HomeMy WebLinkAboutEX_03_RP_CUP_Geotech_Report_241112_v1Geotechnical Engineering Services
Fire Station 16 Replacement
15815 SE 128th Street
Renton, Washington
for
Renton Regional Fire Authority
August 5, 2022
EXHIBIT 3
RECEIVED
12/17/2024 JDing
PLANNING DIVISION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
Geotechnical Engineering Services
Fire Station 16 Replacement
15815 SE 128th Street
Renton, Washington
for
Renton Regional Fire Authority
August 5, 2022
17425 NE Union Hill Road, Suite 250
Redmond, Washington 98052
425.861.6000
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
August 5, 2022 | Page i File No. 26016-001-00
Table of Contents
1.0 INTRODUCTION ........................................................................................................................................... 1
2.0 SCOPE OF SERVICES .................................................................................................................................. 1
3.0 FIELD EXPLORATIONS AND LABORATORY TESTING ................................................................................ 1
3.1. Field Explorations .................................................................................................................................... 1
3.2. Laboratory Testing .................................................................................................................................. 1
4.0 SITE CONDITIONS ........................................................................................................................................ 2
4.1. Area Geology ........................................................................................................................................... 2
4.2. Surface Conditions.................................................................................................................................. 2
4.3. Subsurface Conditions ........................................................................................................................... 2
4.4. Groundwater ........................................................................................................................................... 3
4.5. Geologically Hazardous Areas ................................................................................................................ 3
5.0 CONCLUSIONS AND RECOMMENDATIONS ............................................................................................... 4
5.1. Earthquake Engineering ......................................................................................................................... 6
5.1.1. Seismicity ..................................................................................................................................... 6
5.1.2. 2018 IBC Seismic Design Information ....................................................................................... 6
5.1.3. Liquefaction Potential ................................................................................................................. 7
5.1.4. Other Seismic Hazards ................................................................................................................ 7
5.2. Shallow Foundations .............................................................................................................................. 7
5.2.1. Foundation Settlement ............................................................................................................... 8
5.2.2. Lateral Resistance ....................................................................................................................... 8
5.3. Slab-On-Grade Floors .............................................................................................................................. 8
5.4. Below-Grade Walls and Retaining Walls ................................................................................................ 9
5.4.1. Design Parameters ...................................................................................................................... 9
5.4.2. Wall Drainage ............................................................................................................................ 10
5.5. Earthwork .............................................................................................................................................. 10
5.5.1. Clearing and Site Preparation ................................................................................................... 11
5.5.2. Subgrade Preparation ............................................................................................................... 11
5.5.3. Temporary Slopes and Construction Dewatering .................................................................... 12
5.5.4. Permanent Slopes ..................................................................................................................... 12
5.6. Structural Fill ......................................................................................................................................... 13
5.6.1. Materials .................................................................................................................................... 13
5.6.2. Use of On-site Soils.................................................................................................................... 13
5.6.3. Fill Placement and Compaction Criteria ................................................................................... 13
5.6.4. Weather Considerations ........................................................................................................... 14
5.6.5. Utility Trenches .......................................................................................................................... 15
5.6.6. Sedimentation and Erosion Control ......................................................................................... 15
5.7. Drainage Considerations ...................................................................................................................... 16
5.8. Pavement Design .................................................................................................................................. 16
5.9. Stormwater Infiltration Considerations................................................................................................ 17
6.0 DESIGN REVIEW AND CONSTRUCTION SERVICES ................................................................................. 17
7.0 LIMITATIONS ............................................................................................................................................. 17
8.0 REFERENCES ............................................................................................................................................ 18
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LIST OF FIGURES
Figure 1. Vicinity Map
Figure 2. Site Plan
APPENDICES
Appendix A. Field Explorations
Figure A-1 – Key to Exploration Logs
Figures A-2 through A-11 – Log of Borings
Appendix B. Laboratory Testing
Figures B-1 and B-2 – Sieve Analysis Results
Appendix C. Report Limitations and Guidelines for Use
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1.0 INTRODUCTION
GeoEngineers, Inc. (GeoEngineers) is pleased to submit this geotechnical engineering report for the Renton
Regional Fire Authority (RRFA) Station 16 replacement project to be located at 15815 SE 128th Street in
Renton, Washington. The site consists of three King County parcels (366450-0007, 366450-0008 and
366450-0009) totaling approximately 3 acres located on the south side of SE 128th Street, just east of
158th Avenue SE. The property extends roughly 200 feet along SE 128th Street and just over 600 feet to
the south. The location of the site is shown in the Vicinity Map, Figure 1.
We understand that the project concept consists of a new fire station building located in the north area of
the site, a detached maintenance garage with five bays in the southeast area and surrounding drive aisles
and parking areas. We anticipate that the fire station will be a two-story building, and that the detached
maintenance garage will be a one-story building. Site development may also include infiltration facilities
depending on feasibility. A site plan showing the conceptual overlay on the existing site features is included
as Figure 2.
2.0 SCOPE OF SERVICES
The purpose of our services is to evaluate subsurface soil and groundwater conditions as a basis for
providing geotechnical engineering design and construction recommendations for the proposed Fire
Station 16 replacement project. Our scope of services was completed in general accordance with our
proposal dated April 22, 2022, and authorized on May 5, 2022.
3.0 FIELD EXPLORATIONS AND LABORATORY TESTING
3.1. Field Explorations
Subsurface conditions were evaluated by drilling and sampling ten hollow-stem auger borings (GEI-1
through GEI-10) to depths ranging from about 10½ to 50½ feet below the existing ground surface (bgs).
Approximate locations of the explorations are shown in Figure 2. Descriptions of the field exploration
program and the boring logs are presented in Appendix A.
3.2. Laboratory Testing
Soil samples were obtained during drilling and were transported to GeoEngineers’ laboratory for further
evaluation. Selected samples were tested for the determination of moisture content, percent fines (material
passing the U.S. No. 200 sieve) and grain size distribution (sieve analysis). The tests were performed in
general accordance with test methods of ASTM International (ASTM) or other applicable procedures.
A description of the laboratory testing and the test results are presented in Appendix B.
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4.0 SITE CONDITIONS
4.1. Area Geology
The Puget Sound basin is a region of Quaternary (last 3 million years) sediments that range in thickness
between 800 and 2,400 feet. Bedrock exposures are present on the basin margins to the east and west in
the Cascade and Olympic Mountains, respectively. The basin area has been repeatedly overridden by
Pleistocene (between 11,000 and 3 million years ago) continental glacial ice depositing till, glacial sand
and gravel and glacially formed lake clay and silt. The repeated glacial action has resulted in numerous
north-south trending ridges, with intervening valleys filled with post-glacial alluvium and/or marine deposits
(Galster 1989). The most recent glacial cycle of sediment deposits is referred to as the Vashon Drift,
occurring between 13,500 and 15,000 years ago.
Published geologic information for the project area includes a United States Geological Survey (USGS)
Geologic Map of the Renton Quadrangle, King County, Washington (Mullineaux 1965) and a Geologic Map
of King County (Booth, Troost & Wisher 2007). The mapped surface geologic unit in the project area
includes glacial till (Qgt). Glacial till generally consists of a non-sorted, non-stratified mixture of clay, silt,
sand and gravel with larger constituents up to the size of boulders. The glacial till is very dense and relatively
impermeable but can contain localized zones of interbedded stratified sand and gravel.
Subsurface soil conditions encountered in our explorations are generally consistent with the geologic
mapping. The borings generally encountered very soft/loose fill overlying medium dense to dense
weathered glacial till and dense to very dense glacial till soils.
4.2. Surface Conditions
The site is currently bounded by SE 128th Street to the north, and by single-family residential to the east,
south and west. The site slopes up gently from approximately Elevation 530 feet in the northeast corner to
approximately Elevation 551 feet in the southwest corner. A one-story wood-framed residential structure
and a detached garage are currently located in the north-central portion of the site, and another one-story
wood-framed residential structure is located in the southwestern portion. Gravel surfacing covers the
central and northern areas of the site, and grass lawn is present in the south.
4.3. Subsurface Conditions
GeoEngineers’ understanding of subsurface soil and groundwater conditions at the site is based on review
of existing data and drilling and sampling ten hollow-stem auger borings (GEI-1 through GEI-10) to depths
ranging from about 10½ to 50½ feet bgs at the approximate locations shown in Figure 2. The subsurface
conditions at the site generally consist of crushed gravel surfacing and fill overlying weathered glacial till
and glacial till soils. Each of these deposits are discussed separately below.
■ Crushed Gravel Surfacing (Existing Gravel Driveway): Crushed gravel was encountered in all of the
explorations with the exception of borings GEI-6 through GEI-9, which were completed in landscape
areas. The existing gravel driveway generally consists of approximately 6 inches of crushed rock mixed
with underlying soft/loose fill soils.
■ Fill: Fill was encountered in all of the explorations with the exception of boring GEI-7. The fill generally
consists of soft/loose to medium dense sandy silt/silty sand with variable organic and gravel content.
The fill, where encountered, was observed to be approximately 2 to 7½ feet thick.
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■ Weathered Glacial Till: Weathered glacial till was encountered in all of the explorations below the fill,
and below the surficial topsoil/silty sand in GEI-7. The weathered glacial till generally consists
of medium dense to dense silty sand with variable content and extends to a depth of about 4 to
9 feet bgs.
■ Glacial Till: Very dense unweathered glacial till was encountered in all of the explorations below the
weathered soils. The unweathered glacial till generally consists of very dense silty sand with variable
gravel content, beginning at a depth ranging from about 5 to 10 feet bgs and extending to the depths
explored (up to 50½ feet bgs).
4.4. Groundwater
Groundwater was not observed in the borings at the time of drilling, with the exception of the deepest
boring, GEI-9, which was open for a longer period. We observed groundwater at approximately 10 feet below
the existing ground surface at the time of drilling boring GEI-9. Groundwater observations during drilling are
often inaccurate due to the limited time the hole is left open and variable permeability of adjacent soils.
We anticipate a seasonally perched groundwater present at the site above the relatively impermeable
dense to very dense glacial soils. Perched groundwater is common as seepage from precipitation and
surface water runoff infiltrates through the upper fill and/or weathered glacial till soils and moves laterally
or perches on the underlying dense/very dense glacial till soils. Groundwater conditions at the site are
anticipated to fluctuate and vary as a function of location, precipitation, season and other factors such as
below-grade drainage features.
4.5. Geologically Hazardous Areas
We reviewed the critical areas inventory mapping on City of Renton Map View (COR Maps). Based on our
review and our observations at the site, it is our opinion that the site does not have sensitive or protected
slopes, and has low landslide, erosion, seismic and coal mine hazards. In accordance with City of Renton
Municipal Code, Title IV, Chapter 3, Section 4-3-050G number 5, geologically hazardous areas are defined
as:
1. Steep Slope Types:
Sensitive Slopes: A hillside, or portion thereof, characterized by: (a) an average slope of twenty
five percent (25 percent) to less than forty percent (40 percent) as identified in the City of
Renton Steep Slope Atlas or in a method approved by the City; or (b) an average slope of forty
percent (40 percent) or greater with a vertical rise of less than fifteen feet (15 feet) as identified
in the City of Renton Steep Slope Atlas or in a method approved by the City; (c) abutting an
average slope of twenty five percent (25 percent) to forty percent (40 percent) as identified in
the City of Renton Steep Slope Atlas or in a method approved by the City. This definition
excludes engineered retaining walls.
Protected Slopes: A hillside, or portion thereof, characterized by an average slope of forty
percent (40 percent) or greater grade and having a minimum vertical rise of fifteen feet (15')
as identified in the City of Renton Steep Slope Atlas or in a method approved by the City.
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2. Landslide Hazards:
Low Landslide Hazard (LL): Areas with slopes less than fifteen percent (15 percent).
Medium Landslide Hazard (LM): Areas with slopes between fifteen percent (15 percent) and
forty percent (40 percent) and underlain by soils that consist largely of sand, gravel or glacial
till.
High Landslide Hazards (LH): Areas with slopes greater than forty percent (40 percent), and
areas with slopes between fifteen percent (15 percent) and forty percent (40 percent) and
underlain by soils consisting largely of silt and clay.
