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GSI Field Methods and Procedures Updated August 19, 1994 Page Z Field Screening of Soil Sam les A PID Is used to perform head-space analysis in the field for the presence of organic vapors from the soil sample This test procedure Involves removing soil from the tip of the sampling device or sample liner into a clean glass jar, and immediately covering the lar with aluminum foil secured under a ring-type threaded lid After approximately twenty minutes, the foil Is pierced and the atmosphere within the lar tested using a PID. Head-space screening results are recorded on the boring log Head-space screening procedures are performed and results recorded as reconnaissance data GSI 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 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 Cali fornca-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 GeoStrategies Inc.