HomeMy WebLinkAboutCT 13-02; COASTAL 10; GEOTECHNICAL INVESTIGATION; 2013-01-10EAST COUNTY SOIL CONSULTATION
AND ENGINEERING, INC.
10925 HARTLEY ROAD, SUITE "I"
SANTEE, CALIFORNIA 92071
(619)258-7901
Fax 258-7902
Diversified Development, Inc. January 10, 2013
7668 El Camino Real, 104-280 Project No. 12-1 147G1
Carlsbad, California 92009
Subject: Limited Geotechnica! Investigation
Proposed I 0-Unit Residential Development (Coastal Living 10)
Lot 40 of La Costa South, Unit No. 1
Navarra Drive, Carlsbad, California 92009
Ladies & Gentlemen:
In accordance with your request, we have performed a limited geotechnical investigation at the
subject site to discuss the geotech.nical aspects of the project and provide recommendations for the
proposed development.
Our investigation has found that the proposed building pads are underlain by topsoil and slopewash
to depths ranging from approximately 6 to 1 1 feet below existing grades. These soils were
underlain by dense sandstone/ claystone of the Santiago Formation to the explored depth of 14 feet.
It is our opinion that the development of the proposed residential project is geotechnically feasible
provided the recommendations herein are implemented in the design and construction.
Should you have any questions with regard to the contents of this report, please do not hesitate to
contact our office.
Respectfully submitted,
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Mamadou Saliou Diallo, P.E.
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COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12-1 I47GI
TABLE OF CONTENTS
INTRODUCTION..............................................................................................................................................3
SCOPEOF SERVICES .....................................................................................................................................3
SITE DESCRIPTION AND PROPOSED CONSTRUCTION........................................................................3
FIELD INVESTIGATION AND LABORATORY TESTING .......................................................................4
GEOLOGY.........................................................................................................................................................
GeologicSetting....................................................................................................................................
SiteStratigrapliy ............ . ............. . ................... . ..................................................................................... 4
SEISMICITY............ . ........ . ............................ . ............................... . ................................................................... 5
Regional Seisrnicity.. ............................ ... .... .. ......................... . ........................................ . ... . ................ 5
SeismicAnalysis...................................................................................................................................
2010 CBC Seismic Design Criteria......................................................................................................6
GeologicHazard Assessment...............................................................................................................6
GEOTECHNICALEVALUATION .................................................................................................................7
CompressibleSoils................................................................................................................................7
Expansive Soils .....................................................................................................................................7
Groundwater..........................................................................................................................................7
CONCLUSIONSAND RECOMMENDATIONS ...........................................................................................7
GRADINGAND EARTHWORK ............................................................................. . ....................................... 8
Clearing and Grubbing .......................................................................................................................... 8
StructuralImprovement of Soils...........................................................................................................8
TransitionsBetween Cut and Fill . ........................................................................................................ 9
Method and Criteria of Compaction .....................................................................................................9
ErosionControl .....................................................................................................................................9
StandardGrading Guidelines ................................................................................................................ 9
FOUNDATIONSAND SLABS........................................................................................................................9
SETTLEMENT................................................................................................................................................10
PRESATURATIONOF SLAB SUBGRADE................................................................................................10
RETAININGWALLS .....................................................................................................................................10
TEMPORARYSLOPES .................................................................................................................................. I I
TRENCHBACKFILL .....................................................................................................................................II
DRAINAGE.....................................................................................................................................................12
FOUNDATIONPLAN REVIEW ...................................................................................................................12
LIMITATIONSOF INVESTIGATION ........................................................................................................12
ADDITIONALSERVICES ............................................................................................................................13
PLATES
Plate I - Location of Exploratory Boreholes
Plate 2 - Summary Sheet (Exploration Borehole Logs)
Plate 3 - USCS Soil Classification Chart
PAGEL- 1, LABORATORY TEST RESULTS .............................................................................................16
REFERENCES................................................................................................................................................. 17
J.
COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12-1147G1
INTRODUCTION
This is to present the findings and conclusions of a limited geotechnical investigation for the
proposed construction of a 10-unit residential complex to be located on the south side of Navarra
Drive, in the City of Carlsbad, California.
The objectives of the investigation were to evaluate the existing soils conditions and provide
recommendations for the proposed development.
SCOPE OF SERVICES
The following services were provided during this investigation:
0 Site reconnaissance and review of published geologic, seismological and geotechnical reports
and maps pertinent to the project area
Q Subsurface exploration consisting of four (4) test pits within the limits of the proposed area of
development. The test pits were logged by our Staff Geologist.
Collection of representative soil samples at selected depths. The obtained samples were sealed
in moisture-resistant containers and transported to the laboratory for subsequent analysis.
Laboratory testing of samples representative of the types of soils encountered during the field
investigation
O Geologic and engineering analysis of the field and laboratory data, which provided the basis
for our conclusions and recommendations
O Production of this report, which summarizes the results of the above analysis and presents our
findings and recommendations for the proposed development.
