HomeMy WebLinkAbout3949; Agua Hedionda Lift Station & Force Main; Agua Hedionda Lift Station & Force Main; 2009-08-03
Agua Hedionda Lift Station and Force Main August 3, 2009
Carlsbad, California Project No. 106044002
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TABLE OF CONTENTS
Page
1. INTRODUCTION....................................................................................................................1
2. SCOPE OF SERVICES............................................................................................................1
3. PROJECT DESCRIPTION ......................................................................................................2
4. SITE DESCRIPTION...............................................................................................................2
5. SUBSURFACE EXPLORATION AND LABORATORY TESTING....................................2
6. GEOLOGY AND SUBSURFACE CONDITIONS.................................................................3
6.1. Regional and Geologic Setting.....................................................................................3
6.2. Site Geology.................................................................................................................4
6.2.1. Fill.......................................................................................................................4
6.2.2. Alluvium .............................................................................................................4
6.2.3. Old Paralic Deposits (Terrace Deposits).............................................................5
6.2.4. Santiago Formation.............................................................................................5
6.3. Rippability....................................................................................................................5
6.4. Groundwater.................................................................................................................5
6.5. Geologic Hazards..........................................................................................................6
7. FAULTING AND SEISMICITY.............................................................................................6
7.1. Surface Fault Rupture...................................................................................................7
7.2. Ground Motion.............................................................................................................7
7.3. Liquefaction..................................................................................................................7
7.4. Dynamic Settlement of Saturated Soils........................................................................8
7.5. Ground Subsidence.......................................................................................................9
7.6. Lateral Spread...............................................................................................................9
7.7. Landslides...................................................................................................................10
7.8. Tsunamis and Seiches.................................................................................................10
8. CONCLUSIONS ....................................................................................................................10
9. RECOMMENDATIONS........................................................................................................11
9.1. Earthwork ...................................................................................................................11
9.1.1. Site Preparation.................................................................................................11
9.1.2. Excavation Characteristics................................................................................12
9.1.3. Remedial Grading for Lift Station Building Pad Areas....................................12
9.1.4. Materials for Fill ...............................................................................................13
9.1.5. Compacted Fill..................................................................................................13
9.2. Temporary Excavations..............................................................................................14
9.3. Shoring........................................................................................................................15
9.4. Excavation Bottom Stability.......................................................................................16
9.5. Construction Dewatering............................................................................................16
9.6. Pipe Jacking................................................................................................................16
9.7. Lateral Pressures for Thrust Blocks............................................................................17
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9.8. Modulus of Soil Reaction...........................................................................................17
9.9. Pipe Bedding...............................................................................................................18
9.10. Trench Backfill...........................................................................................................18
9.11. Fill Placement and Compaction..................................................................................19
9.12. Seismic Design Parameters.........................................................................................20
9.13. Foundations.................................................................................................................20
9.13.1. Shallow Foundations.........................................................................................20
9.13.2. Lateral Earth Pressures......................................................................................21
9.13.3. Pile Foundations................................................................................................21
9.13.4. Driven Pile Installation .....................................................................................23
9.14. Retaining Walls and Abutment Walls ........................................................................24
9.15. Underground Structures..............................................................................................24
9.16. Uplift and Special Design Considerations..................................................................25
9.17. Drainage......................................................................................................................25
9.18. Preliminary Pavement Design....................................................................................26
9.19. Corrosion....................................................................................................................27
9.20. Concrete......................................................................................................................27
9.21. Pre-Construction Conference......................................................................................28
9.22. Plan Review and Construction Observation...............................................................28
10. LIMITATIONS.......................................................................................................................29
11. REFERENCES.......................................................................................................................31
Tables
Table 1 – Principal Active Faults.....................................................................................................6
Table 2 – Loading on HDD and Jack-and-Bore Segments of Pipeline..........................................17
Table 3 – Seismic Design Factors..................................................................................................20
Table 4 – Summary of Pile Vertical Capacity Evaluation..............................................................22
Table 5 – Single Pile Lateral Load Capacity .................................................................................22
Table 6 – Lateral Load Group Reduction Factors..........................................................................23
Table 7 – Recommended Pavement Sections ................................................................................26
Figures
Figure 1 – Site Location Map
Figures 2 and 3 – Geotechnical Maps
Figure 4 – Fault Location Map
Figure 5 – Lateral Earth Pressure for Temporary Cantilevered Shoring below Groundwater
Figure 6 – Lateral Earth Pressure for Braced Excavation below Groundwater (Granular Soil)
Figure 7 – Thrust Block Lateral Earth Pressure Diagram
Figure 8 – Retaining Wall Drainage Detail
Figure 9 – Lateral Earth Pressure for Underground Structures
Figure 10 – Uplift Resistance for Underground Structures
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Appendices
Appendix A – Boring Logs
Appendix B – Laboratory Testing
Appendix C – Typical Earthwork Guidelines
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1. INTRODUCTION
In accordance with your request and our revised proposal dated February 28, 2008, we have per-
formed a geotechnical evaluation for the proposed Agua Hedionda sewer lift station and force
main project located in Carlsbad, California (Figure 1). This report presents our conclusions re-
garding the geotechnical conditions at the subject site and our recommendations for the design
and construction of this project.
2. SCOPE OF SERVICES
Ninyo & Moore’s scope of services for this project included review of pertinent background
data, performance of a geologic reconnaissance and subsurface evaluation, and engineering
analysis with regard to the proposed project. Specifically, we performed the following tasks:
• Reviewing background data listed in the References section of this report. The data reviewed
included geotechnical reports, topographic maps, geologic data, fault maps, and a site plan
for the project.
• Obtaining County of San Diego Department of Environmental Health (DEH) boring per-
mits, a City of Carlsbad Right-of-Entry permit, a NRG Energy Right-of-Entry permit, and a
NCTD Railroad Right-of-Way permit.
• Marking the boring locations for clearance of utilities. Underground Service Alert (USA)
was notified to mark the existing underground utilities at the boring locations.
• Performing a geologic reconnaissance of the proposed site, including the observation and
mapping of geologic conditions and the evaluation of possible geologic hazards, which may
impact the proposed project.
• Performing a subsurface evaluation consisting of drilling 24 exploratory borings to evaluate
the subsurface conditions.
• Performing geotechnical laboratory testing on selected soil samples.
• Compiling and analyzing the data obtained.
• Preparing this report presenting our findings, conclusions, and recommendations regarding
the geotechnical design and construction of the project.
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3. PROJECT DESCRIPTION
Based on current plans, the overall proposed pipeline alignment begins at a point just north of the
inlet for Agua Hedionda in the City of Carlsbad, and trends south along the east side of the railroad
tracks, through the NRG Energy (Cabrillo Power) Encina Power Plant site, past Cannon Road, past
Palomar Airport Road, and ends at the Encina Water Pollution Control Facility. The segment of the
alignment from Cannon Road to the Encina Water Pollution Control Facility will trend along
Avenida Encinas. Plans also include the construction of a pipe bridge across Agua Hedionda La-
goon and several microtunneling (jack-and-bore) and horizontal directional drilling (HDD)
segments along the pipeline alignment. The new lift station site is located east of the railroad tracks
and south of the lagoon inlet, a portion of which will be cut into the hillside (Figure 2). We under-
stand that the station will have a wet well with a base elevation of approximately 15 feet above
mean sea level (MSL) to match the existing lift station wet well. The new lift station site will in-
clude an emergency storage tank, grinders, deep wet well, generator room, chemical storage,
metering flume, junction structure, pipelines, and ancillary facilities. The existing lift station, also
on the east side of the railroad tracks, will be replaced by a proposed coastal rail trail.
4. SITE DESCRIPTION
The project site is currently developed and occupied by existing pipelines, the NCTD railway,
Encina Power Plant, and paved roads. The proposed lift station site is in a sloping area, with ele-
vations ranging from approximately 10 feet to 56 feet MSL. A concrete lined basin exists along
the northern boundary of the lift station site. Surface elevations along the pipeline alignment
range from about 10 feet MSL at the northern end to about 78 feet MSL where the pipeline
crosses Palomar Airport Road. Vegetation, in areas not covered by existing improvements, gen-
erally consists of a light to moderate growth of grass and brush.
