HomeMy WebLinkAboutCC Res 2455 1975-07-14
I THE CITY COUNCIL OF THE CITY OF SEAL BEACH DOES HEREBY RESOLVE:
RESOLUTION NO. ~~~:r
A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF
SEAL BEACH ADOPTING A SEISMIC SAFETY-SAFETY ELEMENT
TO THE GENERAL PLAN OF THE CITY OF SEAL BEACH.
WHEREAS, California Government Code Sections 65302.1 and 65302(f) require a
safety and seismic safety element to the City's General Plan; and
WHEREAS, the Planning Commission, citizens and city staff have contributed to
the formulation of a combined Seismic Safety-Safety Element to the General Plan;
and
WHEREAS, the Planning Commission of the City of Seal Beach held a public hearing
as required by law on the proposed Seismic Safety-Safety Element to the General
Plan on June 18, 1975; and
WHEREAS, the Planning Commission of the City of Seal Beach adopted said Seismic
Safety-Safety Element by Resolution No. 920 and recommended that the City
Council adopt said element; and
WHEREAS, on July 14, 1975, the City Council held a public hearing on the
proposed Seismic Safety-Safety Element.
NOW, THEREFORE, BE IT RESOLVED that the City Council of the City of Seal Beach
does hereby adopt the combined Seismic Safety-Safety Element to the General
Plan attached hereto and made a part hereof.
I PASSED, APPROVED AND ADOPTED by t~~ity Council 0 the City of Seal Beach
at a meeting thereof held on the ~day of A , 1975, by the
following vote: 12 ~ t "Hl~ 9.
AYES: Council Members ~&'L-.jJ.;!II..L.~ f/h~ J~
, '1
Council Members ~
ABSENT: Council Members ~~~
NOES:
~~.~y
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Resolution Number
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.I NTRODUCTI ON
The purpose of the combined Seismic Safety Element and the Safety Element is to
develop policies aimed at reducing the present risk from seismic, flood and fire
related hazards. The Element will serve as dn informational resource in the
evaluation of development proposals and future land use planning. The major
sections of the Element include the following:
.
PART I
Goals and objectives for the reduction of seismic, flood and
fi re hazards. .
PART II
Identification of seismic, flood and fire hazards and their
possible effect on Seal Beach.
Analysis of the level of acceptable risk to life and property.
Policies proposed to reduce safety hazards related to land use,
and new and existing structures.
PART I II
PART IV
I A.
Authority for the Safety and Seismic Safety Elements
Government Code Section 65302.1 requires a safety element of all city and county
general plans, as follows:
A safety element for the protection of the community from fires and
geologic hazards including features necessary for such protection as
I evacut'.tion routes, peak load water supply requirements, minimum road
widths. clearances around structures, and geologic hazard mapping in
areas of known geologic hazard.
Government Code Section 65302(f) requires a seismic safety element of all city
and county general plans, as follows:
A seismic safety element consisting of an identification and appraisal
of seism'ic hazards .such as suscept ibil ity to surface ruptures from
faulting, to ground shaking, to ground failures, or to the effects of
seismically 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 othel' hazards such as possible surface
ruptures from faulting, ground shaking, ground failure and seismical~y
induced waves.
I B.
Scope
As a legal jurisdiction, the City of Seal Beach ha~ fixed legal boundaries which
the hazards considered in this Element do not recognize. Seal Beach shal'es many
of its hazards wHh other coastal cities in Orange County. Furtherm01'e, since
the above hazards are difficult to identify and map, this Element is anathel'
steo in the reduction of seismic dnd other safety hazards. This Element also
recognizes that considerable progress has already been made 'in the reduction of
I'i sk due to the hazards descri bed.
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Resolution Number
PART I
GOAL
The basic objective is to minimize the loss of life, 'injury, damage to property,
contamination and economic and social dislocations resulting from:
Fire Hazards
Flood Hazards
Seismic Geologic Hazards.
OBJECTIVES
1.
