Congress appears poised to back President Joe Biden in thwarting a potential holiday rail strike that could cost the U.S. economy $2 billion per day. But the deadline on impacts of a looming strike is barreling down the stretch quicker than some may realize.

“While the actual deadline of the railroads being shut down is the 8th [of December], our real deadline is sooner than that,” Senate Majority Leader Chuck Schumer, D-N.Y., said.

Workers are set to strike starting Dec. 9 if a deal between unions and railroads is not reached, though Congress may force a compromise to avert a costly shutdown.

“Congress, I think, has to act to prevent it,” Biden said. “It’s not an easy call, but I think we have to do it. The economy’s at risk.”

But while the absence of a contract would have workers walking off next Friday, the impacts of the uncertainty begin one week prior, meaning for some industries, the strike effectively starts this weekend.

According to federal safety measures, railroad carriers begin prepping for a strike seven days before the date, prioritizing securing and moving hazardous materials down the line.

The Fertilizer Institute said its deadline is five days before a strike, or Dec. 4, “when ammonia and other fertilizers and inputs will stop moving on the rails.” Chemicals cease to be transported 96 hours before a strike date because they can’t be left unattended en route in case workers go off the job. This practice is particularly impactful for the agricultural industry, as 60% of all U.S. fertilizer moves via rail, according to The Fertilizer Institute.

Critical drinking water and wastewater systems are also at risk, as chlorine would be a part of the early stoppage, threatening water services across the nation.

The American Chemistry Council says $2.8 billion in chemical cargo is moved weekly on the rails. According to an economic analysis by the council, a month-long strike would pull nearly $160 billion out of the economy, while reaching a deal the week of the strike will still have ripple effects throughout the country.