HomeMy WebLinkAboutCT 12-05; LA COSTA RESIDENTIAL; GEOTECHNICAL REPORT OF POSTGRADING; 2015-06-10I -
LOG Cl-
Geotechnical, Inc.
June 10, 2015 [ (!) II ProjectNo 12043-01
FEB 272016 Ms. April Tomillo U U
Taylor Morrison
100 Spectrum Drive, Suite 1450
Irvine, California 92618
Subject: Geotechnical Report of Posigrading, La Costa Residential Development, "Montecina ",
City of Carlsbad, California
In accordance with your request and authorization, LGC Geotechnical, Inc. has provided this report to present
the results of our periodic geotechnical services performed during the postgrading operations for the subject
site. We understand that the postgrading operations for the La Costa Residential Development, "Montecina",
are essentially complete. Our work included periodic observation of sewer, storm drain and interior plumbing
trench backfill, foundation footing excavations, and subgrade preparation.
Should you have any questions regarding this report, please do not hesitate to contact our office. We appreciate
this opportunity to be of service.
Respectfully,
Hy
LGC Geotechnical, Inc
cFR'TIFIED
E9LOGIST 1*)
Tim Lawson, CEO 1821, GE 2626
Geotechnical Engineer/Geologist
TJL/CDH/kmb
Distribution: (3) Addressee (includes 2 wet-signed copies for City Submittal)
TABLE OF CONTENTS
Section Page
1.0 INTRODUCTION .................................................................................................................................. 1
2.0 POSTGRADING OPERATIONS.........................................................................................................2
2.1 Subgrade .................................................................................................................................... 2
2.2 Retaining Wall Footings and Backfill ........................................................................................ 2
2.3 Interior Plumbing Lines .............................................................................................................2
2.4 Foundation Footings ..................................... . ............................................................................. 3
2.5 Sewer Line Trench Backfill ......................................................................................................3
2.6 Storm Drain Trench Backfill ..................................................................................................... 3
2.7 Domestic Water Line Trench Backfill ......................................................................................3
2.8 Pavement Section ....................................................................................................................... 3
2.9 Field and Laboratory Testing....................................................................................................4
3.0 CONCLUSIONS ...................................................................................................................................5
4.0 LIMITATIONS .....................................................................................................................................6
LIST OF ILLUSTRATIONS & APPENDICES
Figure
Figure 1 - Site Location Map (Rear of Text)
Appendix
Appendix A - References
Appendix B - Summary of Field Density Test Results
Appendix C - Laboratory Test Results
C
*
Project No. 12043-01 Page i June 10, 2015
1.0 INTRODUCTION
LGC Geotechnical, Inc. has provided on-call geotechnical services during the postgrading operations for the La
Costa Residential Development, "Montecina", in the city of Carlsbad, California. This report summarizes our
geotechnical observations and the geotechnical conditions encountered during postgrading operations for the
subject site.
Project No. 12043-01 Page 1 June 10, 2015
2.0 POSTGRADING OPERATIONS
Postgrading operations performed by the contractors included: 1) backfill and compaction of trenches for
interior plumbing, sewer, area drains/irrigation, domestic water; and 2) subgrade preparation for the building
foundation, retaining walls, sidewalk, and driveway/approach areas. At the request of the site superintendent,
representatives of our firm performed periodic on-call field observations and testing during the postgrading
operations. Specific observations conducted during postgrading operations are discussed below.
2.1 Subgrade
In general, where observed, subgrade materials for curb and gutter, street, driveway approaches and
sidewalk areas were found to be prepared in general accordance with our geotechnical
recommendations.
2.2 RetaininE Wall Footings and Backfill
Foundation footing excavations were observed for the retaining walL Footings were probed in random
locations to evaluate the suitability of the onsite soils. Where probed, the footings were excavated into
firm and unyielding engineered fill.
A subdrain consisting of 4-inch-diameter perforated pipe surrounded by '/4-inch crushed rock
wrapped in filter fabric was installed behind the subject retaining walls for drainage purposes. The
low-end of the subdrain was outleted into an acceptable drainage system.
