HomeMy WebLinkAbout01 - 4.3 - Geology and SoilsSection 4.3
ry and Soils
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4.3.1 INTRODUCTION
This EIR section describes existing geologic and soil conditions in the Project area, identifies
associated potential geotechnical impacts related to development in accordance with the
proposed Newport Banning Ranch Project, and sets forth measures designed to mitigate
identified significant adverse impacts. Information within this section is based upon the Report of
Geotechnical Studies, Proposed Newport Banning Ranch Development prepared by GMU
Geotechnical, Inc. (GMU 2010), the City of Newport Beach General Plan and Environmental
Impact Report (Newport Beach 2006a and 2006b), and the California Division of Mines and
Geology's Seismic Hazards Mapping (1998 and 2008). The GMU report is included as
Appendix B to this EIR.
This analysis evaluates the environmental impacts relating to the development of the Project,
and includes an evaluation of the grading activities proposed for the Project in the Newport
Banning Ranch Master Development Plan (Development Plan). Grading, for the purposes of
this analysis, includes bluff /slope restoration and remedial grading to address geotechnical and
soils issues, and mass grading within the proposed development areas. Cumulative impacts are
addressed in Section 5.0 of this EIR.
4.3.2 REGULATORY SETTING
Federal
International Building Code
The International Building Code (IBC) is the national model building code providing
standardized requirements for construction. The IBC replaced earlier regional building codes
(including the Uniform Building Code) in 2000 and established consistent construction
guidelines for the nation. In 2006, the IBC was incorporated into the 2007 California Building
Code, and currently applies to all structures being constructed in California (ICC 2008). The
national model codes are therefore incorporated by reference into the building codes of local
municipalities, such as the California Building Code discussed below. The California Building
Code includes building design and construction criteria that take into consideration the State's
seismic conditions.
State
California Building Code
The California Building Code (also known as the "California Building Standards Code" or CBC)
is promulgated under the California Code of Regulations (CCR), Title 24 (Parts 1 through 12)
and is administered by the California Building Standards Commission (CBSC) (CBSC 2009).
The national model code standards adopted into Title 24 apply to all occupancies in California
except for modifications adopted by State agencies and local governing bodies. The CBSC
published the 2007 triennial edition in July 2007, which incorporates the 2006 IBC, discussed
above, and became effective January 1, 2008. The California Building Code may be adopted
wholly or with revisions by State and local municipalities.
Title 24 sets forth the fire, life safety and other building related regulations applicable to any
structure fit for occupancy statewide for which a building permit is sought. Title 24 establishes
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general standards for the design and construction of buildings, including provisions related to
seismic safety. The California Building Code provides standards that must be met to safeguard
life or limb, health, property, and public welfare by regulating and controlling the design,
construction, quality of materials, use and occupancy, location, and maintenance of all buildings
and structures within its jurisdiction. Title 24 applies to all occupancies in California except for
modifications adopted by State agencies and local governing bodies. Chapter 18 of the
California Building Code, Soils and Foundations, specifies the required level of soil
investigation, required by law in California. Requirements in Chapter 18 apply to building and
foundations systems and consider reduction of potential seismic hazards.
Alquist - Priolo Earthquake Fault Zoning Act of 1972
The Alquist - Priolo Earthquake Fault Zoning Act (Alquist- Priolo Act) was adopted by the State of
California in 1972 in order to mitigate surface fault rupture hazards along known active faults
(Public Resources Code [PRC] §2621 at seq.). The purpose of the Alquist - Priolo Act is to
reduce the threat to life and property, specifically from surface fault rupture, by preventing the
construction of buildings used for human occupancy on the surface trace of active faults. Under
the Alquist - Priolo Act, the State California Geological Survey (CGS) has defined an "active" fault
as one that has had surface displacement during the past 11,000 years (Holocene time). This
law directs the State Geologist to establish Earthquake Fault Zones (known as "Special Studies
Zones" prior to January 1, 1994) to regulate development within designated hazard areas. In
accordance with the Alquist- Priolo Act, the State has delineated "Earthquake Fault Zones" along
identified active faults throughout California. City and County jurisdictions must require a
geologic investigation to demonstrate that a proposed development project, which includes
structures for human occupancy, is adequately set back (generally at least 50 feet) from an
active fault prior to permitting (CGS 2010).
Seismic Hazards Mapping Act
The Seismic Hazards Mapping Act (Act) was passed in 1990 and directs the State of California
Department of Conservation Division of Mines and Geology (CDMG) to identify and map areas
subject to earthquake hazards such as liquefaction, earthquake- induced landslides, and
amplified ground shaking (PRC §2690 - 2699.6). Passed by the State legislature after the 1989
Loma Prieta Earthquake, the Act is aimed at reducing the threat to public safety and minimizing
potential loss of life and property in the event of a damaging earthquake event. Seismic Hazard
Zone Maps are a product of the resultant Seismic Hazards Mapping Program and are produced
to identify Zones of Required Investigation; most developments designed for human occupancy
within these zones must conduct site - specific geotechnical investigations to identify the hazard
and to develop appropriate mitigation measures prior to permitting by local jurisdictions. The Act
establishes a statewide public safety standard for the mitigation of earthquake hazards. CGS
Special Publication 117, Guidelines for Evaluating and Mitigating Seismic Hazards in California,
provides guidance for the evaluation and mitigation of earthquake - related hazards for projects
within designated zones of required investigations.
The State's criteria for project approval within zones of required investigation are defined in
CCR Title 14, Section 3724, from which the following has been excerpted:
"The following specific criteria for project approval shall apply within seismic
hazard zones and shall be used by affected lead agencies in complying with the
provisions of the Act:
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(a) A project shall be approved only when the nature and severity of the seismic
hazards at the site have been evaluated in a geotechnical report and
appropriate mitigation measures have been proposed.
(b) The geotechnical report shall be prepared by a registered civil engineer or
certified engineering geologist, having competence in the field of seismic
hazard evaluation and mitigation. The geotechnical report shall contain site -
specific evaluations of the seismic hazard affecting the project, and shall
identify portions of the project site containing seismic hazards. The report
shall also identify any known off -site seismic hazards that could adversely
affect the site in the event of an earthquake. The contents of the geotechnical
report shall include, but shall not be limited to, the following:
(1) Project description.
(2) A description of the geologic and geotechnical conditions at the site, including an
appropriate site location map.
(3) Evaluation of site - specific seismic hazards based on geological and geotechnical
conditions, in accordance with current standards of practice.
(4) Recommendations for appropriate mitigation measures as required in Section
3724(a), above.
(5) Name of report preparer(s), and signature(s) of a certified engineering geologist
and /or registered civil engineer, having competence in the field of seismic hazard
evaluation and mitigation.
(c) Prior to approving the project, the lead agency shall independently review the
geotechnical report to determine the adequacy of the hazard evaluation and
proposed mitigation measures and to determine the requirements of Section
3724(a), above, are satisfied. Such reviews shall be conducted by a certified
engineering geologist or registered civil engineer, having competence in the field of
seismic hazard evaluation and mitigation."
City of Newport Beach
General Plan Safety Element
The primary goal of the City of Newport Beach General Plan's Safety Element is to reduce the
potential risk of death, injuries, property damage, and economic and social dislocation resulting
from natural and human - induced hazards. The Safety Element specifically addresses coastal
hazards, geologic hazards, seismic hazards, flood hazards, wildland and urban fire hazards,
hazardous materials, aviation hazards, and disaster planning. The Project's consistency with
applicable General Plan safety goals and policies is provided later in this EIR section.'
Newport Beach Building Code
The City of Newport Beach (City) has adopted its own building code that regulates excavation
and grading activities, drainage conditions, erosion control, and earthwork construction
(including fills, embankments, and the use of earth materials as a structural component). This
For ease of reading, the policy tables are located at the end of this EIR section.
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code provides for the approval of grading and building plans and inspection of grading
construction and drainage control for projects in compliance with the current Municipal Separate
Storm Sewer System (MS4) Permit issued by the California Regional Water Quality Control
Board, Santa Ana Region (Santa Ana RWQCB) on January 18, 2002, under the National
Pollutant Discharge Elimination System (NPDES).
On May 22, 2009, the Santa Ana RWQCB re- issued the MS4 Permit for the Santa Ana Region
of Orange County (Order No. R8- 2009 - 0030). Re- issuance of the fourth term of this permit will
result in future changes to the 2003 Drainage Area Management Plan (DAMP) and the City's
Local Implementation Plan (LIP) and storm water program. This updated fourth -term permit
includes new requirements pertaining to hydromodification2 and low impact development (LID)
features associated with new developments and redevelopment projects. Within 12 months after
the permit adoption, the County of Orange, as the Principal Permittee, must finalize a new
Model Water Quality Management Plan (WQMP) that incorporates feasibility criteria for LID and
hydromodification requirements. Following the Santa Ana RWQCB's approval of the Model
WQMP, the City will be required to update their LIP and storm water programs and incorporate
the new Model WQMP into their discretionary approval processes for new development and
redevelopment projects.
The he Newport Beach Building Code incorporates by reference the 2007 Edition of the
California Building Code (Volumes 1 and 2, including Appendices F and I, and Appendix Al of
Part 10) and all national codes and standards referenced therein, based on the International
Building Code. The Project would be processed by the City in accordance with the City's
Building Code.
4.3.3 METHODOLOGY
The technical analyses supporting the impact conclusions in the following section were
completed by GMU as presented in the GMU 2010 Report. Data from this report was
supplemented through literature review and application of policies and guidelines of the City of
Newport Beach General Plan, the Alquist - Priolo Act, and the CGS' Special Publication 117.
Consideration of Standard Conditions and Project Design Features has been incorporated into
the impact analyses and is reflected in the impact summary statements.
Area seismicity and faulting on or near the Project site was determined through literature review
and field investigations performed by GMU in support of the GMU 2010 Report. Analysis of field
data recovered (prior to trenching and cone penetrometer testing) was conducted by GMU
(2010) on or in the vicinity of the Project site. Additional trenching to expose subsurface strata
and to identify the location and level of activity for faults on the Project site was performed on
site to supplement existing data or to provide data for portions of the Project site not covered by
prior investigations. GMU recovered fault trench data in areas of thick, natural soil development
to determine (1) whether offsets in the soil horizons could be identified and potentially dated,
and to investigate fault age and (2) possible correlation to Holocene (recent) movement (which
would, in turn, indicate active faulting).
