HomeMy WebLinkAboutStudies APPLICANT 7/12/2021Geotechnical Engineering Report
Ridgeview Gardens
5050 Main Street
Springfield, Oregon
Prepared for:
Ridgeview Gardens, LLC
7070 SW Baylor Street
Portland, Oregon 97223
September 22, 2020
PBS Project 73415.002
PBS
4412 5 CORBETT AVENUE
PORTI.ANO, OR 97239
503.248.1939 MAIN
866.727.0140 FAX
PBSUSA.COM
PBS
Geotechnical Engineering Report
Ridgeview Gardens
5050 Main Street
Springfield, Oregon
Prepared for.
Ridgeview Gardens, LLC
7070 SW Baylor Street
Portland, Oregon 97223
September 22, 2020
PBS Project 73415.002
Prepared by
Dave Eibert, GIT
Staff Geologist
02020 PBS Engineering and Environmental Inc
Reviewed by
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Ryan White, PE, GE
Principal/Geotechnical Engineering Group Manager
4412 5 CORBETT AVENUE, PORTLAND, OR 97239 • 503.248,1939 MAIN • 866 727,0140 FAX • PBSUSA. COM
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KiU8r/iowGardens, LLC
Springfield, Oregon
Table of Contents
1 INTRODUCTION ..............................................................................................................................................
I
i1General ...--.............,.............----~..~.�.~.--,—............,��.........^1
12Purpose and Scope —....~......~................._-.~........_...-.......................1
111Literature and Records Review ...............................................................................
1
1.22Subsurface Explorations .............................................................................................................................................
1
12]Field Infiltration Testing ..............................................................................
............................................................... 1
124Soils Testing ....................................................................................................................................................................
1
{2.5Geotechnical Engineering Analysis ........................................................................................................................
1
1l6Report Preparation ...........................................................................................................................................
........... 1
1.3Project Understanding ..............................................................................................................................
...........1
IS[[E CONDITIONS ...........................................................................................................................................
2
11Surface Description ...... ............................................................................................................................................................
2
Z2Geologic Setting ..........—...............—..,......~....-'-_........,,..~...........-2
111Local Geology .................................................................................................................................................................
3
2.3 Subsurface Conditions .................... ...............................................................................................................
,^^,~~,~,~}
2.4GroVDdwaiec.....-...........................-_.,......
.. .........................................................4
2.5Infiltration Testing ...........................................................................................................................
......................................... 4
3 CONCLUSIONS AND RECOMMENDATIONS ................................................................................................
5
I16e0iecknica|Design Considerations .................................................................................................................................
5
32Shallow Foundations .................................... .........��...-�-��.........��.�--.—......~..,..,.�5
31]Minimum Footing Widths and Design Bearing Pressure. .............................................................................
5
]l2Footing Embedment Depths ...............................................................................................................................
. �. 5
]2.}Footing Preparation ....................................................................................................................................
...... ~�^5
l24Lateral Resistance ..........................................................................................................................................................
5
3.3 Floor Slabs ..-.��.��........-..........��.��.....-�...........~.�..--.~~....~....,~�....6
34Seismic Design Considerations .................................................. ....... . ..................
............................................ ........... 6
3.4.1LoJe'Kased Seismic Design Parameters .............................................................................................................
6
]42Liquefaction Potential .......................................... .......................................................................................
............... 7
3JGround Moisture
7
l51General ................ --....��.���.��.............—_..............��--..��......7
l52Perimeter Footing Drains ..--......................~...~...~.--.—.~...............--..7
333Vapor Flow Retarder ....................................................................................................................................................
7
l6Pavement Design ............................................... ....................................................................................................................
-7
4CONSTRUCTION RECOMMENDATIONS ......................................................................................................
8
41Site Preparation ....................................................................................................... .
. .'......................................... ............... 8
411P000(no|ling/SVbg0deVerification ........................................................................................................................
8
412Wet/Freezing Weather and Wet Soil Conditions .............................................................................................
8
41.3Dry Weather Conditions .............................................................................................................................................
y
4.14Compacting Test Pit Locations ......~...........-.....................—.............,.....9
4.2 Excavation ,.�.,...�.��.....�....~...~....--��.��.���.���.�.-�--�.�...�....�9
43Structural Fill
9
/i3.10A'Siie Soil ...................................................................................................................
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Geotechnical Engineering Report Ridgeview Gardens
Ridgeview Gardens, LLC Springfield, Oregon
4.3.2
Borrow Material...........................................................................................................................................................
10
4.3.3
Select Granular Fill......................................................................................................................................................
10
4.3.4
Crushed Aggregate Base..........................................................................................................................................
10
4.3.5
Utility Trench Backfill.................................................................................................................................................
10
4.3.6
Stabilization Material.................................................................................................................................................
11
5 ADDITIONAL SERVICES AND CONSTRUCTION OBSERVATIONS............................................................ 11
6 LIMITATIONS................................................................................................................................................ 11
7 REFERENCES.................................................................................................................................................. 13
Supporting Data
TABLES
Table 1. Infiltration Test Results
Table 2. USDA Hydrologic Soil Group Parameters
Table 3. 2019 OSSC Seismic Design Parameters
Table 4. Minimum AC Pavement Sections
FIGURES
Figure 1. Vicinity Map
Figure 2. Site Plan
Appendix A: Field Explorations
Table A-1. Terminology Used to Describe Soil
Table A-2. Key to Test Pit and Boring Log Symbols
Figures Al—A8. Logs for Test Pits TP -1 through TP -8
Appendix B: Laboratory Testing
Figure B1. Atterberg Limits Test Results
Figure B2. Summary of laboratory Data
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Geotechnical Engineering Report Ridgeview Gardens
Ridgeview Gardens, LLC Springfield, Oregon
1 INTRODUCTION
1.1 General
This report presents results of PBS Engineering and Environmental Inc. (PBS) geotechnical engineering services
for the proposed housing development located at 5050 Main Street in Springfield, Oregon (site). The general
site location is shown on the Vicinity Map, Figure 1. The locations of PBS' explorations in relation to existing
and proposed site features are shown on the Site Plan, Figure 2.
1.2 Purpose and Scope
The purpose of PBS' services was to develop geotechnical design and construction recommendations in
support of the planned new development. This was accomplished by performing the following scope of
services.
1.2.1 Literature and Records Review
PBS reviewed various published geologic maps of the area for information regarding geologic conditions and
hazards at or near the site.
1.2.2 Subsurface Explorations
PBS excavated eight test pits within the proposed development site to depths of up to 12 feet below the
existing ground surface (bgs). The test pits were logged and representative soil samples collected by a member
of the PBS geotechnical engineering staff, Interpreted test pit logs are included as Figures Al through A8 in
Appendix A, Field Explorations.
1.2.3 Field Infiltration Testing
Two open -hole, falling -head field infiltration tests were completed in test pits TP -2 and TP -7 at depths of 5.5
and 6.0 feet bgs, respectively. Infiltration testing was monitored by PBS geotechnical engineering staff.
1.2.4 Soils Testing
Soil samples were returned to our laboratory and classified in general accordance with the Unified Soil
Classification System (ASTM D2487) and/or the Visual -Manual Procedure (ASTM D2488). Laboratory tests
included natural moisture contents, grain -size analyses, and Atterberg limits. Laboratory test results are
included in the exploration logs in Appendix A, Field Explorations; and in Appendix B, Laboratory Testing,
1.2.5 Geotechnical Engineering Analysis
Data collected during the subsurface exploration, literature research, and testing were used to develop site-
specific geotechnical design parameters and construction recommendations.
