HomeMy WebLinkAboutCT 04-15; LA COSTA GREENS NEIGHBORHOOD 1.07; GEOTECHNICAL REPORT; 2006-01-13640D~ 11 10
UPDATE
GEOTECHNICAL REPORT
VILLAGES OF LA COSTA
THE GREENS - PHASE 2
NEIGHBORHOOD 1.07
LOTS 1 THROUGH 71
CARLSBAD, CALIFORNIA
PREPARED FOR
K. HOVNANIAN COMPANIES
SOLANA BEACH, CALIFORNIA
JANUARY 13, 2006
PROJECT NO. 06403-52-24
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I Project No. 06403-52-24
January 13, 2006
K. Hovnanian Companies V
I . 420 Stevens Avenue, Suite 170 . V
Solana Beach, California 92075
Attention: Mr. Jim Nórum
Subject: VILLAGES OF LA COSTA - THE GREENS, PHASE 2
NEIGHBORHOOD 1.07, LOTS I THROUGH 71.
I CARLSBAD, CALIFORNIA V
UPDATE GEOTECHNICAL REPORT V
I Gentlemen: .
In accordance with your authorization of our Proposal No. LG-05552 dated December 30, 2005, we
I have prepared this update geotechnical report for the subject project. The accompanying report
presents the results of our study and contains conclusions and recommendations pertaining to the
5 geotechnical aspects of the proposed development of the site. Provided that the recommendations
contained in this update report are followed, the site is considered suitable for construction and I support of the proposed structures-and improvements as presently planned. S
V
Should you have any questions regarding this report, or if we may be of further service, please
contact the undersigned at your convenience. . • V
Very truly yours,
GEOCON INCORPORATED
/~Ak,li Shane Rodacker
1EG 1778 RCE 63291
AU
V
14ON4L
aam (6/del) Addressee . . . A NQ I?M CER -0 (1/del) Gouvis Engineering TV
Attention: Mr. Huan Nguyen
(1/del) K Hovnaniàn Homes
Attention: Ms. Nehad K. Hindi
(2) Real Estate Collateral Management Company
c/0 Morrow Development V
Attention: Mr. Tim O'Grady
Michael C. Ertwine
Senior Staff Geologist
MCE:AS:SR:dmc
0/0
co No. 63291
LU Exp. 6/30/06
GEOCON
IN CORPOR AT ED.
V V EOTECHNICA1 CONSULTANTS
Project No. 06403-52-24 .. V
January 13, 2006 V V
K. -Hovnanian Companies V V
.420 Stevens Avenue, Suite 170 V V V
V V
V V
Solana Beach, California 92075 V
Attention: Mr. Jim Norum V V V V
Subject: VILLAGES OF LA COSTA - THE GREENS, PHASE 2
V ' , -NEIGHBORHOOD 1.07, LOTS 1 THROUGH 71.
CARLSBAD, CALIFORNIA .
UPDATE GEOTECHNICAL REPORT V
Gentlemen:
In accordance with your authorization of our Proposal No LG-05552 dated December 30, 2005,' we
have prepared this update geotechnical report' for the subject project. The accompanying report
presents the results, of our study and contains conclusions and recommendations pertaining to the
geotechnical aspects of the proposed development of the site. Provided that the recommendations
contained in this, update report are followed, the site is considered suitable for construction and
support ,of the proposed structures and improvernents as presently planned.
Should.you- have any questions regarding this report, or if we may be of further service, please
contact the undersigned at your. convenience, V ,
Very truly yours,
GEOCON INCORPORATED
Michael C Ertwine <. Al Sadi--- Shane Rodacker
Senior Staff Geologist "CEG 17.78 'V RCE 63291
MCE:AS:SR:dmc V
O.NALQ
.
AU Wo
(6/del) Addressee E33
(1/del) Gouvis Engineering W
Attention: Mr. Huan Nguyen 8.9*—ft7ft 1.
/d an Homes
Attention: Ms. Nehad K. Hindi- Of
CAA
(2) . Real Estate Collateral Management Company
V C/0 Morrow Development -
Attention: Mr. Tim O'Grady
6960 Flanders Drive E San Diego, California 92121.2974 M Telephone (858) 558.6900 IM Fax (858) 558-6159
TABLE OF CONTENTS S
1. PURPOSE AND SCOPE ........................ ...................................
S.. ..
2. PREVIOUS SITE DEVELOPMENT ................................ ............................................................... ,1
3. SITE AND PROJECT DESCRIPTION ................... .......................................................................... I
4. SOIL AND GEOLOGIC CONDITIONS .......................................................................................2
4.1 Compacted Fill (Qcf) ................................................................................................................ 2
4.2 Alluvium (Qal) ......................................................................................................................2
4.3 Terrace Deposits (Qt) ..............................................................................................................2
4.4 Santiago Formation (Ts) ...................... ............................... . ........................... . .......................... 3
5. GROUNDWATER ................................................................................................. ............................. 3
6. GEOLOGIC HAZARDS ..................................................................................................................3
6.1 Faulting and Seismicity ................................................................................. ...... . .................... 3
6.2 Liquefaction...........................................................................................................................4
7. CONCLUSIONS AND RECOMMENDATIONS...........................................................................5
7.1 General ....................................................................................................................................5
7.2 Seismic Design ......................................................................................................................5
7.3 Finish Grade Soil Conditions .................................................................................................6
7.4 Future Grading ............. ..
7.5 Foundations ...........................................................................................................................7
7.6 Retaining Walls .....................................................................................................................11
7.7 Lateral Loads ................................................................................................. . ....................... 12
7.8 Slope Maintenance ..............................................................................................................12
7.9 Site Drainage .......................................................................................................................13
LIMITATIONS AND UNIFORMITY OF CONDITIONS
Figures:
i: Vicinity Map
2. Typical Retaining Wall Drain Detail 0
Tables: S
Summary of As-Graded Building Pad Conditions and Foundation Category
Summary of Finish Grade Expansion Index Test Results
Summary of Laboratory Water-Soluble Sulfate Test Results
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UPDATE GEOTECHNICAL REPORT
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1. PURPOSE ANDSCOPE . . . ..
