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LJ The soil-bentonite (S-B) backfill was composed of four components: 1) soil excavated from the trench, 1 2) high clay content soil material borrowed on-site, 3) slurry removed from the trench heading during excavation, and 4) dry bentonite applied at a rate of 1.5 percent of the dry weight of the backfill soil. OUALITYASSURANCETESTING Construction engineering services were provided by RMC during the slurry wall construction. These services included daily on-site construction observation, surveying, sampling, field testing of various slurry trench parameters, and the assimilation of as-built information. A daily log of construction progress was kept. A material quality control program was followed throughout the slurry wall construction. Test types, frequency, and specified values are summarized on Table 1. In order to provide the quickest possible testing result turn-around time, a testing laboratory was set-up on site. Testing equipment included a mud balance, Marsh funnel, portable electric bench oven, electronic scale, portable sieve shaker, various sieves, wet washing sieve apparatus, ambient temperature filter press, pH meter, sand content kit, and slump cone apparatus. General field results, listed by station, are shown on Table 2. Specific field and offsite test results are provided in Appendix A. A rapid turn-around time of the test results allowed for near real time adjustments to the various slurry trench parameters throughout the project. Testing conformed with industry testing standards, including the American Petroleum Institute -Specifications 13-A, the American Petroleum Institute Recommended Practice -Specification 13-B-2, and ASTM C-143. Slurry viscosity, as measured using a Marsh funnel apparatus, and unit weight, as measured using a mud balance, were maintained in the lower end of the acceptable range (V i 40 seconds-Marsh, S.G. = 1.03 gm/cc to 1.40 gm/cc). In a few instances, the viscosity dipped below 40 seconds-Marsh due to an excess of water in the mix. These cases of low viscosity occurred at either the mixing pond or t discharge hose. The viscosities were corrected at these locations so that the slurry viscosity in the trench was maintained above the minimum acceptable level. Filter cake formation of the slurry and filtrate loss was analyzed using an ambient temperature filter press assembly. Slurry was collected from the trench for this test. Filter cake thickness and filtrate loss was consistently within the acceptable range. Texture of the cake formation ranged from clean to very sandy. A sand content kit was used to measure the percent sand by volume suspended in the slurry. Sand content was found to range from < 0.25 percent to 21 percent. The hydrostatic forces -3-