2015-06-18_GENERAL DOCUMENTS - M1978144

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Colorado Inactive Mine Reclamation Program CLOSEOUT REPORT YUKON TUNNEL BOND FORFEITURE PROJECT Permit Information Permit Number Operator Name Mine Name M-1978-144 Arrigo Mining and Milling Yukon/Gold Hub Type of Mine: Underground with mill Commodity Mined: Tungsten and Base Metals PRE-RECLAMATION SITE CONDITIONS Background The Yukon Tunnel is a circa 1900 tunnel that extends for approximately 7,000 feet to a vein that strikes N10E and dips 60 to 80 degrees west which was rich in Tungsten and other base metals. The site includes a mixture of historic and newly constructed mining features and structures. The large tailings pond and associated smaller dewatering pond were present prior to 1978, but are assumed to have been utilized after 1978. Additionally, most if not all of the mine waste pile was present prior to being permitted in 1978. There are features of the site with historical significance, including the concrete mill foundation and rail and loadout tracks on the top of the mine waste pile. Mining Permit The mining permit was issued by the Mined Land Reclamation Board in 1978 under permit#M-1978-144 (Yukon Tunnel and Arrigo Milling and San Juan Mining). The mining plan included utilizing the pre-existing 7,000 feet of tunnel to reach the vein and perform traditional shrink-stope mining methods. Ore was to be hauled to the surface and stockpiled for processing in the on-site flotation mill and newly constructed tailings impoundment directly below the newer galvanized mill building. Additionally a second portal was started, but never completed, at a level 400 feet above the Yukon Tunnel for secondary escape way and ventilation with an associated road that accessed this portal across BLM land. The extent of operation and disturbance under the 1978 permit is unknown, but it appears that some underground mining occurred with some ore being stockpiled on the surface near the newer galvanized mill buildings. Additionally, the new tailings pond construction was started, but never finished. There is a road that leads to the ventilation and escapeway adit, but the extent of the upper adit workings is minimal or non-existent. Reclamation Plan (1978-2013) The pre-existing 1978 reclamation plan called for reclaiming the site to a wildlife habitat and watershed post-mining land use by removing all structures, regrading both tailings ponds and other disturbed areas, sealing all mine entries and importing topsoil to cover each of the backfilled entries and revegetating all disturbed areas. In late 2000 DMG utilized the$2,375.00 bond and installed a grated adit closure in the Yukon Tunnel. DMG also cleared an internal blockage in the perforated pipe inside the tunnel to prevent water from exiting the portal and leaching into the mine waste pile, successfully re-routing the water back into the buried conveyance that drains into Illinois Gulch. The 2013 Reclamation Plan included: • Installing run-on controls above the mine waste pile to prevent infiltration and leaching of metals from the mine waste pile • Amending, encapsulating, and revegetating the pre-existing tailings pond • Removing and recontouring the linear ditches that were installed in preparation of a new tailings disposal facility to approximate original contour and revegetate. • The buildings and historic structures were left intact at the request of the improvements owner. • Some recent trash and fallen building debris were removed from the site with the approval of the improvements owner and land owner. Bill Simon (ARSG Coordinator) and Kay Zillich (BLM-AML) both assisted with reclamation design of this project. The design ratio for tailings amendment was 1 part lime to 5 parts tailings. The ratio of lime to tailings was determined by composite sampling the tailings by auger drilling at 6 locations across the pond and sending the samples in for acid base accounting and toxicity characteristic leaching procedure (TCLP)for the RCRA 8 metals which includes: Arsenic, Barium, Cadmium, Chromium, Lead, Selenium, Silver, and Mercury. The TCLP tailings sample showed that Lead was above the regulatory limit. Limit is 15 mg/L and sample was 63 mg/L. The Acid Base Accounting indicated that 42 tons of pure calcite/limestone per 1000 tons of was necessary to bring the pH to neutral (7). As an additional check another sample was run using 1