Overview
Lake Vermilion Dam is a high-hazard, water supply dam, owned and operated by Aqua Illinois. Built-in 1925, the dam consists of an earth embankment with a concrete core wall, a gated concrete spillway section with ten radial gates, a non-overflow concrete section, and an upper-level trash gate. Serious gate deficiencies, including fractures in the gate anchors and pervasive section loss and corrosion on the skin plate and secondary gate members, were noted during routine dam safety inspection and evaluation. Replacement of the gates was recommended by Aqua’s consultant including a prioritized replacement sequence.

Scope of Work
The Ballard-Traylor Joint Venture (comprised of Ballard Marine Construction and Traylor Bros., Inc.) was subsequently contracted to replace the ten tainter gates and replace and install a new dam bridge deck. During the Early Contractor Involvement phase, Ballard worked alongside Aqua Illinois and the designer to collaborate on the design and construction sequencing. Ballard was able to provide all the means and methods to perform the work along with cost details for each phase. Ballard provided solutions during the construction sequencing that planned to limit the impact on the public and surrounding homeowners.

Innovative Solutions
The main challenge associated with this project was dam safety while rehabilitating the aging infrastructure. While removing the bridge deck, the dam pier heads were vulnerable to seismic shifting or alignment issues. To counter the issue, the team installed forty-ton ballast blocks between each pier head on the upstream side of the dam. Alignment issues were also a concern as the gates share trunnions, leaving little alignment tolerance. Additional challenges included public impact, environmental control in dealing with potable water, and weather constraints.

Results
The team replaced all spillway gates, installed new hoist and lifting cables, replaced and installed a new remote-operated skate system, replaced a pre-existing 250-foot bridge decking, and removed and installed a pre-existing trash gate. As a result of the trash gate replacement, new stop guides, and fresh concrete were installed in the corresponding areas.

The team partnership between Aqua Illinois, Schnabel Engineering, and the Ballard Traylor Joint Venture was extremely important to the success of this project. The team was consistent in holding weekly progress calls throughout the design phase and through construction to ensure that each stakeholder involved was keeping critical path items moving forward. It was this collective effort that made the success of such a quickly-paced project possible in the face of continued adversity.