HomeMy WebLinkAboutCT 13-03; ROBERTSON RANCH- RANCHO COSTERA; AS GRADED COMPLETION OF GRADING LETTERS; 2016-08-09c-i- 13 -0
LGC Valley, Inc.
Geotechnical Consulting
August 9, 2016 Project No. 133023-07
Mr. Andrew Dewar
Shape!! Properties, Inc.
8383 Wilshire Boulevard, Suite 700
Beverly Hills, California 90211
Subject: As-Graded Completion Letter of Fine Grading, Building Pads 1 through 4, Multi-Family
Residential Development, Planning Areas PA-7 andPA-8, Robertson Ranch, Parcels 1
and 2 of Parcel Map 14-07, Carlsbad, California
Introduction
In accordance with your authorization, LGC Valley, Inc. (LGC) has been performing geotechnical
observation and testing services during the development of the Robertson Ranch West Village multi-family
residential and senior affordable apartments located within Planning Areas PA-7 and PA-8 of Robertson
Ranch in Carlsbad, California. This letter summarizes our geotechnical observation and testing services
during the fine-grading operations for the subject site. As of this date, the rough and fine-grading
operations are essentially complete for the subject building pads. The geotechnical conditions encountered
during the grading operations were generally as anticipated (LGC, 2015a and 2015c).
Summary of Grading Operations
The fine-grading operations for the subject building pads were performed between July 13 and
August 4, 2016 in accordance to the approved grading plan elevations by Alliance Land Planning &
Engineering, Inc. (Alliance, 2016b). Grading of the subject site consisted of reprocessing the upper portion of
the existing sheet-graded pad; moisture-conditioning of the existing fill soils; excavation of minor cuts; and
the placement of fills less than 4 feet deep to create the building pads and the associated parkways and slopes
for Building 1 through 4 of the Robertson Ranch West Village multi-family residential and senior affordable
apartment complex. The grading operations were performed by Heartland Grading under the geotechnical
observation and testing services of LGC Valley, Inc. Our field technician was on site on a part-time basis
during the grading operations while our field and project geologists were on-site on a periodic basis. Grading
of the subject lots include the following.
Site Preparation and Removals
Prior to the placement of additional fill, the area within the limits of the proposed grading was stripped of
surface vegetation and debris and these materials were disposed of off-site. The existing sheet-graded pad
of PA-8 was then reprocessed. The reprocessing included the scarification of the upper 12- to 18-inches
of the existing pad, moisture-conditioning with water trucks and sprinkler systems; and mixing the fill
with a D-6 Dozer and rubber-tired 824 Compactor. The reprocessing grading operations were performed
2420 Grand Avenue, Suite F2, 9 Vista • CA 92081 • (760) 599-7000 • Fax (760) 599-7007
in accordance with the recommendations of the project geotechnical report (LGC, 2015a and 2015c) and
geotechnical recommendations made during the course of grading.
Fill Placement and Compaction
After the completion of the reprocessing operations, the cut material within Planning Area PA-8 and
import fill from Planning Area PA-1 1 was placed as compacted fill. The import soils generally consisted
of the same type of sandy Santiago Formation soils that were present on the existing sheet-graded pad of
PA-8. The fill soil was generally spread in 4- to 8-inch loose lifts; moisture conditioned as needed to
attain a 2-percent over-optimum moisture content, and compacted. A maximum thickness of
approximately 4 feet of compacted fill was placed during the current site grading within Building Pads I
through 4 to achieve design pad grades.
Field density test results performed during the grading operations indicated that the fill soils were
compacted to at least 90 percent of the maximum dry density in accordance with ASTM Test Method
D1557. Compaction of the fill soils was achieved by use of heavy-duty construction equipment (including
rubber-tire an 824 Compactor and a 627 scraper). Areas of fill in Which field density tests indicated
compactions less than the recommended relative compaction, where the soils exhibited non-uniformity, or
had field moisture contents less than approximately 1- to 2-percent over the laboratory optimum moisture
content, were reworked. The reworked areas were then recompacted and re-tested until the recommended
minimum 90 percent relative compaction and the recommended optimum moisture content was achieved.
Field and Laboratory Testinji
Field density testing and observations were performed using the Nuclear-Gauge Method (ASTM Test
Methods D6938). The results and approximate locations of the field density tests will be summarized in
the final as-graded report for the project upon completion of the fine grading operations. The field density
testing was performed in general accordance with the applicable ASTM Standards, the current standard of
care in the industry, and the precision of the testing method itself. Variations in relative compaction
should be expected from the documented results.
Laboratory maximum dry density tests of representative on-site soils were performed in general
accordance with ASTM Test Method D1557. Finish grade laboratory testing (expansion potential, soluble
sulfate content, and corrosion testing) of representative finish grade soils were also performed. The test
results indicate the finish grade soils of Building 1 have a medium expansion potential (i.e. expansion
index of between 51 and 90) while the finish grade soils of Buildings 2 through 4 have a low expansion
potential (i.e. expansion index of between 21 and 50); were found to have a negligible soluble sulfate
content of 0.001%; and were found to be corrosive to very corrosive to metals (minimum resistivity of
710 ohms-cm and a chloride content of 260 ppm). The. maximum dry density, expansion potential, and
corrosion test results are presented in Appendix B.
En2ineerinj! Geology Summary
The geologic or geotechnical conditions encountered during the fine grading of the subject building pads were
essentially as anticipated. Ground water was not encountered or observed during the grading operations. A
comprehensive summary of the geologic conditions (including geologic units, geologic structure and faulting)
will be summarized in the final as-graded report for the project. However, most of these conditions are
discussed in the project update geotechnical report (LGC, 2015c) and were not anticipated to be any different
than those encountered during the current fine-grading operations. Based on our geotechnical' observations
and geologic mapping during the rough and fine grading operations for the Robertson Ranch project, no
Project No. 133023-07 Page 2 August 9, 2016
active faults or evidence of active faulting was encountered.
