REVIEWED BLD-BLD2022-0616+ GEO REPORTRECEIVED
May 11 2022
CITY OF EDMONDS
DEVELOPMENT SERVICES
DEPARTMENT
April 26, 2022
Project No. 22-086
Brian and Nicole Kunkel
752 Walnut Street
Edmonds, WA 98020
BLD2022-0616
...............................................
REVIEWED
BY
CITY OF EDMONDS
BUILDING DEPARTMENT
Subject: Geotechnical Engineering Report
Proposed Remodeling
752 Walnut Street, Edmonds, Washington
Dear Brian and Nicole:
F�LnGEO
C O R P 9 R A T E D
Geotechnical & Earthquake
Engineering Consultants
As requested, PanGEO Inc. completed a geotechnical engineering study to assist the design team
for the proposed remodeling located at 752 Walnut Street in Edmonds, Washington. This study
was performed in general accordance with our mutually agreed scope of work outlined in our
proposal dated February 1, 2022, and subsequently approved by you on February 15, 2022. Our
service scope included reviewing readily available geologic and geotechnical data, drilling two
test borings, conducting a site reconnaissance, performing engineering analysis, and developing
the conclusions and recommendations presented in this report.
SITE AND PROJECT DESCRIPTION
The project site is located at 752 Walnut Street in the City of Edmonds, Washington (see Figure
1, Vicinity Map). The subject property is an approximately 6,524 square foot, rectangular -shaped
lot. It is bordered to the north by Walnut Street, to the south and east by access driveways, and
to the west by an existing single-family residence. The site is currently occupied by a two-story
single-family house. The site grade generally slopes down from south to north with a vertical
relief of about 16 feet and average gradient of about 15%. The layout of the site is shown on
Figure 2, Site and Exploration Plan.
3213 Eastlake Ave E, Ste B
Seattle, WA 98102
Tel (206) 262-0370
Fax (206) 262-0374
Geotechnical Engineering Report - Proposed Remodeling
752 Walnut Street, Edmonds, WA
April 26, 2022
Plate 1. View of the existing house on the north side of
Plate 2. Rear view of the existing house, deck, and patio.
the property, looking south from Walnut Street.
Looking north from the southwest property corner.
We understand that the proposed project consists of a major interior remodel. A new deck and
patio are also planned to be constructed to the west and south of the house. According to the City
of Edmonds GIS maps, the site is mapped within an erosion geologic hazard area. As such, a
geotechnical report will be required for the building permit application.
The conclusions and recommendations outlined in this report are based on our understanding of
the proposed improvements, which is in turn based on the project information provided to us. If
the above project description is substantially different from your proposed improvements, or if
the project scope changes, PanGEO should be consulted to review the recommendations
contained in this study and make modifications, if needed.
SITE GEOLOGY
According to the Geologic Map of the Edmonds East Quadrangle (Minard, 1983), the primary
geologic unit in the vicinity of the site is Advance Outwash (Map Unit Qva). Advance outwash
typically consists of moderately to well sorted, slightly oxidized sand and gravel deposited by
glacial meltwater that was also subsequently overridden by glacial ice. Advance outwash
therefore also typically exhibits low compressibility and high strength characteristics in its
undisturbed state.
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752 Walnut Street, Edmonds, WA
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SUBSURFACE EXPLORATION AND CONDITIONS
CURRENT TEST BORINGS
Two borings (PG-1 and PG-2) were drilled at the site on March 13, 2022, using an acker limited
access drill rig operated by CN Drilling of Seattle, Washington under contract to PanGEO. The
borings were drilled to a maximum depth of about 9 and 11 %2 feet below existing grade when
drilling refusal was met. The approximate boring locations were located in the field by
measuring from property corners and site features and are shown on Figure 2.
The test borings were drilled using 6-inch outside diameter hollow stem augers. Standard
Penetration Tests (SPT) were performed in the borings at 21/2-foot depth intervals using a
standard, 2-inch diameter split -spoon sampler. The sampler was advanced with a 140-pound
drop hammer falling a distance of 30 inches for each strike, in general accordance with ASTM
D-1586, Standard Test Method for Penetration Test and Split Barrel Sampling of Soils. The
number of blows required for each 6-inch increment of sampler penetration was recorded. The
number of blows required to achieve the last 12 inches of sample penetration is defined as the
SPT N-value. The N-value provides an empirical measure of the relative density of cohesionless
soil, or the relative consistency of fine-grained soils.
A geologist from PanGEO was present during the field explorations to observe the drilling, assist
in sampling, and describe and document the soil samples obtained from the borings. The soil
samples were described using the system outlined on Figure A-1. The summary boring logs are
included in Appendix A as Figures A-2 and A-3.
PREVIOUS TEST BORINGS
As part of our study, we collected and reviewed readily available geologic and geotechnical data
in the site vicinity. Specifically, we reviewed the logs of test borings B-1 through B-3 previously
completed at the site for foundation underpinning (see Figure 2). The summary logs for the
previous test borings are included as Appendix B for reference.
