HomeMy WebLinkAboutCT 14-06; AFTON WAY; GEOTECHNICAL UPDATE LETTER PROPOSED AFTON WAY RESIDENTIAL DEVELOPMENT CARLSBAD, CALIFORNIA; PUD 14-09, HDP 14-05, SWG 495-9, DWG 495-9A, GR2016-0050, ROW 2016-0061; SWMP 16-26; 2016-10-05GEOTECHNICAL UPDATE LETTER
PROPOSED AFTON WAY RESIDENTIAL
DEVELOPMENT
CARLSBAD, CALIFORNIA
CT"la..,.-O'=»
PEBBLE CREEK COMPANIES
301 W. 28th Street, Suite A
National City, CA. 91950
Project No. 11436.001
October 5, 2016
C~IVED
OCT l 1 2016
LAN ]PMENT
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A LEIGHTON GROUP COMPANY
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Leighton and Associates, Inc.
A LEIGHTON GROUP COMPANY
Pebble Creek Companies.
301 W. 28th Street, Suite A
National City, CA. 91950
Attention: Mr. Gary Arnold
October 5, 2016
Subject: Geotechnical Update Letter
Introduction
Proposed Afton Way Residential Development
Carlsbad, California
Project No. 11436.001
In accordance with your request, Leighton and Associates (Leighton) has performed a
geotechnical update study for the proposed Afton Way Residential Development,
located in ~arlsbad, California (see Figure 1, Site Location Map). The purpose of our
geotechnical update study was to observe the existing geotechnical conditions of the
subject site, review the referenced geotechnical report (Leighton, 2014), prepare
additional geologic cross sections, perform slope stability analyses and provide update
geotechnical recommendations, as needed.
As part of our geotechnical update study, we are using the grading plans prepared by
BHA Inc., dated August 16, 2016, as the base map for our updated Geotechnical Map
of the site, as shown on the attached Plates 1 and 2. Based on our review of the
grading plans (BHA, 2016), we understands that the proposed development will now
consist of eight residential lots with private driveways, an extension of Afton Way,
several retaining walls, and bioretention basins located in the northeast corner of the
site. It should be noted that the lot numbers have been changed on the new plans.
3934 Murphy Canyon Road, Suite B2051111 San Diego, CA92123-4425
858.292.80301111 Fax 858.292.0771111 www.leightongeo.com
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Existing Site Conditions
Based on our recent site visit and review of the referenced geotechnical report
(Leighton, 2014), the geotechnical conditions of the subject site have not significantly
changed since the completion of the original report. The subject property encompasses
approximately 4.9 acres of land, and is bordered by Carlsbad Village Drive to the north,
and existing residential developments to the east, south, and west. Topographically, the
property consists of gently sloping hillside terrain with elevations ranging from a high of
approximately 280 feet Mean Sea Level (MSL) near the southwestern property line to a
low of approximately 205 feet (MSL) at the property's northeastern corner.
Conclusions and Recommendations
Based on our review of the project geotechnical report (Leighton, 2014) and our recent
site visit, it is our professional opinion that the conclusions and recommendations in the
referenced geotechnical report are still considered applicable and should be adhered to
during the design and construction phase of this project unless superseded by
recommendations presented below. For reference, our previous report is provided as
attachment in Appendix E of the update.
In addition, two additional geological cross sections, B-B' and C-C' were developed for
further evaluation of the proposed grading plan. All of the geological cross sections (i.e.,
A-A', B-B' and C-C') are presented on the attached Plate 3.
It should be noted that in our previous report, we stated that the proposed cut slope
along the western property line may require the construction of buttress or replacement
fill. Based on our recent site visit and review of the current grading plans, the proposed
cut slope for that area will be within the Very Old Paralic Deposits with a retaining wall
at the slope toe (i.e., area west of Lots 5, 6, and 7, as shown on Plate 1 ). At this time,
we do not anticipate any adverse geologic conditions in this area that would require a
buttress or stability fill. However, this conclusion needs to be field verified by a Leighton
Certified Engineering Geologist during site grading, and during the excavation of the
retaining walls.
Slope Stability
Static Slope stability analyses were performed for the proposed fill slopes, retaining walls
and bioretention basins using the software program SLIDE Version 7.014. The slope
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stability, models were constructed using geologic cross sections B-B' and C-C', and soil
strengths derived from laboratory test results, and professional judgments. The values
used in the analyses are summarized in Table 1, below.
Table 1
Soil Strength Parameters
Soil Type Friction Angle Cohesion
(degrees) (psf)
Artificial Fill 30 150
Very Old Paralic 38 100 Deposits
Santiago Formation 28 400
Our deep-seated stability search routines considered optimized circular and non-circular
failure surfaces using Spencer's Method of limit equilibrium analysis. Surficial stability
analysis was performed using the infinite slope mode. It is noted that surficial stability is
sensitive to local variations in strength that occur at the face of a slope. Where more
granular materials with less cohesion are present in the slope face, the materials will be
more susceptible to surficial instability.
The results of the slope stability analysis indicate that the proposed new fill slopes have
factors of safety over 1.5. Plots of the slope stability analyses are presented in
Appendix B.
Infiltration
Based on our field percolation testing, the in-situ percolation rates and calculated
infiltration rates at tested locations and depths are summarized in Table 2 below. It is
important to note that percolation rates are not equal to infiltration rates. As a result, we
have made a distinction between percolation rates where water movement is considered
laterally and vertically versus infiltration rates where only the vertical direction is
considered. We have used the Porchet Method to convert measured percolation rates to
calculated infiltration rates in accordance with County of Riverside Standards (2011 ). In
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addition, we have included a recommended infiltration rate with a minimum factor of
safety of 2 for the preliminary design of potential infiltration systems.
The location of the previous field percolation tests are shown on the attached Plate 2,
Preliminary Geotechnical Map. Applicable field percolation test data have been provided
in Appendix C.
Table 2
Field Percolation & Infiltration Rates
Tested Measured Calculated Recommended
Pere. Depth Soil Type Percolation Infiltration Infiltration
Test No. Rate Rate Rate w/ FS of 2 (ft) (mins/in) (inches/hr) (inches/hr)
P-1 4.7 Sandy 125.0 0.01 0.005 Clay
P-2 4.8 Sandy 125.0 0.01 0.005 Clay
It should be emphasized that the percolation test results are only representative of the
tested location and depth where they are performed. Varying subsurface conditions may
exist outside of the test locations, which could alter the calculated infiltration rates
indicated above.
In addition, it is possible that long term infiltration rates within measured soil strata may be
much lower than the values obtained by our current testing. Long term infiltration can be
influenced by: variable vertical character and limited lateral extent of more permeable soil
strata, reduction of permeability rates over time due to silting of the soil pore spaces, and
other factors not discussed here. Accordingly, the possibility of future surface ponding of
water as well as shallow groundwater impacts on subterranean structures such as
basements, underground utilities, etc. should be anticipated as possible future conditions
in all design aspects of the site.
Based on the results of our previous investigation (Leighton, 2014), the site is considered
a "Non-Infiltration Site" based on the storm water Model BMP Design Manual, San Diego
Region, February 2016. The Form 1-8, Categorization of Infiltration Feasibility Condition,
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11436.001
has been completed and is presented in Appendix D. We attribute this non-infiltration
:, condition to the low permeability of the underlying sandy clay soil.
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Earth Retaining Systems
For preliminary design of MSE walls, we recommend using the following soil properties
presented in Table 3 below.
Table 3
Soil Strength Parameters
Internal Cohesion Gamma Moist
Description Friction Angle Unit Weight (psf) (degrees) (psf)
Reinforced 30 0 128
Retained 28 100 125
Foundation 28 100 125
Grading Plan Review
We have reviewed the current grading plans for Afton Way residential development
prepared by BHA, dated August 16, 2016. Our review was performed to identify
potential conflicts with the intent of the referenced geotechnical document. Based on
our review, we are of the opinion that the plans were prepared in general conformance
with the intent of the geotechnical documents.
Construction Observation
The recommendations provided in this report are based on preliminary design
information and subsurface disclosed by widely spaced excavations. The interpolated
subsurface conditions should be checked by Leighton and Associates, Inc. in the field
during construction. Construction observation of all onsite excavations and field density
testing of all compacted fill should be performed by a representative of this office. We
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recommend that all excavations be mapped by the geotechnical consultant during
n grading to determine if any potentially adverse geologic conditions exist at the site.
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Plan Review
Final project grading and foundation plans should be reviewed by Leighton as part of
the design development process to ensure that recommendations in this report are
incorporated in project plans.
Limitations
Our analyses and recommendations were based in part on data obtained from a limited
number of observations, site visits, soil excavations, samples and tests. Such
information is, by necessity, incomplete. The nature of many sites is such that differing
soil or geologic conditions can be present within small distances and under varying
climatic conditions. Changes in subsurface conditions can and do occur over time.
Therefore, our findings, conclusions and recommendations are based on the
assumption that we (Leighton and Associates, Inc.) will provide geotechnical
observation and testing during construction as the Geotechnical Engineer of Record for
this project.
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If you have any questions regarding this letter, please do not hesitate to contact this
office. We appreciate this opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC.
Mike D. Jensen, CEG 2457
Senior Project Geologist
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Pr&,6e~logist
Attachments: Figure 1 -Site Location Map
Plates 1 and 2 -Geotechnical Map
Plate 3 -Geological Cross Sections
Appendix A -References
Appendix B -Slope Stability
Appendix C -Infiltration Data
Associate Engineer
Appendix D -Form 1-8, Categorization of Infiltration Feasibility Condition
Appendix E -Geotechnical Investigation, dated 9/29/2014
Distribution: 1 addressee
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FIGURES
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Project: 11436.001 Eng/Geol: WOO/BEV
Scale: 1 • = 2,000 ' Date : October 2016
Base Map: ESRI ArcGIS Online 2016
Thematic Information: Leighton
Author: Leighton Geomat,cs (mmurphy)
SITE LOCATION MAP
2200 Afton Way
Carlsbad, California
Map saved as P:\Orafting\11436~01\Maps\11436-001_F01_SLM_201&~9·29.mxd on 9/2912016 11:05:38 AM
Leighton
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APPENDIX A
REFERENCES
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11436.001
APPENDIX A
References
BHA, Inc., 2016, Grading Plans for Afton Way, Project Number CT 14-06, Drawing No.
495-9A, dated August 16, 2016.
California Building Standards Commission (CBSC), 2013, California Building Code
(CBC).
Leighton and Associates, 2014, Geotechnical Investigation, Proposed Afton Way
Residential Development, Carlsbad, California, Project Number
10690.002, dated September 29, 2014.
Rocscience, 2016, Slide Version 7.014
A-1
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APPROXIMATE LOCATION OF LARGE-DIAMETER
BORINGS
APPROXIMATE LOCATION OF TEST PITS
APPROXIMATE LOCATION OF PERCOLATION TESTS
A~PROXIMATE DEPTH OF REMEDIAL REMOVALS
APPROXIMATE GEOLOGIC CONTACT, DOTTED
WHERE BURIED AND QUERIED WHERE UNCERTAIN
APPROXIMATE LOCATION OF GEOLOGIC
CROSS-SECTION
ARTIFICIAL FILL -UNDOCUMENTED
QUATERNARY COLLUVIUM
QUATERNARY SLOPE WASH DEPOSITS (CIRCLED WHERE
BURIED)
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WHERE BURIED)
TERTIARY SANTIAGO FORMATION (CIRCLED WHERE BURIED)
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GEOTECHNICAL MAP
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GEOTECHNICAL MAP
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Eng/Geol: WOO/BEV
Date: October 2016
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' QUATERNARY SLOPE WASH DEPOSITS (CIRCLED WHERE
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A-A'' B-B' AND c-c·
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Scale: 1 "=20' Date: October 2016
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APPENDIX B
SLOPE ST ABILITY ANALYSIS
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SURFICIAL SLOPE ST ABILITY ANALYSIS
FLOWLINES
Project No.: 11436.001
Case: 2H:1V Slope I Compacted Fill@ 90% R.C.
Depth of Saturation (ft), Z
Buoyant Unit Weight of Soil (pcf), Yb
Total Unit Weight of Soil (pcf), y1
Slope Angle, a
Angle of Internal Friction, qi
Cohesion (psf), c
Force Tending To Cause Movement:
F0 = Zy1 sin 2a /2
Force Tending To Resist Movement:
FR = Zyb cos2 a tan q> + ( C)
= 3
= 57.6
= 120
= 26.6
= 30
= 150
= 144.13 lb/ft
= 229.76 lb/ft
2Zyb cos2 a tan qi + 2c
Zy1 sin 2a
F.S. = 1.59
Project Name :
SURFICIAL STABILITY Project Number :
Designed/Checked :
Afton Way, Carlsbad, CA
11436.001
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Results
Method of Analysis: spencer
Factor of Safety: 1. 546
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(deg)
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Results
Method of Analysis: spencer
Factor of Safety: 1.625
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Analysis Description
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IOONTERPRET7.011 Lei g ht on Dilte 9/20/2016 Condition
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Material Name Color Unit Weight
(lbs/ft3)
Afu D 110
Qvop fil] 120
Tsa D 120
At D 120
Retaining Wall • 120
120
Afton Way
Cross Section C-C'
Scale 1:200 Comp;,ny
File Name
Strength Type Cohesion Phi
(psf) (deg)
Mohr-Coulomb 150 30
Mohr-Coulomb 100 38
Mohr-Coulomb 400 28
Mohr-Coulomb 100 30
Infinite strength
Results
Method of Analysis: spencer
Factor of Safety: 2.020
140 160
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APPENDIXC
INFILTRATION DATA
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FIELD PERCOLATION TEST DATA SHEET
,~ Project Name: Afrton Way Project No.: 10690.002
LJ Proj. Address: Afton Way, Carlsbad, Ca
SOIL TYPE I TEST LOCATION I BOREHOLE
Soil Type: Sandy clay
Location: Hole #1 (north)
Hole Dia: 4"
Depth 4.7'
r-1 Tested by:SLR Pre-Saturation Date:6-12-14 Test Date:6-13-14
Notes: Measurements in 1 OOths of foot
Time of Day Interval I Notes Water Level Time of Day Interval I Notes Water Level
8:52 0.65
9:22 30 min (caving) 0.55
9:26 re-start 0,6
9:56 30min 0.65
10:26 30min 0.68
10:56 30min 0.7
11:26 30min 0.72
11:56 30min 0.74
12:26 30 min 0.76
12:56 30min 0.79
1:26 30min 0.82
1:27 add water 0.56
1:57 30min 0.59
2:27 30min 0.61
2:57 30min 0.63
!FOR OFFICE USE ONLY DATE RECEIVED: By:
Notes: 125 min/inch or 0.48 inch/hour
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Leighton
FIELD PERCOLATION TEST DATA SHEET
Project Name: Afton Way Project No.:
Proj. Address: Afton Way, Carlsbad, Ca
SOIL TYPE I TEST LOCATION I BOREHOLE
Soil Type: Sandy clay
Location: Hole #2 (south)
Hole Dia: 4"
Depth 4.8'
" Tested by:SLR Pre-Saturation Date:6-12-14 Test Date:6-13-14
Notes: Measurements in 1 OOths of foot
Time of Day Interval I Notes Water Level lfime of Day Interval I Notes
8:50 0.61
9:20 30min 0.78 ii
9:50 30min 0.84
9:52 add water 0.5
10:22 30min 0.56
10:52 30min 0.62
11:22 30min 0.65
11:52 30min 0.68
12:22 30min 0.7
12:52 30min 0.73
u 1:22 30min 0.75
1:24 add water 0.55
1:54 30min 0.6
2:24 30min 0.62
2:54 30min 0.64
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!FOR OFFICE USE ONLY DATE RECEIVED: By:
L..i Notes: 125 min/inch or 0.48 inch/hour
10690.002
Water Level
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11436.001 Afton Way
Pere Test P-1
D (in)
Hole Depth (ft)
Time 1
Time2
~t (min)
Havg
~H
I (in/hr)
w/FS of 2
Pere Test P-2
D (in)
Hole Depth (ft)
Time 1
Time2
4.00
4.70
r (in)
Hole Depth (in)
2.00 56.io'
Water Level (ft) Water Level (in) Water Depth (in)
o.oo 0.61 7.32 49.0S
30.00 0.63 7.56 . 48.84
10::00 ,ihl§
. iif4
/.gJ):1
0.00
4.00
4.80
Pere Rate 125.0
r (in)
Hole Depth (in)
min/inch
·~.f)d
sf~~
Water Level (ft) Water Level (in) Water Depth (in)
0.00 0.62 1.!J.it 50.16
30.00 o.64 1.as · · i4i.si
~t (min)
Havg
... :?!!tr
···SO~
. <'.·n·;···}.·~.·.:4) ~H ', .:~--~-'~·,
Pere Rate 125.0 min/inch
I (in/hr)
w/FS of 2 0.00
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APPENDIX D
FORM 1-8
l _J {Categorization of Infiltration Feasibility Condition)
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:, ~at~~~ri~a)iD~ QI lal1Iali11:n li~sil>JJi~ ~Qt'lctitiDn FORM I-S . .
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Part 1-Full Infiltration Feasibility Screening Criteria
Would infiltration of the full design volume be feasible from a physical perspective without any undesirable
consequences that cannot be reasonably mitigated?
Criteria
1
Screening Question
Is the estimated reliable infiltration rate below proposed
facility locations greater than 0.5 inches per hour? The response
to this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.2 and Appendix
D.
Provide basis:
Yes No
X
Based on our field percolation testing, the in-situ infiltration rates of the soils at the
subject site are less than 0.5 inches per hour (Leighton, 2014). The calculated
infiltration rates via the Porchet Method with an applied safety factor of 2 are less than
0.01 inches per hour.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability.
2
Can infiltration greater than 0.5 inches per hour be allowed
without increasing risk of geotechnical hazards (slope stability,
groundwater mounding, utilities, or other factors) that cannot
be mitigated to an acceptable level? The response to this
Screening Question shall be based on a comprehensive evaluation of
the factors presented in Appendix C.2.
Provide basis:
X
If the infiltration rates were greater than 0.5 inches per hour, it may be possible that the
risk of geotechnical hazards would not be increased provided mitigation is performed
for any underground utilities/structures, slopes (i.e., setbacks) and undocumented fill
depths greater than 5 feet within the vicinity of the proposed infiltration site.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability.
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3
Can infiltration greater than 0.5 inches per hour be allowed
without increasing risk of groundwater contamination ( shallow
water table, storm water pollutants or other factors) that cannot
be mitigated to an acceptable level? The response to this
Screening Question shall be based on a comprehensive evaluation of
the factors presented in Appendix C.3.
Provide basis:
X
If the infiltration rates were greater than 0.5 inches per hour, it may be possible that the
risk of groundwater contamination would not be increased provided there are no
contaminated soil or groundwater sites within 250 feet of the proposed infiltration site.
In addition, the borings indicate the groundwater is greater than 50 feet bgs.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability.
4
Can infiltration greater than 0.5 inches per hour be allowed
without causing potential water balance issues such as change
of seasonality of ephemeral streams or increased discharge of
contaminated groundwater to surface waters? The response to
this Screening Question shall be based on a comprehensive evaluation
of the factors presented in Appendix C.3.
X
Provide basis:
If the infiltration rates were greater than 0.5 inches per hour, it may be possible that
potential water balance issues would not be affected provided there are no unlined site
drainages/creeks/streams within 250 feet of the proposed infiltration site.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability.
Part 1
If all answers to rows 1 -4 are "Yes" a full infiltration design is potentially feasible.
The feasibility screening category is Full Infiltration
Result* If any answer from row 1-4 is "No", infiltration may be possible to some extent but
would not generally be feasible or desirable to achieve a "full infiltration" design.
