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<br /> <br />4.3 Bentonite <br />The bentonite used for the slurry mixture will be unadulterated powdered premium grade <br />sodium cation montomorrillonite, and will meet the standards described in API Standard <br />13A, "API Specification for Oil-Well Drilling-Fluid Materials". Bentonite stored at the site <br />will be done in such a manner that prevents contamination and water absorption. <br />4.4 Water <br />Fresh water, free of excessive amounts of deleterious substances that adversely affect <br />the properties of the slurry, shall be used to manufacture bentonite slurry. An example <br />of allowable water is as follows. The water will have a pH range of 6 to 8, a maximum <br />hardness of 200 ppm, and total dissolved solids will not exceed 500 ppm. The amounts <br />of oil, organics, acids and alkali levels will not exceed 50 ppm each. The amount of <br />chloride will be tested and reported. If the water does not meet these requirements, it <br />will be treated or conditioned and/or another source of water will be used for the slurry <br />mixture. <br />4.5 Backfill <br />The backfill material for the trench will consist of slurry, dry bentonite, and soils obtained <br />from the designated borrow area, or a source approved by the Engineer. The backfill <br />material will be mixed to obtain a thoroughly mixed and consistent material that will meet <br />the following specifications: <br />Screen Size Percent Passing <br />(U.S. Standard) by Drv Weight <br />3 inch 100 <br />No.4 70-100 <br />No. 200 30 Minimum <br />In order to achieve a low permeability rate for the backfill mixture, the backfill soil will <br />have a minimum Plasticity Index of 10. The density of the backfill must be a minimum of <br />15 pcf greater than any slurry in the trench. <br />