HomeMy WebLinkAboutCT 92-02B; PARKSIDE; GEOTECHNICAL INVESTIGATION; 1999-06-16w -
CHRISTIAN WHEELER
ENGINEERING
REPORT OF GEOTECHNICAL INVESTIGATION
PARKSIDE TOWNHOUSE DEVELOPMENT
HIDDEN VALLEY ROAD
CARLSBAD, CALIFORNIA
PREPARED FOR:
SHEA HOMES, INC.
10721 TREENA STREET, SUITE 200
SAN DIEGO, CALIFORNIA 92131
PREPARED BY:
CHRISTIAN WHEELER ENGINEERING /
4925 MERCURY STREET
SAN DIEGO, CALIFORNIA 92111
4925 Mercury Street + San Diego, CA 92111 + 858-496-9760 + FAX 858-496-9758
W -
CHRISTIAN WHEELER
ENGINEERING
June 16, 1999
Shea Homes CWE 199.096.1
10721 Treena Street, Suite 200
San Diego, California 92131
ATTENTION: Bob Fontana
SUBJECT: REPORT OF GEOTECHNICAL INVESTIGATION, PARKSIDE TOWNHOUSE
DEVELOPMENT, HIDDEN VALLEY ROAD, CARLSBAD, CALIFORNIA.
Ladies and Gentlemen:
In accordance with your request, we have completed a geotechnical investigation for the townhouse
development proposed at the subject site. We are presenting herewith a report of our finding and
recommendations.
In general, we found the site suitable for the proposed development provided the recommendations
contained in the attached report are followed. Only relatively minor geotechriical conditions were
encountered that will impact site development. These conditions include a relatively small of uncompacted
fill that will require removal and replacement as compacted fill, and low to moderately expansive soils.
Recommendations to mitigate for these conditions are presented in the attached report
If you have any questions after reviewing this report, please do not hesitate to contact our offlc,t
opportunity to be of professional service is sincerely appreciated. r'
Respectfully submitted,
CHRISTh\N WHEELER ENGINEERING
a'1' # ~WL
Charles H. Christian, RGE # 00215
0
Curtis R. Burdett CEG # 1090
cc: (6) Submitted
UJ No. 15
\ Exp.-30-01 I
4925 Mercury Street + San Dieg 1(c1A 858-496-9760 + FAX 858-496-9758
TABLE OF CONTENTS
PAGE
Introductionand Project Description .............................................................................................................. 1
Project Scope ............................................................................................... . ............ .............................................. 2
Findings ................................................................................................................................................................. 3
SiteDescription and Grading History.......................................................................................................3
General Geology, and Subsurface Conditions .......................................................................................... 4
Geologic Setting and Soil Description ..................................................... ............................................. 4
Groundwater....................................................................................
.
.......................................................... 5
TectonicSetting ................................................................................................. . ....................................... 5
GeologicHazards .......................................................................................................................................... 6
General......................................................................................................................................................... 6
Groundshaking.......................................................................................................................................... 6
Landslide Potential and slope Stability .................................................................................................. 6
Liquefaction.............................................................................................................................................. 7
Flooding..................................................................................................................................................... 7
Tsunamis...................................................................................................................................................7
Seiches......................................................................................................................................................... 7
Conclusions........................................................................................................................................................... 7
Recommendations...............................................................................................................................................8
Observationof Grading ........................... ................................................................................................ 8
Clearingand Grubbing ............................................................................................................................ 8
SitePreparation ........................................................................................................................................8
ExcavationCharacteristics ....................................................................................................................... 8
Processingof Fill Areas ............................................................................... ........................................ .... 8
Compactionand Method of Filling .................................................. ................................... .................. 9
ImportedFill Material ............................................................................................................................ 10
FillSlope Construction .........................................................................................................................10
SurfaceDrainage ..................................... ................................................................................................ 10
SlopeStability ................................................................................................................................... ........... 10
General.................................................................................................................................................... 10
ErosionControl ..................................................................................................................................... 11
FoundationRecommendations ................................................................................................................. 11
General..................................................................................................................................................... 11
Post-Tension Foundation/Slab Systems ............................................................................................ 11
ConventionalFoundations ..................................................................................................................... 11
BearingCapacity ..................................................................................................................................... 12
FoolingReinforcing ........................... ............................................................. . ...................................... 12
LateralLoad Resistance .........................................................................................................................12
FootingSetbacks................................................................................................................. ................... 12
Foundation Excavation Observation ..................................................................................................12
On-Grade Slabs ..........................................................................................................................................12
InteriorSlabs ............................................................................................................................................ 12
Moisture Protection for Interior Slabs ...............................................................................................13
ExteriorConcrete Flatwork .................................................................................................................. 13
EarthRetaining Walls .................................................................................................................................13
PassivePressure......................................................................................................................................13
ActivePressure .......................................................................................................................... . ............ 13
Backfill.....................................................................................................................................................14
Factorof Safety......................................................................................................................................14
Preliminary Pavement Sections .14
TrafficIndex ........................................................................................................................................... 14
R-Value Test ................. . ......................................................................................................................... 14
Preliminary Structural Section..............................................................................................................14
Limitations..........................................................................................................................................................15
Review, Observation and Testing............................................................................................................15
Uniformityof Conditions .......................................................................................................................... 15
Changein Scope .........................................................................................................................................15
TimeLimitations .......................................................................................................................................... 16
ProfessionalStandard.................................................................................................................................16
Client's Responsibility................................................................................................................................16
FieldExplorations ............................................................................................................................................... 17
LaboratoryTesting ............................................................................................................................................. 17
ATTACHMENTS
TABLES
Table I Maximum Bedrock Accelerations, Page 6
FIGURES
Figure 1 Site Vicinity Map, Follows Page 1
PLATES
Plate I Site Plan
Plates 2-8 Boring Logs
Plate 9 Laboratory Test Results
Plate 10 Retaining Wall Subdrain
APPENDICES
Appendix A References
Appendix B Recommended Grading Specifications - General Provisions
PRELIMINARY GEOTECHNICAL INVESTIGATION
I PROPOSED PARKSIDE RESIDENTIAL SUBDIVISION
HIDDEN VALLEY AND PLUM TREE ROAD
CARLSBAD, CALIFORNIA
- INTRODUCTION AND PROJECT DESCRIPTION
This report presents the results of a preliminary geotechnical investigation performed for a 48-unit townhouse
development, to be constructed on the undeveloped property located east of Hidden Valley Road and south of
Plum Tree Road, in the City of Carlsbad, California. Figure Number 1 presented on the following page provides
a vicinity map showing the location of the property.
The subject property is a nearly polygonal-shaped parcel of land approximately seven acres in area. The
townhouses will be two-story structures that are expected to have conventional spread footings with on-grade
concrete floor slabs or post-tensioned foundation/slab systems. Grading to develop the property is expected to
consist of cuts and fills of less than about five feet from existing grades. Approximately 18,250 cubic yards of fill
material will need to be imported to balance the proposed grading. Cut and fill slopes are expected to be less
than about ten feet in height.
I To aid in the preparation of this report, we were provided with a preliminary set of the grading plans for the
property, prepared by Project Design Consultants. The undated plan identifies the property as Lot 141 of
I Carlsbad Tract 92-02, Sambi Seaside Heights Unit 1, according to Map No. 13378. A copy of this plan was used
as the basis for our geologic mapping and is included herewith as Plate Number 1. We were also provided with
I a mass grading report prepared by Pacific Soils Engineering, Inc., datedJanuary 22, 1997. This report certifies
the previous grading that was performed on the property in between October 1995 and March 1996
This report has been prepared for the exclusive use of Shea Homes and their design consultants for specific
application to the project described herein. Should the project be changed in any way, the modified plans
should be submitted to Christian Wheeler Engineering for review to determine their conformance with our
I recommendations and to determine if any additional subsurface investigation, laboratory testing and/or
recommendations are necessary. Our professional services have been performed, our findings obtained and our
recommendations prepared in accordance with generally accepted engineering principles and practices. This I warranty is in lieu of all other warranties, express or implied.
