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i <br /> Working to Restore Nature <br /> GROUNDWATER MONITORING: FIRST QUARTER 1994 <br /> Groundwater Technology, Inc (GTI) of Concord, California, was contracted by ARCO to <br /> monitor the groundwater in the monitoring wells previously installed at the site, GTI <br /> subsequently forwarded their field notes and the laboratory reports to RESNA RESNA <br /> used these data to evaluate dissolved gasoline hydrocarbon concentrations and the flow <br /> direction and groundwater gradient <br /> On March 23, 1994, a technician from GTI took water-level measurements and collected <br /> groundwater samples from monitoring wells MW-1 through MW-4 for subjective and <br /> laboratory analyses The technician did not observe floating product or product sheen on <br /> samples collected from the wells (Table 1) <br /> The surveyed elevations of the top of casing and the depth-to-groundwater measurements <br /> (summarized in Table 1) were used to evaluate the potentiometric surface beneath the site <br /> On March 23, 1994, the direction of groundwater flow was northwest with a gradient of <br /> approximately 0 02 (Plate 3) The direction of groundwater flow has generally been <br /> northwest since our investigation began The elevation of the groundwater surface has <br /> decreased an average of approximately 105 feet in wells MW-1 through MW-4 since the last <br /> quarterly monitoring event (October 1994) <br /> Groundwater samples from each well were analyzed for total petroleum hydrocarbons as <br /> gasoline (TPHg) and benzene, toluene, ethylbenzene, and total xylene isomers (BTEX) <br /> using Environmental Protection Agency Methods Modified 8015 and 5030/8020 The <br /> samples were analyzed at GTEL Environmental Laboratories, Inc in Concord, California <br /> The results of analyses are summarized in Table 1 Copies of the laboratory analysis reports <br /> are attached Results of analyses indicated TPHg and BTEX concentrations were below <br /> laboratory detection limits in groundwater samples collected from wells MW-1 through MW- <br /> 4 <br /> WORK IN PROGRESS <br /> We understand the second quarter groundwater sampling event is schedule to be conducted <br /> in June 1994 <br /> • 0413ccar/30008-10 2 <br />