HomeMy WebLinkAboutRS_Geotechnical_Report_220812_v1Geotechnical Engineering Services
Longacres Field Entitlement
Renton, Washington
for
Unico Properties, LLC
June 23, 2022
Geotechnical Engineering Services
Longacres Field Entitlement
Renton, Washington
for
Unico Properties, LLC
June 23, 2022
17425 NE Union Hill Road, Suite 250
Redmond, Washington 98052
425.861.6000
Geotechnical Engineering Services
Longacres Field Entitlement
Renton, Washington
File No. 9061-019-00
June 23, 2022
Prepared for:
Unico Properties, LLC
1215 4th Avenue, Suite 600
Seattle, Washington 98161
Attention: Julia Reeve, Development Manager
Prepared by:
GeoEngineers, Inc.
17425 NE Union Hill Road, Suite 250
Redmond, Washington 98052
425.860.6000
Yen Nhi Amy Nguyen, EIT
Staff Geotechnical Engineer
Matthew W. Smith, PE
Senior Principal
YNAN:MWS:tjh
Disclaimer: Any electronic form, facsimile or hard copy of the original document (email, text, table, and/or figure), if provided, and any attachments are only a
copy of the original document. The original document is stored by GeoEngineers, Inc. and will serve as the official document of record.
June 23, 2022 | Page i
File No. 9061-019-00
Table of Contents
1.0 INTRODUCTION ............................................................................................................................................... 1
2.0 SCOPES OF SERVICES .................................................................................................................................... 1
3.0 PROJECT DESCRIPTION .................................................................................................................................. 1
4.0 PREVIOUS SITE EVALUATIONS ....................................................................................................................... 1
5.0 SITE CONDITIONS ............................................................................................................................................ 1
5.1. Surface Conditions...................................................................................................................................... 1
5.2. Subsurface Conditions ............................................................................................................................... 2
5.2.1. Soil Conditions ............................................................................................................................ 2
5.2.2. Groundwater Conditions ............................................................................................................. 2
6.0 CONCLUSIONS AND RECOMMENDATIONS ................................................................................................... 3
6.1. Summary of Key Geotechnical Issues ....................................................................................................... 3
6.2. Earthquake Engineering ............................................................................................................................. 3
6.2.1. Ground Shaking .......................................................................................................................... 3
6.2.2. Seismic Hazards ......................................................................................................................... 4
6.3. Site Preparation and Earthwork ................................................................................................................. 5
6.3.1. Clearing and Site Preparation .................................................................................................... 6
6.3.2. Sedimentation and Erosion Control ........................................................................................... 6
6.3.3. Settlement ................................................................................................................................... 7
6.3.4. Subgrade Preparation................................................................................................................. 7
6.3.5. Structural Fill ............................................................................................................................... 7
6.4. Excavations and Permanent Slopes ....................................................................................................... 10
6.4.1. Temporary Cut Slopes ............................................................................................................. 10
6.4.2. Permanent Cut and Fill Slopes ................................................................................................ 11
6.5. Utility Trenches ......................................................................................................................................... 11
6.6. Pavement Recommendations ................................................................................................................. 11
6.6.1. Subgrade Preparation.............................................................................................................. 11
6.6.2. New Hot Mix Asphalt Pavement .............................................................................................. 11
6.6.3. Portland Cement Concrete Pavement .................................................................................... 12
6.7. Recommended Additional Geotechnical Services ................................................................................. 12
7.0 LIMITATIONS ................................................................................................................................................ 13
8.0 REFERENCES ............................................................................................................................................... 13
LIST OF FIGURES
Figure 1. Vicinity Map
Figure 2. Conceptual Site Plan
Figure 3. Exploration Site Plan
APPENDICES
Appendix A. Boring Logs from Previous Explorations
Appendix B. Report Limitations and Guidelines for Use
June 23, 2022 | Page 1
File No. 9061-019-00
1.0 INTRODUCTION
This report presents the results of our geotechnical engineering services for the entitlement of the fields
for the Seattle Sounders training facility in Renton, Washington. The site is shown relative to surrounding
physical features in Figure 1, Vicinity Map, Figure 2, Site Plan and Figure 3, Exploration Site Plan.
The purpose of this report is to provide preliminary geotechnical engineering recommendations that
satisfies the City of Renton Conditional Use Permit (CUP) requirements. The subject property is
approximately 19.36 acres and consists of five King County Parcels (numbers 088670-0110,
088670-0120, 088670-0130, 088670-0370 and 088670-0140). Our services were performed in general
accordance with our proposal dated February 22, 2022. Signed authorization to proceed with our services
was provided by the Unico Properties, LLC on March 1, 2022.
2.0 SCOPES OF SERVICES
GeoEngineers’ scope of services includes:
■ Review available reports and studies for the subject property and surrounding area available from our
files;
■ Providing preliminary earthwork recommendations for site grading including recommendations for
imported fill, compaction criteria, subgrade preparation, utility trench backfill, site drainage and wet
weather construction considerations; and
■ Preparing this report.
3.0 PROJECT DESCRIPTION
We understand that the planned improvements include constructing five new training fields with both
natural grass and artificial turf at the Longacres site (1901 Oaksdale Avenue SW) in Renton, Washington.
The planned training fields are anticipated to require some fill to raise site grades.
4.0 PREVIOUS SITE EVALUATIONS
The logs of selected explorations from previous site evaluations in the project vicinity were reviewed and
are presented in Appendix A, Exploration Logs from Previous Studies. The approximate locations of these
explorations are shown on Figure 2.
5.0 SITE CONDITIONS
5.1. Surface Conditions
The proposed training fields are bounded by landscaping and a wetland to the north and west, and the
Boeing BCAG Headquarter Building 25-20 and associated surface parking to the east, and private property
to the south. Based on conceptual plans provided by Unico and a survey by NV5 dated April 6, 2021, the
soccer field’s proposed layout is located on Lots 11 through 14 and a portion of Tract B. The site is currently
June 23, 2022 | Page 2 File No. 9061-019-00
occupied by a surface parking lot, landscaping and wetland areas. Existing site grades slope gently down
from west to east from approximately Elevation 17 to 10 feet.
Buried utilities consisting of sanitary sewer, storm drain, gas, water, electric, and telecommunications fiber
are anticipated within the rights-of-way adjacent to the site and through the surface parking lot.
5.2. Subsurface Conditions
5.2.1. Soil Conditions
GeoEngineers’ understanding of subsurface conditions is based on review of existing geotechnical
information in the vicinity of the project site. The approximate locations of the previous explorations are
presented in Figure 2.
The soils encountered in the site vicinity consist of shallow fill overlying alluvial deposits, beach deposits
and glacially consolidated soils.
The fill generally consists of very soft to stiff silt and to medium silty sand with varying amounts of gravel.
Fill in the vicinity of the site ranged to approximately 6 feet thick.
The alluvial deposits were encountered at the existing ground surface or beneath the fill. The alluvial soil
generally consists of loose to medium dense sands and gravels with varying amounts of silt and very soft
to medium stiff silt. The sand and silty sand deposits were generally interbedded with lenses of soft to
medium stiff organic silt. The alluvial deposits in the vicinity of the site range up to approximately 45 feet
deep.
Beach deposits are present below the alluvial deposits and consist of medium dense to very dense sand
and gravel with variable silt content.
The glacially consolidated soils were encountered below the beach deposits and extended to the depths
explored in the borings and cone penetration tests (CPT). The glacially consolidated soils consist of medium
dense to very dense sands with varying amounts of silt and gravel.
Although not encountered in previous explorations, occasional cobbles and boulders are typical of glacially
consolidated soils and may be present at the site and have been encountered in nearby construction
projects.
