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GE000N
NOBTHWEST, INC.
GEOTECHNKAL CONSULTANTS 0
P1475-05-01
February 16,2007
Mr.Doug Frey
908.Deborah Road
Newberg,Oregon
Subject: RED ROCK CREEK
TIGARD BUSINESS CENTER
TIGARD,OREGON
GEOTECHNICAL INVESTIGATION
Dear Mr.Frey:
In accordance with our proposal number P06-05-150,November 1, 2006,and your authorization,we
have performed a geotechnical investigation for the proposed Red Rock Creek Tigard Business
Center in Tigard, Oregon. The accompanying report presents the findings of our investigation and
our conclusions and recommendations regarding the geotechnical aspects of the proposed
construction. Based on the results of this investigation,itis our opinion that the site can be developed
as proposed, provided the recommendations of this report are followed. Important geotechnical
issues addressed herein include perched/shallow groundwater potential, moderately compressible
subsurface soil, deep foundation considerations, shoring and retaining wall evaluation, and grading
recommendations for the moisture sensitive native fine-grained soil. It is highly recommended that
site grading be completed during the summer months to reduce the potential for increased site
preparation costs.
If you have questions regarding this report, or if we may be of further service, please contact the
undersigned at your convenience.
Sincerely, `
GEOCON NORTHWEST,INCORPORATED ti,,ti)PROPe,
c4%4 c, ' N F E21/*
a_ _ I w 4, 18281 , {
B an Wavra,P.E. Wesley fang,P g.►:, ' E. 0,4 Go. O
Geotechnical Engineer President ..JAN 16, 196
BJW:AWS �FSIEY Si*
i !EXPIRATION DATE: 6!30105* j
,...... cc: Mr.James Ponto,Anderson Dabrowski Architects
Mr.Brian Lee,PACE Engineers
8283 SW Cirrus Drive ■ Beaverton, Oregon 97008 ! Telephone (503) 626-9889 t Fax (503) 626-8611
• _ TABLE OF CONTENTS
1 PURPOSE AND SCOPE
1
2 SITE AND PROJECT DESCRIPTION 1
3 REGIONAL GEOLOGY 2
4 SUBSURFACE EXPLORATION AND CONDITIONS 2
4.1 SITE EXPLORATION 2
4.2 . SUBSURFACE CONDITIONS 4
5 SEISMIC HAZARDS 5
5.1 LANDSLIDE HAZARD 5
5.2 CRUSTAL FAULTS 5
5.3 SOIL LIQUEFACTION OR CYCLIC FAILURE POTENTIAL 5
5.4 LATERAL SPREADING 6
5.5 2003 INTERNATIONAL BUILDING CODE SEISMIC DESIGN PARAMETERS 6
6 LABORATORY TESTING 6
7 CONCLUSIONS AND RECOMMENDATIONS 7
7.1 GENERAL 7
7.2 SITE PREPARATION 8
7.3 PROOF ROLLING 10
7.4 FILLS 10
7.5 SURFACE AND SUBSURFACE DRAINAGE 12
7.6 FOUNDATIONS 12
7.7 PERMANENT CUT AND FILL SLOPES 14
7.8 CONCRETE SLABS-ON-GRADE 14
7.9 RETAINING WALLS AND SHORING 15
7.10 UTILITY EXCAVATIONS 16
7.11 PAVEMENT DESIGN 17
8 FUTURE GEOTECHNICAL SERVICES 17
9 LIMITATIONS
18
MAPS AND ILLUSTRATIONS
Figure I,Vicinity Map
Figure 2, Site Plan
Figure 3,2003 IBC Design Response Spectrum
Figure 4,Typical Underslab Drainage Scheme
APPENDIX A
FIELD INVESTIGATION
APPENDIX B
LABORATORY TEST RESULTS
GEOTECHNICAL INVESTIGATION
1 PURPOSE AND SCOPE
This report presents the results of the geotechnical investigation for the proposed Red Rock Creek
Tigard Business Center in Tigard, Oregon. The approximate 4-acre parcel is located at 12625 SW
70th Avenue, which is at the southeast corner of SW 72nd Avenue and SW Dartmouth Street. The
purpose of the geotechnical investigation was to evaluate subsurface soil and geologic conditions at
the site and, based on the conditions encountered, provide conclusions and recommendations
pertaining to the geotechnical aspects of the proposed construction.
The scope of the field investigation consisted of a site reconnaissance,review of published geological
literature,four exploratory borings,and four dilatometer soundings. A detailed discussion of the field
investigation is presented in Section 4 of this report.
Laboratory tests were performed on selected soil samples obtained during the investigation to
evaluate pertinent physical properties. Appendix B presents a summary of the laboratory test results.
The results of laboratory moisture content tests are presented on the exploratory boring logs.
The recommendations presented herein are based on analyses of the data obtained during the field
investigation, laboratory test results, and our experience with similar soil and geologic conditions.
This report has been prepared forthe exclusive use of Mr. Doug Frey and his agents, for specific
application to this project, in accordance with generally accepted geotechnical engineering practice.
This report may not contain sufficient information for purposes of other parties or other uses.
2 SITE AND PROJECT DESCRIPTION
The site is currently vacant and is occupied by overgrown grass, trees, brush, and wetlands areas.
The wetlands areas exhibited saturated soil and perched water at the ground surface at time of the
field investigation. Red Rock Creek extends along the north and northwest boundaries of the
property. Private residences extend along the south margin,and a large block retaining wall has been
constructed for the property adjacent to the east which forms the east perimeter of the subject site.
The topography of the site slopes down to the northwest with maximum elevation of 260 feet at the
southeast corner and minimum elevation of 210 feet at the northwest corner. Several piles of rubbish
were sporadically located across the property, but evidence to suggest the presence of previous
structures at the property was not encountered.
Drawings provided by Anderson Dabrowski Architects and project civil engineer,PACE Engineers,
indicate the development will include the construction of three single-story buildings, on-grade
parking, and SW 70th Avenue. Building A will be positioned along the east half of the north
perimeter,building B at the far west perimeter, and building C at the middle of the south perimeter.
The proposed grading plans indicate that the east portion of the site will require excavation to achieve
P1475-05-01 -1- February 16,2007
i- ,
grade while the west section may receive fill on the order of 15 feet. The excavation/fill transition
' zone extends north/south through proposed buildings A and C. It is understood that the filled
portions of the site will be retained by a retaining structure,and the cut along future SW 70th Avenue
will be supported by a shoring structure.
Red Rock Creek will be diverted to an underground culvert as part of the overall site development.
Due to the City of Tigard building setback criteria, the north wall of Building A and the northwest
corner of Building B may be positioned over the culvert. A discussion of deep foundation support in
these locations is contained herein.
3 REGIONAL GEOLOGY
Based on geologic literature reviewed for the site, the topography of the Tualatin Valley region is
characterized by wide, flat lowlands and prominent uplands that are controlled primarily by the
folding and faulting of the underlying bedrock. The near-surface geology of the project area consists
of Late Pleistocene age deposits of silt and fine-grained sand described as Willamette Silt. These
Pleistocene age deposits are characterized by brown to buff,beds and lenses of fine-grained sand,silt
and clay. Willamette Silts are slack water fluvial and/or lacustrine deposits resulting from repeated
temporary inundation of the Willamette and Tualatin Valleys by Late-Pleistocene glacial outburst
floods. These glacial floods originated in the Missoula Valley of Montana,passed through eastern
Washington, and followed the Columbia River downstream. When these large floods entered the
Portland Basin they flowed up the Willamette River and its tributaries, flooding most of the
Willamette and Tualatin Valleys to an approximate elevation of 350 feet MSL. The last of these
glacial floods,also thought to be one of the largest,occurred about 12 400years
� ago,establishing the
minimum age of the silt deposit. The Willamette Valley silt is underlain by the erosional surfaces of
older bedrock units including the Troutdale Formation.
Well logs on file with Oregon Water Resources Department for the adjacent property to the east
indicate the presence of silt which is underlain by andesitic rock at a depth of approximately 15 feet.
The site west of the subject property is underlain by silt, sand, and clay to the maximum explored
depth of 30 feet
4 SUBSURFACE EXPLORATION AND CONDITIONS
4.1 Site Exploration
The subsurface soil conditions at the site were determined based on the literature review, field
exploration,and laboratory investigation. The field exploration was completed on December 29th and
30th, 2006, and consisted of four exploratory borings and four dilatometer soundings. The borings
were completed using mud rotary drilling techniques to a depth of 31.5 feet below the existing
•
ground surface(bgs). The dilatometer soundings encountered practical refusal at variable depths that
ranged from 17 to 33 feet bgs. The subsurface conditions encountered in the borings and dilatometer
P1475-05-01 -2
February 16,2007
soundings were recorded on the subsurface logs that are located in Appendix A at the end of this
report. The approximate locations of the explorations are shown in Figure 2,Site Plan.
