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10 feet of the bottom of the borehole before gravel placement begins, and shall <br /> be withdrawn as the gravel is placed. The tremie pipe shall be no more than 30 <br /> feet above the top of the gravel during placement. Gravel envelope material shall <br /> be placed with potable water. <br /> 9. Contractor shall minimize bridging of the gravel envelope by placing the gravel <br /> envelope material in the borehole slowly and not in large quantity. Patience shall <br /> be exercised by the Contractor. <br /> 10.Contractor shall monitor the gravel envelope settlement by measuring the gravel <br /> level with a weighted tape. Contractor shall also monitor the top of the well <br /> casing to detect any movement due to settlement. <br /> 11.Contractor shall periodically gently surge the water inside the well casing and <br /> screen to consolidate the gravel envelope while placing the gravel envelope <br /> material. Contractor shall measure the top of the gravel envelope periodically <br /> 12.Contractor shall add gravel envelope material until the gravel envelope is above <br /> the top of the screened interval as shown on the groundwater well figure. <br /> 13.Once the placement of the gravel envelope is completed, the contractor shall <br /> measure and record the depth to the top of the gravel envelope in the presence <br /> of the Engineer. <br /> 14.Contractor shall install a 5-foot bentonite seal in the annular space above the <br /> gravel envelope. Bentonite shall be added gradually and slowly through the <br /> tremie pipe to avoid bridging. Contractor shall measure the depth of the <br /> bentonite seal using a weighted tape. <br /> 15.Contractor shall hydrate the bentonite seal after placement with five (5) gallons of <br /> distilled or Engineer-approved potable water for each 2.5 vertical feet of seal. <br /> 16.Contractor shall add sufficient water to hydrate the bentonite. Contractor shall <br /> add water to the bentonite seal and allow the bentonite to hydrate for minimum of <br /> 30 minutes. Contractor shall measure the water elevation over the bentonite <br /> after adding water and again 30 minutes later. If water elevation has dropped <br /> during that time, then Contractor shall wait for another 30 minutes before <br /> grouting with neat cement. <br /> 17.Contractor shall pump neat cement through a tremie pipe filling the annular <br /> space from the top of the bentonite seal upward. The bottom of the tremie pipe <br /> shall remain submerged in neat cement throughout the grouting process to <br /> prevent free fall and bridging. <br /> 18.Contractor shall place neat cement in a single pour for annular seals up to 100 <br /> feet deep. For seals deeper than 100 feet, the Contractor shall pump neat <br /> cement in 100-foot lifts, each being at least 24 hours after the previous. <br /> 19.Contractor shall place neat cement in the boring up to the existing grade. <br /> Contractor shall allow neat cement to settle overnight. After neat cement <br /> North County G-15&G-16 San Joaquin County <br /> Groundwater Monitoring Well Specifications 8 Public Works Dept <br /> Solid Waste Division <br />