A Probabilistic Seismic Hazard Analysis (PSHA) was prepared to assess future earthquake
ground motion that could occur at the Project site. A PSHA is a mathematical process based on
probability and statistics that is used to estimate the mean number of events per year (annual
Frequency of Exceedance) in which the level of some ground motion parameter exceeds a
specified risk level. The commercial computer program EZ -FRISK (version 7.22) was used to
Hydromodifcation is generally defined as the alteration of natural flow characteristics.
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make the mathematical computations for this analysis. The risk level for the analysis was a
10 percent probability of exceedance in 50 years. In addition, seismic design parameters in
accordance with specified criteria contained in the California Building Code were also provided
(GMU 2010).
Ground motions at the site were also evaluated in accordance with current California
Department of Transportation (Caltrans) procedures as this type of analysis applies to the
Project's proposed pedestrian and bicycle bridge over West Coast Highway. As noted by GMU
(2010), the analysis evaluated ground motions at the site using Caltrans ARS Online Version
1.0.4, which is a web -based program that calculates deterministic and probabilistic acceleration
response spectra based on Appendix B of Caltrans' Seismic Design Criteria.
Bluff retreat rates were calculated through analysis of the movement of the 75 -foot contour
interval over time using historical U.S. Geological Survey (USGS) topographic maps between
1932 and 1965. Measurements were made in ten locations between 16th Street and 18th Street,
and were compared with aerial photography. Analysis of aerial photography was used to
confirm consistency of bluff retreat rates in recent years with the historical topographic data and
also as part of the slope stability assessment. The stability of existing bluff slopes was
evaluated, and three bluff cross sections were selected to represent general worst -case
conditions (i.e., highest and steepest slope) for analysis. Buoyant conditions representative of
soils below groundwater were modeled below an elevation of 0 feet. GMU also performed
rotational and traditional surficial stability analyses to evaluate the maximum proposed fill slope.
Geotechnical laboratory testing characterized the soil materials at the Project site. Sieve
analyses, Atterberg limits (to characterize fine grained soil characteristics), expansion index,
and hydrometer tests were performed to determine soil index properties (please see Appendix B
for descriptions of these testing procedures). Consolidation and hydro - collapse tests were
performed to evaluate the potential for consolidation, and direct shear tests were performed to
develop a strength model to analyze both existing natural slopes and proposed slopes. In
addition, chemical testing and compaction testing were performed to further characterize the
on -site soil and rock materials.
Data and conclusions from the analyses discussed above were used to determine potential
impacts from the Project to and from Project site geology and soils parameters. These impacts
were compared against the Thresholds of Significance set forth below in Section 4.3.6 to
determine their significance.
4.3.4 EXISTING CONDITIONS
Site Topography
The Project site is comprised of two distinct geomorphic regions. Approximately 254 acres of
the 401 -acre in the southeast portion of the Project site are located atop the Newport Mesa
(referred to herein as the "Upland "), a broad flat- topped mesa situated at an elevation of
approximately 50 to 110 feet above mean sea level (msl). The highest elevation is at 105 feet
above msl and is located at the eastern - central portion of the Project site. This portion of the
Project site was used for agricultural purposes prior to the initiation of oil production activities in
the early 1940s. Oil production facilities and associated access roads have topographically
altered the surface of this portion of the site. Bluffs3 subject to surficial slumping and gully
3 As set forth in the Newport Beach Municipal Code Section 20.70, "bluff" is a "high bank or bold headland that
slopes down to a body of water or a plain. A bluff may consist of a gently sloping upper area and a steeper lower
area ".
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Section 4.3
ry and Soils
erosion represent the western edge of the Upland area and rise approximately 50 to 90 feet
above the adjacent Santa Ana River floodplain. This floodplain comprises the northwestern one -
third of the Project site. Two major arroyos, the Northern Arroyo and Southern Arroyo (the
Southern Arroyo being the largest), have incised into the bluff as a result of surface flows and
storm drainage over the bluff edge.
The Lowland area encompasses approximately 147 acres in the northwest portion of the Project
site at an average elevation of 1 to 10 feet above msl. This area consists of remnants of the
Santa Ana River foodpiain and contains channels conveying drainage from surrounding areas
at higher elevations to the Santa Ana River through the Semeniuk Slough (also known as
Oxbow Loop) (see Exhibit 3 -3, Existing Topographic Site Conditions, Section 3.0, Project
Description).
Geologic Setting
Seismic Environment, Faulting and Surface Rupture
Regional Faulting
Three regional fault systems are within approximately six miles of the Project site: the Compton
Thrust Ramp, the Newport- Inglewood Fault Zone, and the San Joaquin Hills Blind Thrust Fault.
Exhibit 4.3 -1, Regional Fault Map: Compton Thrust Ramp, depicts the Project site in relationship
to the Compton Thrust Ramp and the San Joaquin Hills Blind Thrust Fault. Where present, the
depth of the Compton Thrust Ramp is believed to be approximately three to six miles below
ground surface (GMU 2010). Horizontal offsets in the Compton Thrust Ramp's geologic fold
structure imply that the fault can be divided into three segments (the Baldwin Hills, Central, and
Santa Ana segments). The Project site may be located above the Santa Ana segment of the
Compton Thrust Ramp, but the lateral extent of this segment is poorly constrained. The
Compton Thrust Ramp would not pose a risk of surface rupture within the Project site because it
is a buried thrust fault. Based on published studies which document the lack of fault deformation
in deposits (as old as 15,000- 20,000 years), the Compton Thrust Ramp was removed as a
seismic source from the 2008 National Seismic Hazards Maps and California Uniform
Earthquake Rupture forecast.
The Newport- Inglewood Fault is a northwest - southeast trending feature within 1/3 mile of the
Project site that poses the closest source of active seismic activity for the Project. This fault
system enters the region from the Los Angeles basin and passes offshore at Newport Beach.
The fault zone runs onshore between Beverly Hills and Newport Bay. South of Newport Bay, the
fault zone heads offshore and coincides with submarine faults and the existing submarine
canyon located off the end of the Newport Pier. Further offshore, it is believed that the Newport -
Inglewood Fault Zone coincides with the Rose Canyon fault, which runs through the City of San
Diego.
The Newport- Inglewood Fault Zone can be divided into two segments based upon local
characteristics and level of seismic activity. North of Signal Hill, the fault zone orients more to
the north. South of Signal Hill, geomorphic expressions4 of the fault zone can be found in
topographic features including Signal Hill (Long Beach), Landing Hill (in Seal Beach), Bolsa
Chica Mesa, Huntington Mesa, and Newport Mesa. As shown on Exhibit 4.3 -2, Regional
Faulting: Newport- Inglewood Fault Zone, the segment of this fault zone south of Signal Hill can
4 Geomorphic expression: Generalized description of deformational features at the surface that are related to the
fault or fold, such as the size and shape of scarps, offset streams, sag ponds, grabens, shutter ridges, and
faceted spurs (Source: USGS 2009).
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Regional Fault Map: Compton Thrust Ramp Exhibit 4.3 -1
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Regional Faulting: Newport - Inglewood Fault Zone Exhibit 4.3 -2
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Section 4.3
ry and Soils
be further divided into sections, including (from north to south) the Cherry Hill, Northeast Flank,
Reservoir Hill, Seal Beach, and North and South Branch Faults. Since 1920, approximately
15 earthquakes greater than or equal to magnitude 4.0 have occurred along this fault zone north
of Newport Bay. The 1933 Long Beach earthquake was one of the largest of these events, with
a magnitude of 6.9 on the Richter scale. The Project area appears to be within the southern
limits of the 1933 aftershock zone.
South of the City of Huntington Beach, the Newport- Inglewood Fault Zone has a northwesterly
orientation which diverges into splay faults. Splay faults are smaller faults that branch off the
main fault, and constitute zones of seismic activity. Splay faults on the Project site are part of
the "North Branch" of the Newport- Inglewood Fault Zone. Evidence of the North Branch splay
faults on the Project site have been identified through review of prior investigations and existing
literature, as well as GMU's field trenching and subsequent analysis of associated data.
As depicted on Exhibit 4.3 -3, Geologic Map, two fault segments associated with the
Newport- Inglewood Fault Zone's North Branch — Newport Mesa North Segment and the
Newport Mesa South Segment —are generally less than 1,800 feet long and are separated by
1,300 feet of sediments and soils that do not show signs of Holocene fault activity. Within the
Project site, the two segments terminate and do not appear to have experienced a high degree
of seismicity in recent times (evidenced by infrequent movement and low slip rates). Although
they have no obvious geomorphic expression reflected in surface landforms, trench data
indicate that portions of these fault segments could not be proved to be inactive (i.e.,
pre - Holocene) based on California criteria. Therefore, these fault segments are identified as
"faults that could not be proven to be inactive" and "Fault Setback Zones' have been
established to be conservative (GMU 2010).
Ground Motion
Most of Southern California is subject to ground shaking (ground motion) as a result of
movement along active and potentially active fault zones in the region. A probabilistic seismic
hazard analysis (PSHA) of horizontal ground shaking was performed to evaluate the likelihood
of future earthquake ground motion occurring at the site. The PSHA uses seismic sources and
attenuation equations consistent with the 2008 USGS National Seismic Hazard Maps. Table
4.3 -1 presents a list of active earthquake faults that are located within 50 miles of the Project
site. Because the aforementioned Compton Thrust Ramp was removed as a seismic source
from the 2008 National Seismic Hazards Maps and California Uniform Earthquake Rupture
Forecast, it is not defined as a seismic source in the PSHA ground motion analysis and not
included in Table 4.3 -1.
Surficial Deposits, Soils and Stratigraphy
Three basic stratigraphic units are present on the Project site: the San Pedro Formation (Qsp),
marine terrace deposits (Qtm), and river alluvium (Qal). The San Pedro Formation, is the oldest
geologic unit at the Project site, which constitutes a bedrock unit and is comprised of siltstone
and clayey - siltstone that is interbedded with fine to coarse sandstone (Exhibit 4.3 -3). Sediments
covering the Project site's higher elevations are comprised of a 40- to 50 -foot layer of marine
terrace deposits with the remnant components of an active tidal zone, which includes rounded
cobbles, angular shells with mollusk borings, and shell. These deposits consist of sands that
contain lenses of finer (silt to clayey -silt) material.
