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SOP-010 Standard Operating Procedure Well Construction Page 7 of 11 Revision No. 0 March 2020 Sharpe Army Depot The seal should be allowed to hydrate for at least one-half hour before proceeding with the grouting operation. After hydration of the bentonite seal, grout is then pumped through a tremie pipe and filled from the top of the bentonite seal upward. Unless otherwise specified, cement grouts should be mixed using approximately 6 to 7 gallons of water per 94-pound bag of Type I/II Portland cement to a density of approximately 15 pounds/gallon. The addition of bentonite (5 to 10 percent) to the cement grout can be used to both strengthen the mix and delay the setting time. Specific mixtures and other types of cement and/or grout proposed should be evaluated on a case-by-case basis by the field geologist. During grout installation, the bottom of the tremie pipe should be maintained below the top of the grout to prevent free fall and bridging. When using drive casing or hollow-stem auger techniques, the drive casing/augers should be raised in incremental intervals, keeping the bottom of the drive casing/augers below the top of the grout. Grouting will cease when the grout level has risen to within approximately one to two feet of the ground surface, depending on the surface completion type (flush mount versus aboveground). Grout levels should be monitored to assure that grout taken into the formation is replaced by additional grout. If settling of the grout occurs, additional topping off of the grout may be necessary. 4.4.7 Protective Casing For aboveground completions, the protective steel casing will be centered on the well casing and inserted into the grouted annulus. Prior to installation, a 2-inch deep temporary spacer shall be placed between the PVC well cap and the bottom of the protective casing cover to keep the protective casing from settling onto the well cap. After the protective casing has set, a drainage hole may be drilled into the protective casing if required by the project work plans. The drainage hole is positioned approximately two inches above ground surface. The protective casing will be painted with a rust-preventive colored paint. The well head will be labeled to identify, at a minimum, the well number, depth, and date of installation. A minimum of 24 hours after grouting should elapse before installation of the concrete pad and steel guard posts for aboveground completions, or street boxes or vaults for flush mount completions. For aboveground completions, a concrete pad, usually 3-foot by 3-foot by 4-inch thick, is constructed at ground surface around the protective steel casing. The concrete is sloped away from the protective casing to promote surface drainage from the well. For aboveground completions, where traffic conditions warrant extra protection, three steel bucking posts will be embedded to a depth approximately 1.5 feet below the top of the concrete pad. The posts will be installed in concrete-filled post holes spaced equally around the well at a distance of approximately 1.5 feet from the protective steel casing. Where removal of bucking posts is required for well access, mounting sleeves should be embedded into the concrete. For flush mount (or subgrade) completions, a street box or vault is set and cemented in position. The top of the street box or vault will be raised slightly above grade, and the cement sloped to grade to promote surface drainage away from the well.