Laserfiche WebLink
56 Grouting the well annulus <br /> Geoprobe Grout <br /> ' The placement of grout material within Machine <br /> the remaining well annulus provides ad- (GstoOo) <br /> (1 <br /> ditional protection from vertical contami- Plastic Plug <br /> (13227) <br /> nant migration Most grout mixes are <br /> ' composed of neat cement, high-solids <br /> bentonite slurry,or a combination of ce- <br /> ment and bentonite Such mixes must <br /> be delivered with a high-pressure grout <br /> pump When stable formations exist,the <br /> well may be sealed by pouring dry granu- <br /> lar bentonite directly into the annulus <br /> from the ground surface Consult the <br /> appropriate regulatory agency to deter- <br /> mine approved grouting methods This Tremie Tube <br /> section presents the procedure for grout- pump (Flewble Tubing <br /> ing the well annulus with the Geoprobe Bentonite slurry 14299) <br /> Model GS500 or GS l 000 Grout Ma- fills void as rods <br /> are slowly <br /> ' chine Refer to Figure 5 12 as needed withdrawn .f <br /> I Mix an appropriate amount of grout High solids <br /> ' Bentonite slurry <br /> material and place it in the hopper of forms well seal Grout Barrier <br /> t — (20/40 Grade Sand or <br /> he grout machine <br /> Natural Formation) <br /> NOTE It is recommended that an addi- <br /> tional 20 to 25 percent of the calculated <br /> annulus volume be added to the total <br /> grout volume This additional amount <br /> allows for grout that either remains in the <br /> grout hose or moves into the formation <br /> during pumping Including the additional <br /> ' 20 percent, it will take approximately <br /> 0 54 gallons(2,0 L)of grout for each foot FIGURE 5 1 <br /> installing Bentonite Seal with <br /> of riser below ground surface Geoprobe GS1000 Grout Machine <br /> ' 2 Insert tremie tube into the well annu- <br /> lus until the end of the flexible tubing <br /> reaches the top of the bentonite seal Ensure that at least 25 feet(8 m)of tubing extends from the top of <br /> ' the rod string This extra length allows rod retraction with the tubing attached to the pump <br /> 3 Attach the tubing to the grout machine and begin pumping If the bentonite seal was below the water <br /> table(deep well installation),water will be displaced and flow from the probe rods as the annulus is filled <br /> with grout Continue operating the pump until undiluted grout flows from the top probe rod <br /> 4 Reposition the probe unit and prepare to pull rods <br /> 1 <br /> 5 Begin pulling the probe rods while continuing to pump grout Match the pulling speed to grout flow <br /> ' so that the rods remain filled to the ground surface This maintains hydraulic head within the probe rods <br /> and ensures that the void left by the withdrawn rods is completely filled with grout <br /> ' Standard Operating Procedure Page 19 1 0-in x 2 5-in OD Prepack Screen Monitoring Well <br />