SITE DESCRIPTION AND PROPOSED CONSTRUCTION
The subject site is located on the south side of Navarra Drive, in the City of Carlsbad, California.
The vacant property encompasses an area of 21,303 square feet. The lot slopes moderately to the
north. An approximately 9-foot high fill slope runs along the south side of the parcel. Vegetation
consisted of grass, shrub and a few trees. Site boundaries include Navarra Drive to the north,
similar residential developments to the west and east and La Costa Golf Course to the south.
The preliminary site plan prepared by O'Day Consultants of Carlsbad, California indicates that the
proposed construction will include a I 0-unit residential complex. It is our understanding that the
structures will be two and three-story, wood-framed and founded on continuous footings with slab-
on-grade floors. Associated improvements will include a driveway, landscaping and other
appurtenances.
COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12-1/4 7G1
FIELD INVESTIGATION AND LABORATORY TESTING
On December 7, 2012, four (4) test pits were excavated to a maximum depth of approximately 14
feet below existing grade with a Link Belt 225 trackhoe equipped with a 24-inch bucket. The
approximate locations of the test pits are shown on the attached Plate No. I, entitled "Location of
Exploratory Test pits". A continuous log of the soils encountered was recorded at the time of
excavation and is shown on Plate No. 2 entitled "Summary Sheet". The soils were visually and
texturally classified according to the filed identification procedures set forth on Plate No. 3 entitled
"USGS Soil Classification".
Following the field exploration, laboratory testing was performed to evaluate the pertinent
engineering properties of the foundation materials. The laboratory-testing program included
moisture and density, maximum dry density and optimum moisture content, particle size analysis
and expansion index tests. These tests were performed in general accordance with ASTM
standards and other accepted methods. Page L-1 and Plate No. 2 provide a summary of the
laboratory test results.
GEOLOGY
Geologic Setting
The subject site is located within the southern portion of what is known as the Peninsular Ranges
Geomorphic Province of California. The geologic map pertaining to the area indicates that the site is
underlain by saridstone/claystone of the Santiago Formation (Tsa).
Site Stratigraphy
The subsurface descriptions provided are interpreted from conditions exposed during the field
investigation arid/or inferred from the geologic literature. Detailed descriptions of the subsurface
materials encountered during the field investigation are presented on the exploration logs provided on
Plate No. 2. The following paragraphs provide general descriptions of the encountered soil types.
Topsoil
Topsoil is the surficial soil material that mantles the ground, usually containing roots and other organic
materials, which supports vegetation. Topsoil observed in the test pits was approximately 6 inches
thick and consisted of dark brown, silty sand that was dry to moist, loose and porous in consistency
with some organics (roots and rootlets).
Slopewash (Qsw)
Slopewash was underlying the topsoil with a thickness ranging between approximately 6 and 11 feet.
The material generally consisted of reddish brown, sand with silt and gravel that was dry to moist and
loose to medium dense in consistency.
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COASTAL LIVING 10/DIVERSIFIED DEVELOPMENT PROJECT NO. 12-114 7G I
Santiago Formation (Tsa)
Sandstone/claystone of the Santiago Formation was encountered below the slopewash. The material
generally consisted of light-colored sandy clay that was moist and very stiff in consistency.
SEISMICITY
Regional Seisniicitv
Generally, Seismicity within California can be attributed to the regional tectonic movement taking
place along the San Andreas Fault Zone, which includes the San Andreas Fault and most parallel
and subparallel faults within the state. The portion of southern California where the subject site is
located is considered seismically active. Seismic hazards are attributed to groundshaking from
earthquake events along nearby or more distant Quaternary faults. The primary factors in
evaluating the effect an earthquake has on a site are the magnitude of the event, the distance from
the epicenter to the site and the near surface soil profile.
According to the Fault-Rupture Hazard Zones Act of 1994 (revised Aiquist-Priolo Special Studies
Zones Act). quaternary faults have been classified as "active" faults, which show apparent surface
rupture during the last 11,000 years (i.e., Holocene time). Potentially-active" faults are those faults
with evidence of displacing Quaternary sediments between 11,000 to 16,000 years old.
Seismic Analysis
Based on our evaluation, the closest known "active" fault is the Rose Canyon Fault located
approximately 10 kilometers (6.25 miles) to the west. The Rose Canyon Fault is the design fault of
the project due to the predicted credible fault magnitude and ground acceleration.
The Seismicity of the site was evaluated utilizing deterministic methods (Eqseachl Eqfault ver 3.0,
Blake, 2008) for active Quaternary faults within the regional vicinity. The site may be subjected to
a Maximum Probable Earthquake of 6.9 Magnitude along the Rose Canyon fault, with a
corresponding Peak Ground Acceleration of 0.40g. The maximum Probable Earthquake is defined
as the maximum earthquake that is considered likely to occur within a 100-year time period.
