HomeMy WebLinkAboutCUP 2018-0023; BUENA VISTA RESERVOIR SITE (PARK); LIMITED GEOTECHNICAL INVESTIGATION BUENA VISTA RESERVOIR SITE; 2019-01-11- RECORD COPY
Initial Date
LIMITED
GEOTECHNICAL INVESTIGATION
BUENA VISTA RESERVOIR SITE
CARLSBAD, CALIFORNIA
PREPARED FOR
SCHMIDT DESIGN GROUP, INC.
SAN DIEGO, CALIFORNIA
FEBRUARY 9, 2018
REVISED JANUARY 11, 2019
PROJECT NO. G2225-52-01
RECORD COPY
Initial L)a te
LIMITED
GEOTECHNICAL INVESTIGATION
BUENA VISTA RESERVOIR SITE
CARLSBAD, CALIFORNIA
LAND DEVELOPMENT
ENGI NEERING
PREPARED FOR
SCHMIDT DESIGN GROUP, INC.
SAN DIEGO, CALIFORNIA
FEBRUARY 9, 2018
REVISED JANUARY 11, 2019
PROJECT NO. G2225-52-01
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(e-mail) Latitude 33 Planning and Engineering
Attention: Mr. Sean Scaramella
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GEOCON
INCORPORATED
GEOTECHNICAL U ENVIRONMENTAL. MATERIALS
Project No. G2225-52-01
February 9, 2018
Revised January 11, 2019
Schmidt Design Group, Inc.
1111 Sixth Avenue, Suite 500
San Diego, California 92101
Attention: Mr. JT Barr
Subject: LIMITED GEOTECHNICAL INVESTIGATION
BUENA VISTA RESERVOIR SITE
CARLSBAD, CALIFORNIA
Dear Mr. Barr:
In accordance with authorization of our Proposal No. LG-17239 dated September 21, 2017, we herein
submit the results of our limited geotechnical investigation for the subject site. We performed our
investigation to evaluate the underlying soil and geologic conditions and potential geologic hazards
and to assist in the design of the proposed park improvements. The accompanying report presents the
results of our study and conclusions and recommendations pertaining to the geotechnical aspects of the
proposed development. The site is considered suitable for development of a park provided the
recommendations of this report are followed.
Should you have questions regarding this report, or if we may be of further service, please contact the
undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
6960 Flanders Drive 0 Son Diego, California 92121-2974 U Telephone 858.558.6900 0 Fox 858.558.6159
TABLE OF CONTENTS
PURPOSE AND SCOPE .1
SITE AND PROJECT DESCRIPTION...........................................................................................
GEOLOGIC SETTING ..................................................................................................................... 2
SOIL AND GEOLOGIC CONDITIONS ........................................................................................2
4.1 Undocumented Fill (Qudf)....................................................................................................3
4.2 Old Paralic Deposits (Qop)....................................................................................................3
GROUNDWATER..........................................................................................................................3
GEOLOGIC HAZARDS .................................................................................................................4
6.1 Faulting and Seismicity.........................................................................................................4
6.2 Ground Rupture.....................................................................................................................6
6.3 Seiches and Tsunamis ............................ .................................................................
. .............. 6
6.4 Liquefaction and Seismically Induced Settlement.................................................................7
6.5 Landslides..............................................................................................................................7
CONCLUSIONS AND RECOMMENDATIONS...........................................................................8
7.1 General...................................................................................................................................8
7.2 Excavation and Soil Characteristics ......................................................................................9
7.3 Seismic Design Criteria.......................................................................................................10
7.4 Preliminary Grading Recommendations..............................................................................11
7.5 Excavation Slopes................................................................................................................12
7.6 Shallow Foundations...........................................................................................................13
7.7 Drilled Piers.........................................................................................................................14
7.8 Basketball Courts and Concrete Slabs-On-Grade ................................................................ 15
7.9 Concrete Flatwork...............................................................................................................16
7.10 Retaining Walls...................................................................................................................17
7.11 Lateral Loading .................................................................................................................... 19
7.12 Preliminary Flexible and Rigid Pavement Recommendations............................................20
7.13 Site Drainage and Moisture Protection................................................................................23
7.14 Grading and Foundation Plan Review.................................................................................23
LIMITATIONS AND UNIFORMITY OF CONDITIONS
MAPS AND ILLUSTRATIONS
Figure 1, Vicinity Map
Figure 2, Geologic Map
Figure 3, Geologic Cross-Sections
Figure 4, Wall/Column Footing Dimension Detail
Figure 5, Retaining Wall Loading Diagram
Figure 6, Typical Retaining Wall Drain Detail
APPENDIX A
FIELD INVESTIGATION
Figures A-I - A-] 4, Logs of Exploratory Trenches and Infiltration Test Pits
TABLE OF CONTENTS (Concluded)
APPENDIX B
LABORATORY TESTING
Table B-I, Summary of Laboratory Maximum Dry Density and Optimum Moisture Content Test Results
Table B-I!, Summary of Laboratory Direct Shear Test Results
Table B-I!!, Summary of Laboratory Expansion Index Test Results
Table B-IV, Summary of Laboratory Water-Soluble Sulfate Test Results
Table B-V, Summary of Laboratory R-Value Test Results
Figure B-I, Gradation Curves
APPENDIX C
STORM WATER INVESTIGATION
APPENDIX D
RECOMMENDED GRADING SPECIFICATIONS
LIST OF REFERENCES
LIMITED GEOTECHNICAL INVESTIGATION
1. PURPOSE AND SCOPE
This report presents the results of a limited geotechnical investigation related to the proposed public
park to be located in the City of Carlsbad, California (see Vicinity Map, Figure 1). The purpose of this
study is to evaluate the surface and subsurface soil conditions and general site geology, and to identify
geotechnical constraints that may affect development of the property. In addition, the purpose of this
report is to provide foundation design criteria, preliminary pavement recommendations, 2016 seismic
design criteria, concrete flatwork design criteria, retaining wall and lateral loading, and excavation
considerations. The scope of this geotechnical investigation also included a review of readily available
published and unpublished geologic literature (see List of References). A site and grading plan was not
available at the time of this report. To aid in preparing this report we have reviewed Survey Exhibit,
prepared by Latitude 33 Planning & Engineering, dated November 29, 2017 (Job No. 1587.00).
We performed a field investigation that included excavating 10 exploratory trenches to depths ranging
from 4 to 7 feet below existing grade. We also performed 4 test pits to perform infiltration testing
ranging from 3 to 4 feet below grade. The Geologic Map, Figure 2, presents the approximate location of
the trenches and infiltration tests/test pits. Appendix A shows the trench logs and other details of the field
investigation. We tested selected soil samples obtained during the field investigation to evaluate pertinent
physical and chemical soil properties for engineering analyses and to assist in providing
recommendations for site grading and development. Details of the laboratory tests and a summary of the
test results are presented in Appendix B and on the trench logs in Appendix A.
The Geologic Map, Figure 2, depicts the existing soil and geologic conditions. The plan depicts the
mapped geologic contacts based on our site reconnaissance and field excavations. The conclusions and
recommendations presented herein are based on analyses of the data reviewed as part of this study and
our experience with similar soil and geologic conditions.
2. SITE AND PROJECT DESCRIPTION
The site is located on the south side of Buena Vista Way, east of Highland Drive, west of Valley Street
and north of Newland Court in the City of Carlsbad, California (see Vicinity Map, Figure 1). Access to
the site is from a paved driveway along Buena Vista Way. The property contains an existing, out-of-
commission, Buena Creek water storage reservoir. The sides and bottom of the reservoir are below
grade, and the reservoir is uncovered. The concrete sides and bottom remain in place. Several
stockpiles of rock/asphalt/concrete materials exist on the bottom of the reservoir. The existing grades
on the site slope from the edges of the reservoir at approximate elevation 188 feet above Mean Sea
Level (MSL) down and away toward the edges of the property. The lowest portion of the property is at
the northwest corner at approximate elevation 164 feet MSL. The bottom of the reservoir is at about
elevation 177 feet MSL. From the eastern property line, the grades slope down at approximately 2.4 to
-1- February9,2018 Project No. G2225-52-01
Revised January 11, 2019
I (horizontal to vertical) to the top of retaining walls in the backyards of the residences to the east.
Some of the residences along the western side of the property have retaining walls up to 6 feet tall in
their backyards along the property line. An asphalt-lined swale exists several feet inside the western
property line on the northern half of the site.
We understand, based on preliminary information provided by you, that the preliminary concept for
the project includes constructing a new passive park. The proposed park will include a children's play
area, picnic area, gardens, shade structures, paved parking areas, hardscape and other associated
improvements. We understand that stormwater management devices are being proposed for the
northwest portion of the property and may consist of a swale and basin.
3. GEOLOGIC SETTING
The project site is located within the Peninsular Ranges Geomorphic Province. The region is
characterized by northwest-trending structural blocks and intervening fault zones. The rock types in
the Peninsular Ranges include igneous intrusive rocks associated with the Cretaceous-age Southern
California Batholith, intruded into older metavolcanic and/or metasedimentary units in western and
central San Diego County. In the western part of the county and along the coastal areas, the basement
rocks are overlain by a thick sequence of Cretaceous to Tertiary-age marine sedimentary formations,
which are the result of transgressive and regressive cycles of the sea. These deposits in turn are
partially covered by several Quaternary-age terrace deposits that young to the west.
The site is located on the western portion of the geologic coastal plane. The geologic unit nearest
existing grade is an Old Paralic Deposit designated as Units 2 4 with an approximate age varying
from 220,000 to 413,000 years old. This unit is estimated to be 30 to 40 feet thick and likely underlain
by Tertiary age sedimentary geologic units.
4. SOIL AND GEOLOGIC CONDITIONS
We encountered one surficial material (consisting of undocumented fill) and one geologic unit
(consisting of Old Paralic Deposits) during our field investigation. The surficial soil and geologic units
are discussed herein in order of increasing age. The occurrence and distribution of the units encountered,
including descriptions of the units, are shown on the exploratory trench logs in Appendix A. The
approximate lateral extent and subsurface relationships of the geologic conditions is presented on the
Geologic Map and Geologic Cross-Sections, Figures 2 and 3. We prepared the geologic cross-sections
using interpolation between exploratory trenches; therefore, actual geologic conditions between the
trenches may vary from those illustrated and should be considered approximate.
Project No. G2225-52-0I -2- February 9, 2018
Revised January 11, 2019
4.1 Undocumented Fill (Qudf)
The majority of the site is covered with weeds, crushed rock, and gravel with some patches of asphalt
at the surface. The undocumented fill was likely not tested or observed during placement and should
be considered to be highly variable on the property and within adjacent properties and right-of-ways.
The undocumented fill encountered in our exploratory trenches ranged from '/2 to 3 feet thick. We
expect there may be up to 5 to 6 feet of undocumented fill located at the top of slopes around the outer
edges of the existing reservoir. The undocumented fill consists primarily of loose to medium dense,
moist, brown to dark reddish brown, silty, fine- to medium-grained sand and silt. The fill soil
possesses a "very low" expansion potential (expansion index 20 or less). Undocumented fill should
also be considered to possess relatively high hydroconsolidation characteristics. The undocumented
fill within planned areas of development is not considered suitable for structural support or additional
fill placement and will require remedial grading.
Water that is allowed to migrate within the undocumented fill soil cannot be controlled, would
destabilize support for the existing improvements, and would shrink and swell. Therefore, infiltration
associated with storm water management devices should not be allowed within the undocumented fill.
4.2 Old Paralic Deposits (Qop)
We encountered Quaternary-age terrace deposits mapped by Kennedy and Tan (2007) as Old Paralic
Deposits (Units 24) below the undocumented fill in our exploratory trenches to the maximum depth
explored. The unit consists of dense to very dense, damp to moist, light reddish brown to brown, silty,
fine- to medium-grained sandstone. The Old Paralic Deposits are considered suitable for support of
properly compacted fill and structural loading.
We performed infiltration tests within the Old Paralic Deposits. Some areas of the Old Paralic
Deposits are considered adequate for storm water infiltration if designed as discussed herein.
5. GROUNDWATER
We did not encounter groundwater or seepage during our field investigation. We do not expect
groundwater to adversely impact proposed project development. It is not uncommon for groundwater
or seepage conditions to develop where none previously existed. Groundwater elevations are
dependent on seasonal precipitation, irrigation, and land use among other factors and, vary as a result.
Proper surface drainage will be important to future performance of the project.
