2007-12-05_HYDROLOGY - M1976056 - Laserfiche WebLink

Home Browse Search

Mr. Rick Parsons November 28, 2007 Page 2 29.19 acres of exposed surface area. According to the information provided, 5.5 acres of the 29.19 acres exposed at the site were exposed at this location prior to January 1, 1981. Thus the remaining exposed surface area requiring replacement from evaporation is 23.69 acres. The Applicant indicated that as a result of the mining operation, the exposed surface area will increase between one and one-and-a-half acres every two years. Based on this projection, you have estimated 0.625 additional acres being exposed between March 15, 2008 and October 31, 2008. This results in a maximum exposed surface area of 24.32 acres. The monthly net evaporation associated with the exposed surface area was estimated based on the monthly net evaporations rates (33.24 inches per year) decreed in the Farmers' Pawnee Canal Company Recharge Project in case no. 1995CW263. Based on the above assumption for the evaporation rate and the small increase in the surface area of the pond, the annual evaporation depletions at the site are 66.38 acre-feet (see attached Table 1). The pit is located greater than 100 feet from the South Platte River and the resulting depletions have been lagged to account for the delayed effects on the river system. The IDS AWAS stream depletion model was used to estimate the lagged depletions to the South Platte River. The following parameters were used in the model: transmissivity (T) = 204,000 gallons per day per foot, specific yield (SY) = 0.2, the distance from the South Platte River to the edge of the alluvium = 21,500 feet, and the distance from the centroid of the exposed surface water areas to the South Platte River is approximately 1,360 feet. You have provided a monthly breakdown of the maximum annual depletions totaling 66.38 acre-feet of evaporative loss from a maximum of 24.32 acres of exposed groundwater and 1.18 acre-feet of water losses associated with the extraction of an estimated 40,000 tons of aggregate. The total lagged depletions as shown on the attached Table 1 are 54.04 acre-feet which will be replaced under this plan. No phreatophyte credit has been applied to this plan. Replacements The Applicant proposes to provide replacement water for the actual operational depletions by a lease agreement with the North Sterling Irrigation District ("NSID"). The source of water from NSID will be excess recharge credits in accordance with the decree in case no. 1996CW1034. A copy of the lease for replacements with the NSID was provided to the State Engineer's Office on November 27, 2007. The lease provides replacement water only for October, November and December, thus this plan is valid only until December 31, 2007 (subject to condition no. 1 below). I hereby approve the proposed substitute water supply plan in accordance with C.R.S. § 37-90-137(11), subject to the following conditions: Conditions of Approval 1. This substitute water supply plan shall be valid for the period of October 1, 2007 through December 31, 2007, unless otherwise revoked, modified, or superseded by decree. This plan will be extended until September 30, 2008, if the applicant provides a copy of the lease agreement with the North Sterling Irrigation District to cover the January through September gravel pit depletions, by December 31, 2007. A copy of the lease must be provided to the water commissioner and the State Engineer's Office. 2. If this plan will not be made absolute by a water court action by the plan's expiration date, a renewal request must be submitted to this office with the statutory fee (currently $257) no later than December 31, 2007 or August 15, 2008 subject to the requirements of condition 1 above.