HomeMy WebLinkAbout32-RS_Geotechnical_Report_VEK_on_Aberdeen_191106_v1
Corporate Office 17522 Bothell Way Northeast
Bothell, Washington 98011
Phone 425.415.0551 ♦ Fax 425.415.0311
www.riley-group.com
GEOTECHNICAL ENGINEERING REPORT
PREPARED BY:
THE RILEY GROUP, INC.
17522 BOTHELL WAY NORTHEAST
BOTHELL, WASHINGTON 98011
PREPARED FOR:
CENTURY CONSTRUCTION, LLC
13220 42ND AVENUE EAST
TACOMA, WASHINGTON 98446
RGI PROJECT NO. 2018-223
ABERDEEN TOWNHOMES
957 ABERDEEN AVENUE NORTHEAST
RENTON, WASHINGTON
NOVEMBER 27, 2018
Geotechnical Engineering Report i November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
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 ................................................................................................................................................. 3
4.3 SOILS ....................................................................................................................................................... 3
4.4 GROUNDWATER ........................................................................................................................................ 3
4.5 SEISMIC CONSIDERATIONS ........................................................................................................................... 4
4.6 GEOLOGIC HAZARD AREAS .......................................................................................................................... 4
5.0 DISCUSSION AND RECOMMENDATIONS ......................................................................................... 6
5.1 GEOTECHNICAL CONSIDERATIONS ................................................................................................................. 6
5.2 EARTHWORK ............................................................................................................................................. 6
5.2.1 Erosion and Sediment Control ..................................................................................................... 6
5.2.2 Stripping ....................................................................................................................................... 7
5.2.3 Excavations................................................................................................................................... 7
5.2.4 Site Preparation ........................................................................................................................... 8
5.2.5 Structural Fill ................................................................................................................................ 9
5.2.6 Cut and Fill Slopes ...................................................................................................................... 11
5.2.7 Wet Weather Construction Considerations ............................................................................... 11
5.3 FOUNDATIONS ........................................................................................................................................ 11
5.4 RETAINING WALLS ................................................................................................................................... 12
5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 13
5.6 DRAINAGE .............................................................................................................................................. 13
5.6.1 Surface ....................................................................................................................................... 13
5.6.2 Subsurface .................................................................................................................................. 14
5.6.3 Infiltration .................................................................................................................................. 14
5.7 UTILITIES ................................................................................................................................................ 14
5.8 PAVEMENTS ............................................................................................................................................ 14
6.0 ADDITIONAL SERVICES .................................................................................................................. 15
7.0 LIMITATIONS ................................................................................................................................. 15
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
Appendix B .................................................................................................................... Slope Stability
Geotechnical Engineering Report ii November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
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 three test pits to
approximate depths of 9 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 medium
dense silty sand with varying amounts of gravel, becoming dense at depths of three to six
feet, over very stiff silt.
Groundwater: Groundwater seepage was encountered at 5.5 to 6.5 feet at TP-1 during
our subsurface exploration.
Foundations: Foundations for the proposed buildings may be supported on conventional
spread footings bearing on medium dense to dense native soil or structural fill.
Slab-on-grade: Slab-on-grade floors and slabs for the proposed buildings can be
supported on medium dense to dense native soil or structural fill.
Pavements: The following pavement sections are recommended:
For heavy truck traffic areas: 3 inches of Hot Mix Asphalt (HMA) over 6
inches of crushed rock base (CRB)
For general parking areas: 2 inches of HMA over 4 inches of CRB
For concrete pavement areas: 5 inches of concrete over 4 inches of CRB
Geotechnical Engineering Report 1 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
1.0 Introduction
This Geotechnical Engineering Report (GER) presents the results of the geotechnical
engineering services provided for the Aberdeen Townhomes in Renton, Washington. The
purpose of this evaluation is to assess subsurface conditions and provide geotechnical
recommendations for the construction of townhomes on the site. 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 site grading plan, final design drawings
and specifications when available to verify that our project understanding is correct and
that our recommendations have been properly interpreted and incorporated into the
project design and construction.