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Pacific Sots Engineering 31 by GooSyntec(1994)
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Section 4.3
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TABLE 4.3 -1
FAULT ZONES IN THE VICINITY OF NEWPORT BANNING RANCHa
Fault Name
Distance
(km /miles)
Seismology Parameters
Maximum Mw
Fault Type
Slip Rate
(mmlyr)
Newport- Inglewood (Los Angeles Basin)
<1.0/ <1.0
7.1
rl -ss
1.0
San Joaquin Hills Blind Thrust
4.6/2.9
6.6
bt
0.5
Newport- Inglewood (Offshore)
5.4/3.6
7.1
rl -ss
1.5
Palos Verdes
19.1/11:9
7.3
rl -ss
3.0
Puente Hills Thrust
33.3/20.7
7.1
bt
0.4
Whittier
33.6/20.9
6.8
rl -ss
2.5
Chino - Central Avenue
37.1/23.1
6.7
rl -r -o
1.0
Elsinore -Glen Ivy
37.6/23.4
6.8
rl -ss
5.0
Coronado Bank
40.5/21.2
7.6
rl -ss
3.0
San Jose
45.6/28.3
6.4
11-r -o
0.5
Elysian Park Thrust (upper)
50.6/31.4
6.4
r
1.3
Elsinore - Temecula
55.2/34.3
6.8
rl -ss
5.0
Raymond
56.7/35.2
6.5
11 -r -o
1.5
Sierra Madre
56.8/35.3
7.2
r
2.0
Cucamonga
58.3/36.2
6.9
r
5.0
Verdugo
58.7/36.5
6.9
r
0.5
Hollywood
60.2/37.4
6.4
I]-r -o
1.0
Clamshell - Sawpit
60.8/37.8
6.5
r
0.5
Santa Monica
64.8/40.3
6.6
11-r -o
1.0
Malibu Coast
70.2/43.6
6.7
11-r -o
0.3
Rose Canyon
74.4/46.2
7.2
rl -ss
1.5
San Jacinto -San Bernardino
76.6/47.6
6.7
rl -ss
12.0
San Jacinto -San Jacinto Valley
78.4/48.7
6.9
rl -ss
12.0
Northridge (East Oak Ridge)
78.8/49.0
7.0
bt
1.5
Sierra Madre (San Fernando)
78.8/49.0
6.7
r
2.0
Anacapa -Dume
79.8/49.6
7.5
r -11-o
3.0
d: right - lateral; II: left- lateral; as: strike -slip; r: reverse; o: oblique; bt: blind thrust; km: kilometers; Mw: moment magnitude;
mm /yr: millimeter(s) per year
CDMG Statewide Fault Database (CDMG OFR 96 -08)
Source: GMU 2010.
Thick, dark reddish -brown soils have formed over the marine terrace deposits in the Project
site's Upland area. These soils, up to ten feet thick, are fairly old with well developed soil
horizons. Thick clay films occur on many horizon surfaces and are overlain by a grayish or
bleached zone. These soils are used as markers to identify whether fault movement has
occurred within a timeframe that would denote fault activity (i.e., the Holocene period). Given
the relatively old age of these soils, a lack of disturbance within these in -situ soil horizons would
indicate that a fault is not active.
The Lowland area is comprised of alluvial material (Qal) that has been deposited within recent
time (i.e., the Holocene) by Santa Ana River flows and tributary drainages. This alluvial deposit
is approximately 100 feet thick and appears to have been deposited above a late Pleistocene
channel of the Santa Ana River as a result of prior periodic flooding events. Sediment grain
R:TrojectMNewpartU015Mmft EIRW.3 Geology -090211 Eoc 4.3 -8 Newport Banning Ranch
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Section 4.3
ry and Soils
sizes in this area contain gravel, sand, and clay deposits with a coarse to fine gradient toward
the surface. Near the base of the bluffs and forming the western edge of the Upland, this alluvial
material is interfingered with colluvial material (Qcol) from shallow bluff erosion and slumping. In
some areas, these colluvial interbeds consist of fairly thick lenses of material (primarily sandy
and silty clays) at the bluff bases and within arroyos and gullies formed as erosional features on
the face of the steeper slopes. Pockets of artificial fill (Qaf) have also been identified throughout
the Project site, and are largely attributed to construction and oil production facilities
(Exhibit 4.3 -3).
Seismic Hazard Zones
Seismic Hazard Zones are regulatory zones that encompass areas prone to liquefaction and
earthquake- induced landslides. As shown on Exhibit 4.3 -4, Seismic Hazard Zones, the CDMG
has mapped two seismic hazard zones on the Project site (CDMG 2008); these areas are also
identified within the City of Newport Beach General Plan (Newport Beach 2006a). The majority
of the on -site, west- facing bluff slopes have been identified as zones of required investigation
for earthquake- induced landslides; the Lowland area of the Project site has been identified as a
zone of required investigation for liquefaction. There are no designated Alquist - Priolo Fault
Zones within the Project site.
Seismically Induced Ground Shaking
The Project site is subject to fairly high levels of seismically induced ground motion due to its
proximity to the Newport- Inglewood Fault Zone and other significant regional faults. An analysis
of horizontal ground shaking (GMU 2010) was performed to quantify the peak ground
acceleration (PGA) that could be expected at the Project site. (Please refer to Section 4.3.3
above for an overview of the methodology for this analysis; additional details can be found in the
PSHA in the GMU 2010 Report). Assuming a risk level of 10 percent probability of exceedance
in 50 years (i.e., approximate 475 -year average return period), the analysis indicates that the
Peak Horizontal Ground Acceleration (PHGA) is approximately 0.37g.5 Because the Project
proposes a pedestrian and bicycle bridge over West Coast Highway, GMU also conducted a
seismic hazard analysis consistent with Caltrans requirements. This analysis indicates a
deterministic PHGA of 0.608. The PHGA values reported above are considered to be relatively
high although not uncommon for developments throughout Southern California.
Liquefaction and Lateral Spreading
Liquefaction is the loss of soil strength or stiffness due to a buildup of water pressure between
soil particles during severe ground shaking. This condition is associated primarily with loose
(low density), saturated, fine- to medium - grained, cohesionless soils that often make up alluvial
materials. Lateral spreading is the finite, horizontal movement of material associated with pore
pressure build -up or liquefaction. This process can occur in a shallow underlying deposit during
an earthquake in areas susceptible to liquefaction. In order to occur, lateral spreading requires
the existence of a continuous and laterally unconstrained liquefiable zone.
The City of Newport Beach General Plan (Newport Beach 2006a) and the Seismic Hazard Zone
Map for the Newport Beach Quadrangle (CDMG 1998) indicate that the entire Lowland area of
the Project site is susceptible to liquefaction and associated lateral spreading (Exhibit 4.3 -4).
Prior testing of the alluvial soils within the Lowland area confirms this potential for liquefaction
(GMU 2010). In contrast, most of the soil materials within the Project site's Upland area (i.e., the
5 Site acceleration during a seismic event is measured as a percent of gravity, or "g ". For instance, 0.76g is
76 percent of the force of gravity.
R:TroiectMN..partU015M.ft EIM4.3 Geology -090211 Eoc 4.3 -9 Newport Banning Ranch
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r�.
Legend
0`i City Boundary
- Areas with liquefaction
potential
COSTA MESA
_ Areas with landslide
potential
~�
Fault Disclosure Zone for
- real- estate disclosure
UPPER
purposes
2�e NEWPORT
Y
Fault Line
SAY
Major fault traces as
mapped by Morton,
p 1999. Presumed active,
except where shown
otherwise based on
o
geological studies
Southward projection of
active fault traces based
i ^%–. on a subsurface study
on the west bank of the
Santa Ana River
Project Vicinity
E ^o Highway
\_. Local Road
m.:
C County
t'
e4e4Ri FASHION
X
a :5.
4 n
ISLA NO
tlMRR
Q
q ULA t4
F
Source: City of Newport Beach 2006
Seismic Hazard Zones
Exhibit 4.3 -4
Newport Banning Ranch EIR
N
w�e
Cd/!T/'Gj
C O N S U L i 1 N G
(REV: 072911 sje) RlPrpjeds/ NewpoNJ015/ GrayhicslElRlex4.3 4 _seismic.pdf
Section 4.3
ry and Soils
area proposed for development) are the San Pedro Formation and overlying terrace deposits.
These soils are either too dense or too far above the water table for liquefaction and lateral
spreading to occur. There are pockets of colluvial and artificial fill deposits in the Upland on the
top of the bluff within the development area which could be subject to liquefaction if they
become saturated (Exhibit 4.3 -3). However, these areas are so far above the groundwater table
they are not anticipated to reach saturation. As identified in the GMU 2010 Report, colluvium
and artificial fill would be removed by corrective grading below development areas.
Subsidence
Subsidence is a lowering or settlement of the ground surface through collapse of subsurface
void space. This condition can occur in areas where oil or groundwater has moved out of an
area and has created a void space unable to sustain the materials above it or in areas where
subsurface materials are dissolved, leaving little or no support for surface soils or features.
Subsidence can be a dangerous condition for structures and facilities if not accounted for in
project planning and design. There are and have historically been active oil operations on the
Project site; subsidence has been known to occur in oilfields as the space occupied by the oil
deposit collapses as the oil is removed. As noted by GMU, the most recent technical study for
subsidence at or near the Project site was completed by Woodward Clyde in 1985. The study
concluded that ground subsidence from oilfield operations in the West Newport Oilfield has not
occurred (GMU 2010). The conclusions of the Woodward Clyde technical study were consistent
with the results of field investigations performed by GMU which did not indicate any evidence of
subsidence.
Compressible and Collapsible Soils
Alluvial deposits in the Lowland area contain 1- foot -thick to 5- foot -thick zones of highly
compressible materials in the upper 15 feet of the soil. These materials would undergo
significant settlement upon loading and would require an extended period of time to reach a
stable condition. It should be noted that the Project proposes only open space, trails, and
habitat restoration within the Lowland area.
The terrace deposits within the Upland area contain an upper soil zone that ranges from a few
feet thick to over ten feet thick. Based on consolidation testing, these materials are considered
to be low to moderately compressible. Artificial fills anywhere on the Project site range from
stockpile fills to unengineered fills that are considered highly compressible. Standard corrective
grading practices include ensuring that the geotechnical engineer of record oversee grading
operations and perform additional field testing and observations on site during grading in order
to provide direction on removal and recompaction of compressible materials discovered during
grading.
Colluvial soils present at the base of the Upland slopes, in ravines, and in arroyos are a
combination of slope wash and taluss deposits, generally identified as soft and porous when
encountered during field trenching. These colluvial soils are considered moderately to highly
compressible and would be removed and recompacted underneath development areas during
grading.
