HomeMy WebLinkAboutItem 3.23.2
Town of Los Altos Hills November 1, 2007
Staff Report to the Planning Commission
RE: PROPOSED AMENDMENTS TO THE GENERAL PLAN INCLUDING UPDATED
SAFETY AND NOISE ELEMENTS WITH INITIAL STUDY AND NEGATIVE
DECLARATION
FROM: Leslie Hopper, AICP, Project Planner
APPROVED BY: Debbie Pedro, AICP, Planning Director -3)0
RECOMMENDATION That the Planning Commission:
1. Review the proposed amendments to the General Plan and the proposed Initial
Study/Negative Declaration and consider comments from the public.
2. Make a recommendation to the City Council to approve the Initial Study/Negative
Declaration and adopt the proposed amendments to the Los Altos Hills General Plan with
any modifications deemed appropriate.
BACKGROUND
In July 2005 the City Council established the Ad Hoc General Plan Committee and authorized it
to begin updating the General Plan. The broad-based Committee has six members, including a
member of the City Council and a member of the Planning Commission. The Committee has
been meeting twice a month to update six of the nine existing elements of the Town's General
Plan. The City Council approved and adopted the updated Introduction, Conservation Element,
and Open Space & Recreation Element on April 26, 2007. The updated Safety and Noise
Elements are cimently under review.
THE GENERAL PLAN
The General Plan is the Town's blueprint for the future. It provides policy direction for land use
decisions regarding the conservation of resources and the development of the community.
Sometimes described as a local constitution, the General Plan provides a legal foundation for
zoning, site development and subdivision ordinances, all of which must be consistent with the
General Plan. The State mandates that the General Plan include seven elements: Land Use,
Housing, Circulation, Conservation, Open Space, Noise, and Safety. Other elements such as
Recreation and Pathways are optional.
STATE REOUIREMENTS
The State requires the Housing Element to be updated every five years, and the Governor's
Office of Planning and Research (OPR) recommends that the other elements be updated every
eight to ten years. The existing Safety and Noise Elements have not been comprehensively
updated since they were adopted in 1975.
Planning Commission
November 1, 2007
Page 2 of 3
UPDATEPROCESS
The General Plan Committee divided the six elements to be updated into three phases:
Phase 1—Introduction, Open Space & Recreation Element, and Conservation Element
(adopted by the City Council on April 26, 2007)
. Phase 2 --Safety and Noise Elements (currently under review)
. Phase 3—Land Use Element (to be updated in 2008)
The General Plan Committee reviewed the existing Safety and Noise Elements to correct errors,
inaccuracies and obsolete references. The format was updated to produce more accurate, legible
and reproducible documents, including improved graphics that accurately depict existing
conditions in the Town. hl addition, the goals, policies and programs were reviewed to ensure
that they were relevant and appropriate.
PARTICIPATION BY OTHERS
The Los Altos Hills County Fire District actively participated in the development of the draft
Safety Element. In addition, the Town's consulting geotechnical engineers (Cotton, Shires and
Associates) provided assistance. As required by the State, the draft Safety Element was sent to
the Department of Conservation, the Department of Forestry and Fire, and the Office of
Emergency Services for review, and their comments have been incorporated in the draft
document.
The Town's noise consultant (Charles M. Salter Associates) prepared noise contour maps as
required by the State and provided assistance in development of the draft Noise Element.
NEW POLICIES AND PROGRAMS
Most of the policies and programs in the draft Safety and Noise Elements are already included in
the existing General Plan. Proposed new policies and programs are highlighted in yellow in the
text of the public review draft. In addition, they are summarized in Attachment 2. In most cases,
the new policies and programs reflect the Town's current practice. A few new programs commit
the Town to actions such as encouraging participation in the Neighborhood Watch Program and
updating the noise ordinance.
PUBLIC NOTICE
Public notice was published on October 17, 2007 in the Town Crier pursuant to Government
Code Section 65090. In addition, notice was posted and a Townwide mailing was done ten days
prior to the Planning Commission hearing pursuant to LAH Municipal Code Section 10-1.1105.
ENVIRONMENTAL REVIEW
In compliance with the California Environmental Quality Act (CEQA), an Initial Study was
prepared and a Negative Declaration is proposed for the project. The proposed amendments are
intended to fine-tune and strengthen existing policies and programs that preserve the Town's
quiet environment and protect the public from natural and human -caused safety hazards. New
Planning Commission
Nov=W 1, 2007
Page 3 of 3
policies and programs are intended to provide additional environmental protection. No adverse
environmental impacts will result from adoption of the proposed General Plan amendments.
COMMENTS RECEIVED
No comments have been received to date.
ATTACHMENTS
I. Public Review Draft of Proposed Amendments to the Los Altos Hills General Plan
(Noise Element, Safety Element and Appendix A -Household Hazardous Waste)
2. Summary of New Policies and Programs
3. Initial Study and Negative Declaration
4. Existing Safety and Noise Elements of the 1975 General Plan
Attachment 1
Town of Los Altos Hills
GENERAL PLAN UPDATE
2007
PUBLIC REVIEW DRAFT
October 2007
LOSALTOS HILLS
low-,
CALIFORNIA
Town of Los Altos Hills
GENERAL PLAN UPDATE
Phase Two
Public Review Draft
Safety Element
with Appendix A
Noise Element
General Plan Update Committee
Mike O'Malley, Chairman City Councilmember
Carl Cottrell Planning Commissioner
Carol Gottlieb
Dot Schreiner
Elayne Dauber
Janet Vitu
Planning Staff
Debbie Pedro Planning Director
Leslie Hopper CSG Consultants, Inc.
26379 Fremont Road, Los Altos Hills, CA 94022
Phone: 650-941-7222 Fax: 650-941-3160
www.losaltoshills.ca.gov
SAFETY ELEMENT
Public Review Draft
October 17, 2007
LOS ALTOS HILLS GENERAL PLAN
Public Review Draft 10/17/07
Safety Element
INTRODUCTION
Purpose
801. The protection of public safety is one of the principal, if not foremost, responsibilities of
government. Risks to life, property and the environment associated with both natural and
human -caused hazards can affect the entire community by requiring costly public and
private expenditures and physically changing the environment. It is thus the Town's
responsibility to protect the public interest by making informed land use decisions,
requiring safe development practices, and ensuring that Los Altos Hills continues to be a
safe, secure community.
802. The Safety Element identifies safety hazards and establishes goals, policies and programs
that protect the community from natural hazards such as earthquakes, landslides,
flooding, and wildfires. The Safety Element also addresses human -caused threats to
public safety such as structural fees, crime, and hazardous waste. The contents of the
Safety Element are presented in the following sections:
• General Safety Measures
• Seismic and Other Geologic Hazards
• Flood Hazards
• Fire Hazards
• Law Enforcement
• Hazardous Waste
• Disaster Response
803. While the Safety Element has implications for land use policy, it also provides direction
for needed actions in other aspects of Town government. It is of utmost importance that
development regulations such as zoning, subdivision, grading and building codes provide
effective controls and procedures related to Safety Element policies. In addition,
recommendations in the Safety Element relate to programs for disaster response and
recovery, fire protection, law enforcement, and utility systems.
State Requirements
804. State law requires every General Plan to have a Safety Element that addresses natural and
humancauscd hazards and dangers. State law does not dictate what local policy should
be with respect to safety, only that the hazards be recognized and addressed. The Safety
Element is closely related to other General Plan elements and overlaps topics addressed
in the Land Use, Housing, Circulation and Scenic Roadways, Conservation, and Open
Space and Recreation Elements.
Safety Element
Los Altos Hills General Plan
Page I
Public Review Draft 10/17/07
GENERAL SAFETY MEASURES
805. The Town of Los Altos Hills takes the following approach to ensuring the safety of its
residents:
• Use all practical measures to reduce existing high hazard levels, and
• Avoid creating further hazards through prudent planning, building, and
development pmctioes.
Moreover, the Town is committed to the principle that development shall be designed,
located and regulated to minimize the effects of natural hazards such as earthquakes,
landslides, flooding, and wildfire.
806. Thoughtful land use decisions are fundamental to public safety. Structures should not be
built on sites that are subject to high hazard levels unless such construction is
unavoidable or the risk to life and property can be mitigated to acceptable levels. When
development is contemplated in areas subject to natural hazards, issues such as the
stability of the underlying geologic formations, the location of flood plains, and the
ability to prevent and fight fires should be considered. Building or grading should
proceed only after all the likely consequences on the entire neighborhood (not just the
applicant's properly) have been evaluated and approved by competent professionals.
807. Structures should not be built unless the project geologist, architect, engineer, planner
and builder are satisfied that they meet adequate safety standards designed to prevent life-
threatening collapse or major damage in future earthquakes, landslides, flooding or fire.
GOAL
Protect the public from risk of personal injury and
property damage due to natural safety hazards.
Policy 1.1 Open space easements, zoning and other land use regulations shall
be used to limit and, in some cases, prohibit development in areas of
unstable terrain, active fault traces, water channels, flood plains,
excessively steep slopes and other areas determined to be hazardous
to public welfare and safety.
Policy 1.2 Unstable terrain, active fault traces, water channels, flood plains,
excessively steep slopes and other areas determined hazardous to
public welfare and safety shall not be developed unless unobtrusive
corrective measures can assure public safety.
Policy 1.3 The geologic and soils conditions of proposed development sites shall
be analyzed to ensure land stability and foundation hearing
capabilities.
Safety Element
Los Altos Hills General Plan
Page 2
Public Review Draft 10/17/07
SEISMIC AND OTHER GEOLOGIC HAZARDS
808. The primary geologic hazards within Los Altos Hills are landslides and seismic impacts
related to earthquakes. Seismically induced ground shaking, surface fault rupture,
liquefaction and other various forms of earthquake -triggered ground failure are
anticipated during major earthquakes. These geologic hazards present potential risks to
property and public safety.
809.
810.
Earthquakes
The Town of Los Altos Hills is
located in the San Francisco Bay Area, which is
recognized as one of the most active seismic regions in the United States. The U.S.
Geological Survey estimates that there is a 62% probability that at least one earthquake
of magnitude 6.7 or greater will
occur in the San Francisco Bax
a '' '
region before 2032. As shown on
the accompanying map, the
o ,,,•'
greatest probability is that a major
earth uake will occur on the
9
Hayward Fault. There is a 21%
chance of it occurring on the San
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nv. ,,,,,• _ .^^=w`^•°°-_^^_'<^+_
Andreas Fault, which would more
F
directly affect Los Altos Hills.
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While the effects of a major
_ %
earthquake would be widespread,
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the effects would be most intense
a,•
on lands with steeper slopes and3%
°'•'" ^•�°�'^ as
weak soils, which represent much
of the remaining undeveloped land
within Los Altos Hills and its
mw �, S
Sphere of Influence.
Source. Map and data from
Puffin Down Roots in
Earthauake Country a
handbook developed by the
USGS, ABAG, the American
Red Cross -Bay Area and
others specifically for the
Bay Area (2005).
The Town is traversed by three major fault lines, all of which are considered to be
potentially active:
• Berrocal Fault, which runs from the western Town border to the southeastern tip
of the Town boundaries.
• Altamont Fault, which runs parallel to the Berrocal Fault to the north.
• Monte Vista Fault, which meanders from the northwest quadrant to the southeast
quadrant of the Town.
Safety Element
Los Altos Hills General Plan
Page 3
Public Review Draft 10/17/07
811. Additionally, there are two large fault lines within Santa Clara County that are known to
be currently active and could endanger the stability of hillsides in Los Altos Hills:
• San Andreas Fault, located along the west coast.
• Calaveras Fault, located further inland.
Although these two faults do not traverse Los Altos Hills, it is likely that more earth
movement would result within Town limits than within nearby communities due to the
Town's steep topography and unstable soils.
812. In October 1989, the Loma Prieta earthquake
originated in the Santa Cruz Mountains and caused
significant damage in Los Altos Hills, resulting in
the demolition of 7 homes and necessitating
substantial repairs to more than 25 residential units.
The damage seen from the Loma Prieta earthquake
bears out the continued necessity for stringent
seismic safety regulation in Los Altos Hills,
including restrictions on the siting of development
and requirements for high standards of engineering
design to ensure adequate safety levels in the event
of strong earth movement.
F3Ri!
Moat of the development in Los Altos Hills is of
one- or two-story residential woodframe This home on La Cresta Drive was
damaged i
construction. Woodframe structures Inkinglateral t Me 7989 magnitude 8.9
Loma Prieto eadhouake.
bracing adequate to resist seismic forces may suffer
structural failure. Any unreinfamed brick or concrete structures also could receive
considerable damage. Schools, fire stations, major utility lines and installations,
communications systems and freeway interchanges were constructed to meet the seismic
standards that were in effect at the time of construction. A review of such sites with
regard to current standards might be warranted, however.
Ground Failure
814. Most of the valleys and flatlands along the bay are underlain by recent loose materials
that have not been compacted and hardened by long-term natural processes. Landslides
are common on most of the hills and mountains as loose material moves downslope. In
addition, many human activities tend to make earth materials less stable and thus increase
the chance of ground failure. Some of the natural causes of instability are earthquakes,
weak earth materials, stream and coastal erosion, and heavy rainfall. Human activities
that contribute to instability include oversteepening of slopes by undercutting them or
overloading them with artificial fill, extensive irrigation, poor drainage, withdrawal of
groundwater, and removal of stabilizing vegetation. These causes of failure, which
normally produce landslides and differential settlement, are augmented during
earthquakes by strong ground motions that result in rapid changes in the state of earth
materials. These changes, through liquefaction and loss of strength in fine-grained
materials, result in landslides during earthquakes as well as differential settlement,
subsidence, ground cracking, ground lurching, and a variety of transient and permanent
changes in the ground surface.
Safety Element
Los Altos Hills General Plan
Page 4
Public Review Draft 10/17/07
815. It is very difficult to anticipate the extent of probable ground failure in Los Altos Hills in
response to seismic shaking. Experts agree that many seismic induced land failures in the
hills in the Bay Area are certain to occur, especially where man has disturbed the natural
slope equilibrium through cutting, filling and placing structures. One would also assume
that other types of ground failures would occur along valley floors on alluvial materials
that can lose their strength under shaking conditions.
Landslides
816. A landslide is the downhill movement of masses of earth material under the force of
gravity. Landslides can be induced by natural processes such as heavy rainfall or fault
ruptures or by human activities such as grading, construction, or excessive watering.
Damage due to landslides can be reduced in areas undergoing development through
avoidance, removal, or permanent stabilization of slide masses. In all cases, a first and
critical step is to recognize the existence of an old slide or the probability of a future
slide. This is accomplished through detailed geologic mapping, trenching, drilling, and
the photo -interpretation of surface geologic conditions.
817.
Based on available data and experience, it appears that there are probably no massive
landslide areas in most of the Town. However, there are small landslide areas ranging in
size from less than an acre to a few acres. In recent years, landslides have occurred on La
Cresta Drive, Atherton Court, Edgerton
Drive, Page Mill Road and Stonebrook
Avenue near the old quarry. There are
also areas of potential landslide. These
conditions require care on the part of
the Town and developers since even
small slides can destroy or badly
damage homes and streets.
Considerable care should be taken in
development of those portions of Los
Altos Hills where known landslide
hazards exist. Good review procedures
of the geologic aspects of development Landslide on Edgerton Drive in 1998.
are especially critical.
Erosion and Sedimentation
818. Erosion generally involves two distinct problems: the wear and removal of material from
one site, and the deposition of sediment at another. Factors influencing the rate of
erosion at any particular location include climate, weather, rock and soil characteristics,
slope and vegetation. Erosion occurs chiefly on steeper slopes in the upper reaches of
drainage basins where runoff velocities are high. Sedimentation takes place mainly in
the lower reaches of drainages where stream gradients and velocities are reduced.
819. Soils maps of Santa Clam County prepared by the U.S. Soil Conservation Service
indicate that 80% to 90% of Los Altos Hills has soil classifications with high to very
high soil erosion hazard. These soils are in the mountain and hill areas. Moderately high
erosion potential also exists along some short, steep drainages. Sedimentation occurs
along the main creeks and tributary drainages, chiefly where human activities have
altered stream flow characteristics.
Safety Element
Los Altos Hills General Plan
Page 5
Public Review Draft 10/17/07
Expansive Soils
820. Expansive soils are earth materials that greatly increase in volume when they absorb
water and shrink when they dry out. Expansion is most often caused by clay minerals
that attract and absorb water from moisture in the air or ground. When buildings are
placed on expansive soils, their foundations may move and crack, distorting the building
structure and warping the doors and windows. The adverse effects of expansive soils can
be avoided through proper drainage and foundation design. Soils maps indicate that
practically the entire Town is included in soil groups with high shrink -swell
characteristics, with some limited areas noted as having moderate shrink -swell
characteristics.
821. Adequate engineering techniques can control damage from expansive soils and expansive
bedrock, but regulatory vigilance should be exercised and improved to ensure that site
investigations and, if warranted, proper engineering are carried out before construction.
GEOTECHNICAL MAPPING AND
SITE-SPECIFIC INVESTIGATION
The geotechnical and seismic hazards map at right identifies
potential hazard zones where there is a possibility of fault
rupture, slope instability, or ground deformation. In addition, the
California Geological Survey has prepared seismic hazard zone
maps that identify areas susceptible to amplified shaking,
liquefaction, earthquake -induced landslides, and other ground
failures. Pursuant to the California Seismic Hazards Mapping
Act, the Town requires applicants to submit site-specific
geological hazard investigations for construction projects located
within seismic hazard zones.
The site-specific investigation evaluates the site to determine its
ability to support the proposed structures. The Town's consulting
geotechnical engineers review the soils reports and the
recommended mitigation measures to ensure that structures are
safely designed to meet requirements for the geologic conditions
on the site. Soils reports are kept in Town files to provide a
record of site-specific information on geologic conditions and
potential hazards in Los Altos Hills.
Safety Element
Los Altos Hills General Plan
Page 6
Public Review Draft 10/17/07
GOAL
Minimize the risk of personal injury and property damage
due to seismic and other 1?eoloPac hazards.
Policy 2.1 Reduce the potential effects of seismic and other geologic hazards,
including slope instability.
Policy 2.2 Locate development so as to avoid geologic hazards, including slope
instability, to the maximum extent feasible.
Policy 2.3 In areas with known geologic hazards, limit development to minor
structures and improvements when damage would not threaten
human life or cause significant financial loss.
Policy 2.4 In the event that significant structures are required in geologically
hazardous areas, all reasonable measures shall be taken to minimize
the amount of risk involved.
Program 2.1 Maintain a map of known earthquake faults and other geologic hazards
in the Los Altos Hills planning area, and review and update the map as
new information emerges.
Program 2.2 Continue to utilize the geologic hazards map and other available
information from reliable sources such as the United States Geological
Survey and California Geological Survey to evaluate proposed
development and mitigate known geologic hazards.
Program 2.3 Ensure that proper erosion and sedimentation control measures are
undertaken for all development projects.
Program 2.4 Regularly review the Town's development regulations and building
codes and update them as necessary to incorporate the best available
standards for seismic safety and other geologic hazards.
Program 2.5 Continue to require applicants to submit a geotechnical report prepared
by a licensed geotechnical engineer for proposed new residences and
major additions on sites that have a potential geologic hazard. In cases
where a geologic hazard is confirmed, the engineering recommendations
in the geotechnical report shall be implemented to avoid or mitigate the
probable effects of the hazard.
