20-104351-Geotechnical Report_11-06-2020 v1Earth Science + Technology
Geotechnical Engineering Services Report
Redondo Heights Apartments
Federal Way, Washington
for
Shelter Resources, Inc.
August 24, 2020
Geotechnical Engineering Services Report
Redondo Heights Apartments
Federal Way, Washington
for
Shelter Resources, Inc.
August 24, 2020
1101 South Fawcett Avenue, Suite 200
Tacoma, Washington 98402
253.383.4940
Geotechnical Engineering Services Report
Redondo Heights Apartments
Federal Way, Washington
File No. 3625-004-00
August 24, 2020
Prepared for:
Shelter Resources, Inc.
c/o SRI-Rochlin Construction Services
2223 112th Avenue NE, Suite 102
Bellevue, Washington 98004
Attention: James Rochlin
Prepared by:
GeoEngineers, Inc.
1101 South Fawcett Avenue, Suite 200
Tacoma, Washington 98402
253.383.4940
Christopher R. Newton, PE
Geotechnical Engineer
Lyle J. Stone, PE
Associate Geotechnical Engineer 8/24/2020
CRN:LJS:tt
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.
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Table of Contents
1.0 INTRODUCTION AND PROJECT UNDERSTANDING ........................................................................................ 1
2.0 SCOPE OF SERVICES ...................................................................................................................................... 1
3.0 SITE CONDITIONS ............................................................................................................................................ 1
3.1. Geologic Setting .......................................................................................................................................... 1
3.2. Surface Conditions...................................................................................................................................... 1
3.3. Subsurface Conditions ............................................................................................................................... 2
3.3.1. Subsurface Explorations and Laboratory Testing ..................................................................... 2
3.3.2. Soil and Groundwater Conditions .............................................................................................. 2
4.0 CONCLUSIONS AND RECOMMENDATIONS ................................................................................................... 2
4.1. General Geotechnical Considerations ....................................................................................................... 2
4.2. Seismic Design Considerations .................................................................................................................. 3
4.2.1. Seismic Design Parameters ....................................................................................................... 3
4.2.2. Liquefaction................................................................................................................................. 4
4.2.3. Lateral Spreading Potential ........................................................................................................ 4
4.2.4. Surface Rupture Potential .......................................................................................................... 4
4.3. Site Development and Earthwork .............................................................................................................. 4
4.3.1. General ........................................................................................................................................ 4
4.3.2. Clearing and Stripping ................................................................................................................ 5
4.3.3. Erosion and Sedimentation Control ........................................................................................... 5
4.3.4. Temporary Excavations and Cut Slopes .................................................................................... 6
4.3.5. Permanent Cut and Fill Slopes ................................................................................................... 6
4.3.6. Groundwater Handling Considerations ..................................................................................... 6
4.3.7. Surface Drainage ........................................................................................................................ 7
4.3.8. Subsurface Drainage .................................................................................................................. 7
4.3.9. Subgrade Preparation................................................................................................................. 7
4.3.10. Subgrade Protection and Wet Weather Considerations ........................................................... 7
4.4. Fill Materials ................................................................................................................................................ 8
4.4.1. On-Site Soil .................................................................................................................................. 8
4.4.2. Imported Structural Fill ............................................................................................................... 9
4.4.3. Pipe Bedding ............................................................................................................................... 9
4.4.4. Trench Backfill............................................................................................................................. 9
4.5. Fill Placement and Compaction ................................................................................................................. 9
4.5.1. General ........................................................................................................................................ 9
4.5.2. Area Fills and Pavement Bases ................................................................................................. 9
4.5.3. Backfill Behind Walls ............................................................................................................... 10
4.5.4. Trench Backfill.......................................................................................................................... 10
4.6. Foundation Support ................................................................................................................................. 10
4.6.1. General ..................................................................................................................................... 10
4.6.2. Foundation Bearing Surface Preparation ............................................................................... 10
4.6.3. Allowable Soil Bearing Pressure ............................................................................................. 11
4.6.4. Foundation Settlement ............................................................................................................ 11
4.6.5. Lateral Resistance ................................................................................................................... 11
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4.7. Slab-on-Grade Floors ............................................................................................................................... 12
4.8. Retaining Walls and Below-Grade Structures ........................................................................................ 12
4.8.1. Design Parameters .................................................................................................................. 12
4.8.2. Drainage ................................................................................................................................... 13
4.9. Stormwater Infiltration Feasibility ........................................................................................................... 13
4.10. Pavement Recommendations ................................................................................................................. 14
4.10.1. General ..................................................................................................................................... 14
4.10.2. Construction Considerations ................................................................................................... 14
4.10.3. Asphalt Concrete Pavement Design ....................................................................................... 15
5.0 LIMITATIONS ................................................................................................................................................ 15
LIST OF FIGURES
Figure 1. Vicinity Map
Figure 2. Site Plan
APPENDICES
Appendix A. Subsurface Explorations and Laboratory Testing
Figure A-1 – Key to Exploration Logs
Figures A-2 through A-13 – Logs of Test Pits
Figure A-14 – Sieve Analysis Results
Appendix B. Report Limitations and Guidelines for Use
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1.0 INTRODUCTION AND PROJECT UNDERSTANDING
This report presents the results of our geotechnical engineering services for the proposed Redondo Heights
Apartments project. The project site is located south of South 276th Street, about 600 feet east of Pacific
Highway South (HWY 99) in Federal Way, Washington as shown on the Vicinity Map, Figure 1. The site is
currently undeveloped and wooded. Our services have been completed in general accordance with our
signed agreement dated July 31, 2020.
Our understanding of the project is based on our discussions with SRI Rochlin, the project architect
(Bumgardner), and the project civil engineer (KPFF) via phone and electronic mail. We understand that the
development will consist of about four or five two- to three-story apartment buildings and a community
center. The site will also include parking and landscaped open spaces. Some tree retention will be required
at the site; therefore, some areas will remain wooded and undisturbed.
Based on discussions with the KPFF, we understand that stormwater infiltration is not currently anticipated.
It is our understanding that a stormwater retention vault is planned in the lower, northeast, corner of the
site.
2.0 SCOPE OF SERVICES
The purpose of our geotechnical engineering services is to observe subsurface explorations (test pits) and
review other relevant subsurface information at the site to develop geotechnical design and construction
recommendations. Our services have been provided in accordance with our signed agreement dated July
31, 2020.
3.0 SITE CONDITIONS
3.1. Geologic Setting
Our understanding of the site geology is based, in part, on review of the Geologic Map of the Poverty Bay
7.5’ Quadrangle, King and Pierce Counties, Washington (Booth et al. 2004). The geologic map indicates
that glacial soil deposits underlie the site and surrounding areas. These deposits are the result of
glaciations that occurred during the Vashon Stade of the Fraser Glaciation, approximately 10,000 to
15,000 years ago. Surface soils at the site are primarily mapped as glacial till (Qvt). Glacial till is described
as a highly compact mixture of clay, silt, sand and gravel that was deposited below and subsequently
overridden by glacial ice. The upper few feet of till deposits can be weathered and in a loose to dense
condition. Underlying undisturbed glacial till is typically very dense with low permeability.
3.2. Surface Conditions
The property consists of two rectangular-shaped parcels totaling approximately 5 acres and is bounded by
South 276th Street to the north, undeveloped properties to the east and south, and a developed property
to the west. The adjacent developed property consists of an apartment complex with several multiple story
buildings and driveway and parking areas.
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The site is currently occupied by heavy vegetation consisting of young to mature deciduous and coniferous
trees and various underbrush. Site topography generally slopes down gradually to the northeast with
elevation change across the property on the order of 15 to 20 feet.
3.3. Subsurface Conditions
3.3.1. Subsurface Explorations and Laboratory Testing
We observed subsurface conditions at the site by observing 12 test pits (TP-1 through TP-12) at the
approximate locations shown on the attached Site Plan, Figure 2.
Selected samples collected from the test pits were tested in our laboratory to confirm field classifications
and to evaluate pertinent engineering properties. Our laboratory testing program included grain-size
analyses, percent fines determinations and moisture content determinations. A description of our
subsurface exploration program, summary exploration logs, and a summary of our laboratory testing
program and the test results are provided in Appendix A.