2.0 Project description
The project site is located at 957 Aberdeen Avenue Northeast in Renton, Washington. The
approximate location of the site is shown on Figure 1.
Based on the plan provided, the existing residence and parking will be demolished and the
site redeveloped with 13 townhomes, parking and utilities including stormwater control.
The proposed townhomes have been designed to step down with the existing topography
and minimize the site grading necessary.
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 buildings
will be supported on perimeter walls with bearing loads of two to six kips per linear foot,
and a series of columns with a maximum load up to 30 kips. Slab-on-grade floor loading of
250 pounds per square foot (psf) are expected.
3.0 Field Exploration and Laboratory Testing
3.1 FIELD EXPLORATION
On November 13, 2018, RGI observed the excavation of three test pits. The approximate
exploration locations are shown on Figure 2.
Field logs of each exploration were prepared by the geologist 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
Geotechnical Engineering Report 2 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
logs and include modifications based on laboratory observation and analysis of the
samples.
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 of land approximately 1.24 acres in size. The
site is bound to the north and south by residential property, to the east by Aberdeen
Avenue Northeast, and to the west by Puget Sound Energy undeveloped land and Interstate
405.
The eastern portion of the site is occupied by a single family residence with attached shed,
a shed, and a barn. The western portion of the site is occupied by a drainage feature that
descends west to John Creek near the western property line.
The eastern portion of the property descends generally west with an elevation change of
about 28 feet over a horizontal distance of 290 feet. The area is vegetated with grass,
decorative plants and shrubs, a garden, fruit trees, and scattered medium- to large-
diameter trees.
The western portion of the property descends generally west with an elevation change of
about 84 feet over a horizontal distance of 300 feet. Slope gradients range from about 40
percent to over 120 percent. The area is vegetated with medium- to large-diameter trees
with an undergrowth of ferns, mixed brush, and blackberry brambles.
Geotechnical Engineering Report 3 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
4.2 GEOLOGY
Review of the Geologic Map of the Renton Quadrangle, King County, Washington, by D. R.
Mullineaux (1965) indicates that the soil through most of the site is mapped as Ground
morain deposits (Map Unit Qgt), which is thin ablation till over lodgement till comprised of
a nonsorted, nonstratified mixture of clay, silt, sand, and gravel. The soils in the
westernmost portion of the site are mapped as Undifferentiated deposits (Qu) which
include till, glaciofluvial sand and gravel, glaciolacustrine clay and sand, and non-glacial
deposits of clay, sand, and peat. These descriptions are generally similar to the findings in
our field explorations.
4.3 SOILS
The soils encountered during field exploration include loose to medium dense silty sand
with varying amounts of gravel, becoming dense at depths of three to six feet, over very
stiff silt.
More detailed descriptions of the subsurface conditions encountered are presented in the
test pits logs included in Appendix A. Sieve analysis was performed on four selected soil
samples. Grain size distribution curves are included in Appendix A.
4.4 GROUNDWATER
Groundwater seepage was encountered at 5.5 to 6.5 feet at TP-1 during our subsurface
exploration. Surface seepage was observed near TP-1 and adjacent to and within the small
stream channel extending east through the western portion of the site, and in John Creek
extending south through the site near the western property line.
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.
Geotechnical Engineering Report 4 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
4.5 SEISMIC CONSIDERATIONS
Based on the 2015 International Building Code (IBC), RGI recommends the follow seismic
parameters for design.
Table 1 2012/2015 IBC
Parameter Value
Site Soil Class1 D2
Site Latitude 47.498842o N
Site Longitude 122.191919o W
Short Period Spectral Response Acceleration, SS (g) 1.438
1-Second Period Spectral Response Acceleration, S1 (g) 0.540
Adjusted Short Period Spectral Response Acceleration, SMS (g) 1.438
Adjusted 1-Second Period Spectral Response Acceleration, SM1 (g) 0.810
1. Note: In general accordance with Chapter 20 of ASCE 7-10. The Site Class is based on the average characteristics of the upper 100 feet
of the subsurface profile.
2. Note: The 2015 IBC and ASCE 7-10 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 feet, and this seismic site class definition considers that similar 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.
