While it is recognized that no known major earthquake faults are located within the Town limits, the Town is located in a seismically active area of Southern California. The Helendale and North Frontal Faults are located within the Town's Sphere of influence and the San andreas and San Jacinto faults are located in the vicinity. All of these faults are considered active faults that may generate potentially damaging earthquakes.

The purpose of the Seismic Hazard (SH) Overlay District is to provide land use regulations within designated seismic fault zones, as identified in the Alquist-Priolo Special Studies Zone Act and the Safety Element of the General Plan, to protect the public health, safety and welfare and to minimize losses to property and life due to earthquakes by:

A.

Restricting or prohibiting uses that are dangerous to the public health, safety, welfare and property in close proximity to seismic fault lines; and

B.

Requiring that uses vulnerable to earthquakes, including public facilities that serve such uses, shall be protected against earthquake damage at the time of initial construction.

The objectives of the SH district are:

A.

To prohibit occupancy or the encroachment of any structure, improvement or development in close proximity to seismic fault lines; and

B.

To prevent economic loss caused by earthquakes and to prevent the loss of life or property.

The SH district is a supplement to the basic underlying land use district and shall be applied in a uniform manner to those properties that, after considering evidence from seismic experience and geologic investigations, are deemed to be in close proximity to seismic fault lines or are included in a special studies zone.

The Seismic Hazard Overlay District shall be in addition to the underlying zoning district in which it is located. The regulation of both the underlying and overlay district shall apply. In the event of a conflict between these regulations, the more strict regulation shall apply.

In accordance with the provisions of the Alquist-Priolo Special Studies Zone Act (Division 2, Chapter 7.5 of the Public Resources Code), a geologic investigation shall be required for any development proposal involving structures for human occupancy within special study zones. A geologic investigation is also required for areas not in a special study zone but that are deemed, due to seismic experience, to be in close proximity to a seismic fault line.

Exemptions from the provisions of this Section may be granted under the following circumstances:

A.

The proposal involves a single family wood frame residence on a parcel of land for which a geologic investigation has been previously prepared and approved;

B.

The proposal involves a single family wood frame residence not exceeding two (2) stories when such residence is not part of a development of four (4) or more residences. A mobile home that exceeds eight (8) feet in width shall be considered to be a single family wood frame residence not exceeding two (2) stories.

C.

The proposal is limited to an addition or alteration to a structure which does not exceed fifty (50) percent of the value of the structure prior to the proposed addition or alteration.

D.

Exemptions are granted by the Town Engineer and Building Official based upon a determination that there is no undue hazard of significant rupture.

Since active faults may exist outside of identified hazard zones, geologic investigations shall be required for the following critical uses:

A.

Emergency operation centers (EOCs);

B.

Police, fire and communications systems;

C.

Hospitals and other emergency medical facilities;

D.

Ambulance services;

E.

Schools, churches and other public assembly uses;

F.

Those uses that manufacture, handle or store hazardous or explosive materials;

G.

Power plants;

H.

Utility substations;

I.

Dams;

J.

Sewage treatment plants; and

K.

Water works.

A.

General. Geologic investigations shall be prepared by a geologist registered in the State of California and shall be reviewed for acceptance by a geologist registered in the State of California who is either an employee or under contract to the Town. Copies of all geologic investigations shall be kept on file in the office of the Town Engineer. Investigations involving proposals within a special study zone shall be filed with the State Geologist within thirty (30) days of acceptance by the Town.

B.

Contents. Geologic investigations shall consider ground shaking as the greatest potential risk and include a thorough evaluation of potential hazards based on soil types, slope stability, proximity to fault lines and expected magnitude. The subjects listed below should be addressed in any geologic report on faults. Some of the investigative methods listed below should be carried out well beyond the site being investigated. However, it is not expected that all of the methods identified below would be included in each report. The text of the geologic report shall include:

1.

A statement of the purpose and scope of the investigation;

2.

The geologic setting;

3.

A site description and site conditions. Include information on geologic units, graded and filled areas, vegetation, existing structures and other factors that may affect the choice of investigative methods and the interpretation of data.