This report presents the results of the update 'geotechnical study for the proposed residential
I . development of Neighborhood 1.07, Lots 1 through 71 and associated improvements located in
Phase 2 of the Villages of La Costa - The Greens development. The site is situated north of the
Poinsettia Lane, east of 'Alicante Road, and west of the adjacent Bressi Ranch development (see
I Vicinity Map, Figure 1). The purpose of this update report is to provide foundation and retaining wall
design recommendations. .. . . .
The scope of the study included a review of the following:
Update Soil and Geological Investigation, . Volume I and II, Villages of La Costa - The
Greens, Carlsbad, California, prepared by Geocon Incorporated, dated June 25, 2001.
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. (Project No. 06403-12-03). .
Final Report of Testing and Observation Serviôes Performed During Site Grading, Villages
of La Costa - The Greens, Neighborhoods 1.06 and 1.07, Carlsbad, California, prepared by
I Geocon Incorporated, dated December 29, 2005. (Project No. 06403-52-19B).
Grading and Erosion Control Plans for: La Costa Greens Neighborhood 1.06 & 1. 07,
I prepared by Hunsaker and Associates, City of Carlsbad approval dated May 10, 2005.
2. PREVIOUS SITE DEVELOPMENT
I Neighborhood 1.07, Lots I through 71, was graded to finish-pad configuration during mass grading
operations for Phase 2 of The Greens development. Grading was, performed in conjunction with the
I observation and testing services of Geocon Incorporated. A summary of the observations, compaction
test results, and professional opinions pertaining to the grading are presented in the above-referenced
I .report of grading. Mass grading for the subject area has been completed and consisted of developing
71 single-family residential lots and associated streets. Fill and cut slopes were created with design
inclinations of 2:1 (horizontal: vertical) or flatter, with a maximum height of approximately 40 feet.
I The maximum thickness of the compacted fill soils is approximately 71 feet. An "As-Graded"
Geologic Map is provided in the above-referenced report and depicts the existing geologic conditions'
and topography.
I 3. SITE AND PROJECT DESCRIPTION'
The development of The Greens —Neighborhood 1.07 consists of 71 single-family residential homes
and associated improvements. Compacted fill soils are exposed at grade and underlain by the I ' Santiago Formation, Terrace Deposits, and alluvium. The Santiago Formation is also exposed at
grade on cut slopes and within some roadways. The "As-Graded" Geologic Map for the project is
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Project No. 06403-52-24 . - I- January 13, 2006
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included in the above-referenced final report of grading. A summary of the as-graded pad conditions
for the lots is provided on Table I. In general,'the on-site fill materials generally consist of fine sands
and sandy to silty clay. '
The locations, and descriptions of the site and proposed improvements are based on a site
reconnaissance, a review of "the referenced grading plans, and 'our understanding of project
development. If project details vary significantly from those described above, Geocon Incorporated
should be contacted to determine the necessity for review and revision of this report.
4.' SOIL AND GEOLOGIC CONDITIONS
The Santiago Formation, 'Terrace Deposits, alluvium, and compacted fill soils underlie the site. The
predominant materials within 4 feet of grade consist of clayey sand to silty sand and possess a low to
high expansion potential. The soil types and geologic unit are discussed below.
4.1 ' Compacted Fill (Qcf)
In general, the fill materials consist of light yellowish brown, sandy clay and silty sand. The
I maximum fill thickness is approximately 71 feet. Fill soils were placed in conjunction with the
observation and testing services of Geocon Incorporated, which are summarized in. the above-
referenced final report of grading. The compacted fill soils are considered suitable to 'provide
adequate support for the proposed development.
4.2 Alluvium (Qal)
A portion of the southwestern margin of Neighborhood 1.07 along Poinsettia Lane is, underlain by
alluvium (beneath the compacted fill materials); due to the presence of a shallow groundwater table
and the close proximity of the existing roadway embankment, complete removal of alluvium was not
practical and some alluvium was left in place. Consequently, a surcharge and settlement monitoring
program was implemented. Settlement data presented in final report of grading represents measured
vertical movement in the field. Based on the survey measurements, it is our opinion that the primary
settlement was essentially complete after 124 days and the area is suitable to provide support for the
proposed development.
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4.3 Terrace Deposits (Qt)
Stream-deposited Terrace Deposits were exposed within cleanouts in localized portions of
Neighborhood 1.07. The Terrace Deposits generally consisted of medium dense to dense, silty to
clayey sandstone and are considered suitable for the support of the proposed development.
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4.4 Santiago Formation (Is)
'The Eocene-age Santiago Formation, consisting.of dense, massive, white to light green, silty, fine to
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coarse sandstones and hard, greenish-gray to brown claystones' and siltstones, underlies the
compacted fill at the site and are considered suitable for the support of the proposed development.