CWE 199.096.1 August 17, 1999 Page No. 2
PROJECT SCOPE
The scope of our preliminary investigation included: surface reconnaissance; subsurface exploration; obtaining
representative undisturbed and bulk samples; laboratory testing; analysis of the field and laboratory data;
research of available geological literature pertinent to the site; and preparation of this report. More specifically,
the intent of this analysis was to:
Explore the subsurface conditions of the site to the depths of influence of the proposed
development.
Evaluate, by laboratory tests, the engineering properties of the various strata that may influence the
proposed development, including the allowable soil bearing pressures, expansive characteristics and
settlement potential.
Describe the general geology at the site including possible geologic hazards that could have an
effect on the site development.
Address potential construction difficulties that may be encountered due to soil conditions,
groundwater, or geologic hazards, and provide recommendations concerning these problems.
Develop soil engineering criteria for the site grading and provide design information regarding the
stability of cut and fill slopes.
e) Recommend an appropriate foundation system for the type of structures anticipated and develop
soil engineering design criteria for the recommended foundation designs.
Provide design criteria for standard cantilever retaining walls.
Present our opinions in a written report, that includes, in addition to our findings and
recommendations, a site plan showing the location of our subsurface explorations, logs of the
borings and a summary of our laboratory test results.
It is not within the scope of our services to perform laboratory tests to evaluate the chemical characteristics
of the on-site soils in regard to their potentially corrosive impact to on-grade concrete and below grade
improvements. If desired, we can obtain samples of representative soils and submit them to a chemical
CWE 199.096.1 August 17, 1999 Page No. 3
laboratory for analysis. We suggest that such samples be obtained after precise grading is complete and the
I
soils that can affect concrete and other improvements are in place. Further, it should be understood that
Christian Wheeler Engineering does not practice corrosion engineering. If such an analysis is necessary, we
recommend that the developer retain an engineering firm that specializes in this field to consult with them on
I this matter.
FINDINGS
SITE DESCRIPTION AND GRADING HISTORY
The project site is somewhat polygonal shaped and is approximately 7 acres in size. The site is located at the
southeast corner of the Hidden Valley Road and Plum Tree Road intersection in the City of Carlsbad. The
project is further bounded on the east by a single-family residential subdivision and on the south by graded
but undeveloped property.
The site presently exists as a relatively level, vacant lot with a temporary construction trailer located at the
northeast end of the property. The property was previously graded to sheet flow to existing, temporary de-
silting basins located at the northwest corner and center, south end of the site. Existing elevations range from
about 181 feet at the northwest corner of the site to 186 feet at the southeast corner. A composite cut/fill
slope with a maximum height of 25 feet borders the east side and southeast corner of the project. The slope
ascends to the adjacent residential development and appears to be constructed at an approximate 2:1
(horizontal to vertical) slope ratio. Composite slopes up to about ten feet in height descend to Plum Tree
Drive and Hidden Valley Road, and to a portion of the property to the south. A thin veneer of fill soil has
been stockpiled and spread over the central portion of the site, and recently placed end-dumped piles of soil
have been placed over this uncompacted fill. Vegetation on the site consists of scattered wild grasses and
weeds. Mechanically constructed slopes are landscaped with ground cover.
A recent site visit indicated that an area of standing water and very wet soil exists at the toe of the ascending
slope on the east side of the subject property. This condition was limited to the central portion of the
property next to the east property line. This moisture was not observed in June 1998 when the subsurface
explorations were advanced for this investigation, and it appears to be due to the irrigation system installed on
the slope. It is not known if this water is due to a leak in the system or over irrigation. Several irrigation
control valves exist in boxes near the wet area.
CWE 199.096.1 August 17, 1999 1 Page No. 4
Mass grading for the subject site and surrounding areas was performed between October 1995 through
March 1996, under the observation and testing of Pacific Soils Engineering, Inc., (Refer to previously
reference report by PSE). Prior to grading the site, two small canyons crossed the property, intersecting
southwest of and adjacent to the subject site. The site was developed using a cut and fill grading operation;
lowering the elevation of the northern and northeastern portions of the site up to 13 feet and filling
remaining portions of the southerly and southwesterly canyons with up to 20 feet of fill. Subdrain systems
were reportedly placed in the bottom of the canyon fills. All fills placed during the mass grading were
reported to be properly placed and compacted. The reference stated that "in Area D' (located on the subject
site), complete removal of alluvium/colluvium was accomplished prior to the placement of fill".
GENERAL GEOLOGY AND SUBSURFACE CONDITIONS
GEOLOGIC SETTING AND SOILS DESCRIPTION: The subject site is located in the Coastal Plains
Physiographic Province of San Diego County and is underlain with recent alluvium, and Quaternary-age
marine terrace deposits and controlled and uncontrolled fill. These materials are described individually below
in order of increasing age. Also refer to the Test Boring Logs, (Plates 2 through 8) for a more detailed
description of the subsurface conditions. The locations of the subsurface explorations are shown on the
attached Site Plan, Plate No. 1
Uncontrolled Fill (Quaf): Since the mass grading operations were completed, a thin veneer of
uncontrolled fill has been spread over the central portion of the site (See Plate I for location). These
materials range to a maximum of about 3 feet in thickness and consist of loose, dark brown to
brown, clayey sands and soft, tan to light brown clays and clayey silts. In addition, a large number of
end-dumped piles of soil have recently been dumped in the central portion of the site. These
materials were very moist to wet at the time of our investigation. Minor amounts of construction
debris and lumber was scattered throughout the stockpiled fill materials.
Controlled Fill (Qcaf): The on-site canyon remnants were filled with up to 20 feet of soil excavated
in the northern portion of the site or on the property to the east. The placement of the fills was
observed and tested by Pacific Soils Engineering, Inc. (please refer to previously referenced report by
PSE). The fills observed in our test borings appeared to be properly compacted and consist
primarily of dark reddish brown to brown, clayey sands and silty sands.
Alluvium: The majority of the alluvium that was located in the filled canyon areas was reported to
be removed during grading. However, a relatively thin remnant of alluvium was encountered in
CWE 199.096.1 August 17, 1999 Page No.5
Boring No. 2 at a depth of 17 feet. The encountered alluvium was 1.5 feet in thickness and consist
of dark reddish brown, medium dense to dense clayey sand. This minor amount of remaining
alluvium should be inconsequential to the proposed development.
Terrace Deposits: Marine terrace deposits are exposed at or near the ground surface at the northern
and easterly portions of the site and underlies the canyon fill materials. The terrace materials consist
primarily of dense, reddish brown to orange brown, silty sands and clayey sands.
1 GROUND WATER: No groundwater was encountered during the course of our subsurface investigation.
Based on the As-Graded geotechnical report, subdrains were placed in the invert of the canyon prior to
I placing the fill materials to reduce the possibility of groundwater buildup in the fill material. As previously
discussed, standing water and wet soil were noted at the ground surface along the central portion of the slope
I on the east side of the property. This condition was near several boxes containing irrigation valves for the
irrigation of the manufactured slope ascending to the residential development east of the site. It appears that
the wet soils are a result of leaks in the irrigation system or over-watering of the slope.
It should further be recognized that minor groundwater seepage problems might occur after development of
a site even where none were present before development. These are usually minor phenomena and are often
the result of an alteration in drainage patterns and/or an increase in irrigation water. Based on the
permeability characteristics of the soil and the anticipated usage and development, it is our opinion that any
seepage problems which may occur will be minor in extent. It is further our opinion that these problems can
be most effectively corrected on an individual basis if and when they occur.
I TECTONIC SETTING: No major faults are known to traverse the subject site but it should be noted that
much of Southern California, including the San Diego County area, is characterized by a series of Quaternary-age
fault zones which typically consist of several individual, en echelon faults that generally strike in a northerly to
north-westerly direction. Some of these fault zones, and the individualfaults within the zones, are classified as
active while others are classified as only potentially active, according to the criteria of the California Division of
Mines and Geology. Active fault zones are those which have shown conclusive evidence of faulting during the
Holocene Epoch (the most recent 11,000 years) while potentially active fault zones have demonstrated I movement during the Pleistocene Epoch (11,000 to 1.6 million years before the present) but no movement
during Holocene time.
I
A review, of available geologic maps indicates that the active Rose Canyon Fault Zone is located approximately 12
I miles west of the subject site. Other active fault zones in the region that could possibly affect the site include the
CWE 199.096.1 August 17, 1999 Page No. 6
Coronado Bank and San Clemente Fault Zones to the west, the Elsinore and San Jacinto Fault Zones to the
northeast, and the Agua Blanca and San Miguel Fault Zones to the south.