Proceed to Part 2
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FORM 1-8-Page 3 of 4
Part 2 -Partial Infiltration vs. No Infiltration Feasibility Screening Criteria
Would infiltration of water in any appreciable amount be physically feasible without any negative
consequences that cannot be reasonably mitigated?
Criteria
5
Screening Question
Do soil and geologic conditions allow for infiltration in any
appreciable rate or volume? The response to this Screening
Question shall be based on a comprehensive evaluation of the factors
presented in Appendix C.2 and Appendix D.
Provide basis:
Yes No
X
Based on our field percolation testing, the in-situ infiltration rates of the soils at the
subject site are less than 0.01 inches per hour (Leighton, 2014). The calculated
infiltration rates via the Porchet Method with an applied safety factor of 2 are less than
0.01 inches per hour.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability and why it was not feasible to mitigate low infiltration rates.
6
Can Infiltration in any appreciable quantity be allowed without
increasing risk of geotechnical hazards ( slope stability,
groundwater mounding, utilities, or other factors) that cannot
be mitigated to an acceptable level? The response to this Screening
Question shall be based on a comprehensive evaluation of the factors
presented in Appendix C.2.
Provide basis:
X
For a partial infiltration condition (greater than 0.01 inches per hour), the risk of
geotechnical hazards will not be increased by partial infiltration provided mitigation is
performed for any underground utilities/structures, slopes (i.e., setbacks) and
undocumented fill depths greater than 5 feet within the vicinity of the proposed
infiltration site. Mitigation includes subsurface vertical barriers and subdrains to limit
perched ground water mounding conditions.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability and why it was not feasible to mitigate low infiltration rates.
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7
Can Infiltration in any appreciable quantity be allowed without
posing significant risk for groundwater related concerns
(shallow water table, storm water pollutants or other factors)?
The response to this Screening Question shall be based on a
comprehensive evaluation of the factors presented in Appendix C.3.
X
Provide basis:
For a partial infiltration condition (greater than 0.01 inches per hour), the risk of
groundwater contamination will not be increased by partial infiltration provided there
are no contaminated soil or groundwater sites within 250 feet of the proposed
infiltration site. In addition, the borings indicate the groundwater is greater than 50 feet
bgs.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability and why it was not feasible to mitigate low infiltration rates.
8 Can infiltration be allowed without violating downstream water
rights? The response to this Screening Question shall be based on a
comprehensive evaluation of the factors presented in Appendix C.3.
X
Provide basis:
For a partial infiltration condition (greater than 0.01 inches per hour), violation of
downstream water rights is not anticipated based on the site location and that there
are no unlined site drainages/creeks/streams within 250 feet of the proposed
infiltration site.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/ data source applicability and why it was not feasible to mitigate low infiltration rates.
Part2
Result*
If all answers from row 5-8 are yes then partial infiltration design is potentially feasible.
The feasibility screening category is Partial Infiltration.
If any answer from row 5-8 is no, then infiltration of any volume is considered to be
infeasible within the drainage area. The feasibility screening category is No Infiltration.
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APPENDIX E
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GEOTECHNICAL INVESTIGATION
DATED SEPTEMBER 29, 2014
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GEOTECHNICAL INVESTIGATION,
PROPOSED AFTON WAY RESIDENTIAL
DEVELOPMENT
2200 AFTON WAY, CARLSBAD, CALIFORNIA
Prepared for:
PRESIDO MANA CARLSBAD 9, LLC
5927 Balfour Court
Carlsbad, California 92008
Project No. 10690 .002
September 29, 2014
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A. LEiGHTON GROUP COMP/~
Preside Mana Carlsbad 9, LLC
5927 Balfour Court
Carlsbad, California 92008
Attention: Mr. Orville Power
September 29, 2014
Project No. 10690.002
Subject: Geotechnical Investigation
Proposed Afton Way Residential Development,
2200 Afton Way, Carlsbad, San Diego County, California
In accordance with your request and authorization, we have conducted a geotechnical
investigation of the property for the design and construction of the proposed residential
development project.
Based on the results of our study, it is our professional opinion that the site is suitable to
receive the proposed improvements. The accompanying report presents a summary of
our current investigation and provides geotechnical conclusions and recommendations
relative to the proposed site development.
3934 Murphy Canyon Road, Suite 8205 San Diego, CA 92123-4425
858.292.8030 "l! Fax 858.292.0771 ;1 www.leightongroup.com
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If you have any questions regarding our report, please do not hesitate to contact this
office. We appreciate this opportunity to be of service.
Respectfully submitted,
LEIGHTON AND ASSOCIATES, INC. 1Jde b V-e~uJ---
Mike Jensen, CEG 2457
Project Geologist
1,/./L. I.].(!)/ ____ -
William D. Olson, RCE 45283
Associate Engineer
Bryan Voss, PG 8709
Project Geologist
Distribution: (3) Addressee
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Geotechnical Investigation. 2200 Afton Way, Carlsbad. California 10690.002
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TABLE OF CONTENTS
Section
,_J 1.0 INTRODUCTION .............................................................................................. 1
1.1 PURPOSE AND SCOPE ............................................................................................. 1
1.2 SITE LOCATION AND DESCRIPTION ............................................................................ 1
1.3 PROPOSED DEVELOPMENT ...................................................................................... 2
2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING ......... 3
2.1 SITE INVESTIGATION ................................................................................................ 3
2.2 LABORATORY TESTING ............................................................................................ 3
3.0 SUMMARY OF GEOTECHNICAL CONDITIONS ...................................... 4
·3.1 GEOLOGIC SETTING ................................................................................................ 4
3.2 SITE-SPECIFIC GEOLOGY ........................................................................................ 4
1 __ ,i 3.2.1 Artificial Fill -Undocumented -(Afu) ............................................................. 4
3.2.2 Colluvium (Qc) ............................................................................................... 5
3.2.3 Slope Wash Deposits (Qsw) .......................................................................... 5
3.2.4 Very Old Paralic Deposits (Qvop) .................................................................. 5
3.2.5 Santiago Formation (Tsa) .............................................................................. 6
3.3 SURFACE AND GROUND WATER ............................................................................... 6
3.4 ENGINEERING CHARACTERISTICS OF ON-SITE SOILS .................................................. 6
3.4.1 Expansion Potential ....................................................................................... 7
3.4.2 Compressible Soils ........................................................................................ 7
3.4.3 Soil Corrosivity .............................................................................................. 7
3.4.4 Infiltration ....................................................................................................... 7
3.4.5 Excavation Characteristics ............................................................................ 8
3.5 SLOPE STABILITY .................................................................................................... 8
3.6 EARTHWORK SHRINKAGE AND BULKING .................................................................... 9
4.0 SEISMIC AND GEOLOGIC HAZARDS ..................................................... 10
4.1 REGIONAL TECTONIC SETTING ............................................................................... 10
4.2 LOCAL FAUL TING .................................................................................................. 10
4.3 SEISMICITY ........................................................................................................... 10
._J 4.4 SEISMIC HAZARDS ................................................................................................ 10
4.4.1 Shallow Ground Rupture ............................................................................. 11
4.4.2 Mapped Fault Zones ................................................................................... 11
l,_J 4.4.3 Site Class .................................................................................................... 11
4.4.4 Building Code Mapped Spectral Acceleration Parameters .......................... 11
4.5 SECONDARY SEISMIC HAZARDS ............................................................................. 12
4.5.1 Liquefaction and Dynamic Settlement.. ....................................................... 12
4.5.2 Lateral Spread ............................................................................................. 13
4.5.3 Tsunamis and Seiches ................................................................................ 13
Geotechnical Investigation, 2200 Afton Way. Carlsbad, California 10690.002
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TABLE OF CONTENTS (Continued)
Section
4.6 LANDSLIDES ......................................................................................................... 13
4.7 FLOOD HAZARD .................................................................................................... 14
t_c_j 5.0 CONCLUSIONS .............................................................................................. 15
6.0 RECOMMENDATIONS .................................................................................. 17
6. 1 EARTHWORK ........................................................................................................ 17
6.1 .1 Site Preparation ........................................................................................... 17 ,, 6.1.2 Removal of Compressible Soils ................................................................... 17
6.1.3 Cut/Fill Transition Mitigation ........................................................................ 18
6.1.4 Excavations and Oversize Material ............................................................. 18
6.1.5 Engineered Fill ............................................................................................ 19
6.1.6 Import Soils ................................................................................................. 20
6.1. 7 Expansive Soils and Selective Grading ....................................................... 20 ~--)
1, 6.1.8 Buttress/Replacement Fill. ........................................................................... 20
6.2 FOUNDATION AND SLAB CONSIDERATIONS .............................................................. 21
l.) 6.2.1 Conventional Foundations ........................................................................... 21
I I 6.2.2 Foundation Setback .................................................................................... 23
6.2.3 Settlement ................................................................................................... 24
[__j 6.2.4 Moisture Conditioning .................................................................................. 25
6.2.5 Post-Tension Foundation Recommendations .............................................. 26
6.3 LATERAL EARTH PRESSURES AND RETAINING WALL DESIGN .................................... 27
6.4 GEOCHEMICAL CONSIDERATIONS ........................................................................... 29
6.5 CONCRETE FLATWORK .......................................................................................... 29
6.6 PRELIMINARY PAVEMENT DESIGN ........................................................................... 29
6.7 CONTROL OF GROUND WATER AND SURFACE WATERS ............................................ 31
6.8 CONSTRUCTION OBSERVATION .............................................................................. 32
6.9 PLAN REVIEW ....................................................................................................... 32
7.0 LIMITATIONS ................................................................................................. 33
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Geotechnical Investigation, 2200 Afton Way. Carlsbad. California 10690.002
TABLE OF CONTENTS (Continued)
TABLES
TABLE 1 -EARTHWORK SHRINKAGE AND BULKING ESTIMATES-PAGE 9
TABLE 2-2013 CBC MAPPED SPECTRAL ACCELERATION PARAMETERS-PAGE 12
TABLE 3-MINIMUM FOUNDATION AND SLAB DESIGN RECOMMENDATIONS FOR
CONVENTIONAL REINFORCED FOUNDATIONS -PAGE 22
TABLE 4-MINIMUM FOUNDATION SETBACK FROM SLOPE FACES-PAGE 24
TABLE 5-PRESOAKING RECOMMENDATIONS BASED ON FINISHED GRADE
SOIL EXPANSION POTENTIAL -PAGE 25
TABLE 6-POST-TENSIONED FONDATION DESIGN RECOMMENDATIONS-PAGE 26
TABLE ?-STATIC EQUIVALENT FLUID WEIGHT (PCF)-PAGE 28
TABLE 8-PRELIMINARY PAVEMENT SECTIONS-PAGE 30
FIGURE AND PLATES
FIGURE 1 -SITE LOCATION MAP -REAR OF TEXT
PLATE 1 -GEOTECHNICAL MAP-REAR OF TEXT
PLATE 2 -GEOLOGIC CROSS-SECTION A-A' -REAR OF TEXT
APPENDICES
APPENDIX A -REFERENCES
APPENDIX 8 -TEST PIT LOGS AND BORING LOGS
APPENDIX C -LABORATORY TESTING PROCEDURES AND TEST RESULTS
APPENDIX D-GENERAL EARTHWORK AND GRADING SPECIFICATIONS FOR ROUGH GRADING
APPENDIX E -ASSOCIATION OF ENGINEERING FIRMS PRACTICING IN THE GEOSCIENCES
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Geotechnical Investigation. 2200 Afton Way, Carlsbad. California 10690.002
1.0 INTRODUCTION
We recommend that all individuals utilizing this report read the preceding information
sheet prepared by ASFE (the Association of Engineering Firms Practicing in the
Geosciences) and the Limitations, Section 7 .0, located at the end of this report.
1.1 Purpose and Scope
This report presents the results of our geotechnical investigation for the site
located at 2200 Afton Way in the City of Carlsbad, California (Figure 1 ). The
intent of this report is to provide specific geotechnical conclusions and
recommendations for the currently proposed project.
1.2 Site Location and Description
The subject property encompasses approximately 3.92 acres of essentially
undeveloped land located at 2200 Afton Way in Carlsbad, California (see Site
Location Map, Figure 1 ). The site is bordered by Carlsbad Village Drive to the
north, and existing residential developments to the east, south, and west.
Topographically, the property consists of gently sloping hillside terrain with
elevations ranging from a high of approximately 280 feet Mean Sea Level (MSL)
near the southwestern property line to a low of approximately 205 feet (MSL) at the
property's northeastern corner. Currently, the property is occupied by one
residential structure with two sheds. An existing crib wall, approximately 26 foot
high and 300 feet long, is located along the north of the boundary of the site and
appears to have been constructed during the alignment of Carlsbad Village Drive.
It should be noted that the existing cribwall may be impacted by the proposed
improvements and require remedial grading activities. Site drainage is presently
accomplished through a generally southeasterly trending ravine and ultimately
through controlled drainage facilities along Carlsbad Village Drive. Vegetation
consists of native grasses and eucalyptus trees over the majority of the site.
Site Latitude and Longitude
33.1721° N
117.3268° w
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Geotechnical Investigation. 2200 Afton Way. Carlsbad. California 10690.002
1.3 Proposed Development
Based on our review of the provided preliminary grading plan by BHA, Inc. (BHA,
Inc., 2014), the property will be developed with nine, one-or two-story single-family
homes, with associated infrastructure and underground utility improvements. We
further understand that the residential structures would utilize conventional
continuous footings with slab-on-grade and/or post-tension systems. Building
loads are assumed to be typical for these types of relatively light structures.
Currently, no structural plans for the proposed buildings are available.
Typical cut and fill grading techniques would be required to bring the site to design
elevations. Based on our review, cut and fill slopes are proposed at inclinations of
2:1 (horizontal:vertical [H:V]), or flatter, with maximum planned slope heights of
about 10 and 23 feet, respectively. Cuts and fills are currently proposed up to
about 13 and 12 feet in thickness, respectively, (excluding remedial grading
removals). Sewage disposal is understood to be accommodated by tying into the
regional municipal system.
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Geotechnical Investigation. 2200 Afton Way. Carlsbad. California 10690.002
2.1
2.0 SUBSURFACE EXPLORATION AND LABORATORY TESTING
Site Investigation
Our exploration consisted of the excavation, logging, and sampling three large
diameter borings (LD-1 through LD-3) and 6 test pit excavations (TP-1 through
TP-6). Excavation depths ranging from of approximately 9 feet to 51 feet below
the existing ground surface (bgs). The approximate locations of the explorations
are shown on the Geotechnical Map (Plate 1). Subsequent to the subsurface
investigation, the test pits were backfilled with tamped soils and the large
diameter boring excavations were backfilled with spoils and layers of bentonite in
accordance with the San Diego County DEH Boring Permit Wavier. During the
exploration operations, a geologist from our firm prepared geologic logs and
collected bulk and undisturbed samples for laboratory testing and evaluation.
Logs of the explorations are presented in Appendix B.
2.2 Laboratory Testing
Laboratory testing performed on soil samples representative of on-site soils
obtained during the recent subsurface exploration included, expansion potential,
grain size analysis, corrosion test, direct shear tests on drive samples, moisture
test, and atterberg limits. A discussion of the laboratory tests performed and a
summary of the laboratory test results are presented in Appendix C.
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Geotechnical Investigation. 2200 Afton Way, Carlsbad. California 10690.002
3.1
3.0 SUMMARY OF GEOTECHNICAL CONDITIONS
Geologic Setting
The project area is situated in the Peninsular Ranges Geomorphic Province. This
geomorphic province encompasses an area that extends approximately 900
miles from the Transverse Ranges and the Los Angeles Basin south to the
southern tip of Baja California, and varies in width from approximately 30 to 100
miles (Norris and Webb, 1990). The province is characterized by mountainous
terrain on the east composed mostly of Mesozoic igneous and metamorphic
rocks, and relatively low-lying coastal terraces to the west underlain by late
Cretaceous-age, Tertiary-age, and Quaternary-age sedimentary units. Most of
the coastal region of the County of San Diego, including the site, occur within this
coastal region and are underlain by sedimentary units. Specifically, the subject
site is located within the coastal plain section of the Peninsular Range Geomorphic
Province of California, which generally consists of subdued landforms underlain by
sedimentary bedrock.
3.2 Site-Specific Geology
Based on our subsurface exploration and review of pertinent geologic literature
and maps (Appendix A), the geologic units underlying the site consist of localized
undocumented artificial fill, colluvium, and slope wash deposits overlying terrace
deposits (Quaternary-aged Very Old Paralic Deposits) and Tertiary-age Santiago
Formation across the entire site area. A brief description of the geologic units
encountered on the site is presented below. The general distribution of earth
materials are shown on Plate 1 .
3.2.1 Artificial Fill -Undocumented -(Afu)
During our subsurface exploration, an approximately 2-to 10-foot thick
layer of undocumented artificial fill soils was encountered at several of the
exploration locations. The fill was apparently placed during the site's initial
construction and isolated deeper fills may exist that were not observed
during our exploration. An as-graded report was not available for our
review, and it is assumed that no engineering observations of these
localized fill soils were provided at the time of grading. These fill soils
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Geotechnical Investigation. 2200 Afton Way. Carlsbad. California 10690.002
generally consisted of a mixture of silty sand and sandy clay, are dry,
loose and may settle appreciably under additional fill or foundation and
improvement loading. Therefore, all undocumented fills (soil) should be
removed and recompacted. These materials may be reused provided they
are cleared of trash and debris. All trash and debris should be removed,
and properly disposed offsite, prior to fill placement and/or remedial
grading.
3.2.2 Colluvium (Qc)
In general, the southern portion of the site is mantled by a relatively thin
layer of colluvium. The colluvium was generally observed to be reddish
brown to brown, dry, porous, loose, silty sand. Locally roots and rootlets
were noted within these surficial soils. The colluvium was generally
encountered ranging from approximately 2 to 4 feet in thickness. Due to
the potentially compressible nature of these surficial soils, they are
considered unsuitable for the support of structures and/or improvements in
their existing state. Therefore, these soils will need to be removed and
recompacted, if not removed during planned excavation, should
settlement sensitive improvements be proposed within their influence.
3.2.3 Slope Wash Deposits (Qsw)
The northern portion of the site is mantled by a layer of slope wash. The
slope wash was generally observed to be orange brown to grayish brown,
dry to moist, porous, loose, silty sand to clayey sand. The slope wash was
generally encountered ranging from 9 to 10 feet in thickness. Due to the
potentially compressible nature of these surficial soils, they are considered
unsuitable for the support of structures and/or improvements in their
existing state. Therefore, these soils will need to be removed and
recompacted, if not removed during planned excavation, should
settlement sensitive improvements be proposed within their influence.
3.2.4 Very Old Paralic Deposits (Qvop)
Quaternary-aged Very Old Paralic Deposits (previously referred to as
terrace deposits) underlie the colluvium soils at southern portion site. This
unit primarily consists of massively bedded, reddish-to orange brown,
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Geotechnical Investigation. 2200 Afton Way. Carlsbad. California 10690.002
3.3
3.4
oxidized, weakly to moderately cemented, dense to very dense, silty
sandstone and clayey sandstone, and are locally weathered near the
surface. The weathered near surface Very Old Paralic Deposits (upper 1
to 2 feet), where encountered, should be removed and recompacted, if not
removed during planned excavation, should settlement sensitive
improvements be proposed within their influence.
3.2.5 Santiago Formation (Tsa)
Sandstone, clayey siltstone, and claystone sedimentary bedrock
belonging to Eocene-age Santiago Formation, was encountered onsite.
These deposits occur at depth within the property. Where unweathered,
these rocks are considered suitable for structural support. Bedding
structures observed in our large diameter explorations indicate a
northwesterly trend with a southeasterly dip on the order of 10 degrees.