4.1.1. DiIatometer Test
The dilatometer test provides a rational, cost-effective method to determine engineering
parameters for the design of earthworks and structural foundations. It is particularly useful in
silts and sands that can be difficult to sample or test by other methods. The DMT is
performed in situ by pushing a blade-shaped instrument into the soil. The blade is equipped
with an expandable membrane on one side that is pressurized until the membrane moves
horizontally into the surrounding soil. Readings of the pressure required to move the
membrane to a point that is flush with the blade(A—pressure)and to a point 1.1 mm into the
surrounding soil (B —pressure) are recorded. The pressure is subsequently released and, in
permeable soils below the groundwater table,.a pressure reading is recorded as the membrane
returns to the flush position (C — pressure). The test sequence is performed at 0.2-meter
intervals to obtain a comprehensive soil profile. A material index (ID), a horizontal stress
index(Ku)and a dilatometer modulus(ED)are obtained directly from the dilatometer data.
Marchetti (1980) developed a soil classification system based on the material index.
According to this system, soils with ID values less than 0.35 are classified as clay. Soils
classified as sand have an ID value greater than 3.3. Material index values between 0.35—3.3
indicate silty clay to silty sand soils.
Empirical relationships between the horizontal stress index and the coefficient of lateral earth
pressure (Ko) have been developed by Lunne et al. (1990) for clays and by Schmertmann
(1983) for uncemented sands. While Lunne's method makes use of dilatometer data
exclusively,Schmertmann utilizes both DMT and cone penetration data to estimate Ko.
Since the DMT is strain-controlled,the measured difference between the B-pressure and A-
pressure readings (corrected for membrane stiffness) andcavity expansion theory, can be
used to directly measure the soil stiffness. Assuming a Poisson's ratio, the dilatometer
modulus is correlated to shear modulus,Young's modulus,and constrained modulus.
Four dilatometer soundings completed at this site were advanced to depths ranging from 17
to 33 feet below the ground surface,where refusal was encountered. A member of Geocon
Northwest's engineering staff recorded pressure readings every eight inches along the length
of the sounding.
4.1.2. Borings
i Four borings were advanced to a depth of 31.5 feet bgs using a CME-75 track mounted drill
rig equipped with mud rotary drilling capabilities. A member of Geocon Northwest's
PI475-05-01 -3- February 16,2007
geotechnical engineering staff logged the subsurface conditions encountered within the
boring. Standard penetration tests (SPT) were performed in the boring by driving a 2-inch
outside diameter split spoon sampler 18 inches into the bottom of the boring, in general
accordance with ASTM D 1586. The number of blows required to drive the sampler the last
12 of the 18 inches(blow count)are reported on the boring log located in Appendix A at the
• end of this report. Disturbed bag samples were obtained from SPT testing. Service providers
subcontracted by Geocon Northwest completed the borings.
.i 4.2 Subsurface Conditions
The subsurface exploration is assumed to be representative of the subsurface conditions across the
site; however, it is possible that some local variations and possible unanticipated subsurface
conditions exist. Based on the conditions observed during the reconnaissance and field exploration,
the subsurface conditions, in general,consisted of the following:
ORGANIC TOPSOIL—An initial layer of approximately 12 to 24 inches of organic topsoil
was present across the majority of the site. The topsoil will require stripping in all planned
structural and pavement areas. Unsuitable organic soil may locally extend to depths
exceeding 2 feet,particularly where existing trees or large shrubs will be removed. Perched
water was encountered across the entire site within the organic topsoil layer at a depth less
than 12 inches.
CLAYEY SILT TO SILTY CLAY—Medium stiff,wet,dark brown/dark gray/rust,mottled
clayey silt to silty clay was encountered below the organic topsoil to depths ranging from 5 to
10-feet bgs. The mottling is an indicator of periodic saturation due to perched or shallow
groundwater. Moisture contents of this deposit were in excess of 30 percent and will require
substantial drying operations to achieve the optimum moisture content for compaction which
is expected to range from 15 to 20 percent.
SILT — In general, soft to stiff, saturated, brown/gray, silt with varying amounts of fine-
grained sand and clay were encountered below the clayey silt to silty clay to depths ranging
from 23 to 30-feet bgs. The soil consistency was soft in borings B-1 (12 to 24-feet bgs)and
B-2 (15 to 23-feet bgs) with a standard penetration test blowcount value (N-value) of 2.
Atterberg limits tests completed on samples retrieved from this layer had liquid limit values
ranging from 28 to 30 and plasticity index ranging from 1 to 3 which characterizes the soil as
having very low plasticity.
SILTY CLAY— Beneath the silt in borings B-2 and B-4, a layer of very stiff; saturated,
gray/light green, silty clay with seams of completely weathered gravel was encountered
between 23 and 31.5-feet bgs.Blowcount values ranged from 16 to 20.
CEMENTED SILT—A hard,moist,light brown cemented fine-grained sandy silt formation
was encountered in borings B-1,B-2,and B-3 at the terminal depth of 30 to 31.5-feet bgs.
P1475-05-01 -4- February 16,2007
GROUNDWATER—Saturated conditions due to either perched or static groundwater were
observed at depths of 6 to 12 inches bgs. Perched or shallow groundwater should be
anticipated during the majority of the year, particularly during periods of prolonged wet
weather.
5 SEISMIC HAZARDS
5.1 Landslide Hazard
Due to the gently rolling topography across the site,the landslide hazard is considered negligible. A
discussion regarding potential slope/wall instability at the east perimeter of the site during grading is
presented in subsequent sections of this report.
5.2 Crustal Faults
Based on the literature review,there are no identified faults mapped within the boundaries of the site
or within adjacent properties.Evidence was not encountered during the field investigation to suggest
the presence of faults within the property. The potential for fault displacement and associated ground
subsidence at the site is considered remote.
5.3 Soil Liquefaction or Cyclic Failure Potential
Liquefaction can cause aerial and differential settlement, lateral spreading, loss of bearing capacity,
and sudden loss in soil strength. Soils prone to liquefaction are typically loose,saturated sands and,
to a lesser degree, silt. Cyclic failure can result in similar hazards to those of liquefaction, but is a
phenomena related to low-strength, fine-grained silt and clay soils. When ground shaking
commences, the low-strength saturated soils tend to generate excess pore water pressures. The
degree of excess pore water pressure generation is largely a function of the magnitude and duration of
the ground shaking,as well as the density or consistency of the soil.
The sandy soils at the subject site were evaluated for liquefaction potential in accordance with the
procedures presented in NCEER, 1997,while the cyclic failure potential of the fine grained deposits
were assessed using procedures outlined by Boulanger and Idriss, 2004. The liquefaction resistance
of the soils was assessed using methods based on the SPT blow counts and grain size distribution data
obtained during the geotechnical field and laboratory investigation. The undrained shear strength of
the fine-grained deposits were evaluated using the results of the dilatometer soundings. The
seismically induced shear stresses at the site were assessed through the use of a standard-of-practice ...
simplified empirical procedure. The analyses were conducted using the 2003 IBC design level
earthquakes which consisted of a moment magnitude 6 for the crustal source, moment magnitude 7
for the intraslab zone,and a moment magnitude 8.5 for a subduction zone event. Peak ground surface
acceleration values of 12%, 19%, and 30% gravity (0.12g, 0.19g, and 0.30g) were used for the
subduction zone,intraslab zone,and crustal earthquakes,respectively.
P1475-05-01 -5- February 16,2007
•
Based on the results of our analyses,the liquefaction potential at the site is considered remote due to
the lack of sand deposits within the subsurface profile. However,an approximate 5-foot layer of soft
to medium stiff silt initially encountered throughout the site at depths ranging from approximately 10
to 15 feet had a factor of safety against cyclic failure near 1.0 and may experience softening due to
earthquake-induced shear strains. Due to the limited thickness of the soil layer, the effects of this
softening on building foundations is anticipated to be minor and will not affect the building's life
safety. Settlement of the zone of cyclic softening will occur after earthquake shaking has ceased.
According to very preliminary research presented by Boulanger and Idriss, a factor of safety against
cyclic failure of 1 corresponds to about 3 percent shear strain. The results of the analysis indicate a
maximum settlement of 1 to 2 inches may occur due to the design level earthquake loading.
•
5.4 Lateral Spreading
Lateral spreading is a liquefaction related seismic hazard that may adversely impact some sites.
