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www.riley-group.com
GEOTECHNICAL ENGINEERING REPORT
PREPARED BY:
THE RILEY GROUP, INC.
17522 BOTHELL WAY NORTHEAST
BOTHELL, WASHINGTON 98011
PREPARED FOR:
KUSHAL VARMA
4159 NORTHWEST WOODGATE AVENUE
PORTLAND, WASHINGTON97229
RGI PROJECT NO.2024-344-1
ROBERTS SHORT PLAT
3XXX TOLEDO AVENUE SOUTHEAST
RENTON, WASHINGTON
APRIL 16, 2025
Corporate Office: 17522 Bothell Way Northeast, Bothell, WA 98011 Tacoma Office: 708 Broadway Suite #100B Tacoma, WA 98402 Phone 425.415.0551 ♦ Fax 425.415.0311
www.riley-group.com
April 16, 2025
Kushal Varma
4159 Northwest Woodgate Avenue
Portland, Washington97229
Subject: Geotechnical Engineering Report
Roberts Short Plat
3XXX Toledo Avenue Southeast
Renton, Washington
RGI Project No.2024-344-1
Dear Kushal Varma:
As requested, The Riley Group, Inc. (RGI) has performed a Geotechnical Engineering Report
(GER) for the Roberts Short Plat located at 3XXX Toledo Avenue Southeast, Renton,
Washington. Our services were completed in accordance with our proposal dated
November 4, 2024 and authorized by you via email on March 5, 2025. The information in
this GER is based on our understanding of the proposed construction, and the soil and
groundwater conditions encountered in the test pits completed by RGI at the site on March
24, 2025.
RGI recommends that you submit the project plans and specifications to RGI for a general
review so that we may confirm that the recommendations in this GER are interpreted and
implemented properly in the construction documents. RGI also recommends that a
representative of our firm be present on site during portions of the project construction to
confirm that the soil and groundwater conditions are consistent with those that form the
basis for the engineering recommendations in this GER.
If you have any questions or require additional information, please contact us.
Respectfully submitted,
THE RILEY GROUP, INC.
04/16/2025 04/16/2025
Robert K. Teng, PE Kristina M. Weller, PE
Project I Engineer Principal Geotechnical Engineer
Geotechnical Engineering Report i April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
TABLE OF CONTENTS
1.0 INTRODUCTION ............................................................................................................................... 1
2.0 PROJECT DESCRIPTION ............................................................................................................... 1
3.0 FIELD EXPLORATION AND LABORATORY TESTING .......................................................... 1 3.1 FIELD EXPLORATION ................................................................................................................................... 1
3.2 LABORATORY TESTING ................................................................................................................................ 2
4.0 SITE CONDITIONS ........................................................................................................................... 2
4.1 SURFACE .................................................................................................................................................. 2
4.2 GEOLOGY ................................................................................................................................................. 2
4.3 SOILS ....................................................................................................................................................... 2
4.4 GROUNDWATER ........................................................................................................................................ 3
4.5 SEISMIC CONSIDERATIONS ........................................................................................................................... 3
4.6 GEOLOGIC HAZARD AREAS .......................................................................................................................... 4
5.0 DISCUSSION AND RECOMMENDATIONS ................................................................................. 4
5.1 GEOTECHNICAL CONSIDERATIONS ................................................................................................................. 4
5.2 EARTHWORK ............................................................................................................................................. 4
5.2.1 Erosion and Sediment Control ..................................................................................................... 4
5.2.2 Stripping ....................................................................................................................................... 5
5.2.3 Excavations .................................................................................................................................. 6
5.2.4 Site Preparation ........................................................................................................................... 6
5.2.5 Structural Fill ................................................................................................................................ 7
5.2.6 Cut and Fill Slopes ........................................................................................................................ 9
5.2.7 Wet Weather Construction Considerations ................................................................................. 9
5.3 FOUNDATIONS .......................................................................................................................................... 9
5.4 RETAINING WALLS ................................................................................................................................... 10
5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 11
5.6 DRAINAGE .............................................................................................................................................. 11
5.6.1 Surface ....................................................................................................................................... 11 5.6.2 Subsurface .................................................................................................................................. 11
5.6.3 Infiltration .................................................................................................................................. 11
5.6.4 Soil Properties for Groundwater Protection .............................................................................. 12
5.7 UTILITIES ................................................................................................................................................ 13
5.8 PAVEMENTS ............................................................................................................................................ 13
6.0 ADDITIONAL SERVICES .............................................................................................................. 14
7.0 LIMITATIONS ................................................................................................................................. 14
LIST OF FIGURES AND APPENDICES
Figure 1 ..................................................................................................................... Site Vicinity Map
Figure 2 ............................................................................................... Geotechnical Exploration Plan
Figure 3 ............................................................................................... Retaining Wall Drainage Detail
Figure 4 ................................................................................................... Typical Footing Drain Detail
Appendix A .......................................................................... Field Exploration and Laboratory Testing
Geotechnical Engineering Report ii April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
Executive Summary
This Executive Summary should be used in conjunction with the entire Geotechnical
Engineering Report (GER) for design and/or construction purposes. It should be recognized
that specific details were not included or fully developed in this section, and the GER must
be read in its entirety for a comprehensive understanding of the items contained herein.
Section 7.0 should be read for an understanding of limitations.
RGI’s geotechnical scope of work included the advancement of 5 test pits and 1 pilot
infiltration test to approximate depths of 6 to 9.5 feet below existing site grades.
Based on the information obtained from our subsurface exploration, the site is suitable for
development of the proposed project. The following geotechnical considerations were
identified:
Soil Conditions: The soils encountered during field exploration include loose to very
dense silty sands with varying amounts of gravel and medium dense to dense sands with
trace to some silt.
Groundwater: Moderate groundwater seepage was encountered during our subsurface
exploration at 4.5 feet during test pit TP-5
Foundations: Foundations for the proposed residences may be supported on
conventional spread footings bearing on native soil or structural fill.
Slab-on-grade: Slab-on-grade floors and slabs can be supported on native soil or
structural fill.
Geotechnical Engineering Report 1 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
1.0 Introduction
This Geotechnical Engineering Report (GER) presents the results of the geotechnical
engineering services provided for the Roberts Short Plat in Renton, Washington. The
purpose of this evaluation is to assess subsurface conditions and provide geotechnical
recommendations for the construction of a 4-lot residential development with associated
roads and stormwater facilities. Our scope of services included field explorations,
laboratory testing, engineering analyses, and preparation of this GER.
The recommendations in the following sections of this GER are based upon our current
understanding of the proposed site development as outlined below. If actual features vary
or changes are made, RGI should review them in order to modify our recommendations as
required. In addition, RGI requests to review the final design drawings when available to
verify that our project understanding is correct and that our recommendations have been
properly interpreted and incorporated into the project design.