1.2.6 Report Preparation
This Geotechnical Engineering Report summarizes the results of our explorations, testing, and analyses,
including information relating to the following:
• Field exploration logs and site plan showing approximate exploration locations
• Laboratory test results
• Infiltration test results
• Groundwater considerations
• Shallow foundation design recommendations:
o Minimum embedment
o Allowable bearing pressure
g^^moi September 22, 2020
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Geotechnical Engineering Report Ridgedew Gardens
Ridgeview Gardens, LLC Springfield, Oregon
o Estimated settlement (total and differential)
o Sliding coefficient
• Earthwork and grading, cut, and fill recommendations:
o Structural fill materials and preparation, and reuse of on-site soils
o Wet weather considerations
o Utility trench excavation and backfill requirements
o Temporary and permanent slope inclinations
• Seismic design criteria in accordance with the 2019 Oregon Structural Specialty Code (OSSC)
• Slab and pavement subgrade preparation recommendations
• Recommended asphalt concrete (AC) pavement sections
1.3 Project Understanding
PBS understands current plans include developing the approximately 2 -acre site with three, 3 -story, wood -
frame apartment buildings, a single -story office/storage building, and associated paved parking areas and
utilities. Preliminary plans include disposing of stormwater through shallow drywells.
2 SITECONDITIONS
2.1 Surface Description
The site is a trapezoidal parcel of land, extended to the north along its western margin, and is currently
sparsely vegetated. It is bordered to the north by Riverbend Elementary School and a local church, to the south
and west by commercial businesses, and to the east by residential properties. The site is accessed by a north -
south driveway between the two southern businesses off of Main Street.
Review of available Google Earth elevation data shows that the site is relatively flat, with elevations ranging
from approximately 500 to 502 feet above mean sea level (amsl) (DOGAMI, 2020a). The surrounding area is
generally flat in all directions except where shallow river terraces generated from river meanders of the
McKenzie, Middle, and Coastal forks of the Willamette River have reworked valley sediments. Outside of these
river valleys the deeply eroded foothills of the Cascade mountains rise from the valley margins.
2.2 Geologic Setting
The site is located along the southern margin of the Willamette Valley, a tectonic depression within the
physiographic province of the Puget -Willamette Lowland that separates the Cascade Range from the Coast
Range, and extends from the Puget Sound, Washington to Eugene, Oregon (Yeats et al., 1996). The Puget -
Willamette Lowland is situated along the Cascadia Subduction Zone (CSZ) where oceanic rocks of the Juan de
Fuca Plate are subducting beneath the North American Plate, resulting in deformation and uplift of the Coast
Range and volcanism in the Cascade Range. Northwest -trending faults accommodating clockwise rotation of
the North American Plate are found throughout the Puget -Willamette lowland (Brocher et al., 2017; USGS,
2020).
Structural features of the southern Willamette Valley include the north-northeast oriented Eocene age
Harrisburg anticline, numerous northwest- and northeast -trending normal faults, as well as northwest -
trending strike slip faults (McClaughry et al., 2010). Similar structures exist outside of the valley and in the
surrounding Coast Range and Cascade Range. These structures are responsible for deforming and offsetting
basement rocks and are recognized as inactive tectonic features.
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Geotechnical Engineering Report Ridgeview Gardens
Ridgeview Gardens, LLC Springfield, Oregon
The Willamette Valley forms a broad alluvial basin, with the Willamette River draining northward along the axis
of the valley. Extensive valley infilling and catastrophic flooding related to the Missoula Floods during the
Quaternary has subsequently buried older Oligocene and Eocene sedimentary and volcanic basement rocks
and concealed many of the structural features throughout the valley (Wiley, 2006). Willamette River tributaries
exiting the Coast Range and Cascade Range have contributed to terrace formations and broad alluvial fans
protruding from range fronts into the valley.
The Willamette and McKenzie Rivers enter the Willamette Valley south and east of the city of Springfield,
respectively, and form a confluence north of the city of Eugene. These rivers continue to deposit sediments and
reworked older sediments throughout much of the Eugene/Springfield area. Both rivers are positioned within
prominent meander belts. Modern flood plains are readily distinguishable within the DOGAMI LiDAR data and
meandered freely prior to urban development.
The southern Willamette Valley terminates south of Springfield and Eugene where the Cascade and coastal
mountains converge. Along the eastern margin of the valley, Oligocene volcanic rocks of the Cascade
mountains begin to emerge from younger valley sediments that are interfingered with alluvial fans and debris
fans formed from Cascade detritus. West of the Willamette Valley, accreted Eocene to Oligocene deep marine
sedimentary sequences and subaerial volcanism is encountered.
2.2.1 Local Geology
The site is mapped as underlain by Quaternary terrace and fan deposits (McClaughry at al., 2010). The terrace
and fan deposits are described as deeply dissected, unconsolidated to semi -consolidated deposits of gravel,
sand, silt, and clay from the upper alluvial terraces along the Willamette, Coast Fork of the Willamette, and
McKenzie Rivers. These deposits form a broad, once continuous, dissected fan that stretches from the southern
Willamette Valley to the Santiam River in the central Willamette Valley.
2.3 Subsurface Conditions
The site was explored by excavating eight test pits, designated TP -1 through TP -8, to depths of up to 12 feet
bgs. The excavation was performed by Dan J. Fischer Excavating, Inc., of Forest Grove, Oregon, using a Case
508 Super -N backhoe equipped with a 24 -inch toothed bucket.
PBS has summarized the subsurface units as follows:
FILL: Variable fill consisting well -graded gravel and areas of clayey gravel were encountered
at the site from the ground surface to approximately 1 to 2 feet bgs,
LEAN CLAY (CL): Lean clay with sand to sandy lean clay was encountered under the overlying fill to
depths of approximately 4.5 to 5.5 feet bgs. The clay was generally stiff to hard with
unconfined compressive strengths between 1.0 to 4.5 tsf, brown, moist, exhibited low to
medium plasticity, and contained fine- to medium -grained sand.
SANDY SILT (ML): Sandy silt was encountered at the site in test pits TP -3 and TP -6 at depths of 3.5 to 5
bgs and 3 to 5.5 feet bgs, respectively. The material was hard with unconfined
compressive strengths of 4.5 tsf, light brown, moist, exhibited low plasticity, and
contained fine- to medium -grained sand.
WELL -GRADED Well -graded gravel was encountered in all test pits below the fine-grained material at
GRAVEL with SILT approximately 6 feet bgs to the termination depth. The material was generally gray to
(GW -GM): brown, moist to wet, contained fine to coarse rounded gravels, fine- to coarse-grained
sand, and varying amounts of silt.
A 3 -foot -thick zone of silty sand with gravel was encountered within the gravel layer in
TP -4 at a depth of 6.5 feet.
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Geotechnical Engineering Report Ridgeview Gardens
Ridgmew Gardens, LLC Springfield, Oregon
2.4 Groundwater
Static groundwater was encountered during our explorations at approximately 11 feet bgs in several test pits.
Based on a review of regional groundwater elevation mapping of the Eugene -Springfield area, the approximate
groundwater elevation is 480 to 490 feet amsl (USGS, 1973). This groundwater elevation, and the surface
elevation of the site, are consistent with the groundwater levels encountered during our exploration. Please
note that groundwater levels can fluctuate during the year depending on climate, irrigation season, extended
periods of precipitation, drought, and other factors.
2.5 Infiltration Testing
PBS completed two open -hole, falling -head infiltration tests in test pits TP -2 and TP -7 at a depth of 5.5 and 6.0
feet bgs, respectively. The infiltration testing was conducted within the bottom of the test pit exploration. The
test pit was filled with water to achieve an approximately 1 -foot -high water head. After a period of saturation,
the height of the water level in the test pit was then measured initially and at regular, timed intervals. Results of
our field infiltration testing are presented in Table 1.
