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MEMORANDUM <br /> To: Mark Steen—Colorado Milling Company <br /> From; James M. Beck,P.E. <br /> Date: May 15, 2019 <br /> Subject: Evaluation of Risk Potential—Intake Pipeline <br /> In response to your request for an evaluation of the risk and/or damage potential associated with a proposed <br /> water line intake conduit (serving the proposed Times Mine pump station), and more specifically, as <br /> pertaining to the damage potential at three (3) permanent, man-made structures proximal to the pipeline <br /> feature,I provide the following: <br /> You have indicated that there are four (4) privately-owned (by others) wood-framed structures, or <br /> 'outbuildings",present on the subject Mammoth Millsite claim,three(3)of which are situated within 200 <br /> feet of the proposed waterline,with one of those three being within approximately 100 feet of the pipeline. <br /> These structures are stated to be owned by Mr. James K. McCumber and Ms. Any Fortunato, and are <br /> described as being a bunkhouse,music/art studio,and outhouse/privy,respectively(with the outhouse/privy <br /> being the structure that is closest to the pipeline,at a separation distance of approximately 100 feet). None <br /> of the structures are known to possess valid Certificates of Occupancy issued by Boulder County. <br /> You have further indicated that a two(2)inch diameter line will be extended from a point commencing at <br /> or in Left Hand Creek to an approximately 275-feet distant and up gradient pump station. Preliminary <br /> design considerations suggest that this line would commence as a"flat hose"(that is,a woven,collapsible <br /> hose), extending upslope for a distance of approximately 100 feet, at which point it would transition to a <br /> HDPE(or equivalent)rigid pipe material,extending over the remaining approximately 175 feet to the intake <br /> pump inlet, which is to be situated interior to a permanent structure characterized as a "connex" box, or <br /> equivalent) <br /> Based on the parameters of a 275 feet long pipeline of 2-inch ID(inside diameter),the maximum volume <br /> of water that could be present within the entire pipeline segment would be the equivalent of 44.88 gallons, <br /> or approximately forty-five(45)gallons. <br /> My review of the provided Exhibit E-I Mine Plan and the aerial base map entitled"F000dplain—FEMA— <br /> Colorado Milling Co.—Gold Hill Mill Waterline"suggests that greater than 95%of the pipeline's length <br /> (e.g., likely in excess of 265 of its overall 275 feet length) is situated (on-ground, as a temporary feature) <br /> to the east of the structures, and within and along the western edge of the FEMA designated 500-year <br /> floodplain extending southwesterly from Left Hand Creek at that location. <br /> It is my opinion that a`worst-case"pump failure and/or pipeline rupture scenario would likely be a rupture <br /> at the approximate mid-point of the pipeline(as opposed to where the pipeline connects to the pump). In <br /> such a scenario,roughly one-half of the contained volume would be released to the ground surface,whereas <br /> the remainder would likely"backflow"to the creek due to gravitational forces and/or elevation differential. <br /> The mid-point of the pipeline would appear to be roughly cross-gradient of the elevation of the structure(s), <br /> so only that water in the line above that point could theoretically affect the structure(s). While fluids could <br /> theoretically reach the structure(s), assuming a positive flow gradient in that direction, the pump feature's <br /> location (immediately upslope) of the 500-year floodplain demarcation)and the pipeline's location(frilly <br /> within the 500-year floodplain demarcation)would suggest that virtually all fluid loss(at the pipeline mid- <br /> point) would likely be contained within and dispersed along the natural flow course present within the <br />