Atkins Report & Debris Flow Rebuilding FAQs
For parcels where rebuilding sites are subject to debris flow hazards, pre-application Geologic Hazard Clearances (GHCs) have resulted in a requirement for further geologic evaluation before a clearance can be approved. In some cases, debris flows are the only potential geologic hazard on the building site, in other cases there may be other geologic hazards such as slope instability or landsliding present in addition to debris flows. In both cases the further geologic evaluation that was required would produce recommendations on how to mitigate the hazards on site.
The requirement for further geologic evaluation and mitigation comes from Santa Cruz County Code (SCCC) Chapter 16.10, which requires that staff confirm through peer review of technical reports and designs that geologic hazards can be adequately mitigated prior to approving a development. Pursuant to the Board of Supervisors “CZU Rebuild Directive” issued 9/14/21, for eligible, in-kind rebuild projects, property owners may choose to “opt out” of the requirement for geologic reports, County peer review of geologic and geotechnical reports, and County confirmation of the adequacy of proposed mitigation measures .
While the CZU Rebuild Directive allows those rebuilding in-kind to “opt out” of County geologic evaluation and mitigation requirements, the California Building Code still requires submission of a geotechnical report that includes an evaluation of slope instability. Building Plan Check review includes verifying that the geologic report recommendations are incorporated into the building permit plans and calculations. (The term “geotechnical report” is used interchangeably with “soil report”).
Geotechnical engineers typically work with a geologist to define the various parameters necessary to design debris flow mitigation measures. Due to the time and cost to produce site-specific geologic reports, the Community Foundation of Santa Cruz County funded a flood and debris flow hazard study (“Atkins Study”) that, among many broader beneficial uses, assists rebuilders by providing debris flow depth and velocity data for use by geotechnical engineers in lieu of the results of a full geologic evaluation. This depth and velocity data is available for the areas identified in the Atkins report as being within a ”Primary Debris Flow Path”.
The following information should clarify how to interpret the results of the Atkins Study, and how the data provided in the study may streamline the permit process for those rebuilding in-kind in debris flow hazard areas. It is important to note that the first step in the permit process is applying for a Geologic Hazard Clearance. This pre-application review of geologic constraints on a building site will identify whether your site is subject to geologic hazards, and if so, whether the only hazard is debris flow , or if other conditions must be addressed as well.
(Please also note that two other pre-clearances to confirm adequate septic and fire access, are also required prior to making an application for a building permit. This ensures that the technical challenges in these three areas are addressed before investing in final building plans, and that your various professionals are working together as a team.)