09-14-2026 Geologic Safety Agenda Packet

TOWN OF PORTOLA VALLEY Nan Shostak, Chair, Bob Wrucke, Vice Chair Geologic Safety Committee Patricia McCrory, Secretary Regular Meeting Gary Ernst, Member Steve Ingebritsen, Member September 14, 2026 Simon Klemperer, Member 10:00 AM REGULAR MEETING – HISTORIC SCHOOLHOUSE - 765 PORTOLA ROAD ~ PORTOLA VALLEY REMOTE MEETING ADVISORY: On March 1, 2023, all committees in Portola Valley will return to conducting in-person meetings. A Zoom link will be provided for members of the public to participate remotely; however, the Town cannot guarantee there will be no technical issues with the software during the meeting. For best public participation results, attending the meeting in-person is advised. ASSISTANCE FOR PEOPLE WITH DISABILITIES In compliance with the Americans with Disabilities Act, if you need special assistance to participate in this meeting, please contact the Town Clerk at (650) 851-1700 or by email at towncenter@portolavalley.net. Notification 48 hours prior to the meeting will enable the Town to make reasonable arrangements to ensure accessibility to this meeting. VIRTUAL PARTICIPATION VIA ZOOM To access the meeting by computer: https://us06web.zoom.us/j/84439659510?pwd=AlKcnO48hd58qbcQ4gWjUZ5Z8ovaRi.1 Webinar ID: 844 3965 9510 Passcode: 276242 To access the meeting by phone: 1-669-900-6833 or 1-888-788-0099 (toll-free) Mute/Unmute – Press *6 / Raise Hand – Press *9 1. CALL TO ORDER & ROLL CALL 2. ORAL COMMUNICATIONS FOR ITEMS NOT ON THE AGENDA Speakers' time is limited to three minutes. 3. OLD BUSINESS a. Progress reports from subcommittees for ongoing projects: Evacuation, Hazards, Communications and Outreach, Safety Element, Resilience in Japan, External Coordination b. Update on Ross Stein presentation c. Other reports 4. NEW BUSINESS a. Approve minutes of the (1) July 13, 2026 and (2) August 10, 2026 meetings b. Quorum check for upcoming months c. GSC booth at Town picnic September 19 d. Ross Stein presentation October 6—Advertising, preparation, and logistics e. Recommendation to Town Council for map update process f. Fault setbacks—discussion and recommendation 5. ADJOURNMENT This meeting body meets regularly on the second Monday of the month. ******************************************************************************************************************* Land Acknowledgement: The Town of Portola Valley acknowledges the colonial history of this land we dwell upon—the unceded territory of the Ramaytush (rah-my-toosh) Ohlone, Tamien Nation, and Muwekma (mah-WEK-mah) Ohlone, who endured a human and cultural genocide that included removal from their lands and their sacred relationship to the land. Portola Valley recognizes that we profit from the commodification of land seized from indigenous peoples and now bear the ecological consequences. We seek to understand the impact of these legacies on all beings and to find ways to make repair. 1 of 17 Agenda Item #4a(1). Minutes of the July 13, 2026 meeting Minutes of GEOLOGIC SAFETY COMMITTEE MEETING TOWN OF PORTOLA VALLEY Monday, July 13, 2026 Meeting location: Town Council Chamber in the Old Schoolhouse. This meeting was streamed via Zoom; the monitors in the schoolhouse were working. Committee Members Present: Nan Shostak [chair] Bob Wrucke [vice-chair] Patricia McCrory [secretary] Steve Ingebritsen Simon Klemperer Town Council Members Present: Mary Hufty, Town Council liaison MEETING SUMMARY Geologic Safety Committee (GSC) members discussed progress-to-date of the various subcommittees. The members then turned to discussion of suggested revisions pertaining the Seismic and Geologic Hazards portions of the Draft Safety Element. Call to Order & Roll Call: 1007. Chair Nan Shostak called the meeting to order. Oral Communication on Topics not on the Agenda: 1009. Bob Wrucke gave an update on his father’s health. Bob then led a brief overview of Bailey Willis’ controversial views on whether California had hazardous faults. A debate settled by the 1933 Long Beach earthquake. Old Business: 1015. Members provided updates on subcommittee progress. Bob continues to develop district-level evacuation maps for the town. Steve Ingebritsen noted that this year’s severe El Niño may include extreme weather events, such as heavy rains, in central California. Simon Klemperer mentioned that the Town of Woodside is already ordering sandbags. A general discussion of storm drain upkeep followed. Pat McCrory reiterated Ross Stein’s comments from our April meeting, namely that Japan has a more cohesive culture than the U.S. in responding to earthquake and geologic hazards. New Business: 1032. Committee will wait to approve the 08 June 2026 minutes, pending corrections. 1043. Committee approved implementing California’s Teleconferencing Meeting Policy. 1045. Nan led discussion of recommended changes to the Seismic and Geologic Hazards portions of the Safety Element. Nan urged that both the Geologic and Ground Movement maps be updated before release of Final Safety Element. Bob suggested evacuation districts be the same as those delineated by the Woodside Fire Protection District. 