ARCHIVED REPORTS XR0010527 - Laserfiche WebLink

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EXECUTIVE SUMMARY Two soil,borings were drilled in November 2001 to assess residual soil contamination and determine whether groundwater is contaminated by petroleum hydrocarbons at 8125 South El Dorado Street in French Camp, California The site is the location of J & L Market, a gasoline service station, restaurant, and convenience store One boring was drilled to a depth of 35 feet, encountering groundwater between 30 and 35 feet Soil samples were collected at 5-foot intervals from 10 feet to total depth, and gasoline odor was detected in most of the samples A water sample was collected at 33 feet, but groundwater in the boring later rose to a depth of 27 5 feet The other boring was drilled to 30 feet, but only a small amount of groundwater was encountered The boring was then extended to 40 feet, and a more substantial groundwater zone was encountered between 35 and 40 feet Two soil samples and a water sample were collected from this boring No hydrocarbon odors were present in the soil samples, but an unidentified hydrocarbon odor was evident in the water sample Gasoline was detected between the depths of 10 and 25 feet from the boring nearest the station building (JLM-2) and in the water samples from both borings Diesel was also detected in the water sample from the boring near the dispensers (JLM-1) In the soil samples, TPH-g concentrations ranged from 32 to 1300 mg/kg (p'arts per million) and ethylbenzene and xylene concentrations ranged from 089 to 33 parts per million In the water samples, TPH-g concentrations of 460 and 2300 µg/l (parts per billion) were detected, diesel (TPH-d) was detected at 610 parts per billion, and benzene, toluene, ethylbenzene, and xylene (BTEX) were detected at concentrations ranging from 0 63 to 290 parts per billion No gasoline oxygenates were detected in any of the soil samples, but methyl tertiary butyl ether(MTBE) was detected in the two water samples at 1 5 and 120 parts per billion and dichloroethane (1,2-DCA) was detected at 20 and 25 parts per billion Field observations and laboratory data confirm the results of the remedial investigation that was undertaken in 1995, when approximately 4,000 cubic yards of contaminated soil were excavated from the site and transported to a treatment facility When excavation was completed, residual soil contamination was detected near the station building but could not be removed without endangering the building Although boring JLM-2 was drilled as close to the station building as feasible, the lateral limit of contaminated soil was not reached No soil contamination was detected below a depth of 25 feet, which is the apparent vertical lima of contamination The data also confirm that groundwater has been impacted by petroleum hydrocarbons Relatively low concentrations of several hydrocarbons were detected in the water, but the lateral limits of contaminated groundwater are unknown No specific data on the local groundwater flow direction are available, but the 1993 map "Lines of Equal Elevation of Water in Wells"prepared by the San Joaquin County Flood Control District indicates north to northeastward flow in the area 1