city of fremont general plan update 2030

City of Fremont General Plan Update 2030 Health & Safety Background Report

AUGUST 2008

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2 Health & Safety Background Report General Plan 2030

Health & Safety Background Report TABLE OF CONTENTS

1.0 INTRODUCTION 7

2.0 FREMONT’S GEOLOGY 8

2.1 Regional Geology 8 2.2 Local Geology 8 2.3 Unstable Geologic Units 8

3.0 SLOPE INSTABILITY AND SUBSIDENCE 9

3.1 Causes of Landslides 9 3.2 Types of Landslides 10 3.3 Landslides in Fremont 10 3.4 Subsidence 10

4.0 SEISMIC HAZARDS 15

4.1 Regional Faulting and Seismicity 15 4.2 Historical Earthquakes in the Fremont Area 15 4.3 Seismically-Induced Hazards 20 4.4 Structural Hazards 30 4.5 Hazards to Transportation Routes and Utilities 31 4.6 Regulatory Setting 31

5.0 FLOODING 35

5.1 Flood Prone Areas and Flood Control Programs 35 5.2 Dam Failure 36 5.3 Levee Failure 37 5.4 Regulatory Setting 41 5.5 FEMA Flood Maps 42 5.6 Sea-Level Rise 42

6.0 FIRE HAZARDS 47

6.1 Wildfire 47 6.2 Peakload Water Requirements 51 6.3 Fire Prevention 51

Health & Safety Background Report 3 General Plan 2030

7.0 HAZARDOUS MATERIALS 52

7.1 Overview 52 7.2 Sources of Hazardous Materials 53 7.3 Current Contamination Levels 54 7.4 Regulatory Setting 54

8.0 EMERGENCY PREPAREDNESS AND RESPONSE 57

8.1 Overview 57 8.2 Emergency Response 58

9.0 NOISE 59

9.1 Overview 59 9.2 Noise Fundamentals 59 9.3 General Plan 2030 Noise Monitoring Program 63 9.4 Existing Noise Conditions in Fremont 63

10.0 SUMMARY 67


LIST OF TABLES Table 1 Active and Conditionally Active Faults within 50 Miles of

Fremont 16

Table 2 Modified Mercalli Earthquake Intensity Scale 18

Table 3 Magnitude 6.7 or greater Earthquake Probabilities within next 30 years, 2008-2038 19

Table 4 Definitions of Acoustical Terms Used in this Report 60

Table 5 Typical Noise Levels in the Environment 62

Table 6 Noise Measurement Sites and Measurements 64

Table 7 Existing Conditions on Rail Lines in Fremont 66

LIST OF FIGURES Figure 1 Landslide Hazard Area 13

Figure 2 Active Fault Traces and Historic Earthquakes in the SF Bay Region 17

Figure 3 Earthquake Shaking Potential in the Fremont Area 23

Figure 4 Earthquake Fault Zones and Liquefaction Hazard Area 27

Figure 5 Dam Failure Inundation Areas 39

Figure 6 FEMA DFIRM Data 43

Figure 7 San Francisco Bay Scenarios for Sea Level Rise South Bay 45

Figure 8 Fire Hazard Severity 49


Health & Safety Background Report 1.0 INTRODUCTION

This is one of a series of reports that has been prepared to support the 2007-2009 update of the Fremont General Plan. It presents an inventory of environmental hazards in Fremont and provides the technical foundation for the state-mandated Safety and Noise Elements of the General Plan.

Government Code Section 65302 (g) requires each California city and county to adopt a general plan element addressing the “protection of the community from any unreasonable risks associated with the effects of seismically induced surface rupture, ground failure, tsunami, seiche, and dam failure; slope instability leading to mudslides and landslides, subsidence, liquefaction, and other seismic hazards…other geologic hazards; flooding; and wildland and urban fires.” Safety elements must also address evacuation routes, peak-load water supply requirements and minimum road widths and clearances around structures, to the extent these issues relate to identified fire and geologic hazards. In addition, Section 65302 (f) requires a “noise element” which identifies and appraises noise originating from freeways, highways, other streets, railroads, airports, industry, and stationary noise sources. A noise contour map must be prepared as part of this element.

