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SOP: Monitoring <br />Well Installation <br />be used if wells are installed using direct-push methodology or if multiple wells are to be installed in a <br />single borehole. The screen length will be specified in the Work Plan or FSP based on regulatory <br />requirements and specific monitoring objectives. Monitoring well screens aze usually 5 to 10 feet long, but <br />may be up [0 25 feet long in very low permeability, thick geologic formations. The screen length will <br />depend on the purpose for the well and the objectives of the groundwater investigation. Typically, the slot <br />size will be 0.010 inch and the sand pack will be Morie No. 0 or equivalent. In very fine-grained formations <br />where sample turbidity needs to be minimized, it may be preferred to use a 0.006-inch slot size and Morie <br />No. 00 or equivalent sand pack. Alternatively, where monitoring wells are installed in coarse-grained <br />deposits and higher well yield is required, a 0.020-inch slot size and Morie No. I or equivalent sand pack <br />may be preferred. To the extent practicable, the slot size and sand pack gradation will be predetermined in <br />the Work Plan or FSP based on site-specific groin-size analysis or other geologic considerations or <br />monitoring objectives. A blank sump may be attached below the well screen if the well is being installed for <br />dense non-aqueous phase liquid (DNAPL) recovery/monitoring purposes. If so, the annulaz space around the <br />sump will be backfilled with neat cement grout to the bottom of the well screen prior to placing the sand <br />pack around the screen. A blank riser will extend from the top of the screen to approximately 2.5 feet above <br />grade or, if necessary, just below Bade where conditions warrant aflush-mounted monitoring well. <br />5. When the monitoring well assembly has been set in place and the grout has been placed around the sump (if <br />any), place a washed silica sand pack in the annulaz space from the bottom of the boring to a height of 1 to 2 <br />feet above the top of the well screen. The sand pack is placed and drilling equipment extracted in increments <br />until the top of the sand pack is at the appropriate depth. The sand pack will be consistent with the screen <br />slot size and the soil particle size in the screened interval, as specified in the Work Plan or FSP. A hydrated <br />bentonite seal (a minimum of 2 feet thick) will then be placed in the annulaz space above the sand pack. If <br />non-hydrated bentonite is used, the bentonite should be permitted to hydrate in place for a minimum of 30 <br />minutes before proceeding. No coated bentonite pellets will be used in monitoring well drilling or <br />construction. Potable water may be added to hydrate the bentonite if the seal is above the water table. <br />Monitor the placement of the sand pack and bentonite with a weighted tape measure. During the extraction <br />of the augers or casing, acement/bentonite grout will be placed in the annulaz space from the bentonite seal <br />to a depth approximately 2 feet bgs. <br />6. Place a locking, steel protective casing (extended at least L5 feet below grade and 2 feet above grade) over <br />the riser casing and secure with a neat Portland Cement seal. Alternatively, for flush-mount completions, <br />place a steel curb box with abolt-down lid over the riser casing and secure with a neat Portland Cement <br />seal. In either case, the cement seal will extend approximately 1.5 to 2.0 feet below grade and Laterally at <br />least 1 foot in all directions from the protective casing, and should slope gently away to promote drainage <br />away from the well. Monitoring wells will be labeled with the appropriate designation on both the inner and <br />outer well casings or inside of the curb box lid. <br />When an above-grade completion is used, the PVC riser will be sealed using an expandable locking plug <br />and the top of the well will be vented by drilling asmall-diameter (1/8 inch) hole neaz the top of the well <br />casing or through the locking plug, or by cutting a vertical slot in the top of the well casing. When aflush- <br />mount installation is used, the PVC riser will be sealed using an unvented, expandable locking plug. <br />7. During well installation, record construction details and actual measurements relayed by the drilling <br />contractor and tabulate materials used (e.g., screen and riser footages; bags of bentonite, cement, and sand) <br />in the field logbook. <br />8. After completing the well installation, lock the well, clean the azea, and dispose of materials in accordance <br />with the procedures outlined in Section VII below. <br />>>reros <br />SOPo<-Monitor Well Installation-Mine Ew <br />