Surface and Ground Water
The regional groundwater table was not encountered in the explorations, to a
depth of 51 feet deep. Based on our review of the topographic quadrangle map
(USGS, 1967), groundwater level are anticipated at least 200 feet below the site
surface, which corresponds with Buena Vista Lagoon, north of the subject site.
Therefore, we anticipate the lowest site foundations will be well above the
existing static ground water table at the site.
Seeps, springs, or other indications of a high groundwater level were not noted
on the subject property during the time of our field study. However, seepage may
occur locally (due to heavy precipitation or irrigation) in areas where fill soils
overlie silty or clayey soils. Such soils may be encountered at the site. Mitigation
of seepage may be necessary during site grading.
Engineering Characteristics of On-site Soils
Based on the results of our laboratory testing of representative on-site soils, and
our professional experience on similar sites with similar soils conditions, the
engineering characteristics of the on-site soils are discussed below.
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3.4.1 Expansion Potential
Laboratory testing was performed to evaluate the expansion index of
materials characteristic of the site. The sample tested had an expansion
index of 53. Based on our field observations, subsurface investigation, and
laboratory testing, low to medium expansive soils are anticipated for this
site. High expansive soils may be encountered during site grading in
isolated layers.
3.4.2 Compressible Soils
Based on our experience on similar projects in the Carlsbad and our site
specific exploration, we expect that the upper 2 to 10 feet of the site is
underlain by undocumented fill, colluvium, or slope wash deposits which
are considered compressible. Recommendations for remedial grading of
these soils are provided in the following sections of this report.
3.4.3 Soil Corrosivity
A preliminary corrosive soil screening for the on-site materials was
completed to evaluate their potential effect on concrete and ferrous
metals. The corrosion potential was evaluated using the results of
laboratory testing on one representative soil sample obtained during our
subsurface evaluation.
Laboratory testing was performed to evaluate pH, minimum electrical
resistivity, and chloride and soluble sulfate content. The samples tested had
a measured pH of 7.19, and a measured minimum electrical resistivity of
8,240 ohm-cm. Test results also indicated that the samples had a chloride
content of 62.3 ppm, and a soluble sulfate content of less than 0.015
percent.
3.4.4 Infiltration
We performed percolation testing in Percolation Holes P-1 and P-2 to
evaluate suitability of the site for infiltration of storm water. The results of
the percolation test indicated that the site soils had a percolation rate of
greater than 125 minutes per inch (mpi). Generally, a percolation rate less
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3.5
than 120 mpi is considered necessary to consider a site suitable for onsite
infiltration of storm water. Additionally, the presence of shallow clayey
sand and clay materials present in much of the site would be expected to
impede infiltration and a 30-mil HOPE should be considered to line any
proposed infiltration basins. Further evaluation of proposed LIDs is
needed to determine potential down gradient impacts.
3.4.5 Excavation Characteristics
The site is underlain by undocumented fill, colluvium, slope wash deposits,
Very Old Paralic Deposits, and Santiago Formation generally consisting of
silty to clayey sands and sandy claystone to clayey sandstone. With
regards to the proposed project, it is anticipated these on-site soils can be
excavated with conventional heavy-duty construction equipment. Oversize
cobble material (typically over 6 inches in maximum dimension) is present
locally in the Paralic Deposits. Oversize cobble material should be placed
in non-structural areas or hauled off-site.
Slope Stability
Based on the available data, it is anticipated that proposed fill slopes will be
generally stable assuming proper construction and maintenance. Cut slopes, up to
proposed heights of 10 feet, that are constructed in Very Old Paralic Deposits and
earth materials belonging to Santiago Formation, are also anticipated to be
generally stable assuming proper construction and maintenance. However,
southeast-facing cut slopes constructed in the Santiago Formation may exhibit
adverse (out of slope) bedding orientations and may require stabilization and
buttressing. Cut slopes constructed to the anticipated heights in competent
bedrock should perform adequately at gradients of 2:1 (H:V), or flatter, and are
considered to be generally stable assuming proper construction and maintenance.
Additional site specific analysis may be warranted once final 40-scale grading
plans have been developed. All cut slopes constructed will require observation
during grading in order to verify the findings and conclusions presented herein.
The cut slope in the northwestern portion of the site adjacent to Lot 4 will likely
expose slope wash material which will require removal and construction of a
buttress replacement fill with a key way at the toe of slope. Recommendations for
the buttress/replacement fill is presented on the Geotechnical Map (Plate 1 ).
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All slopes may be susceptible to surficial slope instability and erosion given
substantial wetting of the slope face. Surficial slope stability may be enhanced by
providing proper site drainage. The site should be graded so that water from the
surrounding areas is not able to flow over the top of slopes. Diversion structures
should be provided where necessary. Surface runoff should be confined to gunite-
lined swales or other appropriate devices to reduce the potential of erosion. Slopes
should be planted with vegetation that will increase the surficial stability.
3.6 Earthwork Shrinkage and Bulking
The volume change of excavated on-site materials upon recompaction as fill is
expected to vary with materials and location. Typically, the surficial soils and
bedrock materials vary significantly in natural and compacted density, and
therefore, accurate earthwork shrinkage/bulking estimate cannot be determined.
We do not anticipate significant grading at the site where bulking and shrinkage
estimates are necessary. However, if needed, the following factors (based on
evaluation of our subsurface investigation, laboratory testing, geotechnical
analysis and professional experience on similar sites) are provided on Table 1 as
guideline estimates. If possible, we suggest an area where site grades can be
adjusted be provided as a balance area.
Table 1
Earthwork Shrinkage and Bulking Estimates
Geologic Unit Estimated Shrinkage/bulking
Colluvium/Undocumented fill 5 to 15 percent shrinkage
Slope Wash Deposits 4 to 8 percent shrinkage
Paralic Deposits and 2 to 10 percent bulking
Santiago Formation
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4.1
4.0 SEISMIC AND GEOLOGIC HAZARDS
Regional Tectonic Setting
During the late Pliocene, several new faults developed in Southern California,
creating a new tectonic regime superposed on the flat-lying section of Tertiary
and late Cretaceous rocks in the San Diego region. One of these fault systems is
the Rose Canyon Fault Zone.
The principal known onshore faults in southernmost California are the San
Andreas, San Jacinto, Elsinore, Imperial and Rose Canyon faults, which
collectively transfer the majority of this deformation. The balance of the plate
margin slip, is taken by the offshore zone of faults which include the Coronado
Bank, Descanso, San Diego Trough, and San Clemente faults off of the San
Diego and northern Baja California coastline. Most of the offshore faults coalesce
south of the international border, where they come onshore as the Agua Blanca
fault which transects the Baja California peninsula (Jennings, 2010).
4.2 Local Faulting
Our review of available geologic literature (Appendix A) indicates that there are
no known significant or active or potentially active faults transecting, or projecting
toward the site. The nearest active fault is the Rose Canyon I Newport -
Inglewood (offshore) fault zone located approximately 6.9 miles west of the site
within the Pacific Ocean (Treiman, 1993).
4.3 Seismicity
4.4
The site can be considered to lie within a seismically active region, as can all of
Southern California. As previously mentioned above, the Rose Canyon fault zone
located approximately 6.9 miles west of the site, is the 'active' fault considered
having the most significant effect at the site from a design standpoint.
Seismic Hazards
Severe ground shaking is most likely to occur during an earthquake on one of the
regional active faults in Southern California. The effect of seismic shaking may
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be mitigated by adhering to the California Building Code or state-of-the-art
seismic design parameters of the Structural Engineers Association of California.
4.4.1 Shallow Ground Rupture
As previously discussed, no faults are mapped transecting or projecting
toward the site. Therefore, surface rupture hazard due to faulting is
considered very low. Ground cracking due to shaking from a seismic event
is not considered a significant hazard either, since the site is not located
near slopes.
4.4.2 Mapped Fault Zones
The site is not located within a State mapped Earthquake Fault Zone
(EFZ). As previously discussed, the subject site is not underlain by known
active or potentially active faults.
4.4.3 Site Class
Utilizing 2013 California Building Code (CBC) procedures, we have
characterized the site soil profile to be Site Class D based on our
experience with similar sites in the project area and the results of our
subsurface evaluation.
4.4.4 Building Code Mapped Spectral Acceleration Parameters
The effect of seismic shaking may be mitigated by adhering to the
California Building Code and state-of-the-art seismic design practices of
the Structural Engineers Association of California. Provided below in
Table 2 are the risk-targeted spectral acceleration parameters for the
project determined in accordance with the 2013 California Building Code
(CBSC, 2013a) and the USGS Worldwide Seismic Design Values tool
(Version 3.1.0).
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4.5
Table 2
2013 CBC Mapped Spectral Acceleration Parameters
Site Class D
Fa = 1.056 Site Coefficients Fv = 1.573
Mapped MCER Spectral Ss = 1.110
Accelerations S1 = 0.427
Site Modified MCER Spectral SMs = 1.172
Accelerations SM1 = 0.672
Sos = 0.781 Design Spectral Accelerations So1 = 0.448
Utilizing ASCE Standard 7-10, in accordance with Section 11.8.3, the
following additional parameters for the peak horizontal ground
acceleration are associated with the Geometric Mean Maximum
Considered Earthquake (MCEG). The mapped MCEG peak ground
acceleration (PGA) is 0.432g for the site. For a Site Class D, the FPGA is
1.068 and the mapped peak ground acceleration adjusted for Site Class
effects (PGAM) is 0.461 g for the site.
Secondary Seismic Hazards
In general, secondary seismic hazards can include soil liquefaction, seismically-
induced settlement, lateral displacement, surface manifestations of liquefaction,
landsliding, seiches, and tsunamis. The potential for secondary seismic hazards
at the subject site is discussed below.
4.5.1 Liquefaction and Dynamic Settlement
Liquefaction and dynamic settlement of soils can be caused by strong
vibratory motion due to earthquakes. Granular soils tend to density when
subjected to shear strains induced by ground shaking during earthquakes.
Research and historical data indicate that loose granular soils underlain by
a near surface ground water table are most susceptible to liquefaction,
while the most clayey materials are not susceptible to liquefaction.
Liquefaction is characterized by a loss of shear strength in the affected
soil layer, thereby causing the soil to behave as a viscous liquid. This
effect may be manifested at the ground surface by settlement and,
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4.6
possibly, sand boils where insufficient confining overburden is present
over liquefied layers. Where sloping ground conditions are present,
liquefaction-induced instability can result.
The site is underlain at depth by moderately cemented sandstones and
moderately well indurated siltstone and claystone. Since loose surficial fill
and weathered Very Old Paralic Deposits are recommended for removal,
the underlying dense character of the on-site formational deposits, and the
lack of a shallow ground water table, it is our opinion that the potential for
liquefaction and seismic related settlement across the site is nil.
4.5.2 Lateral Spread
Empirical relationships have been derived (Youd et al., 1999) to estimate
the magnitude of lateral spread due to liquefaction. These relationships
include parameters such as earthquake magnitude, distance of the
earthquake from the site, slope height and angle, the thickness of
liquefiable soil, and gradation characteristics of the soil.
The susceptibility to earthquake-induced lateral spread is considered to be
low for the site because of the low susceptibility to liquefaction and
relatively level ground surface in the site vicinity.
4.5.3 Tsunamis and Seiches
Based on a site elevation of approximately 200 feet msl, and the distance
the site is located from the Pacific coastline, there is no potential for flood
damage to occur at the site from a tsunami or seiche.
Landslides
Several formations within the San Diego region are particularly prone to
landsliding. These formations generally have high clay content and mobilize
when they become saturated with water. Other factors, such as steeply dipping
bedding that project out of the face of the slope and/or the presence of fracture
planes, will also increase the potential for landsliding.
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No landslides or indications of deep-seated landsliding were indicated at the site
during our field exploration or our review of available geologic literature,
topographic maps, and stereoscopic aerial photographs. Furthermore, our field
explorations indicate the site is generally underlain by favorable oriented geologic
structure, consisting of sandstone, claystone, and siltstone. Therefore, the
potential for significant landslides or large-scale slope instability at the site is
considered low.
4. 7 Flood Hazard
According to a Federal Emergency Management Agency (FEMA) flood insurance
rate map (FEMA, 2012); the site is not located within a floodplain. Based on our
review of topographic maps, the site is not located downstream of a dam or
within a dam inundation area. Based on this review and our site reconnaissance,
the potential for flooding of the site is considered very low.
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5.0 CONCLUSIONS
Based on the results of our geotechnical investigation of the site, it is our opinion that
the proposed residential development is feasible from a geotechnical standpoint,
provided the following conclusions and recommendations are incorporated into the
project plans and specifications.
• Generally, loose soils having depths of up to approximately 1 to 10 feet locally
underlie the site and are considered compressible. Therefore, these soils are not
considered suitable for the support of structural loads or the support of engineered
fill soils and site improvements in their present condition. Section 6.1.2 of this report
provides specific recommendations regarding mitigation of these soil materials.
• The mapped MCE8 peak ground acceleration (PGA) is 0.432g for the site, and for
site Class D, the mapped peak ground acceleration, adjusted for Site Class effects
(PGAM) is 0.461g.
• Based on the results of our subsurface explorations and our experience with similar
projects in the site area, we anticipate regional ground water to be at a depth of 200
feet or more. Therefore, ground water is not anticipated to be a constraint during site
construction, and we do not anticipate that temporary dewatering will be necessary.
• The underlying Very Old Paralic Deposits and Santiago Formation are not subject to
liquefaction based on their age, generally dense character, and the lack of a shallow
ground water table.
• The cut slope adjacent to Lot 4 will likely require a buttress/replacement fill to
stabilize slope wash material.
• Due to the lack of adverse geologic conditions, landsliding and mass movement is
considered to be unlikely. However, cut slopes should be evaluated during site
grading to verify slope bedding is as anticipated.
• Based on the results of our subsurface exploration, we anticipate that the onsite
materials should be generally rippable with conventional heavy-duty earthwork
equipment. The existing onsite soils are suitable for reuse as engineered fill provided
they are relatively free of organic material, debris, and rock fragments larger than 6
inches in maximum dimension. In addition, unknown items such as buried concrete
footings left from previous site development should be anticipated.
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• Based on laboratory testing and visual classification, materials derived from the on-
site soil materials possess a low to medium expansion potential.
• Although Leighton does not practice corrosion engineering, laboratory test results
indicate the soils present on the site have a negligible potential for sulfate attack on
normal concrete. However, the onsite soils are considered to be moderately
corrosive to buried uncoated ferrous metals.
• It should be noted that the existing cribwall at the north east property line may be
impacted by the proposed improvements and require remedial grading activities.
• The existing onsite soils were found to have a very low permeability and are not
considered suitable for storm water management strategies that utilize infiltration.
Additional investigation regarding the infiltration characteristics of the site soils will
be required before recommendations for the use of infiltration type LID devices can
be provided. The proposed infiltration basins should be lined with a 30-mil HOPE
liner to prevent lateral migration of storm water. In addition, subsurface
improvements down gradient could be affected by some proposed LID measures
and should therefore be fully evaluated before being considered.
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6.1
6.0 RECOMMENDATIONS
Earthwork
We anticipate that earthwork at the site will consist of site preparation, shallow
excavation and fill operations. We recommend that earthwork on the site be
performed in accordance with the following recommendations and the General
Earthwork and Grading Specifications for Rough Grading included in Appendix
D. In case of conflict, the following recommendations supersede those in
Appendix D.
6.1.1 Site Preparation
Prior to grading, all areas to receive structural fill, engineered structures,
or hardscape should be cleared of surface and subsurface obstructions,
including any existing debris and undocumented, loose, compressible, or
unsuitable soils, and stripped of vegetation. Removed vegetation and
debris should be properly disposed off site. All areas to receive fill and/or
other surface improvements should be scarified to a minimum depth of 8
inches, brought to optimum or above-optimum moisture conditions, and
recompacted to at least 90 percent relative compaction based on ASTM
Test Method D1557.
6.1.2 Removal of Compressible Soils
Potentially compressible undocumented fill soils, colluvium, slope wash
deposits, and weathered Paralic Deposits at the site may settle as a result
of wetting or settle under the surcharge of engineered fill and/or structural
loads supported on shallow foundations. Therefore, remedial grading is
recommended across the entire site to remove undocumented fill,
colluvium, slope wash deposits, and weathered Paralic Deposits. These
soils should be removed to undisturbed Paralic Deposits ("Formation")
and/or Santiago Formation and replaced as moisture conditioned
engineered fill. In general, removal depths will range from 2 to 10 feet
below the existing ground surface across the site. The removal depths
should extend to a depth of at least 4 feet below finished building pad
grade. The lateral limits of the removal bottom should extend at least 5
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feet beyond the foundation limits. The bottom of all removals should be
evaluated by a Certified Engineering Geologist to confirm conditions are
as anticipated.
In general, the soil that is removed may be reused and placed as
engineered fill provided the material is moisture conditioned to at least 2
percent above optimum moisture content, and then recompacted prior to
additional fill placement or construction. Soil with an expansion index
greater than 70 should not be used within 5 feet of finish grade in the
building pad. The actual depth and extent of the required removals should
be confirmed during grading operations by the geotechnical consultant.
6.1.3 Cut/Fill Transition Mitigation
Our review of the preliminary grading plans indicates that several lots may
result in the creation of cut/fill transitions. The introduction of materials (fill
compared to native sandstone) having differing permeability and density
into the site may create a condition where surface infiltration of water may
accumulate below grade. As such, overexcavation of the Paralic Deposits
should be sloped at 1 percent toward the streets or deeper fills. To mitigate
the impact of the underlying cut/fill transition condition beneath possible
structures that are planned across existing or future cut/fill transitions, the
cut portion should be over-excavated to at least 3 feet below the bottoms of
proposed foundations. The overexcavation should laterally extend at least 5
feet beyond the building pad area and all associated settlement-sensitive
structures. The over-excavated material should be replaced with properly
compacted fill. Maximum to minimum fill thickness within a given lot should
not exceed ratio of 3:1. As such, deeper over excavation will be necessary
for fill lots with maximum fills in excess of approximately 9 feet. Final
overexcavation depths should be determined and documented in the field
based on site conditions.
6.1.4 Excavations and Oversize Material
Excavations of the onsite materials may generally be accomplished with
conventional heavy-duty earthwork equipment. Due to the generally friable
nature of the fill and Paralic Deposits, temporary excavations, such as
utility trenches with vertical sides, may slough over time.
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In accordance with OSHA requirements, excavations deeper than 5 feet
should be shored or be laid back if workers are to enter such excavations.
Temporary sloping gradients should be determined in the field by a
"competent person" as defined by OSHA. For preliminary planning,
sloping of fill soils at 1 :1 (horizontal to vertical) may be assumed.
Excavations supporting structures or greater than 20 feet in height will
require an alternative sloping plan or shoring plan prepared by a California
registered civil engineer.
6.1.5 Engineered Fill
In areas proposed to receive engineered fill, the existing upper 8 inches of
subgrade soils should be scarified then moisture conditioned to moisture
content at or above the optimum content and compacted to 90 percent or
more of the maximum laboratory dry density, as evaluated by ASTM D
1557. Soil materials utilized as fill should be free of oversized rock,
organic materials, and deleterious debris. Rocks greater than 6 inches in
diameter should not be placed within 2 feet of finished grade. Fill should
be moisture conditioned to at least 2 percent above the optimum moisture
content and compacted to 90 percent or more relative compaction, in
accordance with ASTM D 1557. Although the optimum lift thickness for fill
soils will be dependent on the type of compaction equipment utilized, fill
should generally be placed in uniform lifts not exceeding approximately 8
inches in loose thickness.
In vehicle pavement areas, the upper 12 inches of subgrade soils should
be scarified then moisture conditioned to a moisture content above
optimum content and compacted to 95 percent or more of the maximum
laboratory dry density, as evaluated by ASTM D 1557.
Placement and compaction of fill should be performed in general
accordance with current City of Carlsbad grading ordinances, California
Building Code, sound construction practice, these recommendations and
the General Earthwork and Grading Specifications for Rough Grading
presented in Appendix D.