Generally, the retaining wall was backfi lIed with select sand material which was moisture-
conditioned as needed and compacted. Native soils were then moisture-conditioned as needed and
placed within the upper approximately 18 inches to achieve finish grade, then compacted to a
minimum 90 percent relative compaction. Backfill soils were periodically observed, probed, and
tested for in-place density and moisture content (ASTM Test Method D6938). Where tested, results
indicated that retaining wall backfill materials were compacted in general accordance with the project
specifications (minimum 90 percent relative compaction). Field density test results for retaining wall
backfill are presented in Appendix B.
2.3 Interior Plumbing Lines
In general, interior plumbing lines were backfilled with clean sand to the surface. Where observed, the
sand was jetted for densification. Interior plumbing trench backfill was periodically observed and
probed to verify that the trench backfill was suitable for its intended purpose.
Project No. 12043-01 Page 2 June 10, 2015
2.4 Foundation Footings
Foundation footing excavations were observed for buildings, free-standing walls, and retaining walls.
Footings were probed in random locations to evaluate the suitability of the onsite soils. Where probed,
the footings were excavated into firm and unyielding engineered fill.
2.5 Sewer Line Trench Backfill
In general, sewer lines were bedded and shaded to approximately 1-foot above the top-of-pipe with
3/4-inch gravel. Fill derived from onsite soils was then placed above the gravel, moisture-conditioned as
needed and compacted with a sheepsfoot roller attached to a backhoe, and/or by wheel rolling with a
backhoe. Backfill was periodically observed and probed at random to verify that the trench backfill was
suitable for its intended purpose.
2.6 Storm Drain Trench Backfill
Storm drain lines were generally bedded and shaded with 3/4-inch gravel up to a depth of
approximately 1-foot above the pipe. Compacted fill, derived from onsite soils, was then placed
above the sand, moisture-conditioned as needed, and compacted with heavy-duty or hand-operated
equipment. Compacted soils were periodically observed, probed, and tested for in-place density and
moisture content (ASTM Test Method D6938). Where tested, results indicated that trench backfill
materials were compacted in general accordance with the project recommendations (90 percent
relative compaction or greater). Field density test results are presented in Appendix B.
2.7 Domestic Water Line Trench Backfill
Water lines were generally bedded and shaded with clean sand up to a depth of approximately 1-foot
above the top of the pipe. The sand shading for the water lines was jetted by the contractor for
densification. Compacted fill, derived from onsite soils, was then placed above the sand, moisture-
conditioned as needed, and compacted with heavy-duty or hand-operated equipment. Compacted soils
were periodically observed, probed, and tested for in-place density and moisture content (ASTM Test
Method D6938). Where tested, results indicated that trench backfill materials were compacted in
general accordance with the project recommendations (90 percent relative compaction or greater). Field
density test results are presented in Appendix B.
2.8 Pavement Section
Aggregate base was imported and placed over the compacted subgrade soils, moisture-conditioned, and
compacted with heavy-duty construction equipment. Where tested, field density tests indicated at least
95 percent relative compaction and near-optimum moisture content (ASTM Test Method D6938).
LGC Geotechnical performed field observation, periodic temperature testing, and compaction testing
during asphalt concrete placement operations. Where tested, the asphalt was found to have a relative
Project No. 12043-01 Page 3 June 10, 2015
compaction of at least 95 percent (ASTM Test Method D6938). Maximum density test results for the
asphalt concrete used onsite were obtained from the materials distribution plant through the paving
contractor.
Line, grade, and thickness of street sections were not the purview of the geotechnical consultant.
The results of the subgrade soil, aggregate base, and asphalt concrete density tests are summarized in
Appendix B. Laboratory test results are summarized in Appendix C.
2.9 Field and Laboratory Testinj'
Field density tests were performed during the postgrading operations in general accordance with the
Nuclear Gauge Method (ASTM Test Method D6938). The results of the field density tests performed
are summarized in Appendix B. Field density tests were performed on a periodic and random nature in
general accordance with the current standard of care in the industry to form an opinion of the work
performed. It is ultimately the contractor's responsibility to ensure that all work is performed to the
applicable codes and specifications. Variations in relative compaction and moisture content should be
expected from results documented herein.
