19-105710RECEIVED
DEC 0 6 2019
CITY OF FEDERAL WAY
COMMUNfTY DEVELOPMENT
GEOTECHNICAL REPORT
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East Campus Terrace
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Prepared for:
Panattoni Development Company
Seattle, Washington
November 30, 2004
TERRA ASSOCIATES, Inc.
Consultants in Geotechnical Engineering, Geology
and
Environmental Earth Sciences
November 30, 2004
Project No. T-5629
Ms. Terra Vall-Spinosa
Panattoni Development Company
16400 Southcenter Parkway, Suite 502
Seattle, Washington 98198
Subject: Geotechnical Report
East Campus Terrace
Parcels C and G
South 320th Street and 32nd Avenue South
Federal Way, Washington
Dear Ms. Vall-Spinosa:
As requested, we have conducted a geotechnical engineering study for the subject project. The attached report
presents our findings and recommendations for the geotechnical aspects of project design and construction.
Our field exploration indicates the parcels are generally underlain at shallow depths by medium dense to dense
silty sand with gravel. The exception to this was observed in the southwest comer of Parcel G where, at Test Pits
TP-1, TP-4, and TP-7 through TP-11, 1 to 14 feet of loose, wet, organic fill material was observed overlying the
native soils. The fills observed will not be suitable for support of new construction. In our opinion, complete or
partial removal of these fills will be required to establish suitable support for building foundations, floor slabs,
and pavements. As an alternative for support of buildings, pile foundations can be considered. Undisturbed
bearing surfaces consisting of inorganic native soils will provide suitable support for building foundations, floors,
and site pavement.
We trust the information presented in this report is sufficient for your current needs. If you have any questions or
require additional information, please call.
Sincerely yours,
RRA ASSOCIATES,
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David Pat
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hepI heod mgegtE�Princip
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12525 Willows Road, Suite 101, Kirkland, Washington 98034
RhnnP (42S) R21-7777 ■ Fax (425) 821-4314
TABLE OF CONTENTS
€'a tic No.
1.0
Project Description.......................................................................................................... 1
2.0
Scope of Work................................................................................................................. 1
3.0
Site Conditions................................................................................................................ 2
3.1 Surface................................................................................................................2
3.2 Subsurface........................................................................:.................................2
3.3 Groundwater........................................................................................................2
4.0
Seismic............................................................................................................................ 3
5.0
Discussion and Recommendations.................................................................................. 3
5.1 General...............................................................................................................3
5.2 Site Preparation and Grading............................................................................. 4
5.3 Excavations........................................................................................................ 5
5.4 Foundations.....................................................................................................--- 5
5.5 Slabs-on-Grade...................................................................................................6
5.6 Site Retaining Walls ......................... •--•....................................................... 7
5.7 Drainage............................................................................................................. 7
5.8 Utilities............................................................................................................... 8
5.9 Pavements...........................................................................................................8
6.0
Additional Services ........................ .................................. ............................................... 9
7.0
Limitations.... - -.. . .... ........................................................................................................ 9
Figures
VicinityMap.......................................................................................................................Figure 1
Exploration Location Plan...................................................................................................Figure 2
ExplorationLocation Plan...................................................................................................Figure 3
Typical Wall Drainage Detail..............................................................................................Figure 4
Appendix
Field Exploration and Laboratory Testing....................................................................... Appendix A
Geotechnical Report
East Campus Terrace
Parcels C and G
South 320th Street and 32nd Avenue South
Federal Way, Washington
1.0 PROJECT DESCRIPTION
The project consists of developing Parcels C and G with office buildings, and associated roadway and utility
improvements. As currently shown on conceptual site plans, 4 office buildings ranging in size from 9,000 to
11,500 square feet will be constructed on each parcel. Specific building design information is not yet available;
however, we expect the office buildings will be two to three stories in height with the main floor levels
constructed at grade. Structural loading is expected to be light to moderate, with isolated columns carrying loads
of 100 to 300 kips and bearing walls carrying 2 to 6 kips per foot. Given current site grades, we also expect the
buildings will be terraced from west to east across the two parcels.
The recommendations in the following sections of this report are based upon our understanding of these design
features. We should review design drawings as they become available to verify that our recommendations have
been properly interpreted, and to supplement them if required.
2.0 SCOPE OF WORK
Our work was completed in accordance with our authorized proposal dated November 2, 2004. Accordingly, on
November 9, 2004, we excavated 16 test pits to depths of 5 to 15 feet below existing surface grades. Using the
information obtained from our subsurface exploration, we performed analyses to develop geotechnical
recommendations for project design and construction. Specifically, this report addresses the following:
• Soil and groundwater conditions
• Seismic
■ Site preparation and grading
• Excavations
• Foundation support alternatives
• Earth pressure parameters for retaining wall design
■ Slab -on -grade support
• Drainage
• Utilities
• Pavements
November 30, 2004
Project No. T-5629
3.0 SITE CONDITIONS
3.1 Surface
The project is a combination of two .parcels located in the north section of the East Campus Corporate Park, in
Federal Way, Washington. The approximate location of the site is shown on Figure 1. The project site is
bordered by South 320th Street to the north, 32nd Avenue South to the west, Weyerhaeuser Way South to the
east, and undeveloped parcels to the south. A power substation is located off the northeast comer, and a wetland
sensitive tract is located in the central north section. Generally, the northwestern section of Parcel C has been
unaltered and is a second -growth forest. The southwest section of Parcel G has been graded, and there is a large
fill mound extending eastward from the adjoining parcels. The remaining development portions of the parcels
have been cleared and, in some locations, filled. Most of the central section is covered with small alders and
scotch broom. A thin layer of grass covers the southeast portion. Topographically, the site slopes towards the
southeast with elevation highs in the northwest corner of Parcel C, to lows in the southeast portion of Parcel G.
