HomeMy WebLinkAbout20251017_PLN1416_Geotech Report DRAFT I GEOTECHNICAL REPORT
NWC 212 Street. NE Medical Office Facility
Snohomish County Tax Parcel 3105120020-0400
Arlington, Washington
Project No. T-9205
Terra Associates, Inc.
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Prepared for:
Visconsi Companies Ltd.
Pepper Pike, Ohio
August 19, 2025
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'AsVf 4 , TERRA ASSOCIATES, Inc.
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e �Q s• Consultants in Geotechnical Engineering, Geology
and
Environmental Earth Sciences
August 19,2025
Project No. T-9205
Mr. Shawn A. Jurisch,P.E. [DRAFT
Visconsi Companies Ltd.
30050 Chagrin Blvd., Suite 360
Pepper Pike, Ohio 44124
Subject: Geotechnical Report
NWC 212 Street NE Medical Office Facility
Snohomish County Tax Parcel 3105120020-0400
Arlington,Washington
Dear Mr. Jurisch:
As requested, we conducted a geotechnical engineering study for the subject project. The attached report presents
our findings and recommendations for the geotechnical aspects of project design and construction.
Our field exploration indicates soil conditions observed in the test borings underlying several inches of organic
topsoil and sod, consists of approximately 4.5 feet to 20 feet of loose to very dense silty sand with gravel overlying
medium dense to very dense silty sand with gravel with interbedded sands up to several inches thick to the
termination of the test borings. The soil formation is till-like in nature. In Test Borings B-2, B-4 and B-7 we
observed approximately seven to ten feet of fill consisting of loose to dense silty sand with gravel overlying the
native site soils. We observed light groundwater seepage in Test Borings B-5 and B-7 at depths of approximately
50 and 35 feet, respectively. The seepage was typically observed within interbedded sands in the lower till like
deposits.
In our opinion, the soil and groundwater conditions are suitable for the planned development provided the
recommendations presented in this report are incorporated into project design and construction.
We trust the information presented in this report is sufficient for your current needs. If you have any questions or
require additional information,please call.
Sincerely yours,
TERRA ASSOCIATES,INC.
Maxwell E. Price, L.G.
Staff Geologist [ DRAFT
Theodore J. Schepper,P.E.
Senior Principal Engineer
Project No. T-9205
12220—113th Avenue NE, Ste. 130, Kirkland, Washington 98034 1 Phone (425) 821-7777
TABLE OF CONTENTS
Page No.
1.0 Project Description.......................................................................................................... 1
2.0 Scope of Work................................................................................................................. 1
3.0 Site Conditions ................................................................................................................2
3.1 Surface.....................................................................................................................2
3.2 Soils.........................................................................................................................2
3.3 Groundwater............................................................................................................3
3.4 Geologic Hazards....................................................................................................3
3.4.1 Erosion Hazard Areas....................................................................................3
3.4.2 Landslide Hazard Areas.................................................................................4
3.4.3 Seismic Hazard Areas....................................................................................4
3.5 Seismic Site Class....................................................................................................5
4.0 Discussion and Recommendations..................................................................................5
4.1 General....................................................................................................................5
4.2 Site Preparation and Grading...................................................................................5
4.3 Excavations..............................................................................................................7
4.4 Foundations.............................................................................................................7
4.5 Slab-on-Grade Floors..............................................................................................8
4.6 Lateral Earth Pressures for Retaining Walls............................................................8
4.7 Stormwater Facilities/Infiltration Feasibility...........................................................9
4.8 Drainage ................................................................................................................ 10
4.9 Utilities.................................................................................................................. 10
4.10 Pavements.............................................................................................................. 10
5.0 Additional Services........................................................................................................ 11
6.0 Limitations..................................................................................................................... 11
Fi ures
VicinityMap.........................................................................................................................Figure 1
Exploration Location Plan....................................................................................................Figure 2
Typical Wall Drainage Detail...............................................................................................Figure 3
Appendix
Field Exploration and Laboratory Testing.......................................................................Appendix A
Geotechnical Report
NWC 212 Street NE Medical Office Facility
Snohomish County Tax Parcel 3105120020-0400
Snohomish, Washington
1.0 PROJECT DESCRIPTION
The project consists of redeveloping the site with a 30,000 square foot medical office facility and associated
infrastructure improvements. Based on a preliminary grading and drainage plan prepared by Barghausen Consulting
Engineers, the building will be located in the southeastern portion of the site with access and paved parking to the
north, west and south. Final design grades will require cuts on the order of one to five feet to the north and west
with similar fill depths to the south and east. Up to 8 feet of fill will be required to achieve the finished floor
elevation along the south side of the building. The preliminary grading and drainage plan also proposed using
infiltration galleries installed below the western paved parking area for control of development stormwater.
We expect that the building will be a three-story, steel-framed structure, with the main floor constructed at grade.
Foundation loads are expected to be moderate, with interior columns carrying 300 to 400 kips and bearing walls
carrying 6 to 8 kips per foot.
The recommendations contained in the following sections of this report are preliminary and based on our
understanding of the above design features. We should review design drawings as they become available to verify
that our recommendations have been properly interpreted and incorporated into project design and to amend or
supplement our recommendations, if required.
2.0 SCOPE OF WORK
Our scope of work was completed in accordance with our authorized proposal dated April 2, 2025. Accordingly,
on August 4th, 5th and 6th, 2025,nine test borings were advanced to depths of 10 to approximately 50 feet below
existing grades. At completion, three of the test borings located in the proposed infiltration gallery area were
converted into groundwater monitoring wells to allow for monitoring groundwater levels over the winter season.
Using the results of our field study and laboratory testing, analyses were undertaken to develop geotechnical
recommendations for project design and construction. Specifically,this report addresses the following:
• Soil and groundwater conditions.
• Geologic hazards per the City of Arlington Municipal Code(AMC).
• Seismic site class per the 2021 International Building Code (IBC).
• Site preparation and grading.
• Excavations.
• Foundations.
August 19,2025
Project No. T-9205
• Slab-on-Grade floors.
• Stormwater facilities/infiltration feasibility.
• Utilities.
• Pavements.
It should be noted that recommendations outlined in this report regarding drainage are associated with soil strength,
design earth pressures, erosion, and stability. Design and performance issues with respect to moisture as it relates
to the structure environment are beyond Terra Associates' purview. A building envelope specialist or contactor
should be consulted to address these issues, as needed.
3.0 SITE CONDITIONS
3.1 Surface
The project site consists of an approximately 2.3-acre parcel (Snohomish County tax parcel 3 1 05 1 20020-0400)
located northwest of the intersection of 212th Street Northeast and Medical Center Drive in Arlington,Washington.
The approximate location of the site is shown on Figure 1.
The site is currently undeveloped and covered with grass and several scattered small-to medium- sized trees. Site
topography slopes gently to the south— southeast with about 20 feet of elevation relief carried over a gradient of
about 5 percent. There is a ridge of higher elevation along the east side of the property with slopes off the ridge
descending to the west and south.