The effective ground acceleration at the site is associated with the part of significant ground
motion, which contains repetitive strong-energy shaking, and which may produce structural
deformation. As such the effective or "free field" around acceleration is referred to as the
Repeatable High Ground Acceleration (RHGA). It has been determined by Ploessel and Slosson
(1974) that the RHGA is approximately equal to 65 percent of the Peak Ground Acceleration for
earthquakes occurring within 20 miles of a site. Based on the above, the calculated Credible
RHGA at the site is 0.0.26g.
COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12-1147G]
2010 CBC Seismic Design Criteria
A review of the active fault maps pertaining to the site indicates the existence of the Rose Canyon
Fault Zone approximately 10 km to the west. Ground shaking from this fault or one of the major
active faults in the region is the most likely happening to affect the site. With respect to this
hazard, the site is comparable to others in the general area. The proposed residential complex
should be designed in accordance with seismic design requirements of the 2010 California Building
Code or the Structural Engineers Association of California using the following seismic design
parameters:
PARAMETER VALUE 2010 CBC REFERENCE
Site Class D Table 16 13.5.2
Mapped Spectral Acceleration For
Short Periods, S
1.148 Figure 1613.5(3)
Mapped Spectral Acceleration For a
I-Second Period, S1
0.432 Figure 1613.5(4)
Site Coefficient, Fa 1.041 Table 1613.5.3(l)
Site Coefficient, F 1.568 Table 1613.5 .3(2)
Geologic Hazard Assessment
Ground Rupture
Ground rupture due to active faulting is not considered likely due to the absence of known fault traces
within the vicinity of the project; however, this possibility cannot be completely ruled out. The
unlikely hazard of ground rupture should not preclude consideration of "flexible" design for on-site
utility lines and connections.
Liquefaction
Liquefaction involves the substantial loss of shear strength in saturated soils, usually sandy soils with a
loose consistency when subjected to earthquake shaking. Based on the absence of shallow
groundwater, type and consistency of the underlying bedrock materials, it is our opinion that the
potential for liquefaction is very low.
Landsliding
There is no indication that landslides or unstable slope conditions exist on or adjacent to the project
site. There are no obvious geologic hazards related to landsliding to the proposed development or
adjacent properties.
Tsunamis and Seiches
The site is not subject to inundation by tsunamis due to its elevation and distance to the ocean. The
site is also not subject to seiches (waves in confined bodies of water).
COASTAL LIVING 101DIVERSIFIED DEVELOPMENT PROJECT NO. 12-1 147G/
GEOTECHNICAL EVALUATION
Based on our investigation and evaluation of the collected information, we conclude that the proposed
construction is feasible from a geotechnical standpoint provided the recommendations provided herein
will be properly implemented during structural development.
In order to provide a uniform support for the proposed structures, overexcavation and recompaction of
the structural portions of the building pads will be required. The foundations may consist of
reinforced continuous and/ or spread footings with reinforced concrete slabs-on grade floors.
Recommendations and criteria for foundation design are provided in the Foundation and Slabs
recommendations section of this report.
Comnressible Soils
Our field observations and testing indicate low compressibility within the sandstone/claystone of the
Santiago Formation and part of the slopewash, which underly the site. However, loose topsoil and
slopewash were encountered to a depth of approximately 3 feet below existing grades. These soils are
compressible. Due to the potential for soil compression upon loading, remedial grading of these loose
soils, including overexcavation and recompaction will be required.
Following implementation of the earthwork recommendations presented herein, the potential for soil
compression resulting from the new development has been estimated to be low. The low-settlement
assessment assumes a well-planned and maintained site drainage system. Recommendations
regarding mitigation by earthwork construction are presented in the Grading and Earthwork
recommendations section of this report.
Expansive Soils
Expansion index tests were performed on representative samples of the slopewash and formational
soils to determine volumetric change characteristics with change in moisture content. Expansion
indexes of 3 and 77 were obtained respectively which indicate a very low to medium expansion
potential for the subgrade soils.
Groundwater
Static groundwater was not encountered to the depths of the test pits. The subject site is located at
an elevation of approximately 100 feet above Mean Sea Level. We do not expect groundwater to
affect the proposed construction. Recommendations to prevent or mitigate the effects of poor
surface drainage are presented in the Drainage section of this report.
CONCLUSIONS AND RECOMMENDATIONS
The following conclusions and recommendations are based upon the analysis of the data and
information obtained from our soil investigation. This includes site reconnaissance; field
investigation; laboratory testing and our general knowledge of the soils native to the site. The site is
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COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12-1147G1
suitable for the proposed residential development provided the recommendations set forth are
implemented during construction.
GRADING AND EARTHWORK
Based upon the proposed construction and the information obtained during the field investigation, we
anticipate that the proposed structures will be founded on continuous and/ or spread footings, which
are supported by properly compacted fill. The following grading and earthwork recommendations are
based upon the limited geotechnical investigation performed, and should be verified during
construction by our field representative.
