HomeMy WebLinkAboutCDP 12-04; ARMY & NAVY ACADEMY ATHLETIC FIELD; GEOTECHNICAL OBSERVATIONS & TESTING OF ROUGH GRADING OPERATIONS; 2014-08-05. &17r 11-04
NorCal Engineering
Soils and Gebtechnical Consultants
10641 Humbolt Street Los Alamitos, CA 90720
(562) 799-9469 Fax (562) 799-9459
August 5, 2014 Project Number 16795-13
Hoehn Buick-Cadillac
5475 Car Country Drive
Carlsbad, California 92018
Attn.: Mr. Bill Hoehn
40 RE: Report of Geotechnical Observation and Testing of Rough Grading
Operations - Proposed Hoehn Buick-Cadillac Expansion Development -
Located at 5334 Paseo Del Norte, in the City of Carlsbad, California
Dear Mr. Hoehn:
Pursuant to your request, this firm has provided this geotechnical report to summarize
the observations and testing performed during rough grading operations at the above
referenced project. The geotechnical aspects were conducted in accordance with our
report titled "Geotechnical Engineering Investigation", dated May 22, 2013, Project
Number 16795-13. Our geotechnical services are summarized in the subsequent
• sections of this report.
Site Grading
The purpose of the grading operations was for the placement of fill to provide structural
support of the proposed development. All vegetation and demolition debris was stripped
and removed from the fill area prior to the placement of any fill soils. The upper low
density surface soils were removed to competent native material, the exposed, surface
scarified, moisture conditioned and then recompacted to a minimum of 90% relative
. compaction.
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August 5, 2014 Project Number 16795-13
Page
In the opinion of this firm, the native soils are 'suitable to support the placement of fill
material. Grading extended a minimum of five horizontal feet or to the depth of fill
placed, whichever is greater, beyond the edge of the proposed foundations except
'adjacent to existing building walls as noted below.
S
Fill soils placed were compacted to minimum 90% of the laboratory standard in lifts
not in excess of eight inches in thickness. The maximum depth of fill soils placed was
approximately two feet. A rubber tire loader was utilized for compaction control. A
water truck provided moisture control. Our services did not include any surveying of
excavation bottoms, building corners, or subgrade elevations during grading operations.
Existing building walls were left in place near the middle of the proposed building
and a portion of the east building line. Concrete wall anchors were poured to
temporarily brace the existing walls and will be left in place. The wall anchors
are approximately3 feet by 4 feet and 5 feet in depth. The top of the concrete is
approximately two feet below grade. The approximate locations of the anchors
are shown on the attached plan.
An existing electrical line within the proposed building was left in place at
' approximately 1% feet below pad grade. The electrical line will be
removed/relocated at a later date and is shown on the attached plan.
An existing sewer line located in the parking area south of the proposed building
was left in place at approximately 4 feet below grade. Compaction tests on the
existing fill above the pipe had results of at least 90% relative compaction.,
The proposed pavement areas located west and south of the proposed building
were left approximately two feet below the proposed grade and will be backfilled
at a later date. All fill soils should be compacted to a minimum of 90% relative
compaction.
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August 5, 2014 . Project Number 16795-13
Page 3
Laboratory/Field Testing
The relative compaction was determined by Sand Cone Method (ASTM: D1556-07) and
by the Drive Tube Method (ASTM: D2937-04). The maximum density was obtained by
the laboratory standard (ASTM: D1557-07) and results are shown on Table I. A
. summary of the compaction tests are described in Appendix B with locations shown on
the accompanying plan. Additional laboratory tests were performed on representative
bulk bag samples of the near surface soils at the completion of backfill operations. The
tests consisted of the following:
Expansion index tests in accordance with ASTM D 4829 were performed on
remolded samples of the upper soils to determine the expansive characteristics
and to provide any necessary recommendations for reinforcement of the slabs-
on-grade and. the foundations. Results of these tests are provided on Table II in
Appendix A.
Soluble sulfate tests in accordance with California Test Method 417 were
performed on representative soils samples to estimate the potential for corrosion
of concrete in contact with the on-site soils. Results are provided on Table Ill in
Appendix A.
Foundation Design
All foundations may be designed utilizing the following allowable soil bearing capacities
for an embedded depth of 18 inches into approved-engineered fill or competent native
soils with the corresponding widths:
Allowable Soil Bearing Capacity (psf)
Continuous Isolated
Width (ft) ' Foundation Foundation
1.5 2000 2500
2.0 2075 2575
4.0 2375 2875
6.0 2675 3175
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NorCal Engineering
August 5, 2014 Project Number 16795713
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The bearing value may be increased by 500 psf for each additional foot of depth in
excess of the 24-inch minimum depth, up to a maximum of 4,000 psf. A one third
increase may be used when considering short term loading and seismic forces. A
representative of this firm shall inspect all foundation excavations prior to pouring
concrete..
Slab Design
All concrete slabs shall be at least four inches for office and hardscapeareàs, six inches
for service/showroom areas and placed on approved subgrade soils. Additional
reinforcement requirements and an increase in thickness of the slabs-on-grade may be
necessary based upon soils expansion potential and proposed loading conditions in the
structures and should be evaluated further by the project engineers and/or architect.
