HomeMy WebLinkAboutCT 13-03; RANCHO COSTERA; AS GRADED COMPLETION OF FINAL GRADING; 2016-11-02C113 -03
LGC Valley, Inc.
IE3Geotechnical Consulting
November 2, 2016 Project No. 133023-07
Mr. Andrew Dewar
Shapeil Properties, Inc.
11200 Corbin Avenue, Suite 201
Porter Ranch, California 91326
Subject: As-Graded Completion Letter of Fine Grading, Building Pads 18 through 20 and 22
through 24, Multi-Family Residential Development, Planning Areas PA-7 and PA-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 Building Pads 18 through 20 and 22 through 24. 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 Gradin' Operations
The fine-grading operations for the subject building pads were performed between July 13 and October 3,
2016 in accordance to the approved grading plan 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 .up to
approximately 2 feet in depth to create the building pads and the associated parkways and slopes for
Buildings Pads 18 through 20 and 22 through 24 of the site. 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 building pads included 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-7 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
in accordance with the recommendations of the project geotechnical reports (LGC, 2015a and 2015c) and
geotechnical recommendations made during the course of grading.
2420 Grand Avenue, Suite F2, • Vista • CA 92081 • (760) 599-7000 • Fax (760) 599-7007
Fill Placement and Compaction
After the completion of the reprocessing operations, the cut material within Planning Area PA-7 and
import soil from Planning Area PA-8 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-7. The fill soil was generally spread in 4- to 8-inch loose lifts; moisture conditioned as needed to
attain a near 2-percent over-optimum moisture content, and compacted. A maximum thickness of
approximately 2 feet of compacted fill was placed during the current site grading within Building Pads 18
through 20 and 22 through 24 and the adjacent driveways, parking spaces, hardscape, and landscape areas
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
D15 57. Compaction of the fill soils was achieved by use of heavy-duty construction equipment (including
a rubber-tire 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 Testing
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 fmish grade soils were also performed. The test
results indicate the finish grade soils of Buildings 18 through 20 and 22 through 24 have a medium
expansion potential (i.e. expansion index of between 51 and 90); were found to have a negligible soluble
sulfate content of 0.018 to 0.019 percent; 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.
Engineering 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
active faults or evidence of active faulting was encountered.
Project No. 133023-07 Page 2 November 2, 2016
Conclusions and Recommendations
The fine grading operations for the building pads of Buildings 18 through 20 and 22 through 24 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-7 and PA-8. 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 1- to 2-percent over the optimum moisture content in
accordance with the project geotechnical recommendations.
The expansion potential of • representative finish grade soils of Building Pads 18 through 20 and 22
through 24 was tested and found to have a medium 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
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.
Project No. 133023-07 Page 3 November 2, 2016
Closure
If you should have any questions, please do not hesitate to contact us. The undersigned can be reached at
(760) 599-7000.
Owy,
Randall Wagner, CEG 16...
Senior Project Geologist
RKW/BIH
Respectfully submitted,
LGC Valley, Inc.
*2734 E. W3W13
j(
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 November 2, 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: 480-317, 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 1 dated July 12, 2016.
American Concrete Institute (ACT), 2008, Building Code Requirements for Structural Concrete and
Commentary, ACI 318-08, 471 pages, dated January 2008.
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 PA4, 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 f6r 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 November 2, 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.
LGC Valley, Inc. 2016e, As-Graded Completion Letter of Fine Grading, Building Pads 1 through 4,
Multi-Family Residential Development, Planning Areas PA-7 and PA-8, Robertson Ranch,
Parcels 1 and 2 of Parcel Map 14-07, Carlsbad, California, Project No. 133023-07, dated
August 9, 2016.
LGC Valley, Inc. 2016f, Addendum Geotechnical Recommendations Regarding the Post-Grading of
the Multi-Family Residential Development, Planning Areas PA-7 and PA-8, Robertson
Ranch, Carlsbad Tract No. 13-03, Carlsbad, California Project No. 133023-07, dated August
11, 2016.
LGC Valley, Inc. 2016g, Addendum Geotechnical Recommendations Regarding the Medium
Expansive Soils within Planning Area PA-8, Multi-Family Residential Development,
Planning Areas PA-7 and PA-8, Robertson Ranch, Carlsbad Tract No. 13-03, Carlsbad,
California Project No. 133023-07, dated August 16, 2016.
Project No. 133023-07 Page A-2 November 2, 2016
References (continued)
LGC Valley, Inc. 2016h, As-Graded Completion Letter of Fine Grading, Building Pads 5 through 17,
Multi-Family Residential Development, Planning Areas PA-7 and PA-8, Robertson Ranch,
Parcels 1 and 2 of Parcel Map 14-07, Carlsbad, California, Project No. 133023-07, dated
August 19, 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, 3i 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-3 November 2, 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-m 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 I Expansion Potential
Buildings 18 through 21 62 Medium
Building 22 through 25 90 Medium
Project No. 133023-07 Page B-i November 2 2016
Laboratory Test Results (continued)
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:
Representative Building Pad Sulfate Content (% by Weight) Potential Degree of
Sulfate Attack*
Buildings 18 through 21 0.019% Negligible
Building 22 through 25 0.018% Negligible
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:
Representative Building Pad Chloride Content, ppm
Buildings 18 through 25 260
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 18 through 25 7.96 710
Project No. 133023-07 Page B-2 November 2, 2016