The U.S. Coast Guard has established a safety buffer zone around grain ships calling on Portland and Vancouver as a potential lockout of longshore workers looms.

Owners of Northwest grain terminals, which could impose the lockout at any time, have brought in three towboats with non-union crews on standby, a law enforcement official disclosed Friday. The official spoke on condition of anonymity because of a gag order issued by federal mediators who supervised last-ditch contract talks that ended Wednesday between the owners and the longshore union.

More

Coast Guard officials have also recommended "on-water picket areas" to local leaders of the

, in case of protests on the Columbia and Willamette rivers.

The steps by the Coast Guard and the employers reenforce signs that a lockout or strike is imminent at six of the Northwest terminals that handle a quarter of U.S. grain exports. Mediators say only that the union and the employers are considering options after the talks that continued after Sept. 30, when a longshore labor contract expired.

Coast Guard Capt. Bruce Jones, commanding officer for Oregon and southern Washington, issued safety rules posted Friday in preparation for publication in the Federal Register.

"There is the potential for injury and damage to both protestors and shipping due to the labor dispute," Jones wrote. "The Coast Guard believes that a safety zone is needed ... to ensure that protestors and other river users are not injured by deep-draft vessels ...."

The temporary zone, already in effect, bars people and boats from an area 500 yards ahead of grain vessels and 200 yards beside and behind the big ships. Jones has also recommended safe but prominent areas for any protestors in boats near Columbia Grain Inc. and Temco terminals in Portland and United Grain Corp.'s elevator in Vancouver.

The companies have towboats standing by to replace local boats that maneuver vessels to and from terminal docks, according to the law enforcement official. Towboats that usually handle the work, and that haul grain barges, are operated by members of unions that plan to honor any longshore picket lines.

Towboats that stood by in Longview, Wash., earlier this year, at a terminal where labor protests turned violent, came from as far as the Gulf Coast, via the Panama Canal.

-- Richard Read, twitter: ReadOregonian.