Conclusions and Recommendations
The fine grading operations for the building pads of Buildings I through 4 of the Robertson Ranch West
Village multi-family residential and senior affordable apartment complex were performed in general
accordance with the project geotechnical reports, geotechnical recommendations made during the fine
grading, and the City of Carlsbad requirements. It is our professional opinion that the subject building pads
are suitable for their intended use provided the recommendations included in the project geotechnical reports
and other geotechnical recommendations previously issued (Appendix A) are incorporated into the design and
construction phases of site development. The following is a summary of our conclusions:
Geotechnical conditions encountered during the fine grading were generally as anticipated.
Site preparation and reprocessing were geotechnically observed.
Fill soils were derived from soils within Robertson Ranch Planning Areas PA-8 and PA- 11. Field density
testing indicated that the fill soils were placed and compacted to at least 90 percent relative compaction
(based on ASTM Test Method Dl 557) and at least I - to 2-percent over the optimum moisture content in
accordance with the project geotechnical recommendations.
The expansion potential of representative finish grade soils of the building pads was tested and found to
have a low to medium expansion potential. It should be noted that the soils assumed to be representative
of the finish grade soils on the building pads of Buildings 1 through 17 in our Update Geotechnical
Report (LGC, 2015c) were thought to be in the very low to low expansion potential range. However,
foundation design parameters were provided for very low to low and medium expansive soils. Review of
the structural foundation plans for Building 1/Robertson Ranch Senior Affordable Apartments (Patel
Burica & Associates, Inc., 2016) indicates that the building foundation was designed for to medium
expansive soils.
The fill soils within the building pads of Buildings 1 through 4 was placed at optimum moisture contents
of at least 120 percent needed to satisfy the building foundation subgrade soils presaturation
recommendations (LGC, 2015b). Provided that the near-surface soils on the building pads are not allowed
to dry-out, the presaturation requirement has been met. We do, however, recommend that the foundation
excavations be thoroughly wetted prior to the placement of the foundation concrete.
The potential for soluble sulfate attack on concrete in contact with finish grade soils is considered
negligible based on ACT criteria and are considered corrosive to very corrosive to ferrous metals.
No evidence of active faulting was encountered during site rough and fine grading.
Ground water was not encountered or observed during the grading operations.
Project No. 133023-07 Page 3 August 9, 2016
LGC Valley, Inc.
Limitations
The presence of our field representative at the site was intended to provide the owner with professional
advice, opinions, and recommendations based on observations of the contractor's work. Although the
observations did not reveal obvious deficiencies or deviations from project specifications, we do not
guarantee the contractor's work, nor do our services relieve the contractor or his subcontractor's work, nor
do our services relieve the contractor or his subcontractors of their responsibility if defects are subsequently
discovered in their work. Our responsibilities did not include any supervision or direction of the actual
work procedures of the contractor, his personnel, or subcontractors. The conclusions in this report are
based on test results and observations of the grading and earthwork procedures used and represent our
engineering opinion as to the compliance of the results with the project specifications.
Closure
If you should have any questions, please do not hesitate to contact us. The undersigned can be reached at
(760) 599-7000.
Respectfully submitted,
GN.
Of N.1&12
CEFITIFIEC) a EM3INEE.lN3 * CIE ST *
tp FXP.Y3tf2D'
N o, Randall Wagner, CEO 1612
Senior Project Geologist
RKW/BIH
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Basil Hattar, GE 2734
Principal Engineer
Distribution: (1)
(1)
(1)
(1)
(6)
(1)
Addressee (via e-mail)
MKG Consulting, Inc., Attention Mr. Tim Leonard (via e-mail)
Alliance LP&E, Inc. Attention Ms. Elizabeth Shoemaker (via e-mail)
TB Penick & Sons, Inc. Attention Mr. Dan Curley (via e-mail)
TB Penick & Sons, Inc., Attention Mr. Frank Bruni (Hard Copies)
TB Penick & Sons, Inc., Attention Mr. Frank Bruni (via e-mail)
Project No. 133023-07 Page 4 August 9, 2016
A PPENDJX A
References
Alliance Land Planning & Engineering, Inc., 2016, Grading Plans for Robertson Ranch, Multi-Family
Sites, PA7, 8 Parcels 1, 2, PM 14-07, City of Carlsbad, California, Project No. MS 14-07,
Drawing No. 480-3E, dated May 20, 2016.
Alliance Land Planning & Engineering, Inc., 2016a, Private (Onsite) Sewer and Water System For:
Robertson Ranch West Village, City of Carlsbad, California, Project No. MS 14-07, Drawing
No. 480-3F, dated June 16, 2016.
Alliance Land Planning & Engineering, Inc., 2016b, Grading Plans for Robertson Ranch, Multi-Family
Sites, PA7, 8 Parcels 1, 2, PM 14-07, City of Carlsbad, California, Project No. MS 14-07,
Drawing No. 480-3E, Delta I dated July 12, 2016.
Carlsbad, City of, 2012, Engineering Standards, Volume 1 - General Design Standards, Carlsbad,
California, 2004 Edition, revised November 21, 2012.
LGC Valley, Inc., 2014, Geotechnical and Environmental Recommendations for Robertson Ranch
West, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated
April 29, 2014.
LGC Valley, Inc., 2014a, Clarification of Grading Recommendations for Planning Areas PA-7, PA-8
and PA-11, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project
Number 133023-03, dated October 1, 2014.
LGC Valley, Inc. 2014b, Addendum Remedial Grading Recommendations Concerning
Overexcavation of the Apartment Building Pads, Robertson Ranch PA-8, Carlsbad Tract No.
13-03, Carlsbad, California, Project No. 133023-03, dated October 20, 2014.
LGC Valley, Inc. 2014c, Addendum Remedial Grading Recommendations Concerning
Overexcavation of the Apartment Building Pads, Buildings 3, 5 through 7, 10, 11, and 14,
Robertson Ranch PA-8, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-
03, dated October 27, 2014.