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6.1.6 Import Soils
If import soils are necessary to bring the site up to the proposed grades,
these soils should be granular in nature, environmentally clean, have an
expansion index less than 50 (per ASTM Test Method D4829) and have a
low corrosion impact to the proposed improvements. Import soils and/or
the borrow site location should be evaluated by the geotechnical
consultant prior to import. The contractor should provide evidence that all
import materials comply with DTSC requirements for import materials.
6.1. 7 Expansive Soils and Selective Grading
Based on our laboratory testing and observations, we anticipate the onsite
soil materials possess a low to medium expansion potential (Appendix C).
Should an abundance of medium to highly expansive materials be
encountered, selective grading may need to be performed, such as
placing these materials in the deeper portions of the planned fill areas. In
addition, to accommodate conventional foundation design, the upper 5
feet of materials within the building pad and 5 feet outside the limits of the
building foundation should have a very low to low expansion potential
(El<70).
6.1 .8 Buttress/Replacement Fill
Based on our subsurface exploration (Appendix B), we anticipate the cut
slope in the north western portion of the site adjacent to Lot 4 may be
surficially unstable and may require the construction of buttress or
replacement fill. The replacement fill key should be constructed a
minimum of 15 feet wide, at least 2 feet below the toe-of-slope grade, and
have a minimum 2 percent into-the-slope inclination. The approximate
location of the replacement fill key is presented on the Geotechnical Map
(Plate 1.) A typical detail for stability fill construction is provided in the
attached General Earthwork and Grading Specifications (Appendix D).
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6.2 Foundation and Slab Considerations
At the time of drafting this report, building loads were not known. However, based
on our understanding of the project, the proposed residential buildings may be
constructed with conventional foundations or post-tensioned foundations. In
general foundations and slabs should be designed in accordance with structural
considerations and the following recommendations. The foundation
recommendations below assume that the all building foundations will be
underlain by properly compacted fill.
6.2.1 Conventional Foundations
Conventionally reinforced foundations should be designed and constructed
in accordance with the recommendations contained in Table 3 based on a
very low to low expansion potential. Residential structures placed on deep fill
areas (considered to be greater than 40 feet in depth), underlain by
differential fill thicknesses of 20 or more feet, and/or having moderate to
highly expansive soils (an expansive potential greater than 51) at finish
grade should be constructed with a post-tension foundation (as indicated in
Section 6.2.5) instead of a conventional reinforced foundation.
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Table 3
Minimum Foundation and Slab Design Recommendations For Conventional Reinforced Foundations
Design Criteria
Minimal Fill Thickness, Minimal Fill Differential, and a Very Low to
Low Expansion Potential (an Expansion Potential less than 50)
I -Story Footings All footings 12 inches deep. Reinforcement for continuous footings: two
(See Note 1) No. 5 bar top and bottom.
2-Story Footings All footings 18 inches deep. Reinforcement for continuous footings: two
(See Note I) No. 5 bar top and bottom.
Minimum Footing Width Continuous: 12 inches for 1-story
Continuous: 15 inches for 2-story
Isolated column: 24 inches (18 inches deep minimum)
Garage Door Grade Beam A grade beam 12 inches wide and 18 inches deep
(See Note 2) should be provided across the garage entrance.
Living Area Floor Slabs Minimum 5 inch thick slab with No. 3 bars @ 18 inches on center, each
(See Notes 3, 4 and 6) way (at mid-height) on 2 inches clean sand over moisture barrier over 2
inches clean sand.
Garage Floor Slabs Minimum 5 inch thick concrete slab with No. 3 bars@ 18 inches on center,
(See Notes 4, 5 and 6) each way (at mid-height) on 2 inches sand base over moisture barrier on
pad. Slab should be quarter-sawn.
Presoaking of Living Area 120 percent of the optimum moisture content to a depth of 12 inches.
and Garage Slabs (see note)
Allowable Bearing Capacity 2,000 pounds per square foot (one-third increase for short term loading)
Expected Foundation Deflection: 1/2 inch in 50 feet
Notes:
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
Depth of interior or exterior footing to be measured from lowest adjacent finish grade or drainage
swale flowline elevation.
The base of the grade beam should be at the same elevation as that of the adjoining footings.
Living area slabs should be tied to the footings as directed by the structural engineer.
10-mil non-recycled plastic sheeting is acceptable. Equivalents are acceptable. All laps and
penetrations should be sealed.
Garage slabs should be isolated from stem wall footings with a minimum 3/8-inch expansion joint.
Sand base should have a Sand Equivalent of 30 or greater (e.g. washed concrete sand).
Where the foundation is within 3 feet (horizontally) of adjacent drainage swales, the adjacent
footing should be embedded a minimum depth of 12 inches below the swale flow line.
The recommendations presented above assume that proper maintenance irrigation and drainage
are maintained around the structure.
The vapor barrier recommended in Table 2 should be sealed at all
penetrations and laps. Moisture vapor transmission may be additionally
reduced by use of concrete additives. Moisture barriers can retard but not
eliminate moisture vapor movement from the underlying soils up through the
slabs. We recommend that the floor covering installer test the moisture vapor
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flux rate prior to attempting applications of the flooring. "Breathable" floor
coverings should be considered if the vapor flux rates are high. A slipsheet
or equivalent should be utilized above the concrete slab if crack-sensitive
floor coverings (such as ceramic tiles, etc.) are to be placed directly on the
concrete slab.
Our experience indicates that use of reinforcement in slabs and foundations
will generally reduce the potential for drying and shrinkage cracking.
However, some cracking should be expected as the concrete cures. Minor
cracking is considered normal; in addition, it is often aggravated by a high
water content, high concrete temperature at the time of placement, small
nominal aggregate size, and rapid moisture loss due to hot, dry and/or windy
weather conditions during placement and curing. Cracking due to
temperature and moisture fluctuations can also be expected. The use of low
water content concrete can reduce the potential for shrinkage cracking.
The slab subgrade soils underlying the conventional foundation systems
should be presoaked as indicated in Section 6.2.4 prior to placement of the
moisture barrier and slab concrete.
6.2.2 Foundation Setback
We recommend a minimum horizontal setback distance from the face of
slopes for all structural foundations, footings, and other settlement-
sensitive structures as indicated on the Table 4 below. The minimum
recommended setback distance from the face of a retaining wall is equal to
the height of the retaining wall. The distance is measured from the outside
bottom edge of the footing, horizontally to the slope or retaining wall face,
and is based on the slope or wall height. However, the foundation setback
distance may be revised by the geotechnical consultant on a case-by-case
basis if the geotechnical conditions are different than anticipated.
23
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Table 4
Minimum Foundation Setback from Slope Faces
Slope Height Setback
less than 5 feet 5 feet
5 to 15 feet 7 feet
Please note that the soils within the structural setback area possess poor
lateral stability, and improvements (such as retaining walls, sidewalks,
fences, pavements, etc.) constructed within this setback area may be
subject to lateral movement and/or differential settlement. Potential distress
to such improvements may be mitigated by providing a deepened footing or
a grade beam foundation system to support the improvement.
In addition, open or backfilled utility trenches that parallel or nearly parallel
structure footings should not encroach within an imaginary 1: 1 (horizontal
to vertical) downward sloping line starting 9 inches above the bottom edge
of the footing and should also not be located closer than 18 inches from the
face of the footing. Deepened footings should meet the setbacks as
described above. Also, over-excavation should be accomplished such that
deepening of footings to accomplish the setback will not introduce a cut/fill
transition bearing condition.
Where pipes cross under footings, the footings should be specially
designed. Pipe sleeves should be provided where pipes cross through
footings or footing walls and sleeve clearances should provide for possible
footing settlement, but not less than 1 inch around the pipe.
6.2.3 Settlement
Fill depths between 3 and 13 feet are anticipated beneath the proposed
building foundations following final grading. For conventional footings, the
recommended allowable-bearing capacity is based on a maximum total
and differential static settlement of 3/4 inch and 1/2 inch, respectively.
Since settlements are a function of footing size and contact bearing
pressures, some differential settlement can be expected where a large
24
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differential loading condition exists. However for most cases, differential
settlements are considered unlikely to exceed 1/2 inch.
6.2.4 Moisture Conditioning
The slab subgrade soils underlying the foundation systems should be
presoaked in accordance with the recommendations presented in Table 5
prior to placement of the moisture barrier and slab concrete. The subgrade
soil moisture content should be checked by a representative of Leighton
prior to slab construction.
Presoaking or moisture conditioning may be achieved in a number of ways.
But based on our professional experience, we have found that minimizing
the moisture loss on pads that has been completed (by periodic wetting to
keep the upper portion of the pad from drying out) and/or berming the lot
and flooding for a short period of time (days to a few weeks) are some of
the more efficient ways to meet the presoaking recommendations. If
flooding is performed, a couple of days to let the upper portion of the pad
dry out and form a crust so equipment can be utilized should be
anticipated.
Table 5
Presoaking Recommendations Based on Finish Grade Soil Expansion
Potential
Expansion Potential Presoaking Recommendations
Very Low Near-optimum moisture content to a minimum
depth of 6 inches
Low 120 percent of the optimum moisture content to
a minimum depth of 12 inches below slab
subgrade
Medium 130 percent of the optimum moisture content to
a minimum depth of 18 inches below slab
subgrade
High 130 percent of the optimum moisture content to
a minimum depth of 24 inches below slab
subgrade
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6.2.5 Post-Tension Foundation Recommendations
As an alternative to the conventional foundations for the buildings, post-
tensioned foundations may be used. We recommend that post-tensioned
foundations be designed using the geotechnical parameters presented in
table below and criteria of the 2013 California Building Code and the Third
Edition of Post-Tension institute Manual. A post-tensioned foundation
system designed and constructed in accordance with these
recommendations is expected to be structurally adequate for the support of
the buildings planned at the site provided our recommendations for surface
drainage and landscaping are carried out and maintained through the
design life of the project. Based on an evaluation of the depths of fill
beneath the building pads, the attached Table 6 presents the
recommended post-tension foundation category for residential buildings for
this site.
Table 6
Post-Tensioned Foundation Design Recommendations
Catego[Y I Categorv II Categorv 111 Very Low to
Low Medium High
Design Criteria Expansion Expansion Expansion
Potential Potential Potential (El 50 to 90) (El 90 to 130) (El Oto 50)
Edge Center 9.0 feet 8.3 feet 7.0 feet Moisture Lift:
Variation, Edge 4.8 feet 4.2 feet 3.7 feet em Lift:
Center 0.46 inches 0.75 inches 1.09 inches Differential Lift:
Swell, Ym Edge 0.65 inches 1.09 inches 1.65 inches Lift:
Perimeter Footing 18inches 24inches 30inches Depth:
Allowable Bearing 2,000 psf Capacity
26
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The post-tensioned (PT) foundation and slab should also be designed in
accordance with structural considerations. For a ribbed PT foundation, the
concrete slabs section should be at least 5 inches thick. Continuous
footings (ribs or thickened edges) with a minimum width of 12 inches and a
minimum depth of 12 inches below lowest adjacent soil grade may be
designed for a maximum allowable bearing pressure of 2,000 pounds per
square foot. For a uniform thickness "mat" PT foundation, the perimeter cut
off wall should be at least 8 inches below the lowest adjacent grade.
However, note that where a foundation footing or perimeter cut off wall is
within 3 feet (horizontally) of adjacent drainage swales, the adjacent footing
should be embedded a minimum depth of 12 inches below the swale flow
line. The allowable bearing capacity may be increased by one-third for
short-term loading. The slab subgrade soils should be presoaked in
accordance with the recommendation presented in Table 5 above prior to
placement of the moisture barrier.
The slab should be underlain by a moisture barrier as discussed in
Section 6.2.1 above. Note that moisture barriers can retard, but not
eliminate moisture vapor movement from the underlying soils up through
the slabs. We recommend that the floor covering installer test the moisture
vapor flux rate prior to attempting applications of the flooring. "Breathable"
floor coverings should be considered if the vapor flux rates are high. A slip-
sheet or equivalent should be utilized above the concrete slab if crack-
sensitive floor coverings (such as ceramic tiles, etc.) are to be placed
directly on the concrete slab. Additional guidance is provided in ACI
Publications 302.1 R-04 Guide for Concrete Floor and Slab Construction
and 302.2R-06 Guide for Concrete Slabs that Receive Moisture-Sensitive
Floor Materials.
6.3 Lateral Earth Pressures and Retaining Wall Design
Table 7 presents the lateral earth pressure values for level or sloping backfill for
walls backfilled with and bearing against fully drained soils of very low to low
l_ ) expansion potential (less than 50 per ASTM D4829).
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Table 7
Static Equivalent Fluid Weight (pct)
Conditions Level 2:1 Slope
Active 35 55
At-Rest 55 65
Passive 350 150
(Maximum of 3 ksf) (sloping down)
Walls up to 10 feet in height should be designed for the applicable pressure
values provided above. If conditions other than those covered herein are
anticipated, the equivalent fluid pressure values should be provided on an
individual case-by-case basis by the geotechnical engineer. A surcharge load for
a restrained or unrestrained wall resulting from automobile traffic may be
assumed to be equivalent to a uniform lateral pressure of 75 psf which is in
addition to the equivalent fluid pressure given above. For other uniform
surcharge loads, a uniform pressure equal to 0.35q should be applied to the wall.
The wall pressures assume walls are backfilled with free draining materials and
water is not allowed to accumulate behind walls. A typical drainage design is
contained in Appendix D. Wall backfill should be compacted by mechanical
methods to at least 90 percent relative compaction (based on ASTM 01557). If
foundations are planned over the backfill, the backfill should be compacted to 95
percent. Wall footings should be designed in accordance with the foundation
design recommendations and reinforced in accordance with structural
considerations. For all retaining walls, we recommend a minimum horizontal
distance from the outside base of the footing to daylight as outlined in
Section 6.2.2.
Lateral soil resistance developed against lateral structural movement can be
obtained from the passive pressure value provided above. Further, for sliding
resistance, the friction coefficient of 0.35 may be used at the concrete and soil
interface. These values may be increased by one-third when considering loads of
short duration including wind or seismic loads. The total resistance may be taken
as the sum of the frictional and passive resistance provided that the passive
portion does not exceed two-thirds of the total resistance.
To account for potential redistribution of forces during ·a seismic event, retaining
walls providing lateral support where exterior grades on opposites sides differ by
more than 6 feet fall under the requirements of 2013 CBC Section 1803.5.12
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Geotechnical Investigation, 2200 Afton Way. Carlsbad. California 10690.002
and/or ASCE 7-10 Section 15.6.1 and should also be analyzed for seismic
loading. For that analysis, an additional uniform lateral seismic force of 8H should
be considered for the design of the retaining walls with level backfill, where H is
the height of the wall. This value should be increased by 150% for restrained
walls.
6.4 Geochemical Considerations
6.5
Concrete in direct contact with soil or water that contains a high concentration of
soluble sulfates can be subject to chemical deterioration commonly known as
"sulfate attack." Soluble sulfate results (Appendix C) indicated negligible soluble
sulfate content. We recommend that concrete in contact with earth materials be
designed in accordance with Section 4 of ACI 318-11 (ACI, 2011).
Based on our experience in the site vicinity and laboratory tests, the site soils
have a moderately corrosion potential to buried uncoated metal conduits. We
recommend measures to mitigate corrosion be implemented during design and
construction.
Concrete Flatwork
Concrete sidewalks and other flatwork (including construction joints) should be
designed by the project civil engineer and should have a minimum thickness of 4
inches. For all concrete flatwork, the upper 12 inches of subgrade soils should be
moisture conditioned to at least 3 percent above optimum moisture content and
compacted to at least 90 percent relative compaction based on ASTM Test
Method 01557 prior to the concrete placement.
6.6 Preliminary Pavement Design
The preliminary pavement section design below is based on an assumed Traffic
Index (Tl), our visual classification of the subject site soils, experience with other
projects in the area, and our limited laboratory testing. Actual pavement
recommendations should be based on R-value tests performed on bulk samples
of the soils that are exposed at the finished subgrade elevations across the site
at the completion of the mass grading operations. Flexible pavement sections
have been evaluated in general accordance with the Caltrans method for flexible
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
pavement design. Based on an assumed R-value of 10, preliminary pavement
sections for planning purposes is given in Table 8 below:
Table 8
Preliminary Pavement Sections
Assumed Traffic Asphalt Concrete Aggregate Base
Index (Tl) (inches) (inches)
4.5 4.0 5.0
5.0 4.0 6.0
6.0 4.0 13.0
Prior to placement of the aggregate base, the upper 12 inches of subgrade soils
should be scarified, moisture-conditioned to at least optimum moisture content and
compacted to a minimum 95 percent relative compaction based on American
Standard of Testing and Materials (ASTM) Test Method 01557.
Class 2 Aggregate Base or Crushed Aggregate Base should then be placed and
compacted at a minimum 95 percent relative compaction in accordance with ASTM
Test Method 01557. The aggregate base material (AB) should be a maximum of 6
inches thick below the curb and gutter and extend a minimum of 6 inches behind the
back of the curb. The AB should conform to and placed in accordance with the
approved grading plans, and latest revision of the Standard Specifications Public
Works Construction (Greenbook).
The Asphalt Concrete (AC) material should conform to Caltrans Standard
Specifications, Sections 39 and 92, with a Performance Grade (PG) of 64-10, and
the City of Carlsbad requirements. The placement of the AC should be in
accordance with the approved grading plans, Section 203-6 of the "Greenbook"
Standard Specifications for Public Works Construction, and the City of Carlsbad
requirements. AC sections greater than 3-inches thick, should be placed in two
lifts. The 1st lift should be a 2-inch minimum base course consisting of a 3/4-inch
maximum coarse aggregate. The 2nd lift should be a 2-inch minimum surface
capping course consisting of a 1/2-inch maximum coarse aggregate. No single lift
shall be greater than 3 inches.
If pavement areas are adjacent to heavily watered landscaping areas, we
recommend some measures of moisture control be taken to prevent the subgrade
30
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Geotechnical Investigation, 2200 Afton Way. Carlsbad, California 10690.002
6.7
soils from becoming saturated. It is recommended that the concrete curbing,
separating the landscaping area from the pavement, extend below the aggregate
base to help seal the ends of the sections where heavy landscape watering may
have access to the aggregate base. Concrete swales should be designed if
asphalt pavement is used for drainage of surface waters.
Control of Ground Water and Surface Waters
Regarding Low Impact Development (LID) measures, we are of the opinion that
bioswales, infiltration basins, and other onsite storm water retention and infiltration
systems can potentially create adverse perched ground water conditions both on-
site and off-site. Therefore, given the site geologic conditions, impermeable
subsurface material, and project type, infiltration type LID measures are not
considered to be appropriate for this site and project. 30 mil HOPE Liners should
be used where detention areas are proposed near slopes or retaining walls, near
buildings, or over utilities.
Surface drainage should be controlled at all times and carefully taken into
consideration during precise grading, landscaping, and construction of site
improvements. Positive drainage (e.g., roof gutters, downspouts, area drains, etc.)
should be provided to direct surface water away from structures and improvements
and towards the street or suitable drainage devices. Ponding of water adjacent to
structures or pavements should be avoided. Roof gutters, downspouts, and area
drains should be aligned so as to transport surface water to a minimum distance of
5 feet away from structures. The performance of structural foundations is
dependent upon maintaining adequate surface drainage away from structures.
Water should be transported off the site in approved drainage devices or
unobstructed swales. We recommend a minimum flow gradient for unpaved
drainage within 5 feet of structures of 2 percent sloping away.
