A Contra Costa County school district's use of wood chips in play boxes makes it harder for boys and girls in wheelchairs to get to swings and slides, a violation of the disabled children's rights, a federal judge has ruled.

The decision by U.S. District Judge Claudia Wilken of Oakland could lead to replacement of wood chips with firmer surfaces in public playgrounds at other schools and parks around the country, said a representative of the group that sued the Mount Diablo Unified School District in central Contra Costa.

"Our experts and people with disabilities tell us that wood chip surfaces are not accessible," said Larry Paradis, executive director of Disability Rights Advocates. "They constantly form mounds and gullies ... and they're impossible to maintain. Little kids in wheelchairs are already struggling to get around, they have less muscular strength, and it's important that play structures be easily accessible for them so they can be mainstreamed (with other children) as much as possible."

Wilken ruled this week that the Mount Diablo district, which has 32 elementary schools and 16 middle and high schools, was violating a 2000 agreement to make its playgrounds accessible to the disabled because it uses wood chips. She gave school officials a month to work out a replacement plan with Disability Rights Advocates, representing a student who sued the Concord-based district in 1998.

Paradis said Friday that he would like the district to install rubberized play box matting, which he said costs more to put in than wood chips but less to maintain.

Attorneys for the school district were unavailable for comment on the ruling. In a recent court filing, district lawyer Gregory Widmer said there was "no evidence that any student with a mobility disability ever complained about the accessibility" of play boxes with wood chip surfaces. He also said rubberized mats are eight times as expensive as wood chips and would cost the district more than $2.7 million if installed in 32 play boxes.

But Paradis said wood chips don't meet disabled children's needs for a firm and stable surface, with little or no sloping, to wheel themselves to swings, slides and sandboxes. He said wood chip manufacturers have been boosting their sales and misleading customers by asserting that their product meets the standards of disability laws.

However, a playground designer said Friday that federal regulators have found that engineered wood fiber, the product used in schools and parks, complies with accessibility standards if properly compacted and maintained.

"Most places can't maintain it to that level, and they're probably better off with rubber," to reduce maintenance costs and the likelihood of lawsuits, said Susan Goltsman, whose Oakland firm, MIG, also designs schools and zoos. She said both products are safe, although wood chips are more yielding and may cushion falls better.

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Aesthetically, though, a mix is best, Goltsman said. "If you've got a monoculture of the same surfacing material everywhere, you've got a boring environment," she said. "It's like having asphalt everywhere."

Wilken's ruling follows a report by an MIG consultant who studied the play boxes and their use by disabled children in the 2005-06 school year. Both sides said the consultant's findings supported their position.

Paradis said he hopes the case encourages other districts in California and elsewhere to quit installing new wood chip play boxes and gradually replace the old ones.

"We want districts to learn from Mount Diablo's mistake," he said.