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
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 deposits, 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 mapping on the City of Renton GIS, the site contains
geologically hazardous areas including erosion and high landslide hazard areas. The slope
on the west side of the site also contains sensitive and protected slope areas.
Geotechnical Engineering Report 5 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
To assess the stability of the slopes in the western portion of the site, a slope
reconnaissance was performed on November 13, 2018. The western portion of the site is
occupied by a drainage that descends west to John Creek near the western property line.
The drainage originates on the property to the north, and the head of the drainage is
occupied by a detention tank overflow comprised of a 12 inch Drisco pipe and spillway
constructed of gabion cages and quarry spalls. The drainage appears to have intermittent
flow, with native, glacially consolidated soils exposed along the channel and lower slope
areas.
Soils are generally silty sand in the upper drainage, with silt occupying the channel around
the 135-foot elevation. Light seepage was observed along the sand/silt contact in the
southern bank of the channel, consistent with seasonal perched groundwater collecting
above the generally impermeable silt. Trees with curved trucks were observed that are
indicative of surficial creep, however, the slopes are well vegetated with trees that do not
appear to be effected by large-scale movements. Exposed soils at and near the base of the
drainage are indicative of moderate erosion at the toe of slope during the wetter winter
months.
4.6.1 STEEP SLOPES
The site slopes have gradients in the range of about 40 percent to over 120 percent, and
meet the criteria of Protected Slopes.
4.6.2 LANDSLIDE HAZARDS
The site is mapped as a high landslide hazard area with slopes greater than forty percent in
the western portion of the site. The area also appears to be underlain by silt deposits. The
slopes in the western portion of the site meet the criteria of High Landslide Hazards (LH).
4.6.3 EROSION HAZARDS
Review of the Soil Survey, King County Area, Washington by the USDA Soil Conservation
Service (1973) indicates the eastern portion of the site is underlain by Ragnar-Indianola
association, sloping (RdC) and the western portion of the site is underlain by Ragnar-
Indianola association, moderately steep (RdE). The eastern portion of the site meets the
criteria for a Low Erosion Hazard (EL) and the western portion of the site meets the criteria
of a High Erosion Hazard (EH). The area of the site that is mapped as a high erosion hazard
will not be developed. The portion of the site that will be developed should have erosion
control measure as outlined in section 5.2.1 of this GER.
4.6.4 SEISMIC HAZARDS
The site is not mapped as a seismic hazard area. The site is underlain by glacially
consolidated deposits and seismic induced settlements are not expected.
Geotechnical Engineering Report 6 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
4.6.5 OTHER HAZARDS
There are no coal mine hazards, volcanic hazards or shoreline areas mapped on the site or
within 150 feet of the site.
4.6.6 SLOPE SETBACKS
The proposed townhomes have been designed to step down with the existing topography
and the majority of the development is on the least sensitive area of the site. Three
townhomes are proposed on the top of the slope outside of the sensitive slopes and the
setback from the slope.
Based on the results of our subsurface explorations and slope stability analysis, the
proposal will not increase the threat of the geological hazard to adjacent or abutting
properties beyond predevelopment conditions; and will not adversely impact other critical
areas; and the proposed development can be safely accommodated on the site.
5.0 Discussion and Recommendations
5.1 GEOTECHNICAL CONSIDERATIONS
Based on our study, the site is suitable for the proposed construction from a geotechnical
standpoint. Foundations for the proposed buildings can be supported on conventional
spread footings bearing on medium dense to dense 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
We expect the earth work will consist of excavating the townhome foundations, installing
underground utilities and preparing roadway and slab subgrades. The road grading and
the townhomes slope and step down with the existing topography. We expect shallow cuts
and fill to establish the proposed grades.
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,
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):
Geotechnical Engineering Report 7 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
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 6 to 18 inches of topsoil and rootmass. Deeper areas of stripping may
be required in forested or heavily vegetated areas of the site.
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
dense silty sand with varying amounts of gravel over very stiff silt.
Geotechnical Engineering Report 8 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
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 1H: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, 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 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.
