HomeMy WebLinkAboutAMEND 2018-0003; COASTLINE COMMUNITY CHURCH - 1ST AMENDMENT; UPDATE GEOTECHNICAL REPORT; 2018-10-12GEOCON
INCORPORATED
GEOTECHNICAL
ENVIRONMENTAL
MATERIALS
UPDATE
GEOTECHNICAL REPORT
COASTLINE
COMMUNITY CHURCH EXPANSION
2215 CALLE BARCELONA
CARLSBAD, CALIFORNIA
REcr:1v--"'"' :al ~.: 4~~ ".J
OCT 1 7 2018
CITY OF CARLSRArJ
PLANNING DiVi~:_·2,1
PREPARED FOR
COASTLINE COMMUNITY CHURCH
% GRANT GENERAL CONTRACTORS
CARLSBAD, CALIFORNIA
OCTOBER 12, 2018
PROJECT NO. G1968-11-02
GEOCON
INCORPORATED
GEOTECHNICAL ■
Project No. G 1968-11-02
October 12, 2018
Coastline Community Church
% Grant General Contractors
5051 A venida Encinas
Carlsbad, California 92008
Attention: Mr. Jim Grant
Subject: UPDATE GEOTECHNICAL REPORT
COASTLINE COMMUNITY CHURCH EXPANSION
2215 CALLE BARCELONA
CARLSBAD, CALIFORNIA
Dear Mr. Grant:
In accordance with your authorization of our proposal (LG-18211) dated June 5, 2018, we prepared
this update geotechnical report for use in design and construction of the proposed expansion to the
existing Coastline Community Church facility located at 2215 Calle Barcelona in Carlsbad, California.
The accompanying report presents the results of our study and conclusions and recommendations
pertaining to the geotechnical aspects of the proposed expansion. Provided the recommendations
contained in this update report are followed, the site is considered suitable for construction and support
of the proposed project.
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,
GEOCONINCORPORATED
JH:SFW:dmc
( e-mai I) Addressee
i£Pl~;-
GE 2714
6960 Flanders Drive ■ San Diego, California 92121-2974 ■ Telephone 858.558.6900 ■ Fax 858.558.6159
TABLE OF CONTENTS
1. PURPOSE AND SCOPE ...................................................................................................................... 1
2. PREVIOUS GRADING AND PROPOSED DEVELOPMENT .......................................................... 1
3. SOIL AND GEOLOGIC CONDITIONS ............................................................................................. 2
3.1 Alluvium (Qal) ........................................................................................................................... 3
3.2 Delmar Formation (Td) ............................................................................................................... 3
3.3 Torrey Sandstone (Tt) ................................................................................................................. 3
4. GROUNDWATER ............................................................................................................................... 3
5. GEOLOGIC HAZARDS ...................................................................................................................... 4
5.1 Faulting and Seismicity .............................................................................................................. 4
5.2 Ground Rupture .......................................................................................................................... 5
5.3 Liquefaction ................................................................................................................................ 5
5.4 Seiches and Tsunamis ................................................................................................................. 6
5.5 Buttress Fill ................................................................................................................................. 6
6. CONCLUSIONS AND RECOMMENDATIONS ................................................................................ 7
6.1 General. ....................................................................................................................................... 7
6.2 Excavation and Soil Characteristics ........................................................................................... 7
6.3 Seismic Design Criteria .............................................................................................................. 8
6.4 Temporary Excavations ............................................................................................................ I 0
6.5 Grading ..................................................................................................................................... I 0
6.6 Shallow Foundations and Concrete Slabs-On-Grade Recommendations ................................. 11
6.7 Concrete Flatwork .................................................................................................................... 15
6.8 Retaining Walls ........................................................................................................................ 16
6.9 Lateral Loading ......................................................................................................................... 18
6.10 Preliminary AC and PCC Pavement Recommendations .......................................................... 18
6.11 Interlocking Pervious Concrete Paver Recommendations ........................................................ 21
6.12 Site Drainage and Moisture Protection ..................................................................................... 23
6.13 Foundation Plan Review ........................................................................................................... 24
LIMITATIONS AND UNIFORMITY OF CONDITIONS
MAPS AND ILLUSTRATIONS
Figure 1, Vicinity Map
Figure 2, Geologic Map (Map Pocket)
Figure 3, Wall/Column Footing Dimension Detail
Figure 4, Retaining Wall Loading Diagram
Figure 5, Typical Retaining Wall Drain Detail
LIST OF REFERENCES
-----------------------~-----_,.,.~-..-.,, --,---~
UPDATE GEOTECHNICAL REPORT
1. PURPOSE AND SCOPE
This report presents the results of our update geotechnical study for the proposed expansion project to
the existing Coastline Community Church facility located at 2215 Calle Barcelona in Carlsbad,
California (see Vicinity Map, Figure 1). The purpose of this geotechnical report is to evaluate the
surface and subsurface soil conditions and general site geology, and to identify geotechnical
constraints that may affect the proposed expansion project including faulting, liquefaction and
seismic shaking based on the 2016 CBC seismic design criteria. In addition, this report provides
recommendations for remedial grading, building foundation and slab-on-grade, retaining wall, new
pavement and concrete flatwork for use in design and construction of the expansion project.
The scope of this study included a site visit and a review of:
1. Grading, Streets and Utilities Plan for Coastline Community Church, 2215 Calle Barcelona,
Carlsbad, California, prepared by Fuscoe Engineering, Submittal #3 dated October 12, 2018.
2. Final Report of Testing and Observation Services During Site Grading, Arroyo La Costa
Church Site, Carlsbad, California, prepared by Geocon Incorporated, dated April 13, 1999
(project No. 05871-12-01 ).
3. Final Report of Testing and Observation Services Performed During Site Grading, Coastline
Community Church, Carlsbad, California, prepared by Geocon Incorporated, dated
December 20, 2006 (Project No. 05871-52-24A).
2. PREVIOUS GRADING AND PROPOSED DEVELOPMENT
The site consists of developed land that was graded in 1997 and 2006 creating a graded church site
with an existing building finish pad grade of roughly 104 feet above Mean Sea Level (MSL), storage
shed, play areas, parking lots and driveways. The Geologic Map, Figure 2, shows the current geologic
conditions, existing buildings/improvements and proposed buildings and improvements. The
referenced Fuscoe grading plan was used as the base map for our figure.