SOIL
The test borings advanced at the site generally encountered up to about 11 feet of loose fill
overlying medium dense sand and gravel (Advance Outwash). The soils encountered in the test
borings are generally consistent with the mapped geology at the site. The following is a brief
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description of the soils encountered in the test borings drilled at the site. Please refer to the
summary test boring logs in Appendices A and B for additional details.
UNIT 1: Fill — This soil unit was encountered in all test boring. The fill encountered
generally consisted of loose sand with gravel some debris. This soil unit extended to
about 5 feet below the existing ground surface in PG-1, to about 1 foot in PG-2, to about
8 feet in the previous boring B-1, and to about I I feet in B-2 and B-3. We interpreted this
soil unit as fill.
UNIT 2: Advance Ouwwash (Qva) — Below the fill, each boring encountered medium
dense to dense sand to sandy gravel that extended to the termination depths of the
borings. We interpreted this soil unit as the mapped Advance outwash deposits.
GROUNDWATER
Groundwater was observed within the drilling depth at each of the test borings at depths of about
2 to 5 feet below existing grade during drilling. Generally, the water table follows the existing
grade, and water flows from south to north. The observed groundwater elevations are
summarized in the Table 1 below.
Table 1— Summary of Observed Groundwater at Time of Drilling
Test
Boring
Approximate Ground
Surface Elevation (ft)
Approximate Depth
to Groundwater (ft)
Approximate Groundwater
Elevation (ft)
PG-1
212
5.0
207
PG-2
207
2.0
205
B-1
207
5.0
202
B-2
205
4.0
201
B-3
205
5.0
200
It should be noted that groundwater levels will fluctuate depending on the season, amount of
rainfall, surface water runoff, and other factors. Generally, the water level is higher and seepage
rates are greater in the wetter, winter months (typically October through May).
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GEOLOGICALLY HAZARDOUS AREAS ASSESSMENT
Based on a review of the City of Edmonds GIS map and the Edmonds Community Development
Code (ECDC), the north and south portions of the subject site are mapped within an Erosion
Hazard Area. The rockery and slope along the north property line is considered as a steep slope
(greater than 33% slope).
LANDSLIDE HAZARDS EVALUATION
Based on review of the topographic survey map provided to us and our field observations, the
site generally slopes down from the south to the north with an average slope gradient of about 15
percent. However, the rockery and slope along the north property line, which is approximately 5
feet in height, appears to meet the steep slope definition (33% or greater slopes). Based on the
soil data in the test borings, it is our opinion that this steep slope is the result of the previous
grading due to street and site development. It is also our opinion that the risk for the potential
future landslide is considered minimum, and the site is not mapped as a landslide hazard area.
A site reconnaissance of the subject property was conducted on March 13, 2022. During our site
reconnaissance, we did not observe obvious evidence of past slope instability or ground
movement at the subject site. Based on our field observations and the results of subsurface data
at the subject site, in our opinion, the subject site appears to be globally stable in its current
configuration. Furthermore, it is our opinion that the proposed remodeling as currently planned
are feasible from a geotechnical engineering standpoint. It is our further opinion that the
proposed remodeling as currently planned will not adversely affect the overall stability of the site
or adjacent properties, provided the recommendations outlined herein are followed and the
proposed remodeling is properly designed and constructed.
EROSION HAZARDS EVALUATION
According to USDA Soil Conservation Service Map, the site soil is mapped as the Alderwood-
Urban land complex, 2 to 8 percent slopes. Based on the soils encountered in the test borings and
site topography, the near -surface site soils are anticipated to exhibit slight to moderate erosion
potential. However, due to very minor ground disturbance and excavations planned, 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
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752 Walnut Street, Edmonds, WA
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not limited to installing silt fence at the construction perimeter, limiting removal of vegetation to
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.
23.80.060 DEVELOPMENT STANDARDS — GENERAL REQUIREMENTS
According to ECDC 23.80.060, alterations of geologically hazardous areas or associated buffers
may only occur for activities that:
1. Will not increase the threat of the geological hazard to adjacent properties beyond
predevelopment conditions;
2. Will not adversely impact other critical areas;
3. Are designed so that the hazard to the project is eliminated or mitigated to a level equal to
or less than predevelopment conditions; and
4. Are certified as safe as designed and under anticipated conditions by a qualified engineer
or geologist, licensed in the state of Washington.
Based on the site subsurface information and our understanding of the current plans, it is our
opinion that the proposed project meets the above conditions, and will not have adverse impacts
to the subject and surrounding properties during and after construction, provided that project is
constructed in accordance with the approved plans and commonly accepted practice.
