REVIEWED BLD BLD2022-1104+Geotechnical_Report+8.17.2022_2.17.19_PM+3057348BLD2022-1104- B101
BLD2022-1103- B102
BLD2022-1102- B103
RECEIVED
9/1 /22
CITY OF EDMONDS
DEVELOPMENT
SERVICES DEPARTMENT
...............................................
REVIEWED
BY
CITY OF EDMONDS
BUILDING DEPARTMENT
Prepared for:
Seattle Luxury Homes, LLC
G R A T E D
GEOTECHNICAL REPORT
PROPOSED TOWNHOMES
614 & 616 - 5T" AVENUE SOUTH
EDMONDS, WASHINGTON
Project No. 21-372
September 2021
Geotechnical & Earthquake
Engineering Consultants
3213 Eastlake Avenue East, Ste B
Seattle, Washington 98102-3513
Tel: 206.262.0370 Fax: 206.262.0374
Iran
■ c o a r o e w r e o
Geotechnical & Earthquake
Engineering Consultants
September 21, 2021
Project No. 21-372.200
Mr. Jonathan Kurth
557 Roy St, Suite 125
Seattle, WA 98109
Subject: Geotechnical Report
Proposed Townhomes
614 & 616 — 5" Avenue South, Edmonds, Washington
Dear Mr. Kurth:
Attached please find our geotechnical report for the proposed development at the above site in
Edmonds, Washington. This report documents the subsurface conditions at the site and presents
our geotechnical engineering design recommendations for the proposed townhome development.
In summary, based on test pits excavated at the site, the east portion of the site is generally
underlain by between 8 to 10 feet of fill overlying native, medium dense to dense poorly graded
sand. At the west portion of the site, fill soils were encountered up to about 4 feet below existing
grade overlying native medium dense to dense sand.
In our opinion, the proposed buildings may be supported on conventional shallow footings,
bearing on the dense native soils or compacted structural fill placed on the native dense soils.
Alternatively, a deep foundations system consisting of small diameter steel pipe piles (pin piles)
may be used to support the east buildings, to avoid deep over -excavations below the building
foundations. Temporary unsupported excavations may be sloped as steep as 1 H:1 V
(Horizontal: Vertical).
We appreciate the opportunity to work on this project. Please call if there are any questions.
Sincerely,
Michael H. Xue, P.E.
Principal Geotechnical Engineer
3213 Eastlake Avenue East, Suite B
Seattle, WA 98102
Tel (206) 262-0370
TABLE OF CONTENTS
1.0 INTRODUCTION...................................................................................................................1
2.0 PROJECT AND SITE DESCRIPTION............................................................................... 1
3.0 SUBSURFACE EXPLORATIONS....................................................................................... 2
3.1 CURRENT SUBSURFACE EXPLORATION..................................................................................
2
3.2 PREVIOUS SUBSURFACE EXPLORATION..................................................................................
3
4.0 SITE GEOLOGY AND SUBSURFACE CONDITIONS.................................................... 3
4.1 SITE GEOLOGY.......................................................................................................................
3
4.2 SOIL CONDITIONS..................................................................................................................
3
4.3 GROUNDWATER.....................................................................................................................
4
5.0 CRITICAL AREAS AMF SITE STABILITY..................................................................... 5
5.1 EROSION HAZARD AREA........................................................................................................
5
5.2 SITE STABILITY......................................................................................................................
5
6.0 GEOTECHNICAL RECOMMENDATIONS...................................................................... 6
6.1 SEISMIC DESIGN PARAMETERS..............................................................................................
6
6.2 BUILDING FOUNDATIONS.......................................................................................................
6
6.2.1 General...........................................................................................................................
6
6.2.2 Conventional Footings...................................................................................................
6
6.2.3 Allowable Bearing Pressure...........................................................................................
7
6.2.4 Foundation Performance................................................................................................
7
6.2.5 Lateral Resistance..........................................................................................................
7
6.2.6 Perimeter Footing Drains...............................................................................................
8
6.2.7 Footing Subgrade Preparation and Protection...............................................................
8
6.2.8 Pin Piles.........................................................................................................................
8
6.3 CONCRETE RETAINING WALL DESIGN PARAMETERS...........................................................
11
6.3.1 Lateral Earth Pressures.................................................................................................
11
6.3.2 Wall Surcharge.............................................................................................................
12
6.3.3 Lateral Resistance........................................................................................................
12
6.3.4 Wall Drainage..............................................................................................................
12
6.3.5 Wall Backfill................................................................................................................
13
6.4 CONCRETE SLAB-ON-GRADE...............................................................................................
13
7.0 CONSTRUCTION CONSIDERATIONS..........................................................................13
7.1 DEMOLITION & SITE PREPARATION.....................................................................................
13
7.2 MATERIAL REUSE................................................................................................................
14
7.3 TEMPORARY EXCAVATIONS.................................................................................................
14
7.4 STRUCTURAL FILL PLACEMENT AND COMPACTION.............................................................
15
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Geotechnical Report
Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
7.5 PERMANENT CUT AND FILL SLOPES .............
7.6 EROSION AND DRAINAGE CONSIDERATIONS
7.7 WET EARTHWORK RECOMMENDATIONS ......
...................................................................... 15
...................................................................... 15
...................................................................... 16
8.0 ADDITIONAL SERVICES..................................................................................................17
9.0 LIMITATIONS.....................................................................................................................17
10.0 REFERENCES.................................................................................................................... 19
LIST OF ATTACHMENTS
Figure 1
Figure 2
Appendix A
Figure A-1
Figure A-2
Figure A-3
Figure A-4
Figure A-5
Figure A-6
Figure A-7
Appendix B
Vicinity Map
Site and Exploration Plan
Summary Test Pit Logs
Terms and Symbols for Boring and Test Pit Logs
Log of Test Pit PIT-1
Log of Test Pit PIT-2
Log of Test Pit PIT-3
Log of Test Pit TP-1
Log of Test Pit TP-2
Log of Test Pit TP-3
Previous Test Boring Logs and Laboratory Results
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GEOTECHNICAL REPORT
PROPOSED TOWNHOMES
614 & 616 - 5TH AVENUE SOUTH
EDMONDS, WASHINGTON
1.0 INTRODUCTION
This report presents the results of a geotechnical study that was undertaken to support the design
and construction of the proposed development in Edmonds, Washington. Our study was
performed in general accordance with our mutually agreed -upon scope of work as outlined in our
proposal dated August 2, 2021. Our service scope included reviewing readily available geologic
and geotechnical data at the subject site and in the site vicinity, conducting a site reconnaissance,
excavating six (6) test pits, and developing the geotechnical design recommendations presented
in this report.
2.0 PROJECT AND SITE DESCRIPTION
The project site consists of two adjacent parcels located at 614 and 616 — 5th Avenue South in
Edmonds, Washington (see Figure 1, Vicinity Map). The combined site is an approximate 0.39
acre lot. It is bordered by 5th Avenue South to the east, multi -family residences to the west,
retail establishments to the north, and an improved private alley to the south. The site is currently
occupied by a single -story retail building at the north portion of the site and a single -story retail
building with full basement at the southern portion of the site, with a surface parking lot between
the two buildings. The site generally slopes down from east to west with an approximate grade
change of 10 feet to a vacant vegetated area at the western portion of the site.
According to the City, an erosion hazard (slope gradient between 15% and 40%) is present at the
approximate central portion of the lot, associated with previous grading at the site. No other
geologic hazards are mapped on the property by the City or County.
We understand that you plan to remove the existing buildings, and construct three buildings at
the site, consisting of two live -work townhome buildings (Buildings A and B) along the east
property line and a townhome building (Building C) in the western portion of the site (see Figure
2). Based on review of the preliminary plans, the proposed buildings will be 3-story, wood -frame
structures with concrete slabs on grade. We envisage that site grading for the proposed project
will include cuts and fill up to about 8 to 10 feet for the foundation construction.
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Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
BUILDING A
BUILDING C
u
Plate 1. Typical East-West Building Section, looking North.
The conclusions and recommendations outlined and provided in this report are based on our
understanding of the proposed development, which is in turn based on the project information
provided. If the above project description is incorrect, or the project information changes, we
should be consulted to review the recommendations contained in this study and make
modifications, if needed.
3.0 SUBSURFACE EXPLORATIONS
3.1 CURRENT SUBSURFACE EXPLORATION
Our current subsurface exploration consisted of excavating six (6) test pits (PIT-1, PIT-2, PIT-3
and TP-1, TP-2, TP-3) at the project site on August 4 and August 6, 2021. PIT-1 was initially
excavated to 5.5 feet for infiltration testing and was then excavated to about 9 feet deep after the
test. PIT-2 was initially excavated to 6 feet for infiltration testing and was then excavated to at
about 9 feet deep after the test. PIT-3 was initially excavated to 12 feet for infiltration testing and
was then excavated to practical digging refusal at about 15 feet deep after the test. TP-1 was
excavated to practical digging refusal at 13 feet below grade and TP-2, and TP-3 were each
excavated to about 11 feet below the existing grade. The approximate test pit locations are
shown on the attached Figure 2.