Sheet grading on the property occurred in 1997 during grading operations for the designated Arroyo
La Costa church site pad. The previous grading consisted of the partial removal of surficial soil
extending roughly to the groundwater table on the northeastern portion of the site, complete removal
of surficial soil on the remainder of the site, and the construction of a buttress fill on the southern
portion of the site to stabilize weak formational materials. Alluvium left in place below the
groundwater table has an estimated thickness of approximately IO to 15 feet. Grading consisted of the
placement of compacted fill to achieve sheet-grade elevations. A surcharge fill was placed and
settlement monitoring of the fill and buried alluvium was performed until surveyor readings
Project No. Gl968-11-02 -I • October 12, 2018
essentially showed negligible vertical movements. The 1997 fill was placed under the observation
and compaction testing services of Geocon Incorporated for the overall Arroyo La Costa
development as discussed on our referenced report dated April 13, 1999.
We performed testing and observation services during the fine grading of the existing church facility
and parking lots to achieve its current finish grade elevations as discussed in our referenced report
dated December 20, 2006. Additional fill up to roughly 18 feet thick was placed on the sheet-graded
pad. The construction also included retaining walls, play areas, tot lot, driveways and terraced
parking lots. The existing buildings and improvements were constructed in 2007 or thereafter with
the church community building supported by a post-tensioned foundation system. The majority of the
existing Worship Center Building consists of compacted fill overlying alluvium left in place with the
southwest comer consisting of compacted fill overlying the Delmar Formation. The existing Cafe
Building consists of compacted fill overlying alluvium left in place and the Delmar Formation.
The proposed expansion project will include the following.
• An expansion and tenant improvements of the existing Worship Center and Cafe Buildings
on the northeast portion of the property.
• A new one-story Ministry Building on the northwest portion of the property with a finish
floor elevation of l 00.0 feet MSL.
• A new, two-story Maintenance Building on the southeast comer of the site south of Drive A
with a finish floor elevation of 132.5 feet MSL.
• A new Drive C located between existing Drives A and B. This will include adding 68 parking
stalls.
• Three biofiltration basins and various courtyard and surface improvements.
• Concrete pavers on the west terminus of Drive A.
• Construction of several retaining walls with a maximum height of about 8 feet to achieve
proposed finish grades.
3. SOIL AND GEOLOGIC CONDITIONS
Based on review of the referenced geotechnical reports, the church facility is underlain by previously
placed compacted fill overlying the Delmar Formation and alluvium left in place below the
groundwater table. The existing fill thickness is roughly 20 to 25 feet across the site. Laboratory tests
performed on samples of the on-site fill during previous grading operations indicate the near surface
soil has a "very low" expansion potential ( expansion index of 20 or less) and an "SO" sulfate severity
exposure.
Project No. G 1968-11-02 -2 -October 12, 2018
-------------------------·-·-. --------------'-~---~~·~-----------------
3.1 Alluvium (Qal)
During previous remedial grading operations, the majority of alluvium present at the site was
removed and replaced with compacted fill. However, due to the presence of shallow groundwater, a
portion of the alluvium in the northeastern portion of the site was left in place. Compacted fill was
placed over the alluvium in this area to reach current site elevation. The alluvium generally consists
of dark brown, sandy clays to clayey sands. The maximum thickness of alluvium is estimated to be
approximately 15 feet near the northeast comer of the property. The alluvium left in place is suitable
to support the proposed expansion project.
3.2 Delmar Formation (Td)
The Eocene-aged Delmar Formation, consisting of hard, greenish-gray to brown, claystones and
siltstones with layers of silty, fine to coarse sandstones, underlies the compacted fill soils throughout
the majority of the site. Due to the cover of compacted fill at the site, it is not anticipated that this
formational unit will be encountered during grading operations. The Delmar Formation is suitable to
support the proposed expansion project.
3.3 Torrey Sandstone (Tt)
The Tertiary-aged Torrey Sandstone consists of dense, damp to moist, light tan to orange-brown,
silty, fine sandstone with varying amounts of clay. The Torrey Sandstone was generally deposited
conformably upon the Delmar Formation and appears to dip from horizontal to ten degrees to the
southwest. The contact is approximately located at an elevation of 130 MSL near the southern
property line. The formational Torrey Sandstone is not anticipated to be encountered during grading
operations.
4. GROUNDWATER
We observed groundwater at the base of the surficial soil removals performed in 1999 during the
previous grading operations. We expect that the static groundwater table would be in excess of 15 to
20 feet below existing grades for the existing and new buildings. We do not expect groundwater to
affect the expansion project; however, it is not uncommon for shallow seepage conditions to develop
where none previously existed. Seepage is dependent on seasonal precipitation, irrigation; land use,
among other factors, and vary as a result. Proper surface drainage will be important to future
performance of the building.
Project No. G1968-11-02 -3 -October 12, 2018
5. GEOLOGIC HAZARDS
5.1 Faulting and Seismicity
A review of geologic literature and our knowledge of the general area indicate that the site is not
underlain by active, potentially active or inactive faults. An active fault is defined by the California
Geological Survey (CGS) as a fault showing evidence for activity within the last 11,000 years. The
site is not located within a State of California Earthquake Fault Zone.
According to the computer program EZ-FRISK (Version 7.65), nine 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/Rose Canyon Fault system,
located approximately 5 miles west of the site and is the dominant source of potential ground motion.
Earthquakes that might occur on the Newport-Inglewood/Rose Canyon Faults 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/Rose Canyon Faults are 7.5 and 0.38g, respectively.
Table 5.1.1 lists the estimated maximum earthquake magnitude and peak ground acceleration for the
most dominant faults in relationship to the site location. We calculated peak ground acceleration
(PGA) using Boore-Atkinson (2008) NGA USGS2008, Campbell-Bozorgnia (2008) NGA
USGS2008, and Chiou-Youngs (2007) NGA USGS2008 acceleration-attenuation relationships.
TABLE 5.1.1
DETERMINISTIC SPECTRA SITE PARAMETERS
Maximum Peak Ground Acceleration
Distance Earthquake Fault Name from Site Boore-Campbell-Chiou-
(miles) Magnitude Atkinson Bozorgnia Youngs (Mw) 2008 (g) 2008 (g) 2007 (g)
Newport-Inglewood 5 7.5 0.33 0.30 0.38
Rose Canyon 5 6.9 0.29 0.28 0.32
Coronado Bank 21 7.4 0.19 0.13 0.15
Palos Verdes Connected 21 7.7 0.20 0.14 0.18
Elsinore 23 7.9 0.20 0.13 0.18
Earthquake Valley 40 6.8 0.09 0.06 0.05
Palos Verdes 41 7.3 0.11 0.08 0.08
San Joaquin Hills 43 7.1 0.10 0.09 0.08
San Jacinto 49 7.9 0.12 0.08 0.10
Project No. G 1968-11-02 • 4 -October 12, 2018
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 mapped Quaternary fault is proportional to the faults slip rate. The program accounts for
earthquake magnitude as a function of fault rupture length, 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: (I) 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
USGS2008, Campbell-Bozorgnia (2008) NGA USGS2008, and Chiou-Youngs (2007) NGA
USGS2008 in the analysis. Table 5.1.2 presents the site-specific probabilistic seismic hazard
parameters including acceleration-attenuation relationships and the probability of exceedence.
