Opponents of a Red River diversion channel around Fargo, N.D., and Moorhead, Minn., are asking a judge to halt the project until supporters receive permits from Minnesota to build an upstream dam.
The motion filed Wednesday in federal court says plans by local, state and federal sponsors to move forward on the $2.1 billion project without the permits violate federal and state laws.
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Fargo-Moorhead Diversion Authority attorney Robert Cattanach said he plans to file his response on Thursday.
The Minnesota Department of Natural Resources said in October that it would not grant a permit for the dam because the agency believes the idea is flawed and there are better options for flood control.
Diversion supporters say the DNR's decision should not stop work from starting in North Dakota.