Many California communities choose to combine the Safety and Noise Elements into a single element addressing “environmental hazards.” This was the approach taken by Fremont in 1991; Chapter 10 of the 1991 Plan is entitled “Health and Safety” and covers these mandated topics. Chapter 10 also addressed hazardous materials and emergency preparedness, since both of these issues are important to the health and safety of Fremont residents. Although air and water quality are also environmental hazards, they are addressesd in the Natural Resources Background Report rather than in the Health and Safety Background Report. However, as part of the General Plan update, the Air and Water Quality sections will be located in the updated Safety Element.

Several different sources have been used to assemble this report, including the 1991 General Plan itself. Information in the 1991 Plan has been updated and supplemented in preparation for the 2030 General Plan’s Environmental Impact Report. This report incorporates recent field data on noise conditions and more current data on the City’s emergency preparedness programs, wildfire prevention efforts, and hazardous materials management programs. The following topics are covered in this report:

• Geology • Slope Instability and Subsidence Hazards • Seismic Hazards • Flooding Hazards • Fire Hazards • Hazardous Materials • Emergency Preparedness and Response • Noise


2.0 FREMONT’S GEOLOGY

2.1 Regional Geology

Much of the Bay Area’s landscape is a byproduct of the region’s complex geological history. San Francisco Bay lies within the California Coast Ranges geomorphic and physiographic province, a region dominated by active tectonics astride the intersection of the Pacific and North American tectonic plates. Regional tectonic forces generate an estimated relative motion of approximately two inches per year between these plates. Over time, these forces have created the varied mountainous, valley, and fault-bound blocks seen in the Bay Area today.

The main geologic formation underlying the San Francisco Bay Area is known as the Franciscan complex. During the Miocene Epoch (5 to 24 million years ago), the Pacific and North American plates shifted direction relative to one another. Instead of a convergent margin the plate boundary began moving laterally. This motion continues today and is manifested along the various fault systems in the region.

Two faults considered active with evidence of historic or recent movement are the San Andreas and Hayward Faults, which approximately form the western and eastern boundaries of the broad submerged valley containing San Francisco Bay. Tectonic movement in the region has resulted in a variety of active fault types. Uplift due to the compressive aspect of inter-plate strain along these faults is largely responsible for the formation of the Coast Ranges, including the Hamilton-Diablo Range along the eastern margin of the City of Fremont.

2.2 Local Geology

A deep bedrock trough underlies Fremont. The edges of the trough form the Hamilton-Diablo range at the eastern margin of the city and the Coyote Hills at the Bay margin. This trough is filled with as much as 600 feet of Quaternary alluvium. The alluvium consists of loose to weakly consolidated silt, sand and gravel, generally less than one million years old, and is derived from the nearby uplands of Alameda County. The Coyote Hills consist of Jurassic-aged Franciscan Mélange, a sheared matrix including coherent blocks of sandstone, greenstone, meta-greywacke, chert, shale, meta-chert, basalt, marble, conglomerate, amphibolite, eclogite, and gloucophane schist.

2.3 Unstable Geologic Units

Unstable geologic units are those that lack the integrity to support human-made improvements such as buildings and roadways. This may be due to lack of strength, lack of compaction or low density, or unsuitability of material for a particular foundation. Unstable geologic units may be initially stable but lose stability due to improper drainage or buildup of pore pressure that causes a reduction in strength. Major problems are settlement, lurch cracking, differential settlement, and expansion.


Geologic instability is often due to a range of factors that may be difficult to quantify, but the two primary causes are unstable native materials and unstable fill soils. Unstable geologic units include soft marshy soils that are prone to subsidence, sandy soils with shallow groundwater prone to liquefaction, and friable rock that can fail on slopes. Particularly unstable are fill soils or debris placed over marshes and wetlands to create new land. This includes a variety of heterogeneous mixtures of loose to very well consolidated gravel, sand, silt, clay, rock fragments, organic matter, and human-made debris. Unstable geologic units within the City of Fremont include areas of liquefiable or expansive soil in the flat areas, and steep slopes in easily eroded units such as the Orinda and Briones formations.

