HomeMy WebLinkAboutCT 02-23; VILLAGES OF LA COSTA GREENS 1.08; UPDATE GEOTECHNICAL REPORT; 2004-06-18IiI
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I. :r.,';
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. INCORPORATED
I GEOTECHNICAL CONSULTANTSN
OV/
I i Project No. 06403-52-14
June 18,2004 . .
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H I - Warmington Homes .
701 Palomar Airport Road, Suite 300 ,
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Carlsbad, California 92009
Attention: Mr. Chuck Isbell
I Subject: VILLAGES OF LA COSTA:— THE GREENS
NEIGHBORHOOD 1.08, LOTS 1 THROUGH 82 1
CARLSBAD, CALIFORNIA
I . . UPDATE GEOTECHNICAL REPORT
Gentlemen: .
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In accordance with your authorization f our Proposal No. LG-03565 dated November 4, 2003, we
have prepared this update geotechnical report for the subject project. The accompanying report
I .presents the results of our study and contains conclusions and recommendations pertaining th 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 J.
I support of the proposed structures and improvements 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. .
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Very truly yours, . . . . .
I GEOCON INCORPORATED . . . .
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Michael Cf2 4+d
l Staff Geologist . RCE 63291 CEG.1778
SR:AS:JH:bjl'' '4-i V V OFESS
(6/del) Addressee
40 ENONGERM
6960 Flanders Drive U San Diego, California 92.121-2974 U Telephone (858) 558-6900 U Fax (858) 558-6159 .
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TABLE OFCONTENTS
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1.
. 2.
PURPOSE AND SCOPE............................................
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PREVIOUS SITE DEVELOPMENT .................................................................................................1
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4.
SITE AND PROJECT DESCRIPTION ...................... ............... ................ ............ .............. .................
SOIL-AND GEOLOGIC CONDITIONS ......................... ....................... ...........................................
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2
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4.1 Compacted Fill (Qcf) ..............................................................................................................
4.2 Alluvium (Qal) ..........................................................................................................................3
2
4.3 Terrace Deposits (Qt) ................................................................................................................3.
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4.4 Santiago Formation (Ts)... ..................................... ................ ................................. ..................
GROUNDWATER ................. .................................... ................................ ..................... ..................
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6. GEOLOGICHAZARDS......................................................................................................................3,
6.1 Faulting and Seismicity ............................................................................................................3
6.2 Liquefaction ................................................................ . ............................. ...................... ........... 5
1 7. CONCLUSIONS AND RECOMMENDATIONS ............................................. ................................ 6
7.1 General ...... .................................................................... ............................................................. 6
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7.2 Seismic Design .................................................................... ....................................................
7.3 Finish Grade Soil Conditions ....................................................................................................
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.7.4 Future Grading ......................................................................................... ............... .... .... .........
7.5 Foundations ...............................................................................................................................8
7.6 Retaining Walls .........................................................................................................................12
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7.7 Lateral Loads .......................................................... ................................................................... 13
I 7.9
7.8 Slope Maintenance ...................................................................................................................
Site Drainage .........................................................................................................................14
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LIMITATIONS AND UNIFORMITY OF CONDITIONS .
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Figures:
1. Vicinity Map
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I 2. Typical Retaining Wall Drain Detail ..
. . Tables: . ..
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H.
Summary of As-Graded Building Pad. Conditions andFoundation Category • . • .
Summary of Laboratory Water-Soluble Sulfate lest Results 0 '
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1 .00 '
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UPDATE GEOTECHNICAL REPORT '
1. PURPOSE AND SCOPE
This report presents the results of the update geotechnical study for the proposed residential
development of Neighborhood 1.08, Lots 1 through 82 and associated improvements located in the
Villages of La Costa- The Greens development. The site is situated south of future Poinsettia Lane
and west of theexisting La Costa Resort and Spain Carlsbad, California (see Vicinity Map; Figure 1).
The purpose of this update report is to provide foundation and retaining wall design
recommendations. S .
I The scope of the study included a review of the following:
I i. . 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).
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Final Report of Testing and Observation Services Performed During Site Grading, Villages-of La Costa - The Greens, Neighborhood 1.08, and Alicante Road Station 51+00 to 69+00,
Carlsbad, California, prepared by Geocon Incorporated, dated June .16, 2004 (Project No.
