REVIEWED BLD2023-0501+GEO REPORT+7.20.2023_7.21.57_AM+3678316■------- - - - - - -
Reviewed by
City of Edmonds ;
Planning Division
'---------------
,.,.,.,.,.
REVIEWED
BY
CITY OF EDMONDS
BUILDING DEPARTMENT
Win Group Northwest, Inc.
July 19, 2023
Chris and Pauline Lane
16120 72nd Ave. W
Edmonds, WA 98026
Email: twinpilot@gmail.com
RECEIVED
Jul 20 2023
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
Subject: Geotechnical Report
16120 — 72nd Avenue West
Edmonds, Washington 98026
Geotechnical Engineers, Geologists
& Environmental Specialists
G-5936
BLD2023-0501
Ref: "Geologic Engineering Study, Sequoia Ridge Short Subdivision, Edmonds,
Washington 98026, G-1061-1, GEO Group Northwest, Inc., February 29, 2000."
"Plan Set, Addition and Alterations to Lane Residence, 16120 72nd Ave. W,
Edmonds, WA 98026, Mike Shoffner Architect, May 2, 2023."
"Critical Area Determination (CRA2023-0079), 16120 72nd Ave W, City of
Edmonds Planning & Development Department, May 16, 2023."
Dear Chris and Pauline,
Based on our discussions with Mr. Shoffner and our review of the referenced critical area
determination, we understand the City of Edmonds has requested an updated geotechnical report
and critical areas report be provided for the project. In 2000, we prepared the referenced
geotechnical report that included our evaluation of the mapped geologically hazardous areas at
the project site, and have prepared an addendum letter to the referenced geotechnical report
regarding the proposed addition and alterations to the existing residence at the subject property.
This report includes our description of the site, evaluation of the mapped geologically hazardous
areas at the project site, our geotechnical conclusions & our recommendations regarding the
project.
13705 Bel -Red Road • Bellevue, Washington 98005
Phone 425/649-8757 • Fax 425/649-8758
July 19, 2023 G-5936
16120 — 72nd Ave W, Edmonds, WA Page 2
SITE CONDITIONS
The project site (Parcel No. 00513100005204) is located in the Meadowdale neighborhood of
Edmonds, Washington. The project site is approximately 37,897 square feet (0.87) in size, and
approximately wedge shaped. The existing approximately 2200 square feet large two-story
residence and detached garage were constructed in 2001 near the south-central limit of the site.
Public utility improvements (sanitary sewer, stormwater) were also constructed during previous
development of the project site. The project site is bounded by developed residential lots to the
north, east & south, and is bounded by the Lorian Woods residential property to the west.
The site is characterized by steeply sloping topography near the site's eastern and western limits,
and relatively flatter topography near the site's south-central limit. The sloped area near the site's
western limit slopes downwards to the west, and the sloped are near the site's eastern limit slopes
downwards towards the northeast. The sloped area near the site's western limit has an average
grade of approximately 100 percent (1H:IV), and an average vertical relief of approximately 80
feet at the project site. The sloped area extends downwards towards 73rd Place West, and has an
average vertical relief of approximately 150 feet for the entire slope. The sloped area near the
site's eastern limit has an average grade of approximately 50 percent (2H:1 V), and an average
vertical relief of approximately 70 feet at the project site. The sloped area extends downwards
towards North Meadowdale Road, and has an average vertical relief of approximately 85 feet for
the entire slope. Sloped areas at the project site are generally undisturbed, and are heavily
vegetated with shrubs, vines, grasses & deciduous trees.
PROJECT DESCRIPTION
Based on our review of the referenced plan set, we understand the proposed construction at the
site consists of alterations and additions to the existing residence that includes replacement of the
existing roof, repair of the existing main floor & upper floor decks, replacement of the existing
concrete steps and landing area near the residence's front entry, and repair of the existing
covered entry area. It is our understanding that the proposed lot coverage is approximately 32
square feet greater than the existing lot coverage, which includes the enlargement of an existing
upper floor deck (approx. 11 SF) & the residence's roof (approx. 21 SF) near the south-central
extent of the residence. It is our understanding that minimal exterior grading or earthwork is
proposed, and five interior concrete footings are proposed near the center, and southern extent of
the residence.