Identify hazard areas in order to determine the relative risk to people and
property in Seal Beach.
Determine guidelines for future structures that are acceptable within zones
of potentially higher risk.
Insure that high occupancy and critical (vital) structures dnd pipelines
are designed to sustain minimum damage and continue to function in the
event of a disaster.
3.
5.
Encourage publ ic awareness of seismic, flood and fit'e hazards.
Develop and continually revise emergency disaster plans dealing with
identified hazards.
The Seismic Safety-Safety Element should be periodically revised to reflect
advances in technology.
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Resolution,Numb~r
PART II
HAZARD IDENTIFICATION
SEISMIC HAZARD - HISTORY
The March 10, 1933, ~ong Beach earthquake, the largest known in this area, had
a magnitude of 6.3 on the Richter Scale. Although this shock WqS not of major
magnitude, it ranks as'the third most destructive earthquake in United States
history, with a property loss of about $40 million and the loss of 120 lives.
Most of the lives lost and property damage could have been avoided if the
unreinforced lime mortar brick buildings had been constructed with concrete and
steel using present day building codes. The relatively low loss or life and
property damage from the 6.6 Richter Scale San Fernando earthquake over a more
heavily populated area with many multi-story buildings demonstrates that structures
can be designed to withstand the destructive earthquake forces.
Cracks appeared in alluvium at various places within the quake region at the
time of the Long Beach quake, including the Alamitos Bay-Seal Beach area and in
the unconsolidated deposits of the Los Angeles River floodplain in Compton.
Water wlls ejected from sandy or muddy alluvium, and sand boils or mud "volcanoes"
formed in the Seal B.each area near the Newport-InglE:wood structural zone, near
the mouth of the Santa Ana River, and at Cabrillo Beach (San Pedro). Because
similar features developed at places away from the zone, they are most logically
explained as being caused by "lurching"--that is, inelastic response of
unconsolidated water-saturated mate~ial~ to ground motion during the earthquake.
Between 1933 and 1940 at least 250 earthquakes were reported in ar~as close to
the Newport-Inglewood structural zone. Many of these probably originated along
the ,zone and were aftershocks associated with the Long Beach and Signal Hill
earthquakes. From 1935 to 1939 an average of 13 earthquakes a year were felt
near the zone.
At least 20 earthquakes with Richter magnitudes greater than 3.0 occurred along
the Newport-Inglewood structural zone since the 5.4 magnitude Signal Hill event
of October 2, 1933. This was the strongest earthquake along the zon~ since the
Long Beach Quake. In 1939 a 4.5 shock caused some damage in the Huntington Park-
Long Beach area.
Duri ng the 1940s several dozen earthquakes ~Ifth epi centers along the Ne~lp~rt-
Inglewood structural zone were reported. Most of these were highly local. Two
of them, one in 1941 and one in 1944, involved subsurface movement on faults in
oil fields, resulting in damage to oil wells at depths of 5,000 to 7,000 feet.
None of the above earthquakes including the 1933 quakes caused any surface fault
displacement.
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SEISMIC HAZARD.- FAULT DISPLACEMENT
Fault displacement occurs when earth on one side of a fault moves in relation to
earth on the other side. (See diagram) Althuugh the earth is crisscrossed with
faults, only those faults which are active pose potential hazard. The Council
of Intergovernmental Relations (CIR) guidel'ines define a fault as acti'''e \'Ihich
has If,oved in recent geologic time (10,000 years or less) and Ivhich is likely to
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Resolution,Numb~r
move again in the next 100 years. The Newport-Inglewood fault is an active one
but has not experienced surface fault displacement even f~om the two ~ajor
1933 quakes.
