GEO REPORT 5.9.19 - from BLD2019-0528-0530November 14, 2018
Project No. 18-358
Michael McMurray
Seattle -Snohomish Mill Company, Inc.
533 5th Avenue South
Edmonds, WA 98020
Subject: Geotechnical Report
Proposed Development
550 Main Street, Edmonds, Washington
Dear Mr. McMurray,
FtinGE@
O R P O R A T E D
Geotechnical & Earthquake
Engineering Consultants
RECEIVED
MAY 0 9 20119
DEVEI.OPNIEW SthViUcS CTR.
CITY OF EDMONDS
Attached please find our geotechnical report for your proposed project. In summary, our test
borings completed at the site encountered about 4 feet of generally dense fill overlying medium
dense to dense native soils. In our opinion, conventional footings and concrete slab -on -grade
floors are feasible to support the proposed new building and as well as the renovation of the
existing building. The proposal art panels and signs may be supported on conventional footings
or piles, depending on the magnitude of uplift forces. In our opinion, if practical, conventional
footings should be used in lieu of piles/shafts as footing construction generally has less
construction uncertainties than piles, and likely more economical than piles.
We appreciate the opportunity to work on this project. Please call if there are any questions.
Sincerely,
Siew L. Tan, P.E.
Principal Geotechnical Engineer
Encl.: Geotechnical Report
�21 I .ntlahr \vCIltic I_a"t. Suite 13
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el (206) 262-03)7II
1 av (200) 262-017.4
TABLE OF CONTENTS
1.0 INTRODUCTION...................................................................................................................1
2.0 PROJECT AND SITE DESCRIPTION............................................................................... 1
3.0 SUBSURFACE EXPLORATIONS....................................................................................... 2
4.0 SUBSURFACE CONDITIONS............................................................................................. 2
4.1 SOIL....................................................................................................................................... 2
4.2 GROUNDWATER.....................................................................................................................
3
5.0 GEOTECHNICAL RECOMMENDATIONS.....................................................................
4
5.1 SEISMIC DESIGN PARAMETERS...............................................................................................
4
5.2 FOUNDATION..........................................................................................................................
4
5.2.1 Building Foundation......................................................................................................
4
5.2.2 Foundation for Art Panels and Signs.............................................................................
6
5.3 RETAINING WALL DESIGN PARAMETERS...............................................................................
6
5.4 CONCRETE SLAB ON GRADE..................................................................................................
8
5.5 PERMANENT DRAINAGE CONSIDERATIONS............................................................................
8
5.6 PERMANENT SLOPES..............................................................................................................
H
6.0 CONSTRUCTION CONSIDERATIONS............................................................................ 9
6.1 FOOTING SUBGRADE..............................................................................................................
9
6.2 TEMPORARY EXCAVATION AND DEWATERING......................................................................
9
6.3 STRUCTURAL FILL AND COMPACTION....................................................................................
9
6.4 EROSION AND DRAINAGE CONSIDERATIONS........................................................................
10
6.5 WET EARTHWORK RECOMMENDATIONS..............................................................................
10
6.6 INFILTRATION CONSIDERATIONS..........................................................................................
1 1
7.0 LIMITATIONS..................................................................................................................... 11
8.0 REFERENCES...................................................................................................................... 14
LIST OF ATTACHMENTS
Figure 1 Vicinity Map
Figure 2 Site and Exploration Plan
Appendix A
Summary Boring Logs
Figure A-1
Terms and Symbols for Boring an Test Pit Logs
Figure A-2
Log of Test Boring PG-1
Figure A-3
Log of Test Boring PG-2
Figure A-4
Log of Test Boring PG-3
Figure A-5
Log of Test Boring PG-4
GEOTECHNICAL REPORT
MAIN STREET COMMONS
550 MAIN STREET, EDMONDS, WASHINGTON
1.0 INTRODUCTION
This report presents the results of our geotechnical studies that were undertaken to support the
design and construction of the proposed project. We performed our geotechnical evaluations in
general accordance with the scope of work outlined in our proposal dated October 23, 2018,
which was subsequently approved by you on October 24, 2018. Our service scope included
reviewing readily available geologic data, conducting a site reconnaissance, drilling four test
borings at the site, and developing the conclusions and recommendations presented in this report.