GEO Group Northwest, Inc.
July 19, 2023 G-5936
16120 — 72nd Ave W, Edmonds, WA Page 3
GEOLOGIC CONDITIONS
According to published mapping of the project site and its vicinity (Geologic map of the
Edmonds East and part of the Edmonds West quadrangles, Washington, Minard, 1983), the site
is underlain by Quaternary age advance outwash deposits. Advance outwash deposits typically
consist of sands and gravels deposited by meltwater streams during the advancement of the Puget
glacial lobe into the region during the last glacial period, approximately 13,000 to 11,000 years
ago.
From our referenced geotechnical report, the site is located east of the Meadowdale Landslide
Complex, which was mapped and characterized by Roger Lowe and Associates (RLA, 1979),
GeoEngineers (GeoEngineers, 1985), and Landau Associates (Landau Associates, 2007). The
Meadowdale Landslide complex is a large area of historical landsliding (slumps and debris
flows) extending approximately 3,200 feet from north -to -south, and approximately 650 feet from
east -to -west. The sloped area at the western limit of the project site is a portion of the eastern
margin of the landslide complex, and is the headwall of the landslide zone. The initial movement
is believed to have occurred approximately 7,000 years ago. Historic landsliding in the area has
primarily occurred within an approximately 400 feet wide zone located immediately east of the
Burlington Northern railroad tracks (approximately 800 feet west of the project site's western
limit). The most recent movements in the landslide complex (in 1946-47, 1955-56, 1970-71, and
1996-97) have occurred in the central and western portions of the landslide complex, away from
the project site.
Based on the reported findings from our subsurface exploration performed at the site, the project
site and existing residence are underlain by up to approximately 30 feet of dense to very dense
brownish gray fine-grained sand, consistent with the published mapping of the site. Groundwater
was not reportedly encountered in the boring during its advancement. A log of the soils
reportedly encountered in the boring we completed at the site has been included in Appendix A —
USCS Classification and Boring Log. The approximate location of the boring is illustrated on the
attached Plate 1— Site Plan.
GEOLOGICALLY HAZARDOUS AREAS IDENTIFICATION AND EVALUATION
The City of Edmonds' definitions for geological hazard areas are provided in Edmonds'
Community Development Code (ECDC) Chapter 23.80.020. It is our understanding that the
existing residence is located in areas mapped by Edmonds as erosion and landslide hazard areas.
An earth subsidence and landslide area is mapped near the project site's western limit. A map
GEO Group Northwest, Inc.
July 19, 2023 G-5936
16120 — 72nd Ave W, Edmonds, WA Page 4
illustrating locations of the mapped geological hazard areas, existing, and proposed site features
are provided on Plate 2 — Geologic Hazard Map (ECDC 23.80.050).
Erosion Hazard Area
Approximately 30 percent of the project site is mapped as an erosion hazard area by the City of
Edmonds. The existing residence is partially located within a mapped erosion hazard area. The
proposed addition is located near the south-central extent of the residence, which is not mapped
as an erosion hazard area by the city of Edmonds. Mapped erosion hazard areas at the project site
extend onto the adjacent residential properties to the north, and east of the project site.
According to the U.S. Department of Agriculture's Soil Conservation Service (SCS) soil survey,
surficial soils at the project site consist of Alderwood gravelly sandy loam on 8 to 15 percent
slopes and Alderwood-Everett gravelly sandy loam on 25 to 70 percent slopes. Surficial soils
underlying the proposed project area at the project site (existing residence's footprint) consist of
Alderwood gravelly sandy loam on 8 to 15 percent slopes. Each of these soil types have
moderate to high erosion potential, according to the SCS soil survey. Alderwood soils have
medium erosion potential and can be susceptible to sheet flow and rill erosion, if exposed.
Per ECDC Chapter 23.80.020(A), areas with Alderwood soils on slopes of 15 percent or greater
are identified as erosion hazard areas. Per this criterion, the proposed project area near the center
of the site that underlies the existing residence is not an erosion hazard area. As such, we believe
the potential for soil erosion has been minimized by the proposed project's design, as minimal
work outside of the existing residence's footprint is proposed (replace existing concrete steps and
landing area), and the proposed work would not result in increased impervious surface coverage.