23.80.070 DEVELOPMENT STANDARDS — SPECIFIC HAZARDS
The portions of subject site are mapped as erosion hazard areas. However, based on the soil
conditions and proposed improvements, it is our opinion that building setback and buffer
distance are not required for the currently proposed improvements. ECDC 23.80.070 states that
alterations of an erosion or landslide area hazard area, minimum building setback and/or buffer
may only occur for activities for which a hazards analysis is submitted and certifies that:
a. The alteration will not increase surface water discharge or sedimentation to adjacent
properties beyond predevelopment conditions;
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b. The alteration will not decrease slope stability on adjacent properties; and
c. Such alterations will not adversely impact other critical areas.
In our opinion, the proposed improvements as currently planned meet the above conditions.
GEOLOGIC HAZARDS MITIGATIONS
Based on the results of our evaluation of the potential geologic hazards at the site, it is our
opinion that no specific mitigation, other than the erosion measure discussed above, is required
for the proposed improvements.
GEOTECHNICAL DESIGN RECOMMENDATIONS
SEISMIC SITE CLASS
We anticipate that the seismic design of the structures will be accomplished using the 2018
editions of the International Building Code (IBC), which specifies a design earthquake having a
2% probability of occurrence in 50 years (return interval of 2,475 years). Based on site soil
conditions, it is our opinion that Site Class D (stiff soils) should be used for this project.
BUILDING FOUNDATIONS
Based on the subsurface conditions encountered at the site and our understanding of the planned
remodeling, it is our opinion that the proposed building may be supported on conventional
footings. The footings should bear on medium dense to dense native soils or on properly
compacted structural fill placed on competent native soils. Exterior foundation elements should
be placed at a minimum depth of 18 inches below final exterior grade. Interior spread
foundations should be placed at a minimum depth of 12 inches below the top of slab.
Soil Bearing Pressure
We recommend that an allowable soil bearing pressure of 2,000 pounds per square foot (psf) be
used to size the footings. The recommended allowable bearing pressure is for dead plus live
loads. For allowable stress design, the recommended bearing pressure may be increased by one-
third for transient loading, such as wind or seismic forces. Continuous and individual spread
footings should have minimum widths of 18 and 24 inches, respectively.
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752 Walnut Street, Edmonds, WA
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In designing the footings, the shape of footings will need to be considered in regard to 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 in order to conserve space and to
allow the temporary excavations to be made within the property limits.
Foundation Performance
Footings designed and constructed in accordance with the above recommendations should
experience total settlement of less than one inch and differential settlement of about 1/2 inch.
Most of the anticipated settlement should occur during construction as dead loads are applied.
Lateral Resistance
Lateral loads on the structures may be resisted by passive earth pressure developed against the
embedded faces of the foundation system and by frictional resistance between the bottom of the
foundation and the supporting subgrade soils. For footings bearing on the firm native soil or
compacted structural fill, a frictional coefficient of 0.35 may be used to evaluate sliding
resistance developed between the concrete and the compacted subgrade soil. Passive soil
resistance may be calculated using an equivalent fluid weight of 320 pcf, assuming properly
compacted structural fill will be placed against the footings. The above values include a factor of
safety of 1.5. Unless covered by pavements or slabs, the passive resistance in the upper 12 inches
of soil should be neglected.
Perimeter Footing Drains
Footing drains should be installed around the building perimeters, at or just below the invert of
the footings. 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.
Footing Subgrade Preparation
All footing subgrades should be in a firm and unyielding condition prior to setting forms and
placing rebar. Any loose or softened soil should be removed from the footing excavations. The
adequacy of the footing subgrade soils should be verified by a representative of PanGEO, prior
to placing forms or rebar.
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752 Walnut Street, Edmonds, WA
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PIPE PILES
Based on the results of test boring PG-1, the southwest portion of the site is underlain
approximately five feet of very loose to loose fill. The depth of bearing soil is estimated about
five feet below existing grade. Depending on the final footing elevations, estimated 3 to 5 feet of
over -excavation may be required to reach the bearing soil. As such, the proposed deck footings
on the west side of the building may be supported on pin piles in lieu of over -excavation.
Nominal two-inch diameter pin piles are typically installed using portable, handheld equipment
and are suited for areas where limited site access exists. The number of piles required depends
on the magnitude of the design load. An allowable axial compression capacity of 3 tons (6 kips)
may be used per 2-inch diameter pile. Larger pin piles will require machine -mounted pile
hammer, and therefore may not be practical for this project.
The lateral capacity of 2-inch diameter pin piles should be ignored. In addition, the friction at
the base of pile -supported footings should also be ignored. An allowable passive pressure of 250
pcf may be used to calculate the lateral resistance of foundation elements. If needed, the pin
piles may be battered to provide additional lateral capacity.
We recommend that the following specifications be included on the foundation plan for two-inch
diameter pin piles:
1. 2-inch diameter piles should consist of Schedule-80, ASTM A-53 Grade "A" pipe.
2. 2-inch diameter piles shall be driven to refusal with a minimum 90-lb jackhammer.