3.2 Subsurface
In general, we found that the site has a thin mantle of topsoil/sod in various locations, and forest duff with
organics in other locations. The top three to four feet of most of the test pits excavated consisted of reddish -
brown to brown silty sand with gravel. Occasionally, we encountered a layer of brown to grayish -brown silty
sand with gravel in a wet and medium dense condition underneath the reddish -brown silty sand. All of the test
pits were terminated in a grayish -brown to gray silty sand with gravel to sandy silt with gravel (glacial till). The
glacial till varied in density and moisture throughout the site. In general, the glacial till was in a moist, dense, and
semi -cemented to cemented condition when first encountered, becoming very dense with depth.
We also observed uncontrolled fill in Test Pits TP-1, TP-4, and TP-7 through TP-11 excavated in the southwest
portion of Parcel G. The fill varied from wet to saturated, loose, gray silty sand with gravel to brown organic silt
with sticks and roots. We observed that the fill thickness varied from approximately 1 to 14 feet.
The Geologic Map of the Poverty Bay Quadrangle, King County, Washington, by Howard H. Waldron (1961),
shows the soils on the project site as ground moraine deposits (Qgt). These materials consist of mostly thin,
medium dense ablation till over dense lodgement till. Native soils we observed at the test pits are generally
consistent with this classification.
The preceding discussion is intended to be a brief review of the soil conditions encountered on the site. More
detailed descriptions are presented on the test pit logs in Appendix A.
3.3 Groundwater
We observed groundwater seepage at 4 of the 16 test pits. These included Test Pits TP-1, TP-3, TP-4, and TP-10.
The groundwater seepage at Test Pits TP-1 and TP-3 was noted at the contact between the upper weathered and
lower, un-weathered glacial till. At Test Pits TP-4 and TP-10, the seepage was observed near the contact between
the upper fill and underlying native soils. The seepage we observed is typical for a glacial till site. In general,
surface water that infiltrates. through the upper weathered soil or loose fill zone becomes perched on the
underlying dense cemented till. The till has a relatively low permeability that impedes the downward migration
of the infiltrated surface water. As a result, the water becomes perched and will flow laterally along the till
contact.
Page No. 2
November 30, 2004
Project No. T-5629
Fluctuations in groundwater seepage levels should be expected on a seasonal and annual basis. The amount of
seepage will be highest during and shortly following the normally wet winter season.
4.0 SEISMIC
Based on the soil conditions encountered and the local geology, per Section 1615 of the 2003 International
Building Code (IBC) for seismic conditions, site class "C" should be used in design of the structures.
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. 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, eliminating the soil's strength.
Based on the soil and groundwater conditions we encountered, in our opinion, there is no risk for liquefaction to
occur at this site during an earthquake.
5.0 DISCUSSION AND RECOMMENDATIONS
5.1 General
With the exception of the existing fill observed in the southwest corner of Parcel G, soil conditions at the site will
be suitable for support of development as proposed. Undisturbed bearing surfaces composed of native inorganic
soils or structural fill placed above these native soils would provide suitable support for conventional spread
footings, floor slabs, and pavement. The existing fill observed in the southwest comer of Parcel G will require
complete removal for support of building foundations. Depending on final building grades, it may be possible to
leave a portion of this fill in place beneath floors and pavement. As an alternative to removal, supporting the
building located in this area of the parcel on piles can also be considered.
Because of the organic content, the existing fill observed in the southwest comer of Parcel G will not be suitable
for reuse as structural fill. The native soils encountered at the site contain a significant amount of fines and will
be difficult to compact as structural fill when too wet. The ability to use native soil from site excavations as
structural fill will depend on its moisture content and the prevailing weather conditions at the time of
construction. If grading activities will take place during the winter season, the contractor should be prepared to
import free -draining granular material for use as structural fill and backfill.
Detailed recommendations regarding these 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.
Page No. 3
November 30, 2004
Project No. T-5629
5.2 Site Preparation and Grading
To prepare the parcels for construction, all vegetation, organic surface soils, and other deleterious materials
should be stripped and removed from below areas of new construction. Surface stripping depth of about 12
inches to remove the organic surface layer and expose native mineral soils should be expected over the area of
Parcel C, and within the northeastern portion of Parcel G. Excavation depths of 2 to 14 feet will be required in
the southwest comer of Parcel G to remove unsuitable existing fill. An excavation easement will be required
from the adjacent parcel owners in order to complete this excavation with safe stable side slopes. To avoid
removal of this existing fill, the building located in this area of the site would need to be supported on piles.