, Areas subject to lateral spreading are underlain by liquefiable sediments and are sites that slope or are
1 flat sites adjacent to an open face. Due to the gently sloping topography and lack of open face
adjacent to the site, the potential lateral spreading hazard is considered negligible. Furthermore,it is
our opinion that
p potential lateral movements due to cyclic softening of the fine-grained deposits will
be substantially less than the magnitude of the vertical strain potential that was discussed in the
previous paragraph.
5.5 2003 International Building Code Seismic Design Parameters
The structures will be designed in accordance with the 2003 International Building Code (IBC). A
soil characteristic called"Soil Profile Type" is used to account for the effect of the underlying soil
conditions on bedrock motion. Based on the subsurface conditions encountered during the field
11 investigation, Geocon Northwest's previous geotechnical engineering work in the site vicinity, and
F the geological literature reviewed for the site, it is estimated that the material in the upper 100 feet,
determined in accordance with the procedures outlined in IBC Section 1615 "Site Categorization
Procedure", has an average bloweount (N) value between 15 and 50 and an average shear wave
velocity between 600 and 1200 feet per second. The preceding criteria characterizes the site as Soil
Profile Type D. It is recommended that the 2003 International Building Code seismic factors and
coefficients given in Table 1 at the end of this report be used for seismic design.Figure 3, shown at
the end of this report,illustrates the design response spectrum.
6 LABORATORY TESTING
Laboratory testing was performed on selected soil samples to evaluate moisture content, gradation,
consolidation characteristics,and plasticity. Visual soil classification was performed both in the field
and laboratory, in general accordance with the Unified Soil Classification System. Moisture content
determinations(ASTM D2216) were performed on soil samples to aid in classifying the soil. Grain
-r ) size analyses were performed on selected samples using procedures ASTM D1140 and ASTM D422.
i `
The plasticity index was determined in general accordance with ASTM D431.8. Consolidation testing
was completed in general accordance with ASTM D2435. Moisture contents are indicated on the
P1475-05-01 -6- February 16,2007
boring logs and are located in Appendix A of this report. Other laboratory test results for this project
are summarized in Appendix B.
7 CONCLUSIONS AND RECOMMENDATIONS
7.1 General
7.1.1 It is our opinion that the proposed construction of the Red Rock Creek Tigard Business
Center project is geotechnically feasible, provided the recommendations of this report are
followed.
7.1.2 The primary geotechnical concern associated with the project development is the
consolidation of the moderately compressible soils when subjected to the planned fill
surcharge. Settlement analyses were completed for the fills anticipated for each of the three
structures. The results indicate settlements of 1 to 2 inches within building A,2 to 4 inches
within building B, and 0.5 to 1-inch within building C. Monitoring of the settlement in fill
locations is recommended to determine when the majority of primary consolidation has
occurred prior to the construction of the buildings. Analyses and experience with similar
soils indicate that surcharge-induced settlement should be near complete after approximately
90 to 150 days.
7.1.3 The placement of structural fill should completed in staged intervals to prevent a bearing
capacity failure of the low-strength fine-grained soil below the site. Recommendations for
p fill construction are provided in Section 7.4.4.
7.1.4 Red Rock Creek will be diverted to an underground culvert as part of the overall site
development. Due to the City of Tigard building setback criteria,the north wall of Building
A and the northwest corner of Building B may be positioned over the culvert. The building
may not be supported on a shallow foundation that is positioned above or near the
underground culvert. A discussion of potential foundation support in these locations is
contained herein.
7.1.5 Retaining walls and shoring will be required around the majority of the property,the types of
which have not yet been finalized. The retaining structures along the north, south, and west
perimeters will retain structural fill soils and, potentially be subject to surcharging from
building foundations. Retaining walls in these locations may consist of a mechanically
stabilized earth (MSE) wall, or a cast in place concrete retaining wall. An excavation is
planned adjacent to the proposed SW 70th Avenue alignment. It is our opinion that the
shoring structure must provide active restraint during excavation to prevent instability issues
with the large block retaining wall on the east property margin. A shoring wall with soldier -
piles and pretensioned tie-back elements is recommended.
l ) 7.1.6 The existing organic topsoil layer is unsuitable for structural foundation or pavement support. -
Recommendations for site stripping and fill removal in structural locations are provided
herein. Stripping depths exceeding 12 inches are likely.
P1475-05-01 -7- February 16,2007
7.1.7 Recommendations regarding drainage and vapor retarders are provided in subsequent
sections of this report. Perched water was present at a depth of less than 12 inches at the time
of the field investigation. Recommendations for underslab drainage in building pads located
• at or below the existing ground surface are provided. Underslab drainage is not
recommended in locations where the building pad is founded on structural fill above the
existing ground surface elevation.
7.1.8 Instability of excavations below the groundwater surface should be anticipated. Excavations
made below the groundwater surface should be sloped or shored in conformance with OSHA
regulations. Shoring systems are typically contractor designed.
7.1.9 Wet weather construction techniques should be anticipated during the majority of theyear
due to the presence of the moisture sensitive, near-surface soils. Recommendations for wet
weather construction are provided in subsequent sections of this report. It is recommended
that the project budget include costs for wet weather site preparation, regardless of the time
of year construction is scheduled to occur. Extra costs associated with wet weather
construction may include overexcavation of soft soils, geotextile separator fabric, crushed
rock backfill,and use of crushed rock for structural fills.
7.2 Site Preparation
7.2.1 Prito beginning construction, the areas of the site to receive fill, footings or pavement
should be stripped of vegetation, il, on-engineered fill, previous subsurface
improvementsor , debris, and otherwise unsuitable material, down to firm native soil. The
majority of the site is anticipated to be underlainnby at least 12 inches of organic topsoil
which will require stripping prior to construction. Additional removal and
recompaction/replacement should be anticipated within the areas currently occupied by large
trees to provide a stable subgrade. Excavations made to remove previous subsurface
improvements should be backfilled with structural fill per Section 7.4 of this report.
7.2.2 Staging areas and haul roads specifically constructed to accommodate anticipated
construction loading must be installed by the contractor to minimize future overexcavation of
deteriorated subgrade soil. All concrete slab-on-grade and pavement sections presented in
the following sections of this report do not include an allowance for construction traffic.Past
experience suggests that 18 inches of rock underlain by a geotextile separator fabric typically
provides adequate work pad/haul road thickness. The recommended design sections may be
"overbuilt"to obtain the necessary working thickness and subsequently reduced to the design
section for possible cost savings in lieu of overexcavation of suitable subgrade soil.
Alternatively, the working surface may be incorporated into the final design.
• Recommendations for.wet weather haul roads and working pads should be implemented in
areas of the site that will experience significant construction traffic.
; 1 7.2.3 Moisture contents of near-surface soils were significantly wet of optimum at the time of the
field investigation. Due to the moisture sensitive nature of the near-surface soils, it is
recommended that earthwork-related construction take place during dry weather.
P1475-05-01
-8- February 16,2007
Recommendations for both dry weather and wet weather site preparation are provided in the
following sections. Wet weather is defined as any time o£year that adequate moisture
control cannot be obtained. Increased costs, associated with subgrade stabilization,
should be anticipated regardless of the time of year of construction.
7.2.4 Dry Weather Construction
Native soil subgrades in pavement and structural areas that have been disturbed during
stripping, cutting, or demolition operations should be scarified to a depth of at least eight-
inches. The scarified soil should be moisture conditioned as necessary to achieve the proper
moisture content,then compacted to at least 92%of the maximum dry density as determined
by ASTM D 1557. Minimum compaction for the 8 inches immediately underlying pavement
sections should be 95%0. Even during dry weather it is likely that most areas of the subgrade
will become soft or may"pump,"particularly in poorly drained areas. Soft or wet areas that
cannot be effectively dried and compacted should be prepared in accordance with Section
7.2.5.
7.2.5 Wet Weather Construction
During wet weather, defined as whenever adequate soil moisture control is not possible,inchet
maybe necessary to install a granular working blanket to support construction equipment and
provide a firm base on which to place subsequent fills and pavements. Commonly, th
working blanket consists of a bank run gravel or pit run quarry rock {six to eight
maximum size with no more than 5%o by weight passing a No. 200 sieve). A member ef
Geocon Northwest's engineering staff should be contacted to evaluate the suitability of th
material before installation.
