DENVER (KDVR) — The United Food and Commercial Workers union strike in Colorado King Soopers grocery stores could take a while.

The union rejected King Soopers’ final contract negotiation Tuesday and began its strike on Wednesday. King Soopers’ proposal, referred to as the “Last, Best and Final Offer” submitted Tuesday morning put an investment of $170 million over the next three years including wage investments plus ratification bonuses for all associates on the table. In response, the union called several of the offer’s features even worse than the original offer.

Historically, UFCW strikes last about 33 days on average, according to work stoppage records from the U.S. Bureau of Labor Statistics. Those are strikes with over 1,000 workers, but the UFCW Local 7 said it has at least 10,000 workers that will participate in the strike.

The last time the union’s workers went on strike in Denver, it lasted 19 days. In 2000, over 1,100 workers went on strike at Kaiser Permanente. Before that, 12,000 UFCW workers at King Soopers and Safeway stores in the Denver area went on strike for 43 days.

UFCW strikes range from a weekend to several months. UFCW workers are planning to strike for three weeks, the union said.

The shortest – a Shaw’s Supermarkets Inc. strike in 1997 – lasted only two days. The longest strike of Albertsons, Ralphs, and Vons Markets workers in 2003-2004 lasted 140 days.