GEOLOGIC HAZARDS
GENERAL: No geologic hazards of sufficient magnitude to preclude development of the site as presently
contemplated are known to exist. In our professional opinion and to the best of our knowledge, the site is
suitable for the proposed development.
GROUND SHAKING: A likely geologic hazard to affect the site is ground shaking as result of movement
along one of the major active fault zones mentioned above. The maximum bedrock accelerations that would be
attributed to a maximum probable earthquake occurring along the nearest fault segments of selected fault zones
that could affect the site are summarized in the following Table I.
TABLE I
Fault Zone Distance Maximum Probable Earthquake Maximum Bedrock Acceleration
Rose Canyon 4 miles 6.5 magnitude 0.30 g
Coronado Bank 24 miles 7.0 magnitude 0.16 g
Elsiore 25 miles 7.3 magnitude 0.169
San Jacinto 48 miles 7.8 magnitude 0.12 g
Probable ground shaking levels at the site could range from slight to moderate, depending on such factors as the
magnitude of the seismic event and the distance to the epicenter. It is likely that the site will experience the
effects of at least one moderate to large earthquake during the life of the proposed structures.
Generally two-thirds of the peak bedrock accelerations is considered when designing for seismic conditions.
CDMG Open File Report 92-1, 'Peak Acceleration from Maximum Credible Earthquakes In California" (Rock
and Stiff Soil Sites) shows a recommended design value of 0.3 g for the project area (lvlualchin and Jones, 1992).
LANDSLIDE POTENTIAL AND SLOPE STABILITY: As part of this investigation we reviewed the
I publication, "Landslide Hazards in the Northern Part of the San Diego Metropolitan Area" by Tan and Giffen,
1995. This reference is a comprehensive study that classifies San Diego County into areas of relative landslide
I susceptibility. The subject site is located in area 3-1. The 3-1 classification is assigned to areas considered
CWE 199.096.1 August 17, 1999 Page No. 7
generally susceptible to slope movement. Natural slopes Within the 3-1 classification are considered at or near
their stability limits due to their steep inclinations and can be expected to fail locally when adversely modified.
Sites within this classification are located outside the boundaries of known landslides but may contain observable
unstable slopes that may be underlain by weak materials and/or adverse geologic structure. Based on the results
of our site-specific study, it is our opinion that due to the site's gently sloping topography and the competent
nature of the materials forming the hillside, the potential for deep-seated lancisliding at the subject site is
considered negligible.
LIQUEFACTION: The subject property is underlain by dense sandy soils that are not susceptible to
liquefaction. In addition, the absence of groundwater makes liquefaction a non-issue at the site.
FLOODING: The site is not located within a potential flood plain. Therefore, the proposed structures will be
constructed at elevations above historical flood elevations, in accordance with local building codes and
ordinances. Properly designed site drainage will further minimize sheet flooding potential.
TSUNAMIS: Tsunamis are great sea waves produced by submarine earthquakes or volcanic eruptions. Due to
the site's elevation and location, it will not be affected by a tsunami.
SEICHES: Seiches are periodic oscillations in large bodies of water such as lakes, harbors, bays or reservoirs. It
is not likely that the site will be affected by seiches.
CONCLUSIONS
In general, we found that the subject property is suitable for the proposed development, provided the
recommendations provided herein are followed. The only significant geotechnical conditions that will have an
impact on the site grading as proposed is the presence of the uncompacted and undocumented fill in the central
portion of the site that will need to be removed and replaced as uniformly compacted fill. Another condition is
the moderate expansion potential of some of the soils near the surface of the site. Unless an elect grading
operation in performed, it will be necessary to design the foundations and on-grade concrete slabs for
moderately expansive conditions.
CWE 199.096.1 August 17, 1999 Page No. 8
RECOMMENDATIONS
GRADING AND EARTHWORK
OBSERVATION OF GRADING: Continuous observation by the Geotechnical Consultant is essential
during the mass grading operation to confirm conditions anticipated by our investigation, to allow adjustments
in design criteria to reflect actual field conditions exposed, and to determine that the grading proceeds in general
accordance with the recommendations contained herein.
CLEARING AND GRUBBING: Site grading should begin with the removal of all vegetation and other
deleterious materials from the portions of site that will be graded and/or will receive improvements. This
should include all root balls from the trees in the landscaped slopes, any natural brush to be removed and all
significant root material. The resulting materials should be disposed of off-site. It is anticipated that some
underground irrigation lines will be encountered that are associated with the existing perimeter landscaped
slopes. These lines should be removed from the areas to be graded.
SITE PREPARATION: After clearing and grubbing, site preparation should begin with the removal from
areas to receive fill or improvements of all undocumented and uncompacted fill material that was placed on the
site after the mass grading operation performed in 1995-1996, to the depths determined in the field by our
project geologist. The existing fill material placed during the mass grading operation was found to be well
compacted, even near the surface where decompaction often occurs. The wet and saturated soils noted near the
toe of the slope on the east side of the property should be removed to firm ground, moisture conditioned and
replaced as uniformly compacted fill. The irrigation system should be repaired if leaks are occurring and the
slope irrigation should be monitored for proper watering duration. Any loose or disturbed fill material that is
exposed on the site should be removed and replaced with compacted fill material. In addition, any fill material
disturbed by the removal of the two storm drain inlets and all sediments collected in the retention basin should
be removed. All removal areas should be approved by a member of our staff prior to placing any new fill
material.
EXCAVATION CHARACTERISTICS: In general, we found that the formational soils at the site can be
excavated with the normal grading equipment and light trenching equipment..
PROCESSING OF FILL AREAS: Prior to placing any new fill soils or constructing any new improvements
in areas that have been cleaned out to receive fill, the exposed soils should be scarified to a depth of 12 inches,
moisture conditioned, and compacted to at least 90 percent relative compaction. In areas to support fill slopes,
CWE 199.096.1 August 17, 1999 Page No. 9
keys should be cut into the competent supporting materials. The keys should be at least ten feet wide and be
sloped back into the hillside at least two-percent. The keys should extend at least one foot into the competent
supporting materials.
A retaining wall will be constructed along the toe of the existing cut slope Hidden Valley Road and the face of
the slope will moved outward by about two feet. Since fill cannot be properly placed on a cut slope, it will be
necessary to cut the slope back at least one equipment width and rebuild the slope with relatively level layers of
compacted fill. Since the face of the slope will not be able to be track-walked when completed, the slope should
be either overfilled and cut back to grade or be compacted with a grid roller.
No other special ground preparation is anticipated at this time.
COMPACTION AND METHOD OF FILLING: All structural fill placed at the site should be compacted
to a relative compaction of at least 90 percent of its maximum dry density as determined by ASTM Laboratory
Test D1557-91, Method Aor C. Fills should be placed at or slightly above optimum moisture content, in lifts
six to eight inches thick, with each lift compacted by mechanical means. Fills should consist of approved earth
material, free of trash or debris, roots, vegetation, or other materials determined to be unsuitable by our soil
technicians or project geologist. Fill material should be free of rocks or lumps of soil in excess of twelve inches
in maximum dimension. However, in the upper two feet of pad grade, no rocks or lumps of soil in excess of six
inches should be allowed.
Fills should be benched into all temporary slopes and into competent natural soils when the natural slope is
steeper than an inclination of 5:1 (horizontal to vertical). Keys should be constructed at the toe of all fill slopes.
The keys should extend at least 12 inches into firm natural ground and should be sloped back at least two
percent into the slope area. Slope keys should have a minimum width of 10 feet.
Utility trench backfill within five feet of the proposed structures and beneath all pavements and concrete
flatwork should be compacted to a minimum of 90 percent of its maximum dry density. The upper twelve
inches of subgrade beneath paved areas should be compacted to 95 percent of the materials maximum dry
density. This compaction should be obtained by the paving contractor just prior to placing the aggregate base
material and should not be part of the mass grading requirements or operation.
All grading and fill placement should be performed in accordance with the City of Carlsbad Grading Ordinance,
the Uniform Building Code, and the Recommended Grading Specifications and Special Provisions attached
hereto as Appendix B.