Landslide Hazard Area
Approximately 60 percent of the project site is mapped as a landslide hazard area by the City of
Edmonds. The areas at the project site that are mapped as landslide hazard areas include the
steeply sloping topography near the site's eastern, and western limits, as well as landscaped areas
near the site's north central limit. The north-eastern extent of the existing residence is located
within a landslide hazard area, as mapped by the City of Edmonds. Proposed construction within
this area consists of repairs to the existing residence's entry porch, concrete steps, and landing.
Landslide hazard areas mapped at the project site extend onto the adjacent residential properties
to the north, east, south, and west. The proposed enlarged deck addition near the residences
south-central extent, is not located within a mapped landslide hazard area.
GEO Group Northwest, Inc.
July 19, 2023 G-5936
16120 — 72nd Ave W, Edmonds, WA Page 5
According to the geotechnical reports by RLA, GeoEngineers, and Landau Associates, the slope
mapped as a landslide hazard area near the project site's western limit has a five (5) percent
probability of failure within 25 years, and the slope mapped as a landslide hazard area near the
project site's eastern limit has a two (2) percent probability of failure within 25 years. The
criteria used in these reports for determining the landslide risk included steepeness of slope,
height of slope, soil types, presence and evidence of previous landsliding, and the presence of
groundwater seepage or springs. Previous studies of the mapped landslide hazard area
determined the primary cause of sloughing and small slumps near the site's western limit have
been caused primarily by erosion by groundwater springs and seepage.
Based on the criteria described in ECDC 23.80.020(B), hillsides with a slope greater than 15
percent that have intersecting geologic contacts with a relatively permeable sediment (i.e.,
advance outwash) overlying a relatively impermeable sediment (i.e., glacial till), and springs or
groundwater seepage are considered a landslide hazard area. Based on this criterion, the slope
near the site's western limit is a landslide hazard area.
Based on the referenced plan set, and available mapping of geologically hazardous areas at the
project site by the City of Edmonds, the western extent of the existing residence is located
approximately 35 feet from the mapped landslide hazard area (approximately 50 feet from the
earth subsidence and landslide area), and the proposed deck addition is approximately 60 feet
from the mapped landslide hazard area (approximately 75 feet from the earth subsidence and
landslide area) located near the site's western limit.
Per our referenced geotechnical report, our recommended building setback of 50 feet from the
top of the slope for the project site was previously approved by the City of Edmonds. The
proposed addition and alterations incorporate this setback in their design as well.
Our previously prepared "Geotechnical Declaration and Statement of Risk" dated December 20,
2000 for the project site included tabulated numerical factors of safety for shallow sloughing and
deep failures for the slope near the site's western limit. The slope stability calculations analyzed
the factors of safety for the west facing slope against deep seated slides and shallow sloughing.
Based on our previous analysis, the west facing slope had a factor of safety of 1.1 against
shallow sloughing, indicating that some shallow sloughing was anticipated over time. The west
facing slope had a calculated factor of safety of 1.8 against deep seated slides, indicating a low
probability of deep-seated slope failure that would affect the existing residence. As minimal
ground disturbance is proposed for the project, we believe the previous analysis is sufficient for
GEO Group Northwest, Inc.
July 19, 2023
16120 — 72nd Ave W, Edmonds, WA
G-5936
Page 6
characterizing the probability for shallow sloughing and deep-seated slope failures at the mapped
earth subsidence and landslide area near the site's western limit.
Due to the minimal work proposed outside of the existing residence's footprint, and the
incorporation of our building setback recommendations in the project's design, It is our opinion
that the proposed addition and alterations to the existing residence can be completed as proposed
without increasing surface water discharge or sedimentation to adjacent properties beyond
existing conditions, without decreasing slope stability on adjacent properties, and without
adversely impacting other critical areas, so long that our geotechnical recommendations have
been incorporated in the project's final design (ECDC 23.80.070).