Clearirni and Grubbin
All areas to be graded or to receive fill and/or structures should be cleared of vegetation. Vegetation
and the debris from the clearing operation should be properly disposed of off-site. The area should be
thoroughly inspected for any possible buried objects, which need to be rerouted or removed prior to
the inception of, or during grading. All holes, trenches, or pockets left by the removal of these objects
should be properly backfihled with compacted fill materials as recommended in the Method and
Criteria of Compaction section of this report.
Structural improvement of Soils
Information obtained from our field and laboratory analysis indicates that loose topsoil and slopewash
cover the site to a depth of approximately 3 feet below existing grade. These subgrade soils are
susceptible to settlement upon loading. Based upon the soil characteristics, we recommend the
following:
Subgrade soils to a minimum depth of 3 feet below existing grade should be completely
removed from areas, which are planned to receive compacted fills and/or structural
improvements. The bottom of the removal area should expose competent materials as
approved by ECSC&E geotechnical representative. Prior to the placement of new fill, the
bottom of the removal area should be scarified a minimum depth of 6 inches, moisture-
conditioned within 2 percent above the optimum moisture content, and then recompacted to at
least 90 percent relative compaction (ASTM D1557 test method).
Overexcavation should be completed for the structural building pads to a minimum depth of
2 feet below the bottom of the proposed footings. The limit of the required areas of
overexcavation should be extended a minimum of 5 feet laterally beyond the perimeter
footings (building footprints).
Soils utilized as fill should be moisture-conditioned and recompacted in conformance with the
following Method and Criteria of Compaction section of this report. The depth and extent of
any overexcavation and recompaction should be evaluated in the field by a representative of
ECSC&E.
N.
COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12-114701
Transitions Between Cut and Fill
The proposed structures are anticipated to be founded in properly compacted fill. Cut to fill transitions
below the proposed structures should be eliminated during the earthwork construction as required in
the previous section.
Method and Criteria of Compaction
Compacted fills should consist of approved soil material, free of trash debris, roots, vegetation or other
deleterious materials. Fill soils should be compacted by suitable compaction equipment in uniform
loose lifts of 6 to 8 inches. Unless otherwise specified, all soils subjected to recorhpaction should be
moisture-conditioned within 2 percent over the optimum moisture content and compacted to at least
90 percent relative compaction per ASTM test method D155 7.
The on-site soils, after being processed to delete the aforementioned deleterious materials, may be
used for recompaction purposes. Should any importation of fill be planned, the intended import
source(s) should be evaluated and approved by ECSCE prior to delivery to the site. Care should be
taken to ensure that these soils are not detrimentally expansive.
Erosion Control
Due to the granular characteristics of the on-site soils, areas of recent grading or exposed ground may
be subject to erosion. During construction, surface water should be controlled via berms, gravel/
sandbags, silt fences, straw wattles, siltation basins, positive surface grades or other method to avoid
damage to the finish work or adjoining properties. All site entrances and exits must have coarse
gravel or steel shaker plates to minimize offsite sediment tracking. Best Management Practices
(BMPs) must be used to protect storm drains and minimize pollution. The contractor should take
measures to prevent erosion of graded areas until such time as permanent drainage and erosion control
measures have been installed. After completion of grading, all excavated surfaces should exhibit
positive drainage and eliminate areas where water might pond.
Standard Grading Guidelines
Grading and earthwork should be conducted in accordance with the standard-of-practice methods for
this local, the guidelines of the current edition of the Uniform Building Code, and the requirements of
the jurisdictional agency. Where the information provided in the geotechnical report differs from the
Standard Grading Guidelines, the requirements outlined in the report shall govern.
FOUNDATIONS AND SLABS
a. Continuous and spread footings are suitable for use and should extend to a minimum depth of 24
inches below the lowest adjacent grade for the proposed two and three-story structures into the
properly compacted fill soils. Continuous footings should be at least 18 inches in width and
reinforced with four #4 steel bars; two bars placed near the top of the footings and the other two
bars placed near the bottom of the footings. Isolated or spread footings should have a minimum
width of 24 inches. Their reinforcement should consist of a minimum of #4 bars spaced 12 inches
We
COASTAL LIVING 10/ DIVERSIFIED DE J'ELOPMENT PROJECT NO. 12-1147G1
on center (each way) and placed horizontally near the bottom. The minimum reinforcement
recommended is based on geotechnical considerations and is not intended to supercede the
structural engineer requirements.
Interior concrete floor slabs should be a minimum 5-inch thick. Reinforcement should consist of
#3 bars placed at 16 inches on center each way within the middle third of the slabs by supporting
the steel on chairs or concrete blocks "dobies'. The slabs should be underlain by 2 inches of clean
sand over a 10-mil visqueen moisture barrier. The effect of concrete shrinkage will result in cracks
in virtually all-concrete slabs. To reduce the extent of shrinkage, the concrete should be placed at a
maximum of 4-inch slump. The minimum steel recommended is not intended to prevent shrinkage
cracks.