4.

Methods of investigation

a.

A review of published and unpublished literature and records concerning geologic units, faults, groundwater barriers, and other factors.

b.

Stereoscopic interpretation of aerial photographs and other remotely sensed images to detect fault related topography, vegetation and soil contrasts, and other lineaments of fault origin.

c.

Surface observation, including mapping of geologic and soil units and structures, geomorphic features, springs, deformation of manmade structures due to fault creep, both on and beyond the site.

C.

Subsurface Investigation. Subsurface investigation shall include the following:

1.

Trenching and other extensive excavations to permit detailed and direct observation of continuously exposed geologic units and features that must be carefully logged;

2.

Borings and test pits to permit collection of data on geologic units and ground water at specific locations. Data points must be sufficient in number and adequately spaced to permit valid correlation and interpretation.

D.

Geophysical Investigations. Geophysical investigations are indirect methods that require a knowledge of specific geologic conditions for reliable interpretations. They should not be employed alone without knowledge of the geology. Geophysical methods alone never prove the absence of a fault nor do they identify how recent the activity. The types of equipment and techniques used should be described, which include the following:

1.

Seismic refraction;

2.

Magnetic intensity; and

3.

Other (e.g., electrical resistivity, seismic reflection, ground-penetrating radar, gravity).

E.

Other Methods. Other methods should be included when special conditions permit, or requirements for critical structures demand, a more intensive investigation. These methods may include, among possible others:

1.

Aerial reconnaissance overflights;

2.

Geodetic and strain measurements, microseismicity monitoring, or other monitoring techniques; and

3.

Radiometric analysis (14C, K-Ar), stratigraphic correlation (fossils, mineralogy), soil profile development, paleomagnetism (magnetostratigraphy), or other age dating techniques to identify the age of faulted or unfaulted units or surfaces.

F.

Conclusions. The geologic report shall contain appropriate conclusions including, at a minimum, the following:

1.

Location and existence (or absence) of hazardous faults on or adjacent to the site;

2.

Type of faults and nature of anticipated offset, including sense and magnitude of displacement, if possible;

3.

Probability of or relative potential for future surface displacement. The likelihood of future ground rupture seldom can be stated mathematically, but may be stated in semi-quantitative terms such as low, moderate, or high, or in terms of slip rates determined for specific fault segments; and

4.

Degree of confidence in and the limitations of data and conclusions.

G.

Recommendations. Recommendations relating to the following shall be included in the geologic report:

1.

Setback distances from hazardous faults, if appropriate. State and local law may dictate minimum standards;

2.

Need for additional studies; and

3.

Risk evaluation relative to the proposed development.

H.

The geologic report shall include references, illustrations, appendices and authentication described as follows:

1.

References. References shall include:

a.

Literature and records cited or reviewed, citations shall be complete;

b.

Aerial photographs or images interpreted, list the type, date, scale, source and index numbers; and

c.

Other sources of information, including well records, personal communications and other data sources.

2.

Illustrations. Illustrations are essential to the understanding of the report and to reduce the length of text. They shall include:

a.

Location map. Identify the site locality, significant faults, geographic features, regional geology, seismic epicenters, and other pertinent data; a scale of 1:24,000 is recommended;

b.

Site development map. Show site boundaries, existing and proposed structures, graded areas, streets, exploratory trenches, borings, geophysical traverses, and other data; a scale of 1:200, or larger, is recommended;

c.

Geologic map. Shows distribution of geologic units (if more than one), faults and other geologic structures, geomorphic features, aerial photo lineaments, and springs; on a topographic map, a scale of 1:24,000 is recommended;

d.

Geologic cross-sections, if needed to provide a three-dimensional picture;

e.

Logs of exploratory trenches and borings. Show details of observed features and conditions; should not be generalized or diagrammatic. Trench logs should show topographic profile and geologic structure at a 1:1 horizontal to vertical scale; and

f.

Geophysical data and geologic interpretations.

3.

Appendices. Appendices shall include supporting data not included above (e.g., water well data).

4.

Authentication. Authentication shall include the signature and registration number of the investigating geologist.