The impact of heavy irrigation or inadequate runoff gradient can create perched
water conditions, resulting in seepage or shallow ground water conditions where
previously none existed. Maintaining adequate surface drainage and controlled
irrigation will significantly reduce the potential for nuisance-type moisture
problems. To reduce differential earth movements such as heaving and shrinkage
due to the change in moisture content of foundation soils, which may cause
distress to a structure and improvements, moisture content of the soils surrounding
31
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6.8
the structure should be kept as relatively constant as possible. Below grade
planters should not be situated adjacent to structures or pavements unless
provisions for drainage such as catch basins and drains are made.
All area drain inlets should be maintained and kept clear of debris in order to
function properly. In addition, landscaping should not cause any obstruction to site
drainage. Rerouting of drainage patterns and/or installation of area drains should
be performed, if necessary, by a qualified civil engineer or a landscape architect.
All area drain inlets should be maintained and kept clear of debris in order to
function properly. In addition, landscaping should not cause any obstruction to site
drainage. Rerouting of drainage patterns and/or installation of area drains should
be performed, if necessary, by a qualified civil engineer or a landscape architect.
Construction Observation
The recommendations provided in this report are based on preliminary design
information and subsurface conditions disclosed by widely spaced excavations.
The interpolated subsurface conditions should be checked by Leighton and
Associates, Inc. in the field during construction. Construction observation of all
onsite excavations and field density testing of all compacted fill should be
performed by a representative of this office. We recommend that all excavations
be mapped by the geotechnical consultant during grading to determine if any
potentially adverse geologic conditions exist at the site.
6.9 Plan Review
Final project grading and foundation plans should be reviewed by Leighton and
Associates as part of the design development process to ensure that
recommendations in this report are incorporated in project plans.
32
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7.0 LIMITATIONS
The conclusions and recommendations presented in this report are based in part upon
data that were obtained from a limited number of observations, site visits, excavations,
samples, and tests. Such information is by necessity incomplete. The nature of many
sites is such that differing geotechnical or geological conditions can occur within small
distances and under varying climatic conditions. Changes in subsurface conditions can
and do occur over time. Therefore, the findings, conclusions, and recommendations
presented in this report can be relied upon only if Leighton has the opportunity to
observe the subsurface conditions during grading and construction of the project, in
order to confirm that our preliminary findings are representative for the site.
33
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. .
APPROXIMATE LOCATION OF LARGE-DIAMETER
BORINGS
APPROXIMATE LOCATION OF TEST PITS
APPROXIMATE GEOLOGIC CONTACT
QUERIED WHERE UNCERTAIN
ARTIFICIAL FILL -UNDOCUMENTED
QUATERNARY COLLUVI UM
QUATERNARY VERY OLD PARALIC DEPOSITS
TERTIARY SANTIAGO FORMATION
I
!
' '
!
' -· ... ·--·~· ,.
A'
1--280
·-·· ·-·· -· 1--260
... --t--220
•..•.. -1--200
z
0
~ ""
GEOLOGIC CROSS-SECTION A·A'
2200 AFTON WAY
CARLSBAD, CALIFORNIA
Proj: 10690.002 Eng/Geel: WDO/BEV/MDJ
Scale: 1 "=20' Date: September 2014
I
'
PLATE 2
Leighton
--,
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t I
Appendix A
References
u
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
APPENDIX A
REFERENCES
California Geologic Survey (CGS), 2007, Fault Rupture Hazard Zones in California,
Special Publication No. 42, Revised 2007 (Interim Version).
California Building Standards Commission (CBSC), 2013, California Building Code,
Volumes 1 and 2.
FEMA, 2012, Flood Insurance Maps, Panel 1035 of 2375, dated May 16.
Jennings, C.W., 2010, Fault Activity Map of California and Adjacent Areas: California
Division of Mines and Geology, California Geologic Map Series, Map No. 6
Kennedy, M.P., and Tan, S.S., 2007, Geologic Map of the Oceanside Quadrangle,
California, California Geologic Survey, 1:100,000 scale.
Kennedy, M.P. and Tan, S.S., 2005, Geologic Map of the San Diego 30' X 60'
Quadrangle, California Compiled by Michael P. Digital Preparation by Kelly R. Bovard,
Anne G. Garcia and Diane Burns, California Geological Survey .
Tan, S.S., and Kennedy, M.P, 1996, Geologic Maps of the Northwestern Part of San
Diego County, California, Plate 1, Scale 1 :24,000.
Treiman, J.A., 1993, The Rose Canyon Fault Zone, Southern California: California
Division of Mines and Geology, Open File Report 93-02, 45p.
United States Department of Agriculture, 1953, Aerial Photographs, Flight AXN-BM,
Numbers 75 and 76, scale approximately 1 :24,000, dated March 31.
A-1
)
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L.J
Appendix B
Test Pit and Boring Logs
l ./
( 1
~.)
'~)
\. J
\ )
-----
L-[_ ~~ _J _J
LOG OF TRENCH: _ _,_T_.-1 __ _
Project Name: Aftoo YJl..a't-Logged by: BV
Elevation: ?54 feet mean sea level ENGINEERING PROPERTIES Project Number: 10690 002
Equipment: Bacls:bce Location/Grid: S011tbem Sample Moisture Density uses GEOLOGIC DATE: 6/12/14 DESCRIPTION: GEOLOGIC No. (%) (pcf) ATTITUDES UNIT
COLLUVIUM Qc
@ 0-2': Silty SAND, brown, dry, loose; roots and rootlets, porous, fine to SM
medium grained, weakly cemented
VERY OLD PARALIC DEPOSITS Qvop
@ 2'-11 ': Silty SAND, orang-brown, dry, medium dense to very dense with SM B-1
depth; massive @
0'-4'
GRAPHICAL REPRESENTATION: SCALE: 1 "=5' SURFACE SLOPE: 2-4°NE TREND:
\' i, c, :) ./ .
1 \ .
• ... t, \ .... .,, ,.
"" , r ' '
\ . ' / Total Depth= 11 Feet ~·-.; No Ground Water Encountered
Backfilled: 6/12/14
L"
Project Name: Aftoa Way_ Logged by: BV
Project Number: 10690 002 Elevation: 242 feet mean sea level
Equipment: Backbce Location/Grid: Middle Sc11tb
GEOLOGIC DATE: 6/12/14 DESCRIPTION: ATTITUDES
COLLUVIUM
@ 0-2': Silty SAND, dark brown, dry, loose
VERY OLD PARALIC DEPOSITS
@ 2'-4': Silty SAND, orange brown to reddish brown, dry, medium dense to
dense with depth; massive, grades into clayey sand at 4 feet
SANTIAGO FORMATION
@4'-12': Clayey SANDSTONE, light brown, moist, very stiff, massive, caliche
strings along fractures
L_ _,)
GEOLOGIC
UNIT
Qc
Qvop
TsA
--,
__ )
LOG OF TRENCH: _ _.Tc.:.-2....._ __ _
ENGINEERING PROPERTIES
Sample Moisture Density uses No. (%) (pcf)
SM B-1
@
0'-4'
SM
B-2
@
8'-12'
SC
GRAPHICAL REPRESENTATION: SCALE: 1 "=5' SURFACE SLOPE: 2-4°NE TREND:
)
~ ~
t ~-. ~ ·. </ ~ .
\ L----' . ' I
,, ' [;1 ' ' <
' %< \
/ ·/
\ /,/' t/ Total Depth= 12 Feet >--< No Ground Water Encountered
Backfilled: 6/12/14
' / LJ
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Project Name: Afton Way
Project Number: 10690 002
Equipment: Backbae
Logged by:
Elevation:_
(--
L
Location/Grid: -
) "--
BV
256 feet mean sea level
Middle West
GEOLOGIC ATTITUDES I DATE: 6/12/14 DESCRIPTION:
CQll..UVIUM
@ 0-2': Silty SAND, dark brown, dry, loose; roots and rootlets, porous
VERY OLD PARALIC DEPOSITS
@ 2'-7': Silty SAND, reddish brown, dry, dense
@ 7': Gravel lense
@ 7'-12': Silty SAND, orange-brown, dry to moist, very dense
-,
_J
r -~ L ~ L ~
LOG OF TRENCH: _.....,T=-3..,__ __ _
ENGINEERING PROPERTIES
GEOLOGIC I uses I Sample I Moisture I Density
UNIT No. (%) (pct)
Qc
I SM I
Qvop
I
SM I B-1
@
2'-3'
GRAPHICAL REPRESENTATION: SCALE: 1 "=5' SURFACE SLOPE: 2-3°NE TREND:
-~--------17 w . ·.=' ~· \ ;~J ,· \, 5 ·P:Y
\~ J.. \
___l_.:....c;.-----
I\ . ~ \-J
/
Total Depth = 12 Feet
No Ground Water Encountered
Backfilled: 6/12/14
L_
Project Name: Afton Way Logged by:__ _ _IDL
Project Number: 10690 002 Elevation: 254 feet mean sea level
Equipment: Backboe Location/Grid: _ Srnrthern
GEOLOGIC I DATE· 6/12/14 ATIITUDES · DESCRIPTION:
CQl..1...UVIUM
@ 0-4': Silty SAND, brown, dry, loose, roots and rootlets
VERY OLD PARALIC DEPOSITS
@4'-8': Silty SAND, orange-brown, dry, dense, massive
@8'-10': Becomes very dense
'c~ -_-r'' t:..._ \'......_ l_ L
LOG OF TRENCH: ___ T._-4...__ __ _
ENGINEERING PROPERTIES
GEOLOGIC I uses I Sample I Moisture I Density
UNIT No. (%) (pct)
QC
I
SM I
Qvop
I
SM
GRAPHICAL REPRESENTATION: SCALE: 1 "=5' SURFACE SLOPE: 1-2°NE TREND:
' ~/ '· . ) \ (
r • ( •
'
\ 1 ti 1 . ' -7 . I ~ /
\
Total Depth = 10 Feet
No Ground Water Encountered
Backfilled: 6/12/14
'-[
Project Name: ~flee Wa'Y,. Logged by: RV
Project Number: 10690 002 Elevation: 264 feet mean sea level
Equipment: Bacls:boe Location/Grid: S011tbeco
GEOLOGIC DATE:v6/12/14 DESCRIPTION: ATTITUDES
ARTIFICIAL FILL-undocumented
@ 0-2.5': Silty SAND, brown, dry, loose
SLOPE WASH
@2.5'-9': Clayey SAND, grayish-brown, moist, loose
SANTIAGO FORMATION
@9'-12': Silty CLAYSTONE, olive-gray to light brown, moist, medium stiff
r··
t_ __
GEOLOGIC
UNIT
Afu
Qsw
Tsa
J L ~) \......_ r-
L
LOG OF TRENCH: -....JI=-5...._ __ _
ENGINEERING PROPERTIES
Sample Moisture Density uses No. (%) (pcf)
SM B-1
@
4'-6'
SC
B-2
@
CL 9'-10'
GRAPHICAL REPRESENTATION: SCALE: 1 "=5' SURFACE SLOPE: 0-1°NE TREND:
I ( .
I-·
I I I • ,--.__ \ ,; ' ' ' f,· ' / ' } ----/· . -r
1::// ( / ' ~ ,' ------
7"
----'
. // I ~ . / -' -
/ Total Depth = 12 Feet
~--· '\ No Ground Water Encountered l' / Backfilled: 6/12/14
/ -·/ "" -. / ~ ""-/
Project Name:
Project Number:
Equipment:
GEOLOGIC
ATTITUDES
8f:tca Way_
10690 002
Backboe
c __
Logged by:
Elevation:
r----
1_
Location/Grid:
DATE: 6/12/14 DESCRIPTION:
ARTIFICIAL FILL-undocumented
R\/
224 feet mean sea level
So11tbem
@0-10': Sandy CLAY, brown to yellowish brown, moist, loose to stiff with
depth; trash 2 6'; asphalt debris at 8'
SANTIAGO FORMATION
@ 10'-12': Sandy CLAYSTONE, light brown, moist, stiff to very stiff
GEOLOGIC
UNIT
Afu
Tsa
-,
)
,-
,:___ __ ' I'-----
LOG OF TRENCH: _ .... Ji.:-6...._ __ _
ENGINEERING PROPERTIES
Sample Moisture Density uses No. (%) (pcf)
CL B-1
@
0'-6'
GRAPHICAL REPRESENTATION: SCALE: 1 "=5' SURFACE SLOPE: S-8°NE TREND:
\ r--;--
-----------\// " -------------
\ -
1----------
I
\-
\, Total Depth = 12 Feet
/// No Ground Water Encountered
-.,,,,___ Backfilled: 6/12114
~--~
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Project No.
Project
Drilling Co.
Drilling Method
Location
C .2 .... u .c .... :Ea, -Cl) ""'CD 111 Cl) Cl.ri, c.o :u. ~u. l!..J
(!)
GEOTECHNICAL BORING LOG KEY
KEY TO BORING LOG GRAPHICS
0 Ill l:' 0,-;je. Ill Cl)
Cl) z 111.C "iii ... -"C Cl) 3u c .... ::,""" .... c ::, a. o.5 CDU UICD -cc. ·--E ffico oc ...
ui--:-IIIU, 111 • -o O, -"' "ci:j
Date Drilled
Logged By
Hole Diameter
Ground Elevation
Sampled By
SOIL DESCRIPTION
This Soil Description applies only to a location of the exploration at the
time of sampling. Subsurface conditions may differ at other locations
and may change with time. The description is a simplification of the
!J Ill Cl)
I-.... 0
Cl) t ~ w 111 ::EO Cl. u, Cl) C 0 u,-actual conditions encountered. Transitions between soil types may be >, a. I-
N s gradual.
0 Asphaltic concrete
I"" .i:,. ~.;'f;, .. ?::~~: .. ,.4!-Portland cement concrete
I~ CL Inorf anic clay oflow to medium plasticity; gravelly clay; sandy
c ay; silty clay; lean clay
1// CH Inorganic clay; high plasticity, fat clays
) ) ) OL Organic clay; medium to plasticity, organic silts
5 ML Inorganic silt; clayey silt with low plasticity
MH Inorganic silt; diatomaceous fine sandy or silty soils; elastic silt
-~;;:; ,/1 f§:~ ML-CL Clayey silt to silty clay
•• Ill ' '• &.• • GW Well-graded gravel; gravel-sand mixture, little or no fines
ovu, GP Poorly graded gravel; gravel-sand mixture, little or no fines
10 1'0 (\o a
l.~'KH,' GM Silty gravel; gravel-sand-silt mixtures
I~ GC Clayey gravel; gravel-sand-clay mixtures
6 .. 6 D SW Well-graded sand; gravelly sand, little or no fines
SP Poorly graded sand; gravelly sand, little or no fines
SM Silty sand; poorly graded sand-silt mixtures
15 I~ SC Clayey sand; sand-clay mixtures
I~ Bedrock
-I 7 Ground water encountered at time of drilling
-B-1 Bulk Sample
20-C-1 Core Sample
-G-1 \'l Grab Sample
-R-1 Modified California Sampler (3" O.D., 2.5 I.D.)
-SH-I Shelby Tube Sampler (3" O.D.)
-S-1 Standard Penetration Test SPT (Sampler (2" O.D., 1.4" I.D.)
25-PUSH Sampler Penetrates without Hammer Blow
-
-
-
-
SAMPLfTYPES: TYPE OF TESTS:
"
B BULK SAMPLE -200 % FINES PASSING OS DIRECT SHEAR SA SIEVE ANALYSIS
C CORE SAMPLE AL ATTERBERG LIMITS El EXPANSION INDEX SE SAND EQUIVALENT
G GRAB SAMPLE CN CONSOLIDATION H HYDROMETER TR THERMAL RESISTIVITY
R RING SAMPLE co COLLAPSE MD MAXIMUM DENSITY UC UNCONFINED COMPRESSIVE STRENGTH
S SPLIT SPOON SAMPLE CR CORROSION pp POCKETPENETROMETER
T TUBE SAMPLE cu UNDRAINED TRIAXIAL RV RVALUE
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * * Page 1 of 1
( .,
11.._ ___ J
I '\
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GEOTECHNICAL BORING LOG LD-1
Project No. 10690.002 Date Drilled 7-1-14
Project Afton Way_ logged By FJW
Drilling Co. Alro Hole Diameter 26"
Drilling Method Bucket Auger -0-24=2,400lb Ground Elevation 274'
location Sampled By FJW/BEV
0 Ill a, o,'iif'!. ui--:-SOIL DESCRIPTION C Ill CII u z ·;;; .5? .... .c.,.. :EC) CII 111.S::. ... n I/It/)
"C CII 3: u c .... :::s .... C'CI • This Soil Description applies only to a location of the exploration at the ""'CII .,..CII .... c -o C'Cla, a.a, a.o :::s a. o.5 CIIU U'ICII (.) . 6'i~ ~~ I!-' -ca. ·---"' time of sampling. Subsurface conditions may differ at other locations
C) ~ E ffico ~ oc ·c;:; and may change with time. The description is a simplification of the iii C'CI ... :E 0
ti) CII C (.) ,,,_. actual conditions encountered. Transitions between soil types may be CL gradual. IN s
0 B-1 SM COLLUVIUM
-@0-5' @ 0-3': Silty SAND, reddish brown, dry, loose
-.
-+--~--+---l - - -
---I---~ --SM -VERY OLD PARALIC DEPOSITS (Qyop)
@ 3': Silty SAND, reddish brown, dry to moist, medium dense 270 -
5-·.
-
-
-
R-1
B-2
@5'-8'
7
11
265
R-2
B-3
. B:N<io--=-srn:-@s·.:fs·
·8SE
---'-------
@ 8': Silty SAND, reddish brown to orange, dry to moist, medium
dense
SM !---TERTIARY SANTIAGO FORMATION (Tsa) --------,,.
-
260 -
15-
-
-
-,
255 -·
20-
-.
-
-
250 -
25-
-
-
-·
245 -·
SAMPL,TYP~S:
B BULK SAMPLE
C CORE SAMPLE
G GRAB SAMPLE
R RING SAMPLE
·BN50E,
. SSE
S SPLIT SPOON SAMPLE
T TUBE SAMPLE
R-3 10/10" 111
@15'-16
R-4
B-4
@20'-25
12
TYPE OF TESTS:
114
-200 % FINES PASSING
AL ATTERBERG LIMITS
CN CONSOLIDATION
CO COLLAPSE
CR CORROSION
CU UNDRAINED TRIAXIAL
8
9
@ 9': Silty SANDSTONE, pale, olive-gray, moist, medium dense
@ 15': Silty SANDSTONE with gravel, gray to olive, damp, dense,
fine to medium grained, very little to no bedding
@ 20': Silty SANDSTONE with gravel, gray to olive, damp, dense,
fine to medium grained, very httle to no bedding
@ 24': 1/4 inch gypsum layer, horizontal
@ 25'· Silty SANDSTONE, gray to olive, moist, fine grained sands,
dense
DS DIRECT SHEAR SA SIEVE ANALYSIS
SE SAND EQUIVALENT
5G SPECIFIC GRAVITY
El EXPANSION INDEX
H HYDROMETER
MD MAXIMUM DENSITY
PP POCKET PENETROMETER
RV RVALUE
UC UNCONFINED COMPRESSIVE STRENGTH
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * *
.I!! Ill CII I-.... 0
CII a. ?:
Page 1 of 2
GEOTECHNICAL BORING LOG LD-1
Project No. 10690.002 Date Drilled 7-1-14
Project Afton Way_ Logged By FJW
Drilling Co. Alro Hole Diameter 26"
u Drilling Method Bucket Auger -0-24=2,4001b Ground Elevation 274'
Location Sampled By FJW/BEV
,:--1
C: .2 .... .c..., .... OJ -OJ 111 OJ Q.OJ 6'ju. ~u.
jjj
L __ J
240
r,-,
\~,J 235
230 -
45-
-
-
-
225 -
50-
-
-
-
220 -
55-
-
-
' :
u :Ee, a.o l!..J
C)
N B
Ill OJ "Cl ::::s -i:! <
ci z
OJ Q.
