LIVERMORE — Building BART as far east as Livermore has been on transportation planners’ wish lists for decades, but stretching it eastward just to Isabel Avenue — much less to Greenville Road and a connection with the Altamont Corridor Express from Stockton — has proven a surprisingly frustrating slog.

“This was first proposed in the ’60s; the first extension (of BART) was to be to Livermore,” said John Marchand, that city’s mayor and a witness to decades of frustration in getting BART to his city.

But he and other local officials have renewed optimism that this extension will finally get on the fast track to reality, thanks largely to creation of the Tri-Valley-San Joaquin Valley Regional Rail Authority. That new agency’s specific, focused task: to deliver a public-transit connection from the San Joaquin Valley (Stockton-Modesto-Tracy area) to BART.

“This agency has a single goal, and that should make it effective,” said Marchand, Livermore’s lead representative on the Regional Rail Authority board. Added San Ramon City Councilman Phil O’Loane, that city’s chief board representative, “I’d like us to be more than just an irritant to BART.”

While the appeal of a BART-ACE connection for San Joaquin County residents is obvious — access to points all over the Bay Area without getting in a car and onto increasingly congested Interstate 580 — that connection would also help Tri-Valley residents, who already have easy access to ACE and BART.

“To the extent people from Tracy get pulled off the freeway and lessen freeway congestion, that’s a big deal,” said O’Loane, an advocate of passenger rail in general. “That directly affects I-580 and 680 where we live.”

The authority’s first meeting is in January, and the member cities have been naming their representatives and alternates over the past few weeks.

This new body was created by Assembly Bill 758, authored by Assemblywoman Catharine Baker, R-San Ramon, and Assemblywoman Susan Eggman, D-Stockton. It will being together nine municipalities (Livermore, Dublin, San Ramon, Danville, Pleasanton, Tracy, Manteca, Lathrop and Stockton), Alameda and San Joaquin counties, BART, the San Joaquin Regional Rail Commission (ACE), the Livermore Amador Valley Transit Authority (WHEELS) and the Mountain House Community Services District.

The agency, technically a joint powers authority, has “all of the powers necessary for planning, acquiring, leasing, developing, jointly developing, owning, controlling, using, jointly using, disposing of, designing, procuring and constructing facilities to achieve transit connectivity … .” Several area politicians said they envision the new authority’s role as similar to that of the Santa Clara Valley Transportation Authority (VTA), which was a full partner in bringing BART south from Fremont toward San Jose.

That “connectivity” likely would be the aforementioned physical link between the existing standard rail service of the Altamont Corridor Express — which connects Stockton and the Tri-Valley to San Jose — and BART, probably somewhere near the Interstate 580-Greenville Road interchange. Marchand said. Another possibility — many years away, at this stage — would be to extend BART over Altamont Pass to Tracy or Stockton using diesel multiple units (or electric multiple units), substantially cheaper than standard BART cars and tracks. (Similar “DMUs” will carry BART passengers east from Pittsburg/Bay Point to Antioch for the foreseeable future, starting soon).

While a far more expensive proposition than connecting BART with the ACE train, the DMUs to Stockton — needing their own right-of-way — would ultimately provide much more frequent service to and from Stockton than ACE’s four westbound trains each weekday morning and four eastbound trains each weekday night, Marchand said.

BART is supposed to decide on a route beyond Isabel Avenue, and a “mode” (diesel cars, electric cars, full BART) by July 1, 2018, Marchand said. The new Regional Rail Authority is required to turn in a report to the public by July 1, 2019, on the plans for how BART and ACE will connect. Baker, co-author of AB 758, said ratcheting up the pace on BART to Livermore and the ACE train connection is long overdue and that the new authority will help expedite things.

“This has lagged for a very long time, and I think this is the road forward and the most effective way to connect these two (transit) systems,” she said.

While Baker suggested that the new authority will help get some of the work toward the Livermore extension off BART’s crowded plate, John McPartland said he believes the new authority will be seen as much as a nuisance as help.

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“BART’s irritation is that they have only one vote on that new board,” said McPartland, the BART board’s director from District 5, which includes Livermore. He notes that planning to get BART as far east as Isabel Avenue is well underway, with a draft environmental report on the extension due this spring. Even so, McPartland figures BART service east to Isabel won’t begin until at least 2026.

McPartland, much like Marchand, hopes the new authority will get BART past Isabel more quickly than it otherwise would.

“It’s the only leverage I’m going to get,” he said.