HomeMy WebLinkAboutCT 05-16; La Costa Oaks North 3.4 & 3.5; Addendum to the update Geotechnical Report; 2010-07-29GEOCON
INCORPORATED
GEOTECHNICAL • ENVIRONMENTAL • MATERIALS
Project No. 06105-52-27
July 29, 2010
Pulte Homes, Incorporated
27101 Puerto Real, Suite 300
Mission Viejo, California 92619
Attention: Mr. David Hutchins
Subject: VILLAGES OF LA COSTA - THE OAKS NORTH
NEIGHBORHOOD 3.4 AND 3.5
CARLSBAD, CALIFORNIA
ADDENDUM TO THE UPDATE GEOTECHNICAL REPORT
Reference: Update Geotechnical Report, Villages of La Costa - The Oaks North, Neighborhoods
3.4 and 3.5, Lots 1 through 83, Carlsbad, California, Prepared by Geocon
Incorporated, dated January 5, 2010 (Project No. 06105-52-27).
Dear Mr. Hutchins:
In accordance with your request, we have prepared this correspondence to provide additional
recommendations for design of the foundation systems for the planned development. We understand
that post tensioned foundation system has been selected for the project. In the referenced report, we
have provided three foundation categories based on the underlying fill thickness and the expansion
potential of the near surface soils. We recommended that the post-tensioned systems should be
designed by a structural engineer experienced in post-tensioned slab design and design criteria of the
Post-Tensioning Institute (PTI), Third Edition, as required by the 2007 California Building Code
(CBC Section 1805.8). Foundation systems for the buildings that possess a foundation Category I and
a 'Very low" expansion potential (expansion index of 20 or less) can be designed using the method
described in Section 1 805 of the 2007 CBC. However, the post-tensioned foundation system should
be designed with a total and differential deflection of 1 inch. Geocon Incorporated should be
contacted to review the plans and provide additional information, if necessary. Table I presents the
revised foundation categories to include Foundation Category IA.
Should you have questions regarding this report, or if we may be of further service, please contact the
undersigned at your convenience.
Very truly yours,
GEOCON INCORPORATED
"All Sadr
CEG 1778
(2) Addressee
lawn Foy Weedon
GE2714
o
U!
X
6960 Flanders Drive • San Diego, California 92121-2974 • Telephone 858.558.690C - ,UA ooo.358.6159
TABLE I
SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
AND RECOMMENDED FOUNDATION CATEGORIES FOR
VILLAGES OF LA COSTA -THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5
LOTS 1 THROUGH 83
Lot No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Pad Condition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Fill
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Fill
Fill
Fill
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
hard rock
Undercut due to
hard rock
Undercut due to
hard rock
Undercut due to
cut-fill transition
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Approximate
Maximum
Depth of Fill
(feet)
5
8
22
29
29
27
24
25
35
20
15
5
5
4
3
6
9
11
13
13
12
12
16
19
18
24
26
Approximate
Maximum
Depth of FU1
Differential
(feet)
1
3
15
26
26
24
18
17
24
15
11
2
1
1
0
2
4
2
3
4
5
4
10
11
11
15
16
Expansion
Index
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
2
2
2
2
2
2
2
0
0
0
Recommended
Foundation
Category
IA
IA
II
III
III
III
II
II
in
ii
ii
IA
IA
IA
IA
IA
IA
IA
IA
IA
IA
IA
II
II
II
II
II
Project No. 06105-52-27 July 29, 2010
TABLE I (Continued)
SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
AND RECOMMENDED FOUNDATION CATEGORIES FOR
VILLAGES OF LA COSTA -THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5
LOTS 1 THROUGH 83
Lot No.
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Pad Condition
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Undercut due to
hard rock
Undercut due to
hard rock
Undercut due to
hard rock
Undercut due to
hard rock
Undercut due to
hard rock
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Fill
Fill
Fill
Fill
Fill
Undercut due to
cut-fill transition
Undercut due to
hard rock
Undercut due to
hard rock
Undercut due to
hard rock
Approximate
Maximum
Depth of Fill
(feet)
26
26
26
28
30
32
33
41
4
4
4
4
4
9
10
7
14
18
20
20
30
23
20
14
6
6
4
Approximate
Maximum
Depth of Fill
Differential
(feet)
14
14
15
16
15
17
4
14
1
1
1
1
1
5
6
3
10
10
9
9
15
6
9
10
3
1
1
Expansion
Index
0
0
0
0
0
0
0
0
18
18
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Recommended
Foundation
Category
II
II
II
II
II
II
II
II
IA
IA
IA
IA
IA
IA
IA
IA
II
II
II
II
II
II
II
II
IA
IA
IA
Project No. 06105-52-27 July 29, 2010
TABLE I (Continued)
SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
AND RECOMMENDED FOUNDATION CATEGORIES FOR
VILLAGES OF LA COSTA -THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5
LOTS 1 THROUGH 83
Lot No.
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
Pad Condition
Undercut due to
hard rock
Fill
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Approximate
Maximum
Depth of Fill
(feet)
8
21
18
15
17
24
35
40
40
38
35
38
43
50
50
54
46
44
42
39
23
24
27
29
28
25
21
13
14
Approximate
Maximum
Depth of Fill
Differential
(feet)
6
13
15
11
10
10
14
9
6
10
7
18
15
20
18
21
23
11
6
5
15
11
17
20
14
11
9
4
11
Expansion
Index
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
22
22
22
0
0
0
0
1
1
1
1
1
Recommended
Foundation
Category
IA
II
II
II
II
II
II
II
II
II
II
II
II
III
III
III
III
II
II
II
II
II
II
III
II
II
II
IA
II
Project No. 06105-52-27 July 29, 2010
IGAl
N
UPDATE
GEOTECHNICAL REPORT
VILLAGES OF LA COSTA -
THE OAKS NORTH
NEIGHBORHOODS 3.4 AND 3.5
LOTS 1 THROUGH 83
CARLSBAD, CALIFORNIA
PREPARED FOR
PULTE HOMES
MISSION VIEJO, CALIFORNIA
JANUARYS, 2010
PROJECT NO. 06105-52-27
GEOCON
INCORPORATED
GEOTECHNICAL CONSULTANTS
Project No. 06105-52-27
January 5, 2010
Pulte Homes
27101 Puerta Real, Suite 300
Mission Viejo, California 92619
Attention: Mr. David Hutchins
Subj ect: VILLAGES OF LA COSTA - THE OAKS NORTH
NEIGHBORHOODS 3.4 AND 3.5
LOTS 1 THROUGH 83
CARLSBAD, CALIFORNIA
UPDATE GEOTECHNICAL REPORT
Dear Mr. Hutchins:
In accordance with your request and our proposal (LG-09313) dated December 4, 2009, we have
prepared this update geotechnical report for the subject project. The accompanying report presents the
results of our study and conclusions and recommendations pertaining to the geotechnical aspects of
proposed development of the site.