Refusal is defined as no more than 1 inch of penetration for 1 minute of continuous
driving.
3. 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.
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IT to 18,.
Pipe I D.
2" to 6"
I I
New Steel Pipe Section
--�— ---1 T 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
4. The geotechnical engineer of record or his/her representative shall provide full time
observation of pile installation.
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.
CONCRETE SLAB -ON -GRADE
Conventional slab -on -grade concrete floors, if needed, may be used for this project. The floor
slabs should be supported on competent native soil or structural fill placed on competent native
soils. Any over -excavations, if needed, should be backfilled with structural fill.
The concrete slab -on -grade floors should be underlain by at least 4 inches of capillary break,
which consists of free -draining, clean crushed rock or well -graded gravel compacted to a firm
and unyielding condition. The capillary break material should have no more than 20 percent
passing the No. 4 sieve and less than 5 percent by weight of the material passing the U.S.
Standard No. 100 sieve. We also recommend that a minimum 10-mil polyethylene vapor barrier
be placed below the proposed floor slabs.
UNDERSLAB DRAIN
Due to the groundwater encountered near the proposed lower floor, a subslab drainage system is
recommended below the concrete slabs in addition to perimeter footing drains. In general, the
under -slab drainage system should consist of minimum 4-inch diameter perforated drainpipes
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Geotechnical Engineering Report - Proposed Remodeling
752 Walnut Street, Edmonds, WA
April 26, 2022
placed in narrow, approximately 18-inch deep trenches (measured from the bottom of slab)
spaced about 15 feet apart. The trenches should be backfilled with clean, free -draining 3/8-inch
washed gravel (City of Seattle Type 9) or 3/4-inch washed sandy gravel (City of Seattle Type 26).
Water collected in these drainpipes should be conveyed to a permanent sump pump and
discharged to an appropriate outlet. The design of the slab drain may be refined based on the
final design of the building.
RETAINING WALL DESIGN PARAMETERS
Retaining walls, if needed, should be 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 collect behind the walls.
Lateral Earth Pressures
Cantilever walls should be designed for an equivalent fluid pressure of 35 pcf for a level backfill
condition behind the walls assuming the walls are free to rotate. If the walls are restrained at the
top from free movement, such as basement walls with a floor diaphragm, an equivalent fluid
pressure of 45 pcf should be used for a level backfill condition behind the walls. Permanent
walls should be designed for an additional uniform lateral pressure of 8H psf for seismic loading,
where H corresponds to the height of the buried depth of the wall.
The recommended lateral pressures assume the backfill behind the walls consists of a free
draining and properly compacted fill with adequate drainage provisions.
Surcharge
Surcharge loads, where present, should also be included in the design of retaining walls. We
recommend that a lateral load coefficient of 0.3 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.
Lateral Resistance
Lateral forces from 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 wall foundation. Passive resistance values may be
determined using an equivalent fluid weight of 320 pcf. This value includes a factor of safety of
1.5, assuming the footing is backfilled with structural fill. A friction coefficient of 0.35 may be
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used to determine the frictional resistance at the base of the footings. The coefficient includes a
factor of safety of 1.5.
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. 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.
Wall Backf ill
Retaining wall backfill should consist of free draining granular material. The site soils are
relatively silty and would not meet the requirements for wall backfill. We recommend importing
a free draining granular material, such as Seattle Type 17 or a soil meeting the requirements of
Gravel Borrow as defined in Section 9-03.14(1) of the WSDOT Standard Specifications for
Road, Bridge, and Municipal Construction (WSDOT, 2022). In areas where space is limited
between the wall and the face of excavation, pea gravel may be used as backfill without
compaction.
Wall backfill should be properly moisture conditioned, placed in loose, horizontal lifts less than
12 inches in thickness, and compacted to a dense and unyielding condition. If density tests will
be performed, the test results should show at least 95 percent of the maximum dry density, as
determined using test method ASTM D-1557 (Modified Proctor). Within 5 feet of the wall, the
backfill should be compacted with hand -operated equipment to at least 90 percent of the
maximum dry density.
CONSTRUCTION CONSIDERATIONS
SITE PREPARATION
Site preparation for the proposed project includes removing existing deck and patio, stripping
and clearing of surface vegetation and excavations to the design subgrade. All stripped surface
materials should be properly disposed off -site or be "wasted" on site in non-structural landscaping
areas.
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Following site clearing and excavations, the adequacy of the subgrade where structural fill,
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 also be over -
excavated and replaced with compacted structural fill.
TEMPORARY EXCAVATIONS
As currently planned, the proposed construction may require excavations up to five feet below
the existing grade. We anticipate the excavations to mainly encounter loose fill over medium
dense to dense native soils. 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.