3.2 Soils
In general, soil conditions observed in the test borings underlying several inches of organic topsoil and sod, consist
of approximately 4.5 feet to 20 feet of loose to very dense silty sand with gravel overlying medium dense to very
dense silty sand with gravel with interbedded sands to the termination of the test borings. Sand interbeds were
observed to be several inches thick. There were two exceptions to this general condition. In Test Borings B-2,B-
4 and B-7 we observed approximately seven to ten feet of fill soil,consisting of loose to dense silty sand with gravel
overlying the native site soils. In Test Boring B-5 we observed very dense silt with sand and gravel near the 50-
foot termination depth of the boring.
The Geologic map of the Arlington East quadrangle, Snohomish County, Washington by J.P. Minard(1985)maps
the site as Vashon recessional outwash known locally as Arlington Gravel Member (Qvra). Vashon recessional
outwash is described as well-drained,stratified outwash sand and gravel deposited by meltwater from the stagnating
and receding Vashon Glacier. The area immediately to the north and northwest of the subject site is mapped as
Vashon till(Qvt). Vashon till is described as consisting of a non-sorted mixture of clay-silt, sand,pebbles,cobbles
and boulders. The soil conditions observed in the test borings are generally more consistent with the description of
the Qvt geologic map unit.
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Project No. T-9205
The preceding discussion is intended to be a general review of the soil conditions encountered. For more detailed
descriptions, please refer to the Test Boring Logs in Appendix A. The approximate locations of the Test Borings
are shown on Figure 2.
3.3 Groundwater
We observed light groundwater seepage in Test Borings B-5 and B-7 at depths of approximately 50 and 35 feet,
respectively. The seepage was typically observed within interbedded sands in the lower dense silty sand deposits.
In addition, mottled soils were observed in all of the test borings within the upper weathered soil zone. Mottled
soils typically indicate the presence of perched groundwater seepage throughout much of the site. The occurrence
of shallow perched groundwater is typical for sites underlain by fine-grained soils. We expect perched groundwater
levels and flow rates will fluctuate seasonally and will typically reach their highest levels during and shortly
following the wet winter months (November through May). To evaluate the seasonal weather influence, three of
the test borings were converted to observation wells.
3.4 Geologic Hazards
Chapter 20.93.600.a of the City of Arlington Municipal Code (AMC) defines geologically hazardous areas as
"...areas susceptible to erosion, sliding, earthquakes, liquefaction, or other geological events. Geologically
hazardous areas shall be classified based upon the history or existence of landslides,unstable soils, steep slopes,
high erosion potential or seismic hazards." Discussions related to erosion, landslide, mine, and seismic hazards
are presented below.
3.4.1 Erosion Hazard Areas
Chapter 20.93.600.b.1 of the AMC defines erosion hazard areas as areas that are"... as defined by the USDA Soil
Conservation Service,United States Geologic Survey,or by the Department of Ecology Coastal Zone Atlas. The
following classes are high erosion hazard areas:
a) Class 3, class U(unstable) includes severe erosion hazards and rapid surface runoff areas;
b) Class 4, class UOS (unstable old slides) includes areas having severe limitations due to slope; and,
c) Class 5, class URS (unstable recent slides)."
We did not observe any indication of erosion or sediment deposition at the site. The vast majority of the site soils
are mapped as Alderwood gravelly sandy loam,0 to 8 percent slopes by the United States Department of Agriculture
Natural Resources Conservation Service (MRCS). A small portion at the southeast corner of the site is mapped as
Ragnar fine sandy loam, 0 to 8 percent slopes. Over the site with existing slope gradients,both of these soils will
have a slight potential for erosion when exposed. Therefore, the site is not an erosion hazard as defined by the
AMC.
Regardless, the site soils will be susceptible to erosion when exposed during construction. In our opinion, proper
installation and maintenance of Best Management Practices (BMPs) for erosion prevention and sedimentation
control would adequately mitigate the erosion potential in the proposed development areas. All BMPs for erosion
prevention and sedimentation control should conform to the Snohomish County requirements.
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Project No. T-9205
3.4.2 Landslide Hazard Areas
Chapter 20.93.600.b.2 of the AMC defines landslide hazard areas as "...areas subject to severe risk of landslide
based on a combination of geologic, topographic and hydrologic factors. Some of these areas may be identified
in the Department of Ecology Coastal Zone Atlas,or through site-specific criteria.Landslide hazard areas include
any of the following:
a) Areas characterized by slopes greater than fifteen percent and impermeable soils (typically silt and clay)
frequently interbedded with permeable granular soils (predominantly sand and gravel) or impermeable
soils overlain with permeable soils or springs or groundwater seepage;
b) Any area that has exhibited movement during the Holocene epoch (from ten thousand years ago to
present) or which is underlain by mass wastage debris of that epoch;
c) Any area potentially unstable due to rapid stream incision, stream bank erosion or undercutting by wave
action;
d) Any area located on an alluvial fan presently subject to or potentially subject to inundation by debris
flows or deposition of steam-transported sediments;
e) Any area with a slope of thirty-three percent or greater and with a vertical relief of ten or more feet except
areas composed of consolidated rock;
f) Any area with slope defined by the United States Department of Agriculture Soil Conservation Service
as having a severe limitation for building site development; and
g) Any shoreline designated or mapped as class U, UOS, or URS by the Department of Ecology Coastal
Zone Atlas."
Site topography, as shown on the Snohomish County PDS Map Portal, slopes gently to the south—southeast with
about 20 feet of elevation relief carried over a gradient of about 5 percent. There is a ridge of higher elevation along
the east side of the property with slopes off the ridge descending to the west and south. None of the criteria listed
above apply to the site, therefore, it is our opinion that slopes on the site show little to no risk of mass movement
due to geologic,topography, or hydrologic factors and that a landslide hazard does not exist at the site.
3.4.3 Seismic Hazard Areas
Chapter 20.93.600.b.4 of the AMC defines seismic hazard areas as "... areas subject to severe risk of earthquake
damage as a result of seismic induced settlement, shaking, slope failure or soil liquefaction. These conditions
occur in areas underlain by cohesion less soils of low density usually in association with a shallow groundwater
table."
A review of a map titled Faults and Earthquakes in Washington State, dated 2014 by Jessica L. Czajkowski and
Jeffrey D. Bowman shows the site does not reside within any active fault zone. The nearest fault,which is a spur
of the Darrington-Devils Mountain Fault, is categorized as"Class B"and is located approximately 5.8 miles north
of the site. Accordingly, during a seismic event,the risk of ground rupture along a fault line at the site is low.
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Project No. T-9205
Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in
water pressure induced by vibrations. Liquefaction mainly affects geologically recent deposits of fine-grained sands
underlying the groundwater table. Soils of this nature derive their strength from intergranular friction. The
generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular
friction;thus, eliminating the soil's strength.
Based on the soil and groundwater conditions observed, in our opinion, the potential for soil liquefaction and
settlement within the native soils is negligible. Groundwater seepage was typically perched with minimal flow.