5.2.2. Groundwater Conditions
The ground water levels in the vicinity of the site will fluctuate as a function of season, precipitation and
water levels in the Green River. Based on our review of the available subsurface information, the regional
groundwater table in the project vicinity varies seasonally at the site and is near the ground surface
elevation during extended periods of wet weather.
June 23, 2022 | Page 3 File No. 9061-019-00
6.0 CONCLUSIONS AND RECOMMENDATIONS
6.1. Summary of Key Geotechnical Issues
Based on our review of available subsurface information and experience on other projects within the area,
we conclude that the planned field improvements can be constructed satisfactorily as planned with respect
to geotechnical elements. The key geotechnical issues for the project include:
■ The site is designated as seismic Site Class F per the 2018 International Building Code (IBC)
(IBC 2018), due to the presence of potentially liquefiable soils. Site-response analysis is required for
Site Class F sites; however, an exception is made for structures that have fundamental periods of
vibration less than 0.5 second (sec). Based on our conversation with the structural engineer, we
understand that the fundamental period of vibration of the proposed structure will be less than 0.5 sec
and therefore this exception applies. Because of this, the response spectrum for Site Class E can be
assumed for preliminary design based on the standard penetration test (SPT) blow counts obtained in
nearby previous borings.
■ The existing fill and alluvial deposits encountered in the explorations contain a high percentage of fines
and are highly moisture sensitive. We expect that operation of equipment on these soils will be difficult
during the wet season (typically October through May) and in wet weather conditions.
■ On-site soils free of organics and organic silt may be used as structural fill during dry weather conditions
(typically June through September) provided the material is properly moisture conditioned (likely need
to be dried) to achieve proper compaction. Organic soils and organic silt should be removed from the
site, if encountered during grading. Site preparation and earthwork should be completed during the
drier months to reduce costs associated with these activities. Imported gravel borrow should be used
as structural fill during wet weather conditions and during the wet season (typically October through
May).
■ Design of the fields should consider estimated site settlement because of the underlying fill and alluvial
deposits. In addition to being susceptible to liquefaction, the alluvial soils are compressible and are
expected to settle under new/increased loading conditions. Static settlements will depend on the
thickness of new fill placed.
These geotechnical issues and other considerations are discussed further and recommendations
pertaining to geotechnical aspects of the project are presented in the following sections.
6.2. Earthquake Engineering
6.2.1. Ground Shaking
There is a risk of earthquake induced ground shaking at the site, as with all sites in the Puget Sound region,
and the intensity of the ground shaking could be severe. The severity of ground shaking will be mostly a
function of the earthquake magnitude and proximity to the site. We recommend that the seismic ground
shaking at the site be evaluated in accordance with the 2018 International Building Code (IBC).
6.2.1.1. 2018 IBC Seismic Design Information
The 2018 IBC references ASCE 7-16 for the Site Class determination and the development of seismic
design parameters. The loose to medium dense granular soils below the water have moderate to high
liquefaction potential. Accordingly, the site is Site Class F per ASCE 7-16 Section 20.3.1. Site response
June 23, 2022 | Page 4 File No. 9061-019-00
analysis is required for Site Class F sites per Section 11.4.8. However, Section 20.3.1 provides an exception
for structures that have a fundamental period of vibration equal to or less than 0.5 seconds, whereby the
Site Class may be determined in accordance with Section 20.3 and the corresponding site coefficients
determined per Section 11.4.4 to derive prescriptive seismic design parameters. The seismic design
parameters presented in Table 1 below assume that the proposed structures will have a fundamental
period of vibration equal to or less than 0.5 seconds, based on conversations we have had with the
structural engineer.
Accordingly, based on the subsurface data from the borings completed in the project vicinity, the response
spectrum for Site Class E can be used for preliminary design for the purpose of developing seismic design
parameters. Further, per ASCE 7-16 Supplement 3 Section 11.4.8, a site-specific ground motion hazard
analysis and/or ground response analysis is required to determine design ground motions for structures
on Site Class E sites with SS ≥1.0 or S1≥0.2. The mapped SS and S1 values for this site are 1.45 and 0.49,
respectively; therefore, these provisions apply. Alternative to performing a site-specific evaluation, the
parameters listed in Table 1 below may be used provided Exceptions 1 and 2 of ASCE 7-16 Supplement 3
Section 11.4.8 are used. Refer to ASCE 7-16 Supplement 3 Section 11.4.8 for further details.
We recommend the use of the following 2018 IBC parameters for short period spectral response
acceleration (SS), 1-second period spectral response acceleration (S1) and seismic coefficients (FA and FV)
for the project site.
TABLE 1. 2018 IBC DESIGN PARAMETERS
2018 IBC Parameter1 Recommended Values
Site Class E
Short Period Spectral Response Acceleration, SS (g) 1.448
1-Second Period Spectral Response Acceleration, S1 (g) 0.493
Seismic Coefficient, FA 1.202
Seismic Coefficient, FV 2.213
Peak Ground Acceleration (g) 0.616
Site Amplification Factor for PGA, FPGA 1.1
TS (seconds) 0.63
Notes:
1 Parameters developed based on latitude 47.4622 and longitude -122.2343 using the Applied Technology Council (ATC) Hazards
online tool (https://hazards.atcouncile.org/).
2 Per ASCE 7-16 Supplement 3 Section 11.4.8 Table 11.4-1.
3 For calculating TS, determination of Seismic Design Category, linear interpolation for intermediate values of S1, and when taking the
exceptions under Items 1 and 2 of ASCE 7-16 Supplement 3 for the calculation of SD1.
6.2.2. Seismic Hazards
6.2.2.1. Liquefaction Potential
Liquefaction is a phenomenon where strong vibration or ground shaking, usually from earthquakes, results
in development of excess pore pressures in loose, saturated soils and subsequent loss of strength in the
soil deposits so affected.
June 23, 2022 | Page 5 File No. 9061-019-00
Ground settlement, lateral spreading and/or sand boils may result from soil liquefaction. Structures
supported on liquefied soils could suffer foundation settlement or lateral movement that could be severely
damaging to the structures.
Conditions favorable for liquefaction occur in loose to medium dense, clean to moderately silty sand that
is below the groundwater level. Based on our evaluation of the subsurface conditions encountered in the
explorations completed at the site, it is our opinion that potentially liquefiable soils are present below the
proposed fields.
We evaluated the liquefaction triggering potential (Youd and Idriss 2001; Idriss and Boulanger 2014) for
the soils at the site using the simplified method.
Our analysis indicates that the loose to medium dense sand which underlies the site has a moderate to
high risk of liquefying. Structures such as utilities or walkways which are supported on-grade will likely
experience liquefaction-induced and differential settlement during a design seismic event. The amount of
settlement is difficult to estimate because of the complexity of conditions that cause liquefaction. Some
cracking and/or structural damage may be experienced by structures supported on-grade as a result of
liquefaction induced settlement. Structures should be designed per the IBC/ASCE 7-16 criteria for
differential settlement, lateral spreading and bearing capacity. In the event that structures supported on
shallow foundations do not meet the code criteria for differential settlement, lateral spreading and bearing
capacity, deep foundations or ground improvement may be required to mitigate the liquefaction hazard.
Additional explorations in the vicinity of planned structures are recommended during the design phase to
assess the liquefaction hazard further and to meet the code criteria.
6.2.2.2. Lateral Spreading
Lateral spreading is associated with liquefaction and involves lateral displacements of large volumes of
liquefied soil. It can occur on near-level ground as blocks of surface soils displace relative to adjacent
blocks. It also occurs as blocks of surface soils are displaced toward a nearby slope or free-face by
movement of the underlying liquefied soil. Site specific explorations should be completed during the design
phase to further assess the lateral spreading hazard and to determine if additional measures will be
required to meet the IBC/ASCE 7-16 code criteria for planned buildings.
