2019-12-19_HYDROLOGY - M1977560 - Laserfiche WebLink

Home Browse Search

Mr. Paul Bruss, P.E. December 19, 2019 Page 2 of 5 the property. The combined exposed water surfaces from Ponds 3 and 4 which are located on the East Parcel have been estimated to be 15.3 acres, based on the aerial images in Figure 1. Permit No, WDID Total Exposure Pre-1981 Exposure Post-1981 Exposure (acres) (acres) (acres) 52017-F 1705986 15.3 0.0 15.3 Valco has retained the portion of the Rocky Ford East pit property east of County Road 22 ("East Property"), which includes Ponds 3 and 4 as shown on the attached Figure 1, and intends to backfill the remaining ponds on the East Property. According to correspondence with the Applicant, Valco has analyzed the property and confirmed that there is adequate fill material on site to completely backfill the remaining ponds on the East Property. Additionally, Valco has obtained a lease agreement with the Upper Arkansas Water Conservancy District ("UAWCD") to replace depletions through July 31, 2022 and with the Colorado Water Protective and Development Association ("CWPDA"). 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. The DRMS letter identified four approaches to satisfy this requirement. In accordance with approach no. 1, a bond has been obtained for $193,678 through the DRMS to assure that depletions from groundwater evaporation do not occur in the unforeseen event, or events, that would lead to the abandonment of the Rocky Ford East Pit. DEPLETIONS The Rocky Ford East pit is in the process of reclamation. This SWSP renewal is to replace depletions resulting from evaporation from the ponds and from the water contained in the previously mined product. Evaporative depletions have been calculated using the maximum surface area of the pit, which is 15.3 acres of post-1981 exposed groundwater surface area. Depletions have been lagged back to the Arkansas River using a Glover analysis with the following inputs: Distance from river: 31020 ft Distance from alluvial boundary: 81720 ft Transmissivity: 71,000 gpd/ft Specific yield: 0.2 Lagged depletions due to current SWSP operations were calculated to be 45.91 acre-feet for the period November 1, 2019 through October 31, 2020 and 52.80 acre-feet for the period November 1, 2020 through October 31, 2021. Lagged depletions due to rp for SWSP operations were calculated to be 10.54 acre-feet for the period November 1, 2019 through October 31, 2020 and 3.50 acre-feet for the period November 1, 2020 through October 31, 2021. Total lagged depletions for the period November 1, 2019 through October 31, 2020 are 56.45 acre-feet, and total lagged depletions for the period November 1, 2020 through October 31, 2021 are 56.31 acre-feet. (see attached Table 4).