All temporary excavations deeper than a total of 4 feet should be sloped or shored. Based on the
soil conditions at the site, for planning purposes, it is our opinion that temporary excavations for
the proposed construction may be sloped 1H:1V (Horizontal:Vertical) or flatter. Based on our
current understanding of the anticipated building layout and finished floor elevation, it appears
that sufficient space is available for unsupported open cuts. Where space may be limited, the use
of L-shaped footings may be required to conserve space for the temporary cuts. In event that
sufficient space is not available for unsupported open cuts, temporary shoring will be needed to
support the temporary excavations.
The temporary excavations and cut slopes should be re-evaluated in the field during construction
based on actual observed soil conditions, and may 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.
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. In our opinion, the on -site
soils are relatively silty with high moisture content and will be difficult to compact to a dense
condition. As such, on -site sand is not suitable to be used as structural fill, but can be used as
wall backfill and general fill in the non-structural areas. If use of the on -site soil is planned, the
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excavated soil should be stockpiled and protected with plastic sheeting to prevent softening from
rainfall in the wet season.
STRUCTURAL FILL PLACEMENT AND COMPACTION
Structural fill, if needed, should consist of imported, well -graded, granular material, such as City
of Seattle Type 17, WSDOT Section 9-03.9(3) Crushed Surfacing Base Course (WSDOT 2022),
or an approved equivalent.
Structural fill should be properly moisture conditioned, placed in loose, horizontal lifts less than
12 inches in thickness, and compacted to a dense and unyielding condition. The adequacy of
compaction should be verified by a PanGEO representative. Alternatively, if density tests will
be performed, the test results should indicate a minimum 95 percent relative compaction level as
determined using ASTM D-1557 (Modified Proctor).
The procedure to achieve proper density of a compacted fill depends on the size and type of
compaction equipment, the number of passes, thickness of the lifts being compacted, and certain
soil properties. If the excavation to be backfilled is constricted and limits the use of heavy
equipment, smaller equipment can be used, but the lift thickness will need to be reduced to
achieve the required relative compaction.
Generally, loosely compacted soils are a result of poor construction technique or improper
moisture content. Soils with high fines contents are particularly susceptible to becoming too wet
and coarse -grained materials easily become too dry, for proper compaction. Soils with a
moisture content too high for adequate compaction should be dried as necessary, or moisture
conditioned by mixing with drier materials, or other methods.
WET WEATHER EARTHWORK
In our opinion, the proposed construction may be accomplished during wet weather (such as in
winter) without adversely affecting the site stability. However, earthwork construction
performed during the drier summer months likely will be more economical. Winter construction
will require the implementation of best management erosion and sedimentation control practices
to reduce the chance of off -site sediment transport. Some of the site soils contain a high
percentage of fines and are moisture sensitive. Any footing subgrade soils that become softened
either by disturbance or rainfall should be removed and replaced with structural fill, Controlled
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Density Fill (CDF), or lean -mix concrete. General recommendations relative to earthwork
performed in wet conditions are presented below:
• Site stripping, excavation and subgrade preparation should be followed promptly by the
placement and compaction of clean structural fill or CDF;
• The size and type of construction equipment used may have to be limited to prevent soil
disturbance;
• 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;
• Structural fill should consist of less than 5% fines; and
• Excavation slopes should be covered with plastic sheets.
SURFACE DRAINAGE AND EROSION CONSIDERATIONS
Surface runoff can be controlled during construction by careful grading practices. Typically, this
includes the construction of shallow, upgrade perimeter ditches or low earthen berms in
conjunction with silt fences to collect runoff and prevent water from entering excavations or to
prevent runoff from the construction area from leaving the immediate work site. Temporary
erosion control may require the use of hay bales on the downhill side of the project to prevent
water from leaving the site and potential storm water detention to trap sand and silt before the
water is discharged to a suitable outlet. All collected water should be directed under control to a
positive and permanent discharge system.
Permanent control of surface water should be incorporated in the final grading design. Adequate
surface gradients and drainage systems should be incorporated into the design such that surface
runoff is directed away from structures. Potential problems associated with erosion may also be
reduced by establishing vegetation within disturbed areas immediately following grading
operations.
ADDITIONAL SERVICES
To confirm that our recommendations are properly incorporated into the design and construction
of the proposed remodeling, PanGEO should be retained to conduct a review of the final project
plans and specifications, and to monitor the construction of geotechnical elements. Modifications
22-086 752 walnut St GeoRpt Page 15 PanGEO, Inc.
Geotechnical Engineering Report - Proposed Remodeling
752 Walnut Street, Edmonds, WA
April 26, 2022
to our recommendations presented in this report may be necessary, based on the actual
conditions encountered during construction.
CLOSURE
We have prepared this report for Brian and Nicole Kunkel and the project design team.
Recommendations contained in this report are based on a site reconnaissance, a subsurface
exploration program, 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 locations of 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.
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.
22-086 752 walnut St Geoxpt Page 16 PanGEO, Inc.
Geotechnical Engineering Report - Proposed Remodeling
752 Walnut Street, Edmonds, WA
April 26, 2022
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,
PanGEO, Inc.