S. GROUNDWATER
I Groundwater was encountered during grading operations in the alluvial soils but is not anticipated to
adversely impact the development of the property. Due to the nature of the . Santiago Formation,
which consists of interbedded sandstone and claystone/siltstone, seepage was encountered in several
cut slopes and mitigated by Construction of drained stability fills. It is not uncommon for groundwater
or seepage. conditions to develop where none previously existed. Groundwater elevations are
I .dependent on seasonal precipitation, irrigation and land use, among other factors, and vary as a result.
Proper surface drainage of -irrigation and rainwater will be important to future performance of the
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project
6. GEOLOGIC HAZARDS
6.1 Faulting and Seismicity . .. . . . .
I Our review of pertinent geologic literature, the previously referenced geotechnical investigation
report dated June 25, 2001, and our experience with the soil and geologic conditions in the general
area indicate that no known active, potentially active, or inactive faults are located within the site.
The nearest known "active" faults are-the Rose Canyon Fault and the Newport-Inglewood (offshore)
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located approximately 7 and 10 miles, respectively, to the west and the Coronado, Banks Fault Zone,
which lies approximately 22 milesto the southwest. Portions of the Rose Canyon Fault have been
included in a Special Study Earthquake Fault Zone. A Maximum Credible seismic event of
I Magnitude 7.2 is postulated for the Rose Canyon Fault with an estimated Maximum Credible peak
site acceleration of 0.32 g based on the Sadigh, et al. (1997) acceleration-attenuation relationship.
The seismicity of the site is influenced by both local and regional fault systems within the southern
California and northern Baja California region. Table 6.1 lists the fault zones that present the greatest
I . seismic impact to the site. .
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TABLE 6.1
FAULT SYSTEMS WITHIN THESOUTHERN CALIFORNIA AND
NORTHERN BAJA CALIFORNIA REGION
Fault Name Distance from Site
(miles)
Maximum
Credible Earthquake
Maximum Credible
Site Acceleration (g)
Rose Canyon 7 7.2 0.32
Newport—Inglewood (Offshore) 10 7.1 0.25
Coronado Banks Fault Zone • 22 7.6 0.17
Elsinore—Julian 23 7:1 . 0.13
Elsinore—Temecula . 23 6.8 . 010
Palos Verdes 41 . 7.3 0.08
Elsinore—GlenIvy 37 6.8 0.06
San Jacinto—Anza 49 7.2 0.06
In the event of a major earthquake along any of the above-referenced faults or other faults in the
soUthern California region, the site could. be subjected to moderate to severe ground shaking. With
respect to seismic shaking, the site is considered comparable to others in the general vicinity. While
listing peak accelerations is useful for comparison of potential effects of fault activity in the region,
other considerations are impOrtant in seismic design, including the frequency and duration of motion
and the soil conditions underlying the site. We recommend that seismic design of structures be
performed in accordance with the Uniform Building Code (UBC) currently adopted by the City of
Carlsbad. . . . . . . . .
6.2 Liquefaction
Liquefaction typically occurs when a site is located in a zone with seismic activity, onsite soils are
cohesionless, groundwater is encountered within 50 feet Of the surface, and soil relative densities are
less than about 70 percent. If all four previous criteria are met, aseismic event could result in a rapid-
pore water pressure increase from the earthquake-generated ground accelerations. Due to the dense
nature of formational materials, the fine-grained characteristic of the alluvium; and the additional
consolidation from the loading induced by the compacted fill, the potential for liquefaction occurring
at the site is considered to be very low. •
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Project No. 06403-52-24 - 4 - January 13, 2006
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 No soil or geologic conditions, were encountered during previous geotechnical
investigations or grading operations that, in our opinion, would preclude the continued
development of the property as presently planned, provided that the recommendations of
this report are followed. ' ' : . . .•
7.1.2 ' The site is considered suitable .for the use of conventional foundations and slab-on-grade,
and/or a post-tensioned foundation system. We understand that a post-tensioned foundation
system will be used throughout the project. Therefore, conventional footing
recommendations are not included in' this report but can be provided upon, request. Design
criteria for post-tensioned slabs are provided in Section 7.5.
7.2 Seismic Design
7.2.1 . The'site is located within'Seismic Zone 4according to UBC'Figure 16-J. Compacted fill
soils underline the proposed buildings. For seismic design, the site is characterized' as soil
types Sc and SD. Table 7.2.1 summarizes site design criteria. The values listed in
Table 7.2.1 are for the Rose Canyon Fault, which is identified as a Type B fault. The Rose
Canyon Fault is located approximately 7 miles west of the site. Table 7.2.2 presents a
summary of soil profile type for each building and the corresponding valUes from
Table 7.2.1 should be used for seismic design.
TABLE 7.2.1
SITE SEISMIC DESIGN CRITERIA
Parameter 'Soil Profile Type
UBC Reference Sc . SD
Seismic Zone Factor , 0.40 ' 0.40 ' • Table 16-1
Soil Profile ' Sc SD ' Table 16-J
Seismic Coefficient, C. 0.40 0.44 Table 16-Q
Seismic Coefficient, C 0.56 • 0.64 Table 16-R
Near-Source Factor, Na 1.0 1:0 Table 16-S
Near-Source Factor, NV 1.0 ' 1.0 Table 16-T
Seismic Source B B Table 16-U
Project No. 06403-52-24 -5 - January 13, 2006
7.2.2 Based on a review of the as-graded conditions presented in the as-graded report. referenced
below, as well as the seismic setting, the lots are assigned the seismic design parameters as
indicated in the following table.
TABLE 7.2.2
SUMMARY OF SOIL PROFILE.TYPE
. Unit . Lot Nos. . UBC Classification
1.07 . 1 through 4 . S0
1.07 . 5 through 9 .