Collapsible soils are defined as soils that undergo a significant reduction in volume when
inundated with water. This process is commonly referred to as "hydro- collapse ". Alluvial
sediments in the Lowland area are not susceptible to hydro - collapse due to the high water table
6 A sloping mass of rocky fragments at the base of a cliff or slope; a slope.
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Section 4.3
ry and Soils
under these sediments and the fact that the sediments have been flooded or under water
numerous times in recent geologic history. This level of saturation does not result in residual
capacity for additional hydro - collapse. Based on geotechnical laboratory testing (GMU 2010),
the marine terrace deposits and underlying San Pedro Formation sediments in the Upland area
generally have a low potential for hydro - collapse; however, certain pockets may be locally
porous and require corrective grading when encountered. As described above, a geotechnical
engineer of record would be on site during grading operations to visually identify and test these
materials and to provide required supplemental corrective grading measures (i.e., local deeper
removals).
Bluff Slope Stability
Bluffs comprising the western and southern edge of the Upland area have been historically
subject to bluff retreat from Santa Ana River flooding, coastal wave erosion, surface flow, and oil
production activities. In recent decades, the most significant factors affecting bluff retreat are
surficial weathering, erosion, and oil production activities. These bluffs generally have slopes of
30 to 40 degrees with locally flatter and steeper sections and show signs of erosive weathering
in the form of gullies and arroyos. Slopes that descend into the 2 primary arroyos on site are
relatively flatter than the outer bluff slope faces and average about 20 degrees in steepness.
Evidence of shallow slumping has been encountered in the sediments overlying the San Pedro
Formation. These slope failures have been attributed to surface runoff, erosion, and possibly
previous seismic events (GMU 2010). There was no evidence found of large, deep- seated
landslides or slope failures on the Project site.
An analysis of bluff stability at the Project site indicates that significant causal factors for historic
bluff erosion include (1) Santa Ana River flooding; (2) direct wave action; (3) slope failure;
(4) rainfall and channel development on the mesa; and (5) oilfield activities (i.e., earthwork for
oilfield facility construction and consequent concentration of storm water runoff over the bluff
face). However, since the 1940s, improvements along the Santa Ana River system have
removed Santa Ana River flooding as a factor in future bluff alteration. Earthwork for oil facility
construction increased bluff slope retreat rates by physically modifying the terrain and locally
increasing runoff and associated erosion. Oilfield activities, shallow slumping along the bluff
faces, and rainfall and channel development on the mesa have become the primary factors in
bluff erosion in recent years; of these three factors, oilfield activities have probably had the
greatest effect.
Consequently, although average historical bluff retreat rates have been calculated at 2 feet per
year with a potential annual variation of between 0.6 and 4.2 feet, future bluff retreat is not likely
to continue at the same average rate. These historic bluff retreat rates are statistically skewed
by the effects of the flood of 1938 (which caused greater bluff retreat) and grading activities on
the Upland associated with oil production facilities. Completion of off -site flood - control
improvements along the Santa Ana River has removed the potential for riverine erosion of the
bluffs by the Santa Ana River.
Global climate change and sea level rise have become considerations in project design
throughout the State of California, potentially influencing future Project performance as well as
Project effects. The range of global climate change and sea level rise scenarios constitute
predictions based on current understanding of the underlying causal processes at work;
therefore, there is a degree of uncertainty in how the future scenarios would unfold. In May
2009, the California Climate Change Center (CCCC), with funding from three California State
agencies, published a paper entitled "The Impacts of Sea -level rise on the California Coast".
This study proposes a worst -case prediction of sea level rise along the California coast of
R TrojectMNewpartU015Mrafi EIRW.3 Geology -090211 Eoc 4.3 -11 Newport Banning Ranch
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Section 4.3
ry and Soils
55 inches, or 4.6 feet, by 2100 (CCCC 2009b). This potential scenario is similar to other studies
regarding sea level rise along the California coast (Fuscoe 2010b).
Global climate change and sea level rise could potentially result in flood flows backing up into
the Lowland under severe flood events. Sea level rise could increase the potential for high flood
water depths in the Semeniuk Slough to occur against the toe of the existing bluffs bordering the
development areas. Sea level rise is not expected to result in direct wave attack on the bluff
faces and associated coastal bluff erosion; this issue is address later in the impacts analysis.
Groundwater
Shallow groundwater levels (less than 50 feet below the ground surface [bgs]) are known to
occur along the coast, around Newport Bay, and along the major drainages in the Newport
Beach area; these levels are achieved from percolation of Santa Ana River flow, infiltration of
precipitation, and injection into wells. There are no designated groundwater recharge areas in
the City (Newport Beach 2006b). Field monitoring well and exploratory boring data collected
between 1985 and 1998 indicate that groundwater elevation is generally at mean sea level in
the Lowland and Upland areas. Perched groundwater above mean sea level may exist
sporadically within the Upland. Although groundwater flow direction is to the west in the northern
portion of the Project site, no evidence of seepage through the bluff face was observed in 1998
field investigations (GMU 2010). Groundwater flow direction close to the Santa Ana River
beneath the Lowland is generally to the south and parallel to the river.
Mineral Resources
Oil drilling in Newport Beach began as early as 1904 when oil production became the primary
mineral extraction activity in and around the City. Two separate production and reserve areas
exist within the City's Sphere of Influence: (1) the Newport Oilfield, which lies under the Pacific
Ocean but has land -based tanks and extraction pumps just outside the municipal boundary in
West Newport and (2) the West Newport Oilfield, which is located in the Newport Banning
Ranch area. The majority of the Project site has been developed for oil operations and is
currently in active oil production (see Exhibit 3 -4, Oil Operations, in Section 3.0, Project
Description).
The Project site contains 489 oil well sites and related oil facility infrastructure, including but not
limited to pipelines, storage tanks, power poles, machinery, improved and unimproved
roadways, buildings, and oil processing facilities. Of the approximately 489 oil well sites, the City
operates 16 wells and an oil processing facility near the southwestern boundary of the Project
site, as accessed from West Coast Highway near the southwest corner of the Project site.
Private access to the oil operations undertaken by West Newport Oil Company' is at West
Coast Highway and at the terminus of 17`h Street at the easterly boundary of the Project site.
4.3.5 PROJECT DESIGN FEATURES AND STANDARD CONDITIONS
Proiect Desian Features
PDF 4.3 -1 Habitable structures will be set back a minimum of 60 feet from the tops of bluff
edges, as required in the Master Development Plan and the Newport Banning
Ranch Planned Community Development Plan, and will not be constructed within
identified fault setback zones.
West Newport Oil Company and the mineral resources are wholly owned by Horizontal Drilling LLC, an entity
separate and independent of the surface owners.
R:TrojectMNewpartU015Mmft EIM4.3 Geology -090211 doc 4.3 -12 Newport Banning Ranch
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ry and Soils
PDF 4.3 -2 The Master Development Plan identifies drainage devices to be constructed
along slopes adjacent to the development edge to eliminate existing surface flow
over bluffs to the extent feasible. Landscape and irrigation plans will be designed
to minimize irrigation near natural areas /slopes through the use of drought -
tolerant vegetation and low -flow irrigation.
PDF 4.3 -3 The Master Development Plan includes a Bluff /Slope Restoration Plan that
requires eroded portions of bluff slopes to be repaired and stabilized. In order to
stabilize slopes and help avoid erosion, bluff areas devoid of vegetation after
repair and stabilization efforts will be planted with native vegetation that does not
require permanent irrigation.
Standard Conditions and Requirements
SC 4.3 -1 Prior to the issuance of any grading permits, the City of Newport Beach
Community Development Department, Building Division Manager or his /her
designee shall review the grading plan for conformance with the grading shown
on the approved tentative map. The grading plans shall be accompanied by
geological and soils engineering reports and shall incorporate all information as
required by the City. Grading plans shall indicate all areas of grading, including
remedial grading, and shall extend to the limits outside of the boundaries of an
immediate area of development as required by the City. Grading shall be
permitted within all Land Use Districts and outside of an area of immediate
development, as approved by the City, for the grading of public roads, highways,
park facilities, infrastructure, and other development - related improvements.
Remedial grading for development shall be permitted in all Land Use Districts
and outside of an immediate development area, as approved by the City, to
adequately address geotechnical or soils conditions. Grading plans shall provide
for temporary erosion control on all graded sites scheduled to remain unimproved
for more than 30 days. If the Applicant submits a grading plan that deviates from
the grading shown on the approved tentative map (specifically with regard to
slope heights, slope ratios, pad elevations or configurations), as determined by
the Building Manager, s /he shall review the plan for a finding of substantial
conformance. If the Building Manager finds the plan not to be in substantial
conformance, the Applicant shall process a revised tentative map or, if a final
map has been recorded, the Applicant shall process a new tentative map. A
determination of CEQA compliance shall also be required.
SC 4.3 -2 Prior to the recordation of a subdivision map or prior to the issuance of any
grading permit, whichever comes first, and if determined necessary by the City of
Newport Beach Community Development Department, Building Division
Manager, the Applicant shall record a Letter of Consent from any affected
property owners permitting off -site grading, cross lot drainage, drainage
diversions, and /or unnatural concentrations. This process will ensure that
construction activities requiring encroachment permits or having temporary
effects on adjacent parcels are properly noticed and coordinated.
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Section 4.3
ry and Soils
4.3.6 THRESHOLDS OF SIGNIFICANCE
The following significance criteria are from the City of Newport Beach Environmental Checklist.
The Project would result in a significant impact related to geology and soils if it would:
Threshold 4.3 -1 Expose people or structures to potential substantial adverse effects,
including the risk of loss, injury, or death from 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.
Threshold 4.3 -2 Expose people or structures to potential substantial adverse effects,
including the risk of loss, injury, or death involving strong seismic ground
shaking.
Threshold 4.3 -3 Expose people or structures to potential substantial adverse effects
including the risk of loss, injury, or death from seismic - related ground
failure, including liquefaction.
Threshold 4.3 -4 Expose people or structures to potential substantial adverse effects
including the risk of loss, injury, or death from landslides.
Threshold 4.3 -5 Result in substantial soil erosion or the loss of topsoil.
Threshold 4.3 -6 Be located on a geologic unit or soil that is unstable, or that would
become unstable as a result of the project, and potentially result in on- or
off -site landslide, lateral spreading, subsidence, liquefaction or collapse.