5. SUBSURFACE EXPLORATION AND LABORATORY TESTING
Our field exploration of the subject site included a geologic reconnaissance conducted in May of
2007 and subsurface exploration conducted in November 2008 and June 2009. The subsurface
evaluation consisted of drilling 24 exploratory borings to depths of up to approximately 165 feet.
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With the exception of borings B-3 and B-4, the borings were drilled using a truck-mounted drill rig
equipped with 8-inch diameter hollow-stem augers. Boring B-3 was drilled using a truck-mounted
drill rig equipped with mud rotary capability and boring B-4 was drilled using a limited-access drill
rig equipped with 6½-inch hollow-stem augers, also using the mud rotary drilling technique. The
boring locations were selected based on the results of our background review, field reconnaissance,
and discussions with the client. The approximate locations of the exploratory borings are presented
on Figures 2 and 3. The boring logs are presented in Appendix A.
Laboratory testing of representative soil samples included in-situ dry density and moisture con-
tent, gradation, percent passing the 200 sieve, Atterberg limits, sand equivalent, direct shear tests,
Proctor density, California Bearing Ratio (CBR), R-value, and soil corrosivity. The results of the
in-situ dry density and moisture content tests are presented on the boring logs in Appendix A.
The results of the other laboratory tests performed are presented in Appendix B.
6. GEOLOGY AND SUBSURFACE CONDITIONS
Our findings regarding regional and site geology and groundwater conditions at the subject site
are provided in the following sections.
6.1. Regional and Geologic Setting
The project area is situated in the Peninsular Ranges Geomorphic Province. This geomor-
phic province encompasses an area that extends approximately 900 miles from the
Transverse Ranges and the Los Angeles Basin south to the southern tip of Baja California
(Norris and Webb, 1990). The province varies in width from approximately 30 to 100 miles.
In general, the province consists of rugged mountains underlain by Jurassic metavolcanic
and metasedimentary rocks, and Cretaceous igneous rocks of the southern California batho-
lith. In the coastal portion of the province in San Diego County, that includes the project
area, the metamorphic and granitic basement rocks are overlain by sedimentary materials
that are Cretaceous, Tertiary, and Quaternary age.
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The Peninsular Ranges Province is traversed by a group of sub-parallel faults and fault
zones trending roughly northwest. Several of these faults, which are shown on Figure 4, are
considered active faults. The Whittier–Elsinore, and San Jacinto faults are active fault systems
located northeast of the project area and the Rose Canyon, Agua Blanca–Coronado Bank
and San Clemente faults are active faults located west of the project area. Major tectonic ac-
tivity associated with these and other faults within this regional tectonic framework consists
primarily of right-lateral, strike-slip movement. Further discussion of faulting relative to the
site is provided in the Faulting and Seismicity section of this report.
6.2. Site Geology
Geologic units encountered during our reconnaissance and subsurface evaluation included
fill, alluvium, old paralic deposits (terrace deposits), and Santiago Formation at depth. Gen-
eralized descriptions of the units encountered are provided in the subsequent sections. More
detailed descriptions are provided on the boring logs in Appendix A.
6.2.1. Fill
Fill materials were encountered in borings B-1 through B-22 and B-24 from the ground sur-
face to depths of up to approximately 16.5 feet (depth explored) in borings B-1 and B-2. As
encountered, the materials generally consisted of various shades of brown, dry to saturated,
loose to very dense, silty/clayey sand to clayey gravel and cobbles with sand to stiff clay.
6.2.2. Alluvium
Alluvium was encountered in borings B-3, B-4, B-6, and B-23 underlying fill to depths
of up to approximately 165 feet (depth explored) in boring B-3. As encountered, the ma-
terials generally consisted of various shades of gray and brown, damp to saturated,
loose to very dense, clean sand and silty/clayey sand to very stiff, silt and silty clay. A
dense, fine gravel layer was encountered in boring B-3 at approximately 155 feet ex-
tending to the depth of exploration.
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6.2.3. Old Paralic Deposits (Terrace Deposits)
Old paralic deposits (previously designated as terrace deposits) were encountered in
borings B-7 thru 21 and borings B-23 and B-24 from beneath the fill and/or alluvium to
depths of up to approximately 47 feet in boring B-20. As encountered, the materials
generally consisted of various shades of brown, reddish brown and gray, damp to wet,
medium dense to dense, clean sand to silty/clayey sand and firm to hard sandy clay.
Trace gravel were encountered occasionally in the samples.
6.2.4. Santiago Formation
Materials of the Santiago Formation were encountered beneath the fill, alluvium, and/or
old paralic deposits to the depths explored in borings B-4 through B-10, B-15, and B-17,
through B-22. Although not encountered in boring B-16, based on interpolation from bor-
ings B-15 and B-17, we anticipate that it will be present at a rough elevation of 35 feet
MSL at this location. As encountered, the materials generally consisted of alternating beds
of gray, damp to saturated, moderately to strongly cemented, silty and clayey fine to
coarse-grained sandstone to fine sandy siltstone with trace amounts of clay and moist,
strongly indurated silty claystone.
6.3. Rippability
Based on our site reconnaissance and subsurface evaluation, the on-site materials are ex-
pected to be generally rippable with normal heavy-duty earthmoving equipment. Strongly
cemented “concretions” or zones within the Santiago Formation are likely to be encountered
and will entail the use of heavy drilling, ripping, or rock breaking equipment.
6.4. Groundwater
Based on our experience in the vicinity of the site, nearby subsurface investigations, and due
to the proximity of the site to the Pacific Ocean and Agua Hedionda Lagoon, we anticipate
that the regional groundwater table is likely to be encountered at or near sea level as indicated
by borings B-3 and B-4. Perched groundwater was encountered in several of our borings at
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depths as shallow as 9 feet corresponding to elevations ranging from 29 to 41 feet above MSL.
Variations in groundwater level may occur due to tidal influence, variations in ground surface
topography, subsurface geologic conditions and structure, rainfall, and other factors.
6.5. Geologic Hazards
In general, hazards associated with seismic activity include ground surface rupture, strong
ground motion, tsunamis, liquefaction, and landsliding. These considerations and other geo-
logic hazards such as landsliding are discussed in the following sections.
7. FAULTING AND SEISMICITY
The subject site is not located within a State of California Earthquake Fault Zone (formerly
known as an Alquist-Priolo Special Studies Zone) (Hart and Bryant, 1997). However, the site is
located in a seismically active area, as is the majority of southern California, and the potential for
strong ground motion in the project area is considered significant during the design life of the
proposed structure. Figure 4 shows the approximate site location relative to the major faults in
the region. The active Rose Canyon fault is located approximately 4.6 miles west of the site.
Table 1 lists selected principal known active faults that may affect the subject site, the maximum
moment magnitude (Mmax) as published by the Cao, et al. (2003) for the California Geological
Survey (CGS). The approximate fault-to-site distances were calculated using the computer pro-
gram FRISKSP (Blake, 2001).
Table 1 – Principal Active Faults
Fault Distance
miles (kilometers) 1,2 Moment Magnitude2
Rose Canyon 4.6 (7.4) 7.2
Newport-Inglewood (Offshore) 5.5 (8.8) 7.1
Coronado Bank 20.6 (33.1) 7.6
Elsinore (Temecula Segment) 24.5 (39.5) 6.8
Elsinore (Julian Segment) 24.7 (39.7) 7.1
Elsinore (Glen Ivy Segment) 34.4 (55.4) 6.8
Notes: 1 Blake (2001) 2 Cao, et al. (2003)
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The principal seismic hazards at the subject site are surface fault rupture, ground motion, lique-
faction, dynamic settlement, ground subsidence, lateral spreading, landslides, tsunamis and
seiches. A brief description of these hazards and the potential for their occurrences on site are
discussed below.
7.1. Surface Fault Rupture
Based on our review of the referenced literature and our site reconnaissance, no active faults
are known to cross the project site. Therefore, the probability of damage from surface fault
rupture is considered to be low. However, lurching or cracking of the ground surface as a re-
sult of nearby seismic events is possible.
7.2. Ground Motion
The 2007 California Building Code (CBC) recommends that the design of structures be
based on the horizontal peak ground acceleration (PGA) having a 2 percent probability of
exceedance in 50 years which is defined as the Maximum Considered Earthquake (MCE).