The site was graded as part of the Villages of La Costa - Oaks North development. The grading for
Lots 1 through 83 was completed in September 2007. Compacted fill and formational materials of
Santiago Peak Volcanics and Escondido Creek Granodiorite underlie the site. Provided the
recommendations contained in this update report are followed, the site is considered suitable for
construction and support of the proposed residential structures.
Should you have questions regarding this report, or if we may be of further service, please contact the
undersigned at your convenience.
GEOCON INCORPORATED
Ali Sadr
CEG 1778
(4/del) Addressee
Shawn Weedon
GE2714
6960 Flanders Drive • San Diego, California 92121-2974 • Telephone |858) 558-6900 • Fax (858) 558-6159
TABLE OF CONTENTS
1. PURPOSE AND SCOPE 1
2. SITE AND PROJECT DESCRIPTION 1
3. PREVIOUS SITE DEVELOPMENT 2
4. SOIL AND GEOLOGIC CONDITIONS 2
4.1 Compacted Fill (Qcf&Quc) 2
4.2 Santiago Peak Volcanics (Jsp) 3
4.3 Escondido Creek Granodiorite (Ke) 3
5. GROUNDWATER 3
6. GEOLOGIC HAZARDS 3
6.1 Faulting and Seismicity 3
6.2 Liquefaction 6
7. CONCLUSIONS AND RECOMMENDATIONS 7
7.1 General 7
7.2 Finish Grade Soil Conditions 7
7.3 Seismic Design Criteria 8
7.4 Future Grading 9
7.5 Foundation and Concrete Slabs-On-Grade Recommendations 9
7.6 Retaining Walls and Lateral Loads 14
7.7 Slope Maintenance 15
7.8 Site Drainage 16
7.9 Foundation Plan Review 17
LIMITATIONS AND UNIFORMITY OF CONDITIONS
FIGURES
1. Vicinity Map
2. Wall/Column Footing Dimension Detail
3. Typical Retaining Wall Drain Detail
TABLES
I. Summary of As-Graded Building Pad Conditions and Recommended Foundation Categories
II. Summary of Laboratory Expansion Index Test Results
III. Summary of Finish Grade Expansion Index Test Results
IV. Summary of Laboratory Water-Soluble Sulfate Test Results
V. Summary of Soil 2007 CBC Site Class
UPDATE GEOTECHNICAL REPORT
1. PURPOSE AND SCOPE
This report presents the results of the update geotechnical study for Lots 1 through 83 located at the
Villages of La Costa - The Oaks North, Neighborhoods 3.4 and 3.5. The purpose of this update
report is to provide information regarding the geologic conditions underlying the site and to provide
foundation and retaining wall design recommendations.
The scope of the study included a review of:
1. Update Geotechnical Investigation, Villages of La Costa-The Oaks, Carlsbad, California,
prepared by Geocon Incorporated, dated August 3, 2001 (Project No. 06105-12-04).
2. Final Report of Testing and Observation Services Performed During Site Grading, Villages
of La Costa - The Oaks North, Neighborhood 3.4, Lots 40 through 83, prepared by Geocon
Incorporated, September 10, 2007 (Project No. 06403-52-20).
3. Final Report of Testing and Observation Services Performed During Site Grading, Villages
of La Costa - The Oaks North, Neighborhood 3.5, Lots 1 through 39, prepared by Geocon
Incorporated, October 30, 2007 (Project No. 06403-52-20).
4. Rough Grading and Erosion Control Plans for La Costa Oaks North Neighborhood 3.4 &
3.5, Drawing No. 446-6A, City of Carlsbad approval date July 12, 2007
2. SITE AND PROJECT DESCRIPTION
The subject lots are within the Villages of La Costa - The Oaks North, Neighborhoods 3.4 and 3.5
development located north and south of the intersection of Rancho Santa Fe Road and Avenida
Soledad in the City of Carlsbad, California (see Vicinity Map, Figure 1). Proposed development
includes the construction of 83 single-family residential homes and associated improvements.
Compacted fill is exposed at grade and is underlain by volcanic rock consisting of Santiago Peak
Volcanics and granitic rock consisting of Escondido Creek Granodiorite. A summary of the as-graded
pad conditions for each lot is provided on Table I. In general, the on-site fill materials vary between
angular gravels and boulders produced by on-site blasting of hard rock to silty, fine to coarse sand
and sandy clay derived from the surficial soil and weathered formational materials.
The locations and descriptions of the site and proposed improvements are based on a site
reconnaissance, observations during site grading, a review of the referenced reports and grading
plans, and our understanding of project development. If project details vary significantly from those
described herein, Geocon Incorporated should be contacted to review and revise this report.
Project No. 06105-52-27 - 1 - January 5, 2010
3. PREVIOUS SITE DEVELOPMENT
The subject lots were graded to the current configuration during mass grading operations for the
Villages of La Costa - The Oaks North. We performed observation and testing services during the
grading operations. A summary of the observations, compaction test results, and professional
opinions pertaining to the grading operations is presented in the referenced reports dated September
10, 2007 and October 30, 2007. The majority of the grading operations consisted of removal and
recompaction of surficial soil, placing compacted fill, and performing cuts within formational
material to the design elevations. Due to the difficult excavation characteristics of the volcanic and
granitic rock, cut lots were undercut approximately three to four feet and replaced with compacted fill
to the design elevations. In addition, lots that possessed a cut-fill transition were undercut
approximately three to four feet and replaced with compacted fill. A summary of the as-graded pad
conditions for the lots are presented in Table I.
4. SOIL AND GEOLOGIC CONDITIONS
The site is underlain by compacted fill and geologic formations of the Jurassic-aged Santiago Peak
Volcanics and Cretaceous-aged Escondido Creek Granodiorite. The predominant materials within
three to four feet of grade consist of silty sand and gravel and possess a "very low" to "low"
expansion potential (expansion index of 50 or less). The soil type and geologic units are discussed
herein.
4.1 Compacted Fill (Qcf & Quc)
In general, structural fill placed and compacted at the site consisted of material that can be classified
into three zones:
Zone A 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 an
approximate maximum particle dimension of 6 inches.
