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• <br />• <br />• For this reason, this portion of the slurry wall was built inside the final slurry wall alignment, and <br />ended up as an extra length which can be abandoned. Comers of the slurry wall alignment were <br />constructed to be radial curves or made by cross-cutting straight line segments. This was done to <br />• ensure the slurry wall was keyed in three feet past the top of competent, unweathered bedrock along <br />i <br />• the entire alignment. <br />i <br />Prior to construction of the slurry wall, berms were constructed along the inside of the slurry wall <br />alignment. These berms consisted of overburden soils from on-site, as well as dry fine-grained ~ <br />• bentonite delivered from offsite. The granular bentonite was added at a rate of approximately 0:5 <br />• percent of dry weight of the backfill soils. i <br />A shiny mixing/holding pond was constructed near the center of the site. A reservoir of hydrated <br />. slurry was produced by combining and mixing bulk bentonite powder with water using a conicil <br />• static mixer. Groundwater was pumped from an on-site sump to the slurry pond and used for <br />making the slurry. The slurry in the holding pond was continuously circulated until thoroughly I <br />hydrated. The finished slurry product was pumped through afour-inch high density polyethylene <br />tubing to the open trench section under construction. Pond re-circulation and slurry delivery was <br />• accomplished using two eight-inch pumps. <br />The soil-bentonite (S-B) backfill was composed of four components: 1) soil excavated from the <br />trench, 2) high clay content soil material borrowed on-site, 3) slurry removed from the trench ' <br />• heading during excavation and mixing operations, and 4) dry bentonite applied at an approximate <br />• rate of 0.5 percent of the dry weight of the backfill soils. ~ <br />QUALITY CONTROL TESTING <br />• Resident engineering services were provided by D&A during the slurry wall constmction. These <br />• services included continuous on-site construction observation, sampling, field testing of soils For <br />various slurry trench parameters, and the assimilation of as-built information. A daily log of <br />construction progress was kept. A sunnnary of the quality control test results is presented in ~ <br />i <br />• Appendix A. , <br />A specified material quality control program was followed throughout the slurry wall construction. <br />. Test types, frequency, and specified values aze summarized on Table 1. In order to provide the <br />quickest possible testing result tum-around time, a testing laboratory was set up on-site. Testing <br />i equipment included a mud balance, Marsh funnel, portable electric bench oven, electronic scale; <br />triple-beam balance, portable sieve shaker, various sieves, wet washing apparatus, ambient ' <br />temperature filter press, pH meter, sand content kit, and slump cone apparatus. <br />. A rapid turn-around time of the test results allowed for near real-time adjustments to the various <br />slurry trench parameters throughout the project. Testing conformed to industry standards, including <br />the American Petroleum Institute -Specification 13A, the American Petroleum Institute <br />Recommended Practice -Specification 13-B-2, and ASTM C-143. Specific test results are shown <br />• in Appendix A. <br />' <br />• - 3 - Januaty~2005 <br />S~agewach Final Contwaion Repon da <br />• <br />