► ZyW C��-K,'
Gam'�_La
0412612022
Chien -Lin (Johnny) Chen, P.E.
Senior Geotechnical Engineer
Attachments:
Figure 1 Vicinity Map
Figure 2 Site and Exploration Plan
Appendix A — Summary Test Boring Logs
Figure A-1
Terms and Symbols for Boring and Test Pit Logs
Figure A-2
Log of Test Boring PG-1
Figure A-3
Log of Test Boring PG-2
Appendix B — Previous Test Boring Logs
22-086 752 walnut St Geoxpt Page 17 PanGEO, Inc.
Geotechnical Engineering Report - Proposed Remodeling
752 Walnut Street, Edmonds, WA
April 26, 2022
REFERENCES
ASTM International (ASTM), 2021, Annual book of standards, Section 04.08 Soil and Rock (I):
D420-D5876: West Conshohocken, Pennsylvania.
International Code Council, 2018, International Building Code (IBC).
Minard, J.P., 1983, Geologic map of the Edmonds East and part of the Edmonds West
Quadrangles, Washington: U.S. Geological Survey Miscellaneous Field Studies Map MF-
1541, scale 1:24000.
City of Seattle, 2020, Standard Specifications for Road, Bridges, and Municipal Construction.
South Fork Geosciences, PLLC, 2019, Williams Settlement Assessment, 752 Walnut Street,
Edmonds, Washington, dated December 20, 2019, Project No. 19081.
Washington State Department of Transportation (WSDOT), 2022, Standard Specifications for
Road, Bridge and Municipal Construction, M 41-10.
Washington Administrative Code (WAC), 2021, Chapter 296-155 - Safety Standards for
Construction Work, Part N - Excavation, Trenching, and Shoring, Olympia, Washington.
22-086 752 walnut St GeoRpt Page 18 PanGEO, Inc.
.'
`. �•r :` -
- '{iJ�.-� - .1_; i _=�UT.-_
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• •-
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P P—P
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eY
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tl
—ww
w—W
W
ENE./SE.j8
FB2
V
EtE.J e'caNc.196sa• *%
WD (6W PLAT)
N 88.46'07' W 59.92'
(60' PLAT)
LEGEND:
Approx. Test Boring Location - PanGEO, 2022
(Approx. Depth to Bearing Soil, ft)
Approx. Previous Boring Location -
South Fork Geosciences, 2019
FbnGEe Proposed Remodeling
752 Walnut Street
I N C O R P O R A T E D Edmonds, Washington
zo
O yl j
AO Z
I • � wC
111 •'
z.a
J d -
�11.9J t
r'VC
x.DD'
NORTH
SEr
R®M/CM
Approx. Scale:
1"=20'
Note: Base map modified from Topographic &
Boundary Survey by Terrane dated 08/03/2021
SITE AND EXPLORATION PLAN
Project No. Figure No.
22-086 2
APPENDIX A
SUMMARY TEST BORING LOGS
RELATIVE DENSITY / CONSISTENCY
SAND / GRAVEL
SILT / CLAY
SPT
Approx. Relative
SPT
Approx. Undrained Shear
Density
N-values
Density (/o)
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
GP :
Poorly -graded GRAVEL
fraction retained on the #4
sieve. Use dual symbols leg.
o D
.....:
GM:
......................................................
Silty GRAVEL
GP -GM) for 5% to 12% fines.
GRAVEL (>12% fines)
••
GC :
......................................................
Clayey GRAVEL
..........................................................
..............................................................
SW:
Well -graded SAND
Sand
SAND (<5 /o fines)
50% or more of the coarse
''
%
SP :
Poor/ raded SAND
Poorly -graded
fraction passing the #4 sieve.
Use dual symbols leg. SP-SM)
..............................:....>..
" " '
.........................................................
SM :
Silty SAND
for 5% to 12% fines.
...............................
SAND (>12% 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
.......................... ......................................
HighlyOrganic Soils
u
.............................................................
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 togs.
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
Atterberg Limit Test
Comp
Compaction Tests
Con
Consolidation
DID
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
Sample/In Situ test types and intervals
2-inch OD Split Spoon, SPT
(140-lb. hammer, 30" drop)
OD Spilt Spoon
H3.25-inch
(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
PanGE@) Terms and Symbols for
I N C O R P O R A T E D Boring and Test Pit Logs Figure A-1
Phone: 206.262.0370
Project: Proposed Remodeling
Surface Elevation: 212.Oft
Job Number: 22-086
Top of Casing Elev.: N/A
Location: 752 Walnut Street, Edmonds, WA
Drilling Method: HSA
Coordinates: Northing: 47.80702, Easting:-122.36987
Sampling Method: SPT
N-Value A
o
Z
T
C:
U)
p
PL Moisture LL
Q
a
;
~
E
MATERIAL DESCRIPTION
p
E
U)
1=
U)
El Recovery
0
0 50 100
0
3
Loose, mixed dark and orange -brown, slightly silty and gravelly SAND;
moist; poorly graded, iron oxide staining, trace debris, disturbed
S-1
3
appearance [Fill].