Table 1. Infiltration Test Results
based on field infiltration rate
The infiltration rates listed in Table 1 are not permeabilities/hydraulic conductivities, but field -measured rates,
and do not include correction factors related to long-term infiltration rates. The design engineer should
determine the appropriate correction factors to account for the planned level of pre-treatment, maintenance,
vegetation, siltation, etc. Field -measured infiltration rates are typically reduced by a minimum factor of 2 to 4
for use in design.
Soil types can vary significantly over relatively short distances. The infiltration rates noted above are
representative of one discrete location and depth. Installation of infiltration systems within the layer the field
rate was measured is considered critical to proper performance of the systems. At the time of this report, the
locations of proposed stormwater facilities were not certain. Once the facility locations are finalized, additional
infiltration testing should be completed at these locations and depths.
The United States Department of Agriculture (USDA) categorizes soils in four hydrologic soil groups, A through
D, and are designated mainly by particle size and hydraulic conductivity. Table 3 below shows general
characteristics of each group as they are identified by the USDA.
Table 2. USDA Hydrologic Soil Group Parameters
Hydrologic Soil Group
Soil Properties A B C D
Saturated Hydraulic
Conductivity (k) k>5.67 1.42<k<5.67 0.14<k<lA2 k<0.14
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Field Measured
Recommended
Test Location
Depth (feet bgs)
Infiltration Rate
Soil Classification
Hydrologic Soil
(in/hr)
Group*
Well -graded
TP -2
5.5
4.5
B
GRAVEL (GW)
TP -7
6.0
21
Well -graded GRAVEL
B
with silt (GW -GM)
based on field infiltration rate
The infiltration rates listed in Table 1 are not permeabilities/hydraulic conductivities, but field -measured rates,
and do not include correction factors related to long-term infiltration rates. The design engineer should
determine the appropriate correction factors to account for the planned level of pre-treatment, maintenance,
vegetation, siltation, etc. Field -measured infiltration rates are typically reduced by a minimum factor of 2 to 4
for use in design.
Soil types can vary significantly over relatively short distances. The infiltration rates noted above are
representative of one discrete location and depth. Installation of infiltration systems within the layer the field
rate was measured is considered critical to proper performance of the systems. At the time of this report, the
locations of proposed stormwater facilities were not certain. Once the facility locations are finalized, additional
infiltration testing should be completed at these locations and depths.
The United States Department of Agriculture (USDA) categorizes soils in four hydrologic soil groups, A through
D, and are designated mainly by particle size and hydraulic conductivity. Table 3 below shows general
characteristics of each group as they are identified by the USDA.
Table 2. USDA Hydrologic Soil Group Parameters
Hydrologic Soil Group
Soil Properties A B C D
Saturated Hydraulic
Conductivity (k) k>5.67 1.42<k<5.67 0.14<k<lA2 k<0.14
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Geotechnical Engineering Report Ridgaview Gardens
Ridgeview Gardens, LLC Springfield, Oregon
3 CONCLUSIONS AND RECOMMENDATIONS
3.1 Geotechnical Design Considerations
The subsurface conditions at the site consist of a generally thin, continuous layer of undocumented fill,
underlain by fine-grained clay overlying gravel. Based on our observations and analyses, conventional
foundation support on shallow spread footings is feasible for the proposed new building bearing on
undisturbed native material; however, footings should not be supported on undocumented fill. Excavation with
conventional equipment is feasible at the site. Depending on design elevation of proposed stormwater
facilities at the site, groundwater elevations observed at the time of our explorations may control the final
design elevation. Infiltration rates within fine-grained materials at the site will likely be significantly lower than
the gravel in which infiltration testing was performed.
3.2 Shallow Foundations
Shallow spread footings bearing on native fine-grained soils may be used to support loads associated with the
new structures, provided the recommendations in this report are followed. Footings should not be supported
on undocumented fill.
3.2.1 Minimum Footing Widths and Design Bearing Pressure
Continuous wall and isolated spread footings should be at least 18 and 24 inches wide, respectively. Footings
should be sized using a maximum allowable bearing pressure of 2,500 pounds per square foot (psf). This is a
net bearing pressure and the weight of the footing and overlying backfill can be disregarded in calculating
footing sizes. The recommended allowable bearing pressure applies to the total of dead plus long-term live
loads. Allowable bearing pressures may be increased by one-third for seismic and wind loads.
Footings will settle in response to column and wall loads. Based on our evaluation of the subsurface conditions
and our analysis, we estimate post -construction settlement will be less than 1 inch for the column and
perimeter foundation loads. Differential settlement will be on the order of one-half of the total settlement.
3.2.2 Footing Embedment Depths
PBS recommends that all footings be founded a minimum of 18 inches below the lowest adjacent grade. The
footings should be founded below an imaginary line projecting upward at a 1HAV (horizontal to vertical) slope
from the base of any adjacent, parallel utility trenches or deeper excavations.
3.2.3 Footing Preparation
Excavations for footings should be carefully prepared to a neat and undisturbed state. A representative from
PBS should confirm suitable bearing conditions and evaluate all exposed footing subgrades. Observations
should also confirm that loose or soft materials have been removed from new footing excavations and
concrete slab -on -grade areas. Localized deepening of footing excavations may be required to penetrate loose,
wet, or deleterious materials.
PBS recommends a layer of compacted, crushed rock be placed over the footing subgrades to help protect
them from disturbance due to foot traffic and the elements. Placement of this rock is the prerogative of the
contractor; regardless, the footing subgrade should be in a dense or stiff condition prior to pouring concrete.
Based on our experience, approximately 4 inches of compacted crushed rock will be suitable beneath the
footings.
3.2.4 Lateral Resistance
Lateral loads can be resisted by passive earth pressure on the sides of footings and grade beams, and by
friction at the base of the footings. A passive earth pressure of 250 pounds per cubic foot (pcf) may be used for
MENgl7,�r September 022
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Geotechnical Engineering Report Ridgeview Gardens
Ridgeview Gardens, LLC Springfield, Oregon
footings confined by native soils and new structural fills. The allowable passive pressure has been reduced by a
factor of two to account for the large amount of deformation required to mobilize full passive resistance.
Adjacent floor slabs, pavements, or the upper 12 -inch depth of adjacent unpaved areas should not be
considered when calculating passive resistance. For footings supported on native soils or new structural fills,
use a coefficient of friction equal to 0.35 when calculating resistance to sliding. These values do not include a
factor of safety (FS).
3.3 Floor Slabs
Satisfactory subgrade support for building floor slabs can be obtained from the native silty sand to sandy silt
or gravel fill subgrade prepared in accordance with our recommendations presented in the Site Preparation,
Wet/Freezing Weather and Wet Soil Conditions, and Select Granular Fill sections of this report. A minimum 6 -
inch -thick layer of imported granular material should be placed and compacted over the prepared subgrade.
Thicker aggregate sections may be necessary where undocumented fill is present, soft/loose soils are present
at subgrade elevation, and/or during wet conditions. Imported granular material should be composed of
crushed rock or crushed gravel that is relatively well graded between coarse and fine, contains no deleterious
materials, has a maximum particle size of 1 inch, and has less than 5 percent by dry weight passing the US
Standard No. 200 Sieve.
Floor slabs supported on a subgrade and base course prepared in accordance with the preceding
recommendations may be designed using a modulus of subgrade reaction (k) of 150 pounds per cubic inch
(Pci).
