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r " <br /> I <br /> i <br /> 09 July 1998 <br /> AGE-NC Project No 95-0184 <br />' Page 2 of 4 <br />' custody to McCampbell Analytical, Inc (MAI) in Pacheco, California The samples were analyzed <br /> for <br /> • total petroleum hydrocarbons quantified as gasoline (TPH-g) in accordance with EPA <br />' Method 5030/8015m ` <br /> • volatile aromatics hydrocarbons (benzene,toluene,ethylbenzene and xylenes,BTE&X)with <br /> - methyl tertiary-butyl ether (MTBE) in accordance with EPA Method 602/8020 s <br /> • volatile organic compounds and oxygenated compounds in accordance with EPA Method <br /> 8260 <br /> The sample from MW-4 was also analyzed for total petroleum hydrocarbons quantified as diesel <br />' (TPH-d) in accordance with EPA Method 8015m <br />' 3.0 FINDINGS <br /> 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT <br /> The average depth to ground water at the site was 35 12 feet below the well casing taps during the <br />' April 1998 monitoring event Ground water elevation increased an average of 3 62 feet between <br /> January and April 1998 Ground water was approximately 20 feet above the screened interval in <br /> monitoring wells MW-1, MW-2 and MW-3 Groundwater elevations in these wells were higher than <br />' in the surrounding wells at the site However, the ground water gradient and flow direction <br /> calculated using these three wells was similar to that calculated using the surrounding wells Vapor <br /> well VW-5 was installed at an angle of approximately 15° from vertical and therefore was not used <br />' foi calculating the ground water flow direction <br /> rr� <br /> The inferred ground water flow direction in April 1998 was toward the northeast with a gradient of <br />' approximately 0 004 ft/ft (Figure 3) Traces of free product were measured in MW-4, VW-2B,'VW- <br /> 3, VW-4 and VW-513 with the interface probe during the April 1998 monitoring event <br /> I <br /> 32 ANALYTICAL RESULTS OF GROUND WATER SAMPLES <br />' TPH-g was detected in each well sampled, with concentrations as high as 160,000 parts per billion <br /> (ppb, reported as micrograms per liter) Benzene was detected at concentrations as high as 39,000 <br />' ppb TPH-d was detected in the sample from MW-4 at a concentration of 9,900 ppb Di-isopropyl <br /> ether (DIPS) was detected in the sample from MW-1 at a concentration of 5 1 ppb MTBE was <br /> detected in samples collected from VW-'2B, VW-3 and VW-4 at concentrations of 1,200 ppb, 790 <br /> Advanced GcoEnriron mental,Inc <br /> I ' i <br />