2024-03-28_REVISION - M2015030 (2)

Home Browse Search

Chavers Mining Resource DRMS Permit No.M-2015-030 Amendment No.2(AM-02) March 2024 Page 4 • Industrial Well: In addition to sand and gravel pit mining, a concrete production plant is located at the Site. The concrete production plant utilizes groundwater from the on-site industrial alluvial well (Well Permit No. 80120-F) located near the southeast corner of the Site. ASCI maintains annual replacement water lease(s) and Substitute Water Supply Plan (SWSP) approved by the Division of Water Resources (DWR) to account for out-of-priority depletions resulting from the water diversions and impoundments. 6.4.4 (D) SIZE OF AREA(S) TO BE WORKED ON AT ANY ONE TIME The maximum pit size to be worked on at any one-time is approximately 26 acres (i.e., current extent of the pit). The current depth of the excavation ranges between 19 to 28 feet below ground surface (ft bgs). Backfilling will occur concurrently with mining activities. The historic high groundwater elevation is 4,910.33 feet above mean sea level (ft amsl) in monitoring well MW-3 which is located near the midpoint of the Site. This indicates that a midpoint baseline backfill elevation of 4,912 ft amsl will provide sufficient coverage to eliminate exposed groundwater in the pit(i.e., 1.67 feet). Cut and fill calculations to balance the affected area to the midpoint backfill elevation of 4,912 ft amsl are presented in the table below. Cut/Fill Calculation to Eliminate Exposed Groundwater Fill Volume(Required) 764,398 CYs Cut Volume(Currently On-Site) 680,718 CYs Off-site Material Required 83,680 CYs The primary source of backfill material will be clean,uncontaminated material consistent with the Construction Material Rule No. 1, Section 1.1 (22) that will be imported from off-site. ASCI obtains this material from contractors who generate the material as part of construction projects in the vicinity (e.g., excavations for new housing). Based on 2022, ASCI will obtain sufficient off- site material to offset the volume required to eliminate exposed groundwater in approximately one (1) year; however, annual off-site volumes are expected to increase as construction continues to expand in the Northern Front Range area. Off-site material received will be temporarily stored at backfill staging areas around the excavation (e.g., typically no longer than one to two weeks) or processed as part of the recycling operation on-site prior to being placed in the pit.Backfill material will be managed separately from topsoil and overburden stockpiles at the Site. 6.4.4 (E) APPROXIMATE TIMETABLE FOR MINING OPERATION Approximately 75 of the 87 acres of affected area at the Chavers Mining Resource are mineable. Of the 75 mineable acres, approximately 53 acres have been or are currently being mined. The