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1 DIVISION 2-SITE WORK SECTION 02168 -SLURRY WALL CONSTRUCTION PART 1 -GENERAL 1.01 SLURRY TRENCH CUT-OFF The work consists of furnishing all plant, labor, equipment, and materials and of performing all operations as required to construct the slurry trench cut-off wall. A low permeability slurry trench cut-off wall shall be constructed to the lines, grades, and cross- sections as indicated on the drawings. The trench shall have essentially vertical walls, a minimum width of 24 inches, and shall extend through the foundation materials and into the bedrock. A generalized description of the overburden through which the slurry trench cut-off is to be excavated is indicated by geologic cross-sections included in the Drawings. PART 2 -MATERIALS 2.01 SLURRY Slurry shall consist of a stable colloidal suspension of bentonite in water and shall be controlled in accordance with the most current API Standard 136, "Standard Procedure for Testing Drilling Fluids," and the following requirements: ' A. At the time of introduction of the slurry into the trench, the slurry shall be a mixture of not less than 12.5 pounds per barrel (42 gallons) of bentonite and water. Additional bentonite may be required depending on the hardness and temperature of the water and the quality of the bentonite. The slurry shall have a minimum apparent viscosity of 40-seconds reading through a Marsh Funnel Viscosimeter, a maximum filtrate loss of 30 cubic centimeters in 30 minutes at 100 psi, and a pH of not less than 8. B. The slurry mixture in the trench will have a unit weight not less than 64 pcf (1.03 gm/cc), not greater than 87 pcf (1.40 gm/cc), or as approved by the Engineer. C. The slurry mixed with backfill material shall be either slurry taken from the trench or slurry meeting the requirements of slurry introduced into the trench. 2.02 BENTONITE Bentonite used in preparing slurry shall be pulverized (powder) premium grade sodium cation montomorillonite and shall meet the most current API Standard 13A, "API Specification (or Oil-Well Drilling- Fluid Materials." 2.03 WATER Fresh water, free of excessive amounts of deleterious substances that adversely affect the properties of the slurry shall be used to manufacture bentonite slurry. It is the responsibility of the Contractor that ' the slurry resulting from the water shall always meet the standards of this Specification. ' 07/97 Section 02168 -Page 1 of 5