EPA to Rule on Imperial County’s Dusty Air Quality

Wafting dust forms a gauzy veil over Imperial County, a broad, sun-baked floor of tilled fields and open desert that has some of the nation’s worst levels of airborne particles.

But after years of trying, the county may be on the verge of convincing the federal government that it is not to blame for the disturbing levels of dust and soot.

The chief culprit, county officials argue, is Mexicali, a fast-growing Mexican city of 760,000 that is thought responsible for tons of dust that drifts daily into the air basin shared with Imperial County on the U.S. side of the border.

The U.S. Environmental Protection Agency will rule in coming weeks on whether Imperial County violates federal standards for airborne particles--a finding that could spell new controls on airborne dust in a region dependent on dirt-churning activities, such as farming, but also troubled by asthma and other respiratory problems.

The decision will be closely watched by farmers who fear potentially costly new regulations and by environmentalists skeptical of the claim that the county would have clean air if not for wind-carried dust from Mexico.

The action comes in response to a lawsuit filed last year by the Sierra Club seeking to force the EPA to rule in 15 communities nationwide that were found not to meet U.S. air-quality standards.

Under the Clean Air Act of 1990, Imperial County was given until the end of 1994 to prove to the EPA that it would have been in compliance with the law if not for drifting Mexican dust, but the federal agency failed to act. The EPA could have found Imperial County a “serious” violator, but instead left it in a category requiring less stringent pollution controls.

In July, the EPA agreed to settle the Sierra Club lawsuit by vowing to determine by Sept. 30 whether the county should be held responsible for the airborne dust, which amounts to nearly 250 tons a day and is the worst in California when averaged over a year.

“It’s clear that the levels do exceed our standards. It’s spread throughout the year, it’s not just one time of year,” said Amy Zimpfer, deputy director of the air division for the EPA’s Pacific region office in San Francisco. “This is a problem that needs to be addressed. It’s complicated by the percentage that comes across the border.”

The EPA is leaning toward accepting the county’s long-held contention that it effectively controls home-grown dust and soot. The agency is awaiting written comments from the public before ruling. The comment period closes Sept. 10.

The EPA decision carries high stakes for local farms, which cover 581,000 acres--about a fifth of the county--and pump nearly $1 billion yearly into an otherwise wobbly local economy. A finding that the county does not comply with U.S. air standards could force farmers to take new steps to reduce dust, such as by paving some dirt roads, restricting travel on them or, some fear, by curbing tilling.

‘Fugitive Dust’ Is Biggest Problem

The biggest problem north of the border is “fugitive dust” that billows primarily from fields and from the more than 5,400 miles of unpaved roads countywide. Most of the roads serve farms or the huge network of irrigation channels that have transformed a big chunk of desert into a verdant farm belt.

“If we get bumped up to the next category of non-attainment, that triggers a whole bunch of more restrictive controls that have to be done,” said Stephen L. Birdsall, agriculture commissioner and air-pollution control officer for the county. “There’s a potential to try to implement controls on agricultural operations, which could be devastating to our already faltering agricultural economy.”

The county has spent more than $500,000 to make its latest case. Consultants examined dust measurements, wind data and other readings from the two years preceding the 1994 deadline, concluding that the Mexican emissions were a factor during most of the nine days on which air standards were violated. A previous study estimated that Mexico was the source of 60% of dust measured in Calexico, which sits on the U.S. side of the border about 120 miles east of San Diego.

But the Sierra Club’s attorneys said they will likely oppose such an EPA finding of compliance, arguing that high dust levels cannot be attributed solely to Mexico.

“We are skeptical that even without emissions from Mexico the area would have clean air,” said David Baron, an attorney at Earthjustice Legal Defense Fund, a Washington, D.C.-based group.

Baron said a dust reading at the border in Calexico in 1999 was 10 times higher than the federal standard. “Even if three-quarters of that high reading were from Mexico, they’d still be in violation,” Baron said. “It’s not appropriate for the EPA to just let them off the hook by saying it’s all from Mexico.”

The contaminants are blamed for aggravating asthma and other breathing problems--a big concern. Children 15 and younger were taken to Imperial County hospital emergency rooms for asthma attacks at four times the rate in San Diego County, according to 1998 figures provided by Imperial County’s health department. Asthma-attack admissions also were higher for adults.

County officials and farm advocates point out that dust is inevitable in a region that is, after all, a broad desert. Agriculture officials say growers already farm in ways that keep dust at a minimum, such as flooding alfalfa fields to irrigate and planting year-round crops, thus cutting fallow acreage that is a source of windblown dirt.

Stricter Guidelines for Airborne Dust

The county is writing stricter guidelines for limiting airborne dust, including requiring farmers to more quickly clean up mud tracked by farm vehicles onto paved roads and ordering that large parking lots be paved. The plan, which requires EPA approval, could help move the county from its status as a “moderate” violator to being compliant.

The county also plans to urge federal agencies to cut dust along primitive roads in the desert wilderness. One problem is the U.S. Border Patrol’s practice of dragging a row of tires to smooth unpaved border roads so agents can more easily spot the footprints of undocumented immigrants. Zimpfer said the EPA is working with the Border Patrol to find ways to control the dust.

U.S. and Mexican officials have expanded efforts to monitor airborne dust to get better data on how much is produced around Mexicali, where many roads and streets remain unpaved.

Imperial County officials say they are more worried about emissions from two power plants being built in Mexicali and a third one that is planned. They have lobbied the utilities to use the strictest pollution controls available.