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Gettler-Ryan Inc Field Methods and Procedures November 21, 1996 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 G-R 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 bonngs 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 constructer) 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 I' Y A-2