2018-12-26_REVISION - M2008078 (27)

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Page 3 of 5 Total Consumptive Use The total amount of groundwater consumptive use from operation of the West Farm Pit during the proposed term of this plan will be 13.55 acre-feet (2.51 acre-feet of evaporation + 11.04 acre- feet of moisture content removal). This amount is shown in Table 2. Mining Stream Depletions Depletions to the Arkansas River from the mining of aggregate from the gravel pit are lagged since the centroid of the mining site is approximately 3,300 feet from the river. Lagged stream depletions were determined using the Integrated Decision Support Group's (IDS) Alluvial Water Accounting System (AWAS) model, version 1.5.85. A stream depletion factor(SDF) of 88 days' was used to lag the stream depletions. The SDF of 88 days was used in the prior approval of DRMS-M- 2008-78 and is maintained in this request. Previous mining operations have been included in the modeling and the results with the projected mining under this plan are shown in Table 3. The total stream depletion that will occur during this plan year will be 8.15 acre-feet. Replacement Water GP currently owns 284 LAWMA common shares. The proposed allocation for a LAWMA common share in 2018 has been set at 100%. Therefore, GP must dedicate 9 LAWMA common shares for augmentation of the lagged stream depletions under this plan. If GP were to continue operating the gravel pit in the same manner for the next 25-years and the same monthly total consumptive use from the operational uses then the maximum stream depletion would occur in the 25th year in the amount of 12.8 acre-feet. While this amount doesn't quite represent a steady-state condition one must take into account the expected life of the gravel pit. There is a limited amount of aggregate that can be mined from the existing site. Each year LAWMA will re-evaluate GP's need for LAWMA shares to ensure that GP has dedicated the proper amount to any requested renewal of the plan. Table 3 shows the proposed replacement schedule of the stream depletions in this plan. LAWMA has been fully-augmenting the entire operation of the West Farm Pit(i.e. evaporative losses from the dewatering trench and settling pond, water lost as moisture content in the aggregate and water pumped from the well for gravel washing and dust suppression) within its augmentation plan. Moving forward, ongoing lagged stream depletions from past operations of the West Farm Pit and future depletions from use of the well for aggregate washing and dust suppression will continue to be augmented under LAWMA's augmentation plan. Evaporative depletions from the dewatering trench and settling pond and water lost as moisture content in the mined aggregate will be replaced under this plan and future plans pursuant to C.R.S. § 37-90-137(11). ' Interpolated from"Stream Depletion Factors,Arkansas River Valley, Southeastern Colorado"by C.T,Jenkins and O. James Taylor(USGS OFR 72-192).