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<br />z <br />through the earthen embankment. <br />noted during the visit. <br /> <br />Tears in the liner material were <br />The only instrumentation installed at this site were two water <br />quality monitoring wells located downstream of the embankment. <br />These wells were reportedly functioning properly. <br />The pond is completely filled with sand and slimes from the <br />processing of gold ore. Mr Tatman informed me the only chemicals <br />in the pool were soda ash, pine oil (for floatation of the <br />sediment) and sodium isopropyl carbinol. Reportedly, the PH of <br />the liquid is usually near 8. <br />The only outlet at this structure was a t <br />pipe located near the southwest corner of <br />water level was approximately four-inches <br />pipe. Exact elevations of the pool level <br />unavailable but it appeared the available <br />than one foot before the embankment would <br />pro-inch vertical PVC <br />the pool area. The <br />below the inlet of the <br />and crest were <br />storm storage was less <br />be overtopped. <br />The 6-hr 100-year storm for this area would be approximately 3.6 <br />inches. If this storm were to occur, it is likely that the storm <br />could be contained but freeboard would be minimal. This is not <br />considered current prudent engineering practice. This office <br />recommends a minimum freeboard during a design storm of at least <br />3 feet. A small diversion ditch runs around the upstream edge of <br />the pond. This ditch is not ver<~ well maintained and should be <br />upgraded to be certain it is capable of passing excess runoff <br />from any storms that could occur in this area. <br />The Company is planning to raise this dam by approximately 10 <br />feet in the near future. Mr. Tatman stated that he has contacted <br />a consultant in Wyoming to design the next stage for this <br />facility. It will be built of crushed rock from a borrow area <br />located west of the dam. He said the maximum rock size will be <br />4~,4 inches. The plastic liner material will be extended to the <br />crest of the dam and the 2:1 slopes will be maintained. The <br />extension will be built utilizing the downstream construction <br />method where additional fill material will be placed downstream <br />of the existing embankment and brought up in compacted horizontal <br />layers. This addition will provide approximately 1 year of <br />additional storage of mine tailings. At that time, the tailings <br />facility will be abandoned and a new tailings facility will be <br />constructed. <br />RECOI~II~IENDATI ONS <br />1. The diversion ditch upstream of the pond area should be <br />repaired and enlarged to ensure that any storm runoff will be <br />safely routed around the structure. <br />