3.3.2. Soil and Groundwater Conditions
At the surface of all the explorations except TP-9, we observed about 9 to 12 inches of forest duff. At TP-9
we observed approximately 12 inches of what we interpret to be fill. Fill consisted of approximately 10- to
12-inch quarry spalls overlying loose silty sand with gravel and occasional debris (plastic bags). Beneath
the fill and forest duff, we observed loose to dense silty sand with variable gravel content, varying iron-oxide
staining and occasional organics (¼- to 8-inch diameter tree roots). We interpret these soils as weathered
glacial till. Weathered glacial till extended to depths ranging from approximately 3 to 5 feet below the
ground surface (bgs). Underlying the weathered glacial till in all our explorations, we encountered what we
interpret to be undisturbed glacial till soils. Undisturbed glacial till typically consisted of very dense silty
sand with gravel or silty gravel and varying iron-oxide staining. All our explorations were completed in
undisturbed glacial till soils at depths between approximately 8 and 10.5 feet bgs.
We did not observe groundwater in the explorations. Upon completion of TP-6 and TP-12, the two
excavations were left open about 5 to 6 hours. At the end of this time, no groundwater seepage was
observed within the excavations. Though not encountered in our explorations, perched groundwater could
be present in other areas at the site. The interface between more permeable and less permeable zones,
such as the contact between weathered glacial till and undisturbed glacial till, are likely locations for
accumulation of perched groundwater. Perched groundwater levels can depend on rainfall amounts,
irrigation activities and other factors. We anticipate that perched groundwater, if it occurs, will be most
prevalent during the wet season, typically October through May.
4.0 CONCLUSIONS AND RECOMMENDATIONS
4.1. General Geotechnical Considerations
Based on our understanding of the project, the explorations performed for this study, review of subsurface
information near or within the project vicinity and our experience, it is our opinion that the proposed
improvements can be designed and constructed generally as envisioned with regard to geotechnical
considerations. A summary of the primary geotechnical considerations for the project is provided below and
is followed by our detailed recommendations.
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■ The site is identified as being located within the Asarco Smelter Plume. An appropriate soil
management plan will be required.
■ Soils observed at the site contain a significant quantity of fines and will likely be difficult or impossible
to work with when wet or become easily disturbed if exposed to wet weather. Depending on the
intended use of the material and the moisture/weather conditions, it may be difficult to use on-site
soils as structural fill.
■ Clearing and stripping depths for surficial soils at the site will typically be at least 9 to 12 inches.
■ Proposed structures at the site can be supported using shallow foundations and slabs-on-grade,
provided that the foundation bearing surfaces are prepared as recommended. We do not anticipate
that significant overexcavation will be required unless isolated areas of loose, or otherwise unsuitable
areas are encountered near foundation grade.
■ Encountered site soils are relatively impermeable and, therefore, stormwater infiltration rates at this
site are likely very low.
■ Groundwater was not observed during subsurface explorations. However, the relatively impermeable
glacial till can create perched groundwater conditions. This can be especially prevalent around building
foundations where footing excavation can create a “bathtub” effect. Subsurface drainage including
foundation or perimeter drains should be considered as a method for reducing or controlling moisture
in buildings.
4.2. Seismic Design Considerations
4.2.1. Seismic Design Parameters
We understand seismic design of proposed structures will be performed using procedures outlined in the
2018 International Building Code (IBC). The 2018 IBC states structures shall be designed and constructed
to resist the effects of earthquake motions in accordance with American Society of Civil Engineers (ASCE)
7-16.
We used map-based values as recommended by the United States Geological Survey (USGS) to determine
the seismic design spectrum in accordance with ASCE 7-16. Based on conditions observed in our
explorations, our review of geologic maps and our experience in the area, we anticipate soils below our
explorations and extending to depth are glacially consolidated and dense to very dense. For seismic design
and analysis, we recommend using a response spectrum for Site Class C. We recommend the parameters
provided in Table 1 below be used for design.
TABLE 1. SEISMIC DESIGN CRITERIA
2018 IBC (ASCE 7-16) Seismic Design Parameters
Spectral Response Acceleration at Short Periods (SS) 1.346g
Spectral Response Acceleration at 1-Second Periods (S1) 0.462g
Site Class C
Design Peak Ground Acceleration (PGAM) 0.684g
Design Spectral Response Acceleration at Short Periods (SDS) 1.077g
Design Spectral Response Acceleration at 1-Second Periods (SD1) 0.462g
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4.2.2. Liquefaction
Liquefaction refers to a condition where vibration or shaking of the ground, usually from earthquake forces,
results in development of excess pore pressures in loose, saturated soils and subsequent loss of strength
in the deposit of soil so affected. In general, soils that are susceptible to liquefaction include loose to
medium dense sands to silty sands that are below the water table. The Liquefaction Susceptibility Map of
King County, Washington (Palmer, et al. 2004) indicates the site soils have a “very low” liquefaction
potential. Based on the soil and groundwater conditions observed in our explorations and our experience,
we conclude that the risk for liquefaction at the site is low.
4.2.3. Lateral Spreading Potential
Lateral spreading related to seismic activity typically involves lateral displacement of large, surficial blocks
of non-liquefied soil when a layer of underlying soil loses strength during seismic shaking. Lateral spreading
usually develops in areas where sloping ground or large grade changes (including retaining walls) are
present. Based on our understanding of the liquefaction risk at the site and the proposed improvements, it
is our opinion that the risk of lateral spreading is low.
4.2.4. Surface Rupture Potential
According to the Washington State Department of Natural Resources Interactive Natural Hazards Map
(accessed August 14, 2020), there are no mapped faults or other seismogenic features within about 1 mile
of the site. Furthermore, the bedrock in the project area is covered by several hundred feet of glacial soils.
Based on the distance to the nearest mapped fault or seismogenic feature and the geologic conditions, it
is our opinion the risk for surface rupture at this site is low.
4.3. Site Development and Earthwork
4.3.1. General
We anticipate site development and earthwork activities will include: clearing and stripping vegetated
areas; site grading; establishing subgrades for driveways, parking areas and building foundations; and
placing and compacting fill and backfill materials.
The site is identified as being located within the Asarco Smelter Plume. An appropriate soil management
plan will be required. There might also be additional costs and testing protocols associated with removing
soil or stripped materials from the site.
We expect the site grading and earthwork can be accomplished with conventional earthmoving equipment.
However, glacial till can be encountered in a very dense condition and may take some effort during
excavation. The earthwork contractor should be prepared to encounter dense soil conditions at the site.
Larger excavators with toothed buckets and bulldozers with rippers could be used for more efficient
excavation.
The following sections provide specific recommendations for site development and earthwork.
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4.3.2. Clearing and Stripping
We anticipate that clearing and stripping depths at the site will typically be on the order of about 9 to
12 inches to remove forest duff, vegetation and associated root network at the surface. However, it is likely
that greater stripping depths will be required in areas of heavier vegetation or relatively lower lying areas.
During stripping operations excessive disturbance of surficial soils can occur, especially if left exposed to
wet conditions. Glacial till soils expected to be exposed after clearing and stripping have a relatively high
fines content and can be easily disturbed during wet weather. Clearing and stripping at the site should be
performed during dry weather and/or exposed soils should be promptly covered and protected to avoid
excessive disturbance. Disturbed soils may require additional compaction or remediation during
construction and grading.
Cobbles and boulders can be present in glacial till soils in the project area. Although no boulders were
observed, the contractor should be prepared to remove cobbles and boulders if encountered during grading
or excavation. Boulders may be removed from the site or used in landscape areas. Voids caused by boulder
removal should be backfilled with structural fill.
4.3.3. Erosion and Sedimentation Control
Erosion and sedimentation rates and quantities can be influenced by construction methods, slope length
and gradient, amount of soil exposed and/or disturbed, soil type, construction sequencing and weather.
Implementing an Erosion and Sedimentation Control Plan will reduce impacts to the project where erosion-
prone areas are present. The plan should be designed in accordance with applicable county and/or state
standards. The plan should incorporate basic planning principles, including:
■ Scheduling grading and construction to reduce soil exposure;
■ Re-vegetating or mulching denuded areas;
■ Directing runoff away from exposed soils;
■ Reducing the length and steepness of slopes with exposed soils;
■ Decreasing runoff velocities;
■ Preparing drainage ways and outlets to handle concentrated or increased runoff;
■ Confining sediment to the project site; and
■ Inspecting and maintaining control measures frequently.
Temporary erosion protection should be used and maintained in areas with exposed or disturbed soils to
help reduce erosion and reduce transport of sediment to adjacent areas and receiving waters. Permanent
erosion protection should be provided by paving, structure construction or landscape planting.