The
workingblanket should be installed on a stripped subgrade in a single lift with trucks
end-dumping off an advancing pad of granular fill. It should be possible to strip most of the
site with careful operation of track-mounted equipment. However, during prolonged wet
weather, or in particularly wet locations, operation of this type of equipment may cause
excessive subgrade disturbance. In some areas final stripping and/or cutting may need to be
accomplished with a smooth-bucket trackhoe, or similar equipment, working from an
advancing pad of granular fill. After installation, the working blanket should be compacted
by a minimum of four complete passes with a moderately heavy static steel drum or grid
roller. It is recommended that Geocon Northwest be retained to observe granular working
blanket installation and compaction.
The working blanket must provide a firm base for subsequent fill installation and
compaction. Past experience indicates that about 18 inches of working pad is normally
required. This assumes that the material is placed on a relatively undisturbed subgrade
prepared in accordance,with the preceding recommendations. Areas used as haul routes for
' areas mayrequire a work pad thickness
heavy construction equipment or construction staging q
of two feet or more.
-9- February 16,2007
P1475-05-01
In particularly soft areas, a heavy-grade, non-degradable geotextile fabric installed on the
subgrade may reduce the thickness of working blanket required. The fabric should have a
minimum puncture resistance of 80 pounds and a minimum Mullen Burst strength of 300 psi.
Construction practices can affect the amount of work pad necessary. By using tracked
equipment and special haul roads,the work pad area can be minimized. The routing of dump
trucks and rubber tired construction equipment across the site can require extensive areas and
thicknesses of work pad. Normally, the design, installation and maintenance of a work pad
are the responsibility of the contractor.
Cement treatment may be a suitable alternative for construction traffic or wet-weather
subgrade stabilization at this site. Successful cement treatment is dependent upon moisture
content of the subgrade soils,cement percentage,weather conditions at the time of treatment,
depth of treatment, and adequate mixing and compaction of the soil and cement. Past
experience indicates that approximately 5%to 8%cement by weight,tilled to a depth of 12 to
14 inches, is typically sufficient to produce an acceptable subgrade. It is generally
recommended that cement amended soil be compacted within a four-hour window. It is
recommended that cement treated soils have a three-day,unconfined compressive strength of
250 psi. Cement treatment design is typically the responsibility of the contractor. The high
soil moisture content may require multiple cement treatment operations.
7.3 Proof Rolling
7.3.1 Regardless of which method of subgrade preparation is used (i.e., wet weather or dry
weather), it is recommended that, prior to on-grade slab construction, the subgrade or
granular working blanket be proof-rolled with a fully-loaded 10- to 12-yard dump truck.
Areas of the subgrade that pump, weave, or appear soft or muddy should be scarified, dried
and compacted, or overexcavated and backfilled with structural granular fill per Section 7.4.
If a significant length of time passes between fill placement and commencement of
construction operations,or if significant traffic has been routed over these areas,the subgrade
should be similarly proof-rolled before slab construction. It is recommended that a member
of our geotechnical engineering staff observe the proof-roll operation.
7.4 Fills
7.4.1 Structural fills should be constructed on a subgrade that has been prepared in accordance with
the recommendations in Section 7.2 of this report. Structural fills should be installed in
horizontal lifts not exceeding approximately eight inches in thickness and should be
compacted to at least 92%of the maximum dry density for the native soils,95%for imported
granular material, and should be within 2% of the optimum moisture content. Compaction
t, ) should be referenced to ASTM D1557 (Modified Proctor). The compaction criteria may be
reduced to 85%in landscape,planter,or other non-structural areas.
P1475-05-01 -10- February 16,2007
7.4.2 During dry weather when moisture control is possible, structural fills may consist of native
material,free of topsoil,debris and organic matter,which can be compacted to the preceding
specifications. However, if excess moisture causes the fill to pump or weave,those areas
should be scarified and allowed to dry. The soil should then be recompacted,or removed and
j backfilled with compacted granular fill as discussed in Section 7.2 of this report. Past
experience suggests that the native soil has a maximum dry density ranging from 110 to 115
lbs/ft at an optimum moisture content between 15 and 20 percent. Moisture contents of the
near surface native soil were typically greater than 30 percent at the time of the field
investigation. Extensive drying of the native soil will be required if used as structural fill
during construction.
7.4.3 During wet-weather grading operations, Geocon Northwest recommends that fills consist of
well-graded, angular, granular soils (sand or sand and gravel)that do not contain more than
5%material by weight passing the No. 200 sieve. In addition,it is usually desirable to limit
this material to a maximum of six inches in diameter for future ease in the installation of
utilities.
7.4.4 The site is underlain by relatively low-strength, moderately compressible soil. Current
grading plans indicate the fills up to 15 feet high will be placed along the west margin of
building B. The depth of fill decreases to the east with the excavation/fill transition zone
extending north/south through proposed buildings A and C. The fill placement will create
excess pore water pressure and,in turn,decreased strength in the underlying soil. To prevent
— a failure of the soil during fill construction, it is recommended that piezometers and
settlement cells be installed prior to the commencement of grading operations. The
piezometers will used to monitor excess porewater pressure and settlement cells to evaluate
both total and time-rate of consolidation. It our opinion that both monitoring devices are
essential for successful fill construction and to mitigate the potential for a bearing capacity
failure.
7.4.5 Preliminary analyses indicate that a maximum of 8 feet of fill may initially be placed without
a bearing failure. Settlement and pore pressure measurements should be evaluated to
determine when approximately 80 percent of consolidation has occurred prior to additional
fill placement.
7.4.6 Settlement analyses were completed for the fills planned for each of the three structures. The
results indicate settlements of 1 to 2 inches within building A,2 to 4 inches within building
B, and 0.5 to 1-inch within building C. Monitoring of the settlement in fill locations is
recommended to ensure the majority of primary consolidation has occurred prior to the
construction of the buildings.
7.4.7 The results of our engineering analyses indicate that the structural fill-induced settlement
should be near completion after approximately 90 to 150 days. Our experience with previous
�.,
surcharges in the Willamette Valley has shown that evaluating the time rate of surcharge
settlement from laboratory testing is extremely difficult. This difficulty arises from the small
dimension and uniformity of laboratory test samples compared to the larger dimensions and
P1475-05-01 -11- February 16,2007
non-uniformity of native soil(particularly with respect to drainage conditions). The time rate
of surcharge settlement may be modified as settlement and piezometer data is interpreted
during construction.
7.4.8 The time rate of settlement may be accelerated using wick (strip)drains if the construction
schedule does not allow for the settlement time estimate. Wick drains are typically spaced 7
to 10 feet on center and would extend down to a depth of approximately 30 feet. The wick
drains provide a shorter drainage path and significantly increases the time rate of settlement.
It is estimated that the installation of wick drains would reduce the time rate of settlement at
the site by 50%to 75%.
7.5 Surface and Subsurface Drainage
7.5.1 During site contouring,positive surface drainage should be maintained away from foundation
and pavement areas. Additional drainage or dewatering provisions may be necessary if soft
spots, springs,or seeps are encountered in subgrades or cut slopes. Where possible, surface
runoff should be routed independently to a storm water collection system. Surface water
should not be allowed to enter subsurface drainage systems.
7.5.2 Due to the proximity of groundwater to the surface, an underslab drainage system is
recommended for those locations where slab-on-grade subgrade elevations will be at or
below the existing surface elevation. An underslab drainage system is not recommended in
fill locations where slab on grade elevations will be greater than existing grade. It is typically
recommended that the underslab drainage system consist of 4-inch diameter PVC perforated
pipe placed within granular fill at 15-foot centers beneath the building footprint. The
granular fill should consist of a minimum 8-inch thick layer of crushed rock or gravel with
less than 5%by weight passing the No. 200 sieve. The PVC pipe should be wrapped with a
geotextile filter fabric. Figure 4 presents a cross-section of the underslab drainage system.
Final design of the underslab drainage system should be completed by the project civil
engineer,with consultation from Geocon Northwest.
7.5.3 Drainage systems should be sloped to drain by gravity to a storm sewer or other positive
outlet.
7.5.4 Drainage and dewatering systems are typically designed and constructed by the contractor.
Failure to install necessary subsurface drainage provisions may result in premature
foundation or pavement failure.
7.6 Foundations
7.6.1 Spread and perimeter foundation support for proposed structures may be obtained from the
near-surface, non-organic native soil, or from structural fill installed in accordance with our
previous recommendations. If unsuitable fill soils, or soft, saturated soil are encountered at
l! footing elevation, the unsuitable soils should be removed to firm soil. If these unforeseen
conditions are encountered, a member of Geocon Northwest's engineering staff should be
contacted to evaluate the suitability of the material before installation. Overexcavation
P1475-05-01 -12- February 16,2007
•
should be expected in cut locations across the site due to the potential for perched water near
the existing ground surface.