TABLE 5.1.2
PROBABILISTIC SEISMIC HAZARD PARAMETERS
Peak Ground Acceleration
Probability of Exceedence Boore-Atkinson, Campbell-Bozorgnia, Chiou-Youngs,
2008 (g) 2008 (g) 2007 (g)
2% in a 50 Year Period 0.51 0.43 0.50
5% in a 50 Year Period 0.38 0.32 0.36
10% in a 50 Year Period 0.30 0.24 0.27
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 California Building Code (CBC) guidelines currently adopted by the City of Carlsbad.
5.2 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 the earth surface. The potential for ground rupture is
considered to be negligible due to the absence of active faults at the subject site.
5.3 Liquefaction
Liquefaction typically occurs when a site is located in a zone with seismic activity, onsite soil is
cohesionless/silt or clay with low plasticity, groundwater is encountered within 50 feet of the surface,
Project No. GI 968-11-02 -5 -October 12, 2018
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. Based on our review of previous reports and review of published geologic
literature, it is our opinion that the potential for liquefaction is very low considering the dense nature
of the underlying compacted fill, densified alluvial soil from the placement of fill and previous
surcharge, and very dense formational materials.
5.4 Seiches and Tsunamis
Seiches are caused by the movement of an inland body of water due to the movement from seismic
forces. The potential of seiches to occur is considered to be very low due to the absence of a nearby
inland body of water.
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 site is located approximately 3 miles from the Pacific Ocean at an elevation of at
least 90 feet above Mean Sea Level. Therefore, the risk of tsunamis affecting the site is negligible.
5.5 Buttress Fill
A drained buttress fill was constructed to mitigate potential gross and surficial slope instability at the
site. The buttress fill was constructed where a landslide and bedding plane shears were previously
identified. The landslide was completely removed, and a keyway was excavated. A heel drain was
installed during construction of the buttress fill on the site. The heel drain was "as-built" for location
and elevation by the project civil engineer. The heel drain generally consisted of a 6-inch-diameter
PVC perforated pipe placed in crushed aggregate surrounded by Mirafi 140N filter fabric. The drain
was generally placed at the heel of the buttress fill keyway and constructed at a gradient of at least
1 percent. In addition, drainage panels (Miradrain 5000) were placed at 30 feet on center along the
face of the stabilization fill backcut and were connected to the heel drain. The heel drain was
extended to the desilting basin in the northwest comer of the site and discharges at surface grade. A
concrete wall was constructed at the outlet point to protect against blockage or destruction of the heel
drain outlet. The heel drain outlet should be maintained regularly to prevent sediment and debris from
obstructing the free flow of water out of the heel drain system. The heel drain location is shown on
the Geologic Map (Figure 2). The results of our prior analyses for gross stability indicate that the
existing buttress fill has a calculated factor of safety in excess of 1.5.
Project No. Gl968-l l-02 -6 -October 12, 2018
6. CONCLUSIONS AND RECOMMENDATIONS
6.1 General
6.1.1 From a geotechnical engineering standpoint, it is our opinion that the proposed expansion
project to the existing Coastline Community Church facility is suitable provided the
recommendations presented herein are implemented in design and construction of the
project.
6.1.2 With the exception of possible moderate to strong seismic shaking, we did not observe or
know of significant geologic hazards to exist on the site that would adversely affect the
proposed project.
6.1.3 The referenced previous geotechnical reports indicate the site is underlain by compacted
fill, alluvium and the Delmar Formation. Fill depths of roughly 20 to 25 exist beneath the
site based on information presented in the referenced geotechnical reports. Based on our
observations from a limited site reconnaissance, it appears the existing fill has provided
suitable bearing support for the existing buildings and improvements, and we expect it
should be suitable for the expansion project including new foundations and slab-on-grade.
6.1.4 We expect that the planned structures will be supported by a foundation system founded
into properly compacted fill with conventional shallow foundation systems or a post-
tensioned foundation system.
6.1.5 We do not expect groundwater or seepage to be encountered during construction of the
proposed improvements. However, development during the rainy season can cause wet soil
conditions and localized seepage near ponded water.
6.1.6 Excavation of the existing fill should generally be possible with moderate effort using
conventional, heavy-duty grading and trenching equipment.
6.2 Excavation and Soil Characteristics
6.2.1 Excavation of the in-situ soil should be possible with moderate to heavy effort using
conventional heavy-duty equipment. Excavation of the formational materials will require
very heavy effort and may generate oversized material using conventional heavy-duty
equipment during the grading operations. Oversized rock (rocks greater than 12-inches in
dimension) may be generated with the formational materials that can be incorporated into
landscape use or deep compacted fill areas, if encountered.
Project No. GI 968-11-02 -7 -October 12, 2018
6.2.2 Based on the soil encountered in the previous grading operations for the site, we expect the
near surface soil to be "non-expansive" ( expansion index of 20 or less) as defined by 2016
California Building Code (CBC) Section 1803.5.3. Table 6.2 presents soil classifications
based on the expansion index. Based on the reported results of previous laboratory testing,
we expect the on-site materials will possess a "very low" expansion potential (Expansion
Index of20 or less).
TABLE 6.2
EXPANSION CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (El) Expansion Classification 2016 CBC
Expansion Classification
0-20 Very Low Non-Expansive
21 -50 Low
51-90 Medium
91 -130 High Expansive
Greater Than 130 Very High
6.2.3 Previously reported laboratory water-soluble sulfate content test results indicate an "SO"
sulfate severity 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
concentrations. Additionally, over time landscaping activities (i.e., addition of fertilizers
6.2.4 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore,
further evaluation by a corrosion engineer may be performed if improvements that could be
susceptible to corrosion are planned.
6.3 Seismic Design Criteria
6.3.1 We used the computer program U.S. Seismic Design Maps, provided by the USGS.
Table 6.3 .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. The new and existing building structures and
improvements should be designed using a Site Class D. We evaluated the Site Class based
on the discussion in Section 1613.3.2 of the 2016 CBC and Table20.3-1 of ASCE 7-10.
The values presented in Table 6.3. l are for the risk-targeted maximum considered
earthquake (MCfa).