Until permanent erosion protection is established and the site is stabilized, site monitoring may be required
by qualified personnel to evaluate the effectiveness of the erosion control measures and to 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. Where sloped areas are
present, some sloughing and raveling of exposed or disturbed soil on slopes should be expected. We
recommend that disturbed soil be restored promptly so that surface runoff does not become channeled.
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4.3.4. Temporary Excavations and Cut Slopes
Based on observations made during excavation of our test pits and our experience with other projects in
similar soil conditions, we anticipate that shallow or even moderately deep (about 10-foot) excavations
could maintain vertical slopes for extended periods of time with only minor caving. However, excavations
deeper than 4 feet should be shored or laid back at a stable slope if workers are required to enter. Shoring
and temporary slope inclinations must conform to the provisions of Title 296 Washington Administrative
Code (WAC), Part N, “Excavation, Trenching and Shoring.” Regardless of the soil type encountered in the
excavation shoring, trench boxes or sloped sidewalls will be required under Washington Industrial Safety
and Health Act (WISHA). We recommend contract documents specify that the contractor is responsible for
selecting excavation and dewatering methods, monitoring the excavations for safety and providing shoring,
as required, to protect personnel and structures.
In general, we recommend that for planning purposes all temporary cut slopes be inclined no steeper than
about 1½H to 1V (horizontal to vertical) if workers are required to enter the excavation. This guideline
assumes all surface loads are kept at a minimum distance of at least one-half the depth of the cut away
from the top of the slope and that seepage is not present on the slope face. Flatter cut slopes will be
necessary where seepage occurs or if surface surcharge loads are anticipated. Temporary covering with
heavy plastic sheeting should be used to protect these slopes during periods of wet weather.
4.3.5. Permanent Cut and Fill Slopes
We recommend permanent slopes be constructed at a maximum inclination of 2H to 1V to manage erosion.
Where 2H to 1V permanent slopes are not feasible, protective facings and/or retaining structures should
be considered.
To achieve uniform compaction of fill slopes, we recommend fill slopes be overbuilt and subsequently cut
back to expose well-compacted fill. Fill placement on existing slopes steeper than 5H to 1V should be
benched into the slope face. The configuration of benches depends on the equipment being used and the
inclination of the existing slope. Bench excavations should be level and extend into the slope face at least
half the width of the compaction equipment used.
Exposed areas should be re-vegetated as soon as practical to reduce surface erosion and sloughing.
Temporary protection should be used until permanent protection is established.
4.3.6. Groundwater Handling Considerations
Based on our understanding of the proposed site improvements and our explorations we do not anticipate
that the regional groundwater table will be encountered during excavations at the site.
Although not encountered in our explorations, areas of perched groundwater could be encountered at the
site. The interface between more permeable and less permeable zones, such as the contact between
weathered glacial till and undisturbed glacial till, are likely locations for accumulation of perched
groundwater. Perched groundwater could also develop in site excavations as relatively permeable fill and
backfill soils are placed over undisturbed glacial till.
Groundwater handling needs will typically be lower during the summer and early fall months. We anticipate
that shallow perched groundwater can be handled adequately with sumps, pumps, and/or diversion ditches,
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as necessary. Ultimately, we recommend that the contractor performing the work be made responsible for
controlling and collecting groundwater encountered.
4.3.7. Surface Drainage
Surface water from roof downspouts, driveways and landscape areas should be collected and controlled.
Curbs or other appropriate measures such as sloping pavements, sidewalks and landscape areas should
be used to direct surface flow away from buildings, erosion sensitive areas and from behind retaining
structures. Roof and catchment drains should not be connected to wall or foundation drains.
4.3.8. Subsurface Drainage
Based on our subsurface explorations, the site generally consists of low permeable, undisturbed glacial till
soils at relatively shallow depths (on the order of 3 to 5 feet bgs). Excavations that extend into undisturbed
glacial till, such as foundation excavations, will likely create a perched groundwater condition. Utility
trenches that extend into undisturbed glacial till and are backfilled with structural fill could also create
perched groundwater due to difference in permeability between trench backfill and undisturbed glacial till.
To manage perched groundwater within site excavations, we recommend that subsurface drainage,
including foundation drains, be considered where groundwater or high moisture would be detrimental to
structures or other site improvements. Special drainage details could be required to clear groundwater
accumulation in utility trenches and other excavations near structures.
4.3.9. Subgrade Preparation
Subgrades that will support structures and roadways should be thoroughly compacted to a uniformly firm
and unyielding condition on completion of stripping and before placing structural fill. We recommend that
subgrades for structures and roadways be evaluated, as appropriate, to identify areas of yielding or soft
soil. Probing with a steel probe rod or proof-rolling with a heavy piece of wheeled construction equipment
are appropriate methods of evaluation.
If soft or otherwise unsuitable subgrade areas are revealed during evaluation that cannot be compacted to
a stable and uniformly firm condition, we recommend that: (1) the unsuitable soils be scarified (e.g., with a
ripper or farmer’s disc), aerated and recompacted, if practical; or (2) the unsuitable soils be removed and
replaced with compacted structural fill, as needed.
4.3.10. Subgrade Protection and Wet Weather Considerations
Near-surface soils observed at the site contain a significant quantity of fines and will be susceptible to
disturbance during periods of wet weather. The wet weather season generally begins in October and
continues through May in western Washington; however, periods of wet weather can occur during any
month of the year. It may be possible to conduct earthwork at the site during wet weather months provided
appropriate measures are implemented to protect exposed soil. If earthwork is scheduled during the wet
weather months, we offer the following recommendations:
■ Measures should be implemented to remove or eliminate the accumulation of surface water from work
areas. The ground surface in and around the work area should be sloped so that surface water is
directed away and 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.
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■ Earthwork activities should not take place during periods of heavy precipitation.
■ Slopes with exposed soils should be covered with plastic sheeting.
■ The contractor should take necessary measures to prevent on-site soils and other 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 exposed soils by rolling with a smooth-drum roller prior to periods of precipitation will help
reduce the extent to which these soils become wet or unstable.
■ Construction traffic should be restricted to specific areas of the site, preferably areas that are surfaced
with working pad materials not susceptible to wet weather disturbance.
■ Construction activities should be scheduled so that the length of time that soils are left exposed to
moisture is reduced to the extent practical.
■ Protective surfacing such as placing asphalt-treated base (ATB) or haul roads made of quarry spalls or
a layer of free-draining material such as well-graded pit-run sand and gravel may be considered to limit
disturbance to completed areas. Minimum quarry spall thicknesses should be on the order of 12 to
18 inches. Typically, minimum gravel thicknesses on the order of 24 inches are necessary to provide
adequate subgrade protection.
4.4. Fill Materials
4.4.1. On-Site Soil
Based on our subsurface explorations and experience, it is our opinion that existing site soils, excluding the
forest duff, may be considered for use as structural fill, provided the soils can be adequately moisture
conditioned, placed and compacted as recommended and do not contain organics or other deleterious
material. The glacial till soils present at the site contain a significant quantity of fines and are extremely
moisture sensitive and will be very difficult or impossible to properly compact when wet.
Based on our laboratory testing, glacial till samples collected during the explorations were typically at or
slightly above optimum moisture content for compaction. Once disturbed, these soils can quickly absorb
moisture and become unstable. In addition, fill or weathered soils located just above undisturbed glacial
till in the perched groundwater zone are more likely to have moisture contents above optimum.
If the on-site soils will be used as fill we recommend that: (1) earthwork be scheduled for spring or summer
months where extended periods of dry weather are more likely; (2) earthwork is staged such that material
is placed and compacted shortly after it is excavated, even covered stockpiles should be avoided if
practical, as loose soil more readily absorbs moisture from precipitation; and (3) cut and fill quantities
should assume that some material will become wet, unworkable, and must be removed from the site.
Alternatively, a non-structural area could be designated on site for disposal of wet and unworkable material.
If earthwork occurs during the wet season, or if the soils are persistently wet and cannot be dried back to
near optimum due to prevailing wet weather conditions, we recommend the use of imported structural fill
or select granular fill as described below.