3.4 Seismic Design Considerations
3.4.1 Code -Based Seismic Design Parameters
The current seismic design criteria for this project are based on the 2019 Oregon Structural Specialty Code
(OSSC). Based on subsurface conditions encountered during our exploration, Site Class D is appropriate for use
in design. The seismic design criteria, in accordance with the 2019 OSSC, are summarized in Table 3.
Table 3. 2019 OSSC Seismic Design Parameters
Parameter
Short Period
1 Second
Maximum Credible Earthquake Spectral Acceleration
Ss = 0.64 g
St = 0.37 g
Site Class
D
Site Coefficient
F, = 1.29
F„ = 1.93*
Adjusted Spectral Acceleration
S,s = 0.83 g
Smi = **
Design Spectral Response Acceleration Parameters
Sos = 0.55 g
Sol = **
McsG Peak Ground Acceleration
PGA = 0.30 g
Site Amplification Factor at PGA
FPGA = 1.3
Site Modified Peak Ground Acceleration
PGA,, = 0.39 g
g= Acceleration due to gravity
• This value of F. shall only be used to calculate T,
•" Site-specific site response analysis is not required for structures on Site Class D sites with S, greater than or equal to 0.2, provided the
value of the seismic response coefficient C, is determined by Eq. (12.8-2) for values of T s 1.51, and taken as equal to 1.5 times the value
computed in accordance with either Eq. (12.8-3) for TL >_ T> IST, or Eq. (12.8-4) for T> Ti.
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Geotechnical Engineering Report Ridgeview Gardens
Ridoeview Gardens, LLC Springfield, Oregon
3.4.2 Liquefaction Potential
Liquefaction is defined as a decrease in the shear resistance of loose, saturated, cohesionless soil (e.g., sand) or
low plasticity silt soils, due to the buildup of excess pore pressures generated during an earthquake. This
results in a temporary transformation of the soil deposit into a viscous fluid. Liquefaction can result in ground
settlement, foundation bearing capacity failure, and lateral spreading of ground.
Based on a review of the Oregon Statewide Geohazard Viewer (HazVu), the site is not located in a liquefaction
hazard area. Based on the soil types and relative density/consistency of site soils encountered in our
explorations, our current opinion is that the risk of structurally damaging liquefaction settlement at the site is
low.
3.5 Ground Moisture
3.5.1 General
The perimeter ground surface and hard-scape should be sloped to drain away from all structures and away
from adjacent slopes. Gutters should be tight -lined to a suitable discharge and maintained as free-flowing. All
crawl spaces should be adequately ventilated and sloped to drain to a suitable, exterior discharge.
3.5.2 Perimeter Footing Drains
Due to the relatively low permeability of surficial site soils and the potential for perched groundwater at the
site, we recommend perimeter foundation drains be installed around all proposed structures.
The foundation subdrainage system should include a minimum 4 -inch diameter perforated pipe in a drain rock
envelope. A non -woven geotextile filter fabric, such as Mirafi 140N or equivalent, should be used to completely
wrap the drain rock envelope, separating it from the native soil and footing backfill materials. The invert of the
perimeter drain lines should be placed approximately at the bottom of footing elevation. Also, the subdrainage
system should be sealed at the ground surface. The perforated subdrainage pipe should be laid to drain by
gravity into a non -perforated solid pipe and finally connected to the site drainage stem at a suitable location.
Water from downspouts and surface water should be independently collected and routed to a storm sewer or
other positive outlet. This water must not be allowed to enter the bearing soils.
3.5.3 Vapor Flow Retarder
A continuous, impervious barrier must be installed over the ground surface in the crawl space and under slabs
of all structures. Barriers should be installed per the manufacturer's recommendations.
3.6 Pavement Design
The provided pavement recommendations were developed based on our experience with similar
developments and references the associated Oregon Department of Transportation (ODOT) specifications for
construction.
The minimum recommended pavement section thicknesses are provided in Table 4. Depending on weather
conditions at the time of construction, a thicker aggregate base course section could be required to support
construction traffic during preparation and placement of the pavement section.
Table 4. Minimum AC Pavement Sections
Traffic Loading
AC (inches)
Base Course (inches)
I Subgrade
Pull -in Car Parking Only
2.5
6
Stiff subgrade as verified by
PBS personnel'
PBS September 22, 2020
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Geotechnical Engineering Report
Ridoeview Gardens, LLC
Ridgeview Gardens
Springfield, Oregon
Traffic Loading
AC (inches)
Base Course (inches)
Subgrade
Drive Lanes and Access
3
9
Stiff subgrade as verified by
Roads
PBS personnel'
Subgrade must pass proofroll
The asphalt cement binder should be selected following ODOT SS 00744.11 — Asphalt Cement and Additives.
The AC should consist of 1/z -inch hot mix asphalt concrete (HMAC) with a maximum lift thickness of 3 inches.
The AC should conform to ODOT SS 00744.13 and 00744.14 and be compacted to 91 percent of the maximum
theoretical density (Rice value) of the mix, as determined in accordance with ASTM D2041.
Heavy construction traffic on new pavements or partial pavement sections (such as base course over the
prepared subgrade) will likely exceed the design loads and could potentially damage or shorten the pavement
life; therefore, we recommend construction traffic not be allowed on new pavements, or that the contractor
take appropriate precautions to protect the subgrade and pavement during construction.
If construction traffic is to be allowed on newly constructed road sections, an allowance for this additional
traffic will need to be made in the design pavement section.
4 CONSTRUCTION
4.1 Site Preparation
Construction of the proposed structure will involve clearing and grubbing of the existing vegetation or
demolition of possible existing structures. Demolition should include removal of existing pavement, utilities,
etc., throughout the proposed new development. Underground utility lines or other abandoned structural
elements should also be removed. The voids resulting from removal of foundations or loose soil in utility lines
should be backfilled with compacted structural fill. The base of these excavations should be excavated to firm
native subgrade before filling, with sides sloped at a minimum of IRIV to allow for uniform compaction.
Materials generated during demolition should be transported off site or stockpiled in areas designated by the
owner's representative.
4.1.1 Proofrolling/Subgrade Verification
Following site preparation and prior to placing aggregate base over shallow foundation, floor slab, and
pavement subgrades, the exposed subgrade should be evaluated either by proofrolling or another method of
subgrade verification. The subgrade should be proofrolled with a fully loaded dump truck or similar heavy,
rubber -tire construction equipment to identify unsuitable areas. If evaluation of the subgrades occurs during
wet conditions, or if proofrolling the subgrades will result in disturbance, they should be evaluated by PBS
using a steel foundation probe. We recommend that PBS be retained to observe the proofrolling and perform
the subgrade verifications. Unsuitable areas identified during the field evaluation should be compacted to a
firm condition or be excavated and replaced with structural fill.
4.1.2 Wet/Freezing Weather and Wet Soil Conditions
Due to the presence of fine-grained clay and sands in the near -surface materials at the site, construction
equipment may have difficulty operating on the near -surface soils when the moisture content of the surface
soil is more than a few percentage points above the optimum moisture required for compaction. Soils
disturbed during site preparation activities, or unsuitable areas identified during proofrolling or probing,
should be removed and replaced with compacted structural fill.
Site earthwork and subgrade preparation should not be completed during freezing conditions, except for mass
excavation to the subgrade design elevations.
