ODNR: Mt. Gilead Dam Improvements

Mt. Gilead, Ohio


The Ohio Department of Natural Resources awarded Mosser Construction the dam improvement project at the Mt. Gilead Ohio State park. The project scope consisted of draining the parks 32-acre upper and lower lakes, demolishing the lower dam, and refinishing the upper dam face. The need for this project was due to a leaking lower dam that was originally built in 1930. The dam was determined by the state to be a class one high hazard structure. The replacement dam design is referred to as a labyrinth spillway which is the first of its kind in the state of Ohio. 

Per spec, Mosser was only able to drop the water level one foot per day while performing a controlled demolition of the dam. While draining the lake, Mosser worked with the Division of Wildlife to relocate the thousands of fish from the lake to a downstream creek located a few hundred yards from the dam.

The new dam is made up of more than 3,200 cy of concrete, 400,000 lbs of resteel, and 7,000 of waterstop. Over 73,000 cy of dirt was placed back into the embankment of the dam in eight inch lifts. Additionally, 4,200 tons of #8 stone and over 12,000 tons of sand were installed to provide proper drainage for the embankment chimney drain as well.  

Some of the obstacles that were faced during the course of construction included:

  • Removal of the original lake bed sediment within the construction limits that totaled over 17,000 cy of muck; 
  • The installation of the proposed soil anchors that the ODNR decided to change and go the route of anchoring the tendons into rock; 
  • Numerous flood conditions led to an extended completion date; 
  • Poor subgrade conditions that made haul roads and laydown areas challenging.