E 111 U)
R-5
B-5
@30'-35
--1-----
R-6
~
~
~
c-
Ill ~ OJ?fe. OJ 111.r:. 'iii ... ~ 3: u c: ... ::::s-.. c: o.l: OJU Ill OJ ca. ...... ijjw ~ 0 C: ... :::iO OJ C (.) D.
25
ui-:-SOIL DESCRIPTION
IIIU, 111 • This Soil Description applies only to a location of the exploration at the -CJ (.) . -"' time of sampling. Subsurface conditions may differ at other locations
'6::j and may change with time. The description is a simplification of the u,--actual conditions encountered. Transitions between soil types may be
gradual.
CL @ 30': Sandy CLAYSTONE, gray, dry to moist, hard
@ 30': Grades to silty SANDSTONE
------r --· -CL-SM-@30': Contact between SANDSTONE and CLAYSTONE,
horizontal
@ 33'-34': Contact between CLA YSTONE and SANDSTONE, horizontal
~ 18 --~SC-SM~@ 40':. Silty to clayey SAND, gray to olive, dry to moist, medium
gramed
Geotoy;calt Lojged = 40.5 Feet Total ept = 4 .5 Feet
No ~undwater encountered at time of drilling Bae illed with bentonite and soil on 7 /1/14
\. __ ) -
215 -
SAMPLfTYPES:
B BULK SAMPLE
C CORE SAMPLE
G GRAB SAMPLE
R RING SAMPLE
S SPLIT SPOON SAMPLE
T TUBE SAMPLE
TYPE OF TESTS:
-200 % FINES PASSING
AL ATTERBERG LIMITS
CN CONSOLIDATION
CO COLLAPSE
CR CORROSION
CU UNDRAINED TRIAXIAL
DS DIRECT SHEAR
El EXPANSION INDEX
H HYDROMETER
MD MAXIMUM DENSITY
PP POCKET PENETROMETER
RV RVALUE
SA SIEVE ANALYSIS
SE SAND EQUIVALENT
SG SPECIFIC GRAVITY
UC UNCONFINED COMPRESSIVE STRENGTH
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * *
ll Ill OJ I-... 0
OJ Q.
~
Page 2 of 2
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GEOTECHNICAL BORING LOG LD-2
Project No. 10690.002 Date Drilled 7-1-14
Project Afton Way Logged By FJW
Drilling Co. Alro Hole Diameter 26"
Drilling Method Bucket Auger -0-24=2,400lb Ground Elevation 263'
Location Sampled By FJW/BEV
0 C Ill .2 ... u a, z .c.., :c C) "Cl a, -a, ... a, 111 a, C.a, c.o :II Q.
~LL ~LL f..J ...
C> ~ E iii 111 en
'N s
0
-
-.
260 -----
-· FR:N30\\,
5-·90
R-1
B-1 -@5'-10'
-
255 -
-
10 R-2
-
-.
250 -.
-
15~ f-
-f-
-
245 -.
-·
20-· R-3
-
-
240 -
-
25-
-
-
235 -.
Ill ,a, a,"cf!. ui-:--SOIL DESCRIPTION a,
111.C ·;; ... ft Ill(/) ~u c .... ::::s-111 • This Soil Description applies only to a location of the exploration at the ..,c -o o.E a, u Ill a, O· time of sampling. Subsurface conditions may differ at other locations cc. ·--_en iijco ~ oc ·o:::, and may change with time. The description is a simplification of the .. :::il:0 a, C 0 en--actual conditions encountered. Transitions between soil types may be a. gradual.
SM COLLlMUM
@ 0-3': Silty SAND, reddish brown, dry, loose
---1--------------SM VERY OLD PARALIC DEPOSITS (Ovo11)
@ 3': Silty SAND, reddish-brown, dry to damp, medium dense
10 115 8 @ 5': Silty SAND, light brown, damp, medium dense
~12--126 ~-9-~SM -TERTIARYSANTIAGOFORMATION(Tsa)
@ 10': Silty SANDSTONE, light brown, moist, medium dense to
dense, massive
10/10" 129 8 SM @ 20': Silty SANDSTONE, light brown, moist, dense, massive
SAMPL,TYPES: TYPE OF TESTS:
B BULK SAMPLE
C CORE SAMPLE
G GRAB SAMPLE
R RING SAMPLE
S SPLIT SPOON SAMPLE
T TUBE SAMPLE
-200 % FINES PASSING
AL ATTERBERG LIMITS
CN CONSOLIDATION
CO COLLAPSE
CR CORROSION
CU UNDRAINED TRIAXIAL
OS DIRECT SHEAR
El EXPANSION INDEX
H HYDROMETER
MD MAXIMUM DENSITY
PP POCKET PENETROMETER
RV RVALUE
SA SIEVE ANALYSIS
SE SAND EQUIVALENT
SG SPECIFIC GRAVITY
UC UNCONFINED COMPRESSIVE STRENGTH
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * *
.I! Ill a, I-
'5
a,
Q, ~
Page 1 of 2
/-I
L.c.J
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GEOTECHNICAL BORING LOG LD-2
Project No.
Project
Drilling Co.
Drilling Method
Location
r:: .2-CJ .c..., :E 0, -Cl) .... Cl) CISCI) Cl.Cl) c.o &'jLL !LL !,!..J
(!) jjj
N
30
s
.. -
-.
230 -
-
35-
-
-
225 -
-
40-
-
-
220 -
-
45-
-
-
215 -
-
50-
-
-
210 -
-
55-
-
-
205 -
-
SAMPL~\YPES:
B BULK SAMPLE
C CORE SAMPLE
G GRAB SAMPLE
R RING SAMPLE
10690.002
Afton Way
Alroy
Bucket Auger -0-24=2,400lb
0 Ill ~ Ill GI GI z 111.C 'iii "C GI ,:CJ r:: .... ::, a. o.E QIU -cc. i E i:ijco c':' CIS ..
U) Cl) C a.
R-4 29
f-
f-
f-
f-
f-
f-
TYPE OF TESTS:
-200 % FINES PASSING
AL ATTERBERG LIMITS CN CONSOLIDATION
CO COLLAPSE
S SPLIT SPOON SAMPLE CR CORROSION
T TUBE SAMPLE cu UNDRAINED TRIAXIAL
e~ Iii-:-tilt/) ::, .... CIS • -r:: -CJ tllCI) CJ • ·--_u, or: ·s::;; :!!!:O CJ u,-
SM
Date Drilled
Logged By
Hole Diameter
Ground Elevation
Sampled By
SOIL DESCRIPTION
7-1-14
FJW
26"
263'
FJW/BEV
This Soil Description applies only to a location of the exploration at the
time of sampling. Subsurface conditions may differ at other locations
and may change with time. The description is a simplification of the
actual conditions encountered. Transitions between soil types may be
gradual.
@ 30': Silty SANDSTONE, light brown, moist, dense, massive
Geolof;cai lojrd to 30.5 Feet Total ept = .5 Feet
No ~undwater encountered at time of drilling Bae tiled with bentonite and soil on 711/14
.l!l Ill GI I-.... 0
Cl)
Cl. ~
4 DS DIRECT SHEAR SA SIEVE ANALYSIS
El EXPANSION INDEX SE SAND EQUIVALENT
H HYDROMETER SG SPECIFIC GRAVITY
MD MAXIMUM DENSITY UC UNCONFINED COMPRESSIVE STRENGTH
PP POCKET PENETROMETER
RV RVALUE
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * * Page 2 of 2
u
,-,-1
u
\ ___ J
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l j
GEOTECHNICAL BORING LOG LD-3
Project No.
Project
Drilling Co.
Drilling Method
Location
C CJ .!2 .. .c,... :Ea, +'G) +'a, as CP C.a, c.o
~LL ~LL f..J
c.:> w
IN
0
-
-.
-.
260 -
5
-
-.
-.
255 -
10
-
-.
-.
250 -
15-
-
-
-
245 -·
20-·.
-
-.
-.
240 -
25-
-
-
-
235
SAMPLiJ\ypes:
B BULK SAMPLE
C CORE SAMPLE
G GRAB SAMPLE
R RING SAMPLE
10690.002
Afton Way_
Alroy_
Bucket Auger -0-24=2,400lb
0 Ill ~ Ill CP z CP 111.C Ill "Cl CP ~CJ c-::::s Q. o..5 CPU ... cc. ~ E ffico ~ as ...
U) Cl) C ll. s
-----~6--107 ~ R-1
B-1
@5'-10'
-----· B:N30-5CE, R-2 10 118
· JOSE
-B:N55E,
· JOSE
R-3 10/10" 124
B-2
@18'20'
R-4 11 124
R-5 20 114
TYPE OF TESTS:
-200 % FINES PASSING
AL ATTERBERG LIMITS
CN CONSOLIDATION
CO COLLAPSE
S SPLIT SPOON SAMPLE
T TUBE SAMPLE
CR CORROSION
CU UNDRAINED TRIAXIAL
Date Drilled 6-30-14
Logged By FJW
Hole Diameter 26"
Ground Elevation 264'
Sampled By FJW/BEV
a,'#. tn--:-SOIL DESCRIPTION
... -I/IU) ::::s-as • This Soil Description applies only to a location of the exploration at the ... c -(.) Ill Cl) (.) . ·---"' time of sampling. Subsurface conditions may differ at other locations oc "S::i and may change with time. The description is a simplification of the :EO (.) cn-actual conditions encountered. Transitions between soil types may be
gradual.
SM ARTIFICIAL FILL-undocumented (Afu)
~ 0-2': Silty SAND, brown, dry, loose
0-5': Fill, roots to rootlets
@ 2'-5': Silty SAND, light brown, moist, medium dense
~sM -QUATERNARY SLOPE WASH (Qsw) 2
@ 5': Silty SAND, orange-brown, dry, medium dense, porous,
loose, roots and rootlets 3-9% organics
~---------------------------~ 7 SM TERTIARY SANTIAGO FORMATION (Tsa)
@ IO': Silty SANDSTONE, light brown, damp, medium dense
@ 13'-18': Manganese staining vertical
8 @ 15': Silty SAND, light brown, moist, medium dense to dense
9 @ 20': Silty SAND, light brown, moist, medium dense to dense
13 @ 25': Sandy SILTSTONE, olive-gray, moist, hard
@26': Silty SANDSTONE over sandy SILTSTONE
OS DIRECT SHEAR SA SIEVE ANALYSIS
SE SANO EQUIVALENT
SG SPECIFIC GRAVITY
El EXPANSION INDEX
H HYDROMETER
MD MAXIMUM DENSITY
PP POCKET PENETROMETER
RV RVALUE
UC UNCONFINED COMPRESSIVE STRENGTH
J!! Ill CP I--0
Cl) C. >, I-
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * * Page 1 of 2
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Project No.
Project
Drilling Co.
Drilling Method
Location
C CJ .5?. ... .c.,.. :EC> ""'GI -GI ca GI a.GI c.o
~LL ~LL ~...I
jjj C>
IN s
30
-
I -
230
35-
-
225 -v v~
40
-
-.
-.
220 -
45-
-
-
215 --
so-·.
-
-
210 -
55-
-
-
-
205 -
SAMPLfTYPES:
B BULK SAMPLE
C CORE SAMPLE
G GRAB SAMPLE
R RING SAMPLE
GEOTECHNICAL BORING LOG LD-3
10690.002 Date Drilled 6-30-14
Afton Way_ Logged By FJW
Alro Hole Diameter 26"
Bucket Auger -0-24=2,400lb Ground Elevation 264'
II)
GI "Cl ::::, -~
--
---
--
--
Sampled By FJW/BEV
0 II) ~ a,'#. ui---:-SOIL DESCRIPTION GI z 111.C 'iii ... ~ Ult/)
GI ~ CJ Cr. ::::J""' ca • This Soil Description applies only to a location of the exploration at the GI CJ .. c: -u a. o.5 Ill GI (.) . time of sampling. Subsurface conditions may differ at other locations cc. ·--_ti) E iii«> ~ 0 C: ·o::; and may change with time. The description is a simplification of the ca .. ::i!:10 "' GI C (.) rn-actual conditions encountered. Transitions between soil types may be Q. gradual.
R-6 27
---
SM-ML 130': Clayey SANDSTONE, light olive-gray, moist, dense
30': Sandy SILTSTONE, gray, moist, dense
30'-32': Clayey SANDSTONE, sandy SILTSTONE, gray, moist,
~ -----~ --~ CL "'-@ f ;~s~LA YSTONE, laminated, polished surfaces, discontinuous,_,,,
hard
@ 35': Grades into CLA YSTONE, olive-gray, moist, hard
1-----
---I---r----sM -@36': Grades intOsilty SANDSTONE, olive-gray, moist, dense
1--------~ --~ --SM-CL -@ 38': Interbedded CLA YSTONE and SANDSTONE
---R-7 -29-------~ SM ~ @40': Silty SANDSTONE, gray, moist, very dense, friable
R-8 50110"
TYPE OF TESTS:
-200 % FINES PASSING
AL ATTERBERG LIMITS
CN CONSOLIDATION
CO COLLAPSE
SM @ 50': Silty SANDSTONE, gray, moist, very dense, friable
Geologically Logged= 48 Feet
Total Depth= 51 Feet
No groundwater encountered at time of drilling
Backfilled with bentonite and soil on 6/30/14
DS DIRECT SHEAR
El EXPANSION INDEX
H HYDROMETER
MD MAXIMUM DENSITY
SA SIEVE ANALYSIS
SE SAND EQUIVALENT
SG SPECIFIC GRAVITY
UC UNCONFINED COMPRESSIVE STRENGTH
S SPLIT SPOON SAMPLE
T TUBE SAMPLE
CR CORROSION
CU UNDRAINED TRIAXIAL
PP POCKET PENETROMETER
RV RVALUE
J!3 II)
GI I-.... 0
GI C. ~
* * * This log is a part of a report by Leighton and should not be used as a stand-alone document. * * * Page 2 of 2
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Appendix C
Laboratory Testing Procedures and Test Results
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
APPENDIX C
Laboratory Testing Procedures and Test Results
Moisture Tests: Moisture content determinations were performed on disturbed samples
obtained from the test borings. The results of these tests are presented in the boring logs.
Atterberg Limits: The Atterberg Limits were determined in accordance with ASTM Test
Method D4318 for engineering classification of the fine-grained materials and presented
in the table below:
Liquid Limit Plastic Limit Plasticity Index uses Soil Sample Location (%) (%) (%) Classification
8-1 at 30 to 35 45 18 27 CL feet
Particle Size Analysis (ASTM D6913): Particle size analysis was performed by
mechanical sieving methods according to ASTM D6913. Plots of the sieve results are
provided on the Figures in this appendix.
Direct Shear Tests: A direct shear test (ASTM D 3080) was performed on selected
sample which was soaked for a minimum of 24 hours under a surcharge equal to the
applied normal force during testing. After transfer of the sample to the shear box and
reloading of the sample, the pore pressures set up in the sample (due to the transfer)
were allowed to dissipate for a period of approximately 1-hour prior to application of
shearing force. The samples were tested under various normal loads utilizing a motor-
driven, strain-controlled, direct-shear testing apparatus at a strain rate of 0.0025 inches
per minute. After a shear strain of 0.2 inches, the motor was stopped and the sample was
allowed to "relax" for approximately 15 minutes. The stress drop during the relaxation
period was recorded. It is anticipated that, in a majority of samples tested, the 15 minutes
relaxing of the samples is sufficient to allow dissipation of pore pressures that may have
set up in the samples due to shearing. The drained peak strength was estimated by
deducting the shear force reduction during the relaxation period from the peak shear
values. The shear values at the end of shearing are considered to be ultimate values and
are presented on the attached figure. The samples were either remolded to 90% relative
compaction, undisturbed, or the samples were tested in a torsional shear machine to
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
APPENDIX C (Continued)
evaluate the remolded clay seam properties. The test results are provided on the Figures
in this appendix.
Chloride Content: Chloride content was tested in accordance with Caltrans Test Method
CT 422. The results are presented below:
Sample Location Sample Description Chloride Content
(ppm)
T-1 @ 0.0-4.0 Brown Silty Sand 62.3 feet
Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in
general accordance with California Test Method 643. The results are presented in the
table below:
Sample Location pH Minimum Resistivity
(ohms-cm)
T-1 @ 0.0-4.0 feet 7.19 8,240
Soluble Sulfates: The soluble sulfate contents of selected samples were determined by
standard geochemical methods (Caltrans Test Method CT417). The test results are
presented in the table below:
Sample Location Sample Description Sulfate Potential Degree
Content(%) of Sulfate Attack*
T-1 @0.0 to 4.0 Brown Silty Sand <0.015 Negligible feet
* Based on the 2005 edition of American Concrete Institute (ACI) Committee 31 BR,
Table No. 4.3. 1.
C-2
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Geotechnical Investigation, 2200 Afton Way, Carlsbad, California 10690.002
APPENDIX C (Continued)
Expansion Index Tests: The expansion potential of selected materials was evaluated by
the Expansion Index Text, ASTM Test Method 4829. A specimen is molded under a given
compactive energy to approximately 50 percent saturation. The prepared 1-inch thick by
4-inch diameter specimen is loaded to an equivalent 144 psf surcharge and is inundated
with water until volumetric equilibrium is reached. The result of this test is presented in the
table below:
Sample Location Description Expansion Expansion
Index Potential
TP-3@0.5 to Brown Clayey Sand 53 Medium 3.0 feet
C-3
_j l. .) L ·1 -'-..J ·~
I GRAVEL SAND FINES I I COARSE I FINE COARSE I MEDIUM FINE SILT I CLAY I
U.S. STANDARD SIEVE OPENING U.S. STANDARD SIEVE NUMBER HYDROMETER
3.0" 11/2" 3/4" 3/8" #4 #8 #16 #30 #50 #100 #200
100 ---
I --,.. -r--~
90 I I".
I I \ .J 80 I --' ---
' 70 j-j--------f--------·-~---,-
I ' I
I-60 ·-t· r-!----·---+--·--" ----
:::c \ ~ I 1 I l w -1 '\ -~ 50 --_,_, __________ -----------------------·· ----------------·-·-·----------. -----------_,_ ---~-----1-----------------------
>-\ ID
n::: \. w 40 r--· ~ -~------r--~ --z
l~ U:::
I-1'. z 30 w -----------·----~ ' --0 n::: I" .... w 0..
20 l-----·--
I
I
10 I t-·---
I
I
I 0 i I I
100.000 10.000 1.000 0.100 0.010 0.001
PARTICLE -SIZE (mm)
Project Name: AFTON WAY
Project No.: 10690.002 Exploration No.: B-1 Sample No.: B-3
Depth (feet): 8.0-15.0 Soil Type: SM -PARTICLE -SIZE ~ Leighton
Soil Identification: SM: SILTY SAND, Grayish-Yellow DISTRIBUTION
ASTM D 6913 GR:SA:FI: (%) 0 : 75: 25 JUl·l~
S/E\IEB-1 B3
, __ j '--L_
I GRAVEL I SAND
I COARSE I FINE I COARSE 1 MEDIUM FINE
U.S. STANDARD SIEVE OPENING U.S. STANDARD SIEVE NUMBER
3.0" 1 1/2" 3/4" 3/8" #4 #8 #16 #30 #50 #100 #200
']i~lHfl_]II I U~ 1
--
SILT
,-
'--L
FINES
I
HYDROMETER
I I I -
L
CLAY
-r--,.~ I I I -
80 lill[i 11-.. 1 I --+1 I l+-"--. -.,, I t1i ---~-1111 I 1--1
70 ~ ,-. _ __ l . . _ ~ +-r-. _ · f T ---------l
~ I I ----i------1t ' t -~--,
; :: i ' I-+---+ ... ~-.. -t -' . . . . .. . .. . . -t I H 1-1
~ I ! I l Ii I
w 30 r+~~ --,-~-~ I , I ffi I I I I i i
o.. ' I I
20 i I - ' -: it--H i-
': '.H, ! . 1
1 * 1
1 I I i I
J J
100,000 10.000 1.000 0.100 0.010 0.001
Project Name: AFTON WAY
Project No.: 10690.002
~ tif Leighton
PARTICLE · SIZE
DISTRIBUTION
ASTM D 6913
PARTICLE -SIZE (mm)
Exploration No.: B-1
Depth (feet): 30.0-35.0
Sample No.: B-5
Soil Type : (CL)s
Soil Identification: {CL}s: LEAN CLAY WITH SAND. Yellowish-Brown
GR:SA:FI : (%) 0 : 26 : 74 JUI-H
.~/FIii= R-1 R_&;
100
90
80
70
I-60 ::c
(!)