2.0 Project description
The project site is located at 3XXX Toledo Avenue Southeast in Renton, Washington. The
approximate location of the site is shown on Figure 1.
The site is currently a vacant lot with a one lot pad established in the middle-west of the
parcel and a concrete pad in the middle-east part of the parcel. We understand that a 4-lot
residential development with associated roads and stormwater facilities will be
constructed onsite.
At the time of preparing this GER, building plans were not available for our review. Based
on our experience with similar construction, RGI anticipates that the proposed building will
be supported on perimeter walls with bearing loads of two to four kips per linear foot. Slab-
on-grade floor loading of 150 pounds per square foot (psf) are expected.
3.0 Field Exploration and Laboratory Testing
3.1 FIELD EXPLORATION
On March 24, 2025, RGI observed the excavation of 5 test pits and 1 pilot infiltration test.
The approximate exploration locations are shown on Figure 2.
Field logs of each exploration were prepared by the geotechnical engineer that
continuously observed the excavation. These logs included visual classifications of the
materials encountered during excavation as well as our interpretation of the subsurface
conditions between samples. The test pits logs included in Appendix A represent an
interpretation of the field logs and include modifications based on laboratory observation
and analysis of the samples.
Geotechnical Engineering Report 2 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
3.2 LABORATORY TESTING
During the field exploration, a representative portion of each recovered sample was sealed
in containers and transported to our laboratory for further visual and laboratory
examination. Selected samples retrieved from the test pits were tested for moisture
content and grain size analysis to aid in soil classification and provide input for the
recommendations provided in this GER. The results and descriptions of the laboratory tests
are enclosed in Appendix A.
4.0 Site Conditions
4.1 SURFACE
The subject site is a rectangular-shaped parcel (1463400052) of land approximately 1.26
acres in size. The site is bound to the north by a construction storage yard, to the east and
south by residential property, and to the west by Toledo Avenue Southeast.
The existing site is vacant land covered by trees and other vegetation. The site is slopes
downhill towards the southwest with an overall elevation difference of approximately 21
feet.
4.2 GEOLOGY
Review of the Geologic Map of the Renton quadrangle, King County, Washington, by
Mullineaux, D.R. (1993) indicates that the soil in the project vicinity is mapped as Ground
moraine deposits (Qgt), which is thin ablation till over lodgment till. Lodgment till is
generally compact, coherent, unsorted mixture of sand, silt, clay and gravel, commonly
termed hardpan. Layer thickness is typically 5 to 30 feet thick. Ablation till, similar, but
much less compact and coherent is typically 2 to 10 feet thick. Mapped nearby is Vashon
recessional deposits (Qpa) which is sandy pebble and cobble gravel in easternmost terraces
grades to interbedded sand and pebble gravel at Renton and to sand at north edge of
quadrangle. These descriptions are generally similar to the findings in our field
explorations.
4.3 SOILS
The soils encountered during field exploration include loose to very dense silty sands with
varying amounts of gravel and medium dense to dense sands with some silt. Fill soils were
encountered in test pit, TP-4 extending up to 5 feet below the existing grade.
More detailed descriptions of the subsurface conditions encountered are presented in the
test pits included in Appendix A. Sieve analysis was performed on two selected soil samples.
Grain size distribution curves are included in Appendix A.
Geotechnical Engineering Report 3 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
4.4 GROUNDWATER
Moderate groundwater seepage was encountered at 4.5 feet during our subsurface
exploration in test pit TP-5. The groundwater is perched over the top of the dense glacially
compacted layer. Surface water was observed puddling near the vicinity of test pit TP-2.
It should be recognized that fluctuations of the groundwater table will occur due to
seasonal variations in the amount of rainfall, runoff, and other factors not evident at the
time the explorations were performed. In addition, perched water can develop within
seams and layers contained in fill soils or higher permeability soils overlying less permeable
soils following periods of heavy or prolonged precipitation. Therefore, groundwater levels
during construction or at other times in the future may be higher or lower than the levels
indicated on the logs. Groundwater level fluctuations should be considered when
developing the design and construction plans for the project.
4.5 SEISMIC CONSIDERATIONS
Based on the International Building Code (IBC), the seismic parameters below may be used
for design in accordance with ASCE 7-16. Additional seismic criteria or updated can be
obtained from https://ascehazardtool.org/ or similar sites based on the current edition of
IBC and ASCE 7 at the time of building permit submittal.
Table 1 IBC
Parameter Value
Site Soil Class1 D2
Short Period Spectral Response Acceleration, SS (g) 1.37
1-Second Period Spectral Response Acceleration, S1 (g) 0.469
1. Note: In general accordance with Chapter 20 of ASCE 7-16, the Site Class is based on the average characteristics of the upper 100 feet
of the subsurface profile.
2. Note: ASCE 7-16 require a site soil profile determination extending to a depth of 100 feet for seismic site classification. The current scope of our services does not include the required 100 foot soil profile determination. Test pits extended to a maximum depth of 9.5
feet, and this seismic site class definition considers that very dense soil continues below the maximum depth of the subsurface
exploration. Additional exploration to deeper depths would be required to confirm the conditions below the current depth of
exploration.
Note: In accordance with ASCE 11.4.8, a ground motion hazard analysis is not required for the following cases:
• Structures on Site Class E sites with SS greater than or equal to 1.0, provided the site coefficient Fa is taken as equal to that of Site Class C.
• Structures on Site Class D sites with S1 greater than or equal to 0.2, provided that the value of the seismic response coefficient Cs is determined by Eq. 12.8-2 for values of T ≤ 1.5Ts and taken as equal to 1.5 times the value computed in accordance with
either Eq. 12.8-3 for TL ≥ T > 1.5Ts or Eq. 12.8-4 for T > TL.
• Structures on Site Class E sites with S1 greater than or equal to 0.2, provided that T is less than or equal to Ts and the equivalent
static force procedure is used for design.
The above exceptions do not apply to seismically isolated structures, structures with damping systems or structures designed using the
response history procedures of Chapter 16.
Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength
due to an increase in water pressure induced by vibrations from a seismic event.
Liquefaction mainly affects geologically recent deposits of fine-grained sands that are
Geotechnical Engineering Report 4 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
below the groundwater table. Soils of this nature derive their strength from intergranular
friction. The generated water pressure or pore pressure essentially separates the soil grains
and eliminates this intergranular friction, thus reducing or eliminating the soil’s strength.
RGI reviewed the results of the field and laboratory testing and assessed the potential for
liquefaction of the site’s soil during an earthquake. Since the site is underlain by glacially
consolidated material, RGI considers that the possibility of liquefaction during an
earthquake is minimal.
