Geology Reports: When Required & Who Can Prepare?

  • Whenever a significant potential hazard to a proposed development is identified by a Geologic Hazards Assessment (GHA), or similar technical or field review by the County Geologist. Please see the requirements for a Geologic Hazards Assessment and definitions for “Development/Development Activities.”
  • Land divisions and critical structures and facilities in the areas defined as Earthquake Fault Zones on the state Alquist-Priolo Earthquake Fault Zoning Act maps, or County designated fault zones,
  • New reservoirs to serve major water supplies,
  • When a property has been identified as “Unsafe to Occupy” due to adverse geologic conditions, no discretionary approval or building permit (except approvals and permits that are necessary solely to mitigate the geologic hazard) shall be issued prior to the review and approval of geologic reports and the completion of mitigation measures, as necessary
  • For all new water tanks in excess of 10,000 gallons either as a single tank or multiple tanks on a site, which are located in an area of geologic hazards as identified by the County Geologist.

Engineering geology reports must be prepared by a geologist licensed by the State of California Board for Professional Engineers, Land Surveyors and Geologists. Only reports prepared by a properly licensed professional will be accepted for review by the County. A list of local engineering geologists can be found here.

The primary concern with hiring a consultant should be that they know about the County report guidelines and are willing to meet these in a cost effective manner. The applicant should consult several sources, such as project design professionals, for references or recommendations of specific consultants. It is also advisable to obtain proposals and cost estimates from several different firms before a consultant is chosen. In many cases, several different firms should be consulted about report scope and cost before one is chosen.

Large projects, or development on geologically complex sites, can often require a team of professionals including an engineering geologist, a soils (geotechnical) engineer and a civil engineer. It is important that these professionals coordinate and communicate with one another; this coordination should be specifically included in their proposals. Coordination between the engineering geologist and the soils engineer is particularly important. The Soils Report prepared by the Soils Engineer will rely heavily on the geologic information contained in the Engineering Geology Report. Similarly, the civil engineer, who may design the foundation, retaining walls or other structural elements, will rely on the recommendations and design specifications laid out by the soil engineer. Ultimately, the final development plans will need to be reviewed by each professional to ensure consistency with their respective recommendations.