LGC Valley, Inc. 2014d, Settlement Monument Recommendations for Robertson Ranch PA-7 and
PA-8, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-03, dated
November 13, 2014.
LGC Valley, Inc. 2015, Preliminary Foundation Design for the Proposed Multi-Family Residential
Development, Robertson Ranch Planning Areas PA-7 and PA-8, 4980 El Camino Real,
Carlsbad, California, Project No. 133023-07, dated April 15, 2015.
LGC Valley, Inc., 2015a, As-Graded Report of Mass-Grading, Planning Areas PA-7 and PA-8,
Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, California, Project
133023-03, dated August 7, 2015.
Project No. 133023-07 Page A-i August 9, 2016
References (continued)
LGC Valley, Inc. 2015b, Preliminary Pavement Design, Robertson Ranch Planning Areas PA-7 and
PA-8, Carlsbad Tract No. 13-03, 4980 El Camino Real, Carlsbad, California, Project No.
133023-07, dated September 15, 2015.
LGC Valley, Inc. 2015c, Update Geotechnical Report, Proposed Multi-Family Residential
Development, Robertson Ranch Planning Areas PA-7 and PA-8, Carlsbad, California, Project
No. 133023-07, dated December 15, 2015.
LGC Valley, Inc. 2016, Geotechnical Foundation Plan Review for The Robertson Ranch West
Village Senior Affordable Apartments within Planning Area 8 (PA-8), Robertson Ranch,
Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-07, dated February 29,
2016.
LGC Valley, Inc. 2016a, Geotechnical Foundation Plan Review for The Robertson Ranch West
Village Recreation Building within Planning Area 8 (PA-8), Robertson Ranch, Carlsbad
Tract No. 13-03, Carlsbad, California, Project No. 133023-07, dated February 29, 2016.
LGC Valley, Inc. 2016b, Geotechnical Foundation Plan Review for The Robertson Ranch West
Village Market Rate Tuck-Under Apartments within Planning Areas 7 and 8 (PA-7 and PA-
8), Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-07,
dated March 21, 2016.
LGC Valley, Inc. 2016c, As-Graded Completion Letter of Additional Rough-Grading, Planning
Areas PA-7 and PA-8, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California,
California, Project No. 133023-07, dated May 19, 2016.
LGC Valley, Inc. 2016d, Updated Retaining Wall Design Parameters for the Proposed Multi-Family
Residential Development, Robertson Ranch Planning Areas PA-7 and PA-8, Carlsbad,
California, Project No. 133023-07, dated June 10, 2016.
Patel Burica & Associates, Inc., 2016, Robertson Ranch West Village Senior Affordable Apartments,
Foundation Plans, Details, and General Notes, 2nd Building Department Submittal, Carlsbad,
California, Project Number 1054A0, 27 Sheets, dated January 11, 2016.
Patel Burica & Associates, Inc., 2016a, Robertson Ranch West Village Recreation Building,
Foundation Plans, Details, and General Notes, 3 d Building Department Submittal, Carlsbad,
California. Project Number 1063A0, dated February 29, 2016.
Patel Burica & Associates, Inc., 2016b, Robertson Ranch West Village Market Rate Tuck-Under
Apartments, Foundation Plans, Details, and General Notes, 3rd Building Department
Submittal, Carlsbad, California. Project Number 1063A0, dated March 21, 2016
Project No. 133023-07 Page A-2 August 9, 2016
APPENDIX B
Laboratory Test Results
Maximum Dry Density Tests: The maximum dry density and optimum moisture content of typical materials
were determined in accordance with ASTM Test Method D1557. The results of these tests are presented in
the table below.
Sample
Number Sample Description
Maximum
Dry Density
(pci)
Optimum
Moisture
Content (%)
4 Dark gray brown clayey fine SAND 123.5 11.0
5 Medium brown f-rn SAND 124.5 11.0
9 Pale gray silty f-rn SAND 127.5 10.5
10 Medium brown clayey SAND 128.0 10.0
11 Light brown clayey SAND 122.0 12.5
13 Pale brown fine sandy CLAY to clayey SAND 125.5 11.0
Expansion Index Tests: The expansion potential of selected materials was determined in accordance with
AST D4829 and evaluated by the Expansion Index Test, U.B.C. Standard No. 18-I-B. The results of these
tests are presented in the table below:
Representative Building Pad Expansion Index Expansion Potential
Building 1 60 Medium
Buildings 2 through 4 43 Low
Project No. 133023-07 Page B-i August 9, 2016
Laboratory Test Results (continued)
Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard geochemical
methods (Caltrans 4177). The test results are presented in the table below:
Representative Building Pad Sulfate Content (% by Weight) Potential Degree of
Sulfate Attack*
Building 1 0.001% Negligible
Buildings 2 through 4 0.001% Negligible
* ACI 318R-08 Table 4.3.1
Chloride Content: Chloride content was tested in accordance with Caltrans Test Method (CTM) 422. The
results are presented below:
Representative Building Pad Chloride Content, ppm
Buildings I through 4 260
Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in general
accordance with CTM 643 and standard geochemical methods. The electrical resistivity of a soil is a measure
of its resistance to the flow of electrical current. As results of soil's resistivity decreases corrosivity increases.
The results are presented in the table below:
Representative Building Pad pH Minimum Resistivity (ohms-cm)
Buildings 1 through 4 7.96 710
Project No. 133023-07 Page B-2 August 9, 2016
LGC Valley, Inc.
Geotechnical Consulting
June 6, 2016 Project No. 133023-06
Mr. Greg Deacon
Toll Bros., Inc.