Stripped vegetation debris should be removed from the site. The existing fill and organic topsoil will not be
suitable for use as structural fill but may be used for limited depths in non-structural areas.
Once clearing and stripping operations are complete, cut and fill operations can be initiated to establish desired
building grades. Prior to placing fill, all exposed surfaces should be proofrolled to determine if any isolated soft
and yielding areas are present. Proofrolling should also be performed in cut areas that will provide direct support
for new construction. If excessively yielding areas are observed, and they cannot be stabilized in place by
compaction, the affected soils should be excavated and removed to firm bearing, and grade restored with new
structural fill. If the depth of excavation to remove unstable soils is excessive, use of a geotextile re-
enforcing/separation fabric, such as Mirafi 50OX or equivalent, can be considered in conjunction with structural
fill. Our experience has shown that, in general, a minimum of 18 inches of a clean, granular structural fill over
the geotextile fabric should establish a stable bearing surface.
Our study indicates that the native soils contain a sufficient percentage of fines (silt- and clay -size particles) that
will make them difficult to compact as structural fill if they are too wet or too dry. Accordingly, the ability to use
native soils from site excavations as structural fill will depend on their moisture content and the prevailing
weather conditions when site -grading activities take place. Native soils that are too wet to properly compact
could be dried by aeration during dry weather conditions or mixed with an additive such as cement, cement kiln
dust (CKD), or lime to stabilize the soil and facilitate compaction. If an additive is used, additional Best
Management Practices (BMPs) for its use will need to be incorporated into the temporary erosion and
sedimentation control plan (TESC) for the project.
If grading activities are planned during the wet winter months, or if they are initiated during the summer and
extend into fall and winter, the owner should be prepared to import wet weather structural fill. For this purpose,
we recommend importing a granular soil that meets the following grading requirements:
U.S. Sieve Size
Percent Passim
6 inches
100
No. 4
75 maximum
No. 200
5 maximum*
*Based on the 3/4-inch fraction.
Prior to use, Terra Associates, Inc. should examine and test all materials imported to the site for use as structural
fill.
Page No. 4
November 30, 2004
Project No. T-5629
Structural fill should be placed in uniform loose layers not exceeding 12 inches and compacted to a minimum of
95 percent of the soil's maximum dry density, as determined by American Society for Testing and Materials
(ASTM) Test Designation D-698 (Standard Proctor). The moisture content of the soil at the time of compaction
should be within two percent of its optimum, as determined by this ASTM standard. In non-structural areas or for
backfill in utility trenches below a depth of 4 feet, the degree of compaction can be reduced to 90 percent.
5.3 Excavations
All excavations at the site associated with confined spaces, such as utility trenches and lower building levels, must
be completed in accordance with local, state, or federal requirements. Based on current Occupational Safety and
Health Administration (OSHA) regulations, the existing fill and upper weathered native silty sand with gravel are
categorized as Group C soil. The underlying cemented glacial till is considered a Group A soil.
Accordingly, for excavations more than 4 feet and less than 20 feet deep, side slopes should be laid back at a
minimum slope inclination of 1.5:1 (Horizontal:Vertical) in the upper Group C materials. Excavation side slopes
extending into the lower till can be completed with a gradient of 0.75:1. If there is insufficient room to complete
the excavations in this manner or if excavations greater than 20 feet deep are planned, you may need to use
temporary shoring to support the excavations. For utility trenches, a properly designed and installed shoring
trench box can be used to support the excavation sidewalls.
Some groundwater seepage should be anticipated within excavations that extend near or below the cemented
glacial till contact. Based on our study, the volume of water and rate of flow into the excavation should be
relatively minor and would not be expected to impact the stability of the excavations when completed as
described. Conventional sump pumping procedures and a system of collection trenches, if necessary, should be
capable of mainta.ini.ng a relatively dry excavation for construction purposes.
This information is provided solely for the benefit of the owner and other design consultants, and should not be
construed to imply that Terra Associates, Inc. assumes responsibility for job site safety. Job site safety is the sole
responsibility of the project contractor.
5.4 Foundations
Spread Footings
The buildings may be supported on conventional spread foundations bearing on competent native soils or on
structural fills placed above competent native soils. Foundation subgrade should be prepared as recommended in
Section 5.2 of this report. As noted, for building construction in the southwest portion of Parcel G, excavation
and removal of up to 14 feet of unsuitable fill will be required. Perimeter foundations exposed to the weather
should bear at a minimum depth of 1.5 feet below final exterior grades for frost protection. Interior foundations
can be constructed at any convenient depth below the floor slab.
Foundations supported on undisturbed bearing surfaces composed of the upper weathered native soil or structural
fill can be dimensioned for a net allowable bearing capacity of 3,000 pounds per square foot (psf). Foundations
supported on the deeper cemented glacial till, typically observed at a depth of four to five feet on Parcel C, can be
designed for an allowable bearing capacity of 8,000 psf. For short-term loads, such as wind and seismic, a one-
third increase in this allowable capacity can be used. With structural loading as anticipated and these bearing
stresses applied, estimated total foundation settlement ranges from one-half to one inch.
