Laserfiche WebLink
i <br /> G. Sand pack shall be added in the presence of the on-site geologist until its height is <br /> 5 feet above the top of the screened interval. The driller shall gently surge the <br /> water inside the well casing and screen to compress the sand pack. The top of the <br /> sand pack shall be re-measured and additional sand shall be added to acquire the <br /> desired height of sand pack. This is to ensure that the sand pack does not <br /> compress after installation of the bentonite seal and cause bridging within the <br /> annulus of the well bore. <br /> H. Once the placement of the sand packed interval is completed, the depth to the top <br /> of the pack is measured and recorded on the Driller's Log. <br /> I. The Contractor shall install a 5-foot thick bentonite seal in the annular space on <br /> top of the sand pack. The pellets or chips shall be added gradually to avoid <br /> bridging. The Contractor shall take depth soundings using a weighted tape to <br /> ascertain the top of the bentonite seal. The bentonite seal shall be allowed to <br /> hydrate for at least one hour before proceeding with the grouting operation. <br /> J. The Contractor shall pump the neat cement through a tremie pipe filling the <br /> annular space from the top of the bentonite seal upward. The bottom of the tremie <br /> pipe shall be maintained below the top of the cement to prevent free fall and <br /> bridging. When drilling with hollow stem augers, the hollow stem augers may be <br /> substituted for the tremie pipe, provided the bottom of the augers are no more <br /> than 10 feet above the top of the neat cement. <br /> K. The Contractor shall cease grouting when the cement level has risen to two feet <br /> from the ground surface. Cement levels shall be monitored by the Contractor to <br /> assure that cement taken into the formation is replaced by additional cement, this <br /> will allow placement of the steel protective casing. If settling of the cement <br /> occurs, additional topping-off of the cement seal will be necessary. <br /> L. The Contractor shall install a protective steel surface casing around the well <br /> casing and insert it into the grouted annulus approximately 2 feet. Prior to <br /> installation, a 2-inch thick temporary spacer will be placed between the PVC well <br /> cap and the bottom of the protective casing cover to keep the protective casing <br /> from settling onto the well cap. Typical well design is shown on Figure 4. <br /> M. The Contractor shall record the following additional information on the Driller's <br /> Log: <br /> I. Depth of all encountered water-bearing zones <br /> 2. Total depth of bore hole <br /> 3. Depth from ground surface to top and bottom of the bentonite interval <br /> 4. Depth from ground surface to top and bottom of the sand pack interval <br /> 5. Depth from ground surface to top and bottom of the well screen interval <br /> 6. Depth from ground surface to base of installed well string <br /> Coral Hollow EMP WRDOC Page 6 o/8 February 28,2007 <br />