Fault‑zone trenching: Procter Terrace shows possible faulting; Hidden Valley shows no fault evidence in school redevelopment study

Santa Rosa City Schools released results of geologic trenching and seismic surveys Sept. 24 for Procter Terrace and Hidden Valley elementary campuses after the 2024 update of the Alquist‑Priolo Earthquake Fault Zone.

Findings - Hidden Valley Elementary: Geologists with Miller Pacific Engineering said trenching and geophysical surveys found no evidence of a surface fault crossing the site. The team dug through sediments older than 11,000 years, meeting state criteria for “no evidence of fault” on the tested area. Because the state regulatory zone extends beyond the site, a narrow 50‑foot strip was identified for further study before it could be designated fully buildable; additional non‑invasive geophysical surveys could be done on neighboring parcels with owner permission. - Procter Terrace Elementary: Miller Pacific reported layers and deformations in trench walls that indicate possible past ground movement near the southwest portion of the site. Because the trenching did not reach material old enough to demonstrate “absence of fault” under state rules, the report recommends a no‑build zone for habitable structures in a specified portion of the campus. District engineers said the no‑build recommendation applies to new habitable construction; fields, parking and non‑occupancy uses remain possible in the restricted area.

District and engineering response Director Eric Oden and Mike Jewett of Miller Pacific told the board that ZFA structural engineers examined Procter Terrace’s existing buildings and found no evidence of imminent structural failure. The buildings date to 1949 and were built to standards that pre‑date current codes; maintenance and ordinary repairs remain possible but any major renovation or a full re‑roof that triggers Division of State Architect (DSA) review could be constrained in the recommended no‑build area.

Practical implications District staff said typical maintenance such as patching remains permissible, but DSA review would be required for projects above routine maintenance and for any substantial remodel or replacement in the no‑build area. Portables remain a possible near‑term solution for rising enrollment; staff said portable installation could be completed before the next school year if the board directs them to proceed and if site logistics allow.

Ending: The district said it will factor the trench results into the facilities master plan and any future bond or state funding requests; staff will return to the board with recommendations for space‑management (including temporary classrooms) and the options for longer‑term site reuse.