Project No. G2225-52-01 -3- February 9, 2018
Revised January 11, 2019
6. GEOLOGIC HAZARDS
6.1 Faulting and Seismicity
Based on a review of geologic literature and experience with the soil and geologic conditions in the
general area, it is our opinion that known active, potentially active, or inactive faults are not located at
the site. In addition to our background review, the site is not mapped in the vicinity of geologic
hazards such as landslides, liquefaction areas, or faulting and is not located within the State of
California Earthquake Fault Zone. An active fault is defined by the California Geological Survey
(CGS) as a fault showing evidence for activity within the last 11,000 years.
According to the computer program EZ-FRJSK (Version 7.65), ten known active faults are located
within a search radius of 50 miles from the property. We used the 2008 USGS fault database that
provides several models and combinations of fault data to evaluate the fault information. Based on this
database, the nearest known active fault is the Newport-Inglewood Fault system, located
approximately 5 miles from the site and is the dominant source of potential ground motion.
Earthquakes that might occur on this fault system or other faults within the southern California and
northern Baja California area are potential generators of significant ground motion at the site. The
estimated deterministic maximum earthquake magnitude and peak ground acceleration for the
Newport-Inglewood Fault are 7.5 and 0.38g, respectively. Table 6.1.1 lists the estimated maximum
earthquake magnitude and peak ground acceleration for these and other faults in relationship to the site
location. We used acceleration attenuation relationships developed by Boore-Atkinson (2008) NGA
USGS2008, Campbell-Bozorgnia (2008) NGA USGS, and Chiou-Youngs (2007) NGA USGS2008
acceleration-attenuation relationships in our analysis. Table 6.1.1 lists the estimated maximum
earthquake magnitude and peak ground acceleration for the Newport-Inglewood and Rose Canyon
Faults and other faults in relationship to the site location.
TABLE 6.1.1
DETERMINISTIC SPECTRA SITE PARAMETERS
Maximum Peak Ground Acceleration
Approximate Earthquake Fault Name Distance from Magnitude Boore- Campbell- Chiou-
Site (miles) Atkinson Bozorgnia Youngs (Mw) 2008(g) 2008 (g) 2007 (g)
Newport-Inglewood 5 7.5 0.31 0.30 0.38
Rose Canyon 6 6.9 0.25 0.27 0.29
Coronado Bank 22 7.4 0.15 0.11 0.12
Palos Verdes 22 1 7.7 1 0.17 1 0.12 0.15
Elsinore 23 7.9 0.17
1 0.10
0.12 0.16
Palos Verdes 34 7.3 0.07 0.07
Project No. G2225-52-01 -4- February 9, 2018
Revised January 11, 2019
Fault Name
Approximate
Distance from
Site (miles)
Maximum
Earthquake
Magnitude
(Mw)
Peak Ground Acceleration
Boore-
Atkinson
2008(g)
Campbell-
Bozorgnia
2008 (g)
Chiou-
Youngs
2007 (g)
Newport-Inglewood 5 7.5 0.31 0.30 0.38
Rose Canyon 6 6.9 0.25 0.27 0.29
Coronado Bank 22 7.4 0.15 0.11 0.12
Palos Verdes 22 7.7 0.17 0.12 0.15
Elsinore 23 7.9 0.17 0.12 0.16
Palos Verdes 34 7.3 0.10 0.07 0.07
San Joaquin Hills 35 7.1 0.09 0.09 0.08
Earthquake Valley 44 6.8 0.06 0.05 0.04
San Jacinto 46 7.9 0.10 0.07 0.09
Chino 46 6.8 0.06 0.05 0.04
We used the computer program EZ-FRISK to perform a probabilistic seismic hazard analysis. The
computer program EZ-FRISK operates under the assumption that the occurrence rate of earthquakes on
each mappable Quaternary fault is proportional to the faults slip rate. The program accounts for fault
rupture length as a function of earthquake magnitude, and site acceleration estimates are made using
the earthquake magnitude and distance from the site to the rupture zone. The program also accounts
for uncertainty in each of following: (1) earthquake magnitude, (2) rupture length for a given
magnitude, (3) location of the rupture zone, (4) maximum possible magnitude of a given earthquake,
and (5) acceleration at the site from a given earthquake along each fault. By calculating the expected
accelerations from considered earthquake sources, the program calculates the total average annual
expected number of occurrences of site acceleration greater than a specified value. We utilized
acceleration-attenuation relationships suggested by Boore-Atkinson (2008) NGA USGS 2008,
Campbell-Bozorgnia (2008) NGA USGS 2008, and Chiou-Youngs (2007) NGA USGS 2008 in our
analysis in the analysis. Table 6.1.2 presents the probabilistic seismic hazard parameters including
acceleration-attenuation relationships and the probability of exceedance.
Project No. 02225-52-01 -5 - February 9, 2018
Revised January 11, 2019
TABLE 6.1.2
PROBABILISTIC SEISMIC HAZARD PARAMETERS
Probability of Exceedence
Peak Ground Acceleration
Boore-Atkinson
2008 (g)
Campbell-Bozorgnia
2008 (g)
Chiou-Youngs
2007 (g)
2% in a 50 Year Period 0.42 0.38 0.42
5% in a 50 Year Period 0.30 1 0.26 0.28
10% in a 50 Year Period 0.22 1 0.18 0.19
While listing peak accelerations is useful for comparison of potential effects of fault activity in a
region, other considerations are important in seismic design, including the frequency and duration of
motion and the soil conditions underlying the site. Seismic design of the structures should be evaluated
in accordance with the 2016 California Building Code (CBC) or other applicable guidelines.
It is our opinion the site could be subjected to moderate to severe ground shaking in the event of an
earthquake along any of the faults listed on Table 6.1.1 or other faults in the southern California!
northern Baja California region. We do not consider the site to possess a greater risk than that of the
surrounding developments.
6.2 Ground Rupture
Ground surface rupture occurs when movement along a fault is sufficient to cause a gap or rupture
where the upper edge of the fault zone intersects that earth surface. The potential for ground rupture is
considered to be very low due to the absence of active or potentially active faults at the subject site.
6.3 Seiches and Tsunamis
A seiche is a run-up of water within a lake or embayment triggered by fault- or landslide-induced
ground displacement. The site is not located in the vicinity of or downstream from such bodies of
water. Therefore, the risk of seiches affecting the site is negligible.
A tsunami is a series of long-period waves generated in the ocean by a sudden displacement of large
volumes of water. Causes of tsunamis include underwater earthquakes, volcanic eruptions, or offshore
slope failures. The property is located at an elevation of at least 160 feet above MSL and is about 1.2
miles from the Pacific Ocean; therefore, the risk of tsunamis affecting the site is negligible.
Project No. G2225-52-01 -6- February 9, 2018
Revised January 11, 2019
6.4 Liquefaction and Seismically Induced Settlement
Liquefaction typically occurs when a site is located in a zone with seismic activity, on-site soils are
cohesionless/silt or clay with low plasticity, groundwater is encountered within 50 feet of the surface,
and soil relative densities are less than about 70 percent. If the four previous criteria are met, a seismic
event could result in a rapid pore-water pressure increase from the earthquake-generated ground
accelerations. Seismically induced settlement may occur whether the potential for liquefaction exists
or not. Due to the absence of a near surface groundwater elevation and the dense to very dense nature
of the existing fill and formational materials, the potential for liquefaction and seismically induced
settlement occurring at the property is considered negligible.
6.5 Landslides
Examination of aerial photographs in our files, review of published geologic maps for the site vicinity,
and the relatively level topography, it is our opinion landslides are not present at the subject property.
Project No. G2225-52-01 - 7 - February 9, 2018
Revised January 11, 2019
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 We did not encounter soil or geologic conditions during the investigation that, in our
opinion, would preclude the development of the property as presently planned, provided the
recommendations of this report are followed.
7.1.2 Our field investigation and review of the referenced documents indicate the site is generally
underlain by approximately V2 to 3 feet of undocumented fill overlying Old Paralic Deposits.
We expect there may be up to 5 to 6 feet of undocumented fill located at the top of slopes
around the outer edges of the existing reservoir. The undocumented fill is not suitable for
support of improvements or structures and will require remedial grading.
7.1.3 We did not observe groundwater or seepage in the exploratory trenches to the total depths
explored and we do not expect it to be encountered during construction of the proposed park
site development. It is not uncommon for groundwater or seepage conditions to develop
where none previously existed due to the permeability characteristics of the geologic units
on site. During the rainy season, seepage conditions may develop that would require special
consideration.
7.1.4 Excavations of the existing fill should generally be possible with moderate effort using
conventional, heavy-duty equipment during grading and trenching operations. Excavations
into the Old Paralic Deposits could require very heavy effort.
7.1.5 Site or grading plans have not been provided for our review. Geocon Incorporated should
review the plans prior to the submittal to regulatory agencies for approval. Additional
analyses may be required once the plans have been provided.
7.1.6 Subsurface conditions observed may be extrapolated to reflect general soil and geologic
conditions; however, variations in subsurface conditions between exploratory trenches
should be expected.
7.1.7 Adequate drainage provisions are imperative to the performance of the development. Site
drainage should be maintained to direct surface runoff into controlled drainage devices.
Positive site drainage should be maintained away from structures, improvements and tops of
slopes and directed to storm drain facilities.
Project No. G2225-52-01 - 8 - February 9, 2018
Revised January 11, 2019
7.1.8 We do not expect site development will not impact adjacent sites and will not create
settlement to public improvements.
7.1.9 This report is considered limited because we were not able to extend exploratory
excavations in the area of the existing reservoir. Also, we should update this report when
development plans have been prepared for the property.
7.2 Excavation and Soil Characteristics
7.2.1 Excavation of the in-situ fill soil should be possible with moderate effort using conventional
heavy-duty equipment. Excavations within the Old Paralic Deposits could require special
excavation equipment and very heavy effort, where very dense or cemented materials are
encountered.
7.2.2 The soil encountered in the field investigation is considered to be "non-expansive"
(expansion index [El] of 20 or less) as defined by 2016 California Building Code (CBC)
Section 1803.5.3. However, we expect some of the soil may be considered "expansive" (El
greater than 20). Table 7.2 presents soil classifications based on the expansion index. We
expect a majority of the soil encountered possess a "very low" to "low" expansion potential
(expansion index of 50 or less) in accordance with ASTM D 4829.
TABLE 7.2
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (El) ASTM D 4829 Expansion
Classification
2016 CBC
Expansion Classification
0-20 Very Low Non-Expansive
21-50 Low
Expansive
Very High
51-90 Medium
91-130 High
Greater Than 130
7.2.3 We performed laboratory tests on samples of the site materials to evaluate the percentage of
water-soluble sulfate content. Results from the laboratory water-soluble sulfate content tests
are presented in Appendix B and indicate that the on-site materials at the locations tested
possess "SO" sulfate exposure to concrete structures as defined by 2016 CBC Section 1904
and ACI 318-14 Chapter 19. The presence of water-soluble sulfates is not a visually
discernible characteristic; therefore, other soil samples from the site could yield different
Project No. G2225-52-01 -9- February 9, 2018
Revised January 11, 2019
concentrations. Additionally, oyer time landscaping activities (i.e., addition of fertilizers and
other soil nutrients) may affect the concentration.
7.2.4 Geocon does not practice in the field of corrosion engineering. Therefore, further evaluation
by a corrosion engineer may be performed if improvements susceptible to corrosion are
planned.
7.3 Seismic Design Criteria
7.3.1 We used the computer program US. Seismic Design Maps, provided by the USGS.
Table 7.3.1 summarizes site-specific design criteria obtained from the 2016 California
Building Code (CBC; Based on the 2015 International Building Code [IBC] and ASCE 7-
10), Chapter 16 Structural Design, Section 1613 Earthquake Loads. The short spectral
response uses a period of 0.2 second. We evaluated the Site Class based on the discussion in
Section 1613.3.2 of the 2016 CBC and Table 20.3-1 of ASCE 7-10. The site is classified as
a Site Class C in accordance with the 2016 CBC Section 1613. The values presented in
Table 7.3.1 are for the risk-targeted maximum considered earthquake (MCER).