The relative in -situ density of cohesionless soils, or the relative consistency of fine-grained soils,
was estimated from the excavating action of the excavator, probing the sidewalls with a 1/2-inch
diameter steel rod, and the stability of the test pit sidewalls. Where soil contacts were gradual or
undulating, the average depth of the contact was recorded in the log. After the test pits were
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Geotechnical Report
Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
completed, the excavations were backfilled with the excavated soils and the surface was tamped
and re -graded smooth.
A geologist from our firm was present throughout the explorations to assist in sampling, and to
document the soil samples obtained from the explorations. The summary test pit logs are
included in Appendix A.
3.2 PREVIOUS SUBSURFACE EXPLORATION
In addition to the current explorations at the site, we also reviewed readily available subsurface
data in the site vicinity. Specifically, we reviewed five boring logs (B-1 through B-5) at the
subject site by Zipper Geo Associates, LLC (ZGA) in October 2015. The previous test boring
logs and laboratory results are included in Appendix B for reference.
We also observed two existing monitoring wells (Department of Ecology Well Tags BKH-527
and BKH-528) installed by others at the site. Details of these monitoring wells are not known,
and they could not be found on the Department of Ecology Well Report Viewer. These
groundwater monitoring wells will need to be decommissioned per the Washington State
Department of Ecology's standards prior to, or during construction.
4.0 SITE GEOLOGY AND SUBSURFACE CONDITIONS
4.1 SITE GEOLOGY
Based on our review of the Composite Geologic Map of the Sno-King Area, Central Puget
Lowland (Booth, 2004), the site is underlain by Pre -Fraser Deposits (geologic map unit Qpf).
Pre -Fraser Deposits generally consist of interbedded sand, gravel, and silt that has been glacially
overridden and typically dense to very dense. This unit is similar to the younger Vashon
Advance Outwash but is characterized by its stratigraphic position and generally heterogenous
grain size.
4.2 SOIL CONDITIONS
For a detailed description of the subsurface conditions encountered at each exploration location,
please refer to our summary test pit logs provided in Appendix A and previous test boring logs in
Appendix B. The stratigraphic contacts indicated on the logs represent the approximate depth to
boundaries between soil units. Actual transitions between soil units may be more gradual or
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Geotechnical Report
Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
occur at different elevations. The descriptions of groundwater conditions and depths are likewise
approximate. The following is a generalized description of the soils encountered in the test pits.
UNIT 1: Fill — Test pits PIT-1, PIT-2, and TP-1, excavated in the western portion of the
site, test pits, generally encountered approximately 4 to 4.5 feet of fill below surface
vegetation. The fill encountered in these test pits generally consisted of loose to medium
dense silty to poorly graded sand with some plastic, asphalt, and brick debris. Test pits PIT-
3, TP-2, and TP-3, excavated in the central and eastern portion of the site, encountered
approximately 8 to 10 feet of fill below the surface asphalt. The fill generally consisted of
loose to medium dense silty sand with gravel with varying amounts of wood, concrete, and
construction debris.
UNIT 2: Pre -Fraser Deposits — Directly below the fill in each test pit, medium dense to
dense poorly graded sand was observed in the test pits extending to the bottom of test pits.
We interpreted this unit as the mapped pre -Fraser Deposits within the project vicinity.
Our subsurface descriptions are based on the conditions encountered at the time of our
exploration. Soil conditions between our exploration locations may vary from those encountered.
The nature and extent of variations between our exploratory locations may not become evident
until construction. If variations do appear, PanGEO should be requested to reevaluate the
recommendations in this report and to modify or verify them in writing prior to proceeding with
earthwork and construction.
Previous Test Borings: The previous test borings by ZGA generally encountered fill up to 13
feet overlying medium dense to dense native sand that extended to a maximum depth of about 24
feet below the surface.
4.3 GROUNDWATER
Groundwater or seepage was not observed in our test pits or previous test borings by ZGA at the
time of exploration. Groundwater was measured in the previously installed groundwater
monitoring wells on August 5, 2021 at a level of approximately 25 feet below ground surface in
the parking lot area (approximate EL 59 feet) and 16.5 feet below ground surface in the lower
vegetated area (approximate EL 57.5 feet). No groundwater was encountered within the drilling
depths in the borings by ZGA.
It should be noted that groundwater elevations may fluctuate depending on the seasonal rainfall,
local subsurface and groundwater conditions, and other factors. In general, the water level is the
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Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
highest and the seepage rate in the greatest during the winter and early spring (typically October
through May).
5.0 CRITICAL AREAS AMF SITE STABILITY
5.1 EROSION HAZARD AREA
The site is mapped as an erosion hazard area in accordance with the City of Edmonds Critical
Areas Map and City of Edmonds Development Code Section 23.80.020, due to presence of
slopes with gradient between 15 and 40 percent. Based on the USDA Soil Survey data and the
test pits/borings, the site soils (Alderwood/Everett series) are anticipated to exhibit low to
moderate erosion potential when disturbed and left unprotected. However, in our opinion, the
potential erosion hazards at the site can be effectively mitigated with the best management
practice during construction and with properly designed and implemented landscaping for
permanent erosion control. During construction, the temporary erosion hazard can be effectively
managed with an appropriate erosion and sediment control plan, including but not limited to
installing silt fence at the construction perimeter, limiting removal of vegetation near the
construction area, placing rocks or hay bales at the disturbed/traffic areas and on the downhill
side of the project, covering stockpile soil or cut slopes with plastic sheets, constructing a
temporary drainage pond to control surface runoff and sediment trap if needed, placing rocks at
the construction entrance, etc. Permanent erosion control measures should include establishing
vegetation, landscape plants, and hardscape established at the end of project.
5.2 SITE STABILITY
As part of our study, we conducted a site reconnaissance on August 4, 2021 to observe the
conditions of the slope. Based on our observations, the slope follows the east -west grade break
located at the approximate center of the two parcels. The earthen slope at the center of the two
parcels has a gradient of approximately 35 to 40 percent with a vertical height of about 7 feet.
The slope area is currently heavily vegetated. No evidence of groundwater seepage was observed
on or near the slope.
Based on the results of our field exploration and our field observations, it is our opinion that the
site is currently stable. It is also our opinion that the proposed development as currently planned
will not adversely impact the subject site and surrounding properties, provided that the proposed
project is properly designed and constructed.
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Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
6.0 GEOTECHNICAL RECOMMENDATIONS
6.1 SEISMIC DESIGN PARAMETERS
We understand that the project will be designed in conformance with the 2018 edition of the
International Building Code (IBC). The 2018 International Building Code (IBC) is based on a
design level earthquake event having a 2% probability of occurrence in 50 years (return interval
of 2,475 years), and the 2008 USGS seismic hazard maps. Based on site soils conditions, it is
our opinion that Site Class D (Stiff Soil) may be assumed for the seismic design of the proposed
structures.
6.2 BUILDING FOUNDATIONS
6.2.1 General
Based on the subsurface conditions and current design plans, it is our opinion that the proposed
buildings may be supported by conventional shallow footings, bearing on dense native soils or
structural fill/controlled density fill (CDF) placed on the competent native soils. However, use of
this foundation system will require over -excavation of fill/loose soils and backfill of structural
fill/CDF. Over -excavations of existing fill below foundations will be up to about 4 feet for the
west building and will be up to about 10 to 12 feet for the two east buildings. Alternatively, to
avoid deep over-excavations/structural backfill and the need for temporary shoring, it is our
opinion that a deep foundation system consisting of small diameter steel pipe piles (pin piles)
may be considered to support the east buildings. It should be noted that large concrete pieces
were encountered in the test pits in the existing fill. As such, obstructions may be encountered
during pin pile installation and pile locations may need to be moved to avoid obstructions.
Alternatively, the obstructions may be removed by the excavator, where encountered, to
facilitate pile installation. The following sections present our design recommendations for
shallow conventional footings and pin piles.
6.2.2 Conventional Footings
In our opinion, the proposed west building may be supported on conventional footings bearing
on the medium dense to dense, undisturbed native soils (Soil Unit 2: Pre -Fraser Deposits).
Footings may also be founded on properly compacted structural fill placed on undisturbed native
soil. The structural backfill should extend horizontally with an approximately I H: IV line beyond
the footing edges. It is our opinion that it will be more appropriate to support the two east
buildings with pin piles. Please note that the competent bearing soil depths in the vicinity of our
test pits are approximate. The actual amount of over -excavation required will need to be
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Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
determined during construction based on actual soil conditions found at the proposed footing
locations and elevations.