2.0 PROJECT AND SITE DESCRIPTION
The site consists of two parcels at 550 Main Street of Edmonds, Washington. The site is
bordered to the north by Main Street, east by 61h Avenue South, south by an improved alley, and
to the west by a mixed -use building. The site is currently occupied to the west by a commercial
building, which will be remodeled during this project, and to the east by an asphalt parking lot to
be removed for the additional proposed structures. The existing building has a partial basement
that extends about 8 to 9 feet below the existing site grade.
Based on the project topographic
survey, the existing site grade
descends gently from the east to the
west property line, with a total
elevation relief of about 8 feet, over a
length of about 180 feet. A current
view of the site is shown in Plate 1, at
right.
We understand that the existing arch -
roofed building will be remodeled,
and a new building will be
constructed at the parking lot located
immediately east of the existing
building, in the northeast quadrant of
Plate 1: Current view of 550 Main Street; looking northwest
(1110712018)
Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
the site. We also understand that three billboard type structures for art panels will be constructed
at the property.
3.0 SUBSURFACE EXPLORATIONS
Four test borings (borings PG-1 thru PG-4) were completed at the site on November 7, 2018.
The approximate boring locations are shown on Figure 2. Boring PG -I was drilled to a depth of
about 21 feet, while PG-2, PG-3, and PG-4 were drilled to a depth of 11'/z feet. These borings
were progressed using a EC95 track -mounted drill rig owned and operated by Boretec, Inc. The
drill rig was equipped with a 6-inch outside diameter hollow stem auger, and soil samples were
obtained from the borings at 2'/z- and 5-foot depth intervals in general accordance with Standard
Penetration Test (SPT) sampling methods (ASTM test method D-1586) in which the samples are
obtained using a 2-inch outside diameter split -spoon sampler. The sampler was driven into the
soil a distance of 18 inches below the tip of the auger using a 140-pound weight falling a
distance of 30 inches. The number of blows required for each 6-inch increment of sampler
penetration was recorded. The number of blows required to achieve the last 12 inches of sample
penetration is defined as the SPT N-value. The N-value provides an empirical measure of the
relative density of cohesionless soil, or the relative consistency of fine-grained soils.
A geologist from PanGEO was present throughout the field exploration program to observe the
drilling, assist in sampling, and to document the soil samples obtained from the borings. The
completed borings were backfilled with bentonite chips and patched with asphalt. The soil
samples retrieved from the borings were described using the system outlined on Figure A-1 of
Appendix A and the summary boring logs are included as Figures A-2 and A-5.
4.0 SUBSURFACE CONDITIONS
4.1 SOIL
According to the Geologic Map of the Edmonds East Quadrangle (Minard, 1983), the project site
is underlain by Transitional Beds (Qtb) with Olympia Gravel (Qog) mapped to the north of the
site. Transitional Beds are described as glacial and non -glacial deposits typically composed of
both thick and thin beds of fine clay silt and sand particles, with gravel near to the base of the
formation. These beds typically have a high water content. Olympia Gravel is described as a
weakly cemented fluvial sand with pebble sized gravels.
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Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
Based on our interpretation of the soil samples from the test borings, it appears that the site soil
conditions are consistent with the mapped geology, with Transitional Beds overlying Olympia
Gravel. A description of the generalized soil units encountered in our test borings is presented
below:
Asphalt — All 4 test borings were drilled through the existing parking lot pavement, and
encountered 4 to 8 inches of asphalt.
Soil Unit 1: Fill — Directly below the asphalt, the test borings encountered approximately
4 feet of fill. The fill generally consisted of a medium dense to dense, moist, grey to
brown, slightly silty fine to medium sand with gravels. Based on the SPT N-values
recorded in the test borings, the site fill appeared generally well compacted.
Soil Unit 2: Transitional Beds (Qtb) — Below the fill, a medium dense to very dense,
moist to wet layer of brown to grey silty fine to medium sand with gravel was
encountered. Evidence of iron -oxide staining and perched groundwater was present
throughout this unit. Borings PG-2, PG-3, and PG-4 were terminated in this unit. In
boring PG-1 this unit ended at about 16 '/2 feet below ground surface. This unit appears
consistent with the mapped Transitional Beds at the site.