Very High Landslide Hazards (LV): Areas of known mapped or identified landslide deposits.
3. Erosion Hazards:
Low Erosion Hazard (EL): Areas with soils characterized by the Natural Resource Conservation
Service (formerly U.S. Soil Conservation Service) as having slight or moderate erosion potential,
and a slope less than fifteen percent (15 percent).
High Erosion Hazard (EH): Areas with soils characterized by the Natural Resource Conservation
Service (formerly U.S. Soil Conservation Service) as having severe or very severe erosion
potential, and a slope more than fifteen percent (15 percent).
4. Seismic Hazards:
Low Seismic Hazard (SL): Areas underlain by dense soils or bedrock. These soils generally have
site classifications of A through D, as defined in the International Building Code, 2012.
High Seismic Hazard (SH): Areas underlain by soft or loose, saturated soils. These soils
generally have site classifications E or F, as defined in the International Building Code, 2012.
5. Coal Mine Hazards:
Low Coal Mine Hazards (CL): Areas with no known mine workings and no predicted subsidence.
While no mines are known in these areas, undocumented mining is known to have occurred.
Medium Coal Mine Hazards (CM): Areas where mine workings are deeper than two hundred
feet (200 feet) for steeply dipping seams, or deeper than fifteen (15) times the thickness of
the seam or workings for gently dipping seams. These areas may be affected by subsidence.
High Coal Mine Hazard (CH): Areas with abandoned and improperly sealed mine openings and
areas underlain by mine workings shallower than two hundred feet (200 feet) in depth for
steeply dipping seams, or shallower than fifteen (15) times the thickness of the seam or
workings for gently dipping seams. These areas may be affected by collapse or other
subsidence.
No regulated (sensitive and/or protected) slopes are mapped by COR Maps or were observed at the site.
Therefore, it is our opinion that these geologically hazards will not adversely impact and/or limit the
proposed development.
5.0 CONCLUSIONS AND RECOMMENDATIONS
Based on our explorations, testing, and analyses, it is our opinion that the site is generally suitable for the
proposed project from a geotechnical engineering standpoint, provided the recommendations in this report
are included in design and construction. The following summary is presented for introductory purposes only
and should be used in conjunction with the complete recommendations presented in this report.
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■ The site is designated as Site Class C per the 2018 International Building Code (IBC), based on the
average blowcounts in borings completed at the site.
■ The on-site soils contain a sufficient percentage of fines (material passing the U.S. Standard No.200
sieve) and are highly moisture sensitive. These soils will become disturbed from earthwork occurring
during periods of wet weather (October through May), or when the moisture content of the soil is more
than a few percentage points above optimum. Wet weather construction practices will be required
unless earthwork occurs during the dry summer months (typically mid-July to mid-September).
■ A majority of the site is mantled with fill with variable organic content. The upper portion of the fill
encountered in the borings completed within the footprint of the proposed structures was soft/loose.
These soils will need to be removed and replaced with structural fill for building and slab support. We
recommend shallow foundations be supported on a minimum 2-foot thickness of structural fill, or on
the recompacted medium dense glacial soils. The structural fill pad should extend a minimum distance
outside the footing as described in Section 5.2.
■ We recommend an allowable soil bearing pressure of 3,000 pounds per square foot (psf) where
footings are founded on compacted structural fill or the recompacted medium dense native glacial soils
as described above. A higher bearing pressure of 6.000 psf is feasible at depth where very dense
unweathered glacial till was encountered. Based on the conditions in the borings, the top of the very
dense glacial till varies from 5 to 10 feet below the existing ground surface.
■ Fill material encountered at subgrade elevation should be evaluated by GeoEngineers during
construction. Soft/loose fill or fill with significant debris or unsuitable material should be removed to
firm material and replaced with compacted structural fill. The depth of overexcavation will be based on
the soils encountered and the type of structural improvement (e.g. footings, pavement or other
hardscape).
■ New slabs-on-grade should be supported on a minimum 18-inch thickness of structural fill. We
recommend a minimum 6-inch-thick capillary break layer beneath all slabs to provide uniform support
and drainage. A subgrade modulus of 125 pounds per cubic inch (pci) may be used for design.
■ We recommend temporary slopes be inclined at 1½H:1V (horizontal to vertical) or flatter. Steeper cut
slopes are possible in the dense to very dense native glacial soils (up to 1H:1V) provided groundwater
seepage is not encountered or is controlled during construction. Slope inclinations may have to be
modified by the contractor if localized sloughing occurs (particularly if loose fill soils are encountered).
We recommend the Geotechnical Engineer evaluate the stability of cut slopes to confirm subsurface
soils are as anticipated.
■ Design of infiltration facilities will be constrained at the site because of the relatively high percentage
of fines and low permeability of the native glacial soils. We anticipate the native glacial soils will have
a very slow infiltration rate (permeability on the order of 10-5 to 10 6 centimeters per second or typical
infiltration rates less than 0.1 inches per hour). Furthermore, we anticipate a seasonally perched
groundwater will be present above the weathered glacial till and/or relatively unweathered glacial till
soils. Depending on the design configuration, below-grade infiltration facilities are likely not feasible
due to seasonally perched groundwater and the hydraulic restrictive layers encountered at the site.
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5.1. Earthquake Engineering
5.1.1. Seismicity
The Puget Sound region is located at the convergent continental boundary known as the Cascadia
Subduction Zone (CSZ), which extends from mid-Vancouver Island to Northern California. The CSZ is the
zone where the westward advancing North American Plate is overriding the subducting Juan de Fuca Plate.
The interaction of these two plates results in three potential seismic source zones: (1) a shallow crustal
source zone; (2) the Benioff source zone; and (3) the CSZ interplate source zone.
The shallow crustal source zone is used to characterize shallow crustal earthquake activity within the
North American Plate at depths ranging from 3 to 19 miles bgs. The closest known fault is the Seattle Fault
Zone, which is mapped roughly 1 mile northwest of the project. Washington Department of Resources
Geological Survey and the USGS both recently (2021) updated their late Quarternary faults in western
Washington and have the same traces. The Seattle fault zone is 4 to 6 km wide and extends approximately
70 kilometers (km) in the east-west direction across the Puget Lowland. It consists of south-dipping thrust
faults and interpreted north-dipping back thrusts that partly underlie the Seattle metropolitan area.
Evidence suggests the Seattle fault zone is kinematically linked to active faults that border the Olympic
Massif including the Saddle Mountain deformation zone (Lamb et al. 2012). Paleoseismic evidence
suggests a Mw 7 earthquake occurred on the Seattle Fault at 900-930 A.D. (Ten Brink et al. 2002). Per the
2014 United States National Seismic Hazard Map, the recurrence times for the events on the Seattle fault
range from 1,000 to 5,000 years (Petersen et al. 2014). The Seattle Fault is capable of producing
earthquakes up to about magnitude 7.2. The Yelm Canal Hydroelectric project is about 52 to 57 km south
of the Seattle fault zone.
The Benioff source zone is used to characterize intraplate, intraslab or deep subcrustal earthquakes.
Benioff source zone earthquakes occur within the subducting Juan de Fuca Plate at depths between 20
and 40 miles. In recent years, three large Benioff source zone earthquakes occurred that resulted in some
liquefaction in loose alluvial deposits and significant damage to some structures. The first earthquake,
which was centered in the Olympia area, occurred in 1949 and had a Richter magnitude of 7.1. The second
earthquake, which was centered between Seattle and Tacoma, occurred in 1965 and had a Richter
magnitude of 6.5. The third earthquake, which was located in the Nisqually valley north of Olympia,
occurred in 2001 and had a Richter magnitude of 6.8.
The CSZ interplate source zone is used to characterize rupture of the convergent boundary between the
subducting Juan de Fuca Plate and the overriding North American Plate. The depth of CSZ earthquakes is
greater than 40 miles. No earthquakes on the CSZ have been instrumentally recorded; however, through
the geologic record and historical records of tsunamis in Japan, it is believed that the most recent CSZ
event occurred in 1700.
5.1.2. 2018 IBC Seismic Design Information
For the site, we recommend the following 2018 IBC parameters for Site Class C, mapped risk-targeted
maximum-considered earthquake (MCER) spectral response acceleration at short period (Ss), mapped
MCER spectral response acceleration at 1-second period (S1), short period site coefficient (Fa), long period
site coefficient (Fv), design spectral acceleration at 0.2-second period (SDS) and the design spectral
acceleration at 1.0-second period (SD1).
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TABLE 1. 2018 IBC DESIGN PARAMETERS
2018 IBC Parameter1 Recommended Value
Site Class C
Short Period Spectral Response Acceleration, SS (percent g) 137.1
1-Second Period Spectral Response Acceleration, S1 (percent g) 46.9
Seismic Coefficient, Fa 1.2
Seismic Coefficient, FV 1.5
Short Period Design Spectral Response Acceleration, SDS (percent g) 109.7
1-Second Period Design Spectral Response Acceleration, SD1 (percent g) 46.9
Risk Category, Essential Facility IV
Note:
1Parameters developed based on latitude 47.4872744 and longitude -122.1293471 using the Applied Technology Council (ATC)
Hazards online tool (https://hazards.atcouncil.org/).
5.1.3. Liquefaction Potential
Liquefaction is a phenomenon where soils experience a rapid loss of internal strength as pore water
pressures increase in response to strong ground shaking. The increased pore water pressure may
temporarily meet or exceed soil overburden pressures to produce conditions that allow soil and water to
flow, deform, or erupt from the ground surface. Ground settlement, lateral spreading and/or sand boils may
result from soil liquefaction. Structures, such as buildings and other site facilities, supported on or within
liquefied soils may suffer foundation settlement or lateral movement that can be damaging. In general,
soils that are susceptible to liquefaction include very loose to medium dense, clean to silty sands and some
silt soils that are below the groundwater table.
Based on the subsurface soil and groundwater conditions encountered in the explorations completed at
the site, it is our opinion that the site has a low risk of liquefaction for a moderate to large design
earthquake.
5.1.4. Other Seismic Hazards
Due to the location of the site and the site’s topography, the risk of adverse impacts resulting from
seismically induced slope instability, differential settlement, surface displacement due to faulting or lateral
spreading is considered to be low.
5.2. Shallow Foundations
We recommend that foundations for new structures be supported on recompacted medium dense to dense
native glacial soils or on a minimum 2-foot thickness of structural fill. The zone of structural fill should
extend beyond the faces of the footing a distance at least equal to the thickness of the structural fill and
be compacted as recommended in the “Structural Fill” section of this report. The base of the excavation
should be evaluated by a member of our firm prior to placing the structural fill zone. Any existing fill which
contains significant organic material should be removed prior to placing structural fill. Where footings are
founded on native medium dense to dense glacial soils, loose or disturbed soils should be removed and
the subgrade should be compacted to a firm and unyielding condition following excavation.
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We recommend minimum widths of 16 and 24 inches for continuous and isolated spread footings,
respectively. The exterior footings should be founded at least 18 inches below lowest adjacent finished
grade. Interior footings should be founded at least 12 inches below bottom of slab or adjacent finished
grade. For footings founded on structural fill or on the recompacted medium dense to dense native glacial
soils, an allowable soil bearing pressure of 3,000 psf may be used for design. A higher bearing pressure of
6,000 psf can be utilized at depth where very dense glacial till is present. Based on our explorations, the
depth to unweathered very dense glacial till varies from about 5 to 10 feet bgs. These values include a
factor of safety of 3 and may be increased by one-third when considering transient loads, such as wind or
seismic. The weight of the footing and any backfill over the footing may be neglected in determining the
applied bearing pressure. The shallow foundation subgrade should be prepared as recommended in the
“Subgrade Preparation” section below.
5.2.1. Foundation Settlement
We estimate that the total static settlement of shallow foundations designed and constructed as
recommended above will be less than 1 inch. We estimate that the differential settlement between
comparably loaded isolated spread footings or along a 25-foot section of continuous footings will be less
than ½-inch over a distance of 25 feet. The settlements will occur rapidly, essentially as loads are applied.