Representative soil samples were tested for maximum dry density and optimum moisture content in
accordance. with ASTM Test Method D1557. Laboratory test results are summarized in Appendix C.
Project No. 12043-01 Page 4 June 10, 2015
3.0 CONCLUSIONS
Based on the results of our periodic observation, it is our opinion that postgrading operations for the La Costa
Residential Development, "Montecina", were performed in general accordance with the project specifications
and the geotechnical recommendations made during construction. From a geotechnical perspective, we
consider the subject site to be suitable for its intended use.
It should be noted that the previously provided geotechnical recommendations were intended to provide
sufficient information to develop the site in general accordance with the California Building Code (CBC,
2013) requirements. With regard to the potential occurrence of potentially catastrophic geotechnical hazards
such as fault rupture, earthquake-induced landslides, liquefaction, etc., the previously provided geotechnical
recommendations should render adequate protection for the proposed development to the extent required to
reduce seismic risk to an "acceptable level." The "acceptable level" of risk is defined by the California Code
of Regulations as "that level that provides reasonable protection of the public safety, though it does not
necessarily ensure continued structural integrity and functionality of the project" [Title 14, Article 10,
Section 3721(a)]. Therefore, repair and remedial work of the proposed improvement may be required after a
significant seismic event. With regards to the potential for less significant geologic hazards to the proposed
development, the previously provided recommendations are intended to provide a reasonable protection
against the potential damaging effects of geotechnical phenomena such as expansive soils, fill settlement,
groundwater seepage, etc. It should be understood that, although our recommendations are intended to
maintain the structural integrity of the proposed development and structures given the site geotechnical
conditions, they cannot preclude the potential for some cosmetic distress or nuisance issues to develop as a
result of the site geotechnical conditions.
Project No. 12043-01 Page 5 June 10, 2015
4.0 LIMITATIONS
Our services were performed using the degree of care and skill ordinarily exercised, under similar
circumstances, by reputable soils engineers and geologists practicing in this or similar localities. Na other
warranty, expressed or implied, is made as to the conclusions and professional advice included in this report.
Our services were provided in order to form an opinion concerning the suitability of the proposed development
relative to the geotechnical aspects of the site. The data and information provided in this report are based on
periodic observations made by representatives of our firm during the grading and construction operations
performed by others. This report is not a warranty of the work performed by others. The presence of our
personnel during the work process did not involve the direction or supervision of the contractor.
Project No. 12043-01 Page 6 June 10, 2015
II!XU 10 L U
io SUBJECT SITE
/
ri
PROJECT NAME La Costa Town Center -Montecina
I FIGURE 1 PROJECT NO. 12043-01
Site Location Map ENG. / GEOL. TA
V~6eotechnical, Inc. SCALE Not to Scale
DATE June 2015
Appendix A
References
A PPENDIX A
References
California Building Standards Commission, 2013, California Building Code, Califdrnia Code of Regulations
Title 24, Volumes 1 and 2, dated July 2013.
JD Reinforcing Company, 2013, Post-Tension Foundation Plans for La Costa Residential, Sheets I through 9,
dated October 2, 2013.
Latitude 33 Planning and Engineering, 2013a, Grading and Erosion Control Plans for La Costa Residential,
Sheets 1 through 12, dated January 30, 2013.
2013b, Improvement Plans for La Costa Residential, Sheets 1 through 12, dated January 30, 2013.
Leighton and Associates, Inc., 2012, Geotechnical Update and Addendum to Geotechnical Investigation
Proposed La Costa Town Center Residential Development Carlsbad, California, Project No. 042631-
0Ol, dated November 16,2012.
LGC Geotechnical, Inc., 2014, As-Graded Geotechnical Report of Rough Grading and Construction
Operations for the Proposed La Costa Town Center Residential Development, Carlsbad, California,
Project No. 12043-01 dated January 17, 2014.
