WORK PLANS - Laserfiche WebLink

Home Browse Search

with potable site water. The grout mix was pumped by the RCM® unit through a pipe to a hose and then through the swivel/drill stem assembly to the jet sub and bit. The jet-grout procedure used on Wells MW-1, 2, and 5 was to rotate the bit with the drill rig rotary head (7 to 8 revolutions per minute). After rotation was started, grout was pumped under pressures ranging from 3,000 to 6,000 pounds per square inch (psi) at each selected perforation interval for approximately 20 to 30 seconds. The intervals perforated and grouted were selected according to the confining properties of the soil as determined from a review of the well installation logs. The intent of this technique was to create a "pancake" of soil/grout extending beyond the well annulus into the native soil deposits. ' The procedure used to abandon Wells MW-3 and 4 was modified to eliminate the bit and drill stem 'bind-up" problems encountered in MW-1 and 2. The ' modification included the elimination of the proposed perforation interval of the bottom of the well casing and filling of the casing with grout (bit at the bottom of casing) to the second perforation proposed within the screened ' section of the well. The procedure used on MW-6 was similar to that used for MW-3 and 4 except the casing was filled with grout until groundwater was displaced and flowed from the top of the well casing to create a positive head ' of grout inside the casing. 2.3 Grout Spoil Storage - The return flow from the jet grout operation was placed 1 into five-foot diameter polyethylene pools for solidification. The spoil material consisted primarily of grout mix materials with some well pack materials, and pieces of PVC pipe. Excess grout and washout water from the Halliburton pump truck was placed inside a storage pool eight feet by eight feet by two feet deep which was lined with six-mil polyethylene film. 2.4 Surface Closure - Surface closure was performed on June 11 and consisted of saw cutting the pavement material (three-feet by three-feet minimum) at Wells MW-1, 3, 4, and 6. Well MW-5 was cut four-feet by four-feet to remove ' old concrete. Well MW-2 was located within a landscape area; therefore, no saw cut was required at this location. After removing the pavement material, the area surrounding the well casing was excavated with a backhoe and by ' hand to approximately three feet below existing site grade. The annulus surface seal along with the grout-filled well casing perforated at approximately three feet was removed from the excavation. The loose materials were ' removed from the excavation and the excavation was backfilled with a 5-sack portland cement concrete mix to approximately four inches below the top of ' existing pavement at Wells MW-1, 3, 4, 5, and 6. At Well MW-2, the excavation was backfilled with clean site soil and compacted with the backhoe bucket. At Wells MW-1, 3, 4, 5 and 6, the concrete backfill was capped with approximately a 4-inch thick lift of asphalt which was compacted with a plate compactor. 3 • &Associates