2012-02-03_HYDROLOGY - M1998013 - Laserfiche WebLink

Home Browse Search

Mr. Andy Rodriguez, P.E Page 3 of 5 Shores SWSP January 26, 2012 If not already installed, a totalizing flow meter must be installed on all dewatering operations. No accretion credits will be given to unmetered dewatering activities. Future SWSPs will not be approved until all dewatering discharges are properly metered regardless if accretions credits are sought. Replacements The sources of replacement water are 0.5 Rural Ditch Company ( "RDC ") shares owned by the Applicant, and fully consumable water leased from the City of Longmont. The North Farm Property (area to be mined) was historically irrigated with 1.3 RDC shares. Bestway's ownership consists of all 1.3 of these shares, of which 0.5 shares are to be used for this plan. A historical consumptive use analysis on the Shores gravel mine property (Booth Farm) was performed by Civil Resources for Central Colorado Water Conservancy District in water court case 01CW255. The diversions and potential consumptive use information from that change case was utilized for these North Farm shares. RDC consist of 50 total shares. As shown in Table 1, the average farm head gate delivery (for the period of 1967 through 1996) is 5,679 acre -feet per year. This equates to a pro -rata average diversion of 147.7 acre -feet per year for Bestway's 1.3 shares. Using a ditch Toss of 15 %, the total farm head gate delivery represented by Bestway's 1.3 shares is approximately 125.5 acre -feet per year. On average, the 1.3 shares were historically used to irrigate 11.4 acres of corn, 2.1 acres of sugar beets, and 23.6 acres of pasture grass, all of which have been taken out of production due to the gravel mining operation. A consumptive use analysis using the modified Blaney - Criddle method within the IDSCU model estimates a historic consumptive use of 57.5 acre -feet per year for the 37 acres of the North Farm Property. Actual crop consumption was limited to the lesser of the potential consumptive use and the product of the farm head gate delivery times the assumed irrigation efficiency of 55 %. The actual consumptive use of the RDC shares averaged 47.8 acre -feet per year for the 37 acres of the North Farm Property. Return flows were estimated to be 40% surface runoff and 60% deep percolation. The return flows from deep percolation were lagged to Saint Vrain Creek using a Glover analysis. The following parameters were used in the model to lag the deep percolation return flows: transmissivity (T) = 72,300 gallons per day per foot, specific yield (SY) = 0.2, the distance to the creek (X) = 2,520 feet, and a now flow boundary (W) = 10,000 feet. The attached Table 2 provides a monthly schedule of total lagged deep percolation return flows to the river system, shown to be 46.62 acre -feet for this plan period. Bestway has obtained a lease from the City of Longmont ( "Longmont ") for 62.24 acre -feet of fully consumable water to be released from Longmont's municipal wastewater treatment plant (WDID 0502300), or to be delivered by Longmont at the confluence of Spring Gulch and the Saint Vrain Creek located in the SE' /4 of Section 7, T2N, R68W of the 6 P.M. A copy of this lease was submitted to this office on January 25, 2012 and is attached to this letter. The applicant has allowed for a transit loss of 0.5% per mile for the 8.15 miles the replacement source is upstream of the pit location. This lease is for January 2012 through October 2012, and is the basis for the duration of this SWSP approval. A monthly breakdown of depletions and replacement is shown on the attached Table 7 that was submitted to our office on January 12, 2012. Conditions of Approval I approve the proposed substitute water supply plan in accordance with Section 37 -90- 137(11), C.R.S., subject to the following conditions: 1. This SWSP shall be valid for the period of January 1, 2012 through October 31, 2012,