6.2.2.3. 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, or surface displacement due to faulting is
considered to be low.
6.3. Site Preparation and Earthwork
Based on the subsurface soil conditions encountered in the explorations, we expect that the soils at the
site may be excavated using conventional heavy duty construction equipment. The materials anticipated to
be encountered in planned excavations include very soft to stiff and loose to medium dense fill and loose
to medium dense alluvial deposits.
The on-site fill and alluvial soils contain significant fines (particles passing the U.S. Standard No. 200 sieve)
and are highly moisture-sensitive and susceptible to disturbance, especially when wet. 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 support for construction equipment.
June 23, 2022 | Page 6 File No. 9061-019-00
Dry weather construction will help reduce earthwork costs and increase the potential for reusing the
existing fill and native soils as structural fill.
Trafficability on the site is not expected to be difficult during dry weather conditions. However, the fill and
native soils will be susceptible to disturbance from construction equipment during wet weather conditions
and pumping and rutting of the exposed soils under equipment loads may occur.
6.3.1. Clearing and Site Preparation
Construction of the proposed improvements will require clearing and stripping. We expect that there will be
relatively minor site demolition of existing hardscape and utilities. Concrete and asphalt material should be
removed from the site along with other construction debris.
Areas to be developed or graded should be cleared of surface and subsurface deleterious matter including
debris, shrubs, trees and associated stumps and roots. Graded areas should be stripped of organic
materials and topsoil. Based on previous explorations and site observations, we estimate that stripping
depths will be on the order of 2 to 6 inches to remove topsoil within existing field and lawn areas.
The stripped organic soils can be stockpiled and used later for landscaping purposes. Materials that cannot
be used for landscaping should be removed from the project site.
6.3.2. Sedimentation and Erosion Control
Construction activities including stripping and grading will expose soils to the erosional effects of wind and
water. The amount and potential impacts of erosion are partly related to the time of year that construction
actually occurs. Wet weather construction will increase the amount and extent of erosion and potential
sedimentation.
Effective methods of erosion control at construction sites include efficient surface water management,
minimization of the size of disturbed areas, and erosion resistant slope covers. Erosion and sedimentation
control measures should include proper channeling of surface water runoff into lined diversion ditches that
incorporate energy dissipaters, and use of straw bales and geotextile silt fences, as appropriate. Surface
water must not be directed toward the top of slopes or onto slopes.
Management of surface water runoff during construction is the responsibility of the contractor. Grading
must be completed in a manner that avoids concentrated runoff onto fill areas, cut or fill slopes, natural
slopes, or other erosion-sensitive areas.
Erosion and sedimentation control measures may be implemented by using a combination of interceptor
swales, straw bale barriers, silt fences and straw mulch for temporary erosion protection of exposed soils.
Disturbed areas should be finish graded and seeded as soon as practicable to reduce the risk of erosion.
Erosion and sedimentation control measures should be installed and maintained in accordance with the
requirements of the approved project plans and specifications.
6.3.2.1. Erosion Control
To reduce potential erosion and to help establish permanent vegetation on existing and newly created
slopes, we recommend that erosion protection of the slopes include hydroseeding in conjunction with
installation of an erosion control blanket. We recommend that the erosion control blanket be staked to
June 23, 2022 | Page 7 File No. 9061-019-00
disturbed slopes to help reduce the risk of erosion during wet work periods and after the work is completed.
We recommend that the erosion control blanket consist of Curlex 1, manufactured by American Excelsior
Company, or SC150, manufactured by North American Green. We recommend that the erosion control
blanket be installed in accordance with the manufacturer's recommendations and that the installation and
stapling methods be observed during construction.
Hydroseeding and installation of the erosion control blanket should occur as soon as possible and prior to
the wet winter months. Hydroseeding should occur to allow proper germination before the winter. We also
recommend that the hydroseed mix include a tackifier to increase adhesion between the hydroseed mixture
and the fine grained native soils.
6.3.3. Settlement
The site is underlain by compressible silts and organics silts that vary up to approximately 8 feet in
thickness. Placement of fill over the silt and organic silt deposits will result in long term ground settlement
as the silts consolidate. The amount of settlement will depend on factors such as the thickness of the fill,
thickness of the silt and organic silt layers, and groundwater levels at the time fill is placed. We anticipate
that most of the settlement will occur within a period of 1 to 2 months after fill placement.
6.3.4. Subgrade Preparation
Prior to placing new fills, pavement or synthetic turf field base course materials subgrade areas should be
evaluated by proof rolling or probing to locate zones of soft or pumping soils. Prior to proof rolling, unsuitable
soils should be removed from below planned field areas.
Proof rolling can be completed using a piece of heavy tire-mounted equipment such as a loaded dump
truck. During wet weather, the exposed subgrade areas should be probed to determine the extent of soft
soils. If zones of soft or pumping soils are identified, they should be removed and replaced with structural
fill.
Once approved, the subgrade areas should be recompacted to a firm condition, if possible. The degree of
compaction that can be achieved will depend on when construction is performed. If the work is performed
during dry weather conditions, we recommend that subgrade areas be recompacted to at least 95 percent
of the maximum dry density (MDD) obtained using the American Society for Testing and Materials (ASTM)
D 1557 test procedure (modified Proctor). If the work is performed during wet weather conditions, it may
not be possible to recompact the subgrade to 95 percent of the MDD. In this case, we recommend that the
subgrade be compacted to the extent possible without causing undue weaving or pumping of the subgrade
soils.
Subgrade disturbance or deterioration could occur if the subgrade is wet and cannot be dried. If the
subgrade deteriorates during compaction or while being subjected to construction traffic, it may become
necessary to modify the compaction criteria or methods.
6.3.5. Structural Fill
New fill, whether on-site or imported fill for support of the fields, pavement areas and as backfill for utility
trenches should meet the criteria for structural fill presented below. Structural fill soils should be free of
organic matter, debris, man-made contaminants and other deleterious materials, with no individual
June 23, 2022 | Page 8 File No. 9061-019-00
particles larger than 4 inches in greatest dimension. The suitability of soil for use as structural fill depends
on its gradation and moisture content.
6.3.5.1. Fill Criteria
Materials used under the planned fields, new pavement areas, used to construct embankments, or to
backfill utility trenches are classified as structural fill for the purpose of this report. Recommended
structural fill material quality varies depending upon its use as described below:
■ Structural fill placed in the planned fields, parking lot, sidewalk areas, and in utility trenches should
consists of Gravel Borrow as described in Section 9-03.14(1) of the 2022 Washington State
Department of Transportation (WSDOT) Standard Specifications, with the additional restriction that the
fines content be limited to no more than 5 percent, especially if the work occurs in wet weather or
during the wet season (October through May). However, if earthwork occurs during the normally dry
months (June through September) on-site soils that are properly moisture conditioned (dried) and that
can be properly compacted may be used as structural fill in these areas.
■ Crushed surfacing base course below pavements should conform Section 9-03.9 (3) of the 2022
WSDOT Standard Specifications.
■ Utility pipe bedding should conform to Section 9-03.12(3) of the 2022 WSDOT Standard Specifications
unless required otherwise by the civil engineer.
We recommend that the suitability of structural fill soil from proposed borrow sources be evaluated by a
representative of our firm before the earthwork contractor begins transporting the soil to the site.
6.3.5.2. Reuse of On-site Soils
The existing fill and native soils contain a high percentage of fines and will be sensitive to changes in
moisture content and difficult to handle and compact during wet weather.