06403-52-09).
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Grading and Erosion Control Plans for: La Costa Greens Neighborhood 1. 08, prepared by ' I . Hunsaker and Associates, City of Carlsbad approval dated May 6, 2004.
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. 2. PREVIOUS SITE DEVELOPMENT ,
Neighborhood 4.08, Lots 1 through 82; was graded to finish-pad cnfigurati'on during mass grading
operations for the Villages of La Costa - The Greens development. Grading was performed in
conjunction with the observation and testing services. of Geocon Incorporated. A' summary of the
observations, compaction test results, and professional opinions pertaining, to the grading are I' presented in the above-referenced final report of grading. Mass grading for the site has been
completed and consisted of developing 82 single-family residential lots and associated streets. Fill
I slopes were constructed with design inclinations of 2:1 (horizontal: vertical) or, flatter, with a
maximum, height of approximately 40 feet. Maximum thickness of the fill soils is approximately 85
feet. An "As-Graded" Geologic Map is provided in the above-referenced, final report and depicts the
existing geologic conditions and topography.
I ' 3.: SITE AND PROJECT DESCRIPTION
The development of The Greens - Neighborhood 1.08 consists of 82 single-family residential homes
I and 'associated improvements. 'Compacted fill soils are exposed at grade, underlain by the Sanfiago
Formation, stream-deposited Terrace Deposits and alluvium. A summary of the as-graded pad
Project No. 06403-52-14 -1- . ,
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conditions for the lots is provided on Table I. In general, the on-site fill materials generally vary
between angular gravels and boulders produced . by onsite blasting of hard metavolcanic rocks to
clayey, fine sands, sandy to silty clay, and sandy to clayey gravels, derived from excavations within
the surficial soils and the Santiago Formation.
The locations and descriptions . of the site and prdposed 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, stream-deposited Terrace Deposits, alluvium, and compacted fill soils
underlie the site. The predominant materials within 4 feet of grade generally consist of clayey to silty
sand and sandS' clay and typically possess a low to medium expansion potential. The soil type and
geologic unit are discussed below. ••
4.1 Compacted Fill (Qcf) . . ,••
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In general, structural fill placed and compacted at the site consists of material which can be classified
into thiee zones:
Zone A L. Material placed within 3 feet from pad grade, 6 feet from parkway grade, and
within roadways to at\least 1 foot below, the deepest utility consisted of 'soil" fill with a
maximum particle dimension of 6 inches. .
Zone B— Material placed within 10 feet from pad grade and below ZoneA consisted of "sOil.
rock" fill .with a maximum particle dimension of 12 inches.. In addition, material placed on
the outer 6 feet of fill slopeg and 2 feet below Zone A for fills in roadways and parkways
-consisted of "soil rock" fill with a maximum particle dimension of 12 inches.
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Zone C - Material placed below Zone B consisted of "soil rock" fill and "rock" fill with a
maximum particle dimension of 48 inches. It should also be noted that larger rocks with a
maximum dimension of approximately 8 feet were buried individually, during, "rock" fill
grading operations. . .• . . .
The maximum fill thickness is approximately 85 feet. Fill soils were placed in conjunction with the
observation and testing services of Geocon Incorporated and will be'included in the above-referenced
final report of grading.'The compacted fill soils are considered suitable to provide adequate support
for the proposed development: • • •
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Project No. 06403-52-14 - . -2- • . . June 18,2004
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I .4.2 Alluvium (Qal) . . . .
Alluvium was encountered along the western margins of Neighborhood 1.08 and generally consisted
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of soft, dark brown sandy clays to clayey sands. Due to the presence of groundwater and the close
proximity of the property boundary to the canyon drainage, total removal and compaction of the
alluvial soils was -not practical, and some alluvium was . left in place. The alluvium was stabilized I prior to fill placement with the use of geofabric and gravel. The alluvium left in place is slightly
compressible with minor post-construction settlement anticipated. Modified foundation
I recommendations are provide herein for lots with alluvium left in place adjacent to the pads.
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4.3 Terrace Deposits (Qt)*.. .
Stream-deposited Terrace Deposits were encountered overlying the Santiago Formation, mostly
I . within the lower portions of the major drainages. These sediments consist of moderately dense,
yellowish to reddish brown, clayey sand and silty sand with some clay, and are considered suitable
for the suppOrt. of the proposed development. .