Safety Element
Los Altos Hills General Plan
Page 8
Public Review Draft 10/17/07
FLOOD HAZARDS
822. Although most of the Town is outside the 100 -year flood plain boundary defined by the
Federal Emergency Management Agency (FEMA), certain areas along the creeks are
subject to flooding in a 100 -year storm. These areas are designated as a Special Flood
Hazard Area on FEMA's Flood Insurance Rate Map and are regulated under the Flood
Plain Management provisions of the Town's Municipal Code to minimize erosion,
maintain natural creek characteristics, and ensure safe housing conditions. While minor
flooding can oceur in undrained depressions or poorly graded areas in Los Altos Hills, the
main concern for flooding is centered on major creeks such as Adobe Creek and adjoining
areas. The Town has been working with the Santa Clara Valley Water District, which is
responsible for flood control, to minimize flooding along Adobe Creek and other flood -
prone areas.
Flood maps
published by the
Federal Emergency
Management
Agency am
available online at
the FEMA Map
Service Center at
www.lanmgov.
li
�. �M
Adobe Creek
near Edah Park
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urns vw.
xanz
823. One factor that contributes to flooding in Los Altos Hills is the reduced percolation
potential of the land caused by increased development and/or paving. During extended
periods of heavy rainfall, open/undeveloped lands are not sufficient to absorb the rainfall
and become saturated. Once soils are saturated, rainfall will sheet flow toward the lower
elevations, seeking available outlets. If an adequate storm drainage system is not in place
to dispose of the surface runoff, the end result will be flooding.
824. Traditionally the Town's approach to drainage has been to utilize natural drainage
channels rather than to install pipe drainage systems or to increase capacity by
straightening, widening, or lining creek channels. Given the policy of the Town to
preserve the natural quality of creeks and riparian corridors, it is important to prevent
development from increasing runoff to the point that channels become overloaded, and to
avoid new development in natural flood plains.
Safety Element
Los Altos Hills General Plan
Page 9
Public Review Draft 10/17/07
GOAL
Minimize the risk of personal injury and
property damage due to flooding.
Policy 3.1 Leave natural channels and flood plains in a natural state,
unencumbered by development to the maximum extent feasible.
Exceptions shall be made only in situations where it is essential to
protect established property values or for public safety.
Program 3.1 Continue to cooperate with the Santa Clam County Valley Water District
in planning to minimize flood problems.
Program 3.2 Continue to limit the amount of runoff in site development projects.
Program 3.3 Continue to implement the Flood Plain Management provisions of the
Municipal Code.
Program 3.4 Continue to maintain an adequate storm drain system.
Flooding has occurred along
this stretch of Adobe Creek,
where it passes through
Edith Park.
Concerned citizens formed the Adobe
Creek Watershed Group, which worked
with the Santa Clare Valley Water DisInct
to prevent flooding, erosion and loss of
habitat. The group received an
environmental stewardship award in
recognition of its efforts.
Safety Element
Los Altos Hills General Plan
Page 10
Public Review Draft 10/17/07
FIRE HAZARDS
825. Native plants and brush, combined with steep hillsides and canyons, make Los Altos
Hills a high-risk area for wildland fires. In July of 1985, extreme weather conditions
and dry vegetation fueled a fire that spread unchecked over an area of approximately 150
acres. Nine residences and three outbuildings were destroyed, with property damage
totaling more than $9 million. Wildfires such as this usually occur in the "fire season"
when high temperatures, low humidity and sustained or erratic winds combine with dry,
flammable vegetation to create highly volatile fires. Additional factors such as steep
terrain, limited access for emergency vehicles, and lack of water for firefighting can
make wildfires very difficult to combat.
826. Structural fires also pose a threat. Structural fires can occur any time of the year and are
generally contained by the use of fire resistant construction materials and building
setbacks, as well as the provision of adequate emergency vehicle access, water supplies,
and fire department emergency operations.
827. Emergency access roads, also known as fire
roads, are located at strategic locations
throughout Los Altos Hills. Fire roads allow
emergency vehicles access to neighborhoods
that do not have a through road. They are
typically secured by chain and padlock to
prevent through traffic from using the fire
roads except in emergencies. Figure C4 in
the Circulation and Scenic Roadways
Element illustrates the Town's network of
emergency roads.
Space Preserve /orfire hazards.
828. Fire protection, suppression and safety services are provided by the Los Altos Hills
County Fire District. The District contracts with the Santa Clara County Fire Department
for paramedic and fire protection services in the Town and neighboring unincorporated
areas. The District augments County Fire Department services by purchasing equipment
such as specialized fire apparatus for use in the high hazard brush and grass fire areas. In
addition, the District funds the following programs:
• Replacement of undersized water mains and installation of
new water mains and fire hydrants
• Brush chipping program to reduce flammable vegetation
• Garden debris drop-off program to eliminate stockpiling
• Fuel reduction/fire break program at Byrne Preserve and
other Town -owned properties
• Annual mailing of fire prevention and emergency
preparedness information to all Los Altos Hills residents
The Fire District also maintains emergency access roads and provides citizen emergency
preparedness training and peak -load staffing (additional personnel during the fire season).
Ambulance service is provided by EMS Santa Clara County on contract with the Fire
District.
Safety Element
Los Altos Hills General Plan
Page 11
Public Review Draft 10/17/07
GOAL
Strive to prevent and reduce potential damage related to fire hazards.
Policy 4.1 Development shall not be permitted unless an acceptable level of fire
protection and adequate water supplies can be provided.
Policy 4.2 Emergency vehicle access shall be provided through adequately
designed roads, streets and driveways, as well as alternate
emergency roads to reach potentially "cut-off' neighborhoods.
Program 4.1 Continue to cooperate with the Santa Clara County Fire Department in
undertaking programs to minimize the fire hazards in the Town,
particularly in remote areas with heavy vegetation.
Program 4.2 Continue to refer plans for proposed site development projects to the
Santa Clara County Fire Department for review and comment.
Program 4.3 Educate properly owners on the benefits of reducing and mitigating fire
hazards.
Program 4.4 Work with water purveyors, the Los Altos Hills County Fire District and
the Santa Clare County Fire Department to ensure the availability of
adequate water, particularly during peakload periods, to meet fire-
fighting needs.
Program 4.5 Continue to enforce the Town's landscaping ordinance requiring the
removal of certain types of eucalyptus trees when building permits for
new residences or major additions are issued.
Program 4.6 Require public roads, private roads, and driveways to be constructed and
maintained according to Fire Department standards in order to
accommodate fire trucks and other emergency vehicles.
Program 4.7 Emergency access roads shall be maintained by the Los Altos Hills
County Fire District according to District fire road standards and
consistent with pathway requirements.
Program 4.8 Encourage the use of fire resistant building materials and fire sprinklers.
Safety Element
Los Altos Hills General Plan
Page 12
The E/ Monte Fire Station is
owned by the Los Altos Hills
County Fire District and
staffed by the Santa Clara
County Fire Department.
Public Review Draft 10/17/07
LAW ENFORCEMENT
829. The Town of Los Altos Hills is a safe, quiet residential community with a low rate of
crime. Like several other small cities, the Town contracts with the Santa Clam County
Sheriffs Department for law enforcement and public safety services. The Sheriff has an
office in the Heritage House next to Town Hall.
GOAL
Minimize the risk of personal injury and property damage
due to crime.
Policy 5.1 Continue to provide law enforcement services that maintain the
community's low crime rate and ensure a high level of public safety.
Program 5.1 Continue to support the Santa Clam County Sheriffs efforts to minimize
crime in Los Altos Hills.
Program 5.2 Encourage residents to participate in the Neighborhood Watch Program
and coordinate with the Santa Clara County Sheriffs Department to
implement it.
Program 5.3 Use the Town's emergency notification phone system to alert
neighborhoods to potential danger from criminal activities.
NEIGHBORHOOD WATCH PROGRAM
Neighborhood Watch is a nationwide crime prevention program that
enlists the active participation of citizens in cooperation with law
enforcement agencies to reduce crime in their communities.
The program involves:
• Neighbors getting to know each other and
working together in a program of mutual
assistance. VA&I
• Citizens being trained to recognize and report
suspicious activities in their neighborhoods.
• Education in crime prevention techniques such
as home security, bicycle safety, and
identification of belongings.
ALL SUSPICIOUS PERSONS AND ACTIVITIES
Contact the Santa Clara County Sheriff's Department
for additional information.
Safety Element
Los Altos Hills General Plan
Page 13
Public Review Draft 10/17/07
HAZARDOUS WASTE
830. Federal, State and local laws regulate the production, storage, handling, and disposal of
hazardous materials and waste. Hazardous materials are those that, because of quantity,
concentration, or physical or chemical characteristics, pose a significant present or
potential hazard to human health and safety or to the environment. Hazardous materials
most commonly used in Los Altos Hills include pesticides and garden chemicals,
combustible fuels, motor oil, paint and cleaning supplies, batteries, and pool chemicals.
Computers and other electronic equipment also contain hazardous materials that must be
disposed of properly. A more detailed list of household hazardous wastes is provided in
Appendix B.
831. Improper storage and disposal of hazardous waste can result in environmental
contamination of surface and groundwater. Heavy metals such as lead, zinc, copper,
nickel, mercury and cadmium can enter the waste stream via residential sewage and
urban runoff. To ensure proper disposal, Los Altos Hills joined with Santa Clara County
and the other cities in the county in developing the County Hazardous Waste
Management Plan. The CHWMP establishes a comprehensive and coordinated
countywide approach to hazardous waste management.
832. Los Altos Hills residents may safely dispose of household hazardous waste through the
Santa Clara Countywide Household Hazardous Waste Program. The County and 14
cities (including Los Altos Hills) participate in the program and share costs based on the
number of households served from each jurisdiction. The program provides safe
methods of recycling and disposing of household hazardous waste. An increased number
of disposal sites would make drop-offs more convenient and improve participation in the
program.
GOAL
Reduce dangers from hazardous materials.
Policy 6.1 Facilitate the proper disposal of hazardous waste.
Program 6.1 Continue to work with Santa Clam County and participating cities to
implement the County Hazardous Waste Management Plan and the
Countywide Household Hazardous Waste Program.
Program 6.2 Provide information to all user groups about:
• Commonly used hazardous materials.
• Environmentally friendly alternatives.
• Safe recycling and disposal methods.
Program 6.3 Encourage the Santa Clara County Household Hazardous Waste Program
to sponsor drop-off days that are convenient for residents of Los Altos
Hills.
Safety Element
Los Altos Hills General Plan
Page 14
Public Review Draft 10/17/07
833.
DISASTER RESPONSE
The Town's Emergency Operations Center (EOC) is located in the Heritage House
adjacent to Town Hall. The EOC serves as the headquarters for coordinated response to
disasters such as a major earthquake or fire. Town
staff includes a Public Safety Officer who is
responsible for overseeing emergency services.
834. In compliance with state and federal guidelines, the
Town has adopted an Emergency Operations Plan
(EOP) that identifies and allocates resources in
response to emergencies, from preparation through
recovery. The EDP identifies the Town's
emergency planning, organizational, and response
policies and procedures and establishes how they
will be coordinated with emergency responses from
other levels of government.
The Emergency Operations Center
is in the Hentage House next to
Town Hall.
835. The Emergency Operations Plan assigns key roles in the EOC, at Town Hall, and in the
field in response to a disaster. The main function of the EOC is to collect, analyze and
disseminate information to fust responders, residents, Council members, media and the
State Office of Emergency Services. The EOC also manages volunteers such as
Emergency Communications Committee (ECC) members and Community Emergency
Response Team (CERT) members wishing to assist in a disaster. These volunteers have
special skills and training and are sworn in as Disaster Service Workers. They will
provide emergency communications to staff in the EOC and will also assist with
information gathering during an emergency. CERT members may be called upon to
assist first responders such as firefighters and law enforcement personnel.
836. The Town's Emergency Response Program also is proactive in educating the community
on emergency preparedness for all hazards. The Town collaborates with the Palo Alto
Chapter of the American Red Cross and the Los Altos Hills County Fire District to
provide residents with valuable knowledge to better prepare their families for a disaster.
837. The ability to respond to emergencies depends, in large part, on the continued operation
of critical facilities—facilities that house emergency responders and those that provide
emergency services. Critical facilities owned and operated by the Town include Town
Hall, the Emergency Operations Center, and the Corporation Yard. Constructed in 2006,
Town Hall is built according to up-to-date standards for seismic safety and fire
protection. All Town facilities should be maintained up to code.
Safety Element
Los Altos Hills General Plan
Page 15
Public Review Draft 10/17/07
GOAL
Provide quick, coordinated response to emergencies.
Policy 7.1 Minimize damage from all hazards through planning for emergency
management.
Policy 7.2 In the event of a disaster, the major transportation, communication
and emergency facilities shall be capable of continued functioning.
Policy 7.3 In times of emergency, evacuation routes shall be determined and
implemented by fire protection and law enforcement personnel.
Program 7.1 Inform residents of potential hazards from earthquakes, landslides,
Safety Element
Los Altos Hills General Plan
Page 16
An emergency generator
at Town Hall ensures
continued operation of critical
facilities-
Safety
acilities
flooding and fire, and of reasonable precautions that can be taken.
Program 7.2
Train and equip Town emergency personnel so they will be able to make
a quick, coordinated response to emergencies.
Program 7.3
Review the Emergency Operations Plan and update it on a regular basis
to ensure that it provides for adequate response to the full range of
disasters identified in the Safety Element.
Program 7.4
Operate and maintain critical facilities owned by the Town, including
Town Hall, the Emergency Operations Center, and the Corporation Yard,
to withstand seismic shaking, fire and other hazards.
Program 7.5
Work with other agencies through programs such as the Silicon Valley
Regional Interoperability Project (SVRIP) to improve communications
and provide a coordinated emergency response on a regional level.
Program 7.6
In conjunction with the Los Altos Hills County Fire District, provide an
emergency notification telephone system.
Safety Element
Los Altos Hills General Plan
Page 16
An emergency generator
at Town Hall ensures
continued operation of critical
facilities-
Safety
acilities
APPENDIX A
Household Hazardous Waste
This quick reference is based on information provided by
the Santa Clara County Household Hazardous Waste Program.
Aerosol cans
Asbestos
Automotive fluids (antifreeze, oils, various fluids, and other chemicals)
Batteries (vehicle batteries as well m household alkaline and
rechargeable batteries)
Battery acid
Chemistry sets
Clemers/household chemicals
Cooking oil
Cosmetics and toiletries
Degreasers/solvents
Electronic equipmentPeadcldes
Fertilizers, weed killers and pesticides
Fire extinguishers
Fireworks
Flares (except airborne flares)
Fluorescent tubes, spinal and compact bulbs
Freon
Gasoline/fuels
Gun powder and ammunition
Helium and oxygen tanks
Lead
Mace
Ferelizenr and weed killers
Mercury (including thermostats, button batteries, relays, etc.)
Motor oil and oil filters
Paint supplies and cans
Pesticides
Photo chemicals
Prescription medicines
Propane tanks Paint
Refrigerators
Syringes and needles
For information about recycling and
disposal
disposal of household hazardous RpLWing &
waste, contact the RC{.�:1
Santa Clara County HHW Hotline at W$pOU
(408)299-7300. a• a
Safety Element
Los Altos Hills General Plan
Public Rcvie,c Draft—October 17, 2007
NOISE ELEMENT
Public Review Draft
October 17.2007
LOS ALTOS HILLS GENERAL PLAN
Public Review Draft 10/17/07
Noise Element
INTRODUCTION
Puroose
701. Freedom from excessive noise is a major factor in the quality of life for Los Altos Hills
residents. Noise can disrupt sleep, cause stress and tension, and interfere with
conversation and many other aspects of day-to-day life. The Noise Element is intended
to protect residents from unwanted noise, thereby assuring their continued enjoyment of
the quiet, peaceful community envisioned in the Introduction to the General Plan.
Los Altos Hills should be a community dedicated to
maintaining a semi -rural atmosphere, where people
can live in the midst of open space, exposed to
minimum noise, congestion, and confusion, and with
sufficient space on each lot to allow activities such as
gardening, cultivating vineyards and orchards,
keeping horses, and enjoying outdoor recreation.
Community Goal 1
Introduction to the General Plan
SCO129
702. The Noise Element provides a basis for evaluating noise issues and limiting the exposure
of the community to excessive noise levels. The Noise Element identifies current noise
conditions and projects future noise conditions resulting from continued growth in Los
Altos Hills and surrounding communities. It establishes policies and programs to
mitigate the current and future potential impacts of noise. In addition, it provides
direction for reviewing existing Town standards and establishing new standards and
criteria, as appropriate, for the mitigation of noise impacts determined to be unacceptable.
State Requirements
703. State law requires every General Plan to have a Noise Element that identifies noise
problems in the community and works toward their resolution. The State also provides
guidelines for the preparation of the Noise Element. These guidelines were initially
adopted by the Office of Noise Control, California Department of Health, in 1976. The
Los Altos Hills Noise Element has been prepared in recognition of these guidelines and
the requirements of State law.
Relationship to Other Elements
704. Since traffic is one of the major sources of noise, there is a direct relationship between
the Noise Element and the Circulation & Scenic Roads Element. The Noise Element is
also closely related to the Housing Element and the Open Space & Recreation Element,
which address two of the Town's most noise -sensitive land uses—residential
development and open space. All of these components are integrated in the Land Use
Element, which provides for the compatibility of land uses.
Noise Element
Los Altos Hills General Plan
Page 1
Public Review Draft 10/17/07
NOISE BASICS
Subjective Factors
705. Defined simply as unwanted sound, noise is a subjective phenomenon that depends upon
the listener's attitude toward the sound. The degree to which noise is irritating depends
on a variety of factors, some independent of the noise source itself Time of day,
background sound level, the listener's activity, and surrounding land use can all influence
the degree to which a particular sound is perceived as annoying. Value judgments also
enter into tolerance for urban sound levels. Most people tolerate emergency sirens and
loud lawnmowers because they represent necessary actions related to public safety and
neighborhood upkeep. However, loud noises from cars with defective or modified
mufflers are usually perceived as annoyances.
Noise Measurements
706. Three important characteristics of noise are its level of intensity or loudness, its
frequency range, and the variation in noise level with time. Each of these factors is
addressed in the following methods of measurement:
1. Noise levels we measured in decibels
(dB). A decibel is a unit for describing
the amplitude of sound.
The A -weighted filter network adjusts
the measured noise level to account for
the frequency range of noise so that it
most closely relates to human perception
of loudness. The A -weight filter de-
emphasizes the very low and very high
frequency components of sound in a
manner similar to the response of the
human ear and gives good correlation
with subjective reactions to noise.
Typical sound levels measured in the A -
weighted scale (dBA) are shown in
Figure 7-1.
Typical sound levels
measured in dBA
Stock car races
13C
Chainsaw,
12:
Band concert
12C
LeaPolower, power saw
it(
School dance
10C
Tractor, truck
9C
Manual machine, tools
8C
Freeway traffic
7C
Normal conversation
6C
Large office
5C
Library
4(
Secluded woods
3(
Whisper (at 5 feet)
2(
Source: New Levels in Our Environment
League for the Ham of Hearing, 2007
3. The Community Noise Equivalent Level (CNEL) is the average equivalent A -
weighted sound level during a 24-hour day, obtained after adding 5 decibels to
sound levels in the evening from 7 pm to 10 pm, and 10 decibels to sound levels
in the night from 10 pm to 7 am. The State has adopted the Community Noise
Equivalent Level (CNEL) as the standard metric because it corresponds well to
community annoyance over noise.
