Laserfiche WebLink
Groundwater Monitoring <br /> Well Installation and <br /> ARCADIS Sampling Work Plan <br /> PG&E McDonald Island <br /> Compressor Station <br /> borehole will be over-drilled using 8-inch outside diameter hollow-stem auger <br /> equipment to approximately 16 feet bgs to facilitate well construction. <br /> 3.3 Monitoring Well Construction <br /> Upon completion of the 8-inch diameter boreholes to approximately 4 feet below <br /> encountered groundwater,the monitoring wells will be installed using 2-inch-diameter <br /> schedule 40 poly vinyl chloride(PVC)casing with 10 feet of screened interval of 0.010- <br /> inch slotted PVC at the base of the well.A clean sand filter pack consisting of No.2/12 <br /> Monterey Sand will be placed around the well from the bottom of the borehole to <br /> approximately 1 foot above the screen interval.A 0.5-foot-thick hydrated bentonite <br /> slurry seal will be placed above the sandpack. The remainder of the annular space will <br /> be tremie grouted with neat cement to approximately 1 foot bgs. The neat cement mix <br /> generally will consist of a 94-pound bag of Portland Cement Type 1/II and 6 gallons of <br /> water. Each well will be fitted with a well cap and completed with a locking, traffic-rated <br /> flush mounted well box that includes a'Monitoring Well' label. <br /> 3.4 Monitoring Well Development <br /> A minimum of 72 hours after installation, the newly installed monitoring wells will be <br /> developed using a combination of surging, bailing, and pumping. A surge block will be <br /> moved up and down across the screened interval to remove fine-grained deposits from <br /> the formation near the monitoring well and boring wall and from the filter material.After <br /> surging the monitoring well, a bailer will be used to remove water containing <br /> suspended sediments from the casing.Additional purging activities will be conducted <br /> with a submersible pump placed near the bottom of the well.The final development <br /> task will consist of pumping the well at a steady flow rate while monitoring groundwater <br /> parameters(including pH, conductivity,turbidity,dissolved oxygen, and <br /> reduction/oxidation potential)using a water quality meter with a flow-through cell. <br /> Pumping will continue until at least three casing-volumes of water had been removed <br /> and consecutive groundwater parameter readings have stabilized as follows: <br /> • pH to within 0.1 unit <br /> • Specific conductivity to within 3 percent <br /> • Turbidity to within 10 percent <br /> • Dissolved oxygen to within 10 percent <br /> Modonald Island Addtl MW Installation Work Plan.00cx 6 <br />