Additionally,the site is rated as having very low potential for liquefaction on the Washington State Department of
Natural Resources Natural Hazards Single-Topic Map. Therefore,the site would not meet the seismic hazard area
criteria, as described above.
3.5 Seismic Site Class
Based on soil conditions observed in the test pits, and our knowledge of the area geology, per Chapter 20 of the
2021 International Building Code(IBC), Site Class"D"should be used in structural design.
4.0 DISCUSSION AND RECOMMENDATIONS
4.1 General
In our opinion, there are no geotechnical conditions that would preclude the planned development. The medical
office building can be supported on conventional spread footings bearing on competent native soils below the
organic topsoil layer or on structural fill placed above the competent native soils. Existing fill soils observed in the
eastern ridge at test borings B-2,B-4 and B-7 are not suitable for building support in their current condition. Over
excavation and structurally recompacting these existing fills will be required. Floor slabs and pavements can be
similarly supported.
The native and existing fill soils encountered at the site contain a significant amount of fines and will be difficult to
compact as structural fill when too wet. The ability to use the existing fill and native soils from site excavations as
structural fill will depend upon its moisture content and the prevailing weather conditions at the time of construction.
If grading activities take place during winter, the owner should be prepared to import clean granular material for
use as structural fill and backfill.
The following sections provide detailed recommendations regarding the preceding issues and other geotechnical
design and construction considerations. These recommendations should be incorporated into the final design
drawings and construction specifications.
4.2 Site Preparation and Grading
To prepare the site for construction, all vegetation, organic surface soils, and other deleterious material should be
stripped and removed from the site. Surface stripping depths of approximately two to four inches should be
expected to remove the organic surface soils and vegetation. Organic topsoil will not be suitable for use as structural
fill but may be used for limited depths in nonstructural areas.
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Project No. T-9205
The existing fill soils observed in the upper ten feet in Test Borings B-4 and B-7 are currently in a very loose to
loose condition and will need to be over excavated and recompacted structurally below all building elements. We
recommend removing the existing fill to a depth that leaves two feet of the fill in place. At that depth the fill should
be compacted structurally with the soils then replaced in uniform lifts and compacted structurally as recommended
below.
Once clearing and stripping operations are complete, cut and fill operations can be initiated to establish desired
building grades. Prior to placing fill, all exposed bearing surfaces should be observed by a representative of Terra
Associates, Inc. to verify soil conditions are as expected and suitable for support of new fill or building elements.
Our representative may request a proofroll using heavy rubber-tired equipment to determine if any isolated soft and
yielding areas are present. If excessively yielding areas are observed and they cannot be stabilized in place by
compaction, the affected soils should be excavated and removed to firm bearing and grade restored with new
structural fill. If the depth of excavation to remove unstable soils is excessive,the use of geotextile fabrics such as,
Mirafi 500X or an equivalent fabric can be used in conjunction with clean granular structural fill. Our experience
has shown, in general, a minimum of 18 inches of a clean, granular structural fill placed and compacted over the
geotextile fabric should establish a stable bearing surface.
Our study indicates that both the existing fill soils and native soils at the site contain a sufficient amount of soil
fines that will make them difficult to compact as structural fill when too wet or too dry. The ability to use these
soils from site excavations as structural fill will depend upon its moisture content,the prevailing weather conditions
at the time of construction and the contractor's ability to compact the native silt soils. If wet soils are encountered,
the contractor will need to dry the soils by aeration during dry weather conditions. Alternatively, the use of an
additive, such as Portland cement or lime to stabilize the soil moisture can be considered. If the soil is amended,
additional Best Management Practices (BMPs) addressing the potential for elevated pH levels will need to be
included in the Stormwater Pollution Prevention Program (SWPPP) prepared with the Temporary Erosion and
Sedimentation Control(TESC)plan. The relatively clean sand and gravels observed throughout the site, should be
suitable to reuse as structural fill in most weather conditions.
If grading activities are planned during the wet winter months,or if they are initiated during the summer and extend
into fall and winter,the owner should be prepared to import wet-weather structural fill.
For this purpose,we recommend importing a granular soil that meets the following grading requirements:
U.S. Sieve Size Percent Passing
6 inches 100
No. 4 75 maximum
No. 200 5 maximum*
*Based on the 3/4-inch fraction.
Prior to use, Terra Associates, Inc. should examine and test all materials imported to the site for use as structural
fill.
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Project No. T-9205
Structural fill should be placed in uniform loose layers not exceeding 12 inches and compacted to a minimum of 95
percent of the soil's maximum dry density, as determined by American Society for Testing and Materials (ASTM)
Test Designation D-1557 (Modified Proctor). The moisture content of the soil at the time of compaction should be
within two percent of its optimum, as determined by this ASTM standard. In nonstructural areas, the degree of
compaction can be reduced to 90 percent.
4.3 Excavations
All excavations at the site associated with confined spaces, such as lower-building level retaining walls, must be
completed in accordance with local, state, and federal requirements. Based on the Washington State Safety and
Health Administration (WSHA) regulations, the loose to dense fill and native weathered till soils would typically
be classified as Type "C" soils. The native dense to very dense unweathered till would be classified as Type "A"
soils.
Accordingly, temporary excavations in Type C soils should have their slopes laid back at an inclination of 1.5:1
(Horizontal: Vertical) or flatter, from the toe to the crest of the slope. Side slopes in Type A soils can be laid back
at a slope inclination of 0.75:1 or flatter. For temporary excavation slopes less than 8 feet in height in Type A soils,
the lower 3.5 feet can be cut to a vertical condition, with a 0.75:1 slope graded above. For temporary excavation
slopes greater than 8 feet in height up to a maximum height of 12 feet,the slope above the 3.5-foot vertical portion
will need to be laid back at a minimum slope inclination of 1:1. No vertical cut with a backslope immediately above
is allowed for excavation depths that exceed 12 feet. In this case, a four-foot vertical cut with an equivalent
horizontal bench to the cut slope toe is required.
All exposed temporary slope faces that will remain open for an extended period of time should be covered with a
durable reinforced plastic membrane during construction to prevent slope raveling and rutting during periods of
precipitation.
Groundwater seepage may be encountered within excavations during the wet winter season. We anticipate that the
volume of water and rate of flow into the excavation will be relatively minor and is not expected to impact the
stability of the excavations when completed, as described. Conventional sump pumping procedures, along with a
system of collection trenches, if necessary, should be capable of maintaining a relatively dry excavation for
construction purposes.
This information is provided solely for the benefit of the owner and other design consultants and should not be
construed to imply that Terra Associates, Inc. assumes responsibility for job site safety. It is understood that job
site safety is the sole responsibility of the project contractor.
4.4 Foundations
The building may be supported on conventional spread footing foundations bearing on competent native soils or on
structural fill placed above competent soils. Foundation subgrades should be prepared as recommended in Section
4.2 of this report. Foundations exposed to the weather should bear at a minimum depth of one and one-half feet
below adjacent exterior grades for frost protection. Interior foundations should be supported at a minimum depth
of one foot below the finished floor elevation.
