GEOTECHNICAL REPORT - Pavilion Construction · Geotechnical Report Proposed Development – 1701...
Transcript of GEOTECHNICAL REPORT - Pavilion Construction · Geotechnical Report Proposed Development – 1701...
Geotechnical & Earthquake
Engineering Consultants
GEOTECHNICAL REPORTPROPOSED DEVELOPMENT
1701 DEXTER AVENUE NORTH SEATTLE, WASHINGTON
2021A Minor Avenue EastSeattle, Washington 98102-3513Tel: 206.262.0370 Fax: 206.262.0374
Project No. 13-245February 2014
Prepared for:
H-HABIT DEXTER LLC
Image Credit: Bushnaq Studio, LLC
________________________________________________
3213 Eastlake Avenue E, Ste B
Seattle, WA 98102
Tel (206) 262-0370
Fax (206) 262-0374
Geotechnical & Earthquake
Engineering Consultants
February 5, 2014
File No. 13-245
Mr. Jim Daly
N-HABIT Dexter LLC
1101 North Northlake Way, #106
Seattle, WA 98103
Re: Geotechnical Report
Proposed Development
1701 Dexter Avenue North, Seattle, Washington
Dear Jim,
Please find attached our geotechnical report to assist you and your project team with the design
and construction of the proposed development at 1701 Dexter Avenue North in Seattle,
Washington. This report documents the subsurface conditions at the site and our geotechnical
engineering recommendations for the proposed project.
In summary, the property is underlain by relatively thick colluviual and slide deposits that extend
to over 30 feet below the existing grades. Based on the soil conditions anticipated at the
foundation level, we recommend that either a structural mat foundation or a mixed shallow
foundation system consisting of a structural mat foundation in the eastern portion of the building
and spread/continuous footings in the western portion of the building be used to support the
proposed building. The temporary excavation for basement construction may be accomplished
with a combination of an unsupported cut along the east basement wall and temporary
cantilevered/tieback soldier pile walls along the north, south, and west walls. Temporary
construction easements will be needed in order to install tiebacks.
We appreciate the opportunity to work on this project. Please call if there are any questions.
Sincerely,
H. Michael Xue, P.E.
Senior Geotechnical Engineer
Encl: Geotechnical Report
13-245_1701 Dexter Ave N_Report i PanGEO, Inc.
TABLE OF CONTENTS
1.0 INTRODUCTION................................................................................................................... 1
2.0 PROJECT AND SITE DESCRIPTION ............................................................................... 1
3.0 SUBSURFACE EXPLORATIONS ....................................................................................... 3
3.1 SUBSURFACE EXPLORATION (PANGEO, 2008) ...................................................................... 3
3.2 PREVIOUS EXPLORATIONS ...................................................................................................... 4
3.3 LABORATORY TESTING .......................................................................................................... 5
4.0 SUBSURFACE CONDITIONS ............................................................................................. 5
4.1 SITE GEOLOGY ....................................................................................................................... 5
4.2 SOIL CONDITIONS................................................................................................................... 6
4.3 GROUNDWATER CONDITIONS ................................................................................................. 7
5.0 ECA CONSIDERATIONS AND SITE STABILITY .......................................................... 7
5.1 STEEP SLOPE CONSIDERATIONS ............................................................................................. 7
5.2 HISTORICAL LANDSLIDES AND SITE STABILITY ..................................................................... 7
6.0 GEOTECHNICAL RECOMMENDATIONS ...................................................................... 8
6.1 SEISMIC DESIGN PARAMETERS ............................................................................................... 8
6.2 TEMPORARY EXCAVATION AND SHORING .............................................................................. 9
6.2.1 Unsupported Cuts........................................................................................................... 9
6.2.2 Solider Pile Wall .......................................................................................................... 10
6.2.3 Tiebacks ....................................................................................................................... 11
6.2.4 Lagging ........................................................................................................................ 14
6.2.5 Baseline Survey and Monitoring ................................................................................. 14
6.2.6 Temporary Dewatering ................................................................................................ 15
6.3 BUILDING FOUNDATIONS ..................................................................................................... 16
6.3.1 Mat Foundation ............................................................................................................ 16
6.3.2 Spread/Continuous Footings ........................................................................................ 17
6.3.3 Foundation Performance .............................................................................................. 17
6.3.4 Lateral Resistance ........................................................................................................ 18
6.4 FLOOR SLABS ....................................................................................................................... 18
6.5 BASEMENT WALLS ............................................................................................................... 19
6.5.1 Lateral Earth Pressures ................................................................................................ 19
6.5.2 Wall Surcharge ............................................................................................................. 19
6.5.3 Lateral Resistance ........................................................................................................ 20
6.5.4 Wall Drainage .............................................................................................................. 20
6.5.5 Wall Backfill ................................................................................................................ 20
7.0 CONSTRUCTION CONSIDERATIONS .......................................................................... 21
7.1 DEMOLITION AND SITE PREPARATION .................................................................................. 21
7.2 SOLDIER PILE INSTALLATION ............................................................................................... 21
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7.3 MATERIAL REUSE ................................................................................................................ 22
7.4 STRUCTURAL FILL AND COMPACTION .................................................................................. 22
7.5 EROSION AND DRAINAGE CONSIDERATIONS ........................................................................ 22
7.6 WET EARTHWORK RECOMMENDATIONS .............................................................................. 23
8.0 ADDITIONAL SERVICES.................................................................................................. 23
9.0 LIMITATIONS ..................................................................................................................... 24
10.0 REFERENCES .................................................................................................................... 26
LIST OF FIGURES
Figure 1 Vicinity Map
Figure 2 Site and Exploration Plan
Figure 3 Generalized Subsurface Profile A – A’
Figure 4 Design Lateral Pressures – Soldier Pile Wall, Cantilevered and One Row Tieback
Figure 5 Design Lateral Pressures – Solider Pile Wall, Multiple Row Tiebacks
LIST OF APPENDICES
Appendix A Summary Boring Logs (PanGEO, 2008)
Figure A-1 Terms and Symbols for Boring and Test Pit Logs
Figure A-2 Log of Test Boring BH-1
Figure A-3 Log of Test Boring BH-2
Figure A-4 Log of Test Boring BH-3
Appendix B Summary Boring Logs from Previous Explorations and Past Street
Grading Profile
Boring Logs B-1 and B-2 for 1707 Dexter Avenue N (Geotech Consultant 2005)
Boring Logs B-1 through B-3 for 1620 Dexter Avenue N (Terra Associates 1992)
Boring Logs B-2 and B-3 for 1735 Aurora Avenue N (RZA 1988)
Boring Logs B-1 and P-2 through P-4 for 1701 Dexter Avenue N (Shannon & Wilson
1978)
Street Grading Profile along Dexter Avenue North
Appendix C Summary of Laboratory Test Results
Figure C-1 Grain Size Distribution
Figure C-2 Atterberg Limits
GEOTECHNICAL REPORT
PROPOSED DEVELOPMENT
1701 DEXTER AVENUE NORTH
SEATTLE, WASHINGTON
______________________________________________________________________________
1.0 INTRODUCTION
This report presents the results of a geotechnical engineering study that was undertaken to
support the design and construction of the proposed development at 1701 Dexter Avenue North
in Seattle, Washington. PanGEO previously prepared a geotechnical report for a proposed
modular apartment building at the subject site in 2008. Our current study was performed in
accordance with our proposal dated September 25, 2013. The scope of our work included
reviewing published geologic and geotechnical data in the site vicinity, reviewing our previous
report for the subject property prepared in 2008, reviewing current design plans, conducting a
site reconnaissance, performing engineering analysis, and developing the conclusions and
recommendations presented in this report. We received your authorization to proceed on
November 5, 2013.
2.0 PROJECT AND SITE DESCRIPTION
The subject property is located at 1701 Dexter Avenue North on the west side of Dexter Avenue
North, near the intersection of Dexter Avenue North and Hayes Street, in Seattle, Washington
(see Vicinity Map, Figure 1). The site consists of an approximately 16,230 square-foot,
rectangular-shaped parcel that extends approximately 150 feet in the north-south direction along
Dexter Avenue North and approximately 108 feet in the east-west direction (See Plate 1 on Page
2). The subject site is bound to the north by two townhome buildings, to the south by a
commercial property occupied by a four level building, to the east by Dexter Avenue North, and
to the west by an asphalt-paved alleyway.
The site is located on a highly developed hillside that descends east toward Lake Union. The
northern half of the subject site is currently occupied by a vacant two-story office building
(including a daylight basement) and the southern half of the site is mostly an asphalt-paved
parking lot (see Plate 2 on Page 2). Based on our field observations, it appears that the existing
office building has been benched into the east-facing hillside. In addition, significant cuts were
made to reach the existing grade in the relatively level parking area. An approximately 10-foot
high, cast-in-place concrete retaining wall is located on the west side of the parking area (Plate
2). An approximately 15-foot high slope ascends from the top of the wall to the alleyway (west
property line) at an estimated inclination of 1½H:1V (Horizontal:Vertical).
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Plate 1. An aerial view of the existing site (Modified from Google Maps).
Based on a review of City of
Seattle ECA maps and
topographic survey map, the
east-facing slope at the west and
southwestern portions of the site
is a steep slope (40% or greater).
The subject site is also mapped
as a potential landslide area
because of past landslides in the
project vicinity and the site
geologic conditions.
Based on a review of the current plans, we understand that the proposed development will
consist of demolishing the existing building, and constructing a 4-story apartment building with
one level of below grade parking below Dexter Avenue North level (see Plate 3 on Page 3). We
also understand that the below-grade parking and first level will be concrete structures with post-
tension slabs, and the floors above that will be light-weight wood frame construction. The
Plate 2. Partial panoramic view of the site with the retaining
wall and the existing building, looking north and northwest
from the southeast corner of the site.
Dexter Avenue N
SUBJECT SITE
Alley N
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basement excavation will be about 12 to 14 feet deep along Dexter Avenue North, and as much
as 35 feet deep along the west property line.
Plate 3. The East-West Building Section, Looking North.
The conclusions and recommendations outlined in this report are based on our understanding of
the current development plans, which is in turn based on the project information provided. If the
above project description is substantially different from your proposed improvements, or if the
project scope changes, PanGEO should be consulted to review the recommendations contained
in this study and make modifications, if needed.
3.0 SUBSURFACE EXPLORATIONS
3.1 SUBSURFACE EXPLORATION (PANGEO, 2008)
PanGEO completed three test borings (BH-1 through BH-3) on April 17, 2008 to explore the
subsurface conditions at the site. The approximate boring locations were taped from existing
features at the site and are indicated on the attached Figure 2. The borings were drilled to depths
of about 26½ to 46½ feet using a small track-mounted drill rig owned and operated by Geologic
Drill of Nine Mile Falls, Washington. The small track-mounted drill rig was equipped with an 8-
inch outside diameter hollow stem auger. Soil samples were obtained from the borings at 2½-
and 5-foot intervals in general accordance with Standard Penetration Test (SPT) sampling
methods (ASTM test method D-1586) in which the samples are obtained using a 2-inch outside
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diameter split-spoon sampler. The sampler was driven into the soil a distance of 18 inches using
a 140-pound weight falling a distance of 30 inches. The number of blows required for each 6-
inch increment of sampler penetration was recorded. The number of blows required to achieve
the last 12 inches of sample penetration is defined as the SPT N-value. The N-value provides an
empirical measure of the relative density of cohesionless soil, or the relative consistency of fine-
grained soils. The completed borings were backfilled with drill cuttings and bentonite chips.
The surface for BH-1 and BH-2 was patched with concrete.
