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Kleinfelder observed Hydro -Search's field operation on April 27, 28, 29, <br />and May 6, 1988. Monitoring well construction techniques were in keeping <br />with the accepted standard of care for monitoring well installation in <br />northern California. Ground water was not encountered during <br />Hydro -Search's drilling operation. <br />Hydro -Search used a HNU PID to monitor for methane. in shallow borings. A <br />PID using a 10.2 eV bulb cannot detect the presence of methane, which has <br />an ionization potential of greater than 12 eV. Readings of 0.2 ppmv <br />recorded on the PID at MB -7 and M3-8 may have been due to machine <br />variance, while the readings at MB -9 and MB -10 may have been from diesel <br />vapors due to the proximity of a diesel tank. <br />The zero readings recorded on the combustible gas analyzers suggest <br />methane gas is probably not present in the near—surface soil at the 10 <br />soil—gas borings. <br />Water samples were collected from an onsite domestic well and analyzed for <br />halogenated volatile organic compounds by EPA Method 601. Analytical <br />results of the water samples show trans-1,2-dichloroethene is present with <br />a concentration of 0.6 ug/l in the first round sample collected April 28, <br />1988. The laboratory detection limit is 0.2 ug/1. No source for the <br />occurrence of trans— l,2—dichloroethene in water from the domestic well is <br />known at this time. Possible laboratory error or contaminated sample <br />containers could be the cause for the occurrence of the <br />trans-1,2—dichloroethene. Since the analysis of the second round of <br />samples (May 6, 1988) show no trans-1,2—dichloroethene, and the <br />concentration of it detected in the first round sample was close to the <br />detection limit, we feel the occurrence of the trans-1,2—dichloroethene is <br />of little significance. <br />104-88-683 13 <br />