I,. . . . . . . .. 4.4 Santiago Formation (Ts) . .. . .
I . The Eocene-aged Santiago Formation, consisting ofdense, massive, white to light green, silty, fine to
coarse sandstones and hard, greenish-gray to brown claystones and siltstones underlie the compacted
I . fill and alluvium at the site and are considered suitable for the support of the proposed development.
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5. GROUNDWATER
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Groundwater was encountered during grading operations at the base of the cleanouts. However, it is
I not anticipated to adversely impact the development of the property due to the installation of canyon
ubdrains and the use of stabilization methods. Due to the variable nature of the Santiago Formation,
which onsists of interbedded sandstone and claystone/siltstone, seepage was mitigated during
I remedial grading by subdrain installation. It is not uncommon for groundwater or seepage conditions
to develop where none . previously existed. Groundwater elevations are dependent on seasonal.
I 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 project.
I . 6.. GEOLOGIC HAZARDS .
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6.1 FaultingandSeismicity . . .
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 I . . area indicate that no known active potentially active, or inactive faults are located at the site.
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Project No. 06403-52-14 - 3 - . . June 18, 2004
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The nearest known "active" faults are the Rose Canyon Fault and-the Newport-Inglewood (offshore) '
located approximately 7 and 10 miles, respectively, 'to the west and'the Coronado Banks Fault Zone;''
which lies approximately 22 miles to the southwest. Portions of the Rose Canyon Fault have been
I ' included' 'in a Special Study 'Earthquake Fault Zone. A Maximum Credible seismic event of
Magnitude 7.2 is postulated for the 'Rose Canyon Fault with an estimated Maximum Credible peak
I site acceleration of 0.32 gbased on the Sádigh, et al. (1997), acceleration-attenuation 'relationship.
The seismicity of the site is influenced by both local and regional fault 'systems within the southern I . California and northern Baja California region. Table 6.1 lists the fault zones that present the. greatest
' seismic impact to the site.
TABLE 6.1
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.FAULT SYSTEMS WITHIN THE SOUTHERN CALIFORNIA AND
NORTHERN'BAJA'CALIFORNIA REGION
Fault Name Distance from Site. '
. (nules)
' ' Maximum
Credible Earthquake
Maximum Credible'
' Site Acceleration (g)
Rose Canyon ' . ' . ' 7 ... 7.2 ' '. 0.32
Newport—Inglewood (Offshore) . 10 ' ' . .. '.' ' ' '7j '.. . : .. . 0.25
Coronado Banks Fault Zone ' 22 . '7.6 ' 0.17
Elsinore—Julian S ' 23 ._.- ' 7.1 ' 0.13
Elsinore—Temecula' ' 23 6.8 0.10.
Palos Verdes" .' 41 ' '7.3 '' ' 0.08
Elsinore—Glen Ivy, .
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.' 37 : 6.8 0.06
San Jacinto—Anza ' ' ' ' . 49 . 7.2 . 0.06
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In ,the event of a major earthquake along, any of the above-referenced faults or other faults in the
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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 ib the general vicinity. While
I ' listing peak accelerations is useful for comparison of potential effects, of fault 'actii'ity. 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.'
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ProjectNo. 06403-52-14 ' .
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7.1.2
7.2
7.2.1
7. CONCLUSIONS AND RECOMMENDATIONS
General ..
No soil or geologic conditions were encountered during previous geotechrncal
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.
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
recómmendations are not included in this report but can be provided uponrequest. Design
criteria for post-tensioned slabs are provided in Section 75.
Seismic Design
The site is located within Seismic Zone 4 according to UBC Figure 16-J. Compacted fill
soils underline the proposed buildings For seismic design the site is characterized as soil
types Sc and 5D 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 S0
Seismic Zone Factor, 1. 0.40 0.40 Table 16-I
Soil Profile SD Table 16-J
Seismic Coefficient, Ca 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 . Table16-S
Near-Source Factor, N 1.0 1.0 Table 16-T
Seismic Source B B Table 16-U
Project No. 06403-52-14 -6-. June 18,2004
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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 Table 7.2.2. .
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TABLE 7.2.2
'SUMMARYOFSOILPROFILETYPE . . '..,'i '- ..
