School buses running cleaner School buses running cleaner (May 04, 2005)

By David Boyce

Almanac Staff Writer

The school buses operated by the Las Lomitas School District pollute less than they used to now that they've been fitted with filters to trap particulate matter in the exhaust systems.

In December, the district had a filter installed on each of the district's four buses to extract tiny particles of soot from the exhaust stream. A $20,000 grant from the Bay Area Air Quality Management District paid for the modifications, said Dennis Hatfield, the district's maintenance supervisor.

Similar modifications were done around the same time to several buses operated by the Sequoia Union High School District, said William Jackson, the maintenance supervisor. The Sequoia district operates 34 buses, some of which run on compressed natural gas, said Mr. Jackson.

The diesel soot is stored in a box-like container that can be vacuumed out, which at Las Lomitas will be done once a year, said Mr. Hatfield.

The soot -- all but invisible without a microscope -- contains carcinogenic substances and can worsen respiratory illnesses such as asthma, according to a 2004 report on school bus exhaust by the Environmental Protection Agency.

State law requires drivers of school buses and commercial diesel-powered vehicles that visit schools to shut off their engines "upon arriving at a school" and to not restart them until 30 seconds before departure.

The Las Lomitas district spends about $250,000 annually to operate and maintain the school buses. Las Lomitas and Sequoia were two of the early applicants for grant money, said Karen Chi, a planner with the Low Emission School Bus Program of the Air Quality Management District.

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