GRAND RAPIDS, Mich. (WOOD) — The focus of the fight to protect the Great Lakes from invasive carp centers on the Brandon Road Lock and Dam — and rightfully so. The facility sits about 25 miles southwest of Chicago and serves as the key pinch point between the Mississippi River System and the Great Lakes Basin. It is such a pivotal point that the U.S. Army Corps of Engineers and state agencies are working on a billion-dollar project to shore up any potential weaknesses that could let the fish through.

But it’s not the only crossing point. In fact, the USACE has identified 18 places where invasive carp could theoretically cross into the Great Lakes.

According to Jeff Zuercher, the project management director for the USACE’s Chicago District, the Chicago Area Waterway System is the only permanent connection between the Mississippi River and the Great Lakes — connected through the Des Plaines River that runs through the Brandon Road Lock and Dam. But there are other potential pathways.

“We are mostly concerned with (the Brandon Road Lock and Dam) because that provides the easiest and most direct pathway between the two basins,” Zuercher told News 8. “The other 18 pathways are all intermittent or they would require several things to occur in order for a connection between the two basins to happen.”

The 18 theoretical pathways are spread across several states, from East Mud Lake in western New York to the Swan River in northern Minnesota. Wisconsin holds eight of them. There are also four in Ohio and three in Indiana.

Zuercher says several factors must come together to allow those points to connect.

“For example, there is a creek in Ohio that, if it flooded in the right way, it would connect the Ohio River to the Great Lakes,” he said.

While these connections aren’t probable, they are possible, and the USACE is taking action to prevent them from happening.

“In most cases we are talking about a very large flood, like a 100-year flood. … It would take that level of a flood in order for the basins to be connected,” Zuercher said. “And there are a lot of ifs in those other 18 locations in terms of when it would happen and what it would look like. Is it really deep enough to transport the invasive species between those two basins while that’s happening? We had to look at all of those factors and try and determine whether that actually warrants any concern.”

The USACE has already completed projects to shore up two of those 18 locations, including the one that was the highest concern: Eagle Marsh in Indiana.

“There are these marsh lands that flood. And when they do, they provide an easy connection between the two basins. There was a berm that was put in place to alleviate the possibility of that happening even in a 100-year flood,” he explained. “We actually had to scale it back slightly because when you build a levy or a berm like that, you can cause further damage by preventing water from going where it wants to go. … They couldn’t build it to the top height that they wanted to, so they put a fence in to prevent fish from crossing between the two basins.”

The second completed project is at the Erie Canal in Ohio. A nearby creek connects to the Ohio River, and if that creek overflowed, it would flow into the Erie Canal, which flows into Lake Erie.

While the Brandon Road Lock and Dam is a giant, billion-dollar behemoth, some of the actions are small and simple. Zuercher cited one flood plain that includes a pair of culverts that flow under I-80. To ensure fish couldn’t get through in the event of a major flood, they added grates to allow water to flow through and filter out any fish.

While the solutions may be simple, sometimes they are anything but for the USACE, as evidenced by the site project in the works right now on Killbuck Creek in Ohio.

“We had a farmer who was not interested in having berms built on his land. So, we were trying to acquire land. He built his own berm to prevent some flooding, but it wasn’t up to standards, and it wasn’t doing what we wanted to do for the entire length,” Zuercher said. “He is a farmer and he doesn’t want to lose a lot of his land to farm off of, which is understandable. We get that. So, we are working with them to come up with the best solution.”

The USACE is designing and completing the projects as they come, using funding from the Great Lakes Restoration Initiative, and tackling the ones that they view as the highest risk first.

Meanwhile, talks continue on the final plans for the Brandon Road project. The project is expected to cost more than $1.1 billion. Now, it is up to the USACE and state governments to figure out who will cover the costs.

“Rock Island District is working very diligently to negotiate with the state of Illinois to try and sign that project partnership agreement,” Zuercher said. “There has been some movement in the not-too-distant past, where they have come to some agreements on what they want to see in that project partnership agreement. So, they are really looking to move that forward.”

The designs for phase one are almost ready. Zuercher expects work to “really take off” once the financial deal is approved.