TABLE 7.3.1
2016 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2016 CBC Reference
Site Class C Section 1613.3.2
MCER Ground Motion Spectral Response 1.131g Figure 1613.3.1(1) Acceleration - Class B (short), Ss
MCER Ground Motion Spectral Response 0.434g Figure 1613.3.1(2) Acceleration - Class B (1 sec), 1
Site Coefficient, FA 1.000 Table 1613.3.3(1)
Site Coefficient, Fv 1.366 Table 16 13.3.3(2)
Site Class Modified MCER 1.131g Section 1613.3.3 (Eqn 16-37) Spectral Response Acceleration (short), SMS
Site Class Modified MCER 0.593g Section 1613.3.3 (Eqn 16-38) Spectral Response Acceleration (1 sec), SMI
5% Damped Design
Spectral Response Acceleration (short), Sis 0.754g Section 1613.3.4 (Eqn 16-39)
5% Damped Design
Spectral Response Acceleration (I sec), SDI 0.395g Section 1613.3.4 (Eqn 16-40)
7.3.2 Table 7.3.2 presents additional seismic design parameters for projects located in Seismic
Design Categories of D through F in accordance with ASCE 7-10 for the mapped maximum
considered geometric mean (MCEG).
Project No. G2225-52-01 _10 - February 9, 2018
Revised January 11, 2019
TABLE 7.3.2
2016 CBC SITE ACCELERATION DESIGN PARAMETERS
Parameter Value ASCE 7-10 Reference
Mapped MCEQ Peak Ground Acceleration, PGA 0.444 Figure 22-7
Site Coefficient, FPGA 1.000 Table 11.8-1
Site Class Modified MCEG
Peak Ground Acceleration, PGAM 0.444 Section 11.8.3 (Eqn 11.8-1)
7.3.3 Conformance to the criteria in Tables 7.3.1 and 7.3.2 for seismic design does not constitute
any kind of guarantee or assurance that significant structural damage or ground failure will
not occur if a large earthquake occurs. The primary goal of seismic design is to protect life,
not to avoid all damage, since such design may be economically prohibitive.
7.4 Preliminary Grading Recommendations
7.4.1 Grading should be performed in accordance with the Recommended Grading Specifications
in Appendix D. Where the recommendations of this report conflict with Appendix D, the
recommendations of this section shall take precedence.
7.4.2 Earthwork should be observed and compacted fill tested by representatives of Geocon
Incorporated.
7.4.3 A pre-construction conference with the city inspector, landscape architect, contractor, civil
engineer, and geotechnical engineer in attendance should be held at the site prior to the
beginning of grading operations. Special soil handling requirements can be discussed at that
time.
7.4.4 Site preparation should begin with removal of deleterious material and vegetation. The
depth of removal should be such that material to be used as fill is relatively free of organic
matter. Material generated during stripping and/or site demolition should be exported from
the site and not used as fill unless approved by Geocon Incorporated.
7.4.5 The abandoned reservoir concrete walls and bottom and buried utilities (if encountered)
should be removed and the resultant depressions and/or trenches should be backfilled with
properly compacted material as part of the remedial grading. Concrete that is supported on
Old Paralic Deposits, is deeper than 3 feet from proposed elevation and is below the planned
Project No. G2225-52-01 - 11 - February 9, 2018
Revised January 11, 2019
utilities may be left in place, if desired. In addition, the concrete slab of the reservoir can be
left in place if 4-inch diameter cores are installed at least 10 feet on center in both directions.
7.4.6 The existing undocumented fill is not considered suitable for the support of additional fill or
structural loads in the present condition and will require remedial grading. The existing
surficial soils should be removed to expose the underlying Old Paralic Deposits and
replaced with properly compacted fill. The undocumented fill can be reused as new
compacted fills.
7.4.7 In addition, the upper 3 feet of soil should be removed and replaced with properly
compacted fill below planned structures. The removals should extend laterally at least 5 feet
beyond the perimeter of the proposed structures, where possible. Geocon Incorporated
should evaluate the removal limits during the grading operations.
7.4.8 Prior to the placement of compacted fill, the exposed bottom should be scarified, moisture
conditioned as necessary, and properly compacted. Excavated soil generally free of
deleterious debris can be placed as fill and compacted in layers to the design finish grade
elevations. Fill and backfill soil should be placed in horizontal loose layers approximately 6
to 8 inches thick, moisture conditioned as necessary, and compacted to a dry density of at
least 90 percent of the laboratory maximum dry density near to slightly above optimum
moisture content in accordance with ASTM D 1557.
7.4.9 Import fill, if necessary, should consist of granular materials with a "very low" to "low"
expansion potential (El of 50 or less) free of deleterious material or stones larger than
3 inches and should be compacted as recommended herein. Geocon Incorporated should be
notified of the import soil source and should perform laboratory testing of import soil prior
to its arrival at the site to evaluate its suitability as fill material.
7.5 Excavation Slopes
7.5.1 The recommendations included herein are provided for stable excavations. It is the
responsibility of the contractor to provide a safe excavation during the construction of the
proposed project.
7.5.2 Temporary excavations should be made in conformance with OSHA requirements. The
undocumented fill should be considered a Type C soil, properly compacted fill can be
considered a Type B Soil (Type C soil if seepage or groundwater is encountered), and the
Old Paralic Deposits can be considered a Type A soil (Type B soil if seepage or
groundwater is encountered) in accordance with OSHA requirements. In general, special
Project No. G2225-52-01 -12- February 9, 2018
Revised January 11, 2019
shoring requirements may not be necessary if temporary excavations will be less than 4 feet
in height. Temporary excavations greater than 4 feet in height, however, should be sloped
back at an appropriate inclination. These excavations should not be allowed to become
saturated or to dry out. Surcharge loads should not be permitted to a distance equal to the
height of the excavation from the top of the excavation. The top of the excavation should be
a minimum of 15 feet from the edge of existing improvements. Excavations steeper than
those recommended or closer than 15 feet from an existing surface improvement should be
shored in accordance with applicable OSHA codes and regulations. Table 7.5 presents the
allowable slope inclination for different soil types based on the information presented by
OSHA assuming seepage is not encountered.
TABLE 7.5
ALLOWABLE SLOPE INCLINATIONS FOR EXCAVATIONS
LESS THAN 20 FEET FOR UNDERGROUND CONTRACTORS
Maximum aximum Soil or On-Site Geologic Unit Inclination Slope Angle
Rock Type (horizontal-vertical) from Horizontal
(degrees)
Type A Old Paralic Deposits %:1 53
Type B Properly Compacted Fill 1:1 45
Type C Undocumented Fill 1 '/2:1 34
7.6 Shallow Foundations
7.6.1 The proposed structures (i.e. shade structures, gazebos) can be supported on a shallow
foundation system founded in newly compacted fill or Old Paralic Deposits. Foundations for
the structure should consist of continuous strip footings and/or isolated spread footings.
Continuous footings should be at least 12 inches wide and extend at least 18 inches below
lowest adjacent pad grade. Isolated spread footings should have a minimum width of 2 feet
and should also extend at least 18 inches below lowest adjacent pad grade. Steel
reinforcement for continuous footings should consist of at least four No. 4 steel reinforcing
bars placed horizontally in the footings, two near the top and two near the bottom. Steel
reinforcement for the spread footings should be designed by the project structural engineer.
A wall/column footing dimension detail is presented in Figure 4. In addition, footings
should be deepened such that the bottom outside edge of the footing is at least 7 feet
horizontally from the face of the slope.
7.6.2 The recommendations presented herein are based on soil characteristics only (El of 50 or
less) and is not intended to replace reinforcement required for structural considerations.
Project No. G2225-52-01 - 13- February 9, 2018
Revised January 11, 2019
7.6.3 The recommended allowable bearing capacity for foundations with minimum dimensions
described herein is 2,000 pounds per square foot (psf) for foundations bearing in properly
compacted fill and 4,000 pounds per square foot (psf) for foundations bearing in the Old
Paralic Deposits. The allowable soil bearing pressure may be increased by an additional 500
psf for each additional foot of depth and width, to a maximum allowable bearing capacity of
4,000 psf and 6,000 psf for foundations bearing in compacted fill and Old Paralic Deposits,
respectively. The values presented herein are for dead plus live loads and may be increased
by one-third when considering transient loads due to wind or seismic forces.
7.6.4 We estimate the total and differential settlements under the imposed allowable loads to be
about V2 inch based on a 6-foot square footing.
7.6.5 Foundation excavations should be observed by the geotechnical engineer (a representative
of Geocon Incorporated) prior to the placement of reinforcing steel to check that the
exposed soil conditions are similar to those expected and that they have been extended to
the appropriate bearing strata. If unexpected soil conditions are encountered, foundation
modifications may be required.
7.7 Drilled Piers
7.7.1 A deep foundation system consisting of drilled piers may be used to support proposed shade
or light structures. The drilled piers can be founded in the properly compacted structural fill
or in the Old Paralic Deposits.
7.7.2 Drilled piers for the shade structures should be a minimum of 18 inches in diameter and
should be embedded a minimum of 5 feet below the ground surface. In addition, footings
should be deepened such that the bottom outside edge of the footing is at least 7 feet
horizontally from the face of slopes.
7.7.3 Piers should have a minimum center-to-center spacing of at least three pile diameters.
Drilled piers can be designed to develop support by end bearing and skin friction within the
existing materials. Axial compression capacity may be designed using an allowable skin
friction resistance of 200 psf and 300 psf can be used for that portion of the drilled pier
embedded in fill soil and the Old Paralic Deposits, respectively. Uplift capacity may be
assumed to be 75 percent of the axial capacity in compression. The allowable downward
capacity and allowable uplift capacity may be increased by one-third when considering
transient wind or seismic loads. Where not protected by pavement, the upper 12 inches of
soil should be ignored when calculating axial capacity.
Project No. G2225-52-0I -14- February 9, 2018
Revised January 11, 2019
7.7.4 Piles bearing in compacted fill material may be designed for an allowable bearing capacity
of 2,000 psf. Piles bearing in Old Paralic Deposits may be designed for an allowable bearing
capacity of 4,000 psf.
7.7.5 We expect the maximum expected total and differential settlement for shade structures
supported on piers deriving support in the compacted fill is about Y2 inch. Settlement of the
foundation system is expected to occur on initial application of loading.
7.7.6 Because a significant portion of the pier capacity will be developed by end bearing, the
bottom of the borehole should be cleaned of all loose cuttings prior to the placement of steel
and concrete. Experience indicates that backspinning the auger does not remove loose
material and a flat cleanout plate or hand cleaning is necessary. Concrete should be placed
within the pier excavation as soon as possible after the auger/cleanout plate is withdrawn to
reduce the potential for discontinuities or caving. Pier sidewall instability may randomly
occur if cohesionless soils are encountered. We do not expect seepage will be encountered
during the drilling operations. However, casing may be required to maintain the integrity of
the pier excavation, particularly if seepage or sidewall instability is encountered. The fill
and the formational materials contain gravel, cobble and some boulders. The formational
materials may possess very dense and cemented zones, and difficult drilling conditions
during excavations for the piers should be anticipated.
7.8 Basketball Courts and Concrete Slabs-On-Grade
7.8.1 Concrete slabs should possess a thickness of at least 5 inches and reinforced with a
minimum of No. 4 steel reinforcing bars at 18 inches on center in both horizontal directions.
The structural engineer should design the steel required for the planned loading conditions.
The reinforcing steel should be placed in the upper third of the slab with a minimum of 2
inches of cover. Proper positioning of the reinforcement is critical to future performance of
the slab. The contractor should take extra measures to provide proper steel placement. The
concrete should have a compressive strength of at least 3,000 psi.
7.8.2 If possible, crack-control joints (weakened plane joints) should be included in the design of
the concrete pavement slab to control the location and spread of concrete shrinkage cracks.
Crack-control joints should not exceed 30 times the slab thickness with a maximum spacing
of 12.5 feet for the 5-inch-thick slabs and should be sealed with an appropriate sealant to
prevent the migration of water through the control joint to the subgrade materials. The depth
of the crack-control joints should be determined by the referenced ACI report discussed in
the pavement section herein. Cuts at least ¼ inch wide are required for sealed joints, and a %
Project No. G2225-52-01 -15- February 9, 2018
Revised January II, 2019
inch wide cut is commonly recommended. Coverings on the concrete slab should be
installed in accordance with the manufacturer's recommendations.
7.8.3 The slab should be underlain by a minimum of 6 inches of compacted Class 2 Base or
Crushed Aggregate Base (CAB). The slab should be constructed with a thickened edge that
extends at least 12 inches below finish grade and is at least 12 inches wide.