~ 50 >-ID a:: w 40 z U::
I-z w 30 CJ a:: w a. 20
10
j
GRAVEL
COARSE FINE
U.S. STANDARD SIEVE OPENING
3.0" 1 1/2" 3/4" 3/8" #4
! ---. I -r 1 ;
L _., "J L
SAND
COARSE MEDIUM
U.S. STANDARD SIEVE NUMBER
'· I
FINE
#8 #16 #30 #50 #100
L ' ' L __)
FINES
SILT CLAY
HYDROMETER
#200
I 1· I ~ l
I . I I --
I --··--· -·--'-~·!-_ --rrrt-1-++--+·--l--·-1
I
I \ ----·--,++-+--L.J I ----i--+---·--
1 ---' " _ -r11t--t-+-1---1-
! ---'-i--~---------------L .. I:~ -C-___ ,__ I - ' -------"" ----I -
\ I --
. ·-. --·--~· ......... , ,__ I
I ---
1 I ---1,t-r++'\"+---1-----L-. 1--' --\. --l-1-·
c,_ _ __ _ "-. ---Trt1-t-+-+---J.-_J__ '---
" ··-r-t·-t-+--1---L I -~,-I ,,, -11t·H_-tl-+-+--_j_ __
. I 0
100.000 10.000 1.000 0.100 0.010 0.001
Project Name: AFTON WAY
Project No.: 10690.002
4 PARTICLE -SIZE
DISTRIBUTION
ASTM D 6913
PARTICLE -SIZE (mm)
Exploration No.: T-5 Sample No.: B-1
Depth (feet): 4.0-6.0 Soil Type : SC
Soil Identification: SC: CLAYEY SAND. Grayish-Brown
GR:SA:FI : (%) 0 : 85 : 15 Jun-I"!-
SIEVE T,5.81
'-
I GRAVEL
I COARSE I FINE
U.S. STANDARD SIEVE OPENING
3.0" 11/2" 3/4" 3/8"
100 -----,_ -~ -,-I
I
90
80 ---f-·-r-
I
70
I-60 ~--~-
::c C!)
jjj
~ 50 ' ------------
>-m a:: w 40 •------z I U:::
I-z 30 -f 1---
w --
0 a:: w c..
20 -~ ---
I 10
0 i
100.000 10.000
Project Name: AFTON WAY
Project No.: 10690.002 -
--,, I [ -j _) J
I SAND
I COARSE I MEDIUM FINE
U.S. STANDARD SIEVE NUMBER
#4 #8 #16 #30 #50 #100 #200
-
I
I ---... "-... N.,._ I ....__ I I ....,~ l
i-a.... ~ I -I
I
I
--~
----------------------------··· - ---------I
I
--t__ ___________
--------~ 1-------
--------I --~-
I I
I I
1.000 0.100
PARTICLE -SIZE (mm)
Exploration No.: T-6
Depth (feet): 0.0-6.0
i _.J
--
,--,-
C.. L _ L_
FINES
SILT I
HYDROMETER
-
-------
--·--·-----------------, __ ---------
I
---~--~-
0.010
Sample No.: B-1
Soil Type: s(Cl)
PARTICLE -SIZE tiJI Leighton
Soil Identification: s(Cl): SANDY LEAN CLAY, Yellowish-Brown DISTRIBUTION
ASTM D 6913 GR:SA:FI: (O/o) 1 : 15: 84
L t _
I
CLAY I
I
-------------
------
--
0.001
Jun-14
S/FVF T-6Fl1
I
I
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I
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~ 4.00 -------------+---------+----------I
~
(/)
(/) t 3.00 +--l-----------'!'....,..--------t---------1
Cl)
0.00 --------------------------
0 0.1 0.2 0.3
Horizontal Deformation (in.)
5.0 -.----.-------.----,----------.
4.0
c-<I) ~ 3.0
<I)
<I) .. ~ .. ..
u5 ... ... .......... -ca 2.0 Q) .c en
1.0
0.0 ~--------------!
0.0 1.0 2.0 3.0 4.0 5.0
Normal Stress (ksf)
Boring No. B-1 Normal Stress (kip/ft2) 1.000 2.000 4.000
Sample No. R-5 Peak Shear Stress (kip/ft2) e 1.270 • 1.943 A4.769
Depth (ft) 30-31 Shear Stress @ End of Test (ksf) O 1.236 D 1.311 f::.. 2.405
SamgleTt~: RING Deformation Rate (in,/min.) 0.0017 0.0017 0.0017
Soil Identification: Initial Sample Height (in.) 1.000 1.000 1.000
CL: LEAN CLAY'STONE', Olive Diameter (in.) 2.415 2.415 2.415
Initial Moisture Content(%) 10.16 10.16 10.16
strenath Par "' Dry Density (pcf) 111.6 114.6 120.5
C (psf) d> (0) Saturation (%) 53.7 58.3 68.8
Peak -143.0 50.2 Soil Height Before Shearing (in.) 0.9958 0.9845 0.9848
Ultimate 689.0 22.4 Final Moisture Content(%) 22.3 20.0 18.1
Project No.: 10690.002
Leighton DIRECT SHEAR TEST RESULTS
Consolidated Drained -ASTM D 3080 AFTON WAY
07-14
I
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I
I
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~ 2.00 -t-----,r----------t--t:--------t-----------t
6
ti)
ti) ~ 1.50 +-----.f'--------t---------+---------u5 ... (IJ i 1.00 ~.._____.,__ ____ __......,~--------+---------I en
0.00 -------------t---------t--------~
0 0.1 0.2 0.3
Horizontal Deformation (in.)
4.0 ..------.----.......-------,,.----,
3.0
,,,'
C
,,,,····'
"' c ,,'
"' ,,
"' ,,' ~ 2.0 ,
ii5 .... cu Cl) .c (f)
1.0
0.0 +----------------i
0.0 1.0 2.0 3.0 4.0
Normal Stress (ksf)
Boring No. B-1 Normal Stress (kip/ft2) 0.500 1.000 2.000
Sample No. R-2 Peak Shear Stress (kip/ft2) e 0.858 • 1.355 A 2.701
Depth {ft) 10-11 Shear Stress @ End of Test (ksf) O 0.538 D 0.852 t::.. 1.704
SamQleT¥~: RING Deformation Rate (in./min.) 0.0025 0.0025 0.0025
Soil Identification: Initial Sample Height (in.) 1.000 1.000 1.000
SC: CLAYEY SAND'STONE', Diameter (in.) 2.415 2.415 2.415
Pale Olive Initial Moisture Content (%) 8.19 8.19 8.19
h Par . ~-"' Dry Density (pcf) 113.1 115.3 114.5
C (psf) 1P (o) Saturation (%) 45.1 47.9 46.9
Peak 185.0 51 .2 Soil Height Before Shearing (in.) 0.9982 0.9942 0.9886
Ultimate 112.0 38.2 Final Moisture Content(%) 16.5 15.6 15.2
Project No.: 10690.002
Le ighton DIRECT SHEAR TEST RESULTS
Consolidated Drained -ASTM D 3080 AFTON WAY
07-14
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Appendix D
General Earthwork and Grading Specifications for Rough Grading
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LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
1.0 General
1.1
1.2
These General Earthwork and Grading Specifications are for the grading
and earthwork shown on the approved grading plan(s) and/or indicated in
the geotechnical report(s). These Specifications are a part of the
recommendations contained in the geotechnical report(s). In case of
conflict, the specific recommendations in the geotechnical report shall
supersede these more general Specifications. Observations of the
earthwork by the project Geotechnical Consultant during the course of
grading may result in new or revised recommendations that could
supersede these specifications or the recommendations in the
geotechnical report(s).
The Geotechnical Consultant of Record
Prior to commencement of work, the owner shall employ the Geotechnical
Consultant of Record (Geotechnical Consultant). The Geotechnical
Consultants shall be responsible for reviewing the approved geotechnical
report(s) and accepting the adequacy of the preliminary geotechnical
findings, conclusions, and recommendations prior to the commencement
of the grading.
Prior to commencement of grading, the Geotechnical Consultant shall
review the "work plan" prepared by the Earthwork Contractor (Contractor)
and schedule sufficient personnel to perform the appropriate level of
observation, mapping, and compaction testing.
During the grading and earthwork operations, the Geotechnical Consultant
shall observe, map, and document the subsurface exposures to verify the
geotechnical design assumptions. If the observed conditions are found to
be significantly different than the interpreted assumptions during the
design phase, the Geotechnical Consultant shall inform the owner,
recommend appropriate changes in design to accommodate the observed
conditions, and notify the review agency where required. Subsurface
areas to be geotechnically observed, mapped, elevations recorded, and/or
tested include natural ground after it has been cleared for receiving fill but
before fill is placed, bottoms of all "remedial removal" areas, all key
bottoms, and benches made on sloping ground to receive fill.
The Geotechnical Consultant shall observe the moisture-conditioning and
processing of the subgrade and fill materials and perform relative
compaction testing of fill to determine the attained level of compaction.
The Geotechnical Consultant shall provide the test results to the owner
and the Contractor on a routine and frequent basis.
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LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
1.3 The Earthwork Contractor
The Earthwork Contractor (Contractor) shall be qualified, experienced,
and knowledgeable in earthwork logistics, preparation and processing of
ground to receive fill, moisture-conditioning and processing of fill, and
compacting fill. The Contractor shall review and accept the plans,
geotechnical report(s), and these Specifications prior to commencement of
grading. The Contractor shall be solely responsible for performing the
grading in accordance with the plans and specifications.
The Contractor shall prepare and submit to the owner and the
Geotechnical Consultant a work plan that indicates the sequence of
earthwork grading, the number of "spreads" of work and the estimated
quantities of daily earthwork contemplated for the site prior to
commencement of grading. The Contractor shall inform the owner and
the Geotechnical Consultant of changes in work schedules and updates to
the work plan at least 24 hours in advance of such changes so that
appropriate observations and tests can be planned and accomplished.
The Contractor shall not assume that the Geotechnical Consultant is
aware of all grading operations.
The Contractor shall have the sole responsibility to provide adequate
equipment and methods to accomplish the earthwork in accordance with
the applicable grading codes and agency ordinances, these
Specifications, and the recommendations in the approved geotechnical
report(s) and grading plan(s). If, in the opinion of the Geotechnical
Consultant, unsatisfactory conditions, such as unsuitable soil, improper
moisture condition, inadequate compaction, insufficient buttress key size,
adverse weather, etc., are resulting in a quality of work less than required
in these specifications, the Geotechnical Consultant shall reject the work
and may recommend to the owner that construction be stopped until the
conditions are rectified.
2.0 Preparation of Areas to be Filled
2.1 Clearing and Grubbing
Vegetation, such as brush, grass, roots, and other deleterious material
shall be sufficiently removed and properly disposed of in a method
acceptable to the owner, governing agencies, and the Geotechnical
Consultant.
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LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
The Geotechnical Consultant shall evaluate the extent of these removals
depending on specific site conditions. Earth fill material shall not contain
more than 1 percent of organic materials (by volume). No fill lift shall
contain more than 5 percent of organic matter. Nesting of the organic
materials shall not be allowed.
If potentially hazardous materials are encountered, the Contractor shall
stop work in the affected area, and a hazardous material specialist shall
be informed immediately for proper evaluation and handling of these
materials prior to continuing to work in that area.
As presently defined by the State of California, most refined petroleum
products (gasoline, diesel fuel, motor oil, grease, coolant, etc.) have
chemical constituents that are considered to be hazardous waste. As
such, the indiscriminate dumping or spillage of these fluids onto the
ground may constitute a misdemeanor, punishable by fines and/or
imprisonment, and shall not be allowed.
2.2 Processing
2.3
Existing ground that has been declared satisfactory for support of fill by
the Geotechnical Consultant shall be scarified to a minimum depth of
6 inches. Existing ground that is not satisfactory shall be overexcavated
as specified in the following section. Scarification shall continue until soils
are broken down and free of large clay lumps or clods and the working
surface is reasonably uniform, flat, and free of uneven features that would
inhibit uniform compaction.
Overexcavation
In addition to removals and overexcavations recommended in the
approved geotechnical report(s) and the grading plan, soft, loose, dry,
saturated, spongy, organic-rich, highly fractured or otherwise unsuitable
ground shall be overexcavated to competent ground as evaluated by the
Geotechnical Consultant during grading.
2.4 Benching
Where fills are to be placed on ground with slopes steeper than 5: 1
(horizontal to vertical units), the ground shall be stepped or benched.
Please see the Standard Details for a graphic illustration. The lowest
bench or key shall be a minimum of 15 feet wide and at least 2 feet deep,
into competent material as evaluated by the Geotechnical Consultant.
Other benches shall be excavated a minimum height of 4 feet into
competent material or as otherwise recommended by the Geotechnical
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General Earthwork and Grading Specifications
2.5
Consultant. Fill placed on ground sloping flatter than 5:1 shall also be
benched or otherwise overexcavated to provide a flat subgrade for the fill.
Evaluation/Acceptance of Fill Areas
All areas to receive fill, including removal and processed areas, key
bottoms, and benches, shall be observed, mapped, elevations recorded,
and/or tested prior to being accepted by the Geotechnical Consultant as
suitable to receive fill. The Contractor shall obtain a written acceptance
from the Geotechnical Consultant prior to fill placement. A licensed
surveyor shall provide the survey control for determining elevations of
processed areas, keys, and benches.
3.0 Fill Material
3.1 General
Material to be used as fill shall be essentially free of organic matter and
other deleterious substances evaluated and accepted by the Geotechnical
Consultant prior to placement. Soils of poor quality, such as those with
unacceptable gradation, high expansion potential, or low strength shall be
placed in areas acceptable to the Geotechnical Consultant or mixed with
other soils to achieve satisfactory fill material.
3.2 Oversize
Oversize material defined as rock, or other irreducible material with a
maximum dimension greater than 8 inches, shall not be buried or placed
in fill unless location, materials, and placement methods are specifically
accepted by the Geotechnical Consultant. Placement operations shall be
such that nesting of oversized material does not occur and such that
oversize material is completely surrounded by compacted or densified fill.
Oversize material shall not be placed within 10 vertical feet of finish grade
or within 2 feet of future utilities or underground construction.
3.3 Import
If importing of fill material is required for grading, proposed import material
shall meet the requirements of Section 3.1. The potential import source
shall be given to the Geotechnical Consultant at least 48 hours (2 working
days) before importing begins so that its suitability can be determined and
appropriate tests performed.
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LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
4.0 Fill Placement and Compaction
4.1
4.2
4.3
4.4
Fill Layers
Approved fill material shall be placed in areas prepared to receive fill (per
Section 3.0) in near-horizontal layers not exceeding 8 inches in loose
thickness. The Geotechnical Consultant may accept thicker layers if
testing indicates the grading procedures can adequately compact the
thicker layers. Each layer shall be spread evenly and mixed thoroughly to
attain relative uniformity of material and moisture throughout.
Fill Moisture Conditioning
Fill soils shall be watered, dried back, blended, and/or mixed, as
necessary to attain a relatively uniform moisture content at or slightly over
optimum. Maximum density and optimum soil moisture content tests shall
be performed in accordance with the American Society of Testing and
Materials (ASTM Test Method D1557).
Compaction of Fill
After each layer has been moisture-conditioned, mixed, and evenly
spread, it shall be uniformly compacted to not less than 90 percent of
maximum dry density (ASTM Test Method D1557). Compaction
equipment shall be adequately sized and be either specifically designed
for soil compaction or of proven reliability to efficiently achieve the
specified level of compaction with uniformity.
Compaction of Fill Slopes
In addition to normal compaction procedures specified above, compaction
of slopes shall be accomplished by backrolling of slopes with sheepsfoot
rollers at increments of 3 to 4 feet in fill elevation, or by other methods
producing satisfactory results acceptable to the Geotechnical Consultant.
Upon completion of grading, relative .compaction of the fill, out to the slope
face, shall be at least 90 percent of maximum density per ASTM Test
Method D1557.
4.5 Compaction Testing
Field-tests for moisture content and relative compaction of the fill soils
shall be performed by the Geotechnical Consultant. Location and
frequency of tests shall be at the Consultant's discretion based on field
conditions encountered. Compaction test locations will not necessarily be
selected on a random basis. Test locations shall be selected to verify
adequacy of compaction levels in areas that are judged to be prone to
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LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
5.0
4.6
inadequate compaction (such as close to slope faces and at the
fill/bedrock benches).
Frequency of Compaction Testing
Tests shall be taken at intervals not exceeding 2 feet in vertical rise and/or
1,000 cubic yards of compacted fill soils embankment. In addition, as a
guideline, at least one test shall be taken on slope faces for each
5,000 square feet of slope face and/or each 10 feet of vertical height of
slope. The Contractor shall assure that fill construction is such that the
testing schedule can be accomplished by the Geotechnical Consultant.
The Contractor shall stop or slow down the earthwork construction if these
minimum standards are not met.
4.7 Compaction Test Locations
The Geotechnical Consultant shall document the approximate elevation
and horizontal coordinates of each test location. The Contractor shall
coordinate with the project surveyor to assure that sufficient grade stakes
are established so that the Geotechnical Consultant can determine the
test locations with sufficient accuracy. At a minimum, two grade stakes
within a horizontal distance of 100 feet and vertically less than 5 feet apart
from potential test locations shall be provided.
Subdrain Installation
Subdrain systems shall be installed in accordance with the approved
geotechnical report(s), the grading plan, and the Standard Details. The
Geotechnical Consultant may recommend additional subdrains and/or changes in
subdrain extent, location, grade, or material depending on conditions
encountered during grading. All subdrains shall be surveyed by a land
surveyor/civil engineer for line and grade after installation and prior to burial.
Sufficient time should be allowed by the Contractor for these surveys.
6.0 Excavation
Excavations, as well as over-excavation for remedial purposes, shall be
evaluated by the Geotechnical Consultant during grading. Remedial removal
depths shown on geotechnical plans are estimates only. The actual extent of
removal shall be determined by the Geotechnical Consultant based on the field
evaluation of exposed conditions during grading. Where fill-over-cut slopes are
to be graded, the cut portion of the slope shall be made, evaluated, and accepted
by the Geotechnical Consultant prior to placement of materials for construction of
the fill portion of the slope, unless otherwise recommended by the Geotechnical
Consultant.
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LEIGHTON AND ASSOCIATES, INC.
General Earthwork and Grading Specifications
7.0 Trench Backfills
7.1
7.2
7.3
Safety
The Contractor shall follow all OSHA and Cal/OSHA requirements for
safety of trench excavations.
Bedding and Backfill
All bedding and backfill of utility trenches shall be performed in
accordance with the applicable provisions of Standard Specifications of
Public Works Construction. Bedding material shall have a Sand
Equivalent greater than 30 (SE>30). The bedding shall be placed to 1 foot
over the top of the conduit and densified. Backfill shall be placed and
densified to a minimum of 90 percent of relative compaction from 1 foot
above the top of the conduit to the surface.
The Geotechnical Consultant shall test the trench backfill for relative
compaction. At least one test should be made for every 300 feet of trench
and 2 feet of fill.
