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J j+ MEMORANDUM TO: ' FROM: SUBJECT: March 20, 1992 United States Department of the Interior OFFICE OF SURFACE MINING RECL4hIATION AND ENFORCEMENT BROOKS TOWERS 1020 15TH STREET DENVER, COLORADO 80202 Director Albuquerque Field Office Assistant Director western Support Center iii iiiiiiiiniiiiii 999 \ ~ rr -. . ~e ~~ ~. ~~~ ~ ^ In Reply Refer To: Technical Assistance - Canadian Strip Mine Phase II Bond Release: Permanent Impoundment In response to your memorandum dated February 21, 1992, the above subject has been reviewed, and further analysis using watershed information provided by the Colorado Mined Land Reclamation Division (CMLRD) has been completed for Pond 2, which exists on Public Land administered by the Bureau of Land Management, (BLM). We conclude that Pond 2 meets the Colorado Rule 4.05.9(i)(b). Our conclusion is based on the following factors: ® The annual precipitation of the Canadian Strip Mine area is 12 inches, which along with its 8200 feet elevation characterizes the area as semiarid. The water level would be variable during the dry season indicated by the historical data obtained from inspection reports over a 6-year period. This record indicates that the pond meets BLM's impoundments criteria, that a pond have water in it for some period between May and August. ® As indicated in CMLRD's January 29, 1992 letter to AFO, Pond 2 is located near the east side of a 3,525 acre allotment that has livestock water sources including four springs, three "reservoirs" and portions of two intermittent streams in other parts of the allotment. The land user is not dependent on a single source of water, i.e. Pond 2. CMLRD and WSC have performed SEDCAD~ analysis of runoff for current watershed conditions (31 acre D.A. CN=82, ground cover = 44$, Total cover = 75~) showing that a 2- year, 24-hour precipitation event (1.o inches) would yield 0.29 acre feet and an l0-year, Z~t-hour event (1.6