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i <br />~ . <br />The outlets of the culverts are protected against downstream channel erosion by discharge <br />tubes, conveyor belt, or energy dissipaters dependent upon the slope of the discharge channel. <br />The upper five culverts have plastic discharge tubes attached to the culvert which conduct the <br />flow from the culvert to the natural channel below the culvert. Addition of the discharge tubes <br />was the result of an OSM oversight inspection on May 26, 1983. The tubes protect the <br />outslope of the steeper portions of the mine road from excessive erosion so that additions of <br />suspended solids to the downstream flow are prevented. The tubes are maintained to ensure <br />that they are functioning properly and repaired or replaced as necessary. <br />The discharge end of the sixth culvert down the road from the mine site has been modified <br />to prevent downstream erosion. The end of the culvert was cut allowing the end to be lowered <br />into the channel where the flow discharges onto a length of conveyor belt. The conveyor belt <br />and energy dissipaters protect the downstream portions of the channel from erosion. <br />All other culverts are installed in the streambed where small plunge pools and rock lining <br />have prevented erosion since the culverts were installed. The plunge pools have stabilized and <br />do not exhibit a tendency to enlarge further. <br />shown below. <br />Atypical sketch of the entire culvert system with trap, culvert and discharge tube are <br />DITCH SEDIMENT TRAP CULVERT <br />DISCHARGE TUBE <br />\\~ <br />ENERGY <br />\ DISSIPATER <br />• <br />MU VOL. V <br />PAGE-14 <br />12-9-96 <br />