Something strange happened yesterday when the Board of Supervisors prepared to take up the ongoing effort to block the construction of two single-family houses on undeveloped land along Folsom Street, near the intersection with Chapman.

As Bernalwood described earlier in the week, a group of nearby neighbors have opposed the construction of two new homes at 3516 and 3526 Folsom, and they recently appealed to block the project based on concern about Line 109, a PG&E gas pipeline that runs underneath the South Bernal length of Folsom Street — and alongside the lots where the two homes would be built. PG&E has said that the pipeline is safe and inspected regularly, and that building homes alongside the pipeline route would be routine.

Last year, after compiling a 903 page project docket and twice voting unanimously to approve on the matter, the San Francisco Planning Department gave the plan to build the houses an unequivocal thumbs-up, in the form of a Categorical Exemption that eliminates the need for an expensive and time-consuming Environmental Impact Report.

All that was the backdrop going into yesterday’s meeting, where neighbors who oppose the new homes brought their last-ditch appeal to the Board of Supervisors in the hope that the Supervisors would vote to overturn the Planning Department’s Categorical Exemption and send the project back for further environmental review.

Yet as soon as the full Board of Supervisors began to consider the matter, it immediately turned weird. Lisa Gibson, a representative from the Planning Department announced that it was reversing itself, and summarily rescinding the Categorical Exemption that it had previously issued.

The sudden move appeared to come as a surprise to everyone — project sponsors, appellants, and Supervisors alike — and much chaos then ensued.

D9 Supervisor Hillary Ronen spoke up to say that while she felt further environmental review of the project seemed necessary, the Planning Department’s last-minute move to reverse itself was “incredibly unprofessional and frustrating.” In response, Lisa Gibson, the Planning Department’s acting environmental review officer, took to the mike to explain that the decision to withdraw the Categorical Exemption had been made on that same day, based on concerns expressed in two December 2016 letters from project opponents, and as a result Planning wanted to explore the risk of potential “vibratory impacts” on the adjacent pipeline that might occur while the homes are under construction.

The explanation seemed to put Supervisor Ronen at ease. Although she again expressed frustration with the last-minute action on the part of the Planning Department, she added that “additional environmental review is required, because if [Planning] is finding that there is an unusual circumstance that requires additional investigation on the environmental impact of this project, then perhaps a Categorical Exemption is not appropriate.”

There was also a lot of frustration among the members of the public who had come to comment on the project, however. Lawyers for the families hoping to build the new houses said they had only been notified about the Planning Department’s decision to rescind the Categorical Exemption at 2:30 that day, or 30 minutes after the Board of Supervisors meeting had started.

An exasperated man, who appeared to represent the project sponsors, complained that the circuitous planning process had already resulted in a two-year delay and significant additional cost. “We’ve been here for two years now, waiting for two single-family houses,” he said. “Go and explain that to the mother of those children, who are wondering where are they going to live and what’s going to happen here.”

Meanwhile, several project opponents, including a representative from the executive committee of the San Francisco Sierra Club, said that while they were happy about the outcome, they were sad to have wasted an an otherwise lovely afternoon attending a meeting that was moot from the outset.

And so, with no Categorical Exemption to uphold or deny, the Board of Supervisors voted to table the matter. In practical terms, that leaves the proposal to build the two homes on Folsom in limbo, again, as Planning will require further environmental study before taking it up again.

Yet what really happened? Why did the Planning Department reverse course on its Categorical Exemption, and at such a late hour? It’s difficult to know for sure, but sources familiar with San Francisco’s planning process say such last-minute reversals are unusual, and may indicate Planning Department staff had come under pressure from other City officials to subject the project to further scrutiny.