Page No. 5
November 30, 2004
Project No. T-5629
For designing foundations to resist lateral loads, a base friction coefficient of 0.35 can be used. Passive earth
pressures acting on the side of the footing wall can also be considered. We recommend calculating this lateral
resistance using an equivalent fluid weight of 350 pounds per cubic foot (pcf). We recommend not including the
upper 12 inches of soil in this computation because it can be affected by weather or disturbed by future grading
activity. This value assumes the foundation will be constructed neat against competent native soil or backfilled
with structural fill as described in Section 5.2 of this report. The values recommended include a safety factor of
1.5.
Piling
If it is not feasible to excavate and remove the existing fill material in the southwest corner of Parcel G, we
recommend supporting the building planned in this area of the site on piling. Given the depth of the fill material,
and the relatively light building loads, in our opinion, the use of small -diameter pipe piles would be an effective
and economical solution for building support.
Pipe piles should be three- to four -inch diameter extra strong (schedule 80) steel pipe. The piles should be driven
through the existing fill into the underlying native soils using a hydraulic impact hammer having a minimum
weight of 650 pounds. Refusal should be considered as less than one inch of penetration following 15 seconds of
continuous impact by the pile -driving hammer. Three- and four -inch diameter pipe pile driven to this refusal
criteria, can be designed for axial loading of 16 and 20 kips, respectively. Due to the upper fill material and the
small -diameter pipe, the piles will have limited lateral capacity. Battered piles should be used to resist lateral
loading, where required.
Based on the thickness of the existing fill material, we expect pipe pile lengths will vary from 10 to 20 feet.
5.5 Slabs -on -Grade
Slabs -on -grade may be supported on the subgrade prepared as recommended in Section 5.2 of this report.
Immediately below the floor slab, we recommend placing a four -inch thick capillary break layer composed of
clean, coarse sand or fine gravel that has less than three percent passing the 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.
The capillary break layer will not prevent moisture intrusion through the slab caused by water vapor transmission.
Where moisture by vapor transmission is undesirable, such as covered floor areas, a common practice is to place a
durable plastic membrane on the capillary break layer and then cover the membrane with a layer of clean sand or
fine gravel to protect it from damage during construction, and aid in uniform curing of the concrete slab. It
should be noted that if the sand or gravel layer overlying the membrane is saturated prior to pouring the slab, it
will be ineffective in assisting uniform curing of the slab, and can actually serve as a water supply for moisture
seeping through the slab and affecting floor coverings. Therefore, in our opinion, covering the membrane with a
layer of sand or gravel should be avoided if floor slab construction occurs during the wet winter months and the
layer cannot be effectively drained.
Page No. 6
November 30, 2004
Project No. T-5629
5.6 Site Retaiuinsr Walls
As noted earlier, we expect that the office building elevations will be terraced with the natural topography of the
parcels. Site walls will likely be required to accommodate near -vertical grade breaks. Within Parcel C and the
northeastern portion of Parcel G, based on soil conditions we observed at the test pits, near -vertical grade breaks
of up to eight feet could, in our opinion, be faced with conventional rockery construction. While rockeries are not
engineered retaining walls, the native glacial till soils are inherently stable in near -vertical exposures, and would
only require protection from erosion and sloughing of the near -surface soils exposed in the cut. This protection is
commonly achieved by facing the cut with a rockery wall. Rockeries should be constructed by an experienced
contractor following guidelines established by the Association of Rockery -Contractors (ARC).
If surcharge loading will be imposed on the grade behind the vertical grade transitions, and where fill soils are
present, the grade transitions should be supported by an engineered structural wall. The magnitude of earth
pressure development on engineered retaining walls will partly depend on the quality of the wall backfill. We
recommend placing and compacting wall backfill as structural fill as described in Section 5.2 of this report. To
guard against hydrostatic pressure development, wall drainage must also be installed. A typical recommended
wall drainage detail is shown on Figure 3.
With wall backfill placed and compacted as recommended, and drainage properly installed, we recommend
designing unrestrained walls for an active earth pressure equivalent to a fluid weighing 35 pcf. To account for
typical traffic surcharge loading, the walls can be designed for an additional imaginary height of two feet (two -
foot soil surcharge). These values assume a horizontal backfill condition and that no other surcharge loading,
sloping embankments, or adjacent buildings will act on the wall. If such conditions exist, then the imposed
loading must be included in the wall design. 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 5.5 of this report.
5.7 Drainage
Surface
Final exterior grades should promote free and positive drainage away from the site at all times. Water must not be
allowed to pond or collect adjacent to foundations, or within the immediate building areas. We recommend
providing a gradient of at least three percent for a minimum distance of ten feet from the building perimeters. If
this gradient cannot be provided, surface water should be collected adjacent to the structures and disposed to
appropriate storm facilities.
Subsurface
We recommend installing perimeter foundation drains. Roof and foundation drains should be tightlined
separately to the storm drains. Subsurface drains must be laid with a gradient sufficient to promote positive flow
to a controlled point of approved discharge. All drains should be provided with cleanouts at easily accessible
locations.
Page No. 7
5.8 -Utilities
Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) or
the City of Federal Way specifications. As a minimum, trench backfill should be placed and compacted as
structural fill, as described in Section 5.2 of this report. As noted, most native soils excavated on the site should
be suitable for use as backfill material during dry weather conditions. However, if utility construction takes place
during the wet winter months, it will likely be necessary to import suitable wet weather fill for utility trench
backfilling.
5.9 Pavements
Pavement subgrade should be prepared as described in Section 5.2 of this report. Regardless of the degree of
relative compaction achieved, the subgrade must be firm and relatively unyielding before paving. The subgrade
should be proofrolled with heavy construction equipment to verify this condition.
The pavement design section is dependent upon the supporting capability of the subgrade soils and the traffic
conditions to which it will be subjected. For traffic consisting mainly of light passenger and commercial vehicles,
with only occasional heavy traffic, and with a stable subgrade prepared as recommended, we recommend the
following pavement sections:
■ Two inches of asphalt concrete (AC) over four inches of crushed rock base (CRB)
* Two inches of AC over three inches of asphalt -treated base (ATB)
The paving materials used should conform to the Washington State Department of Transportation (WSDOT)
specifications for Class B asphalt concrete, ATB, and CRB surfacing.
As an alternative to the preceding pavement section, consideration can be given to supporting the AC on a soil
cement base (SCB). Considering the light traffic loading expected, in our opinion, two inches of AC constructed
over six inches of SCB would be an adequate pavement section for the planned office development. However, if
heavy construction vehicles will traverse the section, we recommend increasing the AC section to three inches.
For construction access, an initial 1 %Z-inch AC lift should be placed on the SCB, on which construction traffic
would travel. Once load impacts from heavy construction vehicles are completed, failed areas, if any, can be
repaired followed by placement of the final 1 %Z-inch AC lift.
Soil cement can be constructed with the native inorganic silty sand with gravel soil. Type I Portland cement
should be blended uniformly with the native soil at a rate of 3 to 3 '/z psf of surface area for the six-inch depth of
SCB. Prior to mixing, the soil's moisture content should be at or slightly above the soil's optimum moisture. If
required, water should be added during mixing to maintain this moisture conditioning. Once blended and
moisture conditioned, initial compaction of the mixture should be accomplished with a sheep's foot compactor.
Following this initial compaction, the soil cement can be graded with final compaction then achieved with a static
smooth -drum roller. The soil cement should be compacted to a minimum relative compaction of 95 percent per
ASTM Test Designation D-698 (Standard Proctor). Grading and final compaction of the soil cement should occur
within three hours of initial mixing. Once completed, traffic on the soil cement subgrade should be kept to a
minimum, and the soil cemeiit allowed to cure a minimum of three days prior to paving. During this time, the
surface of the soil cement should not be allowed to dry excessively. Watering with a water truck or covering the
surface with tarps should be completed as necessary to prevent the SCB from excessive drying during this initial
curing period.
Page No. 8
November 30, 2004
Project No. T-5629
November 30, 2004
Project No. T-5629
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, we recommend surface drainage gradients of at least
two percent. 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
Terra Associates, Inc. should review the final design drawings and specifications in order to verify that earthwork
and foundation recommendations have been properly interpreted and implemented in project design. We should
also provide geotechnical services during construction to observe compliance with our design concepts,
specifications, and recommendations. This will allow for design changes if subsurface conditions differ from
those anticipated prior to the start of construction.
7.0 LEMTATIONS
We prepared this report in accordance with generally accepted geotechnical engineering practices. No other
warranty, expressed or implied, is made. This report is the copyrighted property of Terra Associates, Inc., and is
intended for specific application to the East Campus Terrace, Parcels C and G project. This report is for the
exclusive use of Panattoni Development Company and their authorized representatives.
The analyses and recommendations presented in this report are based on data obtained from the test pits excavated
on the site. Variations in soil conditions can occur, the nature and extent of which may not become evident until
construction. If variations appear evident, Terra Associates, Inc. should be requested to re-evaluate the
recommendations in this report prior to proceeding with construction.
Page No. 9
REFERENCE: THOMAS GUIDE, CD-ROM. KING/PIERCE/SNOHOMISH COUNTIES, 2004
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Terra
Associates!! Inc.
Consultants In Geotechnical Engineering
Geology and
Environmental Earth Sciences
NOT TO SCALE
VICINTY MAP
EAST CAMPUS TERRACE
PARCELS C AND G
FEDERAL WAY, WASHINGTON
Proj. No. T-5629 I Date NOV 2004 1 Figure 1
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Proj. No. T-5828 I Date NOV 2004 1 Figure 2
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EAST CAMPUS TERRACE
PARCEL C
FEDERAL WAY, WASHINGTON
Proj, No. T-5629 1 Date NOV 2004 ` F1gure 3
12" MINIMUM 3/4"
MINUS WASHED
GRAVEL
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MIRADRAIN G10ON PREFABRICATED DRAINAGE PANELS OR SIMILAR
PRODUCT CAN BE SUBSTITUTED FOR THE 12-INCH WIDE GRAVEL
DRAIN BEHIND WALL. DRAINAGE PANELS SHOULD EXTEND A MINIMUM
OF 6-INCHES INTO 12-INCH THICK DRAINAGE GRAVEL LAYER
OVER PERFORATED DRAINPIPE.
TYPICAL WALL DRAINAGE DETAIL
Terra EAST CAMPUS TERRACE
PARCELS C AND G
Associates Inca FEDERAL WAY, WASHINGTON
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Consultants in Geotechnical Ingineering
Geology and j
pro . No. T-5629 Date NOV 2004 Figure 4
Environmental Earth Sciences
APPENDIX A
FIELD EXPLORATION AND LABORATORY TESTING
East Campus Terrace
Parcels C and G
Federal Way, Washington
On November 9, 2004, we performed our field explorations using a rubber -tired backhoe. We explored
subsurface soil conditions at the site by excavating 16 test pits to a maximum depth of 14 feet below existing
surface grades. The test pit locations are shown on Figures 2 and 3. The test pit locations were approximately
determined by measurements from existing site features. The test pit logs are presented on Figures A-2 through
A-9.
An engineering geologist front our office conducted the field exploration, classified the soil conditions
encountered, maintained a log of each test pit, obtained representative soil samples, and observed pertinent site
features. All soil samples were visually classified in accordance with the Unified Soil Classification System
(USCS) described on Figure A-1.
Representative soil samples obtained from the test pits were placed in closed containers and taken to our
laboratory for further examination and testing. The moisture content of each sample was measured and is
reported on the test pit logs.
Project No. T-5629
E '
MAJOR DIVISIONS LETTFR TYPICAL DESCRIPTION
SYMBOL
_� rn
O N
U) 'Fn
s
Z E
a o p
0
ua o
W CZ
Q ca
2Z
C 0
rn
O °' cCv
4
0 �Z_N
Z4)
cc
W E
o
Z 0
LL
Clean
GRAVELS Gravels
GW
Well -graded gravels, gravel -sand mixtures, little or no
fines.
GP
Poorly -graded gravels, gravel -sand mixtures, little or
no fines.
(less than
More than 5% fines)
50% of coarse
fraction is Gravels
larger than No. with fines
4 sieve
Silty gravels, gravel -sand -silt mixtures, non -plastic
fines.
-
Clayey gravels, gravel -sand -clay mixtures, plastic fines.
GM
GC
I
SANDS
Clean SW
Sands
ell -graded sands, gravelly sands, little or no fines.
Wv
Poorly -graded sands or gravelly sands, little or no
fines.
More than
50% of coarse
(less than
5% fines) SP
fraction is
smaller than
No. 4 sieve
S M
Sands
with fines
SC
Silty sands, sand -silt mixtures, non -plastic fines.
Clayey sands, sand -clay mixtures, plastic fines.
inorganic silts, rock flour, clayey silts with slight
plasticity.
SILTS AND CLAYS
ML
CL
Inorganic clays of low to medium plasticity, (lean clay).
Liquid limit is less than 50%
OL
Organic silts and organic clays of low plasticity.
SILTS AND CLAYS
Liquid limit is greater than 50%
HIGHLY ORGANIC SOILS
w
Density
p
Very loose
to
Loose
=
Medium dense
0
Dense
v
Very dense
Consistency
w
>
Very soft
w
Soft
=
Medium stiff
U
Stiff
Very stiff
Hard
MH I Inorganic silts, elastic.
CH I inorganic clays of high plasticity, fat clays.
OH I Organic clays of high plasticity.
PT f Peat.
DEFINITION OF TERMS AND SYMBOLS
Standard Penetration
Resistance in Blows/Foot
0-4
4-10
10-30
30-50
>50
Standard Penetration
Resistance in Blows/Foot
0-2
2-4
4-8
8-16
16-32
>32
T 2" OUTSIDE DIAMETER SPLIT
L SPOON SAMPLER
2.4" INSIDE DIAMETER RING SAMPLER
OR SHELBY TUBE SAMPLER
Z WATER LEVEL (DATE)
Tr TORVANE READINGS, tsf
Pp PENETROMETER READING tsf
DID DRY DENSITY, pounds per cubic foot
LL LIQUID LIMIT, percent
PI PLASTIC INDEX
N STANDARD PENETRATION, blows per foot
Terra UNIFIEDSOCLASSIFICATION
CAMPUS TERRACE
SYSTEM
EAS
Associates, Inc. PARCELS C AND G
Consultants in Geotechnical Engineering FEDERAL WAY, WASHINGTON
Geology and
Environmental Earth Sciences Proj. No. T-5629 I Date NOV 2004 1 Figure A-1
Test Pit No. TP-3
Logged by: DPL
Date: 11/09/04
Depth
(ft.)
0
5
15
Approximate Elev. 446
Moisture
nt
Soil Description C (%I nt
(4 to 6 inches TOPSOIUSOD)
Reddish -brown to brown silty SAND with gravel, trace roots, some
cobbles, fine grained, medium dense, moist to wet. (SM)
10.4
12.1
12.2
Grayish -brown to gray silty SAND with gravel, slightly mottled, fine
grained, medium dense, wet. (SM)
Gray silty SAND with gravel, tine grained, trace cobbles, cemented,
8.2
dense, ?''foist. (SM) (Glacial Till)
9.1
Test pit terminated at 10 feet.
Slight groundwater seepage observed at 8 feet.
Logged by: DPL
Date: 11 /09/04
Depth
(ft.)
0�
FILL: grayish -brown silty sand with gravel, fine gralned, trace sticks,
loose to medium dense, wet to moist.
Test Pit No. TP-4
Approximate Elev. 438
Moisture
ent
Soil Description C (%)
13.4
__
_!ILL: forest duff, sticks, organics, wet, soft.
FiLL: grayish -brown silty sand with gravel, trace quarry spalls, loose, wet. V
Grayish -brown to gray silty SAND with gravel, cemented, fine grained, 14.2
dense, moist. (SM) (Glacial Till)
10 � Test pit terminated at 9 feet.
Slight groundwater seepage observed at 6 feet.
15
TEST PIT LOGS
Terra EAST CAMPUS TERRACE
Associates, Inc. PARCELS C AND G
• consultants In Geotechnical Engineering FEDERAL WAY, WASHINGTON
Geology and
Environmental Earth Sciences Proj. No. T 5629 I Date NOV 2004 Figure A-3
Logged by: DPL
Date: 11 /09/04
Depth
(ft.)
0
5
10
15
Test Pit No. TP-5
Soil Description
Approximate Elev. 444
Moisture
Content
( QI4)
(6 inches TOPSOIUSOD)
Reddish -brown to brown silty SAND with gravel, fine grained, mottled at
11.0
3.5 feet, some roots, medium dense, wet. (SM)
Gray silty SAND with gravel, fine grained, cemented, dense to very
8.7
dense, wet to moist. (SM) (Glacial Till)
Test pit terminated at 9 feet.
No groundwater seepage observed.
Logged by: DPL
Date: 11 /09/04
Depth
(ft.)
0 ern,
Test Pit No. TIP-6
Soil Description
Approximate Elev. 440
Moisture
Content
(°Io}
Re dish -brown silty SAND with gravel, some roots, fine grained, medium dense, 10.9
Brown to grayish -brown silty SAND with gravel, trace mottling, fine
grained, medium dense, wet. (SM) 11.5
5 Gray silty SAND with gravel, cemented, fine grained, dense to very 8.3
dense, moist. (SM) (Glacial Till)
10 Test pit terminated at 9 feet.
No groundwater seepage observed.
f &I
TEST PIT LOGS
Terra EAST CAMPUS TERRACE
FRO. A Associates, Inc. PARCELS C AND G
Consultants in Geotechnlcal Engineering FEDERAL WAY, WASHINGTON
Geology and
Environmental Earth Sciences Proj. No. T-5629 I Date NOV 2004 , Figure A-4
Test Pit No. T 7
Logged by: DPL
Date: 11 /09/04
Depth
{ft.}
0
Soil Description
Approximate Elev, 437
(Trace TOPSOIUSOD)
FILL: brown to black organics and duff, sticks, trace silty sand with
gravel, wet. _
Gray silty SAND with some gravel, mottled at 4 feet, fine grained,
5 medium dense to dense, wet to moist. (SM)
Test pit terminated at 5 feet
No groundwater seepage observed.
10
15
Logged by: DPL
Date: 11 /09/04
Depth
(ft.}
0
Test Pit No. TP-8
Soil Description
Moisture
Cojjnt1ent
lip)
16.3
Approximate Elev. 438
Moisture
Content
(Trace TOPSOIUSOD)
FILL: gray silty sand with gravel, fine grained, loose, wet to saturated.
11.0
inches DUFF, RGOTS
ff6
Reddish•brown to brown silty sand with gravel, fine grained, medium dense to
5 dense, moist. SM _ 10.4
Gray silty SAND with gravel, fine grained, cemented, dense to very dense,
moist. (SM)
Test pit terminated at 6.5 feet.
No groundwater seepage observed.
10
15
Terra EASTEST PIT
T CAMPUS TOGS RRACE
E�op Associates, Inc. PARCELS C AND G
Consultants in Geotechnical Engineering FEDERAL WAY, WASHINGTON
Geology and
Environmental Earth Sciences Proj. No. T-5629 Date NOV 2004 Figure A-5
Test Pit No. TP@9
Logged by: DPL
Date: 11 /09/04
Depth
(ft.)
0
5
10
15
Soil Description
Approximate Elev. 452
Moisture
Content
[°IQ]
(Trace TOPSOIUSOD)
FILL: gray silty sand with gravel, medium dense to loose, wet to
saturated.
FILL: brown organic sandy silt with some gravel.
(Forest Duff Strippings)
Lots of old roots, sticks, small logs, soft, wet.
36.1
15.4
Grayish -brown silty SAND with gravel, dense, moist. (SM)
Test pit terminated at 14 feet. No groundwater seepage observed.
Logged by: DPL
Date: 11 /09/04
Depth
(ft. )
0
Test Pit No. TP-10
Soil Description
Approximate Elev. 452
Moisture
Content
(Trace TOPSOIUSOD)
FILL: gray silty sand with gravel, fine grained, medium dense to loose, 7.8
wet to saturated.
5 -� 111.7
10
15
(Sidewalls easily caved below 4 feet.)
1
Grayish -brown silty SAND with gravel, dense, moist. (SM)
Test pit terminated at 12.5 feet.
Moderate groundwater seepage at 11 feet.
Terra TEST PIT LOGS
EAST CAMPUS TERRACE
Associates, Inc. PARCELS C AND G
Consultants in Geotechnical Engineering FEDERAL WAY, WASHINGTON
Geology and
Environmental Earth Sciences Proj. No. T-5629 I Date NOV 2004 Figure A-6
Test Pit No. TP-11
Logged by: -DPL
Date: 11 /09/04
Depth
(ft.)
0
5
10
Soil Description
Approximate Elev, 450
Moisture
Content
(Trace TOPSOIUSOD) I
FILL: gray- silty sand with gravel, medium dense to loose, wet. IV 7.4
FILL: brown silty sand with gravel, some old roots, sticks, loose, wet.
FILL: dark brown organic sand silt with gravel, old roots, sticks, small 16.5
logs, soft, wet.
Test pit terminated at 13 feet.
15No groundwater. seepage observed.
• -
Logged by: DPL
Date: 11 /09/04
Depth
(ft.)
Test Pit No. TP-1 2
Soil Description
11.2
Approximate Elev. 454
Moisture
Content
(12 inches FOREST DUFF) _
Reddish -brown silty SAND with gravel, medium dense, moist. (SM) 10.5
Brownish -gray silty SAND with gravel, fine gralned, cemented, dense to
very dense, moist. 11.4
5 --
Test pit terminated at 6 feet.
No groundwater seepage observed.
10
15
Terra EASTEST PIT
T CAMPUS TEE RACE
Associates, Inc. PARCELS C AND G
- FEE . Consultants in Geotechnicai Engineering FEDERAL WAY, WASHING TON
Geology and
Environmental Earth Sciences Proj. No. T-5629 Date NOV 20041 Figure A-7
Test Pit No. TP-13
Logged by: DPL
Date: 11 /09/04
Approximate Elev. 462
Depth Moisture
Content
(ft.� Soil Description
0 (12 Inches FOREST DUFF)
Reddish -brown to brown silty SAND with gravel, fine grained, some
roots, medium dense, moist. (SM) 72
Grayish -brown to gray silty SAND with gravel, fine grained, cemented, 9.0
5 dense to very dense, moist. (SM) (Glacial Till)
10
15
Test pit terminated at 7 feet.
No groundwater seepage observed.
Test Pit No. TP-14
Logged by: DPL
Approximate Elev, 460
Date: 11 /09/04
Depth Moisture
Content
(ft.) Soil Description Cont
[nt
0 (8 to 10 inches FOREST DUFF)
Reddish -brown silty SAND with gravel, roots, fine grained, medium 15.3
dense, moist to wet. (SM)
Grayish -brown to gray silty SAND with gravel, fine grained, cemented, 6.1
r� dense to very dense, moist. (SM) (Glacial Till)
10.7
10 Test pit terminated at 7.5 feet.
No groundwater seepage observed.
15
Terra TEST PIT LOGS
EAST CAMPUS TERRACE
Associates, Inc. PARCELS C AND G
Consultants in Geotechnical Engineering FEDERAL WAY, WASHINGTON
Geology -and
Environmental Earth Sciences Prof. No. T 5629 Date NOV 20041 Figure A-8
Logged by: DPL
Date: 11/09/04
Depth
Test Pit No. TP-15
Soil Description
Approximate Elev. 470
Moisture
Content
0 (12 inches FOREST DUFF)
19.9
Reddish -brown to -brown silty SAND with gravel, some roots, fine
grained, medium dense, moist. (SM)
— - - 9.0
Gray silty SAND with gravel, fine grained, cemented, dense to very
dense, moist. (SM) (Glacial Till) 7.4
Test pit terminated at 7 feet.
No groundwater seepage observed.
1Q
15
Test Pit No. TP-16
Logged by: DPL
Approximate Elev. 470
Date: 11 /09/04
Depth Moisture
Content
(ft.) Soil Description Cont
tnt
0 (12 inches FOREST DUFF)
Reddish -brown to brown silty SAND with gravel, some roots, fine 12.1
grained, medium dense, moist. (SM)
Grayish -brown to gray silty SAND with gravel, fine grained, cemented, 9.1
5 dense to very dense, moist. (SM) (Glacial Till)
4.1
10 Test pit terminated at 7.5 feet.
No groundwater seepage observed.
15
Terra TEST PIT LOGS
EAST CAMPUS -TERRACE
Eiog Associates, Inc. PARCELS C AND G
Consultants in Geotechnical Engineering FEDERAL WAY, WASHINGTON
Geology -and
Environmental Earth Sciences Prof. No. T-5629 Date NOV 20041 Figure A-9