SC
1.07 . 10through24 .SD
1.07 . 25 through 27 . Sc
1.07 '28 through 35 . SD
- 1.07 36 and 37 S
1.07 . 38 through 62 . . SD
1.07 . 62
1.07 . 63 through 71 SD
7.3 Finish Grade Soil Conditions
7.3.1 Observations and laboratory test results indicate that the prevailing soil conditions within
the upper approximately 4 feet of finish grade have an 'expansion potential of "low" to
"high" (Expansion Index of 130 or less) as defined by Uniform Building Code (UBC)
Table 18-I-B. Expansion Index test results for each lot are included on Table I.
7.3.2 It should be noted that although rocks larger than 6-inch-diameter were not intentionally
placed within the upper 4 feet of pad grades, some larger, rocks may exist at random
locations. • - S •
7.3.3 Random samples obtained throughout the , subject neighborhoods were subjected to
water-soluble sulfate testing to evaluate the amount of water-soluble sulfates within the
finish-grade soils. These test results are used to determine the potential for sulfate attack on
normal Portland Cement concrete. The test results indicate sulfate contents that correspond
to "negligible" to "severe" sulfate- exposure ratings as defined by UBC Table 19-A-4. The
results of the soluble-sulfate tests are summarized on Table III. Table 7.3 presents a
summary of concrete requirements set forth byUBC Table 19-A-4.
Project No. 06403-52-24 -6- January 13, 2006
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TABLE 7.3
REQUIREMENTS FOR CONCRETE EXPOSED TO
SULFATE-CONTAINING SOLUTIONS
Sulfate Water-Soluble Cement • Maximum Water Minimum
Exposure Sulfate Percent Type to Cement Ratio Compressive
by Weight - by Weight Strength (psi)
Negligible 0.00-0.10 --. -- --
Moderate 0.10-0.20 'II 0.50 4000
Severe 0.20-2.00 V 0.45 4500
Very Severe >2.00 0.45 4500
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7.3.4 Geocon Incorporated does not practice in the field of corroskn engineering. Therefore, if
I improvements that could be susceptible to corrosion are planned, it is recommended that
further evaluation' by a corrosion engineer be performed.
7.4 Future Grading
I 7.4.1 Any additional grading performed at the site should be accomplished in conjunction with
our observation and compaction testing services. Grading, plans for any future grading
I should be reviewed by Geocon Incorporated prior to finalizing. All trench and wall backfill
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should be compacted to a dry density of at least 90-percent of the laboratory maximum dry
density at or slightly above optimum moisture' content. This office should be notified at
I least 48 hours prior to commencing additional grading or backfill operations.
I 7.5 Foundations
7.5.1 . The foundation recommendations that follow are for one- or two-story residential
I structures and are separated into categories dependent on the thickness and geometry of the
underlying fill soils as well as the Expansion Index (El) of the prevailing subgrade soils of
a particular building pad. Finish-grade Expansion Index test results are presented 'on
I ' Table II, attached. The category criteria are summarized herein.
I Category I: Maximum fill thickness is less than 20 feet and Expansion Index is less
than or equal to 50.
I , Category II: Maximum fill, thickness is less than 50 feet and Expansion Index is less
than or equal to 90, or variation in fill thickness is between 10 feet and 20
feet.
I Category III: Fill thickness exceeds 50 feet, or variation in fill thickness exceeds 20
feet, or Expansion Index exceeds 90 but is 130 or less, or underlain by
alluvium:
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Notes:
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All footings should have a minimum width of 1 inches
Footing depth is measured from lowest adjacent subgrade. These. depths 'apply to
both exterior and interior footings.
All interior living area concrete slabs sh6uld be at least 5 inches thick. This applies
to both building, and garage slabs-on-grade. S. -
All interior concrete slabs should be 'underlain by at least 4 inches of clean sand.
All slabs expected to receive moisture-sensitive floor coverings or used to store
moisture-sensitive materials should be underlain by a vapor barrier placed at the
midpoint of the clean sand recommended in No. 4 above.
7.5.2 The post-tensioned systems should be designed by a structural engineer experienced in
post-tensioned slab design and the design criteria of the Post-Tensioning Institute.(UBC
Section 1816). Although this procedure was developed for expansive soils, it is understood
that it can also be used to reduce the potential for foundation distress due to differential fill
settlement. The post-tensioned design should incorporate the geotechnical parameters
presented in the following table forthe particular foundation category designated, for each
lot as presented on Table I.
TABLE 7.5
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (PT!) ' Foundation Category
Design Parameters
Thornthwaite Index ' -20 ' -20 , -20
Clay Type .- Montmorillonite -. Yes Yes Yes
Clay Portion (Maximum) ' 30% . 50% 70%
Depth to Constant Soil Suction 7.0 ft. . 7.0 ft. 7.0 ft.
Soil Suction ' 3.6 ft. ' 3.6 ft. 3.6 ft.
Moisture Velocity 0.7 in/mo. 0.7 in/mo. 0.7 in/mo.
Edge Lift Moisture Variation Distance 2.6 ft. 2.6 ft. 2.6 ft.
Edge Lift S 0.41 in. 0.78 in. 1.15 in.
Center Lift Moisture Variation Distance 5,3 ft. 5.3 ft. 5.3 ft.
Center Lift 1 2.12 in: ' 3.21 in. 4.74 in.