Southern California Soil & Testing, Inc., 2012, Update Geotechnical Investigation, La Costa Town Square,
North Residential Development, Carlsbad, California, dated January 3, 2012.
Project No. 12043-01 A-i June 10, 2015
Appendix B
Summary of Field Density Test Results
a
Test
No.
Test
Method
Test
Date
Test
of
Tech
Initials
Approximate
Test
Location
Approx.
Test Elevation
(It)
Soil
Type
Dry Density
(pcf)
Field
Moisture
Content (%)
Field
Relative
Compaction
(%) Remarks
Subgrade
I N 6/6/2014 SW TTP Station 182+00 FG 9 126.8 8.1 96
_2_ N 6/9/2014 sw TTP Station 178+00 FG 1 - 119.9 10.1 95
3 N 6/9/2014 sw TTP Station 177+20 FG - - 120.3 9.9 95
4 N 7/21/2014 CO TTP Adjacent to lot 22 FG - - 121.1 10.1 95
5 N 7/21/2014 ST UP Adj to lot 26 FG - - 119.9 11.0 95
6 N 7/30/2014 CO UP Adj to lot 19 FG - - 121.0 11.6 95
7 N 7/30/2014 ST UP Adj to lot 17 FG - - 121.1 10.1 95
8 N 7/30/2014 CG UP Adj to lot 16 FG - - 122.0 10.3 96
9 N 8/6/2014 ST UP Adj to lot 8 FO - - 119.9 11.1 95
10 N 8/6/2014 CG TTP Adj to lot 16 FO - - 121.5 9.8 96
Ii N 8/6/2014 ST UP Adj to lot 14 FG 9 128.8 8.7 98
12 N 9/30/2014 SW UP Adj to lot 3 FG . - - 120.1 1 9.2 95
Retaining Wall
I - N 6/26/2014 B UP Lot 27 -3' - 9 125.5 10.2 95
2 N 6/26/2014 B UP Lot 27 -3' 9 124.3 10.8 94
3 N 6/27/2014 B UP Lot 28 -3' 9 122.8 9.8 93
4 N 6/27/2014 B UP Lot 27/28 -2 - 9 123.0 9.9 93
5 N 6/30/2014 B UP Lot 28 -2 - 9 127.7 10.8 97
_6_ N 7/1/2014 B UP Lot 28 -2 - 9 124.7 11.0 95
7 N 7/2/2014 B UP Lot 28 FG - 9 125.5 9.7 1 95
Sewer
N 1/27/2014 M UP Sta. 9+05 -2' 16 107.9 16.0 91
2 N 1/27/2014 M UP Sta. 8+50 FG 16 106.8 15.7 90
3 N 1/27/2014 M UP Sta. 8+25 -1' 16 109.0 15.2 92
4 N 1/28/2014 M UP Sta. 7+50 FG 16 108.2 16.1 91
5 N 1/28/2014 M TTP Sta. 6+75 -2 16 107.1 15.7 90
6 N 1/28/2014 M UP Sta. 6+25 FG 16 106.5 16.8 90
7 N 1/29/2014 M UP Sta. 5+50 -2' 17 104.3 14.5 93
_8_ N
1
1/29/2014 M TTP Sta. 4+75 FG 17 105.0 14.0 93
9 N 1/29/2014 M TTP Sta. 5+25 FG 16 109.1 15.1 92
Storm Drain
1 N 2/13/2014 MH TTP MH structure at station 6+00 -2' 16 - 153 13.0 97
2 N 2/13/2014 MH TTP MH structure at station 6+00 FG 16 - 106 12.1 93
- - N 2/14/2014 M TTP Slope atSW end of site, @headwall FG 16 - 12.1 11.6 95
- - N 2/21/2014 M UP Sta. 1+30 -2' 16 111.0 13.2 94
- - N 2/24/2014 M TTP Sta. 1+55 -2' 16 108.6 12.0 92
- - N 2/24/2014 M UP Sta. 1+50 FG 16 112.1 134 95
Domestic Water = - N 6/17/2014 M TTP STATION 4+75 -3' IMP-I 129.5 10.9 . 95
N 6/17/2014 M TTP STATION5+80 -3' IMP-1 128.7 11.5 95
- - N 6/17/2014 M UP STATION11+30 -3' IMP-I 130.3 11.0 96
- = N 6/17/2014 M TTP STATION13+20 -3' IMP-I 131.5 10.8 97
- N 6/19/2014 M TTP STATION8+15 -2' 9 127.7 11.8 97
- - N 6/19/2014 M TTP 1 12+25 -2' 9 126.1 11.1 96
7 N 10/21/2014 M UP I relocated dw line @ site entrance -1' 21 117.4 10.9 1 95
8 N 11/13/2014 M TTP I trench in intersection of lupino & brezo -1' 21 118.2 9.8 1 95
Project No. /2043-01 B-I June 2015
Appendix B
Summary of Field Density Test Results
Test
No.