Soil Unit 3: Olympia Gravel (Qog) — Below the Transitional Beds in PG-1, a very dense,
blue -grey, silty fine sand with pebble -sized gravels was encountered and extended to the
maximum depth of the boring. This soil unit appears consistent with the Olympia Gravel
mapped in the area just north of the site.
4.2 GROUNDWATER
Perched groundwater seepage and evidence of iron -oxide staining was commonly present within
the Transitional Beds of the test borings during drilling. In PG-1, at a depth of 20 feet,
groundwater was reached and subsequently filled the boring with water to approximately 9'/z
feet below ground surface.
It should be noted that groundwater elevations are likely to vary depending on the season, local
subsurface conditions, and other factors. Groundwater levels are normally highest during the
winter and early spring. Presence of perched water at the fill contact is common during wet
winter -spring months.
18-358 550 main street, edmonds 3 PanGEO, Inc.
Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
5.0 GEOTECHNICAL RECOMMENDATIONS
5.1 SEISMIC DESIGN PARAMETERS
The following provides seismic design parameters for the site that are in conformance with the
2015 International Building Code (IBC), which specifies a design earthquake having a 2%
probability of occurrence in 50 years (return interval of 2,475 years), and the 2008 USGS
seismic hazard maps. It is our opinion that Site Class D is appropriate for this project.
5.2 FOUNDATION
5.2.1 Building Foundation
Based on the site subsurface condition encountered in our test borings, it is our opinion that
conventional footings can be utilized for the proposed building renovation and the new building.
The footings may be founded on the existing site fill, provided that the fill at the footing
locations are well compacted, or on the undisturbed native soils below the fill. We recommend
that the adequacy of all footing bearing surface be verified by PanGEO before placing
reinforcing steel and formwork. Any loose soils should be completely removed from the footing
excavations and replaced with properly compacted structural fill.
Allowable Bearing Pressure — In our opinion, for footings placed on the suitable bearing
soils or properly compacted structural fill as discussed above, the footings may be sized
using a maximum allowable bearing pressure of 4,000 psf. For allowable stress design, the
recommended allowable bearing pressure may be increased by 1/3 for transient conditions
such as wind and seismic loadings. Spread and continuous footings should have minimum
widths of 24 and 18 inches, respectively.
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) for level backfill. This value includes a factor safety of at least 1.5
assuming that properly compacted structural fill will be placed adjacent to the sides of the
footings. A friction coefficient of 0.35 may be used to determine the frictional resistance at
the base of the footings. This coefficient includes a factor of safety of approximate 1.5.
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Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
Foundation Performance — Total and differential settlements are anticipated to be within
tolerable limits for footings designed and constructed as discussed above. Footing
settlement under static loading conditions is estimated to be less than approximately 1 inch,
and differential settlement between adjacent columns should be less than about '/2 inch.
Most settlement will occur during construction as loads are applied.
Our observations of the existing building performance indicate that localized footing settlement
had occurred near the southeast corner of existing building (see rotated door frame in Plate 2,
below). It is probable that a portion of the existing footings was constructed on loose soils.
Depending on the final foundation design of the proposed building renovation, it may be
necessary to locally retrofit the existing footings.
Plate 2. Footing settlement resulted in twisted door frame and
cracks in wall. SE corner of building, looking north.
18-358 550 main street, edmonds 5 PanGEO, Inc.
Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
5.2.2 Foundation for Art Panels and Signs
We understand that art panels and signs will be installed. The loading conditions on its
foundation are not available at this time, but we understand that the foundation may be subjected
to uplifts. It is our opinion that, if the uplift forces are not significant, and can be addressed with
the mass of concrete footings, it is our opinion that footings should be used in lieu of piles. The
recommendations outlined in Section 5.2.1 are also applicable for footings supporting the art
panels and signs.
However, if the uplift forces are significant and piles are needed, we recommend using cast -in -
place concrete piles, such as augercast piles or drilled shafts. For design purposes, we
recommend that an allowable skin friction of 1 ksf be used to size the augercast piles or drilled
shafts, assuming the piles/shafts are at least 15 feet deep. An allowable end bearing of 20 ksf
may also be used for piles/shafts in compression loads.