On-site soils are expected to be suitable for structural fill, provided the work is completed during the
normally dry season (June through September) and that the soil can be properly moisture conditioned.
On-site soils with significant debris, large particles (greater than 4 inches in largest dimension) or organic
matter, including organic silt soils, should not be used as structural fill.
It may be necessary to import Gravel Borrow to achieve adequate compaction during wet weather
construction. Imported structural fill consisting of Gravel Borrow should be planned for this project unless
the earthwork takes place during the normally dry season.
The contractor should plan to cover and maintain all fill stockpiles with plastic sheeting if they will be used
as structural fill. The reuse of on-site soils is highly dependent on the skill of the contractor and schedule,
and we will work with the design team and contractor to maximize the reuse of on-site soils during the wet
and dry seasons.
6.3.5.3. Fill Placement and Compaction Criteria
Structural fill should be mechanically compacted to a firm, non-yielding condition. Structural fill should be
placed in loose lifts not exceeding 12 inches in thickness if using heavy compactors and 6 inches if using
hand operated compaction equipment. The actual lift thickness will be dependent on the structural fill
material used and the type and size of compaction equipment. Each lift should be conditioned to the proper
June 23, 2022 | Page 9 File No. 9061-019-00
moisture content and compacted to the specified density before placing subsequent lifts. Structural fill
should be compacted to the following criteria:
■ All fill placed under the proposed field area should be placed as structural fill compacted to at least
95 percent of the MDD estimated using the ASTM D 1557 test method, unless otherwise required by
the project civil engineer.
■ Structural fill to form permanent fill slopes should be compacted to at least 90 percent of the MDD.
■ Structural fill in new pavement and hardscape areas, including utility trench backfill, should be
compacted to at least 90 percent of the MDD, 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 as crushed surfacing base course below pavements and the synthetic turf fields
should be compacted to 95 percent of the MDD.
■ Non-structural fill, such as fill placed in landscape areas, should be compacted to at least 90 percent
of the MDD.
An adequate number of in-place moisture and density tests should be performed during the placement and
compaction of structural fill to evaluate whether the specified degree of compaction is being achieved.
6.3.5.4. Weather Considerations
Disturbance of near surface soils should be expected, especially if earthwork is completed during periods
of wet weather. During dry weather, the soils will: (1) be less susceptible to disturbance; (2) provide better
support for construction equipment; and (3) be more likely to meet the required compaction criteria.
The wet weather season generally begins in October and continues through May in western Washington;
however, periods of wet weather may occur during any month of the year. For earthwork activities during
wet weather, we recommend that the following steps be taken:
■ The ground surface in and around the work area should be sloped so that surface water is directed
away from the work area. The ground surface should be graded so that areas of ponded water do not
develop. Measures should be taken by the contractor to prevent surface water from collecting in
excavations and trenches. Measures should be implemented to remove surface water from the work
area. Surface water must not be directed towards slopes and we recommend that storm water drainage
ditches be constructed where needed along the crest of slopes to prevent uncontrolled surface water
runoff.
■ Earthwork activities should not take place during periods of moderate to heavy precipitation.
■ Slopes with exposed soils should be covered with plastic sheeting.
■ The contractor should take necessary measures to prevent on-site soils and soils to be used as fill from
becoming wet or unstable. These measures may include the use of 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 help reduce the
extent that these soils become wet or unstable.
■ The contractor should cover all soil stockpiles that will be used as structural fill with plastic sheeting.
June 23, 2022 | Page 10 File No. 9061-019-00
■ Construction activities should be scheduled so that the length of time that soils are left exposed to
moisture is reduced to the extent practical.
6.4. Excavations and Permanent Slopes
The stability of open cut slopes is a function of soil type, groundwater seepage, slope inclination, slope
height and nearby surface loads. The use of inadequately designed open cuts could impact the stability of
adjacent work areas and existing utilities, and endanger personnel. The contractor performing the work has
the primary responsibility for protection of workers and adjacent improvements.
In our opinion, the contractor will be in the best position to observe subsurface conditions continuously
throughout the construction process and to respond to variable soil and groundwater conditions. Therefore,
the contractor should have the primary responsibility for deciding whether or not to use open cut slopes for
much of the excavations rather than some form of temporary excavation support, and for establishing the
safe inclination of the cut slope. Acceptable slope inclinations for utilities and ancillary excavations should
be determined during construction. Because of the diversity of construction techniques and available
shoring systems, the design of temporary shoring is most appropriately left up to the contractor proposing
to complete the installation. Temporary cut slopes and shoring must comply with the provisions of Title 296,
Washington Administrative Code (WAC), Part N, “Excavation, Trenching and Shoring.”
Because the contractor has control of the construction operations, the contractor should be made
responsible for the stability of cut slopes, as well as the safety of the excavations. The contractor should
take all necessary steps to ensure the safety of the workers near the slopes.
6.4.1. Temporary Cut Slopes
For planning purposes, temporary unsupported cut slopes more than 4 feet high may be inclined at 1.5H:1V
in the fill and alluvial soils. These inclinations may need to be flattened by the contractor if significant
caving/sloughing or groundwater seepage occurs. For open cuts at the site, we recommend that:
■ No traffic, construction equipment, stockpiles, or building supplies be allowed at the top of cut slopes
within a distance of at least 5 feet from the top of the cut.
■ The excavation does not encroach on a 1H:1V influence line projected down from the edges of nearby
or planned foundation elements.
■ Exposed soil along the slope be protected from surface erosion using waterproof tarps or plastic
sheeting.
■ Construction activities be scheduled so that the length of time the temporary cut is left open is reduced
to the extent practicable.
■ Erosion control measures be implemented as appropriate such that runoff from the site is reduced to
the extent practicable.
■ Surface water be diverted away from the excavation.
■ The general condition of the slopes be observed periodically by GeoEngineers to confirm adequate
stability.
June 23, 2022 | Page 11 File No. 9061-019-00
6.4.2. Permanent Cut and Fill Slopes
Permanent slopes may be constructed at inclinations of 2H:1V or flatter. Fill to create permanent slopes
should be compacted to at least 90 percent of the MDD. To achieve uniform compaction, we recommend
that fill slopes be slightly overbuilt (2 to 3 feet) and cut back to expose well-compacted fill.
To reduce erosion, newly constructed slopes and disturbed existing 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 necessitate localized repairs and reseeding. Temporary
covering, such as clear heavy plastic sheeting, or erosion control blankets (such as American Excelsior
Curlex 1 or North American Green SC150) could be used to protect the slopes during periods of rainfall.
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, City of Renton requirements, or other suitable
procedures specified by the project civil engineer. The fill soils and alluvial deposits 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 lifts of 12 inches or less (loose
thickness) when using heavy compaction equipment, and 6 inches or less when using hand 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. The backfill should be compacted in
accordance with the criteria discussed above.
6.6. Pavement Recommendations
6.6.1. Subgrade Preparation
We recommend the subgrade soils in new pavement areas be prepared and evaluated as described in the
“Site Preparation and Earthwork” section of this report. All new pavement and hardscape areas should be
supported on subgrade soils that have been proof rolled or probed as described in the Site Preparation
section of this report. If the exposed subgrade soils are loose or soft, it may be necessary to excavate
localized areas and replace them with structural fill or gravel base course. Pavement subgrade conditions
should be observed during construction and prior to placing the subbase materials in order to evaluate the
presence of zones of unsuitable subgrade soils and the need for over-excavation and replacement of these
zones.
6.6.2. New Hot Mix Asphalt Pavement
In light-duty pavement areas (e.g., automobile parking or trails), we recommend a pavement section
consisting of at least a 2-inch thickness of ½-inch HMA (PG 58-22) per WSDOT Sections 5-04 and 9-03,
over a 4-inch thickness of densely compacted crushed surfacing base course per WSDOT Section 9-03.9(3).
