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Aft 600 South Airport Road, Suite A-205 <br /> ZilichnabetLongmont, Colorado 80503 <br /> 303-651-1468 <br /> TECHNICAL MEMORANDUM <br /> TO: Jerry Jergensen DATE: 7/18/2022 <br /> COMPANY: Colorado Milling Company, LLC SUBJECT: Time Mine Bulkhead Design Calculations <br /> ADDRESS: 50 West 100 South Street PROJECT 22690002.000 <br /> Moab, Utah 80342 NAME/NO.: <br /> FROM: Mark Kroncke, PE CC: Ben Langenfeld <br /> Christoph Goss, PhD, PE <br /> This document summarizes the design calculations for the proposed Times Mine Bulkhead Extension Project. <br /> It is to be used in conjunction with the Schnabel Engineering 90% design plans dated 6-29-2022. <br /> While the calculated minimum bulkhead extension length is less than 2 feet, we have considered a longer <br /> bulkhead for constructability. Given the relatively shallow amount of cover, potential for hydraulic jacking, and <br /> the vein that runs along the long axis of the adit, we believe that a grout ring in the rock mass around the <br /> bulkhead is required. To safely pressure grout the rock mass, rock bolts are needed to keep rock blocks from <br /> popping out. Assuming a 2-foot spacing for equipment to install a row of rock bolts and a grout ring, a 6-foot- <br /> long bulkhead is the shortest feasible length. Table 1 represents a summary of the Factors of Safety (FS) <br /> calculated based on both a 6 and 8-foot long design bulkhead, as both were considered. These calculations <br /> were revisited after a site visit on April 21, 2022 where more exact bulkhead dimensions were measured. <br /> BACKGROUND <br /> The Times Mine consists of a 450-foot-long adit and 180-foot-long drift on the Times Vein. According to <br /> historical mapping (McLellan 1947), the adit includes one stope of unknown height and two raises. Based on <br /> information provided by CMC, the raises are more accurately exploratory stopes that end before reaching the <br /> surface. CMC noted that there are no workings above the Times Mine. The Times Mine Drift is stoped to 40 <br /> feet along the west section. At the intersection of the adit and vein is a chamber above the Wynona Winze. <br /> Schnabel Engineering assumes that this chamber once contained the hoist and headframe for the Wynona <br /> Winze. The extents of the Times Mine are shown on the 90% design plans. <br /> Based on Byron 1934, the Wynona Mine consists of a vertical shaft connecting four mine levels (50, 100, 150, <br /> 200 foot levels). The extents of the levels and stopes are not known to Schnabel Engineering. CMC states in <br /> the 12/8/2018 response letter that the main working levels extend 1500 feet towards the northeast and <br /> southwest. The Wynona 150' level is connected to the Times Mine via the Wynona Winze (correction from the <br /> Project 22690002.000 7/18/2022 Page 1 Schnabel Engineering,LLC <br />