Lateral forces from wind or seismic loading may be resisted by a combination of passive earth
pressures acting against the embedded portions of the pile cap, and by the structural stiffness of
the piles. If needed, PanGEO is available to perform a laterally -load pile analysis, based on the
geometry and loading conditions provided by the structural engineer.
5.3 RETAINING WALL DESIGN PARAMETERS
Presented below are our geotechnical recommendations for the design and construction of
retaining walls.
Lateral Earth Pressure — Cantilevered walls should be designed for an equivalent fluid
pressure of 35 pcf for level backfills behind the walls assuming the walls are free to rotate.
If walls are to be restrained at the top from free movement, such as basement walls,
equivalent fluid pressures of 45 pcf should be used for level backfills behind the walls.
Permanent walls should be designed for an additional uniform lateral pressure of 7H psf for
seismic loading, where H corresponds to the buried depth of the wall. The recommended
lateral pressures assume that the backfill behind the wall consists of a free draining and
properly compacted fill with adequate drainage provisions.
Wall Surcharge — Surcharge loads, where present, should also be included in the design of
retaining walls. We recommend that a lateral load coefficient of 0.35 be used to compute
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Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
the lateral pressure on the wall face resulting from surcharge loads located within the height
dimension of the wall.
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) for level backfill. A friction coefficient of 0.30 may be
used to determine the frictional resistance at the base of footings. Both values include a
safety factor of at least 1.5.
Wall/Foundation Drainage — We recommend that perimeter wall/footing drains be
installed to prevent a buildup hydrostatic pressure behind walls. As a minimum, 4-inch
diameter perforated drainpipes should be installed next to the base of the footings and
embedded in 12 to 18 inches of pea or washed gravel. The gravel should be wrapped in a
geotextile filter fabric to prevent the migration of fines into the drain system. The drainpipe
should be graded to direct water to a suitable outlet and should not be allowed to daylight
over the slope.
If the proposed basement wall will be constructed against the temporary shoring wall
(soldier pile wall with timber lagging), prefabricated drainage mats, such as Mirafi 6000 or
equivalent, may be installed behind the basement walls and the collected water should be
directed to a 4-inch diameter perforated collector pipe located along the inside perimeter of
wall footing and discharged to an appropriate outlet.
Wall Backfill — Wall backfill, if needed, should consist of free draining granular soils. In
our opinion, the native excavated soils consist of a high fines content, and are not suitable to
be re -used as wall backfill. Imported wall backfill such as City of Seattle Type 17 Mineral
Aggregates (Section 9.03.10 (1) of the 2017 Seattle Standard Specifications) or Gravel
Borrow (Section 9.03.14 (1) of the 2018 WSDOT Standard Specifications) should be
assumed for this project.
The structural fill should be moisture conditioned to near its optimum moisture content,
placed in loose, horizontal lifts less than 8 to 12 inches 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
18-358 550 main street, edmonds 7 PanGEO, Inc.
Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
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.
Damp Proofing — Waterproofing considerations are beyond our scope of work. We
recommend that a building envelope specialist be consulted to determine appropriate damp -
proofing or water -proofing measures.
5.4 CONCRETE SLAB ON GRADE
Conventional on -grade concrete slabs may be utilized for this project. The slab may be
constructed on densely compacted fill, or undisturbed native soils. Interior concrete slab -on -
grade floors should be underlain by a capillary break consisting of at least of 4 inches of
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 dense subgrade or subgrade that has been compacted to a dense and unyielding
condition. A 10-mil polyethylene vapor barrier should also be placed directly below the interior
slab.
5.5 PERMANENT DRAINAGE CONSIDERATIONS
Permanent control of surface water and roof runoff should be incorporated in the final grading
design. In addition to these sources, irrigation and rain water infiltrating into the proposed
landscaped and planter areas adjacent to paved areas or building foundations should also be
controlled. All collected runoff should be directed into conduits that carry the water away from
the pavement or structure and into storm drain systems or other appropriate outlets and should
not be discharged onto the slope. Adequate surface gradients should be incorporated into the
grading design such that surface runoff is directed away from structures.