A geologist from our firm was present throughout the field exploration to observe the drilling,
assist in sampling, and to document the soil samples obtained from the borings. The soil samples
were described using the system outlined on Figure A-1 in Appendix A. Summary boring logs
are included as Figures A-2 through A-4.
3.2 PREVIOUS EXPLORATIONS
In addition to the three borings advanced at the site, we also reviewed previous geotechnical
explorations in the vicinity and the past street grading profiles along Dexter Avenue North
obtained from the City of Seattle. Specifically, previous geotechnical data for the following sites
and the street grading profiles along Dexter Avenue North were reviewed:
1620 Dexter Avenue North - Prepared by Terra Assoc. (TA), 1992.
1701 Dexter Avenue North (Subject Site) - Prepared by Shannon & Wilson, Inc. (SW),
1978.
1707 Dexter Avenue North - Prepared by Geotech Consultants, Inc. (GC), 2006.
1735 Dexter Avenue North - Prepared by Rittenhouse-Zieman & Assoc., Inc. (RZA),
1988.
Street grading profile along Dexter Avenue North.
The summary boring logs for the previous explorations and past grading profile are included in
Appendix B for reference purposes.
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3.3 LABORATORY TESTING
Grain size distribution, Atterberg Limits, and natural moisture contents tests were conducted on
selected representative soil samples obtained from the borings. The test results from the
moisture content tests are indicated at the appropriate depths on the boring logs. The grain size
distribution test results are included in Figure C-1 in Appendix C. The Atterberg Limits test
results are summarized on the logs and in Figure C-2 in Appendix C.
4.0 SUBSURFACE CONDITIONS
4.1 SITE GEOLOGY
Based on a review of The Geologic Map of Seattle (Troost, et. al., 2005), the surficial geologic
units in the project vicinity consist of landslide deposits, advance outwash, Lawton clay, and Pre-
Fraser glaciation aged deposits. A brief description of each mapped soil unit listed from
youngest to oldest follows:
Landslide Debris (Map Unit Qls) – Material transported down-slope triggered by a
landslide event. The relative density/consistency of landslide deposits is highly variable
and can range from very loose or soft to very dense or hard. Surface vegetation often
becomes incorporated into the deposit. Landslide deposits in the Seattle area are
common where coarse-grained deposits overlie fine-grained deposits.
Vashon Advance Outwash (Map Unit Qva) - This deposit consists of sediment
deposited in front of the advancing ice sheet by glacial meltwater (glaciofluvial) and was
subsequently overridden by the glacial ice, and is typically dense.
Lawton Clay (Map Unit Qvlc) - Fine grained sediments deposited in proglaicial lakes
that indicate a transition between non-glacial and earliest glacial time. Transitional beds
typically consist of very stiff to hard silt, clayey silt, and silty clay. This unit can be
laminated to massive and is also known as transitional beds.
Pre-Fraser Deposits (Map Unit Qpf) – Interbedded sand, gravel, silt, and diamicts that
were overridden by Pre-Fraser glaciations and are typically very dense or hard.
According to The Geologic Map of Seattle, the Dexter Avenue North right-of-way in the vicinity
of the site is mapped as modified land. A review of the street grading records in the Seattle
Department of Transportation’s (SDOT) records vault indicates that grading on the west side of
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Dexter Avenue North (approximately east property line) involved cuts on the order of 8 to 12
feet to reach the current street grade.
4.2 SOIL CONDITIONS
In summary, our borings encountered loose to medium dense silty sand or soft to stiff clay and
silt overlying very stiff Lawton clay. The following is a summary of the soil units encountered at
the site. A generalized subsurface profile is presented in Figure 3.
UNIT 1: Colluvium – This unit was encountered in all borings from surface to about
14½ feet. The colluvium encountered consisted of brown to dark brown, loosed to
medium dense, silty sand with some gravel. Thin layers of medium stiff to stiff silt and
sandy silt of about 6-inch and 2 feet thick were also encountered within this unit in BH-1
and BH-2.
UNIT 2: Landslide Deposits – This unit was encountered in all borings, directly below
the colluvium. The landslide deposits encountered consisted of gray, soft to stiff, fat clay
to silty clay. This unit extended to the bottom of BH-1 and BH-2 at about 31½ and 26½
feet below the existing grade, respectively. This unit extended to about 40 feet in BH-3.
UNIT 3: Lawton Clay – Lawton clay consisting of gray, very stiff, silty clay/clayey silt
was encountered below Unit 2 in BH-3 extended to the maximum depth of BH-3 at 46½
below the surface.
Two test borings advanced at the neighboring property to the north (GC, 2006) encountered
about 14 to 19 feet of medium dense to dense sand overlaying medium dense to very dense silt to
about 31 feet below existing grades. Landslide deposits were not noted in these two borings.
The borings drilled at this site indicated a denser soil condition.
The borings advanced on the east side of Dexter Avenue North (RZA, 1991), however, generally
encountered similar soil conditions to what was observed in our borings at the subject site.
Those three borings encountered approximately 10 to 25 feet of loose to medium dense silty sand
over medium stiff to hard fat clay.
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4.3 GROUNDWATER CONDITIONS
Perched groundwater was encountered at depths of about 7 and 9 feet in Borings BH-1 and BH-2
that were drilled in the parking lot. Boring BH-3 drilled in the alleyway also encountered
perched groundwater at about 20 feet below the existing grade. We anticipate that localized
areas of groundwater seepage will occur throughout the disturbed soils or perched on top of silt
or clay layers. It should be noted that groundwater elevations may vary depending on the season,
local subsurface conditions, and other factors. Groundwater levels are normally highest during
the winter and early spring.
5.0 ECA CONSIDERATIONS AND SITE STABILITY
5.1 STEEP SLOPE CONSIDERATIONS
Our review of City of Seattle ECA maps and topographic survey map indicate the east-facing
slope at the west and southwestern portions of the site meets DPD steep slope ECA definition.
Site grades in the sloping area appear to have been modified by several different grading
activities, as the over-steepened slope was most likely the cuts to facilitate the construction of the
existing building and parking lot on the east side of the retaining wall. A review of street
grading records at the City of Seattle SDOT indicates that the current grade 40 ft west of Dexter
Avenue North centerline (approximate the east property line) was lowered up to 12 feet (see
Grading profile in Appendix B). Based on the past street grading information, the subsurface
conditions encountered in the borings, and the existing site topographic features, it is our opinion
that the steep slope on the property was the man-made cut slopes associated with past street
grading and previous site grading for the existing building and parking lot construction. As such,
in our opinion, the subject site qualifies for a Relief from Steep Slope Development Standards
due to previous grading activities.
5.2 HISTORICAL LANDSLIDES AND SITE STABILITY
The site is also mapped as a potential landslide hazard area by the City of Seattle due to its
geologic conditions. As part of our study, we reviewed records of historical landslides in the
Seattle Landslide Study commissioned by the Seattle Public Utilities (SPU) to gain a general
understanding of the past landslide activities in the project vicinity. Our review of the Seattle
Landslide Study indicated that there were two past known landslides within the same block of
subject property as listed below:
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1520 Dexter Avenue N – Occurred in April 1967
1747 Dexter Avenue N – Occurred in February 1986
According to the City records, the landslide at 1520 Dexter Avenue North was reported to be
associated with the failure of fill soils placed illegally and the fill was subsequently removed.
The slide is at 1747 Dexter Avenue North is reported to be a small shallow colluvium slide
which did not affect the structures. The areas affected by the slope failures at both address have
since been stabilized.
Due to the marginal nature of the on-site soils, the steep slope portion of the site soils is
considered conducive to down slope movements. However, based on our understanding of the
proposed project, the new construction will remove the existing steep slope on the subject
property, and provided that the basement walls of the development are designed in accordance
with the recommendations presented in this report, in our opinion, the proposed development
will improve the stability of the subject and surrounding properties.
6.0 GEOTECHNICAL RECOMMENDATIONS
6.1 SEISMIC DESIGN PARAMETERS
Table 1 below provides seismic design parameters for the site that are in conformance with the
2012 and later editions of the International Building Code (IBC), which specifies a design
earthquake having a 2% probability of occurrence in 50 years (return interval of 2,475 years),
and the 2008 USGS seismic hazard maps:
Table 1 – Seismic Design Parameters
Soil Liquefaction - Because of the high fines content of the soils underlying the site, and
sporadic seams of perched groundwater, in our opinion the potential for earthquake-induced soil
Site
Class
Spectral
Acceleration
at 0.2 sec. (g)
SS
Spectral
Acceleration
at 1.0 sec. (g)
S1
Site
Coefficients
Design
Spectral
Response
Parameters
Control
Periods
(sec.)
Design
PGA
(SDS/2.5)
Fa Fv SDS SD1 TO TS
D 1.33 0.51 1.0 1.5 0.88 0.51 0.12 0.58 0.35
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liquefaction is considered to be low. As such, special design considerations associated with soil
liquefaction are not necessary for this project.
6.2 TEMPORARY EXCAVATION AND SHORING
As currently planned, the temporary excavations will be about 12 feet deep along the east
basement wall and about 30 to 35 feet deep along the west building line (alley). Based on our
test borings, we anticipate that the site excavations will generally encounter loose sand and soft
to very stiff silt and clay.
Zero lot line construction will be utilized for the basement construction except along the east
basement wall where it will be setback approximately 13 feet from the east property line. As
such, in our opinion, an unsupported open cut may be used along the east basement wall.
However, temporary shoring will be needed to support the excavations along north, west, and
south walls. Based on the soil and groundwater conditions encountered in the borings advanced
at the site, in our opinion, a combination of cantilever and tieback soldier pile walls is considered
the most appropriate temporary shoring system to retain the proposed excavation. It is our
opinion that a soil nail shoring wall would not be feasible due to the marginal soils at the site (i.e.
colluvium over landslide deposits) and high risk of ground movements. The shoring system
should be designed to provide adequate protection for the workers, adjacent structures, utilities,
and other facilities. . The contractor is responsible for maintaining safe excavation slopes and/or
shoring.
It should be noted that installation of tiebacks will require construction easements from the City
and adjacent property owners. If construction easements cannot be obtained, an internally
braced shoring system should be used in-lieu of tieback shoring system. PanGEO can provide
detailed design recommendations if such shoring system will be used.
The design recommendations for the unsupported cut and shoring walls are provided in the
following sections.
6.2.1 Unsupported Cuts
As previously indicated, an unsupported slope cut may be used along the east basement wall. All
temporary excavations should be performed in accordance with Part N of WAC (Washington
Administrative Code) 296-155. For planning purposes, the unsupported slope cut could be
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sloped to as steep as 1H (Horizontal):1V (Vertical). If areas of seepage are encountered during
construction, the slopes may need to be flattened. The contractor is responsible for maintaining
safe excavation slopes. The stability of temporary excavation slopes should be evaluated in the
field during construction based on actual observed soil conditions.
6.2.2 Solider Pile Wall
A soldier pile wall consists of vertical steel beams, typically spaced from 6 to 8 feet apart along
the proposed excavation wall, spanned by timber lagging. Prior to the start of excavation, the
steel beams are installed into holes drilled to a design depth and then backfilled with lean mix or
structural concrete. As the excavation proceeds downward and the steel piles are subsequently
exposed, timber lagging is installed between the piles to further stabilize the walls of the
excavation. Due to the height of the proposed excavation along the north, west, and western half
of the south property lines, one or more levels of tie-backs will most likely be required.
Tiebacks are typically used for wall heights greater than about 12 feet to achieve a more
economical design.
