Under federal law, employers can take that step when parties reach a bargaining impasse. The last contract expired Sept. 30 and negotiations have stalled.
"This is not a lock out," the employers said in a statement. "The companies informed the union that ILWU members are welcome to come to work under the new terms and conditions of employment."
Wednesday's action puts the International Longshore and Warehouse Union on the spot. Its options include accepting the offer, calling for a strike or seeking further bargaining while working under the new terms.
The union is reviewing the owners' letter, ILWU spokeswoman Jennifer Sargent said in a statement. For now, employees "intend to continue working despite the substandard provisions of the employer's last offer," she said.
The owners submitted their final offer Nov. 16 and it was rejected by union membership 94 percent to 6 percent. The union, contending talks were not at an impasse, offered additional dates.
Though it's unknown for how long the longshoremen will work under terms they oppose, each day without a strike or lockout is good for farmers and their customers in Asia. More than a quarter of all U.S. grain exports and nearly half of U.S. wheat exports move through grain terminals on the Willamette River and Puget Sound.
The dispute initially involved six of those terminals that operate under a single collective bargaining agreement with the ILWU:
Japan-based Marubeni Corp. (Columbia Grain in Portland).
Japan-based Mitsui & Co. (United Grain in Vancouver, Wash.).
Amsterdam-based Louis Dreyfus Commodities (grain elevators in Seattle and Portland).
United States-based Cargill and CHS Inc. (elevators in Tacoma and Portland).
But one of the four owners, the Cargill and CHS joint venture, has broken away from the consortium and is believed to be negotiating separately with the union. It was not included in the letter the other owners emailed Wednesday to Leal Sundet, an ILWU coast committeeman, informing him of their decision to implement the terms of the last offer.
Both sides have said workplace rules and management rights have been the sticking point during talks.
Northwest grain terminals based in the Washington cities of Longview and Kalama operate under separate agreements with the ILWU. Terminals operators in Portland, Seattle and Vancouver say they are at a competitive disadvantage because the longshoremen at their facilities have more favorable rules than those in Kalama and Longview.
The owners want to eliminate perks such as paying workers a half-hour's wages for working as little as six minutes. They also want greater discretion in hiring and staffing decisions and, according to a statement, "the ability to hold the union to its agreement not to engage in work stoppages."