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1 7.5.3 UBC Chapter 18, Div. III, §1816 uses interior stiffener beams-An its structural design
procedures. If the structural engineer proposes a post-tensioned foundation design method
other than.UBC.Chapter 18, Div. HI, §1816, the following recommendations apply:
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. The deflection criteria presented in Table 7.5 are still applicable.
. Interior stiffener beams be used for Foundation Categories II and III.
I . The depth of the perimeter foundation should be at least 12 inches for Foundation
Category I, 18 inches for Foundation Category 11, and 24. inches for Foundation
Category III. . .
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. Geocon Incorporated should be consulted to provide additional design parameters as-
required bythe structural engineer. .
7'. 5.4 During the construction of the post-tension foundation system, the concrete should be
placed monolithically. Under no circumstances should cold joints form between the I . footings/grade beams and the slab duriig the construction of the post-tension fouhdation
system. S
7,5.5 Our experience indicates post-tensioned slabs are susceptible to excessive edge lift,
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. regardless of the underlying soil conditions, unless reinforcing steel is placed at the bottom
of the perimeter footings and the interior stiffener beams. Current PTI design procedures
primarily address the potential center lift of slabs but, because of the placement of the
I reinforcing tendons in the top of the slab, the resulting eccentricity after tensioning reduces
the ability of the system to mitigate edge lift. The structural engineer should design the
. . foundation system to reduce the potential of edge lift occurring forthe proposed structures.
- 7.5.6 Foundations for Category I, 11 or III may be designed for an allowable soil bearing pressure
I of 2,000 pounds per square foot (psi) (dead plus live load). This bearing pressure may be
increased by one-third for transient loads such as. wind or seismic forces.
7.5.7 The use of isolated footings that are located beyond the perimeter of the building and
support structural elements connected to the building is not recommended for Category III. I Where this condition cannot be avoided, the isolated footings should be connected to the
building foundation system with grade beams.
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- 7.5.8 No special subgrade presaturation is deemed necessary prior to placing concrete; however,
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.the exposed foundation and slab subgrade soils should .be moisture conditioned, as
necessary, to maintain a moist condition as would be expected in any such concrete
placement. S .
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1 7.5.9 Consideration should be given to connecting patio slabs that exceed 5 feet in width to the
building foundation to reduce the potential for future separation to occur.
7.5.10 Where buildings or other improvements are planned near the top of a slope steeper than 3:1
(horizontal: vertical), special foundations and/or design considerations are recommended
I - due to the tendency for lateral soil movement to occur.
For cut and fill slopes, building footings should be deepened such that the bottom
outside edge of the footing is at least 7 feet horizontally from the face of the slope.
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. Where the height of the fill slope exceeds 20 feet, the minimum horizontal distance
should be increased to H/3 (where H equals the vertical distance from the top of
the slope to the toe) but need not exceed 40 feet. For composite (fill over cut)
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.slopes, H equals the vertical distance from the top of the slope to the bottom of the
fill portion of the slope. An acceptable alternative to deepening the footings is the
use of a bst-tensioned slab and foundation system or increased footing and slab
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. reinforcement. Specific design parameters or recommendations for either of these
alternatives can be provided once the building location and fill slope geometry
have been determined. .
.I. • Swimming pools located within 7 feet of the top of cut or fill slopes are not
recommended. Where such a condition cannot be avoided, it is recommended that
the portion of the swimming pool wall within 7 feet of the slope face be designed
I with the assumption that the adjacent soil provides no lateral support. This
recommendation applies to fill slopes up to 30 feet in height and cut slopes
regardless of height. For swimming pools located near the top of fill slopes greater
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. than 30 feet in, height, additional recommendations may be required and Geocon
Incorporated should be contacted for a review of specific site conditions.
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. Although other improvements that are relatively rigid or brittle (such as concrete
flatwork or masonry walls) may experience some distress if located near the top of
a slope, it is generally not economical to mitigate this potential. It may be possible,
however, to incorporate design measures that would permit some lateral soil
1 • movement without causing extensive distress. Geocon Incorporated should be
consulted for specific recommendations.
I 7.5.11 Exterior slabs not subject to vehicle loads should be at least 4 inches thick and reinforced
with 6x6-W2.9/W2.9 (6x6-6/6) welded wire mesh. The mesh should be placed within the
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upper one-third of the slab. Proper mesh positioning is critical to future performance of the
slabs. It has-been our experience that the mesh must be physically pulled up into the slab
after concrete placement. The contractor should take extra measures to provide proper
1 mesh placement. Prior to construction of slabs, the subgrade should . be moisture
conditioned to at least optimum moisture content and compacted to at least 90 percent of
the laboratory maximum dry density. . .
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7.5.12 All concrete slabs should be provided with adequate construction joints and/or expansion
joints to control unsightly shrinkage cracking. The design of joints should consider criteria
of the American Concrete Institute when establishing crack-control spacing patterns.
7.5.13 , Where exterior flatwork' abuts the structure at entrant or extant points, the exterior slab
should be dowelled into the structure's foundation stemwall. This recommendation is
intended to reduce the potential for differential elevations that could result from* differential
settlement or minor heave of the flatwork. Dowelling details should be designed by the
project structural engineer. '•
7.5.14 The recommendations of this -report are intended to reduce the potential for cracking of
slabs due to expansive 'soils (if present), differential settlement of deep fills, or fills of
varying thicknesses. However, even. with the incorporation of the recommendations
presented herein, foundations, stucco walls, and slabs-on-grade placed on such conditions
may still exhibit some cracking due to soil movement and/or shrinkage. The occurrence of
concrete 'shrinkage cracks is independent of the supporting soil characteristics. Their
occurrence may be reduced 'and/or controlled by limiting the slump of the concrete, proper
concrete placement 'and curing, and the placement of crack-control joints at periodic
intervals, particularly where re-entrant slab corners occur.