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Ridgeview Gardens, LLC Springfield, Oregon
Protection of the subgrade is the responsibility of the contractor. Construction of granular haul roads to the
project site entrance may help reduce further damage to the pavement and disturbance of site soils. The actual
thickness of haul roads and staging areas should be based on the contractors' approach to site development,
and the amount and type of construction traffic. The imported granular material should be placed in one lift
over the prepared undisturbed subgrade and compacted using a smooth -drum, non -vibratory roller. A
geotextile fabric should be used to separate the subgrade from the imported granular material in areas of
repeated construction traffic. The geotextile should meet the specifications of COOT SS Section 02320.10 and
SS 02320.20, Table 02320-1 for soil separation. The geotextile should be installed in conformance with COOT
SS Section 00350 — Geosynthetic Installation.
4.1.3 Dry Weather Conditions
Clay soils should be covered within 4 hours of exposure by a minimum of 4 inches of crushed rock or plastic
sheeting during the dry season. Exposure of these materials should be coordinated with the geotechnical
engineer so that the subgrade suitability can be evaluated prior to being covered.
4.1.4 Compacting Test Pit Locations
The test pit excavations were backfilled using the excavator bucket and relatively minimal compactive effort;
therefore, soft spots can be expected at these locations. We recommend that the relatively uncompacted soil
be removed from the test pits to a depth of at least 3 feet below finished subgrade elevation in pavement
areas and to full depth in building areas. The resulting excavation should be backfilled with structural fill.
4.2 Excavation
The near -surface soils at the site can be excavated with conventional earthwork equipment. Sloughing and
caving should be anticipated. All excavations should be made in accordance with applicable Occupational
Safety and Health Administration (OSHA) and state regulations. The contractor is solely responsible for
adherence to the OSHA requirements. Trench cuts should stand relatively vertical to a depth of approximately
4 feet bgs, provided no groundwater seepage is present in the trench walls. Open excavation techniques may
be used provided the excavation is configured in accordance with the OSHA requirements, groundwater
seepage is not present, and with the understanding that some sloughing may occur. Trenches/excavations
should be flattened if sloughing occurs or seepage is present. Use of a trench shield or other approved
temporary shoring is recommended if vertical walls are desired for cuts deeper than 4 feet bgs. If dewatering is
used, we recommend that the type and design of the dewatering system be the responsibility of the
contractor, who is in the best position to choose systems that fit the overall plan of operation.
4.3 Structural Fill
The extent of site grading is currently unknown; however, PBS estimates that cuts and fills may be on the order
of up to 2 feet. Structural fill should be placed over subgrade that has been prepared in conformance with the
Site Preparation and Wet/Freezing Weather and Wet Soil Conditions sections of this report. Structural fill
material should consist of relatively well -graded soil, or an approved rock product that is free of organic
material and debris, and contains particles not greaterthan 4 inches nominal dimension.
The suitability of soil for use as compacted structural fill will depend on the gradation and moisture content of
the soil when it is placed. As the amount of fines (material finer than the US Standard No. 200 Sieve) increases,
soil becomes increasingly sensitive to small changes in moisture content and compaction becomes more
difficult to achieve. Soils containing more than about 5 percent fines cannot consistently be compacted to a
dense, non -yielding condition when the water content is significantly greater (or significantly less) than
optimum.
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Ridgeview Gardens
Springfield, Oregon
If fill and excavated material will be placed on slopes steeper than 5H:1 V, these must be keyed/benched into
the existing slopes and installed in horizontal lifts. Vertical steps between benches should be approximately 2
feet.
4.3.1 On -Site Soil
On-site soils encountered in our explorations are generally suitable for placement as structural fill during
moderate, dry weather when moisture content can be maintained by air drying and/or addition of water. Due
to the moderate plasticity of the clay soils at the site, even during dry conditions, regular, frequent aerating of
soils will be required to reach the optimum moisture for compaction. Due to the time required to moisture
condition site soils and the seasonal limitations, reuse of on-site soils may not be economically feasible. The
fine-grained fraction of the site soils are moisture sensitive, and during wet weather, these soils may become
unworkable because of excess moisture content.
If used, the material should be placed in lifts with a maximum uncompacted thickness of approximately 8
inches and compacted to at least 92 percent of the maximum dry density, as determined by ASTM D1557
(modified proctor).
4.3.2 Borrow Material
Borrow material for general structural fill construction should meet the requirements set forth in ODOT SS
00330.12 — Borrow Material. When used as structural fill, borrow material should be placed in lifts with a
maximum uncompacted thickness of approximately 8 inches and compacted to not less than 92 percent of the
maximum dry density, as determined by ASTM D1557.
4.3.3 Select Granular Fill
Selected granular backfill used during periods of wet weather for structural fill construction should meet the
specifications provided in ODOT SS 00330.14—Selected Granular Backfill. The imported granular material
should be uniformly moisture conditioned to within about 2 percent of the optimum moisture content and
compacted in relatively thin lifts using suitable mechanical compaction equipment. Selected granular backfill
should be placed in lifts with a maximum uncompacted thickness of 8 to 12 inches and be compacted to not
less than 95 percent of the maximum dry density, as determined by ASTM DI 557.
4.3.4 Crushed Aggregate Base
Crushed aggregate base course below floor slabs, spread footings, and asphalt concrete pavements should be
clean crushed rock or crushed gravel that contains no deleterious materials and meets the specifications
provided in ODOT SS 02630.10 — Dense -Graded Aggregate, and has less than 5 percent by dry weight passing
the US Standard No. 200 Sieve. The crushed aggregate base course should be placed in lifts with a maximum
uncompacted thickness of 8 to 12 inches and be compacted to at least 95 percent of the maximum dry density,
as determined by ASTM D1557.
4.3.5 Utility Trench Backfill
Pipe bedding placed to uniformly support the barrel of pipe should meet specifications provided in ODOT SS
00405.12 — Bedding. The pipe zone that extends from the top of the bedding to at least 8 inches above utility
lines should consist of material prescribed by ODOT SS 00405.13 — Pipe Zone Material. The pipe zone material
should be compacted to at least 90 percent of the maximum dry density, as determined by ASTM D1557, or as
required by the pipe manufacturer.
Under pavements, paths, slabs, or beneath building pads, the remainder of the trench backfill should consist of
well -graded granular material with less than 10 percent by dry weight passing the US Standard No. 200 Sieve,
ON PBS 10 September
73415.002
Geotechnical Engineering Report Ridgeview Gardens
Ridgeview Gardens, LLC Springfield, Oregon
and should meet standards prescribed by ODOT SS 00405.14— Trench Backfill, Class B or D. This material
should be compacted to at least 92 percent of the maximum dry density, as determined by ASTM D1557 or as
required by the pipe manufacturer. The upper 2 feet of the trench backfill should be compacted to at least 95
percent of the maximum dry density, as determined by ASTM D1557. Controlled low -strength material (CLSM),
ODOT SS 00405.14 —Trench Backfill, Class E, can be used as an alternative.
Outside of structural improvement areas (e.g., pavements, sidewalks, or building pads), trench material placed
above the pipe zone may consist of general structural fill materials that are free of organics and meet ODOT SS
00405.14— Trench Backfill, Class A. This general trench backfill should be compacted to at least 90 percent of
the maximum dry density, as determined by ASTM D1557, or as required by the pipe manufacturer or local
jurisdictions.
4.3.6 Stabilization Material
Stabilization rock should consist of pit or quarry run rock that is well -graded, angular, crushed rock consisting
of 4- or 6 -inch -minus material with less than 5 percent passing the US Standard No. 4 Sieve. The material
should be free of organic matter and other deleterious material. ODOT SS 00330.16 — Stone Embankment
Material can be used as a general specification for this material with the stipulation of limiting the maximum
size to 6 inches.