An existing cantilever soldier pile and concrete wall about 10 to 12 feet in height was installed
along the western half of the north property line (see Plate 4 on page 11), which was installed to
retain fill when the site grade on the adjacent property to the north was raised. The temporary
shoring wall for this project should be designed to accommodate the surcharge load from this
wall.
Design Lateral Pressures – For a cantilevered soldier pile wall or a soldier pile wall with one
level of tiebacks, the earth pressures depicted on Figure 4 should be used for design. For a
soldier pile wall with more than one level of tiebacks, the earth pressures depicted on Figure 5
should be used for design. The lateral earth pressures shown on Figures 4 and 5 should be
increased for any surcharge loads resulting from traffic, construction equipment, building loads
or excavated soil if they are located within the height dimension of the wall.
Above the bottom of excavation, the recommended active earth and surcharge pressures should
be applied over the full width of pile spacing. Below the bottom of excavation, the active and
surcharge pressures should be applied over one pile spacing, and the passive resistance should be
applied over two times the pile diameter.
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Vertical Capacity – We recommend the vertical capacity of the soldier piles be determined
using an allowable skin friction value of 0.5 ksf for the portion of the pile below the bottom of
the excavation, and an allowable end bearing value of 10 ksf.
Construction Considerations - We anticipate that the soldier piles will extend through layers of
saturated sandy soils and it is likely that the drilled holes may cave in when drilled through such
layers. As a result, temporary casings may be
needed to stabilize the drilled holes.
An existing soldier pile and concrete wall is
located along the north property line to retain the
yard on the neighboring property to the north (see
Plate 4 on the right). Drilling of the soldier pile
holes along the north property line could
potentially reduce the passive resistance of the
existing pile wall, which may cause significant
movement of the existing soldier pile wall. As
such, new soldier piles should be located
sufficiently away from existing piles and the use
of temporary casing during installation may be
required. The shoring designer should carefully
evaluate the loading conditions for design of the
temporary shoring wall along the north property
line. If necessary, the existing soldier pile wall
may be braced/supported prior to drilling of new
soldier pile holes.
6.2.3 Tiebacks
All tiebacks will extend beyond the property boundaries. As a result, construction easements
will be needed from the neighboring property owners, including the City of Seattle Department
of Transportation. The easements should be obtained as early in the design process as possible
because the project costs could be significantly impacted without the construction easements.
Plate 4. Partial view of the existing soldier
pile and concrete wall along the north
property line, looking west from Dexter
Avenue N sidewalk.
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Excessive pile top deflection could occur before the first row of tiebacks is installed. To
improve the performance of the tieback wall, it may be necessary to limit the first row of
tiebacks to no more than 10 feet below pile top unless steel beams of sufficient size will be used
to limit the magnitude of the cantilever deflection. The cantilevered condition of the soldier pile
wall prior to installation of the tiebacks should be analyzed for the sufficient size and deflection.
The bond length of the tiebacks must be located behind a no-load zone defined as a plane
projected upward at a 60 degree angle from the base of the excavation, and setback from the face
of the wall a minimum distance of 5 feet or H/4, where H is the exposed height of the wall. The
tiebacks should have a minimum bond length of 15 feet beyond the no-load zone.
The manner in which the tieback anchors carry load will depend on the type of anchor selected,
the method of installation, and the soil conditions surrounding the anchor. Accordingly, we
recommend use of a performance specification requiring the shoring contractor to install anchors
capable of satisfactorily achieving the design structural loads, with a pullout resistance factor of
safety of 2.0. For planning purposes, however, the anchors may be sized for an allowable skin
friction value of 2.5 kips per lineal foot of anchor bond length, assuming that small diameter
(about 6 inches) pressure-grouted tiebacks will be used. Post-grouting may also be needed in
order to achieve the design capacity. We recommend that the allowable tieback loads be limited
to about 100 kips per anchor.
The tiebacks for this project should be installed by experienced personnel. We recommend the
tiebacks along the west and north walls be drilled with temporary casings to prevent excessive
ground loss. Because the boring logs indicated the presence of perched ground water and
disturbed soil, casings may also be needed along the north and south walls to prevent excessive
caving and allow for proper installation in the disturbed ground or when drilling through
saturated soil layers. In addition, the use of compressed air to flush the drill cuttings must be
properly controlled; the use of excessive amount of compressed air while drilling tiebacks could
lead to reduction of soil strength and ground movements.
The actual capacity of the anchors should be checked with 200 percent verification tests. At
least two 200-percent tests should be performed prior to installing production anchors. All
production anchors should be proof tested to 150% of the design load. The anchor installations
should be conducted in accordance with the latest edition of the Post Tensioning Institute (PTI)
“Recommendations for Prestressed Rock and Soil Anchors”. Elements of the testing are as
follows:
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Verification Tests (200% Tests)
Prior to installing production anchors, perform a minimum of two tests each on each
anchor type, installation method and soil type with the tested anchors constructed to the
same dimensions as production anchors.
Test locations to be determined in conjunction and approved by the geotechnical
engineer.
Test anchors, which will be loaded to 200% of the design load, may require additional
prestressing steel (steel load not to exceed 80% of the ultimate tensile strength) or
reinforcing of the soldier pile.
Load test anchors to 200% load in 25% design load increments, holding each incremental
load for at least 5 minutes and recording deflection of the anchor head at various times
within each hold to the nearest 0.01inch.
At the 200% load, the holding period shall be at least 60 minutes.
At least one verification test along the west wall should be held at the 200% load for 4
hours to test for creep.
A successful test shall provide a measured creep rate of 0.04 inches or less at the 200%
load between 1 and 10 minutes, and 0.08 inches or less between 6 and 60 minutes and 24
and 240 minutes, and all time increments shall have a creep rate that is linear or
decreasing with time. The applied load must remain constant during all holding periods
(i.e. no more than 5% variation from the specified load).
Proof Tests (150% load tests on all production anchors)
Load test all production anchors to 150% of the design load in 25% design load
increments, holding each incremental load until a stable deflection is achieved (record
deflection of the anchor head at various times within each hold to the nearest 0.01inch).
Please note that the recommended 150% proof test is slightly higher than the typical
proof tests (133%) for anchors in better soil conditions.
At the 150% load, the holding period shall be at least 10 minutes
A successful test shall provide a measured creep rate of 0.04 inches or less at the 150%
load between 1 and 10 minutes with a creep rate that is linear or decreasing with time.
The applied load must remain constant during the holding period (i.e. no more than 5%
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variation from the 150% load). Anchors failing this proof testing creep acceptance
criteria may be held an additional 50 minutes for creep measurement. Acceptable
performance would equate to a creep of 0.08 inches or less between 5 and 50 minutes
with a linear or decreasing creep rate.
Verification tested anchors or extended creep proof tested anchors not meeting the acceptance
criteria will require a redesign by the contractor to achieve the acceptance criteria.
In the tieback construction, a bond breaker shall be constructed in the no load zone when the
installation procedures use single stage grouting.
Performance – Generally, the shoring walls should be designed to limit lateral and vertical
deflection to about 1 inch. However, portions of the north and south walls, where the existing
buildings are located within 5 feet of the property lines, shoring walls should be designed to limit
pile top deflections to less than ½ inch to minimize the potential lateral movement of the
building foundation. Ground settlements outside the excavation are expected to be less than 1
inch and practically negligible beyond 100 feet from the shoring wall.
6.2.4 Lagging
Lagging design recommendations for general conditions are presented on Figures 4 and 5.
Lagging located within 10 feet of the top of the shoring which may be subjected to surcharge
loads from construction equipment or material storage should be designed for an additional
uniform surcharge pressure of 200 psf. This pressure approximately corresponds to a vertical
uniform surcharge load of 500 psf at the top of the wall. Point loads located close to the top of
the wall, such as outriggers of heavy cranes, may apply additional loads to the lagging. These
loads may need to be individually analyzed. However, lagging designed for a uniform load of
600 psf in the top 10 feet of the wall should be able to accommodate most crane outrigger loads.
We recommend that the voids behind lagging be immediately backfilled with Control Density
Fill (CDF).
6.2.5 Baseline Survey and Monitoring
Ground movements will occur as a result of excavation activities. As such, ground surface
elevations of the adjacent property and city streets should be documented prior to commencing
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earthwork to provide baseline data. As a minimum, optical survey points should be established
at:
The top of every other soldier pile. These monitoring points should be monitored
twice a week as required by the SDOT before the first elevated concrete slabs are
completed, and the monitoring frequency may be reduced thereafter;
The curbs and the centerlines of Dexter Avenue North and alley. All monitoring
points should be spaced no more than 20 feet apart. After the initial baseline reading
has been surveyed, these monitoring points do not need to be surveyed unless the pile
top deflections exceed about one-half of an inch; and
The adjacent buildings and existing soldier pile wall to the north and south.
Monitoring points should be spaced no more than 20 feet apart along the north and
south walls (the walls next to the shoring walls) of the adjacent buildings and soldier
pile wall. After the initial baseline reading has been surveyed, these monitoring points
do not need to be surveyed unless the pile top deflections exceed about one inch
The monitoring program should include changes in both the horizontal (x and y directions) and
vertical deformations. The monitoring should be performed by a licensed surveyor, and the
results be promptly submitted to PanGEO and SDOT for review. The results of the monitoring
will allow the design team to confirm design parameters, and for the contractor to make
adjustments if necessary.
We also recommend that the existing conditions long the public right-of-way and the adjacent
private properties be photo-documented prior to commencing any earthworks at the site.
6.2.6 Temporary Dewatering
Because groundwater seepage and perched groundwater were encountered in the test borings
during our field exploration, the contractor should be prepared to provide temporary dewatering
systems for the excavation. Based on our understanding of the project and site conditions, we
anticipate that a conventional dewatering system consisting of trenches, sumps and pumps will
be adequate to dewater the temporary excavation. We also anticipate that the seepage quantities
should be relatively small, likely less than 5 gallons per minute.
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6.3 BUILDING FOUNDATIONS
Based on the results of the borings drilled at the site, we anticipate that the soils at the proposed
foundation elevation on the eastern half of the site generally consist of loose and wet silty sand
and medium stiff silt and clay. The foundation soil on the western half of the site is anticipated
to consist of stiff to very stiff silt and clay (see Figure 3). Based on the subsurface conditions
anticipated at the foundation level and our understanding of the building design, it is our opinion
that conventional strip and spread footings are appropriate to support the western half of the
building. However, we recommend a mat foundation be used to support the eastern half of the
building to reduce potential for unacceptable differential settlements due to presence of less
competent soil conditions at the footing level. Alternatively, for the simplicity of design and
construction, the entire basement may be supported on a mat foundation.
A deep foundation system, such as augercast piles, is also feasible if a higher level of foundation
performance is desired. However, based on our experience and discussion with the project
design team, either a mat foundation or a combination of spread/continuous footings and mat
foundation will be the most cost effective foundation system to provide foundation support for
the proposed development. PanGEO can provide design recommendations for the deep
foundations if needed.
6.3.1 Mat Foundation
A mat foundation should be used to support the eastern half of the building, including the north-
south trending shear wall in the middle of the basement. A mat foundation will distribute the
loads from the structure over a wide area, and based on our understanding with the structural
engineer, will impose a bearing pressure of less than about 1000 psf. To improve the
performance of the mat foundation, we recommend removing one foot of soil below the slab and
replace it with structural fill compacted to 95% of its maximum dry density, as determined by
ASTM D 1557 (Modified Proctor). Import free-draining granular fill, such as Seattle Type 2 or
approved equivalent, should be used as structural fill as the existing on-site material has a high
fines content and may be too wet to compact. Following removal of the existing soil, and prior
to structural fill placement, the subgrade at the over-excavation level should be compacted to a
firm and unyielding condition. If the existing soils have a high moisture content, a heavy static
roller should be used to compact the subgrade. Any areas of soft fine-grained or organic soils
that cannot be properly compacted to a firm condition should be removed and replaced with
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compacted structural fill. With the subgrade improvement discussed above, we recommend the
use of a modulus of subgrade reaction of 150 pci for the mat slab design.