In designing the footings, the shape of footings will need to be considered regarding the
available space for temporary excavations. Where space may be limited for an unsupported open
cut, it may be necessary to use L-shaped perimeter footings to conserve space and to allow the
temporary excavations to be made within the property limits.
6.2.3 Allowable Bearing Pressure
We recommend that an allowable soil bearing pressure of 2,500 pounds per square feet (psf) be
used to size the footings, bearing on medium dense to dense native soil, or structural fill/lean-
mix concrete placed on the competent native soils. Continuous and individual spread footings
should have minimum widths of 18 and 24 inches, respectively. Footings should be placed at
least 18 inches below final exterior grade. Interior footings should be placed at least 12 inches
below the top of slab.
6.2.4 Foundation Performance
Total and differential settlements are anticipated to be within tolerable limits for foundation
designed and constructed as discussed above. For the proposed buildings supported by
conventional footings bearing on competent native soils and structural fill/lean-mix concrete, the
building settlement under static loading conditions is estimated to be approximately one inch,
and differential settlement should be on the order of about 1/2 inch. Most settlement should occur
during construction as loads are applied.
6.2. S 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 foundations 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 densely compacted structural fill will be placed adjacent to the sides of
the foundation. A friction coefficient of 0.35 may be used to determine the frictional resistance at
the base of the foundation. This coefficient includes a factor of safety of approximately 1.5.
Unless covered by pavements or slabs, the passive resistance in the upper 12 inches of soil
should be neglected.
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Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
6.2.6 Perimeter Footing Drains
Footing drains should be installed around the perimeter of the building, at or just below the
invert of the footings. The footing drains should consist of 4-inch diameter, schedule 40 PVC or
SDR 35, perforated pipe embedded in washed drain rock/pea gravel and wrapped in filter fabric.
Under no circumstances should roof downspout drain lines be connected to the footing drain
systems. Roof downspouts must be separately tightlined to appropriate discharge locations.
Cleanouts should be installed at strategic locations to allow for periodic maintenance of the
footing drain and downspout tightline systems.
6.2.7 Footing Subgrade Preparation and Protection
All footing subgrades should be carefully prepared. The adequacy of footing subgrade should be
verified by a representative of PanGEO, prior to placing forms or rebar. The footing subgrade at
should be in a firm/dense condition prior to concrete pour. Any over -excavations in the footing
areas should be backfilled with compacted structural fill. Footing excavations should be
observed by PanGEO to confirm that the exposed footing subgrade is consistent with the
expected conditions and adequate to support the design bearing pressure.
It should be noted that site soils are highly moisture sensitive and can be easily disturbed when
exposed to moisture. As such, the exposed footing subgrade should be adequately protected. This
may be accomplished with placing quarry spalls or crushed surfacing base course (CSBQ on the
footing subgrade immediately after excavations if excavations are planned during inclement
weather.
6.2.8 Pin Piles
In the eastern portion of the site where upwards of 13 feet of fill was observed in our test pits and
previous borings, it is our opinion that 3- and 4-inch diameter driven pin piles may be considered
in -lieu of deep over -excavation and structural backfill. Three- and four -inch diameter pin piles
are typically driven with a hammer mounted to a small excavator.
Pin Pile Capacity — The number of piles required depends on the magnitude of the design load
and the pile size. Table 1, below, provides the allowable axial capacities in compression for pin
piles with an approximate factor of safety of at least 2.0.
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Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
Table 1— Pin Pile Capacities
Pile Diameter
(in)
Allowable Axial Capacity in
Compression (tons)
3
6
4
10
Penetration resistance required to achieve the capacities will be determined based on the hammer
used to install the pile. The tensile and lateral capacities of pin piles should be ignored in design
calculations.
It is our experience that the driven pipe pile foundations should provide adequate support with
total settlements on the order of 1/2-inch or less.
Pin Pile Specifications — We recommend that the following specifications be included on the
foundation plan:
1. 3-inch and 4-inch diameter piles should consist of Schedule-40, ASTM A-53 Grade "A"
pipe.
2. 3-inch piles shall be driven to refusal with a minimum 600-lb hydraulic hammer. We
recommend the following refusal criteria based on the size of hammer utilized:
Table 2 — Three-inch Pile Refusal Criteria
Hammer
Approx.
Refusal Criteria
Blows per
Size
Minute
(3-inch pile)
600 lbs
1000
12 seconds per inch
850 lbs
900
10 seconds per inch
1100 lbs
900
6 seconds per inch
The driving criteria recommended in the table above will be verified by a static load test
program (see discussion in Item 5).
3. 4-inch piles shall be driven to refusal with a minimum 850-lb hydraulic hammer. We
recommend the following refusal criteria based on the size of hammer utilized:
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Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
Table 3 — Four -inch Pile Refusal Criteria
Hammer
Approx.
Refusal Criteria
Blows per
Size
Minute
(4-inch pile)
)
850 lbs
900
16 seconds per inch
1100 lbs
900
10 seconds per inch
2000 lbs
600
4 seconds per inch
The driving criteria recommended in the table above will be verified by a static load test
program (see discussion in Item 5).
4. Piles shall be driven in nominal sections and connected with compression fitted sleeve
couplers (see detail below — Courtesy of McDowell Pile King, Kent, WA). We
discourage welding of pipe joints, particularly when galvanized pipe is used, as we have
frequently observed welds broken during driving.
Pipe 10
2" to 6"
New Steel Pipe Section
to 1�� S 1 1/4" to 2" wide X-Strong Steel Ring
1/4" filet welded to pipe sleeve
Driven Steel Pipe Section
Beveled End to aid insertion
5. At least 3 percent (but no more than 5) of the 3-inch and 4-inch pin piles should be load
tested. All load tests shall be performed in accordance with the procedure outlined in
ASTM D1143. The maximum test load shall be 2 times the design load. The objective of
the testing program is to verify the adequacy of the driving criteria, and the efficiency of
the hammer used for the project.
6. The geotechnical engineer of record or their representative shall provide full time
observation of pile installation and testing.
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Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
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The quality of a pin pile foundation is dependent, in part, on the experience and professionalism
of the installation company. We recommend that a company with experienced personnel be
selected to install the piles.
Lateral Resistance — Lateral capacity of vertical pin piles should be ignored in design
calculations. Some resistance to lateral loads may be accomplished by battering the piles to a
slope of l (H):4(V), or steeper. Passive soil resistance values for embedded pile caps and grade
beams may be determined using an equivalent fluid weight of 250 pounds per cubic foot (pcf).
This value includes a factor of safety of at least 1.5 assuming that a properly compacted
structural fill will be placed adjacent to the sides of the pile caps and grade beams. Friction at
the base of pile cap should be ignored in the design calculations. For the seismic condition, the
recommended passive pressure may be increased by one third.
Estimated Pile Length — The subsurface conditions at the site may vary across the site. Based on
the soil conditions at the site and our experience in the project area, for planning and cost
estimating purposes, we estimate that pile length may range from about 20 to 25 feet. A
minimum pile length of 10 feet should also be specified in the project plans.
Obstructions — Construction and concrete debris was encountered in test pits PIT-3, TP-2, and
TP-3 beneath the existing parking area. In so, obstructions may be encountered during pile
driving. Where possible, the obstructions should be removed to facilitate the pile driving. If
obstructions cannot be removed, the structural engineer of record should be notified to revise the
pile layout to accommodate the adjustment.
6.3 CONCRETE RETAINING WALL DESIGN PARAMETERS
Retaining 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 that may be present behind the wall. Our geotechnical
recommendations for the design and construction of the retaining and below -grade walls are
presented in the sections below.
6.3.1 Lateral Earth Pressures
We recommend that concrete cantilever walls that are free to rotate be designed for an equivalent
fluid pressure of 35 pcf for level backfills behind the walls; and 50 pcf with a backslope no
steeper than 2H:IV. Restrained walls such as basement walls should be designed for 50 and 60
pcf for level and 2H:1 V backslope, respectively.
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For the seismic condition, we recommend a uniform lateral earth pressure of 8H psf (where H is
the wall height) be added to the static pressure for sizing the retaining and basement walls. The
recommended lateral pressure assumes that adequate wall drainage will be incorporated into the
design and construction of the walls to prevent the development of hydrostatic pressure.