725 W. Town and Country Road, Suite 200
Orange, California 92868
Subject: As-Graded Completion Letter, Robertson Ranch Community Center, Planning Area PA-
4, Robertson Ranch, Carlsbad Tract No. 13-03, 4980 El Camino Real, Carlsbad,
California
Introduction
In accordance with your authorization, LGC Valley, Inc. (LGC) has been performing geotechnical
observation and testing services during the development of the Robertson Ranch/Rancho Costera project
located in Carlsbad, California. This letter summarizes our geotechnical observation and testing services
during the rough and fine grading operations for the Robertson Ranch Community Center, Planning Area
PA-4, located in Carlsbad, California. The rough, fine, and precise grading operations of PA-4 included the
remedial grading and placement of fill creating the sheet-graded pad; excavation of a storm water detention
basin; overexcavation of the cut portion of the proposed recreation center and pool; placement of fill in the
overexcavations; the backfill of the temporary storm water detention basin, and the precise grading creating
the building pads and finish grade for the community park site improvements on the site. As of this date,
the rough, fine, and precise grading operations are essentially complete for the subject site. The
geotechnical conditions encountered during the grading operations were generally as anticipated.
Summary of GradinL' Operations
The rough grading operations for the Robertson Ranch Community Center were performed between October
2014 and January 2015. The rough grading operations included the removal of potentially compressible
topsoil and the placement of up to approximately 15 feet of fill on the lot creating a relatively level sheet-
graded pad at an approximate elevation of 129.5 to 131.5 feet (mean sea level). After the completion of
grading, a storm water retention basin was excavated within a portion of the site.
In May 2015, the proposed location of the recreation center building pad and pool was overexcavated to
eliminate the existing cut/fill transition condition within the proposed location of the building and pool. In
accordance with the project geotechnical recommendations (Appendix A), the cut portion of the building pad
was overexcavated a minimum of 5 feet below the proposed finish grade elevation while the pool was
overexcavated a minimum of 8 feet below the proposed finish grade elevation of the pool deck. At the same
time, the existing storm water detention basin was partially filled-in creating a smaller basin.
2420 Grand Avenue, Suite F2, • Vista • CA 92081 9 (760) 599-7000 • Fax (760) 599-7007
In November 2015, the finished grade elevation of the sheet-graded pad of both Planning Areas PA-4 and
PA-8 was raised two feet. The grading operations included scarification, moisture-conditioning, and
recompaction of the existing ground surface and the placement of 2 additional feet of fill. In late April 2016,
the smaller storm water detention basin was filled in with compacted fill and the site was precise graded. The
precise grading consisted of minor cuts on the order of 1-foot or less creating the community/clubhouse
building pad, cabana pads, pool deck, and associated improvements. Our field technician was on site on a
full-time basis during the grading operations while our field and project geologist were on-site on a periodic
basis.
Laboratory and Field Density Test Results
Laboratory maximum dry density tests of representative on-site soils were performed in general accordance
with ASTM Test Method Dl 557. Expansion potential and soluble sulfate content tests of representative finish
grade soils were also performed in accordance with Uniform Building Code (UBC) 18-2 and standard
geochemical methods, respectively. Expansion potential and soluble sulfate content tests indicate the
representative finish grade soils have a low expansion potential and a negligible soluble sulfate content based
on ACT criteria (ACT 318R-08 Table 4.3.1). Based on the corrosivity testing of representative finish grade
soils on the lots, the tested soil has a pH of 9.0; a chloride content of 20 ppm, and a minimum resistivity of
1,400 (ohms-cm). Based on these test results, the site is considered corrosive per Caltrans criteria. The
laboratory test results are presented in Appendix B.
Field density test results performed during the grading operations indicated that the fill soils were compacted
to at least 90 percent of the maximum dry density in accordance with ASTM Test Method D1557.
Compaction of the fill soils was achieved by use of heavy-duty construction equipment (including a rubber-
tire compactor, scrapers, and dozers). Field density testing and observations were performed using the
Nuclear-Gauge Method (ASTM Test Method D6938). The field density testing was performed in general
accordance with the applicable ASTM Standards, the current standard of care in the industry, and the
precision of the testing method itself. Variations in relative compaction should be expected from the
documented results. The field density test summary is presented in Appendix C.
Engineering Geology Summary
The geologic or geotechnical conditions encountered during the grading of the subject site were essentially as
anticipated. Ground water was not encountered or observed during the grading operations. Based on our
geotechnical observations and geologic mapping during the rough and fine grading operations for the
Robertson Ranch Sky Ranch project, no active faults or evidence of active faulting was encountered.
Conclusions and Recommendations
The rough and fine grading operations of Planning Area PA-4 were performed in general accordance with the
project geotechnical reports, geotechnical recommendations made during the fine grading operations, and the
City of Carlsbad requirements. It is our professional opinion that the subject site is suitable for the intended
use provided the recommendations included in the project geotechnical report (LGC, 2014 and 2015a) are
Project No. 133023-06 Page 2 June 6, 2016
incorporated into the design and construction phases of site development. The following is a summary of our
conclusions:
Geotechnical conditions encountered during the grading operations were generally as anticipated.
Site preparation and removals were geotechnically observed.
The cut/fill transition condition in the building pad and pool areas was mitigated by overexcavation of the
cut portion of the building pad a minimum of 5 feet below the proposed finish grade elevation while the
pool was overexcavated a minimum of 8 feet below the proposed finish grade elevation of the pool deck.
Compacted fill was then placed to the design finish grade.
Field density testing (Appendix C) indicated that the fill soils were placed and compacted to at least 90
percent relative compaction (based on ASTM Test Method D1557) and near-optimum moisture content in
accordance with the project recommendations.
The expansion potential of representative finish grade soils of the building pad was tested and found to
have a low expansion potential.
The potential for soluble sulfate attack on concrete in contact with finish grade soils is considered
negligible based on ACT criteria while the onsite soils are considered moderately corrosive to ferrous
metals.
No evidence of active faulting was encountered during site rough and fine grading.
Ground water was not encountered or observed during the grading operations.
Limitations
Our services were performed using the degree of care and skill ordinarily exercised, under similar
circumstances, by reputable engineers and geologists practicing in this or similar localities. No other
warranty, expressed or implied, is made as to the conclusions and professional advice included in this report.
