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GSI Ficld Methods and Procedures <br /> Updated August 16, 1995 <br /> Field Screening' of Soil Samples <br /> A PID is used to perform head-space analysis in the field for the presence of organic vapors <br /> from the soil sample This test procedure involves removing soil from the tip of the <br /> sampling device or sample liner into a clean glass far, and immediately covering the.jar with <br /> aluminum foil secured under a ring-type threaded lid After approximately twenty minutes, <br /> the foil is pierced and the atmosphere within the ,jar tested using a PID Head-space <br /> screening results are recorded on the boring log Head-space screening procedures are <br /> performed and results recorded as reconnaissance data GSI does not consider field <br /> screening techniques to be verification of the presence or absence of hydrocarbons <br /> Construction of Monitoring Wells <br /> Monitoring wells are constructed in the exploratory soil borings with Schedule 40 polyvinyl <br /> chloride(PVC) casing All joints are thread-joined, no glues, cements, or solvents are used <br /> in well construction The screened interval is constructed of machine-slotted PVC well <br /> screen which extends from the total well depth to a point above the groundwater An <br /> appropriately-sized sorted sand is placed in the annular adjacent to the entire screened <br /> interval A bentonite seal is placed in the annular space above the sand, and the remaining <br /> annular space is sealed with neat cement or cement grout <br /> Wellheads are protected with water-resistant traffic-rated vault boxes placed flush with the <br /> ground surface The top of the well casing is sealed with a locking waterproof cap A lock <br /> is placed on the well cap to prevent vandalism and unintentional introduction of materials <br /> into the well <br /> Measurement of Water Levels <br /> The top of the newly-installed well casing is surveyed by a California-licensed Land <br /> Surveyor to mean sea level (MSL) Depth-to-groundwater in the well is measured from the <br /> top of the well casing with an electronic water-level indicator Depth-to-groundwater is <br /> measured to the nearest 0 01-foot, and referenced to MSL <br /> Well Development and Sam" <br /> lin <br /> purpose of well development is to improve hydraulic communication between the well <br /> and the surrounding aquifer Prior to development, each well is monitored for the presence <br /> of floating product and the depth-to-water is recorded Wells are then developed by <br /> A-2 <br />