6.3.2 Wall Surcharge
The retaining and basement walls should be designed to accommodate traffic surcharge
pressures if the traffic load is located within the height dimension of the wall. As a minimum,
the traffic surcharge should be considered equivalent to 2 feet of soils surcharge (i.e., 80 psf of
horizontal uniform pressure). Similarly, surcharge loads from construction equipment or
soil/material stockpiles should be considered in the retaining and basement wall design. We
recommend that a lateral load coefficient of 0.4 be used to compute the lateral pressure on the
wall face resulting from surcharge loads located within a horizontal distance of one-half wall
height.
6.3.3 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
0.35 may be used to determine the frictional resistance at the base of the footings. This
coefficient also includes a safety factor of at least 1.5.
6.3.4 Wall Drainage
Provisions for wall drainage should consist of a 4-inch diameter perforated drainpipe behind and
at the base of the wall footings, embedded in 12 to 18 inches of clean crushed rock and pea
gravel wrapped with a layer of filter fabric. Where applicable, in -lieu of conventional footing
drains, weep holes (2" diameter of 10 feet on center) may be used for site retaining walls. A
minimum 18-inch-wide zone of free draining granular soils (i.e., pea gravel or washed rock) is
recommended to be placed adjacent to the wall for the full height of the wall. Alternatively, a
composite drainage material, such as Miradrain 6000, may be used in lieu of the clean crushed
rock or pea gravel. The drainpipe at the base of the wall should be graded to direct water to a
suitable outlet.
21-372 - 614 & 616 5th Ave S - Geotech Rpt.doc Page 12 PanGEO, Inc.
Geotechnical Report
Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
6.3. S Wall Backfill
Wall backfill should consist of free draining granular soils. In our opinion, the on -site fill soils
have a high fines content, and are not suitable to be re -used as wall backfill. Imported wall
backfill such as Gravel Borrow (Section 9.03.14 (1) of the 2020 WSDOT Standard
Specifications) should be assumed for this project.
The fill should be moisture conditioned to near its optimum moisture content, placed in loose,
horizontal lifts less than about a foot in thickness, and systematically compacted to a dense and
relatively unyielding condition. The adequacy of the compaction should be verified by PanGEO.
If density tests will be performed, the test results should indicate 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.
6.4 CONCRETE SLAB -ON -GRADE
The floor slabs for the proposed buildings may be constructed using conventional concrete slab -
on -grade floor construction. The floor slabs should be supported on competent native soil or
compacted structural fill. Any loose soils at the slab subgrade should be either recompacted to a
dense condition or over -excavated to expose dense undisturbed native soils. Over -excavation
should be replaced with compacted structural fill.
Interior concrete slab -on -grade floors should be underlain by a capillary break consisting of at
least of 4 inches of pea gravel or compacted 3/4-inch, clean crushed rock (less than 3 percent
fines). The capillary break material should also 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 should be placed on the subgrade that has been compacted to a dense and
unyielding condition. A 10-mil polyethylene vapor barrier should also be placed directly below
the slab. We also recommend that construction joints be incorporated into the floor slab to
control cracking.
7.0 CONSTRUCTION CONSIDERATIONS
7.1 DEMOLITION & SITE PREPARATION
We envisage site preparation for the proposed project includes demolishing the existing
structures, stripping and clearing of surface vegetation, and excavations to the design subgrade.
All footings and floor slabs of the existing buildings, as well as building debris and concrete
rubble should be removed from the site prior to the start of excavations or grading. All stripped
21-372 - 614 & 616 5th Ave S - Geotech Rpt.doc Page 13 PanGEO, Inc.
Geotechnical Report
Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
surface materials should be properly disposed off -site or be "wasted" on site in non-structural
landscaping areas.
Following site clearing and excavations, the adequacy of the subgrade where foundations, slabs, or
pavements are to be placed should be verified by a representative of PanGEO. The subgrade soil in
the improvement areas, if recompacted and still yielding, should be over -excavated and replaced
with compacted structural fill or CDF/lean-mix concrete.
The test pits for this study were backfilled with the excavated soils. The backfill was tamped
with the excavator bucket and the ground surface leveled. The backfill was not compacted to the
requirements of structural fill. During construction of the project, the earthwork contractor
should locate the test pits, remove the loose backfill and replace it with properly compacted
structural fill.
7.2 MATERIAL REUSE
In the context of this report, structural fill is defined as compacted fill placed under footings,
concrete stairs and landings, and slabs, or other load -bearing areas. The contractor should be
aware that the site soils are poorly graded and may be difficult to compact to the requirements of
structural fill. As a result, the excavated site materials may not be suitable for use as structural
backfill, particularly during periods of wet weather. If import structural fill is needed, it should
consist of a well -graded granular material, such as WSDOT CSBC, Gravel Borrow or approved
equivalent.
Well -graded recycled concrete may also be considered as a source of structural fill. Use of
recycled concrete as structural fill should be approved by the geotechnical engineer. The on -site
soil can be used as general fill in the non-structural and landscaping areas. If use of the on -site
soil is planned, the excavated soil should be stockpiled and protected with plastic sheeting to
prevent softening from rainfall in the wet season.
7.3 TEMPORARY EXCAVATIONS
As currently planned, excavations on the order of 10 feet are needed for the foundation
construction. As such, we anticipate that unsupported slope cuts may be incorporated into the
excavation design. All temporary excavations should be performed in accordance with Part N of
WAC (Washington Administrative Code) 296-155. The contractor is responsible for maintaining
safe excavation slopes and/or shoring.
21-372 - 614 & 616 5th Ave S - Geotech Rpt.doc Page 14 PanGEO, Inc.
Geotechnical Report
Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
In general, vertical cuts should be limited to 4 feet in areas not close to the property lines. The
vertical cuts should be limited to 2 feet along the property lines. Temporary excavations deeper
than a total of 4 feet should be sloped, benched, or shored. Excavations more than 2 feet along
property lines, will also need to be sloped or supported if sufficient space is not available to lay
back the excavations without encroaching into neighboring properties. If temporary shoring is
needed to support the excavations, PanGEO can provide shoring design recommendations if
requested.
For planning purposes, the temporary unsupported excavation may be sloped as steep as 1 H:1 V
(Horizontal: Vertical). The cut slopes may also need to be flattened in the wet seasons and
should be covered with plastic sheets. We also recommend that heavy construction equipment,
building materials, excavated soil, and vehicular traffic should not be allowed within a distance
equal to 1/3 the slope height from the top of any excavation.
7.4 STRUCTURAL FILL PLACEMENT AND COMPACTION
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.
Depending on the type of compaction equipment used and depending on the type of fill material,
it may be necessary to decrease the thickness of each lift to achieve adequate compaction.
PanGEO can provide additional recommendations regarding structural fill and compaction
during construction.
7.5 PERMANENT CUT AND FILL SLOPES
Based on the anticipated soil that will be exposed in the planned excavation, we recommend
permanent cut and fill slopes be constructed no steeper than 2H:1V (Horizontal:Vertical).
7.6 EROSION AND DRAINAGE CONSIDERATIONS
Surface runoff can be controlled during construction by careful grading practices. Typically, this
includes the construction of shallow, up -grade 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 an approved City storm sewer.
21-372 - 614 & 616 5th Ave S - Geotech Rpt.doc Page 15 PanGEO, Inc.
Geotechnical Report
Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
It should be noted that the site soils are prone to surficial erosion. Special care should be taken to
avoid surface water on open cut excavations. As previously mentioned in Section 7.3, we
recommend that the exposed temporary slopes be covered with plastic sheeting.
Permanent control of surface water and roof runoff should be incorporated in the final grading
design. In addition to these sources, irrigation and rainwater infiltrating into landscape and
planter areas adjacent to paved areas or building walls should also be controlled. All collected
runoff should be directed into conduits that carry the water away from the pavement or structure
and into City 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.
7.7 WET EARTHWORK RECOMMENDATIONS
General recommendations relative to earthwork performed in inclement weather or in wet
conditions are presented below:
• All surface of the foundation subgrade should be protected against inclement weather.
It is the contractor's responsibility to protect the footing subgrade from disturbance.
One option is to place a 2- to 3-inch-thick layer of lean -mix concrete on the footing
subgrade as soon as the subgrade is exposed.
• 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 3/4-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.
• 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.
21-372 - 614 & 616 5th Ave S - Geotech Rpt.doc Page 16 PanGEO, Inc.
Geotechnical Report
Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
• Excavation slopes and soils stockpiled on site should also be covered with plastic
sheets.
8.0 ADDITIONAL SERVICES
To confirm that our recommendations are properly incorporated into the design and construction
of the proposed development, PanGEO should be retained to conduct a review of the final
project plans and specifications, and to monitor the construction of geotechnical elements.
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 Jonathan Kurth and the project design team.
Recommendations contained in this report are based on a site reconnaissance, review of pertinent
subsurface information, 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 has been prepared for planning and design purposes for specific application to the
proposed project in accordance with the generally accepted standards of local practice at the time
this report was written. No warranty, express or implied, is made.