Settlement could be greater than estimated if loose or disturbed soils are not removed prior to placing
concrete.
5.2.2. Lateral Resistance
The soil resistance available to resist lateral loads is a function of the frictional resistance which can
develop on the base of footings and floor slab, and the passive resistance which can develop on the face
of below-grade elements of the structure as these elements tend to move into the soil. For footings founded
on structural fill placed and compacted in accordance with our recommendations in this report, the
allowable frictional resistance may be computed using 0.35 applied to vertical dead-load forces. The
allowable passive resistance on the face of footings may be computed using an equivalent fluid density of
300 pounds per cubic foot (pcf) (triangular distribution) where footings are poured neat against dense
native soils or where surrounded by structural fill compacted to at least 95 percent of maximum dry density
(MDD) (ASTM D 1557). The above coefficient of friction and passive equivalent fluid density values include
a factor of safety of about 1.5.
Resistance to passive pressure should be calculated from the bottom of adjacent floor slabs and paving,
or below a depth of 1 foot where the adjacent area is unpaved. If soils adjacent to footings are disturbed
during construction, the disturbed soils must be recompacted, otherwise the lateral passive resistance
value must be reduced.
5.3. Slab-On-Grade Floors
We recommend that conventional slabs be supported on a minimum 18-inch thickness of structural fill or
on recompacted medium dense to dense native glacial soils. Where existing fill is present the subgrade
should be over-excavated a minimum of 18 inches and the exposed fill should be re-compacted to a firm
and unyielding condition, followed by placement of the minimum 18 inches of structural fill in two lifts.
Additional over-excavation will be required if the existing fill cannot be compacted to a firm and unyielding
condition. For slabs designed as a beam on an elastic foundation, a modulus of subgrade reaction of
125 pci may be used for subgrade soils prepared as recommended in the “Subgrade Preparation” section
below.
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We recommend that slab-on-grade floors be underlain by a minimum 6-inch-thick capillary break to provide
uniform support and drainage. The capillary break should consist of clean crushed gravel, with a maximum
particle size of 1½ inches and negligible sand or silt such as the AASHTO Grading No. 67 in Section
9-03.1(4)C of the 2022 Washington State Department of Transportation (WSDOT) Standard Specifications.
Because of the presence of fine-grained on-site soils, moisture should be expected at the subgrade surface.
Where moisture vapor emission through the slab must be minimized (e.g., where tiled or carpeted floors
will be utilized), a vapor retarding membrane or vapor barrier below the slab should be utilized. The
contractor should be made responsible for maintaining the integrity of the vapor retarder during
construction. It may also be prudent to apply a sealer to the slab to further retard the migration of moisture
through the floor.
We estimate that the total static settlement of slab-on-grade floors constructed as recommended above
will be less than 1 inch. Settlement could be greater than estimated if loose or disturbed soils are not
removed prior to placing concrete. We recommend that concrete slabs be jointed around columns to allow
the individual structural elements to settle differentially.
5.4. Below-Grade Walls and Retaining Walls
The following recommendations should be used for the design of below-grade walls that are intended to
act as retaining walls and for other retaining structures that are used to achieve grade changes.
5.4.1. Design Parameters
Lateral earth pressures for design of below-grade walls and retaining structures should be evaluated using
an equivalent fluid density of 35 pcf provided that the walls will not be restrained against rotation when
backfill is placed. If the walls will be restrained from rotation, we recommend using an equivalent fluid
density of 55 pcf. Walls are assumed to be restrained if top movement during backfilling is less than
H/1000, where H is the wall height. These lateral soil pressures assume that the ground surface behind
the wall is horizontal. For unrestrained walls with backfill sloping up at 2H:1V, the design lateral earth
pressure should be increased to 55 pcf, while restrained walls with a 2H:1V sloping backfill should be
designed using an equivalent fluid density of 75 pcf. These lateral soil pressures do not include the effects
of surcharges such as floor loads, traffic loads or other surface loading. Surcharge effects should be
included as appropriate. Seismic earth pressures should also be considered in design using a rectangular
distribution of 8H in psf, where H is the wall height.
If vehicles can approach the top of the wall to within half of the height of the wall, a traffic surcharge should
be added to the wall pressure. For car parking areas, the traffic surcharge can be approximated by the
equivalent weight of an additional 1 foot of soil backfill (about 125 psf) behind the wall. For fire truck,
delivery truck parking areas and access driveway areas, the traffic surcharge can be approximated by the
equivalent weight of an additional 2 feet (250 psf) of soil backfill behind the wall. Positive drainage should
be provided behind below-grade walls and retaining structures as discussed below.
These recommendations assume that all retaining walls will be provided with adequate drainage. The
values for soil bearing, frictional resistance and passive resistance presented for shallow foundation design
are applicable to retaining wall design. Walls located in level ground areas should be founded at a depth of
18 inches below the adjacent grade. Deeper embedment will be required where walls are founded on
sloping ground and should be evaluated when the wall location and site grades are determined.
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5.4.2. Wall Drainage
To reduce the potential for hydrostatic water pressure buildup behind retaining walls, we recommend that
the walls be provided with adequate drainage. Wall drainage can be achieved by using free draining wall
drainage material with perforated pipes to discharge the collected water.
Wall drainage material may consist of Gravel Backfill for Drains per the WSDOT Standard Specifications
Section 9-03.12(4) surrounded with a nonwoven geotextile filter fabric such as Mirafi 140N (or approved
equivalent), or imported Gravel Borrow with less than 5 percent fines may be used in conjunction with a
geocomposite wall drainage layer. The zone of wall drainage material should be 2 feet wide and should
extend from the base of the wall to within 2 feet of the ground surface. The wall drainage material should
be covered with a geotextile separator (such as Mirafi 140N) within about 2 feet of the ground surface and
overlain by less permeable material such as the on-site silty sand that is properly moisture conditioned and
compacted.
A 4-inch-diameter perforated drainpipe should be installed within the free-draining material at the base of
each wall. We recommend using either heavy-wall solid pipe (SDR-35 PVC) or rigid corrugated polyethylene
pipe (ADS N-12, or equal). We recommend against using flexible tubing for the wall drainpipe. If gravel
borrow is used against the wall in conjunction with a geocomposite wall drainage layer, then the drainage
pipe at the base of the wall should be surrounded with at least 12 inches of Gravel Backfill for Drains per
the WSDOT Standard Specifications Section 9-03.12(4) that is wrapped with a nonwoven geotextile filter
fabric such as Mirafi 140N (or approved equivalent).
The pipes should be laid with minimum slopes of one-quarter percent and discharge into the storm water
collection system to convey the water off site. The pipe installations should include a cleanout riser with
cover located at the upper end of each pipe run. The cleanouts could be placed in flush mounted access
boxes. Collected downspout water should be routed to appropriate discharge points in separate pipe
systems.
5.5. Earthwork
Based on the subsurface soil and groundwater conditions encountered in the explorations completed at
the site, we anticipate the fill and native glacial soils at the site may be excavated with conventional
heavy-duty construction equipment, such as trackhoes or dozers. It may be necessary to rip the glacial soils
in localized areas to facilitate excavation. Glacial deposits in the area commonly contain cobbles and
boulders that may be encountered during excavation, and the contractor should be prepared to deal with
these conditions during construction. Likewise, the surficial fill may contain foundations and/or utilities
from previous site development, as well as debris, rubble, and/or cobbles and boulders. We recommend
that procedures be identified in the project specifications for measurements and payment of work
associated with obstructions.
The fill and native glacial soils contain a high percent of fines (material passing the U.S. Standard No.200
sieve) and are highly moisture-sensitive and susceptible to disturbance, especially during wet weather
construction (October through May). Repeated construction traffic will result in considerable disturbance
during wet weather. Ideally, earthwork should be undertaken during extended periods of dry weather (June
through September) when the surficial soils will be less susceptible to disturbance and provide better
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support for construction equipment. Dry weather construction will help reduce earthwork costs. We suggest
that a contingency be included in the project schedule and budget to account for increased subgrade
preparation and import costs, and placement of an all-weather access pad if construction occurs during
the wet season.
5.5.1. Clearing and Site Preparation
All areas to receive fill, structures or pavements should be cleared of vegetation, topsoil, existing asphalt
and concrete. Clearing should consist of removal of all shrubs, sod, and other vegetation within the
designated clearing limits. All existing foundations and subsurface structures should be removed. Debris
associated with building and site work demolition should be removed from the site. Organic materials could
be chipped/composted and reused in landscape areas, if desired.
We anticipate that the depth of stripping to remove topsoil will be up to 2 feet, where present. Actual
stripping depths should be determined based on field observations at the time of construction. We
recommend materials that cannot be used for landscaping or protection of disturbed areas be removed
from the project site.
5.5.2. Subgrade Preparation
We recommend that prepared subgrades for slab-on-grade floors, foundations or pavement be observed
by a representative of GeoEngineers to evaluate the suitability of the subgrade and identify any area of soft,
yielding, pumping or otherwise unsuitable soils. The exposed foundation subgrade areas should be probed
with a ½-inch-diameter steel probe rod, while new slab-on-grade and pavement subgrade areas should be
proof-rolled with a loaded dump truck or equivalent. If unsuitable soils are revealed during probing and/or
proof-roll, the unsuitable soils should be removed and replaced with structural fill, as needed.
Fill material at subgrade elevation should be evaluated by GeoEngineers during construction. Soft/loose fill
or fill with significant debris or unsuitable material should be removed as recommended and replaced with
compacted structural fill. The width of the overexcavation should extend beyond the edge of the footing a
distance equal to the depth of the overexcavation below the base of the footing.
We recommend loose or disturbed soils be removed before placing concrete and reinforcing steel.
Foundation bearing surfaces should not be exposed to standing water. If water infiltrates and pools in the
excavation, the water, along with any disturbed soil, should be removed before placing reinforcing steel. A
thin layer (2 to 3 inches) of crushed rock can be used to provide protection to the subgrade from light foot
traffic. Compaction should be performed as described in the “Fill Placement and Compaction Criteria”
section.
We recommend GeoEngineers observe all foundation excavations before placing concrete forms and
reinforcing steel to determine that bearing surfaces have been adequately prepared in accordance with our
recommendations and the project plans and specifications and the soil conditions are consistent with those
observed during our explorations.
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5.5.3. Temporary Slopes and Construction Dewatering
We recommend temporary cut slopes in the existing fill and medium dense to dense weathered glacial till
deposits be inclined at 1½H:1V or flatter, and dense to very dense glacial till deposits be inclined at 1H:1V
or flatter. Flatter slopes may be necessary if seepage is present on the face of the cut slopes or if localized
sloughing occurs. However, temporary cuts should be discussed with the geotechnical engineer during final
design development to evaluate suitable cut slope inclinations for the various portions of the excavation.
Temporary cut slopes should be planned such that they do not encroach on a 1H:1V influence line projected
down from the edges of nearby or planned foundation elements.
The above guidelines assume that surface loads such as traffic, construction equipment, stockpiles or
building supplies will be kept away from the top of the cut slopes a sufficient distance so that the stability
of the excavation is not affected. We recommend that this distance be at least 5 feet from the top of the
cut for temporary cuts made at 1H:1V or flatter and less than 10 feet high, and no closer than a distance
equal to one-half the height of the slope for cuts more than 10 feet high.
Water that enters the excavations must be collected and routed away from prepared subgrade areas. We
expect that this may be accomplished by installing a system of drainage ditches and sumps along the toe
of the cut slopes. Some sloughing and raveling of the cut slopes should be expected. Temporary covering,
such as heavy plastic sheeting with appropriate ballast, should be used to protect these slopes during
periods of wet weather. Surface water runoff from above cut slopes should be prevented from flowing over
the slope face by using berms, drainage ditches, swales or other appropriate methods.
If temporary cut slopes experience excessive sloughing or raveling during construction, it may become
necessary to modify the cut slopes to maintain safe working conditions. Slopes experiencing problems can
be flattened, regraded to add intermediate slope benches, or additional dewatering can be provided if the
poor slope performance is related to groundwater seepage.
