HomeMy WebLinkAboutDEV 2017-0030; 906 PINE AVENUE; FINAL SOILS REPORT; 2018-04-24Geotechnical C Geologic C Coastal C Environmental
5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com
April 24, 2018
W.O. 7099-B-SC
Mr. Richard Smerud
906 Pine Avenue
Carlsbad, California 92014
Subject:Geotechnical Report of Grading and Building Pad Construction,
at 906 Pine Avenue, Carlsbad, San Diego County, California
References:1. “Grading Plans for: Multi-Family Residence, 906 Pine Avenue, Carlsbad,” 5 Sheets,
Project No: 2017-0030, Drawing No.: GR501-6A, Not Dated, by dk Greene Consulting, Inc.
2. “Technical Memorandum, Grading Plan Review, Multi-Family Residence, 906 Pine
Avenue, Carlsbad, California,” W.O. 7099-A1-SC, dated November 17, 2017, by
GeoSoils, Inc.
3. “Geotechnical Update and Plan Review for Proposed Construction at 906 Pine Avenue,
Carlsbad, San Diego County, California,” W.O. 7099-A1-SC, dated October 12, 2017,
GeoSoils, Inc.
4. “Geotechnical Evaluation for Proposed Construction at 906 Pine Avenue, Carlsbad,
San Diego County, California,” W.O. 7099-A-SC, dated August 12, 2016, by GeoSoils, Inc.
Dear Mr. Smerud:
In accordance with your request, and as required by the City, GeoSoils, Inc. (GSI) has
prepared this geotechnical report of grading for the proposed residential structure.
Observations and field compaction testing for this specific construction task generally
occurred between April 9 through 19, 2018. Grading was observed and fill was selectively
tested by a representative of GSI, on a part-time, as-needed basis. The scheduling of such
was solely determined by your field representative. Line and grade was provided by others
and not GSI. Unless specifically superceded herein, the conclusions and
recommendations in the referenced geotechnical reports prepared by this firm (see
Reference Nos. 2, 3 and 4) remain valid and applicable and should be appropriately
implemented during the balance of construction.
Purpose of Grading
The primary purpose of grading was to mitigate potentially compressible soils within the
influence of the planned residential structure, and to create a building pad for the planned
three-story multi-family residential structure. The first floor (ground floor) of the proposed
development consists of garage/storage areas, and bedrooms for the superjacent
dwellings. The second and third floors generally consists of bedrooms, living areas, and
decks.
GeoSoils, Inc.
Richard Smerud W.O. 7099-B-SC
906 Pine Avenue, Carlsbad April 24, 2018
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Engineering Geology
The geologic conditions exposed in excavations during the process of remedial grading
for the planned residential structures were observed on a part-time basis by a
representative from our firm. Earth materials encountered during grading consisted of
existing undifferentiated and underlying Quaternary-age, older paralic deposits (considered
suitable formation). Evidence of adverse geologic structure or unusual
geologic/subsurface conditions, were not observed in the earthwork excavations. The site
plan prepared by dk Greene Consulting, Incorporated (Reference No. 1) was used a base
for the Field Density Location Map (Plate 1).
Groundwater
Regional groundwater was not encountered within the earthwork excavations and therefore
is not anticipated to be a major factor in the future performance of the planned residential
structure, provided the recommendations contained in this and our prior report are
properly incorporated into the balance of construction and post-development landscape
practices. Due to the nature of the site earth materials, perched groundwater conditions
may manifest in the future along zones of contrasting permeabilities and densities
(i.e., fill/bedrock deposits contacts, fill lifts, geologic discontinuities), as a result of
excessive precipitation, over-irrigation, and/or damaged underground utilities. The
potential for perched groundwater occurrence should be anticipated and disclosed to all
interested/affected parties. Should such conditions occur in the future, GSI could provide
recommendations for mitigation.
Geotechnical Engineering
Remedial Earthwork
1.Prior to grading, existing vegetation was removed and hauled offsite.
