2013-10-22_HYDROLOGY - M1987049 - Laserfiche WebLink

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Julia Keedy RMCC Combined SWSP October 21, 2013 Page 3of9 Condition 12 of the previous SWSP approval required the Applicant to demonstrate to the State Engineer's Office that they have commenced backfilling or lining of Ready Mixed Pit No. 1. The slurry wall has been installed around Cell 3 /RMP1 was approved by the SEO on September 17, 2013. Minimal dewatering occurred over the last few months at Cell3 /RMP1. According to the Applicant, dewatering pumping totaled 3.3 acre -feet in May 2013 with no dewatering in June. Dewatering quantities are reported in the monthly accounting submitted for this SWSP. Any dewatering that occurs after liner approval can be returned to the stream system through surface flow or ground water recharge without need for replacement so long as the operator does not put the water to beneficial use. A water court application for a permanent augmentation plan for the North Tower Pit was filed on March 1, 1990 under case no. 1990CW39. The approval of this plan does not imply a position by our office on any litigation associated with case no. 1990CW39 or any other case. Condition 13 of the previous SWSP required the Applicant to describe steps taken toward a final decree in the case. Since the last SWSP approval, several opposers have stipulated out of the case. A revised draft decree was most recently filed on July 19, 2013. Depletions SWSP depletions are from evaporation of exposed ground water, dewatering, water used to wash mined product, and water lost in mined product. Table 1A (attached) summarizes projected depletions through December 2015. Some mining will occur above the ground water surface and some will occur below the ground water surface. For the projected depletions, all projected mining is assumed to be below the ground water surface and has been charged 4% water loss by weight. Actual accounting will track where the mining occurs and only assess 2% water loss by weight where mining is above the ground water surface. For August 2013 through July 2014, RMCC projects 1,600,000 tons of gravel production at this site. This projects to a maximum water loss of 44.1 acre -feet. The area of exposed ground water is expected to be 53.2 acres or less for the period of August 2013 through July 2014. This gross evaporation rate is 44.5 inches per year, which is consistent with the North Tower engineering report revised on March 9, 2012. Using the effective precipitation of 10 inches per year and historical North Tower Pit ET credit of 2.8 acre - feet per year, the projected net evaporative loss from August 2013 through July 2014 is 150.2 acre -feet. The total consumptive use at this site from August 2013 through July 2014 is 41.35 acre - feet with an additional 453 acre -feet from dewatering pumping returned to the South Platte. These depletions do not hit the river instantaneously and thus must be lagged back to the river. With the recent approval of the liner for Bromley Cell 3 /Lot 1, the Applicant has separated the lagging analysis for the Plant Site and Lot 2, which are located east of the McCanne Ditch, with the lined gravel pit expected to block most of the depletions from impacting the South Platte River. Rather, for the Plant Site and Lot 2, the Applicant performed a lagging analysis to the McCanne Ditch, which flows year round and discharges to the South Platte River. The Glover parameters applied for the Plant Site and Lot 2 beginning in November 2013 are as follows: specific yield = 0.2 transmissivity = 100,000 gpd /ft distance from centroid of mining area to McCanne Ditch = 600 feet