The existing fill soils and native soils will be easily disturbed by normal construction activity particularly when wet.
Care will need to be exercised during construction to avoid excessively disturbing the subgrade. If disturbed, the
material should be removed, and footings lowered to undisturbed material or grade restored with structural fill.
During wet-weather conditions,to avoid disturbance,consideration should be given to protecting the fill foundation
subgrade with a four-inch layer of crushed rock or lean mix concrete.
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Project No. T-9205
We recommend designing foundations bearing on competent structural fill soils for a net allowable bearing capacity
of 3,000 pounds per square foot(psf). Foundations that are supported on competent native soils below the fills can
be designed for and allowable bearing capacity of 5,000 psf. For short-term loads,such as wind and seismic,a one-
third increase in this allowable capacity can be used. With the expected building loads and this bearing stress
applied, in general, total, and differential settlements should not exceed one inch and one-half inch, respectively.
Settlements will occur in and immediate nature as building loads are applied. The one-half inch differential
settlement would be expected to occur between isolated interior columns and perimeter continuous footings.
For designing foundations to resist lateral loads, a base friction coefficient of 0.35 can be used. Passive earth
pressures acting on the sides of the footings should be considered. We recommend calculating this lateral resistance
using an equivalent fluid weight of 350 pounds per cubic foot(pcf). We do not recommend including the upper 12
inches of soil in this computation because it can be affected by weather or disturbed by future grading activity. This
value assumes the foundation will be backfilled with structural fill, as described in Section 4.2 of this report. The
values recommended include a safety factor of 1.5.
4.5 Slab-on-Grade Floors
Slab-on-grade floors may be supported on a subgrade prepared as recommended in Section 4.2 of this report.
Immediately below the floor slab,we recommend placing a four-inch-thick capillary break layer composed of clean,
coarse sand or fine gravel that has less than five percent passing the No. 200 sieve. This material will reduce the
potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor
slab.
The capillary break layer will not prevent moisture intrusion through the slab caused by water vapor transmission.
Where moisture by vapor transmission is undesirable, such as covered floor areas, a common practice is to place a
durable plastic membrane on the capillary break layer and then cover the membrane with a layer of clean sand or
fine gravel to protect it from damage during construction, and aid in uniform curing of the concrete slab. It should
be noted that if the sand or gravel layer overlying the membrane is saturated prior to pouring the slab, it will be
ineffective in assisting uniform curing of the slab and can actually serve as a water supply for moisture seeping
through the slab and affecting floor coverings. Therefore, in our opinion, covering the membrane with a layer of
sand or gravel should be avoided if floor slab construction occurs during the wet winter months and the layer cannot
be effectively drained. We recommend floor designers and contractors refer to the current American Concrete
Institute(ACI)Manual of Concrete Practice for further information regarding vapor barrier installation below slab-
on-grade floors.
4.6 Lateral Earth Pressures for Retaining Walls
The magnitude of earth pressures developing on below-grade walls will depend upon the quality and compaction
of the wall backfill. We recommend placing and compacting wall backfill as structural fill,as described in Section
4.2 of this report. To prevent overstressing the walls during backfilling,heavy construction machinery should not
be operated within five feet of the wall. Wall backfill in this zone should be compacted with hand-operated
equipment. To prevent hydrostatic pressure development, wall drainage must also be installed. A typical wall
drainage detail is shown on Figure 3.
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Project No. T-9205
With wall backfill placed and compacted as recommended, and drainage properly installed, we recommend
designing unrestrained walls for an active earth pressure equivalent to a fluid weighing 35 pounds per cubic foot
(pcf). For restrained walls, an additional uniform load of 100 psf should be added to the 35 pcf. To account for
typical traffic surcharge loading,the walls can be designed for an additional imaginary height of two feet(two-foot
soil surcharge). For evaluation of wall performance under seismic loading, a uniform pressure equivalent to 8H
psf,where H is the height of the below-grade portion of the wall, should be applied in addition to the static lateral
earth pressure. These values assume a horizontal backfill condition and that no other surcharge loading, sloping
embankments, or adjacent buildings will act on the wall. If such conditions exist, then the imposed loading must
be included in the wall design. Friction at the base of foundations and passive earth pressure will provide resistance
to these lateral loads. The values for these parameters are provided in Section 4.4 of this report.
4.7 Stormwater Facilities/Infiltration Feasibility
Based on the preliminary grading and drainage plan by Barghausen Consulting Engineers,development stormwater
will be routed to infiltration galleries located below the western pavement areas. In our subsurface exploration,we
observed predominantly dense till like soils composed of silty sand with gravel to the termination of the test borings.
The native weathered and unweathered till like deposits at the site contain a significant amount of soil fines and is
a poorly drained soil unit. These soil conditions are not suitable for discharge of development stormwater using
infiltration facilities. Conventional stormwater detention with controlled release to existing stormwater
infrastructure should be used to manage development stormwater.
Detention Vault
If onsite detention is provided by a buried vault,we expect the bottom of the excavation would likely expose native,
dense to very dense silty sand with gravel or very stiff to hard silt with sand and gravel. Vault foundations supported
by these native soils may be designed for an allowable bearing capacity of 5,000 psf provided that the foundation
subgrade is at least eight feet below current site grades. For short-term loads, such as seismic, a one-third increase
in this allowable capacity can be used. Wet subgrade conditions that are easily disturbed by construction traffic
will be exposed at the bottom of the vault excavation.
Vault walls should be designed as below-grade retaining walls following the parameters outline in Section 4.6 of
this report. Any portion of the wall for which drainage cannot be provided should be designed for an earth pressure
equivalent to a fluid weighing 85 pcf. Where applicable, a uniform horizontal traffic value of 75 psf should be
included in the design of vault walls.
Detention Pond
If fill berms are constructed,the berm locations should be stripped of topsoil,duff,and soils containing organic material
prior to the placement of fill. The fill berms should be constructed by placing structural fill in accordance with
recommendations outlined in Section 4.2 of this report. Material used to construct pond berms should consist
predominately of granular soils with a maximum size of 3 inches and a minimum of 20 percent fines. Terra
Associates, Inc. should examine and test all onsite or imported materials proposed for use as a fill berm prior to
their use.
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Project No. T-9205
In our opinion,establishing the interior pond slopes at a 3:1 (Horizontal:Vertical)gradient will significantly reduce
or eliminate the risk of periodic shallow instability or sloughing of the exposed soils due to fluctuating stored water
levels. Finished slope faces should be thoroughly compacted and vegetated to guard against erosion.
We should review the stormwater plans when they are completed and revise our recommendations, if required.
4.8 Drainage
Surface
Final exterior grades should promote free and positive drainage away from the building areas. We recommend
providing a positive drainage gradient away from the building perimeters. If a positive gradient cannot be provided,
provisions for collection and disposal of surface water adjacent to the structures should be provided.
Subsurface
We recommend installing a continuous drain along the outside lower edge of the perimeter building foundations.