In heavy-duty pavement areas, we recommend a pavement section consisting of at least a 3-inch thickness
of ½-inch HMA (PG 58-22) over a 6-inch thickness of densely compacted crushed surfacing base course.
The base course should be compacted to at least 95 percent of the MDD obtained using ASTM D 1557.
We recommend that proof rolling of the subgrade and compacted base course be observed by a
June 23, 2022 | Page 12 File No. 9061-019-00
representative from our firm prior to paving. Soft or yielding zones observed during proof rolling may require
over-excavation and replacement with compacted structural fill.
The pavement sections recommended above are based on our experience. Thicker asphalt sections may
be needed based on the actual traffic data, bus or truck loads and intended use. All paved and landscaped
areas should be graded so that surface drainage is directed to appropriate catch basins.
6.6.3. Portland Cement Concrete Pavement
Portland cement concrete (PCC) sections may be considered for areas where concentrated heavy loads
may occur. We recommend that these pavements consist of at least 6 inches of PCC over 6 inches of
crushed surfacing base course. A thicker concrete section may be needed based on the actual load data
for use of the area. If the concrete pavement will have doweled joints, we recommend that the concrete
thickness be increased by an amount equal to the diameter of the dowels. The base course should be
compacted to at least 95 percent of the MDD.
We recommend PCC pavements incorporate construction joints and/or crack control joints spaced at
maximum distances of 12 feet apart, center-to-center, in both the longitudinal and transverse directions.
Crack control joints may be created by placing an insert or groove into the fresh concrete surface during
finishing, or by saw cutting the concrete after it has initially set-up. We recommend the depth of the crack
control joints be approximately one fourth the thickness of the concrete; or about 1½ inches deep for the
recommended concrete thickness of 6 inches. We also recommend the crack control joints be sealed with
an appropriate sealant to help restrict water infiltration into the joints.
6.7. Recommended Additional Geotechnical Services
Throughout this report, recommendations are provided where we consider additional geotechnical services
to be appropriate. These additional services are summarized below:
■ GeoEngineers will complete a design-level engineering report for the project during the design phase
of the project. Additional subsurface borings and cone penetration tests are required to better
characterize the subsurface soils for field design and settlement analysis during the design phase.
GeoEngineers should also be retained to review the project plans and specifications when complete to
confirm that our design recommendations have been implemented as intended, as required by the City
of Renton.
■ During construction, GeoEngineers should observe stripping and grading, observe and evaluate any
playfield subgrades, evaluate temporary and permanent slope conditions, observe and test structural
backfill, observe installation of subsurface drainage measures, evaluate the suitability of pavement
subgrades and other appurtenant structures, and provide a summary letter of our construction
observation services. The purposes of GeoEngineers’ construction phase services are to confirm that
the subsurface conditions are consistent with those observed in the explorations, to provide
recommendations for design changes should the conditions revealed during the work differ from those
anticipated, to evaluate whether or not earthwork and foundation installation activities are completed
in accordance with our recommendations, and other reasons described in Appendix B, Report
Limitations and Guidelines for Use.
June 23, 2022 | Page 13 File No. 9061-019-00
7.0 LIMITATIONS
We have prepared this report for use by the Unico Properties, LLC and other members of the project team
for the Longacres Field Entitlement project.
Within the limitations of scope, schedule and budget, our services have been executed in accordance with
generally accepted practices in the field of geotechnical engineering in this area at the time this report was
prepared. No warranty or other conditions, express or implied, should be understood.
Any electronic form, facsimile or hard copy of the original document (email, text, table, and/or figure), if
provided, and any attachments are only a copy of the original document. The original document is stored
by GeoEngineers, Inc. and will serve as the official document of record.
Please refer to Appendix B, titled Report Limitations and Guidelines for Use, for additional information
pertaining to use of this report.
8.0 REFERENCES
ASCE (2016) “SEI/ASCE 7-16, Minimum Design Loads for Buildings and Other Structures,” American
Society of Civil Engineers.
GeoEngineers, 1991. “Geotechnical Engineering Services, Boeing Longacres Park, Renton, Washington,
For Boeing Support Services.”
GeoEngineers, 1997. “Geotechnical Engineering Services, Boeing BCAG, Headquarters Building 25-20,
Boeing Longacres Park, Renton, Washington.”
Idriss, I.M., and R.W. Boulanger 2014. “Soil Liquefaction during Earthquakes.” Earthquake Engineering
Research Institute MNO-12.
International Code Council, 2018, “International Building Code.”
Landau Associates, 2008, “Report, Phase II Environmental Site Assessment, Boeing Longacres, Renton,
Washington.”
Landau Associates, 2021, “Report, Phase II Environmental Site Assessment, Boeing Longacres Park,
Renton, Washington.”
Washington State Department of Transportation, 2022, “Standard Specifications for Road, Bridge, and
Municipal Construction.”
Youd, T.L. and Idriss, I.M., 2001. “Liquefaction resistance of soils: summary report from the 1996 NCEER
and 1998 NCEER/NSF workshops on evaluation of liquefaction resistance of soils,” Journal of
Geotechnical and Geoenvironmental Engineering, 127(4), pp. 297-313.
FIGURES
57thAveS56thAveSMacadamRdS58thAveSI
-5Rest
r
i
ct
edLnWestfield
Southcenter
T u k w i l a
SouthcenterPkwy181 ShattuckAveSShattuckAveSPowellAveSWS W 7 t h S t
65t
hAveSS W 1 9 t h S t
SW 3rd Pl
S W 1 2 t h S t
S W 1 6 t h S t Rai
ni
erAveSOakesdal
e
AveSWS
W
S
u
n
s
etBlvd
ValleyFwyBoeing
Longacr es
Indus trial P ark
Family Fun
Centers
Blac k Riv er
Forest
Fort Dent Park
TalbotRdSS W 34t h S t
AndoverParkWS t r a n d e r B l v d
S W 4 1 s t S t
S W 2 7 t h S t
AndoverParkES W 39th St EValleyRdOakesdaleAveSWWValleyHwyValleyFwyOr il l i a TalbotRdSS 5t h S t
S 4 t h S t
S 3 r d S t
TalbotRdSBensonDrSTalbotRdSS E C a rrRdµ
SITE
Vicinity Map
Figure 1
Longacres Field Renovation
Renton, Washington
3
Alpine Lakes
Wildernes s
Kent
Tacoma
Seattle
2,000 2,0000
Feet
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 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.
Projection: NAD 1983 UTM Zone 10N
P:\9\9061019\GIS\9061019_Project\9061019_Project.aprx\906101900_F01_VicinityMap Date Exported: 03/09/22 by glohrmeyer
Figure 2
Longacres Field Renovation
Renton, Wshington
Conceptual Site Plan
P:\9\9061019\CAD\00\Geotech\906101900_F02_Conceptual Site Plan.dwg TAB:F02 Date Exported: 06/22/22 - 11:08 by cdiasWENSFeet
080 80
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 from D.A. Hogan & Associates, Inc., dated 5/23/2022.