21-372 - 614 & 616 5th Ave S - Geotech Rpt.doc Page 17 PanGEO, Inc.
Geotechnical Report
Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
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.
We appreciate the opportunity to be of service.
Sincerely,
Spenser P. Scott, L.G.
Staff Geologist
Michael H. Xue, P.E.
Principal Geotechnical Engineer
21-372 - 614 & 616 5th Ave S - Geotech Rpt.doc Page 18 PanGEO, Inc.
Geotechnical Report
Proposed Townhomes: 614 & 616 — 5th Avenue South, Edmonds, Washington
September 21, 2021
10.0 REFERENCES
ASTM D2488-17, Standard Practice for Description and Identification of Soils (Visual -Manual
Procedures), ASTM International, West Conshohocken, PA, 2017, www.astm.org.
International Code Council, 2018, International Building Code (IBC).
Booth, D. B., Cox, B. F., Troost, K. G., Shimel, S. A., 2004, Composite Geologic Map of the
Sno-King Area, Central Puget Lowland, Washington: Seattle -Area Geologic Mapping
Project, University of Washington, and the United States Geological Survey, scale
1:24000.
Washington Administrative Code (WAC), 2016, Chapter 296-155 - Safety Standards for
Construction Work, Part N - Excavation, Trenching, and Shoring, Olympia, Washington.
Washington State Department of Transportation, 2020, Standard Specifications for Road, Bridge
and Municipal Construction, M 41-10, Washington State Department of Transportation.
Zipper Geo Associates, LLC., February 2016, Geotechnical Engineering Report, Proposed
Home Street Bank, 614 & 616 5' Avenue South, Edmonds, Consultant report prepared for
Home Street Bank.
21-372 - 614 & 616 5th Ave S - Geotech Rpt.doc Page 19 PanGEO, Inc.
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APPENDIX A
SUMMARY TEST PIT LOGS
RELATIVE DENSITY / CONSISTENCY
SAND / GRAVEL
SILT / CLAY
SPT
Approx. Relative
SPT Approx. Undrained Shear
DensityN-values
Density (%)
Consistency
N-values
Strength (psf)
Very Loose
<4
<15
Very Soft
<2
<250
Loose
4 to 10
15 - 35
Soft
2 to 4
250 - 500
Med. Dense
10 to 30
35 - 65
Med. Stiff
4 to 8
500.1000
Dense
30 to 50
65 - 85
Stiff
8 to 15
1000 - 2000
Very Dense
>50
85.100
Very Stiff
15 to 30
2000 - 4000
Hard
>30
>4000
UNIFIED SOIL CLASSIFICATION SYSTEM
MAJOR DIVISIONS
GROUP DESCRIPTIONS
•�'
GW:
Well -graded GRAVEL
Gravel
GRAVEL (<5% fines)
..
.....:
......................................................
50% or more of the coarse
o °
GP :
:
Poorly -graded GRAVEL
fraction retained on the #4
sieve. Use dual symbols leg.
o °
GM
......................................................
Silty GRAVEL
GP -GM) for 5% to 12% fines.
GRAVEL (>12% fines)
••••••••••••••••••••••••••••••
GC :
........................•••
Clayey GRAVEL
......................................................................
..........................................................
SW:
Well -graded SAND
Sand
SAND (<5 /° fines)
''
50% or more of the coarse
....................................:....>
%
SP
Poorly -graded raded SAND
y-g
fraction passing the #4 sieve.
Use duals leg. SP-SM )
;
":r"
............................................................
SM:
Silt SAND
y
%fin
for s%to12%fines.g
SAND (>1 2% fines)
, •••••••••••••••••••••••••••••••••••••••••••••••••••••••••
SC :
Clayey SAND
......................................................................
.............................................................
ML :
SILT
Liquid Limit < 50
............................................................
CL :
Lean CLAY
Silt and Clay
............................................................
OL :
Organic SILT or CLAY
==
—
50%or more passing #200 sieve
:..................................
:......................................................
MH :
Elastic SILT
Liquid Limit > 50
CH
Fat CLAY
OH
Organic SILT or CLAY
— ,
........................... ......................................
Highly Organic Soils
............................................................
PT :
PEAT
Notes: 1. Soil exploration to s contain material descriptions based on visual observation and field tests using a system
modified from the Uniform Soil Classification System (USCS). Where necessary laboratory tests have been
conducted (as noted in the "Other Tests" column), unit descriptions may include a classification. Please refer to the
discussions 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 to s.
Other symbols may be used where field observations indicated mixed soil constituents or dual constituent materials.
DESCRIPTIONS OF SOIL STRUCTURES
Layered: Units of material distinguished by color and/or
Fissured: Breaks along defined planes
composition from material units above and below
Slickensided: Fracture planes that are polished or glossy
Laminated: Layers of soil typically 0.05 to 1 mm thick, max.1 cm
Blocky: Angular soil lumps that resist breakdown
Lens: Layer of soil that pinches out laterally
Disrupted: Soil that is broken and mixed
Interlayered: Alternating layers of differing soil material
Scattered: Less than one per foot
Pocket: Erratic, discontinuous deposit of limited extent
Numerous: More than one per foot
Homogeneous: Soil with uniform color and composition throughout
BCN: Angle between bedding plane and a plane
normal to core axis
COMPONENT DEFINITIONS
COMPONENT
SIZE / SIEVE RANGE
COMPONENT
SIZE / SIEVE RANGE
Boulder:
> 12 inches
Sand
Cobbles:
3 to 12 inches
Coarse Sand:
#4 to #10 sieve (4.5 to 2.0 mm)
Gravel
Medium Sand:
#10 to #40 sieve (2.0 to 0.42 mm)
Coarse Gravel:
3 to 3/4 inches
Fine Sand:
#40 to #200 sieve (0.42 to 0.074 mm)
Fine Gravel:
3/4 inches to #4 sieve
Silt
0.074 to 0.002 mm
Clay
<0.002 mm
TEST SYMBOLS
for In Situ and Laboratory Tests
listed
in "Other Tests" column.
ATT
AtterbergLimit Test
Comp
Compaction Tests
Con
Consolidation
DD
Dry Density
DS
Direct Shear
%F
Fines Content
GS
Grain Size
Perm
Permeability
PP
Pocket Penetrometer
R
R-value
SG
Specific Gravity
TV
Torvane
TXC
Triaxial Compression
UCC
Unconfined Compression
SYMBOLS
Sample/In Situ test types and intervals
2-inch OD Split Spoon, SPT
(140-lb. hammer, 30" drop)
H3.25-inch
OD Spilt Spoon
(300-lb hammer, 30" drop)
Non-standard penetration
test (see boring log for details)
Thin wall (Shelby) tube
Grab
Rock core
®
Vane Shear
MONITORING WELL
SZ
Groundwater Level at
time of drilling (ATD)
1
Static Groundwater Level
Cement / Concrete Seal
Bentonite grout / seal
Silica sand backfll
Slotted tip
Slough
Bottom of Boring
MOISTURE CONTENT
Dry
Dusty, dry to the touch
Moist
Damp but no visible water
Wet
Visible free water
GPmE® Terms and Symbols for
I IN C 0 R P 0 R A T E D Boring and Test Pit Logs Figure A-1
Phone: 206.262.0370
Test Pit No. PIT-1
Approximate ground surface elevation (NAVD88): 74 feet
Coordinates (Washington State Plane - North): 297653, 1260821
Death ft
Material Description
Light vegetation above loose to medium dense, gray -brown, silty fine SAND
0-2
with gravel; trace plastic, asphalt, and brick debris, some angular rock, trace
-----------------------
rootlets; disrupted texture, non -plastic, dry to moist
----------------------------------------------------------------------------------------------------------------------------
Medium dense, light brown, poorly graded fine SAND; trace silt, trace angular
2 — 4.5
rock, trace roots, burnt wood fragments; iron -oxide staining; disrupted texture
non -plastic, moist [Fill]
Dense, gray -brown, poorly graded fine SAND; trace gravel, trace silt; non-
4.5 — 9
plastic, moist [Qpf — Pre -Fraser Deposits]
- Becomes dense, gray, poorly graded fine SAND from 7 to 9 feet
o•
JI
-Av_ _
- � �
l
_
yy 1
ti_ s
eve
Photo PIT-1 (left): Shows PIT-1 at approximately 5.5 feet in depth before testing
Photo PIT-1 (right): Shows spoils from PIT-1 at approximately 9 feet in depth after testing
PIT-1 was terminated approximately 5.5 feet below grade for infiltration testing. After the test,
PIT-1 was over -excavated to 9 feet in depth to check for shallow groundwater or groundwater
mounding.
No groundwater seepage was encountered during explorations.