Threshold 4.3 -7 Be located on expansive soil, as defined in Table 18 -1 -B of the Uniform
Building Code (1994), creating substantial risks to life or property.
Threshold 4.3 -8 Conflict with any applicable plan, policy, or regulation of an agency with
jurisdiction over the project (including, but not limited to the general plan,
specific plan, local coastal program, or zoning ordinance) adopted for the
purpose of avoiding or mitigating an environmental effect.
As previously discussed in Section 1.6.1, Effects Found Not to be Significant, the City has
determined that the proposed Project would not have a significant impact for the following
thresholds because the Project would not use septic systems or alternative waste water
disposal systems.
Have soils incapable of adequately supporting the use of septic tanks or alternative
waste water disposal systems where sewers are not available for the disposal of waste
water.
4.3.7 ENVIRONMENTAL IMPACTS
Threshold 4.3 -1 Would the project expose people or structures to potential
substantial adverse effects, including the risk of loss, injury, or
death from rupture of a known earthquake fault, as delineated on the
most recent Alquist - Priolo Earthquake Fault Zoning Map issued by
R:Trojects\Newpoeuoisuorzfi EiRwa Geology-09021 iaoo 4.3 -14 Newport Banning Ranch
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Section 4.3
ry and Soils
the State Geologist for the area or based on other substantial
evidence of a known fault?
Threshold 4.3 -2 Would the project expose people or structures to potential
substantial adverse effects, including the risk of loss, injury, or
death involving strong seismic ground shaking?
The Project site is not located within an Alquist - Priolo Earthquake Fault Zone (Exhibit 4.3 -1).
The site encompasses a portion of the North Branch of the Newport- Inglewood Fault zone.
Within this fault zone, local faults generally trend to the northwest, dip steeply to the southwest,
and displace San Pedro Formation materials. However, many of these faults do not displace the
thick soils in the Upland area, which indicates inactivity during the Holocene (recent) period at a
minimum.
The CGS and the USGS have placed the City in an area designated to have a moderate to high
potential for ground shaking associated with regional earthquake activity (CGS and
USGS 2008). A site - specific analysis of the Project site's potential to experience significant
seismic ground motion was conducted and concludes that, although the Project site is not
located within a designated Alquist - Priolo Earthquake Fault Zone, strong ground shaking due to
regional seismic activity is anticipated.
The City of Newport Beach General Plan indicates that, in 50 years, the Newport Beach area
has a 10 percent chance of experiencing ground acceleration in the high to very high range for
Southern California. These levels of shaking can be expected to cause damage particularly to
older and poorly constructed buildings (Newport Beach 2006b). All existing on -site buildings
would be demolished as a part of the Project. Seismic design of on -site structures (excluding
bridges) would be in accordance with the 2007 California Building Code (CBC) criteria. Seismic
design of the proposed pedestrian and bicycle bridge would be in accordance with Caltrans
standards. The CBC provides minimum standards for building design in California. Chapter 16
of the California Building Code deals with General Design Requirements, including (but not
limited to) regulations governing seismically resistant construction (Chapter 16, Division IV) and
construction to protect people and property from hazards associated with excavation cave -ins
and falling debris or construction materials. Chapters 18 and A33 deal with site demolition,
excavations, foundations, retaining walls, and grading, including but not limited to requirements
for seismically resistant design, foundation investigations, stable cut and fill slopes, and
drainage- and erosion - control measures. All Project development would be required to comply
with these design standards. To accommodate the effects from seismic shaking, all on -site
Project structures would be required to comply with the seismic design standards contained
within the California Building Code as adopted by the City. Policies contained in the City's
General Plan would ensure that adverse effects caused by seismic and geologic hazards (such
as strong seismic ground shaking) are minimized through Project consistency with General Plan
policies. In addition, a rationally designed stiffened slab (such as a post- tensioned slab) would
be required (GMU 2010). This would serve to structurally tie the foundation system together
forcing it to act more monolithically during a seismic event. The comprehensive geotechnical
investigation conducted for the proposed Project as a part of this EIR adequately addresses the
potential impacts and recommends mitigation to mitigate risks associated with seismic hazards.
Mitigation Measure (MM) 4.3 -1 requires a design -level geotechnical investigation based on the
approved development plan to determine specific geotechnical measure to ensure compliance
with building and seismic State and local requirements.
There are two discrete segments of the Newport- Inglewood Fault Zone North Branch (the
Newport Mesa North Segment and the Newport Mesa South Segment) potentially within the
R TrojectMNewpartU015Mrafi EIRW.3 Geology -090211 doc 4.3 -15 Newport Banning Ranch
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ry and Soils
Project site. Portions of these fault segments were not conclusively shown to have Holocene
surface rupture, and therefore are not demonstrably "active'. However, some faults could not be
proven to be pre - Holocene (i.e., "inactive ") due to uncertainty in dating the latest fault rupture
events. Using a conservative assumption, the faults that could not conclusively be shown to be
pre - Holocene (i.e., "inactive') and which exhibited evidence for disturbance of more recent soils
were treated as "active'. More appropriately, these faults are classified as "faults that could not
be proved to be inactive'; therefore, Fault Setback Zones were established. Fault and bluff
setbacks have been incorporated into the Project as a Project Design Feature (PDF) to
accommodate seismic site features and mitigate the potential for any slope instability impacting
proposed structures. Bluff setbacks are in excess of those required by the California Building
Code. These setbacks are reflected in the Project development assumptions (see PDF 4.3 -1)
and the grading plan (see Exhibit 3 -20, Soil Disturbance Map, in Section 3.0, Project
Description).
As depicted in Exhibit 4.3 -5, Fault Setback Zones, the Project assumes the extension of
conservative fault setback zones off the ends of each fault segment, where fault projection is
uncertain. These setback zones would assure no potentially significant impact to proposed
Project development from surface fault rupture. If the Applicant proposes to modify or reduce
these setbacks, Mitigation Measure (MM) 4.3 -2 requires that additional trenching occur in the
1,300- foot -long gap area between the 2 fault setback zones to provide additional data on fault
activity and the risk of surface rupture. Therefore, these setback zones may be altered, reduced,
or increased once the additional trenching data become available as a part of more detailed
development plans for the proposed Project. Additional trenching data and incorporation of
updated fault setback zones would refine setback limits in compliance with existing State
standards.
Extensive fault trenching has already been performed at the Project site providing technical
support for development of the fault setback zones incorporated into Project design. Existing
trench data suggests that surface faulting is not present in the gap area between the fault
setback zones, but additional fault trenching would be performed as a conservative precaution if
final development plans include structures in the gap area between the two proposed fault
setback zones. Since conservative setback distances have been incorporated into the proposed
Project, Project impacts from the risk of surface rupture would be less than significant.
State laws and local ordinances require that, prior to construction, potential seismic hazards be
identified and mitigated, as needed, to protect public health and safety from substantial risks
through appropriate engineering practices. Compliance with PDF 4.3 -1, SCs 4.3 -1 and 4.3 -2,
and MMs 4.3 -1 through 4.3 -3 would ensure that impacts related to strong seismic ground
shaking remain at a less than significant level. PDF 4.3 -1 identifies that habitable structures on
the Project site would be set back a minimum of 60 feet from the top of bluff edges. SC 4.3 -1
identifies that the issuance of grading permits is subject to approval of geological and soils
engineering reports. SC 4.3 -2 provides directive if off -site grading or infrastructure connections
are required. MMs 4.3 -2 and 4.3 -3 require additional trenching in the Upland prior to preparation
of final site plans to determine if the identified fault setback zone must be modified.
Supplemental geotechnical analysis would be prepared as necessary.
Impact Summary. Less Than Significant With Mitigation. The Project site is in a
seismically active area with faults within the proposed development that
could not be proven to be inactive. Habitable structures on the Project site
near these faults are subject to fault setback zones and seismic design
parameters that would appropriately address seismic building standards.
Impacts associated with surface fault rupture and seismic shaking would
R:TrojectslNewpartU015\IDrafi EIRW.3 Geology -090211 Eoc 4.3 -16 Newport Banning Ranch
Draft Environmental Impact Report
L
f
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19th STREET
18th STREET
Newport Mesa
North Segment Faults
_ 17th STREET
West Mesa Faults
16th STREET
TNewport Mesa
. / South Segment Faults
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PLACE
15th STREET
EXPLANATION
Strike and Dip of Beds
Horizontal Bedding
Geologc C ortar , Approximately LocateQ
Dotted W here Concealed and Doh d
W here Uncertain
C m¢inuous, Unhroken Pre - Holocene
Age Deposits
Active Faun (Bed), Showing Strike and Dip
tractive Fault (Black), Showing Strike and Dip
Paleo-Channel in Dsp Formation Deposits
Landslide, Stowing Mmrement Direction
Fault Setback Zones
Newport Banning Ranch EIR
H
w�e
s
LeWon & Associates CPT Sounding (1 %7)
Leighton & Associates Hallow Stem Auger
But, (1997)
GORman, McCormick & Urber, Inc.,
CPT Sounding(1998)
G offmar, McCormick & Urban, Inc.,
Bucket Auger Boring (I 9S)
Pacific Soils Engineering Bucket Amcor
Borirg(1993)
Pacific Soils Engineering Hollow Stem
Auger Boring (1993)
W oadward Clyde Consultants CPT
Soudirg n 985)
Fault Trench, by Gofirwn, McCormick &
Urban, I.., This Study, 51fowing5tation "e9"
I
\ I �
Fault Trerth by Earth TechnoId,, (1988)
Fault Trench by Comrerse Con ultants n%4)
Fault Trench By EC I, Inc, for Leig ton &
Associates, Inc (I W7)
Test Pits by GoRman, McCormick &
Urbar, Inc. (1998)
Woodward Clyde Consultants Hollow
Stem Auger Boring (1985)
Groundwater Monitoring W ell Installed
by GeoSyntat (I 994)
HilBker Wall
Geologc C mss Section Lire
z v
Source: City of Newport Beach 2006
Exhibit 4.3 -5
C o N s U L T t N G
(REV: 072911 sje) R lProjeotslNewporVJ015IGraphir /ElR Eg4.3- 5_FSZ.pdf
Section 4.3
ry and Soils
be mitigated to a level considered less than significant with the
incorporation of fault setback zones (which may be refined after additional
trenching data becomes available) and with the implementation of PDF
4.3 -1, SCs 4.3 -1 and 4.3 -2, and MMs 4.3 -1 through 4.3 -3.
