ASCE 1994 Annual Convention & Exposition

The Miami Conservancy District built five flood control dams after the catastrophic flood of 1913 in Dayton, Ohio. Lockington Dam was one of these five hydraulic fill structures. The Ohio State Department of Natural Resources (ODNR) issued new regulations in 1981 requiring that design flood for class I dams be considered equal to the Probable Maximum Flood (PMF). Flood routing studies performed for the PMF calculated inflow indicated that the reservoir rose to the crest of the dam. Therefore, the existing dam core required extending to the crest level to maintain dam safety. The extension was constructed using a deep soil mix soil-cement cutoff wall. This paper will describe the cutoff wall from conceptual design through to construction, including alternates considered, construction methods and data obtained, both prior to and during construction. While Deep Soil Mixing (DSM) has been used on contaminated sites as a method of containment and for dam foundations to decrease the risk of liquefaction, Lockington Dam represents one of the first applications as a conventional cutoff on an existing dam. Introduction The largest single project under construction in the United States in 1919 was the flood control works of the Miami Conservancy District. Started in 1918, the five flood control dams and 73 miles of levees which made up the project, would not be completed until 1921 (ENR, 1994). Work was initiated in response to ten major floods which had inundated Ohio’s Miami Valley at various times over the previous century, claiming more than 1,000 lives and causing more than $100 million in property damage. Historically, Project Manager, Geo-Con, Inc., 4075 Monroeville Boulevard, Monroeville, PA 15146 this project saw the first ever use of electrical draglines on a large construction contract. Power shovels excavated raw materials from the pits which were then mixed with water to form a slurry and pumped by dredge pipes to the dams. The water gradually drained and the dam rose in layers of impervious clay in the center, providing the waterproof core, with sand and gravel forming the dam shell. this use of hydraulic fill, while not a first, was one of the largest such applications ever recorded. One of the five structures, the twenty-one meter high Lockington Dam, is located on Loramic Creek, a tributary of the Great Miami River, north of Piqua, Ohio. The 1,950 meter long dam is founded on Cedarville limestone bedrock with a combined central low level outlet and emergency spillway (Figure 1). No permanent reservoir exists upstream of the dam as it is operated purely as a flood control project with storage only occurring when the upstream runoff exceeds the capacity of the outlet structure. Figure 1. Aerial View of Lockington Dam The central impervious core was built to about 4 meters below the dam crest which corresponded, at that time, to the maximum reservoir level for the Official Plan Flood (OPF).