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West Elk Coal Com«y, Inc. <br />Post Office Box 591 <br />Somerset, Colorado 81434 <br />Telephone 303 929 5015 <br />June 8, 1984 <br />Mr. Philip Salleta & Robert Liddle <br />State of Colorado <br />Dept. of Natural Resources <br />Mine Land Reclamation Division <br />1313 Sherman St., Room 423 <br />Denver, Colorado 80203 <br />Gentlemen: <br />~ III IIIIIIIIIIIIIIII <br />999 <br />RECEIVED <br />JUPI 1 1 1984 <br />MINED LAND RECLAMATION DIyIgION <br />Colo. Dept. of Natural Resources <br />As you requested this letter and the attached sketch and map <br />will describe the events causing the April 1984 "landslide" <br />(slump) above the portal bench and the remedial action taken. <br />'The slump accured on April 18th and 19th in an area approximately <br />100' x 200' located between the portal bench and the upper <br />diversion ditches #2 and #4. (see attached map) The diversion <br />ditches were constructed with french drains in the bottom of the <br />ditches. In the bottom of the french drains are 4" 0` perforated <br />plastic drain pipes. These ditches and french drains empty into <br />a 30" ¢ CMP which drains to MB1 Sediment pond. (see sketch and <br />map attached) The end finish on the 30" CMP, where the ditches <br />dump in was constructed of riprap to prevent errosion but was not <br />sealed with concrete to prevent leakage. <br />The slump was caused by water seeping through the riprap along <br />the 30" CMP and satuating the soils. When the soils were <br />sufficiently saturated to cause the Ch1P to settle, it pulled <br />apart and dumped more water into the soils resulting in about <br />a four foot scarp and 100' x 200' slump. <br />A 12" ¢ plastic pipeline was run around the slump into the manhole <br />located at N 402936, E1446480. (see the attached map) This pipe- <br />line dried up the water which was saturating the slump and stabilized <br />the ground. <br />If you have any further questions please contact me. <br />S i n/~~I y`~7 <br />C. G. Hansen <br />Chief Engineer <br />CGH/clt <br />ARC 6022 <br />