Zone B Material placed within 10 feet from pad grade and below Zone A, outer 6 feet of fill
slopes 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.
Zone C Material placed below Zone B consisted of "soil rock" fill with a maximum particle
dimension of 48 inches. Larger rocks with a maximum dimension of approximately
8 feet were buried individually during "rock" fill grading operations.
The maximum fill thickness is approximately 54 feet. The compacted fill is considered suitable to
provide support for the proposed development.
Project No. 06105-52-27 -2- January 5, 2010
4.2 Santiago Peak Volcanics (Jsp)
The Jurassic-aged Santiago Peak Volcanics comprises a portion of the underlying bedrock. These
rocks were deposited as an alternating succession of volcanic flows, tuffs, and breccias and typically
have an andesite or dacite composition. Subsequently, this sequence of rocks was folded, faulted, and
weakly metamorphosed. As encountered during grading, this unit is highly fractured. Closely spaced
parallel fractures and joints form "sheeted" zones containing colorful alterations and/or oxidation
minerals such as limonite and hematite. Even though the majority of the Santiago Peak Volcanics
appears to be highly fractured and altered, the "sheeted" zones typically have steeply dipping, clay-
filled fractures.
4.3 Escondido Creek Granodiorite (Ke)
The Cretaceous-aged Escondido Creek Granodiorite intruded the surrounding Jurassic-aged Santiago
Peak Volcanics and comprises a portion of the underlying bedrock. In published literature, this unit is
described as a "leucogranodiorite" because of the overall light color, but averages of composition are
typically granodiorite. During grading operations, the exposed bedrock consisted of light brown to
olive, very siliceous, blocky and very strong granitic rock, with little or no weathering. The granitic
rock is considered suitable for the support of the planned development.
5. GROUNDWATER
We did not encounter groundwater during grading operations. Groundwater is not expected to
adversely impact the development of the property. Due to the fractured nature of the formational
materials, we encountered some areas of seepage. Subdrains were installed during remedial grading.
It is not uncommon for groundwater or seepage conditions to develop where none previously existed.
Groundwater elevations are dependent on seasonal precipitation, irrigation, and land use, among
other factors, and vary as a result. Proper drainage will be important to future performance of the
project.
6. GEOLOGIC HAZARDS
6.1 Faulting and Seismicity
A review of the referenced geologic materials and our knowledge of the general area indicate that the
site is not underlain by active, potentially active, or inactive faults. The site is not located within a
State of California Earthquake Fault Zone established for known active faults. An active fault is
defined by the California Geological Survey (COS) as a fault showing evidence for activity within
the last 11,000 years.
According to the computer program EZ-FRISK (Version 7.35), nine known active faults are located
within a search radius of 50 miles from the property. The nearest known active fault is the Rose
Project No. 06105-52-27 ~- January 5, 2010
Canyon Fault, located approximately 8 miles west of the site and is the dominant source of potential
ground motion. Earthquakes that might occur on the Rose Canyon Fault Zone or other faults within
the southern California and northern Baja California area are potential generators of significant
ground motion at the site. The estimated maximum earthquake magnitude and peak ground
acceleration from a deterministic analysis for the Rose Canyon Fault are 7.2 and 0.29g, respectively.
Table 6.1.1 lists the estimated maximum earthquake magnitude and peak ground acceleration for the
faults within 50 miles of the site location. We calculated peak ground acceleration (PGA) using
Boore-Atkinson (2008) NGA USGS2008, Campbell-Bozorgnia (2008) NGA USGS 2008, and Chiou-
Youngs (2008) NGA acceleration-attenuation relationships.
TABLE 6.1.1
DETERMINISTIC SITE PARAMETERS
Fault Name
Rose Canyon
Newport-Inglewood
Elsinore (Julian)
Elsinore (Temecula)
Coronado Bank
Earthquake Valley
Elsinore (Glen Ivey)
San Joaquin Hills Thrust
Palos Verdes
Distance
from Site
(miles)
8
12
23
23
23
38
38
43
43
Maximum
Earthquake
Magnitude
(Mw)
7.2
7.1
7.1
6.8
7.6
6.5
6.8
7.4
7.3
Peak Ground Acceleration
Boore-
Atkinson
2008 (g)
0.29
0.26
0.26
0.22
0.24
0.14
0.17
0.14
0.18
Campbell-
Bozorgnia
2008 (g)
0.17
0.15
0.11
0.10
0.12
0.07
0.07
0.08
0.08
Chiou-
Youngs
2008 (g)
0.22
0.18
0.13
0.12
0.16
0.06
0.08
0.07
0.09
We also used the computer program EZ-FRISK to perform a probabilistic seismic hazard analysis.
The computer program EZ-FRISK operates under the assumption that the occurrence rate of
earthquakes on each mappable Quaternary fault is proportional to the faults slip rate. The program
accounts for fault rupture length as a function of earthquake magnitude, and site acceleration
estimates are made using the earthquake magnitude and distance from the site to the rupture zone.
The program also accounts for uncertainty in: (1) earthquake magnitude, (2) rupture length for a
given magnitude, (3) location of the rupture zone, (4) maximum possible magnitude of a given
earthquake, and (5) acceleration at the site from a given earthquake along each fault. By calculating
the expected accelerations from considered earthquake sources, the program calculates the total
average annual expected number of occurrences of site acceleration greater than a specified value.
We utilized acceleration-attenuation relationships suggested by Boore-Atkinson (2008) NGA
USGS2008, Campbell-Bozorgnia (2008) NGA USGS 2008, and Chiou-Youngs (2008) in the
Project No. 06105-52-27 -4-January 5, 2010
analysis. Table 6.1.2 presents the site-specific probabilistic seismic hazard parameters including
acceleration for each attenuation relationships and the probability of exceedence.
TABLE 6.1.2
PROBABILISTIC SEISMIC HAZARD PARAMETERS
Probability of Exceedence
2% in a 50 Year Period
5% in a 50 Year Period
10% in a 50 Year Period
Peak Ground Acceleration
Boore-Atkinson,
2007 (g)
0.75
0.61
0.51
Campbell-Bozo rgnia,
2008 (g)
0.33
0.27
0.23
Chiou-Youngs,
2008 (g)
0.39
0.32
0.27
The California Geologic Survey (COS) has a program that calculates the ground motion for a
10 percent of probability of exceedence in 50 years based on an average of several attenuation
relationships. Table 6.1.3 presents the calculated results from the Probabilistic Seismic Hazards
Mapping Ground Motion Page from the CGS website.