Where moisture sensitive floor coverings are anticipated over the slabs, the 10-mil plastic
moisture barrier should be underlain by a capillary break at least 2 inches thick, consisting of
coarse sand, gravel or crushed rock not exceeding 3/4 inch in size with no more than 5 percent
passing the 4200 sieve.
An allowable soil bearing value of 2,000 pounds per square foot may be used for the design of
continuous and spread footings at least 12 inches wide and founded a minimum of 12 inches into
properly compacted fill soils as set forth in the 2010 California Building Code, Table 1804.2. This
value may be increased by 400 psf for each additional foot of depth or width to a maximum value
of 4,000 lb/ft2.
Lateral resistance to horizontal movement may be provided by the soil passive pressure and the
friction of concrete to soil. An allowable passive pressure of 250 pounds per square foot per foot
of depth may be used. A coefficient of friction of 0.35 is recommended. The soils passive pressure
as well as the bearing value may be increased by 1/3 for wind and seismic loading.
SETTLEMENT
Settlement of compacted fill soils is normal and should be anticipated. Because of the minor
thickness of the fill soils anticipated under the proposed footings, total and differential settlements
should be within acceptable limits.
PRESATURATION OF SLAB SUBGRADE
Due the granular characteristics of the foundation soils, presoaking of subgrade prior to concrete
pour is not required. However, subgrade soils in areas receiving concrete should be watered prior
to concrete placement to mitigate any drying shrinkage, which may occur following site grading.
RETAINING WALLS
Cantilevered retaining walls should be designed for an 'active" lateral earth pressure of 35 psf7ft (35
pcfEFP) for approved granular and level backfill conditions. Where the walls support 2H:IV sloping
backfill, the equivalent fluid pressure should be increased to 45 pcf. Cantilever walls subject to
uniform surcharge loads should be designed for an additional uniform lateral pressure equal to one-
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COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12-1147G1
third (1/3) the anticipated surcharge pressure. An additional lateral earth pressure due to earthquake
motions of 25 pcf(EFP) may be applied using an inverted triangular distribution if required.
Restrained walls such as basement walls should be designed utilizing an 'at-rest earth pressure of 60
psf/ft (60 pcf EFP) for approved granular and level backfill. Restrained walls subject to uniform
surcharge loads should be designed for an additional uniform lateral pressure equal to one-half (1/2)
the anticipated surcharge. For earthquake motions, an additional lateral earth pressure of 35 pcf(EFP)
may be applied using an inverted triangular distribution if required.
Soil design criteria, such as bearing capacity, passive earth pressure and sliding resistance as
recommended under the Foundation and Slab Recommendations section. may be incorporated into the
retaining wall design.
Footings should be reinforced as recommended by the structural engineer and appropriate back
drainage provided to avoid excessive hydrostatic wall pressures. As a minimum we recommend a
fabric-wrapped crushed rock and perforated pipe system. At least 2 cubic feet per linear foot of free-
drainage crushed rock should be provided.
The remaining wall backfill should consist of approved granular material. This fill material should
be compacted to a minimum relative compaction of 90 percent as determined by ASTM D-1557
test method. Flooding or jetting of backfill should not be permitted. Granular backfill should be
capped with 18 inches (minimum) of relatively impervious fill to seal the backfill and prevent
saturation. It should be noted that the use of heavy compaction equipment in close proximity to
retaining structures can result in wall pressures exceeding design values and corresponding wall
movement greater than that associated with active or at-rest conditions. In this regard, the
contractor should take appropriate precautions during the backfill placement.
TEMPORARY SLOPES
For the excavation of foundations and utility trenches, temporary vertical cuts to a maximum height of
4 feet may be constructed in fill or natural soil. Any temporary cuts beyond the above height
constraints should be shored or further laid back following a 1:1 (horizontal to vertical) slope ratio.
OSHA guidelines for trench excavation safety should be implemented during construction.
TRENCH BACKFLLL
Excavations for utility lines, which extend under structural areas should be properly backfilled and
compacted. Utilities should be bedded and backfilled with clean sand or approved granular soil to
a depth of at least one foot over the pipe. This backfill should be uniformly watered and
compacted to a firm condition for pipe support. The remainder of the backfill should be on-site
soils or non-expansive imported soils, which should be placed in thin lifts, moisture-conditioned
and compacted to at least 90% relative compaction.
11
COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12-1147G]
DRAINAGE
Adequate measures should be undertaken to properly finish grade the site after the structures and
other improvements are in place, such that the drainage water within the site and adjacent
properties is directed away from the foundations, footings, floor slabs and the tops of slopes via
rain gutters, downspouts, surface swales and subsurface drains towards the natural drainage for this
area. A minimum gradient of 1 percent is recommended in hardscape areas. For earth areas, a
minimum gradient of 5 percent away from the structures for a distance of at least 5 feet should be
provided. Earth swales should have a minimum gradient of 2 percent. Drainage should be directed
to approved drainage facilities. Proper surface and subsurface drainage will be required to
minimize the potential of water seeking the level of the bearing soils under the foundations,
footings and floor slabs, which may otherwise result in undermining and differential settlement of
the structure and other improvements.