5 ADDITIONAL SERVICES AND CONSTRUCTION OBSERVATIONS
Inmost cases, other services beyond completion of a final geotechnical engineering report are necessary or
desirable to complete the project. Occasionally, conditions or circumstances arise that require additional work
that was not anticipated when the geotechnical report was written. PBS offers a range of environmental,
geological, geotechnical, and construction services to suit the varying needs of our clients.
PBS should be retained to review the plans and specifications for this project before they are finalized. Such a
review allows us to verify that our recommendations and concerns have been adequately addressed in the
design.
Satisfactory earthwork performance depends on the quality of construction. Sufficient observation of the
contractor's activities is a key part of determining that the work is completed in accordance with the
construction drawings and specifications. We recommend that PBS be retained to observe general excavation,
stripping, fill placement, footing subgrades, and/or pile installation. Subsurface conditions observed during
construction should be compared with those encountered during the subsurface explorations. Recognition of
changed conditions requires experience; therefore, qualified personnel should visit the site with sufficient
frequency to detect whether subsurface conditions change significantly from those anticipated.
6 LIMITATIONS
This report has been prepared for the exclusive use of the addressee, and their architects and engineers, for
aiding in the design and construction of the proposed development and is not to be relied upon by other
parties. It is not to be photographed, photocopied, or similarly reproduced, in total or in part, without express
written consent of the client and PBS. It is the addressee's responsibility to provide this report to the
appropriate design professionals, building officials, and contractors to ensure correct implementation of the
recommendations.
The opinions, comments, and conclusions presented in this report are based upon information derived from
our literature review, field explorations, laboratory testing, and engineering analyses. It is possible that soil,
rock, or groundwater conditions could vary between or beyond the points explored. If soil, rock, or
PBJ S Pas
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ON 11 s Project 73415.002
Geotechnical Engineering Report Ridgedew Gardens
Ridgevim Gardens, LLC Springfield, Oregon
groundwater conditions are encountered during construction that differ from those described herein, the client
is responsible for ensuring that PBS is notified immediately so that we may reevaluate the recommendations of
this report.
Unanticipated fill, soil and rock conditions, and seasonal soil moisture and groundwater variations are
commonly encountered and cannot be fully determined by merely taking soil samples or completing
explorations such as test pits. Such variations may result in changes to our recommendations and may require
additional funds for expenses to attain a properly constructed project; therefore, we recommend a contingency
fund to accommodate such potential extra costs.
The scope of work for this subsurface exploration and geotechnical report did not include environmental
assessments or evaluations regarding the presence or absence of wetlands or hazardous substances in the soil,
surface water, or groundwater at this site.
If there is a substantial lapse of time between the submission of this report and the start of work at the site, if
conditions have changed due to natural causes or construction operations at or adjacent to the site, or if the
basic project scheme is significantly modified from that assumed, this report should be reviewed to determine
the applicability of the conclusions and recommendations presented herein. Land use, site conditions (both on
and off site), or other factors may change over time and could materially affect our findings; therefore, this
report should not be relied upon after three years from its issue, or in the event that the site conditions
change.
ONPBS September 22, 2020
� J 12 PBS Project 73415.002
Geotechnical Engineenng Report Ridgeview Gardens.
Ridgeview Gardens, LLC Springfield, Oreqon
7 REFERENCES
ASCE. (2016). Minimum Design Loads for Buildings and Other Structures (ASCE 7-16).
Brocher, T. M., Wells, R. E., Lamb, A. P., and Weaver, C. S. (2017). Evidence for distributed clockwise rotation of
the crust in the northwestern United States from fault geometries and focal mechanisms. Tectonics, Vol. 36,
No.S, pp. 787-818.
DOGAMI. (2020a). [Interactive Map]. DOGAMI Liter Viewer. Oregon Department of Geology and Mineral
Industries, Oregon Lidar Consortium. https://gis.dogami.oregon,gov/maps/lidawiewer/.Accessed
September 2020.
DOGAMI. (2020). [Interactive Map]. Oregon HazVu: Statewide Geohazards Viewer. Oregon Department of
Geology and Mineral Industries, Earthquake Liquefaction. https://gis.dogami.oregon.gov/maps/hazvu/.
Accessed September 2020.
McClaughry, J. D., Wiley, T. J., Ferns, M. L., and Madin, I. P. (2010). Digital geologic map of the southern
Willamette Valley, Benton, Lane, Linn, Marion, and Polk Counties, Oregon. DOGAMI Open -File Report 0-
10-03.
ODOT SS. (2018). Oregon Standard Specifications for Construction. Salem, Oregon. Oregon Department of
Transportation.
OSSC. (2019). Oregon Structural Specialty Code (OSSC). Based on IBC. (2018 International Building Code).
Country Club Hills, IL Intemational Code Council, Inc.
US Geological Survey (2020). Quaternary fault and fold database for the United States, accessed September
2020 from USGS website: https://earthquake.usgs.gov/hazards/gfaults/.
US Geological Survey (1973). Ground Water in the Eugene -Springfield Area, Southern Willamette Valley,
Oregon. United States Geological Survey. Geological Survey Water -Supply Paper No. 2018.
Wiley, T.1. (2006). Preliminary Geologic Map of the Albany Quadrangle, Linn, Marion, and Benton Counties,
Oregon. Oregon Department of Geology and Mineral Industries (DOGAMI), open -file report 0-06-26.
Yeats, R. S., Graven, E. P., Werner, K. S., Goldfinger, Chris, and Popowski, T. A. (1996). Tectonics of the
Willamette Valley, Oregon, in Rogers, A. M., Walsh, T. 1., Kockelman, W. 1., and Priest, G. R., eds., Assessing
earthquake hazards and reducing risk in the Pacific Northwest: US Geological Survey Professional Paper
1650, v. 1, p. 183-222.
ON��J�+ September 22, 2020
13 PBS Project 73415.002
Geotechnical -Engineering Report
The Geoprofessional Business Association (GBA)
has prepared this advisory to help you — assumedly
a client representative — interpret and apply this
geotechnical -engineering report as effectively as
possible. In that way, you can benefit from a lowered
exposure to problems associated with subsurface
conditions at project sites and development of
them that, for decades, have been a principal cause
of construction delays, cost overruns, claims,
and disputes. If you have questions or want more
information about any of the issues discussed herein,
contact your GBA-member geotechnical engineer.
Active engagement in GBA exposes geotechnical
engineers to a wide array of risk -confrontation
techniques that can be of genuine benefit for
everyone involved with a construction project.
Understand the Geotechnical -Engineering Services
Provided for this Report
Geotechnical -engineering services typically include the planning,
collection, interpretation, and analysis of exploratory data from
widely spaced borings and/or test pits. Field data are combined
with results from laboratory tests of soil and rock samples obtained
from field exploration (if applicable), observations made during site
recomrais since, and historical information to form one or more models
of the expected subsurface conditions beneath the site. Local geology
and alterations of the site surface and subsurface by previous and
proposed construction are also important considerations. Geotechnical
engineers apply their engineering training, experience, and judgment
to adapt the requirements of the prospective project to the subsurface
modelbe). Estimates are made ofthe subsurface conditions that
will likely be exposed during construction as well as the expected
performance offoundations and other structures being planned and/or
affected by construction activities.
The culmination ofthese geotechnical -engineering services is typically a
geotechnicatengineering report providing the data obtained, a discussion
ofthe subsurface model(s), the engineering and geologic engineering
assessments and analyses made, and the recommendadons developed
to satisfy the given requirements of the project. These reports maybe
tided investigations, explorations,studies, assessments, or evaluations.
Regardless ofthe tide used, the geotechnical -engineering report is an
engineering interpretation of the subsurface conditions within the context
ofthe project and does not represent a close examination, systematic
inquiry, or thorough investigation of all site and subsurface conditions.
