The city is working with state and federal agencies to determine the span of the proposed Christina Street Bridge.
The bridge is scheduled for replacement in the summer of 2019.
According to City Engineer Jonathan Zimmermann, the goal is to prevent localized flooding further downstream at the Washington Avenue span.
The federal agency is requesting 85 percent of the stream cross section for the bridge opening. He explained that by increasing the bridge opening cross section to 85 percent it may cause flooding issues at the Washington Avenue bridge, which is downstream from the Christina Street Bridge.
The current bridge opening is about 50 percent of the stream cross section and the proposed bridge is 70 percent of the stream’s cross section, he added.
“The Army Corps of Engineers has said we need to expand it more,” he told the personnel, finance and public works committee Tuesday night. “We have to maintain an 85 percent opening based on the cross section of the existing stream.”
Zimmermann will create a hydraulic model of the bridge to see how increasing the capacity will impact the Washington Avenue bridge. If it would cause localized flooding, as expected, the city will have to ask the Corps to allow a lower opening or hydraulic capacity.
Additionally, the city will have to work through the federal Land and Water Conservation Fund Acts 6(f) process. The National Park Service oversees impact analysis and mitigation projects for property protected under the Land and Water Conservation Fund Act.
Zimmermann said that because the city applied for federal funds in the mid-’70s, the parking lot on Christina Street by the tennis courts falls into a federally protected area.
The city has to get permission to move the roadway over and use some of the parking lot for the bridge project.
“The project has become a little more complicated than it was originally,” Zimmermann said. “We will be working with the Corps of Engineers and the Department of Natural Resources moving forward.”
The Corps also suggested demolishing the bridge and not replacing it, but Zimmermann said that option is not feasible.