7.8.4 Prior to the placement of base, the upper 12 inches of soil subgrade should be scarified,
moisture conditioned near to slightly above optimum moisture content, and recompacted to
a dry density of at least 90 percent of the laboratory maximum dry density per ASTM 1557.
The base material should also be compacted to a dry density of at least 90 percent of the
laboratory maximum dry density near to slightly above optimum moisture content.
7.8.5 If the slab will receive a moisture-sensitive covering, a vapor retarder should be placed on
the subgrade below the base as indicated on the attached detail. The vapor retarder should be
consistent with the guidelines presented in the American Concrete Institute's (AC!) Guide
for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials (ACI 302.2R-06). In
addition, the membrane should be installed in accordance with manufacturer's
recommendations and ASTM requirements and installed in a manner that prevents puncture.
The project architect should specify the type of vapor retarder used based on the type of
covering that will be installed. A Stego 15-mil product is typically used for vapor retarders.
7.8.6 The foundation design engineer should provide appropriate concrete mix design criteria and
curing measures to assure proper curing of the slab by reducing the potential for rapid
moisture loss and subsequent cracking and/or slab curl. We suggest that the foundation
design engineer present the concrete mix design and proper curing methods on the
foundation plans. It is critical that the foundation contractor understands and follows the
recommendations presented on the foundation plans.
7.8.7 Special subgrade presaturation is not deemed necessary prior to placing concrete; however,
the exposed foundation and slab subgrade soil should be moisturized to maintain a moist
condition as would be expected in any such concrete placement.
7.9 Concrete Flatwork
7.9.1 Exterior concrete flatwork not subject to vehicular traffic should be constructed in
accordance with the recommendations herein. Slab panels should be a minimum of 4 inches
thick and, when in excess of 8 feet square, should be reinforced with
6 x 6 - W2.91W2.9 (6 x 6 - 6/6) welded wire mesh or No. 3 reinforcing bars at 18 inches on
Project No. G2225-52-01 -16- February 9, 2018
Revised January 11, 2019
center in both directions to reduce the potential for cracking. In addition, concrete flatwork
should be provided with crack control joints to reduce and/or control shrinkage cracking.
Crack control spacing should be determined by the project structural engineer based upon
the slab thickness and intended usage. Criteria of the American Concrete Institute (AC!)
should be taken into consideration when establishing crack control spacing. Subgrade soil
for exterior slabs not subjected to vehicle loads should be compacted in accordance with
criteria presented in the grading section prior to concrete placement. Subgrade soil should be
properly compacted and the moisture content of subgrade soil should be checked prior to
placing concrete.
7.9.2 Even with the incorporation of the recommendations within this report, the exterior concrete
flatwork has a likelihood of experiencing some uplift due to expansive soil beneath grade;
therefore, the reinforcing steel should overlap continuously in flatwork to reduce the
potential for vertical offsets within flatwork. Additionally, flatwork should be structurally
connected to the curbs, where possible, to reduce the potential for offsets between the curbs
and the flatwork.
7.9.3 Where exterior flatwork abuts the structure at entrant or exit points, the exterior slab should
be dowelled into the structure's foundation stemwall. This recommendation is intended to
reduce the potential for differential elevations that could result from differential settlement
or minor heave of the flatwork. Dowelling details should be designed by the project
structural engineer.
7.9.4 The recommendations presented herein are intended to reduce the potential for cracking of
slabs and foundations as a result of differential movement. However, even with the
incorporation of the recommendations presented herein, foundations and slabs-on-grade will
still crack. The occurrence of concrete shrinkage cracks is independent of the soil supporting
characteristics. Their occurrence may be reduced and/or controlled by limiting the slump of
the concrete, the use of crack control joints and proper concrete placement and curing.
Literature provided by the Portland Concrete Association (PCA) and American Concrete
Institute (AC!) present recommendations for proper concrete mix, construction, and curing
practices, and should be incorporated into project construction.
7.10 Retaining Walls
7.10.1 Retaining walls not restrained at the top and having a level backfill surface should be
designed for an active soil pressure equivalent to the pressure exerted by a fluid density of
35 pounds per cubic foot (pcf). Where the backfill will be inclined at 2:1 (horizontal to
Project No. G2225-52-0I -17- February 9, 2018
Revised January 11, 2019
vertical), we recommend an active soil pressure of 50 pcf. Soil with an expansion index (El)
of greater than 50 should not be used as backfill material behind retaining walls.
7.10.2 Retaining walls should be designed to ensure stability against overturning sliding, excessive
foundation pressure and water uplift. Where a keyway is extended below the wall base with
the intent to engage passive pressure and enhance sliding stability, it is not necessary to
consider active pressure on the keyway.
7.10.3 Unrestrained walls will move laterally when backfilled and loading is applied. The amount
of lateral deflection is dependent on the wall height, the type of soil used for backfill and
loads acting on the wall. The retaining walls and improvements above the retaining walls
should be designed to incorporate an appropriate amount of lateral deflection as determined
by the structural engineer.
7.10.4 The recommendations presented herein are generally applicable to the design of rigid
concrete. In the event that other types of walls (such as crib-type walls) are planned, Geocon
Incorporated should be consulted for additional recommendations.
7.10.5 The structural engineer should determine the Seismic Design Category for the project in
accordance with Section 1613.3.5 of the 2016 CBC or Section 11.6 of ASCE 7. For
structures assigned to Seismic Design Category of D, E, or F, retaining walls that support
more than 6 feet of backfill should be designed with seismic lateral pressure in accordance
with Section 1803.5.12 of the 2016 CBC. The seismic load is dependent on the retained
height where H is the height of the wall, in feet, and the calculated loads result in pounds per
square foot (psf) exerted at the base of the wall and zero at the top of the wall. A seismic
load of 14H should be used for design. We used the peak ground acceleration adjusted for
Site Class effects, PGAM, of 0.444g calculated from ASCE 7-10 Section 11.8.3 and applied
a pseudo-static coefficient of 0.3. Figure 5 presents a retaining wall loading diagram.
7.10.6 The retaining walls may be designed using either the active and restrained (at-rest) loading
condition or the active and seismic loading condition as suggested by the structural
engineer. Typically, it appears the design of the restrained condition for retaining wall
loading may be adequate for the seismic design of the retaining walls. However, the active
earth pressure combined with the seismic design load should be reviewed and also
considered in the design of the retaining walls.
7.10.7 Drainage openings through the base of the wall (weep holes) should not be used where the
seepage could be a nuisance or otherwise adversely affect the property adjacent to the base
Project No. G2225-52-01 -18 - February 9, 2018
Revised January 11, 2019
of the wall. The recommendations herein assume a properly compacted granular (El of 50 or
less) free-draining backfill material with no hydrostatic forces or imposed surcharge load.
Figure 6 presents a typical retaining wall drainage detail. If conditions different than those
described are expected, or if specific drainage details are desired, Geocon Incorporated
should be contacted for additional recommendations.
7.10.8 In general, wall foundations having a minimum depth and width of 1 foot may be designed
for an allowable soil bearing pressure of 2,000 psf. The allowable soil bearing pressure may
be increased by an additional 300 psf for each additional foot of depth and width, to a
maximum allowable bearing capacity of 3,000 psf. The proximity of the foundation to the
top of a slope steeper than 3:1 could impact the allowable soil bearing pressure. Therefore,
retaining wall foundations should be deepened such that the bottom outside edge of the
footing is at least 7 feet horizontally from the face of the slope.
7.10.9 Unrestrained walls will move laterally when backfilled and loading is applied. The amount
of lateral deflection is dependent on the wall height, the type of soil used for backfill, and
loads acting on the wall. The retaining walls and improvements above the retaining walls
should be designed to incorporate an appropriate amount of lateral deflection as determined
by the structural engineer.
7.10.10 Soil contemplated for use as retaining wall backfill, including import materials, should be
identified in the field prior to backfill. At that time, Geocon Incorporated should obtain
samples for laboratory testing to evaluate its suitability. Modified lateral earth pressures
may be necessary if the backfill soil does not meet the required expansion index or shear
strength. City or regional standard wall designs, if used, are based on a specific active lateral
earth pressure and/or soil friction angle. In this regard, on-site soil to be used as backfill may
or may not meet the values for standard wall designs. Geocon Incorporated should be
consulted to assess the suitability of the on-site soil for use as wall backfill if standard wall
designs will be used.
7.11 Lateral Loading
7.11.1 To resist lateral loads, a passive pressure exerted by an equivalent fluid density of
350 pounds per cubic foot (pcf) should be used for the design of footings or shear keys. The
allowable passive pressure assumes a horizontal surface extending at least 5 feet, or three
times the surface generating the passive pressure, whichever is greater. The upper 12 inches
of material in areas not protected by floor slabs or pavement should not be included in
design for passive resistance.
Project No. G2225-52-01 _19- February 9, 2018
Revised January 11, 2019
7.11.2 If friction is to be used to resist lateral loads, an allowable coefficient of friction between
soil and concrete of 0.35 should be used for design. The friction coefficient may be reduced
depending on the vapor barrier or waterproofing material used for construction in
accordance with the manufacturer's recommendations.
7.11.3 The passive and frictional resistant loads can be combined for design purposes. The lateral
passive pressures may be increased by one-third when considering transient loads due to
wind or seismic forces.
7.12 Preliminary Flexible and Rigid Pavement Recommendations
7.12.1 We calculated the flexible pavement sections in general conformance with the Caltrans
Method of Flexible Pavement Design (Highway Design Manual, Section 608.4) using an
estimated Traffic Index (TI) of 5.0, 5.5, 6.0, and 7.0 for parking stalls, driveways, medium
truck traffic areas, and heavy truck traffic areas, respectively. The project civil engineer and
owner should review the pavement designations to determine appropriate locations for
pavement thickness. The final pavement sections should be based on the R-Value of the
subgrade soil encountered at final subgrade elevation. We have assumed an R-Value of 20
and 53 for the subgrade soil, based on the results of our laboratory tests, and 78 for the base
materials, for the purposes of this preliminary analysis. Table 7.12.1 presents the
preliminary flexible pavement sections.
TABLE 7.12.1
PRELIMINARY FLEXIBLE PAVEMENT SECTION
Location
Assumed
Traffic
Index
Assumed
Subgrade
R-Value
Asphalt
Concrete
(inches)
Class 2
Aggregate
Base (inches)
Parking stalls for automobiles
and light-duty vehicles 5.0 20 3 7
Driveways for automobiles
and light-duty vehicles
53 3 4
20 3 9
Medium truck traffic areas 6.0 53 3.5 4
20 3.5 10
Driveways for heavy truck traffic 7.0 53 4 4
20 4 1 12
7.12.2 Prior to placing base materials, the upper 12 inches of the subgrade soil should be scarified,
moisture conditioned as necessary, and recompacted to a dry density of at least 95 percent of
Project No. G2225-52-01 -20- February 9, 2018
Revised January 11, 2019
the laboratory maximum dry density near to slightly above optimum moisture content as
determined by ASTM D 1557. Similarly, the base material should be compacted to a dry
density of at least 95 percent of the laboratory maximum dry density near to slightly above
optimum moisture content. Asphalt concrete should be compacted to a density of at least
95 percent of the laboratory Hveem density in accordance with ASTM D 2726.
7.12.3 Base materials should conform to Section 26-1.028 of the Standard Specifications for The
State of California Department of Transportation (Caltrans) with a %-inch maximum size
aggregate. The asphalt concrete should conform to Section 203-6 of the Standard
Specifications for Public Works Construction (Greenbook).
7.12.4 The base thickness can be reduced if a reinforcement geogrid is used during the installation
of the pavement. Geocon should be contact for additional recommendations, if required.
7.12.5 A rigid Portland cement concrete (PCC) pavement section should be placed in driveway
entrance aprons and trash bin loading/storage areas. The concrete pad for trash truck areas
should be large enough such that the truck wheels will be positioned on the concrete during
loading. We calculated the rigid pavement section in general conformance with the
procedure recommended by the American Concrete Institute report ACI 330R-08 Guide for
Design and Construction of Concrete Parking Lots using the parameters presented in Table
7.12.2.
TABLE 7.12.2
RIGID PAVEMENT DESIGN PARAMETERS
Design Parameter Design Value
Modulus of subgrade reaction, k 100 pci
Modulus of rupture for concrete, MR 500 psi
Traffic Category, IC A and C
Average daily truck traffic, ADTT 10 and 100
Project No. G2225-52-01 -21 - February 9, 2018
Revised January 11, 2019
7.12.6 Based on the criteria presented herein, the PCC pavement sections should have a minimum
thickness as presented in Table 7.12.3.
