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13. Contractor shall install a bentonite seal in the annular space above the sand pack. Add bentonite gradually to avoid bridging. Contractor shall measure the depth of the bentonite plug using a weighted tape. 14. Contractor shall hydrate the bentonite seal after placement with five (5) gallons of distilled or Engineer-approved water for each 2.5 vertical feet of seal. 15. Contractor shall add sufficient water to hydrate the bentonite. Contractor shall add water to the bentonite seal and allow the bentonite to hydrate for minimum of 30 minutes. Contractor shall measure the water elevation over the bentonite after adding water and again 30 minutes later. If water elevation has dropped during that time, then Contractor shall wait for another 30 minutes. before grouting with neat cement. 16. Contractor shall pump neat cement through a tremie pipe filling the annular space from the top of the bentonite seal upward. The bottom of the tremie pipe shall be maintained below the top of the cement to prevent free fall and bridging. 17. Contractor shall place neat cement in a single pour for wells up to 100 feet deep. For wells deeper than 100 feet, the Contractor shall pour neat cement in two pours, the second pour being at least 24 hours after the first pour. 18. When drilling with hollow stem augers, the hollow stem of the auger may be substituted for the tremie pipe, provided the bottom of the augers are no more than 10 feet above the top of the neat cement layer within the well. 19. Contractor shall place neat cement in the boring up to the existing grade. Contractor shall allow neat cement to settle overnight. After neat cement settlement, Contractor shall place additional neat cement to a level as indicated in the Drawings. 20. Contractor shall install the well enclosure and do the surface completion only after the neat cement has hardened. E. Contractor shall record the following information on the Driller's Log: 1. Depth to water-bearing zones 2. Total depth of bore hole 3. Depth from ground surface to top and bottom of the well screen interval 4. Depth from ground surface to top of the sand pack interval 5. Depth from ground surface to top of the bentonite plug 6. Height above the ground surface of the top of the well casing 7. Height above the ground surface of the top of the steel protective casing. On-Call Driller RFB 6820 San Joaquin County Groundwater Monitoring Well Specifications 8 Public Works Dept Solid Waste Division