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"$1
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Lot Nos. - ' ., .
£
UBC Classification
1arid 2 Ar
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4 Sr
3,SC
4thr0ugh10 -.SD
11 Sc.
12 and 13 .. .Sb
14 through 17 . '. . Sc
l8through,37 , . 'SD
38. . . S
39 through .47. . .' . ' . ' SD
, 48 . . ,. . -
S.
49 through 55 , . ' SD
56 through 59 • " . . . Sc
60 through 66 . ' .. SD
67 through 70 . . •, . 5c ' -
71 through 82 ' .. . "Sn — ' ' •---'--•-- . . .
7.3 , Finish Grade Soil Conditions
• I , 7.3.1 , Observations and laboratory test results indicate that: the prevailing soil conditidns' within
the upper approximately 4 feet of finish grade have an expansion potential of "low" to
"medium" (Expansion Index, of 90 or less) as'defined by Uniform Building Code (UBC)
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Table 18-I-B. Expansion Index test results for each lot are included on Table I.
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7.3.2 It should be noted that although rocks larger than 6-inch-diameter were not intentionally
placed within the upper 4 feet .f pad grades, 'some larger, rocks may exist at random
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locations.
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' 7.3.3 Randoni samples obtained throughout the neighborhood were subjected to water-soluble'
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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 siilfate ttaçk on normal Portland I
No 06403 52-14 7 June 18 2004
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.Cement concrete. The test results indicate sulfate contents that correspond to "negligible"
to "severe" su1fateexosiire ratings as defined by UBCTable 19-A-4. The results of the
soluble-sulfate tests are'summarized in Table H. Table 7.3 presents a summary of concrete
requirements get forth by .UBC .Tab1e 19-A-4. It is recommended that the concrete used in
Neighborhood L08 meet the requirements for ,"sévere" sulfate expdsure rating, as provided
in Table 7.3. .
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TABLE 7.3 .. I . REQUIREMENTS FOR CONCRETE EXPOSED TO
SULFATE-CONTAINING SOLUTIONS
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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 V . 0.45 4500
7.3.4 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore, if
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. improvements that could be susceptible to dorrosion are planned, it is recommended -that
further evaluation by a corrosion engineer be performed:
7.4 C7FIdiureGradin9 . . . . .
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7.4.1 . Any additional grading performed at the site should be accomplished, in conjunction with
our observation and compaction testing services. Gra1ing plans for any future grading
should be reviewed by Geocon Incorporated prior to finalizing. All trench and wall bacldill
I (should be compacted io a dry dnsity of at least .90 percnt of the laboratory maximum dry
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density at or slightly above'. optimum moisture content.. This office should be notified at
least 48 hours prior to commencing additional gading or backfill operations.
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7.5 . . . Foundations . .
I 7.5.1. The foundation recommendations that follow are for one- or two-story. residential
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structures and are separated into categories dependent On the thickness and geometry of the
Expansion Index underlying fill soils as well as the (El) of the prevailing subgrade soils of
a particular building pad. The categOry criteria are summarized herein.
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Project No. 06403-52-14 . .
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Category I: Maximum fill thickness is less than 20 feet and Expansion Index is less than or
I equal to 50.
Category II: Maximum fill thickness is less than 50 feet and Expansion Index is less than or
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equal to 90, or variation in fill thickness is between 10 feet and 20 feet.
Ill: Fill thickness exceeds 50 feet, or variation in fill thickness exceeds 20 feet, or
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Expansion Index exceeds 90 but is less than 130, or underlain by alluvium.
Notes:
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All footings should have a minimum width of 12 inches.
'. Footing depth is measured from lowest adjacent subgrade (including topsoil, if planned).
These depths apply to both exterior and interior footings.
All building concrete slabs should be at least5 incheshick.
1 1 All building oncrete slabs should be. underlain by at least 4 inches. (3 inches for Category III)
of clean sand or crushed rock. S
I . - All slabs expected to receive moisture-sensitive floor coverings or used to store moisture-
sensitive materials should be underlain by a vapor barrier covered with at least 1½ inches 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
I . 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 can also be
used to reduce the potential for foundation distress due to differential fill settlement. The
I post -tensioned design should incorporate the geotechnical parameters presented in Table
7.5.2 for the particular foundation category designated for each lot as presented in Table I.
