ARCHIVED REPORTS XR0009919 - Laserfiche WebLink

Home Browse Search

Working to Restore Nature tr �' Monitoring Well Construction The monitoring well was constructed in the boring with thread jointed, 2-inch-inner- diameter, Schedule 40 PVC casing. No chemical cements, glues, or solvents were used in well construction. The screened portion of the well consisted of factory-perforated casing with 0.020-inch-wide slots. The well screen extends from the total depth of the well to approximately 5 to 10 feet above the groundwater surface. This screened interval allows sampling at the air-water interface during seasonal fluctuations of the groundwater level. The annular space in the well was packed with number 3 sand to approximately 1 to 2 feet above the slotted interval. A 3-foot thick bentonite plug was added above the sand pack to 46- prevent the cement from entering the well pack. The remaining annulus was backfilled to grade with a bentonite cement slurry. The well was 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 46, 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 waited a minimum of 24 hours after well installation before developing the groundwater monitoring well to allow the grout to seal. Before developing the monitoring well, a water sample was 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. Floating product was not encountered. The well was developed with a surge block and pump. Well development continued until the discharge water was clear of silt and sand. Clay-size i' sediments derived from the screened portion of the formation cannot be entirely eliminated by well development. After the wells stabilized for a minimum of 24 hours, the well was purged of stagnant water and a sample was collected for laboratory analysis. The well was 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 well was stored in labeled,55-gallon, steel drums approved for this use by the Department of Transportation until suitable disposal options were selected based on laboratory analysis. 4 i.r 1213ccar/30003-9