Project No. G1968-1 l-02 -8 -October 12, 2018
TABLE6.3.1
2016 CBC SEISMIC DESIGN PARAMETERS
Parameter Value 2016 CBC Reference
Site Class D Table 1613.3.2
MCER Ground Motion Spectral Response 1.070g Figure 1613.3.1(1) Acceleration -Class B (short), Ss
MCER Ground Motion Spectral Response 0.413g Figure 1613.3.1(2) Acceleration -Class B ( 1 sec), S,
Site Coefficient, FA 1.072 Table 1613.3.3(1)
Site Coefficient, F v 1.587 Table 1613.3.3(2)
Site Class Modified MCER Spectral 1.147g Section 1613.3.3 (Eqn 16-37) Response Acceleration (short), SMs
Site Class Modified MCER Spectral 0.655g Section 1613.3.3 (Eqn 16-38) Response Acceleration (1 sec), SM,
5% Damped Design Spectral 0.765g Section 1613.3.4 (Eqn 16-39) Response Acceleration (short), Sos
5% Damped Design Spectral 0.437g Section 1613.3.4 (Eqn 16-40) Response Acceleration ( 1 sec), SDI
6.3.2 Table 6.3.2 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 (MCEo).
TABLE6.3.2
2016 CBC SITE ACCELERATION DESIGN PARAMETERS
Parameter Value ASCE 7-10 Reference
Mapped MCEo Peak Ground Acceleration, PGA 0.422g Figure 22-7
Site Coefficient, F PGA 1.078 Table 11.8-1
Site Class Modified MCE0 0.455g Section 11.8.3 (Eqn 11.8-1) Peak Ground Acceleration, PGAM
6.3.3 Conformance to the criteria in Tables 6.3.1 and 6.3.2 for seismic design does not constitute
any kind of guarantee or assurance that significant structural damage or ground failure will
not occur if a maximum level earthquake occurs. The primary goal of seismic design is to
protect life and not to avoid all damage, since such design may be economically
prohibitive.
Project No. G 1968-11-02 -9 -October 12, 2018
6.3.4 The project structural engineer and architect should evaluate the appropriate Risk Category
and Seismic Design Category for the planned structures. The values presented herein
assume a Rick Category of I, II or III and resulting in a Seismic Design Category D.
6.4 Temporary Excavations
6.4.1 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.
6.4.2 The stability of the excavations is dependent on the design and construction of the shoring
system and site conditions. Therefore, Geocon Incorporated cannot be responsible for site
safety and the stability of the proposed excavations. It is the responsibility of the
contractors during excavations to follow all applicable safety standards and industry
protocols when performing excavations during the construction of the proposed project.
6.4.3 Temporary excavations should be made in conformance with OSHA requirements. The
properly compacted fill can be considered a Type B soil (Type C soil if seepage or
groundwater is encountered) and the formational materials (without weak bedding planes)
should be considered a Type A soil (Type B soil if seepage or groundwater is encountered)
in accordance with OSHA requirements. In general, special 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.
6.5 Grading
6.5.1 Grading should be performed in accordance with the recommendations presented herein.
We should perform the testing and observation services during the grading and
improvement operations.
6.5.2 Prior to commencing grading, a preconstruction conference should be held at the site with
the owner or developer, grading contractor, city inspector, civil engineer and geotechnical
engineer in attendance. Special soil handling requirements can be discussed at that time.
Project No. G 1968-11-02 -10 -October 12, 2018
-------------------,.----,-·-~~-~
6.5.3 Site preparation should begin with the removal of vegetation and debris and the demolition
of the existing hardscape and landscaping in the area of the proposed improvements. The
depth of removal should be such that material to be used as fill is generally free of organic
matter. Material generated during stripping operations should be exported from the site.
6.5.4 We expect that the near surface soil will consist of previously compacted fill that will be
loose and dry or locally saturated in landscape and basin areas. The upper 1 to 3 feet of the
existing soil should be removed below existing grade with the depth dependent on its
density and moisture content prior to placing new fill soil. The bottom of the removal
should be processed, moisture conditioned as necessary and properly compacted within the
limits of proposed improvements. We should be present during removals to evaluate the
limits of the remedial grading. Deeper removals may be required where relatively soft, dry,
or saturated soil is encountered.
6.5.5 Excavated soil generally free of deleterious debris can be placed as new fill by compacting
in layers to the design finish-grade elevations. Fill and backfill soil should be compacted to
a dry density of at least 90 percent of laboratory maximum dry density near to slightly
above optimum moisture content as determined by ASTM Test Procedure D 1557.
6.5.6 Import fill (if necessary) should consist of granular materials with a "very low" to "low"
expansion potential (EI of 50 or less), free of deleterious material or rock 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 determine its suitability as fill material.
6.6 Shallow Foundations and Concrete Slabs-On-Grade Recommendations
6.6.1 The proposed new buildings and building expansions can be supported on shallow
foundations bearing on compacted fill. Foundations should consist of continuous strip
footings and/or isolated spread footings. Continuous footings should be at least 12 inches
wide and extend at least 24 inches below lowest adjacent pad grade. Isolated spread
footings should have a minimum width of 2 feet and should also extend at least 24 inches
below lowest adjacent pad grade. A wall/column footing dimension detail is presented on
Figure 3.
6.6.2 Steel reinforcement for continuous footings should consist of at least four No. 5 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.
Project No. GI 968-11-02 -11 -October 12, 2018
6.6.3 Footings for buildings and retaining walls should be deepened such that the bottom outside
edge of the footing is at least 7 feet horizontally from the face of slopes.
6.6.4 The recommendations herein are based on soil characteristics only (EI of 50 or less) and
are not intended to replace reinforcement required for structural considerations.
6.6.5 The recommended allowable bearing capacity for foundations with minimum dimensions
described herein and bearing in compacted fill is 2,000 pounds per square foot (pst). 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.
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.
6.6.6 We estimate the total and differential settlements under the imposed allowable loads to be
about 1 inch and½ inch, respectfully, based on a 5-foot square footing.
6.6.7 New concrete floor slabs should possess a thickness of at least 5 inches and reinforced with
a minimum of No. 3 steel reinforcing bars at 18 inches on center in both horizontal
directions placed in the middle of the slab based on soil conditions. The structural engineer
should design the steel required for the planned expansion.
6.6.8 Slabs that may receive moisture-sensitive floor coverings or may be used to store moisture-
sensitive materials should be underlain by a vapor retarder. The vapor retarder design should
be consistent with the guidelines presented in the American Concrete Institute's (ACI) 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 vapor retarder used should be specified by the project architect or developer based on the
type of floor covering that will be installed and if the structure will possess a humidity-
controlled environment.
6.6.9 As an alternative to the conventional foundation recommendations, consideration should be
given to the use of post-tensioned concrete slab and foundation systems for the support of
the proposed structures. The post-tensioned systems should be designed by a structural
engineer experienced in post-tensioned slab design and design criteria of the
Post-Tensioning Institute (PTI) DC 10.5 as required by the 2016 California Building Code
(CBC Section 1808.6.2). Although this procedure was developed for expansive soil
conditions, we understand it can also be used to reduce the potential for foundation distress
due to differential fill settlement. The post-tensioned design should incorporate the
Project No. Gl968-l l-02 -12 -October 12, 2018
6.6.10
6.6.11
6.6. 12
6.6.13
geotechnical parameters presented on Table 6.6. The parameters presented in Table 6.6 are
based on the guidelines presented in the PTI, DC 10.5 design manual.