4.6 GEOLOGIC HAZARD AREAS
Regulated geologically hazardous areas include erosion, landslide, earthquake, or other
geological hazards. Based on the King County iMap and City of Renton GIS data, the site
contains a regulated slope between 15 and 25 percent. The mapped regulated slope is part
of the northeast corner of the existing pad that was cut and shaped to be lower than the
surrounding area. Slopes are approximately 5-6 feet in vertical height and are shaped to
roughly a 1H:1V.
According to the Critical Areas Regulations under Renton Municipal Code (4-3-050B), the
slope does not meet the criteria of being greater than 15 feet in vertical rise, and thus is
not considered to be a hazard.
5.0 Discussion and Recommendations
5.1 GEOTECHNICAL CONSIDERATIONS
Based on the information obtained from our subsurface exploration and our observations
onsite, the site is suitable for the proposed construction from a geotechnical standpoint.
Foundations for the proposed residences can be supported on conventional spread
footings bearing on native soil or structural fill. Slab-on-grade floors and pavements can be
similarly supported.
Detailed recommendations regarding the above issues and other geotechnical design
considerations are provided in the following sections. These recommendations should be
incorporated into the final design drawings and construction specifications.
5.2 EARTHWORK
Site earthwork is expected to include cuts and fills to provide lot and roadway grade,
installation of underground utilities, and preparation of road and sidewalk grades. After
stripping, the existing fill soils encountered in the fill pad should be evaluated for removal.
5.2.1 EROSION AND SEDIMENT CONTROL
Potential sources or causes of erosion and sedimentation depend on construction
methods, slope length and gradient, amount of soil exposed and/or disturbed, soil type,
Geotechnical Engineering Report 5 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
construction sequencing and weather. The impacts on erosion-prone areas can be reduced
by implementing an erosion and sedimentation control plan. The plan should be designed
in accordance with applicable city and/or county standards.
RGI recommends the following erosion control Best Management Practices (BMPs):
Scheduling site preparation and grading for the drier summer and early fall months
and undertaking activities that expose soil during periods of little or no rainfall
Retaining existing vegetation whenever feasible
Establishing a quarry spall construction entrance
Installing siltation control fencing or anchored straw or coir wattles on the downhill
side of work areas
Covering soil stockpiles with anchored plastic sheeting
Revegetating or mulching exposed soils with a minimum 3-inch thickness of straw
if surfaces will be left undisturbed for more than one day during wet weather or
one week in dry weather
Directing runoff away from exposed soils and slopes
Minimizing the length and steepness of slopes with exposed soils and cover
excavation surfaces with anchored plastic sheeting (Graded and disturbed slopes
should be tracked in place with the equipment running perpendicular to the slope
contours so that the track marks provide a texture to help resist erosion and
channeling. Some sloughing and raveling of slopes with exposed or disturbed soil
should be expected.)
Decreasing runoff velocities with check dams, straw bales or coir wattles
Confining sediment to the project site
Inspecting and maintaining erosion and sediment control measures frequently (The
contractor should be aware that inspection and maintenance of erosion control
BMPs is critical toward their satisfactory performance. Repair and/or replacement
of dysfunctional erosion control elements should be anticipated.)
Permanent erosion protection should be provided by reestablishing vegetation using
hydroseeding and/or landscape planting. Until the permanent erosion protection is
established, site monitoring should be performed by qualified personnel to evaluate the
effectiveness of the erosion control measures. Provisions for modifications to the erosion
control system based on monitoring observations should be included in the erosion and
sedimentation control plan.
5.2.2 STRIPPING
Stripping efforts should include removal of pavements, vegetation, organic materials, and
deleterious debris from areas slated for building, pavement, and utility construction. The
test pits encountered 4 to 8 inches of topsoil and rootmass. In test pits TP-2, TP-3 and TP-
Geotechnical Engineering Report 6 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
4 about an inch of topsoil was encountered followed by about 11 inches of gravel. Deeper
areas of stripping may be required in forested or heavily vegetated areas of the site.
The existing single pad lot fills encountered in test pit TP-2 should be evaluated for potential
removal. During test pit TP-3, also within the pre-existing pad, a large tree root was
discovered 2.5 feet down. Material removed from the existing pad may be unsuitable for
re-use if more organics are encountered.
5.2.3 EXCAVATIONS
All temporary cut slopes associated with the site and utility excavations should be
adequately inclined to prevent sloughing and collapse. The site soils consist of loose to very
dense silty sands with varying amounts of gravel and medium dense to dense sands with
some silt.
Accordingly, for excavations more than 4 feet but less than 20 feet in depth, the temporary
side slopes should be laid back with a minimum slope inclination of 1.5H:1V
(Horizontal:Vertical). If there is insufficient room to complete the excavations in this
manner, or excavations greater than 20 feet in depth are planned, using temporary shoring
to support the excavations should be considered. For open cuts at the site, RGI
recommends:
No traffic, construction equipment, stockpiles or building supplies are allowed at
the top of cut slopes within a distance of at least five feet from the top of the cut
Exposed soil along the slope is protected from surface erosion using waterproof
tarps and/or plastic sheeting
Construction activities are scheduled so that the length of time the temporary cut
is left open is minimized
Surface water is diverted away from the excavation
The general condition of slopes should be observed periodically by a geotechnical
engineer to confirm adequate stability and erosion control measures
In all cases, however, appropriate inclinations will depend on the actual soil and
groundwater conditions encountered during earthwork. Ultimately, the site contractor
must be responsible for maintaining safe excavation slopes that comply with applicable
OSHA or WISHA guidelines.
5.2.4 SITE PREPARATION
RGI anticipates that some areas of loose or soft soil will be exposed upon completion of
stripping and grubbing. Proofrolling and subgrade verification should be considered an
essential step in site preparation. After stripping, grubbing, removal of unsuitable fill soils,
and prior to placement of structural fill, RGI recommends proofrolling building and
pavement subgrades and areas to receive structural fill. These areas should moisture
conditioned and compacted to a firm and unyielding condition in order to achieve a
Geotechnical Engineering Report 7 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
minimum compaction level of 95 percent of the modified proctor maximum dry density as
determined by the American Society of Testing and Materials D1557-09 Standard Test
Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort (ASTM
D1557).
Proofrolling and adequate subgrade compaction can only be achieved when the soils are
within approximately ± 2 percent moisture content of the optimum moisture content. Soils
which appear firm after stripping and grubbing may be proofrolled with a heavy compactor,
loaded double-axle dump truck, or other heavy equipment under the observation of an RGI
representative. This observer will assess the subgrade conditions prior to filling. The need
for or advisability of proofrolling due to soil moisture conditions should be determined at
the time of construction. In wet areas it may be necessary to hand probe the exposed
subgrades in lieu of proofrolling with mechanical equipment.