Hazard Mitigation Statement
Per the requirements described in ECDC Chapters 23.80 and 29.10, we recommend the
following measures be incorporated during construction to reduce hazards and mitigate impacts
at the project site:
- No ground disturbance outside of the residence's footprint should occur during Edmond's
seasonal grading restriction (October 1st to May 1')
- Although no areas are proposed for the project, areas of ground disturbance outside of the
residence's footprint that will not to be covered with impervious surfaces upon
completion of the project should be amended with topsoil (6" min. thickness) and planted
with non-invasive plant or shrub species.
SITE SEISMIC DESIGN CLASSIFICATION AND EVALUATION
Per the procedures specified in ASCE Standard 7-16, the project site can be assigned a seismic
design classification as Site Class C (Very Dense Soil Profile). This conclusion is based on
review of the geologic mapping of the site vicinity, the reported conditions encountered in the
boring drilled on the site, and our understanding and interpretation of deeper subsurface
condition at the site. Seismic design parameters applicable for the site are as follows:
Ss = 1.326g SMs = 1.591g SDs = 1.06g
Si = 0.47lg SMi = 0.707g SDI = 0.47lg
The peak ground acceleration for the site, adjusted for the assigned site class, is 0.684g per
current seismic hazard design mapping and calculations conforming to ASCE Standard 7-16.
GEO Group Northwest, Inc.
July 19, 2023 G-5936
16120 — 72nd Ave W, Edmonds, WA Page 7
CONCLUSIONS AND RECOMMENDATIONS
It is our professional opinion that the site is geotechnically suitable for the existing residence's
proposed addition and alterations without increasing the risk of soil instability at the project site or
adjacent properties. Based on the reported results of our subsurface investigation, the property is
underlain with dense to very dense, native advance outwash deposits that are consistent with
available geologic mapping of the vicinity. These competent soils were previously anticipated below
depths of approximately 3.0 feet below ground surface at the existing residence, and their presence
was verified during previous geotechnical inspections during construction of the existing residence.
Details of our recommendations regarding the geotechnical aspects of the proposed addition and
alterations are described in the following sections of this report.
Subgrade Preparation
Soils in areas to receive concrete slabs should be prepared to a firm, unyielding condition. The
prepared subgrade should be observed and approved by the geotechnical engineer. Any detected soft
spots or disturbed areas should be excavated and replaced with a clean crushed rock (minimum 1/4"
clast size, maximum 1 1/4" clast size) as directed by the geotechnical engineer.
Interior Concrete Foundations
Soils that are acceptable for building support are anticipated to be encountered at depths of
approximately 3.0 feet below the ground surface at the existing residence, as reported in the
attached Appendix B — Geotechnical Field Inspections. If soft soils are encountered following the
excavations to the foundation elevations, we recommend over excavating locations where soft
soils are present and replacing these soils with clean crushed rock, which can adequately support
interior concrete foundations.
Interior Spread Footings
Interior spread footings should bear directly on undisturbed, dense to very dense native soils or
on clean crushed rock that has been placed on a dense or very dense native soil subgrade. Our
recommended design criteria for interior spread footings constructed on native soils or clean
crushed rock are provided below:
- Allowable bearing pressure, including all dead and live loads:
Undisturbed, dense native soil = 2,000 psf
Crushed rock placed on dense native soil = 2,000 psf
GEO Group Northwest, Inc.
July 19, 2023 G-5936
16120 — 72nd Ave W, Edmonds, WA Page 8
- Minimum depth to bottom of interior footings below top of floor slab = 12 inches
- Minimum lateral dimension of column footings = 24 inches
- Estimated post -construction settlement = %2 inch
- Estimated post -construction differential settlement across building width = %2 inch
A one-third increase in the above allowable bearing pressures can be used when considering
short-term transitory wind or seismic loads.
Lateral loads against the building foundations can be resisted by friction between the foundation
and the supporting compacted fill subgrade or by passive earth pressure acting on the buried
portions of the foundations. For the latter case, the foundations must be poured "neat" against the
existing undisturbed soil or be backfilled with compacted structural fill. Our recommended
parameters are as follows:
- Passive Pressure (Lateral Resistance)
350 pcf, equivalent fluid weight, for structural fill or competent undisturbed
native soil
- Coefficient of Friction (Friction Factor)
0.35 for structural fill or competent undisturbed native soil
We recommend that GEO Group Northwest, Inc. be retained to observe excavations for the
residence's interior footings prior to installation of the footings to verify whether subgrade soils
will be able to support the design allowable soil bearing capacity, and that construction of the
interior footings conforms with the recommendations presented in this report. Soil bearing
verification may also be required by the City of Edmonds.
