DETROIT (AP) — A group of U.S. senators is urging the U.S. Army Corps of Engineers not to fall behind on a study of how a key waterway chokepoint could be used to keep Asian carp from reaching the Great Lakes.

The corps is considering ways to strengthen defenses against the invasive carp at the Brandon Road Lock and Dam near Joliet, Illinois. An August report estimated the upgrades could cost $275 million and take until 2025 to finish.

The corps recently announced it was extending a public comment period and scheduling another public hearing in New Orleans.

Senators from Michigan, Ohio and Wisconsin complained about the delay in letters to the corps released Monday.

Sens. Debbie Stabenow and Gary Peters of Michigan said the corps’ time frame was “unacceptable.”