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4.4.2. Imported Structural Fill
Imported structural fill should consist of well-graded sand and gravel or crushed rock with a maximum
particle size of 6 inches and less than 5 percent fines by weight based on the minus ¾-inch fraction. Organic
matter, debris or other deleterious material should not be present. In our opinion, material with gradation
characteristics similar to Washington State Department of Transportation (WSDOT) Specifications 9-03.9
(Aggregates for Ballast and Crushed Surfacing), 9-03.14(1) (Gravel Borrow), or 9-03.14(2) (Select Borrow)
is suitable for use as imported structural fill, with the exception that the fines content is less than 5 percent
(based on the minus ¾-inch fraction) and the maximum particle size is 6 inches.
If prolonged dry weather prevails during the earthwork phase of construction, materials with a somewhat
higher fines content may be acceptable.
4.4.3. Pipe Bedding
Trench backfill for the bedding and pipe zone should consist of well-graded granular material similar to
“Gravel Backfill for Pipe Zone Bedding” described in Section 9-03.12(3) of the WSDOT Standard
Specifications. The material must be free of roots, debris, organic matter and other deleterious material.
Other materials may be appropriate depending on manufacturer specifications and/or local jurisdiction
requirements.
4.4.4. Trench Backfill
We recommend that trench backfill within structural areas such as roadways and within building footprints
consist of Imported Structural Fill, as described above. In non-structural areas the excavated glacial till can
be reused as backfill provided it is free of debris, organic material, and rock fragments larger than 6 inches.
4.5. Fill Placement and Compaction
4.5.1. General
To obtain proper compaction, fill and backfill material should be placed in uniform horizontal lifts and
compacted near the optimum moisture content. Lift thickness and compaction procedures will depend on
the moisture content and gradation characteristics of the soil and the type of compaction equipment used.
The maximum allowable moisture content varies with the soil gradation and should be evaluated during
construction. Generally, 8- to 12-inch loose lifts are appropriate for steel-drum vibratory roller compaction
equipment. Compaction should be achieved by mechanical means. During fill and backfill placement,
sufficient testing of in-place density should be conducted to check that adequate compaction is being
achieved.
4.5.2. Area Fills and Pavement Bases
Fill placed to raise site grades and materials under pavements and structural areas should be placed on
subgrades prepared as previously recommended. All fill material placed below structures and footings and
extending beyond the edge of the structures a distance equal to the depth of the fill should be compacted
to at least 95 percent of the theoretical maximum dry density (MDD) per ASTM International (ASTM) D 1557.
Fill material placed shallower than 2 feet below pavement sections should be compacted to at least
95 percent of the MDD. Fill placed deeper than 2 feet below pavement sections should be compacted to
at least 92 percent of the MDD. Fill material placed in landscaping areas should be compacted to a firm
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condition that will support construction equipment, as necessary, typically around 85 to 90 percent of the
MDD.
4.5.3. Backfill Behind Walls
Backfill behind retaining walls or below-grade structure walls should be compacted to between 90 and
92 percent of the MDD. Over compaction of fill placed directly behind walls should be avoided. We
recommend use of hand-operated compaction equipment and maximum 6-inch loose lift thickness when
compacting fill within about 5 feet behind walls.
4.5.4. Trench Backfill
For utility excavations, we recommend that the initial lift of fill over the pipe be thick enough to reduce the
potential for damage during compaction, but generally should not be greater than about 18 inches above
the pipe. In addition, rock fragments greater than about 1 inch in maximum dimension should be excluded
from this lift.
Trench backfill material placed below structures and footings should be compacted to at least 95 percent
of the MDD. In paved areas, trench backfill should be uniformly compacted in horizontal lifts to at least
95 percent of the MDD in the upper 2 feet below subgrade. Fill placed below a depth of 2 feet from
subgrade in paved areas must be compacted to at least 92 percent of the MDD. In non-structural areas,
trench backfill should be compacted to a firm condition that will support construction equipment as
necessary.
4.6. Foundation Support
4.6.1. General
Based on our understanding of the proposed development it is our opinion the proposed structures can be
adequately supported on shallow foundations, reinforced mat foundations, and slabs-on-grade. Exterior
footings should be established at least 18 inches below the lowest adjacent grade. Interior footings can be
founded a minimum of 12 inches below the bottom of the floor slab. Isolated column and continuous wall
footings should have minimum widths of 24 and 18 inches, respectively.
Based on the groundwater conditions in our explorations and our understanding of the proposed footing
elevations (bottom of footings established within a few feet of existing site grade), it is our opinion footing
drains are not necessary to maintain bearing support as provided in this report. However, it is possible and
even likely that perched groundwater zones will develop within fill placed over native glacial till soils at the
site. Footing drains or perimeter drains should be considered to reduce the potential for perched
groundwater accumulation in the fill around building foundations.
The sections below provide our recommendations for foundation bearing surface preparation and
foundation design parameters.
4.6.2. Foundation Bearing Surface Preparation
Foundations should bear on existing glacial till soils or on structural fill extending to these soils. If existing
fill material is present at the base of foundation excavations, we recommend it be overexcavated and
replaced with structural fill. We recommend that glacial till soils exposed at the base of foundation
excavations be proof compacted to a firm and unyielding condition. Loose or disturbed materials present
August 24, 2020| Page 11
File No. 3625-004-00
at the base of foundation excavations should be removed or compacted prior to placement of formwork
and reinforcing steel.
If structural fill is placed below foundations as either replacement of overexcavated soils or to establish a
bearing pad, we recommend the structural fill extend laterally beyond the foundation perimeter a distance
equal to the depth of fill (measured from the base of the footing where necessary), or 3 feet, whichever is
less.
Foundation bearing surfaces should not be exposed to standing water. If water is present in the excavation,
it must be removed before placing formwork and reinforcing steel. A 6-inch-thick layer of crushed rock or a
3- to 4-inch layer of lean-mix concrete, could be used to protect the base of excavations and limit
disturbance to bearing surfaces during construction.
Prepared foundation bearing surfaces should be evaluated by a member of our firm prior to placement of
formwork or reinforcing steel to verify that bearing surface has been prepared in accordance with our
recommendations or to provide recommendations for remediating unsuitable bearing soils.
4.6.3. Allowable Soil Bearing Pressure
Shallow foundations bearing on subgrades prepared as recommended may be designed using an allowable
soil bearing pressure of 3,500 pounds per square foot (psf) when bearing on proof-compacted glacial till
(weathered or undisturbed) or structural fill extending to proof compacted glacial till. This bearing pressure
applies to the total of dead and long-term live loads and may be increased by one-third when considering
total loads, including earthquake or wind loads. These are net bearing pressures. The weight of the footing
and overlying backfill can be ignored in calculating footing sizes.
Significantly higher bearing pressures can be achieved for foundations bearing directly on undisturbed
glacial till, but these higher bearing pressures must be considered on a case-by-case basis and might
require special or more detailed bearing surface preparation recommendation to limit settlement. If higher
bearing pressures would be beneficial to the design, please contact us for further recommendations.
4.6.4. Foundation Settlement
Disturbed soil must be removed from the base of footing excavations and the bearing surface should be
prepared as recommended. Provided these measures are taken, we estimate the total static settlement of
shallow foundations will be on the order of 1 inch or less for the bearing pressures presented above.
Differential settlements could be on the order of ¼ to ½ inch between similarly loaded foundations or over
a distance of 50 feet of continuous footings. The settlements should occur rapidly, essentially as loads are
applied. Settlements could be greater than estimated if disturbed or saturated soil conditions are present
below footings.
4.6.5. Lateral Resistance
The ability of the soil to resist lateral loads is a function of the base friction, which develops on the base of
foundations and slabs, and the passive resistance, which develops on the face of below-grade elements of
the structure as these elements move into the soil. For cast-in-place foundations supported in accordance
with the recommendations presented above, the allowable frictional resistance on the base of the
foundation may be computed using a coefficient of friction of 0.40 applied to the vertical dead-load forces.
If precast foundations are included as part of project plans, we can provide specific recommendations for
August 24, 2020| Page 12
File No. 3625-004-00
base friction resistance for precast foundations. The allowable passive resistance on the face of the
foundation or other embedded foundation elements may be computed using an equivalent fluid density of
290 pounds per cubic foot (pcf).
These values include a factor of safety of about 1.5. The passive earth pressure and friction components
may be combined provided that the passive component does not exceed two-thirds of the total. The top
foot of soil should be neglected when calculating passive lateral earth pressure unless the area adjacent
to the foundation is covered with pavement or a slab-on-grade.