7.6.2 Red Rock Creek will be diverted to an underground culvert as part of the overall site
development. Due to the City of Tigard building setback criteria,the north wall of Building
A and the northwest corner of Building B will likely be positioned over the culvert. The
building may not be supported on a shallow foundation that is located within a horizontal
distance equal to the depth of the pipe(1H:1V). Potential deep foundation schemes that may
be feasible would include helical anchors, augercast piles,driven pipe, or driven H-piles. A
deep foundation using an open-hole installation system is not preferred given the presence of
near surface saturated soil and the potential for caving or"necking"of the borehole. Geocon
Northwest should be contacted for deep foundation design recommendations as the building
layout and project plans are finalized.
7.6.3 The following shallow foundation recommendations are based on maximum anticipated
column and wall loads of 150 kips and 4 kips/foot, respectively. Furthermore, it was
assumed that site grading will be limited to maximum cuts of 5 feet. Geocon Northwest
should be consulted for potential modifications to the following recommendations if either of
these assumptions are not correct.
7.6.4 Spread and perimeter footings should be at least 18 inches wide and should extend at least 18
inches below the lowest adjacent pad grade.Foundations having these minimum dimensions
that are founded on firm soils or engineered fill may be designed for an allowable soil
bearing pressure of 2,000 pounds per square foot(psf). If unsuitable soils are encountered at
footing elevation,the unsuitable soils should be overexcavated and replaced with compacted
structural fill per the recommendation of Geocon Northwest during construction.
7.6.5 A minimum of 12 inches of compacted crushed rock should be placed beneath footings
located in cut locations of buildings A and C due to the presence of near surface soft,
saturated soil. Deeper rock sections may be locally required.
7.6.6 Foundation subgrades that are anticipated to be exposed to inclement weather prior to
concrete placement should be protected to guard against future over-excavation of unsuitable
soil.
7.6.7 Gravel or lean concrete may need to be placedin the bottom of the footing excavations to
reduce soil disturbance during foundation forming and construction during wet weather.
7.6.8 The allowable bearing pressure given above may be increased by one-third for short term
transient loading,such as wind and seismic forces.
7.6.9 Lateral loads may be resisted by sliding friction and passive pressures. A base friction of
40% of the vertical load may be used against sliding. An equivalent fluid weight of 300 pcf
may be used to evaluate passive resistance to lateral loads.
• 7.6.10 Foundation settlements for the loading conditions expected for this project are estimated to
be less than one inch,with not more than one-half inch occurring as differential settlement.
P1475-05-01 -13-
February 16,2007
These values assume that site cuts will be less than 5 feet. This settlement is only attributed
to the aforementioned building loads and does not include the estimated settlement that will
occur below planned structural fills. It is recommended that building construction commence
once primary consolidation has been complete due to the structural fill placement.
7.6.11 Geocon Northwest, Inc. recommends that foundation drains be installed at or below the
elevation of perimeter footings to intercept potential subsurface water that may migrate under
the building area.
7.7 Permanent Cut and Fill Slopes
7.7.1 New permanent cut slopes should be sloped no steeper than 2H:IV. These values assume
that the slopes will be protected from erosion and that significant drainage will not occur over
the face of the slope. They further assume that no loads will be imposed within a horizontal
distance of one-half of the slope height measured from the top of the slope face. Cut slopes
should be constructed with a smooth bucket excavator to minimize subgrade disturbance.
Slope drainage may be required if springs, seeps,or groundwater are encountered.
•
7.7.2 Excavation should not be completed in the vicinity of the block retaining wall at the east
perimeter of the property without the employment of an active shoring system as described in
Section 7.9.
7.73 If permanent fills are placed in areas where ground slopes exceed 5H:1V,the fills should be
keyed and benched into existing native, undisturbed non-organic soil. Fill slopes should be
obtained by placing and compacting material beyond the design slope and then excavating
back to the desired grade or by other means that will result in a dense,compacted sloped face.
Filled slopes should not be graded steeper than 2H:1 V. The face of the fill slope should be
protected from erosion by applying vegetation or other approved erosion control material as
soon as practicable after construction. Fill compaction should be as stated in Section 7.4. If
slopes higher than ten feet above the original grade are proposed, Geocon Northwest should
be contacted to evaluate slope stability conditions.
7.8 Concrete Slabs-on-Grade
7.8.1 Subgrades in floor slab areas should be prepared in accordance with Section 7.2 of this
report. Floor slab areas should be proof-rolled with a fully loaded 10-to 12-yard dump truck
to detect areas that pump,weave,or appear soft or muddy. When detected these areas should
be overexcavated and stabilized with compacted granular fill.
7.8.2 A minimum six-inch thick layer of compacted Y4-inch minus material should be installed over
the prepared subgrade to provide a capillary barrier and to minimize subgrade disturbance
during construction. The crushed rock orgravel material should be poorly graded, angular,
and contain no more than 5%by weight passing the No.200 Sieve. The thickness of crushed
~� rock should be increased to 12 inches in cut locations where slab on grade subgrade elevation
will be less than existing grade. The underslab drainage system is only recommended in
P1475-05-01 -14- February 16,2007
planned cut locations where finished subgrade elevation will be at or lower than existing
grade.
7.8.3 A subsurface drainage system is recommended due to the potential for shallow groundwater
during the winter months. It is recommended that the underslab drainage system consist of
4-inch diameter PVC perforated pipe placed within granular fill at 15-foot centers beneath the
building footprint. The granular fill should consist of a minimum 8-inch thick layer of
crushed rock or gravel with less than 5%by weight passing the No.200 sieve. The thickness
of granular fill is in addition to the 12 inches recommended in Section 7.8.2 The PVC pipe
should be wrapped with a geotextile filter fabric. Figure 4 presents a cross-section of the
underslab drainage system.
7.8.4 A modulus of subgrade reaction of 125 pci is recommended for design.
7.8.5 The fine-grained near-surface soils at the site have high natural moisture contents and low
permeability. These characteristics indicate that high ground moisture may develop under
floor slabs during the life of the project. This moisture condition, coupled with differential
temperatures and humidity between the subgrade soils and the building interior,can create a
differential in vapor pressure between the above- and below-slab environments. The
resulting water vapor pressure differential will force migration of moisture through the slab.
This migration can result in the loosening of flooring materials attached with mastic, the
warping of wood flooring,and in extreme cases,mildewing of carpets and building contents.
To retard the migration of moisture through the floor slab, Geocon Northwest recommends
installing a 10-mil polyethylene vapor retarding membrane below the concrete slab. Care
should be exercised to ensure that any moisture accumulation on the vapor retarder surface,
from either construction activities or precipitation, should be removed prior to the concrete
pour. A concrete mix of low water/cement ratio (i.e. less than 0.48) is recommended.
Thorough curing of the concrete,using water when possible,should be provided.
7.9 Retaining Walls and Shoring
7.9.1 The information presented in the following section is a general discussion of retaining walls
and shoring that may be utilized at the site. Geocon Northwest should be contacted for
specific design recommendations as project plans are finalized and the following discussion
may be modified accordingly.
7.9.2 Retaining wall support in locations of the site that will be filled above existing grade will
likely be accomplished using a mechanically stabilized earth (MSE) retaining wall or, less
likely, a cast-in-place concrete cantilever retaining wall. The latter is not as likely due to
expected height of the retaining structure, lateral soil pressure to resist, fill soil settlement,
and potential surcharge from the new buildings. Several MSE wall-types are possible, the
majority of which are designed as a proprietary system. The MSE wall construction may be
complicated by the interference of geogrid reinforcing with underground footings and utilities
for the buildings. The construction of the walls will need to be in accordance with the
recommendations provided in Section 7.4 to prevent a bearing capacity failure. Additional
P1475-05-01 -15- February 16,2007
rock may need to be placed below retaining wall footings for subgrade stabilization. Geocon
Northwest should be contacted to provide consultation for retaining structures as project
plans become finalized.
7.9.3 Shoring support of the proposed cut along the east property margin should be accomplished
using a soldier pile and tieback system. This system provides active restraint to limit wall
movements, due to the tensioning of tiebacks prior to excavating below the current tieback
level. Limiting wall movements and limiting the removal of soil buttressing the existing
block retaining wall at the east property margin is critical in maintaining the stability of this
wall.
Soil nail excavation support is a system that consists of installing steel bars into the retained
soil to provide an in-place"retaining wall"that resists the lateral soil pressures. A soil nail
structure is a passive excavation support system as no tensioning of the steel bars(soil nails)
is typically performed before excavating to the next level. The soil nail system develops
resistance due to excavation-induced soil movements which mobilize soil-structure
interaction within the soil nail mass. It is our opinion that a soil nail wall would not provide
the degree of stability and restraint as that of a soldier pile and tieback system and may
compromise the stability of the existing block retaining wall.