Projection: WA State Plane, North Zone, NAD83, US Foot
CPT-1
CPT-5
CPT-2
CPT-4
CPT-6
CPT-3
B-8CPT-7
TP15
TP14
TP13
TP12
TP11
TP10
TP9
TP8
TP5
TP4
LAI-13
LAI-18
LAI-14
LAI-10
LAI-17
LAI-15
Oakesdale Ave SW
LAI-16
TP-6
B-20
TP-5
TP-7
TP-16
TP-15
TP-8
B-21
TP-4
TP-10
TP-9
TP-3
TP-12
TP-14
TP-17
TP-11
Bldg 25-20
Figure 3
Longacres Field Renovation
Renton, Wshington
Exploration Site Plan
P:\9\9061019\CAD\00\Geotech\906101900_F03_Exploration Site Plan.dwg TAB:F03 Date Exported: 06/22/22 - 11:05 by cdiasWENSFeet
0150 150
B-20 Boring by GeoEngineers, 1997
CPT-1 Cone Penetration Test Pit by GeoEngineers, 1997
TP-3 Test Pit by GeoEngineers, 1997
B-5 Boring by GeoEngineers, 1991
TP1 Test Pit Landau Associates, 2008
LAI-10 Test Pit Landau Associates, 2020
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: Aerial from King County Imap dated 2019.
Projection: WA State Plane, North Zone, NAD83, US Foot
Legend
Site Boundary
APPENDICES
APPENDIX A
Boring Logs from Previous Explorations
June 23, 2022 | Page A-1 File No. 9061-019-00
APPENDIX A
BORINGS LOGS FROM PREVIOUS EXPLORATIONS
Included in this section are logs from previous studies completed in the immediate vicinity of the project
site.
■ The log of one boring completed be GeoEngineers, in 1991 for Boeing Longacres Park;
■ The log of two borings, 14 test pits and seven cone penetration tests completed by GeoEngineers, in
1997 for the Boeing BCAG Headquarters Building 25-20;
■ The log of 10 test pits by Landau Associates, in 2008 for the Boeing Longacres Property Park Phase II
Environmental Site Assessment; and
■ The log of seven direct push borings by Landau Associates, in 2021 for the Boeing Longacres Property
Park Phase II Environmental Site Assessment.
TP-3 (4-6)
Boring Completed 01/07/08
Total Depth of Boring = 7.0 ft.
SW
SM
Log of Boring TP-3
Light brown, fine to medium SAND with
interbedded gray silt and trace organics,
(medium dense, moist), (no odor, no
sheen)
d
Light brown, fine to medium SAND with silt
and gravel, (medium dense, moist), (no
odor, no sheen)
Dark brown, fine to medium SAND with
trace silt, (medium dense, wet), (no odor,
no sheen)
SW
SM
Dark brown, fine to medium SAND with
organics, (medium dense, moist), (no
odor, no sheen)
A-20
SAMPLE DATA
Sampler TypeNotes:
SOIL PROFILE
Depth (ft)Drilling Method:
1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.PID (ppm)Figure25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGBoeing Longacres
Renton, WashingtonSample Number& IntervalUSCS SymbolGroundwater not encountered.
GROUNDWATER
TP-3
0
2
4
6
8
10 Blows/FootRubber-tired Backhoe
Ground Elevation (ft):25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGGraphic Symbol
0
2
4
6
8
10
Dark brown, fine to medium SAND with
organics, (loose, moist), (no odor, no
sheen)
d
Log of Boring TP-4
SW
ML
ML/
CL
SM
TP-4 (0-6)
Boring Completed 01/07/08
Total Depth of Boring = 8.5 ft.
A-21
Gray/brown, sandy SILT wtih organics,
(medium stiff, low plasticity), (no odor, no
sheen)
SAMPLE DATA GROUNDWATER
Sampler TypeNotes:
SOIL PROFILE
Depth (ft)Drilling Method:
1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.PID (ppm)Figure25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGBoeing Longacres
Renton, WashingtonSample Number& IntervalUSCS SymbolLight brown, clayey SILT with organics,
(stiff, low plasticity), (no odor, no sheen)
-Becomes gray
Dark brown, fine to medium SAND with
silt, (dense, wet), (no odor, no sheen)
Groundwater not encountered.
TP-4
Rubber-tired Backhoe
Ground Elevation (ft):25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGGraphic SymbolBlows/Foot
Log of Boring TP-7
Boring Completed 01/07/08
Total Depth of Boring = 7.0 ft.
Brown, sandy GRAVEL with concrete and
organics, (loose, moist), (no odor, no
sheen)
Light brown, fine to medium SAND with
silt, (medium dense, moist), (no odor, no
sheen)
GP
SM
SM Dark brown, medium SAND with silt and
trace organics, (medium dense, wet), (no
odor, no sheen)
0
2
4
6
8
10 Notes:
SOIL PROFILE
Depth (ft)Sample Number& IntervalSampler TypeA-24
GROUNDWATER
Figure25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGBoeing Longacres
Renton, Washington
1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.Graphic SymbolBlows/FootUSCS SymbolRubber-tired Backhoe
Ground Elevation (ft):25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGGroundwater not encountered.
TP-7
Drilling Method:PID (ppm)SAMPLE DATA
TP-8 (6-7)
Boring Completed 01/07/08
Total Depth of Boring = 7.0 ft.
SM
Log of Boring TP-8
Gray, SILT with fine SAND, (stiff, low
plasticity), (no odor, no sheen)
d
Dark brown, medium SAND with gravel,
(dense, moist), (no odor, no sheen)
Brown, fine to medium SAND with silt,
(medium dense, moist), (no odor, no
sheen)
SW
ML
GROUNDWATER
Notes:
SOIL PROFILE
Depth (ft)Sample Number& Interval0
2
4
6
8
10
A-25
SAMPLE DATA
Figure25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGBoeing Longacres
Renton, Washington
1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Rubber-tired Backhoe
Groundwater not encountered.Blows/FootSampler TypeUSCS SymbolPID (ppm)Ground Elevation (ft):25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGGraphic SymbolTP-8
Drilling Method:
Boring Completed 01/07/08
Total Depth of Boring = 5.0 ft.
Log of Boring TP-10
0
2
4
6
8
10
Groundwater not encountered.
TP-10 (3-5)
SM Brown, fine to medium SAND with silt,
(medium dense, moist), (no odor, no
sheen)
d Blows/FootDepth (ft)Sample Number& Interval1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Notes:
SOIL PROFILE
Figure25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGBoeing Longacres
Renton, Washington A-2725185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGUSCS SymbolRubber-tired Backhoe
Ground Elevation (ft):Graphic SymbolTP-10
Drilling Method:PID (ppm)SAMPLE DATA GROUNDWATER
Sampler Type
TP-11 (4-5)
Boring Completed 01/07/08
Total Depth of Boring = 6.0 ft.
SM
Log of Boring TP-11
Brown, sandy SILT, (stiff, low plasticity),
(no odor, no sheen)
d
Light brown, fine to medium SAND with
trace silt and organics, (medium dense,
moist), (no odor, no sheen)
Black to dark brown, fine to medium SAND
with silt, (medium dense, moist), (no odor,
no sheen)
SW
ML
GROUNDWATER
Notes:
SOIL PROFILE
Depth (ft)Sample Number& Interval0
2
4
6
8
10
A-28
SAMPLE DATA
Figure25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGBoeing Longacres
Renton, Washington
1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Rubber-tired Backhoe
Groundwater not encountered.Blows/FootSampler TypeUSCS SymbolPID (ppm)Ground Elevation (ft):25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGGraphic SymbolTP-11
Drilling Method:
Log of Boring TP-12
0
2
4
6
8
10
Brown, fine to medium SAND with silt,
(medium dense, moist), (no odor, no
sheen)
d
Boring Completed 01/08/08
Total Depth of Boring = 6.0 ft.
