# ST. MARYS DAM SPILLWAY REPLACEMENT — OHIO DEPARTMENT OF NATURAL RESOURCES

- **Sector:** Flood Control Systems
- **Client:** Ohio Department of Natural Resources
- **Location:** Celina, OH
- **State:** Ohio
- **Status:** complete

## By the Numbers

- 7,000 CY Mass Concrete
- 750 FT Sheet Pile Cofferdam
- 55K CY Silt and Sediment Removal
- 25K CY Clay Embankment Numerous Operations from Floating Barges

## Challenge

Replace an aging spillway with a massive gravity dam within one of Ohio’s largest and most heavily silted water bodies while maintaining lake-level control and flood protection throughout construction. Manage extensive sediment removal, cofferdam construction in open water, and complex mass-concrete placement under challenging hydraulic and environmental conditions.

## Solution

ESW implemented a comprehensive in-water construction strategy that included extensive sediment removal, construction of a 750-foot sheet pile cofferdam installed from a floating barge, and installation of a temporary spillway to maintain lake-level control throughout construction. By safely isolating the work area and executing the complex mass-concrete dam construction in phases, ESW successfully replaced the failing spillway and delivered a long-term flood-control solution for Grand Lake St. Marys.

## Project Scope

E.S. Wagner served as the prime contractor for the Ohio Department of Natural Resources’ Grand Lake St. Marys Spillway Replacement project, designed to address chronic flooding and replace a deteriorating spillway structure. The project included construction of a new 160-foot horseshoe-shaped concrete gravity dam extending into Ohio’s largest manmade lake, along with an 80-foot bridge supporting the perimeter roadway. Construction required removal of 55,000 cubic yards of silt and sediment, placement of 25,000 cubic yards of clay embankment, and excavation of a deep concrete keyway to anchor the dam foundation. The dam utilized 7,000 cubic yards of mass concrete and was constructed within a cofferdam formed by a 750-foot steel sheet pile wall installed from barges and stabilized with 20,000 tons of stone. A temporary spillway consisting of two 60-inch pipes was maintained throughout construction to provide emergency lake overflow capacity. The new structure improved flow management and reduced chronic flooding.