5.6 PERMANENT SLOPES
It is our opinion that permanent slopes should be graded no steeper than 2H:IV. It is also our
opinion that permanent slopes against the foundation or retaining wall should be graded no steep
than 3H:IV.
18-358 550 main street, edmonds 8 PanGEO, Inc.
Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
6.0 CONSTRUCTION CONSIDERATIONS
6.1 FOOTING SUBGRADE
Any loose or softened soil should be removed from the foundation excavation. Foundation
excavations and over -excavations should be observed by PanGEO to confirm that the exposed
subgrade is consistent with the expected conditions and adequate to support the proposed
building. Foundation over -excavation, if needed, should extend horizontally at least 1 foot
beyond the edge of the footings.
The footing subgrade will need to be protected from moisture -related disturbance if works will
be performed during wet weather. One option is to pour 2 to 3 inches of lean -mix concrete or 4
to 6 inches of crushed rock on the exposed foundation subgrade to protect against moisture.
Alternatively, the reinforcing steel can be prefabricated, and the placement of the steel and
concrete can be placed immediately after the footing excavation is completed. This will
minimize the exposure of the footing subgrade to moisture.
6.2 TEMPORARY EXCAVATION AND DEWATERING
All temporary excavations should be performed in accordance with Part N of WAC (Washington
Administrative Code) 296-155. Excavations more than 4 feet should be sloped or shored. The
contractor is responsible for maintaining safe excavation slopes and/or shoring. For planning
purposes, the temporary unsupported excavation may be sloped as steep as 1 H:1 V
(Horizontal: Vertical). If areas of seepage are encountered during construction, the above -
referenced angles of slope cuts may need to be flattened.
We anticipate that the excavation will not be significantly impacted by groundwater. If
groundwater seepage is encountered, we anticipate that the use of drainage ditches and sump
pumps will provide adequate construction dewatering.
6.3 STRUCTURAL FILL AND COMPACTION
The on -site soils generally have a high fines content, and are not suitable to be used as structural
fill. For planning and budgeting purposes, we recommend granular import fill such as the City
of Seattle Type 17 Mineral Aggregates (Section 9.03.10 (1) of the 2017 Seattle Standard
Specifications) or Gravel Borrow (Section 9.03.14 (1) of the 2018 WSDOT Standard
Specifications).
18-358 550 main street, edmonds 9 PanGEO, Inc.
Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
Soil Compaction — The structural fill should be moisture conditioned to near its optimum
moisture content, placed in loose, horizontal lifts less than about 12 inches 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 EROSION AND DRAINAGE CONSIDERATIONS
We recommend that the exposed slopes be covered with plastic sheeting. Surface runoff can be
controlled during construction by careful grading practices. This could include 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. 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.
6.5 WET EARTHWORK RECOMMENDATIONS
It is our opinion that construction of the project can be accomplished during wet season.
However, perfonning earthwork activities during wet season is anticipated to be more costly than
during dry weather conditions. General recommendations relative to earthwork performed in
wet weather or in wet conditions are presented below:
• All footing surface should be protected against inclement weather unless the footings
can be poured immediately after the subgrade is exposed. It is the contractor's
responsibility to protect the footing subgrade from disturbance. One option is to
place 2 to 3 inches of lean -mix concrete or 4 to 6 inches of crushed rock on the
exposed foundation subgrade as soon as the subgrade is exposed. Alternatively, the
footing pour may be made immediately after the footing excavation is completed.
This will require the reinforcing steel to be pre -fabricated and lowered into the
footing excavation once the excavation is completed.
• 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
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Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
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.
• Excavation slopes and soils stockpiled on site should also be covered with plastic
sheets.
6.6 INFILTRATION CONSIDERATIONS
Based on the site soil and groundwater conditions encountered in our test borings (i.e., multiple
perched groundwater zones and iron staining), from the geotechnical engineering perspective, it
is our opinion that infiltration of stormwater is not feasible at the site. It is our opinion that non -
infiltration design approaches should be considered for stormwater management for this project.
7.0 LIMITATIONS
We have prepared this report for use by Seattle -Snohomish Mill Company, Inc. and the project
design team. Recommendations contained in this report are based on a site reconnaissance,
review of pertinent subsurface information, a subsurface exploration program, 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.
18-358 550 main street, edmonds 1 I PanGEO, Inc.
Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
The scope of our work does not include services related to construction safety precautions. Our
recommendations are not intended to direct the contractors' methods, techniques, sequences or
procedures, except as specifically described in our report for consideration in design.
Additionally, the scope of our work specifically excludes the assessment of environmental
characteristics, particularly those involving hazardous substances. We are not mold consultants
nor are our recommendations to be interpreted as being preventative of mold development. A
mold specialist should be consulted for all mold -related issues.
This report may be used only by the client and for the purposes stated, within a reasonable time
from its issuance. Land use, site conditions (both off and on -site), or other factors including
advances in our understanding of applied science, may change over time and could materially
affect our findings. Therefore, this report should not be relied upon after 24 months from its
issuance. PanGEO should be notified if the project is delayed by more than 24 months from the
date of this report so that we may review the applicability of our conclusions considering the
time lapse.
It is the client's responsibility to see that all parties to this project, including the designer,
contractor, subcontractors, etc., are made aware of this report in its entirety. The use of
information contained in this report for bidding purposes should be done at the contractor's
option and risk. Any party other than the client who wishes to use this report shall notify
PanGEO of such intended use and for permission to copy this report. Based on the intended use
of the report, PanGEO may require that additional work be performed and that an updated report
be reissued. Noncompliance with any of these requirements will release PanGEO from any
liability resulting from the use this report.
Within the limitation of scope, schedule and budget, PanGEO engages in the practice of
geotechnical engineering and endeavors to perform its services in accordance with generally
accepted professional principles and practices at the time the Report or its contents were
prepared. No warranty, express or implied, is made.
We appreciate the opportunity to be of service to you on this project. Please feel free to contact
our office with any questions you have regarding our study, this report, or any geotechnical
engineering related project issues.
18-358 550 main street, edmonds 12 PanGEO, Inc.
Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
Sincerely,
PanGEO, Inc.
Spenser Scott
Staff Geologist
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S�V . A L
Siew L. Tan, P.E.
Principal Geotechnical Engineer
18-358 550 main street, edmonds 13 PanGEO, Inc.
Geotechnical Report
Main Street Commons: 550 Main Street, Edmonds, Washington
November 14, 2018
8.0 REFERENCES
ASTM International (ASTM), Annual book of standards, Section 04.08 Soil and Rock (1): D420-
D5876: West Conshohocken, Pennsylvania
City of Seattle, 2017, Standard Specifications for Road, Bridges, and Municipal Construction,
Seattle, Washington.
International Building Code (IBC), 2015, International Code Council.
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.
Washington State Department of Transportation (WSDOT), 2018, Standard Specifications for
Road, Bridges, and Municipal Construction, Olympia, Washington.
Washington Administrative Code (WAC), 2013, Chapter 296-155 - Safety Standards for
Construction Work, Part N - Excavation, Trenching, and Shoring, Olympia, Washington.
18-358 550 main street, edmonds 14 PanGEO, Inc.
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Proposed Development VICINITY MAP
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t N CUR PON AT@D Edmonds WA
' I'iulcr.l No 18-358 Piclwo No 1
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Legend:
Approx. Boring Locations
PanGEO, Inc., November 2018
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Base map modified from Site Plan by DiMarco Architecture.
dated October 31,
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SUMMARY 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
0
GP :
Poorly -graded GRAVEL
fraction retained on the #4
sieve. Use dual symbols leg.
....................
o
..... :......................................
GM
..... ..........
SiltyGRAVEL
GP -GM) for 5% to 12% fines.
GRAVEL (>12% fines)
GC :
..................................
Clayey GRAVEL
.................................................a........
..............................................................
SW :
Well -graded SAND
Sand
SAND (<5!° fines)
:::.....:
.................................. I ...................
50% or more of the coarse
ays
r,,,
i
SP :
oor
Pl raded SAND
Poorly -graded
fraction passing the #4 sieve.
Use dualsymbols e . SP-SM )
SM :
SiltySAND
fors% to 1% fines.
SAND (>12%fines)
..........................................................
SC :
Clayey SAND
......................................................................
ML :
:.
SILT
Liquid Limit < 50
CL :
...................................I—..............
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
........................y........................................
OH :
................... .......... I ...... I.................