7.6 Retaining Walls
7.6.1 Retaining walls not restrained at the top and having a level backfill surface should be
designed for an active soil pressure equivalent to the pressure exerted by .a fluid density of
35 pounds per cubic foot (pet). Where the backfill will be inclined at no steeper than 2 to 1,
an active soil pressure of 45 pcf is recommended. These soil pressures assume that the
backfill materials within an area bounded by the wall and a 1:1 plane extending upward
from the base-of the wall possess an Expansion Index of less than 90. For those lots with
finish-grade soils having an Expansion Index greater than 90 and/or where backfill
materials do not conform to the above criteria, Geocon Incorporated should be consulted
for additional recommendations.
7.6.2 Unrestrained walls are those that are allowed to rotate more than 0.00IH (where H equals
the height of the retaining wall portion of the wall in feet) at the top of the wall. Where
walls are restrained from movement at the top, an additional uniform pressure of 7H psf
should, be added to the above active soil pressure. For retaining walls subjected to vehicular
loads within a horizontal distance equal to two-thirds of the wall height, a surcharge
equivalent to 2 feet soil should be added.
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Project No. 06403-52-24 • - 11 - • January 13, 2006
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I . 7.6.3 All retaining walls should be provided with a drainage system adequate to prevent the
• buildup of hydrostatic forces and should be waterproofed as required by the project
architect. The use of drainage openings through the base of the wall (weep holes, etc.) is
I . not recommended, where the seepage could be a nuisance or otherwise adversely impact the
property adjacent to the base of the wall. A typical retaining wall drainage system is
presented as Figure 2. The above .,recommendations assume a properly compacted granular
(Expansion Index less than 90) backfill material with no hydrostatic forces or imposed
surcharge load: If conditions different than those described are anticipated, or if specific
drainage details are desired, Geocon Incorporated shou!d be contacted for additional
'recommendations.
7.6.4 In general, wall foundations having a minimum depth and width of one foot may be
designed for an allowable soil bearing pressure of 2,000 psf, provided the soil within 3 feet
below the base of the wall has an Expansion Index of less than 90. The proximity of the
foundation to the top of a slope steeper than 3:1 could impact the allowable soil bearing
I . pressure. Therefore, Geocon 'Incorporated should be consulted where such a condition is
anticipated. The' location, of the wall footings, however, should comply with the
recommendations presented in Section 7.5.10.
7.7 Lateral Loads .'
I. 7.7.1 For resistance to lateral, loads, an allowable passive earth pressure equivalent to a fluid
density of 300 pcf is recommended for footings or shear keys poured neat against properly
I compacted granular fill soils or undisturbed natural soils. The allowable passive pressure.
- assumes a horizontal surface extending at least 5 feet or 'three times the surface generating
I the passive pressure, whichever is greater. The upper 12 inches of material not protected by
floor slabs or pavement should not be inckided in the design for lateral resistance. An
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' allowable friction coefficient of 0.4 may be used- for resistance to sliding between soil and
concrete. This friction coefficient may be combined with the allowable passive earth
pressure when determining resistance to lateral loads.
I . • ' ' 7.7.2 The recommendations presented above are generally applicable to the design of rigid
I. concrete or masonry retaining walls having a maximum height of 8 feet. In the event that
walls higher than 8 feet or other types of walls (such as crib-type walls) are 'planned,
Incorporated should be consulted for additional recommendations.
I
Geocon
7.8 Slope Maintenance
1 7.8.1 Slopes that are steeper than 3:1 (horizontal: vertical) may, under conditions that are both
difficult to prevent and predict, be susceptible to near-surface (surficial) slope instability.
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Project No. 06403-52-24 - 12 - ' January 13, 2006
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I The instability is typically limited to the, outer 3 feet of a portion of the slope and usually
does not directly impact the improvements on the pad areas above or below the slope. The
occurrence of surficial instability is more prevalent on fill slopes and is generally preceded
by a period of heavy rainfall, excessive irrigation, or the migration of subsurface seepage.
The disturbance and/or loosening of the surficial soils, as might result from root growth,
I soil expansion, or excavation for irrigation lines and slope planting, may, also be a
significant contributing factor to surficial instability It is therefore recommended that, to
I the maximum extent practical: (a) disturbed/loosened surficial soils be either removed or
properly recompacted; (b) irrigation systems be periodically inspected and maintained to
eliminate leaks and excessive irrigation; and (c) surface drains on and adjacent to slopes be
I ' periodically maintained to preclude ponding or erosion. It should be noted that although the
incorporation of the above recommendations should reducethe potential for surficial slope
instability, it will not eliminate the possibility, and, therefore, it may be necessary to.
rebuild or repair a portion of the project's slopes- in the future.
7.9 Site Drainage
7.9.1 Adequate drainage is critical to reduce the potential for differential soil movement, erosion
and subsurface seepage. Under no circumstances should water be allowed to pond adjacent
to footings or behind retaining walls. The site should be graded and maintained such that
I -
'surface drainage' is directed away from structures and the top of slopes into swales or other
controlled drainage devices. Roof and pavement drainage should be directed into conduits
that carry runoff away from the proposed structure.
