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Leodville Mining & Milling had completed a shakedown run and produced <br />some tailings which were ponded in the tailings disposal area. We sampled the <br />tailings and gradation and Atterberg tested (see Fig. 4) the sample. <br />CONCLUSIONS <br />The tailing disposal area soils generally have low permeabilities. Our tests <br />measured average permeabilities between 2 ft/yr and 230 ft/yr. The higher <br />permeability was in P-I which was located at the uphill edge of the disposal area. <br />We saw in the existing trench and measured a more permeable (5000 ft/yr) lens in <br />P - I at about 8 feet. This lens in was obout I.5 feet thick. <br />We have concluded the clays overlying the gravel lens and the clayey gravels <br />and clayey sands are comparatively impervious. For comparison, some sandy <br />compacted clays have permeabilities of the order of 1 ft/yr. We suggest <br />excavation which might reduce the natural clay cover over the gravel lens be <br />omitted or minimized to the minimum to leave the natural clay surface layer <br />uninterrupted or nearly uninterrupted. The pond bottom should be stripped and <br />compacted before filling with tailings to decrease the permeability of the ground <br />immediately under the tailings. <br />Should the gravel lens be exposed we recommend such exposures be blocked <br />with 3 feet of the shallow clays densely compacted in thin lifts. <br />