Because the contractor has control of the construction operations, the contractor should be made
responsible for the dewatering of the site, shoring, stability of cut slopes, as well as the safety of the
excavations. The contractor is present at the site continuously and is best able to observe changes in site
and soil conditions and monitor the performance of excavations. Slope inclinations may have to be modified
by the contractor if localized sloughing occurs or if seepage occurs. All dewatering, shoring and temporary
slopes should conform to applicable local, state, and federal safety regulations.
5.5.4. Permanent Slopes
We recommend that permanent cut and fill slopes be constructed no steeper than 2H:1V. To achieve
uniform compaction, we recommend that fill slopes be overbuilt slightly and subsequently cut back to
expose properly compacted fill.
To reduce erosion, newly constructed slopes should be planted or hydroseeded shortly after completion of
grading. Until the vegetation is established, some sloughing and raveling of the slopes should be expected.
This may require localized repairs and reseeding. Temporary covering, such as jute fabric, loose straw or
excelsior matting should be used to protect the slopes during periods of rainfall and aid in effective
revegetation.
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5.6. Structural Fill
5.6.1. Materials
We recommend that the 2022 WSDOT Standard Specifications be used to specify structural fill materials.
Materials used to raise site grades, support structures, placed behind retaining structures, placed below
pavements and sidewalks, and for utility trench backfill is classified as structural fill for the purpose of this
report. Structural fill material requirements vary depending upon their use as described below:
1. As a minimum, structural fill placed in pavement areas, sloped fill embankments, hardscape features
such as sidewalks, utility trench backfill and beneath new foundations and floor slabs should meet the
criteria for Common Borrow, Section 9-03.14(3) of the WSDOT Standard Specifications. Common
Borrow will be suitable for use as structural fill during prolonged dry weather conditions only and must
be moisture conditioned to within 2 percent of the optimum moisture content.
2. During wet weather, structural fill should consist of imported material meeting the requirements of
Gravel Borrow, Section 9-03.14(1) of the WSDOT Standard Specifications, with the restriction that the
fines content (material passing the U.S. No. 200 sieve) be limited to no more than 5 percent.
3. Structural fill placed as capillary material should consist of a 6-inch-thick layer of clean crushed gravel
with a maximum particle size of 1½ inches and negligible sand or silt and meet the requirements of
AASHTO Grading No. 67 in Section 9-03.1(4)C of the WSDOT Standard Specifications.
4. Structural fill placed behind retaining walls should meet the requirements of Gravel Backfill for Walls,
Section 9-03.12(2) of the WSDOT Standard Specifications.
5. Structural fill placed around perimeter footing drains and cast-in-place wall drains should meet the
requirements of Gravel Backfill for Drains, Section 9-03.12(4) of the WSDOT Standard Specifications.
6. Structural fill placed as crushed surfacing base course (CSBC) below pavements and sidewalks should
meet the requirements of Crushed Surfacing, Section 9-03.9(3) of the WSDOT Standard Specifications.
5.6.2. Use of On-site Soils
The on-site soils contain a high percentage of fines (silt and clay) and are therefore moisture sensitive.
These soils will be difficult to handle and compact during wet weather conditions (typically October through
May). Additionally, the results of our laboratory analyses indicate the moisture content of the surficial soils
are more than double the optimum content required for adequate compaction. These soils will only be
suitable if prolonged aeration/disking can be provided on site. Soils excavated below a depth of about
5 feet have lower moisture contents, and are likely suitable for reuse as common borrow during the dry
season. Based on these conditions, we recommend the contract documents provide provisions for import
structural fill.
5.6.3. Fill Placement and Compaction Criteria
Structural fill should be mechanically compacted to a firm, non-yielding condition. In general, structural fill
should be placed in loose lifts not exceeding 12 inches in thickness when using heavy compaction
equipment and 6 inches when using hand operated compaction equipment. Each lift should be conditioned
to the proper moisture content and compacted to the specified density before placing subsequent lifts.
Structural fill should be compacted to the following criteria:
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■ Structural fill placed below foundations, on-grade slabs, and within the top 2 feet of pavement subgrade
should be compacted to at least 95 percent of the MDD estimated in accordance with ASTM D 1557.
Structural fill placed below the top 2 feet of pavement subgrade should be compacted to at least
90 percent of the MDD.
■ Structural fill placed in new pavement or hardscape areas, including utility trench backfill, should be
compacted to 90 percent of the MDD estimated in general accordance with ASTM D 1557, except that
the upper 2 feet of fill below final subgrade should be compacted to at least 95 percent of the MDD.
■ Structural fill placed behind below-grade or retaining walls, within a distance equal to the height of
the wall, should be compacted to between 90 and 92 percent of the MDD estimated in general
accordance with ASTM D 1557. Care should be taken when placing fill near the face of walls to avoid
over-compaction and, hence overstressing the walls.
■ Structural fill placed as crushed rock base course below pavements should be compacted to at least
95 percent of the MDD estimated in accordance with ASTM D 1557.
We recommend that a representative from our firm observe and evaluate (proof-rolling and/or probing) the
exposed subgrade soils in structure and pavement areas prior to placement of structural fill and during the
placement and compaction of structural fill. Our representative would evaluate the adequacy of the
subgrade soils and identify areas needing further work, perform in-place moisture-density tests in the fill to
evaluate if the work is being done in accordance with the compaction specifications, and advise on any
modifications to procedures that may be appropriate for the prevailing conditions.
5.6.4. Weather Considerations
As discussed previously, the native soils contain a sufficient percentage of fines (silt and clay) to be
moisture sensitive. When the moisture content of these soils is appreciably above the optimum moisture
content, these soils become muddy and unstable, operation of equipment on these soils will be difficult,
and it will be difficult to meet the required compaction criteria. These soils should be protected from
moisture and precipitation in order to be re-used as structural fill. Additionally, disturbance of these near
surface soils should be expected if earthwork is completed during periods of wet weather. During wet
weather conditions we recommend that:
■ The ground surface in and around the work area should be sloped so that surface water is directed
away from work area to a sump or discharge location.
■ The ground surface should be graded such that areas of ponded water do not develop.
■ The contractor should take measures to prevent surface water from collecting in excavations and
trenches.
■ Measures should be implemented to remove surface water from the work area.
■ Earthwork activities should not take place during periods of heavy precipitation.
■ Slopes with exposed soils should be covered with plastic sheeting or similar means, as practical.
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■ The contractor should take necessary measures to prevent soils to be used as fill from becoming wet
or unstable. These measures may include covering stockpiles with plastic sheeting, sumps with pumps
and grading. The site soils should not be left uncompacted and exposed to moisture. Sealing the
surficial soils by rolling with a smooth-drum roller prior to periods of precipitation will reduce the extent
to which these soils become wet or unstable.
■ Construction activities should be scheduled so that the length of time that soils are left exposed to
moisture is reduced to the extent practicable.
■ Structural fill placed during the wet season should meet the requirements previously recommended in
the “Materials” section of this report.
5.6.5. Utility Trenches
Trench excavation, pipe bedding, and trench backfilling should be completed using the general procedures
described in the 2022 WSDOT Standard Specifications or other suitable procedures required by the City of
Renton or specified by the project civil engineer. The soils encountered at the site are generally of low
corrosivity based on our experience in the Puget Sound area.
Utility trench backfill should consist of structural fill and should be placed in loose lifts not exceeding
12 inches in thickness when using heavy compaction equipment and not more than 6 inches when using
hand operated compaction equipment such that adequate compaction can be achieved throughout the lift.
Each lift must be compacted prior to placing the subsequent lift. Prior to compaction, the backfill should be
moisture conditioned to within 2 percent of the optimum moisture content, if necessary. The backfill should
be compacted in accordance with the criteria discussed above.
5.6.6. Sedimentation and Erosion Control
Potential sources or causes of erosion and sedimentation depend upon construction methods, slope length
and gradient, amount of soil exposure or disturbance, soil type, construction sequencing and weather.
The project impact on erosion-prone areas and adjacent areas can be reduced by implementing an erosion
and sedimentation control plan. The plan should be designed in accordance with applicable City standards.
The plan should incorporate basic planning principles that include:
■ Scheduling grading and construction to reduce soil exposure,
■ Retaining existing vegetation whenever feasible,
■ Prevent erosion from occurring by minimizing the area of disturbance; providing blanket protection of
disturbed areas and grading to avoid concentration of surface runoff onto or off of cut or fill slopes,
access roadways or natural slopes,
■ Intercept surface runoff onto or off of disturbed areas to minimize sediment transport by use of brush
barriers, straw wattles, swales, etc.,
■ Provide erosion control system redundancies. For example, combine the above preventive measures
with installation of silt fences, straw bales, and rock check dams where appropriate to provide the
desired redundancy,
■ Inspect and maintain erosion control measures frequently; and
■ Hydroseed or place crushed rock surfacing on disturbed areas as soon as possible after completion.
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Erosion protection of finished surfaces may be obtained by planting vegetation and covering the area with
mulch or matting. Numerous products are available to cover the exposed area including jute matting,
excelsior matting, woven straw matting, synthetic fiber matting, seed impregnated sheeting and sprayed
fibers.
Until the permanent erosion protection is established, and the site is stabilized, site monitoring should be
performed by qualified personnel to evaluate the effectiveness of the erosion control measures and repair
and/or modify them as appropriate. Provisions for modifications to the erosion control system based on
monitoring observations should be included in the erosion and sedimentation control plan.
5.7. Drainage Considerations
The finished ground surface adjacent to the new structures should be sloped so that surface runoff flows
away from the structure. Roof drains should be tightlined to an appropriate discharge point and should not
be connected to footing or wall drains. All drains should be tightlined to the existing or new drainage system.
A perimeter footing drain should be constructed around the perimeter of buildings and discharge into the
stormwater collection system.
5.8. Pavement Design
New pavement subgrade areas should be proofrolled and evaluated by the geotechnical engineer prior to
placing base course. It is critical that all construction traffic be kept off the silty subgrade soils during wet
weather to prevent disturbance (rutting and weaving) from occurring. We recommend the minimum
6-inch-thick crushed surfacing base course contain less than 5 percent passing the U.S. No. 200 sieve to
perform as a drainage layer between the silty soils and the pavement section. The minimum thickness is
not intended to serve as a working surface for construction traffic during wet weather. Additional subbase
will likely be required if earthwork and site grading is not completed during the dry season.
Based on our previous experience with similar projects, we recommend the minimum pavement sections
outlined in Table 2. Portland cement concrete (PCC) sections may be considered for areas where
concentrated heavy loads may occur. If site specific traffic data and load information is available, we can
refine our recommendations for the conditions at Station 16.
TABLE 2. RECOMMENDED PAVEMENT SECTIONS
Section
PCC Thickness
(inches)
HMA
Thickness (inches)
CSBC Thickness
(inches)
Heavy-Duty (fire truck access) 10 - 6
Heavy-Duty (drive aisles and access road) - 4 8
Light-Duty (automobile parking) 2½ 6
Notes:
HMA – hot-mix asphalt
If the City has a thicker standard thickness of concrete for the fire truck aprons, the City standard should
be used. We recommend the CSBC conform to WSDOT Standard Specifications Section 9-03.9(3), “Crushed
Surfacing.” The top 2 inches may conform to the gradation for “Top Course and Keystone,” the underlying
base course should conform to the gradation for “Base Course.” We recommend the CSBC be placed as
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previously recommended and compacted to at least 95 percent of the MDD based on ASTM D 1557.
Hot-mix asphalt (HMA) pavement should be compacted to at least 92 percent of the theoretical Rice
Density. Our recommended PCC thickness is based on the assumption that the PCC slab will consist of
plain-jointed (non-doweled) concrete.
5.9. Stormwater Infiltration Considerations
We understand that shallow infiltration may be considered at the site within the northeast area (topographic
low). The opportunity for shallow infiltration will be limited and constrained because of the relatively high
percentage of fines and low permeability of the underlying native glacial soils. Very dense glacial till was
encountered at a depth of 7 feet in our exploration (GEI-1). This layer is considered a hydraulic restrictive
layer per the 2017 City of Renton Surface Water Design Manual (CORSWDM). A seasonally perched
groundwater condition is also likely, further restricting infiltration at the site.