The drains can be laid to grade at an invert elevation equivalent to the bottom of footing grade. The drains can
consist of four-inch diameter perforated PVC pipe that is enveloped in washed one half-to three-quarter-inch gravel-
sized drainage aggregate. The aggregate should extend six inches above and to the sides of the pipe. The foundation
drains and roof downspouts should be tightlined separately to an approved point of controlled discharge. All drains
should be provided with cleanouts at easily accessible locations. These cleanouts should be serviced at least once
each year.
4.9 Utilities
Utility pipes should be bedded and backfilled in accordance with American Public Works Association(APWA) or
City of Arlington specifications. At minimum,trench backfill should be placed and compacted as structural fill as
described in Section 4.2 of this report. As noted, soils excavated onsite should generally be suitable for use as
backfill material provided, they are near optimum moisture when excavated and are placed during dry weather
conditions. However, the site soils are fine grained and moisture sensitive; therefore, moisture conditioning may
be necessary to facilitate proper compaction. If utility construction takes place during the winter, it may be
necessary to import suitable wet-weather fill for utility trench backfilling.
4.10 Pavements
Pavements should be constructed on subgrades prepared as recommended in Section 4.2 of this report. Regardless
of the degree of relative compaction achieved, the subgrade must be firm and relatively unyielding before paving.
Proof-rolling the subgrade with heavy construction equipment should be completed to verify this condition.
The pavement design section is dependent upon the supporting capability of the subgrade soils and the traffic
conditions to which it will be subjected.
Page No. 10
August 19,2025
Project No. T-9205
For traffic consisting mainly of light passenger vehicles with only occasional heavy traffic, and with a stable
subgrade prepared as recommended,we recommend the following pavement sections:
• Two inches of hot mix asphalt(HMA)over six inches of crushed rock base (CRB).
• Four inches full depth HMA over prepared subgrade.
The paving materials used should conform to the Washington State Department of Transportation (WSDOT)
specifications for%2-inch class HMA and CRB.
Long-term pavement performance will depend upon surface drainage. A poorly drained pavement section will be
subject to premature failure as a result of surface water infiltrating into the subgrade soils and reducing their
supporting capability. For optimum pavement performance, we recommend surface drainage gradients of at least
two percent. Some degree of longitudinal and transverse cracking of the pavement surface should be expected over
time. Regular maintenance should be planned to seal cracks when they occur.
5.0 ADDITIONAL SERVICES
Terra Associates, Inc., should review the final designs and specifications in order to verify that earthwork and
foundation recommendations have been properly interpreted and implemented in project design. We should also
provide geotechnical services during construction in order to observe compliance with our design concepts,
specifications,and recommendations. This will allow for design changes if subsurface conditions differ from those
anticipated prior to the start of construction.
6.0 LIMITATIONS
We prepared this report in accordance with generally accepted geotechnical engineering practices. No other
warranty, expressed or implied, is made. This report is the copyrighted property of Terra Associates, Inc. and is
intended for specific application to the NWC 212th St. NE Medical Office Facility project in Arlington,
Washington. This report is for the exclusive use of Visconsi Companies. Ltd and their authorized representatives.
No other warranty, expressed or implied,is made.
The analyses and recommendations presented in this report are based on data obtained from our onsite test pits.
Variations in soil conditions can occur,the nature and extent of which may not become evident until construction.
If variations appear evident, Terra Associates, Inc. should be requested to reevaluate the recommendations in this
report prior to proceeding with construction.
Page No. 11
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REFERENCE: https://www.bing.com/maps~ ACCESSED 2025
Terra VICINITY MAP
NWC 212 ST. NE MEDICAL OFFICE FACILITY
Associates, Inc. ARLINGTON, WASHINGTON
Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences Proj.No. T-9205 Date: AUG 2025 Figure 1
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NOTE: LEGEND:
THIS SITE PLAN IS SCHEMATIC. ALL LOCATIONS AND & APPROXIMATE BORING LOCATION
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REFERENCE ONLY AND SHOULD NOT BE USED FOR
DESIGN OR CONSTRUCTION PURPOSES.
APPROXIMATE SCALE IN FEET
REFERENCE:SITE PLAN PROVIDED BY BING MAPS.
Terra EXPLORATION LOCATION PLAN
NWC 212 ST. NE MEDICAL OFFICE FACILITY
Associates, Inc. ARLINGTON, WASHINGTON
Consultants in Geotechnical Engineering
Geology and Pro No. T-9205 Date: AUG 2025 Figure2
Environmental Earth Sciences �•
12" MINIMUM 3/4"
MINUS WASHED
GRAVEL SLOPE TO DRAIN
12"
............................................................... .............................................
j
COMPACTED j
n STRUCTURAL FILL ;: ;::: /
..%
i
...
SEE NOTE
"' EXCAVATED SLOPE
EE REP
(SORT
TEXT
FOR APPROPRIATE
6"(MIN.) ............................................... INCLINATIONS)
G
0 0 0 0 0 12" OVER PIPE
3" BELOW PIPE
4" DIAMETER PERFORATED PVC PIPE
NOT TO SCALE
NOTE:
MIRADRAIN G100N PREFABRICATED DRAINAGE PANELS OR SIMILAR
PRODUCT CAN BE SUBSTITUTED FOR THE 12-INCH WIDE GRAVEL
DRAIN BEHIND WALL. DRAINAGE PANELS SHOULD EXTEND A MINIMUM
OF SIX INCHES INTO 12-INCH THICK DRAINAGE GRAVEL LAYER
OVER PERFORATED DRAIN PIPE.
Terra TYPICAL WALL DRAINAGE DETAIL
NWC 212 ST. NE MEDICAL OFFICE FACILITY
Associates, Inc. ARLINGTON, WASHINGTON
Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences Proj.No. T-9205 Date: AUG 2025 Figure 3
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
NWC 212 Street NE Medical Office Building
Arlington,Washington
On August 4, 5, and 6, 2025, we observed soil and groundwater conditions in nine test borings advanced with
a hollow-stem auger to maximum depths of approximately 50 feet below existing site grades. The test
boring locations were approximately determined in the field using GPS coordinates and by sighting and
pacing from existing surface features. The approximate test boring locations are shown on Figure 2. The Test
Boring Logs are presented as Figures A-2 through A-10.
A geologist from our office conducted the field exploration. Our representative classified the soil conditions
encountered, maintained a log of each test boring, obtained representative soil samples, and recorded water
levels observed during drilling. During drilling, soil samples were obtained in general accordance with
ASTM Test Designation D-1586. Using this procedure, a 2-inch(outside diameter) split barrel sampler is driven
into the ground 18 inches using a 140-pound hammer free falling from a height of 30 inches. The number of
blows required to drive the sampler 12 inches after an initial 6-inch set is referred to as the Standard Penetration
Resistance value or N value. This is an index related to the consistency of cohesive soils and relative density of
cohesionless materials.N values obtained for each sampling interval are recorded on the Test Boring Logs,Figures
A-2 through A-10. All soil samples were visually classified in accordance with the Unified Soil Classification
System (USCS) described on Figure A-1.