TABLE6.6
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (PTI) Value DCl 0.5 Design Parameters
Thornthwaite Index -20
Equilibrium Suction 3.9
Edge Lift Moisture Variation Distance, eM (feet) 4.9
Edge Lift, YM (inches) 1.58
Center Lift Moisture Variation Distance, eM (feet) 9.0
Center Lift, YM (inches) 0.66
If the structural engineer proposes a post-tensioned foundation design method other than the
2016 CBC:
• The criteria presented in Table 6.6 are still applicable.
• Interior stiffener beams should be used.
• The width of the perimeter foundations should be at least 12 inches.
• The perimeter footing embedment depths should be at least 24 inches. The
embedment depths should be measured from the lowest adjacent pad grade.
Our experience indicates post-tensioned slabs are susceptible to excessive edge lift,
regardless of the underlying soil conditions. Placing reinforcing steel at the bottom of the
perimeter footings and the interior stiffener beams may mitigate this potential. Current PTI
design procedures primarily address the potential center lift of slabs but, because of the
placement of the reinforcing tendons in the top of the slab, the resulting eccentricity after
tensioning reduces the ability of the system to mitigate edge lift. The structural engineer
should design the foundation system to reduce the potential of edge lift occurring for the
proposed structures.
The foundations for the post-tensioned slabs should be embedded in accordance with the
recommendations of the structural engineer. If a post-tensioned mat foundation system is
planned, the slab should possess a thickened edge with a minimum width of 12 inches and
extend below the clean sand or crushed rock layer.
During the construction of the post-tension foundation system, the concrete should be
placed monolithically. Under no circumstances should cold joints form between the
Project No. GI 968-11-02 -13 -October I 2, 2018
6.6.14
6.6.15
6.6.16
6.6.17
6.6.18
6.6.19
footings/grade beams and the slab during the construction of the post-tension foundation
system unless designed by the project structural engineer.
Isolated footings, if present, should have the minimum embedment depth and width
recommended for conventional foundations. The use of isolated footings, which are located
beyond the perimeter of the building and support structural elements connected to the
building, are not recommended. Where this condition cannot be avoided, the isolated
footings should be connected to the building foundation system with grade beams.
Consideration should be given to using interior stiffening beams and connecting isolated
footings and/or increasing the slab thickness. In addition, consideration should be given to
connecting patio slabs, which exceed 5 feet in width, to the building foundation to reduce
the potential for future separation to occur.
The bedding sand thickness should be determined by the project foundation engineer,
architect, and/or developer. It is common to have 3 inches of sand for 5-inch thick slabs in
the southern California region. However, we should be contacted to provide
recommendations if the bedding sand is thicker than 6 inches. 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.
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.
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.
The foundation and concrete slab-on-grade recommendations are based on soil support
characteristics only. The project structural engineer should evaluate the structural
requirements of the concrete slabs for supporting expected loads.
Project No. GI 968-11-02 -14 -October 12, 2018
6.6.20
6.6.21
6.6.22
Concrete slabs should be provided with adequate crack-control joints, construction joints
and/or expansion joints to reduce unsightly shrinkage cracking. The design of joints should
consider criteria of the American Concrete Institute when establishing crack-control
spacing. Additional steel reinforcing, concrete admixtures and/or closer crack control joint
spacing should be considered where concrete-exposed finished floors are planned.
The recommendations of this report are intended to reduce the potential for cracking of
slabs due to expansive soil (if present), differential settlement of existing soil or soil with
varying thicknesses. However, even with the incorporation of the recommendations
presented herein, foundations, stucco walls, and slabs-on-grade placed on such conditions
may still exhibit some cracking due to soil movement and/or shrinkage. The occurrence of
concrete shrinkage cracks is independent of the supporting soil characteristics. Their
occurrence may be reduced and/or controlled by limiting the slump of the concrete, proper
concrete placement and curing, and by the placement of crack control joints at periodic
intervals, in particular, where re-entrant slab corners occur.
Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
6. 7 Concrete Flatwork
6.7.1 Exterior concrete tlatwork 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 -W2.9/W2.9 (6 x 6 -6/6) welded wire mesh or No. 3 reinforcing bars spaced at
18 inches on center in both directions to reduce the potential for cracking. In addition,
concrete tlatwork 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 (ACI) 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.
6.7.2 Even with the incorporation of the recommendations within this report, the exterior
concrete tlatwork has a likelihood of experiencing some movement due to swelling or
settlement; therefore, the reinforcing steel should overlap continuously in tlatwork to
reduce the potential for vertical offsets within tlatwork.
Project No. Gl968-l l-02 -15 -October 12, 2018
6.7.3 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.
6.8 Retaining Walls
6.8. l 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 (pct). Where the backfill will be inclined at 2:1 (horizontal to
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.
6.8.2 Unrestrained walls are those that are allowed to rotate more than 0.001H (where H equals
the height of the retaining portion of the wall) at the top of the wall. Where walls are
restrained from movement at the top (at-rest condition), an additional uniform pressure of
7H psf should be added to the active soil pressure for walls 8 feet or less. For walls greater
than 8 feet tall, an additional uniform pressure of 13H psf should be applied to the wall
starting at 8 feet from the top of the wall to the base of the wall. For retaining walls subject
to vehicular loads within a horizontal distance equal to two-thirds the wall height, a
surcharge equivalent to 2 feet of fill soil should be added.
6.8.3 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 7-10. 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 (pst) exerted at the base of the wall and zero at the top of the wall. A
seismic load of 16H should be used for design. We used the peak ground acceleration
adjusted for Site Class effects, PGAM, of0.455g calculated from ASCE 7-10 Section 11.8.3
and applied a pseudo-static coefficient of 0.3. Figure 4 presents a retaining wall loading
diagram.
6.8.4 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
Project No. Gl968-l l-02 -16 -October 12, 2018
earth pressure combined with the seismic design load should be reviewed and also
considered in the design of the retaining walls.
6.8.5 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
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 5 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.
6.8.6 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: I could affect 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.
6.8. 7 The recommendations presented herein are generally applicable to the design of rigid
concrete or masonry retaining walls. In the event that other types of walls (such as
mechanically stabilized earth [MSE] walls, soil nail walls, or soldier pile walls) are
planned, Geocon Incorporated should be consulted for additional recommendations.
6.8.8 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.
6.8.9 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.