4.7. Slab-on-Grade Floors
Slab-on-grade floors should bear on glacial till soils or on structural fill extending to these soils and should
be prepared as recommended in the “Subgrade Preparation” section of this report. We recommend the
slab subgrades be observed by a member of our firm during construction. Disturbed areas should be
compacted, if possible, or removed and replaced with compacted structural fill. In all cases, the exposed
soil should be compacted to a firm and unyielding condition.
We recommend the slab-on-grade floors be underlain by a minimum 6-inch-thick capillary break layer
consisting of clean sand and gravel, crushed rock, or washed rock. The capillary break material should
contain less than 3 percent fine material based on the percent passing the ¾-inch sieve size. Provided that
loose soil is removed, and the subgrade is prepared as recommended, we recommend slabs-on-grade be
designed using a modulus of subgrade reaction of 200 pounds per cubic inch (pci). We estimate that
settlement for slabs-on-grade constructed as recommended will be less than ¾ inch for a floor load of up
to 300 psf.
Based on our understanding of subsurface conditions at the site, it is our opinion that an underslab drain
system is not necessary provided that footing or perimeter drains are provided. If dry slabs are required
(e.g., where adhesives are used to anchor carpet or tile to slab), a waterproof liner may be placed as a
vapor barrier below the slab.
4.8. Retaining Walls and Below-Grade Structures
4.8.1. Design Parameters
We recommend the following lateral earth pressures be used for design of conventional retaining walls and
below-grade structures. Our design pressures assume that the ground surface around the retaining
structures will be level or near level. If drained design parameters are used, drainage systems must be
included in the design in accordance with the recommendations presented in the “Drainage” section below.
The active soil pressure condition assumes the wall is free to move laterally 0.001 H, where H is the wall
height. The at-rest condition is applicable where walls are restrained from movement. The above
recommended lateral soil pressures do not include the effects of sloping backfill surfaces or surcharge
loads, except as described. Overcompaction of fill placed directly behind retaining walls or below-grade
structures must be avoided to limit lateral pressures placed on the wall. We recommend use of hand-
operated compaction equipment and maximum 6-inch loose lift thickness when compacting fill within about
5 feet of retaining walls and below-grade structures.
■ Active soil pressure may be estimated using an equivalent fluid density of 35 pcf for the drained
condition.
August 24, 2020| Page 13
File No. 3625-004-00
■ Active total soil and hydrostatic pressure may be estimated using an equivalent fluid density of 80 pcf
for the undrained condition; this value includes hydrostatic pressures.
■ At-rest soil pressure may be estimated using an equivalent fluid density of 55 pcf for the drained
condition.
■ At-rest total soil and hydrostatic pressure may be estimated using an equivalent fluid density of 90 pcf
for the undrained condition; this value includes hydrostatic pressures.
■ For seismic considerations, a uniform lateral pressure of 16*H psf (where H is the height of the retaining
structure or the depth of a structure below ground surface) should be added to the lateral earth
pressure.
■ A traffic surcharge can be estimated should be included if vehicles are allowed to operate within a zone
equal to the height of the retaining walls. This can be estimated with a uniform horizontal load of 70 psf,
or by assuming an additional 2 feet of fill. This is based on a uniform surface load of 250 psf, other surface
loads should be considered on a case-by-case basis.
Retaining wall foundations may be designed using the recommendations presented above for building
foundation design. We estimate settlement of retaining structures will be similar to the values previously
presented for structure foundations.
4.8.2. Drainage
If retaining walls or below-grade structures are designed using drained parameters, a drainage system
behind the structure must be included to collect water and prevent the buildup of hydrostatic pressure
against the structure. We recommend the drainage system include a zone of free-draining backfill against
the back of the wall. This drainage layer can consist of either a 24-inch thick layer of a graded drainage
material such as WSDOT Specification 9-03.12(2) (Gravel Backfill for Walls) or a 12-inch thick layer of pea-
gravel with a non-woven geotextile designed for soil separation placed between the pea-gravel and backfill.
Drain boards or other prefabricated drainage systems can be used provided they can be adequately
connected to an appropriate collection and discharge pipe system.
A perforated, rigid, smooth-walled drain pipe with a minimum diameter of 4 inches should be placed along
the base of the structure within the free-draining backfill and extend for the entire wall length. The drain
pipe should be metal or rigid PVC pipe and be sloped to drain by gravity. Discharge should be routed to
appropriate discharge areas and to reduce erosion potential. Cleanouts should be provided to allow routine
maintenance. Roof downspouts or other types of drainage systems must not be connected to retaining wall
drain systems.
4.9. Stormwater Infiltration Feasibility
We anticipate that stormwater facilities on site, if planned, will be designed in accordance with the 2016
King County Surface Water Design Manual (SWDM), which has been adopted by the City of Federal Way.
According to the SWDM, measured infiltration rates shall be determined using a Pilot Infiltration Test (PIT)
or single-ring percolation test. The manual does not allow the use of soil grain-size analysis to determine
design infiltration rates and grain-size analysis is very inaccurate in glacially consolidated soils like those
observed on site. Additionally, detailed infiltration analyses including performance testing and groundwater
mounding analysis are noted in the SWDM and may also be required for final design.
August 24, 2020| Page 14
File No. 3625-004-00
The site is generally underlain by undisturbed glacial till at relatively shallow depths (on the order of 3 to
5 feet bgs). In our experience with similar soil and density conditions (undisturbed glacial till), PITs typically
measure very slow infiltration rates, on the order of 0.05 to 0.25 inches per hour without correction factors
and in some cases, no infiltration can be measured.
If infiltration of on-site stormwater is pursued, alternative testing methods such as a PIT, will likely be
required to establish the final design infiltration rates. However, as discussed above we anticipate that
design infiltration rates will be very low.
4.10. Pavement Recommendations
4.10.1. General
We anticipate that pavements for the proposed improvements will include new parking areas and
driveways. Our recommended pavement sections provided below are based on our explorations and
experience in the area. We understand asphalt concrete (AC) may be used for the proposed improvements.
The recommended pavement sections below may not be adequate for heavy construction traffic loads such
as those imposed by concrete transit mixers, dump trucks or cranes. Additional pavement thickness may
be necessary to prevent pavement damage during construction. An asphalt-treated base (ATB) section can
also be used during construction to protect partially constructed pavement sections and pavement
subgrades. The recommended sections assume final improvements surrounding the pavement areas will
be designed and constructed such that stormwater or excess irrigation water from landscape areas does
not accumulate below the pavement section or pond on pavement surfaces. If pavements in parking areas
slope inward (toward the center of the parking area) full depth curbs or other measures should be used to
prevent water from entering and ponding on the subgrade and within the base section.
4.10.2. Construction Considerations
Existing pavements, hardscaping or other structural elements should be removed prior to placement of new
pavement sections. Pavement subgrade should be prepared to a uniformly firm, dense and unyielding
condition as previously described. Crushed surfacing base course and subbase should be moisture
conditioned to near optimum moisture content and compacted to at least 95 percent of the MDD (ASTM D
1577).
Crushed surfacing base course (CSBC) should conform to applicable sections of 4-04 and 9-03.9(3) of the
WSDOT Standard Specifications. Subbase should conform to applicable sections of 4-02 “Gravel Base” and
9-03.10 “Aggregate Gravel for Base” of the WSDOT Standard Specifications. Hot mix asphalt should
conform to applicable sections of 5-04, 9-02 and 9-03 of the WSDOT Standard Specifications. Portland
cement concrete (PCC) mix design should conform with Section 5-05.3(1) of the WSDOT Standard
Specifications. Aggregates for PCC should conform to applicable sections of 9-03.1 of the WSDOT Standard
Specifications.
Some areas of pavement may exhibit settlement and subsequent cracking over time. Cracks in the
pavement will allow water to infiltrate to the underlying base course, which could increase the amount of
pavement damage caused by traffic loads. To prolong the effective life of the pavement, cracks should be
sealed as soon as possible.
