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Gettler-Ryan Inc. Field Methods and Procedures Field Screening of Soil Samples A PID is used to perform head-space analysis in the field for the presence of organic vapors from the soil sample. A plastic cap is placed over the end of the sample tube that will not be saved for chemical analyses . The PID probe is placed through a hole in the cap , and the concentrations of organic vapors in the headspace between the plastic cap and the soil is recorded . PID screening results are recorded on the boring log as reconnaissance data . GR does not consider field screening techniques to be verification of the presence or absence of hydrocarbons . Construction of Monitoring Wells Monitoring wells are constructed in the exploratory soil borings with Schedule 40 polyvinyl chloride (PVC) casing . All joints are thread joined ; no glues , cements , or solvents are used in well construction. The screened interval is constructed of machine-slotted PVC well screen which generally extends from the total well depth to a point above the groundwater . An appropriately-sized sorted sand is placed in the annular adjacent to the entire screened interval . A bentonite seal is placed in the annular space above the sand , and the remaining annular space is sealed with neat cement or cement grout. Wellheads are protected with water-resistant traffic-rated vault boxes placed flush with the ground surface . The top of the well casing is sealed with a locking waterproof cap . A lock is placed on the well cap to prevent vandalism and unintentional introduction of materials into the well . Measurement of Water Levels The top of the newly-installed well casing is surveyed by a California-licensed Land Surveyor to mean sea level (MSL) . Depth-to-groundwater in the well is measured from the top of the well casing with an electronic water-level indicator . Depth-to-groundwater is measured to the nearest 0 . 01 -foot, and referenced to MSL. A-2