2020-12-28_GENERAL DOCUMENTS - M1977300 (22)

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PERMIT#: M-1977-300 INSPECTOR'S INITIALS:AME INSPECTION DATE: October 8,2020 OBSERVATIONS This inspection of the Schwartzwalder Mine (Permit No. M-1977-300)was conducted by Amy Eschberger of the Division of Reclamation, Mining and Safety(Division). The operator was represented by Billy Ray during the inspection. The site is located approximately 6 miles northwest from Golden, CO in Jefferson County. Access to the site is off Glencoe Valley Road. This site is on a quarterly inspection frequency. This inspection serves as the 41" quarter inspection for 2020. However, the Division anticipates an additional inspection will be conducted this quarter in association with the North Waste Rock Pile (NWRP) diversion channel project (discussed below) and/or the Amendment application (AM-5) currently under review. Photos 1-28 taken during the inspection are included with this report. The primary purpose of this inspection was to review the Phase 2 construction work completed for the NWRP diversion channel project approved under Technical Revision No. 28 (TR-28; approved on March 27, 2020). Because the NWRP is considered an Environmental Protection Facility,per Rule 7.3.1(1), construction work shall be done in phases, and no construction work shall begin on any subsequent phases of the facility without first obtaining Division acceptance. The Division inspected the Phase 1 work completed(water capture structure concrete seal trench) on August 4, 2020 and authorized the operator to proceed with the next construction phase in its August 6, 2020 inspection report. The Phase 2 inspection was to be scheduled after the subgrade for the channel is completed and during installation of the Geoweb components. The Geoweb components include a three-liner base system composed of a geosynthetic liner sandwiched between two non- woven geotextile liners, and the Geoweb panels installed across the top of the liner system. At the time of the inspection, the channel subgrade was complete, the bottom non-woven geotextile liner and middle geosynthetic liner had been installed across the entire channel, the top non-woven geotextile liner had been installed across approximately the upper%of the channel, and workers were installing the Geoweb panels across the top of the 3-liner base system. According to the operator, the channel subgrade was completed two days prior to the inspection, and installation of the Geoweb components began the day before the inspection. The manufacturer representative, Joe Kaul estimated installation of the Geoweb components would be completed by the end of the day. Prior to the geotextile installation, an as-built survey was performed on the subgrade to verify the design slopes have been achieved and the subgrade was prepared in accordance with the earthwork specification. The channel subgrade was also inspected and accepted by the manufacturer prior to geotextile installation. The bottom width of the channel is approximately 3 feet wide. The channel depth varies from 2 feet to 3 feet. The side slopes of the channel have a 1 H:1 V slope gradient. During channel excavation, there were some areas where the excavation went deeper than the 3 foot thick layer of clean cover material that exists on the NWRP, and waste rock material was exposed. Any waste rock material removed during the project was transported to the Minnesota Mine for disposal and the exposed waste rock surface was capped in place with the Geoweb liner system,per TR-28. No heavy equipment is required for installation of the Geoweb components. The Geoweb panels are connected via tendons and ATRA tendon clips which work together to provide a load transfer and suspension system over the Geoweb system. The tendons are attached to 4 inch solid wall PVC deadman pipes inside the channel side trenches,which will be backfilled prior to concrete placement. Two workers had started backfilling these trenches in the upper section of the channel. At the upper end of the diversion channel, the water intake structure has been installed in the ephemeral drainage above the NWRP, including the concrete seal wall, the perforated pipeline (buried), and the riprap layer placed upstream of the seal wall (across a granular bedding). A clean out is installed at each end of the seal wall for the buried intake pipe. All that remains at the intake area is to complete a mechanical attachment of the Geoweb components to the upstream face of the headwall. According to the design drawings, the Geoweb Page 2 of 19