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I <br /> I <br /> I Table 3.2.5 <br /> Maintenance of Control Structures and Catchbasins <br /> Maintenance Results Expected When <br /> I Component Defect Condition When Maintenance is Needed Maintenance is Performed <br /> Catch Basin Cover Not in Cover is missing or only partially in place.Any Catch basin cover is closed. <br /> Cover Place open catch basin requires maintenance. <br /> Locking Mechanism cannot be opened by one maintenance Mechanism opens with proper tools. <br /> Mechanism person with proper tools.Bolts into frame have <br /> Not Working less than 1/2 inch of thread. <br /> Cover One maintenance person cannot remove lid after Cover can be removed by one <br /> I Difficult to applying normal lifting pressure. maintenance person. <br /> Remove <br /> (Intent is keep cover from sealing off access to <br /> maintenance). <br /> I Ladder Ladder Ladder is unsafe due to missing rungs,not Ladder meets design standards and <br /> Rungs securely attached to basin wall,misalignment, allows maintenance person safe <br /> Unsafe rust,cracks,or sharp edges. access. <br /> I Metal Grates Grate Grate with opening wider than 7/8 inch. Grate opening meets design <br /> (If opening standards. <br /> Applicable) Unsafe <br /> Trash and Trash and debris that is blocking more than 20% . Grate free of trash and debris. <br /> 1 Debris of grate surface inletting capacity. <br /> Damaged or Grate missing or broken member(s)of the grate. Grate is in place and meets design <br /> Missing. standards. <br /> I <br /> Methods of Analysis This section presents the methods and equations for design of control <br /> I structure restrictor devices. Included are details for the design of <br /> orifices, rectangular sharp-crested weirs,v-notch weirs, sutro weirs, <br /> and overflow risers. <br /> I Orifices. Flow-through orifice plates in the standard tee section or <br /> turn-down elbow may be approximated by the general equation: <br /> IQ =C A.j2gh (equation 4) <br /> where Q =flow(cfs) <br /> C=coefficient of discharge (0.62 for plate orifice) <br /> A=area of orifice (ft2) <br /> h=hydraulic head(ft) <br /> g=gravity(32.2 ft/sec2) <br /> IFigure 3.2.12 illustrates this simplified application of the orifice <br /> equation. <br /> I <br /> I <br /> Volume III—Hydrologic Analysis and Flow Control BMPs—August 2012 <br /> 3-57 <br />