Geotechnical Engineering Report 9 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
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
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
Geotechnical Engineering Report 10 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
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.
The site soils are moisture sensitive and may require moisture conditioning prior to use as
structural fill. 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 as specified in Table 3. The soil’s maximum density
and optimum moisture should be determined by ASTM D1557.
Table 3 Structural Fill Compaction ASTM D1557
Location Material Type
Minimum
Compaction
Percentage
Moisture Content
Range
Foundations On-site granular or approved
imported fill soils: 95 +2 -2
Retaining Wall Backfill On-site granular or approved
imported fill soils: 92 +2 -2
Slab-on-grade On-site granular or approved
imported fill soils: 95 +2 -2
General Fill (non-
structural areas)
On-site soils or approved
imported fill soils: 90 +3 -2
Pavement – Subgrade
and Base Course
On-site granular or approved
imported fill soils: 95 +2 -2
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.
Geotechnical Engineering Report 11 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
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. 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 proposed building foundations can be
supported on conventional spread footings bearing on medium dense native soil or
structural fill. Loose, organic, or other unsuitable soils may be encountered in the proposed
building footprints. If unsuitable soils are encountered, they should be overexcavated and
backfilled with structural fill.
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.
Geotechnical Engineering Report 12 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
Table 4 Foundation Design
Design Parameter Value
Allowable Bearing Capacity 2,500 psf1
Friction Coefficient 0.30
Passive pressure (equivalent fluid pressure) 250 pcf2
Minimum foundation dimensions Columns: 24 inches
Walls: 16 inches
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 and passive resistance 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 in the building area, RGI recommends cast-in-place concrete
walls be used. Grade changes outside of the building areas may be completed with slopes
or modular block retaining walls.
The magnitude of earth pressure development on cast-in place 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, and drainage properly installed,
RGI recommends using the values in the following table for design.
Geotechnical Engineering Report 13 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
Table 5 Retaining Wall Design
Design Parameter Value
Allowable Bearing Capacity 2,500 psf
Active Earth Pressure (unrestrained walls) 35 pcf
At-rest Earth Pressure (restrained walls) 50 pcf
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
Once site preparation has been completed as described in Section 5.2, suitable support for
slab-on-grade construction should be provided. 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.
For the anticipated floor slab loading, we estimate post-construction floor settlements of
1/4- to 1/2-inch.
5.6 DRAINAGE
5.6.1 SURFACE
Final exterior grades should promote free and positive drainage away from the building
areas. Water must not be allowed to pond or collect adjacent to foundations or within the
immediate building areas. 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.
Geotechnical Engineering Report 14 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
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
The site soils are not conducive to infiltration. We do not recommend infiltration on the
site due to the relatively impermeable soils and the slopes on the west side of the site.
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. As noted, soils excavated onsite should be
suitable for use as backfill material provided to soils can be moisture conditioned. Imported
structural fill meeting the gradation provided in Table 2 may be necessary for trench backfill
if the native soils cannot be moisture conditioned.
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)
For general parking areas: 2 inches of HMA over 4 inches of 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 15 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
For concrete pavement areas: 5 inches of concrete over 4 inches of CRB
The paving materials used should conform to the WSDOT specifications for HMA, concrete
paving, CRB surfacing (9-03.9(3) Crushed Surfacing), and gravel base (9-03.10 Aggregate for
Gravel Base).
