South Platte River Basin District 64 Diversion Structure Invent

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August 4, 2004 South Platte River Basin District 64 Diversion Structure Inventory or vertical lift gate(s), stairs and decking (concrete or timber) with handrail for access/maintenance. The regulator gate is commonly connected to the diversion structure by means of a concrete wall (abutment, keyed into one of the banks of the river), and is located perpendicular to the river. G" Low-Level Dam/Spillway - Vertical or sloped concrete dam with basin, which is connected to the regulator gate(s) and spans the remaining width of the river. Can also consist of a series of concrete piers with timber stoplog gates. Typically has a concrete endwall (abutment), which is keyed into the bank of the river that is opposite from the Regulator Gate(s)" Acts as a "check structure", or grade control structure, allowing natural aggradation (upstream) and degradation (downstream) to occur, creating a more stable (less erosive) slope of the river between the structures. The low-level dam will overtop frequently, resulting in the downstream side functioning as a spillway. 3.2 Type As stated above, the components of a structure would typically include a diversion with headgate(s), regulator 9ate(s) and a low-level dam/spillway. Structures such as these were referred to as a "dam", as indicated on the Field Inventory forms. The river was purposely obstructed by the structure, causing the water surface to raise and widen. With this abrupt increase in width and depth, the speed or velocity of the water is decreased. The water is then more easily and effectively controlled and therefore diverted to the ditch" 3,,3 Condition The condition of each structure was classified as very good, good, fair or poor. A very good rating was given to structures where all components were in excellent working condition and appeared have been built or repaired within the past five years. A good structure had no obvious problems other than hairline cracks or standard maintenance. The structure appeared to be in good working condition and was built or repaired within the past ten years. A fair classification was given when problems such as damaged concrete, more significant cracking or rust were apparent in a structure between ten and fifty years old" Considerable annual maintenance is required to keep the structure operating correctly for fair structures. Structures that looked as if they were over fifty years old with obvious structural failure or serious damage were considered poor. The structures may have had many repairs to make them somewhat operational, but still require more. In some cases, it may be more cost effective to completely replace a structure in poor condition" A visual inspection with the gate(s) fully closed is recommended prior to final design of the diversion structure or regulator gate improvements. Continuous flow through the structures made a thorough inspection of the dam/spillway basin or diversion structure concrete apron (floor) difficult or impossible. The components of the structures that are normally submerged should be made visible for a complete and accurate evaluation" l~'arns);vorth (;roup Pa,ge 2