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of "sanitary landfills", together with the preparation of a con- <br />tingency plan for control of any ground -water pollution which <br />might be detected by the wells. <br />Under authority of the Federal Water Pollution Control. Act, <br />EPA has promulgated final regulations which define "hazardous <br />materials in harmful quantities". The March 13, 1978 regulations <br />provide that 10 pounds of sodium cyanide is a "hazardous material <br />in a harmful quantity". Spills of such material must be reported <br />to the EPA. In addition, EPA has proposed, in the Federal Regis- <br />ter of September 1, 1978, that facilities with the potential for <br />spilling "hazardous materials in harmful quantities" must prepare <br />a Spill Prevention Control and Countermeasures (SPCC) plan. <br />RECOMMENDATIONS <br />Based upon the hydrogeologic reconnaissance, conducted <br />August 23 and 24, it appears that water is moving downward into <br />the colluvial material throughout the tailings basin, reaching <br />an area of sand deposited as a stream channel, and moving later- <br />ally under the dam and cut-off trench, at a depth somewhere in <br />excess of 20 ft. beneath the original land surface, to discharge <br />as seeps where the old stream channel intersects the two washes <br />and in the pipe ditch cut by Homestake Mining Company. Thus, <br />it would seem that the old stream channel was serving as a drain <br />under the dam, and supplementing the planned drain system in- <br />stalled during construction. Monitoring should be planned to <br />assess any increase in the flow of ground water through this sand <br />channel, the potential for uplift forces in the sand and underlying <br />