Geologic instability poses a substantial danger to property and human safety and must be a major consideration in land use planning and construction. Billions of dollars and hundreds of lives have been lost due to such conditions in California. Common geologic hazards that affect Fremont include slope instability, landslides, subsidence, ground rupture along faults, strong seismic shaking, and liquefaction.

3.0 SLOPE INSTABILITY AND SUBSIDENCE

3.1 Causes of Landslides

Landslides have many causes, but for geologic hazard evaluation they are generally divided into those that are natural and those that are human-induced. Natural causes include steep slopes, weak rock, unfavorably inclined planes of weakness (bedding, joints, and faults), undercutting by streams and waves, intense rainfall, vegetation removal (fire), and earthquakes. Humans can cause landslides by improperly designing or constructing roads, buildings, and septic systems; excavating the toe of a slope or over-loading the upper part of a slope, removing vegetation, mining, and introducing water sources to steep slopes (through lawn watering, leach fields, storm drains, broken water lines, etc.).

Regardless of whether they result from human activity or natural processes, all landslides share some common origins. The first is that slopes become unstable as a result of a decrease in the resisting forces that hold soil in place or an increase in the driving forces that facilitate its movement. The second is that water is almost always a key factor. Water increases the weight of soil, thereby increasing the driving forces. Water also acts as a lubricant and serves to decrease the resisting forces. The March 22, 1998, Mission Peak landslide illustrates this concept well. The Alameda County Water District gauge at Niles Canyon recorded 35.2 inches of rain during the 1997-98 rainy season, the second highest total since recording began in 1870. The high amount of rainfall saturated the soil to a degree that created unstable conditions on the west side of Mission Peak. Eventually, the land mass separated and the landslide occurred.


3.2 Types of Landslides

Geologists classify landslides into several different types that reflect differences in the type of material and movement. The five most common types are translational, rotational, earth flow, rock fall and debris flow.

Mudslide is a term that appears in non-technical literature to describe shallow landslides saturated by water that travel rapidly down slope as muddy slurries. Mudslides commonly travel at speeds greater than 20 mph, although in some occurrences speeds in excess of 100 mph have occurred. They flow like water and typically follow watercourses. Most mudslides are localized and threaten only buildings in their direct path. They are often overlooked hazards because they can travel thousands of feet or even miles from the source and may occur in areas with no known previous hazards.

Mudslides are most likely to occur on steep loose soils that are saturated with water. Most rainstorms are not intense enough to trigger mudslides, it can happen. Mudslides can also be triggered by broken water pipes or misdirected runoff. Most originate in areas where vegetation has been removed, including hilly areas denuded by wildfire.

3.3 Landslides in Fremont

Landslides are common in the hilly areas of Fremont due to the combination of steep slopes, locally fractured and weak rocks, and occasional periods of intense rainfall. Extensive landslide-prone areas are found along I-680 south of Curtner Road, in Niles Canyon and on the westerly slopes of Mission Peak, Mt. Allison and Monument Peak. They are especially common in the southeastern portion of the city on the slopes of Mission Peak.1 This was the site of a mile-long landslide in 1998 which impacted 85 acres and was one of the largest in the recent history of the Bay Area.2 The harder, Cretaceous-age Great Valley units in the central hill area have experienced fewer landslides, but some do occur as a result of steep slopes.3 There have also been minor landslides in the Franciscan bedrock of the Coyote Hills.

When landslides occur, creeks and streams below the slide area may become dammed with debris and cause flooding. Additionally, landslides can block major access roads in the hill area due to slope failure. This has occurred in the past on major access routes such as Morrison Canyon Road, Mill Creek Road, Interstate 680, Niles Canyon Road and Sabercat Road.

Figure 1 shows landslide zones in the Fremont area. The map is general in nature; the potential for landslides on individual parcels must be determined by site specific geotechnical analysis.

