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S West Elk Coal Company, Inc. ~ Posl Olfice Box 591 Somerset. Colorado 81434 Telephone 303 929 5015 August 18, 1986 e~, f>~. .. ~ .~.... ~ .... ~ ' I. 'Ibtn Schreiner AUG 2 ^ i98~ Reclamation Specialist --~•,-.-, ; ~,,, .: _.,. Colorado Mined Land Reclamation Division ''- "-'~+f..; ~:'_t;!_: - 1313 Sherman Street - -~''='~. Oi ~.....-r:<'. ~:~ . Denver, CO 80203 Re: Landslides, Upper Diversion Ditch Mt. Gunnison No. 1 Mine, CMLRD Permit No. C-007-80 Dear Tom: As you are aware from previous inspections of the Mt. Gunnison No. 1 Mine Site, several landslides have crossed the upper diversion ditch during the Spring of 1986. The slides are near the eastern end of the ditch. Some of these slides were ones which occurred in the last t~ years and .ere repaired by placing culverts in the ditch. At least one other was a new slide which occurred in 1986. Although approximately 15 to 20 percent of the eastern end of the upper diversion ditch was blocked during the Spring runoff period in 1986, there were no problems with compliance related to the upper ditch. The mine site sediment ponds .ere able to contain all runoff generated. Thece may be several reasons why the upper diversion ditch does not appear to carry Spring or storm runoff presently, or historically. Some reasons are as follows: - Tt;e dcainage area above the upper ditch has a short, wide, and steep slope. The vegetation cover is very high, probably 60 to 80 percent. All of these factors except slope would tend to lower the amount of peak discharge from the area. Also, the slope is North facing which ~..ould slow snow melt to a large extent. - Soil infiltration and storage capacity may be high thereby further reducing runoff to a large extent. - There may be naturally existing rock fractures, similar to the adjacent Sylvester Gulch, along the outcropping rock units which allow localized infiltration further reducing surface runoff. ?hICO-n; 0=