The City of Seal Beach includes a segment of the Newport-Inglewood fault which
is known in this area as the Seal Beach fault. Geological investigation of
this fault zone has led to the classification of the zone as an a~ea of "wrench
faulting" characterized by a wide fault zone in which displacement may be
expected to occur along discontinuous and intertwined faults rat~er than along
anyone continuous fault. This complex zone of faults'present in the sedimentary
bedrock beneath the Los Angeles-Orange County coastal plain is though to be due
to the presence of a master fault in the crystalline basement rock that underlies
the sedimentary bedrock of the Los Angeles basin. Movement on this master fault
has placed continuing stress on the overlying sedimentary bedrock, \'/hich has
responded by folding and. rupturing in the complex "\~rench" pattern discussed
above.
I
This complex pattern of folding. faulting, and uplift described above has
developed because of the inherent weakness of the sedimentary rock. This rock
has been able to absorb, within recent historic times, the stress placed upon it
by internal adjustment (folding and faulting) at considerable depths. Stress
has apparently not accumulated to the point where stress relief by surface
faulting and folding has occurred.
The Newport-Inglewood fault zone is believed capable of generating a 7.0+
magnitude earthC]uake within the next 50-100 year's. (See Orange County Technical
Report, Chapter 12.)
The Newport-Inglewood fault zone extends into Seal Beach. However, the fault
trace is not visible because it is buried under alluvial soils. Although
published sources agree as to the general location of buried fault traces,
the plotted locations can be assumed to be only approximately correct, based
on the best information available. .
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SEISMIC HAZARD - GROUND,SHAKING
I
Earthquake shaking is largely due to release of energy during periods of sudden
displacement along a fault. Examination of damage caused by previous earthquakes
has resulted in numerous code changes that require different materials of
construction, comprehensive foundation investigations for major structures,
and structural design procedures to resist the forces created by the energy
released when sudden displacement occurs along an earthquake fault. The components
of'the forces are impossible to predict exactly. The codes developed since
1933 have resulted in safer building construction. Each major' earthquake provides
more refinement. in the engineering pi'ocedures used to improve the design of
earthquake resistant buildings.
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The soils under Seal Beach consist of alluvial and colluvial materials overlying
marine terrace deposits. Considerable ground \~ilteY' is also present.
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a) Na:nes of 50m2 of the romponcnls of faults. b) !\Jorm{11 Fault, in wbich the f':(lll!!ing wall has lI1('lv~d c!u\.'m relative to the
fOlJt w.:l!I. Lj Rc'.crse Fault, 5Oll1etirnes C:i!l"rj ThHi'it Fault, ill \.,hirl1 thcfhanijll'g w311 !i65 r,lo\tea up relath'>1 to the foot viall.
d) L&te:"al Fendt, S'omctii~e"i c.alled Strikl1-SIIP Fault, in \"Jhich thE' rock~ on either slde of the fLlult h~\I:J moved sid(1ways past
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Resolution Numb~r
If severe ground shaking we Fe t.o occur these soils could lose some of their
adhesive qualities and some damage to buildings could result because of
settlement.
OTHER GEOPHYSICAL HAZARDS
SUBSIDENCE
Subsidence (sinking) of the land surface is a result of the withdrawal of oil,
gas or water. The only significant subsidence that has occurred in the general
area has been in Long Beach. The subsidence was a result of oil extraction
operations. This problem is now being monitored and steps are being taken to
control the problem.
TSUNAMI .
Tsunami s are great oceani c \~aves generated by earthquakes, submarine vol cani c
eruptions or large submarine landslides. Of the 500 tsunamis recorded, a majority
have occurred in the Pacific basin area.
Assessing the hazards from tsunamis is very difficult because of very limited
historic~l data along the Orange County Coast. No tsunami of a magnitude
exceeding that of high storm tide has reached the Southern California coast.
Assuming a high tide and a tsunami are in phase, the lowland areas of Seal Beach
could be inundated and subject to moderate damage from flood. The probability
of a high tide and tsunami occurring at the same time is extremely remote in
Southern California.