Noise Terminoloev
707. The ambient noise level is the composite of noise from all sources near and far. The
ambient noise level constitutes the normal or existing level of environmental noise at a
given location.
Noise attenuation is the reduction of sound intensity by various means.
Noise Element
Los Altos Hills General Plan
Page 2
Public Review Draft 10/17/07
THE NOISE ENVIRONMENT
708. Residents of Los Altos Hills enjoy a relatively quiet noise environment. Because the
community is characterized by low-density residential development and has no industrial
or commercial areas, a majority of noise -producing sources normally found in Bay Area
cities are not located within its boundaries. Noise is not confined by city limits, however,
and the community's noise environment is affected by noise -producing sources in
neighboring cities. It is not possible to control all noise sources that affect Los Altos
Hills, but the negative impacts of excessive noise can and should be mitigated to the
greatest extent possible.
709. As in most Bay Area communities, motor vehicle traffic is the primary source of noise in
Los Altos Hills. The level of noise produced by vehicular traffic generally fluctuates in
relation to the volume of traffic, the percentage of trucks, and average traffic speed.
Other sources of community noise include air traffic, construction activities, the use of
home maintenance equipment such as chainsaws and gas -powered leaf blowers, and the
operation of residential pool equipment and air conditioning units. The noise issues of
greatest concern to the communityare briefly described below, including suggestions for
evaluating noise problems and mitigating thew impacts.
Motor vehicle traffic
710. The Town is bisected by Interstate 280, which is the primary source of noise in the
community. Freeway noise has often affected the normal use of residential properties
and associated activities, both indoors and outdoors. In addition, it is likely that some
property values have decreased as a result of freeway noise. Another major win" of
noise is traffic on Foothill Expressway and Arastradero Road, portions of which are
maintained by Santa Clara County and the City of Palo Alto. The Town should continue
to work with the appropriate agencies to minimize noise generated by Interstate 280,
Foothill Expressway and Arastradero Road. To a lesser degree, traffic on local roadways
also can be a significant source of noise for adjacent residents. Vehicle noise is regulated
by the State's noise emissions standards, and cities are generally prohibited from
applying stricter standards. The Sheriffs Department will continue to enforce the State's
noise emission standards for all vehicles, including motorcycles.
711. Air traffic
Low-flying airplanes and helicopters are another significant source of noise. Most of the
air traffic is generated by the San Francisco, Oakland and San Jose airports, as well as
Moffett Field. In addition, medical transport airplanes and helicopters fly in and out of
Stanford Medical Center. The Regional Airport Planning Commission (RAPQ serves as
a public forum for issues such as airport noise. Town residents should continue to work
with the RAPC and the Federal Aviation Administration to minimize air traffic noise and
flight patterns that impact Los Altos Hills.
Schools, recreation facilities and other conditional uses
712. Public and private recreation facilities, schools, churches and other conditional uses can
be a significant source of noise, particularly at peak -use periods. Noise generated by the
use of these facilities can be disruptive to neighboring residents. The conditional use
permits for these uses typically restrict the hours of operation and the use of loud
speakers so that noise impacts are minimized.
Noise Element
Los Altos Hills General Plan
Page 3
Public Review Draft 10/17/07
Construction activities
713. Although construction noise usually lasts only a limited period of time, it can severely
restrict the enjoyment of residential properties. Due to the topography of the community,
noise from construction activities such as grading and the operation of other heavy
equipment often carries for great distances. The Town's Municipal Code limits the hours
and days of outside construction activities to 8:00 a.m. to 5:30 p.m. Monday through
Saturday, with no construction allowed on Sundays or public holidays. (These
restrictions do not apply to the use of domestic power tools by homeowners.) All
construction equipment operating within the Town should be encouraged to be equipped
with the most up-to-date muffling devices generally available.
Residential activities
714. Amplified music, loud parties and other social gatherings, barking dogs, crowing
roosters, auto repair and the operation of power mowers, chainsaws, workshop
equipment, home improvement tools and similar equipment are sources of potentially
annoying noise. Under provisions of the Town's Municipal Code, homeowners are
prohibited from keeping or permitting barking dogs, and the use of power tools is
generally limited to the hours of 8:00 a.m. and sunset on weekdays and between 9:00
a.m. and sunset on weekends.
Los Altos Hills Municipal Code
Sec. 6-1.510. Barking dogs
It is unlawful for any person to keep, maintain or permit in or
upon any premises within the Town any barking dog that is
under the control of that person. "Barking dog" means a dog
that barks, bays, cries, howls or makes any other noise
continuously and incessantly for a period of ten (10)
minutes within a fifteen (15) minutes period to the
disturbance of any other person. The issuance of a citation
shall be within the discretion of the Animal Control Officer or
other enforcement person.
Air conditioning units and pool equipment
715. The operation of heating, ventilating and air conditioning (HVAC) units, pool equipment,
generators and similar equipment can be noisy. The recent trend to construct larger
homes has in some cases involved the installation of commercial -scale equipment, which
is even more likely to annoy neighbors. To protect them from excessive noise, the Town
does not allow HVAC or pool equipment to be located in setback areas. HVAC
equipment, pool equipment, generators, and similar types of equipment should be
enclosed as much as possible, and the enclosures should be insulated to minimize noise
impacts. Specific standards for this type of equipment should be developed and
implemented through the Town's planning and building permit process.
Noise Element
Los Altos Hills General Plan
Page 4
• Public Review Draft 10/17/07
The Noise Ordinance
The Town's Noise Ordinance identifies a series of noise sources and
specifies the maximum decibel levels for day and night (defined as
the period between sunset and 7:00 a.m.). Violation of these
standards constitutes a public nuisance and is subject to nuisance
abatement. Exceptions are made for alerting persons to the
existence of an emergency and the performance of emergency work,
neither of which are subject to the maximum noise levels established
in the ordinance. The Noise Ordinance should be periodically
reviewed and updated to ensure that the noise standards are
appropriate and attainable.
Los Altos Hills Municipal Code
Title 5, Chapter 2
Noise Contours
716. The noise environment for Los Altos Hills can be described with noise contour maps that
have been developed for land use planning purposes. Noise contours define areas of
equal noise exposures based on noise measurements at given locations. Figures N-2 and
N-3 are noise contour maps for present-day conditions (Year 2007) and future conditions
(2030) based on projected local and regional growth.
Existing Conditions
717. Larger roadways such as Interstate 280, Foothill Expressway and Arastradero Road are
condors with high noise levels generated by heavy volumes of traffic. As shown on
Figure 7-2, the high -noise contours extend a considerable distance beyond the roadways,
indicating greater noise impacts on residents living within those contours. In contrast,
residents who live farther away from the roadways and outside the high -noise contours
experience a significantly quieter environment, with CNELs in the low 50s and 40s and
noise levels sometimes dropping down to 30 dbA at night. Roadways that were not
modeled for noise contours also experience traffic noise, with noise levels along local
streets expected to be similar or quieter than those on modeled streets.
Future Conditions
718. Figure 7-3 shows the noise contours projected to 2030 based on traffic growth projections
by the Santa Clara Valley Transportation Authority and the Metropolitan Transportation
Commission. The projected contours are similar to existing noise conditions, with
significant increases in noise levels occurring at major freeway intersections, especially at
EI Monte Road. The increase in traffic will result primarily from regional growth, over
which the Town has no control. However, the Town can and should require new
development in high -noise contours to include noise mitigation measures.
Noise Element
Los Altos Hills General Plan
Page 5
Public Review Draft 10/17/07
Figure 7-2
NOTE: Community Noise Equivalent Level (CNEL) is the average equivalent A-welghted sourw level aunng a
24-hour day, obtained after adding 5 decibels to sound levels in the evening from 7 pm to 10 pm, and 10 decibels
to sound levels in the night from 10 pm to 7 am.
Noise Element
Los Altos Hills General Plan
Page 6
Public Review ]haft 10/17/07
Figure 7-3
NOTE: Community Noise Equivalent Level (CNEL) is the average equivalent A -weighted sound level during a
24-hour day, obtained after adding 5 decibels to sound levels in the evening from 7 pm to 10 pm, and 10 decibels
to sound levels in the nicht from 10 om to 7 am.
Noise Element
Los Altos Hills General Plan
Page 7
Public Review Draft 10/17/07
GOAL
Minimize noise levels so that residents may enjoy the amenities
of living in a quiet, semi -rural community.
Policy 1.1 Noise levels shall be compatible with the Town's semi -rural
atmosphere and consistent with Town standards.
Policy 1.2 All appropriate methods for reduction of noise at the source (i.e.
automobile, aircraft, etc.) shall be supported.
Policy 1.3 Individual use of noise -generating equipment should not interfere
with the normal use and enjoyment of outdoor or indoor areas on
surrounding properties.
Policy 1.4 Noise generated by construction equipment shall be attenuated to
the maximum extent possible. Hours of construction activity shall be
regulated to minimize the impact of noise on surrounding residential
properties.
Program 1.1 Update the Noise Ordinance to provide for clear interpretation of the
Noise Element
Los Altos Hills General Plan
Page 8
regulations and appropriate standards based on the A -weighted scale.
Program 1.2
Continue to restrict the hours of non -emergency grading and construction
activities to specified days of the week and times of day to minimize
noise impacts on neighboring residents and other sensitive land uses.
Program 1.3
Encourage construction contractors to use construction equipment that
incorporates the best available noise control technology.
Program 1.4
Continue to prohibit the location of heating, ventilating and air
conditioning (HVAC) equipment, pool equipment, pumps and similar
equipment in setbacks. Develop siting and noise attenuation standards
for HVAC equipment, pool equipment, pumps and similar equipment.
Program 1.5
Encourage the use of quiet pavement materials in repaving projects
including the repaving of interstate 280.
Program 1.6
Work with appropriate State, regional and local agencies such as
Caltrans, Santa Clam County and the City of Palo Alto to reduce noise
from roadways adjacent to Los Altos Hills.
Program 1.7
Work with the Federal Aviation Administration, the Regional Airport
Planning Commission and other appropriate agencies to reduce noise
levels generated by aircraft flying over Los Ahos Hills.
Program 1.8
Continue to address potential noise impacts when reviewing applications
for new or renewed conditional use permits.
Noise Element
Los Altos Hills General Plan
Page 8
Public Review Draft 10/17/07
LAND USE COMPATIBILITY
719. In larger cities, many undesirable noise effects can be reduced or avoided if noise
conditions are considered when assigning uses to specific parcels of land. In Los Altos
Hills however, there is limited opportunity to address land use compatibility in this
manner because the community is almost fully developed, little growth is anticipated,
and major land uses are primarily single-family residential, open space and recreation,
and institutions such as schools and churches. The community has no commercial or
industrial uses. Moreover, the Town has little or no control over major sources of noise
generated by motor vehicle traffic on Interstate 280, Arastradero Road and the Foothill
Expressway.
720. Compatibility of land uses in Los Altos Hills is best achieved through analysis of each
proposed use on a case-by-case basis through the site development review process. To
ensure that new development is not adversely impacted by noise sources, or is itself a
source of noise, the Town uses land use compatibility guidelines as part of planning and
site development review. Figure N-2 summarizes the compatibility of specific land uses
with various noise levels.
Mitigation Measures
721. The potential impacts of traffic noise and other unwanted sound should be identified and
mitigation measures required as needed to meet the Town's noise standards. The most
effective measures for noise attenuation include the following:
• Site planning that is sensitive to potential noise impacts
• Careful orientation of buildings and placement of windows
• Increased setbacks
• Buffers consisting of earthen berms and landscaping
• Sound proofing and double -glazed windows
• Use of acoustically treated or quiet -design equipment such m furnaces, fans,
motors, compressors, generators, pool equipment and air conditioning units
722. In determining the best combination of noise attenuation techniques for a specific
project, noise mitigation measures should be weighed against other community values
such m open space and aesthetics. Noise mitigation is usually less expensive and mote
effective if it is included during the design phase of a project rather than as an after-
thought.
Sound Walls
723. In many communities, sound walls are used to reduce freeway noise impacts on adjacent
residences. In Los Altos Hills, however, sound walls are prohibited on private property
adjacent to Interstate 280, primarily because they block views of surrounding countryside
and tend to bounce sound to other locations. Although the Town has no authority to
prohibit the construction of sound walls in the State right-of-way, it should convey its
sound wall policy to Caltrans. In the event that sound walls are constructed, the Town
should work with Caltrans to ensure that the walls are screened with evergreen trees,
vines and other landscaping to soften their visual impact.
Noise Element
Los Altos Hills General Plan
Page 9
Public Review Draft 10/17/07
Figure 7-4
Land Use and Noise Compatibility Guidelines
Exterior Noise Exposure
Land Use Category (Ldn or CNEL, dB)
55 60 65 70 75 80
Single-family residential and
open space
Outdoor sports and recreation,
Neighborhood parks and playgrounds
Schools, libraries, museums,
hospitals, personal care, meeting
halls, churches
Office buildings, business
commercial, and professional
(such as Town Hall)
Auditoriums, concert halls, amphi-
theatres
F-1NORMALLY ACCEPTABLE Specified land use is satisfactory, based
on the assumption that any buildings involved are of normal conventional
construction, without any special insulation requirements.
FCONDITIONALLY ACCEPTABLE Specified land use may be
permitted only after detailed analysis of the noise reduction requirements and
needed noise insulation features included in the design.
.UNACCEPTABLE New construction or development should generally
not be undertaken because mitigation is usually not feasible to comply with
noise element policies.
Source: Adapted from General Plan Guidelines,
Office of Planning and Research, Appendix C, 2003.
Noise Element
Los Alms Hills General Plan
Page 10
^
I Public Review Draft 10/17/07
Program 2.1 Evaluate noise impacts on surrounding land uses during the site
development review and permitting process.
Program 2.2 Utilize the Land Use and Noise Compatibility Guidelines as a basis for
determining the compatibility of land uses.
Program 2.3 To determine noise exposure, use the noise contour maps or more
detailed noise analysis if appropriate.
Program 2.4 Require the mitigation of all significant noise impacts as a condition of
project approval.
Program 2.5 Convey the Town's sound wall policy to Caltrans and work with the
agency to develop more acceptable alternatives such as landscaped
berms along Interstate 280.
Noise Element
Los Altos Hills General Plan
Page I1
GOAL
Provide compatible noise environments for new development.
Policy 2.1
All development adjacent to Interstate 280, Arastradero Road or
Foothill Expressway should be designed so as to minimize the
impacts of noise generated by traffic movement.
Policy 2.2
Residential construction in high -noise -level areas shall include
provisions for structural insulation as necessary to ensure maximum
possible noise attenuation.
Policy 2.3
Mitigation measures such as site planning, building orientation,
window placement, increased setbacks, landscaped berms, and
sound -proofing shall be required in new development when
necessary to reduce the impacts of noise.
Policy 2.4
The construction of sound walls on private property adjacent to
Interstate 280 shall be prohibited, and sound walls within the State
right-of-way shall be discouraged.
Policy 2.5
The potential for new development to generate noise levels higher
than Town standards shall be evaluated, and significant impacts
shall be appropriately mitigated.
Policy 2.6
Work with adjoining municipalities and public and private
landholders to assure noise -compatible land uses across
jurisdictional boundaries.
Program 2.1 Evaluate noise impacts on surrounding land uses during the site
development review and permitting process.
Program 2.2 Utilize the Land Use and Noise Compatibility Guidelines as a basis for
determining the compatibility of land uses.
Program 2.3 To determine noise exposure, use the noise contour maps or more
detailed noise analysis if appropriate.
Program 2.4 Require the mitigation of all significant noise impacts as a condition of
project approval.
Program 2.5 Convey the Town's sound wall policy to Caltrans and work with the
agency to develop more acceptable alternatives such as landscaped
berms along Interstate 280.
Noise Element
Los Altos Hills General Plan
Page I1
Attachment 2
Summary of Proposed New Policies and Pro¢rams
Most of the proposed new policies and programs reflect the Town's current
practice and are consistent with already -established policy. In a few cases, new
programs commit the Town to new actions such as encouraging participation in the
Neighborhood Watch Program or updating the Town's noise ordinance.
FIRE HAZARDS—Safety Element
Program 4.7 Emergency access roads shall be maintained by the Los Altos Hills County Fire District
according to District fire road standards and consistent with pathway standards.
LAW ENFORCEMENT—Safety Element
Program 5.2 Encourage residents to participate in the Neighborhood Watch Program and coordinate
with the Santa Clam County Sheriff's Department to implement it.
Program 5.3 Use the Town's emergency notification phone system to alert neighborhoods to potential
danger from criminal activities.
HAZARDOUS WASTE—Safety Element
Program 6.3 Encourage the Santa Clam County Household Hazardous Waste Program to sponsor
drop-off days that are convenient for residents of Los Altos Hills.
DISASTER RESPONSE—Safety Element
Policy 7.3 In times of emergency, evacuation routes shall be determined and implemented by
fire protection and law enforcement personnel.
Program 7.4 Operate and maintain critical facilities owned by the Town, including Town Hall, the
Emergency Operations Center, and the Corporation Yard, to withstand seismic shaking,
fire and other hazards.
Summary of New Policies & Programs
November 1, 2007
Page 1
Attachment 2
THE NOISE ENVIRONMENT—Noise Element
Program 1.1 Update the Noise Ordinance to provide for clear interpretation of the regulations and
appropriate standards based on the A -weighted scale.
Program 1.4 Continue to prohibit the location of heating, ventilating and air condition (HVAC)
equipment, pool equipment, pumps and similar equipment in setbacks. Develop siting
and noise attenuation standards for HVAC equipment, pool equipment, pumps and
similar equipment.
Program 1.5 Encourage the use of quiet pavement materials in repaving projects including the
repaving of Interstate 280.
LAND USE COMPATIBILITY—Noise Element
Policy 2.4 The construction of sound walls on private property adjacent to Interstate 280 shall
be prohibited, and sound walls within the State right-of-way shall be discouraged.
Program 2.5 Convey the Town's sound wall policy to Caltrans and work with the agency to develop
more acceptable alternatives such as landscaped berms along Interstate 280.
Summary of New Policies & Programs
November 1, 2007
Page 2
Attachment 3
TOWN OF LOS ALTOS HILLS
NEGATIVE DECLARATION
PROJECT TITLE:
Los Altos Hills General Plan Update (Phase 2)
PREPARED BY:
Debbie Pedro, AICP, Planning Director
NAME AND ADDRESS OF PROJECT SPONSOR:
Town of Los Altos Hills
26379 Fremont Road
Los Altos Hills, California 94022
LOCATION OF PROJECT:
Town of Los Altos Hills (Townwide)
PROJECT DESCRIPTION:
The proposed project is Phase 2 of a comprehensive update to the
Los Altos Hills General Plan. The updated elements have been
developed by the General Plan Update Committee as part of the
Town's 2007 General Plan Update project.
Phase I included an update to the Introduction, the Open Space
& Recreation Element, and the Conservation Element, all of
which were adopted by the City Council on April 26, 2007.
Phase 2 includes the updated Safety Element and Noise Element.