TABLE 6.1.3
PROBABILISTIC SITE PARAMETERS FOR SELECTED FAULTS
CALIFORNIA GEOLOGIC SURVEY
Calculated Acceleration (g)
Firm Rock
0.25
Calculated Acceleration (g)
Soft Rock
0.27
Calculated Acceleration (g)
Alluvium
0.31
While listing peak accelerations is useful for comparison of potential effects of fault activity in a
region, other considerations are important in seismic design, including the frequency and duration of
motion and the soil conditions underlying the site. Seismic design of the structures should be
evaluated in accordance with the California Building Code (CBC) guidelines currently adopted by the
County of San Diego.
In the event of a major earthquake along the 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. Seismic design of structures should be performed in
accordance with the 2007 California Building Code (CBC) currently adopted by the City of Carlsbad.
Project No. 06105-52-27 -5-January 5, 2010
6.2 Liquefaction
Liquefaction typically occurs when a site is located in a zone with seismic activity, onsite soils are
cohesionless or silt/clay with low plasticity, groundwater is encountered within 50 feet of the surface,
and soil relative densities are less than about 70 percent. If the four previous criteria are met, a
seismic event could result in a rapid pore water pressure increase from the earthquake-generated
ground accelerations. Due to the dense nature of the compacted fill and the formational materials and
absence of a permanent groundwater table, the potential for liquefaction occurring at the site is
considered to be very low.
Project No. 06105-52-27 - 6 - January 5, 2010
7. CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 No soil or geologic conditions were encountered during previous geotechnical
investigations or grading operations, which 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 underlain by compacted fill and formational materials of the Santiago Peak
Volcanics and Escondido Creek Granodiorite. We observed the placement of compacted
fill during mass grading operations and performed in-place density tests to evaluate the dry
density and moisture content of the fill material. In general, the in-place density test results
indicate that the fill soil has a dry density of at least 90 percent of the laboratory maximum
dry density near to slightly above optimum moisture content at the locations tested.
7.1.3 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 is being considered and recommendations are included herein.
7.1.4 Excavations within the fill materials should generally be possible with moderate to heavy
effort using conventional heavy-duty equipment. Excavations below the fill and into the
Santiago Peak Volcanic or Escondido Creek Granodiorite may require localized blasting
and may generate oversize rocks.
7.2 Finish Grade Soil Conditions
7.2.1 Observations and laboratory test results obtained during mass grading operations indicate
that the prevailing soil conditions within the upper approximately three to four feet of
finish grade pads have is considered to be "non-expansive" and "expansive" (expansion
index [El] of 20 or less and greater than 20) as defined by 2007 California Building Code
(CBC) Section 1802.3.2. Table 7.2 presents soil classifications based on the expansion
index. The prevailing soil conditions possess a "very low" to "low" expansion potential
(expansion index of 50 or less). Tables II and III present the laboratory expansion index
testing for the project.
Project No. 06105-52-27 - 7 - January 5, 2010
TABLE 7.2
SOIL CLASSIFICATION BASED ON EXPANSION INDEX
Expansion Index (El)
0-20
21-50
51-90
91-130
Greater Than 130
Soil Classification
Very Low
Low
Medium
High
Very High
7.2.2 We performed laboratory tests on samples of the site materials to evaluate the percentage
of water-soluble sulfate content. Results from the laboratory water-soluble sulfate content
tests are presented in Table IV and indicate that the on-site materials at the locations tested
possess "negligible" sulfate exposure to concrete structures as defined by 2007 CBC
Section 1904.3 and ACI 318. The presence of water-soluble sulfates is not a visually
discernible characteristic; therefore, other soil samples from the site could yield different
concentrations. Additionally, over time landscaping activities (i.e., addition of fertilizers
and other soil nutrients) may affect the concentration. Table IV presents the laboratory
water-soluble sulfate testing.
7.2.3 Geocon Incorporated does not practice in the field of corrosion engineering. Therefore, if
improvements that could be susceptible to corrosion are planned, further evaluation by a
corrosion engineer should be performed.
7.3 Seismic Design Criteria
7.3.1 We used the computer program Seismic Hazard Curves and Uniform Hazard Response
Spectra, provided by the USGS to calculate the seismic design criteria. Table 7.3
summarizes site-specific design criteria obtained from the 2007 CBC, Chapter 16
Structural Design, Section 1613 Earthquake Loads. The short spectral response has a
period of 0.2 second.
Project No. 06105-52-27 -8-January 5, 2010
TABLE 7.3
2007 CBC SEISMIC DESIGN PARAMETERS
Parameter
Site Class
Fill Thickness, T (Feet)
Spectral Response - Class B (short), Ss
Spectral Response - Class B (1 sec), Si
Site Coefficient, Fa
Site Coefficient, Fv
Maximum Considered Earthquake
Spectral Response Acceleration (short), SMS
Maximum Considered Earthquake
Spectral Response Acceleration - (1 sec), SMI
5% Damped Design
Spectral Response Acceleration (short), SDS
5% Damped Design
Spectral Response Acceleration (1 sec), Sm
Value
C
T<20
1.082g
0.408g
1.000
1.392
1.082g
0.568g
0.722g
0.379g
D
T>20
1.082g
0.408g
1.067
1.592
1.155g
0.649g
0.770g
0.433g
IBC-06 Reference
Table 1613.5.2
-
Figure 1613.5(3)
Figure 1613.5(4)
Table 1613.5.3(1)
Table 1613.5.3(2)
Section 1613.5.3 (Eqn 16-37)
Section 1613.5.3 (Eqn 16-38)
Section 1613.5.4 (Eqn 16-39)
Section 1613.5.4 (Eqn 16-40)
7.3.2 Based on a review of the as-graded conditions presented in the referenced as-graded report,
the lots are assigned the seismic design parameters as indicated in Table V.
7.3.3 Conformance to the criteria for seismic design in Table 7.3 does not constitute any kind of
guarantee or assurance that significant structural damage or ground failure will not occur if
a maximum level earthquake occurs. The primary goal of seismic design is to protect life
and not to avoid damage, since such design may be economically prohibitive.
7.4 Future Grading
7.4.1 Additional grading performed at the site should be accomplished in conjunction with our
observation and compaction testing services. Grading plans for future grading should be
reviewed by Geocon Incorporated prior to finalizing. Trench and wall backfill should be
compacted to a dry density of at least 90 percent of the laboratory maximum dry density
near to slightly above optimum moisture content. This office should be notified at least 48
hours prior to commencing additional grading or backfill operations.