EROSION
Beach erosion is a concern of the City of Seal Beach. This century old process
is 'influenced by manmade changes and obstructions in the ocean affecting the
coastline. (Beach erosion is dealt with in the Conservation Element of the
General Plan)
FI RE HAZARD
The degree of fire hazard of the City of Seal Beach is closely related to its
,land use and development characteristics. Residential use dominates the developed
urban area and constitutes a major consideration in determining fire hazard
potential. This is especially true in high density multi-family areas where
COlllmon attics, limited access and security fences make fire suppression more
difficult. Busin~ss and commercial complexes require immediate fire control
forces if fire loss is to be kept within acceptable limits. Public facilities,
especially in disaster related fires, need prompt ~ire control to insure their
continued use. Other factors necessary to consider in determining the City's
fire hazard are the Hellman oil wells and the proximity of the Naval Weapons
Station.
The Seal Beach Fire Department has the capability of combating all normal fi,'e
potential. if a large area fire or conflagration were to occur, the department
could receive automatic assistance from the cities of Westminster, Hur.tington
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Resolution Number
Beach and Fountain Valley. This mutual aid pact greatly increases fire control
service by not only increasing the number of available men and units, but greatly
shortening response time. Hm'/ever, it should be noted that 'in time of a general
disaster affecting all the co~nunities, Seal Beach would have to rely on its
own resources.
The location of water lines, fire stations and equipment defines the basic fire
protection of any area. Most areas ir. Seal Beach are served by a response time
of three minutes. The response time standard of five minutes i~ not exceeded
anywhere in the City.
Certain areas of the City present a greater fire hazard potential than others:
1.
The dense concentration of multi-story units in the Surfside area present
problems with access for .fire control vehicles end a greater potential for
the spread of fire.
The houses concentratp.d along Seal Way adjacent to the coast suffer' from
the same fire control handicaps.
The dwellings abutting the narrow streets in the Coastal District where
parking is allowed on both sides of the street. The narrow streets create
access difficulties for fire control vehicles. This area is bounded bv
Electric Avenue, 12th Street, Pacific Coast Highway and Seal Beach Bouievard.'
This same type of congestion is also experienced on Dolphin Avenue and
Marine Avenue.
2.
If fires develop after major earthquake activity creating severe surface
displacement, the water mains in Seal Beach Boulevard and in the Department of
Water and Power private road could rupture to severely restrict the water supply
for fire suppression.
FLOOD HAZARD
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Western Orange County is located on a portion of a large coastal plain that
extends north and west from the base of the Santa Ana Mountains. This broad
expanse of land includes the lower drainage basins of the San Gabriel River.
The coastal plain fed by the flow of this river has flooded in the past prior
to improvement of the river banks.
In December of 1974 the City experienced rainfall equalling or exceeding a
100-year rainstornl. The high intensity rainfall caused inundation of about
100 residences in a small area of the Coastal District near Electric Avenue
and Seal Beach Boulevard. A new storm drain will be constructed under Electric
Avenue this summer. This new drain will reduce future flooding problems in
this area. f
An overflow from the San Gabriel River, the Santa Ana River or high waves from
the ocean could flood homes in the city particularly in the Coastal District.
However, it is difficult to determine or predict \~hat flooding \~ould occur from
these sources. Owners of residences along the low lying beach area are
encouraged to purchase Federal flood insurance.
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Resolution Number
PART I II
RISK
There is some risk involved in almost any human activity. The basic objective
is to reduce the loss of life and property damage in the event of a seismic,
flood or fire hazard to an acceptable level. Since it is not possible nor
practical to eliminate all risk to life and property, each community must
decide what it can spend to minimize the hazard to attain a lev~l of risk it
is ~illing to accept.
The acceptable risk is usually inversely proportional to the amount of money
that is spent on a facility to reduce the hazardous condition. The risk of
damage to future and existing structures is reduced if more money is spent to
minimize the hazard.
The following general guidelines should serve as a guide for future decision-
making:
1 1.