A vapor retarder should be utilized in areas which would be sensitive to the infiltration of
moisture. This retarder shall meet requirements of ASTM E 96, Water Vapor
Transmission of Materials and ASTM E 1745, Standard Specification for Water Vapor
Retarders used in Contact with Soil or Granular Fill Under Concrete Slabs. The vapor
retarder shall be installed in accordance with procedures stated in ASTM E 1643,
Standard practice for Installation of Water Vapor Retarders used in Contact with Earth
or Granular Fill Under Concrete Slabs.
The moisture retarder may be placed directly upon approved subgrade soils, although
one to two inches of sand beneath the membrane is desirable. The subgrade upon
which the retarder is placed shall be smooth and free of rocks, gravel or other
protrusions which may damage the retarder. Use of sand above the retarder is under
the purview of the structural engineer; if sand is used over the retarder, it should be
placed in a dry condition.
Corrosion Design Criteria
Representative samples of the surficial soils revealed negligible sulfate concentrations.
Therefore, all concrete in contact with on site soils shall be designed in accordance with
Table 4.3.1 of ACt 318 Building Code and Commentary. Sulfate test results may be
found on the attached Table Ill.
NorCal Engineering
S
Respecifully subniiffr1
NORCAL ENGINE
Keith D. Tucker
Project Engineer
R.G.E. 841
11)Ae-14r,
Walter K. Mott
Project Manager
August 5, 2014 Project Number 16795-13
Page 5
Expansive Soil
S
The upper soils at the site are "very low" in expansion potential. On sites with expansive
soils (Expansion Index >20) special attention during project design and. maintenance is
necessary. The attached Expansive Soil Guidelines should be reviewed by the
. engineers, architects, owner, maintenance personnel and other interested parties and
considered during the design of the project and future property maintenance.
Limitations
It should be noted that our work does not warrant or guarantee that the contractor
responsible for each phase of the project has performed his work in accordance with the
project specifications.
S We appreciate this opportunity to be of service to you; If you have any further
questions, please do not hesitate to contact the undersigned.
S
S
NorCal Engineering
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August 5, 2014 Project Number 16795-13
Page 6
Expansive Soil Guidelines
The following expansive soil guidelines are provided for your project. The intent of
these guidelines is to inform you, the client, of the importance of proper design and
maintenance of projects supported on expansive soils. You, as the owner or other
interested party, should be warned that you have a duty to provide the
information contained in the soil report including these guidelines to your design
engineers, architects, landscapers and other design parties in order to enable
them to provide a design that takes into consideration expansive soils.
In addition, you should provide the soil report with these guidelines to any property
manager, lessee, property purchaser or other interested party that will have or assume
the responsibility of maintaining the development in the future.
Expansive soils are fine-grained silts and clays which are subject to swelling and
contracting. The amount of this swelling and contracting is subject to the amount of
fine-grained clay materials present in the soils and the amount of moisture either
introduced or extracted from the soils. Expansive soils are divided into five categories
ranging from "very low' to "very high". Expansion indices are assigned to each
classification and are included in the laboratory testing section of this report. If the
expansion index of the soils on your site, as stated in this report, is 21 or higher, you
have expansive soils. The classifications of expansive soils are as follows:
Classification of Expansive Soil*
Expansion Index Potential Expansion
0-20 Very Low
21-50 Low
51-90 Medium
91-130 High
Above 130 Very High
*From Table 18A-1-B of California Building Code (1988)
When expansive soils are compacted during site grading operations, care is taken to
place the materials at or slightly above optimum moisture levels and perform proper
compaction operations. Any subsequent excessive wetting and/or drying of expansive
soils will cause the soil materials to expand and/or contract. These actions are likely to
cause distress of foundations, structures, slabs-on-grade, sidewalks and pavement over
the life of the structure. It is therefore imperative that even after construction of
improvements, the moisture contents are maintained at relatively constant levels,
allowing neither excessive wetting or drying of soils.
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NorCal Engineering
August 5, 2014 Project Number 16795-13
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Evidence of excessive wetting of expansive soils may be seen in concrete slabs, both
interior and exterior. Slabs may lift at construction joints producing a trip hazard or may
crack from the pressure of soil expansion. Wet clays in foundation areas may result in
lifting of the structure causing difficulty in the opening and closing of doors and windows,
as well as cracking in exterior and interior wall surfaces. In extreme wetting of soils to
depth, settlement of the structure may eventually result. Excessive wetting of soils in
landscape areas adjacent to concrete or asphaltic pavement areas may also result in
expansion of soils beneath pavement and resultant distress to the pavement surface.
Excessive drying of expansive soils is initially evidenced by cracking in the surface of
the soils due to contraction. Settlement of structures and on-grade slabs may also
eventually result along with problems in the operation of doors and windows.