CWE 199.096.1 August 17, 1999 Page No. 10
IMPORTED FILL MATERIAL: It is anticipated that approximately 2300 cubic yards of fill material will
need to be imported in order to grade the site as planned. Imported fill material should be evaluated and
approved by the Geotechnical Consultant prior to being imported. At least two working days notice of a
potential import source should be given to the Geotechnical Consultant so that appropriate testing can be
accomplished. The type of material considered most desirable for import is a nondetrimentally expansive
(expansion index of less than 50), granular material with some silt or clay binder. The imported soil should
contain no rocks or lumps of soil larger than three inches in diameter, and should not have more that 30 percent
finer than a standard No. 200 sieve.
FILL SLOPE CONSTRUCTION: Fill slopes may be constructed at an inclination of 2:1 or flatter
(horizontal to vertical). Compaction of slopes should be performed by back-rolling with a sheeps foot
compactor at vertical intervals of four feet or less as the fill is being placed, and track-walking the face of the
slope when the slope is completed. As an alternative, the fill slopes may be overfilled by at least three feet and
then cut back to the compacted core at the design line and grade. Keys should be made at the toe of fill slopes
in accordance with the recommendations presented above under "Compaction and Method of Filling."
SURFACE DRAINAGE: Surface runoff into graded areas should be minimized. Where possible, drainage
should be directed to suitable disposal areas via non-erodible devices such as paved swales, gun' brow
ditches, and storm drains. Pad drainage should be designed to collect and direct surface water away from
proposed structures and the top of slopes and toward approved drainage areas. For earth areas, a minimum
gradient of one percent should be maintained.
The ground around the proposed buildings should be graded so that surface water flows rapidly away from the
buildings without ponding. In general, we recommend that the ground adjacent to buildings slope away at a
gradient of at least two percent. Densely vegetated areas where runoff can be impaired should have a minimum
gradient of five percent within the first five feet from the structure.
SLOPE STABILITY
GENERAL: The only significant slope planned at the subject site is the reconstruction of the slope along
Hidden Valley Road, where the slope will be moved our a few feet from the existing face. This slope will be
constructed at a slope ratio of 2:0 horizontal units to 1.0 vertical unit (2:1) or flatter, and will have a height about
ten feet. Based on the relatively high strength parameters of the on-site granular soils, it is our opinion that this
slope will be stable in regards to deep-seated slope failure and surficial slope failure. Further, the proposed slope
CWE 199.096.1 August 17, 1999 Page No. 11
will have a factor of safety against failure in excess of the normally required minimum safety factor of 1.5. All
fill slopes should be constructed in accordance with the grading recommendations presented above.
EROSION CONTROL: The placement of cohesionless soils at the face of slopes should be avoided. Slopes
should be planted as soon as feasible after grading. Sloughing, deep ruling and slumping of surficial soils may be
anticipated if slopes are left unplanted for a long period of time, especially during the rainy season. Irrigation of
slopes should be carefully monitored to insure that only the minimum amount necessary to sustain plant life is
used. Over-irrigating could be extremely erosive and should be avoided.
FOUNDATION RECOMMENDATIONS
GENERAL: Our investigation indicated that the proposed buildings may be supported by conventional
continuous and isolated spread footings or by post-tensioned foundation/slab systems. Due to the generally
moderately expansive potential of the some of the prevailing soils, special consideration and design for
expansive soils will be required. The recommendations herein assure a moderately expansive soil condition.
POST-TENSION FOUNDATION/SLAB SYSTEMS: We recommend that all post-tension
foundation/slab systems have a perimeter footing embedded of at least 12 inches below pad grade. We also
recommend that the Post-Tensioning Institute design method be utilized to design the post-tension foundation
systems. Based on this and the anticipated soil conditions, we recommend using the following design criteria.
Post-Tension Foundation/Slab Design Criteria
Edge Moisture Variation, em
Center Lift: 5.2 feet
Edge Lift: 2.5 feet
Differential Swell, Ym
Center Lift: 3.02 inches
Edge Lift: 0.70 inch
Differential Settlement: 0.75 inch
Bearing Capacity 2500 psf
CONVENTIONAL FOUNDATIONS: Spread footings supporting the two-story structures should be
embedded at least 18 inches below finish pad grade. Continuous and isolated footings should have a minimum
width of 15 inches and 18 inches, respectively.
CWE 199.096.1 August 17, 1999 Page No. 12
BEARING CAPACITY: Conventional spread footings with the above minimum dimensions may be
designed for an allowable soil bearing pressure of 2500 pounds per square foot. This value may be increased by
one-third for combinations of temporary loads such as those due to wind or seismic loads.
FOOTING REINFORCING: Reinforcement requirements for foundations-should be provided by a
structural engineer. However, based on the existing soil conditions, we recommend that the minimum
reinforcing for continuous footings consist of at least one No. 5 bar positioned three inches above the bottom
of the footing and one No. 5 bar positioned approximately two inches below the top of the footing.
LATERAL LOAD RESISTANCE: Lateral loads against foundations may be resisted by friction between the
bottom of the footing and the supporting soil, and by the passive pressure against the footing. The coefficient
of friction between concrete and soil may be considered to be 0.40. The passive resistance may be considered
to be equal to an equivalent fluid weight of 400 pounds per cubic foot This assumes the footings are poured
tight against undisturbed soil. If a combination of the passive pressure and friction is used, the friction value
should be reduced by one-third.
FOOTING SETBACKS: If footings for structures are proposed adjacent to the top of slopes, we
recommend that a minimum horizontal setback from the outer edge of the footing to the adjacent slope face be
provided. In general, the minimum setback from the slope face recommended is 5 feet from slopes 0 to 15 feet.
The building setback distance from the top of slopes may be modified by using deepened footings. Footing
setback is measured from competent soil and should neglect any loose or soft native soils that may occur at the
top of a natural slope. Plans for any footings that will not comply with the specified setbacks should be
submitted to the Geotechnical Engineer for specific review and approval prior to construction.
FOUNDATION EXCAVATION OBSERVATION: All foundation excavations should be observed by
the Geotechnical Consultant prior to placing concrete to determine if the foundation recommendations
presented herein are complied with. All footing excavations should be excavated neat, level and square. All
loose or unsuitable material should be removed prior to the placement of concrete.
ON-GRADE SLABS
INTERIOR SLABS: For conventional slabs, the minimum slab thickness should be four inches. Interior
slabs should be reinforced with at least No. 3 bars placed at 18 inches on center each way. The slab reinforcing
bars should extend at least six inches into the perimeter footings. Slab reinforcing should be positioned on
chairs at mid-height in the floor slab. The garage slabs may be constructed independent of the garage perimeter
CWE 199.096.1 August 17, 1999 Page No. 13
footings. These slabs should have the same reinforcing and thickness recommended above for the living area of
the house. The slab thickness and reinforcing for post-tensioned slabs should be specified be the post-tension
design engineer.
MOISTURE PROTECTION FOR INTERIOR SLABS: Interior concrete on-grade slabs that will
support moisture-sensitive floor coverings should be underlain by a moisture barrier. We recommend that the
minimum configuration of the subsiab moisture barrier consist of a four-inch-thick blanket of coarse, clean sand
and a visqueen vapor barrier. The sand should have 100 percent material passing the 1/4-inch sieve and less
than ten percent and five percent passing the No. 100 and No. 200 sieves, respectively. The visqueen vapor
barrier should have a minimum thickness of 10 mil and should be placed in the center of the sand blanket.
EXTERIOR CONCRETE FLATWORK Exterior slabs should have a minimum thickness of four inches.
Reinforcement should be placed in exterior concrete flatwork to reduce the potential for cracking and
movement. Control joints should be placed in exterior concrete flatwork to help control the location of
shrinkage cracks. Spacing of control joints should be in accordance with the American Concrete Institute
specifications. When patio, walks and porch slabs abut perimeter foundations they should be doweled into the
footings.
EARTH RETAINING WALLS
PASSIVE PRESSURE: The passive pressure for the prevailing soil conditions may be considered to be 400
pounds per square foot per foot of depth. This pressure may be increased one-third for seismic loading. The
coefficient of friction for concrete to soil may be assumed to be 0.40 for the resistance to lateral movement.
When combining frictional and passive resistance, the friction should be reduced by one-third. The upper 12
inches of exterior retaining wall footings should not be included in passive pressure calculations where abutted
by landscaped areas.