7.5 Foundation and Concrete Slabs-On-Grade Recommendations
7.5.1 The foundation recommendations herein are for proposed one- to two-story residential
structures. The foundation recommendations have been separated into three categories
Project No. 06105-52-27 -9-January 5, 2010
based on either the maximum and differential fill thickness or Expansion Index. The
foundation category criteria are presented in Table 7.5.1.
TABLE 7.5.1
FOUNDATION CATEGORY CRITERIA
Foundation
Category
I
II
III
Maximum Fill
Thickness, T (Feet)
T<20
20<T<50
T>50
Differential Fill
Thickness, D (Feet)
—
10<D<20
D>20
Expansion Index (El)
EI<50
50<EI<90
90<EI<130
7.5.2 Table 7.5.2 presents minimum foundation and interior concrete slab design criteria for
conventional foundation systems. A typical wall/column dimension detail is presented in
Figure 2.
TABLE 7.5.2
CONVENTIONAL FOUNDATION RECOMMENDATIONS BY CATEGORY
Foundation
Category
I
II
III
Minimum Footing
Embedment
Depth (inches)
12
18
24
Continuous Footing
Reinforcement
Two No. 4 bars
one top and one bottom
Four No. 4 bars
two top and two bottom
Four No. 5 bars
two top and two bottom
Interior Slab
Reinforcement
6x6 -10/10 welded wire
mesh at slab mid-point
No. 3 bars at 24 inches
on center, both directions
No. 3 bars at 18 inches
on center, both directions
7.5.3 The embedment depths presented in Table 7.5.2 should be measured from the lowest
adjacent pad grade for both interior and exterior footings. The conventional foundations
should have a minimum width of 12 inches and 24 inches for continuous and isolated
footings, respectively.
7.5.4 The concrete slab-on-grade should be a minimum of 4 inches thick for Foundation
Categories I and II and 5 inches thick for Foundation Category III.
7.5.5 Concrete slabs on grade should be underlain by 4 inches of clean sand (3 inches for a 5-
inch-thick slab) to reduce the potential for differential curing, slab curl, and cracking. Slabs
that may receive moisture-sensitive floor coverings or may be used to store moisture-
sensitive materials should be underlain by a vapor retarder placed near the middle of the sand
Project No. 06105-52-27 -10-January 5, 2010
bedding. The vapor retarder used should be specified by the project architect or developer
based on the type of floor covering that will be installed. The vapor retarder design should be
consistent with the guidelines presented in Section 9.3 of the American Concrete Institute's
(ACT) Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials
(ACI 302.2R-06).
7.5.6 As an alternative to the conventional foundation recommendations, consideration should be
given to the use of post-tensioned concrete slab and foundation systems for the support of
the proposed structures. The post-tensioned systems should be designed by a structural
engineer experienced in post-tensioned slab design and design criteria of the Post-
Tensioning Institute (PTI), Third Edition, as required by the 2007 California Building Code
(CBC Section 1805.8). Although this procedure was developed for expansive soil
conditions, we understand it can also be used to reduce the potential for foundation distress
due to differential fill settlement. The post-tensioned design should incorporate the
geotechnical parameters presented on Table 7.5.3 for the particular Foundation Category
designated. The parameters presented in Table 7.5.3 are based on the guidelines presented
in the PTI, Third Edition design manual. Conventional foundations located outside of the
post-tensioned slab area should be embedded in accordance with the conventional shallow
foundation recommendations.
TABLE 7.5.3
POST-TENSIONED FOUNDATION SYSTEM DESIGN PARAMETERS
Post-Tensioning Institute (PTI)
Third Edition Design Parameters
Thornthwaite Index
Equilibrium Suction
Edge Lift Moisture Variation Distance, eM (feet)
Edge Lift, yM (inches)
Center Lift Moisture Variation Distance, eM (feet)
Center Lift, yM (inches)
Foundation Category
I
-20
3.9
5.3
0.61
9.0
0.30
II
-20
3.9
5.1
1.10
9.0
0.47
III
-20
3.9
4.9
1.58
9.0
0.66
7.5.7 The foundations for the post-tensioned slabs should be embedded in accordance with the
recommendations of the structural engineer. If a post-tensioned mat foundation system is
planned, the slab should possess a thickened edge with a minimum width of 12 inches and
extend below the clean sand or crushed rock layer.
Project No. 06105-52-27 -11-January 5, 2010
7.5.8 If the structural engineer proposes a post-tensioned foundation design method other than
PTI, Third Edition:
• The deflection criteria presented in Table 7.5.3 are still applicable.
• Interior stiffener beams should be used for Foundation Categories II and III.
• The width of the perimeter foundations should be at least 12 inches.
• The perimeter footing embedment depths should be at least 12 inches, 18 inches
and 24 inches for foundation categories I, II, and III, respectively. The embedment
depths should be measured from the lowest adjacent pad grade.
7.5.9 Our experience indicates post-tensioned slabs are susceptible to excessive edge lift,
regardless of the underlying soil conditions. Placing reinforcing steel at the bottom of the
perimeter footings and the interior stiffener beams may mitigate this potential. Current PTI
design procedures primarily address the potential center lift of slabs but, because of the
placement of the reinforcing tendons in the top of the slab, the resulting eccentricity after
tensioning reduces the ability of the system to mitigate edge lift. The structural engineer
should design the foundation system to reduce the potential of edge lift occurring for the
proposed structures.
7.5.10 During the construction of the post-tension foundation system, the concrete should be
placed monolithically. Under no circumstances should cold joints form between the
footings/grade beams and the slab during the construction of the post-tension foundation
system.
7.5.11 Category I, II, or III foundations may be designed for an allowable soil bearing pressure of
2,000 pounds per square foot (psf) (dead plus live load). This bearing pressure may be
increased by one-third for transient loads due to wind or seismic forces. The estimated
maximum total and differential settlement for the planned structures due to foundation
loads is 1 inch and '/2 inch, respectively.
7.5.12 Isolated footings, if present, should have the minimum embedment depth and width
recommended for conventional foundations for a particular foundation category. The use of
isolated footings, which are located beyond the perimeter of the building and support
structural elements connected to the building, are not recommended for Category III.
Where this condition cannot be avoided, the isolated footings should be connected to the
building foundation system with grade beams.