Project No. G 1968-11-02 -17 -October 12, 2018
6.9 Lateral Loading
6.9.1 To resist lateral loads, a passive pressure exerted by an equivalent fluid weight of
300 pounds per cubic foot (pct) should be used for the design of footings or shear keys
poured neat in compacted fill. The 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.
6.9.2 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.
6.9.3 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.
6.10
6.10.1
6.10.2
Preliminary AC and PCC Pavement Recommendations
We calculated the flexible, asphalt concrete (AC) pavement sections in general
conformance with the Ca/trans Method of Flexible Pavement Design (Highway Design
Manual, Section 608.4) using a Traffic Index (TI) of 5.0 and 5.5 for the private drives and
parking stalls, respectively. The final pavement sections should be based on the R-Value of
the subgrade soil encountered at final subgrade elevation. We used an R-Value of 20 for
the subgrade soil based on previous laboratory test results and an R-Value of 78 for base
materials, respectively, for the purposes of this preliminary analysis. Table 6.10. 1 presents
the preliminary flexible pavement sections.
TABLE 6.10.1
PRELIMINARY FLEXIBLE PAVEMENT SECTION
Assumed Asphalt Class 2
Location Assumed Subgrade Concrete (AC) Aggregate Base Traffic Index R-Value (inches) (inches)
Parking Stalls 5.0 20 4.0 5.0
Driveways 5.5 20 4.0 6.0
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 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
Project No. G 1968-11-02 -18 -October 12, 2018
6.10.3
6.10.4
6.10.5
6.10.6
--------..------------
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.
A rigid Portland cement concrete (PCC) pavement section can also be used for vehicular
pavement. 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 6.10.2.
TABLE 6.10.2
RIGID PAVEMENT DESIGN PARAMETERS
Design Parameter Design Value
Modulus of subgrade reaction, k 50 pci
Modulus of rupture for concrete, MR 500 psi
Traffic Category, TC AandB
Average daily truck traffic, ADTT 10 and 25
Based on the criteria presented herein, the PCC pavement sections should have a minimum
thickness as presented in Table 6.10.3.
TABLE 6.10.3
RIGID PAVEMENT RECOMMENDATIONS
Location Portland Cement Concrete (inches)
Parking Stalls (TC= A) 6.0
Driveways (TC = B) 7.0
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 material
will not be required beneath concrete improvements.
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
Project No. G 1968-11-02 -19 -October 12, 2018
6.10.7
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.
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 slabs thicker than 6 inches ( e.g. a 7-inch-thick slab would have a
15-foot spacing pattern), 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.
6.10.8 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, I -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 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.
6.10.9 The performance of pavement is highly dependent on providing positive surface drainage
away from the edge of the pavement. Ponding of water on or adjacent to the pavement will
likely result in pavement distress and subgrade failure if not mitigated. Drainage from
landscaped areas should be directed to controlled drainage structures. Landscape areas
adjacent to the edge of asphalt pavements are not recommended due to the potential for
surface or irrigation water to infiltrate the underlying permeable aggregate base and cause
distress. Where such a condition cannot be avoided, consideration should be given to
incorporating measures that will significantly reduce the potential for subsurface water
migration into the aggregate base. If planter islands are planned, the perimeter curb should
extend at least 6 inches.
Project No. G1968-l l-02 -20 -October 12, 2018
6.11
6.11.1
6.11.2
6.11.3
6.11.4
6.11.5
----,,-~-------..., __________________ _
Interlocking Pervious Concrete Paver Recommendations
We understand vehicular pervious concrete pavers will be installed on at the western
terminus of Drive A. The concrete paver thickness should not be less than 3½ inches. The
pavers should be installed and maintained in accordance with the manufacturer's
recommendations. In addition, the concrete pavers should be installed in a pattern
acceptable for vehicular traffic. A subdrain should be installed within the base materials at
the low point of the subgrade as discussed herein.
We calculated the concrete paver pavement sections in general conformance with the
Ca/trans Method of Flexible Pavement Design (Highway Design Manual, Section 608.4).
We used an R-Value of20 for the subgrade soil for our analysis and an R-Value of 78 for
the base materials per Caltrans specifications.
We understand that Class 2 aggregate base will be placed below the concrete pavers. We
calculated the base section based on an equivalent asphalt concrete section equal to the
thickness of the concrete vehicular paver (about 3 inches or 80 mm) in accordance with the
Interlocking Concrete Pavement Institute, Tech Spec Number 4. The paver pavement
sections can be increased as required by manufacturer's recommendations. Table 6.11
presents the recommended interlocking paver pavement sections.
TABLE 6.11
INTERLOCKING PAVER PAVEMENT SECTIONS
Estimated Bedding Minimum
Location Traffic Subgrade Paver Sand Thickness Class 2 Aggregate
Index R-Value Thickness (inches) Base Thickness
(inches) (inches)
Driveway 5.5 20 3¼ 1-2 9
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 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.
The property owner should be informed by the manufacturer of their responsibility for the
paver maintenance program. In addition, pavers tend to shift vertically and horizontally
during the life of the pavement and should be expected. The pavers normally require a
Project No. Gl968-l l-02 -21 -October 12, 2018
6.11.6
6.11.7
6.11.8
6.11.9
concrete border to reduce the magnitude of lateral movement from traffic. The concrete
border surrounding the pavers should be embedded at least 6 inches from finish grade
surface. We understand that the space between concrete pavers will be pervious to allow
water infiltration into the underlying base materials. The recommendations for draining the
base of water as discussed herein should be included in design.
Concrete pedestrian pavers can be used at the site as long as surface runoff is not
concentrated toward the permeable paver areas. The pedestrian concrete pavers can also be
designed as permeable if desired with the addition of a subdrain placed within the base.
Therefore, the bottom of permeable paver areas do not need to be lined.
Based on the Interlocking Concrete Pavement Institute (ICPI), the pavers should possess a
minimum thickness of 60 millimeters overlying l to 1 ½ inch of sand. The sand should be
underlain by at least 4 inches of Class 2 aggregate base or #57 aggregate in accordance
with ASTM C 33 and in accordance with the manufacturer's recommendations. The
aggregate section can be thickened to increase the water capacity as required by the project
civil engineer.
Prior to placing aggregate materials, the subgrade soil should be scarified, moisture
conditioned as necessary, and recompacted to a dry density of at least 90 percent of the
laboratory maximum dry density near to slightly above optimum moisture content as
determined by ASTM D 1557. The depth of compaction should be at least 12 inches.
Similarly, the aggregate base materials 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.
The subgrade of the pervious pavers should be graded to allow water to flow to a subdrain at
a minimum gradient of 2 percent. A subdrain should be installed within the base materials at
the low point of the subgrade to reduce the potential for water to build up within the paving
section. The subdrain can be elevated above the subgrade a maximum of 3 inches within the
base section. The subdrain should be connected to an approved drainage device. The subdrain
should consist of at least 3-inch diameter perforated Schedule 40, PVC pipe.