Geotechnical -Engineering Services are Performed
for Specific Purposes, Persons, and Projects,
and At Specific Times
Geotechnical engineers structure their services to meet the specific
needs, goals, and risk management preferences of their clients. A
geotechnicafeagineering study conducted for a given civil engineer
will =likely meet the needs of a civil -works constructor or even a
different civil engineer. Because each geotechnical -engineering study
is
unique, each gameclsnical-engineering report is unique, prepared
solely for the client.
Likewise, geotechnical -engineering services are performed for a specific
project and purpose. For example, it is unlikely that a geotechnical -
engineering study for a refrigerated warehouse will be the same as
one prepared for a parking garage; and a few borings drilled during
a prelimmary study to evaluate site feasibility will Rat be adequate to
develop geotechnical design recommendations for the project
Do rsF rely on this report ifyour geotechnical engineer prepared in
• for a different client;
• for a different project or purpose;
• for a different site (that may or may not include all or a portion of
theoriginal site); or
• before important events occurred at the site or adjacent to it;
e.g., man-made events like construction or environmental
remediation, or natural events like floods, droughts, earthquakes,
or groundwater fluctuations.
Note, too, the reliability of a geotechnical -engineering report can
be affected by the passage of time, because of factors like changed
subsurface condition,; new or modified rade,, standards, or
regulations; or new techniques or tools. If yea are the least bit uncertain
about the continued reliability of this report, contact your geotechnical
engineer before applying the recommendations in it. A minor amount
of additional testing or analysis after the passage of time - if any is
required at all - could prevent major problems.
Read this Report in Full
Costly problems have occurred because those relying on a geotechnical -
engineering report did not read the report in its entirety. Doipt rely on
an executive summary. Do fad read selective elements only. Read and
refer to the report in full.
You Need to Inform Your Geotechnical Engineer
About Change
Your geotechnical engineer considered unique, project -specific factors
when developing the scope of study behind this report and developing
the confirmation -dependent recommendations the report conveys.
Typical changes that could erode the reliability of this report include
these that affect:
• the site's size or shape;
the elevation, configmation, location, orientation,
function or weight of the proposed structure and
the desired performance criteria;
• the composition of the design ream; or
• projectownership.
As a general rode, always inform your geotechnical engineer of project
or site changes - even minor ones - and request an assessment of their
impact. Die geotechnical engineer who prepared this report cannot accept
responsibility or liability for problems that arise because the geotechnical
engineer was not informed about developments the engineer otherwise
would have considered.
Most of the "Findings" Related in This Report
Are Professional Opinions
Before construction begins, geotechnlcal engineers explore a site's
subsurface using various sampling and testing procedures. Geotechnical
engineers can observe actual subsurface conditions only at those specific
locations where sampling and testing is performed. 'the data derived from
that sampling and testing were reviewed by your geotechnical engineer,
who then applied professional judgement to form opinions about
subsurface conditions throughout the site. Actual sitew ale -subsurface
conditions may differ- maybe significantly- Ikon these indicated in
this report. Confront that risk by retaining your geotechnical engineer
to serve on the design team through project completion to obtain
informed guidance quickly, whenever needed.
This Report's Recommendations Are
Confirmation -Dependent
'the recommendations included in this report - including any options or
alternatives - are confirmation -dependent. In other words, they are net
hand, because the geotechnical engineer who developed them relied heavily
on judgement and opinion to do so. Your geotechnical engineer can fmalve
the remrmnemimkgs only after observing actual subsnfae, conditions
exposed during construction. If through observation Yom geotechnlal
engineer confirms that the conditions assumed to exist actually do exist,
the recommendations can be relied upon, assuming no other changes have
occurred the gentechnical engineer who prepared this report cannot assume
rerynnobility or llabililyfirr, confirmation -dependent recommendations id you
fail to retain that engineer to pe arm contraction observation.
This Report Could Be Misinterpreted
Other design professionals' misinterpretation ofgeotechnical-
engineerhng reports has resulted in costly problems. Confront that risk
by having your geotechnical engineer serve as a continuing member of
the design team, to:
• confer with other design -team members;
help develop specifications;
• review pertinent elements of other design professionals' plans and
specifications; and
• beavailablewhenevergeotechnical-mgineeringguidmaisneeded.
You should also confront the risk ofemistructors misinterpreting this
report Do so by retaining your geoteclmical engineer to participate in
prebid and preconstruction conferences and to perform construction -
plane observations.
Give Constructors a Complete Report and Guidance
Some owners and design professionals mistakenly believe they can shift
unanticipated -subsurface -conditions liability to constructors by limiting
the information they provide for bid preparation. To help prevent
the costly, contentious problems this practice has caused include the
complete geotechnical -engineering report, along with any attachments
or appendices, with your contract documents, but be certain to note
conspicuously that you've included the material for information purposes
only 7b avoid misunderstanding, you may also want to note that
"informational purpose.," means constructors have no right to rely on
the interpretational, opinions, conclusions, or recommendations in the
report,
rrai
Be ten that constructors know they may learn about specific
project requirements, including options selected from the report, only
from the design drawings and specifications. Remind constructors
that they may perform their own studies if they want be and be sure to
allow enough time to permit them to do so. Only then might you be in
a position to give constructors the information available to you, while
requiring then+ to at least share some of the financial responsibilities
stemming from unanticipated conditions. Conducting prebid and
precanstmctlon conferences can also be valuable in this respect.
Read Responsibility Provisions Closely
Some client representatives, design professionals, and constructors do
not realize that geotechnical engineering is far less exact than other
engineering disciplims. This happens in part because soil and rock on
project sites are typically heterogeneous and not manufactured materials
with well-defined engineering properties like steel and concrete. That
lack ofuadersmnding has nattured unrealistic expectations that have
resulted in disappointments, delays, cost overruns, claims, and disputes.
To confront that risk, geotechnical engineers commonly include
explanatory provisions in their reports. Sometimes labeled "limitations,"
many of these provisions indicate where geotechnical engine
responsibilities begin and end, to help others recognize their own
responsibilities and risks. Read these provisions closely. Ask questions.
Yomgeotechnical engineer should respond fully and frankly.
Geoenvironmental Concerns Are Not Covered
The personnel, equipment, and techniques used to perform an
environmental study - e.g., a "phase -one" or'phao-twd' environmental
site assessmertt- differ significantly from those used to perform a
geotechnical -engineering study. For that crown, a geotechnical -engineering
report does not usually provide environmental findings, conclusions, or
recommendations; e.g., about the likelihood of encountering underground
storage tanks or regulated contaminants. Unanticipated subsurface
environmental problems have led to project failmrs. Ifyou have not
obtained your own environmental information shout the project site,
ask your geotechxucal consultant for a recommendation on how to find
environmental risk -management guidance.
Obtain Professional Assistance to Deal with
Moisture Infiltration and Mold
While your geotechnical engineer may have addressed groundwater,
water infiltration, or similar issues in this report, the engineer's
services were not designed, conducted, or intended to prevent
migration of moisture - including water vapor - from the soil
through building slabs and walls and into the building interim, where
it can cause mold growth and material -performance deficiencies.
Accordingly, proper implementation of the geotechnical engineer's
reuommendatiorse will not of itself be sufficient to prevent
moisture infiltration. Confront the risk of moisture infiltration by
including building -envelope or mold specialists on the design team.
Geotechnical engineers are not building- envelope or mold specialists.
