Upper Arkansas River Divsion 2 Diversion Structure Inventory.pd

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Upper Arkansas River Division 2 Diversion Structure Inventory C. Low-Level Dam/Spillway - Vertical or sloped concrete or earth dam with basin, which is connected to the headgate(s) and spans the remaining width of the river or diversion channel. The low-level dam/spillway can also consist of a series of concrete piers with timber stoplog gates. They typically have a concrete endwall or abutment which is keyed into the bank of the river that is opposite from the Regulator Gate(s). The low-level dam/spillway also acts as a "check structure", or grade control structure, allowing natural upstream aggradation and downstream degradation to occur, creating more stable or less erosive slopes along the river between the structures. The low-level dam will overtop frequently, resulting in the downstream side functioning as a spillway. The low-level dam will raise the level of the river or diversion channel to help direct flow to the diversion structure. 3.2 Type On the Field Inventory Forms structures were referred to as a Low-Level Dam/Spillway, a Diversion Channel with Low-Level Dam/Spillway, a Diversion Channel with Return Flow Structure, or a Submerged Culvert. A Low-Level Dam/Spillway spans the entire width of the main body of the river and raises the level of the river to divert flow to a diversion structure along the bank of the river. A Diversion Channel with Low-Level Dam/Spillway consists of a diversion channel that splits off from the main body of the river that diverts flow to a low-level dam/spillway that raises the level of water along the diversion channel so that it can be captured by a diversion structure along the bank of the diversion channel. A Diversion Channel with Return Flow Structure also consists of a diversion channel that splits off from the main body of the river, but the diversion structure spans the entire width of the diversion channel and return flow is typically regulated by a vertical lift gate or stop-log gate at the diversion structure or along the bank of the diversion channel or ditch. Diversion channels typically split off from the main body of the river and then connect back into the river upstream of the diversion structure" Submerged Culverts are typically submerged aqueducts that direct water to pump stations. 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 with components that were in excellent working condition and appeared to have been built or repaired within the past five years. A good structure had no obvious problems other than hairline cracks, and required only standard maintenance. The structure appeared to be in good working condition and appeared to have been built or repaired within the past ten years. A fair classification was given to structures with defects such as damaged Olsson Associates Page 2 June 2005