samples from within the boreholes, and the chemical analyses <br /> of the collected soil samples. <br /> The soil sampling program, conducted through the reverse air-circulation hammer-drill process <br /> at eight locations around the former diesel tank and spray rack site, collected a total of 61 soil <br /> samples to the maximum depth of 90 feet below the ground surface. The soil samples were <br /> forwarded to a state certified laboratory for chemical analyses. Thirty-two soil samples were <br /> subjected to the Total Petroleum Hydrocarbons as Diesel analysis. Test results indicate <br /> detectable levels of diesel in soils samples collected from the upper 20 feet at four boring <br /> locations. <br /> A review of the boring locations and diesel concentrations in soil samples indicate diesel <br /> contaminants generally occur within a small area about 30 feet by 30 feet, centered around the <br /> former tank pit. The highest level of diesel contamination exists in the upper 10 feet of soils. <br /> The concentration level of diesel contaminants decreases markedly with depth. There are no <br /> detectable levels of diesel at or below 25 feet depth. <br /> _ Based on data gathered during this investigation, AllWest concludes that the soils impacted by <br /> diesel are limited to a 30-foot by 30-foot area of the former diesel tank pit and within 20 feet of <br /> the ground surface. There is no evidence that the detected diesel contamination has impacted <br /> the site's groundwater since the water table is greater than 100 feet in depth. However remote, <br /> the diesel contaminated soils are a potential source of groundwater contamination. AllWest <br /> recommends that the impacted soils be excavated and remediated. AllWest also recommends <br /> informing the appropriate regulatory agencies of the investigation findings and to obtain their <br /> concurrence of the recommended remedial actions. <br /> 1 <br />