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measured at the surface with calibrated field instruments. Groundwater samples will be collected in <br /> appropriate containers and delivered to a California ELAP-certified laboratory for analysis in properly <br /> chilled coolers. Samples requiring preservation with acids will be checked to confirm that sufficient acid <br /> has been added to attain a pH of less than 2. In the case of samples collected for metals analysis, an <br /> aliquot of the sample will be poured into the bottle cap, checked for pH, and discarded. In the case of <br /> samples collected for VOC analysis,the check vial will be discarded. <br /> 4.2.4.5 Surface Water Sampling <br /> There is no surface water body at the Site, therefore, surface water sampling will not be conducted for the <br /> PEA. <br /> 4.2.4.6 Air Sampling <br /> The scope of work does not include the collection of air samples at the Site for analysis by an offsite <br /> laboratory. Measurements of total VOCs will be taken throughout the Site with a field instrument as <br /> discussed herein. <br /> 4.2.4.7 Background Sampling <br /> Background sampling will not be conducted as part of this PEA. Based on discussions with DTSC <br /> personnel and as indicated in the scope of work, metal concentrations detected in soils at the Site will be <br /> compared to selected background values collected for a nearby school site. The background data set for <br /> metals will be provided by the DTSC. <br /> 4.2.4.8 Field Instrument Calibration <br /> An OVM-type PID or equivalent PID will be used for health and safety monitoring and field screening <br /> during soil sampling. The data will be used as an immediate indicator of volatile organic vapors in <br /> subsurface materials and the worker breathing zone. The PID must be calibrated in order to display <br /> concentration in units equivalent to parts per million (ppm). A Span Gas, containing a known <br /> concentration of an ionizable gas or vapor, is used to set the sensitivity. Isobutylene at 100 ppm in air <br /> will be used as the Span Gas. The OVM PID instrument will be calibrated as follows: <br /> 1. Connect the calibration adapter to the gas inlet tube of the PID, and connect the calibration <br /> adapter to the Span Gas cylinder. Hand tighten the fittings. <br /> 2. Turn the flow controller knob counterclockwise about half a turn to start the flow of gas. <br /> 3. Wait for the instrument reading to stabilize within ±0.1 ppm. This usually takes about 30 to 40 <br /> seconds. When stabilized,press the [enter] key to complete the procedure. <br /> 4. Turn the flow controller knob fully clockwise to turn off the flow of gas. Disconnect the <br /> calibration adapter from the PID. <br /> In order to abort the calibration, the [menu] key may be pressed any time before pressing the [enter] key <br /> in Step 3. In this case, the previously stored calibration data is not changed. The instrument will be <br /> calibrated at a minimum of once per day prior to use. <br /> A field instrument will be used to measure methane at each soil gas probe location and depth. Calibration <br /> will be the responsibility of the soil gas survey subcontractor. Other field instruments may be used for <br /> groundwater sampling, if required, in order to obtain turbidity, temperature, pH, and specific conductivity <br /> measurements. The manufacturer's calibration steps will be employed. Fresh calibration solutions that <br /> Page 19 PAPEA Lockeford\Work Plan\Lockeford WP.doc <br />