Soils & Engineering Reports

What are Soils and Geology Reports?

Soils engineering (or geotechnical engineering) and engineering geology reports are used to better understand earth conditions affecting a proposed home or other development. The Engineering Geology Report is prepared by a Registered Geologist specializing in Engineering Geology. It describes and evaluates the geologic factors such as landslides, faults, seismicity (ground shaking), ground cracking, erosion and other such features that can affect the safety of development at a particular site. The Geology Report's findings and recommendations are considered by a Registered Civil Engineer experienced in soils engineering who prepares the Soils Engineering Report. Their work concentrates on testing the earth to design the foundation of the structures, mitigate any geologic concerns, and analyze how the geologic and soil conditions will affect grading. The actual design of the foundation is completed by the Soils Engineer and is one of the most prominent aspects of the Soils Report.

When Are Soils Engineering And Engineering Geology Reports Required?

These reports are required when soils or geologic concerns affect a site's development. Typical conditions that require geology reports are areas of high relief and bluff areas where landslides, faults, mud flows, erosion, etc., affect a proposed development. Certain geologic hazard areas (including flood zones and fault zones) are shown on maps maintained by the Planning Department and are available for review at the Zoning Counter. However, in most cases the determination as to whether an Engineering Geology Report is required is based on a field inspection of the actual development site by County staff. In most cases, this determination is made through the Geologic Hazards Assessment (GHA) process. Where the GHA identifies potential geologic hazards that require in-depth investigation, an Engineering Geology Report is required. Soils Engineering Reports are required to help mitigate geologic concerns, soil constraints such as expansive soils and areas of soil collapse, or when special foundations (such as pier and grade beam) are needed to compensate for the site's relief or geologic constraints.They are also needed when significant grading will occur. Please refer to the Soil Report Requirement Guidelines for more information on when a soils report is required.

Both soils and geology reports are becoming more common as larger houses are being built on steeper terrain. Applicants who wish to know as early as possible whether geology reports will be required can apply for a GHA prior to submitting their development plans. Information from the GHA and/or engineers reports can be utilized in the design of the project, thus providing for a quicker review of the actual development application.

Who Can Prepare Soils Engineering And Engineering Geology Reports?

Soils Engineering reports must be prepared by a licensed geotechnical engineer or registered civil engineer experienced in soils engineering. Engineering Geology Reports must be prepared by a registered geologist experienced in engineering geology. Only reports prepared by


properly licensed professional will be accepted for review by the County.

County Review Of Soil Engineering And Engineering Geology Reports

All reports must be reviewed and accepted by registered County personnel before development can be approved. There is a fee for report review, payable at the Zoning Counter at the time the reports are submitted. Report review focuses on the completeness of the reports as compared with published County guidelines and an overall review of the findings and conclusions of the reports to determine whether they adequately address soils and geologic concerns. If the report(s) are found to have deficiencies, a letter will be mailed to the consultant (with a copy to the applicant) describing the deficiencies. When the report is accepted, the owner will be notified of its acceptance and any special requirements such as the need for the Geologist and/or Engineer to review the final plans for conformance with report recommendations.

How Should a Consultant Be Hired?

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 constants. 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.

Coordination of Professionals

Large projects, or development on geologically complex sites, can often require a team of professionals including an engineering geologist, a 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 geotechnical engineer is particularly important. The Soils Engineering Report prepared by the Geotechnical Engineer will rely heavily on the geologic information contained in the 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 geotechnical engineer. Ultimately, the final development plans will need to be reviewed by each professional to ensure consistency with their respective recommendations.

For Further Information

Consult the County's Geologic Hazards Ordinance (County Code Chapter 16.10) for a detailed discussion of regulations applicable in areas with geologic hazards. The County Geologist can be reached at (831) 454-3175 or email.