Lake Lotawana Dam and Spillway Rehabilitation

Lake Lotawana is a 480-acre residential lake located in eastern Jackson County, Missouri. The dam and reservoir were originally constructed in the late 1920s and included a zoned earth embankment with an overall crest length of approximately 1900 ft. The original dam had a height of 50.7 feet above the valley floor. In the 1930's, a WPA project modified the spillway at the reservoir to include a 200 ft wide broad crested weir located in the north abutment of the dam. The spillway system also included a 7 ft deep by 12 ft wide gated drawdown channel. The weir emptied into a concrete lined channel that narrowed from 200 ft to 42 ft at its entrance into the plunge pool, The dam also served as the only road for access to the eastern side of the lake. A wooden deck bridge with an overall length of 200 ft was constructed over the spillway channel. From the 1930s to the late 1980s the dam and spillway functioned without severe incident, although several homes around the lake were subject to flooding. Photographs taken in the late 1970s show the spillway flowing at near its capacity. The dam was apparently overtopped for a short duration in the 1950s. In April 1988 an inspection of the Lake Lotawana dam was made and the spillway system determined inadequate. The dam was classified as a Class I downstream environment zone for purposes of the original inspection and evaluation of spillway capacity. The State reported that the spillway system was incapable of passing the Class I structure design flood without overtopping the dam, Therefore, the spillway capacity would have to be increased to accommodate a computed flow of approximately 30,000 cubic ft per second. The capacity of the existing spillway channel was calculated to be 7,000 cfs. The State advised the dam owners that in order to modify the dam and spillway, they were required to obtain the services of a registered professional engineer. During this same period of time, the Lake Lotawana Association (LLA) was in the process of negotiating with the Lotawana Development Company to take over ownership of the lake, road system and other common areas. The Property Owners Association's Board of Directors formed a steering committee to coordinate all aspects of the dam and spillway renovation, and to investigate methods to fund the capital improvement project. The steering committee was aware that something needed to be done to the dam but were unaware of the magnitude of the modifications and cost to bring the dam and spillway into conformance with the Class I criteria. 12 pp.