If limited infiltration is being considered in the upper weathered zones, these facilities will require
underdrain pipes decanting excess flows from a storage layer to both provide treatment of stormwater and
take advantage of limited infiltration through the glacial deposits. Additional evaluation is required to
determine feasibility of limited infiltration, such as evaluation of seasonal changes in groundwater and on-
site small scale pilot infiltration tests.
6.0 DESIGN REVIEW AND CONSTRUCTION SERVICES
Recommendations provided in this report are based on the assumptions and preliminary design
information stated herein. We welcome the opportunity to review and discuss construction plans and
specifications for this project as they are being developed. In addition, GeoEngineers should be retained to
review the geotechnical-related portions of the plans and specifications to evaluate whether they are in
conformance with the recommendations provided in this report.
Satisfactory foundation and earthwork performance depend to a large degree on quality of construction.
Sufficient monitoring of the contractor’s activities is a key part of determining that the work is completed
in accordance with the construction drawings and specifications. Subsurface conditions observed during
construction should be compared with those encountered during the subsurface explorations. Recognition
of changed conditions often requires experience; therefore, qualified personnel should visit the site with
sufficient frequency to detect whether subsurface conditions change significantly from those anticipated.
We recommend that GeoEngineers be retained to observe construction at the site to confirm that
subsurface conditions are consistent with the site explorations and to confirm that the intent of project
plans and specifications relating to earthwork and foundation construction are being met.
7.0 LIMITATIONS
We have prepared this report for the exclusive use of Renton Regional Fire Authority (RRFA) and their
authorized agents and/or regulatory agencies for the proposed Station 16 replacement project at 15815
SE 128th Street in Renton, Washington.
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This report is not intended for use by others and the information contained herein is not applicable to other
sites. No other party may rely on the product of our services unless we agree in advance and in writing to
such reliance.
Within the limitations of scope, schedule and budget, our services have been executed in accordance with
generally accepted practices in the area at the time this report was prepared. No warranty or other
conditions, express or implied, should be understood.
Please refer to Appendix C, Report Limitations and Guidelines for Use, for additional information pertaining
to use of this report.
8.0 REFERENCES
ASCE 7-16, 2016, “Minimum design loads for buildings and other structures.”
Applied Technology Council, “Hazards by Location, Seismic” accessed via: https://hazards.atcouncil.org/#/
on July 7, 2022.
Booth, D.B, Troost, K.A., and Wisher, A. P. 2007. “Geologic Map of King County.”
Idriss, I.M. and Boulanger, R.W. (2008), “Soil Liquefaction During Earthquakes.” Earthquake Engineering
Research Institute (EERI), Monograph MNO-12.
International Code Council, 2018 International Building Code.
Mullineaux, D.R. 1965, United States Geologic Survey, Geologic Quadrangle, “Geologic Map of the Renton
Quadrangle, King County, Washington.”
Tokimatsu, K. and Seed, H.B. (1987). “Evaluation of Settlement in Sands due to Earthquake Shaking,”
Journal of Geotechnical Engineering, ASCE, Vol. 113, No. 8, August 1987, pp. 861-878.
Washington State Department of Transportation, 2022, “Standard Specifications for Road, Bridge and
Municipal Construction.”
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NE7thPl
SE116thSt
NE6thSt NE6thSt
156thAveSE
NE10thSt NE10thSt
NE17thSt
NE8thSt
HoquiamAveNE
155thAveSE
SE128thSt
138thAveSE
148thAveSE
NESunset Blvd
CoalfieldPark
MayValleyPark
EastRenton
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160thAveSE
S
E144thSt SE144thSt
SE145thPl
SE2ndStSE2ndPl
NE2ndSt
SE142ndSt
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SE141st St
156thAveSE
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MaplewoodGolf
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RonRegisPark
MayCreek
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SE134thSt
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SE144thSt
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Vicinity Map
Figure 1
Renton Regional Fire Authority,Station 16 Replacement,Renton, Washington
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Data Source: ESRI
Notes:
1. The locations of all features shown are approximate.2. This drawing is for information purposes. It is intended to assist inshowing features discussed in an attached document. GeoEngineers, Inc.cannot guarantee the accuracy and content of electronic files. The masterfile is stored by GeoEngineers, Inc. and will serve as the official record ofthis communication.
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Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
GEI-1
GEI-2
GEI-3
GEI-4
GEI-7
GEI-8
GEI-6
GEI-5
GEI-9
GEI-10
Figure 2
Renton Regional Fire Authority,
Station 16 Replacement,
Renton, Washington
Site Plan
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Notes:
1.The locations of all features shown are approximate.
2.This drawing is for information purposes. It is intended to assist in showing
features discussed in an attached document. GeoEngineers, Inc. cannot
guarantee the accuracy and content of electronic files. The master file is stored
by GeoEngineers, Inc. and will serve as the official record of this communication.
Data Source: Background data from TCA dated 03/17/22.
Projection: WA State Plane, North Zone, NAD83, US Foot
Feet
0
Legend
100 100
GEI-1 Boring by GeoEngineers, Inc., 2022
SE 128th St
15
8
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Site Boundary
Proposed Fire
Station
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Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
APPENDIX A Field Explorations
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
August 5, 2022 | Page A-1 File No. 26016-001-00
APPENDIX A
FIELD EXPLORATIONS
Subsurface soil and groundwater conditions at the site were evaluated by drilling ten geotechnical
hollow-stem auger borings (GEI-1 through GEI-10). The borings were completed to depths of about 10½ to
50½ feet below existing site grade. The borings were completed by Holocene Acquisition Company, LLC on
June 20 through 22, 2022. The approximate locations of the explorations are shown in the Site Plan,
Figure 2.
Borings
The borings were completed using track-mounted, continuous-flight, hollow-stem auger drilling equipment.
The borings were continuously monitored by a geotechnical engineer from our firm who examined and
classified the soils encountered, obtained representative soil samples, observed groundwater conditions
and prepared a detailed log of each exploration.
The soils encountered in the borings were generally sampled at 2½- and 5-foot vertical intervals with a
2-inch outside-diameter split-barrel standard penetration test (SPT) sampler. The disturbed samples were
obtained by driving the sampler 18 inches into the soil with a 140-pound automatic hammer free-falling
30 inches. The number of blows required for each 6 inches of penetration was recorded. The blow count
(“N-value”) of the soil was calculated as the number of blows required for the final 12 inches of penetration.
This resistance, or N-value, provides a measure of the relative density of granular soils and the relative
consistency of cohesive soils. Where very dense soil conditions precluded driving the full 18 inches, the
penetration resistance for the partial penetration was entered on the logs. The blow counts are shown on
the boring logs at the respective sample depths.
Soils encountered in the borings were visually classified in general accordance with the classification
system described in Figure A-1. A key to the boring log symbols is also presented in Figure A-1. The logs of
the borings are presented in Figures A-2 through A-11. The boring logs are based on our interpretation of
the field and laboratory data and indicate the various types of soils and groundwater conditions
encountered. The logs also indicate the depths at which these soils or their characteristics change, although
the change may actually be gradual. If the change occurred between samples, it was interpreted. The
densities noted in the boring logs are based on the blow count data obtained in the borings and judgment
based on the conditions encountered.
Observations of groundwater conditions were made during drilling. The groundwater conditions
encountered during drilling are presented in the boring logs. Groundwater conditions observed during
drilling represent a short-term condition and may or may not be representative of the long-term groundwater
conditions at the site. Groundwater conditions observed during drilling should be considered approximate.
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
Measured groundwater level in exploration,well, or piezometer
Measured free product in well or piezometer
Distinct contact between soil strata
Approximate contact between soil strata
Contact between geologic units
SYMBOLS TYPICAL
DESCRIPTIONS
GW
GP
SW
SP
SM
FINEGRAINED
SOILS
SILTS ANDCLAYS
NOTE: Multiple symbols are used to indicate borderline or dual soil classifications
MORE THAN 50%RETAINED ONNO. 200 SIEVE
MORE THAN 50%PASSINGNO. 200 SIEVE
GRAVEL
ANDGRAVELLYSOILS
SC
LIQUID LIMITLESS THAN 50
(APPRECIABLE AMOUNTOF FINES)
(APPRECIABLE AMOUNTOF FINES)
COARSEGRAINEDSOILS
MAJOR DIVISIONS GRAPH LETTER
GM
GC
ML
CL
OL
SILTS AND
CLAYS
SANDS WITHFINES
SANDANDSANDY
SOILS
MH
CH
OH
PT
(LITTLE OR NO FINES)
CLEAN SANDS
GRAVELS WITHFINES
CLEAN GRAVELS
(LITTLE OR NO FINES)
WELL-GRADED GRAVELS, GRAVEL -SAND MIXTURES
CLAYEY GRAVELS, GRAVEL - SAND -CLAY MIXTURES
WELL-GRADED SANDS, GRAVELLYSANDS
POORLY-GRADED SANDS, GRAVELLYSAND
SILTY SANDS, SAND - SILT MIXTURES
CLAYEY SANDS, SAND - CLAYMIXTURES
INORGANIC SILTS, ROCK FLOUR,CLAYEY SILTS WITH SLIGHTPLASTICITY
INORGANIC CLAYS OF LOW TOMEDIUM PLASTICITY, GRAVELLYCLAYS, SANDY CLAYS, SILTY CLAYS,LEAN CLAYS
ORGANIC SILTS AND ORGANIC SILTYCLAYS OF LOW PLASTICITY
INORGANIC SILTS, MICACEOUS ORDIATOMACEOUS SILTY SOILS
INORGANIC CLAYS OF HIGHPLASTICITY
ORGANIC CLAYS AND SILTS OFMEDIUM TO HIGH PLASTICITY
PEAT, HUMUS, SWAMP SOILS WITHHIGH ORGANIC CONTENTSHIGHLY ORGANIC SOILS
SOIL CLASSIFICATION CHART
MORE THAN 50%OF COARSEFRACTION RETAINEDON NO. 4 SIEVE
MORE THAN 50%OF COARSEFRACTION PASSINGON NO. 4 SIEVE
SILTY GRAVELS, GRAVEL - SAND -SILT MIXTURES
POORLY-GRADED GRAVELS,GRAVEL - SAND MIXTURES
LIQUID LIMIT GREATERTHAN 50
Continuous Coring
Bulk or grab
Direct-Push
Piston
Shelby tube
Standard Penetration Test (SPT)
Contact between soil of the same geologicunit
Material Description Contact
Graphic Log Contact
NOTE: The reader must refer to the discussion in the report text and the logs of explorations for a proper understanding of subsurface conditions.Descriptions on the logs apply only at the specific exploration locations and at the time the explorations were made; they are not warranted to berepresentative of subsurface conditions at other locations or times.
Groundwater Contact
Blowcount is recorded for driven samplers as the number ofblows required to advance sampler 12 inches (or distance noted).See exploration log for hammer weight and drop.
"P" indicates sampler pushed using the weight of the drill rig.
"WOH" indicates sampler pushed using the weight of thehammer.