1118. Simon asked for the committee to request that members be able to review the maps before they are adopted. Pat asked for clarification regarding which earthquake regulations are mandated by the state and which are mandated by the town, in particular, building setbacks as defined by mapped fault traces. 1147. Simon suggested holding a special committee session with Catherine Engberg (Town Attorney), Sarah Cawrse (Director of Planning and Building), and Russ Graymer (USGS earthquake geologist) to clarify how the various regulations are implemented (via Ordinance 18.58.030 - Special building setbacks along earthquake 2 of 17 faults, available online). Simon requested preliminary “cheat sheets” for the discussions and drafted a letter with questions. 1155. Committee approved the revised text for Seismic and Geologic Hazards portions of the Safety Elements with additional tweaks as discussed in meeting. 1210. Pat left the meeting. Committee continued discussion. Adjournment: 1225. Committee voted to adjourn meeting. 3 of 17 Addendum #1 to Agenda Item #4a(1). Defining Faults. Simon Klemperer’s draft questions and notes on Town’s fault ordinance (written and discussed during the July meeting) 1. Alquist-Priolo defined active traces – in PV, ONLY San Andreas multiple traces – LEGALLY ACTIVE 2. Alquist-Priolo studied faults found NOT to have surface breaks in last 11000 years, so LEGALLY INACTIVE—I think MANY in PV, but I don’t know which. I think Hermit=Monte Vista; I think Berrocal, Butano, … These are generally mapped as Quaternary, Nan’s “Secondary Faults”, Pilarcitos Fault. Frog Pond Fault. Does the LEGAL definition of inactivity at a specific site mean that LEGAL inactivity is propagated along the entire named section? If a trench finds there is no fault, even though the trench was excavated across the nominal trace of the fault, does the fault get removed from the map? Or does the fault get moved on the map to avoid the trench? 3. Fault traces shown on maps that have not been the subject of specific study and therefore cannot LEGALLY be determined to be Active or Inactive. Black Mountain. Also faults suspected but not shown on existing maps. 4. Additional soil-condition ordinances and landslide-vulnerability ordinances Role of hypocentral locations? Bob recommends we read Nancy Lund’s “History of Portola Valley” Dwight Crowder (USGS) – his role in constructing the PV ordinances around fault hazard. Dwight was (maybe?) the first Chair of the GSC. George Mader (Stanford, AES, consulting professor) was Consulting Town Planner and took the PV ordinance to Sacramento that eventually developed into Alquist-Priolo. 4 of 17 Addendum #2 to Agenda Item #4a(1). GSC Submitted Comments and Recommendations for Changes for the May 2026 Draft Safety Element (emailed to PV Planning Director 8/14/2026) Geologic Safety Committee Comments and Recommended Changes for the May 2026 Draft Safety Element The GSC Safety Element subcommittee reviewed the Draft Safety Element of May 2026 and presented its recommendations for full-committee approval before submission to the Planning and Building Department. At its 7/13/2026 meeting, the GSC reviewed the subcommittee’s work. The GSC’s recommendations and suggested changes to the Draft Safety Element are described below: 1. The GSC approved the subcommittee’s changes to the written sections of the Draft Safety Element but did not approve the maps, which had numerous significant errors. The GSC recommends that it be given the opportunity to review the maps in the Seismic and Geologic Hazards section before the final document is submitted to the Planning Commission/Town Council for approval. 2. Consolidation of the subcommittee’s many comments and changes was thought to be particularly important for pages 15, 18, and 23. The changes to those pages are below. 3. All other comments and recommendations for changes to the Draft Safety Element remain as annotations in the Draft as previously submitted to the Planning Director. Page 15 Seismic and Geologic Hazards Seismic and other geologic hazards are traditionally addressed together because they both involve the movement of the Earth's surface. Although some geologic events (landslides, subsidence, erosion, etc.) can and do occur independently, the primary catalyst for their occurrence is often a seismic event, commonly called an earthquake. A key consideration for seismic hazards is the potential for cascading effects (a “chain reaction”) resulting from an event. A large earthquake commonly triggers secondary seismic hazards such as movement on nearby faults, fire, landslides, soil liquefaction, ground deformation, and failure of infrastructure (communications, roads, and utilities). Breach of a dam from shaking or direct rupture can lead to flooding. 5 of 17 Page 15 Seismically Induced Surface Rupture [BOX] The Earth's crust is composed of large tectonic plates that are in constant motion, moving toward, away from, or past one another. This constant movement means that where two plates grind past each other, a r