Threshold 4.3 -3 Would the project expose people or structures to potential
substantial adverse effects including the risk of loss, injury, or death
from seismic - related ground fai lure, including liquefaction?
Threshold 4.3 -4 Would the project expose people or structures to potential
substantial adverse effects including the risk of loss, injury, or death
from landslides?
Threshold 4.3 -6 Would the project be located on a geologic unit or soil that is
unstable, or that would become unstable as a result of the Project,
and potentially result in on- or off -site landslide, lateral spreading,
subsidence, liquefaction or collapse?
Proposed Grading Overview
Grading is required for several purposes: mass grading; bluff restoration; remediated soil
disposition; and open space grading. Mass grading is the over - excavation and cut and fill
associated with the land development plan (see Exhibit 3 -20, Soil Disturbance Map, and
Exhibit 3 -21, Cut and Fill Map, in Section 3.0, Project Description). For the proposed Project,
mass grading is considered to be within the development envelope and includes the parks,
roads, and development lots. Mass grading also includes the over - excavation and recompaction
of soils, as required. Buff restoration is needed along portions of the south- and west - facing
bluffs to restore areas impacted by oil operations, uncontrolled drainage and erosion, and soil
degradation. These areas would require grading in order to restore and revegetate the
bluff /slope edge and to limit further degradation; these areas are assumed within the limits of
grading /soil disturbance for the proposed Project. As part of the oil well consolidation process,
the existing oil wells within development and habitat restoration areas would be abandoned or
reabandoned and remediated. Hydrocarbon -laden soils would be treated, tested, and placed in
deep fills or outside the proposed development areas. Grading would also be required in the
open space to establish trail grades; prepare habitat mitigation areas; implement bluff
restoration; and allow for public access, maintenance access, and water quality basin creation
areas. Proposed grading in the open space areas would be conducted in a manner that would
minimize impacts to open space resources. For example, to the extent feasible, the multi -use
trails would be located over existing oil roads. In areas where habitat mitigation or restoration is
proposed, minor grading to repair localized erosion features or compact loose soil is anticipated.
It is expected that this work effort would be done by hand or with small equipment.
As conceptually proposed, grading activities would occur subsequent to remediation of the
Project site and is proposed to occur in stages (see Table 3 -3, Proposed Implementation Plan,
in Section 3.0, Project Description). The first stage of grading is anticipated to take
approximately nine months; the second is anticipated to take an additional nine months.
Grading may extend into the development area associated with subsequent development to
achieve an overall earthwork balance.
Table 4.3 -2 summarizes the earthwork quantities for the proposed Project. Total excavation on
the site is estimated to total approximately 2,500,000 cubic yards (cy) including approximately
900,000 cy of cut and fill and 1,455,000 cy of cut and fill corrective grading. To the extent
R TrojectMNewpartU015Mrafi EIRW.3 Geology -090211 Eoc 4.3 -17 Newport Banning Ranch
Draft Environmental Impact Report
Section 4.3
ry and Soils
feasible, all grading would be balanced on site. However, an estimated 25,000 cy of export is
assumed for removing remediated materials that are not suitable for retention on site.
TABLE 4.3 -2
EARTHWORK QUANTITIES
Activity
Cut (cy)
Fill (cy)
Mass Excavation
900,000
833,500
Corrective Grading
1,455,100
1,455,100
Lowland Remediation/ Recycled
156,000
156,000
Soil
Subtotal Grading
2,511,100
2,444,600
Mass Grading Shrinkage (4 %)
(36,000)
We
Corrective Grading Shrinkage
(64,500)
n/a
Lowland Remediation/ Recycled
(6,000)
We
Soil Shrinkage (4 %)
Subtotal Shrinkage
(106,500)
0
Subtotal (grading and
2,404,600
2,444,600
shrinkage)
Import from Sunset Ridge Park
40,000
0
Site
Total
2,444,600
2,444,600e
cy: cubic yards
Total excavation is 2,511,100 cy.
Source: Fuscoe Engineering 2009.
Cuts are anticipated to vary from 1 foot to 10 feet with localized cuts up to approximately
25 feet. Fills are anticipated to vary between 1 foot and 30 feet but may be up to 60 feet
associated with bluff repairs with gradients between 2:1 and 3:1. The larger fills would be placed
in selected arroyos where the bluffs would undergo repair and restoration from erosion damage.
Corrective /remedial grading is expected to be from 3 feet to 30 feet below the proposed
landform elevations. Oil consolidation and remediation operations would produce
bio- remediated soils, asphalt -like materials, and concrete from abandoned oil production
facilities; these materials would likely be used in deep fills (fills ten feet or greater from finished
grade) or placed outside of the residential and commercial building areas. The primary location
for placement of the treated soil would be in the deeper over - excavation portions of the northern
development area.
Liquefaction /Lateral Spreading
On -site soils subject to liquefaction and lateral spreading are located in the Lowland
(Exhibit 4.3 -5). As identified by GMU, site investigations and analysis by Leighton & Associates
in 1997 concluded that local soils in the Lowland area were subject to liquefaction and seismic
settlement of one to six inches (GMU 2010). No habitable structures are proposed as a part of
the Project in the Lowland; this area is proposed for open space, trails, and oil facilities and their
associated infrastructure. Residential, commercial, active recreation, and resort inn uses would
only occur in the Upland area.
Soils in the Upland, except for existing colluvial deposits when subjected to saturated
conditions, are too dense, cemented, or too far above the water table for liquefaction and lateral
R:TroiectMNewpartU015Mmft EIRW.3 Geology -090211 Eoc 4.3 -18 Newport Banning Ranch
Draft Environmental Impact Report
Section 4.3
ry and Soils
spreading to occur. Colluvial materials would be removed down to competent San Pedro
Formation or terrace deposits. These corrective grading practices would result in replacement of
unsuitable materials with suitable engineered fill materials over San Pedro Formation or terrace
deposits. The resulting configuration (i.e., engineered fill over San Pedro Formation or terrace
deposits) would not be subject to liquefaction. An assessment of hazards related to landslides
and liquefaction and the incorporation of PDFs to mitigate this hazard has been completed
consistent with the standards set forth in the California Building Code and the CGS Special
Publication 117. There are no known geologic conditions on the Project site that would render
the required design features infeasible. The City has also included policies in its Safety Element
to achieve the goal of minimizing the risk of injury, loss of life, and property damage caused by
earthquake hazards or geologic disturbances. Policies S 4.1 through S 4.6 require new
development to be in compliance with the most recent seismic and other geologic hazard safety
standards, and help protect community health and safety through the implementation of
effective, state -of- the -art standards for seismic design of structures. Therefore, the risk
associated with seismic - related ground failure and associated liquefaction, lateral spreading, or
subsidence is less than significant.
Subsidence
GMU (2010) performed geotechnical field investigations and observations at the Project site that
concluded the site conditions relative to subsidence history and potential are consistent with
those cited in a prior investigation by Woodward Clyde in 1985. These field investigations and
the Woodward Clyde report concluded that significant ground subsidence from oilfield
operations has not occurred (GMU 2010). There is no surficial evidence of subsidence on the
Project site, and there have been no reports of subsidence - related impacts on oil production
facilities. Accordingly, subsidence is not considered a significant risk to or from Project
implementation and impacts from subsidence are considered less than significant.
Collapsible /Compressible Soils
Some materials within the area proposed for development on the Project site have the potential
for compression and hydro - collapse. Hydro - collapse is the condition under which soils undergo
a significant reduction in volume following inundation with water. For development proposed for
the Upland area (i.e., residential, commercial, active recreational, mixed -use, and resort inn
uses), corrective grading would remove and recompact at least the upper three to five feet of
the soil horizon as well as any locally compressible and /or porous zones within the terrace
deposits. These actions would provide uniform bearing conditions for proposed structures and
would offset the effects of collapsible and compressible soils. Locally, deeper removal zones
would extend to depths of five to ten feet, if necessary. Surface drainage and subdrains below
bioswales would reduce the amount of surface flow infiltration into on -site soils further reducing
any hydro - collapse potential. Colluvial soils have a low to moderate potential for hydro - collapse.
Standard corrective grading practices and excavation of these colluvial soils down to competent
terrace deposits or San Pedro Formation material would result in no significant impacts to the
Project from these soils. In addition, the cut portion of proposed lots or building pads that occurs
across cut and fill transitions would be over - excavated to provide a more uniform bearing
condition.
The alluvial materials in the Lowland contain highly compressible material in the uppermost one
to five feet of soil. As previously indicated, the proposed Project does not include structural
development within the Lowland area where recent alluvial deposits susceptible to compression
are most common.
R:TrojectMNewpartU015Mmft EIRW.3 Geology -090211 Eoc 4.3 -19 Newport Banning Ranch
Draft Environmental Impact Report
Section 4.3
ry and Soils
Impacts from the Project relative to on- or off -site landslides are less than significant with the
incorporation of the PDF 4.3 -1, SCs 4.3 -1 and 4.3 -2 described in the Mitigation Program. In
addition, MMs 4.3 -1 through 4.3 -3 would ensure that impacts related to strong seismic ground
shaking remain at a less than significant level.
Impact Summary. Less Than Significant With Mitigation. Two fault segments on the
Project site have not been confirmed as inactive, and development
setbacks have incorporated into the Project (PDF 4.3 -1). The fault
setback zones would reduce the risk of surface fault rupture. Based on
the GMU 2010 Report, strengthened building foundations and structural
design would accommodate strong seismic shaking on the Project site,
and habitable structures would be restricted to the Upland area, avoiding
soils that may liquefy or undergo lateral spreading. The City of Newport
Beach General Plan and the CDMG (1998) indicate that there is some
existing on -site potential for landslides under dynamic seismic conditions.
Where necessary, corrective grading would ensure all structures are
placed on competent foundation materials. With the incorporation of
PDF 4.3 -1, SCs 4.3 -1 and 4.4 -2, and MMs 4.3 -1 through 4.4 -3, impacts
from seismic - related ground failure, liquefaction, lateral spreading, soil
collapse, and landslides would be less than significant.
Threshold 4.3 -5 Would the project result in substantial soil erosion or the loss of
topsoil?