ACTIVE PRESSURE: The active soil pressure for the design of unrestrained earth retaining structures with
level backfill may be assumed to be equivalent to the pressure of a fluid weighing 30 pounds per cubic foot. An
additional 13 pounds per cubic foot should be added to this value for 2:1 (horizontal to vertical) sloping backfill.
These pressures do not consider any other surcharge. If any are anticipated, this office should be contacted for
the necessary increase in soil pressure. These values assume a drained backfill condition. Waterproofing details
should be provided by the project architect. A suggested wall subdrain detail is provided on the attached Plate
Number 9. We recommend that the Geotechnical Consultant be retained to observe all retaining wall subdrains
to verify proper construction.
CWE 199.096.1 August 17, 1999 Page No. 14
BACKFILL: All backfill soils should be compacted to at least 90 percent relative compaction. Expansive or
clayey soils should not be used for backfill material. The wall should not be backfllled until the masonry has
reached an adequate strength.
FACTOR OF SAFETY: The above values, with the exception of the allowable soil friction coefficient, do not
include a factor-of-safety. Appropriate factors-of-safety should be incorporated into the design to prevent the
walls from overturning and sliding.
PRELIMINARY PAVEMENT SECTIONS
TRAFFIC INDEX: In consideration of the type of traffic that is expected to be generated by the proposed
townhouse complex, a traffic index of 5.5 and 4.5 was assumed for the driveways and general parking areas in
order to determined of the required structural pavement section. This assumes general light truck and
automobile traffic with occasional moving vans and daily trash trucks.
R-VALUE TEST: An R-Value test was not performed at this time on the material that is expected to be
present in most of the pavement subgrade. However, based on our experience, we estimate that the subgrade
soils will have an R-value of at least 35. This value was used in determining the preliminary structural pavement
sections. We recommend that when the site grading is completed, representative samples of the subgrade soil
be obtained and tested for their R-Value so that final pavement design recommendations can be provided.
PRELIMINARY STRUCTURAL SECTION: Based on the above parameters, it was determined that the
preliminary structural pavement section should consist of the following sections;
DRIVEWAYS
3.0 Inches of Asphalt Concrete pavement
on 6.0 Inches of Crushed Aggregate Base
GENERAL PARKING AREAS
3.0 Inches of Asphalt Concrete Pavement
on 4.0 Inches of Crushed Aggregate Base.
CWE 199.096.1 August 17, 1999 Page No. 15
I Prior to placing the base material, the subgrade soils should be scarified to a depth of 12 inches, moisture
conditioned and compacted to at least 95 percent of its maximum dry density. The Crushed Aggregate Base
I material should conform with the requirements set forth in Section 200-2.2 of the Standard Specifications for
Public Works Construction. All paving methods and materials should conform with good engineering and
I paving practices and with the requirements of the City of Carlsbad.
LIMITATIONS
REVIEW, OBSERVATION AND TESTING
The recommendations presented in this report are contingent upon our review of final plans and specifications.
Such plans and specifications should be made available to the Geotechi-iical Engineer and Engineering Geologist
so that they may review and verify their compliance with this report and with Chapter 70 of the Uniform
Building Code.
It is recommended that Christian Wheeler Engineering be retained to provide continuous soil engineering
services during the earthwork operations. This is to verify compliance with the design concepts, specifications
or recommendations and to allow design changes in the event that subsurface conditions differ from those
anticipated prior to start of construction.
UNIFORMITY OF CONDITIONS
The recommendations and opinions expressed in this report reflect our best estimate of the project
requirements based on an evaluation of the subsurface soil conditions encountered at the subsurface exploration
locations and on the assumption that the soil conditions do not deviate appreciably from those encountered. It
should be recognized that the performance of the foundations and/or cut and fill slopes may be influenced by
undisclosed or unforeseen variations in the soil conditions that may occur in the intermediate and unexplored
areas. Any unusual conditions not covered in this report that may be encountered during site development
should be brought to the attention of the Geotechnical Engineer so that he may make modifications if
I
necessary.
CHANGE IN SCOPE
I
This office should be advised of any changes in the project scope or proposed site grading so that we may
1 determine if the recommendations contained herein are appropriate. It should be verified in writing if the
CWE 199.096.1 August 17, 1999 Page No. 16
recommendations are found to be appropriate for the proposed changes or our recommendations should be
modified by a written addendum.
TIME LIMITATIONS
The findings of this report are valid as of this date. Changes in the condition of a property can, however, occur
I with the passage of time, whether they are due to natural processes or thework of man on this or adjacent
properties. in addition, changes in the Standards-of-Practice and/or Government Codes may occur. Due to
I such changes, the findings of this report may be invalidated wholly or in part by changes beyond our control.
Therefore, this report should not be relied upon after a period of two years without a review by us verifying the
I suitability of the conclusions and recommendations.
PROFESSIONAL STANDARD
In the performance of our professional services, we comply with that level of care and skill ordinarily exercised
by members of our profession currently practicing under similar conditions and in the same locality. The client
recognizes that subsurface conditions may vary from those encountered at the locations where our borings,
surveys, and explorations are made, and that our data, interpretations, and recommendations are based solely on
the information obtained by us. We will be responsible for those data, interpretations, and recommendations,
but shall not be responsible for the interpretations by others of the information developed. Our services consist
of professional consultation and observation only, and no warranty of any kind whatsoever, express or implied,
is made or intended in connection with the work performed or to be performed by us, or by our proposal for
consulting or other services, or by our furnishing of oral or written reports or findings.
CLIENT'S RESPONSIBILITY
It is the responsibility of Shea Homes, or their representatives to ensure that the information and
I
recommendations contained herein are brought to the attention of the structural engineer and architect for the
project and incorporated into the project's plans and specifications. It is further their responsibility to take the
I
necessary measures to insure that the contractor and his subcontractors carry out such recommendations during
construction.
CWE 199.096.1 August 17, 1999 Page No. 17
FIELD EXPLORATIONS
Seven subsurface explorations were made at the locations indicated on the site plan included herewith as Plate
Number Ion June 14, 1998. These explorations consisted of borings drilled with a truck-mounted drill rig using
a hollow stem continuous flight auger. The fieldwork was conducted under the observation and direction of
engineering geology personnel employed by Southern California Soil and Testing, Inc.
The explorations were careflilly logged when made. The logs of the borings are presented on the following
Plate Numbers 2 through 8. The soils are described in accordance with the Unified Soils Classification. In
addition, a verbal textural description, the wet color, the apparent moisture and the density or consistency are
provided. The density of granular soils is given as either very loose, loose, medium dense, dense or very dense.
The consistency of silts or clays is given as either very soft, soft, medium stiff; stiff, very stiff, or hard.
Undisturbed samples of typical and representative soils were obtained and returned to the laboratory for testing.
The undisturbed samples were obtained by driving a 2- 3/8-inch inside diameter split-tube sampler ahead of the
auger using a 140-pound weight free-falling a distance of 30 inches. The number of blows required to drive the
sampler each foot was recorded and this value is presented on the attached boring logs as "Penetration
Resistance." Bulk samples of disturbed soil and undisturbed chunk samples were also collected in bags from the
auger cuttings during the advancement of the borings and from the test trench excavations and returned to the
laboratory for testing.
LABORATORY TESTING
Laboratory tests were performed by Southern California Soil and Testing, Inc. in accordance with the generally
accepted American Society for Testing and Materials (ASTIVI) test methods or suggested procedures. A brief
description of the tests performed is presented below.
CLASSIFICATION: Field classifications were verified in the laboratory by visual examination. The
final soil classifications are in accordance with the Unified Soil Classification System.
MOISTURE-DENSITY: In-place moisture contents and dry densities were determined for
representative soil samples. This information was an aid to classification and permitted recognition of
variations in material consistency with depth. The dry unit weight is determined in pounds per cubic
foot, and the in-place moisture content is determined as a percentage of the soil's dry weight. The
results of these tests are summarized in the boring logs.
CWE 199.096.1 August 17, 1999 Page No. 18
GRAIN SIZE DISTRIBUTION: The grain size distribution was determined from a
representative sample of the alluvial soil in accordance with ASTM D422. The results of this test are
presented on Plate Numbers 9.