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Project No. 06403-52-14 ' -9.- June 18, 2004
TABLE 7.5.2
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post Tensioning Institute (I'll) Foundation Category
Design Parameters
1 Thornthwaite Index 20 20 20
Clay Type - Montmorillonite Yes Yes Yes
Clay Portion (Maximum) 30% 50% 70%
4 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 0.41 in. 0.78 in. 1.15 in.
7.5.3
7.5.4 The post-tensioned systems should be designed to resist the amount of edge lift indicated
on Table 7.5.2. Our experience indicates that unless reinforcing steel 'is placed at the
bottom of the perimeter footing and interior stiffener beams, post-tensioned slabs are
susceptible to excessive edge lift regardless of underlying soil conditions Current PTI
design procedures primarily address the potential for center lift of slabs but because of the
placement of reinforcing. tendons near the top 'of the slab, the resulting stress eccentricity
after tensioning reduces the ability of the system to mitigate edge lift. Therefore, post-
tensioned foundation systems should be designed to resist a total of 2 inches of edge lift.
7:5.5 Foundations for Category I, 11-or ifi may be designed for an allowable soil bearing pressure
of 2,000 pounds per square foot (psO (dead plus live load) This bearing pressure may be
increased by one-third for transient loads such as wind or seismic forces
Project No. 06403-52-14 , -10,- , June 18, 2004
Center Lift Moisture Variation Distance 5.3 ft. 5.3 ft. 5.3 ft.
Center Lift ' 2.12 in. 3.21 in. 4.74 in.
UBC Section 1816 uses interior stiffener beams in its structural design procedures If the
'structural engineer proposes a post-tensioned foundation design 'method other' than UBC
Section 1816, it is recommended that interior stiffener, beams be used for Foundation
Categories II and III. The depth of the perimeter foundation should be at least 12 inches for
Foundation Category I. Where the Expansion Index for a particular building pad exceeds
50 but is less than 91 the perimeter footing depth should be at least 18 inches. Geocon
Incorporated should be consulted to provide additional design parameters as required by
the structural engineer.
7.5.6 [The "use "àf isolated footings that are located beyond" the perimeter of the building and
support structural elements connected to the building is not recommended for Category ifi.
Where this condition cannot be avoided, the isolated footings should be connected to the
LbiiiLdfng foundation system with. grade beams.
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No pecial subgrade presaturation is deemed necessary prior to placing concrete; however,
the exposed foundation and slab subgrade soils should be moisture conditioned, as
necessary, to maintain a moist .condit'iôn as would be expected in any such concrete
placement.
7.5.8 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.
7.5.9 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
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.
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)
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 post-tensioned slab and foundation system or increased footing and slab
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.
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
with the assumption that, the adjacent soil provides no lateral support. This
recommendation, on 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
than 30 feet in height, additional recommendations may be required and Geocon
Incorporated should be contacted for a review of specific site conditions.
' 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
movement without causing extensive' distress. Geocon Incorporated should be,
consulted for specific recommendations.
Project No. 06403-52-14 • . - 11 - , June 18, 2004
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7.5.10 '-Exterior slabs not subject to vehicle loads should be at least 4 inches thick and reinforced
with 6x6-W2.91W2.9 (6x6-6/6) welded wire mesh. The mesh should be placed within the
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
I mesh placement. Prior to construction of eterior slabs, the, subgrade should be moisture
conditioned to at least optimum moisture content and compacted to a dry density of at least
90 percent of the laboratory maximum dry density.
7.5.11 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.
I . 7.5.12 Whefe '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
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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. .
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7.5.13 The recommendations of this report are intended to reduce the potential for cracking of
differential deep fills, fills slabs due to expansive soils ('if present), settlement of or 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
I concrete shrinkage cracks is independent of the supporting soil characteristics. Their
be by limiting occurrence may reduced and/or controlled the slump of the concrete, proper
concrete placement and curing, and the placement of crack-control joints at periodic ,
I intervals, particularly where re-entrant slab corners occur.
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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 (pcf). 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
I backfill materials within an area bounded by the wall and a 1:1 plane extending upward
from the base of the wall posess an Expansion Index of less than 90. For those lots with
I . 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.