The statistical return period for PGAMCE is approximately 2,475 years. The probabilistic
PGAMCE for the site was calculated as 0.53g using the United States Geological Sur-
vey (USGS, 2008) ground motion calculator (web-based). The design PGA was estimated to
be 0.35g using the USGS ground motion calculator. These estimates of ground motion do
not include near-source factors that may be applicable to the design of structures on site.
7.3. Liquefaction
Liquefaction is the phenomenon in which loosely deposited granular soils with silt and clay
contents of less than approximately 35 percent and non-plastic silts located below the water
table undergo rapid loss of shear strength when subjected to strong earthquake-induced
ground shaking. Ground shaking of sufficient duration results in the loss of grain-to-grain
contact due to a rapid rise in pore water pressure, and causes the soil to behave as a fluid for
a short period of time. Liquefaction is known generally to occur in saturated or near-
saturated cohesionless soils at depths shallower than 50 feet below the ground surface. Fac-
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tors known to influence liquefaction potential include composition and thickness of soil lay-
ers, grain size, relative density, groundwater level, degree of saturation, and both intensity
and duration of ground shaking.
Liquefaction potential of subsurface soils in the vicinity of the Agua Hedionda Lagoon pipeline
crossing and at the lift station was evaluated using the soil sampler blow counts recorded at
various depths in exploratory borings B-3 through B-6 and our laboratory test results. The liq-
uefaction analysis was based on the National Center for Earthquake Engineering
Research (NCEER) procedure (Youd, et al., 2001) developed from the methods originally rec-
ommended by Seed and Idriss (1982) using the computer program LiquefyPro (CivilTech
Software, 2007a). A historic high groundwater table located at El. +1 (MSL) was used in our
evaluation. Our liquefaction analysis indicates that the relatively loose to medium dense, granu-
lar soil layers occurring below the historic high groundwater level and up to a depth of
approximately 12 feet below the ground surface at the southern abutment of the Agua Hedionda
Lagoon pipeline crossing are susceptible to liquefaction during the design seismic event.
Our subsurface exploration and laboratory testing indicate that the lift station and the pipe-
line alignment are underlain by relatively dense sands and silts and/or stiff clays or
competent formational material. Accordingly, it is our opinion that liquefaction and liquefac-
tion-related seismic hazards (e.g., dynamic settlement, ground subsidence, and/or lateral
spreading) are not design considerations for the lift station and the pipeline alignment.
7.4. Dynamic Settlement of Saturated Soils
As a result of liquefaction, the proposed Agua Hedionda pipeline crossing structure may be
subject to several hazards, including liquefaction-induced settlement. In order to estimate the
amount of post-earthquake settlement, the method proposed by Tokimatsu and Seed (1987)
was used in which the seismically induced cyclic stress ratios and corrected N-values are re-
lated to the volumetric strain of the soil. The amount of soil settlement during a strong
seismic event depends on the thickness of the liquefiable layers and the density and/or con-
sistency of the soils. Under the current conditions, a post-earthquake total settlement of up to
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approximately 3 inches is calculated at the southern abutment. The liquefaction-induced set-
tlement at the northern abutment is estimated to be less than 0.5 inches.
7.5. Ground Subsidence
Based on the design curves developed by Ishihara (1995) and considering the thickness of
the non-liquefiable surface layer (above the historic high groundwater table) overlying the
liquefiable soil layer, ground subsidence or seismically induced bearing failure is not a de-
sign consideration for the project.
7.6. Lateral Spread
Lateral spread of the ground surface during an earthquake usually takes place along weak
shear zones that have formed within a liquefiable soil layer. Lateral spread has generally
been observed to take place in the direction of a free-face (i.e., retaining wall, slope, chan-
nel, etc.) but has also been observed to a lesser extent on ground surfaces with gentle slopes.
An empirical model developed by Youd, et al. (2002) is typically used to predict the amount
of horizontal ground displacement within a site. For sites located in proximity to a free-face,
the amount of lateral ground displacement is correlated with the distance of the site from the
free-face. Other factors such as earthquake magnitude, distance from the causative fault,
thickness of the liquefiable layers, and the fines content and particle sizes of the liquefiable
layers also influence the amount of lateral ground displacement.
Based on the topography of the site, the distance to the free-face, the thickness of the poten-
tially liquefiable layer, and the corrected sampler blow counts (i.e., [N1]60-CS) within the
liquefiable layers that are in excess of 15, the site is considered to be susceptible to seismi-
cally induced lateral spread. Our evaluation of lateral spread indicates that up to about
7 inches of lateral displacement may occur at the southern abutment in the direction of the
lagoon following the seismic event. However, lateral spread may be mitigated through the
use of deep foundations and the removal and recompaction of the surface soils at the site.
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7.7. Landslides
Landslides may be induced by strong vibratory motion produced by earthquakes. Research
and historical data indicate that seismically induced landslides tend to occur in weak soil and
rock on sloping terrain. The process for zoning earthquake-induced landslides incorporates
expected future earthquake shaking, existing landslide features, slope gradient and strength
of earth materials on the slope. The project area is not mapped in an area considered suscep-
tible to seismically induced landslides. Based on our review of the relevant geologic maps,
aerial photographs, and our geologic reconnaissance, landslide hazards are not a design con-
sideration for the project.
7.8. Tsunamis and Seiches
Tsunamis are long wavelength seismic sea waves (long compared to ocean depth) generated
by the sudden movements of the ocean floor during submarine earthquakes, landslides, or
volcanic activity. Seiches are waves generated in a large enclosed body of water. Based on
our review of the tsunami hazards map prepared by the CDMG (1972) and the location of
the site from the Pacific Ocean and nearby large lakes and/or reservoirs, damage due to tsu-
namis or seiches is a design consideration. Appropriate mitigation measures, if applicable,
should be considered in project planning.
8. CONCLUSIONS
Based on our review of the referenced background data, geologic field reconnaissance, subsur-
face exploration, and laboratory testing, it is our opinion that construction of the proposed project
is feasible from a geotechnical standpoint. Geotechnical considerations include the following:
• Based on our observations during the subsurface evaluation, the project site is underlain by
fill, alluvium, old paralic deposits, and materials of the Santiago Formation.
• The on-site materials are expected to be excavatable with conventional heavy-duty earth-
moving equipment in good working condition. However, strongly cemented “concretions”
or zones are likely to be encountered within the Santiago Formation and will entail the use
of heavy drilling, ripping, or rock breaking equipment.
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• Based on current project plans, a significant portion of the jack-and-bore and microtunneling
segments will be performed through Santiago Formation materials. Materials of the Santiago
Formation contain a high percentage of silica grains and variable states of cementation. High
wear rates for tunneling or drilling machinery operating in Santiago Formation materials
should be anticipated.
• Groundwater was encountered in our exploratory borings for the Agua Hedionda Lagoon
pipeline crossing at or near sea level. Perched groundwater was encountered in several bor-
ings along the pipeline alignment at elevations ranging from 29 to 41 feet MSL.
• No active faults are reported underlying or adjacent to the site. The active Rose Canyon
Fault zone has been mapped approximately 4.6 miles west of the site.
• The majority of the site soils are granular and may be used in the trench zone. However,
clayey soils were encountered in several of the borings and are not suitable for use in the
trench zone.
• Based on Caltrans criteria, the project site would be classified as corrosive.
9. RECOMMENDATIONS
Based on our understanding of the project, the following recommendations are provided for the
design and construction of the proposed lift station, the cut-and-cover trench sections, and the
jack-and-bore and microtunneling sections of the sewer pipeline.
9.1. Earthwork
In general, earthwork should be performed in accordance with the recommendations pre-
sented in this report. Ninyo & Moore should be contacted for questions regarding the
recommendations or guidelines presented herein. In addition, Typical Earthwork Guidelines
for the project are included as Appendix C. In the event of a conflict, the recommendations
presented in the following sections of this report should supersede those in Appendix C.
9.1.1. Site Preparation
Prior to excavation, the project site should be cleared of abandoned utilities (if present)
and stripped of rubble, debris, vegetation, any loose, wet, or otherwise unstable soils, as
well as surface soils containing organic material. Materials generated from the clearing
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operations should be removed from the site and disposed of at a legal dumpsite away
from the project area.