6.11.10 A continuous impermeable liner or rigid concrete cutoff wall should be installed along the
sides of the pervious paver section to prevent water migration. The sidewall liner is not
required if the concrete border wall is installed to an elevation of the bottom of the base
materials. The sidewall liner should consist of a high density polyethylene (HDPE) with a
minimum thickness of 15 mil or equivalent with the liner or concrete cutoff wall extending to
the subgrade elevation. The liner/barrier should be sealed at the connections in accordance
Project No. G1968-l l-02 -22 -October 12, 2018
with manufacturer recommendations and should be properly waterproofed at the drain
connection.
6.11.11 The performance of pavement is highly dependent on providing positive surface drainage
away from the edge of the pavement. Ponding of water on or adjacent to the pavement will
likely result in pavement distress and subgrade failure. Drainage from landscaped areas
should be directed to controlled drainage structures. Landscape areas adjacent to the edge of
asphalt pavements are not recommended due to the potential for surface or irrigation water to
infiltrate the underlying permeable aggregate base and cause distress. Where such a condition
cannot be avoided, consideration should be given to incorporating measures that will
significantly reduce the potential for subsurface water migration into the aggregate base. If
planter islands are planned, the perimeter curb should extend at least 6 inches below the level
of the base materials.
6.12
6. 12.1
6.12.2
6.12.3
6.12.4
Site Drainage and Moisture Protection
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. The site should be graded and maintained such that surface drainage is
directed away from structures in accordance with 2016 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 structures.
In the case of building walls retaining landscaping areas, a waterproofing system should be
used on the wall and joints, and a Miradrain drainage panel ( or similar) should be placed
over the waterproofing. The wall drains should extend to groundwater levels near the base
of the wall. The project architect or civil engineer should provide detailed specifications on
the plans for all waterproofing and drainage.
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.
Two new biofiltration basins (BMP 2 and 3) are proposed at the site and should be lined in
accordance with a "No Infiltration" design using an impermeable liner that has sufficient
strength and thickness to resist puncture during construction and use. However, the existing
biofiltration basin (BMP I) is being renovated to meet current stormwater standards and
Project No. GI 968-11-02 -23 -October 12, 2018
6.13
6.13.1
will not need to be lined. The liner should be placed on the sides and bottom of the new
basins to prevent lateral migration of water.
Foundation Plan Review
Geocon Incorporated should review the foundation plans for the project prior to final
design submittal to evaluate if additional analyses and/or recommendations are required.
Project No. G 1968-11-02 -24 -October 12, 2018
LIMITATIONS AND UNIFORMITY OF CONDITIONS
1. 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.
2. 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.
3. This report is issued with the understanding that it is the responsibility of the owner or 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.
4. 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.
Project No. G 1968-11-02 October 12, 2018
THE GEOGRAPHICAL INFORMATION MADE AVAILABLE FOR DISPLAY WAS PROVIDED BY GOOGLE EARTH,
SUBJECT TO A LICENSING AGREEMENT THE INFORMATION IS FOR ILLUSTRATIVE PURPOSES ONLY: IT IS
NOT INTENDED FOR CLIENT'S USE OR RELIANCE AND SHALL NOT BE REPRODUCED BY CLIENT. CLIENT
SHALL INDEMNIFY. DEFEND AND HOLD HARMLESS GEOCON FROM ANY LIABILITY INCURRED AS A RESULT
OF SUCH USE OR RELIANCE BY CLIENT.
VICINITY MAP
t
N
NO SCALE
GEOCON
l NCOR PORATED
GEOTECHNICAL ■ ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900 -FAX 858 558-6159
COASTLINE COMMUNITY CHURCH EXPANSION
22 15 CALLE BARCELONA
CARLSBAD, CALI FORNIA
JH /CW I I DSK/GTYPD DATE 10 -12 -2018 I PROJECT NO. G1968-1 1 -02 I FIG. 1
PIOtted:10/12/2018 HSAM I By·ALVIN LADRILLONO I File Locatioo:Y·\1_GEOTECHIG1000\G 1968-11-0212018\2018· 10-12\0ETAILS\G19611-11-02 VicmrtyMap.dwg
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GEOCON LEGEND
Qcf1 ....... COMPACTED FlU. (2006)
Qcf 2 ...... COMPACTED FlU. (1997) (Dotted-•• Buoed)
Qaf.. ...... Al.LIMUM (Dotted-•• Bu_,)
Tf ....... TORREY SANDSTONE (Dotted\1Yhe1e Buned)
T d ....... DELMAR FORMATION (Dotted 1/v'here Bur1ed)
,-...••••• ....... APPROX. LOCATION OF GEOLOGIC CONTACT
lDotted Where Buried)
.APPROX. ELEVATtoNATBASE OF FILL tFeet, MSLJ
... APPROX. LIMITS OF BUTTRESS FILL
GEOLOGIC MAP
COASTLINE COMMUNITY CHURCH EXPANSION
2215 CALLE BARCELONA
CARLSBAD, CALIFORNIA
GEOCON -.\ 1·=so· 10-,2-20,e ~ _, .. ,.
lfllf:(111,ollJt.TJ:I) ~ ""°"ICTNO, ..,.,_ GfOT~•ENW:ONMl:NUJ.■MAltllAtS G1968-11-02
6"60RA,,i)fl:SOIIM-~N!)CG() ~ tm'l•2'1•
Olo,t•:!11""6f01.)•JUISf5.»f>JSe, SHEET OF 2
CONCRETE SLAB
-~ -.
1, PAD GRADE
SAND AND VAPOR
RETARDER IN
ACCORDANCE WITH ACI
,r,,.· . 4<l
.; b:r:
~I-I-Q. QUJ ao u.
SAND AND VAPOR
RETARDER IN
ACCORDANCE WITH ACI
CONCRETE SLAB
4 . . .., 4 . .. . ..
/
CJ :I: z I-Fa. 0 LU oo "1444,.4 u. 4
. .. ·:· _l
• . . .o· .,, 1
" . . .
1 .. '
4 •• L -·:.,
.i<:11.S .d•,S 4 .,, . .:3 44 "'.1
~I ~~~~
·.:! .