FOUNDATION PLAN REVIEW
Our firm should review the foundation plans during the design phase to assure conformance with the
intent of this report. During construction, foundation excavations should be observed by our
representative prior to the placement of forms, reinforcement or concrete for conformance with the
plans and specifications.
LIMITATIONS OF INVESTIGATION
Our investigation was performed using the skill and degree of care ordinarily exercised, under similar
circumstances, by reputable soils engineers and geologists practicing in this or similar localities. No
other warranty, expressed or implied, is made as to the conclusions and professional advice included in
this report. This report is prepared for the sole use of our client and may not be assigned to others
without the written consent of the client and ECSC&E, Inc.
The samples collected and used for testing, and the observations made, are believed representative of
site conditions; however, soil and geologic conditions can vary significantly between exploration
trenches, boreholes and surface exposures. As in most major projects, conditions revealed by
construction excavations may vary, with preliminary findings. If this occurs, the changed conditions
must be evaluated by a representative of ECSC&E and designs adjusted as required or alternate
designs recommended.
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 project architect and engineer. Appropriate recommendations should be incorporated
into the structural plans. The necessary steps should be taken to see that the contractor and
subcontractors carry out such recommendations in the field.
The findings of this report are valid as of this present date. However, changes in the conditions of a
property can occur with the passage of time, whether they are due to natural processes or the works of
man on this or adjacent properties. In addition, changes in applicable or appropriate standards may
occur from legislation or the broadening of knowledge. Accordingly, the findings of this report may
12
COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12-1147G]
be. invalidated wholly or partially by changes outside of our control. Therefore, this report is subject to
review and should be updated after a period of two years.
ADDITIONAL SERVICES
The review of plans and specifications, field observations and testing under our direction are integral
parts of the recommendations made in this report. If East County Soil Consultation and Engineering,
Inc. is not retainedfor these services, the client agrees to assume our responsibility for any potential
claims that may arise during construction. Observation and testing are additional services, which are
provided by our firm, and should be budgeted within the cost of development.
Plates No. I through 3, Page L-1 and References are parts of this report.
4
EAST COUNTY SOIL CONSULTATION
& ENGINEERING, INC.
10925 HARTLEY RD.. SUITE 1. SANTEE, CA 92071
(619) 258.7901 Fax (619) 258-7902 t r
1"I'2r '
COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12- 114 7G /
PLATE NO.2
SUMMARY SHEET
TEST PIT NO. 1
DEPTH SOIL DESCRIPTION Y
Surface TOPSOIL
dark brown, dry to moist, loose, porous, silty sand with rootlets
0.5' SLOPEWASH (Qsw)
reddish brown, dry to moist, loose to medium dense, sand with silt
2.0' " . 119.7
3.0' becomes moist and medium dense
4.5' " .. .. 131.3
5.0' abundant gravels
7.0' SANTIAGO FORMATION (Tsa)
light gray, moist to wet, medium dense to dense, sandstone! claystone
7.5' cc 14 44 vi 105.9
9,0' bottom of test pit, no caving, no groundwater
test pit backfilled and compacted with sheepsfoot roller 12/7/12
--------------------------------------------------------------------------------------------------------------------
TEST PIT NO.2
DEPTH SOIL DESCRIPTION Y
Surface TOPSOIL
(lark brown, dry to moist, loose, porous, silty sand with rootlets
0.5' SLOPE WASH (Qsw)
reddish brown, dry, loose, sand with silt and gravel
3.0' becomes moist and medium dense
6.0' SANTIAGO FORMATION (Tsa)
light gray, moist to wet, medium dense to dense, sandstone! claystone
8.0' 105.3
9.0' bottom of test pit, caving in upper 3 feet, no groundwater
--------------------------------------------------------------------------------------------------------------------
test pit backfilled and compacted with sheepsfoot roller 12/7/12
Y = DRY DENSITY IN PCF M = MOISTURE CONTENT IN %
