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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

Geotechnical Report Proposed Development – 1701 Dexter Ave. North, Seattle, WA February 5, 2014

13-245_1701 Dexter Ave N_Report PanGEO, Inc. ii

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



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).


13-245_1701 Dexter Ave N_Report PanGEO, Inc. 2

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



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



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.



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



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.



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:



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



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



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.



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.



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:



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%



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



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.



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



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.



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.



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.



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.



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.



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.



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;



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



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



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.

13-245

Proposed Development1701 Dexter Avenue NSeattle, Washington

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


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


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


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


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


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


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.


1

2

3

4

5

6

7

8

9

332

100

343

466

654

443

122

532

689


0

5

10

15

20

25

30

35



Figure A-3

Oth

er T

ests

Sam

ple

No.


Dep

th,

(ft)


13-245

Seattle, WA



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:


Drilling Method:

Sampling Method:


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


0

5

10

15

20

25

30

35



Figure A-4

Oth

er T

ests

Sam

ple

No.


Dep

th,

(ft)


13-245

Seattle, WA



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:


Drilling Method:

Sampling Method:


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).


11

12

13

586

7910

81015


35

40

45

50

55

60

65

70



Figure A-4

Oth

er T

ests

Sam

ple

No.


Dep

th,

(ft)


13-245

Seattle, WA



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:


Drilling Method:

Sampling Method:


N-Value

0

Moisture LL

50

PL

RQD Recovery

100

APPENDIX B

SUMMARY LOGS OF PREVIOUS EXPLORATIONS

AND HISTORIC STREET GRADING PROFILES

13-245


Seattle, Washington

N/A

BORING LOGS BY OTHERS


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


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


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


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


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


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

geotechnical report - pavilion construction · geotechnical report proposed development – 1701...

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