If fill is placed in areas of the site where existing slopes are steeper than 5:1
(Horizontal:Vertical), the area should be benched to reduce the potential for slippage
between existing slopes and fills. Benches should be wide enough to accommodate
compaction and earth moving equipment, and to allow placement of horizontal lifts of fill.
Subgrade soils that become disturbed due to elevated moisture conditions should be
overexcavated to reveal firm, non-yielding, non-organic soils and backfilled with
compacted structural fill. In order to maximize utilization of site soils as structural fill, RGI
recommends that the earthwork portion of this project be completed during extended
periods of warm and dry weather if possible. If earthwork is completed during the wet
season (typically November through May) it will be necessary to take extra precautionary
measures to protect subgrade soils. Wet season earthwork will require additional
mitigative measures beyond that which would be expected during the drier summer and
fall months.
5.2.5 STRUCTURAL FILL
Once stripping, clearing and other preparing operations are complete, cuts and fills can be
made to establish desired building grades. Prior to placing fill, RGI recommends proof-
rolling as described above.
RGI recommends fill below the foundation and floor slab, behind retaining walls, and below
pavement and hardscape surfaces be placed in accordance with the following
recommendations for structural fill. The structural fill should be placed after completion of
site preparation procedures as described above.
The suitability of excavated site soils and import soils for compacted structural fill use will
depend on the gradation and moisture content of the soil when it is placed. As the amount
of fines (that portion passing the U.S. No. 200 sieve) increases, soil becomes increasingly
sensitive to small changes in moisture content and adequate compaction becomes more
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3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
difficult or impossible to achieve. Soils containing more than about 5 percent fines cannot
be consistently compacted to a dense, non-yielding condition when the moisture content
is more than 2 percent above or below optimum. Optimum moisture content is that
moisture that results in the greatest compacted dry density with a specified compactive
effort.
Non-organic site soils are only considered suitable for structural fill provided that their
moisture content is within about two percent of the optimum moisture level as determined
by ASTM D1557. Excavated site soils may not be suitable for re-use as structural fill
depending on the moisture content and weather conditions at the time of construction. If
soils are stockpiled for future reuse and wet weather is anticipated, the stockpile should be
protected with plastic sheeting that is securely anchored.
Even during dry weather, moisture conditioning (such as, windrowing and drying) of site
soils to be reused as structural fill may be required. Even during the summer, delays in
grading can occur due to excessively high moisture conditions of the soils or due to
precipitation. If wet weather occurs, the upper wetted portion of the site soils may need
to be scarified and allowed to dry prior to further earthwork, or may need to be wasted
from the site.
If on-site soils are or become unusable, it may become necessary to import clean, granular
soils to complete site work that meet the grading requirements listed in Table 2 to be used
as structural fill.
Table 2 Structural Fill Gradation
U.S. Sieve Size Percent Passing
4 inches 100
No. 4 sieve 22 to 100
No. 200 sieve 0 to 5*
*Based on minus 3/4 inch fraction.
Prior to use, an RGI representative should observe and test all materials imported to the
site for use as structural fill. Structural fill materials should be placed in uniform loose layers
not exceeding 12 inches and compacted to 95 percent of the maximum dry density. The
soil’s maximum density and optimum moisture should be determined by ASTM D1557.
Placement and compaction of structural fill should be observed by RGI. A representative
number of in-place density tests should be performed as the fill is being placed to confirm
that the recommended level of compaction is achieved.
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3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
5.2.6 CUT AND FILL SLOPES
All permanent cut and fill slopes should be graded with a finished inclination no greater
than 2H:1V. Slopes above modular block walls should not exceed 3H:1V. Upon completion
of construction, the slope face should be trackwalked, compacted and vegetated, or
provided with other physical means to guard against erosion. All fill placed for slope
construction should meet the structural fill requirements as described in Section 5.2.5.
Final grades at the top of the slopes must promote surface drainage away from the slope
crest. Water must not be allowed to flow in an uncontrolled fashion over the slope face. If
it is necessary to direct surface runoff towards the slope, it should be controlled at the top
of the slope, piped in a closed conduit installed on the slope face, and taken to an
appropriate point of discharge beyond the toe of the slope.
5.2.7 WET WEATHER CONSTRUCTION CONSIDERATIONS
RGI recommends that preparation for site grading and construction include procedures
intended to drain ponded water, control surface water runoff, and to collect shallow
subsurface seepage zones in excavations where encountered. It will not be possible to
successfully compact the subgrade or utilize on-site soils as structural fill if accumulated
water is not drained prior to grading or if drainage is not controlled during construction.
Attempting to grade the site without adequate drainage control measures will reduce the
amount of on-site soil effectively available for use, increase the amount of select import fill
materials required, and ultimately increase the cost of the earthwork phases of the project.
Free water should not be allowed to pond on the subgrade soils. RGI anticipates that the
use of berms and shallow drainage ditches, with sumps and pumps in utility trenches, will
be required for surface water control during wet weather and/or wet site conditions.
5.3 FOUNDATIONS
Following site preparation and grading, the foundations for the proposed residences can
be supported on conventional spread footings bearing on native soil or structural fill. Loose,
organic, or other unsuitable soils may be encountered in the proposed building footprint.
If unsuitable soils are encountered, they should be overexcavated and backfilled with
structural fill. If a below grade vault is needed, foundations may be designed for the dense
native soils provided the vault is at least 8 feet below grade and founded on the dense
native soils.
Perimeter foundations exposed to weather should be at a minimum depth of 18 inches
below final exterior grades. Interior foundations can be constructed at any convenient
depth below the floor slab. Finished grade is defined as the lowest adjacent grade within 5
feet of the foundation for perimeter (or exterior) footings and finished floor level for
interior footings.
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3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
Table 3 Foundation Design
Design Parameter Value
Allowable Bearing Capacity – shallow footings
Dense native soils at least 8 feet below grade
2,000 psf1
4,000 psf
Friction Coefficient 0.30
Passive pressure (equivalent fluid pressure) 250 pcf2
1. psf = pounds per square foot
2. pcf = pounds per cubic foot
The allowable foundation bearing pressures apply to dead loads plus design live load
conditions. For short-term loads, such as wind and seismic, a 1/3 increase in this allowable
capacity may be used. At perimeter locations, RGI recommends not including the upper 12
inches of soil in the computation of passive pressures because they can be affected by
weather or disturbed by future grading activity. The passive pressure value assumes the
foundation will be constructed neat against competent soil or backfilled with structural fill
as described in Section 5.2.5. The recommended base friction value includes a safety factor
of about 1.5.
With spread footing foundations designed in accordance with the recommendations in this
section, maximum total and differential post-construction settlements of 1 inch and 1/2
inch, respectively, should be expected.
5.4 RETAINING WALLS
If retaining walls are needed for the residences or for vaults, RGI recommends cast-in-place
concrete walls be used. Modular block walls may be used for grade changes in other areas.