9.1.2. Excavation Characteristics
Our evaluation of the excavation characteristics of the on-site materials at the subject
site is based on the results of our subsurface exploration and our experience with similar
materials. In our opinion, the on-site materials are expected to be excavatable with nor-
mal heavy-duty earthmoving equipment. However, strongly cemented “concretions”
and/or zones within the Santiago Formation will be encountered which will entail the
use of heavy drilling, ripping, or rock breaking equipment. Excavations close to or be-
low groundwater will encounter wet and loose or soft ground conditions.
9.1.3. Remedial Grading for Lift Station Building Pad Areas
Due to the compressible nature of the near-surface fill materials, we recommend that the
existing fill soils be removed from the lift station building pad areas and replaced with
compacted fill. The removal operation should extend to competent formational or allu-
vial materials. For the purpose of this report, a building pad is defined as the area
underlying any settlement-sensitive structure and extending a horizontal distance of
5 feet beyond the limits of the structure and extending downward at a 1:1 (horizontal to
vertical) inclination. Deeper removals may be needed if unsuitable materials are ex-
posed at the excavation bottom during grading. The depth and extent of the removal
should be further evaluated in the field by Ninyo & Moore.
The resultant excavation subgrade should be scarified to a depth of 8 inches, moisture
conditioned to a moisture content generally above the laboratory optimum and recom-
pacted to a relative compaction of 90 percent as evaluated by the American Society for
Testing and Materials (ASTM) Test Method D 1557.
Wet soils may be encountered in the remedial excavations and the subsequent drying
and additional handling of these soils should be anticipated. Loose, soft, or otherwise
deleterious material encountered at the bottom of excavation should be overexcavated
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and recompacted in accordance with the recommendations provided herein. Additional
stabilization efforts may be used in lieu of the additional removal at the bottom of the
excavations, Ninyo & Moore should be consulted regarding the usage of an approxi-
mately 1-foot thick layer of crushed aggregate into the excavation in conjunction with
geosynthetic materials or placement of a lean concrete mud mat.
9.1.4. Materials for Fill
On-site soils with an organic content of less than approximately 3 percent by volume (or
1 percent by weight) are suitable for use as fill. Fill material should generally not con-
tain rocks or lumps over approximately 4 inches, and generally not more than
approximately 40 percent larger than ¾-inch. Utility trench backfill material should not
contain rocks or lumps over approximately 3 inches in general. Soils classified as silts
or clays should not be used for backfill in the pipe zone. Larger chunks, if generated
during excavation, may be broken into acceptably sized pieces or disposed of off site.
Imported fill material, if needed for the project, should generally be granular soils with
a very low to low expansion potential (i.e., an EI of 50 or less as evaluated by
ASTM D 4829). Import material should also be non-corrosive in accordance with the
Caltrans (2003) corrosion guidelines. Materials for use as fill should be evaluated by
Ninyo & Moore’s representative prior to filling or importing.
9.1.5. Compacted Fill
Prior to placement of compacted fill, the contractor should request an evaluation of the
exposed ground surface by Ninyo & Moore. Unless otherwise recommended, the exposed
ground surface should then be scarified to a depth of approximately 8 inches and watered
or dried, as needed, to achieve moisture contents generally above the optimum moisture
content. The scarified materials should then be compacted to a relative compaction of
90 percent as evaluated in accordance with ASTM D 1557. The evaluation of compaction
by the geotechnical consultant should not be considered to preclude any requirements for
observation or approval by governing agencies. It is the contractor's responsibility to no-
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tify the geotechnical consultant and the appropriate governing agency when the project
area is ready for observation, and to provide reasonable time for that review.
Fill materials should be moisture conditioned to generally above the laboratory opti-
mum moisture content prior to placement. The optimum moisture content will vary with
material type and other factors. Moisture conditioning of fill soils should be generally
consistent within the soil mass. Prior to placement of additional compacted fill material
following a delay in the grading operations, the exposed surface of previously compacted
fill should be prepared to receive fill. Preparation may include scarification, moisture
conditioning, and recompaction.
Compacted fill should be placed in horizontal lifts of approximately 8 inches in loose
thickness. Prior to compaction, each lift should be watered or dried as needed to achieve
a moisture content generally above the laboratory optimum, mixed, and then compacted
by mechanical methods, using sheepsfoot rollers, multiple-wheel pneumatic-tired rollers
or other appropriate compacting rollers, to a relative compaction of 90 percent as evalu-
ated by ASTM D 1557. Successive lifts should be treated in a like manner until the
desired finished grades are achieved.
9.2. Temporary Excavations
We recommend that trenches and excavations be designed and constructed in accordance
with Occupational Safety and Health Administration (OSHA) regulations. These regulations
provide trench sloping and shoring design parameters for trenches up to 20 feet deep based
on the soil types encountered. Trenches over 20 feet deep should be designed by the Con-
tractor’s engineer based on site-specific geotechnical analyses. For planning purposes, we
recommend that the following OSHA soil classifications be used:
Fill, Alluvium, and Old Paralic Deposits Type C
Santiago Formation Type B
Upon making the excavations, the soil/rock classifications and excavation performance should
be evaluated in the field by Ninyo & Moore in accordance with OSHA regulations. Temporary
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excavations should be constructed in accordance with OSHA recommendations. For trench or
other excavations, OSHA requirements regarding personnel safety should be met by using ap-
propriate shoring (including trench boxes) or by laying back the slopes no steeper than
1.5:1 (horizontal to vertical) in fill, alluvium, or old paralic deposits and 1:1 in Santiago For-
mation. Temporary excavations that encounter seepage may need shoring or may be stabilized
by placing sandbags or gravel along the base of the seepage zone. Excavations encountering
seepage should be evaluated on a case-by-case basis. Wet soils may be subject to pumping un-
der heavy equipment loads. On-site safety of personnel is the responsibility of the contractor.
9.3. Shoring
It is anticipated that segments of the sewer pipeline will be installed with conventional cut-
and-cover trench methods and other segments will use trenchless methods. We anticipate that
shoring systems with bracings will be installed for the jacking and receiving pits as well as for
trenches over 4 feet deep. Shoring systems will be constructed through fill, alluvium, old
paralic deposits, and Santiago Formation materials. The shoring system should be designed
using the lateral earth pressures shown on Figure 5 for cantilevered shoring and Figure 6 for
braced shoring. The recommended design pressures are based on the assumptions that the
shoring system is constructed without raising the ground surface elevation behind the sheet
piles, that there are no surcharge loads, such as soil stockpiles and construction materials,
and that no loads act above a 1:1 (horizontal to vertical) plane extending up and back from
the base of the sheet pile system. The contractor should include the effect of any surcharge
loads on the lateral pressures against the sheet pile wall.
We anticipate that settlement of the ground surface will occur behind the shoring wall during
excavation. The amount of settlement depends heavily on the type of shoring system, the
shoring contractor’s workmanship, and soil conditions. We recommend that struc-
tures/improvements in the vicinity of the planned shoring installation be reviewed with
regard to foundation support and tolerance to settlement. To reduce the potential for distress
to adjacent improvements, we recommend that the shoring system be designed to reduce the
ground settlement behind the shoring system to ½-inch or less. Possible causes of settlement
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that should be addressed include settlement during shoring installation, excavations, con-
struction vibrations, dewatering, and removal of the support system.
The contractor should retain a qualified and experienced engineer to design the shoring sys-
tem, evaluate the adequacy of these parameters and provide modifications for the design.
Shoring plans should be reviewed by the district design engineer. We recommend that the
contractor take appropriate measures to protect workers. OSHA requirements pertaining to
worker safety should be observed.
9.4. Excavation Bottom Stability
In general, we anticipate that the bottom of the excavations will be stable and should provide
suitable support to the proposed improvements. Excavations that are close to or below the
water table (if encountered) may be unstable. In general, unstable bottom conditions may be
mitigated by overexcavating the excavation bottom to suitable depths and replacing with
compacted fill. Recommendations for stabilizing excavation bottoms should be based on
evaluation in the field by the geotechnical consultant at the time of construction.