7.5.13 For Foundation Category III, consideration should be given to using interior stiffening
beams and connecting isolated footings and/or increasing the slab thickness, hi addition,
Project No. 06105-52-27 -12 - January 5, 2010
consideration should be given to connecting patio slabs, which exceed 5 feet in width, to
the building foundation to reduce the potential for future separation to occur.
7.5.14 Special subgrade presaturation is not deemed necessary prior to placing concrete; however,
the exposed foundation and slab subgrade soil should be moisture conditioned, as
necessary, to maintain a moist condition as would be expected in any such concrete
placement.
7.5.15 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 fill slopes less than 20 feet high or cut slopes regardless of height, 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.
• When located next to a descending 3:1 (horizontal:vertical) fill slope or steeper, the
foundations should be extended to a depth where the minimum horizontal distance
is equal to H/3 (where H equals the vertical distance from the top of the fill slope
to the base of the fill soil) with a minimum of 7 feet but need not exceed 40 feet.
The horizontal distance is measured from the outer, deepest edge of the footing to
the face of the slope. An acceptable alternative to deepening the footings would be
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.
• If swimming pools are planned, Geocon Incorporated should be contacted for a
review of specific site conditions.
• Swimming pools located within 7 feet of the top of cut or fill slopes are- not
recommended. Where such a condition cannot be avoided, the portion of the
swimming pool wall within 7 feet of the slope face be designed assuming 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 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, which 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. 06105-52-27 -13- January 5, 2010
7.5.16 The recommendations of this report are intended to reduce the potential for cracking of
slabs due to expansive soil (if present), differential settlement of existing soil or soil with
varying thicknesses. However, even with the incorporation of the recommendations
presented herein, foundations, stucco walls, and slabs-on-grade placed on such conditions
may still exhibit some cracking due to soil movement and/or shrinkage. The occurrence of
concrete shrinkage cracks is independent of the supporting soil characteristics. Their
occurrence may be reduced and/or controlled by limiting the slump of the concrete, proper
concrete placement and curing, and by the placement of crack control joints at periodic
intervals, in particular, where re-entrant slab corners occur.
7.5.17 Geocon Incorporated should be consulted to provide additional design parameters as
required by the structural engineer.
7.6 Retaining Walls and Lateral Loads
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 2:1
(horizontal:vertical), an active soil pressure of 50 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 50 or less. For
those lots with finish-grade soils having an expansion index greater than 50 and/or where
backfill materials do not conform to the criteria herein, Geocon Incorporated should be
consulted for additional recommendations.
7.6.2 Unrestrained walls are those that are allowed to rotate more than 0.001H (where H equals
the height of the retaining portion of the wall) at the top of the wall. Where walls are
restrained from movement at the top, an additional uniform pressure of 7H psf should be
added to the active soil pressure. For retaining walls subject to vehicular loads within a
horizontal distance equal to two-thirds the wall height, a surcharge equivalent to 2 feet of
fill soil should be added.
7.6.3 Retaining walls should be provided with a drainage system adequate to prevent the buildup
of hydrostatic forces and waterproofed as required by the project architect. The use of
drainage openings through the base of the wall (weep holes) is not recommended where the
seepage could be a nuisance or otherwise adversely affect the property adjacent to the base
of the wall. The above recommendations assume a properly compacted free-draining
backfill material (El of 50 or less) with no hydrostatic forces or imposed surcharge load.
Figure 3 presents a typical retaining wall drainage detail. If conditions different than those
Project No. 06105-52-27 -14 - January 5, 2010
described are expected, or if specific drainage details are desired, Geocon Incorporated
should be contacted for additional recommendations.
7.6.4 In general, wall foundations founded in properly compacted fill or formational materials
should possess a minimum depth and width of one foot and 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 90 or less. The proximity of the foundation to the top
of a slope steeper than 3:1 could impact the allowable soil bearing pressure. Therefore,
Geocon Incorporated should be consulted where such a condition is expected.
7.6.5 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
compacted fill soil. The allowable passive pressure assumes a horizontal surface extending
at least 5 feet or three times the surface generating the passive pressure, whichever is
greater. The upper 12 inches of material not protected by floor slabs or pavement should
not be included in the design for lateral resistance. A friction coefficient of 0.35 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.
7.6.6 The structural engineer should determine the seismic design category for the project. If the
project possesses a seismic design category of D, E, or F, the proposed retaining walls
should be designed with seismic lateral pressure. The seismic load exerted on the wall
should be a triangular distribution with a pressure of 22H (where H is the height of the
wall, in feet, resulting in pounds per square foot [psf]) exerted at the base of the wall and
zero at the top of the wall.
7.6.7 Unrestrained walls will move laterally when backfilled and loading is applied. The amount
of lateral deflection is dependant on the wall height, the type of soil used for backfill, and
loads acting on the wall. The retaining walls and improvements above the retaining walls
should be designed to incorporate an appropriate amount of lateral deflection as determined
by the structural engineer.
7.7 Slope Maintenance
7.7.1 Slopes that are steeper than 3:1 (horizontal:vertical) may, under conditions which are both
difficult to prevent and predict, be susceptible to near surface (surficial) slope instability.
The instability is typically limited to the outer three 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
Project No. 06105-52-27 -15- January 5, 2010
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, soil expansion, or excavation for irrigation lines and slope planting, may
also be a significant contributing factor to surficial instability. It is, therefore, recom-
mended that, to 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 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 rebuild or repair a portion of the project's slopes in the future.
7.8 Site Drainage
7.8.1 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
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.
7.8.2 Underground utilities should be leak free. Utility and irrigation lines should be checked
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.
7.8.3 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 is planned adjacent to the pavement, we recommended construction of a cutoff
wall along the edge of the pavement that extends at least 6 inches below the bottom of the
base material.
7.8.4 Adequate site drainage is critical to reduce the potential for differential soil movement,
erosion and subsurface seepage. Under no circumstances should water be allowed to pond
adjacent to footings. The site should be graded and maintained such that surface drainage is
directed away from structures in accordance with 2007 CBC 1803.3 or other applicable
standards. In addition, surface drainage should be directed away from the top of slopes into
Project No. 06105-52-27 - 16 - January 5, 2010
swales or other controlled drainage devices. Roof and pavement drainage should be
directed into conduits that carry runoff away from the proposed structure.
7.8.5 If detention basins, bioswales, retention basins, or water infiltration devices are being
considered, Geocon Incorporated should be retained to provide recommendations
pertaining to the geotechnical aspects of possible impacts and design. Distress may be
caused to planned improvements and properties located hydrologically downstream. The
distress depends on the amount of water to be detained, its residence time, soil
permeability, and other factors. We have not performed a hydrogeology study at the site.