6.3.2 Spread/Continuous Footings
As previously discussed, the western half of the building may be supported on conventional
spread and continuous footings. The footing subgrade should be over-excavated a minimum of
12 inches and replaced with compacted structural fill. The over-excavation should extend 12
inches horizontally beyond the footing edge. The subgrade soil at the over-excavation level
should be compacted to a firm and unyielding condition prior to placement of structural fill. If
the native soil cannot be compacted to a firm and unyielding condition, additional over-
excavation may be required as determined in the field during construction by the geotechnical
engineer.
We recommend that an allowable soil bearing pressure of 2,000 psf be used for sizing
spread/continuous footings bearing on the compacted structural fill. For allowable stress design,
the recommended bearing pressure may be increased by one-third for transient loading, such as
wind or seismic forces.
Continuous and isolated column footings should have minimum widths of 24 inches and 48
inches, respectively. Exterior foundation elements should be placed at a minimum depth of 18
inches below final exterior grade. Interior spread foundations should be placed at a minimum
depth of 12 inches below the top of slab.
6.3.3 Foundation Performance
Total and differential settlements are anticipated to be within tolerable limits for foundation
elements designed and constructed as discussed above. Provided the mat slab subgrade is
prepared as described above, mat foundation settlement is estimated to be approximately ½ inch
with differential settlement on the order of ¼ inch. Total spread/continuous footing settlement is
also anticipated to be on the order of approximately one inch, and differential settlement between
adjacent columns should be less than about ½ inch. The differential settlement between footings
and mat foundation should be on the order of about ¼ inch.
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6.3.4 Lateral Resistance
Lateral forces from wind or seismic loading may be resisted by a combination of passive earth
pressures acting against the embedded portions of the mat foundation and walls, and by friction
acting on the base of the foundations. Passive resistance values may be determined using an
equivalent fluid weight of 300 pounds per cubic foot (pcf). This value includes a factor safety of
at least 1.5 assuming that properly compacted structural fill will be placed adjacent to the sides
of the foundation. A friction coefficient of 0.4 may be used to determine the frictional resistance
at the base of the mat. This coefficient includes a factor safety of approximate 1.5.
6.4 FLOOR SLABS
Conventional slab on grade construction may be used for the western half of the basement floors,
if spread/continuous footings are used. The concrete slabs on grade should be constructed on a
minimum 4-inch thick capillary break placed on the compacted native subgrade soil or structural
fill. The capillary break material should consist of free-draining, crushed rock compacted to a
firm and unyielding condition. The capillary break material should have no more than 10
percent passing the No. 4 sieve and less than 5 percent by weight of the material passing the U.S.
Standard No. 100 sieve. The capillary break material may be omitted for the mat foundation
since it is supported on a minimum of 12 inches of structural fill. We also recommend that a 10-
mil polyethylene vapor barrier be placed below the slab. We also recommend that construction
joints be incorporated into the floor slab to control cracking. If needed, the floor slab design may
be accomplished using a modulus of subgrade reaction of 150 pci.
Under-Slab Drain – Due to the presence of perched groundwater and seepage, we recommend
installing an under-slab drainage system below the floor slabs and the mat foundation. The
under-slab drainage system should consist of 4-inch diameter perforated drainpipes placed in
narrow (one foot or less), approximately 18-inch deep trenches (measured from the bottom of
slab) spaced no more than about 20 feet apart. In addition, a perforated footing drain pipe should
also be installed along the inside perimeter of the basement walls connected to the under-slab
drain pipes. The under-slab drain trenches should be backfilled with clean, free-draining 3/8
inch minus clean crushed rock or pea gravel. Water collected in these drainpipes should be
conveyed to a permanent sump pump and discharged to an appropriate outlet.
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Based on our estimate, the flow rate from the passive drainage system may vary from 10 to 15
gallon per minute (gpm) depending on the time of the year. For design purposes, a factor of
safety of at least 1.5 should be applied to the estimated flow volume. We also recommend that
an overflow be built into the drainage system in the event of extreme flows during a heavy storm.
6.5 BASEMENT WALLS
Basement walls should be properly designed to resist the lateral earth pressures exerted by the
soils behind the wall. Proper drainage provisions should also be provided behind the walls to
intercept and remove groundwater and seepage that may be present behind the wall. Our
geotechnical recommendations for the design and construction of the retaining and basement
walls are presented below.
6.5.1 Lateral Earth Pressures
We recommend that a static lateral earth pressure based upon an equivalent fluid weight of 50
pcf be utilized for design of the basement walls. For the seismic condition, we recommend a
uniform lateral earth pressure of 7H psf (where H is the height of the below grade portion of the
wall) be added to the static pressure for sizing the basement walls for the ultimate/seismic
condition. The recommended lateral pressures assume level backslopes and that the backfill
behind the wall consists of a free draining and properly compacted fill with adequate drainage
provisions. Walls retaining sloping backfills or surcharge loads should be designed for higher
forces. If surcharge loads or building foundations will be located within a horizontal distance
equal to the height of the wall, lateral earth pressures will need to be increased based upon the
type and magnitude of surcharge.
6.5.2 Wall Surcharge
The basement walls should be designed to accommodate traffic surcharge pressures if the traffic
load is located within the height dimension of the wall. Similarly, surcharge loads from
construction equipment or soil/material stockpiles should be considered in the basement wall
design. Along the north and south property lines, the basement wall should also be designed to
accommodate the surcharge pressure from the buildings and soil retained by the existing soldier
pile wall. The lateral pressure acting on the wall from surcharge loads may be determined by the
surcharge diagram found on the attached Figure 4.
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6.5.3 Lateral Resistance
Lateral forces from wind or seismic loading and unbalanced lateral earth pressures may be
resisted by a combination of passive earth pressures acting against the embedded portions of the
foundations and by friction acting on the base of the foundations. Passive resistance values may
be determined using an equivalent fluid weight of 300 pounds per cubic foot (pcf). This value
includes a factor of safety of 1.5, assuming the footing is poured against recompacted native soil
or properly compacted structural fill adjacent to the sides of footing. A friction coefficient of
0.40 may be used to determine the frictional resistance at the base of the footings. This
coefficient also includes a safety factor of approximate 1.5.
6.5.4 Wall Drainage
Provisions for permanent control of subsurface water should be incorporated into the design and
construction of the basement walls. We recommend that prefabricated drainage mats, such as
Mirafi 6000 or equivalent, be installed behind the basement walls to transport the water to the
base of the wall/floor slab, where it should be collected by a 4-inch diameter, rigid drain pipe,
which drains to an appropriate outlet.
We recommend that a building envelope specialist be consulted for damp-proofing and
waterproofing recommendations.
6.5.5 Wall Backfill
Based on the field exploration, the on-site soil would not be suitable for wall backfill due to its
high fines content. Where wall backfill will be needed, free draining granular soils such as
Seattle Mineral Aggregate Type 17 (2011 City of Seattle Standard Specifications, 9-03.12(3)) or
Gravel Borrow (WSDOT 9-03.14(1)) are recommended.
Wall backfill should be moisture conditioned to within about 3 percent of optimum moisture
content, placed in loose, horizontal lifts less than 8 inches in thickness, and systematically
compacted to a dense and relatively unyielding condition and to at least 95 percent of the
maximum dry density, as determined using test method ASTM D 1557. Within 5 feet of the
wall, the backfill should be compacted to 90 percent of the maximum dry density.
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7.0 CONSTRUCTION CONSIDERATIONS
7.1 DEMOLITION AND SITE PREPARATION
Site preparation for the proposed project includes demolishing the existing building, asphalt
concrete, striping and clearing of surface vegetation, and excavations to the design subgrade. All
footings and floor slabs of the existing building, as well as asphalt, building debris and concrete
rubble should be removed from the site prior to the start of excavations or grading. All stripped
surface materials should be properly disposed off-site. Because the north basement wall for the
existing building is located close to the property boundaries, it may be necessary to install the
temporary shoring walls prior to demolishing the below grade walls to prevent disturbance or
ground movements to adjacent properties.
The existing building at the site has a basement at the north portion of the footprint. Demolition
of exiting building basement wall along the north property line could reduce the passive
resistance of the existing soldier pile wall. We recommend installing new soldier pile walls
before demolishing the existing basement wall. The recommended construction sequence should
be noted on the project demolition plan.
7.2 SOLDIER PILE INSTALLATION
Soil caving may occur during drilling due to presence of loose soil and groundwater seepage. As
such, temporary casing may be needed to prevent caving of the soldier pile holes. We
recommend that the following should be incorporated into the project plans and specifications:
The geotechnical engineer shall verify the suitability of all soldier pile holes before
concrete placement;
Temporary casing should be used if caving occurs as determined by the geotechnical
engineer;
Tremie methods shall be used for concrete placement in all holes having 3 or more inches
of accumulated water; and
All soldier pile holes drilled shall be filled with concrete on the same day.
Minimize ground disturbance along north excavation line to avoid movements of existing
soldier pile wall.
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7.3 MATERIAL REUSE
The contractor should be aware that the on-site soils contain a high fines content and will
become disturbed and soft when exposed to inclement weather conditions. As a result, the
excavated site materials will not be suitable for use as structural backfill, but may be used as
backfill in non-structural areas (landscaping areas). If use of the existing soils is planned, any
excavated soil should be stockpiled and protected with plastic sheeting to prevent softening from
rainfall.
7.4 STRUCTURAL FILL AND COMPACTION
Structural fill should consist of imported, City of Seattle Type 2 and 17 or approved equivalent.
Seattle Type 2 material should be used as structural backfill below the footings. Seattle Type 17
may be used as wall backfill. The structural fill should be moisture conditioned to within about 3
percent of optimum moisture content, placed in loose, horizontal lifts less than 8 inches in
thickness, and systematically compacted to a dense and relatively unyielding condition and to at
least 95 percent of the maximum dry density, as determined using test method ASTM D 1557.
7.5 EROSION AND DRAINAGE CONSIDERATIONS
Surface runoff can be controlled during construction by careful grading practices. Typically, this
includes the construction of shallow, upgrade perimeter ditches or low earthen berms to collect
runoff and prevent water from entering the excavation. All collected water should be directed to
a positive and permanent discharge system such as a storm sewer. It should be noted that some
of the site soils are prone to surficial erosion. Special care should be taken to avoid surface
water on open cut excavations, and exposed slopes should be protected with visqueen.
Permanent control of surface water and roof runoff should be incorporated in the final grading
design. In addition to these sources, irrigation and rain water infiltrating into landscape and
planter areas adjacent to paved areas or building foundations should also be controlled. All
collected runoff should be directed into conduits that carry the water away from the pavement or
structure and into storm drain systems or other appropriate outlets. Adequate surface gradients
should be incorporated into the grading design such that surface runoff is directed away from
structures.
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7.6 WET EARTHWORK RECOMMENDATIONS
General recommendations relative to earthwork performed in wet weather or in wet conditions
are presented below:
Earthwork should be performed in small areas to minimize subgrade exposure to wet
weather. Excavation or the removal of unsuitable soil should be followed promptly
by the placement and compaction of clean structural fill. The size and type of
construction equipment used may have to be limited to prevent soil disturbance.