Key to Exploration Logs
Figure A-1
Sampler Symbol Descriptions
ADDITIONAL MATERIAL SYMBOLS
SYMBOLS
Asphalt Concrete
Cement Concrete
Crushed Rock/Quarry Spalls
Topsoil
GRAPH LETTER
AC
CC
SOD Sod/Forest Duff
CR
DESCRIPTIONS
TYPICAL
TS
No Visible SheenSlight SheenModerate SheenHeavy Sheen
Laboratory / Field Tests
2.4-inch I.D. split barrel / Dames & Moore (D&M)
%F%GALCACPCSDDDSHAMCMDMohsOCPMPIPLPPSATXUCUUVS
Sheen Classification
NSSSMSHS
Percent finesPercent gravelAtterberg limitsChemical analysisLaboratory compaction testConsolidation testDry densityDirect shearHydrometer analysisMoisture contentMoisture content and dry densityMohs hardness scaleOrganic contentPermeability or hydraulic conductivityPlasticity indexPoint lead testPocket penetrometerSieve analysisTriaxial compressionUnconfined compressionUnconsolidated undrained triaxial compressionVane shear
Rev 01/2022
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
24
18
18
31
30
41
1
2%F
3SA
4SA
5
6
6
6
12
12
12
18
9
12
52
55
CR
SM
SM
SM
Approximately 6 inches of crushed gravel mixed withdark brown silty fine to medium sand with organicmatter (loose, moist) (existing gravel driveway)
Brown silty fine sand with gravel and organic matter(loose, moist) (fill)
Brownish gray silty fine to medium sand withoccasional gravel, iron oxide staining (loose, moist)(weathered glacial till)
Gray silty fine to medium sand with occasional gravel(very dense, moist) (glacial till)
Notes:
11.5 BA
CC Holocene AcquisitionCompany, LLC Hollow-stem Auger
Diedrich D70 TurboDrillingEquipmentAutohammer140 (lbs) / 30 (in) Drop
WA State Plane NorthNAD83 (feet)1320100180715
535NAVD88
Easting (X)Northing (Y)
Start TotalDepth (ft)
Logged By
Checked By
End
Surface Elevation (ft)Vertical Datum
Drilled
HammerData
SystemDatum
Driller DrillingMethod
Groundwater not observed at time of exploration
6/21/20226/21/2022
Note: See Figure A-1 for explanation of symbols.Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Aerial Imagery.
Sheet 1 of 1Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-1
Renton Regional Fire Authority, Station 16 Replacement
Figure A-2
Da
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%
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(
%
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FIELD DATA
Sa
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)
530
525
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
9 37
1
2
3
4%F
5
6
6
6
12
12
18
18
6
27
50
50
CR
SM
SM/TS
SM
SM
SM
Approximately 6 inches of crushed gravel mixed withdark brown silty fine to medium sand with organicmatter (loose, moist) (existing gravel driveway)
Brown silty fine to medium sand with occasional gravel(loose, wet) (fill)
Dark brown silty fine to medium sand with occasionalgravel and organic matter (loose, moist) (fill/relicttopsoil)
Brownish gray silty fine to medium sand withoccasional gravel, iron oxide staining (loose, moist)(weathered glacial till)
Brown silty fine to medium sand with gravel (mediumdense, moist)
Brown silty fine to medium sand with gravel (dense,moist) (glacial till)
Notes:
11.5 BA
CC Holocene AcquisitionCompany, LLC Hollow-stem Auger
Diedrich D70 TurboDrillingEquipmentAutohammer140 (lbs) / 30 (in) Drop
WA State Plane NorthNAD83 (feet)1320096180541
542NAVD88
Easting (X)Northing (Y)
Start TotalDepth (ft)
Logged By
Checked By
End
Surface Elevation (ft)Vertical Datum
Drilled
HammerData
SystemDatum
Driller DrillingMethod
Groundwater not observed at time of exploration
6/21/20226/21/2022
Note: See Figure A-1 for explanation of symbols.Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Aerial Imagery.
Sheet 1 of 1Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-2
Renton Regional Fire Authority, Station 16 Replacement
Figure A-3
Da
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8
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P
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Mo
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%
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(
%
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FIELD DATA
Sa
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5
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
19
19
34
1
2%F
3MC
4
5
6
6
6
12
18
12
12
20
56
50/6"
50/6"
CR
SM
SM
SM
Approximately 6 inches of crushed gravel mixed withdark brown silty fine to mediums and with organicmatter (loose, moist) (existing gravel driveway)
Dark brown silty fine to medium sand with occasionalgravel (loose, moist to wet) (fill)
Brownish gray silty fine to medium sand withoccasional gravel, iron oxide staining (mediumdense, moist) (weathered glacial till)
Gray silty fine to medium sand with gravel (very dense,moist) (glacial till)
Grades with higher gravel content
Notes:
11 BA
CC Holocene AcquisitionCompany, LLC Hollow-stem Auger
Diedrich D70 TurboDrillingEquipmentAutohammer140 (lbs) / 30 (in) Drop
WA State Plane NorthNAD83 (feet)1320097180410
546NAVD88
Easting (X)Northing (Y)
Start TotalDepth (ft)
Logged By
Checked By
End
Surface Elevation (ft)Vertical Datum
Drilled
HammerData
SystemDatum
Driller DrillingMethod
Groundwater not observed at time of exploration
6/22/20226/22/2022
Note: See Figure A-1 for explanation of symbols.Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Aerial Imagery.
Sheet 1 of 1Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-3
Renton Regional Fire Authority, Station 16 Replacement
Figure A-4
Da
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8
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/
2
2
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a
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:
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REMARKS
Mo
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%
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Fi
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(
%
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FIELD DATA
Sa
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545
540
535
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
12 30
1
2
3SA
4
5
6
6
6
18
18
12
6
36
43
83/11"
50/6"
CR
SM
SM
SM
SM
SM
SM
Approximately 6 inches of crushed gravel mixed withdark brown silty fine sand with organic matter(loose, moist) (existing gravel driveway)
Dark brown silty fine sand with gravel and organicmatter (loose, moist) (fill)
Brown silty fine to medium sand with occasional graveland trace organic matter (loose, moist)
Gray silty fine to medium sand with occasional gravel(dense, moist) (weathered glacial till)
Gray silty fine to medium sand with gravel (dense,moist) (glacial till)
Gray silty fine to medium sand with gravel (very dense,moist to wet)
Gray silty fine to medium sand with occasional gravel(very dense, moist)
Notes:
10.5 BA
CC Holocene AcquisitionCompany, LLC Hollow-stem Auger
Diedrich D70 TurboDrillingEquipmentAutohammer140 (lbs) / 30 (in) Drop
WA State Plane NorthNAD83 (feet)1320009180305
551NAVD88
Easting (X)Northing (Y)
Start TotalDepth (ft)
Logged By
Checked By
End
Surface Elevation (ft)Vertical Datum
Drilled
HammerData
SystemDatum
Driller DrillingMethod
Groundwater not observed at time of exploration
6/22/20226/22/2022
Note: See Figure A-1 for explanation of symbols.Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Aerial Imagery.
Sheet 1 of 1Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-4
Renton Regional Fire Authority, Station 16 Replacement
Figure A-5
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8
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t
e
d
S
a
m
p
l
e
De
p
t
h
(
f
e
e
t
)
0
5
10
Gr
a
p
h
i
c
L
o
g
Gr
o
u
p
Cl
a
s
s
i
f
i
c
a
t
i
o
n
El
e
v
a
t
i
o
n
(
f
e
e
t
)
550
545
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
18
12
10
41
39
1
2
3MC
4%F
5%F
6
7
8
9
10
6
6
18
18
16
18
12
6
6
11
14
46
90/10"
75
50/6"
50/2"
50/6"
50/5"
CR
ML
SM
SM
SM
SM
Approximately 6 inches of crushed gravel mixed withdark brown sandy silt with organic matter (loose,moist) (existing gravel driveway)
Brown sandy silt with occasional gravel and organicmatter (soft, moist to wet) (fill)
Brown silty fine to medium sand with occasional graveland trace organic matter (loose, wet)
Grayish brown silty fine to medium sand with gravel(medium dense, moist) (weathered glacial till)
Brownish gray silty fine to medium sand with gravel(dense, moist)
Gray silty fine to medium sand with gravel (very dense,moist) (glacial till)
Grades to with occasional cobbles
Grades to with lower fines content
Notes:
31 BA
CC Holocene AcquisitionCompany, LLC Hollow-stem Auger
Diedrich D70 TurboDrillingEquipmentAutohammer140 (lbs) / 30 (in) Drop
WA State Plane NorthNAD83 (feet)1320005180676
542NAVD88
Easting (X)Northing (Y)
Start TotalDepth (ft)
Logged By
Checked By
End
Surface Elevation (ft)Vertical Datum
Drilled
HammerData
SystemDatum
Driller DrillingMethod
Groundwater not observed at time of exploration
6/21/20226/21/2022
Note: See Figure A-1 for explanation of symbols.Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Aerial Imagery.
Sheet 1 of 1Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-5
Renton Regional Fire Authority, Station 16 Replacement
Figure A-6
Da
t
e
:
8
/
2
/
2
2
P
a
t
h
:
P
:
\
2
6
\
2
6
0
1
6
0
0
1
\
G
I
N
T
\
2
6
0
1
6
0
0
1
0
0
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
L
I
B
R
A
R
Y
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
G
E
O
T
E
C
H
_
S
T
A
N
D
A
R
D
_
%
F
_
N
O
_
G
W
REMARKS
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
Fi
n
e
s
Co
n
t
e
n
t
(
%
)
FIELD DATA
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Re
c
o
v
e
r
e
d
(
i
n
)
In
t
e
r
v
a
l
Bl
o
w
s
/
f
o
o
t
Co
l
l
e
c
t
e
d
S
a
m
p
l
e
De
p
t
h
(
f
e
e
t
)
0
5
10
15
20
25
30
Gr
a
p
h
i
c
L
o
g
Gr
o
u
p
Cl
a
s
s
i
f
i
c
a
t
i
o
n
El
e
v
a
t
i
o
n
(
f
e
e
t
)
540
53
5
530
525
520
515
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
No recovery with SPT sampler, followed withCalifornia sampler55 blows/foot for SPT
No recovery with SPT sampler, followed withCalifornia sampler60 blows/foot fot SPT
11 38
1
2
3
4
5SA
6
7
8
9
10
6
6
6
4
18
18
0
10
5
6
12
22
40
62
50/3"
50/4"
50/5"
50/6"
TS
ML
TS
SM
SM
SM
SM
Approximately 6 inches of topsoil/sod
Brown sandy silt with occasional gravel and organicmatter (soft, wet) (fill)
Dark brown to black relict topsoil/sod (soft, moist)
Brown silty fine to medium sand with occasionalgravel, iron oxide staining (medium dense, moist)(weathered glacial till)
Brown silty fine to medium sand with gravel andcobbles (very dense, moist) (glacial till)
Grayish brown silty fine to medium sand with graveland cobbles (very dense, moist)
Grayish silty fine to medium sand with gravel (verydense, moist)
Grades to with lower fines content
Grades to with higher fines content
Notes:
30.5 BA
CC Holocene AcquisitionCompany, LLC Hollow-stem Auger
Diedrich D70 TurboDrillingEquipmentAutohammer140 (lbs) / 30 (in) Drop
WA State Plane NorthNAD83 (feet)1320093180656
537NAVD88
Easting (X)Northing (Y)
Start TotalDepth (ft)
Logged By
Checked By
End
Surface Elevation (ft)Vertical Datum
Drilled
HammerData
SystemDatum
Driller DrillingMethod
Groundwater not observed at time of exploration
6/21/20226/21/2022
Note: See Figure A-1 for explanation of symbols.Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Aerial Imagery.
Sheet 1 of 1Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-6
Renton Regional Fire Authority, Station 16 Replacement
Figure A-7
Da
t
e
:
8
/
2
/
2
2
P
a
t
h
:
P
:
\
2
6
\
2
6
0
1
6
0
0
1
\
G
I
N
T
\
2
6
0
1
6
0
0
1
0
0
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
L
I
B
R
A
R
Y
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
G
E
O
T
E
C
H
_
S
T
A
N
D
A
R
D
_
%
F
_
N
O
_
G
W
REMARKS
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
Fi
n
e
s
Co
n
t
e
n
t
(
%
)
FIELD DATA
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Re
c
o
v
e
r
e
d
(
i
n
)
In
t
e
r
v
a
l
Bl
o
w
s
/
f
o
o
t
Co
l
l
e
c
t
e
d
S
a
m
p
l
e
De
p
t
h
(
f
e
e
t
)
0
5
10
15
20
25
30
Gr
a
p
h
i
c
L
o
g
Gr
o
u
p
Cl
a
s
s
i
f
i
c
a
t
i
o
n
El
e
v
a
t
i
o
n
(
f
e
e
t
)
535
53
0
525
520
515
510
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
26
18 42
1
2
3MC
4%F
5
6
7
8
9
10
6
6
18
18
18
18
12
6
5
6
30
17
58
68
50/6"
50/6"
50/5"
50/6"
TS
SM
SM
SM
SM
SM
Black topsoil with occasional gravel and abundantorganic matter
Dark brown silty fine to medium sand with occasionalgravel and organic matter (loose, moist to wet)
Brown silty fine to medium sand with occasional graveland trace organic matter, iron oxide staining(dense, moist to wet) (weathered glacial till)
Grayish brown silty fine to medium sand withoccasional gravel, iron oxide staining (mediumdense, moist)
Brown silty fine to medium sand with occasional gravel(very dense, moist) (glacial till)
Brownish gray silty fine to medium sand with gravel(very dense, moist)
Grades to with lower fines content and higher gravelcontent
Becomes gray
Notes:
30.5 BA
CC Holocene AcquisitionCompany, LLC Hollow-stem Auger
Diedrich D70 TurboDrillingEquipmentAutohammer140 (lbs) / 30 (in) Drop
WA State Plane NorthNAD83 (feet)1320123180364
546NAVD88
Easting (X)Northing (Y)
Start TotalDepth (ft)
Logged By
Checked By
End
Surface Elevation (ft)Vertical Datum
Drilled
HammerData
SystemDatum
Driller DrillingMethod
Groundwater not observed at time of exploration
6/22/20226/22/2022
Note: See Figure A-1 for explanation of symbols.Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Aerial Imagery.