21-372 Test Pit Logs Figure A-2 PanGEO, Inc.
Test Pit No. PIT-2
Approximate ground surface elevation (NAVD88): 73.5 feet
Coordinates (Washington State Plane - North): 297574, 1260814
Death ftj
Material Description
Light vegetation above loose to medium dense, gray -brown, silty fine SAND
0 — 2.5
with gravel; trace asphalt debris, some angular rock, trace rootlets; disrupted
-----------------------
texture, non -plastic, dry to moist
----------------------------------------------------------------------------------------------------------------------------
Medium dense, light brown, poorly graded fine SAND; trace silt, trace angular
2.5-4
rock, some roots, burnt wood fragments; trace iron -oxide staining; disrupted
texture non -plastic, moist [Fill]
Dense, gray -brown, poorly graded fine SAND; trace gravel, trace silt; non-
4-9
plastic, moist [Qpf — Pre -Fraser Deposits]
- Becomes dense, gray, poorly graded fine SAND from 7 to 9 feet
..!t
r
a.
V.. W
Photo PIT-2 (left): Shows PIT-2 at approximately 6 feet in depth before testing
Photo PIT-2 (right): Shows spoils from PIT-2 at approximately 9 feet in depth after testing
PIT-2 was terminated approximately 6 feet below grade for infiltration testing. After the test,
PIT-2 was over -excavated to 9 feet in depth to check for shallow groundwater or groundwater
mounding.
No groundwater seepage was encountered during explorations.
21-372 Test Pit Logs Figure A-3 PanGEO, Inc.
Test Pit No. PIT-3
Approximate ground surface elevation (NAVD88): 83.5 feet
Coordinates (Washington State Plane - North): 297594, 1260886
De th ft
Material Description
Approximate 2-inch asphalt overlay above loose to medium dense, gray -brown,
0-7
-----------------------
slightly silty SAND with gravel and cobble; trace wood debris; non -plastic, moist
----------------------------------------------------------------------------------------------------------------------------
Loose, dark brown to black, slightly organic silty SAND; trace brick debris, wood
7 — 8.5
debris, some concrete and construction debris; disrupted texture; non -plastic,
moist
-----------------------
----------------------------------------------------------------------------------------------------------------------------
Medium dense, light brown to red -brown, poorly graded fine SAND; trace silt,
8.5 — 10
burnt wood fragments; trace iron -oxide staining; disrupted texture non -plastic,
moist [Fill]
Dense, gray -brown, poorly graded fine to medium SAND; trace gravel, trace silt,
10-15
trace iron -oxide staining; non -plastic, moist [Qpf— Pre -Fraser Deposits]
tip "
1
` � _ '7 • . Ate. �,� t}K' : � �' ;
AL
Photo PIT-3 (left): Shows PIT-3 at approximately 12 feet in depth before testing
Photo PIT-3 (right): Shows spoils from PIT-3 at approximately 10 feet in depth after testing
PIT-3 was terminated approximately 6 feet below grade for infiltration testing. After the test,
PIT-3 was over -excavated to 15 feet in depth to check for shallow groundwater or groundwater
mounding.
No groundwater seepage was encountered during explorations.
21-372 Test Pit Logs Figure A-4 PanGEO, Inc.
Test Pit No. TP-1
Approximate ground surface elevation (NAVD88): 74 feet
Coordinates (Washington State Plane - North): 297615, 1260818
Death ftj
Material Description
Light vegetation and gravel above loose to medium dense, gray -brown, silty
0-2
fine SAND with gravel; trace concrete debris, some angular rock, trace rootlets;
-----------------------
disrupted texture, non -plastic, dry to moist
----------------------------------------------------------------------------------------------------------------------------
Medium dense, light brown, poorly graded fine SAND; trace silt, trace angular
2-4
rock, trace roots, burnt wood fragments; iron -oxide staining; disrupted texture
non -plastic, moist [Fill]
Dense, gray -brown to gray, poorly graded fine to medium SAND; trace gravel,
trace silt; non -plastic, moist
4 —13
• Top approximate 2 feet weathered to red -brown w/ iron -oxide staining
• Cobble layer from approximately 11 to 12 feet below ground surface
[Qpf — Pre -Fraser Deposits]
i ! ,t
1.4
1
� l
v
Photo TP-1 (left): Shows TP-1 at approximately 13 feet in depth
Photo TP-1 (right): Shows spoils from TP-1 at approximately 10 feet in depth
TP-1 was terminated approximately 13 feet below grade. No groundwater seepage was
encountered during explorations.
21-372 Test Pit Logs Figure A-5 PanGEO, Inc.
Test Pit No. TP-2
Approximate ground surface elevation (NAVD88): 84 feet
Coordinates (Washington State Plane - North): 297617, 1260919
Death ftj
Material Description
Approximate 2-inch asphalt overlay above loose to medium dense, gray -brown,
0-8
-----------------------
slightly silty SAND with gravel and cobble; trace wood debris; non -plastic, moist
----------------------------------------------------------------------------------------------------------------------------
Loose, dark brown to black, slightly organic silty SAND; trace brick debris, wood
8-9
debris, some concrete and construction debris; disrupted texture; non -plastic,
moist [Fill]
Medium dense, light brown to red -brown, poorly graded fine SAND; trace silt,
9-11
burnt wood fragments; trace iron -oxide staining; disrupted texture non -plastic,
moist [Qpf — Pre -Fraser Deposits]
•
r '•
i
Photo TP-2 (left): Shows TP-2 at approximately 11 feet in depth
Photo TP-2 (right): Shows spoils from TP-2 at approximately 10 feet in depth
TP-2 was terminated approximately 11 feet below grade. No groundwater seepage was
encountered during explorations.
21-372 Test Pit Logs Figure A-6 PanGEO, Inc.
Test Pit No. TP-3
Approximate ground surface elevation (NAVD88): 83 feet
Coordinates (Washington State Plane - North): 297651, 1260854
PeiqthftjMaterial
Description
Approximate 2-inch asphalt overlay above loose to medium dense, gray -brown,
0-7
slightly silty SAND with gravel and cobble, layers of gray, sandy SILT; metal
----------------------------
debris, wood debris, large fragments of concrete slab; non -plastic, moist
------------------------------------------------------------------------------------------------------------------------------------------------------
Loose, dark brown to black, slightly organic silty SAND; metal debris, wood
7-8
debris, some concrete and construction debris; disrupted texture; non -plastic,
moist [Fill]
Medium dense, light brown to red -brown, poorly graded fine SAND; trace silt,
8 —11
burnt wood fragments; trace iron -oxide staining; disrupted texture non -plastic,
moist [Qpf — Pre -Fraser Deposits]
f
4
Photo TP-3 (left): Shows TP-3 at approximately 10 feet in depth
Photo TP-3 (right): Shows spoils from TP-3 at approximately 10 feet in depth
TP-3 was terminated approximately 10 feet below grade. No groundwater seepage was
encountered during explorations.
Date of Test Pit Excavations: August 4 and August 6, 2021
Excavations Logged by: S. Scott and J. Manke
21-372 Test Pit Logs Figure A-7 PanGEO, Inc.
APPENDIX B
PREVIOUS TEST BORING LOGS
AND
LABORATORY RESULTS
10 El
SB-1
a (10 °°TSB-2�
B-3
`n 1
1 _ O oaf °°" po
cl
IB-rJ
u° low=.11�:>!11
ao 0 od o pO
LEGEND
B-1 BORING NUMBER AND
APPROXIMATE LOCATION
30 0 15 30
APPROXIMTATE SCALE IN FEET
w 0q
Fi.. ' 'd o
BASE DRAWING PROVIDED BY HOMESTREET BANK, UNDATED.
Boring Location: See Figure 1, Site and Exploration Plan Drilling Companv: Environmental Bore Hole Dia.: 8"
Top Elevation: - Drilling Method: Hollow Stem Auger Hammer Type: Auto
B-1
Date Drilled: 10/19/2015 Drill Rig: Truck Logged by.. TAJ
aThe
°
SOIL DESCRIPTION
/^
9 vJ
E J
Q
n
(6
0 C
PENETRATION RESISTANCE (blows/foot)
o
U
°
m
0)
W
stratification lines represent the approximate boundaries
between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.
Standard Penetration Test
Hammer Weight and Drop:
0 20 40 60
-0
2 inches asphalt over about 2 inches Crushed Surfacing Base
Course over gravelly SAND with trace to some silt
—i
+✓-+tip+I-++
IIIIIIIII
I I -I I l l-I-I
IIIIIIIII
I I��+�� I...