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, Century Construction, LLC, 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 Aberdeen Townhomes project in
Renton, Washington, and for the exclusive use of Century Construction, LLC 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 16 November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
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, 2014, Mercer Island, Washington
USGS, 2014, Renton, Washington
7.5-Minute Quadrangle
Approximate Scale: 1"=1000'
0 500 1000 2000 N
Site Vicinity Map
Figure 1
11/2018
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Aberdeen Townhomes
RGI Project Number
2018-223
Date Drawn:
Address: 957 Aberdeen Avenue Northeast, Renton, Washington 98056
SITE
TP-2TP1TP-3AA'11/2018Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311Aberdeen TownhomesRGI Project Number2018-223Date Drawn:Address: 957 Aberdeen Avenue Northeast, Renton, Washington 98056Geotechnical Exploration PlanFigure 2Approximate Scale: 1"=80'04080160N= Slope stability cross section= Test pit by RGI, 11/13/18= Site boundary
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
11/2018
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Aberdeen Townhomes
RGI Project Number
2018-223
Date Drawn:
Address: 957 Aberdeen Avenue Northeast, Renton, Washington 98056
Retaining Wall Drainage Detail
Figure 3
Not to Scale
3/4" Washed Rock or Pea Gravel
4" Perforated Pipe
Building Slab
Structural
Backfill
Compacted
Filter Fabric
11/2018
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Aberdeen Townhomes
RGI Project Number
2018-223
Date Drawn:
Address: 957 Aberdeen Avenue Northeast, Renton, Washington 98056
Typical Footing Drain Detail
Figure 4
Not to Scale
Geotechnical Engineering Report November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
On November 13, 2018, RGI performed field explorations using mini excavator. We
explored subsurface soil conditions at the site by observing the excavation of three test pits
to a maximum depth of 9 feet below existing grade. The test pits locations are shown on
Figure 2. The test pits locations were approximately determined by measurements from
existing property lines and paved roads.
A geologist from our office conducted 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 sam1ples 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 pit 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 four
of the samples.
Project Name:Aberdeen Townhomes
Project Number:2018-223
Client:Century Construction, LLC
Test Pit No.: TP-1
Date(s) Excavated:11/13/2018
Excavation Method:Test Pit
Excavator Type:Mini Excavator
Groundwater Level:Seepage from 5.5 to 6.5'
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 957 Aberdeen Avenue Northeast, Renton, Washington
Surface Conditions:Mixed Brush
Total Depth of Excavation:9 feet bgs
Approximate
Surface Elevation 182
Compaction Method Bucket
USCS SymbolTPSL
SM
SM
ML
REMARKS AND OTHER TESTS
23% moisture
22% moisture
21% moisture
17% moisture, 33% fines
17% moisture
19% moisture
23% moisture
18% moistureGraphic LogMATERIAL DESCRIPTION
18" topsoil
Reddish brown silty SAND, loose to medium dense, moist
to wet
Tan silty SAND with trace gravel, medium dense, wet
Becomes mottled
Light to moderate groundwater seepage at 5.5 to 6.5 feet
Becomes dense, moist
Gray SILT, very stiff, moist
Contains pockets of sand with iron oxide staining
Test Pit terminated at 9'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)182
177
172
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Aberdeen Townhomes
Project Number:2018-223
Client:Century Construction, LLC
Test Pit No.: TP-2
Date(s) Excavated:11/13/2018
Excavation Method:Test Pit
Excavator Type:Mini Excavator
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 957 Aberdeen Avenue Northeast, Renton, Washington
Surface Conditions:Grass
Total Depth of Excavation:8.5 feet bgs
Approximate
Surface Elevation 182
Compaction Method Bucket
USCS SymbolTPSL
SM
SM
REMARKS AND OTHER TESTS
13% moisture
16% moisture
8% moisture
6% moisture, 29% fines
10% moisture
8% moistureGraphic LogMATERIAL DESCRIPTION
6" topsoil
Brown silty SAND, loose, moist
Tan silty SAND with some gravel, loose to medium dense,
moist to wet
Becomes medium dense, dry to moist
Becomes dense, dry
Becomes moist, lightly cemented
Trace iron oxide staining
Test Pit terminated at 8.5'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)182
177
172
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Aberdeen Townhomes
Project Number:2018-223
Client:Century Construction, LLC
Test Pit No.: TP-3
Date(s) Excavated:11/13/2018
Excavation Method:Test Pit
Excavator Type:Mini Excavator
Groundwater Level:Not Encountered
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 957 Aberdeen Avenue Northeast, Renton, Washington
Surface Conditions:Grass
Total Depth of Excavation:9 feet bgs
Approximate
Surface Elevation 188
Compaction Method Bucket
USCS SymbolTPSL
SM
REMARKS AND OTHER TESTS
15% moisture
15% moisture, 29% fines
9% moisture
7% moisture
19% moisture
8% moistureGraphic LogMATERIAL DESCRIPTION
10" topsoil
Reddish brown silty SAND with trace gravel, loose, moist
Becomes tan, mottled
Becomes dense, dry to moist
Lightly cemented
Trace iron oxide staining
Contains sand and silt interbeds iron oxide staining in sand
beds
Test Pit terminated at 9'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)188
183
178
Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Aberdeen Townhomes
Project Number:2018-223
Client:Century Construction, LLC
Key to Logs
USCS SymbolREMARKS AND OTHER TESTSGraphic LogMATERIAL DESCRIPTIONDepth (feet)Sample NumberSample TypeElevation (feet)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 Sample Number: Sample identification number.