3.4 Subsidence

Subsidence, or ground settlement, is most likely to occur in areas of moderate to high liquefaction potential related to earthquake activity. Subsidence can also occur through prolonged pumping of groundwater which would lower the water table over a large area and contribute to sinking of the ground elevation. Although Fremont’s groundwater


levels have been lowered due to pumping, no related subsidence has been noted. A groundwater recharge program has been underway for several years under the direction of the Alameda County Water District, and groundwater levels are now stable.


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City of Hayward

City of Milpitas

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UnincorporatedAlameda County

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City of Fremont

0 1 2 30.5Miles

Printed 2008-7-18

LegendCity Boundaries

Landslide Hazard Area

This Land Use Diagram illustrates Landslide Hazard Areasin the Tri-City area. These regulatory zones are establishedby the California State Geologist for use by local agencieswhen planning and regulating new or renewed constructionwhere significant geologic or seismic hazards are likely toexist.

For more detailed information, contact the State of CaliforniaDepartment of Conservation California Geological Survey. O

fficialStateD

ataunavailable

Community Development Department- Planning Division39550 Liberty Street, P.O. Box 5006Fremont, California 94537-5006www.Fremont.gov/CityHall/Departments/Planning.htm

General Plan 2030Health and Safety

Landslide Hazard Area

The information conveyed on this map is dynamic and mayhave changed after this map was printed. Please consult thePlanning Division or other appropriate agency for the mostrecent information or status.

Users should verify designations, policies, regulations,and restrictions before making project commitments.

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FIGURE 1

4.0 SEISMIC HAZARDS

4.1 Regional Faulting and Seismicity

Faults form when geologic stresses overcome the internal strength of rock and cause a fracture. Large faults, such as those between the North American and Pacific plates, develop in response to large regional stresses operating over a long period of time. When enough strain has built up in the earth’s crust to exceed the strength along a fault, a slip between plates occurs and generates an earthquake. Following an earthquake, strain will build once again until the next earthquake. The magnitude of slip is related to the maximum strain that can be built up along a particular fault segment.

Faults are mapped to determine earthquake hazards. Faults with recent activity are presumed to be the best candidates for future earthquakes. However, predicting the location of future earthquakes is complicated. Slip is not always accommodated by faults that intersect the surface along traces, which is the location where the fault reaches the ground surface. The orientation of stresses and strains in the crust can shift. Earthquakes sometimes occur in areas with previously undetected faults or along faults previously thought to be inactive.

The United States Geological Survey has developed a system to assess the activity of faults. Faults are classified active if they have ruptured in the last 11,000 years. Faults that have ruptured in the last 1,600,000 years are considered conditionally active. Other faults are considered inactive.

Active seismicity in the San Francisco Bay area is controlled by the San Andreas Fault system, which is dominated by movement on the San Andreas, Calaveras, and Hayward Faults. The San Andreas Fault traverses San Mateo County, about 10-15 miles west of Fremont. The Calaveras Fault lies on the edge of the Diablo Range, about 10-15 miles east of Fremont. The main trace of the Hayward Fault runs through the eastern part of Fremont and has the most influence on the city, although a large earthquake on any of these faults could impact Fremont and the entire region.

A list of active and conditionally active faults within 50 miles of the City of Fremont is presented as Table 1. A map of active faults and major historical earthquakes in the vicinity of Fremont is presented as Figure 2.

4.2 Historical Earthquakes in the Fremont Area

The entire Bay Area has a history of high seismic activity. The following is a list of historic >6.0 Richter magnitude earthquakes that caused ground shaking in Fremont.4 This list is not exhaustive, but it does confirm the likelihood of Fremont experiencing seismically induced ground shaking in the future. The degree of shaking in these quakes is given using both the Richter Scale and Modified Mercalli Earthquake intensity scale. The Richter scale measures earthquake intensity by the amount of energy dissipated. The latter is a subjective scale based upon structural damage and human experience. The Mercalli scale is presented in Table 2.


• 1838 – San Andreas Fault. A 6.8-7.4 Richter magnitude earthquake ruptured the San Andreas Fault from San Francisco to San Juan Bautista ~140 km in June 1838. There was little registered damage associated with this earthquake due to the low population levels at the time, but an equivalent earthquake in contemporary time would devastate the region.