The samples taken and submitted for laboratory testing, the observations made and the in-situ field testing
performed are believed representative of the entire project; however, soil and geologic conditions revealed by
excavation may be different than our preliminary findings. If this occurs, the changed conditions must be
evaluated by the project soils engineer and geologist and design(s) adjusted as required or alternate design(s)
recommended.
This report is issued with the understanding that it is the responsibility of the owner, or of his/her
representative, to ensure that the information and recommendations contained herein are brought to the
attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are
taken to see that the contractor and/or subcontractor properly implements the recommendations in the field.
The contractor and/or subcontractor should notify the owner if they consider any of the recommendations
presented herein to be unsafe.
Project No. 133023-06 Page 3 June 6, 2016
The findings of this report are valid as of the present date. However, changes in the conditions of a property
can and do occur with the passage of time, whether they be due to natural processes or the works of man on
this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether
they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be
invalidated wholly or partially by changes outside our control.
Closure
If you should have any questions, please do not hesitate to contact us. The undersigned can be reached at
(760) 599-7000.
Respectfully submitted,
LGC Valley, Inc.
icr ( t 12
TWIEO ICL ENGI?ERING J \* cioGIST 1*
\EXP3 18(
Randall Wagner, CEG 1612 \P CO
Senior Project Geologist
Attachments: Appendix A - References
Appendix B - Laboratory Testing Procedures and Test Results
Appendix C - Summary of Field Density Tests
Distribution: (1) Addressee (via e-mail)
(1) Kevin Brickley, Toll Brothers (via e-mail)
Project No. 133023-06 Page 4 June 6, 2016
AFPENDJXA
References
LGC Valley, Inc., 2014, Geotechnical and Environmental Recommendations for Robertson Ranch
West, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03, dated
April 29, 2014.
LGC Valley, Inc., 2015a, Geotechnical Review of the Proposed Recreation Center, Planning Area
PA-4, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, California, Project
No. 133023-06, dated March 30, 2015.
LGC Valley, Inc., 2015b, Geotechnical Foundation Plan Review for the Proposed Recreation Center,
Planning Area PA-4, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California,
Project No. 133023-06, dated July 29, 2015.
LGC Valley, Inc., 2015c, Clarification of Anticipated Settlements for the Proposed Pool within the
Proposed Recreation Center, Planning Area PA-4, Robertson Ranch, Carlsbad Tract No. 13-
03, Carlsbad, California, California, Project No. 133023-06, dated August 21, 2015, revised
August 25, 2015.
LGC Valley, Inc., 2016a, Geotechnical Foundation Plan Review and Response to City of Carlsbad
Plan Check Comments for the Proposed Recreation Center, Planning Area PA-4, Robertson
Ranch, Carlsbad Tract No. 13-03, Carlsbad, California, Project No. 133023-06, dated March
8, 2016.
LGC Valley, Inc., 2016b, Geotechnical Foundation Plan Review for the Proposed Recreation Center,
Planning Area PA-4, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad, California,
Project No. 133023-06, dated April 29, 2016.
O'Day Consultants, 2014, Grading Plans for Rancho Costera, Robertson Ranch West Village, Carlsbad
Tract No. 13-03, Drawing No. 480-3A, 44 Sheets, dated August 25, 2014.
Summer/Murphy & Partners, 2015, Robertson Ranch Recreation Center Plot Plan, 1 Sheet, dated
January 5, 2012.
Suncoast Post-Tension, 2015a, Post-Tension Foundation Calculations for Toll Brothers, Robertson
Ranch Recreation Center, Carlsbad, California. Project No. 15-6427, dated May 20, 2015.
Suncoast Post-Tension, 2015b, Post-Tension Plans and Details for the Robertson Ranch Recreation
Center, Carlsbad, California, Project No. 15-6427, Undated.
Project No. 133023-06 Page A-i June 6, 2016
APPENDIX B
Laboratory Testin2 Procedures and Test Results
Maximum Dry Density Tests: The maximum dry density and optimum moisture content of typical
materials were determined in accordance with ASTM Test Method D1557. The results of these tests are
presented in the table below.
Sample
N b Number Sample Description
Maximum
Dry Density
(pet)
Optimum
Moisture Content
(%)
1 Gray brown sandy CLAY 117.5 16.0
2 Greenish gray silty CLAY 102.0 21.5
3 Red brown sandy CLAY 118.0 13.5
4 Dark gray brown clayey fine SAND 123.5 11.0
5 Medium brown f-rn SAND 124.5 11.0
6 Light brown silty SAND 114.5 13.5
7 Olive gray clayey SILT 111.5 19.5
8 Pale gray silty fine SAND 115.5 14.5
9 Pale gray silty f-m SAND 127.5 10.5
10 Medium brown clayey SAND 128.0 10.0
11 Light brown clayey SAND 122.0 12.5
12 Pale brown fine sandy CLAY to clayey
SAND 124.0
.
12.0
13 Pale brown fine sandy CLAY to clayey
SAND 125.5
.
11.0
14 Light gray silty fine SAND 117.0 15.0
Project No. 133023-06 Page B-i June 6, 2016
Laboratory Testing Procedures and Test Results (continued)
Expansion Index Tests: The expansion potential of selected materials was evaluated by the Expansion
Index Test, U.B.C. Standard No. 18-I-13. Specimens are molded under a given compactive energy to
approximately the optimum moisture content and approximately 50 percent saturation or approximately
90 percent relative compaction. The prepared 1-inch thick by 4-inch diameter specimens are loaded to
an equivalent 144 psf surcharge and are inundated with tap water until volumetric equilibrium is
reached. The results of these tests are presented in the table below:
Location Sample Description Expansion
Index
Expansion
Potential
PA-4 Light gray silty SAND 27 Low
Soluble Sulfates: The soluble sulfate contents of selected samples were determined by standard
geochemical methods (Caltrans 417). The test results are presented in the table below:
Sulfate Content Potential Degree
Location Sample Description of Sulfate (% by Weight) Attack*
PA-4 Light gray silty SAND 0.011 Negligible
* Per ACT 318R-08 Table 4.3.1.