7.10 Utility Excavations
7.10.1 Based on the subsurface explorations,difficult excavation characteristics are not anticipated
within the upper fine-grained soils. Perched
groundwater was encountered less than 12
inches below the existing ground surface and may created trench instability issues. Utility
trench bottoms will likely require stabilization with rock and geotextile fabric.
7.10.2 Excavations deeper than four feet, or those that encounter groundwater, should be sloped or
shored in conformance with OSHA regulations. Shoring systems are typically contractor
designed. Caving of trench sidewalls should be anticipated below the
p groundwater surface.
7.10.3 It is likely that perched groundwater will be encountered in the near surface soil during
periods of wet-weather. Therefore, excavation dewatering may be necessary if substantial
flow of groundwater is encountered. Dewatering systems are typically designed and installed
by the contractor.
7.10.4 Utilities should be bedded in sand within one conduit diameter in all directions,prior to the
placement of coarser backfill. Trench backfill should be lightly compacted within two
diameters or 18 inches, whichever is greater, above breakable conduits. The remaining
backfill,to within 12 inches of finished grade,should be compacted to 92%of the maximum
dry density as determined by ASTM D1557. In structural areas, the upper foot of backfill
should be compacted to 95%of the maximum dry density. The moisture content at the time
of compaction should be within 2%of optimum.
P1475-05-01 -16- February 16,2007
fi.11 Pavement Design
7.11.1 Near surface soil samples were evaluated to determine pavement design parameters. A CBR
( of 3 at 95% compaction and a resilient modulus of 4,500 psi were assumed for pavement
design.
7.11.2 If possible, construction traffic should be limited to unpaved and untreated roadways, or
specially constructed haul roads. If this is not possible,the pavement design should include
an allowance for construction traffic. Construction staging areas and haul roads specially
designed to accommodate anticipated construction loading must be installed by the contractor
to minimize future overexcavation of deteriorated subgrade soil. Past experience suggests 18
inches of rock underlain by a geotextile separator fabric typically provides adequate work
pad/haul road thickness. The recommended sections may be "overbuilt" to obtain the
necessary working thickness and subsequently reduced to the design section for possible cost
•
savings in lieu of overexcavation of suitable subgrade soil. Alternatively, the working
surface may be incorporated into the final design.
7.11.3 Alternate pavement designs for both asphalt and portland cement concrete(pcc)are presented
in Tables 2 and 3. Pavement designs have been prepared in accordance with accepted
AASHTO design methods. A range of pavement designs for various traffic conditions is
provided in the tables. The designs assume that the top eight inches of pavement subgrade
will be compacted to 92% of ASTM D-1557. Specifications for pavement and base course
should conform to current Oregon State Department of Transportation specifications.
Additionally, the base rock should contain no more than 5% by weight passing.a No. 200
Sieve, and the asphaltic concrete should be compacted to a minimum of 91% of ASTM
D2041.A geotextile fabric should be placed below the base rock.
7.11.4 Pavement sections were designed using AASHTO design methods, with an assumed
reliability level(R)of 90%. Terminal serviceability of 2.0 for asphaltic concrete,and 2.5 for
portland cement concrete were assumed. The 18 kip design axle loads are estimated from the
number of trucks per day using State of Oregon typical axle distributions for truck traffic and
AASHTO load equivalency factors, and assuming a 20 year design life. The concrete
designs were based on a modulus of rupture equal to 550 psi,and a compressive strength of
4000 psi. The concrete sections assume plain jointed or jointed reinforced sections with no
load transfer devices at the shoulder.
8 FUTURE GEOTECHNICAL SERVICES
The analyses, conclusions and recommendations contained in this report are based on site conditions
as they presently exist, and on the assumption that the subsurface investi;.tion locations are
representative of the subsurface conditions throughout the site. It is the nature of geotechnical work
for soil conditions to vary from the conditions encountered during a normally acceptable geotechnical
investigation. While some variations may appear slight, their impact on the performance of the
proposed improvements can be significant. Therefore, it is recommended that Geocon Northwest be
retained to observe portions of this project relating to geotechnical engineering,February tg,2007
site
P1475-05-01 -17"
preparation, grading, and compaction. This will allow correlation of observations and findings to
actual soil conditions encountered during construction and evaluation of construction conformance to
the recommendations put forth in this report.
A copy of the plans and specifications should be forwarded to Geocon Northwest so that they may be
evaluated for specific conceptual, design, or construction details that may affect the validity of the
recommendations of this report. The review of the plans and specifications will also provide the
opportunity for Geocon Northwest to evaluate whether the recommendations of this report have been
appropriately interpreted.
9 LIMITATIONS
Unanticipated soil conditions are commonly encountered during construction and cannot always be
determined by a normally acceptable subsurface exploration program. The recommendations of this
report pertain only to the site investigated and are based upon the assumption that the soil conditions
do not deviate from those disclosed in the investigation. If variations or undesirable conditions are
encountered during construction, or if the proposed construction will differ from that anticipated
herein, Geocon Northwest, Inc. should be notified so that supplemental recommendations can be
given.
This report is issued with the understanding that the owner, or his agents, will ensure that the
information and recommendations contained herein are brought to the attention of the architect and
engineer for the project and incorporated into the plans.
The findings of this report are valid as of the present date. However, changes in the conditions of a
property can occur with the passage of time,whether they are due to natural processes or the works of
man on this or adjacent properties. In addition, changes in applicable or appropriate standards may
occur, whether they result from legislation or the broadening of knowledge. Accordingly, the
findings of this report may be invalidated wholly or partially by changes outside our control.
Therefore, the conclusions and recommendations provided in this letter are subject to review should
such changes occur.
If you have any questions regarding the information herewith, or if you desire further information,
please contact the undersigned at(503)626-9889.
GEOCON NORTHWEST,INC.
Bryan Wavra,P.E. Wesle .pang, .D.,P.E.
Project Engineer President
P1475-05-01 -I8- February 16,2007
REFERENCES
Boulanger,R.W.,and Idriss,I.M.,2004,"Evaluating the Potential for Liquefaction or Cyclic Failure
of Silts and Clays," Report No. UCD/CGM-04/O1, Center for Geotechnical Modeling,
Department of Civil & Environmental Engineering College of Engineering University of
California at Davis.
Ishihara, K., 1985, "Stability of Natural Deposits During Earthquakes", Proceedings,
1Ph
International Conference on Soil Mechanics and Foundation Engineering, Vol. 1,pp. 321-
376.
National Center For Earthquake Engineering Research, 1997,"Proceedings of the NCEER Workshop
on Evaluation of Liquefaction Resistance of Soils,"Technical Report NCEER 97-0022.
Seed, H.B., and Idriss, I.M., 1982 Ground Motions and Soil Liquefaction During Earthquakes,
Earthquake Engineering Research Institute
- r-
Table 1: 2003 IBC Seismic Design Recommendations
Seismic Variable Recommended Value
Site Class D
MCE short period spectral response
accel., Sms 1.14
MCE 1-second period spectral
response accel., S 0.61
5%damped short period spectral
response accel., SDS 0.76
5%damped 1-second period
spectral response accel., SDI 0.41
Table 2: Asphalt Concrete Pavement Design
Approximate Approximate
Number of Trucks Number of 18 4o Asphalt Concrete Crushed Rock Base
per Day Design Axle Load Thickness(inches) Thickness(inches)
(each way) (1000)
Auto Parking 10 2.5 8
5 22
3.0 8
10 44 3.0 10
15 66 3.5 10
25 110 4.0 10
50 220 4.0 12
100 440 4.5 12
150 660 5.0 13
ApproximateTable 3:Portland Cement Concrete Pavement Design
Approximate
Number of Trucks Number of 18 Kip P.0 C. Crushed Rock Base
per Day Design Axle Load Thickness(inches) Thickness(inches)
(each way) (1000)
25 110 6.0 6
50 220 7.0 6
100 440 8.0 6
150 660 8.5 6
200 880 8.5 6
250 1100 9.0 6
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S.
