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<br />After dropping from the flume to a forebay on the middle level of the tailings pile, water enters a <br />pipe that passes through the tailings pile to a large drop to the channel bed. The pipe entrance <br />has recently been rebuilt with a concrete headwall, steel grating, and 5.5-foot diameter concrete <br />pipe. The end section of pipe was welded from portions of 6.7-foot diameter steel boiler tank. <br />Photos follow of the pipe entrance and water drop at the downstream end. <br /> <br />- L-.~, ~ ....' '';'-1" .~ -, · :" .~. . <br /> <br />- .. "'..... ..... '.". . <br /> <br />~ ',,: ~" i ,.. ; *' p ~ -~:;: _". I ? ~. - ...- - .. <br />~ ~.. ..~ 1:.:- .... ~ "J1.-" - :t:J. or ,JJ ~ _ r -, - <br />__ . ~ ~_..: ~.: ;'~4'.,~ .~-:. - - · .." . <br /> <br /> <br />.j <br /> <br />~~ <br /> <br /> <br />, ~~ ~ ~ <br /> <br /> <br />Figure 2.2.29. (above) Entrance to Commodore pipe <br />Figure 2.2.30. (right) Drop from Commodore pipe <br />Figure 2.2.31. (below right) Nelson adit, Parshall <br />flume, and mine drainage <br /> <br />The Nelson adit exits on the middle level of the <br />tailings pile and drains through a Parshall flume and <br />into the Commodore pipe. A photo of the Nelson adit <br />drainage follows. Recent studies have found that this <br />drainage may be the largest single source of heavy <br />metal contamination to Willow Creek. A manhole <br />pipe access and a pipe vent have also been added to <br />the Commodore pipe. <br /> <br /> <br />\ I <br />~;~ <br /> <br />JjI <br /> <br />1,1- <br /> <br />Ill' <br />,d! ~ <br /> <br /> <br />'\ .......... <br />.. - ~ <br /> <br />.. .. <br /> <br />....~ <br /> <br />The Commodore flume and pipe were included in the <br />HEC-RAS analysis. A "lid" was placed on the flume ~ <br />... <br />cross-sections to represent the railroad irons that add <br />"wetted perimeter" to the flow area. The Commodore <br />pipe was modeled as a culvert. The pipe was <br />modeled using the 5.5-foot diameter of the concrete <br />pipe. Inlet conditions at the entrance headwall govern <br />flow through the pipe; therefore, use of the smaller <br />diameter to calculate internal pipe head loss does not <br />affect the results. A circular culvert with a concrete <br />headwall is typically modeled with an entrance loss <br />coefficient (Ke) of 0.5. An entrance loss coefficient <br />of 0.7 was used to account for the additional <br />resistance formed by the thick steel grating. <br /> <br />2-33 <br /> <br />..,~- . <br />~... p"; <br />,.~...' <br />I.~ <br />