IIIIIIII-
Loose, wet, gray -brown, gravelly SAND with some silt
Fill
( )
S-1 18
I
IIIIIIIII
+t��th1��
1.J 1
1Ii
rr
IIIIIIIII
��I I I I -I -I
IIIIII
--, rrl-i-I
IIIIIIII
-1-4-4-4�Probable
1 1 1 1 1
II1111�
10
-5
- IIIIII
IIIIIIII,
I
1I- __
4 _
__ .._.
_I I
__ ...
Loose, wet, gray, SAND with silt and gravel (Probable Fill)
T
S-2 11 181,
10
GSA
Loose, moist, gray, gravelly SAND with trace to some silt
Probable Filo__________________________________
1.o9Se,maiSi.dlsbravyn.�aodkSll_T�E�Ii�I�s9il�--------
S3 18"
� I� I I
-rrrrrrr
IIIIIII
I I I I I I I I I
rrr�rl���
111ii1
I I I I I
���
11
7
Loose, moist, orange -brown, SAND with gravel, some silt
111
c L L L1_I
I IIII
111111I11
I_L_I
hill
IIIIIIII-
T
S-4 1151,
9
GSA
LL
I
IIIIIIIII
I I I I I
I I I I I I
S-5 18
I
+
IIII
I I I I I
IIIIIIIII
I I I I I I
IIIIIIII
8
III IIIII
IIIIIIIII
IIIIIIIII
IIIIIIIII
IIIIIIII
IIIII '..-
•15
IIIIIIIII
IIIIIIIII
IIIIII
--------------------------------------------
Dense, moist, light brown, SAND with some silt, some gravel
S-6 I 15"
IIIIII
1 1 1 1
I I I 1
j 1
34
IIIIII
�♦-�FFI
IIIIIIIII
III II
'....� I I I 1-1
- IIIIII
IIIII
-111� ....
IIIIIIII-
Dense, wet, brown, gravelly SAND with silt
Boring completed at approximately 24 feet.
• 25
No groundwater observed ATD.
SAMPLE LEGEND
GROUNDWATER LEGEND
I2-inch O.D. split spoon sample
❑
Clean Sand
3-inch I.D. Shelby tube sample
®
Bentonite
Grout/Concrete
®
Screened Casing
TESTING KEY
❑
Blank Casing
GSA = Grain Size Analysis
VGroundwater
level at
time of drilling (ATD) or
20OW = 200 Wash Analysis
ti
on date of
Consol. = Consolidation Test
N
measurement.
Att. = Atterberq Limits
T- T-F
L_L L.LLI I ._.I_. I I _J__
IIIIIII IIIIII IIIIIIII'
-1 I I IIIIII IIIIIIII-
S-7 18" II q6
I IIIII I IIIII
0 % Fines (<0.075 mm)
O % Water (Moisture) Content
Plastic Limit Liquid Limit
Natural Water Content
Homestreet Bank
614 & 616 5th Ave S.
Edmonds, WA
Date: - Project No.: 1527.01
Zipper Geo Associates BORING
19023 36th Ave. W, Suite D LOG; B_ 1
Lynnwood, WA
Page 1 of 1
See Figure 1, Site and Exploration Plan
10/19/2015
SOIL DESCRIPTION
Z
The stratification lines represent the approximate boundaries
a) between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.
-0
2 - 2.5 inches asphalt over about 2.5 inches CSBC over dark
brown, moist, silty SAND
Drilling Company: Environmental Bore Hole Dia.: 8"
Drilling Method: Hollow Stem Auger Hammer Type: Auto
B-2
Drill Rig: Truck Logged by.. TAJ
PENETRATION RESISTANCE (blows/foot)
U)
Standard Penetration Test
J
o
c
Hammer Weight and Drop:
U
F= <0
o
o
H
U
0 20 40 60
Medium dense, moist, brown -gray, SAND with silt and gravel S-1 151•
I
(Possible Fill)
- 5 Medium dense, moist, brown, SAND with silt and gravel T
(Possible Fillj._Blowcounts ov_erstated_due to gravel- _ _ _ _ _ _ _ _ S-2 I 181,
Very dense, moist, brown, sandy GRAVEL with some silt and
cobbles (Possible Fill) T
Loose, moist, brown, SAND with some silt to with silt, trace to S-3 I 3"
some gravel T
Loose, moist, brown, SAND with some silt to with silt, trace to S-4 I 19
some gravel (2 inches wood at 11 feet; root?)
(Wood in cuttings)
Dense, moist, gray, SAND with silt and gravel to silty SAND s-5 18^
with gravel (Glacial Till -like)
•15
Dense, moist, gray, interbedded fine SAND with trace silt and S-6 I 18"
silty SAND with some gravel
Boring completed at approximately 19 feet.
No groundwater observed ATD.
• 25 '
SAMPLE LEGEND
GROUNDWATER LEGEND
I2-inch O.D. split spoon sample
❑
Clean Sand
3-inch I.D. Shelby tube sample
®
Bentonite
Grout/Concrete
®
Screened Casing
TESTING KEY
❑
Blank Casing
GSA = Grain Size Analysis
VGroundwater
level at
time of drilling (ATD) or
20OW = 200 Wash Analysis
ti
on date of
Consol. = Consolidation Test
N
measurement.
Att. = Atterberq Limits
12 1 GSA
14
_ 9
JJJJ�
I I I I I
I I I I I
1-4 -4 -4 -4
33
Illli
II
i 41
(IIIII (IIIII III
illlillll Iilill IIIIIIII
IIIIIIII 1 l i lllll!'
iIIlI11 till
II11 i
r FF
jlll
--i LLL1 ------------
Illlili 111 Illll'
0 % Fines (<0.075 mm)
O % Water (Moisture) Content
Plastic Limit Liquid Limit
Natural Water Content
Homestreet Bank
614 & 616 5th Ave S.
Edmonds, WA
Date: - Project No.: 1527.01
Zipper Geo Associates BORING
19023 36th Ave. W, Suite D LOG; B_ 2
Lynnwood, WA
Page 1 of 1
See Figure 1, Site and Exploration Plan
10/19/2015
SOIL DESCRIPTION
Z
The stratification lines represent the approximate boundaries
a) between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.
-0
2.5 inches asphalt over about 2.5 inches CSBC over brown,
moist, SAND with silt some gravel
Drilling Company: Environmental Bore Hole Dia.: 8"
Drilling Method: Hollow Stem Auger Hammer Type: Auto
B-3
Drill Rig: Truck Logged by.. TAJ
PENETRATION RESISTANCE (blows/foot)
U)
Standard Penetration Test
J
o
c
Hammer Weight and Drop:
U
F= <0
o
o
H
U
0 20 40 60
Loose, moist, gray, SAND with silt, trace gravel (Probable Fill) s 1 I 18"
-5 1
Medium dense, moist, gray, silty SAND with trace gravel s 2 16"
(Probable Fill)
Loose, damp to moist, gray, SAND with trace to some silt and T
gravel (Probable Fill) _ _ _ _ _ _ _ _ _ _ s-s 18"
I
Loose, damp to moist, dark brown, silty SAND (Relic Topsoil?)
---------------------------------------------
Medium dense, damp to moist, orange -brown grading to
yellow -gray, SAND with trace to some silt trace gravel S-4 T 181,
Medium dense, damp to moist, gray, fine SAND with silt S-5 181,
•15
--------------------------------------------
Very dense, moist, gray, sandy GRAVEL with some silt
S-6 15"
Boring completed at approximately 19 feet.
No groundwater observed ATD.
• 25 '
SAMPLE LEGEND
GROUNDWATER LEGEND
I2-inch O.D. split spoon sample
❑
Clean Sand
3-inch I.D. Shelby tube sample
®
Bentonite
Grout/Concrete
®
Screened Casing
TESTING KEY
❑
Blank Casing
GSA = Grain Size Analysis
VGroundwater
level at
time of drilling (ATD) or
20OW = 200 Wash Analysis
ti
on date of
Consol. = Consolidation Test
N
measurement.
Att. = Atterberq Limits
50/5"
IIIIII IIIIII IIIII
-.....
illllll - IIIIII (IIIIIII-
(IIIIIII I II I llll'�-
IIIIIII till
(III I
r F_F
(LILII
- -L
i
IIIIIII IIIIII Illll'
0 % Fines (<0.075 mm)
O % Water (Moisture) Content
Plastic Limit Liquid Limit
Natural Water Content
Homestreet Bank
614 & 616 5th Ave S.