-Geotextile fabric
SM
TP-12 (5-6)
Groundwater not encountered.Blows/FootDepth (ft)Sample Number& Interval1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Notes:
SOIL PROFILE
Figure25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGBoeing Longacres
Renton, Washington A-2925185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGUSCS SymbolRubber-tired Backhoe
Ground Elevation (ft):Sampler TypeGraphic SymbolTP-12
Drilling Method:PID (ppm)SAMPLE DATA GROUNDWATER
SOIL PROFILE
Depth (ft)Sample Number& Interval1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
A-30
Figure
GROUNDWATER
25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGBoeing Longacres
Renton, Washington Log of Boring TP-13
Slight
0
2
4
6
8
10 Blows/FootWater LevelUSCS SymbolNotes:
Ground Elevation (ft):Sampler Type25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGGraphic SymbolTP-13
Drilling Method:PID (ppm)SAMPLE DATA
Rubber-tired Backhoe
ML
TP-13 (2-3)
TP-13 (4-5)
Boring Completed 01/08/08
Total Depth of Boring = 8.0 ft.
d
SM
d
Brown, fine to medium SAND with silt and
trace organics, (medium dense, moist),
(no odor, no sheen)
-Mottled color and trace organic material
Gray/black, sandy SILT with fine sand and
trace gravel, (stiff, low plasticity), (no odor,
no sheen)
-Traces of concrete and brick debris
Boring Completed 01/08/08
Total Depth of Boring = 5.5 ft.
Log of Boring TP-14
0
2
4
6
8
10 Blows/FootTP-14 (3-5)
SW
-Becomes wet, test pit caving
Brown, fine to medium SAND with trace
silt, (loose, moist), (no odor, no sheen)
d
SOIL PROFILE
Boeing Longacres
Renton, Washington25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGFigure
A-31
1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.Sample Number& IntervalDepth (ft)Graphic SymbolUSCS SymbolRubber-tired Backhoe
Ground Elevation (ft):25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGNotes:
TP-14
Drilling Method:PID (ppm)SAMPLE DATA GROUNDWATER
Sampler Type
Blows/FootGroundwater not encountered.
0
2
4
6
8
10 USCS SymbolHand Implements
Boring Completed 01/08/08
Total Depth of Boring = 2.0 ft.
SM Brown, fine to medium SAND with silt,
(medium dense, moist), (no odor, no
sheen)
SOIL PROFILE
Boeing Longacres
Renton, Washington25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGFigure
A-32
1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.Sample Number& IntervalDepth (ft)Log of Boring TP-15
Notes:Sampler TypeGROUNDWATERSAMPLE DATA
PID (ppm)Drilling Method:
TP-15
Graphic Symbol25185.02 1/30/08 \\EDMDATA\GINT\GINT7\PROJECTS\025185.GPJ SOIL BORING LOGGround Elevation (ft):
d3
AC
SP
ML
SM
Flush-mounted
monument with silicone
cap
Concrete Seal
Hydrated Bentonite
Grout
1/4" Tubing (Teflon)
Dry Granular Bentonite
2/12 Silica Sand
Stainless Steel Vapor
implant
Bentonite chips
Boring Completed 11/04/20
Total Depth of Boring = 5.0 ft.
Soil Gas Well Completed 11/04/20
Total Depth of Soil Gas Well = 4.5 ft.
(ASPHALT)
Brown, gravelly, fine to coarse SAND with
trace silt; no odor, no sheen (loose, damp)
(FILL)
Gray, sandy SILT with organics; no odor, no
sheen (medium stiff to stiff, damp)
(ALLUVIUM)
Brown, silty, fine SAND with trace organics;
no odor, no sheen (medium dense to dense,
damp)
0
2
4
6
8
10
12
14
16 Groundwater not encountered.Not Determined
Water LevelDepth (ft)Sample Number& IntervalUSCS SymbolGeoprobeTM
SAMPLE DATA
LAI-10
SOIL PROFILE
2.25 inGround Elevation (ft):
GROUNDWATER
Blows/FootSampler TypePID (ppm)Drilling Method:Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Notes:
Soil Gas Well Detail
(DOE#: BMY199)
B-11Log of Soil Gas Well LAI-10
Figure0025227.170.171 4/2/21 N:\PROJECTS\0025227.170.GPJ WELL LOGLongacres Phase II ESA
Renton, Washington
0
0
0d3
SM
ML
Flush-mounted
monument with silicone
cap
Concrete Seal
Hydrated Bentonite
Grout
1/4" Tubing (Teflon)
Dry Granular Bentonite
2/12 Silica Sand
Stainless Steel Vapor
implant
Bentonite chips
Boring Completed 11/04/20
Total Depth of Boring = 5.0 ft.
Soil Gas Well Completed 11/04/20
Total Depth of Soil Gas Well = 4.5 ft.
Brown, silty, fine SAND with organics; no
odor, no sheen (loose, damp)
(ALLUVIUM)
Brown, rust-mottled, sandy SILT with trace
organics; no odor, no sheen (medium stiff to
stiff, damp)
0
2
4
6
8
10
12
14
16 Groundwater not encountered.Not Determined
Water LevelDepth (ft)Sample Number& IntervalUSCS SymbolGeoprobeTM
SAMPLE DATA
LAI-13
SOIL PROFILE
2.25 inGround Elevation (ft):
GROUNDWATER
Blows/FootSampler TypePID (ppm)Drilling Method:Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Notes:
Soil Gas Well Detail
(DOE#: BMY198)
B-12Log of Soil Gas Well LAI-13
Figure0025227.170.171 4/2/21 N:\PROJECTS\0025227.170.GPJ WELL LOGLongacres Phase II ESA
Renton, Washington
0d3
AC
GP
SP
SM
Flush-mounted
monument with silicone
cap
Concrete Seal
Hydrated Bentonite
Grout
1/4" Tubing (Teflon)
Dry Granular Bentonite
2/12 Silica Sand
Stainless Steel Vapor
implant
Boring Completed 11/05/20
Total Depth of Boring = 5.0 ft.
Soil Gas Well Completed 11/05/20
Total Depth of Soil Gas Well = 4.5 ft.
(ASPHALT)
Gray and brown GRAVEL with sand and
trace silt; no odor, no sheen (loose, damp)
(FILL)
Brown, gravelly, fine to medium SAND with
trace silt; no odor, no sheen (loose, damp)
Gray, silty, fine SAND; no odor, no sheen
(medium dense, damp)
(ALLUVIUM)
0
2
4
6
8
10
12
14
16 Groundwater not encountered.Not Determined
Water LevelDepth (ft)Sample Number& IntervalUSCS SymbolGeoprobeTM
SAMPLE DATA
LAI-14
SOIL PROFILE
2.25 inGround Elevation (ft):
GROUNDWATER
Blows/FootSampler TypePID (ppm)Drilling Method:Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Notes:
Soil Gas Well Detail
(DOE#: BMY202)
B-13Log of Soil Gas Well LAI-14
Figure0025227.170.171 4/2/21 N:\PROJECTS\0025227.170.GPJ WELL LOGLongacres Phase II ESA
Renton, Washington
0
0
0
0
0
0
d3
d3
d3
SM
ML
SP-
SM
ATD
BOL-
LAI-15-
S(1-3)
BOL-
LAI-15-
S(10-11)
Flush-mounted
monument with silicone
cap
Concrete Seal
1/4" Tubing (Teflon)
Hydrated Bentonite
Grout
Dry Granular Bentonite
2/12 Silica Sand
Stainless Steel Vapor
implant
Bentonite chips
Native Slough
Boring Completed 11/06/20
Total Depth of Boring = 15.0 ft.
Soil Gas Well Completed 11/06/20
Total Depth of Soil Gas Well = 4.5 ft.