August 24, 2020| Page 15
File No. 3625-004-00
4.10.3. Asphalt Concrete Pavement Design
4.10.3.1. Standard-Duty ACP – Automobile Driveways and Parking Areas
■ 2 inches of hot mix asphalt, class ½-inch, PG 58-22
■ 4 inches of CSBC
■ 6 inches of subbase consisting of select granular fill, previously described, to provide a uniform grading
surface, to provide pavement support, to maintain drainage, and to provide separation from fine-
grained subgrade soil (this layer can be omitted for select granular fill subgrades or glacial till subgrades
if dry weather persists through construction and final paving of the section)
4.10.3.2. Subgrade consisting of proof-compacted firm and unyielding conditions or structural fill prepared in
accordance with the “Error! Reference source not found.Heavy-Duty ACP – Areas Subject to Occasional Heavy
Truck Traffic (Garbage or Delivery Truck Routes)
■ 3 inches of hot mix asphalt, class ½ inch, PG 58-22
■ 6 inches of CSBC
■ 6 inches of subbase consisting of select granular fill, previously described, to provide a uniform grading
surface, to provide pavement support, to maintain drainage, and to provide separation from fine-
grained subgrade soil (this layer can be omitted for select granular fill subgrades or glacial till subgrades
if dry weather persists through construction and final paving of the section)
■ Subgrade consisting of proof-compacted firm and unyielding conditions or structural fill prepared in
accordance with the “Subgrade Preparation" and “Area Fills and Pavement Bases" sections of this
report
4.10.3.3. Temporary Construction Surfacing
A temporary surfacing of ATB can be used to protect partially constructed pavement sections and pavement
subgrades during construction. This can provide a relatively clean working surface, prevent construction
traffic from damaging final paving surfaces and reduce subgrade repairs required for final paving. A 2-inch-
thick section of ATB can be substituted for the upper 2 inches of CSBC in either the light-duty or heavy-duty
pavement sections. Prior to placement of the final pavement surface sections, we recommend that any
areas of ATB pavement failure be removed and the subgrade repaired. If ATB is used and is serviceable
when final pavements are constructed, the design asphalt concrete pavement thickness can be placed
directly over the ATB.
Cement treatment of subgrades is sometimes used to create construction surfacing or to control soil
moisture during wet weather construction. In our opinion cement treatment would not likely be cost
effective for creating a construction surface due to the high fines content in the soil. Cement treatment or
cement stabilization would likely only be cost effective as an emergency or contingency action for reducing
soil moisture in the subgrade so that a traditional asphalt pavement could be constructed. It would take a
significant amount of cement (likely on the order of 8 to 12 percent by weight) to create a firm and stable
working surface that could handle wet weather construction.
5.0 LIMITATIONS
We have prepared this report for Shelter Resources, Inc. for the Redondo Heights Apartments project
located in Federal Way, Washington. Shelter Resources, Inc. may distribute copies of this report to owner’s
authorized agents and regulatory agencies as may be required for the Project.
August 24, 2020| Page 16
File No. 3625-004-00
Within the limitations of scope, schedule and budget, our services have been executed in accordance with
generally accepted practices for geotechnical engineering in this area at the time this report was prepared.
The conclusions, recommendations, and opinions presented in this report are based on our professional
knowledge, judgment and experience. No warranty, express or implied, applies to the services or this report.
Please refer to Appendix B titled “Report Limitations and Guidelines for Use” for additional information
pertaining to use of this report.
µ
SITE
Vicinity Map
Figure 1
Redondo Heights ApartmentsFederal Way, Washington
2,000 2,0000
Feet
Data Source: Mapbox Open Street Map, 2016
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 HARN StatePlane Washington South FIPS 4602 Feet
P:\3\3625004\GIS\MXD\362500400_F01_VicinityMap.mxd Date Exported: 08/14/20 by ccabrera
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TP-11
TP-12
TP-9
TP-7
TP-8
TP-6
TP-4
TP-3
TP-1 TP-2
TP-5Pacific Highway S276th Street
Figure 2
Redondo Heights Apartments
Federal Way, Washington
Site Plan
W E
N
S
\\geoengineers.com\WAN\Projects\3\3625004\CAD\00\Geotech\362500400_F02_Site Plan.dwg TAB:F02 Date Exported: 08/18/20 - 14:21 by tbyrdNotes:
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 kpff dated 07/22/20.
Projection: Washington State Plane, North Zone, NAD83, US Foot
Feet
0
Legend
100 100
TP-1
Site Boundary
Test Pit by GeoEngineers, Inc., 2020
APPENDIX A
Subsurface Explorations and Laboratory Testing
August 24, 2020| Page A-1
File No. 3625-004-00
APPENDIX A
SUBSURFACE EXPLORATIONS AND LABORATORY TESTING
Subsurface Explorations
Subsurface conditions for the proposed Redondo Heights Apartments project were explored by excavating
12 test pits between August 6, 2020 at the approximate locations shown on Figure 2. The test pits were
excavated to depths between about 8 and 10½ feet below ground surface (bgs) using a backhoe and
operator provided by SRI-Rochlin Construction Services. After each test pit was completed, the excavation
was backfilled using the generated material and compacted using the bucket of the excavator.
During the exploration program our field representative obtained samples, classified the soils encountered
and maintained a detailed log of each exploration. The relative densities noted on the test pit logs are based
on the difficulty of excavation and our experience and judgment. The samples were collected and retained
in sealed plastic bags and then transported back to our office. The soils were classified visually in general
accordance with the system described in Figure A-1, which includes a key to the exploration logs. Summary
logs of the explorations are included as Figures A-2 through A-13.
The locations of the test pits were determined using an electronic tablet with global positioning system
(GPS) software. The locations of the explorations should be considered approximate. Elevations were
estimated from supplemental survey information provided by SRI-Rochlin Construction Services.
Laboratory Testing
Soil samples obtained from the borings were transported to GeoEngineers laboratory. Representative soil
samples were selected for laboratory tests to evaluate the pertinent geotechnical engineering
characteristics of the site soils and to confirm our field classification.
Our testing program consisted of the following:
■ Four grain-size distribution analyses (sieve analyses [SA])
■ Four percent fines determinations (%F)
■ Seven moisture content determinations (MC)
Tests were performed in general accordance with test methods of ASTM International (ASTM) or other
applicable procedures. The following sections provide a general description of the tests performed.
Sieve Analysis (SA)
Grain-size distribution analyses were completed on selected samples in general accordance with ASTM
Test Method D 6913. This test method covers the quantitative determination of the distribution of particle
sizes in soils. Typically, the distribution of particle sizes larger than 75 micrometers (μm) is determined by
sieving. The results of the tests were used to verify field soil classifications and determine pertinent
engineering characteristics. Figure A-14 presents the results of our sieve analyses.
August 24, 2020| Page A-2
File No. 3625-004-00
Percent Fines (%F)
Selected samples were “washed” through the U.S. No. 200 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 (75 m). Tests were conducted in general
accordance with ASTM D 1140. Test results are used to aid in soil classification and correlation with other
pertinent engineering soil properties and are presented on the exploration logs at the respective sample
depths.
Moisture Content (MC)
The moisture content of selected samples was determined in general accordance with ASTM Test Method
D 2216. The test results are used to aid in soil classification and correlation with other pertinent
engineering soil properties. The results are presented on the test pit logs at the depth tested.
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
FINE
GRAINED
SOILS
SILTS AND
CLAYS
NOTE: Multiple symbols are used to indicate borderline or dual soil classifications
MORE THAN 50%
RETAINED ON
NO. 200 SIEVE
MORE THAN 50%
PASSING
NO. 200 SIEVE
GRAVEL
AND
GRAVELLY
SOILS
SC
LIQUID LIMIT
LESS THAN 50
(APPRECIABLE AMOUNT
OF FINES)
(APPRECIABLE AMOUNT
OF FINES)
COARSE
GRAINED
SOILS
MAJOR DIVISIONS GRAPH LETTER
GM
GC
ML
CL
OL
SILTS AND
CLAYS
SANDS WITH
FINES
SAND
AND
SANDY
SOILS
MH
CH
OH
PT
(LITTLE OR NO FINES)
CLEAN SANDS
GRAVELS WITH
FINES
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 COARSE
FRACTION RETAINED
ON NO. 4 SIEVE
MORE THAN 50%
OF COARSE
FRACTION PASSING
ON NO. 4 SIEVE
SILTY GRAVELS, GRAVEL - SAND -SILT MIXTURES
POORLY-GRADED GRAVELS,GRAVEL - SAND MIXTURES
LIQUID LIMIT GREATER
THAN 50
Continuous Coring
Bulk or grab
Direct-Push
Piston
Shelby tube
Standard Penetration Test (SPT)
2.4-inch I.D. split barrel
Contact between soil of the same geologic
unit
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 be
representative of subsurface conditions at other locations or times.
Groundwater Contact
Blowcount is recorded for driven samplers as the number of
blows 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 the
hammer.
