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3. SOIL-BENTONITE BACKFILLED SLURRY WALL CONSTRUCTION <br />3.1 Bentonite Slurry Mixing and Delivering <br />The Contractor constructed a pit out of native material for the purpose of mixing and hydrating <br />bentonite slurry. The slurry mixing pit was located near the center of the project site. Three <br />thousand-pound bags of bentonite were delivered to the site. The bentonite was mixed with <br />water in the pit using a shear mixer. The water for mixing was obtained from a pre-excavated <br />groundwater pond dug by Loveland Ready Mix adjacent to the mixing pond on the west side. <br />The slurry was delivered from the pit to the open trench using pump(s) and 4-inch HDPE pipe. <br />3.2 Bentonite Slurry Quality Control Results <br />3.2.1 As-Mixed Slurry <br />To ensure proper mixing and hydration of the powdered bentonite, the as-mixed <br />bentonite slurry was tested approximately once per day. Lyman Henn performed <br />density, and viscosity measurements according to API RP 1313-2. Results are presented <br />in Table I. <br />3.2.2 In-Trench Slurry <br />Slurry within the trench was tested approximately twice per day, with samples taken <br />within five feet from the trench bottom with the excavator after backfilling had <br />commenced. Lyman Henn's field representative would coordinate with the excavator <br />operator to collect a sample of the in-trench slurry from the bucket of the excavator <br />after the operator plunged the bucket to the bottom of the trench and retrieved a sample. <br />Lyman Henn performed the required density and viscosity measurements according to <br />API RP 1313-2. Sand content measurements were not required for this project but were <br />occasionally measured in accordance with API RP 1313-2. Results are presented in <br />Table H. <br />3.3 Slurry Trench Excavation <br />The slurry wall trench was excavated using the continuous trench method. The slurry wall <br />trench (not including overlaps due to tie-ins) was 7,360-ft long, a minimum of 30-inches wide, <br />with depths ranging from 26 to 42-ft below ground surface (bgs). The slurry trench was <br />excavated through the alluvium and fractured bedrock to the top of the massive bedrock. <br />Massive bedrock was verified by excavator behavior and visual-manual classification of <br />bedrock obtained by the excavator. The total area excavated is 230,975-sq. ft. The direction of <br />excavation was counter clockwise starting at Contractor Sta. 30+00. <br />The slurry trench was excavated using a track-mounted hydraulic excavator equipped with a 30- <br />inch wide bucket. The bucket was fitted with rock teeth and a large ripping tooth on the back. <br />A Komatsu PC800 was used for excavation of the slurry trench. Excavation was typically <br />performed in 30-ft intervals or "sets" along the alignment. <br />G:\PROJECPS\107021-" Loveland Ready Mix Slurry Wall\R. Records and Correspondence\R.11 Reports\As Built report stunts-built reportFirW doc 3