Organic SILT or CLAY
Highly Organic Soils
u
.....:...................................I...................
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 logs.
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 314 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
Afterberg Limit Test
Comp
Compaction Tests
Con
Consolidation
DO
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
SamplelIn 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
V
Groundwater Level at
1
time of drilling (ATD)
Static Groundwater Level
Cement / Concrete Seal
Bentonite grout I seal
Silica sand backfill
Slotted tip
Slough
Bottom of Boring
MOISTURE CONTENT
Dry
Dusty, dry to the touch
Moist
Damp but no visible water
Wet
Visible free water
Terms and Symbols for
PanGE&
I N C O R P O R A T E D Boring and Test Pit Logs Figure A-1
3 Phone: 206.262.0370
Project: 550 Main Street
Surface Elevation: 87.Oft
Job Number: 18-358
Top of Casing Elev.: N/A
Location: 550 Main Street, Edmonds, WA
Drilling Method: HSA
Coordinates: Northing: , Easting:
Sampling Method: SPT
N-Value A
o
Z
I
c
co
U
p
PL Moisture LL
L
a
H
Q
N
L
E MATERIAL DESCRIPTION
p
E] Recovery
U)
m
O
0 50 100
0
8-inches of asphalt.
Medium dense, moist, brown, slightly silty SAND; trace gravel.
(Fill).
13
S-1
10
Perched groundwater encountered at approximately 4-feet.
s
Stiff, moist, light -grey, CLAY; trace silt, highly mottled.
5
Medium dense, moist to wet, brown, silty fine to medium SAND; trace
— —
14
T. gravel, trace iron -oxide staining.
S 2
14
(Qtb -Transitional Beds).
Ems
14
12
S-3
13
15
Perched groundwater encountered at approximately 8.5-feet.
10
8
Increase in gravel at approximately 10-feet.
S-4
10
10
20
S-5
22
Perched groundwater encountered at approximately 13-feet.
20
15
18
Perched groundwater encountered at approximately 15.5-feet.
S-6
20
20
Disrupted layer of blue -grey to grey fines at base of Qtb.
Very dense, moist to wet, blue -grey, silty fine SAND with pebble -sized
gravel; slighty cemented, trace mottling.
20
(Qog - Olympia Gravel).
S-7
29
32
20
Groundwater encountered at approximately 20-feet.
S-$
45
50/5
Boring terminated at 21 feet below ground surface. Perched
goundwater was observed at approximately 4-feet, 8.5-feet, 10-feet,
13-feet, and 15.5-feet.
Final groundwater level after drilling operations was approximately
9.5-feet.
25
Completion Depth: 21.5ft
Remarks: Boring drilled using an EC95 track drill rig. Standard penetration test (SPT)
Date Borehole Started: 11/7/18
sampler driven with a 140 lb. safety hammer. Hammer operated with a rope and cathead
Date Borehole Completed: 11/7/18
mechanism. Surface elevation estimated from Topographic Survey by Emerald Land
Logged By: S. Scott
Surveying, Inc., dated October 10, 2017.
Drilling Company: Boretec 1
F�GEO LOG OF TEST BORING PGA
I ft C C P P O"•*■ o FigureA-2
The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of 1
Project:
550 Main Street
Job Number:
18-358
Location:
550 Main Street, Edmonds, WA
Coordinates:
Northing: , Easting:
z
T
co
N
X
_N
H
CL
E
a
Z.
N
,
Surface Elevation:
87.Oft
Top of Casing Elev.:
N/A
Drilling Method:
HSA
Sampling Method:
SPT
MATERIAL DESCRIPTION
N-Value
PL Moisture LL
0) C13
p U) U) m O El 10
Recovery
0 0 50 100
E&I
F10
t; U
� 20
4-inches of asphalt.
.........
.........
Medium dense, moist, brown, slightly silty fine to medium SAND; trace
gravel, trace iron -oxide staining.
(Fill).
4
S-1
5
15
Dense to very dense, moist to wet, grey -brown, silty fine to medium
SAND; trace gravel, trace silt stringers, trace iron -oxide staining.
16
(Qtb - Transitional Beds).
S-2
21
23
Perched groundwater encountered at approximately 5-feet.
