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Climax Mine Closure Documentation <br /> CAVR Asbestos Disposal Shaft January 15, 2016 <br /> (Attachment 2), collected following an acceptable visual inspection, were below the CDPHE clearance <br /> guideline of 0.01 fiber/cubic centimeter for Phase Contrast Microscopy(PCM)analysis. <br /> Following successful abatement of the structure, demolition began. Demolition was also performed by <br /> NorthStar, under a Demolition Approval Notice (Attachment 3) issued to LVI Environmental Services by <br /> the CDPHE on August 8, 2014. Complete removal of the structure was completed on August 28, 2014. <br /> Photos 1 and 2 in Attachment 1 show the structure before and after abatement and demolition. Following <br /> demolition the shaft was covered and the area secured to prevent access pending construction of the <br /> concrete cap. <br /> 2.0. SHAFT CAP CONSTRUCTION <br /> Construction of the concrete shaft cap (or plug) was performed in August 2015, as generally described in <br /> this section. The former CAVR ventilation shaft is 10 feet in diameter and more than 660 feet deep. At the <br /> surface of the collar, the shaft expands out to 14 feet in diameter within the concrete floor slab surrounding <br /> the shaft,creating a conical section. Below this conical section the shaft collar consists of a steel liner plate <br /> (10 foot diameter)which extends approximately 70 feet from the surface down through clay, loose boulders <br /> and weathered granite into competent bedrock. <br /> Construction of the concrete shaft cap was performed by Harrison Western Construction Corporation in <br /> accordance with the final construction drawings and concrete construction specifications, included with this <br /> report as Attachments 4 and 5, respectively. Several minor modifications were made to the general <br /> specifications identified in the 2012 Closure Plan. The first modification was the specification of a Type II <br /> or III cement with a minimum 20%Class F Fly Ash substitution in lieu of a Type V cement to provide sulfate <br /> resistance; change made based on local availability of materials. The second modification was that epoxy <br /> coated shear studs were not required; epoxy coated steel for this application, which is primarily to support <br /> the rebar hoops during concrete placement,was not determined necessary for the structural integrity of the <br /> cap. Lastly, the 2012 Closure Plan indicated that the concrete would be sealed with an epoxy coating, <br /> however,due to the thickness of the cap and the use of sulfate resistant cement,the application of a sealant <br /> is not necessary. <br /> Construction details for the concrete shaft cap are presented on Sheets 2 and 3, of Attachment 4, and <br /> several photographs taken during construction are included in Attachment 1. Preparatory work began the <br /> week of August 3,2015 and the concrete was poured on August 12,2015. The shaft cap is a two-foot thick <br /> cast-in-place reinforced concrete 'plug' constructed within the conical section of the existing shaft collar. <br /> Wood formwork was constructed and placed near the bottom of the conical section(Sheet 3). The formwork <br /> was designed to fully support the weight of the wet concrete plus a 100 pounds per square foot (psf) live <br /> load. Three steel reinforcement bars (rebar), or shear studs, were embedded into the existing concrete at <br /> six locations around the circumference of the conical section, primarily to support the three rebar hoops <br /> placed at the locations of the shear studs near the perimeter of the concrete cap section, as illustrated on <br /> Sheet 2. In addition two rebar mats were placed near the top and bottom of the concrete cap. The rebar <br /> mats will resist flexural stresses within the concrete, and the purpose of the hoops is to prevent the transfer <br /> of unacceptable stresses into the existing concrete slab and shaft collar. Because of the placement within <br /> the conical section of the shaft collar, and with the aid of the rebar hoops, the cap will act similar to an arch <br /> structure, allowing it to safely withstand the loading associated with up to 100 feet of overburden soil. Also, <br /> as shown on Sheet 2, the top of the concrete cap extends a minimum of one foot beyond the outside edge <br /> of the existing shaft collar, with the surface of the cap five to eight inches higher than the existing concrete <br /> slab. This overlap feature, with the upper rebar mat included, will minimize the potential for surface water <br /> to enter the shaft and create an air flow barrier. The surface of the cap was sloped, generally south to <br /> Tetra Tech 2 <br />