Due to the highly erosive nature of both the on -site soil materials and bluff slopes, surface
drainage elements would be incorporated into the Project to prevent ponding adjacent to, and
runoff onto, any graded or natural slopes. Areas within the bluff slope setback zone would
contain drainage devices to minimize the surface flow over the bluff slopes. In addition, surface
drainage and bluff slope erosion - control plans would be developed in areas where bluff slopes
are to remain natural. Construction best management practices (BMPs) described in
Section 4.4, Hydrology and Water Quality, would ensure that construction- related impacts on
soil erosion would be less than significant, and post- Project operation and occupancy would not
generate surface flows that result in loss of topsoil or induce erosion. Impacts from the Project
on soil erosion and loss of topsoil would be less than significant. PDFs 4.3 -2 and 4.3 -3 as well
as the construction BMPs as described in Section 4.4, Hydrology and Water Quality, are
applicable. PDF 4.3 -2 requires drainage devices to be constructed to preclude surface flows
over bluffs. PDF 4.3 -3 requires eroded bluff slopes to be repaired and stabilized.
Natural bluff areas bordering the western edge of the Upland would remain a prominent
geomorphic feature of the site upon Project implementation. As demonstrated by analysis of
historical bluff retreat rates and topographic changes, erosion of the bluff face by surface runoff
and local drainage has resulted in shallow erosion, slumping, and localized surficial bluff
instability. Future bluff retreat rates would be expected to be lower than historic bluff retreat
rates since removing oil production activities in the Upland would reduce runoff rates over the
bluffs. Project drainage improvements discussed in Section 4.4, Hydrology and Water Quality,
would also serve to reduce surface runoff over the bluffs and resulting bluff face erosion;
however, surface runoff from precipitation and nuisance flows would not cease entirely. The
Project would also implement subdrain systems to capture infiltrated water and direct it away
from the bluff faces on the Project site, thereby reducing the risk of bluff instability related to
post - development groundwater.
R:TrojectMNewpartU015Mmft EIRW.3 Geology -090211 Eoc 4.3 -20 Newport Banning Ranch
Draft Environmental Impact Report
Section 4.3
ry and Soils
Deep seated bluff stability analyses indicate that the existing bluff slopes meet City
requirements for stability under static and seismic conditions.$ The results under static
conditions indicate that the slopes in their current condition possess safety factors in excess of
1.5 (i.e., acceptable) for deep seated rotational stability. Under pseudo- static conditions, the
slopes possess safety factors in excess of 1.1 (i.e., acceptable). Additional seismic analyses
also show that the level of ground shaking corresponding to a site PGA as determined by a site -
specific PSHA for both 475 and 975 year earthquake return periods would not exceed the level
at which significant bluff failure would occur. Consequently, the potential for major slope failure
during a seismic event is considered low. Shallow slumping on steeper portions of the natural
slope faces may still occur under conditions of extreme moisture and /or during a seismic event.
GMU also performed rotational and traditional surficial stability analyses to evaluate the
maximum proposed fill slope. These analyses indicate adequate safety factors; no significant
impact would be anticipated.
As the sediments within the bluffs possess a fairly high erosion potential, the topographic
alteration of the bluffs would take the form of shallow erosion and surficial slumping of bluff
faces. This process is likely to be reduced, but would continue after Project implementation
since localized surface runoff and precipitation continue to exert erosive forces on bluff
sediments. The Master Development Plan addresses landform restoration and discusses
actions to be taken as part of the Project for bluff stability.9 Areas that have suffered from
erosion would require careful grading in order to restore and revegetate the bluff /slope edge and
to limit further degradation. The drainage overtopping the bluff /slope edge would be intercepted
along the public trail system and redirected into the Project drainage system.
The proposed locations for bluff restoration are depicted on Exhibit 4.3 -6, Bluff Restoration Plan
Bluff restoration in areas where erosion damage to the existing bluff is not readily evident would
consist of carefully removing invasive plants and asphalt -like material where feasible and
revegetating the bluff face with native, drought - tolerant species. In areas where more than
300 linear feet of bluff edge /face have visibly been impacted by ongoing weathering processes
and /or oil operations, conventional grading techniques and equipment would be used to regrade
and stabilize the impacted area to existing bluff slope gradients. Slope- reinforcing fabric or
similar materials would be used where slope gradients exceed 2:1. In areas where localized
sloughing of bluff material has delivered significant amounts of sediment to the Lowland and has
undercut the bluff edge, the sloughed material would be removed, and the bluff face restored to
a stable grade. In this case, repair techniques would use small equipment operating adjacent to
the bluff face, and materials (including fabric and /or soil cement) would also be used as needed
to stabilize the new bluff slope face. In areas showing minor erosion, storm water runoff and
surface flows would be directed away from the bluff edge. Potential locations of bluff
stabilization activities plan (see Exhibit 3 -22, Bluff Restoration Plan, in Section 3.0, Project
Description). Consistency with the City's General Plan requires that slope designs adhere to the
standards contained in Appendix Chapter A33, Excavation and Grading, of the City's Building
Code.
In order to evaluate the long -term cumulative impacts of sea level rise on local area flooding
over the next 90 years (i.e., through 2100), the Project grading plan was overlaid onto the worst -
case sea level rise water elevation data provided by the Pacific Institute. Sea level rise would
increase the potential for future flood water depths to increase near the base of the existing
slopes that border the Upland development areas. Sea level rise is not expected to result in
° The City of Newport Beach relies on the County of Orange standards.
9 See Chapter 11, Landform Restoration and Grading Plan, of the Newport Banning Ranch Master Development
Plan on file at the City of Newport Beach Community Development Department and available for review during
regular business hours.
R TrojectMNewportU015\IOrafl EIRW.3 Geology -090211 Eoc 4.3 -21 Newport Banning Ranch
Draft Environmental Impact Report
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Exhibit 4.3 -6
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Section 4.3
ry and Soils
direct wave attack on the bluff faces and associated coastal bluff erosion. There is a remote
possibility that the increased flood water depths could lead to potential instability at some point
in the future. In the future, adaptive management practices may be required to mitigate bluff
instability under a future sea level rise scenario. Such measure could include the protection of
the lower three feet of the face of the slopes against erosion through the installation of rip rap or
coating the area with soil cement and /or geofabric. These measures are not required as a part
of the Project. With respect to flooding risk, please refer to Section 4.4, Hydrology and Water
Quality.
PDF 4.3 -3 provides for the development of a detailed bluff face repair /improvement plan to
maintain the integrity of bluff slopes and to minimize the potential for shallow slumping to occur.
In addition, PDF 4.3 -1 requires development setbacks to ensure structural development is
adequately protected by appropriate safety features. Facilities and activities within the bluff
setback zones would be limited to trails, lighting, and minor grading for surface drainage control.
Existing arroyos and erosional ravines on bluff faces would be repaired through precise grading
and filling and would be restored to a condition consistent with the existing bluff slope
parameters. The Mitigation Program would ensure that bluff top and bluff face landscaping
would require no permanent irrigation.
Impact Summary. Less Than Significant. Grading activities would increase the potential for
soil erosion and loss of top soil. Analysis has indicated that there is a risk
of shallow slumping on bluff faces associated with surface runoff;
however, Project drainage improvements are expected to reduce runoff
compared to existing conditions. With the incorporation of construction
BMPs as described in Section 4.4, Hydrology and Water Quality, Project
impacts on soil erosion and loss of topsoil would be less than significant.
Upon completion of the Project, soil erosion and the loss of topsoil would
be minimized through the use of engineered grading, surface drainage
improvements, and landscaping (e.g., PDFs 4.3 -2 and 4.3 -3).
Threshold 4.3 -7 Would the project be located on expansive soil, as defined in Table
18 -1 -B of the Uniform Building Code (1994), creating substantial
risks to life or property?
Expansion index (EI) tests were performed to evaluate the expansion potential of on -site soils.
These test results indicate the presence of expansive soils. Without correction, expansive soils
can be unsuitable for building. Expansive soils can be accommodated through strengthened
and stiffened building foundation design that is capable of resisting the effects of expansive
soils. As identified in MM 4.3 -3, compliance with the recommendations of the preliminary
geotechnical report (GMU 2010) would require this type of foundation system for proposed
structures. Significant impacts associated with expansive soils can be mitigated to a level that is
considered less than significant. SCs 4.3 -1 and 4.3 -2 and MMs 4.3 -1 through 4.3 -3 are
applicable. SC 4.3 -1 identifies that the issuance of grading permits is subject to approval of
geological and soils engineering reports. SC 4.3 -2 provides directive if off -site grading or
infrastructure connections are required. MMs 4.3 -2 and 4.3 -3 require additional trenching in the
Upland prior to preparation of final site plans to determine if the identified fault setback zone
must be modified. Supplemental geotechnical analysis would be prepared as necessary.
Impact Summary: Less Than Significant With Mitigation. On -site soils have a low to
medium expansion potential. With the incorporation of SCs 4.3 -1 and
4.3 -2 and MMs 4.3 -1 through 4.3 -3, impacts from the Project associated
with expansive soils would be less than significant.
R:TrojectslNewpartU015\IDrafi EIRW.3 Geology -090211 doc 4.3 -22 Newport Banning Ranch
Draft Environmental Impact Report
Section 4.3
ry and Soils
Threshold 4.3 -8 Would the project conflict with any applicable plan, policy, or
regulation of an agency with jurisdiction over the project (including,
but not limited to the general plan, specific plan, local coastal
program, or zoning ordinance) adopted for the purpose of avoiding
or mitigating an environmental effect?
Tables 4.3 -3 and 4.3 -410 evaluate the consistency of the proposed Project with the applicable
goals and policies of the City's General Plan and the California Coastal Act, respectively.
Impact Summary., No Impact. As identified in Tables 4.3 -3 and 4.3 -4, the proposed Project
would be consistent with the intent of the soils and geology - related goals
and policies of the City of Newport Beach General Plan and the California
Coastal Act.
4.3.8 MITIGATION PROGRAM
Project Design Features
PDFs 4.3 -1 through 4.3 -3 are integrated into the Project and are applicable to geology and soils.
Standard Conditions and Requirements
SCs 4.3 -1 and SC 4.3 -2 are applicable.
Mitigation Measures
MM 4.3 -1 The Applicant shall submit to the City of Newport Beach Community
Development Department, Building Division Manager or his /her designee for
review and approval, a site- specific, design -level geotechnical investigation
prepared for each development parcel by a registered geotechnical engineer.