TABLE 7.12.3
RIGID PAVEMENT RECOMMENDATIONS
Location Portland Cement Concrete (inches)
Automobile Parking Areas (TCA) 6
Heavy Truck and Fire Lane Areas (TC=C) 7
7.12.7 The PCC pavement should be placed over subgrade soil that is compacted to a dry density
of at least 95 percent of the laboratory maximum dry density near to slightly above optimum
moisture content. This pavement section is based on a minimum concrete compressive
strength of approximately 3,000 psi (pounds per square inch). Base materials will not be
required below concrete improvements.
7.12.8 A thickened edge or integral curb should be constructed on the outside of concrete slabs
subjected to wheel loads. The thickened edge should be 1.2 times the slab thickness or a
minimum thickness of 2 inches, whichever results in a thicker edge, and taper back to the
recommended slab thickness 4 feet behind the face of the slab (e.g., a 7-inch-thick slab
would have a 9-inch-thick edge). Reinforcing steel will not be necessary within the concrete
for geotechnical purposes with the possible exception of dowels at construction joints as
discussed herein.
7.12.9 To control the location and spread of concrete shrinkage cracks, crack-control joints
(weakened plane joints) should be included in the design of the concrete pavement slab.
Crack-control joints should not exceed 30 times the slab thickness with a maximum spacing
of 15 feet for the 6- and 7-inch-thick slabs and should be sealed with an appropriate sealant
to prevent the migration of water through the control joint to the subgrade materials. The
depth of the crack-control joints should be determined by the referenced ACI report.
7.12.10 To provide load transfer between adjacent pavement slab sections, a butt-type construction
joint should be constructed. The butt-type joint should be thickened by at least 20 percent at
the edge and taper back at least 4 feet from the face of the slab. As an alternative to the butt-
type construction joint, dowelling can be used between construction joints for pavements of
7 inches or thicker. As discussed in the referenced ACI guide, dowels should consist of
smooth, 1-inch-diameter reinforcing steel 14 inches long embedded a minimum of 6 inches
into the slab on either side of the construction joint. Dowels should be located at the
Project No. G2225-52-01 -22- February 9, 2018
Revised January 11, 2019
midpoint of the slab, spaced at 12 inches on center and lubricated to allow joint movement
while still transferring loads. In addition, tie bars should be installed at the as recommended
in Section 3.8.3 of the referenced ACI guide. The structural engineer should provide other
alternative recommendations for load transfer.
7.13 Site Drainage and Moisture Protection
7.13.1 Adequate site drainage is critical to reduce the potential for differential soil movement,
erosion and subsurface seepage. Under no circumstances should water be allowed to pond
adjacent to footings and improvements. The site should be graded and maintained such that
surface drainage is directed away from structures in accordance with 2013 CBC 1804.3 or
other applicable standards. In addition, surface drainage should be directed away from the
top of slopes into swales or other controlled drainage devices. Roof and pavement drainage
should be directed into conduits that carry runoff away from the proposed structure.
7.13.2 Underground utilities should be leak free. Utility and irrigation lines should be checked
periodically for leaks, and detected leaks should be repaired promptly. Detrimental soil
movement could occur if water is allowed to infiltrate the soil for prolonged periods of time.
7.13.3 Landscaping planters adjacent to paved areas are not recommended due to the potential for
surface or irrigation water to infiltrate the pavement's subgrade and base course. We
recommend that area drains to collect excess irrigation water and transmit it to drainage
structures or impervious above-grade planter boxes be used. In addition, where landscaping
is planned adjacent to the pavement, we recommend construction of a cutoff wall along the
edge of the pavement that extends at least 6 inches below the bottom of the base materials.
7.14 Grading and Foundation Plan Review
7.14.1 Geocon Incorporated should review the grading plans and foundation plans for the project
prior to final design submittal to evaluate whether additional analyses and/or
recommendations are required.
Project No. G2225-52-01 -23 - February 9, 2018
Revised January 11, 2019
LIMITATIONS AND UNIFORMITY OF CONDITIONS
The recommendations of this report pertain only to the site investigated and are based upon
the assumption that the soil conditions do not deviate from those disclosed in the
investigation. If any variations or undesirable conditions are encountered during construction,
or if the proposed construction will differ from that anticipated herein, Geocon Incorporated
should be notified so that supplemental recommendations can be given. The evaluation or
identification of the potential presence of hazardous or corrosive materials was not part of the
scope of services provided by Geocon Incorporated.
This report is issued with the understanding that it is the responsibility of the owner, or of his
representative, to ensure that the information and recommendations contained herein are
brought to the attention of the architect and engineer for the project and incorporated into the
plans, and the necessary steps are taken to see that the contractor and subcontractors carry out
such recommendations in the field.
The findings of this report are valid as of the present date. However, changes in the
conditions of a property can occur with the passage of time, whether they be due to natural
processes or the works of man on this or adjacent properties. In addition, changes in
applicable or appropriate standards may occur, whether they result from legislation or the
broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly
or partially by changes outside our control. Therefore, this report is subject to review and
should not be relied upon after a period of three years.
The firm that performed the geotechnical investigation for the project should be retained to
provide testing and observation services during construction to provide continuity of
geotechnical interpretation and to check that the recommendations presented for geotechnical
aspects of site development are incorporated during site grading, construction of
improvements, and excavation of foundations. If another geotechnical firm is selected to
perform the testing and observation services during construction operations, that firm should
prepare a letter indicating their intent to assume the responsibilities of project geotechnical
engineer of record. A copy of the letter should be provided to the regulatory agency for their
records. In addition, that firm should provide revised recommendations concerning the
geotechnical aspects of the proposed development, or a written acknowledgement of their
concurrence with the recommendations presented in our report. They should also perform
additional analyses deemed necessary to assume the role of Geotechnical Engineer of Record.
February 9, 2018 Project No. G2225-52-01
Revised January 11, 2019
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VICINITY MAP
GEOCON
4 INCORPORATED J'/ I
GEOTECHNICAL • ENVIRONMENTAL IN MATERIALS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121- 2974
PHONE 858 558-6900 - FAX 858 558-6159
KJ/CW DSK/GTYPD
BUENA VISTA RESERVOIR SITE
CARLSBAD, CALIFORNIA
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SCALE 1 "=30' (On 36x24)
wUU1 \1\/\I/1II S\IlS S 1 / \
GEOCON LEGEND
1 1 \
\ \ Qudf UNDOCUMENTED FILL
QOp ...... ..OLD PARALIC DEPOSITS
(Dotted Where Buried)
N J
/
1
7 APPROX LOCATION OF INFILTRATION TEST AND TEST PIT 5_.•__ 25 2 \ \ N .1 I 7
5 /7 T-1 0 APPROX, LOCATION OF EXPLORATORY TRENCH
APPROX. DEPTH TO FORMATION BELOW EXISTING GRADE (In Feet)
B Q' APPROX. LOCATION OF GEOLOGIC CROSS - SECTION
APPROX. LOCATION OF GEOLOGIC CONTACT
I 1' if iiiJ:. •.•':•• I I
PREVIOUS
RESERVOIR
o
\
5) GEOLOGIC MAP
'I :
55
25 /5/
BUENA VISTA RESERVOIR SITE
S
75
/
91 CARLSBAD, CALIFORNIA
ciocoij SCALE 1 = 30
DATE
01 -11-20
N ' 'A
IN COR P ORATED Y PROJECT NO. I FIGU 2'\ I . _____________________________________________ .,22LU - - 01 / ' ', S 7
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Plotted.01111/2019 2:20PM I By:JONATHAN WILKINS I File Location:Y:\PROJECTS\02225-52.01 Buena Vista Reservoir\SHEETS\02225.52-01 GeoMAP.dwg
iLi
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(I)
z
80Q F-
LU
-J LU
50
20
30 60 90 120 150 180 210 240 270 300 330 360 390
DISTANCE (FEET)
GEOLOGIC CROSS-SECTION A-A'
SCALE: 1" = 30' (Vert. = Horiz)
R
2 40
Ls]
1 50
0
20
30 60 90 120 150 180 210 240 270 300 330 360 390 420 435
DISTANCE (FEET)
GEOLOGIC CROSS-SECTION B-B'
SCALE: 1" = 30' (Vert. = Horiz.)
GEOCON LEGEND
Q udf ........UNOOCUMENTED FILL
QO ........OLD PARALIC DEPOSITS
P-4 I
APPROX. LOCATION OF INFILTRATION TEST AND TEST PIT
T-10
APPROX. LOCATION OF EXPLORATORY TRENCH
APPROX. LOCATION OF GEOLOGIC CONTACT
(Queried Where Uncertain)
Plolte:01/1112019 2:20PM! By:JONATHAN WILKINS I File Locstion:Y:\PROJECTS\122225-52.01 Buena Vista Reservoir\SHEETS\G2225-52-01 CrossSsctiondwg
APPENDIX
APPENDIX B
LABORATORY TESTING
We performed laboratory tests in accordance with generally accepted test methods of the American
Society for Testing and Materials (ASTM) or other suggested procedures. We tested selected samples for
their in-place moisture content, maximum dry density and optimum moisture content, shear strength,
expansion index, water-soluble sulfate characteristics, R-value, and gradation. The results of our
laboratory tests are presented on Tables B-I through B-V and Figure B-I. In addition, the in-place moisture
content test results are presented on the boring logs in Appendix A.
TABLE B-I
SUMMARY OF LABORATORY MAXIMUM DRY DENSITY
AND OPTIMUM MOISTURE CONTENT TEST RESULTS
ASTM D 1557
Sample
No. Description (Geologic Unit) Maximum Dry
Density (pci)
Optimum Moisture
Content (% dry wt.)
12-1 Brown, Silty, fine SAND; some gravel (Qudt) 132.1 9.3
134 Reddish brown, Silty, fine SANDSTONE (Qop) 135.4 7.9
TABLE B-Il
SUMMARY OF LABORATORY DIRECT SHEAR TEST RESULTS
ASTM D 3080
Average Average Moisture Peak Peak [Ultimate*]
Sample Geologic Dry Density Content (%)
____________ ____________
lUltimate*l Angle of Shear
No. Unit (pci) (psi) Cohesion Resistance
Initial Final (degrees)
Qudf 119.0 9.0 13.3 700 [575] 26 [26]
T34 Qop 122.0 7.6 12.1 700 [535] 25 [24]
110-2 Qop 110.5 6.9 15.8 575 [565] 26 [25]
*Ultimate defined as the end-of-test strength after about 0.2 inches of deflection.
Sample was remolded to a dry density of about 90 percent of the laboratory maximum dry density.
TABLE B-Ill
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM 04829
Sample No. Depth (feet) Geologic Unit Expansion ASTM Expansion I 2016 CBC
Expansion I
I Index I
Classification
I
Classification I
Project No. G2225-52-01 -B-I - February 9, 2018
Revised January 11, 2019
Sample No. Depth (feet) Geologic Unit Expansion ASTM Expansion 2016 CBC
Expansion Index Classification Classification
TI-1 0.5-1.5 Qudf 0 Very Low Non-Expansive
TABLE B-IV
SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS
CALIFORNIA TEST NO. 417
Sample No. Depth (feet) Geologic Unit Water-Soluble ACI 318 Sulfate
Sulfate (°°) Severity
TI-1 I 0.5-1.5 Qudf 0.0005 I SO
TABLE B-V
SUMMARY OF LABORATORY RESISTANCE VALUE (R-VALUE) TEST RESULTS
ASTM D 2844
Sample No. Depth (feet) Geologic Unit R-Value
TI-1 0.5-1.5 Qudf 53
Project No. G2225-52-01 -B-2 - February 9, 2018
Revised January 11, 2019
APPENDIX
APPENDIX C
STORM WATER MANAGEMENT INVESTIGATION
FOR
BUENA VISTA RESERVOIR SITE
CARLSBAD, CALIFORNIA
PROJECT NO. .G2225-52-01
APPENDIX C
STORM WATER MANAGEMENT INVESTIGATION
We understand storm water management devices will be used in accordance with the City of
Carlsbad BMF Design Manual (February, 2016). If not properly constructed, there is a potential for
distress to improvements and properties located hydrologically down gradient or adjacent to these
devices. Factors such as the amount of water to be detained, its residence time, and soil permeability
have an important effect on seepage transmission and the potential adverse impacts that may occur if
the storm water management features are not properly designed and constructed. We have not
performed a hydrogeological study at the site. If infiltration of storm water runoff occurs,
downstream properties may• be subjected to seeps, springs, slope instability, raised groundwater,
movement of foundations and slabs, or other undesirable impacts as a result of water infiltration.
