BUSES IDLED WHILE MTA SEEKS EXPLOSION'S CAUSE.

Byline: Jaxon Van Derbeken and David Bloom  Daily News Staff Writer

In the wake of last week's fuel tank explosion, the Metropolitan Transportation Authority's natural gas-powered fleet will be idled for at least a week, forcing service cuts and inconveniencing thousands of riders in the San Fernando Valley.

As weekday demand hit Monday, the agency was planning more detailed inspections and gearing up for the installation of shields to prevent road debris from striking the fuel tanks of the nation's largest natural gas fleet.

The Valley was affected most by the action, because its Chatsworth and Sun Valley garages were home to the greatest number of compressed natural gas-fueled buses in the MTA's 2,050-bus fleet, officials said.

Officials said 10 Valley lines were affected, with a total of 16 buses cut from service.

Officials could not predict how long the service would be affected, but said that the problem could ease as the agency borrows from sister agencies to increase its fleet.

On Monday, the agency was 38 buses short of the roughly 1,700 buses needed.

``What the community experienced today was, hopefully, the worst of it,'' said Joseph Drew, MTA's chief executive officer.

The 120-bus fleet was grounded within two days of the Aug. 21 incident when a fuel tank pierced the undercarriage of MTA bus No. 4519 during refueling in a yard in Sun Valley.

Officials for the maintenance workers union said the workers formally refused to refuel the buses Sunday because of safety concerns.

After further testing, the fleet will be retrofitted with protective shields to protect the natural gas tanks from road debris. Drew said testing, retrofitting and certification needed to make the fleet roadworthy could be done within six weeks.

``Given the uncertainty of the cause, we're essentially going to recertify (the safety of) all the buses,'' Drew said. ``If they satisfy the tests and meet all the other considerations,'' the buses will be returned to service. He said the detailed testing of the buses will begin Friday.

``In four to six weeks, we'll be done. That's our current strategy,'' Drew said.

Meanwhile, MTA officials are struggling to revamp mothballed buses as well as scrounging for replacements from sister transit agencies.

Drew said an alert has been sent to other agencies that have natural gas-powered buses and to transit agencies in general.

``We are alerting the operators, that we want them to be aware that we have had an unexplainable event that concerns us greatly, that had very serious overtones concerning safety.''

The cuts on Monday caused greater crowding and an average delay of 10 minutes for bus patrons on those routes cut, but future waits could be as long as 20 minutes, authorities said.

Monday's bus shortage hit Ventura Boulevard Route 424, which lost four of the 33 buses normally in service, said Ellen Levine, the MTA's western regional general manager.

Other Valley service cuts included routes along Van Nuys Boulevard, San Fernando Road and Riverside Drive. In other parts of the city, Wilshire and Venice boulevards had cuts in service.

As a result of the trouble, 22 fewer buses were running on 11 lines in West Los Angeles, the Northeast division and South Central Los Angeles, MTA officials said.

The service cuts come despite the agency's original hopes that it could field all of its natural gas-powered buses by Monday.

An initial inspection done last week did not uncover any serious problems, but the union representing the maintenance workers vowed to not fuel the buses until a more detailed inspection was completed.

While no cause has been pinpointed and the inspections continue, Neoplan USA, the bus manufacturer, will provide at no charge protective mesh undercarriage liners to prevent rocks and other debris from being kicked up against the tanks, said Jeff Johnson, the MTA's director of equipment engineering.

The MTA maintenance crews also will begin making an additional visual inspection of gas cylinders before each refueling, to ensure there are no physical problems, Drew said.

Neal Silver, president of the Amalgamated Transit Union, said Monday that on Sunday, he formally invoked a contract provision that allows workers to refuse to perform hazardous or dangerous tasks without being disciplined.

``I refused on their behalf to management,'' Silver said, adding that workers indicated that fueling was to get started at Chatsworth on Sunday. ``That took care of it, and we finally settled it out. I'm comfortable with what they are doing now.''

Silver said the buses will not be fueled, effectively grounding the fleet, until the tanks undergo two separate tests and the undercarriage portion on each one is retrofitted with a shield against road debris.

``When they finish that, and both checks OK, then the tanks are OK, then they will go ahead and put a shield underneath the bus,'' Silver said.

Silver said the shielding is only prudent given the theory that debris damage might have triggered the explosion.

``It's conjecture, but it's a possibility of what happened,'' he said. ``They want to make sure that doesn't happen - I don't blame them, because liability is too great.''