During wet weather, the allowable fines content of the structural fill should be
reduced to no more than 5 percent by weight based on the portion passing ¾-inch
sieve. The fines should be non-plastic.
The ground surface within the construction area should be graded to promote run-off
of surface water and to prevent the ponding of water.
Bales of straw and/or geotextile silt fences should be strategically located to control
erosion and the movement of soil. Erosion control measures should be installed along
all the property boundaries.
Excavation slopes and soils stockpiled on site should also be covered with plastic
sheets.
8.0 ADDITIONAL SERVICES
We anticipate the City of Seattle will require a plan review and geotechnical special inspections
to confirm that our recommendations are properly incorporated into the design and construction
of the proposed development. Specifically, we anticipate that the following construction support
services may be needed:
Review final project plans and specifications;
Verify implementation of erosion control measures;
Observe the stability of any open cut slopes;
Observe installation of excavation shoring system;
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Evaluate optical survey data provided by others to evaluate the performance of the
shoring system;
Verify adequacy of foundation subgrades;
Confirm the adequacy of the compaction of structural backfill;
Observe installation of subsurface drainage provisions, and;
Other consultation as may be required during construction.
Modifications to our recommendations presented in this report may be necessary, based on the
actual conditions encountered during construction.
9.0 LIMITATIONS
We have prepared this report for use by N-Habit Dexter LLC and the project team.
Recommendations contained in this report are based on a site reconnaissance, a review of
existing subsurface information in the vicinity of the project site, and our understanding of the
project. The study was performed using a mutually agreed-upon scope of work.
Variations in soil conditions may exist between the explorations and the actual conditions
underlying the site. The nature and extent of soil variations may not be evident until
construction occurs. If any soil conditions are encountered at the site that are different from
those described in this report, we should be notified immediately to review the applicability of
our recommendations. Additionally, we should also be notified to review the applicability of our
recommendations if there are any changes in the project scope.
The scope of our work does not include services related to construction safety precautions. Our
recommendations are not intended to direct the contractors’ methods, techniques, sequences or
procedures, except as specifically described in our report for consideration in design.
Additionally, the scope of our work specifically excludes the assessment of environmental
characteristics, particularly those involving hazardous substances. We are not mold consultants
nor are our recommendations to be interpreted as being preventative of mold development. A
mold specialist should be consulted for all mold-related issues.
This report may be used only by the client and for the purposes stated, within a reasonable time
from its issuance. Land use, site conditions (both off and on-site), or other factors including
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advances in our understanding of applied science, may change over time and could materially
affect our findings. Therefore, this report should not be relied upon after 24 months from its
issuance. PanGEO should be notified if the project is delayed by more than 24 months from the
date of this report so that we may review the applicability of our conclusions considering the
time lapse.
It is the client’s responsibility to see that all parties to this project, including the designer,
contractor, subcontractors, etc., are made aware of this report in its entirety. The use of
information contained in this report for bidding purposes should be done at the contractor’s
option and risk. Any party other than the client who wishes to use this report shall notify
PanGEO of such intended use and for permission to copy this report. Based on the intended use
of the report, PanGEO may require that additional work be performed and that an updated report
be reissued. Noncompliance with any of these requirements will release PanGEO from any
liability resulting from the use this report.
Within the limitation of scope, schedule and budget, PanGEO engages in the practice of
geotechnical engineering and endeavors to perform its services in accordance with generally
accepted professional principles and practices at the time the Report or its contents were
prepared. No warranty, express or implied, is made.
We appreciate the opportunity to be of service to you on this project. Please feel free to contact
our office with any questions you have regarding our study, this report, or any geotechnical
engineering related project issues.
Sincerely,
H. Michael Xue, P.E. Siew L. Tan, P.E.
Senior Geotechnical Engineer Principal Geotechnical Engineer
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10.0 REFERENCES
City of Seattle, 2011, Standard Specifications for Road, Bridges, and Municipal Construction.
International Code Council, 2012, International Building Code (IBC).
Troost, K.G., Booth, D. B., Wisher, A. P., Shimmel, S. A., 2005, The Geologic Map of Seattle-A
Progress Report, Seattle, Washington – U. S. Geological Survey Open File Report 2005-
1252, scale 1:24,000.
Washington State Department of Transportation/American Public Works Association, 2012,
Standard Specifications for Road, Bridges, and Municipal Construction.
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1
VICINITY MAP
11-
181
Vic
inity
Map
.grf
2/
2/14
(15
:09
) A
AE
Figure No.Project No.
NNTS
Reference: Google Terrain Map
ApproximateSite Location
13-245
Proposed Development1701 Dexter Avenue North
Seattle, Washington
2
SITE AND EXPLORATION PLAN
07-
198_
Fig
2_S
iteP
lan.
grf
2/4
/14
ST
S
Figure No.Project No.
Note:Base map modified from GIS map obtained from City of Seattle DPD website.
Approx. Scale1" = 100'
Approx. Boring Location (PanGEO, 2008)
Approx. Boring Location (Geotech, 2006)
Approx. Boring Location (Terra, 1992)
Approx. Boring Location (RZA, 1988)
Approx. Boring/Probe Location (SW, 1978)
Legend:Existing Subsurface Data
DE
XT
ER
AV
N
RZA B-2
RZA B-3
Geotech B-2Geotech B-1
Terra B-1 Terra B-2
Terra B-3
SW B-1
Potential Landslide Area
>40% Slopes
DPD Mapped Environmentally Critical Areas
SW P-2
SW P-3
SW P-4
Subject Site
BH-3 BH-2
BH-1A A'
BH-1
B-1
B-3
B-2
P-2
Proposed Development1701 Dexter Avenue North
Seattle, Washington
13-245 3
04-080 cross section BldgA.grf w/ 04-080 soil profile.xlss and 04-080 sticklogs.xls 2/4/14 (15:51) SHE
GENERALIZED SUBSURFACE PROFILE A-A'
Project No. Figure No.
0 10 20 30Scale in Feet
50
60
70
80
90
100
110
120
130
140
Ele
vatio
n (
fee
t)
50
60
70
80
90
100
110
120
130
140
33
14111111
12
14
17
14
19
25
517
129745
17
11854251219
17
15
Notes:1. Ground profile based on the plot plan prepared by Mithun, Inc.2. See Figure 2 for location of Section A-A'3. Subsurface profile based on interpolation of widely-spaced test borings, actual conditions should be anticipated to vary.
Existing Ground Surface
LEGENDBorehole Symbols
?
Silt
Soil description
Groundwater table
Geologic Contact(approximate)
BH-1
SPT N-value
BoringDesignation
7
12
25
26
>50
>50
Approx. Property Limit
Unit 2
Dexter Ave NBH-1
?
?
?
?
?
?
BH-2
W E
?
??
Unit 1
Unit 1: Fill/Colluvium - Loose to medium silty sandUnit 2: Landslide Deposit - Soft to very stiff, silt and clayUnit 3: Lawton Clay - Very stiff to hard, clay and silt
Alley BH-3
Unit 3
Approximate bottomof excavation
13-245
Proposed Development1701 Dexter Avenue North
Seattle, Washington4
DESIGN LATERAL PRESSURESSOLDIER PILE WALL
CANTILEVER WALL AND ONE ROW TIEBACK
Fig
ure
3-E
P d
iag
ram
.grf
2
/4/1
4 (
15:5
7)
JCR
Figure No.Project No.
Base of Excavation
Soldier Pile Wall withTimber Lagging
HE
Passive PressureActive Pressure
X
Surcharge Pressure
45 pcf
1 Z
Notes:1. Embedment (Z) should be determined by summation of moments at the bottom of the soldier piles or at ground anchor location if present. Minimum pile embedment shall be 10 feet.2. A factor of safety of 1.5 has been applied to the recommended passive earth pressure value. No factor of safety has been applied to the recommended active earth pressure values.3. Active and surcharge pressures should be applied over the full width of the pile spacing above the base of the excavation, and over one pile diameter below the base of the excavation.4. Passive pressure should be applied to two times the diameter of the soldier piles.5. Use uniform earth pressure of 200 psf and 250 psf for lagging design with soldier piles spaced at less than or equal to 8 feet and greater than 8 feet, respectively.6. Allowable vertical pile capacity: Skin Friction = 0.5 ksf, End Bearing = 10 ksf7. Refer to report text for additional discussions.
300 pcf
1
Single Rowof Tiebacks
60º
No-Load Zone
H/4 or5' min
X
Fill retained by existing soldier pile wall (along west portion of north property line)
Traffic Surcharge(along east and west property lines)
Hw
Hs = 2 feet (min)
(40 pcf)(HW+HS)
AEHs = Equivalent soil height for general traffic loading (2ft) (Greater for construction surcharge)
Hw = Height of Existing Soldier Pile Wall (ft)
AEHE = Height of Excavation (ft)
Z = Embedment Depth (min 10 ft)
LEGEND
Load Zone
Assumed capacity
for design: 2.5 kips/ft
13-245
Proposed Development1701 Dexter Avenue North
Seattle, Washington
5
DESIGN LATERAL PRESSURESSOLDIER PILE WALL
MULTIPLE ROW TIEBACKS
07-
163
EP
dia
gram
.grf
2
/4/1
4 (
15:
56
) JC
R
Figure No.Project No.
1. Passive Pressure computed as acting on 2 times pile diameter B.
2. Active & Surcharge Pressures computed as acting over full pile spacing above base of excavation, and on one pile diameter B, below base of excavation.
3. Use 80% of the above pressures for computing moments in soldier piles.
4. Determine soldier pile penetration Z by moment equillibrium at bottom of solider piles or at ground anchor level if present.
5. Free drainage assumed behind the wall.
6. Locate anchor bond length behind no-load zone.
7. Design pressure values:
a = 45 pcf
p = 300 pcf AEP = 26 pcf
Where a and AEP have safety factor = 1 and p has safety factor = 1.5.
8. Lagging design: Clear Span (ft) 8 >8 Uniform Pressure (psf) 200 250
9. Allowable vertical pile capacity: Skin Friction = 0.5 ksf End Bearing = 10 ksf
NOTES
Pa, Pp = Active & Passive Forces Below Base of Excavation
Z = Embedment Depth (min 10 ft)
B = Soldier Pile Width
AEP = Apparent Earth Pressure Coefficient (pcf)
AEHs = Equivalent soil height for general traffic loading (2ft) (Greater for construction surcharge)
Hw = Height of Existing Soldier Pile Wall Backfill (ft)
AEHE = Height of Excavation (ft)
a, p = Equivalent Fluid Weights (Active & Passive) (pcf)
LEGEND
p
1a
1
Z
HE
0.2 HE
Base of Excavation
60o
PpPa
pZPassive Pressure
a(HE+Z)Active Pressure
H/4 or5' min
B
Hw
(AEP)(HE)
(40pcf)(HW+HS)
SurchargePressure
Hs= 2 ft (min)
Soldier Pile Wall withTimber Lagging
Tieback
Traffic surcharge(along west property line)
Fill retained by existing soldier pile wall (along west portion of north property line)
No LoadZone
X
X TiebackAssumed capacity inLoad Zone: 2.5 kips/ft
APPENDIX A
SUMMARY BORING LOGS
(PANGEO, 2008)
MONITORING WELL
<1515 - 3535 - 6565 - 8585 - 100
GW
GP
GM
GC
SW
SP
SM
SC
ML
CL
OL
MH
CH
OH
PT
TEST SYMBOLS
50%or more passing #200 sieve
Groundwater Level at time of drilling (ATD)Static Groundwater Level
Cement / Concrete Seal
Bentonite grout / seal
Silica sand backfill
Slotted tip
Slough
<250250 - 500500 - 1000
1000 - 20002000 - 4000
>4000
RELATIVE DENSITY / CONSISTENCY
Fissured:Slickensided:
Blocky:Disrupted:Scattered:
Numerous:BCN:
COMPONENT DEFINITIONS
Dry
Moist
Wet
Units of material distinguished by color and/orcomposition from material units above and belowLayers of soil typically 0.05 to 1mm thick, max. 1 cmLayer of soil that pinches out laterallyAlternating layers of differing soil materialErratic, discontinuous deposit of limited extentSoil with uniform color and composition throughout
Approx. RelativeDensity (%)
Gravel
Sand50% or more of the coarsefraction passing the #4 sieve.Use dual symbols (eg. SP-SM)for 5% to 12% fines.