Brown, silty, fine SAND with organics and
trace medium and coarse sand; no odor, no
sheen (loose, damp)
(ALLUVIUM)
Soil Sample: BOL-LAI-15-S(1-3)
Brown, rust-mottled, sandy SILT with
organics; no odor, no sheen (medium stiff,
damp)
Brown, fine to medium SAND with silt and
trace organics (medium dense, damp)
Soil Sample: BOL-LAI-15-S(10-11)
-becomes wet at 11 ft.
-turns a dark gray, almost black, color at
11.2 ft.
0
2
4
6
8
10
12
14
16
Not Determined
Water LevelDepth (ft)Sample Number& IntervalUSCS SymbolGeoprobeTM
SAMPLE DATA
LAI-15
SOIL PROFILE
2.25 inGround Elevation (ft):
GROUNDWATER
Blows/FootSampler TypePID (ppm)Drilling Method:Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Notes:
Soil Gas Well Detail
(DOE#: BMY206)
B-14Log of Soil Gas Well LAI-15
Figure0025227.170.171 4/2/21 N:\PROJECTS\0025227.170.GPJ WELL LOGLongacres Phase II ESA
Renton, Washington
0
0
0
0
d3
d3
SP-
SM
ML
SM
SP-
SM
ATD
BOL-
LAI-16-
S(1-3)
BOL-
LAI-16-
S(7-9)
Flush-mounted
monument with silicone
cap
Concrete Seal
Hydrated Bentonite
Grout
1/4" Tubing (Teflon)
Dry Granular Bentonite
2/12 Silica Sand
Stainless Steel Vapor
implant
Bentonite chips
Native Slough
Boring Completed 11/06/20
Total Depth of Boring = 10.0 ft.
Soil Gas Well Completed 11/06/20
Total Depth of Soil Gas Well = 4.5 ft.
Gray and black, gravelly, fine to medium
SAND with silt and organics; no odor, no
sheen (loose, moist)
(ALLUVIUM)
Gray, sandy SILT; no door, no sheen
(medium stiff, damp)
Soil Sample: BOL-LAI-16-S(1-3)
Gray, silty fine SAND (medium dense,
damp)
-turns a brown color with rust-mottling at 4.8
ft.
-silt lense from 5 ft to 5.4 ft
Brown, fine to medium SAND with silt; no
odor, no sheen (medium dense, damp to
moist)
Soil Sample: BOL-LAI-16-S(7-9)
0
2
4
6
8
10
12
14
16
Not Determined
Water LevelDepth (ft)Sample Number& IntervalUSCS SymbolGeoprobeTM
SAMPLE DATA
LAI-16
SOIL PROFILE
2.25 inGround Elevation (ft):
GROUNDWATER
Blows/FootSampler TypePID (ppm)Drilling Method:Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Notes:
Soil Gas Well Detail
(DOE#: BMY207)
B-15Log of Soil Gas Well LAI-16
Figure0025227.170.171 4/2/21 N:\PROJECTS\0025227.170.GPJ WELL LOGLongacres Phase II ESA
Renton, Washington
0
0
0d3
AC
SP
ML
SM
Flush-mounted
monument with silicone
cap
Concrete Seal
Hydrated Bentonite
Grout
1/4" Tubing (Teflon)
Dry Granular Bentonite
2/12 Silica Sand
Stainless Steel Vapor
implant
Boring Completed 11/05/20
Total Depth of Boring = 5.0 ft.
Soil Gas Well Completed 11/05/20
Total Depth of Soil Gas Well = 4.5 ft.
(ASPHALT)
Brown, gravelly, fine to medium SAND with
silt (loose, dry)
(FILL)
Gray SILT with sand (medium stiff, dry)
(ALLUVIUM)
-turns a brown color with rust-mottling at 1.1
ft.
Brown, rust-mottled, silty, fine SAND
(medium dense, damp)
0
2
4
6
8
10
12
14
16 Groundwater not encountered.Not Determined
Water LevelDepth (ft)Sample Number& IntervalUSCS SymbolGeoprobeTM
SAMPLE DATA
LAI-17
SOIL PROFILE
2.25 inGround Elevation (ft):
GROUNDWATER
Blows/FootSampler TypePID (ppm)Drilling Method:Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Notes:
Soil Gas Well Detail
(DOE#: BMY201)
B-16Log of Soil Gas Well LAI-17
Figure0025227.170.171 4/2/21 N:\PROJECTS\0025227.170.GPJ WELL LOGLongacres Phase II ESA
Renton, Washington
0
0
0
0
0
0
0
d3
d3
d3
AC
GM
GP
ATD
BOL-
LAI-18-
S(1-3)
Flush-mounted
monument with silicone
cap
Concrete Seal
1/4" Tubing (Teflon)
Hydrated Bentonite
Grout
Dry Granular Bentonite
2/12 Silica Sand
Stainless Steel Vapor
implant
Bentonite chips
Native Slough
Boring Completed 11/05/20
Total Depth of Boring = 15.0 ft.
Soil Gas Well Completed 11/05/20
Total Depth of Soil Gas Well = 4.5 ft.
(ASPHALT)
Brown, sandy GRAVEL with trace silt; no
odor, no sheen (loose, dry)
(FILL)
Soil Sample: BOL-LAI-18-S(1-3)
Brown and rust-mottled GRAVEL with sand;
no odor, no sheen (loose, moist to wet)
-rust-mottling dissipates at 10 ft
Groundwater Sample: BOL-LAI-18-GW
collected from temporary screen installed
from 4 to 14 ft bgs
0
2
4
6
8
10
12
14
16
Not Determined
Water LevelDepth (ft)Sample Number& IntervalUSCS SymbolGeoprobeTM
SAMPLE DATA
LAI-18
SOIL PROFILE
2.25 inGround Elevation (ft):
GROUNDWATER
Blows/FootSampler TypePID (ppm)Drilling Method:Graphic Symbol1. Stratigraphic contacts are based on field interpretations and are approximate.
2. Reference to the text of this report is necessary for a proper understanding of subsurface conditions.
3. Refer to "Soil Classification System and Key" figure for explanation of graphics and symbols.
Notes:
Soil Gas Well Detail
(DOE#: BMY200)
B-17Log of Soil Gas Well LAI-18
Figure0025227.170.171 4/2/21 N:\PROJECTS\0025227.170.GPJ WELL LOGLongacres Phase II ESA
Renton, Washington
APPENDIX B
Report Limitations and Guidelines for Use
June 23, 2022 | Page B-1 File No. 9061-019-00
APPENDIX B
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 use by Unico Properties, LLC and other members of the project team for
the entitlement of the soccer fields for the Seattle Sounders training facility. This report may be made
available to prospective contractors for bidding or estimating purposes; but our report, conclusions and
interpretations should not be construed as a warranty of the subsurface conditions. 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. No one except Unico Properties, LLC and other
members of the design team should rely on this report without first conferring with GeoEngineers. 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 entitlement of the soccer fields for the Seattle Sounders training
facility 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:
■ the function of the proposed structure;
■ elevation, configuration, location, orientation or weight of the proposed structure;
■ composition of the design team; or
■ project ownership.
1 Developed based on material provided by ASFE, Professional Firms Practicing in the Geosciences; www.asfe.org .
June 23, 2022 | Page B-2 File No. 9061-01-00
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.
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
June 23, 2022 | Page B-3 File No. 9061-019-00
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.
Biological Pollutants
GeoEngineers’ Scope of Work specifically excludes the investigation, detection, or assessment of the
presence of Biological Compounds which are Pollutants in or around any structure. Accordingly, this report
includes no interpretations, recommendations, findings, or conclusions for the purpose of detecting,
assessing, or abating Biological Pollutants. The term “Biological Pollutants” includes, but is not limited to,
molds, fungi, spores, bacteria, and viruses, and/or any of their byproducts.