The magnitude of earth pressure development on retaining walls will partly depend on the
quality of the wall backfill. RGI recommends placing and compacting wall backfill as
structural fill. Wall drainage will be needed behind the wall face. A typical retaining wall
drainage detail is shown in Figure 3. With wall backfill placed and compacted as
recommended, level backfill, and drainage properly installed, RGI recommends using the
values in the following table for design.
Table 4 Retaining Wall Design
Design Parameter Value
Active Earth Pressure (unrestrained walls) 35 pcf
At-rest Earth Pressure (restrained walls) 50 pcf
Geotechnical Engineering Report 11 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
For seismic design, an additional uniform load of 7 times the wall height (H) for
unrestrained walls and 14H in psf for restrained walls should be applied to the wall surface.
Friction at the base of foundations and passive earth pressure will provide resistance to
these lateral loads. Values for these parameters are provided in Section 5.3.
5.5 SLAB-ON-GRADE CONSTRUCTION
RGI recommends that the concrete slab be placed on top of medium dense native soil or
structural fill. Immediately below the floor slab, RGI recommends placing a four-inch thick
capillary break layer of clean, free-draining sand or gravel that has less than five percent
passing the U.S. No. 200 sieve. This material will reduce the potential for upward capillary
movement of water through the underlying soil and subsequent wetting of the floor slab.
Where moisture by vapor transmission is undesirable, an 8- to 10-millimeter thick plastic
membrane should be placed on a 4-inch thick layer of clean gravel.
5.6 DRAINAGE
5.6.1 SURFACE
Final exterior grades should promote free and positive drainage away from the building
area. Water must not be allowed to pond or collect adjacent to foundations or within the
immediate building area. For non-pavement locations, RGI recommends providing a
minimum drainage gradient of 3 percent for a minimum distance of 10 feet from the
building perimeter. In paved locations, a minimum gradient of 1 percent should be
provided unless provisions are included for collection and disposal of surface water
adjacent to the structure.
5.6.2 SUBSURFACE
RGI recommends installing perimeter foundation drains. A typical footing drain detail is
shown on Figure 4. The foundation drains and roof downspouts should be tightlined
separately to an approved discharge facility. Subsurface drains must be laid with a gradient
sufficient to promote positive flow to a controlled point of approved discharge.
5.6.3 INFILTRATION
RGI understands that infiltration is being considered for the onsite disposal of water. Field
infiltration test TP-1/IT-1 was completed in the southwest corner of the site as shown in
Figure 2. The small-scale Pilot Infiltration Test (PIT) was completed at a depth of
approximately 3.5 feet below grade and measured 3 feet by 4 feet. The PIT was conducted
in the weathered moraine deposit, a red/gray silty sand with some gravel. The infiltration
test was conducted in accordance with the 2022 City of Renton Surface Water Design
Manual.
Geotechnical Engineering Report 12 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
Table 5 Measured Infiltration Rates
Test Location Test Depth
(feet)
Measured Rate
(inches/hour)
Design Rate
(inches/hour)
TP-1/IT-1 3.5 3.9 1.56
The measured rates in the above table should have appropriate factors of safety
applied prior to use in design. A Total Correction Factor was applied to the field
measured infiltration rate as indicated below for infiltration trench facilities less than 4
feet in width.
Idesign = Imeasured X Ftesting X Fgeometry X Fplugging = 3.9 X 0.5 X 1 X 0.8 = 1.56
Where:
Idesign The design infiltration rate
Imeasured The measured infiltration rate
Ftesting Accounts for uncertainties in the test method (Large-scale PIT and Small-
scale PIT = 0.50)
Fgeometry Accounts for the geometry of the planned facility and the depth to the
water table or impervious strata.
Fgeometry = (4D/W) + 0.05, D = depth from the bottom of the proposed
facility to the maximum wet-season water table or nearest impervious
layer, whichever is less, and W = width of the facility.
Fgeometry = 1 for facilities less than 4 feet in width
Fplugging Accounts for reductions in infiltration rates over long term use due to
the plugging of soils.
Fplugging = 0.8 for fine sands and loamy sands
5.6.4 SOIL PROPERTIES FOR GROUNDWATER PROTECTION
A soil sample from the bottom of the infiltration pit (TP-1/IT-1) was submitted to
Northwest Agricultural Consultants laboratory for analysis of Cation Exchange Capacity
(CEC) and organic content. An infiltration test was also conducted and rate acquired
during the exploration. The infiltration rate, CEC, and organic content were used to
evaluate the soil properties required for groundwater protection, per Section 5.2.1 of
the 2022 City of Renton Surface Water Design Manual.
To meet groundwater protection criteria the CEC must be greater than 5 meq/100g and
the organic content must be 1.0 percent or greater.
Geotechnical Engineering Report 13 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
Table 6 Soil Property Results
Sample Cation Exchange Capacity
(meq/100g)
Organic Content
(percent)
TP-1/IT-1 8.2 3.77
The soil sample meets the soil property requirements for CEC and organic content for
groundwater protection as shown in Table 6.
The second criterion, for sites located outside of groundwater protected areas, is the
soil to have a measured infiltration rate less than or equal to 9 inches per hour. TP-1/IT-
1 had a measured infiltration rate of 3.9 inches per hour as shown in Table 5 and meets
the second soil property criteria.
5.7 UTILITIES
Utility pipes should be bedded and backfilled in accordance with American Public Works
Association (APWA) specifications. For site utilities located within the right-of-ways,
bedding and backfill should be completed in accordance with City of Renton specifications.
At a minimum, trench backfill should be placed and compacted as structural fill, as
described in Section 5.2.5. Where utilities occur below unimproved areas, the degree of
compaction can be reduced to a minimum of 90 percent of the soil’s maximum density as
determined by the referenced ASTM D1557.
5.8 PAVEMENTS
Pavement subgrades should be prepared as described in Section 5.2 and as discussed
below. Regardless of the relative compaction achieved, the subgrade must be firm and
relatively unyielding before paving. The subgrade should be proof-rolled with heavy
construction equipment to verify this condition.
5.8.1 FLEXIBLE PAVEMENTS
With the pavement subgrade prepared as described above, RGI recommends the following
pavement sections for parking and drive areas paved with flexible asphalt concrete
surfacing.
For drive areas: 3 inches of Hot Mix Asphalt (HMA) over 6 inches of crushed rock
base (CRB)
5.8.2 CONCRETE PAVEMENTS
With the pavement subgrade prepared as described above, RGI recommends the following
pavement sections for parking and drive areas paved with concrete surfacing.
Geotechnical Engineering Report 14 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
For concrete pavement areas: 6 inches of concrete for drive areas and 4 inches for
sidewalks over 4 inches of CRB
The paving materials used should conform to the WSDOT specifications for HMA, concrete
paving, and CRB surfacing (9-03.9(3) Crushed Surfacing).