>-· ------FOOTING WIDTH* _____ __,
* .... SEE REPORT FOR FOUNDATION WIDTH AND DEPTH RECOMMENDATION
WALL / COLUMN FOOTING DIMENSION DETAIL
NO SCALE
GEOCON
INCORPORATED 0
GEOTECHNICAL ■ ENVIRONMENT AL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900 -FAX 858 558-6159
COASTLINE COMMUNITY CHURCH EXPANSION
2215 CALLE BARCELONA
CARLSBAD, CALIFORNIA
JH/CW I I DSK/GTYPD DATE 10-12-2018 IPROJECTNO.G1968-11-02 IFIG,3
Plotted:10/12/2018 7:44AM I By:ALVIN LADRILLONO I File Location:Y:\1_GEOTECH\G1000\G1968-11-02\2018\2018-10-12\DETAILS\Wall-Column Footing DImens1on Detail (COLFOOT2).dwg
RETAINING
WALL
H (Feet)
SLAB
FOOTING
ACTIVE
PRESSURE
SEISMIC
(IF REQUIRED)
ACTIVE PRESSURE, A (psf}
EXPANSION LEVEL 2:1 SLOPING
INDEX, El BACKFILL BACKFILL
Els 50 35 50
Els 90 40 55
1.. A SURCHARGE OF 2 FEET OF SOIL (250 PSF VERTICAL LOAD) SHOULD BE ADDED TO THE
DESIGN OF THE WALL WHERE TRAFFIC LOADS ARE WITHIN A HORIZONTAL DISTANCE EQUAL
TO½ THE WALL HEIGHT. OTHER SURCHARGES SHOULD BE APPLIED, AS APPLICABLE.
2... EXPANSION INDEX GREATER THAN 50/90 SHOULD NOT BE USED FOR WALL BACKFILL PER
REPORT.
3... RETAINING WALLS SHOULD BE PROPERLY DRAINED AND WATER PROOFED.
4... THE PROJECT STRUCTURAL ENGINEER SHOULD EVALUATE THE WALLS LOADING
COMBINATIONS.
AT-REST/
RESTRAINED
(IF REQUIRED) r 7H H s 8'
H>B'
l
RETAINING WALL LOADING DIAGRAM
13H psf
GEOCON
INCORPORATED 0
GEOTECHNICAL ■ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900 -FAX 858 558-6159
COASTLINE COMMUNITY CHURCH EXPANSION
2215 CALLE BARCELONA
CARLSBAD, CALIFORNIA
JH/CW I I DSK/GTYPD DATE 10-12 -2018 I PROJECT NO. G1968-11 -02 I FIG. 4
Plotted:10/12/2018 7:42AM I By:ALVIN LADRILLONO I File Location:Y:11_GEOTECHIG1000\G1968-11-021201812018-10-121OETAILS\Retaining Wall Loading Diagram (RWLD-NoGroundwater).dwg
PROPOSED
GRADE
NOTE
WATER PROOFING
PER ARCHITECT
2/3 H
GROUND SURFACE
RETAINING
WALL
2/3 H
GROUND SURFACE
DRAINAGE PANEL
(MIRADRAIN 6000
OR EQUIVALENT)
3/4" CRUSHED ROCK 12"1
•~•.;:r1rv~~~;;;;;~IC
· MIRAFI 140N OR
EQUIVALENT
4" DIA SCHEDULE 40
FOOTING PERFORATED PVC PIPE
, OR TOTAL DRAIN
EXTENDED TO
APPROVED OUTLET
DRAIN SHOULD BE UNIFORMLY SLOPED TO GRAVITY OUTLET
OR TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING
GROUND SURFACE
MIRAFI 140N FILTER FABRIC
(OR EQUIVALENT)
OPEN GRADED
1" MAX. AGGREGATE
4" DIA. PERFORATED SCHEDULE
40 PVC PIPE EXTENDED TO
APPROVED OUTLET
PROPOSED
GRADE
RETAINING
WALL
2/3 H
GROUND SURFACE
DRAINAGE PANEL
(MIRADRAIN 6000
OR EQUIVALENT)
4" DIA. SCHEDULE 40
PERFORATED PVC PIPE
OR TOTAL DRAIN
EXTENDED TO
APPROVED OUTLET
NO SCALE
TYPICAL RETAINING WALL DRAIN DETAIL
GEOCON
INCORPORATED 0
GEOTECHNICAL ■ ENVIRONMENTAL ■ MATERIALS
6960 FLANDERS DRIVE -SAN DIEGO, CALIFORNIA 92121 -297 4
PHONE 858 558-6900-FAX 858 558-6159
JH/CW I I DSK/GTYPD
COASTLINE COMMUNITY CHURCH EXPANSION
2215 CALLE BARCELONA
CARLSBAD, CALIFORNIA
DATE 10-12 -2018 I PROJECT NO. G1968 -11 -02 I FIG. 5
Plotte<U0/1212018 N3AM I By•ALVIN LADRILLONO I File Locat1on.V.\1_GEOTECH\G1000\G1968-11-02\2018\2018-10-12\DETAILS\TypIcal Retaining Wall Drainage Detail (RWDD7A).dwg
LIST OF REFERENCES
1. 2016 California Building Code, California Code of Regulations, Title 24, Part 2, based on
the 2015 International Building Code, prepared by California Building Standards
Commission, July 2016.
2. AC/ 318-14, Building Code Requirements for Structural Concrete and Commentary on
Building Code Requirements for Structural Concrete, prepared by the American Concrete
Institute, dated September, 2014.
3. 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.
4. ASCE 7-10, Minimum Design Loads for Buildings and Other Structures, Second Printing,
April 6, 201 I.
5. Boore, D. M., and G. M Atkinson, Ground-Motion Prediction for the Average Horizontal
Component of PGA, PGV, and 5%-Damped PSA at Spectral Periods Between 0.01 and
10.0 S, Earthquake Spectra, February 2008, Volume 24, Issue 1, pages 99-138.
6. California Department of Conservation, Division of Mines and Geology, Probabilistic
Seismic Hazard Assessment for the State of California, Open File Report 96-08, 1996.
7. California Geological Survey, Seismic Shaking Hazards in California, Based on the
USGSICGS Probabilistic Seismic Hazards Assessment (PSHA) Model, 2002 (revised April
2003). 10% probability of being exceeded in 50 years.
http://redirect.conservation.ca.gov/cgs/rghm/pshamap/pshamain.html
8. Campbell, K. W., Y. Bozorgnia, NGA Ground Motion Model for the Geometric Mean
Horizontal Component of PGA, PGV, PGD and 5% Damped Linear Elastic Response
Spectra/or Periods Ranging.from 0.01 to 10 s, Preprint of version submitted for publication
in the NGA Special Volume of Earthquake Spectra, February 2008, Volume 24, Issue 1,
pages 139-171.
9. 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.
10. Risk Engineering, EZ-FRISK, 2016.
11. USGS computer program, Seismic Hazard Curves and Uniform Hazard Response Spectra,
http://earthquake.usgs.gov/research/hazmaps/design/.
Project No. G 1968-11-02 October 12, 2018