COMPACTION TEST: The maximum dry density and optimum moisture content of typical soils
was determined in the laboratory in accordance with ASTIVI Standard Test D-1557-91, Method A.
The result of these tests are presented on Plate Number 9.
DIRECT SHEAR TEST: Direct shear tests were performed to determine the failure envelope
based on yield shear strength. The shear box was designed to accommodate a sample having a
diameter of 2.375 inches or 2.50 inches and a height of 1.0 inch. Samples were tested at different
vertical loads and a saturated moisture content. The shear stress was applied at a constant rate of
strain of approximately 0.05 inch per minute. The results of these tests are presented on the attached
Plate Number 9.
EXPANSION INDEX TEST: Expansion index tests on remolded samples were performed on
representative samples of soils likely to be present at finish grade. The test was performed on the
portion of the sample passing the #4 standard sieve. The samples were brought to optimum
moisture content and then dried back to a constant moisture content for 12 hours at 230 ± 9 degrees
Fahrenheit. The specimen was then compacted in a 4-inch-diameter mold in two equal layers by
means of a tamper, then trimmed to a final height of 1 inch, and brought to a saturation of
approximately 50 percent. The specimen was placed in a consolidometer with porous stones at the
top and bottom, a total normal load of 12.63 pounds was placed (144.7 psf), and the sample was
allowed to consolidate for a period of 10 minutes. The sample was allowed to become saturated, and
the change in vertical movement was recorded until the rate of expansion became nominal. The
expansion indexes are reported on the attached Plate Number 9 as the total vertical displacement
times the fraction of the sample passing the #4 sieve times 1000.
CLASSIFICATION OF EXPANSIVE SOIL
EXPANSION INDEX POTENTIAL EXPANSION
1-20 very low
21-50 low
51-90 medium
91-130 high
Above 130 very high
LOG OF BORING NUMBER B-i
Date-Excavated: 6/14/98 Logged by: JBR Equipment: Drill Rig Projecf Manager: CHC Surface Elevation (ft): Depth to Water (ft): N/A
SAMPLES o U
--
SUMMARY OF SUBSURFACE CONDITIONS
0 0
P.
a4
FILL (Oj - Brown to reddish brown, moist to very moist, dense,
> Interlayered and Intermixed SILTY SAND SM) and CLAYEY SAND 2 (SC) us flffJ1 2 12.6 113.2 MD El = 81 JIIH DS 4 JJIIJJ
El Rim Minor amounts of SANDY CLAY (CL) CK 89 1089 SA 6
Us 3 93 1188 8
10
CK 114 1092
12
14
CK 12.4 121
16
18 Contact clean and level US 3 87 1056
TERRACE DEPOSITS (Os) - Reddish-brown to orange brown,
very moist, dense, SILTY SAND (S4and CLAYEY SAND (SC) 20
CK
22
24
26
- - Bottom of boring at 26 feet.
28
30
PARKSIDE
AN Hidden Valley Road CHRIS11AN WHEELER. BY D . P_P,. DATE . Jun. 99 ENG!NEEPING
JOB No.: 199.096 Plate No.: 2
LOG OF BORING NUMBER B-2
Date Excavated: 6/14/98 Logged by: JBR Equipment: Drill Rig Project Manager: CHC Surface Elevation (ft): Depth to Water (ft): N/A
SAMPLES
0 U
zi'
0 14
SUMMARY OF SUBSURFACE CONDITIONS z
0 0
c,
— — FILL (Qaf) - Brown to reddish-brown, moist to very moist, dense,
CLAYEY SAND (SC) 2
A EI43 us 2 115 120 '
11111 CK 147 1061 6
Dark brown, moist to very moist, stiff, VERY SANDY CLAY (CL). us 2 11.6 117.3 8
10
CK 13.7 107
12
US 2 9.7 114.5 14
16
Clean contact. ALLUVIUM (Oafl - Dark reddish brown, very moist, medium dense 18 :;.
to dense, CLAYEY SAND (SC) 11.2 117.3
TERRACE DEPOSITS (Q0 Dark reddish-brown, very moist, 20 medium dense to dense, CLAYEY SAND (SC) and SILTY SAND
22
CK
24
Bottom of boring at 25 feet. 26
28
30_ _________________________
P
_
PARKSIDE
Hidden Valley Road CHR1S11AN WHEELER BY: DRR DATE: Jun-99 ENGINEERING
JOB No.: 199.096 Plate No.: 3
LOG OF BORING NUMBER B-3
Date Excavated: 6/14/98 Logged by: JBR Equipment: Drill Rig Project Manager: CRC
Surface Elevation (ft): Depth to Water (ft): N/A
SAMPLES
U
SUMMARY OF SUBSURFACE CONDITIONS z
a4 PQ 0
V4 0
CID
FILL (Oaf) - Tan, wet, soft, SANDY CLAY (CL-CH) with little gravel.
TERRACE DEPOSITS (Qt) - Dark reddish-brown, very rnoist, us
-
>+ medium dense to dense, CLAYEY SAND (S
CK 10 114.5 6
Bottom of boring at 7 feet. 8
10
12
14
16
18
20
22
24
26
28
[30_1
-- -
PARXSIDE
Hidden Valley Road
CHRISTIAN WHEELER BY: DIIt ENGINEERING
DATE: Jun-99
JOB No.: 199.096 Plate No.: 4
LOG OF BORING NUMBER B-4
Date Excavated: 6/14/98 Logged by: JBR
Equipment: Drill Rig Project Manager: CHC
Surface Elevation (ft):
Depth to Water (ft): N/A
SAMPLES
c'i z' •> r4 U
-1 SUMMARY OF SUBSURFACE CONDITIONS Z too
0 o
(ID
FILL (Oafl - Dark reddish-brown, moist, loose to medium dense,
2
CLAYEY SAND (Sq.
Dark reddish-brown, moist, medium dense to dense, CLAYEY CK 7.9 107.6 SAND (S(.
- TERRACE DEPOSITS (Ot) - Dark reddish-brown, moist, medium
6 dense to dense, CLAYEY SAND (Sq. US 4
8 Bottom of boring at 7.5 feet.
10
12
14
16
18
20
22
24
26
28
301 1 1 1 1 1 1
PARKSIDE
Hidden Valley Road CHRISTIAN WHEELER
BY DRR DATE Jun-99 ENGINEERING
JOB No.: 199.096 Plate No.: 5
LOG OF BORING NUMBER B-5
Date Excavated: 6/14/98 Logged by: JBR Equipment: Drill Rig Project Manager: CHC Surface Elevation (ft): Depth to Water (ft): N/A
SAMPLES
U
--
'1
SUMMARY OF SUBSURFACE CONDITIONS Z
o
Cl)
TERRACE DEPOSITS (Qt) - Brown, humid, loose to medium 1!+1 dense, CIAYEY SAND (SQ 2 k'j Dark reddish brown, very moist, medium dense to dense, CLAYEY CK Jf 94 1107 L1 SAND (SC). EI=35
.Dark brown Y(CL..with caliche
6 stringers. . EI=86
Bottom of boring at 6 feet.
8
10
12
14
16
18
20
22
24
26
28
.30_
PARKSIDE
Hidden Valley Road
CHRISTIAN WHEELER BY: DRR DATE: Jun-99
JOB No.: 199.096 Plate No.: 6
LOG OF BORING NUMBE
R
B
-6
Date Excavated: 6/14/98 Logged by: JBR Equipment: Drill Rig Project Manager: CHC Surface Elevation (ft): Depth to Water (ft): N/A
SAMPLES
.04
a4 0
SUMMARY OF SUBSURFACE CONDITIONS
z
TERRACE DEPOSITS (Qt) - Reddish-brown to orange brown,
/f humid to moist, dense, CLAYEY SAND (SC) with small gray, CLAY 2 pockets E110 CK [J 114 1013
Moist to very moist
6 Bottom of boring at 6 feet. -
8
10
12
14
16
18
20
22
24
26
28
30 -
4
CHRISTIAN WHEELER
ENGINEERING
PARKSIDE
Hidden Valley Road
B?: DRR DATE:
JOB No.: 199.096 1 Plate No.: 7
LOG OF BORING NUMBER B-7
Date Excavated: 6/14/98 Logged by: JBR Equipment: Drill Rig Project Manager: CHC Surface Elevation (ft): Depth to Water (ft): N/A
SAMPLES C U
SUMMARY OF SUBSURFACE CONDITIONS
Z
P.