• 1868 – Hayward Fault. A 7.0 Richter magnitude earthquake struck near Hayward

on October 21. Known as “The Great San Francisco Earthquake” until that title was expropriated in 1906, strong ground shaking was pervasive throughout the San Francisco Bay Area. A Modified Mercalli Intensity (MMI) of VIII to IX was estimated in Fremont.

Table 1: Active and Conditionally Active Faults Within 50 Miles of Fremont

Fault Name Miles from Fremont City Hall

Direction Last Surface Rupture

Status* Earthquake Intensity (Richter Scale)

Hayward 1 E Historic Active 7.5

Calaveras 6.5 E Holocene Active 7.5

Williams 10 E Late Quaternary

Conditionally Active

6.0

Las Positas 11 E Historic Active --

Pleasanton 14 NE Holocene Active --

Monte Vista 15 S Late Quaternary


6.5

San Andreas 18 SW Historic Active 8.0

Greenville 19 NE Historic Active 7.25

Marsh Creek 20 NE Holocene Active --

Concord 24 N Historic Active 6.5

Clayton 26 NE Holocene Active --

Seal Cove 27 W Holocene Active --

Midway 27 NE Late Quaternary


6.75

San Gregorio

28 SW Holocene Active 7.5

Green Valley 37 N Holocene Active 6.75

Napa 45 N Holocene Active -- *Faults showing displacement during Holocene time are considered active; faults showing evidence of displacement during Late Quaternary time are considered conditionally active.


NOVATO

SAN RAFAEL

HAYWARD

CONCORD

Pacific Ocean

San Andreas Fault Zone

Hayward Fault Zone

Calaveras Fault Zone

Antioch

Fault Zone

Green Valley

Fault Zone

Concord

Fault Zone

Rodgers

Creek Fault

SAN JOSE

Lake Del Valle

San Antonio Reservoir

Calaveras Reservoir

Feb. 26, 1864M 5.9

Oct. 8, 1865M 6.3

Jul. 1, 1911M 6.6

Apr. 24, 1984M 6.2

Oct. 17, 1989M 7.1

Jun. 1838M 7.0

Nov. 26, 1858M 6.1

Oct. 1, 1868M 6.8

Jun. 1836M 6.8

Mar. 31, 1898M 6.2

Apr. 18, 1906M 8.3

OAKLAND

Mission Fault

Seal Cove - San Gregorio Fault Zone

SAN FRANCISCO

SAN MATEO

FREMONT

City of Fremont and Vicinity

REGIONAL SEISMIC MAP

MILES0 5 10 N

Epicenters with Date andMagnitudeMajor Faults

Suspected Faults

Water Tanks

Concrete Reservoirs

Dammed ReservoirsUpstream from Fremont

Source: California Division of Mines and Geology; National Earthquake Information Center

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FIGURE 2: Active Fault Traces and Historic Earthquakes in the SF Bay Region

Table 2: Modified Mercalli Earthquake Intensity Scale

Scale Intensity Effects I Not felt. II Felt by persons at rest, on upper floors, or favorably placed. III Felt indoors. Hanging objects swing. Vibration like passing of light trucks. IV Hanging objects swing. Vibration like passing of heavy trucks. Standing

motorcars rock. Windows, dishes, doors rattle. Glasses clink. Crockery clashes. In the upper range of IV, wooden walls and frame creak.

V Light Felt outdoors; direction estimated. Sleepers wakened. Liquids disturbed, some spilled. Small unstable objects displaced or upset. Doors swing, close, open. Shutters, pictures move. Pendulum clocks stop, start, change rate.

VI Moderate Felt by all. Many frightened and run outdoors. Persons walk unsteadily. Windows, dishes, glassware broken. Objects fall off shelves. Pictures off walls. Furniture moved or overturned. Weak plaster and poorly constructed or weak masonry cracked. Trees, bushes shaken (visibly, or heard to rustle).