Test
Method
Test
Date
Test
of
Tech
I Initials
Approximate
Test
Location
Approx.
Test Elevation
(ft)
Soil
Type
Dry Density
(pci)
Field
Moisture
Content (%)
Field
Relative
Compaction
(%) Remarks
Aggregate Base
- - N 5/16/2014 S TIP @ Sewer Connection on RSF FG 21 - 186 - 1.8 96
_2_ N 7/21/2014 CG TIP Adj to lot 23 FG 21 - 19.1 - 1.3 96
3 N 7/21/2014 CG TTP Adjto lot 25 FG 21 118.7 - 15 96
4 N 7/21/2014 CG TTP Adj to lot 27 FO 21 - 182 12.4 95
5 N 7/29/2014 CG TTP Adj to lot 2 FO 21 117.8 13.0 95
6 N 7/29/2014 CG TIP Adj to lot 4 FG 21 - 190 12.6 96
N 8/11/2014 1 CG I TIP I Adj to lot 18 FG 21 117.5 10.6 95
_8_1 N 8/11/2014 1 CG TTP Across Street from lot 16 FG 21 118.0 8.9 95
9 1 N 10/23/2014 1 CG TTP Adj to lot I FG 21 119.2 1 9.0 96 1
Ash palt Concrete
- - N 8/1/2014 S TIP Adj to lot 23 FG AC 141.4 N/A 94
2 N 8/1/2014 5 TIP Adj to lot 26 FG AC 144.0 N/A 96
3 N 8/1/2014 5 TTP Parking stall across from lot 28 FG AC 144.8 N/A 97
4 N 8/1/2014 S TTP Adj to lot 3 FG AC 145.0 N/A 97
5 N 8/1/2014 S TTP Adj to lot 4 FG AC 144.9 N/A 97
Appendix C
Laboratory Test Results
APPENDIX C
Laboratory Testing Procedures and Test Results
The laboratory testing program was directed towards providing quantitative data relating to the relevant
engineering properties of the soils. Samples considered representative of site conditions were tested in
general accordance with American Society for Testing and Materials (ASTM) procedure and/or California
Test Methods (CTM), where applicable. The following summary is a brief outline of the test type and a table
summarizing the test results.
Laboratory Compaction: The maximum dry density and optimum moisture content of typical materials were
determined in accordance with ASTM D1557. The results of these tests are presented in the table below.
Sample Maximum Optimum
Location Sample Description Dry Density Moisture Content
(pci) (%)
1* Reddish Brown Silty Sand 126.2 8.9
9* Brown Silty Sand with Rock with 5% Rock 131.0 7.8
16* Light Tan to White Silty Sand 118.0 12.0
17* Tan to Brown Silty Sand/ Sandy Silt with
Clay 112.0 11.0
21 Class 2Base Material 123.5 9.5
Imp-i Import Fill Sand 135.4 8.0
AC Asphalt Concrete 149.0 N/A
*As reported by others (Leighton and Associates 2012)
Project No. 12043-01 C-i June 10, 2015