Projects located in areas of expansive clay soils will be subject to more movement and
"hairline" cracking of walls and slabs than similar projects situated on non-expansive
sandy soils. There are, however, measures that developers and property owners may
take to reduce the amount of movement over the life the development. The following
guidelines are provided to assist you in both design and maintenance of projects on
expansive soils:
Drainage away from structures and pavement is essential to prevent
excessive wetting of expansive soils. Grades of at least 3% should be
designed and maintained to allow flow of irrigation and rain water to
approved drainage devices or to the street. Any "ponding" of water adjacent
to buildings, slabs and pavement after rains is evidence of poor drainage; the
installation of drainage devices or regrading of the area may be required to
assure proper drainage. Installation of rain gutters is also recommended to
control the introduction of moisture next to buildings. Gutters should
discharge into a drainage device or onto pavement which drains to roadways.
•
Irrigation should be strictly controlled around building foundations, slabs and
pavement and may need to be adjusted depending upon season. This
control is essential to maintain a relatively uniform moisture content in the
expansive soils and to prevent swelling and contracting. Over-watering
adjacent to improvements may result in damage to those improvements.
NorCal Engineering makes no specific recommendations regarding
landscape irrigation schedules.
Planting schemes for landscaping around structures and pavement should
be analyzed carefully. Plants (including sod) requiring high amounts of water
may result in excessive wetting of soils. Trees and large shrubs may actually
• extract moisture from the expansive soils, thus causing contraction of the
fine-grained soils.
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NorCal Engineering
August 5, 2014 / Project Number 16795-13
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Thickened edges on exterior slabs will assist in keeping excessive moisture
from entering directly beneath the concrete. A six-inch thick or greater
deepened edge on slabs may be considered. Underlying interior and exterior
slabs with 6 to 12 inches or more of non-expansive soils and providing
presaturation of the underlying clayey soils as recommended in the soil
report will improve the overall performance of on-grade slabs.
• Increase the amount of steel reinforcing in concrete slabs, foundations and
other structures to resist the forces of expansive soils. The precise amount
of reinforcing should be determined by the appropriate design engineers
and/or architects.
• Recommendations of the soil report should always be followed in the
development of the project. Any recommendations regarding presaturation
of the upper subgrade soils in slab areas should be performed in the field
and verified by the Soil Engineer.
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NorCal Engineering
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Li
APPENDICES
(In order of appearance)
Li Appendix A - Laboratory Tests
Table I - Maximum Density Tests
Table II— Expansion Index
Table Ill - Sulfate Tests .
Appendix B - Summary of Compaction Tests
Site Plan.
Summary of Compaction Tests
.
Li
NorCal Engineering
Appendix A
NorCal Engineering
August 5, 2014 Project Number 16795-13
Page
TABLE I
MAXIMUM DENSITY TESTS
(ASTM: D1557-07)
Optimum Maximum Dry
Sample Classification Moisture Density (lbs./cu.ft.)
I Silty SAND 10.0 125.0
II Silty SAND 9.5 128.5
LIM
TABLE II
EXPANSION INDEX TESTS
Expansion
Sample Classification Index
Pad Subgrade Silty SAND 2
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TABLE III
SULFATE TESTS
S Sample Sulfate (% by Weight)
Pad Subgrade 0.008
S
0 NorCal Engineering
Appendix B
NorCal Engineering
J
alORETEN lION - FACILITY = 282
FOUND L&T STAMPED ILS
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Date of Test Percent Unit Wt:
Test No. Location Depth Moisture Ibs./cu.ft. C
7/29/14 101 Site Grading 2.0-2.5 10.8 116.4
7/29/14 102 Site Grading 1.0-1.5 8.5 115.2
7/29/14 103 Site Grading 3.0-3.5 9.7 117.5
7/29/14 104 Site Grading 2.0-2.5 9.9 115.7
7/29/14 105 Site Grading 2.0-2.5 9.6 114.1
7/29/14 106 Site Grading 1.0-1.5 10.1 109.7
7/29114 106A** Site Grading 1.0-1.5 10.7 114.7
7/30/14 107 Site Grading 2.0-2.5 10.3 117.7
7/30/14 108 Site Grading 1.0-1.5 9.1 115.5
7/30/14 109 Site Grading 2.0-2.5 8.3 114.5
7/31/14 110 Site Grading 1.0-1.5 10.1 113.5
7/31/14 111 Site Grading 0.0-0.5 10.9 120.2
7/31/14 112 Site Grading 0.0-0.5 10.7 120.1
7/31/14 113 Site Grading 0.0-0.5 11.2 122.5
7/31/14 114 Site Grading 0.0-0.5 10.9 119.0
7/31/14 115 Site Grading 2.0-2.5 10.1 118.1
7/31/14 116 Site Grading 2.0-2.5 9.7 115.8
iv
S
S
Relative Soil Test
ompaction Type LP
93 I D
92 I D
94 I D
93 I S
91 I D
88 I D
92 I D
94 I S
92 I D
92 I D
91 I D
94 .11 S
93 II D
95 II S
93 II D
94 I D
93 I D
August 5, 2014 Project Number 16795-13
Pagel
SUMMARY OF COMPACTION TEST RESULTS
S
**Retest of failing tests after area reworked
S= Sand Cone Method
D= Drive Tube Method
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S
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NorCal Engineering