5 USCS Symbol: USCS symbol of the subsurface material.
6 Graphic Log: Graphic depiction of the subsurface material
encountered.
7 MATERIAL DESCRIPTION: Description of material encountered.
May include consistency, moisture, color, and other descriptive
text.
8 REMARKS AND OTHER TESTS: Comments and observations
regarding drilling or sampling made by driller or field personnel.
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
SILT, SILT w/SAND, SANDY SILT (ML)Silty SAND (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)
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 Aberdeen Townhomes SAMPLE ID/TYPE TP‐1
PROJECT NO.2018‐223 SAMPLE DEPTH 5'
TECH/TEST DATE EW 11/14/2018 DATE RECEIVED 11/14/2018
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)279.1 Weight Of Sample (gm)241.6
Wt Dry Soil & Tare (gm) (w2)241.6 Tare Weight (gm) 15.9
Weight of Tare (gm) (w3)15.9 (W6) Total Dry Weight (gm) 225.7
Weight of Water (gm) (w4=w1‐w2) 37.5 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2‐w3) 225.7 Cumulative
Moisture Content (%) (w4/w5)*100 17 Wt Ret (Wt‐Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100‐%ret)
% COBBLES 0.0 12.0"15.9 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"15.9 0.00 0.00 100.00 coarse gravel
% F GRAVEL 5.3 2.5" coarse gravel
% C SAND 3.8 2.0" coarse gravel
% M SAND 12.0 1.5"15.9 0.00 0.00 100.00 coarse gravel
% F SAND 46.5 1.0" coarse gravel
% FINES 32.5 0.75"15.9 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"18.0 2.10 0.93 99.07 fine gravel
D10 (mm)#4 27.8 11.90 5.27 94.73 coarse sand
D30 (mm)#10 36.4 20.50 9.08 90.92 medium sand
D60 (mm)#20 medium sand
Cu #40 63.4 47.50 21.05 78.95 fine sand
Cc #60 fine sand
#100 136.7 120.80 53.52 46.48 fine sand
#200 168.3 152.40 67.52 32.48 fines
PAN 241.6 225.70 100.00 0.00 silt/clay
322
DESCRIPTION Silty SAND with trace gravel
USCS SM
Prepared For: Reviewed By:
Century Construction, LLC KMW
01020
30405060708090100
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 Aberdeen Townhomes SAMPLE ID/TYPE TP‐2
PROJECT NO.2018‐223 SAMPLE DEPTH 4.5'
TECH/TEST DATE EW 11/14/2018 DATE RECEIVED 11/14/2018
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)556.1 Weight Of Sample (gm)527.2
Wt Dry Soil & Tare (gm) (w2)527.2 Tare Weight (gm) 15.9
Weight of Tare (gm) (w3)15.9 (W6) Total Dry Weight (gm) 511.3
Weight of Water (gm) (w4=w1‐w2) 28.9 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2‐w3) 511.3 Cumulative
Moisture Content (%) (w4/w5)*100 6 Wt Ret (Wt‐Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100‐%ret)
% COBBLES 0.0 12.0"15.9 0.00 0.00 100.00 cobbles
% C GRAVEL 13.7 3.0"15.9 0.00 0.00 100.00 coarse gravel
% F GRAVEL 6.3 2.5" coarse gravel
% C SAND 3.9 2.0" coarse gravel
% M SAND 10.1 1.5"15.9 0.00 0.00 100.00 coarse gravel
% F SAND 37.6 1.0" coarse gravel
% FINES 28.5 0.75"85.9 70.00 13.69 86.31 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"95.4 79.50 15.55 84.45 fine gravel
D10 (mm)#4 117.9 102.00 19.95 80.05 coarse sand
D30 (mm)#10 137.6 121.70 23.80 76.20 medium sand
D60 (mm)#20 medium sand
Cu #40 189.1 173.20 33.87 66.13 fine sand
Cc #60 fine sand
#100 340.0 324.10 63.39 36.61 fine sand
#200 381.5 365.60 71.50 28.50 fines
PAN 527.2 511.30 100.00 0.00 silt/clay
322
DESCRIPTION Silty SAND with some gravel
USCS SM
Prepared For: Reviewed By:
Century Construction, LLC KMW
01020