9.5. Construction Dewatering
Groundwater was encountered in our exploratory borings. In addition, significant fluctua-
tions in the groundwater levels may occur along the pipeline alignment. Dewatering
measures during excavation operations (if necessary) should be prepared by the contractor’s
engineer and reviewed by the district design engineer. Considerations for construction dewa-
tering should include anticipated drawdown, volume of pumping, potential for settlement,
and groundwater discharge. Disposal of groundwater should be performed in accordance
with guidelines of the Regional Water Quality Control Board (RWQCB).
9.6. Pipe Jacking
We understand that HDD and jack-and-bore methods may be used for the pipeline installa-
tion. Based on our review of the current plans, primarily dense sand and sandstone/siltstone
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may be encountered at the anticipated elevations of the proposed HDD and jack-and-bore
segments of the pipeline. The contractor should take appropriate measures to reduce the loss
of material at the casing head. We recommend that an experienced specialty contractor be
used for the HDD and jack-and-bore operations.
Minor ground surface settlements may occur from the pipe jacking operations. However,
due to the depth of the proposed pipeline, these settlements are not anticipated to impact sur-
face improvements and underground utilities, provided an experienced contractor performs
the work. In order to evaluate the load factors on the 34- and 60-inch sleeves for the pro-
posed 29- and 54-inch pipelines, the loading presented in the following table should be used.
Table 2 – Loading on HDD and Jack-and-Bore Segments of Pipeline
Approximate Depth from Existing
Ground Surface to Top of Pipeline
(feet)
Load on 34” Pipeline
(pounds/lineal foot of pipe)
Load on 60” Pipeline
(pounds/lineal foot of pipe)
5 975 2,240
10 1,500 3,840
15 1,800 5,000
20 1,970 5,830
25 2,060 6,430
30 2,120 6,860
Notes:
Linear interpolation may be used to obtain loading between the depths shown. Loading assumes 34- and 60-inch sleeve
diameter of trenchless section. Loading may need to be modified for different sleeve sizes.
9.7. Lateral Pressures for Thrust Blocks
Thrust restraint for buried pipelines may be achieved by transferring the thrust force to the soil
outside the pipe through a thrust block. Thrust blocks may be designed using the lateral pas-
sive earth pressures presented on Figure 7. Thrust blocks should be backfilled with granular
backfill material, and compacted in accordance with recommendations presented in this report.
9.8. Modulus of Soil Reaction
We anticipate some trenching will be used on this project. The modulus of soil reaction is
used to characterize the stiffness of soil backfill placed at the sides of buried flexible pipe-
lines for the purpose of evaluating deflection caused by the weight of the backfill above the
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pipe. For pipelines constructed in granular fill, alluvium, old paralic deposits, and Santiago
Formation materials, we recommend that a modulus of soil reaction of 1,000 pounds per
square inch (psi) be used for design for 0 to 10 feet deep excavations and 1,500 psi for exca-
vations exceeding 10 feet depth, provided that granular bedding material is placed adjacent
to the pipe, as recommended in this report.
9.9. Pipe Bedding
We recommend that pipes be supported on 6 inches or more of granular bedding material
such as sand with a Sand Equivalent (SE) value of 30 or more. Bedding material should be
placed around the pipe and 12 inches or more above the top of the pipe in accordance with
the recent edition of the Standard Specifications for Public Works Construction (“Green-
book”). We do not recommend the use of crushed rock as bedding material. It has been our
experience that the voids within a crushed rock material are sufficiently large to allow fines
to migrate into the voids, thereby creating the potential for sinkholes and depressions to de-
velop at the ground surface. Where wet and loose or soft soil conditions are encountered, the
trench excavation should be extended to approximately 1 foot or more below the pipe invert
elevation and should be backfilled with gravel wrapped in filter fabric.
Special care should be taken not to allow voids beneath and around the pipe. Compaction of
the bedding material and backfill should proceed up both sides of the pipe. Trench backfill,
including bedding material, should be placed in accordance with the recommendations pre-
sented below.
9.10. Trench Backfill
Fill material, including trench backfill and structure backfill, should consist of granular soil
with low expansion potential that conforms to the latest edition of the Standard Specifica-
tions for Public Works Construction (“Greenbook”) for structure backfill. The clayey
fill/alluvial materials are not considered suitable for usage as trench zone (intermediate)
backfill. The contractor should be prepared to import soil to the site. The sandy fill, old
paralic deposits and Santiago Formation materials are considered suitable for re-use as struc-
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tural fill material. Fill material should be comprised of low-expansion-potential granular soil
and should be free of trash, debris, roots, vegetation, or deleterious materials. Fill should
generally be free of rocks or hard lumps of material in excess of 4 inches in diameter. Rocks
or hard lumps larger than about 4 inches in diameter should be broken into smaller pieces or
should be removed from the site. Wet materials generated from on-site excavations should
be aerated to a moisture content near the laboratory optimum to allow compaction.
On-site clayey and organic soils encountered during excavation should be selectively re-
moved and stockpiled separately. The clayey and organic soils are not considered suitable
for bedding material or structural fill and should be disposed of off site.
Imported materials should consist of clean, granular materials with a low expansion potential,
corresponding to an expansion index of 50 or less as evaluated in accordance with
ASTM D 4829. The corrosion potential of proposed imported soils should also be evaluated if
structures will be in contact with the imported soils. Import material should be submitted to
the geotechnical consultant for review prior to importing to the site. The contractor should be
responsible for the uniformity of import material brought to the site.
9.11. Fill Placement and Compaction
Fill, structure backfill, and trench backfill should be compacted in horizontal lifts to a rela-
tive compaction of 90 percent or more as evaluated by ASTM D 1557. Aggregate base and
the upper 12 inches of subgrade beneath pavement areas should be compacted to a relative
compaction of 95 percent or more. Fill soils should be placed at or above the laboratory op-
timum moisture content as evaluated by ASTM D 1557. The optimum lift thickness of fill
will depend on the type of compaction equipment used, but generally should not exceed
8 inches in loose thickness. Special care should be taken to avoid pipe damage when com-
pacting trench backfill above the pipe.
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9.12. Seismic Design Parameters
Design of the proposed improvements should be performed in accordance with the require-
ments of governing jurisdictions and applicable building codes. Table 3 presents the seismic
design parameters for the site in accordance with CBC (2007) guidelines and mapped spec-
tral acceleration parameters (USGS, 2008).
Table 3 – Seismic Design Factors
Factors Values
Site Class D
Site Coefficient, Fa 1.0
Site Coefficient, Fv 1.504
Mapped Short Period Spectral Acceleration, SS 1.318g
Mapped One-Second Period Spectral Acceleration, S1 0.496g
Short Period Spectral Acceleration Adjusted For Site Class, SMS 1.318g
One-Second Period Spectral Acceleration Adjusted For Site Class, SM1 0.746g
Design Short Period Spectral Acceleration, SDS 0.879g
Design One-Second Period Spectral Acceleration, SD1 0.498g
9.13. Foundations
The following foundation design parameters are provided based on our geotechnical analy-
sis. The foundation design parameters are not intended to preclude differential movement of
soils. Minor cracking (considered tolerable) of foundations may occur. Based on our under-
standing of the project, the proposed lift station will be a relatively light structure and is
anticipated to be founded on spread and/or continuous foundations.
9.13.1. Shallow Foundations
Shallow foundations, either spread or continuous foundations, founded entirely in prop-
erly compacted fill or in competent alluvial or formational materials may be designed
based on an allowable bearing capacity of 2,000 pounds per square foot (psf). The al-
lowable bearing capacity value may be increased by one-third when considering loads
of short duration such as wind or seismic forces. Foundations should be founded at least
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18 inches below lowest adjacent grade. Continuous footings should have a width of
12 inches or more and isolated footings should be 24 inches or more in width.
We recommend that foundations be reinforced in accordance with the recommendations
of the project structural engineer. From a geotechnical standpoint, we recommend that
continuous footings be reinforced with four No. 4 reinforcing bars, two placed near the
top of the footing and two near the bottom.
9.13.2. Lateral Earth Pressures
Allowable lateral passive pressures equal to an equivalent fluid weight of 250 pounds
per cubic foot (pcf) may be used provided the footings are placed neat against com-
pacted fill soils or formational materials (to a maximum of 2,500 psf). Foundations may
be designed using a coefficient of friction between soil and concrete of 0.40.