Key to Exploration Logs
Figure A-1
Sampler Symbol Descriptions
ADDITIONAL MATERIAL SYMBOLS
NS
SS
MS
HS
No Visible Sheen
Slight Sheen
Moderate Sheen
Heavy Sheen
Sheen Classification
SYMBOLS
Asphalt Concrete
Cement Concrete
Crushed Rock/
Quarry Spalls
Topsoil
GRAPH LETTER
AC
CC
SOD Sod/Forest Duff
CR
DESCRIPTIONS
TYPICAL
TS
Percent fines
Percent gravel
Atterberg limits
Chemical analysis
Laboratory compaction test
Consolidation test
Dry density
Direct shear
Hydrometer analysis
Moisture content
Moisture content and dry density
Mohs hardness scale
Organic content
Permeability or hydraulic conductivity
Plasticity index
Point lead test
Pocket penetrometer
Sieve analysis
Triaxial compression
Unconfined compression
Vane shear
%F
%G
AL
CA
CP
CS
DD
DS
HA
MC
MD
Mohs
OC
PM
PI
PL
PP
SA
TX
UC
VS
Laboratory / Field Tests
12 inches forest duff
Tan with iron-oxide staining silty fine to medium sand with gravel and
occasional organic matter (roots) (dense, moist) (weathered glacial
till)
Grades to without roots
Gray with iron-oxide staining silty fine to medium sand with gravel (very
dense, moist) (glacial till)
Grades to without iron-oxide staining
DUFF
SM
SM
1%F
2MC
3
7
8
46
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-1
Figure A-2
SRI-Redondo Heights ApartmentsElevation (feet)331330329328327326325324323Depth (feet)1
2
3
4
5
6
7
8
9 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 9
331.3
NGVD29
1274713
132113
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
12 inches forest duff
Brown silty fine to medium sand with gravel and occasional organic
matter (roots) (loose, moist) (weathered glacial till)
Brown-gray with iron-oxide staining silty fine to medium sand with
gravel and occasional organic matter (roots) (medium dense,
moist)
Gray silty fine to medium sand with gravel (very dense, moist) (glacial
till)
DUFF
SM
SM
SM
1MC
2
10
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-2
Figure A-3
SRI-Redondo Heights ApartmentsElevation (feet)322321320319318317316315314313Depth (feet)1
2
3
4
5
6
7
8
9 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 9.5
322.3
NGVD29
1274820
132111
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
12 inches forest duff
Brown-gray silty fine to medium sand with occasional gravel and
organic matter (roots) (medium dense, moist) (weathered glacial
till)
Gray with occasional iron-oxide staining silty fine to medium sand with
gravel (very dense, moist) (glacial till)
Grades to without iron-oxide staining
DUFF
SM
SM
1
%F
2MC
9
7
33
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-3
Figure A-4
SRI-Redondo Heights ApartmentsElevation (feet)330329328327326325324323Depth (feet)1
2
3
4
5
6
7
8 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 8
330.3
NGVD29
1274647
132222
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
9 inches forest duff
Brown-gray silty fine to medium sand with occasional gravel and
organic matter (roots) (loose, moist) (weathered glacial till)
Grades to medium dense
Gray silty fine to medium sand with gravel (very dense, moist) (glacial
till)
DUFF
SM
SM
1%F
2
7 ¼- to 8-inch diameter roots in upper approximately 2feet32
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-4
Figure A-5
SRI-Redondo Heights ApartmentsElevation (feet)329328327326325324323322321Depth (feet)1
2
3
4
5
6
7
8 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 8.5
329.3
NGVD29
1274672
132341
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
12 inches forest duff
Brown-gray silty fine to medium sand with gravel and occasional
organic matter (roots) (loose, moist) (weathered glacial till)
Grades to trace roots, dense
Gray with iron-oxide staining silty fine to medium sand with gravel (very
dense, moist) (glacial till)
Grades to without iron-oxide staining
DUFF
SM
SM
1
MC
2
12
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-5
Figure A-6
SRI-Redondo Heights ApartmentsElevation (feet)324323322321320319318317316Depth (feet)1
2
3
4
5
6
7
8 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 8.5
324.3
NGVD29
1274785
132320
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
12 inches forest duff
Brown silty fine to medium sand with gravel and occasional organic
matter (roots) (loose, moist) (weathered glacial till)
Grades to brown-gray with iron-oxide staining, medium dense
Grades to dense
Gray silty fine to medium sand with gravel (very dense, moist) (glacial
till)
Gray silty fine to coarse gravel with sand (very dense, moist)
DUFF
SM
SM
GM
1MC
2SA
6
6 Left hole open for approximately 5 hours; nogroundwater seepage observed.30
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-6
Figure A-7
SRI-Redondo Heights ApartmentsElevation (feet)324323322321320319318317316315Depth (feet)1
2
3
4
5
6
7
8
9
10 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 10
324.3
NGVD29
1274884
132369
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
12 inches forest duff
Brown-gray silty fine to medium sand with gravel and occasional
organic matter (roots) (loose, moist) (weathered glacial till)
Tan with iron-oxide staining silty fine to medium sand with occasional
gravel (medium dense, moist)
Grades to dense
Gray silty fine to medium sand with gravel (very dense, moist) (glacial
till)
DUFF
SM
SM
SM
1
%F
2
7 39
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-7
Figure A-8
SRI-Redondo Heights ApartmentsElevation (feet)328327326325324323322321320319318Depth (feet)1
2
3
4
5
6
7
8
9
10 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 10.5
328.3
NGVD29
1274683
132441
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
12 inches forest duff
Brown-gray silty fine to medium sand with gravel and occasional
organic matter (roots) (loose, moist) (weathered glacial till)
Grades to dense
Gray silty fine to medium sand with gravel (very dense, moist) (glacial
till)
DUFF
SM
SM
1SA
2
8 32
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-8
Figure A-9
SRI-Redondo Heights ApartmentsElevation (feet)316315314313312311310309Depth (feet)1
2
3
4
5
6
7
8 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 8
316.3
NGVD29
1274757
132427
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
6 inches quarry spalls (dense, moist) (fill)
Brown silty fine to medium sand with gravel and occasional organic
matter (roots) and deleterious debris (plastic bags) (loose, moist)
Tan with iron-oxide staining silty fine to medium sand with gravel
(medium dense, moist) (weathered glacial till)
Grades to dense
Brown-gray with iron-oxide staining silty fine to medium sand with
gravel (very dense, moist) (glacial till)
Grades to gray with iron-oxide staining
Grades to without iron-oxide staining
CR
SM
SM
SM
1MC
2
3
4
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-9
Figure A-10
SRI-Redondo Heights ApartmentsElevation (feet)320319318317316315314313Depth (feet)1
2
3
4
5
6
7
8 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 8
320.3
NGVD29
1274639
132562
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
12 inches forest duff
Brown silty fine to medium sand with gravel and occasional organic
matter (roots) (medium dense, moist) (weathered glacial till)
Grades to brown-gray with iron-oxide staining, dense
Brown-gray with iron-oxide staining silty fine to medium sand with
gravel (very dense, moist) (glacial till)
Grades to gray and without iron-oxide staining
DUFF
SM
SM
1
2
3
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-10
Figure A-11
SRI-Redondo Heights ApartmentsElevation (feet)320319318317316315314313312311Depth (feet)1
2
3
4
5
6
7
8
9 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 9.5
320.3
NGVD29
1274666
132632
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
12 inches forest duff
Brown silty fine sand with occasional gravel and organic matter (roots)
(loose, moist) (weathered glacial till)
Brown-gray silty fine to medium sand with gravel (medium dense,
moist)
Gray silty fine sand with gravel (very dense, moist) (glacial till)
DUFF
SM
SM
SM
1MC
2
SA
3
10
6 32
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-11
Figure A-12
SRI-Redondo Heights ApartmentsElevation (feet)321320319318317316315314313Depth (feet)1
2
3
4
5
6
7
8
9 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 9
321.3
NGVD29
1274754
132602
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
9 inches forest duff
Brown silty fine to medium sand with gravel and occasional organic
matter (roots) (loose, moist) (weathered glacial till)
Tan silty fine to medium sand with occasional gravel (dense, moist)
Gray with occasional iron-oxide staining silty fine to medium sand with
gravel (very dense, moist) (glacial till)
DUFF
SM
SM
SM
1
2
SA
3
8
1- to 3-inch diameter roots
Left hole open for approximately 6 hours; nogroundwater seepage observed
27
Notes: See Figure A-1 for explanation of symbols.
The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to ½ foot.