Chloride Content: Chloride content was tested in accordance with Caltrans Test Method (CTM)
422. The results are presented below:
Chloride Potential Degree
Location Sample Description Content (ppm) of Chloride
Attack*
PA-4 Light gray silty SAND 20 Negligible
* Extrapolation from California Test Method 532, Method for Estimating the Time to Corrosion of
Reinforced Concrete Substructures and previous experience
Project No. 133023-06 Page B-2 June 6, 2016
Laboratory Testin2 Procedures and Test Results (continued)
Minimum Resistivity and pH Tests: Minimum resistivity and pH tests were performed in general
accordance with CTM 643 and standard geochemical methods. The electrical resistivity of a soil is a
measure of its resistance to the flow of electrical current. As results of soil's resistivity decreases
corrosivity increases. The results are presented in the table below:
Location Sample Description
Minimum
Resistivity 11 Potential Degree of
(ohms-cm) Corrosivity*
PA-4 Light gray silty SAND 1,400 9.0 Moderately
Corrosive
* NACE Corrosion Basics
Project No. 133023-06 Page B-3 June 6, 2016
APPENDIX C
Summary of Field Density Test Results
Project No. 133023-06 Page C-] June 6, 2016
LGC Valley, Inc.
2420 Grand Avenue, Suite F2, Vista, California 92081
760-599-7000/ Fax 760-599-7007
APPENDIX C - SUMMARY OF FIELD DENSITY TESTS
Print Date: June 6, 2016
Project No. 133023-06
Client. Toll Brothers
Project Name: Robertson Ranch
Location: Carlsbad, CA
Reviewed by: RKW
rest#
Noiear
Gauge Test Date Test Location
.
Type Test of
Elevation Moisture (%) Dry Density (pct) Relative Compaction (%)
Comments Field Optimum Field Maximum Obtained Required
N 10/28/2014 PA-4 South Side 11 CF 100.0 12.9% 12.5% 112.1 122.0 92% 90%
N 11/6/2014 PA-4 South Side 9 CF 118.0 12.3% 10.5% 117.3 127.5 92% 90%
- - N 11/6/2014 PA-4 Southeast Side 9 CF 117.0 13.1% 10.5% 116.1 127.5 91% 90%
4 N 1/6/2015 PA-4 Southwest Side 11 CF 123.0 16.4% 12.5% 113.0 122.0 93% 90%
N 5/1/2015 PA-4 Building Pad Center 5 CF 127.0 11.0% 11.0% 113.0 124.5 91% 90%
- - N 5/1/2015 PA-4 Building Pad North Side 13 CF 128.0 12.7% 11.0% 113.8 125.5 91% 90%
N 5/1/2015 PA-4 Pool North Side 13 CF 127.0 12.9% 11.0% 114.0 125.5 91% 90%
N 5/1/2015 PA-4 Pool South Side 11 CF 125.0 13.1% 1 12.5%1 112.9 122.0 1 93% 90%
N 11/9/2015 PA-4 East Side 11 CF 130.0 8.3% 12.5% 109.7 122.0 90% 90%
10 N 11/9/2015 PA-4 West Side 4 CF 131.0 12.0% 11.0% 112.5 123.5 91% 90%
11 N 11/9/2015 PA-4 East Side 11 FG 131.5 8.3% 12.5% 109.7 122.0 90% 90%
12 N 11/9/2015 PA-4 West Side 4 FG 133.0 12.0% 11.0% 112.5 123.5 91% 90%
13 N 4/28/2016 PA-4 Building Pad East Side 11 CF 126.0 14.0% 12.5% 110.1 122.0 90% 90%
14 N 4/28/2016 PA-4 Pool Deck 11 CF 127.0 13.2% 12.5% 111.4 122.0 91% 90%
15 N 4/28/2016 PA-4 Pool East Side 4 CF 129.0 12.9% 11.0% 113.5 123.5 92% 90%
16 N 4/29/2016 PA-4 Building Pad Southeast Side 11 CF 130.0 13.8% 1 12.5% 109.8 1 122.0 90% 90%
17 N 4/29/2016 PA-4 Building Pad East Side 11 CF 131.0 14.2% 12.5% 110.2 122.0 90% 90%
18 N 4/29/2016 PA-4 Building Pad South Side 11 FG 0.0 14.5% 12.5% 112.0 122.0 92% 90%
19 N 4/29/2016 PA-4 Pool Deck West Side 4 CF 129.0 14.7% 11.0% 111.7 123.5 90% 90%
20 N 4/29/2016 PA-4 Pool Deck West Side 11 FG 0.0 15.4% 12.5% 111.1 122.0 91% 90%
Material: S=Soil, ACAsphalt Concrete, ATB = Asphalt Treated Base, AB = Aggregate Base, STS = Cement Treated Soil,
LTS = Lime Treated Soil, 0 = Other
Test of: CF = Compacted Fill, FG = Finish Grade. SF = Slope Face, N = Native Soil, U = Utility Trench, W = Wall Backfill,
SC = Sidewalk, Curb, Gutter, 0 = Other
KEY: FSG = Finish SubGrade, ES = Finish Surface, FBG = Finish BaseGrade, BOF = Bottom of Footing, TOW = Top of Wall
N = Nuclear Gauge, S = Sand Cone
Notes:
Tests were performed by a nuclear density gauge in accordance with the ASTM D2922 method or Sand Cone Method (ASTM 0 1556).
data was tested in accordance with the ASTM 01557 test method (Modified Proctor).
The field density test results represent the moisture content and density only at the depths and locations reported.
No guarantee or warranty of the contractor's work is made or implied.
The maximum dry density and optimum moisture
LGC Valley, Inc.
Geotechnical Consulting
May 25, 2016 Project No. 133023-03
Ms. JoAnn Epstine
Toll Bros., Inc.