Hydrologic Soil Group
The United States Department of Agriculture (USDA), Natural Resources Conservation Services,
possesses general information regarding the existing soil conditions for areas within the United
States. The USDA website also provides the Hydrologic Soil Group. Table C-I presents the
descriptions of the hydrologic soil groups. If a soil is assigned to a dual hydrologic group (AID, BID,
or CID), the first letter is for drained areas and the second is for undrained areas. In addition, the
USDA website also provides an estimated saturated hydraulic conductivity for the existing soil.
TABLE C-I
HYDROLOGIC SOIL GROUP DEFINITIONS
Soil Group Soil Group Definition
Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These
A consist mainly of deep, well drained to excessively drained sands or gravelly sands. These
soils have a high rate of water transmission.
Soils 'having a moderate infiltration rate when thoroughly wet. These consist chiefly of
B moderately deep or deep, moderately well drained or well drained soils that have moderately
fine texture to moderately coarse texture. These soils have a moderate rate of water
transmission.
Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils
C having a layer that impedes the downward movement of water or soils of moderately fine
texture or fine texture. These soils have a slow rate of water transmission.
Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These
D consist chiefly of clays that have a high shrink-swell potential, soils that have a high-water
table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow
over nearly impervious material. These soils have a very slow rate of water transmission.
Project No. G2225-52-01 -C-1 - February 9, 2018
Revised January II, 2019
The property is underlain by a thin layer of surlicial undocumented fill and formational Old Paralic
Deposits. Table C-Il presents the information from the USDA website for the subject property. The
Hydrologic Soil Group Map, provided at the end of this appendix, presents output from the USDA
website showing the limits of the soil units.
TABLE C-Il
USDA WEB SOIL SURVEY - HYDROLOGIC SOIL GROUP
Map Approximate kSAT of Most
Map Unit Name Unit Percentage Hydrologic Limiting
Symbol of Property Soil Group Layer (Inches!
Hour)
Marina loamy coarse sand, 2 to 9 percent MIC 51.5 B 0.57 to 1-.98
slopes
Marina loamy coarse sand, 9 to 30 percent MIE 48.5 B 0.57 to 1.98
slopes
In-Situ Testing
The infiltration rate, percolation rates and saturated hydraulic conductivity are different and have
different meanings. Percolation rates tend to overestimate infiltration rates and saturated hydraulic
conductivities by a factor of 10 or more. Table C-Ill describes the differences in the definitions.
TABLE C-Ill
SOIL PERMEABILITY DEFINITIONS
Term Definition
The observation of the flow of water through a material into the ground
Infiltration Rate downward into a given soil structure under long term conditions. This is
a function of layering of soil, density, pore space, discontinuities and
initial moisture content.
The observation of the flow of water through a material into the ground
Percolation Rate downward and laterally into a given soil structure under long term
i conditions. This s a function of layering of soil, density, pore space,
discontinuities and initial moisture content.
The volume of water that will move in a porous medium under a
Saturated Hydraulic hydraulic gradient through a unit area. This is a function of density,
Conductivity (ksAl, Permeability) structure, stratification, fines content and discontinuities. It is also a
function of the properties of the liquid as well as of the porous medium.
The degree of soil compaction or in-situ density has a significant impact on soil permeability and
infiltration. Based on our experience and other studies we performed, an increase in compaction
results in a decrease in soil permeability.
Project No. G2225-52-01 - C-2 - . February 9, 2018
Revised January II, 2019
We performed 4 Aardvark Permeameter tests at the infiltration test locations mapped on the Geologic
Map, Figure 2. We excavated the borings for the permeameter tests using a 4-inch diameter hand
auger starting at the bottom of test pits dug to depths of 3 to 4 feet below existing grade. The results
of the tests provide parameters regarding the saturated hydraulic conductivity and infiltration
characteristics of on-site soil and geologic units. Table C-IV presents the results of the estimated field
saturated hydraulic conductivity and estimated infiltration rates obtained from the Aardvark
Permeameter tests. The field sheets are also attached herein. We used a factor of safety applied to the
test results on the worksheet values. The designer of storm water devices should apply an appropriate
factor of safety. Soil infiltration rates from in-situ tests can vary significantly from one location to
another due to the heterogeneous characteristics inherent to most soil. Based on a discussion in the
County of Riverside Design Handbook for Low Impact Development Best Management Practices, the
infiltration rate should be considered equal to the saturated hydraulic conductivity rate.
TABLE C-IV
FIELD PERMEAMETER INFILTRATION TEST RESULTS
Field- C.4-1
Test Test Depth Test Geologic Saturated Worksheet
Location Test Number (feet, below Elevation Unit Infiltration Infiltration
grade) (feet, MSL) Rate, k,at Rate', ksat
(inch/hour) (inch/hour)
P-I 4.3 161.7 Qop 0.098 0.049 Northwest
Corner of P-2 4.7 160.3 Qop 0.087 0.043
Site
Average: 0.093 0.046
P-3 4.3 166.2 Qop 0.935 0.468
Western Side P4 5.7 164.3 Qop 0.589 0.295
of Site
Average: 0.767 0.382
Using a factor of safety of 2.
Based on the current BMF Design Manual used by the City of Carlsbad, the infiltration categories
include full infiltration, partial infiltration and no infiltration. Table C-V presents the definitions of
the potential infiltration categories.
TABLE C-V
INFILTRATION CATEGORIES
Infiltration Category Field Infiltration Rate, I
(inches/hour)
Factored Infiltration Rate, I
(inches/hour)
Full Infiltration 1> 1.0 I > 0.5
Partial Infiltration 0.10 <I < 1.0 0.05 <1 < 0.5
No Infiltration (Infeasible) 1 <0.10 1 <0.05
Project No. G2225-52-01 - C-3 - February 9, 2018
Revised January II, 2019
Groundwater
We did not encounter groundwater or seepage during our field investigation. We expect groundwater
is located greater than 100 feet below the site; therefore, we do not expect infiltration would increase
the risk of groundwater contamination or cause water balance issues.
New or Existing Utilities
Utilities will be constructed within the site boundaries and existing utilities that will be left in place
are located on the site. Full or partial infiltration should not be allowed in the areas of the utilities to
help prevent potential damage/distress to improvements. Mitigation measures to prevent water from
infiltrating the utilities consist of setbacks, installing cutoff walls around the utilities and installing
subdrains and/or installing liners. Storm water management devices should be setback at least 10 feet
from the existing and proposed utilities.
Existing and Planned Structures
An existing roadway is adjacent to the northern edge of the site. Water should not be allowed to
infiltrate in areas where it could affect the existing adjacent roadway. Existing residential structures
border the site to the east, south, and west. Mitigation for existing structures consists of not allowing
water infiltration within a 1:1 plane from foundations and extending the infiltration areas at least 10
feet below the existing foundations. Also, the planned storm water management devices should be set
back at least 50 feet from the existing adjacent descending slope.
Slopes and Other Geologic Hazards
At the western property line, existing descending slopes as steep at 1.5:1 (horizontal:vertical) and
retaining walls as tall as tall as 6 feet lie between that property line and the existing residences below
to the west. At the eastern property line, existing slopes as steep as 2.4:1 (horizontal:vertical) descend
from the eastern property line down to the top of retaining walls in the backyards of the existing
residences to the east. Infiltrating in this area could cause buildup of hydrostatic pressures, which
could destabilize the existing slopes or walls. Seepage could occur from the slope that flows into the
adjacent properties. Storm water management devices should be setback at least 50 feet from the
existing slopes.
Storm Water Evaluation Narrative
We evaluated the infiltration rates within the Old Paralic Deposits by performing infiltration tests at
locations where basins would be practical based on the topography of the site and discussions with
Project No. 02225-52-01 - C-4 - February 9, 2018
Revised January II, 2019
the project civil engineer and landscape architect. Infiltration should be considered infeasible within
the undocumented fill materials.
We performed infiltration tests in two areas at the northwest corner and western side of the site,
because this is the lowest elevation for the property. At the northwest corner of the site, our in-place
infiltration tests indicate an average of less than 0.05 inches/hour. At the western side of the site, our
in-place infiltration tests indicate average of between 0.05 and 0.50 inches/hour. Therefore, based on
infiltration rates, the northwestern corner of the site is categorized as infeasible for infiltration, and
the western side of the site is categorized as feasible for partial infiltration. Infiltrating near the slopes
at the property lines could cause buildup of hydrostatic pressures, which could destabilize the existing
slopes or walls. Seepage could occur from the slope that flows into the adjacent properties. Mitigation
measures could include deepening the bottom of the BMP facility and lining the sides down to an
elevation at least 1 foot below the toe of the adjacent slopes or retaining walls. If we were to extend
the basin deeper, we expect the infiltration rates would be reduced to about the rates we obtained
from the northwestern portion of the property due to similar elevations. Therefore, the infiltration
would be considered infeasible. If the devices are setback at least 50 feet from the top of slopes, the
elevations would be too high to practically install infiltration devices.
Conclusions
As discussed herein, the property consists of existing undocumented fill (Qudf) overlying Old Paralic
Deposits (Qop). Water should not be allowed to infiltrate into the undocumented fill within basins as
it will allow for lateral migration to adjacent residences and descending slopes.
An attempt to mitigate this could include deepening the BMP facility and lining the sides down to an
elevation at least 1 foot below the toe of the adjacent slopes or retaining walls or to approximately
elevation 162 feet MSL; however, the infiltration test results from our 4 tests on the site show that the
infiltration rates generally decrease as the test elevation decreases, so infiltration below the toe of
slopes or near elevation 162 feet MSL is likely infeasible, and there is still a risk that hydrostatic
pressures could build up behind the slopes and walls, or seepage from the toe of slopes onto the
neighboring properties could occur. If the devices are setback at least 50 feet from the top of slopes,
the elevations would be too high to practically install infiltration devices. Therefore, the property
should be considered infeasible for storm water infiltration.
Storm Water Management Devices
Liners and subdrains should be incorporated into the design and construction of the planned storm
water devices. The liners should be installed along the sidewalls and base of the proposed infiltration
locations. The liners should be impermeable (e.g. High-density polyethylene, HDPE, with a thickness
of about 30 mil or equivalent Polyvinyl Chloride, PVC) to prevent water migration. The subdrains
Project No. 02225-52-01 - C-5 - February 9, 2018
Revised January 11, 2019
should be perforated within the liner area, installed at the base and above the liner, be at least 3 inches
in diameter and consist of Schedule 40 PVC pipe. The subdrains outside of the liner should consist of
solid pipe. The penetration of the liners at the subdrains should be properly waterproofed. The
subdrains should be connected to a proper outlet. The devices should also be installed in accordance
with the manufacturer's recommendations.
Storm Water Standard Worksheets
The City of Carlsbad BMP Design Manual requests the geotechnical engineer complete the
Categorization of Infiltration Feasibility Condition (Worksheet C.4-1) worksheet information to help
evaluate the potential for infiltration on the property. The attached Worksheet C.4-1 presents the
completed information for the submittal process.
The regional storm water standards also have a worksheet (Worksheet D.5-1) that helps the project
civil engineer estimate the factor of safety based on several factors. Table C-VI describes the
suitability assessment input parameters related to the geotechnical engineering aspects for the factor
of safety determination.
TABLE C-VI
SUITABILITY ASSESSMENT RELATED CONSIDERATIONS FOR INFILTRATION FACILITY
SAFETY FACTORS
Consideration High Medium Low
Concern —3 Points Concern —2 Points Concern - 1 Point
Use of soil survey maps or Use of well permeameter
or simple texture analysis to borehole methods with Direct measurement with
estimate short-term accompanying
continuous boring log.
localized (i.e. small-
infiltration rates. Use of Direct measurement of scale) infiltration testing
Assessment Methods well permeameter or infiltration area with methods at relatively high
borehole methodswithout localized infiltration resolution or use of
accompanying continuous measurement methods extensive test pit
boring log. Relatively (e.g., Infiltrometer). infiltration measurement
sparse testing with direct Moderate spatial
methods.
infiltration methods resolution
Predominant Soil Silty and clayey soils Loamy soils Granular to slightly
Texture with significant fines loamy soils
Highly variable soils Soil boring/test pits Soil boring/test pits
Site Soil Variability indicated from site
assessment or unknown indicate moderately indicate relatively
variability homogenous soils homogenous soils
Depth to Groundwater! <5 feet below 5-15 feet below >15 feet below
Impervious Layer facility bottom facility bottom facility bottom
Project No. G2225-52-0I - C-6 - February 9, 2018
Revised January 11, 2019
Based on our geotechnical investigation and the previous table, Table C-VII presents the estimated
factor values for the evaluation of the factor of safety. This table only presents the suitability
assessment safety factor (Part A) of the worksheet. The project civil engineer should evaluate the
safety factor for design (Part B) and use the combined safety factor for the design infiltration rate.