30405060708090100
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 Aberdeen Townhomes SAMPLE ID/TYPE TP‐3
PROJECT NO.2018‐223 SAMPLE DEPTH 2'
TECH/TEST DATE EW 11/14/2018 DATE RECEIVED 11/14/2018
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)355.6 Weight Of Sample (gm)311.7
Wt Dry Soil & Tare (gm) (w2)311.7 Tare Weight (gm) 15.9
Weight of Tare (gm) (w3)15.9 (W6) Total Dry Weight (gm) 295.8
Weight of Water (gm) (w4=w1‐w2) 43.9 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2‐w3) 295.8 Cumulative
Moisture Content (%) (w4/w5)*100 15 Wt Ret (Wt‐Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100‐%ret)
% COBBLES 0.0 12.0"15.9 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"15.9 0.00 0.00 100.00 coarse gravel
% F GRAVEL 7.4 2.5" coarse gravel
% C SAND 5.3 2.0" coarse gravel
% M SAND 16.7 1.5"15.9 0.00 0.00 100.00 coarse gravel
% F SAND 41.4 1.0" coarse gravel
% FINES 29.1 0.75"15.9 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"27.6 11.70 3.96 96.04 fine gravel
D10 (mm)#4 37.9 22.00 7.44 92.56 coarse sand
D30 (mm)#10 53.7 37.80 12.78 87.22 medium sand
D60 (mm)#20 medium sand
Cu #40 103.1 87.20 29.48 70.52 fine sand
Cc #60 fine sand
#100 191.6 175.70 59.40 40.60 fine sand
#200 225.5 209.60 70.86 29.14 fines
PAN 311.7 295.80 100.00 0.00 silt/clay
322
DESCRIPTION Silty SAND with trace gravel
USCS SM
Prepared For: Reviewed By:
Century Construction, LLC KMW
01020
30405060708090100
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 Aberdeen Townhomes SAMPLE ID/TYPE Outcrop
PROJECT NO.2018‐223 SAMPLE DEPTH Surface
TECH/TEST DATE EW 11/14/2018 DATE RECEIVED 11/14/2018
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)340.1 Weight Of Sample (gm)301.0
Wt Dry Soil & Tare (gm) (w2)301.0 Tare Weight (gm) 16.0
Weight of Tare (gm) (w3)16.0 (W6) Total Dry Weight (gm) 285.0
Weight of Water (gm) (w4=w1‐w2) 39.1 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2‐w3) 285.0 Cumulative
Moisture Content (%) (w4/w5)*100 14 Wt Ret (Wt‐Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100‐%ret)
% COBBLES 0.0 12.0"16.0 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"16.0 0.00 0.00 100.00 coarse gravel
% F GRAVEL 0.4 2.5" coarse gravel
% C SAND 0.5 2.0" coarse gravel
% M SAND 1.3 1.5"16.0 0.00 0.00 100.00 coarse gravel
% F SAND 9.6 1.0" coarse gravel
% FINES 88.2 0.75"16.0 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"16.0 0.00 0.00 100.00 fine gravel
D10 (mm)#4 17.0 1.00 0.35 99.65 coarse sand
D30 (mm)#10 18.5 2.50 0.88 99.12 medium sand
D60 (mm)#20 medium sand
Cu #40 22.2 6.20 2.18 97.82 fine sand
Cc #60 fine sand
#100 31.9 15.90 5.58 94.42 fine sand
#200 49.5 33.50 11.75 88.25 fines
PAN 301.0 285.00 100.00 0.00 silt/clay
322
DESCRIPTION SILT with trace sand
USCS ML
Prepared For: Reviewed By:
Century Construction, LLC KMW
0102030405060708090100
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
Geotechnical Engineering Report November 27, 2018
Aberdeen Townhomes, Renton, Washington RGI Project No. 2018-223
APPENDIX B
SLOPE STABILITY
RGI performed the slope stability analysis by using a computer program, Slide version 6.0,
which was developed by Rocscience. The safety factor for the critical surfaces was
calculated by the Bishop Method. The analyses were performed for the existing conditions
under static and seismic loading condition, as well as the proposed conditions.