14
M
5.6
8.5
15.4
M
COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. 12-1 I47Gi
PLATE NO. 2 (Continued)
SUMMARY SHEET
TEST PIT NO.3
DEPTH SOIL DESCRIPTION Y
Surface TOPSOIL
dark brown, dry to moist, loose, porous, silty sand with rootlets
0.5' SLOPEWASH (Qsw)
reddish brown, dry to moist, loose to medium dense, sand with silt and gravel
4.0' becomes moist to wet and medium dense
9.0' SANTIAGO FORMATION (isa)
light reddish gray, moist, medium dense to dense, sandstone! claystone
11.0' bottom of test pit, no caving, no groundwater
test pit backfilled and compacted with sheepsfoot roller 12/7/12
TEST PIT NO.4
DEPTH SOIL DESCRIPTION . Y
Surface TOPSOIL
dark brown, dry to moist, loose, porous, silty sand with rootlets
0.5' SLOPEWASH (Qsw)
reddish brown, dry to moist, loose to medium dense, sand with silt with gravel
3.0 becomes moist to wet and medium dense
11.0' SANTIAGO FORMATION (isa)
light reddish gray, moist, medium dense to dense, sandstone! claystone
14.0' bottom of test pit, no caving, no groundwater
test pit backfilled and compacted with sheepsfoot roller 12/7/12
-------------------------------------------------------------------------------------------------
Y = DRY DENSITY IN PCF M = MOISTURE CONTENT IN %
15
M
M
MAJOR DIVISIONS SYMBOL DESCRIPTION
GW WELL GRADED GRAVELS OR GRAVEL- SAND
MIXTURES, LITTLE OR NO FINES
GRAVELS GP
(MORE THAN A POORLY GRADED GRAVELS OR GRAVEL-SAND
OF COARSE MIXTURES, LITTLE OR NO FINES
GM FRACTION
>NO. 4 SIEVE SILTY GRAVELS, GRAVEL-SAND-SILT MIXTURES
SIZE)
GC COARSE
GRAINED SOILS
CLAYEY GRAVELS, GRAVEL-SAND-CLAY MIXTURES
(MORE THAN "2 OF SOIL> sw NO. 200 SIEVE SIZE) WELL GRADED SANDS OR GRAVELLY SANDS,
LITTLE OR NO FINES
SANDS SP I
(MORE THAN 'A POORLY POORLY GRADED SANDS OR GRAVELLY SANDS,
OF COARSE OR NO FINES
SM FRACTION
<NO. 4 SIEVE SILTY SANDS, SILT-SAND MIXTURES
SIZE)
SC
J
CLAY SANDS, SAND-CLAY MIXTURES
ML INORGANIC SILTS AND VERY FINE SANDS, ROCK
SILTS & FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY
SILTS WITH SLIGHT PLASTICITY
CLAYS CL INORGANIC CLAYS OF LOW TO MEDIUM
LIQUID LIMIT PLASTICITY, GRAVELLY CLAYS, SANDY CLAYS,
<50 SILTY CLAYS, LEAN CLAYS
OL FINE GRAINED
SOILS ORGANIC SILTS AND ORGANIC SILTY CLAYS OF
LOW PLASTICITY
(MORE THAN "2 OF SOIL
< MH NO. 200 SIEVE SIZE) INORGANIC SILTS, MICACEOUS OR DIATOMACEOUS SILTS & FINE SANDY OR SILTY SOILS, ELASTIC SILTS
CH CLAYS
LIQUID LIMIT INORGANIC CLAYS OF HIGH PLASTICITY, FAT
> 50 __________ CLAYS
OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY,
ORGANIC SILTY CLAYS, ORGANIC SILTS
HIGHLY ORGANIC SOILS Pt PEAT AND OTHER. HIGHLY ORGANIC SOILS
CLASSIFICATION CHART (UNIFIED SOIL CLASSIFICATION SYSTEM)
70
IC
4D CLAY Below No. 200 Below 0.1% 1 cu:a r
GRAIN SIZE CHART ' PLASTICITY CHART
EAST COUNTY SOIL CONSULTATION
AND ENGINEERING, INC.
10925 HARTLEY ROAD, SUITE "I"
SANTEE. CALIFORNIA 9201
U.S.C.S. SOIL CLASSIFICATION
COASTAL LiVING 10 PROJECT
PROJECT NO. 12—i147G1
PL_I\TE NO. 3
i.ittfl. it), 2013
CLASSIFICATION RANGE OF GRAIN SIZES
U.S. STANDARD GRAIN SIZE IN
- SIEVE SiZE MILLIMETERS
BOULDERS Above 12 Inches I Above 305
COBBLES I 12 Inches To 3 Inches 1 305 To 6.2
GRAVEL 3 Inches to No. 4 76.2 to 4.76
Coarse 3 Inches to I. :nch 76.2 to 19.1
Fine '.Inch to No. 4 191 to -1.76
SAND No. 4 to No. 200 4.76 :o :).)-4
Coarse No. 4 to No. 10 4.76 to 2.00
Medium No. 10 to No. 40 2.00 0.20
Fin Mn fl rn Mn flfl 0-20,00 0.071 . 3
SILT _A:
COASTAL LIVING 10/ DIVERSIFIED DEVELOPMENT PROJECT NO. /2-1 147G /
PAGE L-1
LABORATORY TEST RESULTS
EXPANSION INDEX TEST (ASTM D4829)
INITIAL SATURATED INITIAL DRY
MOISTURE MOISTURE DENSITY EXPANSION
CONTENT(%) CONTENT(%) (PC F) INDEX LOCATION
9.3 17.1 111.3 3 TP-2@3.0'
14.5 29.3 98.9 77 TP-2 @ 8.0'
PARTICLE SIZE ANALYSIS (ASTM D422)
U.S. Standard
Sieve Size
Percent Passing
TP-3 @ 6.0'
Slopewash
Percent Passing
TP-4 @ 6.0'
Slopewash
Percent Passing
TP-2 @ 8.0'
Santiago Formation
2" - -
1" - 100 -
1/2" - 83 -
3/8" 100 77 -
#4 99 63 100
48 95 40 99
#16 81 17 98
#30 48 8 96
#50 16 5 93
#100 8 4 87
#200 6 3 79
USCS SP-SM SW CL
16
COASTAL LIVING 10/DIVERSIFIED DEVELOPMENT PROJECT NO. 12-114 7G /
REFERENCES
L 'Limited Geotechnical Investigation, Vista La Costa Residential Development, Parcel 2 of
Certificate of Compliance Recorded August 27, 1984, as Document No. 84-325375, Gibraltar
Street, APN 216-290-20, 21 & 216-290-47, Carlsbad, California 92009", Project No. 12-1147H 1.