Long-term pavement performance will depend on surface drainage. A poorly-drained
pavement section will be subject to premature failure as a result of surface water
infiltrating into the subgrade soils and reducing their supporting capability.
For optimum pavement performance, surface drainage gradients of no less than 2 percent
are recommended. Also, some degree of longitudinal and transverse cracking of the
pavement surface should be expected over time. Regular maintenance should be planned
to seal cracks when they occur.
6.0 Additional Services
RGI is available to provide further geotechnical consultation throughout the design phase
of the project. RGI should review the final design and specifications in order to verify that
earthwork and foundation recommendations have been properly interpreted and
incorporated into project design and construction.
RGI is also available to provide geotechnical engineering and construction monitoring
services during construction. The integrity of the earthwork and construction depends on
proper site preparation and procedures. In addition, engineering decisions may arise in the
field in the event that variations in subsurface conditions become apparent. Construction
monitoring services are not part of this scope of work. If these services are desired, please
let us know and we will prepare a cost proposal.
7.0 Limitations
This GER is the property of RGI, Kushal Varma, and its designated agents. Within the limits
of the scope and budget, this GER was prepared in accordance with generally accepted
geotechnical engineering practices in the area at the time this GER was issued. This GER is
intended for specific application to the Roberts Short Plat project in Renton, Washington,
and for the exclusive use of Kushal Varma and its authorized representatives. No other
warranty, expressed or implied, is made. Site safety, excavation support, and dewatering
requirements are the responsibility of others.
The scope of services for this project does not include either specifically or by implication
any environmental or biological (for example, mold, fungi, bacteria) assessment of the site
or identification or prevention of pollutants, hazardous materials or conditions. If the
owner is concerned about the potential for such contamination or pollution, we can
provide a proposal for these services.
Geotechnical Engineering Report 15 April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
The analyses and recommendations presented in this GER are based upon data obtained
from the explorations performed on site. Variations in soil conditions can occur, the nature
and extent of which may not become evident until construction. If variations appear
evident, RGI should be requested to reevaluate the recommendations in this GER prior to
proceeding with construction.
It is the client’s responsibility to see that all parties to the project, including the designers,
contractors, subcontractors, are made aware of this GER in its entirety. The use of
information contained in this GER for bidding purposes should be done at the contractor’s
option and risk.
USGS, 2023, Maple Valley, Washington
USGS, 2023, Renton, Washington
7.5-Minute Quadrangle
Approximate Scale: 1"=1000'
0 500 1000 2000 N
Site Vicinity Map
Figure 1
04/2025
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Roberts Short Plat
RGI Project Number:
2024-344-1
Date Drawn:
Address: 3XXX Toledo Avenue Southeast, Renton, Washington 98059
SITE
TP-5
TP-3
TP-4
TP-2
TP-1
IT-1
04/2025
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Roberts Short Plat
RGI Project Number:
2024-344-1
Date Drawn:
Address: 3XXX Toledo Avenue Southeast, Renton, Washington 98059
Figure 2
Approximate Scale: 1" = 50'
0 25 50 100 N= Test pit locations by RGI, 03/24/2025
= Site boundary
Geotechnical Exploration Plan
Incliniations)
12" Over the Pipe
3" Below the Pipe
Perforated Pipe
4" Diameter PVC
Compacted Structural
Backfill (Native or Import)
12" min.
Filter Fabric Material
12" Minimum Wide
Free-Draining Gravel
Slope to Drain
(See Report for
Appropriate
Excavated Slope
04/2025
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Roberts Short Plat
RGI Project Number:
2024-344-1
Date Drawn:
Address: 3XXX Toledo Avenue Southeast, Renton, Washington 98059
Retaining Wall Drainage Detail
Figure 3
Not to Scale
Building Slab
Structural
Backfill
Compacted
04/2025
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Roberts Short Plat
RGI Project Number:
2024-344-1
Date Drawn:
Address: 3XXX Toledo Avenue Southeast, Renton, Washington 98059
Typical Foundation Drainage Detail
Figure 4
Not to Scale
Gravel or Crushed Stone
with less than 10% passing
No. 4 (4.75mm) Sieve
12" Minimum
4" Perforated Pipe
(See Report Text)
Approved Filter
Membrane Material
Geotechnical Engineering Report April 16, 2025
3XXX Toledo Avenue Southeast, Renton, Washington RGI Project No. 2024-344-1
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
On March 24, 2025, RGI observed field explorations using a rubber tracked excavator. We
documented subsurface soil conditions at the site by observing the excavation of 5 test pits
to a maximum depth of 9.5 feet below existing grade. The test pit locations are shown on
Figure 2. The test pit locations were approximately determined by measurements from
existing property lines and paved roads.
An engineer from our office observed the field exploration and classified the soil conditions
encountered, maintained a log of each test exploration, obtained representative soil
samples, and observed pertinent site features. All soil samples were visually classified in
accordance with the Unified Soil Classification System (USCS).
Representative soil samples obtained from the explorations were placed in closed
containers and taken to our laboratory for further examination and testing. As a part of the
laboratory testing program, the soil samples were classified in our in house laboratory
based on visual observation, texture, plasticity, and the limited laboratory testing described
below.
Moisture Content Determinations
Moisture content determinations were performed in accordance with ASTM D2216-10
Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil
and Rock by Mass (ASTM D2216) on representative samples obtained from the exploration
in order to aid in identification and correlation of soil types. The moisture content of typical
sample was measured and is reported on the test pits logs.
Grain Size Analysis
A grain size analysis indicates the range in diameter of soil particles included in a particular
sample. Grain size analyses was determined using D6913-04(2009) Standard Test Methods
for Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis (ASTM D6913) on two
of the samples.