The investigation shall comply with all applicable State and local code
requirements and:
a) Include an analysis of the expected ground motions at the site from known
active faults using accepted methodologies;
b) Determine structural design requirements as prescribed by the most current
version of the California Building Code, including applicable City
amendments, to ensure that structures can withstand ground accelerations
expected from known active faults;
c) Determine the final design parameters for walls, foundations, foundation
slabs, utilities, roadways, parking lots, sidewalks, and other surrounding
related improvements;
Project plans for foundation design, earthwork, and site preparation shall
incorporate all of the mitigations in the site - specific investigations. The structural
engineer shall review the site - specific investigations, provide any additional
necessary measures to meet Building Code requirements, and incorporate all
applicable recommendations from the investigation in the structural design plans
'D For ease of reading, the policy tables are located at the end of this EIR section.
R:TrojectMNewpartU015Mmft EIRW.3 Geology -090211 doc 4.3 -23 Newport Banning Ranch
Draft Environmental Impact Report
Section 4.3
ry and Soils
and shall ensure that all structural plans for the Project meet current Building
Code requirements.
The City's registered geotechnical engineer or third -party registered engineer
retained to review the geotechnical reports shall review each site - specific
geotechnical investigation, approve the final report, and require compliance with
all geotechnical requirements contained in the investigation in the plans
submitted for the grading, foundation, structural, infrastructure and all other
relevant construction permits.
The City shall review all Project plans for grading, foundations, structural,
infrastructure and all other relevant construction permits to ensure compliance
with the applicable geotechnical investigation and other applicable Code
requirements.
MM 4.3 -2 Prior to the approval of any applicable final tract map, the Applicant shall have
completed, by a qualified geologist, additional geotechnical trenching and field
investigations and shall provide a supplemental geotechnical report to confirm
the adequacy of Project development fault setback limits in accordance with the
mandates of the Alquist - Priolo Earthquake Fault Zoning Act. The trenching and
report shall be subject to the review and approval of the City of Newport Beach
Public Works Director.
MM 4.3 -3 Prior to the approval of any applicable final tract map, development setbacks
from the Upland fault segments, revised as necessary based upon the findings of
additional trenching investigations, shall be incorporated into the Project
consistent with requirements set forth in the California Building Code and the City
of Newport Beach General Plan. Bluff setbacks consistent with the regulatory
requirements for habitable structures shall be incorporated into the Project
consistent with the beach bluff setback standards in the City of Newport Beach
General Plan. Where applicable, setback distances consistent with
recommendations in the Project's Geotechnical Report (GMU 2010) shall be
incorporated. Prior to the preparation of final Project plans and specifications,
additional trenching shall be conducted within the 1,300 -foot gap between the
2 parts of the existing Fault Setback Zone. This additional trenching shall provide
more information about the potential for active faulting in this portion of the
Project site. If necessary, the development fault setback zones shall be modified
after this information is obtained and analyzed in accordance with the mandates
of the Alquist - Priolo Earthquake Fault Zoning Act. This information shall be
subject to the review and approval of the City of Newport Beach Public Works
Director and Community Development Director.
4.3.9 LEVEL OF SIGNIFICANCE AFTER MITIGATION
With implementation of the PDFs, SCs, and MMs described above, all impacts would be
reduced to a less than significant level.
R:TrojectslNewpartU015\IDrafi EIRW.3 Geology -090211 Eoc 4.3 -24 Newport Banning Ranch
Draft Environmental Impact Report
TABLE 4.3 -3
CITY OF NEWPORT BEACH GENERAL PLAN CONSISTENCY ANALYSIS
City of Newport Beach General Plan
Relevant Goals, Policies, and Progran
Harbor and Bay Element
Policies
HB Policy 8.12: Reduction of Infiltration
Include equivalent BMPs that do not require infiltration,
where infiltration of runoff would exacerbate geologic
hazards. (Policy NR 3.12)
HB Policy 8.16: Siting of New Development
Require that development be located on the most
suitable portion of the site and designed to ensure the
protection and preservation of natural and sensitive site
resources that provide important water quality benefits.
(Policy NR 3.16)
Natural Resources Element
Policies
NR Policy 3.12: Reduction of Infiltration
Include equivalent BMPs that do not require infiltration,
where infiltration of runoff would exacerbate geologic
hazards. (Policy HB 8.12)
NR Policy 3.16: Siting of New Development
Require that development be located on the most
suitable portion of the site and designed to ensure the
protection and preservation of natural and sensitive site
resources that provide important water quality benefits.
(Policy HB 8.16)
Natural Resources Element Goal NR 23
Development respects natural landforms such as
coastal bluffs.
Section 4.3
ry and Soils
The Project is consistent with this policy. The Project
contains a storm drain system that ensures infiltrated
water is directed away from the bluff faces on the
Project site. This storm drain system, which includes
bioswale subdrains, would ensure that the risk of bluff
instability is minimized and that a geologic hazard does
not develop. The Project's subdrain systems would
capture infiltrated water and direct it away from the bluff
faces on the Project site, thereby reducing the risk of
bluff instability related to groundwater. (Please also see
Section 4.4, Hydrology and Water Quality.)
The Project is consistent with this policy. Development
is sited away or buffered from the arroyos and bluffs on
the Project site. Bluff setbacks and a linear bluff edge
park have been incorporated into the site design to
ensure bluff and arroyo vegetation are protected.
Development is also set away and buffered from
wetlands. Bluff restoration and stabilization would occur
as a part of the Project to maintain bluff stability and
respond to changing conditions over time related to sea
level rise.
The Project is consistent with this policy. Please refer to
the response to HB Policy 8.12.
The Project is consistent with this policy. To the degree
feasible, the Project has been designed to avoid
significant impacts. Site - design concepts have been
applied to the Project that maintain site drainage
patterns and incorporate existing natural drainage
features into site design. Natural swales and treatment -
control BMPs ensure that flow rates are controlled and
runoff is treated prior to discharge (see also Section 4.4,
Hydrology and Water Quality).
The Project is consistent with this goal. The Project site
has been subject to prior and ongoing modification
through oil operations, site erosion, and grading. As a
part of the Project, the topography of the site would be
modified through grading and development for proposed
land uses, associated infrastructure (e.g., roads), and
site remediation. However, preservation of the existing
natural coastal .bluffs on site would be achieved through
the incorporation of (1) appropriate bluff setback
distances; (2) a bluff edge linear park; (3) bluff
restoration providing for bluff face re- vegetation; and
(4) Project drainage features that reduce runoff
infiltration near the bluff face. Bluff restoration and
stabilization would minimize alteration of these natural
coastal bluffs by ensuring long -term bluff face stability
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TABLE 4.3 -3 (Continued)
CITY OF NEWPORT BEACH GENERAL PLAN CONSISTENCY ANALYSIS
City of Newport Beach General Plan
Relevant Goals, Policies, and Programs Consistency Analysis
Policies
NR Policy 23.1: Maintenance of Natural Topography
Preserve cliffs, canyons, bluffs, significant rock
outcroppings, and site buildings to minimize alteration of
the site's natural topography and preserve the features
as a visual resource.
NR Policy 23.4: New Development on Blufftops
Require all new blufffop development located on a bluff
subject to marine erosion to be set back based on the
predominant line of development. This requirement shall
apply to the principal structure and major accessory
structures such as guesthouses and pools. The setback
shall be increased where necessary to ensure safety
and stability of the development.
NR Policy 23.5: New Accessory Structures on
Blufftops
Require new accessory structures, such as decks,
patios and walkways that do not require structural
foundations to be sited at least 10 feet from the edge of
bluffs subject to marine erosion. Require accessory
structures to be removed or relocated landward when
threatened by erosion, instability or other hazards.
Safetv Element
Element Goal S 4
Adverse effects caused by seismic and geologic
hazards are minimized by reducing the known level of
risk to loss of life, personal injury, public and private
property damage, economic and social dislocation, and
disruption of essential services.
Policies
S Policy 4.7: New Development
Conduct further seismic studies for new development in
areas where potentially active faults may occur.
Section 4.3
and reduction in causal factors of bluff face
deterioration.
The Project is consistent with this policy. Please refer to
the response to Goal NR 23.
The Project is consistent with this policy. The coastal
bluffs on the Project site are not subject to marine
erosion. Notwithstanding, habitable development within
the Upland area of the Project site would be set back an
appropriate distance from the existing bluff edge to
protect bluffs and to maintain existing natural
topography.
The Project is consistent with this policy. All habitable
development would be set back from the bluff edge and
separated by a linear park area.
The Project is consistent with this goal. All proposed
habitable structures on the Project site would be
excluded from fault setback zones. Additional field
trenching would provide more information within the
.,gap" area, and fault setback zones would be adjusted
accordingly. All habitable development would also be
set back from the bluff edges and separated from the
edqe by a linear park.
The Project is consistent with this policy. Extensive field
testing and geotechnical trenching has been conducted
to provide data on seismic conditions at the Project site.
Additional trenching shall be conducted on the site
during preparation of the final Geotechnical Report to
provide more information about the location of
potentially active fault traces within the "gap" area on the
Project site. This information would be used in adjusting
fault setback zones, if necessary, to ensure seismic
hazards are minimized.
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Section 4.3
TABLE 4.3 -4
CALIFORNIA COASTAL ACT CONSISTENCY ANALYSIS
Relevant California Coastal Act Policies
Consistency Analysis
Development
Section 30253 Minimization of adverse impacts
The Project is consistent with this policy. A comprehensive
New development shall do all of the following:
list of Project Design Features, Standard Conditions, and
Mitigation Measures has been incorporated into the
(a) Minimize risks to life and property in areas of high
Project. These would help to minimize seismic hazards to
geologic, flood, and fire hazard.
proposed Project features and structures. These features,
(b) Assure stability and structural integrity, and neither
conditions, and measures would also provide for structural
create nor contribute significantly to erosion,
setbacks from bluff edges to protect existing natural
geologic instability, or destruction of the site or
landforms and to maintain public safety; they would work
surrounding area or in any way require the
in concert with best management practices (BMPs) to
construction of protective devices that would
ensure that geologic instability caused by surface erosion
substantially alter natural landforms along bluffs
or infiltration in the vicinity of the coastal bluffs does not
and cliffs.
occur. Compliance with air quality, energy consumption,
(c) Be consistent with requirements imposed by an air
and land use compatibility are addressed in Sections 4.10,
pollution control district or the State Air Resources
4.11, and 4. 1, respectively.
Board as to each particular development.
(d) Minimize energy consumption and vehicle miles
traveled.
(e) Where appropriate, protect special communities
and neighborhoods that, because of their unique
characteristics, are popular visitor destination points
for recreational uses.
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Section 4.3
Geology and Soils
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