ARCHIVED REPORTS XR0006438 - Laserfiche WebLink

Home Browse Search

September 15, 1993 Working To Restore Nature Ruiz Grocery, Tracy, California 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 cap to further protect against unauthorized disturbance of the well, until the well is plumbed to a remediation system Monitoring-Well Construction Monitoring wells are constructed in the borings with thread;jointed, 4-inch-inner-diameter, Schedule 40 PVC casing No chemical cements, glues, or solvents are used in well construction The screened portion of each well consists of factory-perforated casing with 0.020-inch-wide slots The well screen extends from the total depth of the well to approximately 5 feet above the groundwater surface. This screened interval allows sampling at the air-water interface during seasonal and other fluctuations of the groundwater level The annular space in the well is packed with sand compatible with well slot size to approximately Il to 2 feet above the slotted interval. A 3-foot thick bentonite plug is added above the sand pack to prevent the cement from entering the well pack The remaining annulus is backfilled to grade with a bentonite cement slurry Wells are protected with a traffic-rated, cast-aluminum utility box equipped with a PVC skirt The box has a watertight seal to protect against surface-water infiltration and must be opened with a special wrench. The design of this box discourages vandalism and reduces the possibility of accidental disturbance of the well Well Development We wait a minimum of 24 hours after well installation before developing the groundwater 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 with a surge block and pump 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 and a sample is collected for laboratory analysis See the section on groundwater sampling Subjective Analysis of Groundwater Samples Groundwater samples are collected for subjective analysis from dust below the air-fluid interface in a monitoring well by lowering approximately half the length of a clean Teflon 123020-IW