San Francisco's Board of Supervisors unanimously approved an eighth-cent sales tax measure for the November election to fund Caltrain during a special meeting Friday -- the last day to place the measure on the county ballots.

If ultimately approved by two-thirds of voters across San Francisco, San Mateo and Santa Clara counties, the tax would generate an estimated $108 million annually. The funding is desperately needed to operate the system as ridership has plummeted during the COVID-19 pandemic, according to the measure's supporters.

San Francisco supervisors already approved the tax measure, authored by Supervisor Shamann Walton, during a meeting last week. That version, however, included conditions calling for Caltrain to change its governance structure and separate itself from the San Mateo County Transportation District, which operates Caltrain.

The move drew criticism from San Mateo County officials, many of whom alleged the condition would make the tax harder for voters to approve, putting Caltrain funding and service altogether in danger.

However, since then officials from all three counties have agreed to remove the governance issues from the measure and pass a new amended version that solely calls for the tax, in the hope that it could get approved by county leaders in all three counties by the Friday deadline.

"Since our last meeting, we have been working with San Mateo and Santa Clara counties literally nightly and in the mornings for most of this last week in order to come up with an agreement that would address our governance concerns and be best for Caltrain," Walton said.

The governance issues instead were presented as recommendations to the Peninsula Corridor Joint Powers Board, which oversees Caltrain and is made up of representatives from the three counties, during a meeting on Thursday. The recommendations, which include, among others, allowing the JPB to appoint its own executive director, special counsel and auditor, separate from SamTrans, were approved.

The San Francisco Board of Supervisors is the last body needed to approve the sales tax measure, effectively placing the measure on the November ballot.

The JPB, the Santa Clara County Valley Transportation Authority Board of Directors, the San Francisco Municipal Transportation Agency Board of Directors, the SamTrans Board of Directors, the Santa Clara County Board of Supervisors, and the San Mateo County Board of Supervisors have all already approved the measure.

"Even though we've had a tumultuous fight and we've had to go through a lot of adversity to get to this point, we will be making history if we can get this two-thirds measure passed, as this will be the first ever dedicated funding source for Caltrain. So, that is something we can all be excited about," Walton said.

"It's official, the measure has passed and will be on the November 2020 ballot! Thank you to everyone who made this happen!" Caltrain officials said Friday on Twitter, following San Francisco supervisors' vote.

If approved by voters, Caltrain could start seeing the funds as early as April 2021.