Project Name:Roberts Short Plat
Project Number:2024-344-1
Client:Kushal Varma
Test Pit No.: TP-1/IT-1
Date(s) Excavated:March 24, 2025
Excavation Method:Test Pit
Excavator Type:Rubber tracked excavator
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By RT
Bucket Size:24 inch
Excavating Contractor:Client Provided
Sampling
Method(s)Grab
Location 3XXX Toledo Avenue Southeast, Renton, Washington
Surface Conditions:Wood Chips
Total Depth of Excavation:6 feet bgs
Approximate
Surface Elevation
Compaction Method Bucket Tamp
US
C
S
S
y
m
b
o
l
SM
SM
SM
Pe
r
c
e
n
t
F
i
n
e
s
,
%
Gr
a
p
h
i
c
L
o
g
Wa
t
e
r
C
o
n
t
e
n
t
,
%
15%
13%
13%
11%
MATERIAL DESCRIPTION
4 inches of wood chips and rootmass
Brown/gray silty SAND with some gravel, medium dense, moist (Fill)
Red/gray silty SAND with some gravel, medium dense, moist (Weathered moraine
deposit)
Becomes dense
Gray silty SAND with some gravel, very dense, moist (Moraine deposit)
Test pit terminated due to very dense soils at 6 feet bgs
De
p
t
h
(
f
e
e
t
)
0
5
10
Sa
m
p
l
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T
y
p
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El
e
v
a
t
i
o
n
(
f
e
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)
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Roberts Short Plat
Project Number:2024-344-1
Client:Kushal Varma
Test Pit No.: TP-2
Date(s) Excavated:March 24, 2025
Excavation Method:Test Pit
Excavator Type:Rubber tracked excavator
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By RT
Bucket Size:24 inch
Excavating Contractor:Client Provided
Sampling
Method(s)Grab
Location 3XXX Toledo Avenue Southeast, Renton, Washington
Surface Conditions:Bare Soil
Total Depth of Excavation:9.5 feet bgs
Approximate
Surface Elevation
Compaction Method Bucket Tamp
US
C
S
S
y
m
b
o
l
SM
Topsoil
SM
SP
SM
Pe
r
c
e
n
t
F
i
n
e
s
,
%
Gr
a
p
h
i
c
L
o
g
Wa
t
e
r
C
o
n
t
e
n
t
,
%
11%
15%
3%
7%
MATERIAL DESCRIPTION
12 inches of gravel, topsoil and rootmass
Dark gray silty SAND with some gravel, medium dense, moist (Fill)
6 inches of topsoil
Brown silty SAND with trace gravel, loose, moist
Gray SAND with trace silt, medium dense, moist (Vashon recessional)
Gray silty SAND with some gravel, very dense, moist (Moraine deposit)
Test pit terminated due to very dense soils at 9.5 feet bgs
De
p
t
h
(
f
e
e
t
)
0
5
10
Sa
m
p
l
e
T
y
p
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El
e
v
a
t
i
o
n
(
f
e
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t
)
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Roberts Short Plat
Project Number:2024-344-1
Client:Kushal Varma
Test Pit No.: TP-3
Date(s) Excavated:March 24, 2025
Excavation Method:Test Pit
Excavator Type:Rubber tracked excavator
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By RT
Bucket Size:24 inch
Excavating Contractor:Client Provided
Sampling
Method(s)Grab
Location 3XXX Toledo Avenue Southeast, Renton, Washington
Surface Conditions:Bare Soil
Total Depth of Excavation:7 feet bgs
Approximate
Surface Elevation
Compaction Method Bucket Tamp
US
C
S
S
y
m
b
o
l
SM
SP
SM
Pe
r
c
e
n
t
F
i
n
e
s
,
%
18.9%
Gr
a
p
h
i
c
L
o
g
Wa
t
e
r
C
o
n
t
e
n
t
,
%
10%
11%
MATERIAL DESCRIPTION
12 inches of gravel, topsoil and rootmass
Red/tan silty SAND with some gravel, medium dense, moist
Large tree root for 12 inches
Tan SAND with trace silt, medium dense, moist (Vashon recessional)
Gray silty SAND with some gravel, very dense, moist (Moraine deposit)
Test pit terminated due to very dense soils 7 feet bgs
De
p
t
h
(
f
e
e
t
)
0
5
10
Sa
m
p
l
e
T
y
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El
e
v
a
t
i
o
n
(
f
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)
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Roberts Short Plat
Project Number:2024-344-1
Client:Kushal Varma
Test Pit No.: TP-4
Date(s) Excavated:March 24, 2025
Excavation Method:Test Pit
Excavator Type:Rubber tracked excavator
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By RT
Bucket Size:24 inch
Excavating Contractor:Client Provided
Sampling
Method(s)Grab
Location 3XXX Toledo Avenue Southeast, Renton, Washington
Surface Conditions:Pine Needles
Total Depth of Excavation:7.5 feet bgs
Approximate
Surface Elevation
Compaction Method Bucket Tamp
US
C
S
S
y
m
b
o
l
SM
SM
SP
SM
SM
Pe
r
c
e
n
t
F
i
n
e
s
,
%
Gr
a
p
h
i
c
L
o
g
Wa
t
e
r
C
o
n
t
e
n
t
,
%
10%
6%
11%
MATERIAL DESCRIPTION
12 inches of gravel, topsoil and rootmass
Brown/gray silty SAND with some gravel, medium dense, moist
Red/brown silty SAND, loose, moist
Tan SAND with trace silt, medium dense, moist (Vashon recessional)
Becomes dense
Gray silty SAND with some gravel, very dense, moist (Moraine deposit)
Test pit terminated due to very dense soils at 7.5 feet bgs
De
p
t
h
(
f
e
e
t
)
0
5
10
Sa
m
p
l
e
T
y
p
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El
e
v
a
t
i
o
n
(
f
e
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t
)
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Roberts Short Plat
Project Number:2024-344-1
Client:Kushal Varma
Test Pit No.: TP-5
Date(s) Excavated:March 24, 2025
Excavation Method:Test Pit
Excavator Type:Rubber tracked excavator
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By RT
Bucket Size:24 inch
Excavating Contractor:Client Provided
Sampling
Method(s)Grab
Location 3XXX Toledo Avenue Southeast, Renton, Washington
Surface Conditions:Bare Soil
Total Depth of Excavation:6 feet bgs
Approximate
Surface Elevation
Compaction Method Bucket Tamp
US
C
S
S
y
m
b
o
l
Topsoil
SM
SP
SP-SM
SM
Pe
r
c
e
n
t
F
i
n
e
s
,
%
1.8%
Gr
a
p
h
i
c
L
o
g
Wa
t
e
r
C
o
n
t
e
n
t
,
%
10%
12%
MATERIAL DESCRIPTION
8 inches of topsoil and rootmass
Red/tan silty SAND, loose. moist
Tan SAND with trace silt, medium dense, moist (Vashon recessional)
Red/gray SAND with some silt and trace gravel, medium dense, moist to wet
(Weathered moraine deposit)
Gray silty SAND with trace gravel, dense, wet (Moraine deposit)
Moderate seepage at 4.5 feet
Test pit terminated due to moderate seepage at 6 feet bgs
De
p
t
h
(
f
e
e
t
)
0
5
10
Sa
m
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Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Roberts Short Plat
Project Number:2024-344-1
Client:Kushal Varma
Key to Logs
US
C
S
S
y
m
b
o
l
Pe
r
c
e
n
t
F
i
n
e
s
,
%
Gr
a
p
h
i
c
L
o
g
Wa
t
e
r
C
o
n
t
e
n
t
,
%
MATERIAL DESCRIPTIONDe
p
t
h
(
f
e
e
t
)
Sa
m
p
l
e
T
y
p
e
El
e
v
a
t
i
o
n
(
f
e
e
t
)
1 2 3 4 5 6 7 8
COLUMN DESCRIPTIONS
1 Elevation (feet): Elevation (MSL, feet).
2 Depth (feet): Depth in feet below the ground surface.
3 Sample Type: Type of soil sample collected at the depth interval
shown.