1.7201.720111.7201.720Material NameColorUnit WeightlStrength TypeCoheionlPhiWater SurfaceRuSilty sand125Mohr-Coulomb20036Piezometric Line 1Silt110Mohr-Coulomb40034None0Safety Factor0.0000.2500.5000.7501.0001.2501.5001.7502.0002.2502.5002.7503.0003.2503.5003.7504.0004.2504.5004.7505.0005.2505.5005.7506.000+275250225200175150125-50-250255075100125150175200225Analysis DescriptionExisting StaticCompanyRiley Group, Inc.Scale1:345Drawn ByELWFile NameExisting Static.slimDate11/20/2018, 10:14:49 AMProjectAberdeen TownhomesSLIDEINTERPRET 6.009
1.1721.172111.1721.172Material NameColorUnit WeightlStrength TypeCoheionlPhiWater SurfaceRuSilty sand125Mohr-Coulomb20036Piezometric Line 1Silt110Mohr-Coulomb40034None0 0.2Safety Factor0.0000.2500.5000.7501.0001.2501.5001.7502.0002.2502.5002.7503.0003.2503.5003.7504.0004.2504.5004.7505.0005.2505.5005.7506.000+275250225200175150125-50-250255075100125150175200225Analysis DescriptionExisting SeismicCompanyRiley Group, Inc.Scale1:345Drawn ByELWFile NameExisting Seismic.slimDate11/20/2018, 10:14:49 AMProjectAberdeen TownhomesSLIDEINTERPRET 6.009
1.7201.72011 150.00 lbs/ft2 150.00 lbs/ft21.7201.720Material NameColorUnit WeightlStrength TypeCoheionlPhiWater SurfaceRuSilty sand125Mohr-Coulomb20036Piezometric Line 1Silt110Mohr-Coulomb40034None0Safety Factor0.0000.2500.5000.7501.0001.2501.5001.7502.0002.2502.5002.7503.0003.2503.5003.7504.0004.2504.5004.7505.0005.2505.5005.7506.000+275250225200175150125-50-250255075100125150175200225Analysis DescriptionProposed StaticCompanyRiley Group, Inc.Scale1:345Drawn ByELWFile NameProposed Static.slimDate11/20/2018, 10:14:49 AMProjectAberdeen TownhomesSLIDEINTERPRET 6.009
1.1721.17211 150.00 lbs/ft2 150.00 lbs/ft21.1721.172Material NameColorUnit WeightlStrength TypeCoheionlPhiWater SurfaceRuSilty sand125Mohr-Coulomb20036Piezometric Line 1Silt110Mohr-Coulomb40034None0 0.2Safety Factor0.0000.2500.5000.7501.0001.2501.5001.7502.0002.2502.5002.7503.0003.2503.5003.7504.0004.2504.5004.7505.0005.2505.5005.7506.000+275250225200175150125-50-250255075100125150175200225Analysis DescriptionProposed SeismicCompanyRiley Group, Inc.Scale1:345Drawn ByELWFile NameProposed Seismic.slimDate11/20/2018, 10:14:49 AMProjectAberdeen TownhomesSLIDEINTERPRET 6.009