PROJ01972 (2) - Laserfiche WebLink

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Executive Summary The purpose of this study is to provide a basis for the South Side Reservoir Company to develop strategy to continue providing irrigation water to 265 shareholders in a safe and efficient manner. This study examines the feasibility of alternatives for rehabilitation of the outlet works and resolution of spillway issues of the South Side Reservoir Dam necessary to improve dam safety and allow storage restrictions to be lifted. The existing dam and reservoir (AKA Bud Mielke Reservoir) was built in 1905 and consists of the earthen embankment, which also serves as a county road, a spillway and the 16" diameter steel outlet with a "center of the dam" gate chamber. The gate chamber is in the county road and presents a hazard to traffic. Two issues significant to the safety of the dam must be addressed. The first issue is the adequacy of the spillway. Based on The State Engineer's Office (SEO) hydrologic calculations, the dam was restricted on July 7, 1978 due to inadequate spillway capacity. A recently completed hydrologic study has been approved by the State Engineer's Office. The essence of this study is that the spillway must pass the 1 DO-year inflow flood safely. The study indicated that the spillway lacked approximately 0.4 feet of required freeboard to allow the spillway to function properly during the 1 DO-year flood event. This issue must be addressed to assure the safety of the Dam and to allow the SEO to consider lifting the restriction on the storage capacity of the reservoir. The second issue is the structural integrity of the outlet works. The service life expected of the steel pipe in the outlet works and gate shaft is considered to be 50-years. The outlet is approaching 1 DO-years of time in service. The outlet works needs a thorough internal investigation and rehabilitation or replacement. Alternatives to address these problems and to improve the safety of the dam have been given consideration and are described as follows: 4