9.13.3. Pile Foundations
Due to the potential for liquefaction and dynamic settlement within zones of loose fill
and alluvium below the water table, we recommend that the Agua Hedionda pipeline
crossing be supported on driven-pile foundations. Based on our discussions with the struc-
tural engineer, the allowable downward design (service) loads for the piles have been
assumed to be 140 kips (Dead Load ), 25 kips (Live Load) and 90 kips (Lateral Seismic
Load). The ultimate capacities and recommended lengths for 14-inch-square precast
prestressed concrete piles and 16-inch steel pipe piles (with 0.5-inch pipe thickness) were ana-
lyzed using the computer program AllPile (CivilTech Software, 2007b). A factor of safety of
2.0 has been used for downward and uplift capacities. The uplift capacity includes the pile
weight. The alluvial deposit soils have a potential for liquefaction in the portion below the
water table, should the design seismic event occur. The capacities presented in Table 4 include
the downward forces due to liquefaction. The ultimate soil capacity may exceed the pile
design capacity as a result of founding the piles in the dense alluvial material. The rec-
ommended tip elevations are based on a ground surface elevation of +10 feet above MSL.
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Table 4 – Summary of Pile Vertical Capacity Evaluation
Ultimate Capacity (kips) Pile Type
Design (Service)
Capacity
(kips) Compression Tension
Recommended Tip
Elevation
(feet, MSL)
14-inch Square Concrete 325 650 47 -18
16-inch Steel Pipe 190 380 46 -33
Lateral load capacities were evaluated assuming both fixed-head and free-head condi-
tions. The analysis was based on the liquefied condition assuming that the material
above the dense alluvial material has liquefied and does not provide resistance. Lateral
resistance is provided by the dense alluvial material. A summary of our evaluation of
lateral capacity is presented in Table 5.
Table 5 – Single Pile Lateral Load Capacity
14-inch Square Concrete 16-inch Steel Pipe Pile Design Parameters Fixed Head Free Head Fixed Head Free Head
Design Shaft Length (feet) 28 28 43 43
Axial Load (kips) 165 165 165 165
Lateral Load (kips) 90 90 90 90
Lateral Deflection of Shaft Head (inch) 7.1 60.4 3.3 18.6
Maximum Positive Moment (kip-foot) 800.8 1933.3 791.7 1408.3
Depth to Maximum Positive Moment (feet) 0.0 14.7 0.0 14.3
Maximum Negative Moment (kip-foot) -467.5 -4.1 -424.2 -78.8
Depth to Maximum Negative Moment (feet) 13.3 27.2 14.3 27.8
Depth to Zero Deflection (feet) 26.6 27.5 28.2 29.5
Our analyses did not account for dynamic loads due to inertial loads from the bridge dur-
ing the design earthquake. However, we assumed that the dynamic loads would not be
higher than the lateral capacities for each pile. Maximum moments generated by the indi-
cated deflections are based on geotechnical considerations. We recommend that the
maximum moment capacities of the piles be evaluated by the structural engineer. Results
for different pile lengths and embedment conditions may be different from those presented.
For lateral loading, piles in a group may be considered to act individually when the cen-
ter-to-center spacing is greater than 3D (where, D is the diameter of the pile) in the
direction normal to loading and greater than 8D in the direction parallel to loading. Ta-
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ble 6 presents the lateral load reduction factors based on a compilation presented by
Mokwa (1999) to be applied for various pile spacings for in-line loading.
Table 6 – Lateral Load Group Reduction Factors
Center-to-Center Pile
Spacing for In-Line Loading
Group Efficiency (Ratio of Lateral Resistance of
Pile in a Group to Single Pile)
8D 1.00
7D 0.94
6D 0.88
5D 0.82
4D 0.76
3D 0.70
9.13.4. Driven Pile Installation
Driven piles should be placed in general accordance with the following recommenda-
tions, and the recommendations of the project structural engineer. Piles should be
checked for alignment and plumbness. The acceptable misalignment of a pile should be
no more than 3 inches from the exact location. The plumbness of the pile should be
within two percent of the plumb position. Piles should be spaced no closer than
2½ times the nominal diameter or dimension of the pile (center-to-center).
Due to the presence of asphalt and/or concrete pavement, predrilling or removal of the
pavement before pile driving will be required. The pile hammer should be an approved,
steam and/or diesel hammer. It should be capable of developing sufficient energy to
drive piles at a penetration rate of not less than ⅛-inch per blow at the design load. For a
design (service) load of 165 kips, a hammer energy of 45,000 ft-lb. or more should be
considered. We recommend that prior to production, that a program of indicator piles be
performed to further evaluate actual pile driving conditions, pile capacities, needed pile
lengths and corresponding embedments. The geotechnical consultant should observe the
pile driving operations.
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9.14. Retaining Walls and Abutment Walls
Retaining walls are proposed at the subject site. For the design of a retaining wall that is not
restrained against movement by rigid corners or structural connections, an active pressure rep-
resented by an equivalent fluid weight of 40 pcf may be assumed. Restrained walls (non-
yielding) may be designed for an at-rest pressure represented by an equivalent fluid weight of
60 pcf. This pressure assumes low-expansive, level backfill and free draining conditions.
Yielding and restrained walls retaining sloping backfill inclined at 2:1 may be designed using
equivalent fluid weights of 65 pcf and 95 pcf, respectively. A drain should be provided behind
the retaining wall as shown on Figure 8. The drain should be connected to an appropriate out-
let. Retaining walls may be founded on a continuous footing based completely in compacted
fill or in formational materials. The foundation may be designed in accordance with our rec-
ommendations presented under the Shallow Foundations section.
For design of pile caps and abutment walls, active lateral earth pressure represented by an
equivalent fluid weight of 40 pcf above groundwater and 19 pcf below groundwater may be
assumed for a level backfill condition. The active earth pressures should be increased to 64
and 31 pcf for a sloping backfill with a 2:1 (horizontal to vertical) slope ratio above and below
groundwater, respectively. Hydrostatic pressure should be added to the recommended active
earth pressure for a submerged backfill. Passive lateral earth pressure resistance represented by
an equivalent fluid weight of 360 pcf above groundwater and 173 pcf below groundwater may
be used. The passive earth pressure values assume lateral soil cover extending 10 feet or more
horizontally from the pile cap. For a 2:1 (horizontal to vertical) sloping ground condition adja-
cent to the pile cap, passive earth pressure should be reduced to 135 and 65 pcf for dry and
submerged conditions, respectively. Hydrostatic pressure should be added to the passive resis-
tance under submerged condition.
9.15. Underground Structures
Underground structures at the lift station may be designed for lateral pressures represented by
the pressure diagram on Figure 9. We recommend the groundwater level should be assumed at
an elevation of +1 feet MSL for evaluation of lateral pressures. It is recommended that the ex-
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terior of all underground walls, horizontal and vertical construction joints be waterproofed, as
indicated by the project civil engineer and/or architect. For pipe wall penetrations into the
storage tank, standard “water-tight” penetration design should be utilized. To minimize rela-
tive pipe to wall differential settlement, which could cause pipe shearing, we recommend that
a pipe joint be located close to the exterior of the wall. The type of joint should be such that
minor relative movement can be accommodated without distress.
9.16. Uplift and Special Design Considerations
We recommend that the underground structures be designed to resist hydrostatic uplift in accor-
dance with Figure 10. Alternative design measures for resisting the anticipated uplift pressure
could include installation of vertical anchors, increasing mass by constructing a thicker concrete
mat foundation, or extending the foundation a selected distance outside the exterior walls of the
storage tank (flanges). The resistance to uplift may then be taken as the sum of the weight of the
storage tank and the weight of the soil wedge within the zone of influence of the flanges shown
on Figure 10. We recommend that the groundwater level be assumed at an elevation of +1 feet
above MSL when calculating the factor of safety against uplift.
9.17. Drainage
Roof and pad drainage should be diverted away from structures to suitable discharge areas
by nonerodible devices (e.g., gutters, downspouts, concrete swales, etc.). Positive drainage
adjacent to structures should be established and maintained. Positive drainage may be ac-
complished by providing drainage away from the foundations of the structure at a gradient
of 2 percent or steeper for a distance of 5 feet outside the building perimeter, and further
maintained by a graded swale leading to an appropriate outlet, in accordance with the rec-
ommendations of the project civil engineer and/or landscape architect.