21
S-3
30
33
S 4
49
33
39
Perched groundwater and increased gravels encountered at
approximately 11-feet.
Boring terminated at 11.5 feet below ground surface. Perched
groundwater was observed at approximately 5-feet and 11-feet.
No groundwater was observed at the bottom of the hole after drilling
operations.
r25L --
Completion Depth:
11.5ft
Date Borehole Started:
11/7/18
Date Borehole Completed:
11/7/18
Logged By:
S. Scott
Drilling Company:
Boretec 1
F�GE@)
I N C O a P O a T■ O
LOG OF TEST BORING PG-2
Figure A-3
The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of 1
Project: 550 Main Street
Surface Elevation: 91.Oft
Job Number: 18-358
Top of Casing Elev.: N/A
Location: 550 Main Street, Edmonds, WA
Drilling Method: HSA
Coordinates: Northing: , Easting:
Sampling Method: SPT
N-Value
p
Z
aL
c
U)
p
PL Moisture LL
p
o
~
E
MATERIAL DESCRIPTION�-
p
RQD Recovery
®12
fA
00
O
0 50 100
0
5-inches of asphalt.
Medium dense, moist, grey to brown, slightly silty SAND with gravel.
(Fill).
10
S-1
X
10
11
Dense, moist to wet, brown, silty fine SAND with gravel; trace silt
5
stringers, trace iron -oxide staining.
19
(Qtb - Transitional Beds).
S-2
23
24
17
Perched groundwater encountered at approximately 7.5-feet.
S-3
X
19
20
10
13
S-4
16
17
Boring terminated at 11.5 feet below ground surface. Perched
groundwater was observed at approximately 7.5-feet.
No groundwater was observed at the bottom of the hole after drilling
operations.
15
20
25
Completion Depth: 11.5ft
Remarks: Boring drilled using an EC95 track drill rig. Standard penetration test (SPT)
Date Borehole Started: 11/7/18
sampler driven with a 140 lb. safety hammer. Hammer operated with a rope and cathead
Date Borehole Completed: 11/7/18
mechanism. Surface elevation estimated from Topographic Survey by Emerald Land
Logged By: S. Scott
Surveying, Inc., dated October 10, 2017.
Drilling Company: Boretec 1
LOG OF TEST BORING PG-3
RinGE@
I W C O a P u R a*■ G FigureA-4
The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of 1
Project: 550 Main Street
Surface Elevation: 90.0ft
Job Number: 18-358
Top of Casing Elev.: N/A
Location: 550 Main Street, Edmonds, WA
Drilling Method: HSA
Coordinates: Northing: , Easting:
Sampling Method: SPT
N-Value
..
o
Z
cCn
N
p
PL Moisture LL
C
a
W
~
L
E MATERIAL DESCRIPTION
CL
p
0
® RQD RecoveryEJ
O
0 50 100
0
5-inches of asphalt.
Very dense, moist, grey to brown, slightly silty SAND; trace gravel.
(Fill).
18
S-1
22
29
Very dense to dense, moist to wet, grey -brown, silty fine SAND; trace
5
coarse sand stringers, trace gravel, trace iron -oxide staining.
18
(Qtb - Transitional Beds).
S-2
zz
Perched groundwater encountered at approximately 5-feet.
28
21
Increase in gravel at approximately 5-feet.
S-3
21
31
10
17
S-4
20
18
Boring terminated at 11.5 feet below ground surface. Perched
groundwater was observed at approximately 5-feet.
No groundwater was observed at the bottom of the hole after drilling
operations.
15
20
25
Completion Depth: 11.5ft
Remarks: Boring drilled using an EC95 track drill rig. Standard penetration test (SPT)
Date Borehole Started: 11/7/18
sampler driven with a 140 lb. safety hammer. Hammer operated with a rope and cathead
Date Borehole Completed: 11/7/18
mechanism. Surface elevation estimated from Topographic Survey by Emerald Land
Logged By: S. Scott
Surveying, Inc., dated October 10, 2017.
Drilling Company: Boretec 1
LOG OF TEST BORING PG-4
F!anGE@)
A M C O R P O R. T■ D FigureA-5
The stratification lines represent approximate boundaries. The transition may be gradual. Sheet 1 Of 1