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,{ STATE OF COLORADO OFFICE OF THE STATE ENGINEER Division of Water Resources Department of Natural Resources 1313 Sherman SVeet, Room 818 Denver, Colorado 80203 Phone (303) 86b-3581 FAX (303) 866.3589 www.watecsfate.co.us May 24, 2004 pF' Cpl Ne0 : ~ r r 18]6 ~ Bill Owens Governor Russell George Cheryl Signs, P.E. Exe<°nveD1ea°` Hal D. Simpson, P.E. Cheryl Signs Engineering RECEIVED State Engineer 109 East Fourth Avenue Denver, co 80203 MAY 2 5 2004 Re: Durham Pit, Substitute Water Supply Plan Oiuision.f Minerals and Geology DMG File No. M-78-056 Sections 3, 9, and 10, T5N, R65W, 6`" P.M. Water Division 1, Water District 3, Weld County, Colorado Dear Ms. Signs: This letter is in response to your application of May 31, 2003 requesting a substitute water supply plan for a sand and gravel pit (Durham Pit) to be operated by Varra Companies, Inc. (Varra). The required fee of $1,343 for the substitute water supply plan has been paid. A conditional plan was approved for the site on July 10, 2003. The anticipated net depletion -for this plan, based on the numbers provided in the substitute water supply plan report, is 194.9 acre-feet per year. The currently exposed groundwater at the site totals 38.1 acres. However, the plan anticipates that a total of 79.2 acres of water surface will be exposed at the site if dewatering ceases. Therefore, this plan will cover replacements for depletions associated with the 79.2 acres. You have provided a monthly breakdown of the annual depletions made up of 184.30 acre-feet of net evaporative loss, 7.8 acre-feet of water lost with the mined product (which represents 267,931 tons of mined product), and 2.8 acre-feet of water used for dust control. According to the information submitted, 44.6 acres of water surface, out of a total of 123.8 acres to be exposed at the site, was exposed within the reclamation permit boundary prior to January 1, 1981. Using the State Engineer's General Guidelines for Substitute Supply Plans for Sand and Gravel Pits, the State Engineer has determined the net depletion for this plan to be 222.99 acre- feet for the 79.2 acres of water surface to be exposed at the site. Based on the above-mentioned guidelines, the net evaporation for the 79.2 acres was calculated as the difference between gross evaporation and the effective precipitation, where the effective precipitation is equal to 70% of the total precipitation. Therefore, for this plan, no benefit was given for the total precipitation, but only for 70% of the total precipitation, which increased the annual evaporative loss from 184.30 acre- feet to 212.06 acre-feet. Phreatophyte credits of 24.2 acre-feet per year have been applied to this plan, which reduced the net evaporation depletions to 187.86 acre-feet per year. The total anticipated net depletions for this plan is 198.48 acre-feet. A monthly breakdown of the annual depletions made up of 187.86 acre-feet of net evaporative loss, 7.8 acre-feet of water lost with the mined product (which represents 267,931 tons of mined product), and 2.8 acre-feet of water used for dust control can be found on the attached Table I.