Sheet 1 of 1Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-7
Renton Regional Fire Authority, Station 16 Replacement
Figure A-8
Da
t
e
:
8
/
2
/
2
2
P
a
t
h
:
P
:
\
2
6
\
2
6
0
1
6
0
0
1
\
G
I
N
T
\
2
6
0
1
6
0
0
1
0
0
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
L
I
B
R
A
R
Y
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
G
E
O
T
E
C
H
_
S
T
A
N
D
A
R
D
_
%
F
_
N
O
_
G
W
REMARKS
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
Fi
n
e
s
Co
n
t
e
n
t
(
%
)
FIELD DATA
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Re
c
o
v
e
r
e
d
(
i
n
)
In
t
e
r
v
a
l
Bl
o
w
s
/
f
o
o
t
Co
l
l
e
c
t
e
d
S
a
m
p
l
e
De
p
t
h
(
f
e
e
t
)
0
5
10
15
20
25
30
Gr
a
p
h
i
c
L
o
g
Gr
o
u
p
Cl
a
s
s
i
f
i
c
a
t
i
o
n
El
e
v
a
t
i
o
n
(
f
e
e
t
)
545
540
535
530
525
520
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
No recovery with SPT sampler, followed withCalifornia sampler50/6" blows/foot for SPT
23
10 32
1
2
3MC
4
5%F
6
7
8
9
10
6
6
12
16
12
6
6
2
1
0
12
50/6"
50/6"
50/6"
50/6"
50/6"
50/4"
TS
SM
SM
SM
SM
SM
Black topsoil with occasional gravel and abundantorganic matter
Brown silty fine to medium sand with occasionalgravel, iron oxide staining (very loose, wet) (fill?)
Grayish brown silty fine to medium sand with tracegravel, iron oxide staining (medium dense, moist towet) (weathered glacial till)
Brownish gray silty fine to medium sand with tracegravel (very dense, moist)
Brownish gray silty fine to medium sand with gravel(very dense, moist)
Gray silty fine to medium sand with occasional gravel(very dense, moist)
Notes:
31 BA
CC Holocene AcquisitionCompany, LLC Hollow-stem Auger
Diedrich D70 TurboDrillingEquipmentAutohammer140 (lbs) / 30 (in) Drop
WA State Plane NorthNAD83 (feet)1320122180318
549NAVD88
Easting (X)Northing (Y)
Start TotalDepth (ft)
Logged By
Checked By
End
Surface Elevation (ft)Vertical Datum
Drilled
HammerData
SystemDatum
Driller DrillingMethod
Groundwater not observed at time of exploration
6/22/20226/22/2022
Note: See Figure A-1 for explanation of symbols.Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Aerial Imagery.
Sheet 1 of 1Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-8
Renton Regional Fire Authority, Station 16 Replacement
Figure A-9
Da
t
e
:
8
/
2
/
2
2
P
a
t
h
:
P
:
\
2
6
\
2
6
0
1
6
0
0
1
\
G
I
N
T
\
2
6
0
1
6
0
0
1
0
0
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
L
I
B
R
A
R
Y
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
G
E
O
T
E
C
H
_
S
T
A
N
D
A
R
D
_
%
F
_
N
O
_
G
W
REMARKS
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
Fi
n
e
s
Co
n
t
e
n
t
(
%
)
FIELD DATA
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Re
c
o
v
e
r
e
d
(
i
n
)
In
t
e
r
v
a
l
Bl
o
w
s
/
f
o
o
t
Co
l
l
e
c
t
e
d
S
a
m
p
l
e
De
p
t
h
(
f
e
e
t
)
0
5
10
15
20
25
30
Gr
a
p
h
i
c
L
o
g
Gr
o
u
p
Cl
a
s
s
i
f
i
c
a
t
i
o
n
El
e
v
a
t
i
o
n
(
f
e
e
t
)
54
5
540
535
530
525
520
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
Perched groundwater observed at approximately10 feet below existing ground surface
26
20
15 30
1
2
3MC
4
5
6MC
7SA
8
9
10
6
6
18
3
3
9
5
5
10
5
11
11
44
70
50/5"
50/4"
50/4"
50/5"
SOD
ML
SM
SM
SM
SM
SM
SM
Approximately 4 inches of topsoil/sod
Brown sandy silt with occasional gravel (very soft, wet)(fill)
Brown silty fine to medium sand with occasional gravel(very loose, wet)
Brown silty fine to medium sand with organic matter(medium dense, wet)
Dark brown silty fine to medium sand with occasionalgravel and organic matter (medium dense, wet)
Brown silty fine to medium sand with occasional gravel(dense, wet) (weathered glacial till)
Brown silty fine to medium sand with gravel (verydense, wet) (glacial till)
Brown silty fine to medium sand with gravel (verydense, moist)
Becomes gray
Grades to with lower fines content
Notes:
50.5 BA
CC Holocene AcquisitionCompany, LLC Hollow-stem Auger
Diedrich D70 TurboDrillingEquipmentAutohammer140 (lbs) / 30 (in) Drop
WA State Plane NorthNAD83 (feet)1320039180602
540NAVD88
Easting (X)Northing (Y)
Start TotalDepth (ft)
Logged By
Checked By
End
Surface Elevation (ft)Vertical Datum
Drilled
HammerData
SystemDatum
Driller DrillingMethod
See "Remarks" section for groundwater observed
6/20/20226/20/2022
Note: See Figure A-1 for explanation of symbols.Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Aerial Imagery.
Sheet 1 of 2Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-9
Renton Regional Fire Authority, Station 16 Replacement
Figure A-10
Da
t
e
:
8
/
2
/
2
2
P
a
t
h
:
P
:
\
2
6
\
2
6
0
1
6
0
0
1
\
G
I
N
T
\
2
6
0
1
6
0
0
1
0
0
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
L
I
B
R
A
R
Y
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
G
E
O
T
E
C
H
_
S
T
A
N
D
A
R
D
_
%
F
_
N
O
_
G
W
REMARKS
Mo
i
s
t
u
r
e
Co
n
t
e
n
t
(
%
)
Fi
n
e
s
Co
n
t
e
n
t
(
%
)
FIELD DATA
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
n
g
Re
c
o
v
e
r
e
d
(
i
n
)
In
t
e
r
v
a
l
Bl
o
w
s
/
f
o
o
t
Co
l
l
e
c
t
e
d
S
a
m
p
l
e
De
p
t
h
(
f
e
e
t
)
0
5
10
15
20
25
30
35
Gr
a
p
h
i
c
L
o
g
Gr
o
u
p
Cl
a
s
s
i
f
i
c
a
t
i
o
n
El
e
v
a
t
i
o
n
(
f
e
e
t
)
535
530
525
52
0
515
510
505
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
11
12
13
14
6
4
6
6
50/6"
50/4"
50/6"
50/6"
Sheet 2 of 2Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-9 (continued)
Renton Regional Fire Authority, Station 16 Replacement
Figure A-10
Da
t
e
:
8
/
2
/
2
2
P
a
t
h
:
P
:
\
2
6
\
2
6
0
1
6
0
0
1
\
G
I
N
T
\
2
6
0
1
6
0
0
1
0
0
.
G
P
J
D
B
L
i
b
r
a
r
y
/
L
i
b
r
a
r
y
:
G
E
O
E
N
G
I
N
E
E
R
S
L
I
B
R
A
R
Y
_
D
F
_
S
T
D
_
U
S
_
J
U
N
E
_
2
0
1
7
.
G
L
B
/
G
E
I
8
_
G
E
O
T
E
C
H
_
S
T
A
N
D
A
R
D
_
%
F
_
N
O
_
G
W
REMARKS
Mo
i
s
t
u
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e
Co
n
t
e
n
t
(
%
)
Fi
n
e
s
Co
n
t
e
n
t
(
%
)
FIELD DATA
Sa
m
p
l
e
N
a
m
e
Te
s
t
i
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g
Re
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v
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r
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d
(
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n
)
In
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l
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d
S
a
m
p
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De
p
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h
(
f
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35
40
45
50
Gr
a
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L
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Gr
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v
a
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(
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t
)
500
495
49
0
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
23
17
15
36
34
38
1
2%F
3SA
4
5%F
6
7
8
9
10
6
6
18
17
17
12
12
4
6
5
23
79/11"
79/11"
50/6"
50/6"
50/4"
50/6"
50/5"
CR
ML
SM
SM
SM
SM
SM
SM
SM
Approximately 6 inches of crushed gravel mixed withdark brown sandy silt with organic matter (loose,moist) (existing gravel driveway)
Dark brown sandy silt with occasional gravel andorganic matter (soft, moist to wet)Becomes brown
Grayish brown silty fine to medium sand with gravel,iron oxide staining (medium dense, moist)(weathered glacial till)
Brown silty fine to coarse sand with gravel (very dense,moist) (glacial till)
Grayish brown silty fine to coarse sand with gravel(very dense, moist)
Brownish gray silty fine to medium sand with gravel(very dense, moist)
Gray silty fine to medium sand with occasional gravel(very dense, moist)
Gray silty fine to medium sand with gravel and cobbles(very dense, moist)
Gray silty fine to medium sand with occasional gravel(very dense, wet)
Notes:
40.5 BA
CC Holocene AcquisitionCompany, LLC Hollow-stem Auger
Diedrich D70 TurboDrillingEquipmentAutohammer140 (lbs) / 30 (in) Drop
WA State Plane NorthNAD83 (feet)1320119180248
548NAVD88
Easting (X)Northing (Y)
Start TotalDepth (ft)
Logged By
Checked By
End
Surface Elevation (ft)Vertical Datum
Drilled
HammerData
SystemDatum
Driller DrillingMethod
Groundwater not observed at time of exploration
6/20/20226/20/2022
Note: See Figure A-1 for explanation of symbols.Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Aerial Imagery.
Sheet 1 of 2Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-10
Renton Regional Fire Authority, Station 16 Replacement
Figure A-11
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(
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0
5
10
15
20
25
30
35
Gr
a
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h
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L
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Gr
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(
f
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t
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545
540
535
530
52
5
520
515
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
11
12
2
5
50/5"
50/5"
SM Dark gray silty fine to coarse sand with gravel andcobbles (very dense, moist to wet)
Boring terminated at shallower depth than planneddue to refusal
Sheet 2 of 2Project Number:
Project Location:
Project:
Renton, Washington
26016-001-00
Log of Boring GEI-10 (continued)
Renton Regional Fire Authority, Station 16 Replacement
Figure A-11
Da
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8
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%
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FIELD DATA
Sa
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(
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t
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510
MATERIALDESCRIPTION
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
APPENDIX B Laboratory Testing
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
August 5, 2022 | Page B-1 File No. 26016-001-00
APPENDIX B
LABORATORY TESTING
Soil samples obtained from the explorations were transported to GeoEngineers’ laboratory and evaluated
to confirm or modify field classifications, as well as to evaluate engineering properties of the soil samples.