Representative soil samples obtained from the test borings were placed in sealed plastic bags and taken to our
laboratory for further examination and testing. The moisture content of each sample was measured and is reported
on the individual Boring Logs. Grain size analyses were performed on select soil samples. The results are shown
on Figures A-11 and A-12.
Project No. T-9205
MAJOR DIVISIONS LETTER TYPICAL DESCRIPTION
SYMBOL
Clean GW Well-graded gravels, gravel-sand mixtures, little or no fines.
GRAVELS Gravels (less
L than 5%
co ��, More than 50% fines) GP Poorly-graded gravels, gravel-sand mixtures, little or no fines.
O co N of coarse fraction
CO —E is larger than No. GM Silty gravels, gravel-sand-silt mixtures, non-plastic fines.
m > 4 sieve Gravels with
Z Co I fines
Q E o GC Clayey gravels, gravel-sand-clay mixtures, plastic fines.
o 0
O oLO o Clean Sands SW Well-graded sands, sands with gravel, little or no fines.
LU
(n cca z SANDS (less than
Q M More than 50% 5%fines) Sp Poorly-graded sands, sands with gravel, little or no fines.
O o of coarse fraction
V :2 is smaller than SM Silty sands, sand-silt mixtures, non-plastic fines.
No. 4 sieve Sands with
fines SC Clayey sands, sand-clay mixtures, plastic fines.
L
ML Inorganic silts, rock flour, clayey silts with slight plasticity.
U .� SILTS AND CLAYS
p Tv Liquid Limit is less than 50% CL Inorganic clays of low to medium plasticity. (Lean clay)
Cn
0 c"o '(n OL Organic silts and organic clays of low plasticity.
LU Eo
Z
Q \o N MH Inorganic silts, elastic.
W U-) o
CD , z SILTS AND CLAYS
w ° CH Inorganic clays of high plasticity. (Fat clay)
Z . M Liquid Limit is greater than 50%
o OH Organic clays of high plasticity.
HIGHLY ORGANIC SOILS PT Peat.
DEFINITION OF TERMS AND SYMBOLS
Standard Penetration 2"OUTSIDE DIAMETER SPILT SPOON SAMPLER
w Density Resistance in Blows/Foot
z 2.4" INSIDE DIAMETER RING SAMPLER OR
O Very Loose 0-4 SHELBY TUBE SAMPLER
U) Loose 4-10
= Medium Dense 10-30 1 WATER LEVEL(Date)
O Dense 30-50
U Very Dense >50
Tr TORVANE READINGS,tsf
Standard Penetration Pp PENETROMETER READING, tsf
Consistancy Resistance in Blows/Foot
w DD DRY DENSITY, pounds per cubic foot
U) Very w Soft Soft 0_� LL LIQUID LIMIT, percent
2
O Medium Stiff 4-8
U Stiff 8-16 PI PLASTIC INDEX
Very Stiff 16-32
Hard >32 N STANDARD PENETRATION, blows per foot
Terra UNIFIED SOIL CLASSIFICATION SYSTEM
NWC 212 ST. NE MEDICAL OFFICE FACILITY
Associates, Inc. ARLINGTON, WASHINGTON
Consultants in Geotechnical Engineering
Geology and Pro .No. T-9205 Date: AUG 2025 Figure A-1
Environmental Earth Sciences � g
LOG OF BORING NO. B-1 Figure No.A-2
Project: NWC 212 St. NE Medical Office Facility Project No:T-9205 Date Drilled: August 5, 2025
Client:Visconsi Companies Ltd. Driller: BoreTec1 Logged By: MEP
Location: Arlington, Washington Depth to Groundwater:N/A Approx. Elev: NA
m
Soil Description
Consistency/ SPT(N) Moisture
a Relative Density Blows/foot Content(%)
Q E
Q <n 10 30 50
0
Grayish-brown silty SAND with gravel,fine to coarse sand,
fine to coarse gravel, moist, mottled. (SM)
• 16
5 • 16 15.0
Medium Dense
• 15 13.2
*Became wet at 7.5 feet.
10 • 13 9.5
Boring terminated at 10 feet.
Minor perched seepage observed at approximately 10 feet.
15
Terra
NOTE:This borehole log has been prepared for geotechnical purposes. This information
pertains only to this boring location and should not be interpeted as being indicative of Associates, Inc.
Ic.
other areas of the site
Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
LOG OF BORING NO. B-2 Figure No.A-3
Project: NWC 212 St. NE Medical Office Facility Project No:T-9205 Date Drilled: August 5, 2025
Client:Visconsi Companies Ltd. Driller: BoreTec1 Logged By: MEP
Location: Arlington, Washington Depth to Groundwater:N/A Approx. Elev: NA
m
Soil Description
Consistency/ SPT(N) Moisture
a Relative Density Blows/foot Content(%)
Q E
Q <n 10 30 50
0
FILL?: Brown silty SAND with gravel,fine to coarse sand,fine
to coarse gravel, dry to moist, scattered rootlets. (SM)
Medium Dense
• 13 20.8
5 • 7 9.0
Loose
---------------------------------------------
Grayish-brown silty SAND with gravel,fine to coarse sand, . 16 18.5
fine to coarse gravel, moist, mottled. (SM)
Medium Dense
10 49 12.0
Dense
Boring terminated at 10 feet.
Minor seepage observed at 10.5 feet deep.
15
. Terra
NOTE:This borehole log has been prepared for geotechnical purposes. This information
pertains only to this boring location and should not be interpeted as being indicative of Associates, Inc.
Ic.
other areas of the site
Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
LOG OF BORING NO. B-3 Figure No.A-4
Project: NWC 212 St. NE Medical Office Facility Project No:T-9205 Date Drilled: August 5, 2025
Client:Visconsi Companies Ltd. Driller: BoreTec1 Logged By: MEP
Location: Arlington, Washington Depth to Groundwater:N/A Approx. Elev: NA
m
Soil Description
Consistency/ SPT(N) Moisture
a Relative Density Blows/foot Content(%)
Q E
Q <n 10 30 50
0
Brown silty SAND with gravel,fine to coarse sand,fine gravel,
dry to moist, scattered rootlets(SM)
Loose
• 7 15.0
Grayish-brown silty SAND with gravel,fine to coarse sand,
5 fine to coarse gravel, moist, mottled. (SM) • 42 12.1
Dense
53 10.7
Very Dense
10 • 42 10.5
Dense
Boring terminated at 10 feet.
No groundwater seepage observed.
15
. Terra
NOTE:This borehole log has been prepared for geotechnical purposes. This information
pertains only to this boring location and should not be interpeted as being indicative of Associates, Inc.
Ic.
other areas of the site
Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
LOG OF BORING NO. B-4 Figure No.A-5
Project: NWC 212 St. NE Medical Office Facility Project No:T-9205 Date Drilled: August 5, 2025
Client:Visconsi Companies Ltd. Driller: BoreTec1 Logged By: MEP
Location: Arlington, Washington Depth to Groundwater:N/A Approx. Elev: NA
m
Soil Description
Consistency/ SPT(N) Moisture
a p Relative Density Blows/foot Content(%)
;= E
Q <n 10 30 50
0
FILL?: Brown silty SAND with gravel,fine to coarse sand,fine
gravel, dry to moist. (SM) Dense 31 10.5
I *Scattered rootlets in the upper 4 feet.
