2022-08-15_HYDROLOGY - M2008078 - Laserfiche WebLink

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Ayrton Hendrix August 15, 2022 Page 2 of 5 The total surface area of the dewatering trenches and sediment ponds will not exceed 5.04 acres for the term of this SWSR The total maximum area of the exposed water surfaces has been used to calculate the evaporative losses for this plan. The evaporation value for this area has been obtained from paragraph A.i of Exhibit R of the decree in Case No. 02CW181, which is 4.11 feet/year. Therefore, the evaporative losses for the exposed water surface is 5.04 acres X 4.11 feet/year, or 20.71 acre-feet/year (Table 1, attached). Water losses in the mined material have been estimated to be 19.87 acre-feet, based on a projected 1,350,000 tons of mined material and a 2% moisture content. The moisture content is less than wet mining (4% loss) due to the fact that the pit is lined with no influx of groundwater. Water losses from dust control and aggregate washing will continue to be augmented under the decree in Case No. 12CW37 which is the decree for the well with WDID 6705373 (Permit no. 79629-F). The total calculated depletion for this plan is 40.58 acre-feet. REPLACEMENTS The proposed source of replacement water is BSG's ownership of 400 common shares in the Lower Arkansas Water Management Association ("LAWMA"). The proposed allocation for a LAWMA common share in 2022 was projected to be 50% at the time of submission. Eighty-two LAWMA shares will be dedicated to this plan for the replacement of the lagged depletions. Accounting will be provided by BSG to LAWMA, which will make replacement deliveries to the Arkansas River using fully consumable water. Depletions to the Arkansas River were determined using the Integrated Decision Support Group's (IDS) Alluvial Water Accounting System ("AWAS") model and a stream depletion factor ("SDF") of 88 days. Although DWR now discourages the use of the SDF method, these depletions were calculated in previous plans using the SDF, and the methodology is maintained in this SWSP request. The total stream depletion that will occur during this plan year is 40.58 acre-feet. In accordance with the letter dated April 30, 2010 from the Colorado Division of Reclamation, Mining, and Safety ("DRMS"), all sand and gravel mining operators must comply with the requirements of the Colorado Reclamation Act and the Mineral Rules and Regulations for the protection of water resources. The April 30, 2010 letter from DRMS requires that you provide information to DRMS to demonstrate you can replace long term injurious stream depletions that result from mining related exposure of groundwater. In accordance with approach nos. 1 and 3, you have indicated that a bond has been obtained for $8,310,769 through the Division of Reclamation, Mining, and Safety ("DRMS"). This bond is for reclamation requirements under the current permit. CONDITIONS OF APPROVAL I hereby approve the proposed SWSP in accordance with S 37-90-137(11), C.R.S., subject to the following conditions: