21-104309-Wetland Delineation-10-14-2021-V1
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GEOTECHNICAL ENGINEERING REPORT
PREPARED BY:
THE RILEY GROUP, INC.
17522 BOTHELL WAY NORTHEAST
BOTHELL, WASHINGTON 98011
PREPARED FOR:
MAGELLAN ARCHITECTS
8383 158TH AVENUE, SUITE 280
REDMOND, WASHINGTON 98052
RGI PROJECT NO. 2020-507-1
MIDWAY SAMOAN AG CHURCH
29276 MILITARY ROAD SOUTH
FEDERAL WAY, WASHINGTON
NOVEMBER 13, 2020
Geotechnical Engineering Report i November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
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 ............................................................................................................................................. 5
5.2.1 Erosion and Sediment Control ..................................................................................................... 5
5.2.2 Stripping and Subgrade Preparation ............................................................................................ 6
5.2.3 Excavations................................................................................................................................... 6
5.2.4 Structural Fill ................................................................................................................................ 7
5.2.5 Wet Weather Construction Considerations ................................................................................. 8
5.3 FOUNDATIONS .......................................................................................................................................... 9
5.4 RETAINING WALLS ................................................................................................................................... 10
5.5 SLAB-ON-GRADE CONSTRUCTION ............................................................................................................... 10
5.6 DRAINAGE .............................................................................................................................................. 11
5.6.1 Surface ....................................................................................................................................... 11
5.6.2 Subsurface .................................................................................................................................. 11
5.6.3 Infiltration .................................................................................................................................. 11
5.7 UTILITIES ................................................................................................................................................ 11
5.8 PAVEMENTS ............................................................................................................................................ 11
6.0 ADDITIONAL SERVICES .............................................................................................................. 12
7.0 LIMITATIONS ................................................................................................................................. 12
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 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
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 eight test pit explorations
to approximate depths of 6 to 10 feet below existing site grades.
Based on the information obtained from our subsurface exploration, the site is challenging
for development. The peat should be removed from the site and backfilled with structural
fill. The following geotechnical considerations were identified:
Soil Conditions: The soils encountered during field exploration include two to seven feet
of medium dense to dense fill comprised of sandy gravel, silty gravel with some sand, silty
sand with varying amounts of gravel, and 5/8” minus crushed rock over native deposits of
soft peat, stiff to very stiff silt with varying amounts of sand, and medium dense silty sand
with varying amounts of gravel and sand with some silt and gravel.
Groundwater: Groundwater seepage was encountered at four location at depths of 4.5 to
8 feet during our subsurface exploration.
Foundations: Foundations for the proposed building may be supported on conventional
spread footings bearing on structural fill after peat is removed.
Slab-on-grade: Slab-on-grade floors and slabs for the proposed building can be supported
on structural fill after peat is removed.
Pavements: The peat below the proposed parking area should be completely removed to
avoid future settlement. However, if some settlement is allowed, the following pavement
sections are recommended:
3 inches of hot mix asphalt (HMA) over 6 inches of crushed rock base (CRB) over
structural fill after recompaction.
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
1.0 Introduction
This Geotechnical Engineering Report (GER) presents the results of the geotechnical
engineering services provided for the Midway Samoan AG Church in Federal Way,
Washington. The purpose of this evaluation is to assess subsurface conditions and provide
geotechnical recommendations for the construction of a church building. 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 29276 Military Road South in Federal Way, Washington. The
approximate location of the site is shown on Figure 1.
The site is currently occupied by a church building, a single-family residence, an outbuilding,
and a concrete slab. RGI understands that the existing structures will be removed and a
new church with a paved parking lot will be constructed on the site.
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 one to three kips per linear foot,
and a series of columns with a maximum load up to 50 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 October 28, 2020, RGI observed the excavation of eight test pit explorations. 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 excavating as well as our interpretation of the subsurface conditions between
samples. The test pit logs included in Appendix A represent an interpretation of the field
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
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 pit explorations 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 an irregular-shaped site comprised of two parcels totaling approximately
2.48 acres in size. The site is bound to the north by a single family residence and wetland,
to the east by a residential development, to the south by a single family residence, and to
the west by Military Road South.
The existing site is occupied by a church building, a single family residence, an outbuilding,
and a concrete slab. The site slopes east with about 10 feet of elevation change across the
site. The eastern portion of the site is occupied by a wetland area with a stream extending
along the eastern property line. The site is vegetated with grass, wetland plants and shrubs
and several scattered medium- to large-diameter trees.
4.2 GEOLOGY
Review of the Lidar-Revised Geologic Map of the Poverty Bay 7.5’ Quadrangle, King and
Pierce Counties, Washington, by R.W. Tabor, etc. (2014) indicates that the soil in the
western edge of the site is mapped as Till (Map Unit Qvt), which is light to dark gray,
nonsorted, nonstratified mixture of clay, silt, sand, and gravel. Most of the site is mapped
as Recessional outwash deposits (Qvr), which is stratified sand and gravel, silty sand, and
silt deposited in outwash channels draining meltwater from the receding glacier. The
descriptions for recessional outwash deposits are generally similar to the findings in our
field explorations with exception that peat was encountered at shallow depth.
4.3 SOILS
The soils encountered during field exploration include two to seven feet of medium dense
to dense fill comprised of sandy gravel, silty gravel with some sand, silty sand with varying
amounts of gravel, and 5/8” minus crushed rock over native deposits of soft peat, stiff to
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
very stiff silt with varying amounts of sand, and medium dense silty sand with varying
amounts of gravel and sand with some silt and gravel.
More detailed descriptions of the subsurface conditions encountered are presented in the
test pit 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 four location at depths of 4.5 to 8 feet during
our subsurface exploration.
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), RGI recommends the follow seismic
parameters for design.
Table 1 IBC
Parameter 2015 Value 2018 Value
Site Soil Class1 D2
Site Latitude 47.3380
Site Longitude -122.2995
Short Period Spectral Response Acceleration, SS (g) 1.304 1.33
1-Second Period Spectral Response Acceleration, S1 (g) 0.498 0.456
Adjusted Short Period Spectral Response Acceleration, SMS (g) 1.304 1.596
Adjusted 1-Sec Period Spectral Response Acceleration, SM1 (g) 0.748 0.841
Numeric seismic design value at 0.2 second; SDS(g) 0.869 1.064
Numeric seismic design value at 1.0 second; SM1(g) 0.499 0.561
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 pit explorations
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
extended to a maximum depth of 10 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.
3. 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
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 generally
medium dense recessional deposits, RGI considers that the possibility of liquefaction during
an earthquake is low to moderate. Review of the Liquefaction Susceptibility Map of King
County, Washington by Stephen P. Palmer, etc. (2004) indicates the western edge of the
site is mapped as having Moderate Liquefaction Susceptibility and the rest of the site is
mapped as having Low to Moderate Liquefaction Susceptibility.
4.6 GEOLOGIC HAZARD AREAS
Regulated geologically hazardous areas include erosion, landslide, earthquake, or other
geological hazards. Based on review of the City of Federal Way Critical Areas Map, the site
does not contain geologically hazardous areas.
5.0 Discussion and Recommendations
5.1 GEOTECHNICAL CONSIDERATIONS
Based on our study, the site is challenging for the proposed development. If the building
foundation is supported on shallow footings bearing on native soil, it will experience a
significant amount of post-construction settlement due to consolidation settlement of
peat. To avoid potential damages to building structures, the peat should be completely
removed in the building pad area and backfilled with structural fill. Foundations for the
proposed building can be supported on conventional spread footings bearing on
competent structural fill. Slab-on-grade floors can be similarly supported on structural fill
after overexcavation of peat.
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
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
The earthwork is expected to include excavating and backfilling the building foundations
and preparing slab subgrades.
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):
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
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
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
control system based on monitoring observations should be included in the erosion and
sedimentation control plan.
5.2.2 STRIPPING AND SUBGRADE PREPARATION
Stripping efforts should include removal of pavements, vegetation, organic materials, and
deleterious debris from areas slated for building, pavement, and utility construction. The
test pit explorations encountered 4 to 10 inches of topsoil and rootmass. Deeper areas of
stripping may be required in forested or heavily vegetated areas of the site.
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.
5.2.3 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 medium
dense silty sand with trace gravel and sand with some silt and gravel, and soft peat and stiff
to very stiff silt with varying amounts of sand.
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
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
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 STRUCTURAL FILL
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 American Society of Testing and Materials D1557-09 Standard Test Methods for
Laboratory Compaction Characteristics of Soil Using Modified Effort (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.
The onsite soils contain organics and are not suitable for use as structural fill. It is necessary
to import clean, granular soils to complete site work that meets the gradation requirements
listed in Table 2 to be used as structural fill.
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
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
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.
5.2.5 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.
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
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
As described above, peat should be removed below the building pad area and backfilled
with structural fill. Based on our test exploration, the depth of peat is about 4.5 feet in the
building area. After the peat is removed, the building foundation can be supported on
spread footing foundation bearing on 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.
Table 4 Foundation Design
Design Parameter Value
Allowable Bearing Capacity – Structural Fill 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 5.2.4. 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.
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
5.4 RETAINING WALLS
If retaining walls are needed in the building area, RGI recommends cast-in-place concrete
walls be used. The retaining wall must be supported on structural fill after peat is
completely removed. 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, and drainage properly installed,
RGI recommends using the values in the following table for design.
Table 5 Retaining Wall Design
Design Parameter Value
Allowable Bearing Capacity – Structural Fill 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
As described above, the peat should be completely removed in the building pad area and
backfilled with structural fill. 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 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.
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
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
The native site soils are not suitable for infiltration due to low permeability and shallow
ground water level. The stormwater should be routed to the storm drainage system in the
right-of-way.
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 Federal Way
specifications. At a minimum, trench backfill should be placed and compacted as structural
fill, as described in Section 5.2.4. 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.
The onsite soil is not suitable for use as backfill material. Imported structural fill meeting
the gradation provided in Table 2 may be necessary for trench backfill. Since the site
contains peat that has a potential of settlements, all utilities pipes should use flexible joints
for connections to structures.
5.8 PAVEMENTS
As described above, peat below the site will cause long term settlement. To avoid
settlement, all peat below the site should be removed and backfilled with structural fill.
Based on test exploration in the proposed parking area, the excavation depth will be from
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Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
7 to 9 feet in order to remove all the peat. If the amount of overexcavation is too much,
the pavement can be supported on existing fill. However, long-term settlement on an order
of several inches will be expected. If it is acceptable to the client, the pavement can be
supported on existing fill.
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.
RGI recommends the following pavement sections for parking and drive areas paved with
flexible asphalt concrete surfacing.
3 inches of Hot Mix Asphalt (HMA) over 6 inches of crushed rock base (CRB) over
existing fill after recompaction
The paving materials used should conform to the WSDOT specifications for HMA, 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, Magellan Architects, and its designated agents. Within the
limits of the scope and budget, this GER was prepared in accordance with generally
Geotechnical Engineering Report 13 November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
accepted geotechnical engineering practices in the area at the time this GER was issued.
This GER is intended for specific application to the Midway Samoan AG Church project in
Federal Way, Washington, and for the exclusive use of Magellan Architects 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.
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, Poverty Bay, Washington
7.5-Minute Quadrangle
Approximate Scale: 1"=1000'
0 500 1000 2000 N
Site Vicinity Map
Figure 1
11/2020
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Midway Samoan AG Church (20-046)
RGI Project Number:
2020-507-1
Date Drawn:
Address: 29276 Military Road South, Federal Way, Washington 98003
SITE
TP-1TP-2TP-3TP-4TP-5TP-6TP-7TP-811/2020Corporate Office17522 Bothell Way NortheastBothell, Washington 98011Phone: 425.415.0551Fax: 425.415.0311Midway Samoan AG Church (20-046)RGI Project Number:2020-507-1Date Drawn:Address: 29276 Military Road South, Federal Way, Washington 98003Figure 2Approximate Scale: 1"=80'04080160N= Test pit by RGI, 10/28/20= Site boundaryGeotechnical 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
11/2020
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Midway Samoan AG Church (20-046)
RGI Project Number:
2020-507-1
Date Drawn:
Address: 29276 Military Road South, Federal Way, Washington 98003
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
11/2020
Corporate Office
17522 Bothell Way Northeast
Bothell, Washington 98011
Phone: 425.415.0551
Fax: 425.415.0311
Midway Samoan AG Church (20-046)
RGI Project Number:
2020-507-1
Date Drawn:
Address: 29276 Military Road South, Federal Way, Washington 98003
Typical Footing Drain Detail
Figure 4
Not to Scale
Geotechnical Engineering Report November 13, 2020
Midway Samoan AG Church, Federal Way, Washington RGI Project No. 2020-507-1
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
On October 28, 2020, RGI performed field explorations using a backhoe. We explored
subsurface soil conditions at the site by observing the excavation of eight test pit
explorations to a maximum depth of 10 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.
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 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 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:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-1
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
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 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:10 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolTPSL
Fill
Fill
ML
ML
SP-SM
REMARKS AND OTHER TESTS
29% moisture
19% moisture
19% moisture
6% moistureGraphic LogMATERIAL DESCRIPTION
4" topsoil
Brown sandy GRAVEL, dense, moist (Fill)
Contains quarry spalls
Brown silty SAND with some gravel, medium dense, moist
(Fill)
Tan mottled SILT with some sand, stiff, moist
Becomes gray, very stiff
Becomes hard
Gray sandy SILT, very stiff, moist to wet
Contains sand interbeds
Gray SAND with some silt and gravel, medium dense, moist
Test Pit terminated at 10'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-2
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:Seepage at 8'
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:8.5 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolTPSL
ML
ML
SM
SP-SM
REMARKS AND OTHER TESTS
27% moisture
14% moisture, 22% fines
22% moistureGraphic LogMATERIAL DESCRIPTION
10" topsoil
Gray SILT with trace sand and gravel, very stiff, moist
Gray sandy SILT, very stiff, moist
Gray silty SAND with trace gravel, medium dense, moist
Heavy iron oxide staining
Occasional cobble
Gray SAND with some silt and gravel, medium dense, moist
Becomes wet, light groundwater seepage
Test Pit terminated at 8.5'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-3
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:5'
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Gravel
Total Depth of Excavation:7.5 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolFill
Fill
Peat
SM
REMARKS AND OTHER TESTS
17% moisture
94% moisture
585% moisture
26% moistureGraphic LogMATERIAL DESCRIPTION
8" gray 5/8" minus crushed rock, dense, moist (Fill)
Brown silty SAND with some gravel, medium dense, moist
(Fill)
Black PEAT, soft, moist
Becomes brown, wet
Becomes saturated
Gray silty SAND with trace gravel, medium dense, wet
Test Pit terminated at 7.5'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-4
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:4.5'
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:9 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolTPSL
Fill
Peat
ML
REMARKS AND OTHER TESTS
765% moisture
25% moistureGraphic LogMATERIAL DESCRIPTION
6" topsoil
Brown silty gravelly SAND, medium dense, moist (Fill)
Contains concrete debris
Black PEAT, soft, wet
Becomes brown
Becomes saturated
Gray SILT with some sand, stiff, moist to wet
Trace organics
Test Pit terminated at 9'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-5
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
Groundwater Level:6'
Test Pit Backfill:Cuttings
Logged By ELW
Bucket Size:N/A
Excavating Contractor:Kelly's Excavating
Sampling
Method(s)Grab
Location 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:8 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolTPSL
Fill
Peat
SM
REMARKS AND OTHER TESTS
20% moisture, 18% finesGraphic LogMATERIAL DESCRIPTION
4" topsoil
Gray silty gravelly SAND, medium dense, moist (Fill)
Contains concrete and asphalt debris
Black PEAT, soft, wet
Heavy seepage
Gray silty fine SAND, medium dense, water bearing
Test Pit terminated at 8'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-6
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
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 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:9.5 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolTPSL
Fill
Peat
ML
REMARKS AND OTHER TESTS
5% moisture, 12% fines
49% moisture
14% moistureGraphic LogMATERIAL DESCRIPTION
5" topsoil
Gray GRAVEL with some sand, medium dense, moist (Fill)
Trace concrete debris
Brown to gray
Black PEAT with wood debris, soft, wet
Becomes brown
Gray sandy SILT with trace gravel, very stiff, moist
Test Pit terminated at 9.5'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-7
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
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 29276 Military Road South, Federal Way, Washington
Surface Conditions:Gravel
Total Depth of Excavation:6.5 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolFill
Fill
Peat
ML
REMARKS AND OTHER TESTS
30% moisture
23% moisture, 87% finesGraphic LogMATERIAL DESCRIPTION
4" 5/8" minus crushed rock, dense, moist (Fill)
Brown silty gravelly SAND, medium dense, moist (Fill)
Trace metal debris
Large boulder
Black PEAT, soft, wet
Gray SILT with trace sand, stiff, moist
Test Pit terminated at 6.5'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
Test Pit No.: TP-8
Date(s) Excavated:10/28/2020
Excavation Method:Test Pit
Excavator Type:Rubber Tired Backhoe
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 29276 Military Road South, Federal Way, Washington
Surface Conditions:Grass
Total Depth of Excavation:6 feet bgs
Approximate
Surface Elevation N/A
Compaction Method Bucket
USCS SymbolFill
Fill
Peat
ML
REMARKS AND OTHER TESTS
362% moisture
21% moistureGraphic LogMATERIAL DESCRIPTION
2" 5/8" minus crushed rock, dense, moist
Brown silty SAND with some gravel, medium dense, moist
(Fill)
Black PEAT, soft, moist to wet
Becomes brown
Gray SILT with some sand and gravel, very stiff, moist
Test Pit terminated at 6'Depth (feet)0
5
10 Sample NumberSample TypeElevation (feet)Sheet 1 of 1
The Riley Group, Inc.
17522 Bothell Way NE, Bothell, WA 98011
Project Name:Midway Samoan AG Church
Project Number:2020-507-1
Client:Magellan Architects
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
AF
SILT, SILT w/SAND, SANDY SILT (ML)
Peat
Silty SAND (SM)
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)
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 Midway Samoan AG Church SAMPLE ID/TYPE TP-2
PROJECT NO.2020-507-1 SAMPLE DEPTH 4'
TECH/TEST DATE EW 10/29/2020 DATE RECEIVED 10/28/2020
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)285.6 Weight Of Sample (gm)252.0
Wt Dry Soil & Tare (gm) (w2)252.0 Tare Weight (gm) 16.1
Weight of Tare (gm) (w3)16.1 (W6) Total Dry Weight (gm) 235.9
Weight of Water (gm) (w4=w1-w2) 33.6 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 235.9 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"16.1 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"16.1 0.00 0.00 100.00 coarse gravel
% F GRAVEL 11.2 2.5" coarse gravel
% C SAND 4.8 2.0" coarse gravel
% M SAND 16.6 1.5"16.1 0.00 0.00 100.00 coarse gravel
% F SAND 45.0 1.0" coarse gravel
% FINES 22.4 0.75"16.1 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"34.9 18.80 7.97 92.03 fine gravel
D10 (mm)#4 42.6 26.50 11.23 88.77 coarse sand
D30 (mm)#10 54.0 37.90 16.07 83.93 medium sand
D60 (mm)#20 medium sand
Cu #40 93.1 77.00 32.64 67.36 fine sand
Cc #60 fine sand
#100 179.4 163.30 69.22 30.78 fine sand
#200 199.2 183.10 77.62 22.38 fines
PAN 252.0 235.90 100.00 0.00 silt/clay
DESCRIPTION Silty SAND with trace gravel
USCS SM
Prepared For:Reviewed By:
Magellon Architechts RW
0
10
20
30
40
50
60
70
80
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 Midway Samoan AG Church SAMPLE ID/TYPE TP-5
PROJECT NO.2020-507-1 SAMPLE DEPTH 7'
TECH/TEST DATE EW 10/29/2020 DATE RECEIVED 10/28/2020
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)449.1 Weight Of Sample (gm)375.7
Wt Dry Soil & Tare (gm) (w2)375.7 Tare Weight (gm) 16.1
Weight of Tare (gm) (w3)16.1 (W6) Total Dry Weight (gm) 359.6
Weight of Water (gm) (w4=w1-w2) 73.4 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 359.6 Cumulative
Moisture Content (%) (w4/w5)*100 20 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.1 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"16.1 0.00 0.00 100.00 coarse gravel
% F GRAVEL 0.0 2.5" coarse gravel
% C SAND 0.0 2.0" coarse gravel
% M SAND 0.8 1.5"16.1 0.00 0.00 100.00 coarse gravel
% F SAND 81.1 1.0" coarse gravel
% FINES 18.1 0.75"16.1 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"16.1 0.00 0.00 100.00 fine gravel
D10 (mm)#4 16.1 0.00 0.00 100.00 coarse sand
D30 (mm)#10 16.1 0.00 0.00 100.00 medium sand
D60 (mm)#20 medium sand
Cu #40 18.9 2.80 0.78 99.22 fine sand
Cc #60 fine sand
#100 238.5 222.40 61.85 38.15 fine sand
#200 310.5 294.40 81.87 18.13 fines
PAN 375.7 359.60 100.00 0.00 silt/clay
DESCRIPTION Silty fine SAND
USCS SM
Prepared For:Reviewed By:
Magellon Architechts RW