4
2
1
--becomes very loose with trace organics.
S-2
0
1
4
28
Dense, gray -brown, sandy GRAVEL; wet; poorly graded, blow count likely
inflated by gravel [Qva - Vashon Advance Outwash].
S-3
16
o'•D:
6
19
17
o'•D:
8
S-4
6
_____________________________
Medium dense, gray, slightly gravelly, silt SAND; wet; poorly graded Qva
9 Y 9 Y 9 Y Y p� Y 9 [
Vashon Advance Outwash].
7
Boring terminated at about 9 feet below ground surface due to practical
drilling refusal on cobble. Groundwater was observed at about 5 feet depth
10
during drilling.
12
14
16
Completion Depth: 9.0ft
Remarks: Boring drilled using an acker portable drill rig. Standard penetration test (SPT)
Date Borehole Started: 3/13/22
sampler driven with a 140 lb. safety hammer. Hammer operated with a rope and cathead
Date Borehole Completed: 3/13/22
mechanism. Surface elevation estimated from Topographic & Boundary Survey by Terrane
Logged By: B. Weitering
dated 08/03/2021.
Drilling Company: CN Drilling
PmGEE) LOG OF TEST BORING PG-1
I N C O R P O R A T E D Figure A-2
The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of 1
Project: Proposed Remodeling
Surface Elevation: 207.Oft
Job Number: 22-086
Top of Casing Elev.: N/A
Location: 752 Walnut Street, Edmonds, WA
Drilling Method: HSA
Coordinates: Northing: 47.807, Easting:-122.36968
Sampling Method: SPT
N-Value A
o
Z
T
C
(n
p
PL Moisture LL
Q
a
;
~
E
MATERIAL DESCRIPTION
p
E
U)
1=
U)
0
El Recovery
0 50 100
0
6
_2"Asphalt Driveway.
--------------------
S-1
6
Medium dense, mixed gray -brown, orange -brown, and brown, slightly silty
and gravelly SAND; moist; poorly graded, trace organics [Fill].
Medium dense, gray- and orange -brown, SAND interlayered with gravelly
5
SAND to sandy GRAVEL; moist; poorly graded, iron oxide staining [Qva -
2
Vashon Advance Outwash].
--becomes wet.
7
a:.:•:.
° .. N.
S-2
12
14
.'
4
4
:o:•:'•.'.
—3" heave, sampled through.
a:.:•:.
S-3
12
6
° ..
14
.•�.
s
10
--2' heave, removed.
°
S-4
15
..
Boring terminated at about 11.5 feet below ground surface due to practical
12
drilling refusal in heave. Groundwater was observed at about 2 feet depth
during drilling.
14
16
Completion Depth: 11.5ft
Remarks: Boring drilled using an acker portable drill rig. Standard penetration test (SPT)
Date Borehole Started: 3/13/22
sampler driven with a 140 lb. safety hammer. Hammer operated with a rope and cathead
Date Borehole Completed: 3/13/22
mechanism. Surface elevation estimated from Topographic & Boundary Survey by Terrane
Logged By: B. Weitering
dated 08/03/2021.
Drilling Company: CN Drilling
PmGEE) LOG OF TEST BORING PG-2
i N C U R P O R A T E D Figure A-3
The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of 1
APPENDIX B
PREVIOUS TEST BORING LOGS
Williams Settlement Assessment
752 Walnut Street
Edmonds, Washington
Soil Exploration Locations
SOUTH FORK GEOSCIENCES, PLLC
PC) Box 1 275
NORTH BEND, WA 98045
425-89❑-4858 1 INF00-SFGEQ.00M
December 20, 2019
Project #19081
Source: Google Maps
South Fork Geosciences
LOG OF BORING B-1
P❑ Box 1275, North Bend, WA 98045
info@Sfgeo.Com
(Page 1 of 1 )
Williams Settlement Assessment
Date Started 12-20-2019 Drilling Co. Geologic Drill Partners
752 Walnut Street.
Date Completed 12-20-2019 Driller Name . Jeremy Coleman
Edmonds, Washington
Hole Diameter 6" oD, 2112" ID Start Time 0846
SFG #19081
Drllling Method HSA Mini Track End Time 0940
Sampling Method . Split Spoon Lagged By Andrew Glandon, LEG
�
Z
C
7
a
DESCRIPTION
81aw Count
Graph
REMARKS
a
rn
C�0
r°
m
❑ 2Q d❑ 6U 6
4
Hand dug to 2.5ft
0-6" - hark mulch, 6"-2.5ft - moist, light brown fine to
Full recovery unless noted
sp
medium SAND with gravel (SP)
otherwise
No recovery
SPT 3-5 -1 6. No Recovery
SP
4-
5
saturated, brown fine to coarse SAND with gravel
SPT 1-1-0=1
2
sw
(SW)
1
3
saturated, brown fine to coarse SAND with fine
gravel, 3" zone of organic silt mid sample (SW)
s
SPT 2-3-6=9
svu
sw
.