MOISTURE CONTENT
2-inch OD Split Spoon, SPT(140-lb. hammer, 30" drop)
3.25-inch OD Spilt Spoon(300-lb hammer, 30" drop)
Non-standard penetrationtest (see boring log for details)
Thin wall (Shelby) tube
Grab
Rock core
Vane Shear
Dusty, dry to the touch
Damp but no visible water
Visible free water
Terms and Symbols forBoring and Test Pit Logs
Density
DESCRIPTIONS OF SOIL STRUCTURES
Breaks along defined planesFracture planes that are polished or glossyAngular soil lumps that resist breakdownSoil that is broken and mixedLess than one per footMore than one per footAngle between bedding plane and a planenormal to core axis
Very LooseLooseMed. DenseDenseVery Dense
SPTN-values
Approx. Undrained ShearStrength (psf)
<44 to 1010 to 3030 to 50
>50
<22 to 44 to 8
8 to 1515 to 30
>30
Layered:
Laminated:Lens:
Interlayered:Pocket:
Homogeneous:
Highly Organic Soils
#4 to #10 sieve (4.5 to 2.0 mm)#10 to #40 sieve (2.0 to 0.42 mm)#40 to #200 sieve (0.42 to 0.074 mm)0.074 to 0.002 mm<0.002 mm
UNIFIED SOIL CLASSIFICATION SYSTEM
MAJOR DIVISIONS GROUP DESCRIPTIONS
Notes:
for In Situ and Laboratory Testslisted in "Other Tests" column.
50% or more of the coarsefraction retained on the #4sieve. Use dual symbols (eg.GP-GM) for 5% to 12% fines.
1. Soil exploration logs contain material descriptions based on visual observation and field tests using a systemmodified from the Uniform Soil Classification System (USCS). Where necessary laboratory tests have beenconducted (as noted in the "Other Tests" column), unit descriptions may include a classification. Please refer to thediscussions in the report text for a more complete description of the subsurface conditions.
2. The graphic symbols given above are not inclusive of all symbols that may appear on the borehole logs.Other symbols may be used where field observations indicated mixed soil constituents or dual constituent materials.
COMPONENT SIZE / SIEVE RANGE COMPONENT SIZE / SIEVE RANGE
SYMBOLSSample/In Situ test types and intervals
Silt and Clay
Very SoftSoftMed. StiffStiffVery StiffHard
Phone: 206.262.0370
Bottom of Boring
CBRComp
ConDDDS%FGS
PermPP
RSGTV
TXCUCC
Boulder:Cobbles:Gravel Coarse Gravel: Fine Gravel:
Sand Coarse Sand: Medium Sand: Fine Sand:SiltClay
> 12 inches3 to 12 inches
3 to 3/4 inches3/4 inches to #4 sieve
SILT / CLAY
GRAVEL (<5% fines)
GRAVEL (>12% fines)
SAND (<5% fines)
SAND (>12% fines)
Liquid Limit < 50
Liquid Limit > 50
Consistency
Well-graded GRAVEL
Poorly-graded GRAVEL
Silty GRAVEL
Clayey GRAVEL
Well-graded SAND
Poorly-graded SAND
Silty SAND
Clayey SAND
SILT
Lean SILT
Organic SILT or CLAY
Elastic SILT
Fat CLAY
Organic SILT or CLAY
PEAT
SAND / GRAVEL
California Bearing RatioCompaction TestsConsolidationDry DensityDirect ShearFines ContentGrain SizePermeabilityPocket PenetrometerR-valueSpecific GravityTorvaneTriaxial CompressionUnconfined Compression
SPTN-values
LOG
KE
Y
06-0
69.G
PJ
PA
NG
EO
.GD
T
5/30
/06
Figure A-1
GS
ATT
4-inch of asphalt concrete.
Loose to medium dense, moist, dark brown, silty SAND (SM);(Colluvium).
Stiff, moist, light brown SILT(ML).
Loose, moist to very moist, reddish-brown, medium to coarse SAND(SP); trace silt, iron oxide staining.
7'- becomes very moist to wet.
Loose, very moist to wet, dark brown to black, medium SAND (SP);with some organics and wood debris.
--with less organics and wood debris.
Soft to medium stiff, moist to very moist, gray, silty CLAY (CL);interbedded with thin lenses of silty fine SAND, scattered organics,medium to high plasticity (Landslide Deposit).--becomes gray, fat CLAY (CH), fractured texture.
Medium dense, wet, gray, silt SAND (SM); scattered organics.
Stiff, moist to very moist, gray SILT (ML), with fine sand seams.
--with thin layers of gray, fine to medium SAND.
--becomes slightly clayey SILT (MH), iron oxide stained, thinlylaminated, blocky to massive texture.
Bottom of boring at 31.5'. Groundwater was encountred atapproximately 7 feet at the time of drilling.
1
2
3
4
5
6
7
8
9
10
456
344
532
213
211
223
557
8811
889
569
Remarks: Boring was drilled with a small, track mounted drill rig. Standard PenetrationTest (SPT) sampler driven with a 140 lb hammer using a rope and cathead dropping 30inches per stroke. Elevation data from site plan provided by client. Hole was backfilledwith cuttings and bentonite chips.
0
5
10
15
20
25
30
35
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-2
Oth
er T
ests
Sam
ple
No.
Completion Depth:Date Borehole Started:Date Borehole Completed:Logged By:Drilling Company:
Dep
th,
(ft)
1701 Dexter Avenue North
13-245
Seattle, WA
Northing: , Easting:
31.5ft4/17/084/17/08Nels ReeseGeologic Drill
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:
Sym
bol
Sam
ple
Typ
e
Blo
ws
/ 6
in.
101.0ft
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING BH-1
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
ATT
2-inch of asphalt concrete.
Medium dense, moist, dark brown, gravelly, silty SAND (SM);(Colluvium).
Loose, moist, brown, medium SAND (SP), trace silt.
Medium stiff, moist, light brown, fine sandy SILT(ML).
Very loose to medium dense, moist to very moist, reddish-brown fineto medium SAND (SP); trace silt, trace fine gravel, heavy iron oxidestaining.
9'- becomes very moist to wet.
--becomes brown, medium SAND (SP) with trace to some silt, wet.
--becomes gray, with iron oxide staining.
Medium stiff, moist to very moist, gray fat CLAY (CH); high plasticity,blocky, fractured texture, slickensides (Landslide Deposit).
19'- thin bed of dark brown, slightly silty SAND.
20'- interbeds of wet, gravelly, silty SAND, fine sandy SILT, and clayeySILT; scattered organics observed in clayey SILT.
25'- becomes stiff, moist, massive to thinly laminated clayey SILT.
Bottom of boring at 26.5'. Groundwater was encountred atapproximately 9 feet at the time of drilling.
1
2
3
4
5
6
7
8
9
332
100
343
466
654
443
122
532
689
Remarks: Boring was drilled with a small, track mounted drill rig. Standard PenetrationTest (SPT) sampler driven with a 140 lb hammer using a rope and cathead dropping 30inches per stroke. Elevation data from site plan provided by client. Hole was backfilledwith cuttings and bentonite chips.
0
5
10
15
20
25
30
35
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-3
Oth
er T
ests
Sam
ple
No.
Completion Depth:Date Borehole Started:Date Borehole Completed:Logged By:Drilling Company:
Dep
th,
(ft)
1701 Dexter Avenue North
13-245
Seattle, WA
Northing: , Easting:
26.5ft4/17/084/17/08Nels ReeseGeologic Drill
Sheet 1 of 1
Project:
Job Number:
Location:
Coordinates:
Sym
bol
Sam
ple
Typ
e
Blo
ws
/ 6
in.
102.0ft
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING BH-2
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
ATT
Dense, moist, gray-brown, gravelly, silty SAND (SM); (Fill).
Loose to medium dense, moist, brown silty SAND (SM); someorganics and gravel (Colluvium).
5'- becomes reddish-brown, iron oxide stained, trace fine gravel.
10'- heavy iron oxide staining, organic rich interbeds. Possibleseasonal perched groundwater.
Medium dense, moist, gray silty fine SAND (SM).
Stiff, moist, gray, silty CLAY (CL-CH); scattered organics, medium tohigh plasticity, iron oxide staining, blocky texture, with thin interbeds ofsilty fine SAND (Landslide Deposit).
Medium dense, wet, gray silty SAND (SM); rapid dilatancy.
Stiff to very stiff, moist, gray, fat CLAY (CH); medium to high plasticity,massive to thinly laminated, wih scattered blocky/fractured zones.
--becomes moist, massive to thinly laminated CLAY with fine sandseams.
--becomes highly fractured, with some slickensides and fine sandseams.
1
2
3
4
5
6
8
9
10
121
112
559
565
456
356
557
568
998
Remarks: Boring was drilled with a small, track mounted drill rig. Standard PenetrationTest (SPT) sampler driven with a 140 lb hammer using a rope and cathead dropping 30inches per stroke. Elevation data from site plan provided by client. Hole was backfilledwith cuttings and bentonite chips.
0
5
10
15
20
25
30
35
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-4
Oth
er T
ests
Sam
ple
No.
Completion Depth:Date Borehole Started:Date Borehole Completed:Logged By:Drilling Company:
Dep
th,
(ft)
1701 Dexter Avenue North
13-245
Seattle, WA
Northing: , Easting:
46.5ft4/17/084/17/08Nels ReeseGeologic Drill
Sheet 1 of 2
Project:
Job Number:
Location:
Coordinates:
Sym
bol
Sam
ple
Typ
e
Blo
ws
/ 6
in.
128.0ft
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING BH-3
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
Stiff to very stiff, moist, gray, fat CLAY (CH); occasional silty fine sandinterbeds, high plasticity, thinly laminated to massive.
Very Stiff, moist, light gray, silty CLAY/clayey SILT (CL-ML); fine sandseams, medium plasticity, massive (Lawton Clay).
Bottom of boring at 46.5'. Groundwater was encountred atapproximately 20 feet at the time of drilling.
11
12
13
586
7910
81015
Remarks: Boring was drilled with a small, track mounted drill rig. Standard PenetrationTest (SPT) sampler driven with a 140 lb hammer using a rope and cathead dropping 30inches per stroke. Elevation data from site plan provided by client. Hole was backfilledwith cuttings and bentonite chips.
35
40
45
50
55
60
65
70
The stratification lines represent approximate boundaries. The transition may be gradual.
MATERIAL DESCRIPTION
Figure A-4
Oth
er T
ests
Sam
ple
No.
Completion Depth:Date Borehole Started:Date Borehole Completed:Logged By:Drilling Company:
Dep
th,
(ft)
1701 Dexter Avenue North
13-245
Seattle, WA
Northing: , Easting:
46.5ft4/17/084/17/08Nels ReeseGeologic Drill
Sheet 2 of 2
Project:
Job Number:
Location:
Coordinates:
Sym
bol
Sam
ple
Typ
e
Blo
ws
/ 6
in.