Downstream properties may be subjected to seeps, springs, slope instability, raised
groundwater, movement of foundations and slabs, or other impacts as a result of water
infiltration.
7.9 Foundation Plan Review
7.9.1 Geocon Incorporated should review the foundation plans for the project prior to final
design submittal to evaluate if additional analyses and/or recommendations are required.
Project No. 06105-52-27 -17- January 5, 2010
LIMITATIONS AND UNIFORMITY OF CONDITIONS
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
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.
2. 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 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
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.
4. The firm that performed the geotechnical investigation for the project should be retained to
provide testing and observation services during construction to provide continuity of
geotechnical interpretation and to check that the recommendations presented for geotechnical
aspects of site development are incorporated during site grading, construction of
improvements, and excavation of foundations. If another geotechnical firm is selected to
perform the testing and observation services during construction operations, that firm should
prepare a letter indicating their intent to assume the responsibilities of project geotechnical
engineer of record. A copy of the letter should be provided to the regulatory agency for their
records. In addition, that firm should provide revised recommendations concerning the
geotechnical aspects of the proposed development, or a written acknowledgement of their
concurrence with the recommendations presented in our report. They should also perform
additional analyses deemed necessary to assume the role of Geotechnical Engineer of Record.
Project No. 06105-52-27 January 5, 2010
THE GEOGRAPHICAL INFORMATION MADE AVAILABLE FOR DISPLAY WAS PROVIDED BY GOOGLE EARTH,
SUBJECT TO A LICENSING AGREEMENT. THE INFORMATION IS FOR ILLUSTRATIVE PURPOSES ONLY; IT IS
NOT INTENDED FOR CLIENTS USE OR RELIANCE AND SHALL NOT BE REPRODUCED BY CLIENT. CLIENT
SHALL INDEMNIFY, DEFEND AND HOLD HARMLESS GEOCON FROM ANY LIABILITY INCURRED AS A RESULT
OF SUCH USE OR RELIANCE BY CLIENT.
NO SCALE
GEOCON <£*
INCORPORATED ^38?
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
AS/RA | | DSK/GTYPD
VICINITY MAP
VILLAGES OF LA COSTA - THE OAKS NORTH
NEIGHBORHOOD 3.4 AND 3.5
LOTS 1 - 83
CARLSBAD, CALIFORNIA
DATE 01 - 05 - 2010 I PROJECT NO. 06105 - 52 - 27 I FIG. 1
Y«14TEMFV_GEOTECt*1_QEOTECH_l»UBENlGEOCON 20KM810M2-27 VILLAGES OF LACOSTA-THE OAKS NORTH (NSQH.3.44.3 Wk***d«8
WALL FOOTING
SAND PAD GRADE
VISQUEEN
FOOTING*
WIDTH
COLUMN FOOTING
CONCRETE SLAB
"WX*' I I \-'^-*v'',{>> - J*'i
VISQUEEN
2°1f
I
s^Vr^
^^V^'*-'"^;'if*''
FOOTING WIDTH*
NO SCALE
*....SEE REPORT FOR FOUNDATION WITDH AND DEPTH RECOMMENDATION
WALL /COLUMN FOOTING DIMENSION DETAIL
GE O C ON
INCORPORATED
GEOTECHNICAL CONSULTANTS
6960 FLANDKS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
VILLAGES OF LA COSTA - THE OAKS NORTH
NEIGHBORHOOD 3.4 AND 3.5
LOTS 1 - 83
CARLSBAD, CALIFORNIA
AS/RA DSK/EOOOO DATE 01-05-2010 PROJECT NO. 061 05 -52 -27 FIG. 2
YSRHTS/R1_QEOTH>»1_GEOTECH_RUBEN\OEOCON201ff06105-52-27 VILLAGES OF lACOSTA-TtC OAKS NORTM (NEIGH.ltJ.9 \COLFOOT2.dwo
GROUND SURFACE-
PROPOSED
RETAINING WALL
.TEMPORARY BACKCUT
PER OSHA
GROUND SURFACE
MIRAFI140N FILTER FABRIC
(OR EQUIVALENT)
OPEN GRADED
3/4- MAX AGGREGATE
DIA. PERFORATED SCHEDULE
40 PVC PIPE EXTENDED TO
APPROVED OUTLET
CONCRETE
BROWDITCH
WALL — *•>.
2f.
OPOSED
GRADE~A
H
V
— 12-
FOOTING
WATERPROOFING
"PER ARCHITECT
DRAINAGE PANEL (MIRADRAIN 6000
" OR EQUIVALENT)
3/4'CRUSHED ROCK
(1 CU.FTJFT.)
FILTER FABRIC ENVELOPE
MIRAFI 140N OR EQUIVALENT
4' DIA. SCHEDULE 40 PERFORATED
PVC PIPE OR TOTAL DRAIN EXTENDED
TO APPROVED OUTLET
NOTE:
DRAIN SHOULD BE UNIFORMLY SLOPED TO GRAVITY OUTLET
OR TO A SUMP WHERE WATER CAN BE REMOVED BY PUMPING
NO SCALE
TYPICAL RETAINING WALL DRAIN DETAIL
GEOCON <Z&
INCORPORATED ^SiT
GEOTECHNICAL CONSULTANTS
6960 FLANDERS DRIVE - SAN DIEGO, CALIFORNIA 92121 - 2974
PHONE 858 558-6900 - FAX 858 558-6159
ASS RKA 1 _L DSK/GTYPD
VILLAGES OF LA COSTA - THE OAKS NORTH
NEIGHBORHOOD 3.4 AND 3.5
LOTS 1 - 83
CARLSBAD, CALIFORNIA
DATE 01-05-2010 j PROJECT NO. 061 05 -52 -27
Y:\R1 4TEUR1_GEOTEOM_QEOTCCH_RUBEt*GEOCON 201CTI06106-SS-27 VILLAGES OF LA COSTA.THE OAKS NORTH
| FIG.3
(HaOH.3.4-3.9 \RWDOBAig
TABLE I
SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
AND RECOMMENDED FOUNDATION CATEGORIES FOR
VILLAGES OF LA COSTA - THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5
LOTS 1 THROUGH 83
Lot No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Pad Condition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Fill
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Fill
Fill
Fill
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to hard rock
Undercut due to hard rock
Undercut due to hard rock
Undercut due to
cut-fill transition
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Approximate
Maximum
Depth of Fill
(feet)
5
8
22
29
29
27
24
25
35
20
15
5
5
4
3
6
9
11
13
13
12
12
16
19
18
24
26
Approximate
Maximum
Depth of Fill
Differential
(feet)
1
3
15
26
26
24
18
17
24
15
11
2
1
1
0
2
4
2
3
4
5
4
10
11
11
15
16
Expansion
Index
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
2
2
2
2
2
2
2
2
0
0
0
Recommended
Foundation
Category
I
I
II
III
III
III
II
II
III
II
II
I
I
I
I
I
I
I
I
I
I
I
II
II
II
II
II
Project No. 06105-52-27 January 5, 2010
TABLE I (Continued)
SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
AND RECOMMENDED FOUNDATION CATEGORIES FOR
VILLAGES OF LA COSTA - THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5
LOTS 1 THROUGH 83
Lot No.