7.9.2 All underground 'utilities should be leak free. Utility and irrigation lines should be checked
I .periodically for leaks for early detection of water infiltration and detected leaks should be
repaired promptly. Detrimental soil movement could occur if water is allowed to infiltrate
the soil for a prolonged period of time.' -
7.9.3 Landscaping planters adjacent to paved areas are not recommended due to the potential for
1 surface or irrigation water to infiltrate the pavement's subgrade and base course. We
recommend that drains to collect excess irrigation water and transmit it to drainage
I structures or impervious above-grade planter boxes be used. In addition, where landscaping
is planned adjacent to the pavement, we recommend construction of a cutoff wall along the
edge of the pavement that extends at least 6 inches below the bottom of the-base material.
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Project No. 06403-52-24 - 13- January 13, 2006
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I LIMITATIONS AND UNIFORMITY OF CONDITIONS
Recommendations of this report'pertain only to the site investigated and are based upon the
assumption that the soil cOnditions do not deviate from those,. disclosed' in the investigation. If
any variations or undesirable conditions are encountered during construction, or if the
proposed construction will differ from that anticipated herein, Geocon Incorporated should be
notified so that supplemental. recommendations can be given. The evaluation or 'identification
of the potential presence of hazardous or corrosive materials was not part of the scope of
services provided by Geocon Incorporated.
This report is issued with the understanding that it is the responsibility of the owner, or of his
representative, to ensure that the information and recommendations contained herein are
brought to the attention of the architect and engineer for the project and incorporated into the
plans, and that the necessary steps are taken to see that the contractor and subcontractors
carry out such recommendations in the field.
The findings of this report are valid as of the present date. However, changes •in the
conditions of a property can occur with the passage of time, whether they 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, whether they result from legislation or the
broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly
or partially by changes outside our control. Therefore, this report is subject to review and
should not be relied upon after a period of three years.
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Project No. 06403-52-24 ' . ' January 13, 2006
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SOURCE: 2006 THOMAS BROTHERS MAP
0
SAN DIEGO COUNTY, CALIFORNIA
REPRODUCED WITH PERMISSION GRANTED BY THOMAS BROTHERS MAPS.
THIS MAP IS COPYRIGHT BY THOMAS BROS. MAPS. IT IS UNLAWFUL TO COPY NO SCALE OR REPRODUCE ALL OR ANY PART THEREOF, WHETHER FOR PERSONAL USE OR
RESALE, WITHOUT PERMISSION.
GEOCON
INCORPORATED
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121- 2974
PHONE 858 558-6900 - FAX 858 558-6159
MCE / RA DSI</GTYPD
ii. yMp
VICINITY MAP
VILLAGES OF LA COSTA - THE GREENS
NEIGHBORHOOD 1.07
CARLSBAD, CALIFORNIA
DATE 1132006 PROJECTNO. 06403-52-24 I0F1G 1
U . S
GROUND SURFACE
1.5
- CONCRETE LINE
1
PROPERLY
. PROPOSED COMPACTED Jl RETAINING WALL
. BACKFILL /
. 5....... ..../
• - . S.. / MIRAFI 140 FILTER
FABRIC OR EQUIVALENT
- 2/3H ... OPEN GRADED 1MAX.
- • AGGREGATE
3' MAX.
GROUND SURFACE
1
FOOTING I cDIA.PERPORATEDPVC
. PIPE MIN. 112% FALL TO
APPROVED OUTLET
I.
NO SCALE 11
RETAINING WALL DRAIN. DETAIL
GEOCON
INCORPORATED
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121-2974
PHONE 858 558-6900 - FAX 858 558-6159
MCE ' RA I •
.
DSKIGTYPD
XJIDETAJL/RE1WALII/DWG.
I.
VILLAGES OF LA COSTA - THE GREENS
NEIGHBORHOOD 1.07
• CARLSBAD, CALIFORNIA
DATE 1-13-2006. •
PROJECT NO. 06403-52-24 1 FIG.2
TABLE
SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
AND FOUNDATION CATEGORY
FOR NEIGHBORHOOD 1.07
'LOT NOS. I THROUGH 71
Lot
No. '
Pad Condition
.
Approximate
Maximum
Depth of Fill
(feet) .
Approximate
Maximum Depth
of Differential Fill
(feet)
Expansion
Index
Foundation
Category
Fill . 36 24 ' 87 III
2 Fill .23 9 87 II
3 ' ' Fill '21 8 87 11
4 Fill .21 16 61 II
5 Undercut due to 4 Cut/Fill_Transition
1 85 U
6 Undercut due to 5 Cut/FillTransition
2, 91 III
7 Undercut due to
' 5' Cut/Fill_Transition
2 .63 II
8 Undercut due to
' 16 ' Cut/Fill_Transition
13 '' 63 . II
9 Undercut due to
Cut/Fill_Transition
.6 . 2 ' 63 II
10 Fill 35 - 32 105 III
11 Fill 41 ' , ' 22 ' 105 III
12 Fill 41 11 105 III
13 . Fill 44 , 14 105 ' III
14 Fill 44 16 64 II
15 Fill 41 18 64 II
16 Fill . 31 26 64 III
17 Fill 57 ' 34 75 III
18 ' Fill 69 25 75 111
19 Fill ' 71 . 16 75 111
20' Fill 66 11 48 Ill
21 Fill 59 '2 48 III
22 Fill , 46 6 , 48 II
23 Fill 39 ' 12 48 II
24 Fill 25 12 60 II
25 Fill 13 6 60 II
26 Undercut due to
Cut/Fill_Transition
7 . 4 60 II
Project No. 064035224 ' . January 13,
TABLE I (Continued)
SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
AND FOUNDATION CATEGORY
FOR NEIGHBORHOOD 1.07,
LOT NOS..1 THROUGH 71
Lot
No.
