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bi <br /> AM <br /> j. H. KLEINFELDER & ASSOCIATES <br /> 3.3 QUALITATIVE FIELD scpEENING <br /> A Photovac TIP using a photolonization detector (PID) will be used to <br /> screen each soil sample collected from the soil borings. The FID measures <br /> total ionizable compounds in air in parts per million by volume (ppmv) in <br /> dard proposed for this <br /> relation to a select standard. The stan <br /> investigation will be a 25 or 50 ppm benzene calibration gas- Calibration <br /> will be performed prior to use ill the field. The PID field screening of <br /> the soil samples Should provide a qualitative indication Of the presence <br /> Selection Of soil samples to be submitted for <br /> of petroleum hydrocarbons. <br /> chemical analysis will be based on the PID results. The screening <br /> procedure Will Consist of sealing a soil sample in a clean mason jar, <br /> allowing the sample to equilibrate for 5 to 15 minutes, and then scanning <br /> the head space for volatile hydrocarbon vapors. The vapor reading will be <br /> e completion of the field investigation. <br /> noted and evaluated at th <br /> For the protection of the field crew, the P7D will also be used to measure <br /> the total volatile concentrations in t1te breathing zone prior to ana <br /> during the drilling Of the soil borings. Total ionizable hydrocarbon <br /> readings in excess of 5 ppm above background in the breathing zone will <br /> rotection measures. This procedure requirement <br /> necessitate respiratory P <br /> will be outlined in a field safety plan for this project <br /> 3.4 MONITORING WELL CONSTRUCTION <br /> The San Joaquin Local Health District generally requires that three ground <br /> water monitoring wells be installed to assess the presence of petroleum <br /> hydrocarbons in the shallow ground water, An attempt should be made to <br /> place one monitoring well upgradient and two monitoring wells downgradient <br /> of the underground storage tank. It is anticipated that the grourd water <br /> flow is generally to north-northwest. The actual ground water gradient <br /> cannot be ascertained until the ground water monitoring wells are <br /> monitoring wells stould be <br /> installed and surveyed. Permits for the three <br /> obtained from the San Joaquin Local Health District prior to drilling- <br /> 4 <br /> 36-87EM <br /> -1037 <br />