Project No. 06403-52-14 . ' . '., ' . -12 - ,
' ' . ' June 18, 2004
I
7.6:2 Unrestrained walls are those that are allowed to rotate more than 0.001H (where H equals
V I 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 V
V V
V
V should be added to the above active soil pressure. For retaining walls subjected to vehicular
V V
loads within a. horizontal distance equal to two-thirds of the wall height, a surcharge
V equivalent to 2 feet soil should be added. V
V V V
7.6.3 V prevent the V * ll itaifliiig Walls should be provided Vwith a drainage -system adequate to
I Vbuildup of hydrostatic forces and should be waterpoofed as required V
Vb the project ' V
V
V
V V V
V V
V raichitect. The use of drainage openings through the base of the wall (weep holes, etc.) is
I V not recommended where the seepage could be a nuisance or otherwise adversely impact the V V
V V
V
V property adjacent to the base of the wall. I A typical retaining wall drainage system is V
V
V
V
V
V
V V
presented asFigure 2. The above recommendations assume a properly compacted granular V V
(Expansion Index less than 90) backfi1l material with no hydrostatic forces or imposed V
V
V surcharge V load. If conditions different than those described are anticipated, V or if VspeéificV
V
I drainage details are desired, Geocon Incorporated should be contacted for additional .
V
V
V
V recommendations.
7.6.4 In general, wall foundations having a minimum. depth and width of one foot may be
V
V
designed for an allowable soil bearing pressure of 2,000 psf provided the soil within 3 feet
V
VV
V below thel base of the wall has an Expansion Index of less than 90. The proximity of the
V V
V V foundation to the top of a slope steeper than 3:1 could impact the allowable soil -bearing V V
I pressure.Therefore, Geocon Incorporated should be consulted where such a condition is
V
V anticipated. The location of the retaining wall footings, however, should comply with the
V recommendations presented:in Section 7.5.9. V V
V
V
V 7.7 Lateral Loads
V 7.7.1 For resistance to lateral loads, an allowable' passive earth press'ur equivalent to .a fluid V V
V
V V density of 300 pcf is recommended. fdifootings or shear keys poured neat against properly
V
V
V
V
1
compacted granular fill soils or undisturbed natural soils. The allowable
passive pressure V
V
assumes a horizontal surface extending at least 5 feet or
Vthree times the surface generating
V
V I V the passive pressure, whichever is greater. The upper 12 inches of material not protected by
*
V I V
V * V floor slabs or pavement should not be included in the design for lateral resistance. An V V V V
V V V V allowable friction coefficient Vof 0.4 may be "used for resistance to sliding between soil and V
V
V *
V
V
V
V
concrete. This
friction coefficient may be combined with the allowable' passive earth , V V
V
V : .pressure when determining resistance to lateral loads.
V V
V
V
V
V
V
V
V 7.7.2 The recommendations presented above are generally applicable to the design of rigid V V V
V
V V concrete or masonry retaining walls having a maximum height of8 feet. In the event that *
V
V
V V Project No. 064035214 13 - V V V June 18, 2004
walls higher than 8 feet or other types of walls (such as crib-type 'walls) are planned,
Geocon Incorporated should be consulted for additional recommendations.
7.8 Slope Maintenance:
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.
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..grbwth,
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
the maximum extent practical: (a) disturbedlloosened surficial soils be either removed or
properly récompacted; b irrigation systems be periodically inspected and maintained to
eliminate leaks and excessive irrigation; and (c) surface drains on and adjacent to slopes be
periodically maintained to preclude ponding or erosion It should be noted that although the
incorporation of the above recommendations 'should reduce the potential for surficial slope
instability, it will not eliminate the possibility, and, therefore, it may be necessary to
7.9.2
.1
rebuild or repair a portionof the project's slopes in the future. '. .
Site Drainage .
,
.
.
. ..
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
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 frorirthe proposè& structure.-:
'All underground utilities should.,be leak free. Utility and irrigation lines should be checked
periodically for leaks for early detection of water iñfilfration' and detected leaks should be
repaired promptly. Detrimental soil movement could occur if water is allowed' to infiltrate
the sail for a prolonged period of time. '
Landscaping planters adjacent to paved areas are not recommended due to the potential for
surface or irrigation water to infiltrate the pavement's ,subgrade and base course. We
recommend . that drains to collect' excess irrigation water and transmit it to drainage
structures or impervious above-grade planter boxes be used. In addition, where landscaping
7.9
7.9.1
i
Project No 06403-52-14. -14 June 18 2004
1• ,. ..