Prepared by East County Soil Consultation and Engineering, Inc., Dated April 24, 2012.
2. "2010 California Building Code, California Code of Regulations, Title 24, Part 2, Volume 2 of 2",
Published by International Code Council.
J. "Eqfault/ Eqsearch, Version 3.0". by Blake, T.F., 2000, Updated 2008.
"Limited Site Investigation, Proposed 26-Unit Apartment Complex, North Side of La Costa Avenue,
West of Romeria Street, City of Carlsbad, California', Project No. 01-I 147G1(1), Prepared by East
County Soil Consultation and Engineering, Inc., Dated June 9, 2001.
"Geotechnical and Foundation Engineering: Design and Construction", by Robert W. Day, 1999.
"1997 Uniform Building Code, Volume 2, Structural Engineering Design Provisions", Published by
International Conference of Building Officials
"Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada to
be used with the 1997 Uniform Building Code", Published by International Conference of Building
Officials.
"Geologic Maps of the Northwestern Part of San Diego County, California", Department of
Conservation, Division of Mines and Geology, by Slang S. Tan and Michael P. Kennedy, 1996.
"Bearing Capacity of Soils, Technical Engineering and Design Guides as Adapted from the US
Army Corps of Engineers, No. 7". Published by ASCE Press, 1994.
"Foundations and Earth Structures, Design Manual 7.2". by Department of Navy Naval Facilities
Engineering Command, May 1982, Revalidated by Change I September 1986.
H. Ground Motions and Soil Liquefaction during Earthquakes". by H.B. Seed and I.M. Idriss, 1982.
17
f 2-
EAST EAST COUNTY SOIL CONSULTATION
AND ENGINEERING, INC.
10925 HARTLEY ROAD, SUITE "I"
SANTEE, CALIFORNIA 92071
619 258-7901
FAX 619 258-7902
Mr. Brian Merritt
Diversified Development
7668 El Camino Real, 104-280
Carlsbad, California 92009
Subject: Pervious Concrete Pavement Recommendations
Proposed 10-Unit Residential Development (Coastal Living 10)
Lot 40 of La Costa South, Unit No. 1
Navarra Drive, Carlsbad, California 92009
February 28, 2014
Project No. 12-1147G1
References: 1. "Preliminary Grading Plan Review, Proposed 10-Unit R
e
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Living 10), Lot 40 of La Costa South, Unit No, 1, Navarra Drive, Carlsbad,
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a
92009", Project No. 12-1 147G1, Prepared by East County Soil Cons
u
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t
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i
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n
d
Engineering, Inc., Dated March 19, 2013.
"Limited Geotechnical Investigation, Proposed 10-Unit Residential
D
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v
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l
o
p
m
e
n
t
(Coastal Living 10), Lot 40 of La Costa South, Unit No. 1, Navarra Dri
v
e
,
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s
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,
California 92009", Project No. 12-1 147G1, Prepared by East County Soi
l
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and Engineering, Inc., Dated January 10, 2013.
Dear Mr. Merritt:
In accordance with your request, we have reviewed the geotechnical report (
R
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n
c
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N
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.
2
)
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a
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the pervious concrete pavement for the proposed driveway at the subject site.
Based on the anticipated soil conditions following site grading and the mi
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q
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of Carlsbad, the following pervious concrete pavement section is recommende
d
.
6-inch pervious concrete
4-inch aggregate bedding (1/2-inch minimum size)
6-inch of open-graded gravel (2" to 3" crushed aggregate) with an underdr
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(Mirafi 160N or equivalent) over the subgrade compacted to amini
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9
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compaction.
If we can be of further assistance, please do not hesitate to contact our o
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.
Respectfully submitted,
k
No. GE 2704 rn . .. . j,-
M'amadou Saliou Diallo, P.1 '
RCE 54071, GE 2704
CAL MSD/md OPd?'