The Land Use Element will be updated in Phase 3 of the project.
The Circulation & Scenic Roadways, Housing, and Pathways
Elements are the more recent sections of the General Plan and
will not be updated at this time.
FINDING: The Town of Los Altos Hills has completed a review of the
proposed project and, on the basis of the attached Initial Study,
has determined that the project will not have a significant effect
^on the environment.
Debbie Pedro, Planning Director Date
TOWN OF LOS ALTOS HILLS
Noticed on: October 17 2007 Adopted
Town of Los Altos Hills
26379 Fremont Road
Los Altos Hills, CA 94022
INITIAL STUDY
In accordance with the policies regarding implementation of the California Environmental Quality Act of
1970, this document, combined with the attached supporting data, constitutes the initial study on the
subject project. This initial study provides the basis for the determination of whether the project may have
a significant effect on the environment. If it is determined that the project may have a significant effect on
the environment, an environmental impact report will be prepared which focuses on the areas of concern
identified by this initial study. If it is determined that the project would not have a significant effect on the
environment, it is eligible for a Negative Declaration If it is determined that the proposed project could have a
significant effect on the environment, however, the significant effects of the project have been reduced to a
less -than -significant level because revisions in the project have been made by or agreed to by the project
applicant, then the project would be eligible for a Mitigated Negative Declaration.
PROJECT TITLE
Los Altos Hills General Plan Update Phase 2
LEAD AGENCY NAME AND ADDRESS
Town of Los Altos Hills
26379 Fremont Road
Los Altos Hills, California 94022
CONTACT PERSON AND PHONE NUMBER
Debbie Pedro, AICP, Planning Director (650) 941-7222
PROJECT LOCATION
Town of Los Altos Hills (Townwide)
PROJECT SPONSOR'S NAME AND ADDRESS
Town of Los Altos Hills
26379 Fremont Road,
Los Altos Hills CA 94022
GENERAL PLAN DESIGNATION
Various
ZONING
Various
DESCRIPTION OF PROJECT
The proposed project is Phase 2 of a comprehensive update to the Los Altos Hills General Plan. The
updated elements have been developed by the General Plan Update Committee as part of the Town's 2007
General Plan Update project.
Phase 1 included an update to the Introduction, the Open Space & Recreation Element, and the
Conservation Element, which were adopted by the City Council on April 26, 2007. Phase 2 includes the
Safety Element and Noise Element. The Land Use Element will be updated in Phase 3 of the project.
Circulation & Scenic Roadways, Housing and Pathways Elements are the more recent sections of the
General Plan and will not be updated at this time.
Elements Required
by State Law
Los Altos Hills
General Plan Elements
Phase t
Amendments
Phase 2
Amendments
Phase 3
Amendments
Introduction
✓
Land Use
Land Use
✓
Circulation
Circulation & Scenic Roadways
—
—
—
Housing
Housing
—
—
—
Open Space
Open Space & Recreation
✓
Conservation
Conservation
✓
Noise
Noise
✓
Safety
Safety
✓
Pathways
—
—
—
The purpose of the update is to correct errors, inaccuracies and obsolete references and to produce a more
accurate, legible, and reproducible document, including improved graphics that accurately depict existing
conditions in the Town. The proposed amendments do not include any changes in land use designations
because the Town is nearly built out and significant population growth is not expected in the future.
Phase 2 of the General Plan update includes amendments to existing goals, policies and programs to
address current issues related to protecting the public from safety hazards and unwanted noise. Most
policies and programs in the updated elements are already existing; changes and additions are made only to
clarify and strengthen existing goals and policies. No new policy directions are being added in this General
Plan update.
The Town is committed to the preservation of a quiet community environment and the protection of the
public from natural and human -caused hazards. Implementation of the updated goals, policies and
programs will protect the environment and will not have any adverse impacts on noise levels or public
safety in the community.
SURROUNDING LAND USES AND SETTING
Incorporated as a general law city on January 27, 1956, the Town of Los Altos Hills is located in Santa
Clara County directly west of the City of Los Altos. It is encircled by the City of Palo Alto along the
north and northeast boundaries. Open space preserves managed by the N idpeninsula Regional Open
Space District are located along the western boundary, and unincorporated areas of Santa Clara County
are located to the east. The Town encompasses approximately 8.4 square miles with an additional 5.7
square miles of unincorporated land adjacent to the Town's boundaries designated as being within its
sphere of influence.
The Town is bisected by Interstate 280, which runs from northwest to southeast. The Town is also
served by Foothill Expressway, which forms part of its northeasterly boundary. Arterial roads including
Page Mill, Arastradero, and El Monte -Moody Road provide channels for primary movement within the
Town.
Characterized as a semi -rural hillside community with rolling hills and picturesque valleys, the Town
serves as a transition area between the urbanized mid -peninsula and the open foothills of the coastal
mountain range. The Town is a low-density suburban residential community on hilly terrain, with dense
vegetation including many oak trees and natural habitats. Although Los Altos Hills is not an agricultural
community, the rugged physical characteristics of the area have helped to maintain its semi -rural quality.
Minor agricultural pursuits including orchards and vineyards are common. Many residents keep
domestic animals, primarily horses, on their properties, adding to the semi -rural character of this
community.
The basic land use categories are residential, institutions, recreation, and open space. There are two
zoning districts for all properties in Town: R -A (Residential Agricultural) and OSR (Open Space
Reserve District). Additional uses such as public and private schools, churches and synagogues, and
recreational clubs are permitted through conditional use permits. There are no commercial or industrial
centers. Commercial, retail, and industrial uses are found in adjoining suburban communities. Many
services to the Town's population including retail stores, post offices, banks, and medical services are
available in adjacent communities such as the City of Los Altos and the City of Palo Alto.
Other public agencies whose approval is required: None
ENVIRONMENTAL FACTORS POTENTIALLY AFFECTED:
The environmental factors checked below would be potentially affected by this project, involving at least one impact
that is a "Potentially Significant Impact" as indicated by the checklist on the following pages.
UAesthetics
U
Agriculture Resources
❑
Air Quality
LlBiological
Resources
U
Cultural Resources
❑
Geology /Soils
❑
Hazards & Hazardous
Materials
L3
Hydrology / Water Quality
L3
Land Use / Planning
Mineral Resources
L)
Noise
❑
Population / Housing
UPublic
Services
U
Recreation
TmesputstioNTmffic
JUtilities
/ Service Systems
Mandatory Findings of Significance
This Initial study has been prepared in accordance with the California Environmental Quality Act. Information and
conclusions in the Initial Study are based upon stafjresearch and the Town's General Plan and Municipal Code.
On the basis of this initial evaluation:
I find that the proposed project COULD NOT have a significant effect on the environment, and a NEGATIVE 0
DECLARATION will be prepared.
I find that although the proposed project could have a significant effect on the environment, there will not be a ❑
significant effect in this case because the mitigation measures described on an attached sheet have been added
to the project. A MITIGATED NEGATIVE DECLARATION will be prepared.
I find that the proposed project MAY have a significant effect on the environment, and an
ENVIRONMENTAL IMPACT REPORT is required.
I find that the proposed project MAY have a significant effect(s) on the environment, but at least one effect 1)
has been adequately analyzed in an earlier document pursuant to applicable legal standards, and 2) has been
addressed by mitigation measures based on the earlier analysis as described on attached sheets, if the effect is a El
"potentially significant impact" or" potentially significant unless mitigated." An ENVIRONMENTAL
IMPACT REPORT is required, but it must analym only the effects that remain to be addressed.
I find that although the proposed project could have a significant effect on the environment, there WILL NOT
be a significant effect in this case became all potentially significant effects (a) have been analyzed adequately
in an earlier EIR pursuant to applicable standards and (b) have been avoided or mitigated pursuant to that
earlier EIR, including revisions or mitigation measures that are imposed upon the proposed project.
Signature: _::�` " — Date: to (1 cl—I
Debbie Pedro, Planning Director
FINDING: The project will have no impact on aesthetics.
MITIGATION: No mitigation is necessary.
Po[enaally
fess rha
rs 'Oim
AESTHETICS
rmoec[
si 'ficenSim
w=d'
m1
'f''a
oOct
.
d
loozadw
ween
project:substantial
Wpmiecc
adverse effect on a scenic vista?tially
Conservation as an optional model to use in assessing impacts on agriculture and farmland. Would the project:
a) Convert Prime Farland, Unique Farmland, or Farmland of
damage scenic resources, including, but not❑❑❑to,
Statewide Importance (Farland), as shown on the maps
Monitoring
❑
❑
trees, rock outcroppings, and historic buildings
0
prepared pursuant to the Farland Mapping and
smm scenic highway?tially
Program of the California Resources Agency, to non-
agricultural me?
degrade the existing visual character or quality
❑
❑
ite and its surroundings?
b) Conflict with existing zoning for agricultural use, or a
❑
❑
d) Create a new source of substantial light or glare which would
❑
❑
❑
adversely affect day or nighttime views in the area?
c) Involve other changes in the existing environment which, due to
❑
❑
FINDING: The project will have no impact on aesthetics.
MITIGATION: No mitigation is necessary.
FINDING: The project will have no impact on agriculture resources.
MITIGATION: No mitigation is necessary.
Po[enaally
Sic
rs 'Oim
H. AGRICULTURE RESOURCES
Nc
[moact
.V�m
simifcaM
N,1ni=
Mid
1
In determining whether impacts to agricultural resources are significant environmental effects, lead agencies may refer to
the California Agricultural Land Evaluation and Site Assessment Model (1997) prepared by the California Dept. of
Conservation as an optional model to use in assessing impacts on agriculture and farmland. Would the project:
a) Convert Prime Farland, Unique Farmland, or Farmland of
Statewide Importance (Farland), as shown on the maps
Monitoring
❑
❑
❑
0
prepared pursuant to the Farland Mapping and
Program of the California Resources Agency, to non-
agricultural me?
b) Conflict with existing zoning for agricultural use, or a
❑
❑
❑
Williamson Act contract?
c) Involve other changes in the existing environment which, due to
❑
❑
❑
their location or nature, could result in conversion ofFamtand,
to non-agricultural use?
FINDING: The project will have no impact on agriculture resources.
MITIGATION: No mitigation is necessary.
FINDING: The project will have no impact on air quality.
MITIGATION: No mitigation is necessary.
IV. BIOLOGICAL RESOURCESifi
pownaally
Isss Than
s'an front
I«
S�
No Mnan
III. AIR QUALITY
Sienitirant
Imoara
with
Si itwnt
N oact
oM
Would the project:
a) Have a substantial adverse effect, either directly or through
MMi genion
1--�
Where available, the significance criteria established by the applicable air quality management or air pollution control
district may be relied upon to make the following determinations. Would the project:
a) Conflict with or obstmct implementation of the applicable air
❑
L3
Llquality
13
plan?
❑
❑
policies, or regulations, or by the California Department of
b) Violate any air quality standard or contribute substantially to
El
❑
Llan
Fish and Game or U.S. Fish and Wildlife Service?
existing or projected air quality violation?
b) Have a substantial adverse effect on any riparian habitat or
c) Result in a cumulatively considerable net increase of any
other sensitive natural community identified in local or
criteria pollutant for which the project region is non -
❑
Ll
plans, policies, regulations or by the California
attainment under an applicable federal or state ambient air
❑
❑
❑
Department of Fish and Game or US Fish and Wildlife Service?
quality standard (including releasing emissions which exceed
c) Have a substantial adverse effect on federally protected
quantitative thresholds for omne precursors)?
wetlands as defined by Section 404 of the Clean Water Act
d) Expose sensitive receptors to substantial pollutant
L]
Ll
Elconcentrations?
(including, but not limited to, marsh, vernal pool, coastal, etc.)
❑
❑
❑
0
through direct removal, filling, hydrological interruption, or
e) Create objectionable odors affecting a substantial number of
Ll
❑
other means.
people?
d) Interfere substantially with the movement of any native
FINDING: The project will have no impact on air quality.
MITIGATION: No mitigation is necessary.
IV. BIOLOGICAL RESOURCESifi
paendally
Ws'ITmt
[cant
rilh
I«
S�
No Mnan
Mooed,
Imoac[
Would the project:
a) Have a substantial adverse effect, either directly or through
habitat modifications, on any species identified as a candidate,
sensitive, or special status species in local or regional plans,
❑
❑
❑
policies, or regulations, or by the California Department of
Fish and Game or U.S. Fish and Wildlife Service?
b) Have a substantial adverse effect on any riparian habitat or
other sensitive natural community identified in local or
❑
❑
Ll
plans, policies, regulations or by the California
Department of Fish and Game or US Fish and Wildlife Service?
c) Have a substantial adverse effect on federally protected
wetlands as defined by Section 404 of the Clean Water Act
(including, but not limited to, marsh, vernal pool, coastal, etc.)
❑
❑
❑
0
through direct removal, filling, hydrological interruption, or
other means.
d) Interfere substantially with the movement of any native
resident or migratory fish or wildlife species or with
❑
❑
❑
0
established native resident or migratory wildlife corridors, or
impede the use of native wildlife nursery sites?
1'otsatla0x
Iess Than
Iz:s Hurn
Nolmo a
e) Conflict with any local policies or ordinances protecting
❑
❑
❑
0
biological resources, such as a tree preservation policy or
a) Expose people or structures to potential substantial adverse
ImoaA
ordinance?
Would the project,
a) Cause a substantial adverse change in the significance of a
❑
❑
f) Conflict with the provisions of an adopted Habitat
Coascrvation Plan, or
❑
❑
❑
0
Conservation Plan, Natural Community
most recent Alquist-Priolo Earthquake Fault Zoning Map
b) Cause a substantial adverse change in the significance of an
❑
❑
other approved local, regional, or state habitat conservation plan?
issued by the State Geologist for the area or based on other
archaeological resource pursuant to '15064.5?
FINDING: The project will have no impact on biological resources
MITIGATION: No mitigation is necessary.
FINDING: The project will have no impact on cultural resources.
MITIGATION: No mitigation is necessary.
GEOLOGY AND SOILS7E,n
1'otsatla0x
Iess Than
Iz:s Hurn
Nolmo a
V. CULTURAL RESOURCES
s mificeat xhm
m °
' Jean[
No Moec[
tmoect
a) Expose people or structures to potential substantial adverse
ImoaA
Would the project,
a) Cause a substantial adverse change in the significance of a
❑
❑
❑
i) Rupture of a known earthquake fault, as delineated on the
historical resource as defined in'l5064.5?
most recent Alquist-Priolo Earthquake Fault Zoning Map
b) Cause a substantial adverse change in the significance of an
❑
❑
❑
issued by the State Geologist for the area or based on other
archaeological resource pursuant to '15064.5?
substantial evidence of a known fault?
c) Directly or indirectly destroy a unique paleontological
❑
❑
❑
if) Strong seismic ground shaking?
resource or site or unique geologic feature?
❑
❑
0
iii) Seismic -related ground failure, including liquefaction?
d) Disturb my humanremams, mcluding those maned Outside offomial
❑
❑
❑
Q
canek!nes?
0
❑
Q
FINDING: The project will have no impact on cultural resources.
MITIGATION: No mitigation is necessary.
GEOLOGY AND SOILS7E,n
[mVI.
Mitt
Sl ;f
Nolmo a
aoa�A
Imoazt
Would theproject:
a) Expose people or structures to potential substantial adverse
effects, including the risk of loss, injury, or death involving:
i) Rupture of a known earthquake fault, as delineated on the
most recent Alquist-Priolo Earthquake Fault Zoning Map
❑
❑
❑
issued by the State Geologist for the area or based on other
substantial evidence of a known fault?
if) Strong seismic ground shaking?
❑
❑
❑
0
iii) Seismic -related ground failure, including liquefaction?
❑
❑
❑
iv) Landslides?
❑
0
❑
Q
b) Result in substantial soil erosion or the loss of topsoil?
❑
❑
❑
c) Be located on agwlogic out orsoHthat isuntreble, orthatwould
s1LM
with
simiifif.
No Mvact
became unstable as aresuh ofthe project, and potentially tenth in on or
❑
❑
❑
Impact
off-ste landslide, lateral spreading subsidence, liquefaction or collapse?
r
d) Be located on expansive soil, as defined in Table 18-1-B of the
❑
Ll
Ll
La
0994), creating substantial risks to life or property?
the routine transport, use, or disposal of hazardous materials?
e) Have soils incapable of adequately supporting the use of
b) Create a significant hazard to the public or the environmentduough
septic tanks or alternative wastewater disposal systems where
❑
❑
❑
❑
sewers are not available for the disposal of wastewater?
release of hazardous materials into the environment?
FINDING: The project will have no impact on geology and soils.
MITIGATION: No mitigation is necessary.
VII. HAZARDS AND HAZARDOUS MATERIALS
n
less Then
s1LM
with
simiifif.
No Mvact
lmv=
Mrtieation
Impact
r
Would the projea:
a) Crean a significant hazard to the public or the environmenttrough
❑
La
❑
the routine transport, use, or disposal of hazardous materials?
b) Create a significant hazard to the public or the environmentduough
reasonably foreseeable upset and accident conditions involving the
❑
❑
❑
release of hazardous materials into the environment?
c) Emit hazardous emissions or handle hazardous or acutely
hazardous materials, substances, or waste within one-quarter
❑
❑
❑
mile of an existing or proposed school?
d) Be located on a site which is included on a list of hazardous
materials sites compiled pursuant to Government Code
L1
Ll
Ll
65962.5 and, as a result, would it create a significant
hazard to the public or the environment?
e) For a project located within an airport land use plan or, where
such a plan has not been adopted, within two miles of a public
Ll
❑
❑
airport or public use airport, would the project result in a safety
hazard for people residing or working in the project area?
f) For a project within the vicinity of a private airstrip, would
the project result in a safety hazard for people residing or
❑
❑
❑
working in the project area?
g) Impair implementation of or physically interfere with an adopted
❑
❑
❑
emergency response plan or emergency evacuation plan?
h) Expose people or structures to a significant risk of loss, injury
or death involving wildland foes, including where wildlands
❑
LJ
❑
are adjacent to urbanized areas or where residences are
intermixed with wildlands?
FINDING: The project will have no impact on hazards and hazardous materials.
MITIGATION: No mitigation is necessary.
FINDING: The project will have no impact on hydrology and water quality.
MITIGATION: No mitigation is necessary.
Potvnfid
LOSS
S nt
Th
VIII. HYDROLOGY AND WATERUss
QUALITY
ifirent
Imoac[
With,
��^
i ifiwnt
No Moxt
Mittia,fign
lmnau
In
Would the project:
a) Violate any water quality standards or waste discharge
❑
❑
❑
requirements?
b) Substantially deplete groundwater supplies or interfere substantially
with groundwater recharge such that there would be a net deficit in
aquifer volume a a lowering ofthe local groundwater table level
❑
❑
❑
(e.g., the pnodt"im me ofpreaxisting nearby wells would drop to
a level which would not support existing land uses Of planned uses
for which permits have been granted)?
c) Substantially alter the existing drainage pattern of the site or
area, including through the alteration of the course of a stream
❑
❑
❑
or river, in a manner which would result in substantial erosion
or siltation on- or off-site?
d) Substantially alter the existing drainage pattern of the site or area,
including through the alteration ofthe course ofa stream or river,
❑
❑
❑
or substantially increase the one or amount of surface nmoff m a
manner which would result in flooding on- or off-site?
e) Create or contribute runoff water which would exceed the
❑
❑
❑
0
capacity of existing or planned storrowater drainage systems
or provide substantial additional sources of polluted runoff?
t) Otherwise substantially degrade water quality?
