Chapter 8.264 — GH DISTRICT (GEOLOGIC HAZARDS DISTRICT REGULATIONS)

San Mateo County Zoning Code · 2026-06 edition · updated 2026-07-25 · San Mateo County

8.264.010 - Purpose Of The Geologic Hazards (“GH”) District. ¶

The purpose of the “GH” District is to safeguard life, limb, property and the public welfare by regulating land development in areas determined to be hazardous for development because of geologic factors.

8.264.020 - Regulations. ¶

The regulations of this Chapter shall apply in the “GH” District. The “GH” District is an “overlay” district which may be combined with any of the districts specified in Article 1 of the San Mateo County Ordinance Code, or other districts which may from time to time be added by amendment to Title 8. The regulations of this Chapter shall apply in addition to the regulations of any district with which the “GH” District is combined. Each Geologic Hazards District shall be numbered in chronological sequence as adopted by County.

8.264.030 - Uses Permitted. ¶

Land use and density shall be determined by the underlying zone except where the regulations of the GH District are more restrictive. In this case, land use and density shall be regulated by the requirements of the “GH” District.

8.264.040 - Geotechnical Investigations And Development Requirements. ¶

Prior to designating an area a GH District, a geotechnical report for the area shall be prepared by a certified engineering geologist under the direction of, or subject to review by, the County Geologist. This report shall meet the requirements set forth in Minimum Standards for Geotechnical Reports prepared by San Mateo County. Within the Coastal zone, applicable portions of the California Division of Mines and Geology publications shall also be incorporated into the report. These are #37 (Guidelines for Geologic/Seismic Reports), and #44 (Recommended Guidelines for Preparing Engineering Geologic Reports).

The conclusions and recommendations set forth in the geotechnical report shall become the standards for review in that GH District and shall govern development. Regulations necessary for safe development in each district will vary according to the geologic conditions of the area.

8.264.050 - Action On Building Permits. ¶

No building permit shall be approved in a “GH” District until:

(1) It has been evaluated by the County Geologist and has met the criteria set forth in the district regulations. The County Geologist shall approve, approve with conditions, or disapprove any building permit in the “GH” District.

San Mateo County, California, Code of Ordinances Title 8 – Zoning & Development Code

(2) The applicant has recorded the following restriction which binds the applicant and any successors in interest on the parcel deed:

This property is located in Zone ____ of the Seal Cove Geologic Hazards District established by Section 8.264.070 of the San Mateo County Ordinance Code. Maps of this district are on file with the County Geologist and the Planning Division, Department of Environmental Management, San Mateo County.

(Prior § 6295.4(2) Amd. Ord. 2890: 06/05/84)

8.264.060 - Modification Of Geologic Information. ¶

The geologic hazard zones, maps and conclusions may be modified upon receipt of new information following review and approval by the Board of Supervisors, Planning Commission and County Geologist.

8.264.070 - Geologic Hazard (“GH”) District - 1 (Seal Cove Area). ¶

1. Area Of Geologic Hazard.

Reference is hereby made to the Geotechnical Hazards Map for the Seal Cove Study Area prepared by William Cotton and Associates dated August 5, 1980, which is on file with the County Geologist and in the Planning Division, Department of Environmental Management, San Mateo County. Reference is further made to the three geotechnical hazard zones designated on the map; Zone 1, Zone 2 and Zone 3 which delineate areas ranging from most hazardous to least hazardous.

2. Description Of Hazardous Zones In Seal Cove Area.

A. Zone 1. A potentially unstable area where risk to development is considered to be extremely high. It is reasonable to conclude that sea cliff retreat and associated landsliding will continue, resulting in property and structural damage. Rapid catastrophic slope failure of portions of the high, steep sea cliff located west of Ocean Boulevard is a possibility. Such an event could involve the loss of life as well as property damage. The feasibility of reducing the risk to acceptable levels in Zone 1 is extremely low.
B. Zone 2. An area of questionable stability, risk to development in this area is considered to be moderate to high. The likelihood of eliminating the risk is very low; however, it may be possible to reduce the impact of the hazard by proper site development.
C. Zone 3. The most stable part of the Seal Cove area; risk to development in this area is considered to be low to moderate. The major geologic hazard in this zone is the possibility of surface faulting along the main traces and subsidiary cross faults of the Seal Cove Fault system. These faults are considered to be

San Mateo County, California, Code of Ordinances Title 8 – Zoning & Development Code

active and capable of producing strong surface rupture and ground failure with associated strong ground shaking. The feasibility of reducing the risks to acceptable levels in this zone is considered generally high.

3. Geotechnical Investigations And Development Requirements.

The regulations of Table 1 shall be applicable in Zones 1, 2 and 3 as defined in the Geotechnical Hazards Map described in Section 8.264.070(1).

(Prior Ch. 19.5 § 6295,6296 Ord. 2777: 04/06/82)

	TABLE 1
ZONE	REQUIREMENT OF GEOTECHNICAL INVESTIGATION	DEVELOPMENT REQUIREMENTS
1 and 2	Prior to any development, there shall be an engineering geologic investigation by a certified engineering geologist and a soil and foundation engineering investigation by a registered civil engineer, or a combined equivalent of the above. Both investigations shall provide a detailed evaluation of the potential landslide hazards in this zone. In most cases, landslide studies will require extensive subsurface work in order to provide the necessary technical data to conduct a detailed slope stability analysis. The geotechnical analysis shall provide acceptable factors of safety to clearly demonstrate stability before construction is allowed in this zone.	No development shall be allowed in Zone 1 or 2 until the required geotechnical investigations have clearly demonstrated reasonable stability, in accordance with current professional standards of land structure.
3	Prior to any development, there shall be an engineering geologic investigation by a certified engineering geologist and a soil and foundation engineering investigation by a registered civil engineer, or a combined equivalent of the above, unless evidence is available to show that such investigations are not required. Engineering geologic investigation shall address the seismic hazards related to the master and branching traces of the Seal Cove fault. Particular emphasis of the engineering geologic investigations shall be placed on the evaluation of possible surface faulting. Investigative techniques within this area will require the use of subsurface trenching and possible geophysical traverses unless clear evidence is established to show that no active fault crosses the parcel in question. The soil and foundation engineering investigation shall address, but not necessarily be confined to, the following items: site preparation and grading, surface and subsurface, drainage, and design parameters for all proposed development.	Development shall be allowed in Zone 3 if suitable mitigation measures including, but not limited to, siting of homes away from active faults, structural and foundation design and adequate surface drainage plans are applied as recommended by any required geotechnical investigation.

San Mateo County, California, Code of Ordinances Title 8 – Zoning & Development Code

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