Portola Valley committee seeks cost estimate from Cottonshers, advances plan to digitize and georeference town geologic maps

The Portola Valley Geologic Safety Committee agreed to pursue a cost estimate from Cottonshers for updating the town's geologic and ground‑movement potential maps and to explore options for digitizing the town's geotechnical reports. Members highlighted gaps between the town's map products and the potential value of a georeferenced GIS layer for planning and evacuation mapping.

Why it matters: committee members said updated, georeferenced maps would allow officials and residents to overlay alternate fault interpretations, toggle USGS/CDMG layers, and better plan evacuation routes and infrastructure resilience. Several speakers noted that many older geotechnical reports remain in physical storage and that digitization and cataloging by parcel would significantly improve public access.

The committee discussed process and responsibilities: members recommended a short meeting with planning and building director Sarah Course and town staff (Darcy) to clarify what the town wants, what records Cottonshers holds, and whether the cost estimate should come from staff or a committee volunteer. The group agreed that confirming the procurement history and contract details with Cottonshers is a necessary first step before asking for map changes.

Simon Clemper outlined preliminary survey work (magnetic, gravity, drone and shallow seismic data over local sites) and cautioned the data remain complex and not yet definitive for broad map edits. He said: "If the town is ready, they should go ahead. They shouldn't wait on any ground‑shaking discoveries from us." Several members urged a peer-review pathway, recommending collaboration with the USGS and the California Geological Survey to secure age-control trenching and formal review before proposing map changes for adoption.

Bob Rucky reported he has converted the town's PDF maps into geotiff files and encountered projection and synchronization issues: topographic contours match but some landslide polygons and other features do not align across the two maps, indicating quality-control work would be required before adopting GIS layers officially.

Next steps: the committee will ask staff whether the town wants them to draft a formal request to Cottonshers for a cost estimate, or whether staff will make that request directly. Members will also meet with Sarah Course to inventory town and Cottonshers holdings, discuss digitization options (flat-file cataloging vs. full scanning), and identify whether phased or per-request access is preferred. The committee recorded a formal motion to accept the minutes (approved by roll-call) and closed the meeting.