Historic Mine Opening Closure Methodology, Specifications, and Details – Utah and Colorado Bureau of Land Management Districts Prepared for Freeport Minerals Corporation December 2017 9191 South Jamaica Street Englewood, CO 80112 Contents Section Page Acronyms and Abbreviations ............................................................................................................. iv Document Overview ......................................................................................................................... 1 Introduction ...................................................................................................................................... 2 Solid PUF Plug with or without Bat Gate ............................................................................................ 3 3.1 Preparation ......................................................................................................................... 3 3.2 Closure Steps ...................................................................................................................... 3 3.3 Material Specifications and Installation ............................................................................. 7 Wire Rope Netting ............................................................................................................................ 8 4.1 Closure Steps ...................................................................................................................... 8 4.2 Material Specifications ....................................................................................................... 9 Fencing ........................................................................................................................................... 10 5.1 Closure Steps .................................................................................................................... 10 5.2 Material Specifications ..................................................................................................... 11 Backfilling ....................................................................................................................................... 12 6.1 Closure Steps .................................................................................................................... 12 6.2 Signage .............................................................................................................................. 13 6.3 Documentation and Monumentation............................................................................... 13 Monitoring, Maintenance, and Reporting ........................................................................................ 14 7.1 Monitoring and Maintenance ........................................................................................... 14 7.2 Monitoring and Maintenance Reporting .......................................................................... 15 Appendices Appendix A Safety Data Sheets Appendix B Site Evaluation Forms Appendix C Detailed Drawings of Polyurethane Foam and Fence Closures Appendix D Specifications Appendix E Standard Operating Procedures PR0616171000DEN iii Acronyms and Abbreviations BLM Bureau of Land Management CFR Code of Federal Regulations Freeport Freeport Minerals Corporation GIS geographic information system HMO hazardous mine opening HMOSP Historic Mine Opening Safety Program ICF insulated concrete form block JHA job hazard analysis PPE personal protective equipment psi pounds per square inch PUF polyurethane foam SDS safety data sheet SOP standard operating procedure PR0616171000DEN iv SECTION 1 Document Overview This document provides detailed methods and typical drawings of closure methods that will be used to close or seal historic mine openings (HMOs) on Bureau of Land Management (BLM)-administered lands in Utah and Colorado. The document also provides material-specification information. Freeport Minerals Corporation (Freeport) or its contractors will complete the work described in this document. The work described in this document consists of closing HMOs by installing polyurethane foam (PUF), backfill, fencing, and wire rope nets within adits, inclines, declines, or shafts. Work includes clearing and grubbing, excavation of loose materials, trimming of openings, furnishing and securing the closure materials, and placing signage and monuments. Closure materials and specifications are generally consistent with the Colorado Department of Natural Resources Division of Mining, Reclamation, and Safety General Bid Specifications Handbook, published March 2009, and the Utah Abandoned Mine Reclamation Program’s “boilerplate” construction contract specifications published February 2011. All work conducted will be executed in accordance with the Proposed Action and National Environmental Policy Act of 1969 Categorical Exclusion that is specific to each project and approved by BLM. PR0616171000DEN 1 SECTION 2 Introduction Historic mine openings (HMOs) represent adits, shafts, trenches, inclines, declines, glory holes, or any other distinct identifiable feature that was used to excavate materials for mining, is no longer in use, and will not be used to excavate or mine materials soon. The following sections describe the five primary approaches used to permanently close HMOs: • Section 3: Solid PUF plug with or without a bat gate • Section 4: Wire rope netting • Section 5: Fencing • Section 6: Backfilling All materials will be prefabricated offsite, brought to the closure location during the time of the closure, and will not be stored onsite. PR0616171000DEN 2 SECTION 3 Solid PUF Plug with or without Bat Gate The process for closing a HMO with a solid PUF plug and installation of a bat gate within PUF are presented together in the following steps. The only difference between a solid PUF plug and a PUF plug with a bat gate is the bat gate. The same steps and approach are taken for each closure technique. HMOs that will be closed with PUF shall follow the steps below. 3.1 Preparation Prior to starting any work at the entrance of an HMO: • A work area inspection shall be completed to identify: − Overhanging debris, high walls, etc. − Fall hazards and appropriate tie-off procedures and points − Chemical and explosive hazards − Locations requiring flagging around the work zone to indicate where fall restraints are required and where only authorized staff are allowed − All other applicable hazards • Air monitoring at the HMO shall be completed to ensure the atmosphere is a safe working environment. − Air monitoring standard operating procedures (FMC HMOSP SOP04-14, Appendix E) shall be followed. − Air monitoring includes: radon, oxygen, lower explosive limit, sulfur dioxide, carbon monoxide, and hydrogen sulfide. • If closing an adit or an HMO in which breaking the entrance plane of the HMO is required, the HMO shall be evaluated for confined space determination. • No openings which meet the definition of confined space shall be physically entered by personnel. 3.2 Closure Steps • Perform a work area inspection by physically walking the area and identifying all potential hazards that may exist in the area. • Complete a job hazard analysis (JHA) for each closure activity. • Control, reduce, or eliminate all potential hazards identified in the JHA. If working on an HMO closure with a fall potential, use proper fall protection procedures while working (FMC HMOSP SOP04-02, Appendix E). • Eliminate tripping hazards around the work area and ensure proper housekeeping. • Maintain control of the supplies and equipment being used in the area. Anchor points may need to be established to maintain the weight of the materials being installed until the mine opening has been sealed. Use of rebar stakes, natural terrain features, or equipment may be necessary. Bat gates, vent pipes, drainage pipes, and bulkheads will be secured either by ropes, fir strips, or any other means possible at mine openings. PR0616171000DEN 3 SECTION 3—SOLID PUF PLUG WITH OR WITHOUT BAT GATE • Clear all set-up planks and walkways of debris and tripping hazards. All planks/walkways will be secured and anchored in a way to eliminate any twisting or falling motions. Personnel using the scaffolding or planks will be tied off with fall protection devices in accordance with the Fall Protection Guidelines. Handrails are not permitted on planks or walkways. • When closing adit-type features, a rock wall will be built while pouring or spraying the PUF in stages. Insulated concrete form block (ICF) may also be used in lieu of rocks. This allows the foam to be used as grout on the interior of the rock or ICF wall, cementing and anchoring the rocks or ICF into the foam. • When closing shaft-type features, the foam will be poured until reaching a depth below the existing ground surface of approximately 2 feet. Cover material will later be placed on top of the foam to blend into the existing ground surface. • If ICFs are to be used in lieu of local rocks for the exterior face, ICFs shall have the exterior face finish of a polymer-modified cement, reinforced with a woven glass fiber, that will be dyed as close as possible to the surrounding environment. ICFs shall be reinforced internally with Grade 60 #4 (0.5-inch diameter) rebar . Exterior face finish shall consist of a polymer-modified cement, Omega DryBond® or equivalent. Add one 50 lbs bag of dry mix to 1.5 gallons of water and mix for 3 to 5 minutes. Add concrete dye as needed prior to mixing. See manufactures recommendations