Surface drainage on the site should generally be provided so that water is not permitted to
pond. A gradient of 2 percent or steeper should be maintained over the pad area and drainage
patterns should be established to divert and remove water from the site to appropriate out-
lets. Care should be taken by the contractor during grading to preserve any berms, drainage
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terraces, interceptor swales or other drainage devices on or adjacent to the property. Drain-
age patterns established at the time of grading should be maintained for the life of the
project. The property maintenance personnel should be made aware that altering drainage
patterns might be detrimental to foundation performance.
9.18. Preliminary Pavement Design
We understand that an asphalt concrete-paved access drive may be constructed on the site
from Avenida Encinas to the lift station. For planning purposes we are providing preliminary
pavement designs. Laboratory testing was performed on representative samples of the on-site
soils to evaluate R-value. The tests were performed in general accordance with California
Test (CT) Method 301 and the results are presented in Appendix B. The test results indicate R-
values ranging from 58 to 66 for the samples tested. We have used an R-value of 58 for the de-
sign of flexible pavements at the project site. Actual pavement recommendations should be
based on R-value tests performed on bulk samples of the soils that are exposed at the finished
subgrade elevations in the areas to be paved once grading operations have been performed.
For design we have used Traffic Indices (TI) of 5.0 for parking areas, 6.0 for site drives, and
7.0 for truck traffic areas. The preliminary recommended pavement sections are as follows:
Table 7 – Recommended Pavement Sections
Area R-Value Traffic
Index
Asphalt
Concrete
(inches)
Class 2 Aggregate Base
(inches)
Parking 58 5.0 3.0 4.0
Driveways 58 6.0 4.0 4.0
Truck Traffic 58 7.0 4.0 6.0
If traffic loads are different from those assumed, the pavement design should be re-evaluated.
In addition, we recommend that the upper 12 inches of the subgrade and the Class 2 aggregate
base be compacted to a relative compaction of 95 percent as evaluated by ASTM D 1557.
We suggest that consideration be given to using portland cement concrete (PCC) pavements
in areas where dumpsters will be stored and where refuse trucks will stop and load. Experi-
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ence indicates that refuse truck traffic can significantly shorten the useful life of asphalt con-
crete sections. We recommend that in these areas, 6-inch thick PCC pavement with a
flexural strength of 600 psi reinforced with No. 3 bars, 18 inches on center, be placed over
18 inches of very low to low expansive soil compacted in accordance with the recommenda-
tions presented under Compacted Fill.
9.19. Corrosion
Laboratory testing was performed on representative samples of the on-site soils to evaluate
pH and electrical resistivity, as well as chloride and sulfate contents. The pH and electrical
resistivity tests were performed in accordance with CT 643 and the sulfate and chloride con-
tent tests were performed in accordance with CT 417 and 422, respectively. These laboratory
test results are presented in Appendix B.
The results of the corrosivity testing indicated electrical resistivities ranging from 540 to
3,685 ohm-cm, soil ph values ranging from 6.0 to 6.4, chloride contents ranging from 140 to
2,625 parts per million (ppm), and sulfate contents ranging from 0.005 to 0.054 percent (i.e.,
50 to 540 ppm). Based on the Caltrans (2003) criteria, the project site would be classified as
corrosive, which is defined as a site having soils with more than 500 ppm of chlorides, more
than 0.2 percent sulfates or a pH less than 5.5.
9.20. Concrete
Concrete in contact with soil or water that contains high concentrations of soluble sulfates
can be subject to chemical deterioration. Laboratory testing indicated sulfate contents rang-
ing from 0.005 to 0.054 percent for the tested samples. Based on the American Concrete
Institute (ACI) criteria (2005), the potential for sulfate attack is negligible for water-soluble
sulfate contents in soils ranging from about 0.0 to 0.10 percent by weight (0 to 1,000 ppm)
and Type II cement may be used for concrete construction. However, due to the potential
variability of site soils, consideration should be given to using Type V cement and concrete
with a water-cement ratio no higher than 0.45 by weight for normal weight aggregate con-
crete and a 28-day compressive strength of 4,500 psi or more for the project.
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In order to reduce the potential for shrinkage cracks in the concrete during curing, we recom-
mend that for slabs-on-grade, the concrete be placed with a slump in accordance with Table
5.2.1 of Section 302.1R of The Manual of Concrete Practice, “Floor and Slab Construction,”
or Table 2.2 of Section 332R in The Manual of Concrete Practice, “Guide to Residential Cast-
in-Place Concrete Construction.” If a higher slump is needed for screening and leveling, a su-
per plasticizer is recommended to achieve the higher slump without changing the required
water-to-cement ratio. The slump should be checked periodically at the site prior to concrete
placement. We also recommend that crack control joints be provided in slabs in accordance
with the recommendations of the structural engineer to reduce the potential for distress due to
minor soil movement and concrete shrinkage. We further recommend that concrete cover over
reinforcing steel for slabs-on-grade and foundations be in accordance with CBC 1907.7. The
structural engineer should be consulted for additional concrete specifications.
9.21. Pre-Construction Conference
We recommend that a pre-construction meeting be held prior to commencement of construc-
tion. The owner or his representative, the agency representatives, the civil engineer, Ninyo &
Moore, and the contractor(s) should be in attendance to discuss the plans, the project, and
the proposed construction schedule.
9.22. Plan Review and Construction Observation
The conclusions and recommendations presented in this report are based on analysis of ob-
served conditions in widely spaced exploratory excavations. If conditions are found to vary
from those described in this report, Ninyo & Moore should be notified, and additional recom-
mendations will be provided upon request. Ninyo & Moore should review the final project
drawings and specifications prior to the commencement of construction. Ninyo & Moore
should perform the needed observation and testing services during construction operations.
The recommendations provided in this report are based on the assumption that Ninyo &
Moore will provide geotechnical observation and testing services during construction. In the
event that it is decided not to utilize the services of Ninyo & Moore during construction, we
Agua Hedionda Lift Station and Force Main August 3, 2009
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request that the selected consultant provide the client with a letter (with a copy to Ninyo &
Moore) indicating that they fully understand Ninyo & Moore’s recommendations, and that
they are in full agreement with the design parameters and recommendations contained in this
report. Construction of proposed improvements should be performed by qualified subcon-
tractors utilizing appropriate techniques and construction materials.
10. LIMITATIONS
The field evaluation, laboratory testing, and geotechnical analyses presented in this geotechnical
report have been conducted in general accordance with current practice and the standard of care
exercised by geotechnical consultants performing similar tasks in the project area. No warranty,
expressed or implied, is made regarding the conclusions, recommendations, and opinions pre-
sented in this report. There is no evaluation detailed enough to reveal every subsurface condition.
Variations may exist and conditions not observed or described in this report may be encountered
during construction. Uncertainties relative to subsurface conditions can be reduced through addi-
tional subsurface exploration. Additional subsurface evaluation will be performed upon request.
Please also note that our evaluation was limited to assessment of the geotechnical aspects of the
project, and did not include evaluation of structural issues, environmental concerns, or the pres-
ence of hazardous materials.
This document is intended to be used only in its entirety. No portion of the document, by itself, is
designed to completely represent any aspect of the project described herein. Ninyo & Moore
should be contacted if the reader requires additional information or has questions regarding the
content, interpretations presented, or completeness of this document.
This report is intended for design purposes only. It does not provide sufficient data to prepare an
accurate bid by contractors. It is suggested that the bidders and their geotechnical consultant per-
form an independent evaluation of the subsurface conditions in the project areas. The independent
evaluations may include, but not be limited to, review of other geotechnical reports prepared for
the adjacent areas, site reconnaissance, and additional exploration and laboratory testing.
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Our conclusions, recommendations, and opinions are based on an analysis of the observed site
conditions. If geotechnical conditions different from those described in this report are encountered,
our office should be notified, and additional recommendations, if warranted, will be provided upon
request. It should be understood that the conditions of a site could change with time as a result of
natural processes or the activities of man at the subject site or nearby sites. In addition, changes to
the applicable laws, regulations, codes, and standards of practice may occur due to government ac-
tion or the broadening of knowledge. The findings of this report may, therefore, be invalidated over
time, in part or in whole, by changes over which Ninyo & Moore has no controls.
