2008-03-31_GENERAL DOCUMENTS - C1981008 (2)

Home Browse Search

A ` ~ r` c ~ United States Department of Agriculture o MRCS Natural Resources Conservation Service Jim Boyd, Resource Conservationist jim.boyd@co.usdagov P. O. Box 29 970-327-4245-OFFICE Norvvood, CO 81423 970.327-4247-FAX March 21, 2008 e~~~dV@d Division of Reclamation, Mining and Safety MAR 3 ~1 2008 Department of Natural Resources -Coal Program 701 Carmino del Rio, Room 315 Uurarl~c Meld c3~ii~ Durango, CO 81301 Division of RaciamatEe~~a and '~ RE: Post Mine Vegetation on Prime Farmland. Dear Concerned Parties: Mining ~' New Horizon Mine, Permit C-81-008 Mr. Gubka, mine engineer for New Horizons Mine in Nucla, Colorado, recently submitted to me data on the amount of irrigation water that the Colorado Cooperative Ditch Company (CC-Ditch) has historically delivered to the Nucla Park. In his analysis of the data he states that: "insufficient water quantity is being transported by the CC-Ditch to the Park to make 50 shares of water equivalent to 1.5 CFS, the amount to satisfy the requiremerrts of three sideroll sprinklers." I will herein counter that this is generally not a relevant concern, nor a completely accurate statement, given the following information. In my previous letter, dated March 4, 2008, I explained design criteria for three sideroll sprinklers serving about 70 acres of irrigated alfalfa, with each sideroll utilizing 0.5 cubic feet per second (cfs) and covering 23 acres. I included in that discussion an irrigation schedule demonstrating that the peak irrigation demands of alfalfa could be satisfied with three siderolls operating simultaneously thirteen (13) out of every fifteen (15) days. This sideroll sprinkler system is conservatively designed to meet the extreme growing conditions of high temperatures, or the peak consumptive water use of the crop. This period typically occurs in the months of June and July, at which time the CC-Ditch is generally able to provide the water quantities needed (see attached spreadsheet). At other times of the growing season, the alfalfa crop needs significantly less water, which can also be consistently supplied by the CC-Ditch Company and adequately applied to the crop by the sideroll sprinkler system. Enclosed is a water budget for alfalfa growing in the Nucla area. The consumptive water use of the crop and the effective precipitation included in the budget are long-term climate induced averages. Irrigation events are scheduled when one half of the available soil moisture is depleted by the crop, in this case 3.8 inches. This depletion occurs at different rates during the growing season, as is evident by the monthly consumptive use column (see water budget). In the month of May only 3.61 inches of water is used by alfalfa, so only one irrigation event that replaces this depletion is necessary in May. In the month of July 6.83 inches of water is used by the crop, so two irrigations are required, each replacing about 3.8 inches of depletion. Since it takes thirteen (13) days for each sideroll to cover its intended area of 23 acres, all three siderolls will need to be operating simultaneously (26 out of 31 days) to meet this peak demand in July. The Natural Resource Conservation Service works in partnership with the American People p~ Equal Opportunity Provider end Empbyer. to conserve and sustain nature) resources on private lands.