2.During grading, potentially compressible unsuitable soils (i.e., existing
undifferentiated colluvium/fill), were removed to expose suitable formational soils.
The depth of excavations necessary to remove potentially compressible soils was
approximately ±2-3 feet below the existing grade. The removal of unsuitable soils
was generally completed to at least 5 feet outside the building footprint (as
determined by others), or to a lateral distance equal to the depth of the removal,
whichever is greater. However, removals along the northeastern perimeter only
extended to approximately 2 feet outside of the building pad due to property
boundary restrictions, with mitigation likely to consist of a deepened footing (at least
24 inches of embedment) at this location. Approximate elevations of removal
and/or undercut bottoms are shown on Plate 1.
3.In order to provide for the uniform support of the structure, the building pad was
undercut to a minimum depth of at least 3 to 4 feet below pad grade to provide for
GeoSoils, Inc.
Richard Smerud W.O. 7099-B-SC
906 Pine Avenue, Carlsbad April 24, 2018
File:e:\wp12\7000\7099b.gro Page 3
a minimum 4-foot thick cap of engineered fill. The undercut portion of the pad was
generally sloped toward the southwest in order to mitigate the potential for perched
water along the fill/formational soils contact beneath the building. At one location,
an apparently abandoned, and previously infilled seepage pit was encountered
within the southeastern portion of the pad area. The area of the seepage pit was
excavated to about 8 feet below pad grade and capped with a 12-inch thick
concrete mat, with the mat extending at least 24 inches past the lateral limits of the
seepage pit.
4.Prior to fill placement, the bottoms of the remedial grading excavations
(i.e., removals and undercuts) were scarified, moisture conditioned to slightly above
optimum moisture conditions, and then re-compacted to at least 90 percent relative
compaction (ASTM D 1557), where tested.
5.All processing of original ground in areas to receive fill, as shown on Plate 1, were
observed by a representative of GSI.
6.Earthwork was performed to provide a uniform building pad for the planned new
structure. Any planned, settlement-sensitive improvements spanning these
transitions, and/or located within areas beyond the limits of fill placed under the
purview of this report, will be subject to an elevated potential for adverse soil
movement and associated distress, if these conditions are not mitigated in the
future. Additional recommendations for treatment of soils in these areas may be
provided on request.
Engineered Fill Placement
Engineered fill materials predominately consisted of the onsite soils derived from the
remedial grading excavations, with import fill material used to complete grading to the
desired elevations. Import fill materials used were evaluated to be consistent with the
native paralic deposits (considered formation). During grading, engineered fills were
placed in approximately 6- to 8-inch lifts, moisture conditioned, mixed to achieve slightly
greater than optimum moisture conditions, and mechanically compacted to a minimum
relative compaction of 90 percent of the laboratory standard (ASTM D 1557), where tested.
In general, the thickness of engineered fill placed under purview of this report was
generally about feet beneath the building pad(s).
Field Testing
1.Field density tests were performed using the nuclear method in general accordance
with ASTM test method D 6938-10 (Procedure A). The compaction test results are
presented in the attached Table 1. The approximate locations of the field density
tests performed during grading operations are presented on Plate 1.
GeoSoils, Inc.
Richard Smerud W.O. 7099-B-SC
906 Pine Avenue, Carlsbad April 24, 2018
File:e:\wp12\7000\7099b.gro Page 4
2.The field dry densities of the engineered fill were evaluated as a percentage of the
maximum dry density attained in the laboratory for the representative soil types
encountered during grading. Where field density testing indicated inadequate
compaction or moisture content, the failure area was reworked until at least
90 percent of the laboratory standard or slightly greater than optimum moisture
(ASTM D 1557) was achieved.
3.Field density tests were taken at periodic intervals and selected locations to check
the compaction and moisture content of the engineered fill placed by the contractor.
