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1 1.3.4 High Velocity Screens 1.3.4.1 Modular Inclined Screen Characteristics. The Modular Incline Screen or MIS is a developing technology that is similar in many ways to the Eicher screen. It is designed for higher approach velocities than conventional screens, and incorporates an incline screen within a pressure conduit. A marked difference is that the MIS is designed to fit within a rectangular conduit. This configuration develops uniform velocities over the screen surface without the need for baffles or varying porosity which in turn reduces the headloss across the screen. The MIS consists of an entrance with trashrack, dewatering stoplog slots, and inclined (100 to 200 to flow) wedge wire screen, and may have a fish bypass (Figure 1-1). Debris is removed by rotating the screen about a pivotal shaft which allows flow across the reversed screen surface. During debris flushing, fish passage or entrainment may occur. The time required for flushing is short and passage or entrainment is expected to be low. Laboratory tests have shown promising results for velocities ranging from 2 to 10 ft/sec and capacities of 500 to 1,000 cfs . Typical Existing Applications. Typically intended for submerged application, the MIS is experimental. Laboratory testing is being conducted to evaluate the best hydraulic design configuration for safe fish passage, and the biological effectiveness in diverting selected fish species to a bypass. A prototype has been designed for the spillway sluicegate at Niagara Mohawk's Green Island facility on the Hudson River. Typical Advantages • Requires no space in forebay area • Can easily be installed at a variety of water intakes • Not affected by icing • Unaffected by changes in forebay water surface elevation • Operation and maintenance costs are small except when fish handling is necessary • High velocities permit smaller screen area to be used Typical Disadvantages • Fish passage or entrainment may occur during debris flushing • Fish bypass and handling occasionally required • Not developed for exclusion of passive or very small life stages (2 mm smallest opening) • Currently developing technology, has not been field tested • May require operational changes to ensure adequate flow to the screen during reservoir filling, low flows and partly submerged conditions Application to Limiting Downstream Passage. This screen can be effective for the subject application when installed at a rectangular bell-mouthed entrance at the upstream end of a pipe type intake (Figure 1-1). Its high velocity criteria makes it desirable from a cost/size standpoint especially where it can be positioned to avoid fish handling. Unfortunately, the backwashing cycle which has a brief period of open passage when it rotates around the center pivot, its relatively large screen openings and its lack of field applications reduces its potential application to the objectives of this study. Control Structure Feasibility Evaluation 1-7 Miller Ecological Consultants, Inc., February 18, 1997