Backers of California's proposed high-speed rail system frequently tout the long-term air-quality benefits of getting people out of cars and planes and onto electric-powered trains.
But any reductions in air pollution won't start for at least a decade, when the trains would start carrying passengers between Merced and the Los Angeles Basin. Meanwhile, building the system in the San Joaquin Valley is expected to pump tons of dust, greenhouse gases and other pollutants into the air. International experts warn it could take years for the benefits of train ridership to make up for the harm caused during construction.
The California High-Speed Rail Authority expects to pay millions of dollars to make up for construction emissions in the Valley.
"Building in an emissions-free manner is not possible, of course," said Lisa Marie Burcar, a spokeswoman for the rail authority. "But offsetting those emissions to result in the same outcome is."
In its environmental impact report for the Merced-to-Fresno section one of the first portions of the statewide train system planned to be built the rail authority allows that "construction ... has the potential to cause temporary and significant localized air quality impacts" on the Valley's air between 2013 and 2022.
Work would include demolition, land grading, earthmoving, pouring concrete, building stations and laying tracks.
All that work, and the equipment used to do it, are expected to produce reactive organic compounds and nitrogen oxides two chemicals that mix in the atmosphere to create ozone as well as dust and carbon dioxide and other greenhouse gases.
The pollution anticipated from high-speed rail construction would be a small fraction of emissions already generated in the region. But in the Valley, already struggling to meet state and federal air-quality standards, any extra pollution is a major worry, said David Barber, of the San Joaquin Valley Air Pollution Control District.
Construction pollution not only has "dire consequences" for healthy air, but it threatens the San Joaquin Valley's ability to comply with federal mandates under the federal Clean Air Act, Barber told rail-authority board members this month in Fresno.
The Valley faces several deadlines over the next 11 years to meet standards for ozone and fine particles, called PM-2.5. PM-2.5 is made up of dust and other particles that are 2.5 microns in size or smaller. A human hair, by comparison, is between 50 and 70 microns in thickness.
Barber said failure to reach those standards will have "dramatic and potentially devastating consequences in the form of federal sanctions on the Valley." Penalties could include severe limits on industrial development and the loss of billions of dollars in federal highway funds.
The rail authority outlined steps it will take to limit air pollution. Contractors will have to use the cleanest possible machinery; and trucks, for example, will have to be newer models. Temporary concrete plants will have to be at least 1,000 feet from daycare centers, schools, hospitals, senior-care centers, homes or parks.
Even so, the authority admits emissions would be significant, so it promises to give the Valley air district money to reduce emissions from other sources to offset rail building pollution.
"The air district strongly believes this is the right approach, given the seriousness of air-quality concerns in the Central Valley," Barber told the authority's board.
Burcar said the authority will include similar requirements in the upcoming environmental report for the Fresno-Bakersfield section. In all, the agency estimates it will spend $10 million to $20 million to counter pollution.
Some of that money could go to the air district's incentive programs, which include helping homeowners replace gas-powered lawnmowers with low-cost electric ones, and helping businesses, farmers and industries replace or upgrade trucks and machinery, said Samir Sheihk, the district's director of strategies and incentives.
"Those programs are always oversubscribed there's always more demand than we have money for," Sheikh said.
In Spain, where high-speed trains have been running for 20 years, some experts said it can take decades for high-speed rail to make up for environmental damage from construction.
High-speed trains "might be green, [but] don't take it for granted," said Germà Bel, a professor of political economics at the University of Barcelona and a former deputy in the Spanish parliament. "Because there is a lot of environmental damage while the construction is on.
"The story does not begin the day that high-speed lines begin service: The story with the environment begins the day on which the first work began."
Disregarding the construction effects "gives the environmental effects of high-speed rail a kind of mythological value," he said.
To make up for construction impacts, a high-speed train line must attract enough people from cars and planes.
"If you have a new line with huge demand, it might be environmentally friendly at a huge cost," Bel said. "If you have medium use of such a line, you take about 30 years to recover the environmental damage done because of construction. If the usage is low, you actually have a very bad effect on the environment.
"The point with high-speed rail is whether you get dozens of millions of trips [per year]. It's very demanding, and it's not the case with any single line in Spain."
Rail officials in California say they'll do such a good job of offsetting pollution while the system is built, there will be nothing to "make up or pay back" by the time the trains would start carrying passengers in 2022.
"Long-term, therefore, the project will improve air quality in the Central Valley."