TERRACE DEPOSITS (Qt) - Reddish-brown, moist to very F1 moist, dense, CLAYEY SAND (SC). 2
CK 9.3 112.4 Light brown to tan, very moist, stiff to very stiff; SANDY CLAY
EI=73 11111
6 - Bottom of boring at 6 feet. - -
8
10
-12
-14
16
18
20
-22
.24
26
28
30 -
----_-
PARKSIDE
Hidden Valley Road CHRISTIAN WHEELER BY: DRR DATE: Jun-99 ENGINEERING
JOB No.: 199.096 Plate No.: 8
I
LABORATORY TEST RESULTS
I PARKSIDE TOWNHOUSE DEVELOPMENT
CARLSBAD, CALIFORNIA
MAXIMUM DENSITY! OPTIMUM MOISTURE CONTENT
Sample Number Boring No. 1 @ 2'— 4'
Description Silty Sand (SM)
Maximum Density 125.3 pcf
Optimum Moisture Content 8.5 Percent
DIRECT SHEAR TEST
Sample Number Boring No. I @ 2' —4'
Description Remolded To 90 Percent
Angle of Friction 14 Degrees
Apparent Cohesion 350 Pounds Per Square Foot
GRAIN SIZE DISTRIBUTION
Sample Number Boring No. 1 @ 0'-4'
Sieve Size Percent Passing
#4
#8 100
#16 98
#30 94
#50 88
#100 51
#200 39
Classification SM
EXPANSION INDEX TEST
- Sample Number Boring 2 @ 2'-4' Boring 2 @ 4'-6' Boring 5 @ 2'-3'
Initial Moisture Content 9.0 Percent 9.0 Percent 8.2 Percent
Initial Dry Density 113.3 pcf 113.0 pcf 117.2 pcf
Final Moisture Content 20.6 Percent 18.3 Percent 16.1 Percent
Expansion Index 81 43 35
Classification
Moderate Low Low
Sample Number Boring 5 @ 4'-5' Boring 6 @ 2'-3' Boring 7 @
Initial Moisture Content 12.2 Percent 10.2 Percent 10.2 Percent
Initial Dry Density 101.9 pcf 108.6 pcf 108.3 pcf
Final Moisture Content 23.4 Percent 21.0 Percent 19.9 Percent
Expansion Index 86 10 73
Classification Moderate Very Low Moderate
CWE 199.096.1 August 17, 1999 Plate No. 9
6" MAX
WATERPROOF BACK OF WALL
PER ARCHiTECT'S SPECIFICATIONS
3/4 INCH CRUSHED ROCK or
MIRADRAIN 60 or EQUIVALENT
GEOFABRIC BETWEEN ROCK AND SOIL
TOP OF GROUND
or CONCRETE SLAB
MINIMUM I.
4 1tGH DIAMETER
PERFORATED PIPE
RETAINING WALL
SUBDRAIN DETAIL
No Scale
Christian Wheeler Engineering
Job Number: 199.096.1
Date: 0615-99
Plate Number: 10
CWE 199.096.1 June 16, 1999 Appendix A, Page Al
REFERENCES
Anderson, J.G.; Rockwell, R.K. and Agnew, D.C., 1989, Past and Possible Future Earthquakes
of Significance to the San Diego Region, Earthquake Spectra, Volume 5, No. 2, 1989.
California Division of Mines and Geology, 1998, Maps of Known Active Fault Near Source-Zones in
California and Adjacent Portions of Nevada,
Countywide Flood Insurance Rate Map, prepared by the Federal Emergency Management Agency, effective
date June 19, 1997.
Jennings, C.W., 1975, Fault Map of California, California Division of Mines and Geology, Map
No. 1, Scale 1:750,000.
Kennedy, M.P. and Peterson, G.L., 1975, Geology of the San Diego Metropolitan Area, California;
California Division of Mines and Geology, Bulletin 200
Kern, P., 1989, Earthquakes and Faults in San Diego County, Pickle Press, 73 pp.
Mualchin, L. and Jones, A.L., 1992, Peak Acceleration from Maximum Credible Earthquakes in
California (Rock and Stiff-Soil Sites) California Division of Mines and Geology Open-File Report 92-1.
Pacific Soils Engineering, Inc., 1997, Project Grading Report for Area D' (Lot 141), Area 'E' (Lot 140)
and Hidden Valley Road, Sambi Seaside Heights Project, in the City of Carlsbad, California, Work Order
400224GH, dated January 22, 1997.
Tan, S.S., 1995, Landslide Hazards in the Northern Part of the San Diego Metropolitan Area, San
Diego County, California, California Division of Mines and Geology Open-File Report 95-03.
Tan, Siang S., and Kennedy, Michael P., 1996, Geologic Maps of the Northwestern Part of San Diego,
County, California, California, California Division of Mines and Geology Open-File Report 96-02.
United States Department of Agriculture, 1970, Soil Survey, San Diego Area, California.
Wesnousky, S.G., 1986, "Earthquakes, Quaternary Faults, and Seismic Hazards in California", in
Journal of Geophysical Research, Volume 91, No. B12, pp 12,587 to 12,631, November 1986.
CWE 199.096.1 June 16, 1999 Appendix A, Page A2
TOPOGRAPHIC MAPS
San Diego County, 1960, 200 Scale Topographic Map, Sheet 346-1677.
San Diego County, 1975, 200 Scale Orthographic-Topographic Map, Sheet 346-1677.
U.S. Geological Survey, 1968 (Photo-revised 1975), 71/2 Minute Topographic Map, Encinitas Quadrangle,
scale 1:24,000.
PHOTOGRAPHS
Aerial Foto-BankjThomas Bros., Inc., Aerial Foto-Map Book, San Diego County, 1995-96, Sheet 1127,
Scale: 1 inch = 2000 feet (approximate).
San Diego County, 1928, Flight 30C, Scale: 1 inch = 1000 feet (approximate).
San Diego County, 1970, Flight 3, Photographs 3 and 4; Scale: 1 inch = 1000 feet (approximate).
San Diego County, 1973, Flight 34, Photographs 9 through 11; Scale: 1 inch = 1000 feet (approximate).
San Diego County, 1978, Flight 15B, Photographs 31 through 33; Scale: 1 inch = 1000 feet (approximate).
San Diego County, 1983, Photographs 244 and 245; Scale: 1 inch = 2000 feet (approximate).
San Diego County, 1989, Photograph 3 through 5; Scale: 1 inch = 2000 feet (approximate).
CWE 199.096.1 June 10, 1999 Page No. B-i
RECOMMENDED GRADING SPECIFICATIONS - GENERAL PROVISIONS
PARKSIDE TOWNHOUSE DEVELOPMENT
CARLSBAD, CALIFORNIA
GENERAL INTENT
The intent of these specifications is to establish procedures for clearing, compacting natural ground,
preparing areas to be filled, and placing and compacting fill soils to the lines and grades shown on the
accepted plans. The recommendations contained in the preliminary geotechnical investigation report and/or
the attached Special Provisions are a part of the Recommended Grading Specifications and shall supersede
the provisions contained hereinafter in the case of conflict. These specifications shall only be used in
conjunction with the geotechnical report for which they are a part. No deviation from these specifications
will be allowed, except where specified in the geotechnical report or in other written communication signed
by the Geotechnical Engineer.
OBSERVATION AND TESTING
Christian Wheeler Engineering shall be retained as the Geotechnical Engineer to observe and test the
earthwork in accordance with these specifications. It will be necessary that the Geotechnical Engineer or his
representative provide adequate observation so that he may provide his opinion as to whether or not the
work was accomplished as specified. It shall be the responsibility of the contractor to assist the Geotechnical
Engineer and to keep him appraised of work schedules, changes and new information and data so that he
may provide these opinions. In the event that any unusual conditions not covered by the special provisions
or preliminary geotechnical report are encountered during the grading operations, the Geotechnical Engineer
shall be contacted for further recommendations.
If, in the opinion of the Geotechnical Engineer, substandard conditions are encountered, such as
questionable or unsuitable soil, unacceptable moisture content, inadequate compaction, adverse weather, etc.,
construction should be stopped until the conditions are remedied or corrected or he shall recommend
rejection of this work.
