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' FIELD METHODS AND PROCEDURES <br /> 1 0 GROUND WATER AND LIQUID-PRASE PETROLEUM HYDROCARBON <br /> DEPTH ASSESSMENT <br /> A water/petroleum interface probe was used to assess the thickness of liquid-phase petroleum hydrocarbons (LPH), <br /> ' if present, and a water level indicator was used to measure ground water depth in monitoring wells that did not <br /> contain LPH Depth to ground water was measured from the top of each monitonng well casing The tip of the <br /> ' water level indicator was subjectively analyzed for LPH sheen <br /> 2 0 SUBJECTIVE ANALYSIS OF GROUND WATER <br /> Prior to purging, a water sample was collected from the monitoring well for subjective analysis The sample was <br /> ' retrieved by gently lowering a clean, disposable bailer to approximately one-half the bailer length past the air/liquid <br /> interface Fhe bailer was then retrieved and the sample contained within the bailer was examined for floating LPH <br /> ' and the appearance of a petroleum sheen <br /> 3 0 MONITORING WELL PURGING AND SAMPLING <br /> Monitoring wells were purged using a submersible pump or bailer until pH, temperature, and conductivity of the <br /> purge water had stabilized and a minimum of three to four well volumes of water had been removed Ground water <br /> removed from the wells was treated with a portable treatment system consisting of a storage tank., particulate filters <br />' and two aqueous phase granular activated carbon columns connected in series The treated purge water was <br /> discharged to the sanitary sewer at the site in accordance to the discharge permit issued by the City of Stockton <br /> After purging, ground water levels were allowed to stabilize A ground water sample was then removed from each <br /> of the wells using a disposable bailer If the well was purged dry, it was allowed to sufficiently recharge and a <br />' sample was collected Samples were collected in air-tight vials, appropriately labeled, and stored in an ice chest <br /> from the time of collection through the time of delivery to the laboratory A chain-of-custody form was completed <br />' to erasure sample integrity, and document possession of the sample Ground water samples were transported to the <br /> laboratory and analyzed within the EPA-specified holding times for the requested analyses <br />' L.RP017 809 <br />