5 1 T • 8 17.5
ILoose 5 20.9
6 20.9
10 1 T .(4-inches organic TOPSOIL with scattered straw)
IGrayish-brown silty SAND with gravel,fine to coarse sand, Dense • 44 8.6
fine to coarse gravel, moist to wet, mottled. (SM)
15 1 T 50/3" 20.8
---------------------------------------------
Gray silty SAND with gravel,fine to coarse sand, fine to Very Dense
20 I coarse gravel, moist. (SM) 65 10.3
25 T 20 10.1
1 Medium Dense
30 T Very Dense 50/6"
1 Boring terminated at 30 feet.
No groundwater seepage observed.
35
40
. Terra
NOTE:This borehole log has been prepared for geotechnical purposes. This information
pertains only to this boring location and should not be interpeted as being indicative of Associates, Inc.
Ic.
other areas of the site
Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
LOG OF BORING NO. B-5 Figure No.A-6
Project: NWC 212 St. NE Medical Office Facility Project No:T-9205 Date Drilled: August 4, 2025
Client:Visconsi Companies Ltd. Driller: BoreTec1 Logged By: MEP
Location: Arlington, Washington Depth to Groundwater:50 feet Approx. Elev: NA
m
Soil Description
Consistency/ SPT(N) Moisture
a Relative Density Blows/foot Content(%)
Q E
Q <n 10 30 50
0
Grayish-brown silty SAND with gravel,fine to coarse sand,
fine to coarse gravel, dry to moist, mottled. (SM) Dense • 44 11.0
I
5 I *Scattered rootlets in the upper 4 feet. Very Dense 55 10.2
•I Medium Dense 25 11.7
10 I *Moist to wet below 7.5 feet. • 32 11.6
I
Dense 50 9.5
15 I • 47 13.4
20 I --------------------------------------------- • 16 16.7
Gray silty SAND with gravel,fine to medium sand, fine to
coarse gravel,wet. (SM)
25 I • 14 12.6
*1"interbeds of fine to medium sand at approximately 25 feet Medium Dense
deep.
30 I • 18 11.7
35 I • 28 11.8
40 Dense • 36 10.4
r-------------------------------------------
45 I Gray silty SAND,fine to coarse sand,wet, trace fine gravel. 50/6" 16.6
(SM) Very Dense
s50 Gray SILT with sand and gravel,fine to medium sand,fine to 52 14.2
I coarse gravel,wet to saturated, 1-2-inch interbeds of medium
to coarse sand. (ML)
55 Boring terminated at 50 feet.
Groundwater seepage observed at 50 feet.
60
. Terra
NOTE:This borehole log has been prepared for geotechnical purposes. This information
pertains only to this boring location and should not be interpeted as being indicative of Associates, Inc.
Ic.
other areas of the site
Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
LOG OF BORING NO. B-6 Figure No.A-7
Project: NWC 212 St. NE Medical Office Facility Project No:T-9205 Date Drilled: August 6, 2025
Client:Visconsi Companies Ltd. Driller: BoreTec 1 Logged By: MEP
Location: Arlington,Washington Depth to Groundwater:NA Approx. Elev: NA
m
Z
c Soil Description Consistency/ SPT(N) Moisture Observ.
v � o
� Q
Relative Density Blows/foot Content(/o) Well
a E
o in 10 30 50
0
Grayish-brown silty SAND with gravel, fine to coarse
sand,fine to coarse gravel, moist, mottled. (SM)
*Scattered rootlets in the upper 4 feet. Very Dense 54 9.9
I
5 I • 23 10.8
• 27 12.1
I
---------------------------------------- Medium Dense
10— Gray silty SAND with gravel,fine to coarse sand,fine to • 16 16.0
coarse gravel,wet. (SM)
• 26 13.0
I
15 50/4" 11.8
I Very Dense
*2-3"interbeds of fine to medium sand at approximately
20 20 feet deep. Medium Dense . 17 14.2
I
Test Boring terminated at approximately 20 feet.
2" PVC monitoring well constructed with a 0.010 slot
screen from 10 to 20 feet.
Samples collected by driving a 2.5 inch O.D.sampler
25 with a 140-pound hammer.
Well Tag#BQU-132
No groundwater seepage observed.
30
Terra
NOTE:This borehole log has been prepared for geotechnical purposes. This information Associates Inc.
pertains only to this boring location and should not be interpeted as being indicative of 7
other areas of the site Consultants in otechnical Engineering
Geology and
Environmental Earth Sciences
LOG OF BORING NO. B-7 Figure No.A-8
Project: NWC 212 St. NE Medical Office Facility Project No:T-9205 Date Drilled: August 4, 2025
Client:Visconsi Companies Ltd. Driller: BoreTec1 Logged By: MEP
Location: Arlington, Washington Depth to Groundwater:35 feet Approx. Elev: NA
m
Soil Description
Consistency/ SPT(N) Moisture
a p Relative Density Blows/foot Content(%)
;= E
Q <n 10 30 50
0
FILL: Brown silty SAND with gravel,fine to coarse sand,fine
I to coarse gravel, moist, occasional charcoal fragments, 9 8
scattered rootlets. (SM)5 Loose • 6 14.7
I
I FILL?: Light brown SILT, moist, mottled, scattered gravel. (ML) • 8 39.4
----------------------------------------------
10 I Grayish-brown silty SAND with gravel,fine to coarse sand, Very Dense 55 15.5
fine to coarse gravel, moist, mottled. (SM) • 23 14.1
I Medium Dense
15 I • 36 13.8
3-4-inch interbed of silt at 15 feet deep.
20 Dense 50 9.6
I
25 Gray silty SAND with gravel,fine to coarse sand, fine gravel, 10 41 10.9
I moist to wet. (SM)
30 I 41 72 9.9
Very Dense
=35 I 50/6" 12.6
40 I Medium Dense • 25 11.6
45 I Very Dense 52 10.3
50 Medium Dense • 25 12.6
I
Boring terminated at 50 feet.
55 Light seepage observed at 35 feet.
60
. Terra
NOTE:This borehole log has been prepared for geotechnical purposes. This information
pertains only to this boring location and should not be interpeted as being indicative of Associates, Inc.