This report is intended exclusively for use by the client. Any use or reuse of the findings, conclu-
sions, and/or recommendations of this report by parties other than the client is undertaken at said
parties’ sole risk.
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11. REFERENCES
American Concrete Institute, 2005, Building Code Requirements for Structural Concrete
(ACI 318-05) and Commentary (ACI 318R-05).
Blake, T.F., 2001, FRISKSP (Version 4.00) A Computer Program for the Probabilistic Estimation of
Peak Acceleration and Uniform Hazard Spectra Using 3-D Faults as Earthquake Sources.
California Building Standards Commission, 2007, California Building Code, Title 24, Part 2,
Volumes 1 and 2.
California Division of Mines and Geology, 1963, Geology and Mineral Resources of San Diego
County, California: County Report 3.
California Department of Conservation, Division of Mines and Geology, 1972, Tsunami Hazards
Map of California, Seismic Safety Information Bulletin 72-5 and 72-6, dated July.
California Geological Survey, 2008, Guidelines for Evaluating and Mitigating Seismic Hazards in
California, Special Publication 117A.
California Division of Mines and Geology, 1998, Maps of Known Active Fault Near-Source Zones in
California and Adjacent Portions of Nevada: International Conference of Building Officials.
California Department of Transportation (Caltrans), 2003, Corrosion Guidelines (Version 1.0), Divi-
sion of Engineering and Testing Services, Corrosion Technology Branch: dated September.
Cao, T., Bryant, W.A., Rowshandel, B., Branum, D., and Wills, C.J., California Geological Sur-
vey (CGS), 2003, The Revised 2002 California Probabilistic Seismic Hazard Maps.
CivilTech Software, 2007a, LiquefyPro (Version 5.5c), A Computer Program for Liquefaction and
Settlement Analysis.
CivilTech Software, 2007b, AllPile (Version 7.9a), A Computer Program for Lateral, Downward
(compression), Uplift, Settlement, Group Analysis of Piles.
Hart, E.W., and Bryant, W.A., 1997, Fault-Rupture Hazard Zones in California, Alquist-Priolo
Earthquake Fault Zoning Act with Index to Earthquake Fault Zone Maps: California De-
partment of Conservation, Division of Mines and Geology, Special Publication 42, with
Supplements 1 and 2 added in 1999.
Ishihara, K., 1985, Stability of Natural Deposits During Earthquakes, Proceedings of the Elev-
enth International Conference on Soil Mechanics and Foundation Engineering, San
Francisco, CA, Vol. 1, pp. 321-376.
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Ishihara, K., 1995, Effects of At-Depth Liquefaction on Embedded Foundations During Earth-
quakes, Proceedings of the Tenth Asian Regional Conference on Soil Mechanics and
Foundation Engineering, August 29 through September 2, Beijing, China, Vol. 2, pp. 16-25.
Jennings, C.W., 1994, Fault Activity Map of California and Adjacent Areas: California Division
of Mines and Geology (CDMG), California Geologic Data Map No. 6, scale 1:750,000.
Kennedy, M.P. and Peterson, G.L., 1975, Geology of the San Diego Metropolitan Area, Califor-
nia: California Division of Mines and Geology, Bulletin 200.
Kennedy, Michael P. and Tan, Siang S., 2005, Geologic Map of the Oceanside 30’ x 60’ Quad-
rangle, California: Regional Geologic Map Series, 1:100,000 Scale.
Mokwa, Robert L., 1999, Investigation of the Resistance of Pile Caps to Lateral Loading, PhD
Thesis, Virginia Polytechnic Institute and State University.
Ninyo & Moore, In-House Proprietary Data.
Norris, R. M. and Webb, R. W., 1990, Geology of California, Second Edition: John Wiley & Sons, Inc.
Public Works Standards, Inc., 2006, “Greenbook,” Standard Specifications for Public Works
Construction.
Seed, H.B., and Idriss, I. M., 1982, Ground Motions and Soil Liquefaction During Earthquakes,
Volume 5 of Engineering Monographs on Earthquake Criteria, Structural Design, and
Strong Motion Records: Berkeley, Earthquake Engineering Research Institute.
Tokimatsu, K., and Seed, H.B., 1987, Evaluation of Settlements in Sands Due to Earthquake
Shaking, Journal of Geotechnical Engineering, American Society of Civil Engineers,
113(8), 861-878.
United States Department of the Interior, Bureau of Reclamation, 1989, Earth Manual.
United States Geological Survey, 1960 (photo-revised 1988), San Luis Rey Quadrangle, Califor-
nia, San Diego County, 7.5-Minute Series (Topographic): Scale 1:24,000.
United States Geological Survey/California Geological Survey, 2003, Probabilistic Seismic Haz-
ards Assessment Model for California.
United States Geological Survey, 2008 Ground Motion Parameter Calculator v. 5.0.9, World
Wide Web, http://earthquake.usgs.gov/research/hazmaps/design/.
Youd, T.L., Hansen, C.M., and Bartlett, S.F., 2002, Revised Multilinear Regression Equations for
Prediction of Lateral Spread Displacement: Journal of Geotechnical and Geoenvironmen-
tal Engineering, Vol. 128, No. 12, pp. 1007-1017.
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Youd, T.L., Idriss, I.M., Andrus, R.D., Arango, I., Castro, G., Christian, J.T., Dobry, R., Finn,
W.D., Harder, L.F., Hynes, M.E., Ishihara, K., Koester, J.P., Liao, S.S.C., Marcuson,
W.F., Martin, G.R., Mitchell, J.K., Moriwaki, Y., Power, M.S., Robertson, P.K., Seed,
R.B., and Stokoe, K.H., II., 2001, Liquefaction Resistance of Soils: Summary Report
from the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction
Resistance of Soils, Journal of Geotechnical and Geoenvironmental Engineering: Ameri-
can Society of Civil Engineering 124(10), pp. 817-833.
AERIAL PHOTOGRAPHS
Source Date Flight Numbers Scale
USDA 5-2-53 AXN-14M 18 & 19 1:20,000
PROJECT NO.
NOTE: ALL DIMENSIONS, DIRECTIONS AND LOCATIONS ARE APPROXIMATE.
REFERENCE: 2005 THOMAS GUIDE FOR SAN DIEGO COUNTY, STREET GUIDE AND DIRECTORY.
AGUA HEDIONDA LIFT STATION AND FORCE MAIN
CARLSBAD, CALIFORNIA
SITE LOCATION MAP
1
106044002fig 1 106044002 slm DATE
FIGURE
8/09
APPROXIMATE SCALE IN FEET
480024000
SITESITE
N
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M E X I C OUSA
San ClementeIsland
Santa CatalinaIsland
P A C I F I COCEAN
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SANTASUSANASIMI-S A N T A R O S A
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S A W P ITCAN Y O N
SUPERSTITION HILLS
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CALIFORNIA
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Kern County
Riverside CountySan Diego County Imperial County
Los Angeles County
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Orange County
Riverside CountySan Bernardino CountyL
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Co
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IndioIrvine
Pomona
Mojave
Anaheim
Barstow
Temecula
Palmdale
El CentroSan Diego
Escondido
Oceanside
SantaAna
Riverside
Tehachapi
Long Beach
Wrightwood
Chula Vista
Los Angeles
Victorville
SanClemente
PalmSprings
Big Bear CityThousandOaksSanBernardino
LakeArrowhead Twentynine Palms
Baker
Desert Center
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!
S a l t o n S e a
NOTES: ALL DIRECTIONS, DIMENSIONS AND LOCATIONS ARE APPROXIMATE
LEGEND
HOLOCENE ACTIVE
CALIFORNIA FAULT ACTIVITY
HISTORICALLY ACTIVE
LATE QUATERNARY (POTENTIALLY ACTIVE)
AGUA HEDIONDA LIFT STATION AND FORCE MAINCARLSBAD, CALIFORNIA
FAULT LOCATION MAP FIGURE
4PROJECT NO.DATE
106044002 8/09
SOURCE: FAULTS - CA DEPT OF CONSERVATION, 2000; BASE - ESRI, 2008
fig4_106044002_fault.mxdSTATE/COUNTY BOUNDARY
QUATERNARY (POTENTIALLY ACTIVE)
CALIFORNIA
0 25 5012.5 MILES
APPROXIMATE SCALE±
!
SITE