Emergency servi ces and pub 1 i c uti 1 iti es requi red to p,'ovide emergency
services during disasters should be very hazard resistant. These include
hospitals, medical clinics, fire and police stations, power plants, water
and sewerage facilities, telephone lines, electrical lines, major highways,
dams, reservoirs, etc.
2. Structures of involuntary use, i.e. nursing homes, convalescent homes,
schools, etc., and high occupancy buildings such as large office buildings,
theaters, large industrial and shopping centers, etc.. should be hazard
resistant.
3. Smaller buildings, apartments and single family residences should be less
hazard resistant than the types of uses described above.
4. Small buildings housing equipment, supplies, etc. need be least resistant
to hazards.
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Resolution Numb~r
PART IV
IMPLEMENTATION POLICIES
It is the intent of the Safety Element to minimize risk.to critical facilities,
structures of involuntary use and high occupancy buildings. The following
recommendations reflect this intent as well as the direction set by the goals
and objectives in Part I.
SEISMIC HAZARD REDUCTION
1. The Alquist-Priolo Geologic Hazards Zone Act requires the State Geolog'ist
to prepare maps showing special study zones along active earthquake faults
and to develop criteria for evaluating construction within these zones.
With the inclusion pf the Newport-Inglewood Fault in the Act, portions of
Seal Beach will be included in the special studies zone. Once the studies
have been completed, the following provisions should be adopted by the
City.
A. No structure for human occupancy shall be permitted to be placed across
a known active fault. Furthermore, the area within fifty (50) feet of
an acti've fault shall be assumed to be underlain by active branches of
that fault unless and until proven otherwise by an appropriate geologic
investigation and submission of a report by a geologist registered
in the State of California.
B. Applications for all developments and structures for human occupan~y
within fifty (50) feet shall be accompanied by a geologic report
prepared by a geologist registered in the State of California, and
directed to the problem of potential surface fault displacement through
the site, unless such studies are waived pursurrnt to Section 2623 of
the Alquist-Priolo Act.
C. One (1) copy of all such geologic reports shall be filed with the State
Geologist.
2.
D. The requirements for a geologic report may be satisfied for a one or
two fanlily residence if, in the judgment of technically qualified
City and County Pey'sonnel, sufficient infor.mation is available from
previous geological reports in the same area.
Require geologic investigations as required by the building code.
Continue to implement the latest Uniform Building Code.
Identify which, if any, of the following structures or facilities present
an unacceptable risk due to seismic hazard: f
A. Critical structures and facilities (e.q., Fire station, utilities)
B. Structures subject to involuntary use (e.q.. hospitals, rest homes)
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.
Resolution Number
and require rehabilitation of private unsafe structures through implementation
of the Uniform Building Code.
FLOOD HAZARD REDUCTION
The City will attempt to mitigate the flood hazards by:
1. Encouraging construction of the protection devices needed to protect the
San Gabriel and Santa Ana watersheds.
2. Improve critical facilities flood resistance in flood hazard areas where
practical, and restrict construction of such facilities in known hazard
areas unless absolutely necessary.
3. Maintain and periodically update flood disaster preparedness plans.
FIRE HAZARD ~EDUCTION
1
1. Continued use of the "Mutual Aid" agreement with bordering cities.
2. Continue to implement zoning, building and parking regulations that insure
adequate access to all areas of the city.
3. Require effective structural fire prevention systems to be instalied in
all high risk structures.
4. Provide adequate supplies of all materials needed to make repairs to water
lines which may be damaged by seismic activity.
DISASTER EMERGENCY PLAN
Revise and update the City Emergency Disaster Plan (with its present civil defense
emphasis) to include explicit operational procedures to deal with major flood,
fire and seismic disasters.
1.
That interdepartmental emergency coordination pr.ocedures be developed and
reviewed by all city department heads. Such procedures should include
provision for adequate emergency water resources and evacuation routes.
1 2.
3.
That such procedures be adopted as part of the normal operations and tested
annually to learn any weaknesses.
That all city employees be informed of disaster plan operations and their
'responsibilities in time of a disaster. t
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