Ic.
other areas of the site
Consultants in Geotechnical Engineering
Geology and
Environmental Earth Sciences
LOG OF BORING NO. B-8 Figure No.A-9
Project: NWC 212 St. NE Medical Office Facility Project No:T-9205 Date Drilled: August 5, 2025
Client:Visconsi Companies Ltd. Driller: BoreTec1 Logged By: MEP
Location: Arlington,Washington Depth to Groundwater:NA Approx. Elev: NA
m
Z
c Soil Description Consistency/ SPT(N) Moisture Observ.
v � o
� Q
Relative Density Blows/foot Content(/o) Well
a E
o in 10 30 50
0
Grayish-brown silty SAND with gravel, fine to coarse
sand,fine to coarse gravel, moist, mottled. (SM) Very Loose
2 19.8
T
5 I 20 11.9
I Medium Dense 16 12.1
10 I 30 12.3
T 50/6"
*1-2-inch interbed of fine to medium sand at 13 feet. Very Dense
15 T Gray silty SAND with gravel,fine to coarse sand,fine 29 10.9
gravel, moist to wet. (SM)
Medium Dense
20 I 29 10.2
25 I Very Dense 53 8.7
Test Boring terminated at approximately 25 feet.
2" PVC monitoring well constructed with a 0.010 slot
screen from 15 to 25 feet.
30 Samples collected by driving a 2.5 inch O.D.sampler
with a 140-pound hammer.
Well Tag#BQU-131
No groundwater seepage observed.
35
Terra
NOTE:This borehole log has been prepared for geotechnical purposes. This information Associates Inc.
pertains only to this boring location and should not be interpeted as being indicative of 7
other areas of the site Consultants in otechnical Engineering
Geology and
Environmental Earth Sciences
LOG OF BORING NO. B-9 Figure No.A-10
Project: NWC 212 St. NE Medical Office Facility Project No:T-9205 Date Drilled: August 6, 2025
Client:Visconsi Companies Ltd. Driller: BoreTec1 Logged By: MEP
Location: Arlington,Washington Depth to Groundwater:NA Approx. Elev: NA
m
Z
c Soil Description Consistency/ SPT(N) Moisture Observ.
v � o
� Q
Relative Density Blows/foot Content(/o) Well
a E
o in 10 30 50
0
Grayish-brown silty SAND with gravel, fine to coarse
sand,fine to coarse gravel, moist, mottled. (SM)
Dense
• 27 12.2
I
5 65 11.0
I
Very Dense
67 9.4
I
I10 Gray silty SAND with gravel,fine to coarse sand,fine to • 45 10.8 coarse gravel, moist to wet. (SM)
• 32 11.8
I Dense
Lm I
15 • 45 11.5
I
Test Boring terminated at approximately 15 feet.
2" PVC monitoring well constructed with a 0.010 slot
screen from 5 to 15 feet.
Samples collected by driving a 2.5 inch O.D.sampler
with a 140-pound hammer.
20
Well Tag#BQU-133
No groundwater seepage observed.
25
Terra
NOTE:This borehole log has been prepared for geotechnical purposes. This information Associates Inc.
pertains only to this boring location and should not be interpeted as being indicative of 7
other areas of the site Consultants in otechnical Engineering
Geology and
Environmental Earth Sciences
Particle Size Distribution Report
C C O O O
C C C C 1Z , .0 .0 pp QQ O N M Q0Q 0 a � N
W M
100
I I I I I I I I l l l l
I I I I I I I I
so I i I
I I I I I I 1 I
I I I I I I I
80 I I I I I I I I I I I I
I I I I I I I I I I I I I
70 I I I I I I I I I I
I I I I I I I I I I I I I I
I I I I I I I I I I I I I
W 60 I I I I I I I I
Z I I I I I I I
LL
I I I I I I
Z 50 I I I I I I I
w I I I I I I I I I I I I I I
W 40 1 1 I
I I I I I I I I I I I
I I I I I I I I I I I I I I
30
I I I I I I I I l I I I I
I I I I I I I I I I I I I
20
I I I I I I I I I I I I I I
I I I I I I I I I I I I I I
10
I I I I I I I I I I I I I I
I I I I I I I I I I I I I I
0
100 10 1 0.1 0.01 0.001
GRAIN SIZE-mm.
%+3„ %Gravel %"Sand %Fines
Coarse Fine Coarse Medium Fine Silt Clay
0 0.0 1.6 18.2 8.2 14.0 21.1 36.9
11 0.0 0.0 2.9 4.4 7.1 61.7 23.9
0 0.0 7.0 13.4 9.5 1 19.0 26.0 25.1
LL PL D Dan D_qn D30 DI r, Din C C
0 7.9936 0.5135 0.2292
❑ 0.3547 0.1966 0.1731 0.1197
0 8.2177 I 0.8276 1 0.4000 0.1457
Material Description USCS AASHTO
o silty SAND with gravel SM
❑ silty SAND SM
o silty SAND with gravel SM
Project No. T-9205 Client: Visconsi Companies Ltd. Remarks:
Project: NWC 212 St NE Medical Office Facility oTested on August 13,2025
❑Tested on August 13,2025
0 Location: Test Boring B-4 Depth: 25 feet Sample Number: 8 oTested on August 13,2025
❑ Location: Test Boring B-5 Depth: 45 feet Sample Number: 12
o Location: Test Bonn-,B-6 Depth: 20 feet Sample Number: 7
Terra Associates, Inc.
Kirkland, WA Figure A-11
Tested By: ZA
Particle Size Distribution Report
C C 0 0 0
C C C � C ._ C O 0 0 0- 0
IIIIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIIIIl IIIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIII IIIIIIIIIIIIIIIII MIIIIIIIIIIIIIIIII
IIIt 3t_ aIIIIIIIIIIIIIIII!
# IIIIIIIIIIIII it
100 I
90
80
7o
Ws ZILLZ50
w�a_ 40
30
20 IIIIIIIIIIIIIIIII XIIIIIIIIIIIIIIIIIk
XIIIIIIIIIIIIIIIIIk
�IIIIIIIIIIIIIIk
_
I I I I I I I I I I I I I I
cli
I I I I I I I I I I I I I I
10
I I I I I I I I I I I I I I
I I I I I I I I I I I I I I
0
100 10 1 0.1 0.01 0.001
GRAIN SIZE-mm.
%+3" %Gravel %Sand %Fines
Coarse Fine Coarse Medium Fine Silt Clay
0 0.0 0.8 17.3 14.8 19.2 16.8 31.1
❑ 0.0 0.0 17.7 9.2 14.1 20.8 38.2
Al0.0 7.2 I 12.9 6.8 11.5 20.5 41.1
LL PL D Do Do D30 DIS D10 C C
0 6.0222 1.2156 0.5146
11 6.3012 I 0.4693 0.2149
0 8.8218 0.3575 0.1744
Material Description USCS AASHTO
o silty SAND with gravel SM
❑ silty SAND with gravel SM
* silty SAND with gravel SM
Project No. T-9205 Client: Visconsi Companies Ltd. Remarks:
Project: NWC 212 St NE Medical Office Facility oTested on August 13,2025
❑Tested on August 13,2025
o Location: Test Boring B-7 Depth: 35 feet Sample Number: 9 oTested on August,13,2025
❑ Location: Test Boring B-8 Depth: 25 feet Sample Number: 7
o Location: Test Boring B-9 Depth: 15 feet Sample Number: 6
Terra Associates, Inc.
Kirkland, WA Figure A-12
Tested By: ZA