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• • Nolte and Associates, Inc. MONITORING WELLS 3.03 CASING AND SCREEN PLACEMENT A. Casing and Screen The Contractor shall construct each monitoring well as indicated in Figure 2. Casing will consist of 4 in. nominal Schedule 40 PVC, with 20 ft of 4 inch well screen, with slot size to be determined after sieve analysis of formation sample. Well bottoms shall be closed. Care shall be taken to install the protective casing and well casing plumb. Centralizers, if used, shall be utilized as per the drawing to center the casing in the bore. Centralizers shall be located to minimize interference with placing the sealing material as specified. Centralizers shall not be attached to the well screen or that part of the well casing exposed to gravel pack. Before and during setting of the casings and screen, the drill fluid level shall be set at ground surface. The casings and screen shall be set in the hole to the required depth, and the annulus space shall be filled with gravel, as specified. B. Gravel Pack and Seal Gravel pack material will be installed around the well screen to at least 5 ft above the well screen. As the 5 ft bentonite seal is placed on top of the pack material, unchlorinated water from the approved source will be added,when necessary, to assure that the pellets expand to form a tight seal. Properly wetted bentonite pellets are the most time-effective form of bentonite for this application. A bentonite-cement grout seal will extend from the top of the bentonite seal to the land surface. The seal shall be at least 2.0 ft deep. Grouting will be completed as a continuous operation. Grout ma�mixed at the well site the Contractor or be purchased from a reputable ready mix supplier provided that such supplier can provide current water quality analyses showing the mix water to be free from VOC, chlorine, inorganics or other contamination. The grout will be pumped into the annular space-undeUressure usin& tremie�i�e placed at the top of the bentonite seal to ensure a continuous grout seal. The protective casing will be sealed in the grout. Grout shall be left undisturbed for 24 hours after placement. After the grout seal has set (approximately 24 hr), it will be checked for settlement, and additional grout of approved composition will be added to fill any depressions. �)The top of the casing shall be 4 in. below the protective casing cap. The protective casing cap shall be weatherproof and lockable. 3.04 WELL PROTECTION AND PAINTING A square concrete pad shall be placed at each monitoring well site, with the well located at the center of the pad. The pad shall measure 8 ft by 8 ft, and will be 6 inches thick. The pad will contain welded wire fabric (6 in. by 6 in. square, of#10 wire) at middle depth throughout. Four 4 in. diameter Schedule 40 steel posts shall be installed around each monitoring well to prevent damage to the well by vehicular operation. Posts shall extend 3-1/2 ft above ground 6