As rising construction costs continue to imperil Palo Alto's infrastructure plans, city officials are preparing to ask the voters for help.

The city is considering putting a tax measure on the November ballot as part of a strategy to close the $56 million gap in the council's infrastructure plan. The list of projects in the plan includes a new police building, two rebuilt fire stations, a bike bridge over U.S. Highway 101, completion of the Charleston-Arastradero streetscape project and various improvements at Byxbee Park.

On Tuesday night, the City Council took a tentative step toward a November ballot measure when its Finance Committee supported moving ahead with a poll to gauge the public's interest. The poll will be conducted by the firm FM3 Research, which had also performed survey work for the city in 2014, when voters passed a hotel-tax increase to pay for infrastructure.

Since that election, the estimated price tag for the projects had risen from $136.6 million to $235 million, according to Public Works staff. The most expensive project on the list -- the new public-safety building -- now has an estimated price tag of $91 million, up from $57 million in 2014.

At the same time, new needs have emerged. Palo Alto is looking for funds to build a new animal shelter (estimated price tag: $10 million and $15 million), assist with construction of the new Junior Museum and Zoo ($5 million) and implement the priority projects in its newly adopted Parks Master Plan (between $40 million and $55 million).

The poll will target a random sample of 600 likely voters and will rely on landlines, cell phones and email, David Metz of FM3 told the committee Tuesday. In addition to asking about about infrastructure projects and potential taxes, it will also ask about respondents' general feelings about local government and quality of life.

The main question that the council is looking to answer is: What type of tax, if any, should go on the ballot? Councilman Greg Scharff, who chairs the Finance Committee, said he would like to see another increase in the hotel-tax rate. In 2014, he supported raising the rate from 12 percent to 15 percent, though the majority ultimately went ahead with 14 percent. On Tuesday, he said he would like to poll residents on raising that additional 1 percent to pay for the gap in the 2014 plan.

If the city's hotel tax (also known as transient-occupancy tax) goes from 14 percent to 15 percent, it would be tied with Anaheim for highest in the state, according to a report from the Administrative Services Department.

"I believe we should move forward and poll for TOT (transient-occupancy tax), at which point we can fund all projects on infrastructure plan and not cut any of them and keep our promises to the voters that we made when we went to the public and asked them for that," Scharff said.

As for the parks improvements, Scharff proposed a quarter cent sales tax increase. That way, the cost of park improvements will be shared by businesses and residents.

Some, including Councilman Tom DuBois, say that city should explore a business tax -- an idea that voters considered and rejected in 2009 as a strategy to pay for the new police building. DuBois, who is not on the Finance Committee, said at the end of Monday's council meeting that he would like to see the poll consider grade separation (the separation of tracks from streets at the city's four rail crossings) and to poll for a business tax as part of the funding strategy for the project.

But Scharff argued that doing so at this time would be premature. Palo Alto is moving ahead with a plan to select its grade-separation alternative by the end of the year. The city should first select its preferred option and get a sense of its cost before going to the voters for help. He agreed that a business tax may be an appropriate way to pay for grade separations. That conversation, however, is more appropriate for 2020 or 2022, he said.

For most of the residents who urged the council to stay the course on its earlier infrastructure promises. Several of them spoke in favor of completing the hardscape improvements on Charleston-Arastradeo, a phased project that has been in the works for more than a decade.

Paul Goldstein, a longtime member of the Palo Alto Pedestrian and Bicycle Advisory Committee, acknowledged that all of the projects on the council's 2014 list remain important. But they should not, he said, come at the expense of bicycle and pedestrian improvements.

"It would be demoralizing and it would undermine faith in our processes, including our Comprehensive Plan process, for the council to go back on its promises to complete these projects," Goldstein said.

Ann Pianetta, a member at Friends of Palo Alto Animal Shelter board of directors, urged the council to support a new animal shelter, which under the current plan would be operated by the city's nonprofit partner, Pets In Need. The city and the nonprofit are now exploring how much they can raise from private funds for the new facility, though the city will likely need to make a contribution to the project as well.

Pianetta urged the council to include the animal shelter on its list of needed improvements.

"Surely, the care of animals is higher on this list of improvement than parking lots," Ann Pianetta said.