WORK PLANS - Laserfiche WebLink

Home Browse Search

26 September 2003 • AGE-NC Project No. 02-0896 Page 7 of 9 4.2. WELL COMPLETION AND WELL ELEVATION SURVEY The 8.25-inch diameter pilot borings will be single-completed as ground water monitoring wells utilizing 2-inch diameter schedule 40 polyvinylchloride (PVC) 0.020-inch slotted well screen and blank well casing. A 20-foot length of well screen is anticipated for installation of the monitoring well. A proposed monitoring well construction diagram is depicted in Figure 3. After installing the well casing in each boring, a filter pack material consisting of pre-washed#2/12 Lonestar sand will be added through the augers over the screen interval to approximately two feet above the screened interval.Following placement of the filter pack,the well will be surged to assist in settling the filter pack. Additional sand will be added if settling occurs. A nominal two-foot bentonite seal(pell plug non-coded bentonite pellets)will be placed above the filter pack to minimize the potential for grout penetration into the screened section of the well. The bentonite seal will be formed by pouring bentonite pellets into the annulus and allowing them to settle on the filter pack. The bentonite pellets will be allowed to hydrate for a minimum of one-half hour prior to grouting. • The remaining annular space will be filled within one foot of the ground surface with a cement grout. The grout mixture will consist of Type IM portland neat cement and not more than 6 gallons of water per 94-pound sack of cement. The grout will be placed by pumping through tremmie pipe. A grouting inspection will be scheduled with EHD personnel.Borings not completed as ground water monitoring wells shall be grouted under the same protocol above. Following completion of the monitoring wells, well elevations and locations will be surveyed by a California-licensed surveyor relative to a San Joaquin County elevation benchmark. 4.3. WELL DEVELOPMENT Development of the proposed wells will consist of a combination of bailing with a stainless steel bailer to remove the major portion of fine-grained sediment from inside the well, surging to flush out or draw in sediment from the filter pack and additional ground water evacuation(purging)with a Waterra bailing pump to finish the removal of fine-grained sediment. Developmental purging activities will be continued until field parameter (pH, electrical conductivity, and temperature) readings have stabilized and purged water is visually sediment-free. • Advanced GeoEnvironmental,Inc.