Faced with few good options for redesigning south Palo Alto's two rail crossings, the City Council agreed Monday to eliminate what they deemed to be the worst of the bunch: a viaduct that would elevate the railroad tracks over Charleston Road and Meadow Drive.

The council's decision to eliminate the viaduct from consideration followed an extensive debate about the pros and cons of all four alternatives that were still on the table for grade separation — the redesign of rail crossings so that the roads and the tracks would no longer intersect.

The elimination of the viaduct leaves the council with three alternatives to choose from: digging a trench for trains between Loma Verde Avenue and the San Antonio Caltrain station in Mountain View; constructing an underpass for drivers and bicyclists under the rail tracks; and advancing a "hybrid" design that combines raising the tracks and lowering the roads.

In debating its options for the two southern crossings, the council agreed that each is flawed in its own way. The trench, while the most popular alternative, is also the most expensive and, from an engineering perspective, the most complex one. It has an estimated price tag of $800 million to $900 million and it would take six years to construct. To build the trench, the city would need to divert Barron and Adobe creeks through siphons and lift stations and pump groundwater along the entire length of the alignment, which would stretch from just south of Loma Verde Avenue to just north of the San Antonio Caltrain station.

The underpass, while less expensive and more politically palatable, has its own problems. It would require more property seizures than the other alternatives and it entails a host of new turning restrictions from Meadow, Charleston, Park Boulevard and Alma Street, including elimination of through traffic on Park Boulevard near East Meadow. To accommodate vehicular traffic, the design for the underpass calls for a roundabout with two lanes on East Charleston Road, west of Mumford Place.

The hybrid, which would create earthen berms for trains, is also relatively unpopular. Mayor Tom DuBois was one of several council members who proposed eliminating the hybrid along with the viaduct, though his colleagues generally agreed to keep it on the list, citing the uncertainties swirling around all the other options.

By a 6-1 vote, the council agreed to eliminate the viaduct and to direct city staff to further refine the underpass alternative, with the goal of addressing its shortcomings when it comes to traffic circulation. The council also directed staff to move ahead with a geotechnical study for the trench option, a step that city staff noted usually occurs later in the design process.

Council member Alison Cormack, the sole dissenter, suggested that it's premature to eliminate the viaduct, an option that she noted appears to fulfill many of the objectives that the council had adopted for its multiyear planning process on grade separations.

For the council, the Monday action represents a rare step forward in the multiyear process of winnowing down its grade separation options. In recent years, the council has consistently failed to meet its approved deadlines for selecting preferred alternatives for the city's four grade crossings: Palo Alto Avenue, Churchill Avenue, Meadow and Charleston. The Expanded Community Advisory Panel (XCAP), a citizens group that the council appointed to aide it in the selection process, had recommended closing Churchill to cars. Palo Alto Avenue, meanwhile, will be explored as part of a broader downtown plan.

The two southern crossings, meanwhile, have befuddled both the citizens panel and the council. The committee could not reach consensus on which alternatives to support for Charleston and Meadow, with none of them mustering more than three votes. They only agreed on gathering more information before endorsing any option. The XCAP report noted that every alternative has negatives and that there was "no enthusiasm for any particular one."

"While neighborhood opposition to the above ground solutions — the hybrid and the viaduct — was vociferous and near unanimous, there was also recognition that the trench, tunnel and underpass have serious challenges," the group's final report stated.

Keith Reckdahl, who served on the committee and who lives in Charleston Meadows, urged the council on Monday to eliminate both elevated alternatives — the viaduct and the hybrid — from consideration. His neighborhood, he said, "almost uniformly opposes elevated alternatives because they would drastically change the neighborhood's quality of life."

Other residents voiced similar sentiments at recent public hearings and in letters to the council.

"Large concrete viaducts and overpasses are ugly and not compatible with a residential neighborhood in a green community," wrote Deborah Ju, who lives on Whitclem Drive, close to the Charleston Road crossing. "Palo Alto would be embarrassed and ashamed by such a structure and future generations will wonder how in the world a City full of smart engineers let this happen."

In addition to removing the viaduct from consideration, the council agreed that the city should advance bike projects, including an underpass near Loma Verde, that would allow bicyclists to cross the tracks during the extensive construction period.

Vice Mayor Pat Burt and council member Eric Filseth both said they would support moving ahead with bike improvements in advance of the broader grade separation project.

"With half of our kids biking to school every day, we need to get a bike and pedestrian plan in place early, before we proceed and potentially shut down major pieces of the current bike and pedestrian infrastructure for a period of multiple years while construction goes on," Filseth said.

The city's effort to redesign the tracks, which began roughly a decade ago and which has proceeded in fits and starts, aims to both improve safety along the tracks and to address the long traffic delays that are projected to occur on and around Alma Street once Caltrain completes its effort to electrify its train service and adds more trains to its fleet.

The effort received a boost with the passage of Measure B in 2016. The Santa Clara County tax measure dedicated $700 million for grade separation in Palo Alto, Mountain View and Sunnyvale. The three cities recently agreed to split the amount based on the number of rail crossings in each jurisdiction. Palo Alto, which has four crossings, would get half of the total sum under the agreement, while Mountain View and Sunnyvale, which have two crossings, would each get 25%.

While the recent agreement between the cities have alleviated some local anxieties about funding for grade separation, the council broadly acknowledged that it would need to pick an alternative before it could access the county cash or apply for state and federal grants.

Both Burt and DuBois also suggested they are unlikely to support the hybrid, which Burt described as "an earthen wall separating the two halves of Palo Alto in that area," the council agreed to keep this option in the mix.

DuBois, who made the motion to eliminate both the viaduct and the hybrid, said both designs go "fairly high into the sky" and have fairly low public support.

"I'm pretty convinced I don't think those options are going to be supported by the community," DuBois said.

Others were more hesitant to abandon the hybrid, which is the cheapest option on the table, with an estimated cost ranging from $190 million to $230 million (the underpass would cost between $340 million and $420 million). Cormack and Filseth both suggested that given its comparatively low costs — and the many unanswered questions pertaining to the other options — eliminating the hybrid would be premature.

Council member Lydia Kou, meanwhile, supported further evaluating the trench option and getting a second opinion on the potential cost of this alternative. The council adopted her suggestion by a 6-1 vote, with Cormack dissenting.

"At this time, it is necessary to find ways to make sure that options do work," Kou said. "If a trench is the way to work and cost is the only thing that's standing (in the way), and there are questions about the costs presented to us, we should have a second opinion on that."