Representative samples were selected for laboratory testing to determine grain size distribution, moisture
content, and percent fines (material passing the U.S. No. 200 sieve). The tests were performed in general
accordance with test methods of ASTM International (ASTM) or other applicable procedures.
Soil Classifications
All soil samples obtained from the explorations were visually classified in the field and/or in our laboratory
using a system based on the Unified Soil Classification System (USCS) and ASTM classification methods
ASTM test method D 2488 was used to visually classify the soil samples, while ASTM D 2487 was used to
classify the soils based on laboratory test results. These classification procedures are incorporated in the
boring logs shown in Figure A-2 through A-11 in Appendix A.
Moisture Content Determinations
Moisture content tests were completed in general accordance with ASTM D 2216 for representative
samples obtained from the explorations. The results of these tests are presented on the exploration logs in
Appendix A at the respective sample depths.
Percent Passing U.S. No. 200 Sieve (#F)
Selected samples were “washed” through the No. 200 mesh sieve to estimate the relative percentages of
coarse and fine-grained particles in the soil. The percent passing value represents the percentage by weight
of the sample finer than the U.S. No. 200 sieve. These tests were conducted to verify field descriptions and
to estimate the fines content for analysis purposes. The tests were conducted in accordance with ASTM
D 1140, and the results of these tests are presented on the exploration logs in Appendix A at the respective
sample depths.
Sieve Analyses
Sieve analyses were performed on selected samples in general accordance with ASTM D 422. The wet
sieve analysis method was used to determine the percentage of soil greater than the U.S. No. 200 mesh
sieve. The results of the sieve analyses were plotted and were classified in general accordance with the
Unified Soil Classification System (USCS) and are presented in Figures B-1 and B-2.
It should be noted that the sieve analyses were performed on soils obtained from samplers that have an
opening size of 1½ inches, so larger sized particles cannot be obtained by the samplers. Therefore, the
sieve results do not account for soil particles that are larger than 1½ inches. Soils with larger sized
materials are described in this report qualitatively based on visual observations and experience on projects
where excavations were made into similar formations.
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
PE
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GRAIN SIZE IN MILLIMETERS
U.S. STANDARD SIEVE SIZE
2”
SAND SILT OR CLAYCOBBLESGRAVEL
COARSE MEDIUM FINECOARSEFINE
Boring Number
Depth
(feet)Soil Description
GEI-1
GEI-1
GEI-4
GEI-6
2.5
5
2.5
7.5
Silty fine to medium sand with gravel (SM)
Silty fine to medium sand (SM)
Silty fine to medium sand with gravel (SM)
Silty fine sand with gravel (SM)
Symbol
Moisture
(%)
18
18
12
11
3/8”3”1.5”#4 #10 #20 #40 #60 #1003/4”
Fi
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B
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t
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20616-001-00 Date Exported: 07/19/2022
Note:This report may not be reproduced,except in full,without written approval of GeoEngineers,Inc.Test results are applicable only to the specific sample on which they were
performed,and should not be interpreted as representative of any other samples obtainedat othertimes,depths or locations,or generated by separate operations orprocesses.
Thegrain size analysis resultswereobtained in general accordance with ASTM C136.GeoEngineers 17425 NE Union Hill Road Ste 250,Redmond,WA 98052
#2001”#140
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000
PE
R
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N
T
P
A
S
S
I
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B
Y
W
E
I
G
H
T
GRAIN SIZE IN MILLIMETERS
U.S. STANDARD SIEVE SIZE
2”
SAND SILT OR CLAYCOBBLESGRAVEL
COARSE MEDIUM FINECOARSEFINE
Boring Number
Depth
(feet)Soil Description
GEI-9
GEI-10
15
2.5
Silty fine to medium sand with gravel (SM)
Silty fine to medium sand with gravel (SM)
Symbol
Moisture
(%)
15
17
3/8”3”1.5”#4 #10 #20 #40 #60 #1003/4”
Fi
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B
-2
Si
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20616-001-00 Date Exported: 07/19/2022
Note:This report may not be reproduced,except in full,without written approval of GeoEngineers,Inc.Test results are applicable only to the specific sample on which they were
performed,and should not be interpreted as representative of any other samples obtainedat othertimes,depths or locations,or generated by separate operations orprocesses.
Thegrain size analysis resultswereobtained in general accordance with ASTM C136.GeoEngineers 17425 NE Union Hill Road Ste 250,Redmond,WA 98052
#2001”#140
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
APPENDIX C Report Limitations and Guidelines for Use
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
August 5, 2022 | Page C-1 File No. 26016-001-00
APPENDIX C
REPORT LIMITATIONS AND GUIDELINES FOR USE1
This appendix provides information to help you manage your risks with respect to the use of this report.
Geotechnical Services Are Performed for Specific Purposes, Persons and Projects
This report has been prepared for the exclusive use of Renton Regional Fire Authority (RRFA) and their
authorized agents and/or regulatory agencies for the proposed Station 16 replacement project at 15815
SE 128th Street in Renton, Washington. This report is not intended for use by others, and the information
contained herein is not applicable to other sites.
GeoEngineers structures our services to meet the specific needs of our clients. For example, a geotechnical
or geologic study conducted for a civil engineer or architect may not fulfill the needs of a construction
contractor or even another civil engineer or architect that are involved in the same project. Because each
geotechnical or geologic study is unique, each geotechnical engineering or geologic report is unique,
prepared solely for the specific client and project site. Our report is prepared for the exclusive use of our
Client. No other party may rely on the product of our services unless we agree in advance to such reliance
in writing. This is to provide our firm with reasonable protection against open-ended liability claims by third
parties with whom there would otherwise be no contractual limits to their actions. Within the limitations of
scope, schedule and budget, our services have been executed in accordance with our Agreement with the
Client and generally accepted geotechnical practices in this area at the time this report was prepared. This
report should not be applied for any purpose or project except the one originally contemplated.
A Geotechnical Engineering or Geologic Report Is Based on a Unique Set of Project-specific
Factors
This report has been prepared for the Station 16 replacement project located at 15815 SE 128th Street in
Renton, Washington. GeoEngineers considered a number of unique, project-specific factors when
establishing the scope of services for this project and report. Unless GeoEngineers specifically indicates
otherwise, do not rely on this report if it was:
■ Not prepared for you,
■ Not prepared for your project,
■ Not prepared for the specific site explored, or
■ Completed before important project changes were made.
For example, changes that can affect the applicability of this report include those that affect:
1 Developed based on material provided by GBA, GeoProfessional Business Association; www.geoprofessional.org.
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
August 5, 2022 | Page C-2 File No. 26016-001-00
■ The function of the proposed structure,
■ Elevation, configuration, location, orientation or weight of the proposed structure,
■ Composition of the design team; or
■ Project ownership.
If important changes are made after the date of this report, GeoEngineers should be given the opportunity
to review our interpretations and recommendations and provide written modifications or confirmation, as
appropriate.
Subsurface Conditions Can Change
This geotechnical or geologic report is based on conditions that existed at the time the study was performed.
The findings and conclusions of this report may be affected by the passage of time, by manmade events
such as construction on or adjacent to the site, or by natural events such as floods, earthquakes, slope
instability or groundwater fluctuations. Always contact GeoEngineers before applying a report to determine
if it remains applicable.
Most Geotechnical and Geologic Findings Are Professional Opinions
Our interpretations of subsurface conditions are based on field observations from widely spaced sampling
locations at the site. Site exploration identifies subsurface conditions only at those points where subsurface
tests are conducted or samples are taken. GeoEngineers reviewed field and laboratory data and then
applied our professional judgment to render an opinion about subsurface conditions throughout the site.
Actual subsurface conditions may differ, sometimes significantly, from those indicated in this report. Our
report, conclusions and interpretations should not be construed as a warranty of the subsurface conditions.
Geotechnical Engineering Report Recommendations Are Not Final
Do not over-rely on the preliminary construction recommendations included in this report. These
recommendations are not final, because they were developed principally from GeoEngineers’ professional
judgment and opinion. GeoEngineers’ recommendations can be finalized only by observing actual
subsurface conditions revealed during construction. GeoEngineers cannot assume responsibility or liability
for this report's recommendations if we do not perform construction observation.
Sufficient monitoring, testing and consultation by GeoEngineers should be provided during construction to
confirm that the conditions encountered are consistent with those indicated by the explorations, to provide
recommendations for design changes should the conditions revealed during the work differ from those
anticipated, and to evaluate whether or not earthwork activities are completed in accordance with our
recommendations. Retaining GeoEngineers for construction observation for this project is the most
effective method of managing the risks associated with unanticipated conditions.
A Geotechnical Engineering or Geologic Report Could Be Subject to Misinterpretation
Misinterpretation of this report by other design team members can result in costly problems. You could
lower that risk by having GeoEngineers confer with appropriate members of the design team after
submitting the report. Also retain GeoEngineers to review pertinent elements of the design team's plans
and specifications. Contractors can also misinterpret a geotechnical engineering or geologic report. Reduce
that risk by having GeoEngineers participate in pre-bid and preconstruction conferences, and by providing
construction observation.
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
August 5, 2022 | Page C-3 File No. 26016-001-00
Do Not Redraw the Exploration Logs
Geotechnical engineers and geologists prepare final boring and testing logs based upon their interpretation
of field logs and laboratory data. To prevent errors or omissions, the logs included in a geotechnical
engineering or geologic report should never be redrawn for inclusion in architectural or other design
drawings. Only photographic or electronic reproduction is acceptable but recognize that separating logs
from the report can elevate risk.
Give Contractors a Complete Report and Guidance
Some owners and design professionals believe they can make contractors liable for unanticipated
subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems,
give contractors the complete geotechnical engineering or geologic report, but preface it with a
clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for
purposes of bid development and that the report's accuracy is limited; encourage them to confer with
GeoEngineers and/or to conduct additional study to obtain the specific types of information they need or
prefer. A pre-bid conference can also be valuable. Be sure contractors have sufficient time to perform
additional study. Only then might an owner be in a position to give contractors the best information
available, while requiring them to at least share the financial responsibilities stemming from unanticipated
conditions. Further, a contingency for unanticipated conditions should be included in your project budget
and schedule.
Contractors Are Responsible for Site Safety on Their Own Construction Projects
Our geotechnical recommendations are not intended to direct the contractor’s procedures, methods,
schedule or management of the work site. The contractor is solely responsible for job site safety and for
managing construction operations to minimize risks to on-site personnel and to adjacent properties.
Read These Provisions Closely
Some clients, design professionals and contractors may not recognize that the geoscience practices
(geotechnical engineering or geology) are far less exact than other engineering and natural science
disciplines. This lack of understanding can create unrealistic expectations that could lead to
disappointments, claims and disputes. GeoEngineers includes these explanatory “limitations” provisions in
our reports to help reduce such risks. Please confer with GeoEngineers if you are unclear how these “Report
Limitations and Guidelines for Use” apply to your project or site.
Geotechnical, Geologic and Environmental Reports Should Not Be Interchanged
The equipment, techniques and personnel used to perform an environmental study differ significantly from
those used to perform a geotechnical or geologic study and vice versa. For that reason, a geotechnical
engineering or geologic report does not usually relate any environmental findings, conclusions or
recommendations, e.g., about the likelihood of encountering underground storage tanks or regulated
contaminants. Similarly, environmental reports are not used to address geotechnical or geologic concerns
regarding a specific project.
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
August 5, 2022 | Page C-4 File No. 26016-001-00
Biological Pollutants
GeoEngineers’ Scope of Work specifically excludes the investigation, detection, prevention or assessment
of the presence of Biological Pollutants. Accordingly, this report does not include any interpretations,
recommendations, findings, or conclusions regarding the detecting, assessing, preventing or abating of
Biological Pollutants and no conclusions or inferences should be drawn regarding Biological Pollutants, as
they may relate to this project. The term “Biological Pollutants” includes, but is not limited to, molds, fungi,
spores, bacteria, and viruses, and/or any of their byproducts.
If Client desires these specialized services, they should be obtained from a consultant who offers services
in this specialized field.
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3
Docusign Envelope ID: 9C8AD163-664C-4B8F-8817-4315F1866DB3