Palo Alto is preparing to significantly expand its list of historic properties to shield them from redevelopment under Senate Bill 9, a state law that allows homeowners to split their lots and build up to four dwellings.

The city already has a list of 165 properties identified by a survey conducted more than 20 years ago as potentially eligible for a listing on the National Register of Historic Places. The vast majority of these properties are in the north Palo Alto neighborhoods of Crescent Park, Downtown North and University South, areas that date back to the city's earliest days.

But the survey, which was conducted between 1997 and 2001 by the firm Dames & Moore, also includes properties farther south, including 2230 Amherst St. in College Terrace, which was developed in the former town of Mayfield as student housing in the first decade of the 20th century.

It also includes 960 Matadero Ave., which was developed in a rural and unincorporated area outside Palo Alto boundaries — what is now the Barron Park neighborhood — by Dr. William Carruth, who surveyed the land in in 1918 and deemed it suitable for development.

Many of the structures that were located at the properties have already been redeveloped or, in 11 cases, demolished, according to planning staff. To date, the vast majority had not come up in public hearings pertaining to city history.

That, however, may soon change. The City Council is scheduled to discuss and possibly approve on Monday night funds for consultants to accelerate the city's effort to get these properties listed on the national registry. And the city's Historic Resources Board is planning to hold a series of public hearings to inform property owners about the effort and give them a chance to weigh in.

The main reason for the new sense of urgency is SB 9, which allows property owners in single-family zones to build up to four dwellings — including accessory dwelling units and junior accessory dwelling units — at sites where one home currently stands. The bill, which the council formally opposed before its adoption last year, explicitly excludes historic properties.

The council has already taken some steps in restricting development standards for SB 9 projects. Last December, the council approved an ordinance that creates new "objective standards" — rules that address details such as window placements, garage locations and roofline styles. At that time, some council members, including Tom DuBois, expressed support for also updating the city's historic registry.

"It's been 21 years and as buildings age, we now have a lot more potentially historic buildings, potentially from the beginning of Silicon Valley," DuBois said during the Dec. 6 meeting. "I would support us planning and budgeting for both the commercial and residential Historic Register update."

The council will have a chance to do just that on Monday, when it considers further changes to its SB 9 rules. It will discuss various proposed designs for lot splits — including side-by-side lots and flag lots — and consider adopting a preferred design. Other possible changes include a new provision that would empower Public Works staff discretion to create standards for curb cuts, roadways and other public improvements that are typically located adjacent to private properties.

While these new rules could take effect soon after adoption, the update of the historic registry would take significantly longer. A property owner who wants to see their property nominated for the registry is currently required to contact city staff, submit forms to the state Department of Parks and Recreation, contribute fees, submit photos and receive recommendations from the Historic Resources Board and the council, according to a new report from the Department of Planning and Development Services.

Efforts to protect historic properties have been in the works for several years. The city has been submitting forms for properties that had been determined to be eligible for historic status since 2017, when the city completed the update of its Comprehensive Plan, which includes the policy, "update and maintain the City's Historic Resource Inventory to include historic resources that are eligible for local, state, or federal listing."

These properties, however, are currently not listed on either the state or the national registry and are thus eligible for redevelopment.

"None of the properties found eligible (for historic status) are protected under the city's existing historic preservation ordinance, unless they are within a listed historic district," the report from the planning department states.

Planning staff acknowledged at a recent retreat of the Historic Resources Board that the city's policy of updating its historic registry has taken on more urgency in light of SB 9. Chief Planning Official Amy French said the effort will require more funding to hire consultants who would help conduct public hearings and notify property owners.

"I think we've been talking about how that's key — because of SB 9 — that we would put it in high priority or highest priority," French said at the March 10 retreat.