Exterior Slabs -on -Grade
Exterior slabs -on -grade should be constructed on a firm, unyielding subgrade. During preparation of
the slab subgrade, any areas of the subgrade that have been disturbed by construction activity should
be either re -compacted or excavated and replace with clean crushed rock.
To avoid build-up of moisture on the subgrade, concrete slabs should be placed on a capillary break,
which is in turn placed on the prepared subgrade. The capillary break should consist of a layer at
GEO Group Northwest, Inc.
July 19, 2023 G-5936
16120 — 72nd Ave W, Edmonds, WA Page 9
least six (6) inches thick, of free -draining crushed rock or gravel containing no more than five (5)
percent material passing a No. 4 sieve.
Site Drainage
The finished ground at the site should be graded such that surface water is directed off the site.
Water should not be allowed to stand in any area where concrete footings or slabs are to be
constructed. During construction, loose surfaces should be sealed at night by compacting the
surface to reduce the potential for moisture infiltration in the soils.
Under no circumstances should roof downspout drain lines be connected to the footing drainage
system. All roof downspouts must be separately tightlined to discharge into the approved storm
water collection system.
LIMITATIONS
This report has been prepared for the specific application to this site for the exclusive use of
Chris and Pauline Lane, and their authorized representatives. Reliance on this report by other
parties is solely at their own risk. We recommend that this report be included in its entirety in the
project contract documents for reference during construction.
The findings and recommendations stated herein are based on field observations, our experience
on similar projects and our professional judgment. The recommendations presented herein are
our professional opinions derived in a manner consistent with the level of care and skill
ordinarily exercised by other members of the profession currently practicing under similar
conditions in this area and within the project schedule and budget constraints. No warranty is
expressed or implied. In the event that site conditions are found to differ from those described in
the referenced geotechnical report, we should be notified so that the relevant recommendations in
this report can be reevaluated and modified if appropriate.
CLOSING
We appreciate the opportunity to provide you with geotechnical engineering services for this
project. Please do not hesitate to contact us if you have any questions regarding this report.
Sincerely,
GEO Group Northwest, Inc.
GEO Group Northwest, Inc.
July 19, 2023 G-5936
16120 — 72nd Ave W, Edmonds, WA Page 10
41
jn)-�4
Andrew Hoff, G.I.T.
Staff Engineering Geologist
Attachments:
Plate I — Site Plan
Dated: 7/ 19/23
William Chang, P.E.
Principal Engineer
Plate 2 — Geologic Hazard Map
Appendix A - USCS Soil Classification and Boring Log
Appendix B Geotechnical Field Inspections
GEO Group Northwest, Inc.
Pl 1005
Pt 122.07 —
PROPOSED
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PROPOSED DECK & ROOF
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PROPERTY LIMITS
ILEGEND
Landslide Hazard
Area (40%)
Sever Erosion
Hazard (15-40%)
Erosion Hazard
Areas (15-40%)
0 Earth Subsidence
�1j & Landslide Area