I .LIMITATIONS AND UNIFORMITY OF CONDITIONS
I . 1.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
I . proposed construction will differ from that anticipated herein, Geocon Incorporated should be
notified so that supplemental recommendatiOns can be given. The evaluation or identification
I of the potential presence of hazardous or corrosive materials was not part of the scope of
services provided by Geocon Incorporated. .
I 2. This report is issued with the understanding that it is the responsibility of the owner, or of his
representative, to ensure that the iiiformation 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..
3. , The findings of this report are valid as of the present date. However, changes in the
I 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
I . 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.
I
I Project No. 06403-52-14 June 18, 2004
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SOURCE 2004 THOMAS BROTHERS MAP
SAN DIEGO COUNTY, CALIFORNIA
REPRODUCED WITH PERMISSION GRANTED BY THOMAS BORThERS MAPS.
THIS MAP IS COPYRIGHT BY THOMAS BROS. MAPS IT IS UNI.AWFULTO COPY
OR REPRODUCE ALL OR ANY PART THEREOF, WHETHER FOR PERSONAL USE OR NO SCALE
RESALE, WITHOUT PERMISSIO N.S
GEOCON So INCORPORATED
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159 5
MCE/MM
S
SI....
DSK/E0000
VICINITY MAP
VILLAGES OF LA COSTA - THE GREENS
NEIGHBORHOOD 1.08
S CARLSBAD, CALIFORNIA S S
DATE 06-18-2004 PROJECT NO. 06403-5?-14
3 . . . . . .
GROUND SURFACE .
CONCRETE ..
)
BROWDIT6H1
PROPERLY P ED
RETAINING WALL COMPACTED i
1 / 3/4
.1
- / APPROVED
• r. . ., FILTER FABRIC
OPEN GRADED
4 I MAX AGGREGATE
.. . . .-, 3MA)C
GROUND SURFACE ____i\ .)
2/3 H.....
.• .
. FOOTING 'RI 4" DIA. PERPORATED PVC
I I PIPE MIN. 1/2% FALL TO .
- - APPROVED OUTLET
NO SCALE
TYPICAL RETAINING WALL 'DRAIN DETAIL .
I 'GEOCON
INCORPORATED
I
GEOTEa-INICAL CONSULTANTS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121-2974
-PHONE 858,558-6000 - FAX 858 558-6159 . .
MCE/MM
•. • • .
DSKJE0000
WIT-v6-l0d.WRe--q WQ .
VILLAGES OF LA COSTA - THE GREENS
NEIGHBORHOOD 1.0,8
•. ... CARLSBAD; CALIFORNIA
rDATE 66182004 PROJECT NO. 06403-52.- 14 IFIG.2
'• - - TABLEl - -
I - SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
- - AND FOUNDATION CATEGORY
- FOR NEIGHBORHOOD LO8 ,.
- I - -
- - 'LOT NOS. I THROUGH 82 -- -
- Approximate Approximate - -
Lot Maximum Maximum Depth Expansion Foundation
No. Pad Condition Depth of Fill . . of Differential Fill Index -
- Category
- -. (feet) - - (feet) - -'
1 - Fill 30 - 17 -52 II
2 Fill - - 25 - - 17 - 52 II -.
3 Fill- -, 11 9 - - .52 II
4 Fill . .31 - - 21 - 52- ifi
5 Fill 31 - 10 - - 46 - - II
6 - Fill - • 30 22 - - 46 III
7 Fill 23 - '-17 _; 46 -II -
8 Fill -. _23 16 46 II - --
9 Undercut due to 29 25 - 58 III cut/fill transition -_- - . --
10 Undercut due to -
22 - 18 - - - 58 - - II - cut/fill transition - -
11 Undercut due to
- 19 - 15 .
-
- 58 II - -cut/filltransition __- - S -
12 Undercut due to
-22 - - 18 - 62- II - cut/fill transition
13 - Fill -. .26 -.- ---18 __.