128.0ft
HSA
SPT
Surface Elevation:
Top of Casing Elev.:
Drilling Method:
Sampling Method:
LOG OF TEST BORING BH-3
N-Value
0
Moisture LL
50
PL
RQD Recovery
100
APPENDIX B
SUMMARY LOGS OF PREVIOUS EXPLORATIONS
AND HISTORIC STREET GRADING PROFILES
13-245
Proposed Development1701 Dexter Avenue North
Seattle, Washington
N/A
BORING LOGS BY OTHERS
Figure No.Project No.
NOTE: Boring B-1 and B-2 logs by Geotech Consultants, Inc. for 1707 Dexter Ave. N.in Seattle, Washington. B-1 and B-2 were drilled on May 25 and May 31, 2005, respectively.Geotech Consultants, Inc. Proj. No. 05189.
. ..
Boring No. Logged by: DBG
Dated:
Graph/ uses
10-20-92
Soil Description Consistency
Brown, silty SAND with gravel, fine to coarse, moist.
Medium dense to dense
Gray fat CLAY, wet. Medium
stiff
very stiff
Boring terminated at 24 feet.
. ' . ,".
. ,
TERRA ASSOCIATES
B~1
Aproximate Elev.
<D Water (N)
Depth 0. E Blows Content
(ft.)
5
10
15
20
0 (ft) (%) (f)
27 16
I 36 8
I 28 11
I 32 19
I 8 . 48
I 15 45
I 12 38 •..
32 32
. :'.' ": ~ .
., ..
BORING LOG DEXTER APARTMENTS
SEATILE, WASHINGTON
LL=65 PL=23 PI=42
65
Geotechnical Consultants Proj. No. T-1605-1 Date 11/92 Rgure 4
: ..... . "
-. ' .. - .. ' -'--~~-*--~.-.... " ., .. - .
Boring No . . ~,~,gf .. ' ..
. .'~. :
Logged by: DBG
Dated: 10-20-92 Approximate
<D Graph/ Water
Depth Q (N)
uses Soil Description · Consistency E Blows Content (ft.) 0 (ft) (%) CI)
Brown silty SAND, fine to Medium 12 11
coarse, moist. (RLL) dense I 10 13
5 I Brown, silty SAND with Medium 12 11
gravel, fine to coarse, moist. dense I 24 14
10 I 10 21.
Dense I 34 15 ..
15 Tan to gray fat CLAY, wet. Medium Stiff
I 9 ... 36
20
Stiff -1 . 16 36
25 ···.···· . , ..
' - ;).:"
31 ·· ·· ·
... Boring terminated at 29 feet. ...
TERRA ASSOCIATES
.. : :... . . ;"
Geotechnical Consultants
BORING LOG DEXTER APARTMENTS
SEATILE, WASHINGTON
Proj. No. T-1605-1 Date 11/92
Elev. 64
Rgure 5
Logged
Dated:
Graph/ USCS
.. ~ /.' -. ' '. . '
, . . .
Boring No. ' by: DBG
10-19-92 '
Soil Description Consistency
Fill, brown to gray, silty SAND Medium with some gravel fine to dense coarse, dry.
Fill, gray, silty, gravelly, SAND, fine to coarse wet.
Loose
Gray, silty SAND with gravel, fine to coarse, wet.
'"
Gray, SAND with gravel, fine to coarse water bearing. Medium "
..
, " .. . dense
. '
"
Gray, fat CLAY, wet.
Very Stiff
-- - ------------------- ---- ---------- ----------------------
TERRA ASSOCIATES
B-3: '
Depth (ft.)
5
10
15
20 "
25
30 '
"
35
40
Approximate Elev. 87
(J)
(N) Water 0. E Blows Content a (ft) (%) (.f)
I 17 6
I 12 6 ,
I 12 7
I 6 20
I 46 10
. ' .. ,' ;' .
I 28 ,20
I 21 43
I 22 41
I 22 39
BORING LOG DEXTER APARTMENTS
SEATILE, WASHINGTON
"
LL=61 PL=26 PI=35
(Continued)
Geotechnical Consultants Proj. No. T-1605-1 Date 11/92 Rgure 6a
.. :
'. ,' .
.....
. .... . .. -, ,
r--------------------------.-- .. -.
Graph/ USCS
':.:
Soil Description
Continued from Rgure 6a
Gray, fat CLAY, moist.
BOring terminated at 64 feet.
Boring No. 's8~B:-· (Continued).: .
Consistency ' Depth (ft.)
Hard
56
55
60
Groundwater encountered at 26 feet during drilling.
'~". .
. :: ... ' .. :. . .. ' .
<D DE o (f)
I
I
I
(N) Water Blows Content
(ft) . (%)
42 32
43 35
49 32
47 · 31
.. -,
. ' . -' .,'
TERRA ASSOCIATES
BORING LOG DEXTER APARTMENTS
SEATILE, WASHINGTON
Geotechn ical Consultants Proj. No. T-1605-1 Date 11/92
. : . . .. ... ....
" .'
Rgure 6b
:'~;.tR" " "" " Z· ·· A ' '::" .. : . ",,,", ., .' ' .:', ,' :!rf~i:'; ... ' ' , . .. ~ZE(AN .. . .....
::1!.:-1 : ·~ RI7TENiIOtrsE~zEJv[AN & ASSOC., .INC.
..... ~ .. ~ ';,: .' ·· AGNI ~jf . .
. ....·lto:f, ! ~- ,
. BORING NUMBS . " :::.i . .. ~ 'C(,Oil'C /1I1 icii / / UydrnSt!(){ogica'i C01l5ulliwts
. W.O. H-S666 .
I j
. ::.-....
SOIL DESCRIPTION
G.rollnd Surface Elevafion Apprexiinately 148 .. Fee·t
Loose to medium Qense,. moist, b~own, gravell y . SAND' and silty gravell y . SAND with some horizons .of · clayeySIlT .
.:..':' -..:- - - - - -- - - - - - - '~ - - -..:.: - ,- '~ - - - ' -- --..:.. - "- _ .
Dense, wet , gray ,fi fie td coa rse SAND ·
~ UJ UJ
. ~
J: '1--. a. UJ 0 '
- 0
5
16
15
en I--en UJ I--
III < ..J
o za: ::>w a ~ . ~?:
. . ST ANDARD PENE-TRA TION RESISTANCE
. . .A. BLOWS PER FOO' .
(140 lb. hammer, 30 inch drop)
o 1,0 . 20 '· 30 40.
,J -- ~ _~~_~~_~ c:. _ ~ _~~~_~ __ :.... ___ ~:.:.. _~ __ ~_ . Hard, wet, gray, SILT an d clayey SILT
, Q .·•· .• ···.· 6 I '" ATD .
20 .
I ' I
I
Il
-
-
J] -
u
·U
u
lJ
LJ
Total depth 34 ,S feet 17 May 1988
SAMPLING I 2' aD SPLIT SPOON SAMPLE ]I 3' 00 SHELBY SAMPLE ~ 2,5' ID RING SAMPLE
B BULK SAMPLE *' SAMPLE NOT RECOVERED
7} 25
1-30
1-35
40
GROUND W A TE~ SEAL '
DATE WATER LEVEL ' ,
AT TIME OF DRILLING ATD OBSERVATION WELL TIP
LABORATORY TESTS
• % WATER CONTENT
NP NON PLASTIC
I ' . I +-- lIOUID LIMIT
! "'--NATURAL WATER CONTENT
PLASTIC LIMIT
.. 50
If~· ·· . RITTENliOLisE-z'lMA71 & ASSOC.;INC: .
.. ' . .. ,C'O/'d"",.}/ HY'/!~i,·;;/ogkol Co"i~/{o"I' .
,, '. . w ' (/) . u.. I- (!l
.. SOIL DESCRIPTION ~ ~ 5.
BORINGNuMB~~~_~r~ ,···: W,O, W"5666 . . ~ • ...#~ .. t;x;: >,:(~I''F:'"'' -. : .. '." .
' .. PRbJ~CT NAME • '~t:~i t ADa rt~en'ts
STANDARD PENETRATION RESISTANCE A BLOWS 'PER FOOT
1- .1- a..
. ~ Grou~d Surface Elevation Ap~r"~lfn"'''''IY 132 Feet .' .~ _j __ .~ .. ,-.. _+i0_1I!-_1~0_1III!I' .. ~2 .. 0_~.·.3~0_~ . .... 4~0 __ III· .5~O o Z .O: ;:) W a Ia:: « (!) ~
(140 lb. hammer, 30 Inch drop)
:8 : Loose , damp' , brown,. gra vei;y fine ·to coarse . SAND
. . ':'
'~n . :..----..,-~ ----- -------::: -'.:'---~ .. ~-------~- -., - Medium dense, mois.t . brown . fi ne-coa.rse 5 .
. gravelly fine to coarse SAND .
-
·· B j . u-~
-:r . ·U ':
j "'~ '
d ill
. :
.. ' Stiff, wet; brown gradlng to ':gray, 'SILT and t .layey · SILT .: .
10
:- .
-.: .: '
4========================:r25
. . ,
D -
1 -
L ,
L
. Tota 1 depth 25 fee t ' . 17 May 1988
30
35
40
I]
1-·-·-·····1······- .. ··,·;, 11 .. .. , •• _....... ..-...•
1·_··'-·1··- ······ .. 1 ~ '''' .1i'''' I ':- . -.... . . --
····· f
~-~--~·~-~~--r-~~';-i ··~···--l .. -- .• I .. ;·-·· ..- ...
• 1 • •. -.. ' .• A; 1- · ··-+ -._ .. -._- l .. . ~.--. . ~~~ : -. -::_ . : .... .- . .. .
--~ .i. --"~. · 1··· .... • ... .
. ..
' . . 1··-··· · t - .... ........
"''''''''' ,.- .' ·_ .. ~ I i~ .... : i ·· .
~ ..... . f- ·- - . . ..... . I
I .. ·~. __ 1_....... 1· ·- .c.. ----. - .... ··1 .. ·· ..
s1 ...... . -.....
A1:D f.- ... -I~ ......... ' I ... -.~ .. : I ~ _· . I · ·~·+ . . a - • ... .. : .
..... _ ... - ! .. : ....... . . "
, t .· .. : -'-;.~ .... . - ...... +. .. ': ". • ........ + .. . : .:..... . ....... '
'.
.. -... .•. ~~.. I ·~ ; · , · "
.: ; .. + ... .. " ..
I- .. - .. ··+ · .. ~·· .. · I·· .. ··: . " -'1~:~
.. 1·--.. - ·1··-· · · .. · . •. /.;. c··-.. •· .. - .... 1--· .. ··.
I ····· .. · · I ····· ~· ·: .... : .
:.1 ...... -..... ······'-.. ·1···· · ··,·······.··· .
. i .... : .. : I .. ·" . .
i· ·'
I.·· . .' :.
.i ...
. •. ! .. ~ ...•
L I ., i
I . I . _._-t-..-...:_}-..... ,;,... . .. ! .... ...:.....-!----., ... -- .. - .. - 1- - 1·_· i ... · .
I···· ·· . 1 .. I · .. ! .--.. - ....... .. '
...... .... -... .
, ... --~.- ~- . . -.-~ } .... -.-. . _ .. ~ !
'~ .. " .. - ..i .. --: 1 ....' - I ... . .-.. ··· .. 1 .... . ; . . ' ,
. ...... - 1 ...... _ ... [. . I 1· '. f · ·· ( .. .I- ········1
. .. - I····· · ' .. , ! l
··· 1 I ..!
l !
