Only one of California's 58 counties, Lake County, is in attainment of the standard. Three counties are unclassified, and the other 54 counties, including Imperial, are in non-attainment.
The PM10 standard is 150 micrograms of particle matter per cubic meter. According to the EPA, the particles are small enough to be inhaled into the lungs.
The Sierra Club's legal arm, Earthjustice, filed the lawsuit to force the EPA to move Imperial County from a designation of moderate to serious non-attainment of the PM10 standard.
The EPA would then have had to impose costly control measures on local farmers and businesses to reduce particle pollution, county officials said.
Earthjustice documents state the county had been in moderate violation of the standard since 1990. The 1990 Clean Air Act required the county to come within the PM10 standard by December 1994.
Since the county was still in violation, Earthjustice sued.
The county was able to scientifically show its violation of the standard from 1992 to 1994 was due to airborne particles that travel into the valley from Mexico, said Brad Poiriez, senior manager at the county Air Pollution Control District.
The EPA can always come back to scrutinize the county from 1995 to the present but probably won't because of evidence the district has already given, Poiriez said.
David Baron, legal counsel for Earthjustice, said the group would consider the possibility of further litigation.
Baron questioned the county's wisdom of having an air pollution control officer who is also the agriculture commissioner. Birdsall fills both positions with the county.
"The Air Pollution Control Officer is supposed to patrol agricultural activities," Baron said.
Baron conceded it is true Imperial County has a problem with pollution that crosses the border but said there is more the county could do to control pollution.
"Our next step is to meet with the EPA and the state Air Resources Board next week to discuss a few things we agreed to negotiate," Birdsall said.
The county Air Pollution Control District agreed to a few modifications. Some of the ideas proposed are:
· stricter controls to lower dust at staging areas, such as truck parking lots over 1 acre in size and agriculture equipment yards.
· faster clean up of track out. Track out is when a vehicle in a dirty lot drives onto a paved road, tracking dirt, and other vehicles drive over the dirt and stir up dust. The proposed rule would change cleanup time for the road dirt from 48 to 24 hours.
· asking the U.S. Bureau of Land Management to supply a dust-control plan. According to Glen Miller, planning/environmental coordinator at the BLM, the bureau controls 1.29 million acres in Imperial County.
· better control of Border Patrol emissions. Some activities, such as dragging tires to help track immigrants, create airborne dust.
Birdsall said these ideas are only proposals and the actual measures the county will take are not yet defined.
The county still must submit a moderate state implementation plan, Poiriez said, referring to the control plan for the area the county will have to design. Once that happens, there will be workshops to solicit public input.
Staff Writer Laura Mitchell can be reached at 337-3452 or firstname.lastname@example.org