4 USCS Symbol: USCS symbol of the subsurface material.
5 Graphic Log: Graphic depiction of the subsurface material
encountered.
6 MATERIAL DESCRIPTION: Description of material encountered.
May include consistency, moisture, color, and other descriptive
text.
7 Water Content, %: Water content of the soil sample, expressed as
percentage of dry weight of sample.
8 Percent Fines, %: The percent fines (soil passing the No. 200
Sieve) in the sample. WA indicates a Wash Sieve, SA indicates a
Sieve Analysis.
FIELD AND LABORATORY TEST ABBREVIATIONS
CHEM: Chemical tests to assess corrosivity
COMP: Compaction test
CONS: One-dimensional consolidation test
LL: Liquid Limit, percent
PI: Plasticity Index, percent
SA: Sieve analysis (percent passing No. 200 Sieve)
UC: Unconfined compressive strength test, Qu, in ksf
WA: Wash sieve (percent passing No. 200 Sieve)
MATERIAL GRAPHIC SYMBOLS
Gravel
Artificial Fill
Silty SAND (SM)
Poorly graded SAND (SP)
Poorly graded SAND with Silt (SP-SM)
Topsoil
TYPICAL SAMPLER GRAPHIC SYMBOLS
Auger sampler
Bulk Sample
3-inch-OD California w/
brass rings
CME Sampler
Grab Sample
2.5-inch-OD Modified
California w/ brass liners
Pitcher Sample
2-inch-OD unlined split
spoon (SPT)
Shelby Tube (Thin-walled,
fixed head)
OTHER GRAPHIC SYMBOLS
Water level (at time of drilling, ATD)
Water level (after waiting, AW)
Minor change in material properties within a
stratum
Inferred/gradational contact between strata
?Queried contact between strata
GENERAL NOTES
1: Soil classifications are based on the Unified Soil Classification System. Descriptions and stratum lines are interpretive, and actual lithologic changes may be
gradual. Field descriptions may have been modified to reflect results of lab tests.
2: Descriptions on these logs apply only at the specific boring locations and at the time the borings were advanced. They are not warranted to be representative
of subsurface conditions at other locations or times.
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Roberts Short Plat SAMPLE ID/TYPE TP-3
PROJECT NO.2024-344 SAMPLE DEPTH 4 feet
TECH/TEST DATE TW/RT 3/25/2025 DATE RECEIVED 3/24/2025
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)1096.3 Weight Of Sample (gm)1000.2
Wt Dry Soil & Tare (gm) (w2)1000.2 Tare Weight (gm) 125.2
Weight of Tare (gm) (w3)125.2 (W6) Total Dry Weight (gm) 875.0
Weight of Water (gm) (w4=w1-w2) 96.1 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 875.0 Cumulative
Moisture Content (%) (w4/w5)*100 11 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"125.2 0.00 0.00 100.00 cobbles
% C GRAVEL 1.7 3.0"125.2 0.00 0.00 100.00 coarse gravel
% F GRAVEL 23.8 2.5" coarse gravel
% C SAND 8.1 2.0"125.2 0.00 0.00 100.00 coarse gravel
% M SAND 15.7 1.5"125.2 0.00 0.00 100.00 coarse gravel
% F SAND 31.7 1.0" coarse gravel
% FINES 18.9 0.75"140.5 15.30 1.75 98.25 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"281.3 156.10 17.84 82.16 fine gravel
D10 (mm)#4 348.6 223.40 25.53 74.47 coarse sand
D30 (mm)#10 419.9 294.70 33.68 66.32 medium sand
D60 (mm)#20 medium sand
Cu #40 557.0 431.80 49.35 50.65 fine sand
Cc #60 fine sand
#100 755.6 630.40 72.05 27.95 fine sand
#200 834.5 709.30 81.06 18.94 fines
PAN 1000.2 875.00 100.00 0.00 silt/clay
DESCRIPTION Silty SAND with some gravel
USCS SM
Prepared For: Reviewed By: RT
Kushal Varma
0
10
20
3040
50
60
7080
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200
THE RILEY GROUP, INC.
17522 Bothell Way NE
Bothell, WA 98011
PHONE: (425) 415-0551
FAX: (425) 415-0311
GRAIN SIZE ANALYSIS
ASTM D421, D422, D1140, D2487, D6913
PROJECT TITLE Roberts Short Plat SAMPLE ID/TYPE TP-5
PROJECT NO.2024-344 SAMPLE DEPTH 2.5 feet
TECH/TEST DATE TW/RT 3/25/2025 DATE RECEIVED 3/24/2025
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)1032.6 Weight Of Sample (gm)935.8
Wt Dry Soil & Tare (gm) (w2)935.8 Tare Weight (gm) 135.4
Weight of Tare (gm) (w3)135.4 (W6) Total Dry Weight (gm) 800.4
Weight of Water (gm) (w4=w1-w2) 96.8 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 800.4 Cumulative
Moisture Content (%) (w4/w5)*100 12 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"135.4 0.00 0.00 100.00 cobbles
% C GRAVEL 4.4 3.0"135.4 0.00 0.00 100.00 coarse gravel
% F GRAVEL 15.2 2.5" coarse gravel
% C SAND 10.6 2.0"135.4 0.00 0.00 100.00 coarse gravel
% M SAND 34.2 1.5"135.4 0.00 0.00 100.00 coarse gravel
% F SAND 33.8 1.0" coarse gravel
% FINES 1.8 0.75"170.3 34.90 4.36 95.64 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"216.1 80.70 10.08 89.92 fine gravel
D10 (mm)0.19 #4 292.3 156.90 19.60 80.40 coarse sand
D30 (mm)0.35 #10 376.9 241.50 30.17 69.83 medium sand
D60 (mm)1.3 #20 medium sand
Cu 6.8 #40 650.8 515.40 64.39 35.61 fine sand
Cc 0.5 #60 fine sand
#100 896.9 761.50 95.14 4.86 fine sand
#200 921.2 785.80 98.18 1.82 fines
PAN 935.8 800.40 100.00 0.00 silt/clay
DESCRIPTION SAND with some gravel and trace silt
USCS SP
Prepared For: Reviewed By: RT
Kushal Varma
0
10
20
3040
50
60
7080
90
100
0.0010.010.11101001000
%
P
A
S
S
I
N
G
Grain size in millimeters
12"3" 2" 1" .75" .375" #4 #10 #20 #40 #60 #100 #200