❑
❑
❑
g) Place housing within a 100 -year flood hazard area as mapped
❑
❑
❑
0
on a federal Flood Hazard Boundary or Flood Insurance Rate
Map in other flood bazard delineation map?
h) Place within a 100 -year flood hazard area structures which
❑
❑
❑
would impede or redirect flood flows?
i) Expose people or structures to a significant risk of loss, injury
❑
❑
❑
0
or death involving flooding, including flooding as a result of
the failure ofa levee or dam?
j) Inundation by seiche, tsunami, or mudflow?
❑
❑
❑
FINDING: The project will have no impact on hydrology and water quality.
MITIGATION: No mitigation is necessary.
IX. LAND USE AND PLANNING
IM.81,�
' ifioant
Lsss i
i ' vent
No Imna<t
X. MINERAL RESOURCES
y
Impact
Midgwoo
It
Imn—
Would the project result in:
Would the project:
a) Physically divide an established community?
❑
❑
❑
a) Result in the loss of availability of a (mown mineral resource
b) Conflict with any applicable land use plan, policy, or
❑
❑
that would be of value to the region and the residents of the
regulation of an agency withjurisdiction over the project
❑
❑
state?
(including, but not limited to the general plan, specific plan,
❑
❑
❑
v7
local coastal program, or inning ordinance) adopted for the
mineral resource recovery site delineated on a local general
purpose of avoiding or mitigating an environmental effect?
❑
❑
Q
plan, specific plan or other land use plan?
c) Conflict with any applicable habitat conservation plan or
❑
❑
❑
natural community conservation plan?
FINDING: The project will have no impact on land use and planning.
MITIGATION: No mitigation is necessary.
FINDING: The project will have no impact on mineral resources.
MITIGATION: No mitigation is necessary.
XI. NOISE
Pdenti 1
Sim
���
sismficant
snan
No Meg
X. MINERAL RESOURCES
y
v�iW
sianifi,t
Nom
Would the project result in:
a) Exposure of persons to or generation of noise levels in excess
MNeetion
la aw
Lovett
Would the project:
a) Result in the loss of availability of a (mown mineral resource
❑
❑
❑
that would be of value to the region and the residents of the
❑
❑
❑
state?
El
L3
L3groundbome
b) Result in the loss of availability of a locally -important
mineral resource recovery site delineated on a local general
❑
❑
❑
Q
plan, specific plan or other land use plan?
FINDING: The project will have no impact on mineral resources.
MITIGATION: No mitigation is necessary.
XI. NOISE
IWanfially
Siv i5J
I- Than
sib
with
th:s Tit
sissifi,t
No Meg
rape
Maisman
Lr�v
Lnoxt
Would the project result in:
a) Exposure of persons to or generation of noise levels in excess
of standards established in the local general plan or noise
❑
❑
❑
ordinance, or applicable standards of other agencies?
b) Exposure of persons to or generation of excessive
El
L3
L3groundbome
vibration or gmundbome noise levels?
10
c) A substantial permanent increase in ambient noise levels in
❑
❑
❑
the project vicinity above levels existing without the project?
,1S u t
"
r
»
d) A substeNal temporary or periotic inaease In ambiardndse levels
❑
❑
❑
in the project vichrhy above levels existing withoulthe project?
l
e) For a project located within an airport land use plan or, where
a) Induce substantial population growth in an area, either
such a plan has not been adopted, within two miles of a public
❑
❑
❑
L3businesses)
airport or public use ahport, would the project expose people
or indirectly (for example, through extension of
residing or working in the project area to excessive noise levels?
roads or other infrastructure)?
t) For a project within the vicinity of a private airstrip, would the
❑
I
❑
❑
i
0
project expose people residing or working in the project area to
necessitating the construction of replacement housing
❑
❑
❑
excessive noise levels?
elsewhere?
FINDING: The project will have no impact on noise level.
MITIGATION: No mitigation is necessary.
FINDING: The project will have no impact on population and housing.
MITIGATION: No mitigation is necessary.
11
porenfialiv
tem
S�titiyaat
IR591'�1Ha
XII. POPULATION AND HOUSING
,1S u t
"
r
»
Nfi.
law
l
Would the project:
a) Induce substantial population growth in an area, either
directly (for example, by proposing new homes and
Ll
El
L3businesses)
or indirectly (for example, through extension of
roads or other infrastructure)?
b) Displace substantial numbers of existing housing,
0
necessitating the construction of replacement housing
❑
❑
❑
elsewhere?
c) Displace substantial numbers of people, necessitating the
❑
❑
❑
construction of replacement housing elsewhere?
FINDING: The project will have no impact on population and housing.
MITIGATION: No mitigation is necessary.
11
XIII. PUBLIC SERVICESsit
pomnsally
[<ss Th�
S'vn frent°4
Sien'ficent
N
Imeaa
t
M�� V'QQ
k�
Moazi
a) Would the project result in substantial adverse physical impacts associated with the provision of new or physically
altered governmental facilities, need for new or physically altered governmental facilities, the construction ofwbich
could cause significant environmental impacts, in order to maintain acceptable service ratios, response times or other
performance objectives for any of the public services:
Fire protection?
❑
❑
❑
❑
Police protection?
❑
❑
❑
Schools?
❑
❑
❑
Parks?
❑
❑
❑
Other public facilities?
❑
❑
❑
❑
FINDING: The project will have no impact on public services.
MITIGATION: No mitigation is necessary.
RECREATION
anXIV.
U.tentlall42ithTtion
xo My
a) Would the project increase the use of existing neighborhood
and regional parks or other recreational facilities such that
Ll
❑
❑
substantial physical deterioration of the facility would occur
or be accelerated?
b) Does the project include recreational facilities or require the
construction or expansion of recreational facilities which
❑
❑
❑
might have an adverse physical effect on the environment?
FINDING: The project will have no impact on recreation.
MITIGATION: No mitigation is necessary.
12
FINDING: The project Will have no impact on transportation and traffic.
MITIGATION: No mitigation is necessary.
n0
$11
uo Thm
Si �CeAI
It55on j
XV. TRANSPORTATION/TRAFFIC
Ira^act
conn
simificent
N�
Ilmoact
Maj.
Imoect
I.P.
Would the project:
a) Cause an increase in traffic which is substantial in relation to
a) Exceed wastewater treatment requirements of the applicable
❑
❑
❑
the existing tic load and capacity of the street system (i.e.,
❑
❑
❑
Q
result in a substantial increase in either the number of vehicle
b) Require or result in the construction of new water or
trips, the volume to capacity ratio on roads, or congestion at
wastewater treatment facilities or expansion of existing
Ll
❑
LJfacilities,
intersections)?
the construction of which could cause significant
b) Exceed, either individually or cumulatively, a level of service
❑
❑
❑
0
standard established by the county congestion management
c) Require or result in the construction of new storm water
agency for designated roads or highways?
drainage facilities or expansion of existing facilities, the
❑
❑
❑
c) Result in a change in as traffic patterns, including either an
❑
❑
❑
0
increase in traffic levels or a change in location that results in
substantial safety risks?
d) Substantially increase haurds due to a design feature (e.g.,
❑
❑
❑
0
sharp curves or dangerous intersections) or incompatible uses
(e.g., farm equipment)?
e) Result in inadequate emergency access?
❑
❑
❑
f) Result in inadequate parking capacity?
❑
❑
❑
g) Conflict with adopted policies, plans, or programs supporting
El
❑
❑
alternative transportation (e.g., bus turnouts, bicycle racks)?
FINDING: The project Will have no impact on transportation and traffic.
MITIGATION: No mitigation is necessary.
13
pwnfially
1.cssn
Significant
`s n�
XVI. UTILITIES AND SERVICE SYSTEMS
si iti
` fh
Si ifiean
& Imnazt
Ilmoact
iM tiaHion
r
I.P.
Would the project:
a) Exceed wastewater treatment requirements of the applicable
❑
❑
❑
Regional Water Quality Control Board?
b) Require or result in the construction of new water or
wastewater treatment facilities or expansion of existing
Ll
❑
LJfacilities,
the construction of which could cause significant
environmental effects?
c) Require or result in the construction of new storm water
0
drainage facilities or expansion of existing facilities, the
❑
❑
❑
construction of which could cause significant environmental
13
effects?
Pmwfialiv
Less Than
d) Have sufficient water supplies available to serve the project
Si iti.
law
Ss ism
L,
ii�t
ter tmm
from existing entitlements and resources, or are new or
❑
❑
❑
expanded entitlements needed?
e) Result in a determination by the wastewater treatment
provider which serves or may serve the project that it has
❑
❑
Ll
adequate capacity to serve the project's projected demand in
❑
❑
❑
addition to the providers existing commitments?
t) Be served by a landfill with sufficient permitted capacity to
El
L3
Ll
the project's solid waste disposal needs?
g) Comply with federal, state, and local statutes and regulations
L)
Ll
related to solid waste?
FINDING: The project will have no impact on utilities and service systems.
NIITIGATION: No mitigation is necessary.
14
Pmwfialiv
Less Than
XVII. MANDATORY FINDINGS OF SIGNIFICANCE
Si iti.
law
Ss ism
L,
ii�t
ter tmm
m� �wearma
i
im
a) Does the project have the potential to degrade the quality of
the environment, substantially reduce the habitat of a fish or
wildlife species, cause a fish or wildlife population to drop
below self-sustaining levels, threaten to eliminate a plant or
❑
❑
❑
animal community, reduce the number or restrict the range of
a rare or endangered plant or animal or eliminate important
examples of the major periods of California history or
prehistory?
b) Does the project have impacts that are individually limited,
but cumulatively considerable? ("Cumulatively considerable"
means that the incremental effects of a project are
Ll
L3
❑
considerable when viewed in connection with the effects of
past projects, the effects of other current projects, and the
effects of probable future projects)?
c) Does the project have environmental effects which will cause
substantial adverse effects on human beings, either directly or
❑
❑
❑
vQ
indirectly?
14
Attachment 4
SAFETY ELEMENT
EXISTING GENERAL PLAN
1975
SEISMIC SAFE1y/SAFCTy ELEMENT
Part I - Inkroduction
Pulse
mol, The basic purpose of Seismic Safety/Safety Elements is to define geo-
logic and fire hazards se these hazards may be taken into account in Gen-
eral Plan policies and implementation measures. In California, important
seismic and other geologic hazards have frequently been ignored in estab-
lishing land use policy in General Plans and implementing regulations and
programs. The same is true, but to a lesser extent, of fire hazards. The
State, in an effort to see that these types of mistakes are not repeated
in the future, now requires that cities and counties establish General
Plan policy regarding these hazards. State law does not dictate what
local policy should be with respect to safety, only that the hazards be
recognized.
Beismi_CS etti�
802• Most of California is seismically active. The Problem is so intense,
in fact, Lhat the State Legislature has supported a Joint Conmrittee on
Seismic Safety which has been in operation since lg69. The Joint Committee
has submitted its final report to the Legislature. A few excerpts from
the report provide insights to the problems faced by local communities:
California is situated in a seismically active region of
the globe, and is laced with earthquake faults that spread
over much of the State, including sone of its most impor-
tant urban areas. Consequently, virtually all of Calif-
ornia is subject to earthauake shaking, and future earth-
quakes capable of producing great damage and disaster are
inevitable.
Accordingly, the basic approach recommended by the Joint
Committee on Seismic Safety is to (1) take all practicable
measures that will reduce the present high hazard levels,
and (2) avoid creating further hazards by discontinuing
imprudent planningbuilding, and development practices.
Such thoughtful seismic safety policies, if persistently
pursued and diligently implemented, can bring dramatic re-
ductions in C,alifornia'searthquake hazard.
- 108-
- 802.(cort.) In broad overview, the works of man loom as the princi-
pal cause of earthquake hazard. In open country, one
should be able to "ride out" a great earthquake in rea-
sonable safety, barring landslides, large-scale lique,.-
faction, and tsunamis. It is primarily the structures
built in seismic regions that create the hazard.
Viewed this way, earthouake safety seems disarmingly
simple to achieve. All that needs to be done is either
leave the landscape untouched or prudently plan where to
build, and design every structure and excavation to mini-
mize any hazard created. Accordingly, the seismic safety
implications of any proposed action should be evaluated
and found acceptable before the action is permitted.
These insights yield useful guidelines for seismic safety
measures and Policies:
First, thoughtful land use decisions are fundamental to
seismic safety. We should make sure not to erect a struc-
ture on ground that is subject to high levels of seismic
or geologic hazard, unless such construction is unavoid-
able, or the risk to life and property can he made accept-
ably low. Sometimes, of course, we are forced to build in
areas of Mob hazard, such as across earthcmake. faults.
A good example is the case of water mains. In such cases,
we must use sophisticated and often expensive designs so
that the structures and principal mains can accommodate
substantial movement, without lass of function. We should,
moreover, also provide adequate back -un capacity and all.er-
native temporary emergency facilities in case the use of
the original facilities is lost.
Second, when contemplatinq grading or construction in seismic
areas, one should first consider the stability of the under-
lying geologic forvations. Wlth around of doubtful stability
under earthquake conditions, buildinq or grading should pro-
ceed only after all the likely consequences have been eval-
uated and approved by competent professionals.
Third, in a seismic reainn like California decision makers
should observe one invariable rule of thumb, namely, that
every significant structure in California can be expected to
undergo at least one major earthquake in its lifetime. All
should therefore be located, designed, and built to withstand
future shaking or ground failure in order to minimize possible
death or injury and avoid unnecessary or unacceptable danmge.
In any event, no action should be taken that will make the
earthquake risk above levels that reasonable people would
presumably consider acceptable. (See Table 1 for a suggested
scale of acceptable risks.)
All of the above considerations are important, but the third
- 109 -
(coot ) is crucial. Every building should be made as secure a -
ane
gainst earthquake shaking as is practicable. To this end,
no structure should be built unless the geologist, archi-
tect, engineer, and builder --as well as the community-- -
are satisfied that it meets adequate standards designed
to prevent life-threatening collapse or damage in future
earthquakes.
_State Planning Law and Guidelines
803. State planning law sets forth the requirements for the Seismic Safety/
Safety Elements in two sections of the Government: Code:
Section 05302(f)
A seismic safety element consisting of an identification
and appraisal of seismic hazards such as susceptibility
to surface ruptures from faulting, to ground shaking, to
grand failure, or to the effects of seisndcall.y induced
waves such as tsunamis and seiches.
The seismic safety element shall also include an appraisal
of mudslides, landslides, and slope stability as necessary
geologic hazards that must be considered simultaneously
with other hazards such as possible surface ruptures from
faulting, ground shaking, ground failure and seismically
induced waves.
Section 65702.1
A safety element for the protection of the community from
fires and geologic hazards including features necessary for
such protection as evacuation routes, peak load water sup-
ply requirements, minimum road widths, clearances around
structures, and geologic hazard mapping in areas of known
geologic hazards.
In order to provide guidance to cities and counties in preparing these
elements, Section 311211.1 of the Government Code requires that the Council
or Intergovernmental Relations prepare and adopt guidelines. Such guide-
lines were adopted by the CIR on September 20, 1973. It is not mandatory
that local ,jurisdictions follow these guidelines; however, they are in-
tended to provide helpful guidance. The main functions of the guidelines
are to define the scope of the elements, methodology for preparation,
relationships to other general plan elements and other agencies, and
suggest methods of implementation.
- 110 -
I — 804, The State Guidelines have been reflected in this Element; however,
deviations have been made where appropriate to address particular cir-
cumstances relating to the local situation.
Relationship to other General Plan Elements_
805. The State Guidelines suggest the desirable relationshins of Seismic
Safety and Safety Elements to other General Plan elements as follows:
The Seismic. Safety Element contributes information on
the comparative safety of using lands for various pur-
poses, types of structures, and occupancies. It provides
primary policy inputs to the Land Use, Housing, Open
Space, Circulation and Safety Elemnnts.
the Safety Element contributes to developing Land Use
standards and policies. These will relate type and
intensity of use to the level of risk from fire and geo-
logic hazard, to the effect of development upon that risk,
and to the availability of services and facilities to com-
bat them.
The Safety Element also contributes basic standards and
requirements to the Circulation and optional public util-
ities elements, and will have important implications for
the Open Space and Conservation Elements.
The Guidelines further state that because of the Close relationship be-
tween the Safety and Seismic Safety Elements, the local planning agency
may wish to prepare these two elements simultaneously or combine the two
elements into a single document. If combined, the Guidelines indicate that
the required content and policies of each element should be clearly iden-
tifiable.
ROG. As suggested by the CII! Guidelines, the Safety and Seismic Safety
Ilements have been combined in this document and are referred to as the
Seismic Safety/Safety Element.
Relationship to City Responsibilities
807. While the Seismic Safety/Safety Element has implications for land use
policy, it also provides direction for needed actions in other aspects of
local government. It is of major importance that the planning requla-
tions such as zoning, subdivision, grading and building erodes provide
effective controls and procedures related to Seismic safety/Safety Ele-
ment policies. In addition, reronuwendatiops in the Seismic Safety/Safety
Element relate to programs for disaster prenare(iness and recovery, fire
protections, and utility systems. Follow-through in each of these subject
areas is required by the community if the general policy of the Seismic
Safety/Safety Element is t.n he adequately implemented.
Data Sources
anw. The nature and quality of available gpolonic data is critical to the
preparation of the Element. Data sources arr listed in APPENDIX A. Most
of the data for Los Altos hills is of a generalized nature, the most re-
cent geologic map being at a scale of 1 : 62,5no or about 1 inch to the
mile. Such data shows only major observed features and therefore can
provide only general guidance. It is therefore not entirely adequate. At
this map scale, significant small features are not large enough to show,
the level of study may miss some rather large important but visually ob-
scure features, and the degree of precision in recording features and
boundaries is not high. Nonetheless, when lacking better data, such in-
formation can serve as a basis for geuer•al policy and will tend to in-
dicate where additional study is needed.
arra Geologic mapping by Dibblee and Pampeyan in the 196n's provides a
general look at the geology of the area. The basic data and interpre-
tive reports of the on-going San Francisco Ilay Pegion.Study of DSGS and
BUD are providing additional data on a wide variety of subjects, Nu1-. at
a scale ware sutitable for regional rather than local planning.
etrr The California Division of Pines and Geology (f.mG) is completing
geologic mapping for Santa Clara County as a part of the County Seismic
810. (con r..)
safety element. This data will in the future be available to the Town and
can then be used to refine the Seismic Safety/Safety Element. Also, CIIMG
completed a study of the Montebello Ridge Area in 1474 which includes a
portion of the Los Altos Hills Planning Area.
811. Currently the Town is funding a study of the Black Mountain Fault,
which P.s being undertaken by a graduate student at Stanford University,
under the supervision of the Town Geologist.
BIZ. In addition, the Town requires geologic reports on many applications
under the planning regulations. These reports are maintained in Town
files and provide additional detailed data for selected portions of the
community.