! i ! ;
I i · W
. SAMPliNG I 2' 00 SPLIT SPOON SAMPLE
][ 3' 00 SHELBY SAMPLE &J 2,5' 10 RING SAMPLE
B BULK SAMPLE
* SAMPLE NOT RECOVERED
GROUND WATE~ SEAL . , ,
DATE ., . .
WATER LEVEL ' AT TIME OF DRILLING A TO OBSERVAJION
. WELL TIP
LABORATORY TESTS
• % WATER CONTENT
NP NON PLASTIC
~..-.I- LlOUID LIMIT
! 'L-NATURAL WATER CONTENT
PLASTIC LIMIT
Ii " U
---_. __ .. _ .... . . _ ... . . .
,Hedi 'umderise ',gray",black. si Ily. graVtlll.y~Hne toO ~ , m'edium SAND (F ILL?) ;" " ,,' , 1
Dense,brown,s j lty. fLile too medium SAND 'III occa~i6nal gr~VeJ and organici: 'moist to Wet.
Sample wet ai6 , ft. Rods 'list at L5 1L
1--------~ _____ ~ ___ ~ _____ ~B.5
,Beditiin sti ff to sti ff. b'lue-gray CLAY w/occasi ona I laminationsof. ,silty. fine sand
.'-.'.
1 ____ ~~~~~~---~~~-~-~16.5 'bottbm of Boring Completed 1/31/18 '
": :" ... . " , .. ' . '
" ......
LEGEHD 12" o.b. split spoon sample
IT 3" 0.0. thili-ull sa mple
• S3mple not reeov~red
1.1terberi I i.i ts:
~LiqHid limit
'",-'hlurel "8tH co nt ent
""--PI.slie limit
',.-.
r Impervious seel
Water I eve I
Piezo meter tip
P S.-lJ!pie pushed
USC Unified Soil
CI.ssific8tion
HOTE: Th e str.tlfieation lines repres&nt the epprox im ete boundHiu , b. \ .. eo n S 0' i I t Y P os • n d the t r 8 n s i \ io n nia y b e ~ r 8 d u. I .
. ~ " 'C:;~ .' ~ >' = ,, 0 ,'
L::i.: Blo1'(S per f oot , , .30 60
" ,0 "
21 , ... . ;:~)J
~ .... /
3 ' 1 0 1---: ~:-t."~~: !:;':...j' 'V_: :--:-~:~' ~-~--l 4+ :~J2i :-:: :::: :: :~: 15t--_~ _~ _~ ..:...~ _:_:-t~_._.~.=:::\:'.r-,-._._.~l 7 ,,'~ .. . ~" . . '
_,- c' , ' : : : : , ::~: :
"
. : .-
." . .~ .. . ......
. . ; .
. :',,:' .
.<
. ....
G S Water content
BEST LOCK COUPANY 1701 DEXTER AYE. N.
LOG OF BOR I NG NO . 'B..:l FEBRUARY 1978 VI-3342-o1
SHANNON 8. 1'ILSON . IIlC . GEDT[CHH I CAl CD~SUlTAHTS
FI G 1..
" U,;: .
LU t::>
". : I,led iurn dense,blaCk, ' grave Ily , silty, ·f.inetci O' 104,0 .·.· 0 medium , SAllOw/metal scraps, organics, moist (FILL)
. r : ::-:-:--' "7' -:....-. -'-. ....,.... ~. .;...-'. ---c'....:...' --'-'-~~-,-. ----15.. . 9~ • 0 !.Ied [urn dense ,b r own to r~d brown, s i I ty , fine to
'; mediuinSANO 'w/occ8sioriai coa.rse· sand and fine · ' grav~I, ' rnoi'st .' '
. r..~~~~~~~~',-.~, ~~~----~~,~, 11 , l.le d) um s i i fft ti s t iff, bl ve - .g ray. C LA Y . t----:--:--~,---~-----:-~-~----'--~12
. , '~
.' : '. '
BoHom of Bo.ring Cornpleted . l/31/78
.. ' .
".:.7'
. . "
. '
LEGEND 12" 0.0 . spl it ' spoon sample
IT 3" 0.0. thin-ul! sampl e
• Sample nol recoyered
.I.1t er b e r £ I·i In its:
~LiQHid limit
'~HBtural waler content
~Plastic limit
",'-:' :
, :~ .
(
. Impervious ~eal
. laler leyel
. :. Piezomeler tip
'p ' Sample pushed
USC Unified Soil
CI~ssif icalio n
HOTE: The .tratific.tion linn repre •• nl the .pproxim.te boundzri .. bBluH soil lypBt and the transilio nmay beiradu~l.
' "
. --:
. . . . ' . .. . . . . . ~ . . . . . ... . ~ ."' .
, ..
~ . : . 0
. " .. ' " .' ' : " ' ~ " -- " " .-__ < "0 :
. : .:.. ' : -\~'" ' .
0 . o ·
" • • • 0. . ....
' ,:.
o ~ Water content
BES~ LOCK COUPANY 1701 DEXTER AVE. N .
LOG OF BORING NO ;P ~2
FEBRUARY 1978 Vi-3342-01 S H ~ HH OH . & 'fILSOH. IHC.
GEOT EC HHICAL C ONS UL T ~HTS
:' .. " . . .... .
f! G 3
.... ...... .; :' . ."; .".
> Surlace [I evati bn: 8.7 :~T.A BOYErO? OF WAll . 0..
...... =
:loos.eto medium .ilense,black, .gravelly, si Ity, .fine 0 ~o medi·um SAllDw/ occasiollalo rganics,moist Hill) ~·~ ____ ~ ____ ~~ ____ ·~ ____ ~~~· ~'~· ~2
.l:1edIum stiff, . light brown, CLAY w/inc lusions ·of orgini·cs ' .
.;;;ac ..... i::x:.: -. ....:: =.""' .. (/,)
\ \ \.4-
16(1.4
'.. 6 4.5I ~_-,,--_-.:.....o.._~~--" __ ~_~ ___ ~.:....-..I . 105 ,LL . ....
aottom .of . 80·rihg · T
Completed 1!31i78 .
.:.::: ,,:
"< .:' .. .. r.· :
":.:.; "
. I ,·: '-:.
LEG EN 0 I 2- 0.0 . spl it spoon s~mple
n 3" 0 .0 , thin-lf211. samp l e ·
• Sample not recovered
Ai terb!f2 I ild ts:
.. ..
. :.,
Impervious seal
laler Level
Piezo ineter lip
:.: ........ . .... ". :' .. : '..-- . ~ \ '." "'''' ..... : . ... .. , "' II. fro " or cp' ) .. _.-~ . ... A . Slolfsper foot . b 0 ·· 30 ··· 60
. .'.: , .. .. . ~
. :'::" ' . '
.' . . .. . . . -
:', ' .
. .;
o ~ Wat er conten t
BEST LOCK COUPA NY 1701 DEXTER AVE. N.
~I'" Liqtlid l im it ~~N8turel utili co·ntent
"'-----Plastic l imit
P S .. anlple .pushed
USC Unified Soil
Classificalion
LOGDFBORING NO.P~3
NOTE: The stratification lines ropro>ent the opproximet. b~un da ti" between soillypes and the transitionmey be2reduel.
FEBRUARY 197-8 1'1-3342-01
SHA-NNON & WILSON. INC .
G£OTECHNICA( CON SULT ANT S
F \G ~
. ' ..... .
... .' \
- . '
' S~fface fleyation: 10.9 FT. A DYE TDPO'FWALL · I.ledi um,den~e. • dark bro~nt f~~e Ily. s 'j I ty, line
tamed I umSAND 'fI' /o~cas IOn£] .coa rse sand. otgani CS,
. . :. . mOist (Fill) I .'
~ . '0... . UJ
= o 1.5
;
::IE : . oe:
. ~
S t iff, Ii gh t b r Oy,' na nil red. 'm 0 ttl ed CLAY
:t----....,.~-=__:_;;_:__;_;_c-~--;---:-""'~-~----'-~4; 5 · 301 · .. ··Bottbm nf Boring :
Completed l/3.t/7a
.. .. '.
',.
' ....
... ........... .. ' . ~ .; ..
. . , ' . , . : -:. : :
;., ..... .. '. '
' .. '.:
..... ::.!= .
.... " . .. MICROFILMED '. "
LEGEND I 2" 0.0, sp l it spoon sample
IT 3" 0.0. t h i n-Ka I I • s a rnp I e
• Sample not recovered
A1ter b efl~ li lllils: l-K I L i q ~ i d I i I!li t
~N8tur~1 lI~ter content
~PI"stic limit
Impervious s881
Wat er I evo I
Pie Z 0 me t e r tip
P Sample push8 d
usc Unified Soil
CI~ ss il ical i on
NOTE; The str8tification linn r 'preH nt the 8p p r o(i m8 te boundaries bet'l!tenseil t ·ypes an d the tr an sit i onma y bBiradual.
" :
. . .
~::!: ~( .0 j 'b, u iiht. 18 '; ¢ii>'p)-' c.=J~ , c.... . . ' A . B.lolIs 'per Loot' '. ,
~ 0 . 30 6b .
. . :
'it.: 51-___ -+ ____ --..,1
, ' .
.-.- ~
. , '
. : . ....
:.' .: ' . ' .-' , .
: ." .:
~ . ., .' ",
..... .
o % Water content
BEST LOC K COUPANY 1701 DEXTER AYE. N.
LOG OF BORING NO.P-4 fEBRUARY 1978 YI-3342-01
SH ~ NNON . & lI'ILSON. I NC , G[OT(CHHIC AL CO NSULTk HTS
. . .. . -. :
; ,
FtG 5 '
APPENDIX C
SUMMARY OF LABORTARY TEST RESULTS
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.1110100
Specimen Identification
1.5 16
D10
GRAIN SIZE DISTRIBUTION
4
0.223 0.123
@ 5.0 ft.
PE
RC
EN
T F
INE
R B
Y W
EIG
HT
Classification
GRAIN SIZE IN MILLIMETERS
3/4
D100 D60 %Gravel84.9
Reddish-brown, medium to coarse SAND
PI
19
8
Cc
10.1
404
GRAVEL
BH-1
COBBLESSAND
fine
5.0BH-1
CuLL
3 60
Specimen Identification
1/23/81
%Silt
medium
6 10 14
50
HYDROMETERU.S. SIEVE OPENING IN INCHES
Figure
U.S. SIEVE NUMBERS
Figure
0.405
coarse
%Sand
6 2
coarse
PL
20
%Clay
100 1403
D30
FigureC-1
fine
30 200
1.00 3.29
5.0
SILT OR CLAY
Project: 1701 Dexter Avenue NorthJob Number: 13-245Location: Seattle, WAPhone: 206.262.0370
GR
AIN
SIZ
E
1701
DE
XT
ER
AV
E N
OR
TH
.GP
J P
AN
GE
O.G
DT
2/
4/14
0
10
20
30
40
50
60
0 20 40 60 80 100
CL
MH
CH
Specimen Identification
BH-1
BH-2
BH-3
MLCL-ML
PLASTICITY
INDEX
Classification
36
40
39
61
67
66
25
27
27
M LL
15.0
15.0
25.0
31
45
35
ATTERBERG LIMITS
Gray, fat CLAY
Gray, fat CLAY
Gray, fat CLAY
FinesPIPL
LIQUID LIMIT
FigureC-2
Project: 1701 Dexter Avenue NorthJob Number: 13-245Location: Seattle, WAPhone: 206.262.0370
AT
TE
RB
ER
G L
IMIT
S
1701
DE
XT
ER
AV
E N
OR
TH
.GP
J P
AN
GE
O.G
DT
2/
4/14