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• 1
, -- - - ---
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, ; ;,, i r- t • ‘ -- -- -:::: ----_-: . I I NO SCALE
_
--- -„Nie.._
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1 Lt ii
GEOCON LEGEND
1 7 '''' . • -” ' ' ;,'
1 . . 1 I 7: '4-, w mo :::: 1 1r; Big APPROX LOCATION OF BORING
..„..„...____ I,
__. _
11,o
---- II I D-4. .APPROX.LOCATION OF D1LATOMETER
t X 1 WNW{ -
i — --
LI,
1 1
1 .• ----------------r-,Nnt
•
I 1 STREET Ittg ...nM1047.. rittg01.1 GEOCON
(g)
1 . W ELMHIRSI"
al..3.&war.-.or=,-...... ..—..,,,,...,--,..,..Z. n I
7 7-tf: I 1
1 NORTHWEST, INC.
GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS
I t t
I 1 1 82835W CIRRUS DRIVE-BEAVERTON,OREGON 97008-5997
PHONE 503 626.9889-FAX 503 626-8611
PROJECT NO.P1475-05-01
FIGURE 2
i SITE PLAN DATE 211612007
' P1475.0.541j162_BW/RSS
, .
i
2003 International Building Code Design Response Spectrum
Red Rock Creek
0.9 Tigard Business Center
0.8
0.7
c 0.6 -172
0
0
a 0.5
{ m
c
0. 0.4
0
s
0.3 5%of Critical Damping
c.N
0.2 -
0.1
0 .
0 0.5 1 1.5 2 2.5 3 3.5 4
Period(s)
Figure 3
•
I "
,,,,,,..,,,..sis,,,,i,_.,_,::,,,,,,s.,.. .,,,:,,,...,,,.,_,,,,.,,._
CONCRETE-SLAB,ON aGRADlE
,,_,,,,,,...,,,,,_,,,,_,_,,,..:_ss.,,,,, ,,,,,:.:.,,,.....,,_,,,,,,,,..,,,.,
i
a :fa 0 MtL VA$OR RE'F4 RDER�, A
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,,,,,,,,,,,,___,,..,"._,,,,,,,.s.,:,,,,..,,
d
El
•
8" ° 10l-15'. . •° d
I 42id • a ° ... 3/4"-0" CRUSHED ROCK ° .
• 4"
,PVC PIPE . d . d• a' 4'" PVC PIPE °
SOIL SUBGRADE
NOT TO SCALE
UNDERSLAB DRAINAGE SYSTEM
RED ROCK CREEK
TIGARD BUSINESS CENTER
2/16/2007 P1475-05-01 _ FIGURE 4
GEOCON
I
NOR THWES T
i
GEOTECHNICAL CONSULTANTS
8270 SW NIMBUS AVENUE-BEAVERTON, OREGON 97008
PHONE 503 626-9889 - FAX 503 626-8611
1
APPENDIX A
FIELD INVESTIGATION
The subsurface soil conditions at the site were determined based on the literature review, field
exploration,and laboratory investigation. The field exploration was completed on December 29th and
• 301, 2006, and consisted of four exploratory borings and four dilatometer soundings. The borings
were completed using mud rotary drilling techniques to a depth of 31.5 feet below the existing
ground surface(bgs). The dilatometer soundings encountered practical refusal at variable depths that
ranged from 17 to 33 feet bgs. The subsurface conditions encountered in the borings and dilatometer
soundings were recorded on the subsurface logs that are located in Appendix A at the end of this
report. The approximate locations of the explorations are shown in Figure 2,Site Plan.
Disturbed bag samples were collected and returned
to the laboratory for further testing. A member of
Geocon Northwest's geotechnical engineering staff logged the subsurface conditions encountered.
Subsurface logs of the conditions encountered are presented in the following pages. Both solid and
dashed contact lines indicated on the logs are inferred from soil samples and drilling characteristics
and should be considered approximate.
"
1
PROJECT NO. P1475-05-01
I- BORING B 1 g U N-
gain Z� �Z
.... ... DEPTH SAMPLE O CLASS VT
.1 SOILELEV.(MSL.) 240' DATE GOMPLETED 12-29.200fi p }MI a o'-
FEET
FEET UJ
NO. _ 7 (U�) z Ur ii a
• '' EQUIPMENT CME MUD ROTARY ° ce 92. m
4
MATERIAL DESCRIPTION
0 Approximately n organicdTOPSOIL
_I -Perched water encountered at time of drilling —
tall.
— 2 Soft,saturated,brown/gray,mottled Silty CLAY to Clayey SILT — 2 31.4
—
4 B1-1 10§1w
—
— �1041 ML Stiff,moist to wet,brown/gray,mottled Clayey SILT with some1p 31.8
— 6 B12 —
— SSA fine-grained sand
1 i — 9 34.9
- g B1-3 p -Becomes saturated,color includes black nut seams —
I il
i • ill— 10 1 5 37.2
— Bl-0 I brown/rust,mottled sandy —
Medium stiff,saturated,light
111
silt with some clay
i — 12 —ML Soft,saturated,gray,SILT wi8r varying amounts of fine grained sand SHELBY 37.3
_ Bl-4s II andGlay —
- 14 I— —
2
Bl-5 I —
— 16
— 20 — 2 35.5
Bl-6 I —
— 22
— 24
Bl-7 IPAi CIJML Medium stilt saturated,gray,Silty CLAY to Clayey SILT _ 5 42.7
— 28 44
rOr -
, 1'
1 - 30
Bl-8 j —ML Bard,moist,light brown,cemented fine-greaten Sandy SILT 54 32.2
— j
I I BORING TERMINAIII)AT 31'/2 FEET
Perched water encountered at 6-inches
P1475-05r04.GPJ
Figure A-1, "
Log of Boring B 1, Page 1 of 1
ID...SHELBY TUBE Il..STANDARD PENETRATION TEST ....DRIVE SAMPLE(UNDISTURBED)
{ =�� . ...DISTURBED OR BAG SAMPLE D•-
t 1 SAMPLE SYMBOLS
...CHUNK SAMPLE T....WATER TABLE OR SEEPAGE
NOTE: ITHE LOG OF T IS NOT WARRANTED ATO BE REPRESENTATIVE OF EON� LOCATION AND AT THE DATE INDICATED.
SUBSURFACE ONDmONS AT OTHER LOCATIONS AND TIMES.
GE0C4N
h
PROJECT NO. P1475-05-01
>- w
BORING B 2 0,F
I.R.
_
.i - DEPTH SAMPLE 5014
FEET NO• z z scs)CLASS ELEV.{MSL.) 24f DATE COMPLETED 12-29 2006 F2 o o a E2 I-
o z2., >--- oz
1 0 EQUIPMENT CME MUD ROTARY Q- m v o
i
1 0 ♦ MATERIAL DESCRIPTION
_ Approximately 12 to 24-inches of organic TOPSOIL
-Perched water encountered at time of drilling —
2 — i' CL/ML Medium
— B2-1 � stiff,wet,dark brown/dark gray,mottled Silty CLAY to
Clayey SILT — 5 30.1
4 —
—
82-2
— - ML Stiff,moist to wet,light brown/rust/light gray,mottled Clayey SILT — 10 30.0
—
,s1
8 with a trace of fine-grained sand
_.
8 B2-3 — 11 32.6
.. -Becomes saturated,color includes black/rust seams —
II
10 B24 OF1 —
— -Mediumsandy —
34.5
stiff;saturated,light brown/rust,mottled fine grained
12 — silt with some clay
._ ——ML Soft oe-to medium ined sand and a tin gray,SILT with varying amounts of
14 — graY —
B2-5 r
={ • 16 — L 4 34.5
18 8I
2-5.5 SHELBY
j —
I 20
B2-6 [ —_
-Soft,saturated,gray,fine 2 40.5
grained sandy silt with some clay
—
22 —
I
— ��
CL Stiff to very stiff,saturated,gray,Silty CLAY with interlayers of
24 —
completely weathered gravel —
I�B2-7 — 20 31.5
26 — —
28 —
! 30 —
82-8 .1ML Hard,moist,light brown,cemented fine-grained Sandy SILT 23 24.2
BORING TERIvIafAILD AT 31%khl;t
Perched water encountered at 6-inches
Figure A-2,
P1478-05-0I.GPJ
•
Log of Boring B 2, Page 1 of 1
'i SAMPLE SYMBOLS CU...SHELBY TUBE .-STANDARD PENETRATION TEST III-,DRIVE SAMPLE(UNDISTURBED)
{
1 .. ..DISTURBED OR BAG SAMPLE
Q...CHUNK SAMPLE T.,WATER TABLE OR SEEPAGE
NOTE THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED.
IT IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
GEOCON
PROJECT NO. P1475-05-01
BORING B 3 °L.
DEPTH Q SOIL �F- w t�j w
IN u.
