TRAVERSE CITY (AP) — Fortifying an Illinois waterway to prevent invasive carp from using it as a path to Lake Michigan could cost nearly three times as much as federal planners previously thought, according to an updated report.

The U.S. Army Corps of Engineers this week released a final strategy plan for upgrading the Brandon Road Lock and Dam near Joliet, Illinois, which experts consider a good location to block upstream movement of Asian carp that have infested the Mississippi and Illinois rivers.

Scientists warn that if the voracious carp become established in the Great Lakes, they could out-compete native species and harm the region’s $7 billion fishing industry.

The Corps’ new plan is similar to a draft from August 2017, but the estimated price tag has jumped from $275 million to nearly $778 million.

“Basically during the past year, some additional engineering and design work changed the scope to bring it up to that current cost,” Allen Marshall, spokesman for the Corps’ district office in Rock Island, Illinois, said Wednesday.

The biggest increase is for building an “engineered channel” at Brandon Road. The lock-and-dam complex is on the Des Plaines River, which forms part of the waterway link between Lake Michigan and the Illinois River, a tributary of the Mississippi.

Under the plan, the channel would contain devices including an electric barrier, noisemakers and an air bubble curtain to deter fish from swimming upstream and remove those that don’t turn back. The adjacent lock would be retooled to flush away unwanted species floating on the water.

The draft had proposed using water jets to dislodge fish that might be stunned or caught in gaps between barges. But the new version says a better method would be generating a continuous, dense curtain of air bubbles in the channel.

The Army Corps is accepting public comments through Dec. 24 and expects to submit the plan to Congress in February.