Onawa Drainage District Improvements |
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The Consulting Engineers Council of Iowa awards to engineering firms participating in projects that are judged to meet the Owner’s needs and demonstrate “Originality, Uniqueness and New Applications of Existing Technology”. The projects must also add to the “Technical Value of the Engineering Profession” and must consider “Social and Economic Factors” as well as be of a complex nature. One of the awards was presented to Kuehl and Payer, Ltd. of Storm Lake, Iowa for their role in the planning, design and construction administration of the Onawa Drainage District’s Flood Control Basin Project.The Onawa Drainage District encompasses the City of Onawa with the District Boundary matching the 1919 city limits of Onawa. The City of Onawa is located on the floodplain of the Missouri River in the north-central portion of Franklin Township, Monona County, Iowa. The Onawa Drainage District was established in 1919 to afford a system of surface ditches to provide drainage to the town of Onawa and adjacent agricultural lands. The surface channels were replaced by storm sewers in the 70’s. However, the only outlets for these storm sewers are open drainage ditches designed, constructed and maintained for drainage of cropped agricultural lands. For years, the City of Onawa has contended with flooding of these open ditches during intense storm events causing the backup of the City’s storm sewers. The standing water in the City’s streets has caused the flooding of the basements, the backup of sanitary sewers, and structural damage to buildings. The Board of Supervisors, acting as Trustees for the Onawa Drainage District hired Kuehl and Payer, Ltd. of Storm Lake and Algona, Iowa for the development and design of a pumping and flood detention basin system to provide flood relief to the east portion of the City of Onawa. Kuehl and Payer's. investigation of the City’s drainage problems lead to the design and construction of a system of surface channels as a means to remove agricultural lands off the City’s storm sewers. This maximized the sewer capacity for the urban area of the City and significantly reduced the storm water needing to be pumped during flooding events. |
 Kuehl and Payer’s unique design for the pumping systems utilized prefabricated corrugated metal sumps typical for agricultural drainage pumping systems, lowered the onsite construction costs, allowing the District to use permanent automated pumping stations. Two axial flow turbine pumps with flow rates of 3,600 and 16,000 gallons per minute pump to two earthen basins sized to store runoff from three day long storm events. The water is temporarily stored in the basins until the flood waters in the open drainage ditches subside allowing the release of the water back to these drainage ditches. The pumps are powered by 15 and 100 house-power electric motors. The pumps use floating switches to automatically start the pumps when the water in the open drainage ditches start to flood the outlets of the City's storm sewers. The design of this pumping system involved a complex hydraulic design of the four major components to the pump stations. The emergency use of the flood basins during construction showed the citizens of Onawa the effectiveness of the pumping system. The flooded streets on the east side of Onawa were drained within twelve hours after use of a portable pump. Since completion of construction in 1996, the flood control pumps have automatically responded to recurring flooding events. The pumping and detention basin system has significantly reduced the threat of flooding in Onawa, providing peace of mind to both home and business owners. The public health, safety and welfare have been enhanced as a result of design and construction of this system. | ||