Acceptable -Risk
813. Inherent in any action to cope with a possible future hazardous e-
vent is some decision as to the amount of risk the derision maker finds
acceptable. Vie all live with rertaiu risks each day and mate decisions
which involve evaluating risks. In planning for a community, the public
should make an informed evaluation of the risks attendant to various
courses of action when faced with possible future hazardous events. The
following excerp%s from "Cry California" discusses some aspects of risk
with respect to conununity responsibility:
....Where does the responsibility lie for Irrotectinc
people and property? An often -heard argument is that
if an individual wants to take the risk of building in
a hazardous area, he should be allowed to do so. The
argument goes on that only IIF will suffer in the event
of a failure. In an isolated location, this position
udght be acceptable.. But in urban and suburban "t-
tings, land failure en an individual property usually
has intense repercussions on the surrounding area: De-
creased property values, possible fire hazards, costly
public assistance, and possible physical impact on ad-
jacent land are frequent major results.
- 113 -
8B. (Cont.)
Similarly, a developer often says he is willing to accept
To the end, of course, that
_
the risk in an unstable area.
is on to purchasers in the development and to
Kinds of sue"V oe
risk passed
the public agency that assumes responsibility for streets
iusually
and Pulicthe
etime a Thusthe
No set percentage (whatever is
out theefailurer occurs.
in the
failure miltitt be catastrophic: nuclear teaclofs, fools dallls,
burden is unfairly shifted to all the taxpayers
couniun i ty. .
able safety)
it: be(,nms clear that geologic hazards are not private
explosives it, toxic materials
platters, but concern the public in general. it, is there-
the in-
2. Slightly higher than
fore incuni)ent upon government to protect public
5 to 25 percent of project costs
ierest.
Table
1, following, indicates a suggested range of acceptable risks for
major
classes of structure and occupancies as proposed by the Joint Com-
mittee
on Seismic Safety together with estimates of extra construction
cost
needed to reduce risk.
r..u- t - s c.-.I...r A.•�.,rddn Rieke
i radian of a single atmelnre may .(feel lubaanuar popnlaamn.
te
3 Thew additional percmll are addition, ited ala an ml.d shat till. murot ncta at a woold Illlot[., 1 nen de'ig we anti built iln ....Idnee with, cn rnt
.1Ken
nor «cupan-Y, . ..ot i
Califmnla Pranlim. Ni.mwm, Ibe nlimalnA additional call Premmn IL'vl anmuuea in Ibis aceepmbla-rink ca,aorV are to embody
adndent ,alely la .....in fu«tbnal IullowlnP as euthgyake.
Failure al. alnale stnudlu, would affect primarily only it.. «mtpanb.
k Tbew .,idinnnd Pewenlaa_a are beard on the assumption last the hate emu b Ila total coat nl ate flooding ar fadlilY when it,
fareuPanry. In addilion, it la roo nmd that the structure' would lure been deslaned end built to .mce
crdanwith notes(
California I,oeli-s. M1lmm�•ar the edimu,d nudhiunal -net preannu the' aNe,ry in tbia accepmiele-risk nte,uni aro to be
sa MilanllY 1a1a to on. r•amnahle anrtnn-. of p ... entire ":bill or bac of lirs dodos and eartiuryakq but ola.'sa. cal .
seri y to remain functional.
3 "Ordinrry d,k': Reeds, minor..ra nuekes willww damn,.; „ht modem, eanhque si wnbont atnrclural In Cali bat with eon.
l,uatioll itsofas.; -,ill malt( eatute,a kn of the i renally err ee•mitY of tba a4mi. vC1a.pmm«eJ In California, without
:.It I but wilt,,ome anm,r6 as well a a ... t"total dram.,.. Inman evuctuma, it u ea ted that towel ... I tlama,e, evert in
era or earthquake, cmdJ be fimfled to repairable aamag.. tslruclutal Eadn"en Aaodalion of C'alifm'--
- 114 -
LeI,I of Arc.. table Rhk
Kinds of sue"V oe
Iledne. Itlak w m d-cgtalGa Lina
—s structure, whose continued functioning is l(I:icai. or whose
No set percentage (whatever is
1, F_,hemcly fowl
failure miltitt be catastrophic: nuclear teaclofs, fools dallls,
required for olaxonam attain -
power laterite systems, plants ori. tfacluring at staring
able safety)
explosives it, toxic materials
2. Slightly higher than
Structures whose use is critically needed atter a disaster:
5 to 25 percent of project costs
under level 1,
important utility centers; hospitals; fire, police, and inner
gency cunanunication facilities' fire stations; and critical
Icamportatiun elements such as bridges and Overpnssea; also
snfaller dams
3. Lowest risk
Structures of Iii l also fesfc , or whit use after a disaster
I Y,
5 to I S percent of project cost"
passible
to occupants of the
it y convenient: schools, churches, large
would be lartiIS,
�u>tels, and other high-riss buildings housing large
sttnclured
lens, large 1
number of people, other places normally attracting large
concentrations of people, civic buildings such as fin
stations, secondary utility structures, extremely large coal-
mercial entelpfises, ,least toads, alternative or noncritical
bridges and overpasses.
—c
4. An "ordinary" level
The vast majority of structures: ain't commercial and
1 r0 2 percent of project -it,
most cases (2. to 10 percent or
of risk to occupants
industrial buildings, small hotels and apathnent buildings,
project cost in a minority of
of the structure
and single family residences.
said
s;,s„s)q
i radian of a single atmelnre may .(feel lubaanuar popnlaamn.
te
3 Thew additional percmll are addition, ited ala an ml.d shat till. murot ncta at a woold Illlot[., 1 nen de'ig we anti built iln ....Idnee with, cn rnt
.1Ken
nor «cupan-Y, . ..ot i
Califmnla Pranlim. Ni.mwm, Ibe nlimalnA additional call Premmn IL'vl anmuuea in Ibis aceepmbla-rink ca,aorV are to embody
adndent ,alely la .....in fu«tbnal IullowlnP as euthgyake.
Failure al. alnale stnudlu, would affect primarily only it.. «mtpanb.
k Tbew .,idinnnd Pewenlaa_a are beard on the assumption last the hate emu b Ila total coat nl ate flooding ar fadlilY when it,
fareuPanry. In addilion, it la roo nmd that the structure' would lure been deslaned end built to .mce
crdanwith notes(
California I,oeli-s. M1lmm�•ar the edimu,d nudhiunal -net preannu the' aNe,ry in tbia accepmiele-risk nte,uni aro to be
sa MilanllY 1a1a to on. r•amnahle anrtnn-. of p ... entire ":bill or bac of lirs dodos and eartiuryakq but ola.'sa. cal .
seri y to remain functional.
3 "Ordinrry d,k': Reeds, minor..ra nuekes willww damn,.; „ht modem, eanhque si wnbont atnrclural In Cali bat with eon.
l,uatioll itsofas.; -,ill malt( eatute,a kn of the i renally err ee•mitY of tba a4mi. vC1a.pmm«eJ In California, without
:.It I but wilt,,ome anm,r6 as well a a ... t"total dram.,.. Inman evuctuma, it u ea ted that towel ... I tlama,e, evert in
era or earthquake, cmdJ be fimfled to repairable aamag.. tslruclutal Eadn"en Aaodalion of C'alifm'--
- 114 -
914
915.
916.
The Seismic Safety/Safety Element consists of Part 11 -Description of
Mazards, Part III -Policy, Parl U -Implementation Program.
Part I1 - Hazards
Three types of hazards are considered in the Element: seismic, other
geologic hazards and fire. The Element includes a description of each
hazard to the extent data is available, defines the level of risk associ-
ated with the hazard, and discusses the implications for existing devel-
opment. Specific policies established by the Element are included in
Part III.
1. Seismic Hazards
Seismic events, or earthquakes, induce a wide variety of what
are called seismic hazards. Such hazards include the destruction
of property, injuries to persons, and loss of life. The earth is
constantly changing, and earthquakes are a natural part of this
process. An earthquake is caused by movement along a fault. The
shaking from such an earthquake can, of course, extend many miles
from the actual location of fault movement. Much is known re-
garding the nature of earthquakes but much is yet to be discovered.
At the nxnnent, therefore, prudent Planning calls for doing tine
best job of anticipating seismic hazards and avo4ding them to the
maximum extent feasible. While all seismic hazards cannot be
avoided, the seismic hazard risk should be reduced to a level
deemed acceptable by the public.
The major seismic hazards in Los Altos Hills relate to ground
shaking, ground failure, and surface faulting. Each of these is
discussed separately.
- 115 -
816.1. (con t.) A, Ground Shaking,. The basic aspects of ground shaking are
briefly described in Geological Circular, fqn, as follows:
Earthquake -generated ground shaking, in many
instances, causes the most widespread earth-
quake damage. However, ground shaking (what
Imrst people and structures react to during
an earthquake) is one of the most difficult
seismic hazards to predict and quantify.
Data from past earthquakes have shown that
the intensity of ground shaking can be sev-
eral times larger on sites underlain by thick
deposits of saturated sediments than on bed-
rock. Consequently, the greatest losses, re-
sulting solely from shaking, may occur where
tall structures are built on thick, relatively
soft, saturated sediments.......and the least
where they are built on firm bedrock.....
In addition to the amplification effects of
local geologic deposits, the amount of around
shaking at a particular site depends nn 0 )
characteristics of the earthquake source (for
example, mannitude, location, and area of
causative fault surface) and (2) distance from
the fault. To anticipate the severity of
ground shaking likely to occur at a site, each
of these factors must he taken into account.
The extent of shaking damage is also dependent
partly on the structural integrity of buildings
before the earthquake.......
Some idea of the passible severity of an ern Lhquake on I:he
San Andreas Fault as it might be experienced in Los Altos Hills
can he obtained from the recent NDAA report, A STUDY OF EARTH-
QUAKE LOSSES IN TUE SAN FRANCISCO BAY AREA. The report indi-
cates that if an R.3 magnitude earthquake., the same magnitude
earthquake as Lhe lgn6 earthquake, were to occur on the. San
Andreas fault, the intensity in most of Los A1Lus Hills would
be Ix as measured on the Modified Mercalli Scale, with some
parts of the Town with an intensity of Vill.
Magnitude is intended to be an objective, instrumentally
determined rating of the size of a given earthquake. Magnitude
- 116-
81E.1.A. (cont.) can tie calculated from the wave amplitude recorded by sies-
mographs at any distance from the source of a quake. Dili
upward step of one magnitude unit, e.g. 3 to 1, means a ten-
fold increase in the amplitude of the recorded waves because
the scale is ingarithmic. The scale has no arbitrary "ceiling"
but 8.9 appears to be the largest magnitude of any known quake.
The Richter Scale is a magnitude scale, and is expressed in
Arabic numerals.
The intensity of an earthquake is a measure of earthquake
effects of all types. Lowest earthquake intensities are based
principally on human reactions, such as "felt indoors by few",
since other effects, such as damage, are usually not present.
The highest intensities are largely measured by geologic ef
fects, such as broad fissures in wet ground, numerous and ex-
tensive landslides, and major surface faulting. The middle
intensity range Is based largely on the denree of damage to
buildings and other man-made structures. Thi, it should be
clearly understood that intensity rations are non -instrumental
and rely on human observations and interpretations. Grades
of intensity at each locality within an area shaken by an
earthquake are rated on the basis of an "earthquake intensity
scale". Grades of Intensity are indicated by Roman numerals
from i to XII. The Modified Mercalli Iu Len,il.y Scale is Lhe
most conrnon and has been used in the united States since 1931.
The report gives the following rationale for selecting
a magnitude 8.3 earthquake for analysis purposes:
The selection of the magnitude R.3 earthquake on
both faults was based on the following rationale:
- 117 -
816.1.A. (cont.) 1. The 19n(1 earthquake is the largest shock that
_ has occurred on the San Andreas Faull. in the
historical record, and while it may be possible
for larger earthquakes to occur on the San An-
dreas Fault, the 1906 earthquake is �:e mainly
near the upper limit of shocks that may be ex-
pected to occur in this area.
2. It was advantageous to use an 11.3 magnitude
earthquake as the largest probable shock for pur-
poses of this study because of the tremendous
quantity of data on the intensity of shaking
available in the report of the Carnegie Commis-
sion ... ...for this magnitude earthquake.
The descriptions of the Modified Mercalli Scale are given in
Table 2, nu the following page.
Most earth scientists agree that a ma.lor earthquake on the
San Andreas Faull: is quite likely. Robert B. Wallace of the
WSCS has described the likelihood of another great earthguake
(an earthquake with a magnitude greater than 8.0 measured on
the Richter Scale) as follows:
The last estimate of the long -tern average rake
of occurence of great earthquakes along the San
Andreas Fault Is about one per one hundrod years.
The lass; such event was seventy years ago, so a
significant probability exists or another within
the next thirty years. Significant additional
losses can be expected with a higher degree of
certainty rrom smaller earthquakes.
With the foregoing description in mind, it is possible to
draw some general conclusions from the geologic map prepared
by Brabb. it would appear that the greatest: shaking intensity
would occur along the valley flom•s io the Town where un-
consolidated alluvial deposil,s exist. these would include the
Adobe, Purissinrr. Matadero and Barron Creek areas in parla cu -
lar. These are shown as Qal and Qoal on the above -referenced
map.
- 118 -
77\D Lf•. 2
ith)INPIEU MERCALLI hlTFNStrY SCALP. (1'131)
Not felt extent by a very few under especially favorable circumstances.
It. Felt only by a few persons at rest, especially on upper floors of luri!dings. Delicately
suspended ubiects may s".ving.
III. Pelt quite noticeably indoors, especially on upper flours of buildings, but many people
do not recognize it ;rs an earthquake. Standing motor cars may rock alightly. Vibration
like passing of buck. Duration estimated.
During the day felt indoors by many, outdoors by few. At night soma awakened.
Dishes, wiuduws, door: disturbed; walls make cracking sound. Sensation like heavy
truck striking building. Standing motor cars rocked noticeably.
V. Felt by nearly everyone; many awakened. Surne dishes, windows, etc.,bruken; a few
instances or cracked plaster; unstable objects overlunrerl. Disturbance or trees, tholes
and other tall objects sometimes noticed. pendulum clocks may stop.
VL Felt by all, unary frightened and nm outdoors. Some heavy furniture moved; a few
instances or fallen plaster or damaged chimneys. Danmgeslight.
VII. Everybody runs outdoors. Damage negligible in buildings of good design and
construction; slight to moderate in well-built ordinary sliuclures; considerable in
poorly built or badly designed structures; some chimneys broken. Noticed by persons
driving motor cars.
VIII. Damage slight in specially designed structures; considerable in ordinmy substantial
buildings with partial collapse; great in poorly built struchnes. panel walls thrown out
of frame structures. Fall of chimneys, Yactory stock„ columns, monumenL¢, walls.
Heavy furniture overturned. Sand and mud ejected in small amounts. Changes in well
water. Disturbs persons driving motor cars.
IX. Damage considerable in specially designed structures; well designed frame strvrtures
thrown out of plumb; great in substantial buildings, wilh partial nollapse.. Buildings
shifted off foundations. Ground cracked conspicuously. Underground pipes broken. .
X Some well-built wooden structures destroyed; most masonry and Game stnictures
destroyed with their foundations; ground badly cracked. Rails bot. Landslides
considerable frorn river banks and steep slopes. Shifted sand and mud Watersplasbed
(slopped) over banks.
X1. Few, if any Onasonry), structures aenrairl standing. Dritil;es destroyed. Mold fissures in
ground. Undeq;runud pipe lines completely oral of service. Earth shnnps and land slips
in soft pround. Rails hent greatly.
XII. Damage total- Waves seen on ground surfaces. l..ins of sight and level distorted.
Objects thrown up.vanl into the air.
NOTE! tAmrilieA Mer Cal 11 Intensity Scale h umrally ';ran in nomm�l thvnerah.
- 119 -
8[6.].A. (cont.) Since most or the development in Los Al Los Hills is of
one or two story wood -frame construction, it is not antici-
pated that widespread major structural failures from shaking
would be expected in the Town. However, wood -frame structures,
lacking lateral bracing, adequate to resist seismic forces,
may suffer structural failure. Any unreinforcrd brick or
concrete structures could receive considerable daumae.
The schools all have been built under tth- Field Act and
should therefore meet current building standards with respect
to expected shaking. A review of school rites in regard to
geologic hazards on the sites might be warranted, however.
Critical structures including fire stations, major utility
lines and installations, communications sysl:ems and freeway
interchanges and underpasses should be reviewed with respect
to their ability to withstand seismic shaking.
B. Ground Failure. The major aspects of ground failure are de-
scribed in Cenlogical Circular 590 as follows:
Earth materials in a natural condition I.end to reach
equilibrium over a long period of time. In geologi-
cally young and active areas such as C,allfornia and
Alaska, there are many regions where earth materials
have not yet reached a natural state of rtaim ity.
For example, most of the valleys and bay margins are
underlain by recent loose materials that have not
been compacted and hardened by long-term natural pro-
cesses. Landslides are common on most of the hills
and mountains as loose material moves downslope. In
addition, many activities of man tend to mnke the
earth materials less stable and hence to increase Lhe
chance of ground failure. some of the natural causes
of instability are earthquakes, weak materials,
stream and coastal erosion, and heavy rainfall, llu-
man activities that contribute to instabilil:y include
oversteepeninq of slopes by undercutting them or over-
loading them with artificial fill, extensive irriga-
tion, poor drainage or even ground -water withdrawal,
- 120 -
816.13.(cmrt.) and removal of stabilizing vegetation. Those
causes of failure, which normally produce land-
slides and differential settlement, are augmen-
ted during earthquakes by strong ground motions
that result in rapid changes in the state of
earth materials. It is these changes, by means
of liquefaction and loss of strength in fine-
grained materials, that result in so marry land-
slides during narthguakes as well as differential
settlement, subsidence, ground rracklog, ground
lurching, and a variety of transient and perma-
nent changes it) the ground surface.
It is very difficult to anticipate the extent of probable
ground failure in Los Altos Hills in resoonse Lo seismic
shaking. There have been no strong earthquakes affecting
the Town, or even the rest of the Bay Area since the vast,
hillside areas have been developed after the 14116 earthquake.
Experts agree that many seismic induced land failures in the
hills in the Bay Area are certain to occur, esngcially where
man has disturbed the natural slope equilibrium through
cutting, filling and placing structures. No would also as-
sume that other tyres of ground failures would occur alonq
valley fluors on alluvial materials which can lose their
strength under shaking conditions. In Los All -os lulls, the
basic stability of hillside materials vary and some are more
resistant to failure than others. Byrand large, however, the
basic stability of the hillside areas appears noderate to
high, based on the manning of Brabb and C101.
C. Surface raultinrL. A basic description of faul Ling is con-
tained in GEOLaGIf.AL SURVEY CIRCULAR 690, portions of which
are excerpted below:
The earth is laced with faults --planes or surfaces in
earth materials along which failure has occurred and
materials on opposite sides have moved relative to
- 121 -
_ 816.1.C.(cont,) one another in response to the accumulation of
stress. most of these faults have not: moved for
hundreds of thousands or even millions of years
and thus can be considered inactive. nlhers,
however, show evidence of current n(A.W :y or
have moved recently enough to be considered ac-
tive, that is, capable of displacement in the
near future. Any fault movement heneath a build-
ing in excess of an inch or two could have cata-
strophic effects on the structure, depending up-
on design and construction and the shah nq stresses
the structure undergoes at the same Hmp......
..
