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Monitoring Well B8 Plans and Specifications <br />Kalitas Counly &Ald Waste <br />2.4.1 BackfillInstal.lation <br />If the targeted screen depth is not at the bottom of the borehole; the CONTRACTOR shall backfill the <br />well with bentonite or pea gravel/filter pack, depending upon the unit observed at completion, with <br />approval from the GEOLOGIST. If the final depth is within the target zone, silica sand filter pack will be <br />placed by the CONTRACTOR prior to lowering the screen assembly. If the target screen zone is greater <br />than 10 feet above the bottom of the borehole, the CONTRACTOR shall place bentonite up to within 5 <br />feet of the target zone. Once the borehole has been backfilled to the desired depth, the CONTRACTOR <br />will then lower the well assembly into place to allow placement of filter pack surrounding the screened <br />zone. <br />Backfill materials shall be placed In the unused borehole prior to installation of the well to ensure the <br />screened interval is located correctly. The backfill includes either bentonite chips, or filter pack. <br />Placement of backfill prior to well construction shall be confirmed with the GEOLOGIST. If voids are <br />encountered during backfilling, the CONTRACTOR shall notify the GEOLOGIST immediately to allow <br />for installation of alternative materials (pea gravel, cement, etc.). These will be billed to the OWNER <br />under minor changes as detailed in Section 4. <br />2A2 Well Asseztibly Installation <br />The CONTRACTOR shall install the well assembly once the desired installation depth has been <br />achieved. The CONTRACTOR shall ensure that the well is properly centered within the borehole and <br />may use centralizers to ensure the well is centered as long as the centralizers do not inhibit placement <br />of pack or seal materials. The well assembly consisting of the Schedule 80 PVC screen and riser pipe <br />shall be lowered into the borehole by the CONTRACTOR to ensure a proper amount of pack material <br />and seal material can be placed in the annular spacing meeting the target zone completions defined <br />by the GEOLOGIST. Once the well assembly has been successfully lowered Into place, the <br />CONTRACTOR shall begin placement of pack and seal. <br />2.4.3 Pack Materia.1/Seal Installation <br />An artificial filter pack of rounded to sub -rounded silica sand (See Section 2.3.4) will be used in the <br />well construction. The filter pack will be placed in the annular space between the well and the borehole <br />wall from the bottom of the screened interval (or up to 5 feet below) to a minimum of 3 feet above the <br />top of the screened Interval. The filter pack shall be placed in such a way as to avoid bridging. <br />A minimum of 3 feet of medium or coarse -grained bentonite chips will be placed directly above the <br />filter pack as a seal. Clean water will be added to fully hydrate the bentonite chips. <br />The remainder of the annular space between the borehole to within 2 feet of land surface shall be <br />sealed by the CONTRACTOR with bentonite in accordance with WAC 173-160 <br />All temporary steel casing shall be withdrawn as the pack material and seal are placed surrounding <br />the permanent well. If permanent steel casing is used, it will be sealed in place with bentonite and/or <br />cement, The details are presented on Sheet A-3. <br />2.4.4 Well Completions <br />The CONTRACTOR shall install a lockable above -ground monument for the final well completion as <br />identified in Section 2.3.6. The protective casing shall be placed with a minimum of 1.5-feet <br />embedded in cement below the ground surface. Three 3-inch diameter steel protective bollards shall <br />also be placed surrounding the monitoring well as described in Section 2.3.7, located in consultation <br />February 2025 1 553-1763.010 13 <br />