Lift Thickness
Lift thickness of trench backfill shall not exceed those allowed in the
Standard Specifications of Public Works Construction unless the
Contractor can demonstrate to the Geotechnical Consultant that the fill lift
can be compacted to the minimum relative compaction by his alternative
equipment and method.
7.4 Observation and Testing
The densification of the bedding around the conduits shall be observed by
the Geotechnical Consultant.
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FILL SLOPE
FILL-OVER-cuT SLOPE
CUT-OVER-FILL SLOPE
PROJECTED PLANE
1 TO 1 MAXIMUM
FROM TOE OF SLOPE
TO APPROVED GROUND
KEYING AND BENCHING
---••---o~--~~---~ --~---------------
REMOVE
UNSUITABLE
MATERIAL
BENCHING SHALL BE DONE WHEN SLOPE'S
ANGLE IS EQUAL TO OR GREATER THAN 5: 1.
MINIMUM BENCH HEIGHT SHALL BE 4 FEET
AND MINIMUM FILL WIDTH SHALL BE 9 FEET.
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL A
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·· 1
OVERSIZE WINDROW
• OVERSIZE ROCK IS LARGER THAN
8 INCHES IN LARGEST DIMENSION.
• EXCAVATE A TRENCH IN THE COMPACTED
FILL DEEP ENOUGH TO BURY All THE
ROCK.
" BACKFILL WITH GRANULAR SOiL JETTED
OR FLOODED iN PLACE TO fill ALL THE
VOIDS.
• DO NOT BURY ROCK WfTHIN 10 FEET OF
FINISH GRADE.
• WfNDROW OF BURIED ROCK SHALL BE
PARALLEL TO THE FINISHED SLOPE.
FINISH GRADE
. . :------------------~----------
GRANULAR MATERIAL TO BE
OENSIFIED lN PLACE BY
FLOODING OR ..,'(TT!NG.
DETAIL
JETTED OR FLOODED -----
GRANULAR MATERIAL
TYPICAL PROFILE ALONG WINDROW
OVERSIZE ROCK
DISPOSAL
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL B
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BENCHING
SUBDRAfN DETAIL
SUBDRAIN
TRENCH
----REMOVE
UNSUITABLE
MATERIAL
SEE DETAll BELOW
FILTER FABRIC
(MIRAFI 140N OR APPROVED
EQUIVALENT)•
COLLECTOR PIPE SHALL
BE MINIMUM 6" DIAMETER
SCHEDULE 40 PVC PERFORATED
PIPE SEE STANDARD DETAIL D
FOR PIPE SPEClf'ICA TIONS
DESIGN FINISH) -~ GRADE /::::::=::\!
_ --·-·-·-·-·-·-·-·-·-----10' MIN Fil TER F ASRIC .• :::::::::::::::aACKFILL (MIRAfl 140N OR APPROVED
--.• ----~=:~~~~ACTE0 0 FtL°L=}.= =:=:=:====----EQUIVALENT)
:::t:::::::~::·--_.-. . '-;;_. • : • ' ' • :_ • • ·. . ----CAL TRANS CLASS 2 PERMEABLE
.-.·.---.·.·-·--• '• • '• • • • ' '· • • ' •. 0 • '•, OR /12 ROCK (9FT"3/FT) WRAPP-0
I I • : • • • . • • . • . • IN FILTER F ABR1C t.
I---' 20· MIN. 5' MIN. I PERF'ORA TEO -
· • • · 6" 0 MlN. PIPE NONPERFORATED 6" 0 MIN.
DETAIL Of CANYON SUBDRAIN OUTLET
CANYON SUBDRAINS GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL C
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CUT-FILL TRANSITION LOT OVEREXCA \/ATION
TRANSITION LOT FILLS
REMOVE
UNSUITABLE
::;ROUND\_ _ _,.-
_,,-
OVEREXCAVATE
AND RECOMPACT
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL E
!:'MIN.<:<
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RETAINING WALL
SOIL BACKFILL. COMPACTED TO
90 PERCENT RELATIVE COMPACTION
8ASEO ON ASTM 01557
~:~:~:~:~:~:-:~:~:~:~:~:~:~ ; ;: . ~~~ ~:~;:~:~:~--. -·--. -
-.......... "" ....... -~ ... -+ -.. -... -_ ... _ ... _-,.-.. -_ ... _ ... __
l I • 3j1 :~~~~~~~:-=~-
6" MIN • -:-::-:-:-:-:-:-~-
WALL WA TERPROOFINC ----I .. OVERLA.P I:=:=:=:=:=::=·· FILTER FABRIC ENVELOPE
PER ARCHITECT'S ~ 0 • <>< -:-:-:----• (MIRAFI 140N OR APPROVED
SPECIFICATIONS '-l ., o • 0 1 :-:-:-:-: EOUIVALENT)0
" 0 ---------
" • • Q (> ::.. =:=:=:
FINISH GRADE
1~ 1,' :'N·.-1v3/4" TO 1-1/2" CLEAN GRAVEL
I· . ~l======
0 • • • S ::::=::_ -----4 * (MIN.) DIAMETER PERFORA TEO
t O ,-:-;{< PVC PIPE (SCHEDULE 40 OR
. &(• o0
.,: :::=:.::~ EOU!VALENT) WITH PERFORATIONS
0 0 :-:-:-:-ORIENTED DOWN AS DEPICTED I ,; • o ,~:::::::: MINl~UM 1 PERCENT GRADIENT
~o O .-:-:-:-: TO :;:;U!TABLE OUTLET
L: -· ::·:-=· 3" MIN.
COMPETENT BEDROCK OR MATERIAL
AS EVALUATED BY THE GEOTECHNICAL
CONSULTANT
NOTE: UPON REVIEW BY THE GEOTECHNiCAl. CONSULTANT,
COMPOS! TE DRAINAGE PRODUCTS SUCH AS MIRADRAIN OR
J-ORAlN MAY BE USED AS AN ALTERNATIVE TO GRAVEL OR
CLASS 2 PERMEABLE MATERIAL INSTALLATION SHOULD 8E
PERFORMED IN ACCORDANCE WITH MANUFACTURER'S
SPEClflCA TIONS.
RETAINING WALL
DRAINAGE
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL F
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ACTIVE
ZONE
I
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·--~----····---·-···-------·---·-------·------·--------
FILTER FABRIC
---..... ~~m /---.-.----
___ /i1;, I REINFORCED!
1
RETAINED! ,'
;'::;-.,: ZONE I ZONE I
{ik[:; ,' ,.____ _ _..,. .• ,,-.;,-,;·: . I --,it~t /
~~~~~~-~~-r.,02~--------------1
1
/~'=RFABRIC --------ra/a
D~:~~LF~• :Y'..'~·::.::·~WALL SUBDRAIN ~~ \
MIN 6" BELOW WALL REAR SUBDRAIN:
BACKDRAIN
T070% OF
WALL HEIGHT
MIN 12" BEHIND UNITS 4" (MIN) DIAMETER PERFORATED PVC PIPE I FOUNDATION SOILS! (SCHEDULE 40 OR EQUIVALENT) WITH
PERFORATIONS DOWN. SURROUNDED BY
NOTES:
1) MATERIAL GRADATION AND PLASTICITY
REINFORCED ZONE·
SIEVE SIZE
1 INCH
N0.4
N0.40
NO. 200
%PASSING
100
20-100
0-60
0-35
FOR WALL HEIGHT< 10 FEET, PLASTICITY INDEX< 20
FOR WALL HEIGHT 10 TO 20 FEET, PLASTICITY INDEX< 10
FOR TIERED WALLS, USE COMBINED WALL HEIGHTS
1 CU. FT/FT OF 3/4" GRAVEL WRAPPED IN
FILTER FABRIC (MIRAFI 140N OR EQUIVALENT)
OUTLET SUBDRAJNS EVERY 100 FEET, OR CLOSER,
BY TIGHTLINE TO SUITABLE PROTECTED OUTLET
GRAVEL DRAINAGE FILL-
SIEVE SIZE % PASSING
1 INCH 100
3/4 INCH 75-100
NO. 4 0-60
NO. 40 0-50
NO. 200 0-5
WALL DESIGNER TO REQUEST SITE-SPECIFIC CRITERIA FOR WALL HEIGHT> 20 FEET
2) CONTRACTOR TO USE SOILS WITHIN THE RETAINED AND REINFORCED ZONES THAT MEET THE STRENGTH REQUIREMENTS OF WALL DESIGN.
3) GEOGRID REINFORCEMENT TO BE DESIGNED BY WALL DESIGNER CONSIDERING INTERNAL, EXTERNAL, AND COMPOUND STABILITY.
3) GEOGRID TO BE PRETENSIONED DURING INSTALLATION.
4) IMPROVEMENTS WITHIN THE ACTIVE ZONE ARE SUSCEPTIBLE TO POST-CONSTRUCTION SETTLEMENT. ANGLE C<-45+¢/2, WHERE¢ IS THE
FRICTION ANGLE OF THE MATERIAL IN THE RETAINED ZONE.
5) BACKDRAIN SHOULD CONSIST OF J-DRAIN 302 (OR EQUIVALENT) OR 6-INCH THICK DRAINAGE FILL WRAPPED IN FILTER FABRIC. PERCENT
COVERAGE OF BACKDRAIN TO BE PER GEOTECHNICAL REVIEW.
SEGMENTAL
RETAINING WALLS
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL G
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Appendix E
Geotechnical Engineering Report
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Important Information about Your
Geotechnical Engineering Report
Subswtace problems are a principal cause of construction delays. cost overruns, claims. and disputes.
While you cannot eliminate all such risks. you can manage them. Tf1e following mformat10n is provided to help.
Geetecllnlcal services Are Performed I•
Specific Purpo81S, Persons, and Projects
Geotechnical engineers structure their services to meet the specific needs of
their clients. A geotechnical engineering study conducted for a civil engi-
neer may not fulfill the needs of a construction contractor or even another
civil engineer. Because each geotechnical engineering study is unique, each
geotechnical engineering report is unfque, preparPrl solely for the client. No
one except you should rely on your geotechnica1 engineering report without
first conferring with the geotechnical engineer who prepared it And no one
-,wt even you-should apply the report for any purpose or project
except the one originally contemplated.
Read tlll Full Rlll)Pt
Serious problems have occurred because those reiy1ng on a geotechnical
engineering report did not read it all. Do not rely on an executive summary.
Do not read selected elements only.
A Gaotecllnical Engineering llelDPt Is Baell on A Dnique let ol PrO.iect-Specilic Factors
Geotechnical engineers consider a number of unique, project-specific fac-
tors when establishing the scope of a study. Typical factors include: the
client's goals, objectives, and risk management preferences: the general
nature of the structure involved, its size, and configuration; the location of
the structure on tl1e site; and other planned or existing site improvements,
such as access roads, parking lots, and underground utilities. Unless the
geotechnical engineer who conducted the study specifically indicates
otherwise, do not rely on a geotechnical engineering report that was:
• not prepared for you,
• not prepared for your project,
• not prepared for ihe specific site explored, or
• completed before important project changes were made.
Typical changes that can erode the reliability of an existing geotechnical
engineering report include those that affect:
• the function of the proposed structure. as when it's changed from a
parking garage to an office building, or from a light industrial plant
to a refrigerated warehouse,
• elevation, configuration, location, orientation, or weight of the
proposed structure,
• composition of the design team, or
• project ownership.
As a general rule, always inform your geotechnical engineer of project
changes-even minor ones-and requesi an assessment of their impact.
Geotecfmical engineers cannot accept responsibility or liability tor problems
that occur because theli" reports do not consider developments of which
they were not informed
SUlls .. ace COllllilions CIII Change
A geo!echnica! engineering report is based on conditions that existed at t11e
time the study was performed. Do not rely on a geotechnical engineering
report whose adequacy may have been affected by: the passage of time; by
man-made events, such as construction on or adjacent to the site; or by
natural events, such as floods, earthquakes, or groundwater fluctuations.
Always contact the geotechnical engineer before applying the report to
determine if it is still reliable. A minor amount of additional testing or
analysis could prevent major problems.
Most Geotechnical findings Are Proressional Opinions
Site exploration identifies subsurface conditions only at those points where
subsurface tests are conducted or samples are taken. Geotechnical engi-
neers review field and laboratory data and then apply their professional
judgment to render an opinion about subsurface conditions throughout the
site. Actual subsurface conditions may differ-sometimes significantly-
from those indicated in your report. Retaining the geotechnical engineer
who developed your report to provide construction observation is the
most effective method of managing the risks associated with unanticipated
conditions.
A Report's Recommendations Are Nat final
Do not overrely on the construction recommendations included in your
report. Those recommendations are not final, because geotechnical engi-
neers develop them principally from judgment and opinion. Geotechnical
engineers can finalize their recommendations only by observing actual
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subsurface conditions revealed during construction. The geotechnical
engineer who developed your report cannot assume responsibility or
liability for the report's recommendations if that engineer does not perform
construction observation.
A Geotechnlcal Engineering Report Is Subject to
Mislnterpretauon
Other design team members' misinterpretation of geotechnical engineering
reports has resulted in costly problems. Lower that risk by having your geo-
technical engineer confer with appropriate members of the design team after
submitting the report. Also retain your geotechnical engineer to review perti-
nent elements of the design team's plans and specifications. Contractors can
also misinterpret a geotechnical engineering report. Reduce that risk by
having your geotechnical engineer participate in prebid and preconstruction
conferences, and by providing construction observation.
Do Not Redraw the Engineer's Logs
Geotechnical engineers prepare final boring and testing logs based upon
their interpretation of field logs and iaboratory data. To prevent errors or
omissions, the logs included in a geotechnical engineering report sl1ould
never be redrawn for inclusion in architectural or other design drawings.
Only photographic or electronic reproduction is acceptable, but recognize
that separating logs from the report can elevate risk.
Give COIIIPactors a Complete Report and
Guidance
Some owners and design professionals mistakenly believe they can make
contractors liable for unanticipated subsurface conditions by limiting what
they provide for bid preparation. To help prevent costly problems, give con-
tractors the complete geotechnical engineering report, but preface it with a
clearly written letter of transmittal. In that letter, advise contractors tl1at the
report was not prepared for purposes of bid development and that the
report's accuracy is limited; encourage them to confer with the geotechnical
engineer who prepared the report (a modest fee may be required) and/or to
conduct additional study to obtain the specific types of information they
need or prefer. A prebid conference can also be valuable. Be sure contrac-
tors have sufficient time to perform additional study. Only then might you
be in a position to give contractors the best information available to you,
while requiring them to at least share some of the financial responsibilities
stemming from unanticipated conditions.
Read Responsibility Provisions Closely
Some clients, design professionals, and contractors do not recognize that
geotechnical engineering is far less exact than other engineering disci-
plines. This lac!< of understanding has created unrealistic expectations that
have led to disappointments, claims, and disputes. To help reduce the risk
of such outcomes, geotechnical engineers commonly include a variety of
explanatory provisions in their reports. Sometimes labeled "limitations"
many of these provisions indicate where geotechnical engineers' responsi-
bilities begin and end, to help others recognize their own responsibilities
and risks. Read these provisions closely. Ask questions. Your geotechnical
engineer should respond fully and frankly.
Ga•nvlronmental Concerns Are Not Covered
The equipment, techniques, and personnel used to perform a geoenviron-
mental study differ significantly from those used to perform a geotechnical
study. For that reason, a geotechnical engineering report does not usually
relate any geoenvironmental findings, conclusions, or recommendations;
e.g., about the likelihood of encountering underground storage tanks or
regulated contaminants. Unanticipated environmental problems have led to
numerous project failures. If you have not yet obtained your own geoenvi-
ronmental information, as!< your geotechnical consultant for risk manage-
ment guidance. Do not rely on an environmental report prepared for
someone else.
Olltain Professional Assistance To Deal willl Mold
Diverse strategies can be applied during building design, construction,
operation, and maintenance to prevent significant amounts of mold from
growing on indoor surfaces. To be effective, all such strategies should be
devised for the express purpose of mold prevention, integrated into a com-
prehensive plan, and executed with diligent oversight by a professional
mold prevention consultant. Because just a small amount of water or
moisture can lead to the development of severe mold infestations, a num-
ber of mold prevention strategies focus on keeping building surfaces dry.
While groundwater, water infiltration, and similar issues may have been
addressed as part of the geotechnical engineering study whose findings
are conveyed in this report, the geotechnical engineer in charge of this
project is not a mold prevention consultant; none of the sendces per-
fanned in connection with the geoteclmical engineer's study
were designed or conducted for the purpose of mold preven-
tion. Proper implement.ation of the recommendations conveyed
in this report will not of itself be sufficient to prevent mold from
growing in or on the structure involved.
Rely on Y•r ASFE-Member Geotechnical Engineer for Additional Assistance
Membership in ASFE/The Geoprofessional Business Association exposes
geotechnical engineers to a wide array of risk management techniques that
can be of genuine benefit for everyone involved with a construction project.
Confer with your ASFE-member geotechnical engineer for more information.
ASFe THE GEOPROFESSIONAl
BUSINESS ASSOCIATION
8811 Colesville Road/Suite G106, Silver Spring, MD 20910
Telephone: 301/565 2733 Facsimile: 301/589-2017
e-mail: info@asfe.org www.asfe.org
Copyright 2004 by ASFE, Inc. Duplication, reproduction, or copying of this document, in whole or in part, by any means whatsoever, is strictly prohibited, except with ASFE's
specific written pennission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission of ASFE, and only tor
purposes of scholarly res1;arch or book review. Only members of ASFE may use /Iris document as a complement to or as an element of a geotechnica/ engineering report Any other
firm, individual, or other entity that so uses this document without being an ASFE member could lie committing negligent or intentional /fraudulent) misrepresentation.
IIGER01115.0MRP
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OUTLET PIPES
4" 0 NONPERFORATEO PIPE,
100' II/AX. 0.C. HORIZONTALLY,
30' MAX O.C. VERTICAll Y
15' MIN.
TRENCH
LOWEST SU80RAIN SHOULD
BE SITUATED AS LOW AS
POSSIBLE TO ALLOW
SUITABLE OUTLET
-----------~~~-~~--~-------~----~--~--'---ol!!lffll'r,'!ll~:~::::::::::::::::::::::::2% M!N. -::::::::::::;::=::::::::· --
C ,.. KEY WH)TH '
AS NOTED ON GRADING PLANS 1r MIN. OVERLAP-:::-1
FROM THE TOP HOG
RIN::; TIED EVERY
KEY DEPTH (15' MIN.)
(2' MIN)
6 f'EET
CAL TRANS CLASS !! ~
PERMEABLE OR /12
ROCK (3 rr3/FT)
WRAPPED IN FIL rm
rABRlC
I-CONNECTION FOR COLlECiOR
PIPE TO OUTLET PIP£
SUBDRAfN TRENCH DETAIL
SUSDRAIN INSTALLATION -subdroin collector pipe shall be installed with perforation down or.
unless otherwise designated by the geotechnicol consultant. Outlet pipes shoU be non-perforoted
pipe. The subdroin pipe shoH hove at leost 8 perfo•otions uniformly spaced per foot. Perforation
shall be 1/4" to 1/2ri if drill holes ore used. All subdroin pipes shalt hove o qradier\t of at
least 2% towards the outlet.
SUBORAIN PIPE -Subdroin pipe sholl be ASTM 02751, SDR 2.3.5 or ASTM 01527. Schedule 40, or
ASTM D.3034, SOR 23 5. Schedule 40 Po;yviny! Chloride Plastic (PVC) pipe.
All outlet pipe shall be placed in o trench no wider than twice the subdrain pipe.
BUTTRESS OR
REPLACEMENT
FILL SUBDRAINS
GENERAL EARTHWORK AND
GRADING SPECIFICATIONS
STANDARD DETAIL D