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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 F= <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 /> 33 .5 c-Fs 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 /> i <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 /> Sy,�,,0,_�6,.,�,oScgarep��`nus, . <br /> Scott Jones , Environmental Engr. <br /> enc. <br /> I <br /> SJ/sj <br />