Therefore, It is important to know not only which
faults may umve but how they may move. Conmm"ly,
faults are regarded as active and of concern to
land -use planning when there is evidence ];hat they
have moved during historic time or, through geol-
ogic evidence, there is a significant likelihood
that they will move during the projected use of a
narticular structure or piece of land........
Knowing that a particular fault is active, however,
is only part of the problem. The other part is pre-
dicting the likely location of fault ruptures during
the next significant earthnuake. rpnlogis Cs gener-
ally accept the premise that the next rapture will
probably occur along the fault trace that runtured
last, especially if there is evidence of repeated
earlier movements on the same fault trace ..... llow-
ever, movement seldom is limited to a singl0 fault
surface throughout the lifetime or a fault system
such as the San Andreas. In many places tens or even
hundreds or thousands of individual fault surfaces
make up the San Andreas in a zone varying In width
from a few hundreds to many thousands nr feet........
The amount of displacement that can occur during a
single earthquake can he related in a general way
to the total length of a fault. The longer the fault,
the greater the pntential for a great earthquake, and
the greater amount of displacement likely ..... ]be
maximum displacement ever recorded during a single
earthnuake is about 42 feet of vertical displacement
.........Horizontal movement of is much as 20 feet
occurred during the 1906 quake along lire San Andreas
Fault......
In addition to the location and amount of displace-
ment, the sense of movement is extremely important
in estimating the amount and type of damage that
might be ornduced. This was evidence!] by the great:
danmge over faults during the moderate (nm1pritude 6.6)
San i'ernando earthquake which produced a reverse or
- 122 -
816.1•C.(cont.) thrust fault movement....: movement occurs along
a similar Plane, but in an opposite direction on
the normal.... Wasatch fault in Utah. Left -lateral
movement..... and rii h_t-lateral movAmenk, rvhlcli1s
common to the San Andreas fa ul L, proTiahly are less
potentially damaging to most structures than normal
or thrust faulting.
Not all surface faulting need be rapid nor need it
occur during major earthquakes. Imperceptibly slow
movement, called "fault creep".. occurs along the
Hayward, Calaveras, and some other faults and may be
accompanied by microearthquakes. Similarly, not all
defnruratiorr of 1Hear1F`s ssrfiace produces fault:
displacements. Strains in the earth deform the rocks
until their strength is exceeded and they rupture,
producing the earthquake. Accompanying this bending,
however, is a certain amount ofllAstic deformation
......Both rupture and plastic dP_formal.ion counwn�y
occur along active fault zones and may he sufficient:
to damage or destroy structures over particularly
strongly deformed rocks. Earthquakes deep within
the earth may result from rupture of deeply buried
rocks but without fault displacement at the ground
surface, although the surface rocks may be deformed.
The major fault of concern within the Los Altos lulls Planning
Area is the Black Mountain Fault. This thrust fault is shown
on the recent map by Brabb. The major nuesl.iou is whether this
should be considered an active fault. lhere is considerable
evidence indicating that it should he considered active. If
it is active, then development should recorinize the hazard.
To answer this question, the study by the. graduate Stanford
student is currently in progress. In the nvaantime or until
evidence is available that the fault is inactive, the prudent
policy appears to be to assume that it is an active fault.
2. Other Geologic Hazards
There are a number of other geologic hazards in addition to
those induced by seismic, activity. For Los Alto, lulls these con-
sist mainly of landslides, flooding, erosion-sertimentat:ion and
expansive soils.
- 123 -
816. 2. (cont. ) A. Landslides. The general nature of laudsl ides is set forl:h
in the iirban Geology Master Plan of California, as follows:
A landslide is the downhill movement of ']losses of earth
material under the force of gravity. Movement may be
rapid or so slaw that a change of position can be
noted only over a period of weeks or .years. The areal
size of a landslide can range from several square feet
to several square miles. Slide thicknesses may range
from less than a foot to several hundred feet. I.and-
slides are a common problem in the hillside areas or
California and, in terms of dollar losses, are one of
the more costly geologic hazards.....
Ramage due to landslides can be reduced in areas under-
going development by such alternatives as avoidance,
removal, or permanent stabilization of slide masses.
In all cases, a first and critical step is to recog-
nize the existence of an old slide or the probability
of a future slide. This is accomplislvrd through de-
tailed geologic mapping, trenching, drilling, and fre-
quoutly the photo -interpretation of surface geologic
conditions.......
Detailed mapping of landslide deposits and a ranking of
slope stability within the Town is riot available at 1 -his time.
SFBRS Basic Data Contribution II, "Estimated Relative Abunr>
dance of Landslides in the San Francisco Bay Region, Califor-
Oil," however, gives a general indication or the abundance of
landslides. The report classifies all lands in the entire
Bay Area in one of seven categories from 1 (least abundant)
to fi (most abundant). Tills is very generalized informa Cion.
The map (scale 1:50(1,090) indicates about the northeastern
one-half of Los Altos fills in category 1, and the balance of
the Town in categories 3 and 4.
Another source of data is the report by fDMS on the Monte-
bello Ridge Area. When this report is reviewed in con,i'n'ction
with the mapping by Brabb, it appears that much of the area to
the east of Interstate 200 has about node race stability, that
- 124-
816.2. A. (coil t.) is, it is neither the best nor the worst. Also, some of the
area is shown as having the least geologic stability.
The seismic triggering of landslides has been disc.ucsed
earlier. Landslides can also be induced by alteration of
the land by non (e.g., grading, placing buildings, excessive
watering, drainage front septic tanks, etc.) or by action:
of nature (heavy rainfall, erosion along creek channels, etc.).
Based on the available data and experience of the Town,
it appears that there are probably nn massive landslide areas
In most of the ]boar. However, there are small landslides
ranging in size, from less than an acre Lo a few acres in size.
There are also areas of potential landslide. these conditions
require care ore the part of the Town and developers since
even small slides can destroy or hadly rdameoe homes and streets.
The foregoing information would indicate that comiderable
care should be. taken in development of Lhe southwestern portion
of the lawn in particular. More detailed geologic informaLion
is needed, however, to better define the problems. In [-he in-
terim, good review procedures of the geologic aspects of de-
velopment are especially critical.
B. Floodiny_ The Urban Geology Master Plan of California describes
the flooding problem as follows:
Flooding is one of the costliest natural hmzards in
California. National statistics show Lhal: California
ranks as one. of the trmior flood problem areas in On
nation and that flooding is one of the princinal fac-
tors to bo considerer) in the severml developmenls and
uses of land resources......
Lr a broad sense, flooding occurs whenever water inundates
- 125 -
_ R16.2.H.(Cont .) areas not normally covered with water. Most urhanized areas
have been developed to accmumodate the normal annual rains and
runoff without interference with man's use of the land. Usu-
ally rainy years or storms may, however, exceed the ability of
the natural and man-made drainage s,Ystenis Ln Handle the runoff
without loss of property and even life.
While minur flooding can occur in undrained depressions,
or in poorly graded areas in Los Altos Ilius, the major con-
certi for flooding is centered on tine major creeks and ad.join-
inq areas. The Master Plan for Storm Water Drainage prepared
for the Town in 1969, addressed the adequacy of drainane facil-
ities to handle major storms. It did not, however, address to
any signiricani. extent the problems of rlondin,l on to private
lands along drainage courses between drainage structures. Each
of the major drainage courses in the Tumor would appear to have
flooding potenl.ial, that is, the water could leave the creek
charnel and inundate adjoining lands. pat, is not available
to describe such possibilities for all such creeks. Some
study, however, has been made of the major problem area, Adobe
Creek.
Interpretive Report 4 of the SF6RS indicated that 4dobe
Creek is subject to flooding in a lot) ,year storm from approxi-
mately francemmint Avenue northeast to the im-In boundary and
beyond. P more definitive study of the Creek Is included in
the CDMG reporl:. That report gives the following description
of the floodinu potential:
Flood Hazards Along Adobe Creek. -- Inumdatlon of part
- 126 -
816. 2. R. (cont.) of tile fiend plain adjacent to Adobe Creek is a po-
tential prxrbleni but does not present, a I.hraat to life,
and would result only in minimal properly loss under
present use (recreational and agricultural). If the
Floor) Plain were to be developed for residential use,
minor property damage (but not loss of life) probably
would be incurred on an average of every five to ten
years.
The Santa Clara County Walser District has responsibility
for flood control in the county. Their jurisdiction is
wide, but but nornmlly they will accept for nnintenance only water
courses with drainage basins of at least VO arses. In Los
Altos Hills, this means they could probably have such .inr-
isdiction on Adobe, Matadero, Barron and Purissima Creeks. In
addition, district regulations prohibit construction or gra-
ding between t.hq banks of any water coiir5e9 or within Err
feet of the top of the banks. Currently Hoe District is
studying the Adobe Creek and will be nmkiuu refo00I@nr111. ions
for minimizing flooding hazards.
Additional flood hazard maps can also be expected from
[IUD in the near, future as a part of the Federal Flood and Mud-
slide Insurance Program. When available, this information should
be carefully reviewed by the Town and changes made to the
Seismic Safety/Safety Element as apuropriaf.e.
In Los Altos Hills the general approach to handling drain-
age has been to utilize natural drainage cl,anuel rather than
to install pine drainage systems or to increase capacil.y by
straightening, widening, or living creek channels. Given the
policy of the Town to preserve the nittral quality of creeks
and creek, borders, it becomes important to not allow develop-
ment to incrense runoff to the point that channels heunae over-
loaded and to not place the works of mmn in nal.ural flood plains.
- 127 -
816.2.(con t.) C. Er_osion_Sedfinentation. The Urban Geologic Piaster plan pro-
vides the following background descripl. iron:
Erosion generally involves two somewhat distinct
prohlems! the wear and removal of nmterial from
one stl.e; its deposition at anothP,r. The removal
of soils through erosion can be damaginq in silua-
tions of sheet and gully erosion of land surfaces;
tine wind-blown denudation of lands; Eire erosion
of stream courses and banks; and the erosion of
coastal cliffs, dunes and beach at -as. Ueposi Lion
damage affects flood plains, rivers, lakes, reser-
voirs, and may clog drainage structures. Activi-
ties by non frequently accelerate erosion -related
damages and losses.........
Erosion is a relatively well undersl.00d and co0-
trollable problem insofar as it affects urban
areas. The vulnerability of natural soil types to
erosion (erodibility) has been Dapped by the U.S.
Soil Conservation Service and othersoils surveys,
especially in more recent projects completed since
196n ....... in most areas underoninq development,
the nal.ural erodibility of the soil is far less im-
portanl. in determining the severil.y of future ero-
sion ishan is the type and amount of land -modifica-
tion beinq performed.
The reduction of erosion losses in urban areas is
the responsibility of both the developer who modi-
fies the land surface by landscaping and construc-
tion of retaining walls and drainage, system's and
the governmental agency which revirws and, to some
extent, controls land modification. Following pro-
ject completion, the user of the property assumes
the cnntinuinq responsibility of Plosion contrvil
t.hrouah maintenance of landscapinq And drainage
systems.........
the 11.5. Soil Conservation Service has napped the soils
of Santa Clara County and prepared the report, Soils of
Santa Clara Count_ The soil naps includeri in the report
indicate Chat go% to 90% of the Town is included in soil
classi(ical.ions marked a5 having hinh to very high soil
erosion hazard. These soils are In the uvnnrtAin and hill
areas. The balance of the Town is included in sot) areas
marker) as having none to moderate erosion hazard.
- 128 -
N 16.2.(cont,) D. Expans ive_ Soils: The Urban Geology Maslcr Plan describes
some as pecks or the expansive soils problem as follows:
Expansive soils are earth materials which greatly
lncrease in volume when they absorb water and shrink
when they dry out. Expansion is most often caused
by clay minerals, primarily montuxrri'llonite and H -
lite.....The basic cause of expansion Is the attrac-
tion and absorption of water into the, expansible
crystal lattices of the clay nAnerals. The waiver
may be derived from moisture in thr air or ground
wager beneath the foundations of buildings. Wheo
buildings are placed on expansive soils, foundat.inus
may rise each wet season and fall each dry season.
Movements may vary under different: p.irts of a
building_ with the result that foundations crack,
various structural portions of the building are
distorted, and doors and windows are warped so
that they do not function properly.....
The adverse effects of expansive sails can be a --
voided l.hrough proper drainage and roundptior• de -
09n. In order to design an adenrate foundation
design, however, the condition most be recorpuized
through appropriate laboratory soils testing......
At the present time, adequate tecimiquos arc in
existence to control damage from expansive soils
and expansive bedrock, but regulatory vigilance.
should he maintained and improved to assure that:
site investigations and, if warranl.ed, proper en-
gineering are carried out before unr. tr oc tion. if
existing ordinances are rigorously enforced, losses
to fubn•e construction could be. reduced to near -
negligible levels.
The Soil Conservation maps indicate that: practically all -
of the Town is included in soil groups described as having
high shrink -swell characteristics, with some limited areas
noted as havlog moderate shrink -swell ,haracteristi(S.
3, fire Hazards and Fire Protection
Fires are classified as structural or non-structural, de-
pending upon their origin. Structural fires usually start
within a building and often are confined to the single building.
Access, water supply, and an early alarm to the Fire Dew rtarent
- 129 -
916.3. (cont,) all contribute to the probability that structural fires can be
contained. Non-structural fires, however, pose significantly
different problems. They originate out-of-doors, usually in
areas covered by vegetation. Outdoor conditions such as hat, dry
weather and highly flammable vegetation combine to make such fires
highly volatile. Additional factors such as diffiColt access,
lack of water, a delay in spotting the fire, and winds can make
these fires very difficult to conbat.
Los Altos Ilills is faced with both strut Loral and non-sl.ruc-
tural fires and hazards. The development standards and fire, fight-
ing capabilities or the Town must recognize and deal with both
types of fires.
Fire protection to the Town of Los Altos Hills is provided by
the Los Altos Fire Protection District. The nioxict serves all
of the Town, and the Town comprises about: 707 uF the enl:lre District
area. The District: contracts with the city of Los Altos and the
City thereby provides the fire protection for i.he District.. In
Practice, the. City of Los Altos Fire Department and the Fire Pro-
tection District overate as a unit. In additinn, the Fire District
has a mutual response agreement with the City of Palo Alto, Stanford
University, and in 1:11e sumner months, California State Ifivislon of
Forestry.
Service is provided from three fire stativus (see Map 1) two
of which are locakcd in Los Altus (Sequoia Station, Almond Avenue:
Loyola Station, Fromont Avenue southeast of Springer Road) and
one in Los Altos Hills (E1 Monte Station, Foothill College on
College property leased to the Fire Uistrict.) In addition, the
- 130-
I SlG.3.(cont.) Fire'Protection Ilistr•ict owns a fire station sitp. at the corner
of Horseshoe Lane and Arastradero Road in Los Al Los lulls.
The Fire Department has always considered the need file n cross -
tie between Flena Road and Page Mill Pood generally in the vicin-
ity of Lupine Read. Such a tie would significantly aid Fire pro-
tection and also make the proposed station location at Ilor!,eshoe
Lane and Arastradero Road more effective.. Also, the District be-
lieves that Stonebrock Drive should be extended to form a through
road.
The rage-Dabcock Report completed in 1970, indicates that
with respect to lire safety in residences "The overall tbrent to
loss of life is therefore considered as above onrvml for this oc-
cupancy type". The reason for this is indicatrd as delay in dis-
covery of fires and resulting delay in response by the Fire De-
partment. The reoort cites the distance of homes Il•om road: and
the typical isolation of living quarters in a large home from the
rest of the home as contributing factors to the delay in discovery
of fires. The reoorl: also indicates remoteness of residential
developments often makes finding a telephone for rcportinq a fire
more difficult. The authors indicate that "fast. history el major
structural fire losses in the District iodicatets) that delayed
alarms in cnmoination with water shortages were the list sr9ni-
ficant cortributino factors."
With respect to property pr•ol.ection to schools the reuort
indicates "With prompt: discovery and notification of fires I:u the
Fire Depat'Lmeot, 1.11fires should he coorine'l L" building of
origin with only sliglit or "Oderate 'tanmge."
- 131 -
816.3.(cont.) With respect to foothill college, the report: indicates tlhe
overall threat to loss of life is considered light.
The report recommends that "emergency response routes link-
ing existing and future dead-end streets should he developed
wherever fire apparatus response time would be significantly
shortened." The report suggests:
Due to the incomplete street configuration in the Town
of Los Altos Mills (present and future) response
distances to portions of the area are qr-rally in-
creased. In order to eliminate through traffic,
soup of the roads are terminated a shore distance
From other roads. There are several methods by
which this same goal could be attained void shill
leave a thoroughfare open for fire apparnl:us (aner-
gency response. Ainong these are posting the "emer-
gency routes" curl imposing stiff penalties In their
usage. A second method would be to block off the
"emergency routes" with gates or chains. Each of
these obstructions would be provided wil:h a renxrtel,y
controlled lock. The locks would he design Pd to
open upon signal from approaching fire service ve-
thicles utilizing a radio tone alert type device or
by the dispatch center over leased telephone lilies.
The fire District: rerohmnends normal tln-ough connections rather
Char; emergency connections; however, the District has helped the
Town establish eurergency connections in a numdur of subdivisions.
The District indicates that complicated locking systems are prone
to failure.
With respect to water service, much has been done to make sub-
stantial improveinents to the water system in the last tea years.
The system is basically quite gond, although there are some areas
where mutual water systems or other private systems do not pro-
vide adequate water for fire protection. In addition, the fire
District is dependrrht upon a single source of water -- Iletch-
Wetchy. Also, parts of the system may be subject to failure in
- 132 -
816.8,(cent .l the event of all earthquake. The Town should ronLinue to im-
prove the water system as a part of the subdivision process, and
the basic nroblems cited above should be. studied by the District.
The District has a continuous program of addinq fire hydrants.
The matter of brush fires is of considerable concern to the
Fire District. III general, the District believes the area is
fortunate in not having had hall fires. The brush covered slopes
have high fire potential and in some instances suffer from in-
adequate access and water. The Fire Prevention Donau has M. -
tempted to educate residents with respect to fire control through
the brush clearance ordinance, but has had only limited success.
While narrow roads are desired for aesthetic reasons by residents,
the District believes they do not act bs satisfactory firr
breaks and do not provide adequate space for the pavement of
emergency vehicles at a time of fire. The Dislocl: points out
that considerable congestion can arise at the tune of a fire from
residents' cars, fir, rquipprent and equipment of I'Lliliy c01,11milies.
The District notes that fire detention syster's within homes can
be important in insuring against lossoflife, Ilii Fire Detrart-
ment indicates certain hazardous areas, which are shown on lhp 1.
The following factors either separately or in combination create
this potential.
a. Heavy concentrations of highly combustible brush.
b. Narrow dead-end streets.
c. Lack of water for fire fighting due to mall water mains
or not enough fire hydrants.
d. Type of building construction.
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Map I — FIRE HAZARDS AND PROTECTION
TOWN OF LOS ALTOS HILLS, CALIFORNIA
3:5-A n� .—
L'
GENERAL PLAN REVISION STUDIES WILUs,.isrrNUE&.\ssac,,c�: •. .... . ;:SI
PART III - POLICY
General Goal
817
The general goal is to reduce loss of life, injurirs, davmM Lo pro-
perty, and economic and social dislocations resulting from earthquake,
other geologic hazards and fires.
objectives
818 1. The land use decisions shall be (rade so that the risk from seismic,
other geologic or fire, hazards is at a level acceptable to the Town.