Edmonds, WA
Date: - Project No.: 1527.01
Zipper Geo Associates BORING
19023 36th Ave. W, Suite D LOG; B-3
Lynnwood, WA
Page 1 of 1
Boring Location: See Figure 1, Site and Exploration Plan Drilling Companv: Environmental Bore Hole Dia.: 8"
Top Elevation: - Drilling Method: Hollow Stem Auger Hammer Type: Auto
B-4
Date Drilled: 10/19/2015 Drill Rig: Truck Logged by.. TAJ
SOIL DESCRIPTION
PENETRATION RESISTANCE (blows/foot)
/^
9 vJ
E J
(6
0)
Standard Penetration Test
aThe
stratification lines represent the approximate boundaries
Hammer Weight and Drop:
o
U
°
between soil types. The transition may be gradual. Refer to
Q o
W
report text and appendices for additional information.
n
°
m
C0
0 20 40 60
-0
_Vyeed�LaysidarkJ)rQvyrl dBDV_tomaiat. siUy-S8UD�IQpwJ
Encountered 1/2-inch diameter PVC pipe at 14 inches
1
IIIIIIIII
IIIIIIIII
IIIIIIII-
Medium dense, damp to moist, brown grading to orange-
S-1 18
I
IIIIIIIII
IIIIIIIII
IIIIIIII
12
GSA
brown, SAND with some silt and 9ravel
!
11
IIIIIIIII
_
IIIIIIII
-5
Loose, damp to moist, yellow -brown, SAND with silt to SAND S-2 18
with some silt
Medium dense, moist, light brown, silty fine SAND S-3
Dense, moist, brown -gray, SAND with some silt
S-4 18"
Boring completed at approximately 11.5 feet
No groundwater observed ATD.
•15
• 25 '
SAMPLE LEGEND
GROUNDWATER LEGEND
I2-inch O.D. split spoon sample
❑
Clean Sand
3-inch I.D. Shelby tube sample
®
Bentonite
Grout/Concrete
®
Screened Casing
TESTING KEY
❑
Blank Casing
GSA = Grain Size Analysis
V
Groundwater level at
time of drilling (ATD) or
20OW = 200 Wash Analysis
ti
on date of
Consol. = Consolidation Test
N
measurement.
Att. = Atterberq Limits
38
T
IIIIII
T
TI I I i l
IIIIIIIII
11
IIIIIIII-
LLL11
JL LIII
LLLJLI-I-I
J JJJJ�
I I I 1 1 1
I I I I
I
I I I I I
I I I I
IIIIIIIII
I
I I I I I
IIIIIIIII
I I I I I I
IIIIIIII-
IIIIIIIII
tt�ti-�FF�
IIIIIIIII
FFI I I -I -I -I I
IIIIIIII-
1�11���-I
- - - - 7 7 F . I i_I_I 11T_
Illllll -I IIIIII IIIIII '..-
IIIIIIIII - IIIIII IIIIIIII-
�Illll I it I
FI FJ
L _ L..L L I I . _.!..._.
IIIIII IIIIII IIIIIIII'
0 % Fines (<0.075 mm)
O % Water (Moisture) Content
Plastic Limit Liquid Limit
Natural Water Content
Homestreet Bank
614 & 616 5th Ave S.
Edmonds, WA
Date: - Project No.: 1527.01
Zipper Geo Associates BORING
19023 36th Ave. W, Suite D LOG; B_ 4
Lynnwood, WA
Page 1 of 1
See Figure 1, Site and Exploration Plan
10/19/2015
SOIL DESCRIPTION
Z
The stratification lines represent the approximate boundaries
a) between soil types. The transition may be gradual. Refer to
report text and appendices for additional information.
-0
JYeeds_aysi Ioospa, soaisL dk.brawrr silty SAND 4Zap3oi - - - -
Medium dense, damp, orange -brown, fine SAND with silt to
silty fine SAND with trace gravel
5
Medium dense, damp to moist, orange -brown and gray, fine
SAND with silt to silty fine SAND
•15
Drilling Company: Environmental Bore Hole Dia.: 8"
Drilling Method: Hollow Stem Auger Hammer Type: Auto
B-5
Drill Rig: Truck Logged by.. TAJ
PENETRATION RESISTANCE (blows/foot)
U)
Standard Penetration Test
J
o
c
Hammer Weight and Drop:
U
F= <0
o
o
H
U
0 20 40 60
Medium dense, moist, gray, SAND with silt
---------------------------------------
Very dense, moist, gray, sandy GRAVEL, with some silt s-s 1e
Boring completed at approximately 11.5 feet
No groundwater observed ATD.
• 25 '
SAMPLE LEGEND
GROUNDWATER LEGEND
I2-inch O.D. split spoon sample
❑
Clean Sand
3-inch I.D. Shelby tube sample
®
Bentonite
Grout/Concrete
®
Screened Casing
TESTING KEY
❑
Blank Casing
GSA = Grain Size Analysis
V
Groundwater level at
time of drilling (ATD) or
20OW = 200 Wash Analysis
ti
on date of
Consol. = Consolidation Test
N
measurement.
Att. = Atterberq Limits
12
21
51
illll�llI lilt hill
llilll l ililllll
�Illll I l i
illjll till
111 i
r FF
111
--i LLLI I ._.i_.
Illlili 111 Illll'
0 % Fines (<0.075 mm)
O % Water (Moisture) Content
Plastic Limit Liquid Limit
Natural Water Content
Homestreet Bank
614 & 616 5th Ave S.
Edmonds, WA
Date: - Project No.: 1527.01
Zipper Geo Associates BORING
19023 36th Ave. W, Suite D LOG; B'.ri
Lynnwood, WA
Page 1 of 1
GRAIN SIZE ANALYSIS Test Results Summary ASTM D 422
100
90
= 80
W
?� 70
In
W 60
W
Z
50
Z
W
U
W 40
W
a
30
20
10
0
1000.000
100.000 10.000 1.000 0.100 0.010 0.001
PARTICLE SIZE IN MILLIMETERS
BOULDERS
COBBLES
Coarse
Fine
Coarse
Medium
Fine
Silt
Clay
GRAVEL
SAND
FINE GRAINED
Comments:
Exploration
Sample
Depth (feet)
Moisture (%)
Fines (%)
Description
B-1
S-2
5 - 6.5 ft.
9.9
26.0
SAND with silt
and gravel
Project No.: 1527.01 Project Name:
Zipper Geo Associates, LLC
Geotechnical and Environmental Consultants Date of Testing: 10/21/2015 Edmonds HomeStreet Bank
GRAIN SIZE ANALYSIS Test Results Summary ASTM D 422
100
90
= 80
W
?� 70
In
W 60
W
Z
50
Z
W
U
W 40
W
a
30
20
10
0
1000.000
100.000 10.000 1.000 0.100 0.010 0.001
PARTICLE SIZE IN MILLIMETERS
BOULDERS
COBBLES
Coarse
Fine
Coarse
Medium
Fine
Silt
Clay
GRAVEL
SAND
FINE GRAINED
Comments:
Exploration
Sample
Depth (feet)
Moisture (%)
Fines (%)
Description
B-1
S-4
10 - 11.5 ft.
6.1
7.4
SAND with gravel,
some silt
Project No.: 1527.01 Project Name:
Zipper Geo Associates, LLC
Geotechnical and Environmental Consultants Date of Testing: 10/21/2015 Edmonds HomeStreet Bank
GRAIN SIZE ANALYSIS Test Results Summary ASTM D 422
100
90
= 80
W
?� 70
In
W 60
W
Z
50
Z
W
U
W 40
W
a
30
20
10
0
1000.000
100.000 10.000 1.000 0.100 0.010 0.001
PARTICLE SIZE IN MILLIMETERS
BOULDERS
COBBLES
Coarse
Fine
Coarse
Medium
Fine
Silt
Clay
GRAVEL
SAND
FINE GRAINED
Comments:
Exploration
Sample
Depth (feet)
Moisture (%)
Fines (%)
Description
B-2
S-1
2.5 - 4 ft.
8.2
21.7
SAND with silt
and gravel
Project No.: 1527.01 Project Name:
Zipper Geo Associates, LLC
Geotechnical and Environmental Consultants Date of Testing: 10/21/2015 Edmonds HomeStreet Bank
GRAIN SIZE ANALYSIS Test Results Summary ASTM D 422
100
90
= 80
W
?� 70
In
W 60
W
Z
50
Z
W
U
W 40
W
a
30
20
10
0
1000.000
100.000 10.000 1.000 0.100 0.010 0.001
PARTICLE SIZE IN MILLIMETERS
BOULDERS
COBBLES
Coarse
Fine
Coarse
Medium
Fine
Silt
Clay
GRAVEL
SAND
FINE GRAINED
Comments:
Exploration
Sample
Depth (feet)
Moisture (%)
Fines (%)
Description
B-4
S-1
2.5 - 4 ft.
6.6
12.0
SAND with some
silt and gravel
Project No.: 1527.01 Project Name:
Zipper Geo Associates, LLC
Geotechnical and Environmental Consultants Date of Testing: 10/21/2015 Edmonds HomeStreet Bank