Day and night, trains crisscross California pulling long strings of tanker cars carrying volatile gas, chemicals and crude oil.

These shipments have long played a key role in powering the state economy, providing materials for medical supplies, computers and fertilizers, as well as fuels for vehicle fleets. But they also pose the risk of catastrophic spills.

Jolted by a series of oil train explosions nationally, including one in Oregon last month, the state this summer has drawn up a list of what it says are the 25 most hazardous materials shipped on rail in California. It plans to impose a new $45 fee later this year on every rail car carrying one of those materials. The money will be used to ramp up the state’s emergency spill and fire response capabilities.

The state Legislature ordered the fee program after a Governor’s Office of Emergency Services analysis that found significant gaps in California’s ability to deal with spills, especially in rural and remote areas.

The fee plan is disputed by the state’s major railroad companies who say they think it’s illegal.

The top 25 list includes materials that are dangerous to humans either by direct contact or because they are highly flammable. They include ammonia, chlorine, propane, butane, fertilizers, acids, petroleum gases and oils.

“When one of these trains derails, it puts lives, property and the economy at risk,” said State Fire and Rescue Chief Kim Zagaris. “And right now, we don’t have surge capacity to deal with a major spill.”

Because of the secrecy shrouding shipments of hazardous materials, it’s hard to know how big a risk they pose. State safety officials and private shippers refuse to disclose the amount, frequency, routes or timing of hazardous material shipments, citing federal safety regulations and state health and safety law restrictions, as well as concerns about terrorist or other criminal acts.

Even local fire departments typically don’t know in detail what materials are coming through, although they can get some after-the-fact information about hazardous materials that have traveled through their areas, if they request it.

Hazardous materials in train tanker cars can be identified, however, at least generically, by the identification numbers on diamond-shaped placards displayed on the sides of cars.

Trains observed by The Sacramento Bee in recent weeks in downtown and midtown Sacramento carried numerous hazardous materials, including liquefied petroleum gas, sulfuric acid and liquids designated hazardous at temperatures above 212 degrees Fahrenheit. A few trains were carrying either cleaning fluid, weed killing fluid, diesel fuel or other flammable liquids. Others were listed as holding unspecified petroleum distillates or petroleum products.

Shippers also have acknowledged transporting Bakken crude oil and Canadian tar sand oil through Sacramento neighborhoods.

California’s planned $45 per-train-car fee will pay for the creation of 12 specially trained hazmat teams to be spread out geographically near “gap” areas where there is a lack of expertise and equipment to deal with major spills, state Office of Emergency Services officials said.

Most will be in the lower Central Valley, on the coast and in Southern California. One hazmat team will be located in Yuba City, not far from the Feather River Canyon, where trains carrying hazardous materials travel the steep mountainside above a river that provides drinking water to urban areas as well as water for Central Valley farms.

Many larger fire departments already have specially trained hazmat teams. There are four in the Sacramento area, one each stationed in Roseville, Natomas, Carmichael and south Sacramento.

Railroad companies contend the proposed fee is illegal under federal law, which prohibits states from putting any constraints on interstate commerce via rail. Under the state plan, the companies that own the hazardous materials must pay the fee, but railroad companies must collect the fee from them and convey it to the state.

The Union Pacific and BNSF – the two main hazardous materials shippers in California – sent letters to the state last month saying the fee interferes in the railroads’ business dealings with their shipper customers and demanding the state desist.

“These emergency regulations violate federal law; therefore, (California) must abandon the process of adoption,” UP assistant vice president Phillip Christensen wrote. “No state can regulate the rates or charges a railroad collects from its customers. This kind of ‘economic regulation’ is categorically prohibited” by federal interstate commerce law.

UP officials declined to be interviewed for the story. The company sent The Bee an email saying that safety is the railroad’s primary focus when transporting hazardous materials. The email did not say whether the railroad might sue the state to stop the fee.

The American Chemistry Council, which represents hazmat shippers, said its members are concerned that California’s actions could lead to dozens of states imposing rail fees, creating what chemistry council spokesman Scott Jensen calls a confusing “patchwork” of regulations without certainty about how the money would be spent, beyond creation of some hazmat teams.

Dow Chemical regulatory affairs official Dale Backlund said his company would like the state to meet more with the industry to talk about the best approach to conducting emergency response training. “Can we slow down the train and think through the implications of this?” he said.

NO STATE CAN REGULATE THE RATES OR CHARGES A RAILROAD COLLECTS FROM ITS CUSTOMERS. Union Pacific’s Phillip Christensen

Despite such complaints, state Office of Emergency Services officials say they plan to impose the fee later this year, although they expect to continue talking with the railroad companies and shippers about fine-tuning the fee program.

“It is law now,” Zagaris said. “We are following the law.”

The state plans to collect up to $10 million annually from hazardous materials shippers, to be placed in the Regional Railroad Accident Preparedness and Immediate Response Fund. The fund will be capped at $20 million.

Although hazardous materials also are shipped on highways, the fee is being applied only to rail shipments, mainly because the threat of a major spill incident is greater on rail, Zagaris said.

“It is a bigger item for us to deal with, takes a larger response, more surge capacity and it puts the public and environment at more risk,” he said. “That’s not to say, at some point, (the state) won’t come back and try to ID things transported on the road.”

Railroads and hazardous materials shippers argue that the risks of oil and hazmat spills are being overplayed by anti-oil advocates and some community leaders. Very few trains derail, they note, and most hazardous material spills are small. A crude oil train crash in a Canadian town three years ago, though, unleashed a firestorm that killed 47 people, some in their sleep.

A Bee review of the state’s rail spill database found that hundreds of hazardous material spills occur annually. The database represents an incomplete listing, based only on initial reports, not on post-response findings. But it does offer a glimpse at the many types of hazardous materials that run on local rails.

Most spills are small and many happen in railyards around the state, such as the Union Pacific yard in Roseville. There were about 50 reported spills in the Roseville yard in 2015. The largest local spill that year, as initially reported, was 300 gallons of diesel fuel that leaked due to an improperly closed locomotive fuel filter cap. Other small spills around the Roseville yard in 2015 involved butane, oil, liquid petroleum gas, anhydrous ammonia, picoline and sodium sulfide.

Larger spills, though rare, can be devastating to wildlife and rural economies. The most notorious modern rail-related toxic spill in California occurred 25 years ago when a train derailed and spilled 19,000 gallons of the pesticide metam sodium into the Sacramento River near Dunsmuir, killing aquatic life on a 40-mile stretch of the river for years. Rail safety improvements have since been made at a tight rail curve at that spill site.

In Sacramento, several dozen trains cross daily in downtown Sacramento on two main freight lines. A Bee review of trains on those tracks recently found that more than half of the trains included at least a few cars carrying hazardous materials.

One freight line is a north-south route that comes through the region between Yuba City and Stockton and passes through midtown Sacramento between 19th and 20th streets. The other is an east-west route that runs through Roseville and on a berm above downtown Sacramento, through the downtown railyard and through Davis, adjacent to downtown and the university campus.

Sacramento City Fire Department hazardous materials coordinator Jerry Apodaca said the Sacramento region, with four hazmat teams, is well positioned to deal with a potential spill. But he and other local fire officials say they remain on alert, not knowing on any given day what shipments are coming through or when.

“We don’t know what’s in those cars until we get there,” he said.