Photo: Santiago Mejia / The Chronicle

The San Francisco Board of Supervisors quashed Mayor London Breed’s proposed charter amendment Thursday that aimed to streamline the approval of affordable housing projects. Breed needed the support of the majority of supervisors to get the plan on the November ballot. She didn’t get it.

Breed’s proposal sought to eliminate some bureaucratic steps in the process of approving affordable and teacher housing, such as the public’s ability to challenge proposed projects. The changes, she said, could have saved millions of dollars and between six and 18 months per project.

The measure — which would have amended the City Charter — would have also streamlined the approval process for middle-income housing for people who earn up to 140% of the area’s median income. But the supervisors were uneasy about how Breed’s proposal would amend the City Charter and eliminate certain public appeals. They were also wary about how the amendment includes streamlined approvals for middle-income housing.

“These problematic definitions should not be set in stone in our City Charter,” said Supervisor Sandra Lee Fewer. “And we should not be granting by-right approval to market-rate developments on publicly owned land under the guise of calling it affordable teacher housing.”

Breed said her charter amendment would help the city retain its middle class, which is increasingly squeezed out of the city amid its skyrocketing rents. She said it also would have saved the city a lot of money: according to the Mayor’s Office of Housing and Community Development, delays results in average project costs increasing by $1.5 million to $6 million due to rising construction costs, which equates to a loss of anywhere between six and 22 affordable homes per project.

Supervisor Aaron Peskin said he didn’t see public input as a barrier to building affordable housing.

“The thing that is the biggest barrier to building affordable housing is money,” he said. “The whole notion that they (affordable housing projects) are being delayed because of public input is just factually without merit.”

The supervisors said a recently passed state law already streamlines the approval process for certain affordable housing projects. But Breed’s charter amendment would have expanded the income requirements to also include more middle-income earners and teachers.

After the vote, Breed assailed the board for knocking down her measure.

“I’m tired of people saying we’re in a housing crisis and then rejecting solutions that will actually make a difference,” she said in a statement. “The status quo means less affordable housing will be built, more people will be priced out, and the crisis will only get worse.”

Two measures related to affordable and teacher housing — one from Breed and another from a group of supervisors are already headed to the November ballot.

If passed by voters, both measures would allow for 100% affordable housing and housing reserved for educators and school staffers to be built on swaths of public land where it’s now prohibited. But their details differ in important ways. It’ll now be up to voters to sort out which plan is best.

Trisha Thadani is a San Francisco Chronicle staff writer. Email: tthadani@sfchronicle.com Twitter: @TrishaThadani