I
Tests used to determine the degree of compaction should be performed in accordance with the following
I American Society for Testing and Materials test methods:
I Maximum Density & Optimum Moisture Content - ASTM D-1557-91
CwE 199.096.1 June 10, 1999 Page No. B-2
Density of Soil In-Place - ASTM D-1556-90 or ASTM D-2922
All densities shall be expressed in terms of Relative Compaction as determined by the foregoing ASTM
testing procedures.
PREPARATION OF AREAS TO RECEIVE FILL
All vegetation, brush and debris derived from clearing operations shall be removed, and legally disposed of.
All areas disturbed by site grading should be left in a neat and finished appearance, free from unsightly debris.
After clearing or benching the natural ground, the areas to be filled shall be scarified to a depth of 6 inches,
brought to the proper moisture content, compacted and tested for the specified minimum degree of
compaction. All loose soils in excess of 6 inches thick should be removed to firm natural ground which is
defined as natural soil which possesses an in-situ density of at least 90 percent of its maximum dry density.
When the slope of the natural ground receiving fill exceeds 20 percent (5 horizontal units to 1 vertical unit),
the original ground shall be stepped or benched. Benches shall be cut to a firm competent formational soil.
The lower bench shall be at least 10 feet wide or 1-1/2 times the equipment width, whichever is greater, and
shall be sloped back into the hillside at a gradient of not less than two (2) percent. All other benches should
be at least 6 feet wide. The horizontal portion of each bench shall be compacted prior to receiving fill as
specified herein for compacted natural ground. Ground slopes flatter than 20 percent shall be benched when
considered necessary by the Geotechnical Engineer.
Any abandoned buried structures encountered during grading operations must be totally removed. All
underground utilities to be abandoned beneath any proposed structure should be removed from within 10
feet of the structure and properly capped off. The resulting depressions from the above described procedure
should be backfllled with acceptable soil that is compacted to the requirements of the Geotechnical Engineer.
This includes, but is not limited to, septic tanks, fuel tanks, sewer lines or leach lines, storm drains and water
lines. Any buried structures or utilities not to be abandoned should be brought to the attention of the
Geotechnical Engineer so that he may determine if any special recommendation will be necessary.
All water wells which will be abandoned should be backfilled and capped in accordance to the requirements
set forth by the Geotechnical Engineer. The top of the cap should be at least 4 feet below finish grade or 3
feet below the bottom of footing whichever is greater. The type of cap will depend on the diameter of the
well and should be determined by the Geotechnical Engineer and/or a qualified Structural Engineer.
CWE 199.096.1 June 10, 1999 Page No. B-3
FILL MATERIAL
Materials to be placed in the fill shall be approved by the Geotechnical Engineer and shall be free of
vegetable matter and other deleterious substances. Granular soil shall contain sufficient fine material to fill
the voids. The definition and disposition of oversized rocks and expansive or detrimental soils are covered
in the geotechnical report or Special Provisions. Expansive soils, soils of poor gradation, or soils with low
strength characteristics may be thoroughly mixed with other soils to provide satisfactory fill material, but only
with the explicit consent of the Geotechnical Engineer. Any import material shall be approved by the
Geotechnical Engineer before being brought to the site.
PLACING AND COMPACTION OF FILL
Approved fill material shall be placed in areas prepared to receive fill in layers not to exceed 6 inches in
compacted thickness. Each layer shall have a uniform moisture content in the range that will allow the
compaction effort to be efficiently applied to achieve the 'specified degree of compaction. Each layer shall be
uniformly compacted to the specified minimum degree of compaction with equipment of adequate size to
economically compact the layer. Compaction equipment should either be specifically designed for soil
compaction or of proven reliability. The minimum degree of compaction to be achieved is specified in either
the Special Trovisions or the recommendations contained in the preliminary geotechnical investigation
report.
When the structural fill material includes rocks, no rocks will be allowed to nest and all voids must be
carefully filled with soil such that the minimum degree of compaction recommended in the Special
Provisions is achieved. The maximum size and spacing of rock permitted in structural fills and in non-
structural fills is discussed in the geotechnical report, when applicable.
Field observation and compaction tests to estimate the degree of compaction of the fill will be taken by the
Geotechnical Engineer or his representative. The location and frequency of the tests shall be at the
Geotechnical Engineer's discretion. When the compaction test indicates that a particular layer is at less than
the required degree of compaction, the layer shall be reworked to the satisfaction of the Geotechnical
Engineer and until the desired relative compaction has been obtained.
Fill slopes shall be compacted by means of sheepsfoot rollers or other suitable equipment. Compaction by
sheepsfoot roller shall be at vertical intervals of not greater than four feet. In addition, fill slopes at a ratio of
two horizontal to one vertical or flatter, should be trackrolled. Steeper fill slopes shall be over-built and cut- -
CWE 199.096.1 June 10, 1999 Page No. B-4
back to finish contours after the slope has been constructed. Slope compaction operations shall result in all
fill material six or more inches inward from the finished face of the slope having a relative compaction of at
least 90 percent of maximum dry density or the degree of compaction specified in the Special Provisions
section of this specification. The compaction operation on the slopes shall be continued until the
Geotechnical Engineer is of the opinion that the slopes will be surficially stable.
Density tests in the slopes will be made by the Geotechnical Engineer during construction of the slopes to
determine if the required compaction is being achieved. Where failing tests occur or other field problems
arise, the Contractor will be notified that day of such conditions by written communication from the
Geotechnical Engineer or his representative in the form of a daily field report.
If the method of achieving the required slope compaction selected by the Contractor fails to produce the
necessary results, the Contractor shall rework or rebuild such slopes until the required degree of compaction
is obtained, at no cost to the Owner or Geotechnical Engineer.
CUT SLOPES
The Engineering Geologist shall inspect cut slopes excavated in rock or lithifled formational material during
the grading operations at intervals determined at his discretion. If any conditions not anticipated in the
preliminary report such as perched water, seepage, lenticular or confined strata of a potentially adverse
nature, unfavorably inclined bedding, joints or fault planes are encountered during grading, these conditions
shall be analyzed by the Engineering Geologist and Geotechnical Engineer to determine if mitigating
measures are necessary.
Unless otherwise specified in the geotechnical report, no cut slopes shall be excavated higher or steeper than
that allowed by the ordinances of the controlling governmental agency.
ENGINEERING OBSERVATION
Field observation by the Geotechnical Engineer or his representative shall be made during the filling and
compaction operations so that he can express his opinion regarding the conformance of the grading with
acceptable standards of practice. Neither the presence of the Geotechnical Engineer or his representative or
the observation and testing shall release the Grading Contractor from his duty to compact all fill material to
the specified degree of compaction.
CWE 199.096.1 June 10, 1999 Page No. B-S
I
SEASON LIMITS
I
Fill shall not be placed during unfavorable weather conditions. When work is interrupted by heavy rain,
I filling operations shall not be resumed until the proper moisture content and density of the fill materials can
be achieved. Damaged site conditions resulting from weather or acts of God shall be repaired before
I acceptance of work.
RECOMMENDED GRADING SPECIFICATIONS - SPECIAL PROVISIONS
RELATIVE COMPACTION: The minimum degree of compaction to be obtained in compacted natural
ground, compacted fill, and compacted backfill shall be at least 90 percent. For street and parking lot
subgrade, the upper six inches should be compacted to at least 95 percent relative compaction.
EXPANSIVE SOILS: Detrimentally expansive soil is defined as clayey soil which has an expansion index of
50 or greater when tested in accordance with the Uniform Building Code Standard 29-2.
OVERSIZED MATERIAL: Oversized fill material is generally defined herein as rocks or lumps of soil
over 6 inches in diameter. Oversized materials should not be placed in fill unless recommendations of
placement of such material is provided by the Geotechnical Engineer. At least 40 percent of the fill soils
shall pass through a No. 4 U.S. Standard Sieve.
TRANSITION LOTS: Where transitions between cut and fill occur within the proposed building pad, the
cut portion should be undercut a minimum of one foot below the base of the proposed footings and
recompacted as structural backfill. In certain cases that would be addressed in the geotechnical report,
special footing reinforcement or a combination of special footing reinforcement and undercutting may be
required.