The U.S. Army Corps of Engineers for the first time has declared its preference for reopening a Minneapolis lock next spring until its federally mandated shutdown in June.

The reopening of the Upper St. Anthony Falls Lock after its annual winter hiatus is something that the barge industry has been pushing for since Congress mandated last summer that the lock close by next June 10 to deter invasive carp from migrating upstream.

The alternative is not reopening the lock at all when the barge shipping season resumes, usually in March. That's a course favored by the Minnesota Department of Natural Resources.

The corps' preference for reopening next spring comes in its environmental assessment of the pending closure, released Friday. The corps labels reopening the locks as its preferred plan; its assessment generally finds only minor differences in the impact of the two shutdown alternatives.

U.S. Rep. Collin Peterson, D-Minn., ranking member of the House Agriculture Committee, wrote to the corps favoring the later shutdown. It's also strongly favored by the Upper Mississippi Waterway Association, which represents barge companies and shippers.

The last vessel to go through the upper lock this fall was the 56-foot-long Becky Sue, a 37-year-old towboat that headed downriver on Nov. 15, according to the corps.

The corps is taking public comments on the assessment through Jan. 23. The mandated closing followed a lobbying effort by those who argued that an operating lock offers a route for the quick-breeding and fast-growing bighead and silver carp, which compete for plant and animal plankton with native organisms, to reach rivers and lakes important to the tourism industry.

The lock will be allowed to open after June 10 only during high-volume river flows, which the corps assessment said would make it hard for fish to fight the current. The assessment found no significant environmental impacts from the closing. It also found little chance that carp would make it past the Coon Rapids Dam if they made it through the upper locks.

The analysis did find likely economic fallout, with a loss of 84 corps and river industry jobs that would be partly offset by an estimated 57 new jobs to drive trucks to haul commodities that no longer will be taken by barge, according to an analysis done for the Metropolitan Council. That found that the cost of concrete could increase by 5 to 9 percent, and that fertilizer prices would rise by $2 per ton.

The corps said that the shutdown will mean no more public access to the visitor center overlooking the lock and adjacent dam, which includes displays. Fewer than 10 people per day, on average, took guided tours of the locks. However, other public agencies are discussing taking over visitor center functions.

Steve Brandt • 612-673-4438

Twitter: @brandtstrib