VII Strong Difficult to stand. Noticed by drivers of motorcars. Hanging objects quiver. Furniture broken. Damage to poorly constructed or weak masonry. Weak chimneys broken at roofline. Fall of plaster, loose bricks, stones, tiles, and cornices. Some cracks in average unreinforced masonry. Waves on ponds; water turbid with mud. Small slides and caving in along sand or gravel banks. Large bells ring. Concrete irrigation ditches damaged

VIII Very Strong

Steering of motorcars affected. Damage to average masonry and partial collapse. Some damage to reinforced masonry, but not to that specially designed for seismic loading. Fall of stucco and some masonry walls. Collapse of chimneys, factory stacks, monuments, towers, and elevated tanks. Frame houses moved on foundations if not bolted down; loose panel walls thrown out. Decayed piling broken off. Branches broken from trees. Changes in flow or temperature of springs and wells. Cracks in wet ground and on steep slopes.

IX Violent General panic. Poorly built or weak masonry destroyed; average unreinforced masonry heavily damaged, sometimes with complete collapse; reinforced masonry seriously damaged. (General damage to foundations.) Frame structures, if not bolted, shifted off foundations. Frames racked. Serious damage to reservoirs. Underground pipes broken. Conspicuous cracks in ground. In alluvial areas sand and mud ejected, earthquake fountains, sand craters.

X Very Violent

Most masonry and frame structures destroyed with their foundations. Some well-built wooden structures and bridges destroyed. Serious damage to dams, dikes, embankments. Large landslides. Water thrown on banks of canals, rivers, lakes, etc. Sand and mud shifted horizontally on beaches and flat land. Rails bent slightly.

XII Very Violent

Rails bent greatly. Underground pipelines completely out of service.

XII Very Violent

Damage nearly total. Large rock masses displaced. Lines of sight and level distorted. Objects thrown into the air.

Source: http://www.abag.ca.gov/bayarea/eqmaps/doc/mmi_plain.html


1892 – Two earthquakes on April 19 and April 21 struck in the Vacaville-Winters area. Richter Magnitude 6.6 and 6.4 earthquakes led to a MMI of about V in the Fremont area. The earthquakes resulted in three deaths and approximately $225,000 in damage.

1906 – San Andreas Fault. A Richter Magnitude 8.3 earthquake struck near San Francisco on April 18. Known as the Great San Francisco Earthquake, it (along with the fire it started) destroyed much of San Francisco. MMI values of VIII to IX were felt in Fremont. An estimated 3,000 lives and $524 million in property were lost. Brick structures in Centerville and Irvington were severely damaged.

1984 – Calaveras Fault. A Richter Magnitude 6.2 earthquake struck about 10 miles east of San Jose, in Santa Clara County on April 24. Seven million dollars in damage was reported, with the most damage reported in the city of Morgan Hill. Other large earthquakes impacting Fremont had previously been recorded on the Calaveras Fault in 1861 and 1979.

1989 – San Andreas Fault. A Richter Magnitude 6.9 earthquake struck in the Santa Cruz Mountains at Loma Prieta, on October 17. Fifty-seven deaths and $6 billion in damages were attributed to the Loma Prieta Earthquake. Locally, there was only minor structural damage to a few historical structures and rupture of a handful of utility lines.

In 2008 the United States Geological Survey (USGS) calculated a 93 percent probability of a strong (M≥6.7) earthquake occurring on one of the faults in the San Francisco Bay area between the years 2008-2038.5 They also calculated rupture probabilities for the individual faults in the region. These probabilities are shown in Table 3. Although he San Andreas Fault poses the greatest chance of rupture, the Hayward Fault most serious threat by far to Fremont due to its location in the city and the intensity of land uses near the fault zone.

Table 3: Magnitude 6.7 or greater Earthquake Probabilities within next 30 years, 2008-2038

Fault Probability

Northern California (entire Region) 93%

Southern San Andreas 59%

Hayward/Rogers Creek 31%

Northern San Andreas 21%

Calaveras 7% Source: http://pubs.usgs.gov/fs/2008/3027, 2008


http://pubs.usgs.gov/fs/2008/3027

city of fremont general plan update 2030

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