2. The works of man shall be so located as to avoid yeologically
hazardous areas to the maximum extent feasible.
3. Development in geologically hazardous areas shall in general be
limited to minor structures and improvements where damage would
not threaten hunian life or cause large potential financial loss.
4. In those few instances where significant structures are required
in geologically hazardous areas, all reasonable measures shall
be taken to minimize Live amount of risk involved.
5. In areas where fire hazards are high, developarenC shall not he
permitted until an acceptable level of protection rmr be provided.
C. In the event of a disaster, the major transportation, communica-
tion and emergency facilities shall lie capable or continued
functioning.
IlccepLible Risk
514. Risk as related to structures and Occupancy shall be kept within the
limits as set forth below:
Level Of_Acceetable _Risk - Kinds of Sl:ructures
1-F—Xt: enrely low* Structures wl— whose
mIghl.{be. ca is
critical, or whose fa llure ml yht be cnCa-
strophic: nuclear reactors, large dares,
Dower intertie systems, plants manufactur-
Ing or storing explosives or toxic materials.
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819.(cont.)
Level of Acceptable RiskKinds of STructures
7.—fiTigi ly h-igiier than _ 3�uctu ees wr—Tse use is i;ritically neednT
under Level 1,* after a disaster; important utility center;
hospitals; fire, police and emergency com-
munication facilities; fire stations; and
critical transportation elenwnts such as
bridges and overpasses; also smaller dams.
3. Lowest possible risk Structures of high occulmocy, or whnse use
to occupants or the after a disaster would he narticularly con-
structure.** venient: schools, churches, theaters, large
hotels, and other high-rise buildings hous-
ing large numbers or peopie, other pinces
norually attracting large concentrations or
people, civic buildings such as fire sta-
tions, secondary utility structures, extre-
mely large comnercial enterprises, most roads
alternative or noncritical, bridges and over-
passes.
4. An 'ordinary" level of The vast majority of structores:most c mmier-
risk to occupants of the tial and industrial buildings, small hotels
structure.** R *** and apartment buildings, and single family
residences.
* Failure of a single structure may affect substantial IHloulatious.
These structures shall be designed to remain functional following
a great earthquake.
** Failure of a single structure would affect primarily only the occupants.
These structures should be designed to provide reasonable assurance that
they will not cause injury or loss of life during any earthquake, but
not necessarily to remain functional.
*** 'Ordinary risk": Resist: minor earthquakes without damoge; resist
moderate earthquakes without structural damage, but with some non-
structural damage; resist major earthquakes of the intensity or se-
verity of the strongest experienced in California, without collapse,
but with some structural as well as unstructural dauage. In m)st
structures it is expected that structural damage, evon in a major
earthquake, could be limited to reparable damage.,
PART IV - IMPLEMENTATION PROGRAM
Mapping
920.' 1. The Town should conmlete the study of the Black MorniLain fault, and
if the fault is found to be active, appropriate land use controls
should be established to minimize the risk to property and life
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820,1.(cont.) from fault movement and related ground deformation. In the in-
terim, buildings for human occupancy should not be permitted where
they might be damaged ly movement on the fault.
2. The Town should prepare an interpretive geologic nnp of OF., en-
tire Towo which ideotl Pies the full range of seismic and oLher
geologic hazards. Mls map should be based upon all available data
and supplemented with appropriate additional invrstigations. The
map scale and level of detail should be adeouate rn provide plan-
ning guidance to the Town. It would not include the detailed in-
vestigation that would be required of land developers on indivi-
dual parcels.
R_egulations
821,, 1. The Town should review all of the planning requlnLTnus (zonin(1,
subdivision, site development, building site approval), the build-
ing code, and EIR requirements, to ensure provisions are included
for proper consideraLion of geologic conditions.
2. Town regulations should establish the functions of the Town Goo-
logist.
3. The Planning regulations and building code should he reviewed and
revised as necessary to ensure that proper erosion and sedimenta-
tion control leasures are undertaken as a part of all development
projects.
4. Particular care should be given to expansive soil problems in re-
viewing and approving development projects.
Cooperative Programs
842, 1. The Town should conLinue to cooperate with the sanrn Clara County
Water District in identifying and planning to intriimize flood
problems. Natural channels and flood plains should be lr.rt in a
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822.1.(cont.)
natural state, unencumbered by the works of man Lo the maximum
extent feasible. Exceptions should be made only in local situa-
tions where essential to protect established property values or
for public safety.
2. In addition to the fire protection recommendations contained in
the land lisp. Element of tire General plan, the Town should cooper-
ate with the fire nist.rict in undertaking programs to minimize
the. fire hazards in the Town, particularly in re.mute areas with
heavy stands of vegetation.
Specific Studies
825 1. Buildings that might surfer critical damage hecause of structural
type (primarily unreinforced brick or concrete) or because (if lo-
cation in identified geologically hazardous areas should be iden-
tified and proper remedial actions taken to help mitigate Poterl-
tial problems.
2. Critical structures including schools, fire stations, major utility
lines and installations, crnmrunications systems and freeway inl:rr-
changes and underpasses, should be reviewed with respect to Po-
tential seismic induced damage.
General Plan
824 As additional information is obtained which better defines seismic
and safety conerrns. Lite other rlements of the General Plnn should be re-
viewed and revisions made as aporopriate to reflect the policies of t:he
Seismic Safety/Safety Element.
Education
825 Residents of the Town should be informed of the potential hazards
from an earthquake, other geologic hazards, and fire, and of reasonable
precautions which they can takc.
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Disaster Preparedness
826. The Town should develop a disaster preparedness plan which will pro-
vide for adequate response to the full range of disaster contained in
this Element.
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NOISE ELEMENT
EXISTING GENERAL PLAN
1975
713. Icunt.)
_ September deadline for preparation of the Noise Element.
714 Results of the special study being conducted by the Division of
Iiighways and the work being done by Santa Clara County should be used
as the basis of more detailed evaluations proposed in the Noise Element.
The information from these studies may also result in revisions to Stan-
rtards and criteria described in the Element.
NOISE ELEMENT
Introduction
715. Due to the character of land use in Los Altos [fills, i.e. low density
residential use devoid of industrial or commercial uses, a majority of
noise -producing sources normally found in Bay Area cities are not a part
of the Town's environment. Noise generated from traffic movement on the
major transportation facilities of Interstate Mn and foothill Expressway,
however, has significant impact on a substantial portion of the Town's
population, particularly IS 28n (see "Suh-Regional Circulation Mao", Part
I, General Provisions). In addition, vehicle noise on local roads, al-
though to a lesser degree than noise associated with major transportation
facilities, affects use of adjoining residential properties.
716The prime thrust of the'Noise Element is directed at dealing with
noise associated with the major state and county transportation facilities
and local roads. Due to the potential negative impact on people of other
types of noise, however, other noise issues and sources must also be con-
sidered. Examples of other noise sources include construction activity,
leisure activity (stereos, home improvement tools), outdoor activity
such as power mowers, chainsaws, etc., refuse collection, and so on.
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717. Contained in sections of the Element, following definition of terms,
is policy related to noise issues. This policy is directed at ntiniariz-
ing effects of existing objectionable noise sources and ensuring that
potential disruptive effects of noise are considered in all future land
use proposals, including imolementation of appropriate mitigative mea-
sures. In addition, significant noise issues are briefly discussed and
suggestions provided for critically evaluating related noise problems
and determining viable solutions to such problems. The basic source of
information used in preparation of policy and proposals for 15 28n was
the noise contour map indicating present: and projected noise levels for
the freewav, prepared by the State Department of Transportation and
titled "Noise Contours for Los Altos Hills", received by the Town in
April 1974. 'fhis map is included as Appendix A of this Element.
Definitions
718 Definitions of technical terms used in the Noise Flement are contained
in Appendix D.
Objective.
719 To provide for reasonable freedom from all tynes of noise which
would interfere with the enjoyment by residents of a lifestyle in which
the natural environment in all its aspects is the dominant: characteristic.
Principles.
720. 1. General
a. Noise level, frequency, time character, when and where it
occurs, and familiarity should be compatible with the Town's
rural atmosphere and consistent with 'own standards.
2. Franvporta+.iun Facilities
a, In nlanninq and develnlmtent, of any n,w maior transnortation
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720. 2. a.(cmit•) facility or improvement of an existing facility, all rea-
sonable measures Tor mitigation of inoact of noise should
he provided.
b. The rinhts-of-way of all roads and hinhways shnuld he nt suf-
fictent width to allow plantings to help buffer residents
from vrl!icle noise.
3. Residential Land uae
a. All land development adjacent to Interstate 28n or Foothill
Expressway should he designed so as to minimize the social,
psychological, physiological, and economic impact of noise
generated by traffic movement, and land developers should
make sure to provide for noise attenuation.
b. Residential construction in high noise level areas should
include provisions for structural insulation as necessary
to ensure maximum possible damping.
c. Individual use of noise -generating aparatuses shouldnot
Interfere with the normal use and enjoyment of outdoor or
indoor areas on surroundinq properties.
4. Plon-Residential Land Use
a. The noise level at the boundary of a parcel occupied by a
non-residential use (e .g. horse stables, private recreation
facilities, schools) should he. on higher Than generally
prevailing for residential land uses.
5. Construction Activity -
a. Noise generated from construction equipment should he at-
tenuated to the maximum extent possible.
b. Hours of construction activity should be. regulated, as
1 I4
720.5.b. (,onuL-1 unu:h as reasonahl,y possible, to ensure miniunnn impact of
noise on surrounding residential properties.
Policy
721 All appropriate methods for reduction of noise at the source (i.e.
automobile, aircraft, etc.) should be supported.
Standards
722. 1. Sound Measurement_: Sound should be measured with a standard
noise level meter switched to the weightinq network labled "A".
2. At a minimum, the following exterior noise level standards*
should hot be exceeded:
Maximum Decibels
Minimum
Prise Source Pay/!Light**Scale
Distance in feel:
Persons
fn/5n
A
50
Animals
65/55
A
611
Motor vehicles
PT/70
A
5n
Farm rracinis
p7/60
A
50
Implements of hus,
handry
55/45
A
3pn
Sound -producing de-
vices (i.e. nub-
55/45
P
inn
lic address sys�-
i:ems, music: am-
plifiers, horns,
explosives,etc.)
Aircraft.
f:0/50
A
101111
Machines, tools, or
appliances
55/115
p
50
* These standards were
adopted by
Ordinance on
March 13, 1971, see
Section 5-2.02, chanter 2, Title 5, Los Altos !ills Municipal
Code. As new inforniation becmaes available
these standards may
need revision.
** Day -time is the period from 7:00 a.m. to ln:on p.m., and night-
time is the period from 10:110 p.m. to 7:nn a.m., inclusive, Pa-
cific Standard Time or Daylight Savinq Time, as then in effect.
3. In all cases not covered by standards contained in M2, above,
noise beinq generated shall not be in excess of five (5) decibels
above the anirient noise level.
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722 tt.t„tt•14. Interior Ngise Levels. Interior community noise equivalent levels
(CNEL) with windows closed, attributable to exterior sources,
should not exceed an annual CNEL of 45 d0A in any habitable room.
By definition, CNEL measurements are not to be exceeded more
than ten percent of the time.
Descri tion
723. Noise issues of greatest concern to the community are briefly described
below, including suggestions for critically evaluating related noise
problems and determining viable solutions to such problems.
1. Major Transportation Facilities
a. State of California Interstate 200. Noise generated by
traffic movement on IS 28n has had significant impact on
residential land use in Los Altos Hills. Normal use of resi-
dential properties, both interior and exterior, has often
had to be modified as a result of noise from the freeway. In
addition, there has been some indication property values
have decreased as a result of freeway noise, relative to
other residential properties in the Town.
Appropriate action for minimizing noise impact on resi-
dential properties adjacent to IS 280 should be determined
and implemented. Determination of appropriate action should
be based on the best information available. potential solu-
tions for noise abatement include barrier walls along the
freeway, special regulatirnis (e.g. additional setbacks) for
new land development proposals, sound proofing, additional
landscaping, including landscaping maintenance provisions,•
fee purchase of offended properties, etc. Alternatives for
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n
723.1.a.(Conr..) barrier walls, in particular, will have to be evaluated in
Lerms of aesthetic impact.
Liaison should be maintained with the State Department: of
Transportation regarding reduction of noise from IS 28n.
b. Coto ty_ of Santa, Clara Foothill Expressway. Noise generated
from traffic nmvement on Foothill Expressway particularly
affects properties in the northeast portion of the Town. The
Impact is significant on these properties and attenuation
measures are needed. All available information on the pro-
blem of noise associated with the expressway, and other rele-
vant information should be evaluated and appropriate action
for noise attenuation determined and implemented.
Liaison should be maintained with Santa Clara County re-
garding reduction of noise from Foothill Expressway.
2. Minor -Transportation Facilities
a. Loral Roads. Noise generated from traffic movement on local
roads generally does not have significant impact on normal
residential uses. However, there are. a few notable exceptions:
E1 Monte from Foothill College to the Town limits; Arastra-
dero-Page Mill Roads to the Town limits,, Stonebrook from the
Town limits to E1 Monte. Local speer) limit laws, and ordin-
ance provisions limiting connxprcial vehicles on many local
roads help to ensure that normal noise levels are maintained
below 55 dDA. Problems have resulted, however, from poorly
muffled motorcycles or mini -hike traffic. The State Vehicle
Code provides for regulation of such vehicles. It appears,
therefore, control of these noise sources is a matter of law
enforcement and voluntary compliance by Town citizens.
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_ 723 3. Other. tjoise issues. The following noise issues are of less
overall concern to community residents than the transportation
issues described above:
a. Noise generated from non-residential land use: The major
sources of non-residential noise, other than sources asso-
ciated with transportation facilities, are private recreation
facilities, elementary schools, and Foothill College. Noise
generated from use of these facilities, particularly at peak
use periods, can be disruptive to those residents on adjacent
parcels. The magnitude of noise problems associated with the
College and such facilities as Adobe Creek Lodge, Fremont
Ilills Country Club and commercial horse stables, should be
fully evaluated and regulation provided to ensure noise levels
generated from these sources are comnatible with adjacent
residential uses.
b. Noise generated from Construction enuipment: Noise generated
from construction equipment, although usually only having
impact for a limited period of time, can severely restrict
enjoyment of use of residential properties. nue. to the topo-
graphy of the community, noise from construction equipment
often carries for great distances. Equipment operation should
be limited to normal week -Jay working hours, and all equip-
ment operating within the Town should be required to be e-
quipped with the most up-tp-date noise -muffling devices gen-
erally available.
c. Noise generated from use of residential properties: Amplified
music, power mowers, chain saws, workshop and other home im-
provement tools, auto repair (e.g. engine run -un), etc., are
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723.3.c. (cont.) all potentially offensive noise. sources. Current standards
should be evaluated in light of recently available general
Information on the social -psychological effects of noise and
revised as necessary. In addition, the Town should, through
the Noise Abatement Committee, provide information to indivi-
dual property owners reminding them of their responsibility
In noise abatement.
d. Miscellaneous Noise: Many noise sources exist which have
varying effects on residents of the community. The following
sources, and any others that are deemed offensive, should
be evaluated, and where found appropriate, standards and cri-
teria established for noise abatement:
1) Aircraft noise (piston and .Jet engines, helicopter blades,
etc.)
2) Refuse collection (trash cans, engine exhaust, loaders,
compactors, etc.)
3) Animals (barking dogs, etc.)
- 103 -
APPENDIX A
724 Noise Contour Mal)
Appendix A is the Noise Contour Map, indicating present add Projected
noise levels for Interstate 280, prepared by the state Department of
Transportation, and titled "Noise Contours for Los Altos Hills', received
by the Town of Los Altos Hills in April 1974. This map is retained in
Town files and hereby incorporated by reference as a part of the Noise
Element of the General Plan.
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APPENDIX B
729 Definition of Teras
The following terns and definitions used in the Noise Element have
been assenirled from basic referenced sources listed in Appendix C:
Nnbient Noise: Background noise. The total of all noise in a system
or situation, independent of the presence of the desired signal.
Attenuation: When used in relation to noise, to weaken the intensity
of a particular noise, either by modification at the source or by means
of some form of barrier.
A -Weighted Sound Level: A quantity, in decibels, read from a standard
sound -level meter that is switched to the weighting network labeled "A".*
The A -weighting network discriminates against the lower frequencies ac-
cording to a relationship approximating the auditory sensitivity of the
human ear at moderate sound levels. The A -weighted sand level measures
approximately the relative "noisiness" or "annoyance" of many common
sounds.
------ - _.._._ _. .....
* The following description, from the League of California Cities'
"Quiet City Report" describes standard sound level metering equipment
being used by cities to measure noise (essentially the same type of equip-
ment has been used by the State and Santa Clara County in preparing exist-
ing and proiecLed noise contours for IS 280 and Foothill Expressway, re-
spectively):
Sound measuring equipment now being used by cities gives a
practical quantitative evaluation of noise based upon the
physical fact that noise and other forms of sound in air are
caused by vibrations in the air pressure around its steady-
state atmospheric value. Such vibrations, in the case of
noise, are characterized by rapidly changing frequencies and
sound pressures. Average hearing responds to frequencies from
about 20 to 2q,nOn hertz, and to sound pressures from about
0.0002 microbars to 2,ono microbars (1 microbar = 1 dyne per
square centimeter), a ratio of ten million to one. To accom-
modate this range of values, it is customary to use a loga-
rithmic scale expressed in decibels (dB). A'reading of 0
d6 corresponds to the threshold of hearing and a reading of
14n d6 is typical of the noise pressure produced by a large
-� aircraft ,let engine. General comnunity noises are usually
in the middle range between these two extremes.
- 105 -
725.(cout•)Damping_: The dissipation of energy with time or distance. The
term is generally applied to the attenuation of sound in a structure owing
to the internal sound -dissipative properties of the structure or owing
to the addition of sound -dissipating materials.
Decibel: The unit in which the levels of various acoustical quan-
tities are expressed. Typical quantities so expressed are sound pressure
level, noise level, and sound power level.
Freguena: The number of oscillations per second (a) of a sine -wave
of sound, and (b) of a vibrating solid object, now expressed in hertz (Ilz),
formerly cycles per second (cps).
Level: The level of an acoustical quantity (e.q. sound pressure),
in decibles, is ten times the logarithm (base 10) of the ratio:of the
quantity to a reference quantity of the same physical kind.
Noise Contour: A line on a map passing through points where the same
sound intensity level prevails. Contours forin bands of varying width
from a noise source.
* Continued from preceding page
To account for subjective loudness frequency response pro-
preties of the ear, a filter is incorporated which weights
the sound Pressure according to its frequency content in
some specific manner. For wuminity noise problems, the
accepted reconmended filter today is the A-weightinq net-
work of a general-purpose sound level meter. This yields
a single number evaluation of noise levels in dB(A) units,
which can promote widespread understanding and interpreta-
tion of common noise conditions. it is also less costly
than most other ways to obtain meaningful results, and
these. noise level readings can be compared easily with
other special psychophysical indices which may be of In-
terest.
- 106 -
726
APPENDIX c
Basic Reference Sources
See General Plan Appendix 3, Items 0 12and13, and Items F h thru I'll,
Inclusive.
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