Laboratory Testing
Maximum Density Testing
The laboratory maximum dry density and optimum moisture content for the major soil type
encountered during grading, were evaluated in general accordance with test method
ASTM D 1557. The following table presents the results:
SOIL TYPE
MAXIMUM
DENSITY (PCF)
MOISTURE CONTENT
(PERCENT)
A - Dark Yellowish Brown, Silty Sand (Import)132.3 7.6
B - Yellow Brown, Silty Sand 128.9 8.8
C - Reddish Brown, Silty Sand w/ Trace Gravel (Import)127.2 8.8
D - Yellowish Brown, Silty Sand w/ Trace Gravel (Import)114.4 13.6
Expansion Potential
Expansion testing was performed on a representative sample of site soil in general
accordance with ASTM D 4829. The results of expansion testing are presented in the
following table.
LOCATION AND DEPTH (FT)EXPANSION INDEX EXPANSION POTENTIAL
Building Pad - Native Soil <20 Very Low
Building Pad - Import Soil <20 Very Low
GeoSoils, Inc.
Richard Smerud W.O. 7099-B-SC
906 Pine Avenue, Carlsbad April 24, 2018
File:e:\wp12\7000\7099b.gro Page 5
Saturated Resistivity, pH, and Soluble Sulfates, and Chlorides
GSI conducted sampling of onsite earth materials for general soil corrosivity and soluble
sulfates, and chlorides testing. The testing included evaluation of soil pH, soluble sulfates,
chlorides, and saturated resistivity. Test results are presented in the following table:
SAMPLE
LOCATION pH
SATURATED
RESISTIVITY
(ohm-cm)
SOLUBLE
SULFATES
(wt. %)
SOLUBLE
CHLORIDE
(ppm)
Building Pad 5.14 - 7.2 1,800 - 4,200 0.0152 - 0.0481 205 - 456
Laboratory testing indicates that tested samples of the onsite soils are strongly acidic to
neutral with respect to soil acidity/alkalinity, are moderately corrosive to corrosive to
exposed, buried metals when saturated, present negligible (“not applicable” per
ACI 318-11) sulfate exposure to concrete, and are somewhat elevated for chloride
exposure. Reinforced concrete mix design for foundations, slab-on-grade floors, and
pavements should minimally conform to “Exposure Class C1” in Table 4.2.1 of ACI 318-11,
as concrete would likely be exposed to moisture. It should be noted that GSI does not
consult in the field of corrosion engineering. The client and project architect should agree
on the level of corrosion protection required for the project and seek consultation from a
qualified corrosion consultant as warranted.
Conclusions
The work performed to date appears to be in general conformance with the preliminary
recommendations contained in Reference Nos. 2, 3, and 4, GSI field recommendations,
Appendix Chapter J of the 2013 California Building Code, and with the grading guidelines
of the City, from a geotechnical standpoint. Field testing indicates that fills placed under
the purview of this report have been minimally compacted to at least 90 percent of the
laboratory standard (ASTM D 1557), where tested. Based on the observation and
compaction testing performed during grading, GSI concludes that the residential building
pad, constructed under GSI observation and testing, is suitable for its intended use.
Unless superceded herein, the conclusions and recommendations regarding site
construction, including foundation design and construction recommendations presented
in Reference Nos. 2, 3, and 4 are considered valid and applicable.
Regulatory Compliance
The soil engineering and engineering geologic aspects of the construction are in general
compliance with approved geotechnical reports and geotechnical aspects of the
GeoSoils, Inc.
As defined in the California Business and Professions Code, Division 3, Chapter 15, Article 5,1
Section 8770.6.
Richard Smerud W.O. 7099-B-SC
906 Pine Avenue, Carlsbad April 24, 2018
File:e:\wp12\7000\7099b.gro Page 6
construction. Furthermore, with respect to the grading plans, GSI will certify that the soil1
engineering and engineering geologic aspects of the grading are in general compliance
with the approved geotechnical reports (see Reference Nos. 2, 3, and 4) and the grading
plan (Reference No.1).