TABLE C-Vu
FACTOR OF SAFETY WORKSHEET DESIGN VALUES - PART A1
Suitability Assessment Factor Category Assigned
(w)
Factor
Value (v)
Product
Weight (p = w x v)
Assessment Methods 0.25 2 0.50
Predominant Soil Texture 0.25 2 0.50
Site Soil Variability 0.25 1 0.25
Depth to Groundwater/ Impervious Layer 0.25 1 0.25
Suitability Assessment Safety Factor, SA = Ep 1.50
The project civil engineer should complete Worksheet D.5-1 using the data on this table. Additional
information is required to evaluate the design factor of safety.
Project No. G2225-52-01 - C-i - February 9, 2018
Revised January 11, 2019
Soil Map—San Diego County Area California
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Conservation Service National Cooperative Soil Survey Page 1 of 3
APPENDIX
APPENDIX D
RECOMMENDED GRADING SPECIFICATIONS
FOR
BUENA VISTA RESERVOIR SITE
CARLSBAD, CALIFORNIA
PROJECT NO. G2226-52-01
RECOMMENDED GRADING SPECIFICATIONS
1. GENERAL
1.1 These Recommended Grading Specifications shall be used in conjunction with the
Geotechnical Report for the project prepared by Geocon. The recommendations contained
in the text of the Geotechnical Report are a part of the earthwork and grading specifications
and shall supersede the provisions contained hereinafter in the case of conflict.
1.2 Prior to the commencement of grading, a geotechnical consultant (Consultant) shall be
employed for the purpose of observing earthwork procedures and testing the fills for
substantial conformance with the recommendations of the Geotechnical Report and these
specifications. The Consultant should provide adequate testing and observation services so
that they may assess whether, in their opinion, the work was performed in substantial
- conformance with these specifications. It shall be the responsibility of the Contractor to
assist the Consultant and keep them apprised of work schedules and changes so that
personnel may be scheduled accordingly.
1.3 It shall be the sole responsibility of the Contractor to provide adequate equipment and
methods to accomplish the work in accordance with applicable grading codes or agency
ordinances, these specifications and the approved grading plans. If, in the opinion of the
Consultant, unsatisfactory conditions such as questionable soil materials, poor moisture
condition, inadequate compaction, and/or adverse weather result in a quality of work not in
conformance with these specifications, the Consultant will be empowered to reject the
work and recommend to the Owner that grading be stopped until the unacceptable
conditions are corrected.
2. DEFINITIONS
2.1 Owner shall refer to the owner of the property or the entity on whose behalf the grading
- work is being performed and who has contracted with the Contractor to have grading
performed.
2.2 Contractor shall refer to the Contractor performing the site grading work.
2.3 Civil Engineer or Engineer of Work shall refer to the California licensed Civil Engineer
or consulting firm responsible for preparation of the grading plans, surveying and verifying
as-graded topography.
2.4 Consultant shall refer to the soil engineering and engineering geology consulting firm
retained to provide geotechnical services for the project.
GI rev. 07/2015
2.5 Soil Engineer shall refer to a California licensed Civil Engineer retained by the Owner,
who is experienced in the practice of geotechnical engineering. The Soil Engineer shall be
responsible for having qualified representatives on-site to observe and test the Contractor's
work for conformance with these specifications.
2.6 Engineering Geologist shall refer to a California licensed Engineering Geologist retained
by the Owner to provide geologic observations and recommendations during the site
grading.
2.7 Geotechnical Report shall refer to a soil report (including all addenda) which may include
a geologic reconnaissance or geologic investigation that was prepared specifically for the
development of the project for which these Recommended Grading Specifications are
intended to apply.
3. MATERIALS
3.1 Materials for compacted fill shall consist of any soil excavated from the cut areas or
imported to the site that, in the opinion of the Consultant, is suitable for use in construction
of fills. In general, fill materials can be classified as soil fills, soil-rock fills or rock fills, as
defined below.
3.1.1 Soil fills are defined as fills containing no rocks or hard lumps greater than
12 inches in maximum dimension and containing at least 40 percent by weight of
material smaller than 3/4 inch in size.
3.1.2 Soil-rock fills are defined as fills containing no rocks or hard lumps larger than
4 feet in maximum dimension and containing a sufficient matrix of soil fill to allow
for proper compaction of soil fill around the rock fragments or hard lumps as
specified in Paragraph 6.2. Oversize rock is defined as material greater than
12 inches.
3.1.3 Rock fills are defined as fills containing no rocks or hard lumps larger than 3 feet
in maximum dimension and containing little or no fines. Fines are defined as
material smaller than 3/4 inch in maximum dimension. The quantity of fines shall be
less than approximately 20 percent of the rock fill quantity.
3.2 Material of a perishable, spongy, or otherwise unsuitable nature as determined by the
Consultant shall not be used in fills.
3.3 Materials used for fill, either imported or on-site, shall not contain hazardous materials as
defined by the California Code of Regulations, Title 22, Division 4, Chapter 30, Articles 9
GI rev. 07/2015
and 10; 40CFR; and any other applicable local, state or federal laws. The Consultant shall
not be responsible for the identification or analysis of the potential presence of hazardous
materials. However, if observations, odors or soil discoloration cause Consultant to suspect
the presence of hazardous materials, the Consultant may request from the Owner the
termination of grading operations within the affected area. Prior to resuming grading
operations, the Owner shall provide a written report to the Consultant indicating that the
suspected materials are not hazardous as defined by applicable laws and regulations.
3.4 The outer 15 feet of soil-rock fill slopes, measured horizontally, should be composed of
properly compacted soil fill materials approved by the Consultant. Rock fill may extend to
the slope face, provided that the slope is not steeper than 2:1 (horizontal:vertical) and a soil
layer no thicker than 12 inches is track-walked onto the face for landscaping purposes. This
procedure may be utilized provided it is acceptable to the governing agency, Owner and
Consultant.
3.5 Samples of soil materials to be used for fill should be tested in the laboratory by the
Consultant to determine the maximum density, optimum moisture content, and, where
appropriate, shear strength, expansion, and gradation characteristics of the soil.
3.6 During grading, soil or groundwater conditions other than those identified in the
Geotechnical Report may be encountered by the Contractor. The Consultant shall be
notified immediately to evaluate the significance of the unanticipated condition
4. CLEARING AND PREPARING AREAS TO BE FILLED
4.1 Areas to be excavated and filled shall be cleared and grubbed. Clearing shall consist of
complete removal above the ground surface of trees, stumps, brush, vegetation, man-made
structures, and similar debris. Grubbing shall consist of removal of stumps, roots, buried
logs and other unsuitable material and shall be performed in areas to be graded. Roots and
other projections exceeding I '/ inches in diameter shall be removed to a depth of 3 feet
below the surface of the ground. Borrow areas shall be grubbed to the extent necessary to
provide suitable fill materials.
4.2 Asphalt pavement material removed during clearing operations should be properly
disposed at an approved off-site facility or in an acceptable area of the project evaluated by
Geocon and the property owner. Concrete fragments that are free of reinforcing steel may
be placed in fills, provided they are placed in accordance with Section 6.2 or 6.3 of this
document.
GI rev. 07/2015
4.3 After clearing and grubbing of organic matter and other unsuitable material, loose or
porous soils shall be removed to the depth recommended in the Geotechnical Report. The
depth of removal and compaction should be observed and approved by a representative of
the Consultant. The exposed surface shall then be plowed or scarified to a minimum depth
of 6 inches and until the surface is free from uneven features that would tend to prevent
uniform compaction by the equipment to be used.
4.4 Where the slope ratio of the original ground is steeper than 5:1 (horizontal:vertical), or
where recommended by the Consultant, the original ground should be benched in
accordance with the following illustration.
TYPICAL BENCHING DETAIL
Finish Grade Original Ground
2
Finish Slope Surface
Remove All - %
As Recommended By Slope To Be
Unsuitable Material
i
Such That Consultant Sloughing Or Sliding
I Varies Does Not Occur
See Note 1 See Note 2
No Scale
DETAIL NOTES: (1) Key width "B" should be a minimum of 10 feet, or sufficiently wide to permit
complete coverage with the compaction equipment used. The base of the key should
be graded horizontal, or inclined slightly into the natural slope.
(2) The outside of the key should be below the topsoil or unsuitable surficial material
and at least 2 feet into dense formational material. Where hard rock is exposed in the
bottom of the key, the depth and configuration of the key may be modified as
approved by the Consultant.
4.5 After areas to receive fill have been cleared and scarified, the surface should be moisture
conditioned to achieve the proper moisture content, and compacted as recommended in
Section 6 of these specifications.
GI rev. 07/2015
5. COMPACTION EQUIPMENT
5.1 Compaction of soil or soil-rock fill shall be accomplished by sheepsfoot or segmented-steel
wheeled rollers, vibratory rollers, multiple-wheel pneumatic-tired rollers, or other types of
acceptable compaction equipment. Equipment shall be of such a design that it will be
capable of compacting the soil or soil-rock fill to the specified relative compaction at the
specified moisture content.
5.2 Compaction of rock fills shall be performed in accordance with Section 6.3.
6. PLACING, SPREADING AND COMPACTION OF FILL MATERIAL
6.1 Soil fill, as defined in Paragraph 3.1.1, shall be placed by the Contractor in accordance with
the following recommendations:
6.1 .1 Soil fill shall be placed by the Contractor in layers that, when compacted, should
generally not exceed 8 inches. Each layer shall be spread evenly and shall be
thoroughly mixed during spreading to obtain uniformity of material and moisture
in each layer. The entire fill shall be constructed as a unit in nearly level lifts. Rock
materials greater than 12 inches in maximum dimension shall be placed in
accordance with Section 6.2 or 6.3 of these specifications.
6.1.2 In general, the soil fill shall be compacted at a moisture content at or above the
optimum moisture content as determined by ASTM D 1557.
6.1.3 When the moisture content of soil fill is below that specified by the Consultant,
water shall be added by the Contractor until the moisture content is in the range
specified.
6.1.4 When the moisture content of the soil fill is above the range specified by the
Consultant or too wet to achieve proper compaction, the soil fill shall be aerated by
the Contractor by blading/mixing, or other satisfactory methods until the moisture
content is within the range specified.
6.1.5 After each layer has been placed, mixed, and spread evenly, it shall be thoroughly
compacted by the Contractor to a relative compaction of at least 90 percent.
Relative compaction is defined as the ratio (expressed in percent) of the in-place
dry density of the compacted fill to the maximum laboratory dry density as
determined in accordance with ASTM D 1557. Compaction shall be continuous
over the entire area, and compaction equipment shall make sufficient passes so that
the specified minimum relative compaction has been achieved throughout the
entire fill.
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6.1.6 Where practical, soils having an Expansion Index greater than 50 should be placed
at least 3 feet below finish pad grade and should be compacted at a moisture
content generally 2 to 4 percent greater than the optimum. moisture content for the
material.
6.1.7 Properly compacted soil fill shall extend to the design surface of fill slopes. To
achieve proper compaction, it is recommended that fill slopes be over-built by at
least 3 feet and then cut to the design grade. This procedure is considered
preferable to track-walking of slopes, as described in the following paragraph.
6.1.8 As an alternative to over-building of slopes, slope faces may be back-rolled with a
heavy-duty loaded sheepsfoot or vibratory roller at maximum 4-foot fill height
intervals. Upon completion, slopes should then be track-walked with a D-8 dozer
or similar equipment, such that a dozer track covers all slope surfaces at least
twice.
6.2 Soil-rock fill, as defined in Paragraph 3.1.2, shall be placed by the Contractor in accordance
with the following recommendations:
6.2.1 Rocks larger than 12 inches but less than 4 feet in maximum dimension may be
incorporated into the compacted soil fill, but shall be limited to the area measured
15 feet minimum horizontally from the slope face and 5 feet below finish grade or
3 feet below the deepest utility, whichever is deeper.