SAMPLE i o CLASS ELEV.(MSL.) 229' DATE COMPLETED 12-29-2006 z p a z
FEET NO' F j (Uses) Wa m
EQUIPMENT CME MUD ROTARY
{ MATERIAL DESCRIPTION
0Appr
�� -Perched
atelywater 12 to 24nt inches of organic ling -
-Perched water encountered at time of'drilling
2 ►�1'{g► CL/ML Medium stiff,wet,dark brown/dark gray/rust,mottled Silty CLAY to _ 4 31.4
1 B3-1 Irpo
/ Clayey SILT4 -
09 30.9
B3-2 1040 --- -Becomes stiff -
6 -
ML Stiff,saturated,light gray/light brown/rust,mottled Clayey SILT with _ 10 33.6
I 8 B3-3 1� 04 fine-grained sand
-
S ��
10 o SHELBY 44.6
I B3-4 ��I - _
I I ML Medium std saturated,dark gray/black,SILT with fine sand/caly -
1211
B3-4.5 and organics - 4 84.9
{ 14 -6-inch seam of woody debris and additional decayed organics
5 48.2
j16 B3-5 -Medium stiff,saturated,gray,silt with fine-grained sand and clay, -
trace organics -
18
20 • 11 34.6
B3 6 _ saturated,gray,silt with fine-grained sand,clay and trace -
I organics
22
24
-
i
B3-7
26 -Becomes soft to medium stiff,no organics
28
30
B3-8 =",' ——— Hard,moist,dark gray,weathered rock or gravel(no sample recovery) 50/2"
BORING TERMINATED AT 31%FEET
Perched water encountered at 6-inches
Pi476-(15.01-L-0PJ
Figure A-3,
Log of Boring B 3, Page 1 of 1
CLI"'SHELBY TUBE
STANDARD PENETRATION TEST ...DRIVE SAMPLE(UNDISTURBED)
SAMPLE SYMBOLS
~}
DISTURBED OR BAG SAMPLE D -.
CHUNK SAMPLE .Z...WATER TABLE OR SEEPAGE
,.. �
NOTE:THE��NOTLOG OF SUBSURFACE
CONDITIONS
SHOWN
HEREON
APPUES
RFACE ONLYCONDAT
THENS AT SPECIFIC
LOCATIONS OR AND CH LOCATION AND AT THE DATE INDICATED.
OF GEOCON
I.
PROJECT NO. P1475-05-01
1- ►
ce W
BORING B 4 z
DEPTH
0 1-
IN
SAMPLE .. LU al
< SOIL O z tl 12' m p_
p CLASS g a,,..co Z LL Z
FEET NO x z ELEV.(MSL.) 215' DATE COMPLETED 12-29-2006 �? w ~
i r- m (uses)
w O p a IW-
n O ZUT� >- Oz
x EQUIPMENT CME MUD ROTARY a cc m in v
I
0 I g MATERIAL DESCRIPTION
- Approximately 12 to 24 inches of organic TOPSOIL
I Perched water encountered at time of drilling -
2
- J B4-1qk
CL/ML Stiff,wet,dark brown/dark gray,mottled Silty CLAY to Clayey SILT
- 8 29.8
4
-
-
B4-2
- I2 31.2
6 - / -Stiff,moist,light brown/brown/light gray,mottled silty clay to clayey -
silt
- S -• B4-3
- 13 28.9
la r -Color change to gray
-
- 10 - B 4-4 r-.n_. - ,.
ML Stiff,saturated,gray,fine-grained Sandy SILT with a trace of organics _ 8 41.5
- 12 -
)34 4.5
SHELBY 38.7
- 14 - -
-
_ _ 1345 [ -
16 - • _ - 8 37.7
16 .
-
- 20 - `— ML Soft to medium stiff;saturated,gray,SILT with fine-grained sand ----
IBob -- 3 • 35.4
j - 22 -
I - -
- 24 B4-7
S-HELBY 32.6
j. - 26 -, ' -
-
-
I Pri,"--
- 28 T CL Very stiff,saturated,light gray/light green,Silty CLAY _ ———-
- 30 - -
- - .
B4-8
- 16 28.7
tY ,....
r .
BORING TERM/NAM)AT 31%FEET
A Perched water encountered at 6-inches
Figure A4, J P1475 t15-01.GPJ
Log of Boring B 4, Page 1 of 1
• ...SAMPLE SYMBOLS ...SHELBY TUBE F...STANDARD PENETRATION TEST III...DRIVE SAMPLE(UNDISTURBED)
-(. ' .. ...DISTURBED OR BAG SAMPLE Q...CHUNK SAMPLE 1...WATER TABLE OR SEEPAGE
NOTE: THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED.
IT IS NDT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES.
GE000N
.. .
•I .
' 1 .
0 0..1.. , . . , ,c,re."........,1.,1,:1)1..................... '.,.DTigardiiatRedo. Bei tatRUteosormiesenkt,eeorCs.uvsr.nael Sounding
eie.I c.ins on got er
t t1 1000 000
C
-V
10
10,
...e.
.c.--. 15 .......41 .44)
ti .......,— .
0 ...
....
00 •
1
f...% %
20 :
e? .
.
f. I
.... . ---Modulus(tsf)
I *),.... .
. cc
/...' / — —Id •
( 1
25 ) '
1/4•\ 41\
I
I .
i -
1 . 30 '
•
•
I .
I • .
f
Red Rock Creek
Tigard Business Center
Ditatometer Sounding #2
Dilatometer Values
0.1
10 100 1000 10000
p
S
or
``� a
t.
se 'It
~r
4 r
••;1
•
C
1
r s-•-
10 o:
t
`,0 r
�� �r
S�rt *+
15 r0 IC
)
"' ell
r 4
Z ...-"- +•
•
20 Lf ~r
7 '
_ i
00' ti•'4
c.0' 1
25 Modulus (tsf) _
;+
r -- -Id
I'
30 ... A -'
(1.1 t.
a
a
` 35
t f
T--' — mmmmMMMMMMMMMMM.......................1._ _ _ '
1
Red Rock Creek
Tigard Business Center
Dilatometer Sounding #3
Dilatometer Values
• 10 100 1000
• 00,1 . , . , ,• 1
j e
N .Z
f •
5
`..
r
// 1-
a !
10
1 of
i r
C
15 C.,�.. j
)
,`dam..
Q ♦� +Pti
20 i I
r •
•
1 rt a
25 •.1
%1
•
30 �� Modulus(tsf)
.. ., _ Kd
P
-- --id
r
} 35
L
•
•
Red Rock Creek
Tigard Business Center
Dilatometer Sounding #4 •
Dilatometer Values
0.1 1 10 100 1000
0 . .
•
•
•
r
I -�
2 f • .
'
r �
M
4 •
•
r s!
s
j rs
6
'
8 },
15
10
0s
110,0
12 �•��- -�
1.
•
lY
14 -
��
sr 1
r. or
•
16 ,� Modulus(tsf)
- - - Kd
•
- -Id
18 -
APPENDIX B
LABORATORY TESTING
Laboratory tests were performed in accordance with generally accepted test methods of the American
Society for Testing and Materials(ASTM)or other suggested procedures. Selected soil samples were
1 tested for their moisture content and gradation. Moisture contents are indicated on the boring logs in
Appendix A. The results of the remaining laboratory tests performed are presented in following
pages.
TABLE B-1
SUMMARY OF PLASTICITY INDEX TEST RESULTS
ASTM D4318
Sample Depth Liquid Plastic Plasticity USCS
Number (ft) Limit Limit Index Classfication
Bl-5 15-16.5 29 27 2 ML
B2-5.5 17-19 28 26 2 ML
B3-7 25-26.5 28 27 1 ML
— B4-7 24-26 30 27 3 ML
r
Consolidation Test(ASTM D 2435)
Project Tigard Business Center Boring Number B2-5.5
Project Number P1475-05-01 Sample Number 5.5
Description of Soil Gray Silt Depth of Sample 17-19
Initial Final
Moisture Content 32.8 24.5
Void Ratio 0.64 0.48
Tigard Business Park
Consolidation Test
B4-7
Depth=25 feet
0.6500
0.6000
0.5500
0
II 'r
�
P
o.5ooa
0.4500
IIIIIII
0.4000
1000 1000 6 1 I 100000
` pressure(psf)
1
i
f Consolidation Test(ASTM D 2435)
Project Tigard Business Center Boring Number 64-7
Project Number P1475-05-01 Sample Number 7
Description of Soil Gray Silt Depth of Sample 24-26
j
Initial Final
Moisture Content 34.9 29.5
Void Ratio 0.83 0.64
•
Tigard Business Park
Consolidation Test
B4 7
Depth=25 feet
i
0.8500
1
0.8000 1111111
0.7500
I
0.7000
s.+
o
0.6500 mug , ■■n 11111111•I
I
I
::::
.
0.5000
i 1000 10000 100000
pressure(psf) •
A