2010-03-01_HYDROLOGY - M1977439 - Laserfiche WebLink

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Ms. Sira Sartori Page 3 February 24, 2010 Computation of the net evaporation during any time that the pits are not completelyr covered by ice shall be determined as the pro-rata amount of the monthly gross evaporation rate distribution amount identified in the State Engineer's General Guidelines for Substitute Supply Plans for Sand and Gravel Pits, subtracting the pro-rata amount of the effective precipitation for that period. Based on the Division 1 Water Court decision in case no. 2009CW49, the replacement of evaporative depletions is not required for ground water exposed to the atmosphere prior to January 1, 1981 through open mining of sand and gravel, regardless of whether open mining operations continued or were reactivated on or after that date. The Water Court effectively held that Senate Bill 120 of 1989, as amended in Senate Bill 93-260, exempted all pre-1981 exposed ground water regardless of whether open mining operations continued or were reactivated on or after January 1, 1981. Accordingly, for the 196.3 acres (118.6 acres exposed prior to January 1, 1981 and 77.7 exposed after December 31, 1980) of ground water currently exposed at the Home Office Pit site, replacement of evaporative depletions is only required from the 77.7 acres exposed after December 31, 1980. You have reported that at the Overland Pond site, all 1.5 acres of exposed ground water were exposed after December 31, 1980, and for the North Taft Hill Expansion site, all 2.3 acres of exposed ground water were exposed after December 31, 1980. The estimated monthly consumptive use and lagged stream depletions due to evaporation and operational losses are shown on the attached Table 1 Replacement The source pf replacement water for this combined plan will be from 5.75 Taylor and Gill Ditch shares. The shares will be diverted into a recharge pit located on the Home Office site. The evaporation losses from the recharge pond during this approval period are estimated at 2.58 acre- feet (see attached Trable 5). In 2006, 2007, 2008, and 2009, the 5.75 Taylor and Gill Ditch shares were diverted into th9z recharge pond to produce accretions to the stream for replacement purposes. The 5.75 shares will be diverted in the recharge pond again in 2010 to provide replacement water for this combined plan. The 5.75 shares were historically used to irrigate 104.5 acres of pasture grass, all of which have been taken out of production. The historical consumptive use of the 5.75 shares was determined to be 122.8 acre-feet (includes consumptive use and return flows). The 5.75 shares will be diverted into the recharge pit each irrigation season. The applicant is required to maintain the return flow obligations from the changed use of the 5.75 shares of the Taylor and Gill Ditch as described in this plan. The attached Table 3 shows the farm headgate delivery of 5.75 Taylor and Gill Ditch shares. Lafarge West, Inc. ("Lafarge") plans to divert the full farm headgate delivery of 240.31 acre-feet into the recharge site each year. A total of 131.5 acre-feet were diverted into the recharge site between May 4 and October 1, 2009. Because of the small volume of recharge in 2009, Lafarge had a shortfall of 12 acre-feet from November 2008 through September 2009. A lease of 12.00 acre-feet (including 7.8 percent transit losses) from the City of Fort Collins made additional replacements during the 2009 water year. A copy of the water lease with the City of Fort Collins was submitted to this office with this plan request. Lafarge will divert the full farm headgate delivery of the 5.75 Taylor and Gill Ditch shares starting in April 201 Q. Accordingly, the monthly timing of 240.32 acre-feet (full farm headgate delivery of the 5.75`; hares) was used in the recharge model to determine the recharge accretion