-
62 - II_-
14 - Undercut, due to - 13 9 62 - - II - -- - - - cut/fill transition - _-
15 - Undercut due to -
- • - . 6 - - 81 II cut/fill transition -• -
16 Undercut due to 17 13 - -- 81 II cut/fill transition
17 Fill -- -- _19 -.10 --: 81 - II
-18 -- Fill - ---21 11 - -81 -II
-19 .Fill 31 -12 _- 48 - -II
20 - -Fill _- -42 .22 48 III
21 - --Fill 38 •- - _12 _• 48 II -
22 -Fill 42 - -_10 _-- 48 .11
23 _- -Fill --39 -21, 48 -III
24 Fill 59 59- - _42 _---. -50 -III
June 18,2OO4 -
I
• TABLE I (Continued)
• SUMMARY OF AS-GRADEDBUILDING PAD CONDITIONS
I AND FOUNDATION CATEGORY
FOR NEIGHBORHOOD 1.08
i
LOT NOS. 1 THROUGH 82
Approximate Approximate
Lot. Pad Condition :. Maximum Maximum Depth Expansion Foundation
No. • Depth of F.11 of Differentia1Fi11 Index Category
(feet) (feat)
25 Fill 62 49 50 III
26 Fill , ,70 _ 17 * 150 III
27 Fill 63 31 50 III
2 Fill 68 36 63 III
29 Fill 61 28 63 III
30 Fill 57 , 28 63 ml
31 Fill 61 37 63 III
32 Fill 74 24 . 54 III
33 Fill, 79 36 1.54 llI'
34 Fill 85 25 54 III
35 Fill 80 28 54 III
36 Fill 48 26 41 III
37 Undercut due to 28 24 41 III cut/fill transition
38 Undercut due to 6 2 41 I cut/fill transition
39 Undercut due to 28 24 57 III cut/fill transition
40 Undercut due to 21 17 57 II cut/fill transition
41 Undercut due to 30 26 57 •
cut/fill transition • _________________ _____________
42 Undercut due to 30 26 57 III cut/fill transition
43 Undercut due to 30. 24 90 cut/fill transition
44 Fill 54 37 90 III
45 Fill 74 46 90 III
46 Fill 77 47 90 III
47 Fill 71 41 90 III
48 Undercut due to 5 52 II cut/fill transition
IHH.
i Project No 0640-52-14
,, '.
TABLE 1. (Continued)
SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
AND.FOUNDATION CATEGORY . *
FOR NEIGHBORHOOD 1.08
- •"
I '
Approximate
A.
Approximate
Lot " Pad.condth9n.I .'çMaximü'm ', J Mximum:Depth' Expânsion 'Foundation
No. 'Dth of Fill 'of Differèiitia! Fill ' Index Category
(feet) (feet) -
49 Fill 33 25 - 52 III
50. Fill 49 ; 20 -52 III
51- Fill 66 " 20 52 -
52 Fill Fill , 59 14 52 III
53 **Fill 45 15 37 II
54 Fill . 43 . 9 37 11
-55 Fill 22 ' 16 . 37 II
56 Undercut due to
- 17 - 13 37 II - cut/fill transition - S
.
Undercut due to -
: . 37 cut/fill transition
58 Undercut due to 4 1 35. I cut/fill transition . -
59• Undercut.dueto 14 10 - 35 II cut/fill transition -
60 Fill . 29 ,- '12 35 . 11
61 Fill . -50 , - 7 , 35 III
62 - Fill . • -50 s -1 . 35. 111k
63 Fill • 51
5
9 - - 53 • III
64 - Fill 5•50 -- - 8 - 53 III
65 ' Fill' 49 - . 34 -53 III
- 66 Fill - 31 - - 20 53
67 Undercut due to
' 19 * ,, : -
- 56 - 11 • . cut/fill transition S*
68 -
Undercut due to 12 8 • - 56 : II cut/fill transition •
-
69 - Undercut due to ••
- .
5.- -
3• - 56 -• 11 • cut/fill transition •
70 Undercut due- to -
'- ' 5 ' - 11 cut/fill transition
71 * Fill 27 _- *:.-18 '- -39'- S .-
-72 "Fill 45 ---21 -.39 -- -III
/ - •
-1 •,' •
•' .'**--, * . .I .
Project No. 06403-52-14 'S - • June18,2004
I
- -•
M
-
• • :t