Limitations
The conclusions and recommendations presented herein are professional opinions. These
opinions have been derived in accordance with current standards of practice, and no
warranty, either express or implied, is given. Standards of practice are subject to change
with time. GSI assumes no responsibility or liability for work or testing performed by
others, or their inaction; or work performed when GSI is not requested to be onsite, to
evaluate if our recommendations have been properly implemented. Use of this report
constitutes an agreement and consent by the user to all the limitations outlined above,
notwithstanding any other agreements that may be in place. In addition, this report may
be subject to review by the controlling authorities.
GeoSoils, Inc.
Richard Smerud W.O. 7099-B-SC
906 Pine Avenue, Carlsbad April 24, 2018
File:e:\wp12\7000\7099b.gro Page 7
If you have any questions or comments regarding this letter, please do not hesitate to
contact the undersigned.
Respectfully submitted,
GeoSoils, Inc.
Robert G. Crisman David W. Skelly
Engineering Geologist, CEG 1934 Civil Engineer, RCE 47857
CWP/RGC/DWS/jh
Attachments:Table 1 - Field Density Test Results
Plate 1 - Field Density Test Location Map
Distribution:(1) Addressee (via email)
(4) Strongside Management, Attn: Martin Volk (4 wet signed)
Table 1
FIELD DENSITY TEST RESULTS
TEST DATE TEST LOCATION TRACT ELEV MOISTURE DRY REL TEST SOIL
NO.NO.OR CONTENT DENSITY COMP METHOD TYPE
DEPTH (ft)(%)(pcf)(%)
1 4/9/18 Pad Area North End 906 Pine Ave.60.5 12.5 118.5 91.9 ND B
2 4/10/18 Pad South East 906 Pine Ave.61.5 10.3 126.3 98.0 ND B
3 4/10/18 Pad North West 906 Pine Ave.61.5 9.0 122.1 94.7 SC B
4 4/12/18 Pit Backfill 906 Pine Ave.58.3 10.1 124.9 96.9 ND B
5 4/12/18 South Pad East Side 906 Pine Ave.61.0 8.9 123.0 95.4 ND B
6 4/12/18 South Pad West Side 906 Pine Ave.61.0 9.4 123.4 95.7 ND B
7 4/13/18 South Half S.E.906 Pine Ave.62.0 10.0 119.9 93.0 ND B
8 4/13/18 South Half N.W.906 Pine Ave.62.0 9.3 121.3 94.1 SC B
9*4/16/18 South Portion 906 Pine Ave.62.5 5.8 116.4 87.9 ND A
9A 4/16/18 South Portion 906 Pine Ave.62.5 8.3 120.1 90.7 ND A
10 4/16/18 North Portion 906 Pine Ave.62.5 9.6 117.3 91.0 ND B
11 4/17/18 North Portion 906 Pine Ave.63.0 14.1 107.6 94.0 ND D
12 4/17/18 South Portion 906 Pine Ave.63.0 13.9 108.7 95.0 ND D
13 4/17/18 N.W. Portion 906 Pine Ave.63.5 9.1 120.1 92.7 ND A
14 4/17/18 S.W. Portion 906 Pine Ave.63.5 8.9 119.9 90.6 ND A
15 4/18/18 Northeast Corner 906 Pine Ave.64.0 10.4 116.9 90.7 ND B
16 4/18/18 Pad @ S.W. Corner 906 Pine Ave.64.0 8.8 121.7 91.9 ND A
FG-17 4/18/18 Pad @ N.E. Corner 906 Pine Ave.64.2 8.8 120.8 91.3 ND A
FG-18 4/19/18 Middle Low Pad 906 Pine Ave.63.7 9.1 123.4 93.2 ND A
FG-19 4/19/18 Southwest Upper Pad 906 Pine Ave.64.2 8.9 121.4 91.7 ND A
FG-20 4/19/18 Southeast Low Pad 906 Pine Ave.63.7 9.0 122.8 92.8 ND A
LEGEND:
* =Failed Test
A =Retest
FG =Finish Grade
ND =Nuclear Densometer
SC =Sand Cone
Richard Smerud
906 Pine Ave., Carlsbad
File: C:\excel\tables\7099b.gro GeoSoils, Inc.
W.O. 7099-B-SC
April, 2018
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