. Pad Condition
Approximate
Maximum
Depth of Fill
(feet) .
. Approximate.
Maximum Depth
of Differential Fill
(feet)
Expansion
Index
Foundation
Category
27 Undercut due to
Cut/Fill Transition
60 II
28 Fill 30 . . 27 58 III
29 Undercut due to
Cut/Fill Transition 24 21
0
58 III
30 Undercut due to 22
Cut/Fill Transition
19 58 II
31 Undercut due to 24
Cut/Fill Transition
21 58 111
32 Undercut due to
Cut/Fill Transition 28 25 58 III
33 Fill 28 12 . 63 II
34 Fill 29. 16 63 II
35 Fill 29 18 63 II
36 Undercut due to
Cut/Fill Transition 17
0
14 67 II
37 Undercut due to
Cut/Fill Transition
. 9 6 67 II
38 Fill 27 24 59 III
39 . Fill 26 . 4 59 II
40 0 Fill 36 15 59 II
41 Fill 0 33 20 59 III
42 Fill 36 27 67 III
Fill 34 27 67 III
44 Fill/Alluvium 31 3 67 111
45 Fill/Alluvium 27 . . 67 111
46 Fill/Alluvium 26 2 67 Ill
47 0 Fill/Alluvium 25 2 50 Ill
48 Fill/Alluvium . 22 1 50 . III
49 Fill 23 . 3 50 II
50 - Fill . 36 7 62 II
51 Fill . 46 5 62 . H
52 . Fill . 40 4 .62 II
53 Fill 28 1 62 II
Project No, 06403-52-24 0
0 January 13, 2006
TABLE I (Continued)
SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
AND FOUNDATION CATEGORY
FOR NEIGHBORHOOD 1.07
LOT NOS. I THROUGH 71
Approximate Approximate
Lot Pad Condition Maximum Maximum Depth Expansion Foundation
No. Depth of Fill of Differential Fill Index Category
(feet) (feet)
54 Fill 33 . . 7 73 S
55 Fill 34 12 73 II
56 Fill . 35 16 73 II
57 Fill 38 . 23 73 III
58 Fill 35 20 . 69 III
59 Fill 33 20 .69 III
60 Fill 29 18 69 .11
61 Undercut due to 20 17. 69 11 Cut/Fill Transition
Undercut due to 62 . 11 Cut/Fill_Transition 8. 77 II
Undercut due to 63 . 24 Cut/Fill_Transition
20 77 III
Undercut due to 64 5 39 Cut/Fill_Transition
36 77 .111
Undercut due to 65 41. Cut/Fill_Transition
37 77 111
Undercut due to 66 25 Cut/Fill_Transition
. 22 77 III
Undercut due to 67 29 Cut/Fill_Transition 26 98 III
Undercut due to 68 Cut/Fill_Transition 29 26 98 III
Undercut due to 69 31 Cut/Fill_Transition
28 98 III
Undercut due to 70 30 Cut/Fill_Transition
. 27 32 III
Undercut due to 71 Cut/Fill_Transition
28 25 32 III
Project No. 06403-52-24 5 January 13, 2006
TABLE II
SUMMARY OF FINISH GRADE EXPANSION INDEX TEST RESULTS
VILLAGES OF LA COSTA; THE GREENS, NEIGHBORHOOD 1.07, LOTS I THROUGH 71
Lot Numbers Sample at
Finish Grade
Expansion
Index
UBC
Classification
I through 3 .EI-E 87 Medium
4 . El-Fa 61 Medium
5 . El-Fb - 85 MedIum
6 El-Fe 91 High
7 through 9 El-G 63 Medium
10 through 13 EI-X 105 High
14 through 16 El-Y . 64 Medium
17 through 19 El-P. . 75 Medium
20 through 23 EI-O . 48 Low
24 through 27 El-N . 60 Medium
28 through 32 El-W . 58 Medium
33 through 35 El-V 63 . Medium
36 and 37 . El-U 67 Medium
38 through 41 El-T 59 . . Medium
42 and 43 - . El-U 67 Medium
44 through 46 . El-S 62 Medium
47 through 49 EI-R 50 Low
50 through 53 E1-J . 62 Medium
54 through 57. El-1 73 Medium
58 through .61 EIH 69 Medium
62 through 66 El-K 7.7 Medium
67 through 69 El-L 98 High
70 and. 71 . El-M 32 Low
Project No. 06403-52-24 -.-. January 13,
TABLE III
SUMMARY OF WATER-SOLUBLE SULFATE LABORATORY TEST RESULTS
CALIFORNIA TEST 417
Sample No. Water-Soluble Sulfate (/o) Sulfate Exposure
IJBC Table 1-A-4
El-E. . . 0.096 . Negligible
El-Fa . . 0.495 : Severe
Ei-Fb .0.120 Moderate
El-Pc 0.255 • Severe
El-G • 0.090 Negligible
El-H - 0.675 Severe
El-1 . 0.540 . Severe
EI-J 0.735 Severe
El-K 0.465. • Severe
El-L . 0.500 • Severe
El-M .0.630 Severe
- • El-N 0.2 10 Severe
El-0 0.705 Severe
El-P 0.645 . Severe
EI-R 0.360 Severe
El-S • 0.600 . Severe
El-T . 0.405 .Severe
El-U 0.435 Severe
El-V 0.255 . Severe
El-W 0.280 Severe
-El-X 0.048 Negligible
El-Y -•• 0.405 Severe
Project No. 06403-52-24 January 13, 2006