6.2.2 Rocks or rock fragments up to 4 feet in maximum dimension may either be
individually placed or placed in windrows. Under certain conditions, rocks or rock
fragments up to 10 feet in maximum dimension may be placed using similar
methods. The acceptability of placing rock materials greater than 4 feet in
maximum dimension shall be evaluated during grading as specific cases arise and
shall be approved by the Consultant prior to placement.
6.2.3 For individual placement, sufficient space shall be provided between rocks to allow
for passage of compaction equipment.
6.2.4 For windrow placement, the rocks should be placed in trenches excavated in
properly compacted soil fill. Trenches should be approximately 5 feet wide and
4 feet deep in maximum dimension. The voids around and beneath rocks should be
filled with approved granular soil having a Sand Equivalent of 30 or greater and
should be compacted by flooding. Windrows may also be placed utilizing an
"open-face" method in lieu of the trench procedure, however, this method should
first be approved by the Consultant.
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6.2.5 Windrows should generally be parallel to each other and may be placed either
parallel to or perpendicular to the face of the slope depending on the site geometry.
The minimum horizontal spacing for windrows shall be 12 feet center-to-center
with a 5-foot stagger or offset from lower courses to next overlying course. The
minimum vertical spacing between windrow courses shall be 2 feet from the top of
a lower windrow to the bottom of the next higher windrow.
6.2.6 Rock placement, fill placement and flooding of approved granular soil in the
windrows should be continuously observed by the Consultant.
6.3 Rock fills, as defined in Section 3.1.3, shall be placed by the Contractor in accordance with
the following recommendations:
6.3.1 The base of the rock fill shall be placed on a sloping surface (minimum slope of 2
percent). The surface shall slope toward suitable subdrainage outlet facilities. The
rock fills shall be provided with subdrains during construction so that a hydrostatic
pressure buildup does not develop. The subdrains shall be permanently connected
to controlled drainage facilities to control post-construction infiltration of water.
6.3.2 Rock fills shall be placed in lifts not exceeding 3 feet. Placement shall be by rock
trucks traversing previously placed lifts and dumping at the edge of the currently
placed lift. Spreading of the rock fill shall be by dozer to facilitate seating of the
rock. The rock fill shall be watered heavily during placement. Watering shall
consist of water trucks traversing in front of the current rock lift face and spraying
water continuously during rock placement. Compaction equipment with
compactive energy comparable to or greater than that of a 20-ton steel vibratory
roller or other compaction equipment providing suitable energy to achieve the
required compaction or deflection as recommended in Paragraph 6.3.3 shall be
utilized. The number of passes to be made should be determined as described in
Paragraph 6.3.3. Once a rock fill lift has been covered with soil fill, no additional
rock fill lifts will be permitted over the soil fill.
6.3.3 Plate bearing tests, in accordance with ASTM D 1196, may be performed in both
the compacted soil fill and in the rock fill to aid in determining the required
minimum number of passes of the compaction equipment. If performed, a
minimum of three plate bearing tests should be performed in the properly
compacted soil fill (minimum relative compaction of 90 percent). Plate bearing
tests shall then be performed on areas of rock fill having two passes, four passes
and six passes of the compaction equipment, respectively. The number of passes
required for the rock fill shall be determined by comparing the results of the plate
bearing tests for the soil fill and the rock fill and by evaluating the deflection
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variation with number of passes. The required number of passes of the compaction
equipment will be performed as necessary until the plate bearing deflections are
equal to or less than that determined for the properly compacted soil fill. In no case
will the required number of passes be less than two.
6.3.4 A representative of the Consultant should be present during rock fill operations to
observe that the minimum number of "passes" have been obtained, that water is
being properly applied and that specified procedures are being followed. The actual
number of plate bearing tests will be determined by the Consultant during grading.
6.3.5 Test pits shall be excavated by the Contractor so that the Consultant can state that,
intheir opinion, sufficient. water is present and that voids between large rocks are
properly filled with smaller rock material. In-place density testing will not be
required in the rock fills.
6.3.6 To reduce the potential for "piping" of fines into the rock fill .from overlying soil
fill material, a 2-foot layer of graded filter material shall be placed above the
uppermost lift of rock fill. The need to place graded filter material below the rock
should be determined by the Consultant prior to commencing grading. The
gradation of the graded filter material will be determined at the time the rock fill is
being excavated. Materials typical of the rock fill should be submitted to the
Consultant in a timely manner, to allow design of the graded filter prior to the
commencement of rock fill placement.
6.3.7 Rock fill placement should be continuously observed during placement by the
Consultant.
7. SUBDRAINS
7.1 The geologic units on the site may have permeability characteristics and/or fracture
systems that could be susceptible under certain conditions to seepage. The use of canyon
subdrains may be necessary to mitigate the potential for adverse impacts associated with
seepage conditions. Canyon subdrains with lengths in excess of 500 feet or extensions of
existing offsite subdrains should use 8-inch-diameter pipes. Canyon subdrains less than 500
feet in length should use 6-inch-diameter pipes.
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8. OBSERVATION AND TESTING
8.1 The Consultant shall be the Owner's representative to observe and perform tests during
clearing, grubbing, filling, and compaction operations. In general, no more than 2 feet in
vertical elevation of soil or soil-rock fill should be placed without at least one field density
test being performed within that interval. In addition, a minimum of one field density test
should be performed for every 2,000 cubic yards of soil or soil-rock fill placed and
compacted.
8.2 The Consultant should perform a sufficient distribution of field density tests of the
compacted soil or soil-rock fill to provide a basis for expressing an opinion whether the fill
material is compacted as specified. Density tests shall be performed in the compacted
materials below any disturbed surface. When these tests indicate that the density of any
layer of fill or portion thereof is below that specified, the particular layer or areas
represented by the test shall be reworked until the specified density has been achieved.
8.3 During placement of rock fill, the Consultant should observe that the minimum number of
passes have been obtained per the criteria discussed in Section 6.3.3. The Consultant
should request the excavation of observation pits and may perform plate bearing tests on
the placed rock fills. The observation pits will be excavated to provide a basis for
expressing an opinion as to whether the rock fill is properly seated and sufficient moisture
has been applied to the material. When observations indicate that a layer of rock fill or any
portion thereof is below that specified, the affected layer or area shall be reworked until the
rock fill has been adequately seated and sufficient moisture applied.
8.4 A settlement monitoring program designed by the Consultant may be conducted in areas of
rock fill placement. The specific design of the monitoring program shall be as
recommended in the Conclusions and Recommendations section of the project
Geotechnical Report or in the final report of testing and observation services performed
during grading.
8.5 We should observe the placement of subdrains, to check that the drainage devices have
been placed and constructed in substantial conformance with project specifications.
8.6 Testing procedures shall conform to the following Standards as appropriate:
8.6.1 Soil and Soil-Rock Fills:
8.6.1.1 Field Density Test, ASTM D 1556, Density of Soil In-Place By the
Sand-Cone Method.
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8.6.1.2 Field Density Test, Nuclear Method, ASTM D 6938, Density of Soil and
Soil-Aggregate In-Place by Nuclear Methods (Shallow Depth).
8.6.1.3 Laboratory Compaction Test, ASTM D 1557, Moisture-Density
Relations of Soils and Soil-Aggregate Mixtures Using 10-Pound
Hammer and 18-Inch Drop.
8.6.1.4. Expansion Index Test, ASTM D 4829, Expansion Index Test.
9. PROTECTION OF WORK
9.1 During construction, the Contractor shall properly grade all excavated surfaces to provide
positive drainage and prevent ponding of water. Drainage of surface water shall be
controlled to avoid damage to adjoining properties or to finished work on the site. The
Contractor shall take remedial measures to prevent erosion of freshly graded areas until
such time as permanent drainage and erosion control features have been installed. Areas
subjected to erosion or sedimentation shall be properly prepared in accordance with the
Specifications prior to placing additional fill or structures.
9.2 After completion of grading as observed and tested by the Consultant, no further
excavation or filling shall be conducted except in conjunction with the services of the
Consultant.
10. CERTIFICATIONS AND FINAL REPORTS
10.1 Upon completion of the work, Contractor shall furnish Owner a certification by the Civil
Engineer stating that the lots and/or building pads are graded to within 0.1 foot vertically of
elevations shown on the grading plan and that all tops and toes of slopes are within 0.5 foot
horizontally of the positions shown on the grading plans. After installation of a section of
subdrain, the project Civil Engineer should survey its location and prepare an as-built plan
of the subdrain location. The project Civil Engineer should verify the proper outlet for the
subdrains and the Contractor should ensure that the drain system is free of obstructions.
10.2 The Owner is responsible for furnishing a final as-graded soil and geologic report
satisfactory to the appropriate governing or accepting agencies. The as-graded report
should be prepared and signed by a California licensed Civil Engineer experienced in
geotechnical engineering and by a California Certified Engineering Geologist, indicating
that the geotechnical aspects of the grading were performed in substantial conformance
with the Specifications or approved changes to the Specifications.
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LIST OF REFERENCES
2016 California Building Code, California Code of Regulations, Title 24, Part 2, based on the
2012 International Building Code, prepared by California Building Standards Commission, dated
2016.
ACI 318-11, Building Code Requirements for Structural Concrete and Commentary, prepared by
the American Concrete Institute, dated August, 2011.
ACI 330-08, Guide for the Design and Construction of Concrete Parking Lots, prepared by the
American Concrete Institute, dated June 2008.
Anderson, J. G., T. K. Rockwell, and D. C. Agnew, Past and Possible Future Earthquakes of
Significance to the San Diego Region: Earthquake Spectra, 1989, v.5, no. 2, p.299-333.
ASCE 7-10, Minimum Design Loads for Buildings and Other Structures, Second Printing, April
6, 2011.
Boore, D. M., and G. M Atkinson (2008), Ground-Motion Prediction for the Average Horizontal
Component of PGA, PG V, and 5%-Damped PSA at Spectral Periods Between 0.01 and 10.05,
Earthquake Spectra, Volume 24, Issue 1, pp. 99-138, February 2008.
California Department of Conservation, Division of Mines and Geology, Probabilistic Seismic
Hazard Assessment for the State of California, Open File Report 96-08, 1996.
California Emergency Management Agency, California Geological Survey, University of
Southern California (2009). Tsunami Inundation Map for Emergency Planning, State of
California, County of San Diego, Del Mar Quadrangle, Scale 1:24,000, dated June 1.
California Geologic Survey (2008), Special Publication 117, Guidelines For Evaluating and
Mitigating Seismic Hazards in California, Revised and Re-adopted September 11.
Campbell, K. W., and Y. Bozorgnia, NGA Ground Motion Model for the Geometric Mean
Horizontal Component of PGA, PG V, PGD and 5% Damped Linear Elastic Response Spectra for
Periods Ranging from 0.01 to 10 s, Preprint of version submitted for publication in the NGA
Special Volume of Earthquake Spectra, Volume 24, Issue 1, pages 139-171, February 2008.
Chiou, Brian S. J., and Robert R. Youngs, A NGA Model for the Average Horizontal Component
of Peak Ground Motion and Response Spectra, preprint for article to be published in NGA
Special Edition for Earthquake Spectra. Spring 2008.
City of Carlsbad (2016). City of Carlsbad Engineering Standards, Volume 5, Carlsbad BMP
Design Manual (Post Construction Treatment BMPs), dated February 16.
County of San Diego, San Diego County Multi Jurisdiction Hazard Mitigation Plan, San Diego,
California - Final Draft, July 2010.
February 9, 2018 Project No. G2225-52-01
Revised January 11, 2019
Jennings, C. W., 1994, California Division of Mines and Geology, Fault Activity Map of
California and Adjacent Areas, California Geologic Data Map SeriesMap No. 6.
Kennedy, M. P., and S. S. Tan, 2007, Geologic Map of the Oceanside 30'x60' Quadrangle,
California, USGS Regional Map Series Map No. 2, Scale 1:100,000.
Risk Engineering, EZ-FRISK, version 7.65, 2016.
United States Geological Survey, US. Seismic Design Maps Web Application,
https://earthguake.usgs.gov/designmaps/us/application.php?
United States Geological Survey, Unified Hazard Tool Web Application,
httos://earihauake.uss.ov/hazards/interactjve/
Unpublished Geotechnical Reports and Information, Geocon Incorporated.
February 9, 2018 Project No. G2225-52-01
Revised January 11, 2019