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<br />I <br />I <br /> <br />~,v <br /> <br />. '- -J .......-:::- <br /> <br />I <br /> <br />SECTION IV <br /> <br />VERTICAL DROP WITH HARD BASIN <br /> <br />'I <br /> <br />I <br /> <br />INTRODUCTION <br /> <br /> <br />The hydraulic phenomenon provided by thiS type of drop is a jet of water which <br /> <br /> <br />overflows the crest wall into the basin below. The jet hits the hard basin and IS <br /> <br /> <br />redIrected horizontally. With suffIcient tailwater, a hydraulic jump is Initiated. <br /> <br /> <br />Without, the flow continues horizontally In a supercrltlcal mode until the specific <br /> <br /> <br />force of the tailwater IS sufficient to force the jump. <br /> <br />I <br /> <br />I <br /> <br />CASES <br /> <br />I <br />I <br /> <br />A varlety of components can be used for both the hard basin and the wall, variOUS <br /> <br /> <br />contraction effects can be Implemented to reduce approach velocIties, and different <br /> <br /> <br />trickle channel optIOns selected. <br /> <br />I <br />I <br /> <br />Case 26 - Goldsmith Gulch near Belleview <br /> <br /> <br />This IS a unique design that creates a drop structure that is a focal plaza and water <br /> <br /> <br />cascade feature in the midst of a grass-lined waterway and detention storage facility. <br /> <br /> <br />In Figures IV-l and 2, one can see that the basic drops are vertical, but the basins <br /> <br /> <br />below have large blocks that also serve to dissipate energy. The design flow is <br /> <br />3000 cfs for the 100-year flood. <br /> <br />I <br /> <br />I <br />I <br />I <br /> <br />The trickle channels are very interesting because in some reaches they are actually <br /> <br /> <br />dIverted to the overbank area. The designers are continuing to perfect the facility, <br /> <br /> <br />which is necessary of course, because there are no prototypes. <br /> <br />I <br />I <br />I <br /> <br />Case 27 - McIntyre Gulch, Center through West VirgInIa Avenue, Lakewood <br /> <br /> <br />Figure IV-4 Illustrates Improvements which Included a grouted rock channel and <br /> <br /> <br />vertical drops. The channel is steep and likely flows at a supercrltical rate, thus <br /> <br /> <br />the channel deserves monitoring. Both the walls and channel banks have sub drainage <br /> <br /> <br />prOVIsions. The specifications on the project called for pumped grout, Vibrating Into <br /> <br />VOIds and cleaning the surface. Graded rlprap was called for. It would have been <br /> <br /> <br />an Improvement to call for a Single layer of rock for constructability, quality <br /> <br />IV-l <br /> <br />I <br />