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�R <br /> July 14 , 1986 <br /> Ms . Candace Thompson <br /> Mined Land Reclamation <br /> 1313 Sherman St . , Room 423 <br /> Denver, CO 80203 <br /> RE : Technical Revision - Savage Pond Permit , C-017-81 <br /> Dear Candace , <br /> In reviewing my calculations for the Savage Pond removal <br /> request , I noticed that a mistake had indeed been made in <br /> determining the peak flows for a ten year and 25 year event. <br /> This error was due to the usage of wrong slope interpolation <br /> factors . After recalculating , I have come up with the fol- <br /> lowing values , which agree with yours , and should supersede <br /> the values listed in our technical revision dated June 19 , <br /> 1986 . <br /> AREA DISTURBED CN SLOPE SLOPE PEAK DISCHARGE <br /> ACREAGE INTERPOLATION TABLE S-lA (SCS ) <br /> FACTOR cfs/ in runoff <br /> 1 11 . 63 93 11 .1 .96 20. 0 <br /> lA 7. 23 75 8 .0 . 92 12 .5 <br /> 2 3 . 49 90 6. 5 1 .06 5. 7 <br /> IN RUNOFF TABLE S-3 (SCS ) PEAK DISCHARGE ( cfs ) <br /> ( cont. ) 10 yr. 24 hr. 25 yr. 24 hr. 10 yr./24 hr. 25 yr. 24 hr. <br /> 1 .22 1 . 50 23 .4 28 .8 <br /> . 33 . 48 3 . 8 5 .5 <br /> 1 . 01 1 . 27 6 .1 7. 7 <br /> Total : 42 . 0 cfs <br /> The existing spillway at the Savage Pond is a tee-shaped 18" <br /> dia. CMP set on a 10% grade. This culvert can handle a flow <br /> of 18 cfs . This is more than enough to handle the 7. 7 cfs of <br /> flow generated during a 25 yr. /24 hr . event in Area 2 . <br /> The existing primary spillways on the four ponds known as <br /> Discharge Point 001 are 18" dia. CMP set on a 10% slope. <br /> These culverts can also handle a flow of 18 cfs . The emer- <br /> gency spillways are ten ft. wide by two ft . deep trapazoidal <br /> channels lined with riprap. The enclosed calculations show <br /> that these channels can handle a 25 yr. /24 hr. event. <br /> If you have any more questions concerning this technical <br /> revision, please feel free to contact me here at the mine . <br /> Sincerely, <br /> Scott Jones , Environmental Engr. <br /> enc. <br /> SJ/sj <br />