Coordinates Data Source: Horizontal approximated based on Aerial Imagery. Vertical approximated based on Locational Survey.Date:8/21/20 Path:P:\3\3625004\GINT\362500400.GPJ DBLibrary/Library:GEOENGINEERS_DF_STD_US_JUNE_2017.GLB/GEI8_TESTPIT_1P_GEOTEC_%FSheet 1 of 1Project Number:
Project Location:
Project:
Federal Way, Washington
3625-004-00
Log of Test Pit TP-12
Figure A-13
SRI-Redondo Heights ApartmentsElevation (feet)316315314313312311310309308307Depth (feet)1
2
3
4
5
6
7
8
9
10 Testing SampleGraphic LogSAMPLE
MATERIAL
DESCRIPTION
GroupClassificationSample NameTestingMoistureContent (%)REMARKS
FinesContent (%)Date
Excavated
Surface Elevation (ft)
Vertical Datum
Coordinate System
Horizontal Datum
Easting (X)
Northing (Y)
Total
Depth (ft)8/6/2020 10
316.3
NGVD29
1274863
132637
WA State Plane North
NAD83 (feet)
CJL
Checked By CRN
Groundwater not observed
Caving not observedEquipment Komatsu PC128
Logged By Excavator SRI-Rochlin
0
10
20
30
40
50
60
70
80
90
100
0.0010.010.11101001000PERCENT PASSING BY WEIGHT GRAIN SIZE IN MILLIMETERS
U.S. STANDARD SIEVE SIZE
2”
SAND SILT OR CLAYCOBBLESGRAVEL
COARSE MEDIUM FINECOARSEFINE
Test Pit Number Depth(feet)Soil Description
TP-6
TP-8
TP-11
TP-12
9.5
2
4.5
6
Silty fine to coarse gravel with sand (GM)
Silty fine to medium sand with gravel (SM)
Silty fine sand with gravel (SM)
Silty fine to medium sand with gravel (SM)
Symbol Moisture(%)
6
8
6
8
3/8”3”1.5”#4 #10 #20 #40 #60 #1003/4”Figure A-14Sieve Analysis ResultsSRI-Redondo Heights ApartmentsFederal Way, Washington3625-004-00 Date Exported: 8/18/20
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 obtained at other times,depths or locations,or generated by separate operations or processes.
The grain size analysis results were obtained in general accordance with ASTM C 136.GeoEngineers 17425 NE Union Hill Road Ste 250,Redmond,WA 98052
#2001”#140
APPENDIX B
Report Limitations and Guidelines for Use
August 24, 2020| Page B-1
File No. 3625-004-00
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.
Read These Provisions Closely
It is important to recognize that the geoscience practices (geotechnical engineering, geology and
environmental science) rely on professional judgment and opinion to a greater extent than other
engineering and natural science disciplines, where more precise and/or readily observable data may exist.
To help clients better understand how this difference pertains to our services, GeoEngineers includes the
following explanatory “limitations” provisions in its reports. Please confer with GeoEngineers if you need to
know more how these “Report Limitations and Guidelines for Use” apply to your project or site.
Geotechnical Services are Performed for Specific Purposes, Persons and Projects
This report has been prepared for Shelter Resources, Inc. and for the Project(s) specifically identified in the
report. The information contained herein is not applicable to other sites or projects.
GeoEngineers structures its services to meet the specific needs of its clients. No party other than the party
to whom this report is addressed may rely on the product of our services unless we agree to such reliance
in advance and in writing. Within the limitations of the agreed scope of services for the Project, and its
schedule and budget, our services have been executed in accordance with our signed Agreement with
Shelter Resources, Inc. dated July 31, 2020 and generally accepted geotechnical practices in this area at
the time this report was prepared. We do not authorize, and will not be responsible for, the use of this report
for any purposes or projects other than those identified in the report.
A Geotechnical Engineering or Geologic Report is based on a Unique Set of Project-Specific
Factors
This report has been prepared for the proposed Redondo Heights Apartments project in Federal Way,
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, it is
important not to 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 ASFE, Professional Firms Practicing in the Geosciences; www.asfe.org.
August 24, 2020| Page B-2
File No. 3625-004-00
■ 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 changes occur after the date of this report, GeoEngineers cannot be responsible for any consequences
of such changes in relation to this report unless we have been given the opportunity to review our
interpretations and recommendations. Based on that review, we can provide written modifications or
confirmation, as appropriate.
Environmental Concerns are Not Covered
Unless environmental services were specifically included in our scope of services, this report does not
provide any environmental findings, conclusions, or recommendations, including but not limited to, the
likelihood of encountering underground storage tanks or regulated contaminants.
Information Provided by Others
GeoEngineers has relied upon certain data or information provided or compiled by others in the
performance of our services. Although we use sources that we reasonably believe to be trustworthy,
GeoEngineers cannot warrant or guarantee the accuracy or completeness of information provided or
compiled by others.
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 man-made events
such as construction on or adjacent to the site, new information or technology that becomes available
subsequent to the report date, or by natural events such as floods, earthquakes, slope instability or
groundwater fluctuations. If more than a few months have passed since issuance of our report or work
product, or if any of the described events may have occurred, please contact GeoEngineers before applying
this report for its intended purpose so that we may evaluate whether changed conditions affect the
continued reliability or applicability of our conclusions and recommendations.
Information Provided by Others
GeoEngineers has relied upon certain data or information provided or compiled by others in the
performance of our services. Although we use sources that we reasonably believe to be trustworthy,
GeoEngineers cannot warrant or guarantee the accuracy or completeness of information provided or
compiled by others.
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 the specific subsurface conditions only at those points where
subsurface tests are conducted or samples are taken. GeoEngineers reviewed field and laboratory data
and then applied its professional judgment to render an informed opinion about subsurface conditions at
other locations. Actual subsurface conditions may differ, sometimes significantly, from the opinions
August 24, 2020| Page B-3
File No. 3625-004-00
presented in this report. Our report, conclusions and interpretations are not a warranty of the actual
subsurface conditions.
Geotechnical Engineering Report Recommendations are Not Final
We have developed the following recommendations based on data gathered from subsurface
investigation(s). These investigations sample just a small percentage of a site to create a snapshot of the
subsurface conditions elsewhere on the site. Such sampling on its own cannot provide a complete and
accurate view of subsurface conditions for the entire site. Therefore, the recommendations included in this
report are preliminary and should not be considered final. GeoEngineers’ recommendations can be
finalized only by observing actual subsurface conditions revealed during construction. GeoEngineers
cannot assume responsibility or liability for the recommendations in this report if we do not perform
construction observation.
We recommend that you allow sufficient monitoring, testing and consultation during construction by
GeoEngineers to confirm that the conditions encountered are consistent with those indicated by the
explorations, to provide recommendations for design changes if the conditions revealed during the work
differ from those anticipated, and to evaluate whether earthwork activities are completed in accordance
with our recommendations. Retaining GeoEngineers for construction observation for this project is the most
effective means of managing the risks associated with unanticipated conditions. If another party performs
field observation and confirms our expectations, the other party must take full responsibility for both the
observations and recommendations. Please note, however, that another party would lack our project-
specific knowledge and resources.
A Geotechnical Engineering or Geologic Report Could Be Subject to Misinterpretation
Misinterpretation of this report by members of the design team or by contractors can result in costly
problems. GeoEngineers can help reduce the risks of misinterpretation by conferring with appropriate
members of the design team after submitting the report, reviewing pertinent elements of the design team’s
plans and specifications, participating in pre-bid and preconstruction conferences, and 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. The logs included in a geotechnical engineering or geologic report should
never be redrawn for inclusion in architectural or other design drawings. Photographic or electronic
reproduction is acceptable, but separating logs from the report can create a risk of misinterpretation.
Give Contractors a Complete Report and Guidance
To help reduce the risk of problems associated with unanticipated subsurface conditions, GeoEngineers
recommends giving contractors the complete geotechnical engineering or geologic report, including these
“Report Limitations and Guidelines for Use.” When providing the report, you should preface it with a clearly
written letter of transmittal that:
■ advises contractors that the report was not prepared for purposes of bid development and that its
accuracy is limited; and
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File No. 3625-004-00
■ encourages contractors to confer with GeoEngineers and/or to conduct additional study to obtain the
specific types of information they need or prefer.
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 adjacent properties.
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.
A Client that desires these specialized services is advised to obtain them from a consultant who offers
services in this specialized field.