0
10
20
30
40
50
60
70
80
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 Midway Samoan AG Church SAMPLE ID/TYPE TP-6
PROJECT NO.2020-507-1 SAMPLE DEPTH 1.5'
TECH/TEST DATE EW 10/29/2020 DATE RECEIVED 10/28/2020
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)466.1 Weight Of Sample (gm)444.8
Wt Dry Soil & Tare (gm) (w2)444.8 Tare Weight (gm) 16.1
Weight of Tare (gm) (w3)16.1 (W6) Total Dry Weight (gm) 428.7
Weight of Water (gm) (w4=w1-w2) 21.3 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 428.7 Cumulative
Moisture Content (%) (w4/w5)*100 5 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.1 0.00 0.00 100.00 cobbles
% C GRAVEL 39.9 3.0"16.1 0.00 0.00 100.00 coarse gravel
% F GRAVEL 23.7 2.5" coarse gravel
% C SAND 5.2 2.0" coarse gravel
% M SAND 8.2 1.5"16.1 0.00 0.00 100.00 coarse gravel
% F SAND 10.6 1.0" coarse gravel
% FINES 12.3 0.75"187.1 171.00 39.89 60.11 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"255.1 239.00 55.75 44.25 fine gravel
D10 (mm)#4 288.9 272.80 63.63 36.37 coarse sand
D30 (mm)#10 311.3 295.20 68.86 31.14 medium sand
D60 (mm)#20 medium sand
Cu #40 346.6 330.50 77.09 22.91 fine sand
Cc #60 fine sand
#100 380.4 364.30 84.98 15.02 fine sand
#200 392.2 376.10 87.73 12.27 fines
PAN 444.8 428.70 100.00 0.00 silt/clay
DESCRIPTION Silty GRAVEL with some sand
USCS GM
Prepared For:Reviewed By:
Magellon Architechts RW
0
10
20
30
40
50
60
70
80
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 Midway Samoan AG Church SAMPLE ID/TYPE TP-7
PROJECT NO.2020-507-1 SAMPLE DEPTH 6'
TECH/TEST DATE EW 10/29/2020 DATE RECEIVED 10/28/2020
WATER CONTENT (Delivered Moisture) Total Weight Of Sample Used For Sieve Corrected For Hygroscopic Moisture
Wt Wet Soil & Tare (gm) (w1)234.3 Weight Of Sample (gm)193.7
Wt Dry Soil & Tare (gm) (w2)193.7 Tare Weight (gm) 16.2
Weight of Tare (gm) (w3)16.2 (W6) Total Dry Weight (gm) 177.5
Weight of Water (gm) (w4=w1-w2) 40.6 SIEVE ANALYSIS
Weight of Dry Soil (gm) (w5=w2-w3) 177.5 Cumulative
Moisture Content (%) (w4/w5)*100 23 Wt Ret (Wt-Tare) (%Retained)% PASS
+Tare {(wt ret/w6)*100}(100-%ret)
% COBBLES 0.0 12.0"16.2 0.00 0.00 100.00 cobbles
% C GRAVEL 0.0 3.0"16.2 0.00 0.00 100.00 coarse gravel
% F GRAVEL 0.0 2.5" coarse gravel
% C SAND 0.2 2.0" coarse gravel
% M SAND 1.5 1.5"16.2 0.00 0.00 100.00 coarse gravel
% F SAND 11.5 1.0" coarse gravel
% FINES 86.8 0.75"16.2 0.00 0.00 100.00 fine gravel
% TOTAL 100.0 0.50" fine gravel
0.375"16.2 0.00 0.00 100.00 fine gravel
D10 (mm)#4 16.2 0.00 0.00 100.00 coarse sand
D30 (mm)#10 16.6 0.40 0.23 99.77 medium sand
D60 (mm)#20 medium sand
Cu #40 19.2 3.00 1.69 98.31 fine sand
Cc #60 fine sand
#100 30.1 13.90 7.83 92.17 fine sand
#200 39.6 23.40 13.18 86.82 fines
PAN 193.7 177.50 100.00 0.00 silt/clay
DESCRIPTION SILT with trace sand
USCS ML
Prepared For:Reviewed By:
Magellon Architechts RW
0
10
20
30
40
50
60
70
80
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