Water at 8 feet after drilling
10
saturated, hrwon Fine to coarse SAND with gravel
SPT 12-25-28=53
4
SQ-SM
.
(SW)
53
H
saturated, brown fine to coarse SAND (SW)
SPT 17-17-7=24
5
SW
24
15
p
wet to saturated, brown fine to coarse SAND with
SPT 23-23-23=46
afine
gravel (SW)
46
N
sw
20
SPT 11-15-20=35
'I
saturated, gray fine to medium SAND with fine gravel
7
sP
L
(SP) - possible older unit based on color and
35
apparent difference in provenance
Total Depth = 21.5 feet
Water at 9 feet bgs after drilling
Boring backfilled with hentonite chips
25
South Fork Geosciences
LOG OF
BORING B-2
PO Box 1275, North Bend, WA 98045
info@sfgeo.com
(Page 1 of 1)
Williams Settlement Assessment
Date Started
12-20-2019
Drilling Co.
Geologic Drill Partners
752 Walnut Street
Date Completed
12-20-2019
Driller Name
- Jeremy Coleman
Edmonds, Washington
Hole Diameter
6" QD, 2 112" ID
Start Time
0945
SFG #19081
Drilling Method
i HSA Mini Track
End Time
1030
Sampling Method
: Split Spoon
Logged By
Andrew Glandon, LEG
m
U_
rl
U
c
m
n
C
E
<
o
DESCRIPTION
n
rn
c�LL
Cuttings
moist, brown fine to coarse SAND with gravel (SW)
SP
Bark mulch in sampler, no soil recovery
SP
5-wet
"
to saturated, brown fine to coarse SAND with
2
$vV-SPI.:
gravel and silt (SP 5M)
saturated, brown -gray fine to coarse SAND with
3
SW -so
gravel and silt (SW-SM)
10
° Blow Count
U
o Graph
m p 2D 40 so
6
15
3
swroL::: saturated, brown fine to coarse SAND with gravel,
4 zone of organic silt in middle of sample approximately 10
4" thick (SWIOL)
SWrOL .
wet to saturated, brown -gray fine to coarse SAND,
n5 H trace gravel (SW) 22
O
"IF1 f
25
Total Depth = 20 feet
Rod was bound up due to heaving sands
Water at 4 feet after drilling
Boring backfilled with bentonite chips
29
14=11M►I122M
Full recovery unless noted
otherwise
SPT 4-3-3=6 No Recovery
Water at 4 feet after driving
SPT 3-6-9=15
SPT 4-2-1=3, 1)3 recovery
SPT 5-5-5=10
SPT 8-9-13=22
SPT 11-12-17=29
South Fork Geosciences
LOG OF BORING B-3
PO Box 1275. North Bend, WA 98045
info@sfgeo.com
(Page 1 of 1)
Williams Settlement Assessment
Date Started 1 Z-20-2019 drilling Ca. Geologic Drill Partners
752 Walnut Street
Date Completed 12-20-20'19 driller Name Jeremy Coleman
Edmonds, Washington
Hole Diameter 6' fl0, 2 IQ` ID Stan Time 1040
SFG #19081
Drilling Method HSA Mini Track End Time 1120
Sampling Method 5plil Spoon Logged By Andrew Gfandon, LEG
m
LL
r
0.1
_
Blow Count
u
U
�,
DESCRIPTION
3
Graph
REMARKS
CL
a
E
to
in
(5
L
L
m
0 20 40 50 9
Q
Cuttings
moist, brown fine to coarse SAND with gravel (SW)
Full recovery unless noted
Sw
otherwise
moist, light brawn fine to coarse SAND,
SPT 2-2-2=4, 213 recovery
1
sw
predominantly medium sand {SW)
a
Water at 5 feet after drilling
5—
moist, black -brown gray fine to medium SAND with
SPT 4-6 4=10
2
U.
gravel and silt, charcoal/wood debris present
14
SP-SM.
` r
.}
(SP-SM)
saturated, brown -gray fine to medium SAND with
sPT 2-0-2:--2
3
sp-SM
gravel and silt (SP-SM)
2
10
saturated, brown fine to medium SAND (SP)
SPT 4-4-7=11
4
SP
11
SP
saturated. brown -gray fuse to coarse SAND with fine
SPT 9-B-10=1 B
gravel (SW)
1B
5
sw
�
SPT 11-14.20=34
g
34
C
r
N
>
No SPT {Heavey
saturated. gray fine to medium SAND (SP)
7
SP
0
20--
Total Depth = 20 feet
Drilled to 20 feet, encountered 2 feet of heave
Water at 5 feet after drilling
Baring backfilled with bentonite chips
25