2016-02-17_HYDROLOGY - M2004078 - Laserfiche WebLink

Home Browse Search

Mr. David M. Heintz Page 4 of 8 MMM South Platte Combined Replacement Plan February 10, 2016 For the purpose of this SWSP the proposed transit loss is accepted however, the transit loss is subject to change if the division engineer or the water commissioner determines that a different transit loss needs to be assessed to the Aurora leased water. In addition, if transit losses change they will be communicated by the Division Engineer via email to the Division One Call List. The total lagged mining depletions and replacements are shown on attached Table 3. Dewatering Dewatering will continue to occur at the Riverbend East Pit during the period of this SWSP. The previous SWSPs for the MMM combined sites included dewatering credits associated with mining operations at the Riverbend East site as a replacement water source. You indicated that water level at the site reached bedrock in the spring of 2015 and MMM has continued to keep the water level constant throughout the remainder of the previous SWSP and will continue to hold dewatering levels steady during the SWSP period. Since the dewatering rates have reached steady state conditions, the Applicant will not use dewatering credits as a replacement water source under this SWSP. As long as the pit is continuously dewatered the water returned to the stream will be adequate to offset the depletions attributable to the dewatering operation. Based upon recent dewatering operations at the Riverbend East site, 100 percent of the dewatering water is pumped back to the South Platte River. Totalizing flow meters must be installed at each discharge location and meter readings must continue to be reported on the submitted accounting. The meter readings will be used in calculating the post-pumping dewatering depletions that need to be replaced at the conclusion of mining at the site. Long Term Augmentation 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 ground water. For Riverbend East, Denver Water is the DRMS permit holder. As municipal entities are not required to post bonds, these sites are not required to be bonded to cover the cost of lining or backfilling the site. For Riverbend West, MMM has posted a bond to cover the cost of backfilling or lining in accordance with approach # 1 and # 3 of the DRMS letter. As this site will include unlined ponds that will permanently exposed ground water, an application to the water court for a plan of augmentation to cover the long term depletions from the site must be filed at least three years prior to the completion of mining. A summary of the final reclamation plans and the approach to replace long term injurious stream depletions are shown in Table E.