2012-09-12_HYDROLOGY - M2010049 - Laserfiche WebLink

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Cheryl Signs, P.E. Page 3 Western Sugar Pit A total of one share of the Last Chance Ditch will be used in this SWSP. The Last Chance Ditch's historical use was previously analyzed in the original SWSP for the Heintzelman Pit No. 116 (M09 -018). This SWSP request utilizes a historical use analysis for an additional Last Chance Ditch share that is different from the one share proposed to be used in the Heintzelman Pit No. 116 SWSP. The one share of the Last Chance Ditch to be used in this SWSP was historically used to irrigate the Von Ohlen property and the one share of the Last Chance Ditch to be used in the Heintzelman Pit 116 SWSP was historically used on the Heintzelman property. The Applicant owns one share of the outstanding 20 shares of the Last Chance Ditch, which was historically used for irrigation on a portion of the Von Ohlen property (90 acres) located in Section 31, Township 3 North, Range 67 West of the 6` P.M. The crop mix is the same as the crop mix used for the Kurtz site analysis. The historical use of the irrigation supply was quantified using the average monthly diversion from 1949 through 1974. The average consumptive use from the dry years of 1954 and 1963 was more than the average period; therefore the average results were used. The ditch loss used in the consumptive use analysis was 10 percent based on the ditch location, its length and previous experience. Water in excess of the irrigation requirement was added to the soil moisture bank, which was assumed to be three feet deep with a water holding capacity of 0.2 inches of water per inch of soil. The consumptive use analysis for the one share averaged 162.20 acre -feet per year with a non - irrigation season return flow obligation of 24.28 acre -feet (Table 5). The subsurface return flow was lagged to the stream using the IDS AWAS stream depletion model to the Cache La Poudre River. The aquifer characteristics used in the model are: transmissivity (T) = 100,000 gallons per day per foot and specific yield (SY) = 0.28 (based on the USGS Water Supply Paper 1662D), the distance from the centroid of the irrigated land to the stream = 716 feet, and the location of the parallel impermeable boundary was estimated to be 4,000 feet from the stream. The Applicant owns 13 shares of the outstanding 183 shares in the Godding Ditch (decreed as Highland South Side Ditch). The 13 shares of the Godding Ditch were historically used for irrigation on the Seewald property (160 acres) located in Section 6, Township 2 North, Range 67 West of the 6th P.M. The crops irrigated were corn, sugar beets, beans and grass. The historical use of the irrigation supply was quantified using the average monthly diversion from 1970 through 2002. The average consumptive use from the dry years of 1977, 1994 and 2002 was less than the average period; therefore an average of the dry years was used. Once mining begins at the Western Sugar Pit, the Seewald parcel will no longer be irrigated. The ditch loss used in the consumptive use analysis was 15 percent based on the ditch location, its length and previous experience. Water in excess of the irrigation requirement was added to the soil moisture bank, which was assumed to be three feet deep with a water holding capacity of 0.2 inches of water per inch of soil. The dry year consumptive use analysis for the 13 shares averaged 151.10 acre -feet per year (Table 4). The subsurface return flow was lagged to the stream using the IDS AWAS stream depletion model to the Saint Vrain Creek. The aquifer characteristics used in the model are: transmissivity (T) = 72,000 gallons per day per foot and specific yield (SY) = 0.25 (based on the USGS Water Supply Paper 1662D), the distance from the centroid of the irrigated land to the stream = 6,400 feet, and the location of the parallel impermeable boundary was estimated to be 8,700 feet from the stream. Rural Ditch water was previously analyzed in the original SWSP for the Durham Pit (M -1978- 056, WDID 0302535). VCI owns four shares in the Rural Ditch that were historically used to irrigate 158.9 acres on the 112 - parcel site. Consumptive use credits from the 4 shares of the Rural Ditch that are not used to replace depletions during the irrigation season will be stored in the 112 Reservoir,