725 W. Town and Country Road, Suite 200
Orange, California 92868
Subject: Addendum As-Graded Completion Letter, Lots 1 through 4 of Planning Area PA-13, The
Vistas, Robertson Ranch, Carlsbad Tract No. 13-03, 4980 El Camino Real, Carlsbad,
California
References: LGC Valley, Inc., 2014, Geotechnical and Environmental Recommendations for Robertson
Ranch West, Carlsbad Tract No. 13-03, Carlsbad, California, Project Number 133023-03,
dated April 29, 2014
LGC Valley, Inc., 2015, As-Graded Completion Letter, Lots 1 through 23, Robertson
Ranch, Carlsbad Tract No. 13-03, 4980 El Camino Real, Carlsbad, California, Project No.
133023-03, dated June 9, 2015
O'Day Consultants, 2014, Grading Plan for Rancho Costera, Robertson Ranch West
Village, PlanningAreas 1-11, 13, 23A, 23B, and23C, Carlsbad Tract No. 13-03, 44 Sheets,
dated August 25, 2014
Introduction
In accordance with your authorization, LGC Valley, Inc. (LGC) has been performing geotechnical
observation and testing services during the development of the Robertson Ranch/Rancho Costera project
located in Carlsbad, California. This letter summarizes our geotechnical observation and testing services
during the addendum fine grading operations for Lots 1 through 4 of Robertson Ranch Planning Area PA-
13. After the completion of the rough and fine grading of Lots 1 through 4 in 2014, the lots were used as a
sales trailer complex and associated parking area with landscaping. Subsequently, the existing
improvements were removed and the lots regraded to the design finish grades as shown on the project
grading plans (O'Day, 2014). As of this date, the addendum grading operations are essentially complete for
the subject lots. The geotechnical conditions encountered during the grading operations were generally as
anticipated.
Summary of the Grading Operations
The rough grading operations for the subject lots were performed between September 3 and October 18, 2014
in accordance with the project geotechnical recommendations (LGC, 2015) and the approved grading plans
2420 Grand Avenue, Suite F2, 9 Vista • CA 92081 • (760) 599-7000 9 Fax (760) 599-7007
(O'Day, 2014). Rough grading of the subject lots included: 1) the removal of the dry, desiccated, and/or
weathered formational material and existing fill soils; 2) preparation of areas to receive fill; 3) the import of
fill soils from Planning Area PA- 11; 4) placement of compacted fill soils to achieve design pad grades; and 5)
trimming the slopes, back-cutting for the proposed retaining walls, and fine grading of the building pads.
Improvements placed after the completion of the rough grading operations included the placement of a sales
trailer on Lot 1 and a permeable parking area with associated landscaping on Lots 2 through 4. The addendum
grading operations were performed between April 26 and May 25, 2016 and consisted of the removal of the
on-site improvements, backfilling of the holes resulting from the removals of the landscape vegetation and the
underground utility line trenches for the sales trailer, and placement of fill to the proposed design grades of
the lots. Our field technician was on site on a full-time basis during the grading operations while our field
geologist was on-site on a periodic basis.
Field Density and Laboratory Test Results
Field density test results performed during the addendum grading operations indicated that the fill soils were
compacted to at least 90 percent of the maximum dry density in accordance with ASTM Test Method DI 557.
Compaction of the fill soils was achieved by use of heavy-duty construction equipment (including a rubber-
tire compactor). Field density testing and observations were performed using the Nuclear-Gauge Method
(ASTM Test Method D6938). A summary of the field density tests taken during the current grading
operations are presented on the attached Table 1. The field density testing was performed in general
accordance with the applicable ASTM Standards, the current standard of care in the industry, and the
precision of the testing method itself. Variations in relative compaction should be expected from the
documented results.
Laboratory maximum dry density tests of representative on-site soils were performed in general accordance
with ASTM Test Method D1557. A summary of the laboratory maximum density test results are presented
on Table 2. Expansion potential and soluble sulfate content tests of representative finish grade soils were also
performed in accordance with Uniform Building Code (UBC) 18-2 and standard geochemical methods,
respectively (LGC, 2015). Expansion potential and soluble sulfate content tests indicate the representative
finish grade soils have a high expansion potential and a negligible soluble sulfate content based on ACT
criteria (ACT 318R-08 Table 4.3.1). Based on the corrosivity testing of representative finish grade soils on
the lots, tested soils have a pH ranging from 7.8 to 7.9; a sulfate content of 110 to 630 parts per million
(ppm); chloride content of 270 to 1,210 ppm, and a minimum resistivity of 230 to 1,200 (ohms-cm). Based
on the test results, the site is considered corrosive per Caltrans criteria.
En'ineerinj Geology Summary
The geologic or geotechnical conditions encountered during the grading of the subject lots were essentially as
anticipated. Ground water was not encountered or observed during the grading operations. Based on our
geotechnical observations and geologic mapping during the rough and fine grading operations for the
Robertson Ranch Sky Ranch project, no active faults or evidence of active faulting was encountered (LGC,
2015).
Project No. 133023-03 Page 2 May 25, 2016
Conclusions and Recommendations
The addendum grading operations of Lots 1 through 4 of planning Area PA- 13 were performed in general
accordance with the project geotechnical reports, geotechnical recommendations made during the fine grading
operations, and the City of Carlsbad requirements. It is our professional opinion that the subject lots are
suitable for their intended use provided the recommendations included in the project geotechnical report
(LGC, 2014) are incorporated into the design and construction phases of site development. The following is a
summary of our conclusions:
Geotechnical conditions encountered during the grading operations were generally as anticipated.
Site preparation and removals were geotechnically observed.
Field density testing (Table 1) indicated that the fill soils were placed and compacted to at least 90 percent
relative compaction (based on ASTM Test Method D1557) and near-optimum moisture content in
accordance with the project recommendations.
The expansion potential of representative finish grade soils of the lots was tested and found to have a high
expansion potential.
The potential for soluble sulfate attack on concrete in contact with finish grade soils is considered
negligible based on ACT criteria and are considered corrosive to very corrosive to ferrous metals.
No evidence of active faulting was encountered during site rough and fine grading.
Ground water was not encountered or observed during the grading operations.