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SOIL CLASSIFICATION & PENETRATION TEST DATA EXPLANATION
MAJOR DIVISION
CLEAN
GRAVELS
GRAVELS
(little or no
COARSE-
(More Than Half
fines)
GRAINED SOILS
Coarse Fraction is
Larger Than No. 4
Sieve)
DIRTY
GRAVELS
(with some
fines)
SANDS
CLEAN
SANDS
(More Than Half
More Than Half by
Coarse Fraction is
(little or no
Weight Larger
Smaller Than No. 4
fines)
Than No. 200
Sieve)
Sieve
DIRTY
SANDS
(with some
fines)
SILTS
Liquid Limit
(BelowA-Line on
<50%
Plasticity Chart,
Liquid Limit
FINE-GRAINED
Negligible
SOILS
Organics)
> 50%
CLAYS
Liquid Limit
(Above A -Line on
< 50%
Plasticity Chart,
Liquid Limit
Negligible
Organics)
> 50%
Less Than Half by
Weight Larger
Liquid Limit
Than No. 200
ORGANIC SILTS
<50°/
Sieve
& CLAYS
(Below A -Line on
Plasticity Chart)
Liquid Limit
>50%
HIGHLY ORGANIC SOILS
UNIFIED SOIL CLASSIFICATION SYSTEM
GROUP TYPICAL DESCRIPTION
SYMBOL
WELL GRADED GRAVELS, GRAVEL -SAND GW
MIXTURE, LITTLE OR NO FINES
C
GP POORLY GRADED GRAVELS, AND GRAVEL -SAND
MIXTURES LITTLE OR NO FINES
GM SILTY GRAVELS, GRAVEL -SAND -SILT MIXTURES
GC CLAYEY GRAVELS, GRAVEL -SAND -CLAY
MIXTURES
WELL GRADED SANDS, GRAVELLY SANDS, LITTLE SW
OR NO FINES
SP POORLY GRADED SANDS, GRAVELLY SANDS,
LITTLE OR NO FINES
SM
6Y�
ML
MH
CL
CH
OL
OH
Pt
SOIL PARTICLE SIZE
U.S. STANDARD SIEVE
FRACTION
Passing
Retained
Size
Sieve
(MMSieve
)
(M M]
SILT/CLAY
#200
0.075
SAND
FINE
#40
0.425
#200
0.075
MEDIUM
#10
2.00
#40
0.425
COARSE
#4
4.75
#10
2.00
GRAVEL
FINE
0.75"
19
#4
4.75
COARSE
3"
76
0.75"
19
COBBLES
76 mm to 203 mm
BOULDERS
> 203 mm
ROCK
> 76 mm
FRAGMENTS
ROCK
>0.76 cubic meter in volume
SILTY SANDS, SAND -SILT MIXTURES
LABORATORY CLASSIFICATION CRITERIA
Cu = (D60 / D10) greater than 4
:ONTENT Cc = (D30)2 / (D10 * D60) between 1 and 3
INES BELOW
5 % CLEAN GRAVELS NOT MEETING ABOVE
REQUIREMENTS
GM: ATTERBERG LIMITS BELOW "A" LINE.
CONTENT
or P.I. LESS THAN 4
OF FINES EXCEEDS
12%
GC: ATTERBERG LIMITS ABOVE "A" LINE.
or P.I. MORE THAN 7
Cu = (D60 / D10) greater than 6
CONTENT
Cc = (D30)2 / (D10 * D60) between 1 and 3
OF FINES BELOW
5%
CLEAN SANDS NOT MEETING ABOVE
REQUIREMENTS
ATTERBERG LIMITS BELOW "A" LINE
with P.I. LESS THAN 4
CONTENT OF FINES
EXCEEDSI2%
ATTERBERG LIMITS ABOVE "A" LINE
CLAYEY SANDS, SAND -CLAY MIXTURES
with P.I. MORE THAN 7
INORGANIC SILTS, ROCK FLOUR, SANDY SILTS 60
OF SLIGHT PLASTICITY
INORGANIC SILTS, MICACEOUS OR
50
DIATOMACEOUS, FINE SANDY OR SILTY SOIL
INORGANIC CLAYS OF LOW PLASTICITY,
40
GRAVELLY, SANDY, OR SILTY CLAYS, CLEAN
X
w
CLAYS
Z
30
INORGANIC CLAYS OF HIGH PLASTICITY, FAT
H
CLAYS
U
F-
20
ORGANIC SILTS AND ORGANIC SILTY CLAYS OF
<
LOW PLASTICITY
d
10
7
ORGANIC CLAYS OF HIGH PLASTICITY
4
0
PLASTICI5PASSING
/
FOR SOILNO.40
/
CH
/
U-Line
/
A -Line
/
CL
MH or OH
L-M
L or
L
ML
0 10 20 30 40 50 60 70 80 90 100
PEAT AND OTHER HIGHLY ORGANIC SOILS LIQUID LIMIT (%)
GENERAL GUIDANCE FOR ENGINEERING PROPERTIES OF SOILS, BASED ON STANDARD
PENETRATION TEST (SPT) DATA
SANDY SOILS
SILTY & CLAYEY SOILS
Unconfined
Blow Counts Relative Friction Angle
Blow Counts
N Density, % x, degrees Description
N
Strength Cju,
Description
tsf
0-4
0 -15
Very Loose
< 2
< 0.25
Very soft
4-10
15 - 35
26 - 30
Loose
2-4
0.25 - 0.50
Soft
10-30
35 - 65
28 - 35
Medium Dense
4-8
0.50 - 1.00
Medium Stiff
30-50
65 - 85
35 - 42
Dense
8 - 15
1.00 - 2.00
Stiff
> 50
85 - 100
38 - 46
Very Dense
15 - 30
2.00 - 4.00
Very Stiff
> 30
> 4.00
Hard
Group Northwest, Inc.
