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OHIO STATE EDITION
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July 1 2017
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Vol. XVIIII • No. 13
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“The Nation’s Best Read Construction Newspaper… Founded in 1957.” Your Ohio Connection: Ed Bryden, Strongsville, OH • 1-800-810-7640
ODNR Replaces Aging Mt. Gilead Dam in Morrow County By Irwin Rapoport CEG CORRESPONDENT
As part of its current $88.5 million statewide capital improvements spending plan, the Ohio Department of Natural Resources (ODNR) is replacing the dam and spillway at Mt. Gilead State Park in Morrow County at a cost of $7.8 million. The dam was built in 1930. Mosser Construction Inc. secured the contract to rebuild the dam and complete the dam infrastructure improvements at Mt. Gilead Lake, which is scheduled for completion this fall. The upper and lower lakes were drained last fall, followed by excavation and concrete construction. The previous Lower Dam, near the Village of Mount Gilead, had a maximum height of 20 ft. and a 90-ft. long concrete ogee spillway that discharged water into Sam’s Creek, which ultimately discharges into Whetstone Creek. The new dam features a concrete labyrinth spillway design that may appear to look like a large accordion, but is a unique design for Ohio dams. A similar labyrinth spillway design is also being utilized by ODNR in current dam improvement projects at Lake Loramie and Indian Lake State Parks. A replacement dam was needed to address serious issues and the Lower Dam was rated as a Class I high-hazard potential structure. “The deficiencies include insufficient storage-discharge capacity and seepage,” according to the project website. “There are additional concerns regarding the instability of the severely deteriorated concrete spillway and the entire
As part of its current $88.5 million statewide capital improvements spending plan, the Ohio Department of Natural Resources (ODNR) is replacing the dam and spillway at Mt. Gilead State Park in Morrow County at a cost of $7.8 million.
dam embankment, along with concerns about the presence of trees and brush on the dam. ODNR previously contracted with Jobes & Henderson and S&ME to provide investigations and preliminary design alternatives. These investigations of the dam structure revealed the concrete spillway is deteriorated and has a very low safety level.” “The project not only allows us to make needed dam improvements at Mt. Gilead,” said John Wisse, an ODNR spokesman of the project, “but also gives us an
opportunity for complete lake rehabilitation leading to improved recreational opportunities such as sport fishing.” According to Brian Afek, civil engineer of Michael Baker International, the firm that designed the new dam, the existing dam was unable to safely pass the design storm event and was not in compliance with current Ohio dam safety regulations. “The labyrinth spillway design is the first of its kind at an Ohio public park,” said Afek. “The design provides a smaller concrete
footprint and allows for outgoing flows to be controlled by the spillway geometry. For this project, a design requirement was to match current outgoing flows of the existing ogee spillway up to the 100year storm event and to pass the probable maximum flood (PMF) event through the spillway without overtopping the embankment. “This was accomplished by modeling the flows through the new spillway and performing design adjustments as needed,” he said. “The principal spillway crest elevation will be raised to eleva-
tion 1106.0 [raised 2.5 ft. compared to existing spillway crest] to provide for a higher normal pool. The increase in normal pool depth will not only increase the life of the lake, but will also allow for more recreation activities [current depth of lake is shallow due to siltation over the years].” The entire existing earthen dam was demolished and is being rebuilt utilizing modern methods of construction and design. “The embankment will feature drains, flatter slopes, and soils that see DAM page 6