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Drainage Basin Flood Control <br /> Flood control management within the three drainage basins <br /> ( Arkansas , Eagle , and Tenmile ) is interrelated in many respects <br /> with the exception of the Arkansas River drainage which, to a <br /> great degree , stands alone . The following discussion of the <br /> various drainage areas is based on the hydrological data pre- <br /> sented in Table 3. <br /> A. Eagle River Drainage . The present spillways for Chalk <br /> Mountain reservoir and Robinson Lake are designed to <br /> handle the probable maximum flood ( PMF) . The lower <br /> impoundment area, No. 4 dam reservoir, also is engi- <br /> neered to handle the PMF as it receives waters from <br /> the two upstream reservoirs and surrounding runoff . <br /> B. Upper Tenmile Creek Drainage . Upon final termination <br /> of operations , the open pit area will form a large <br /> catchment basin with a bottom elevation of approxi- <br /> mately 10, 268 ' msl . Based on Climax' s knowledge of <br /> the fracturing , faulting , and underground openings in <br /> the area, it is believed that the pit basin ultimately <br /> will impound surface and ground waters to the 10 ,868 ' <br /> • msl elevation. The 300 foot difference between the <br /> ultimate surface elevation and the pit rim will pro- <br /> vide the surge capacity to contain the PMF. No <br /> further flood control should be necessary in this <br /> drainage basin. <br /> C . Lower Tenmile Creek Drainage . The flood control <br /> system within the lower Tenmile Creek drainage is the <br /> most extensive and complex . <br /> Beginning at the top of the drainage , Buffehr reser- <br /> voir is designed with a spillway to handle the PMF and <br /> drain to the Robinson tailing pond . Besides Buffehr <br /> reservoir, Robinson tailing pond receives drainage <br /> from the mine/mill complex, E dump, and McNulty dump <br /> areas as well as direct precipitation. During the <br /> approximately ten years needed to stabilize and <br /> reclaim the Robinson tailing pond, the west decant <br /> line will be pl.ug.ged, and water handling facilities <br /> will be constructed around the- .east _-side of -the --pond . <br /> These facilities/structures will be engineered and <br /> designed to accept all of the aforementioned drainages <br /> and carry flood waters to the Tenmile tailing pond <br /> area. <br /> Upon completion of deposition of tailing on the Ten- <br /> mile tailing pond , water handling facilities will be <br /> G-8 <br />