Geotechnical Engineers, Geologists,&
Environmental Scientists
13705 Bel -Red Rd Bellevue, WA 98005
Phone (425) 649-8757 Fax (425) 649-8758 PLATE Al
BORING NO. B — I Page 1 of 1
Logged By: KJ Date Drilled: 5/18/1999 Surface Elev. Approx. 310 ft
Depth
USCS
Description
Sample
SPT
Blow
N Count
�)
Water
Content
Other Tests/
Comments
Loc.
No.
ft.
a)
w
Code
Counts
(%)
Lawn surface
S1
9 20 20
40
2.2
Blow counts
SP-SM
SAND to SILTY SAND, damp, medium dense, fine grained
affected by tree
sand, 10-15% fines, fine subrounded gravel, dark brown
root near surface.
(becomes gray at 2 feet).
S2
11 11 11
22
9.0
5
SP-SM
------------------------------------
S3
21103
13
7.3
SP
SAND, damp, medium dense, fine grained sand, grayish
brown.
SP
As above, dense, fine to medium grained sand, trace gravel,
I
S4
10 14 18
32
8.0
10
occasional lenses of well graded silty sand.
SP
As above, brownish gray, trace coarse sand and gravel.
S5
13 1920
39
7.8
15
SP
As above, very dense, fine grained sand.
T
S6
21 3034
64
8.7
20
SP
As above.
S7
29 50/3"
50+
7.4
25
SP
As above.
T
S8
3250
50+
6.2
30
As above, very fine to fine grained sand, 1" thick silty sand
SP
lens in sample.
S9
23 28 50
78
6.4
Depth of boring: 31.5'.
Drilling Method: Hollow -stem auger.
Sampling Method: 2"-O.D. standard penetration sampler
driven with 140 lb. hammer using cathead.
35
Groundwater not encountered -
LEGEND: Z 2" O.D. SPT Sampler 0 Water Level noted during drilling
IE3" O.D. California Sampler "WF Water Level measured at later time, as noted
BORING LOG
PROPOSED ADDITION & ALTERATIONS
16120 72ND AVE W
Group Northwest, Inc.
_ Geotechnical Engineers, Geologists, &
Environmental scientists
EDMONDS, WA 98026
JOB NO. G-5936
I DATE 7/19/2023
PLATE A2
r
Group Northwest, Inc.
Geoteotinical Engineers, Geologists, &
Environmental Sciertists
13240 NE 20th Street, Ste 12 Bellevue, WA 98005
Phone 425-649-8757 Fax 425-649-8758
Foundation Soil Bearing Verification
DAILY FIELD REPORT
Job # I Date Page # Field Report #
G-1061-A 10/16/01 1 of 1 3 .
le: Hollroyd Residence
16120 - 72nd Ave. W, Sequoia Ridge Dev., Edmonds, WA
Foundation Soil Bearina Verification
On October 15, 2001, Wade Lassey inspected the spread footing foundation subgrade soils
by probing the footing line with a 1/2-inch diameter steel rod. Loose soils were removed
from the footing line. The remaining subgrade soils are dense and meet the 2000 psf soil
bearing requirement.
f.
Copy to: Mr. Phil Holroyd - Owner X continued
Mr. Jeff Shea - Hammerhead Construction Services on next page
Mr. Michael Snook - City of Edmonds, Building Inspector
Ms. Jeanie McConnel - City of Edmonds, CIP Specialist