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Fourth Quarter 1996 Status Report-.-Former Discovery Chevrolet' <br /> - <br /> r!.,_r 7anuary3, 1997 <br /> TPHg and benzene were detected in the groundwatersample from well MW-1 at <br /> concentrations of'510 ppb and 190 ppb, respectively. The groundwater,sample from well <br /> MW-2 did not contain detectable concentrations of TPHg, however, benzene was detected <br /> in this sample at a concentration of 4.7 ppb. MTBE was not detected in the groundwater , <br /> samples from wells MW-1 or MW-2. TPHd, MTBE, or Cl-HCs were not detected in the <br /> groundwater sample from well MW-3. TPHg and BTEX were not detected in the trip blank. <br /> These data have been ..used to construct 1 TPHg/Benzene/TPHd. Concentration ':Map. ' <br /> (Figure,4): <br /> Disposition of Well Purge Water <br /> Purge water generated during the.fourth quarter,1996,sampling of groundwater monitoring <br /> wells MW-1 through MW-3 was`discharged.to,prapeily labelled;drums and stored at the site <br /> pending disposal: <br /> DISCUSSION AND CONCLUSIONS <br /> During 'the fourth quarter 1996 groundwater was measured 0.96 to 1.02 feet above levels. <br /> measured during the third quarter'.,.1996 During '''the fourth quarter 1996 groundwater <br /> appeared to flow toward the north-northwest under,a gradient of..0.003. These.data appear <br /> generally consistent with historical monitoring'"data. <br /> TPHg and benzene were detected in upgradient. well MW-1, however, the concentrations <br /> detected in this well during the fourth quarter 1996 .were much lower than the highest <br /> concentrations detected in this well (third quarter 1995).- Benzene was.detected in well MW- <br /> 2, downgradient.of the former gasoline USTs, but.at,a,concentration .much lower than that,. <br /> detected in the same well during the second quarter,1996. Petroleufn hydrocarbons were not ` <br /> detected in well MW-3. <br /> TPHg, BTEX, or Cl-HCs have never been,detected in groundwater samples from well <br /> MW-3. Groundwater downgradient of the former waste oil UST in the vicinity of well <br /> MW-3 has not been impacted by these .hydrocarbons. TPHd has been detected in well <br /> MW-3 during only three of the eight quarterly sampling events; at concentrations of 200, 60, <br /> and '60.ppb. Based on historical.monitoring data,:additional analysis.of samples from well <br /> MW-3 for Cl-HCs are not,warranted,and the sampling frequency frorn this well should be <br /> changed to an annual basis for <br /> TPHd BTEX .1 <br /> 8I46.034 <br /> 4 <br />