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
Pad Condition
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Undercut due to hard rock
Undercut due to hard rock
Undercut due to hard rock
Undercut due to hard rock
Undercut due to hard rock
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Fill
Fill
Fill
Fill
Fill
Undercut due to
cut-fill transition
Undercut due to hard rock
Undercut due to hard rock
Undercut due to hard rock
Undercut due to hard rock
Fill
Approximate
Maximum
Depth of Fill
(feet)
26
26
26
28
30
32
33
41
4
4
4
4
4
9
10
7
14
18
20
20
30
23
20
14
6
6
4
8
21
Approximate
Maximum
Depth of Fill
Differential
(feet)
14
14
15
16
15
17
4
14
1
1
1
1
1
5
6
3
10
10
9
9
15
6
9
10
3
1
1
6
13
Expansion
Index
0
0
0
0
0
0
0
0
18
18
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Recommended
Foundation
Category
II
II
II
II
II
II
II
II
I
I
I
I
I
I
I
I
II
II
II
II
II
II
II
II
I
I
I
I
II
Project No. 06105-52-25 January 5, 2010
TABLE I (Continued)
SUMMARY OF AS-GRADED BUILDING PAD CONDITIONS
AND RECOMMENDED FOUNDATION CATEGORIES FOR
VILLAGES OF LA COSTA -THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5
LOTS 1 THROUGH 83
Lot No.
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
Pad Condition
Undercut due to
cut-fill transition
Undercut due to
cut-fill transition
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Fill
Approximate
Maximum
Depth of Fill
(feet)
18
15
17
24
35
40
40
38
35
38
43
50
50
54
46
44
42
39
23
24
27
29
28
25
21
13
14
Approximate
Maximum
Depth of Fill
Differential
(feet)
15
11
10
10
14
9
6
10
7
18
15
20
18
21
23
11
6
5
15
11
17
20
14
11
9
4
11
Expansion
Index
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
22
22
22
0
0
0
0
1
1
1
1
1
Recommended
Foundation
Category
II
II
II
II
II
II
II
II
II
II
II
III
III
III
III
II
II
II
II
II
II
III
II
II
II
I
II
Project No. 06105-52-25 Januarys, 2010
TABLE II
SUMMARY OF LABORATORY EXPANSION INDEX TEST RESULTS
ASTM D 4829-03
Sample
No.
EI-A
EI-B
EI-AL
EI-AM
EI-AN
EI-AO
EI-AP
EI-AR
EI-AS
EI-BC
EI-BN
EI-BY
EI-BZ
El-CD
EI-CE
EI-CF
EI-CG
EI-CH
EI-CI
Moisture Content (%)
Before Test
7.4
7.6
7.7
7.6
7.7
7.4
7.5
8.3
8.5
7.7
10.4
10.1
9.1
7.0
7.0
7.7
7.6
7.8
7.5
After Test
13.4
14.6
13.1
13.1
13.3
13.0
13.8
12.0
14.1
12.9
18.7
19.3
15.7
13.1
12.6
13.3
13.7
14.4
14.2
Dry Density
(pcf)
118.7
118.9
118.4
118.4
118.4
118.8
118.8
117.9
117.7
118.5
109.3
109.6
113.1
120.5
120.6
118.5
118.3
118.5
118.6
Expansion
Index
0
0
0
0
0
0
0
0
0
1
18
22
0
0
0
0
0
2
2
Expansion
Classification
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Project No. 06105-52-27 January 5, 2010
TABLE III
SUMMARY OF FINISH GRADE EXPANSION INDEX TEST RESULTS
VILLAGES OF LA COSTA -THE OAKS NORTH, NEIGHBORHOODS 3.4 AND 3.5
LOTS 1 THROUGH 83
Lot No.
1 through 3
4 through 8
9 through 12
13 through 16
17 through 20
21 through 24
25 through 29
30 through 35
36 and 37
38 and 39
40 through 45
46 through 50
51 through 5 5
56 through 60
61 through 65
66 through 68
69 through 71
72 through 74
75 through 78
79 through 83
Sample at
Finish Grade
EI-CE
El-CD
EI-CF
EI-CG
EI-CH
EI-CI
EI-AR
EI-AS
EI-BN
EI-CE
EI-AP
EI-AO
EI-AM
EI-AL
EI-AN
EI-B
EI-A
EI-BY
EI-BZ
EI-BC
Expansion
Index
0
0
0
0
2
2
0
0
18
0
0
0
0
0
0
0
0
22
0
1
Expansion
Classification
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Very Low
Low
Very Low
Very Low
Project No. 06105-52-27 January 5, 2010
TABLE IV
SUMMARY OF LABORATORY WATER-SOLUBLE SULFATE TEST RESULTS
CALIFORNIA TEST 417
Sample No.
EI-A
EI-B
EI-AL
EI-AN
EI-AR
EI-AS
EI-BC
EI-BN
EI-BZ
El-CD
EI-CE
EI-CF
EI-CG
EI-CH
EI-CI
Water-Soluble Sulfate (%)
0.006
0.003
0.004
0.004
0.005
0.006
0.012
0.030
0.060
0.019
0.017
0.016
0.038
0.041
0.038
Sulfate Exposure
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
Negligible
TABLE V
SUMMARY OF SOIL 2007 CBC SITE CLASS
Lot Nos.
land 2
3 through 10
1 1 through 25
26 through 35
36 through 45
46 through 50
51 through 5 5
56
57 through 59
60 through 81
82 and 83
2007 CBC Classification
C
D
C
D
C
D
C
D
C
D
C
Project No. 06105-52-27 Januarys, 2010