ARCHIVED REPORTS_XR0012046 - Laserfiche WebLink

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"SOMA Well Construction Working To Restore Nature The wells are constructed using clean 2-, 4-, or 6-inch-inner-diameter, thread-pointed, Schedule 40 polyvinyl chloride (PVC) casing No chemicals, glues, or solvents are used in construction of the wells The screened portion of the monitoring wells consists of factory- perforated casing with slots and extends from the total depth of the boring to about 5 feet above the depth where water is first encountered The screened portion of the vapor- extraction wells consists of a 10-foot section of factory-perforated casing with slots and extends from the approximately 1 foot above the depth where water was first encountered Unperforated casing is set from the top of the screen to several inches below surface grade The annular space of each well is packed with sorted sand from the total depth of the boring to approximately 1 foot above the top of the screen A plug of bentonite pellets (approximately 2 feet thick) was placed above the sand to prevent cement from entering the sand pack This seal reduces the possibility that hydrocarbons migrating downward through the overlying sand will infiltrate the aquifer The remaining annulus is backfilled to the ground surface with a mixture of water, cement, and bentonite The construction details of the individual wells are shown on the Logs of Borings r The wellheads are secured in cast-aluminum utility boxes with PVC aprons The boxes have watertight seals and are set in concrete approximately flush with the surrounding ground surface to reduce surface-water infiltration A special wrench is required to open the box This design discourages vandalism and reduces the possibility of accidental disturbance to the well Each wellhead is also fitted with a locking well cage to further protect against unauthorized disturbance of the well Well Development and Purging ` RESNA waits a minimum of 24 hours after well installation before developing the ground- water monitoring wells to allow the grout to seal Before developing the monitoring wells, a water sample is collected for subjective analysis from near the water surface in the well with a Teflon bailer cleaned with a laboratory-grade detergent and deionized water The wells are developed by surge blocking the screened interval of the well and pumping approximately 100 gallons, or ten well volumes, of water from the well Well development continues until the discharge water is clear of silt and sand Clay-size sediments derived from the screened portion of the formation cannot be entirely eliminated by well development After the wells stabilize for a minimum of 24 hours, the wells are purged of stagnant water F and a sample is collected for laboratory analysis The wells are purged of approximately 3 to 5 well volumes of water with a submersible pump, or until pH, conductivity, and temperature of the purged water have stabilized Water purged from the wells is stored in labeled, 55-gallon, steel drums approved for this use by the Department of Transportation until suitable disposal options are selected based on laboratory analysis I 38032-i0