Limitations
Our services were performed using the degree of care and skill ordinarily exercised, under similar
circumstances, by reputable engineers and geologists practicing in this or similar localities. No other
warranty, expressed or implied, is made as to the conclusions and professional advice included in this report.
The samples taken and submitted for laboratory testing, the observations made and the in-situ field testing
performed are believed representative of the entire project; however, soil and geologic conditions revealed by
excavation may be different than our preliminary findings. If this occurs, the changed conditions must be
evaluated by the project soils engineer and geologist and design(s) adjusted as required or alternate design(s)
recommended.
This report is issued with the understanding that it is the responsibility of the owner, or of his/her
representative, to ensure that the information and recommendations contained herein are brought to the
attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are
taken to see that the contractor and/or subcontractor properly implements the recommendations in the field.
The contractor and/or subcontractor should notify the owner if they consider any of the recommendations
presented herein to be unsafe.
Project No. 133023-03 Page 3 May 25, 2016
The findings of this report are valid as of the present date. However, changes in the conditions of a property
can and do occur with the passage of time, whether they be due to natural processes or the works of man on
this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether
they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be
invalidated wholly or partially by changes outside our control.
Closure
If you should have any questions, please do not hesitate to contact us. The undersigned can be reached at
(760) 599-7000.
Respectfully submitted,
LGC Valley, Inc.
I ENIERING J GEO1OIST j* \xP219I
Randall Wagner, CEG 1612
Senior Project Geologist
Attachments: Appendix A - Summary of Field Density Tests
Appendix B - Laboratory Testing Procedures and Test Results
Distribution: (1) Addressee (via e-mail)
(1) Kevin Brickley, Toll Brothers (via e-mail)
Project No. 133023-03 Page 4 May 25, 2016
LGC Valley, Inc.
2420 Grand Avenue, Suite F2, Vista, California 92081
760-599-7000 / Fax 760-599-7007
APPENDIX A - REPORT OF COMPACTION TEST DATA
Print Date:
Project No. 133023-03
Client. Toll Brothers
Project Name: Robertson Ranch
Location: Carlsbad, CA
Reviewed by: RKW
rest # oe l
I
Test Date Test Location Soil (N
)
Test of
Relative Compaction (%Gauge Eev iation
orD:pth
Moisture (%) Dry Density (pcI)
Comments Field Optimum] Field Maximum Obtained Required
2451 N 4/26/2016 Lot 3 North Center 11 CF 1 79.0 15.0% 12.5% 111.8 122.0 92% 90%
2452 N 4/26/2016 Lot North Center 1 CF 80.0 17.9% 16.0% 105.4 117.5 90% 90%
2453 N 4/26/2016 Lot South Side 1 CF 81.0 19.1% 16.0% 105.3 117.5 90% 90%
2454 N 4/26/2016 Lot South Side 9 CF 81.0 13.5% 10.5% 118.3 127.5 93% 90%
2455 N 4/26/2016 Lot 3 Center 11 FG 0.0 13.8% 12.5% 109.4 122.0 90% 90%
2456 N 4/26/2016 Lot Center 9 FG 0.0 12.7% 10.5% 114.8 127.5 90% 90%
2457 N 5/24/2016 Lot 2 Center 13 CF 81.0 13.6% 11.0% 115.6 125.5 92% 90%
2458 N 5/24/2016 Lot 1 South Side 13 CF 80.0 13.1% 11.0% 114.1 125.5 91% 1 90%
2459 N 5/25/2016 Lot 2 North Side 13 FG 0.0 14.0% 11.0% 114.4 125.5 91% 1 90%
2460 N 5/25/2016 Lot 1 North Side 13 FG 0.0 11.9% 11.0% 115.3 125.5 92% 90%
cIeriat: 5=Soil, AC=Asphalt Concrete, ATB = Asphalt Treated Base, AD = Aggregate Base, STS = Cement Treated Soil,
LTS = Lime Treated Soil, 0 = Other
st of: CF = Compacted Fill, FG = Finish Grade, SF = Slope Face, N = Native Soil, U = Utility Trench, W = Wall Backfill,
SC = Sidewalk, Curb, Gutter, 0 = Other
tY: FSG = Finish 5ubGrade, FS = Finish Surface, FBG = Finish BaseGrade, BOF = Bottom of Footing, TOW = Top of Wall
= Nuclear Gauge, S = Sand Cone
As were performed by a nuclear density gauge in accordance with the ASTM D2922 method or Sand Cone Method (ASTM D 1556). The maximum dry density and optimum moisture
a was tested in accordance with the ASTM D1557 test method (Modified Proctor).
field density test results represent the moisture Content and density only at the depths and locations reported.
guarantee or warranty of the contractor's work is made or implied.
5/25/2016 Page 1 of 1
APPENDIX B
Laboratory Testing Procedures and Test Results
Maximum Dry Density Tests: The maximum dry density and optimum moisture content of typical
materials were determined in accordance with ASTM Test Method D1557. The results of these tests are
presented in the table below.
Sample
N b Number Sample Description
Maximum
Dry Density
(pci)
Optimum
Moisture Content
(%)
1 Gray brown sandy CLAY 117.5 16.0
2 Greenish gray silty CLAY 102.0 21.5
3 Red brown sandy CLAY 118.0 13.5
4 Dark gray brown clayey fine SAND 123.5 11.0
5 Medium brown f-rn SAND 124.5 11.0
6 Light brown silty SAND 114.5 13.5
7 Olive gray clayey SILT 111.5 19.5
8 Pale gray silty fine SAND 115.5 14.5
9 Pale gray silty f-rn SAND 127.5 10.5
10 Medium brown clayey SAND 128.0 10.0
11 Light brown clayey SAND 122.0 12.5
12 Pale brown fine sandy CLAY to clayey
SAND 124.0 12.0
13 Pale brown fine sandy CLAY to clayey
SAND 125.5
.
11.0
14 Light gray silty fine SAND 117.0 15.0
Project No. 133023-03 Page B-i May 25, 2016