GEOPROFESSIONAL
BUSINESS
RFs ASSOCIATION
Telephone: 301/565-2733
e-mail: info@geoprofessional.org wwwgeoprofessional.org
arivion(GEA). Duplkotiohmprodmarn, or copying of am document, he whale or in pan, by my mems whanoventn u coneav
anal. Examiawg qu.Or, fmovaee exaaaing wording from the documents pension! only with decalvaa wain Perm on of
book review. Only members of GRA may use the document or its woseling as a complement o or el an eleven[ of s report a any Aired
rotoes this dsomentwitMut bemg u case membermWd be a— [hag negligent or intemimul(Gaudelent) misrepresentation.
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Appendix A
Field Explorations
Geotechnical Engineering Report Ricigevlew Gardens
Ridgeview Gardens, LLC Springfield, Oregon
Appendix A: Field Explorations
Al GENERAL
PBS explored subsurface conditions at the project site by excavating test pits to depths of up to 12 feet bgs
on September 2, 2020. The approximate locations of the explorations are shown on Figure 2, Site Plan. The
procedures used to advance the test pits, collect samples, and other field techniques are described in detail in
the following paragraphs. Unless otherwise noted, all soil sampling and classification procedures followed
engineering practices in general accordance with relevant ASTM procedures. "General accordance" means that
certain local drilling/excavation and descriptive practices and methodologies have been followed.
A2 TEST PITS
A2.1 Excavation
Test pits were excavated using a Case 580 excavator equipped with a 24 -inch -wide, toothed bucket provided
and operated by Dan J. Fisher Excavating, Inc., of Forest Grove, Oregon. The test pits were observed by a
member of the PBS geotechnical staff, who maintained a detailed log of the subsurface conditions and
materials encountered during the course of the work.
A2.2 Sampling
Representative disturbed samples were taken at selected depths in the test pits. The soil samples were
examined by a member of the PBS geotechnical staff and sealed in plastic bags for further examination.
A2.3 Test Pit Logs
The test pit logs show the various types of materials that were encountered in the excavations and the depths
where the materials and/or characteristics of these materials changed, although the changes may be gradual.
Where material types and descriptions changed between samples, the contacts were interpreted. The types of
samples taken during excavation, along with their sample identification number, are shown to the right of the
classification of materials. The natural water (moisture) contents are shown farther to the right. Measured
seepage levels, if observed, are noted in the column to the right.
A3 MATERIAL DESCRIPTION
Initially, samples were classified visually in the field. Consistency, color, relative moisture, degree of plasticity,
and other distinguishing characteristics of the soil samples were noted. Afterward, the samples were
reexamined in the PBS laboratory, various standard classification tests were conducted, and the field
classifications were modified where necessary. The terminology used in the soil classifications and other
modifiers are defined in Table A-1, Terminology Used to Describe Soil.
ONPBS A-1 Pas Project 73415002
Table A-1
�►
PBS
Terminology Used to Describe Soil
loft
Soil Descriptions
Soils exist in mixtures with varying proportions of components. The predominant soil, i.e., greater than 50 percent based on
total dry weight, is the primary soil type and is capitalized in our log descriptions (SAND, GRAVEL, SILT, or CLAY). Smaller
percentages of other constituents in the soil mixture are indicated by use of modifier words in general accordance with the
ASTM D2488-06 Visual -Manual Procedure. "General Accordance" means that certain local and common descriptive practices
may have been followed. In accordance with ASTM D2488-06, group symbols (such as GP or CH) are applied on the portion of
soil passing the 3 -inch (75mm) sieve based on visual examination. The following describes the use of soil names and modifying
terms used to describe fine- and coarse-grained soils.
Fine -Grained Soils (SO% or greater fines passing 0.075 mm, No. 200 sieve)
The primary soil type, i.e., SILT or CLAY is designated through visual -manual procedures to evaluate soil toughness, dilatency,
dry strength, and plasticity. The following outlines the terminology used to describe fine-grained soils, and varies from ASTM
D2488 terminology in the use of some common terms.
Plasticity Plasticity
Primary soil NAME, Symbols, and Adjectives
Description Index (PI)
SILT (ML 8t MH) CLAY {CL & CH) _ ORGANIC SOIL {OL 8c OH)
SILT Organic SILT Non -plastic 0-3
SILT Organic SILT Low plasticity 4-10
SILT/Elastic SILT Lean CLAY --Organic SILT/ Organic CLAY Medium Plasticity 10-20
Elastic Sl LT Lean/Fat CLAY 0 rg -an i c CLAY High Plasticity 20-40
Elastic SILT Fat CLAY Organic CLAY Very Plastic >40
Modifying terms describing secondary constituents, estimated to 5 percent increments, are applied as follows:
Description %Composition
With Sand%Sand—>%Gravel
__a___nd__<_.__.%Gravel __--- ----15% to 25% plus No. 200
With Gravel %S
Sandy % Sand _> % Gravel
----------------- -<30% to 50% plus No. 200
Gravelly %Sand<%Gravel
Borderline Symbols, for example CH/MH, are used when soils are not distinctly in one category or when variable soil
units contain more than one soil type. Dual Symbols, for example CL -ML, are used when two symbols are required in
accordance with ASTM D2488.
Soil Consistency terms are applied to fine-grained, plastic soils (i.e., PI > 7). Descriptive terms are based on direct
measure or correlation to the Standard Penetration Test N -value as determined by ASTM D1586-84, as follows. SILT soils
with low to non -plastic behavior (i.e., PI < 7) may be classified using relative density.
Consistency Unconfined Compressive Strength
SPT N -value
Term tsf
Vertsoft___ Less than 2 Less than 0.25 Less than 24
Soft 2-4 — 0.5 24-48
_0.25
Medium stiff 5-8 0.5 — 1.0 48-96
Stiff 9-15 10 2.0 96-192
Verystiff 16-30 20 —_40 192-383
Hard Over 30 Over 4.0 Over 383
�_ Table A-1
Terminology Used to Describe Soil
2 oft
Soil Descriptions
Coarse - Grained Soils (less than 50% fines)
Coarse-grained soil descriptions, i.e., SAND or GRAVEL are based on the portion of materials passing a 3 -inch (75mm) sieve.
Coarse-grained soil group symbols are applied in accordance with ASTM D2488-06 based on the degree of grading, or
distribution of grain sizes of the soil. For example, well -graded sand containing a wide range of grain sizes is designated SW;
poorly graded gravel, GP, contains high percentages of only certain grain sizes. Terms applied to grain sizes follow.
Material NAME Particle Diameter
Inches Millimeters
SAND (SW or SP) 0.003-0.19 0.075-4.8
GRAVEL(GWor GP) 0.19-3 4.8-75
Additional Constituents:
Cobble 3-12 75-300
Boulder 12-120 300-3050
The primary soil type is capitalized, and the fines content in the soil are described as indicated by the following examples.
Percentages are based on estimating amounts of fines, sand, and gravel to the nearest 5 percent. Other soil mixtures will
have similar descriptive names.
Example: Coarse -Grained Soil Descriptions with Fines
>S% to < 15%fines (Dual Symbols) z15%to < 50%fines
Well graded GRAVEL with silt: GW -GM Silty GRAVEL: GM
Poorly graded SAND with clay. SP -SC Silty SAND: SM
Additional descriptive terminology applied to coarse-grained soils follow.
Example: Coarse -Grained Soil Descriptions with Other Coarse -Grained Constituents
Coarse -Grained Soil Containing Secondary Constituents
With sand or with gravel 2 15% sand or gravel
With cobbles; with boulders Any amount of cobbles or boulders.
Cobble and boulder deposits may include a description of the matrix soils, as defined above.
Relative Density terms are applied to granular, non -plastic soils based on direct measure or correlation to the Standard
Penetration Test N -value as determined by ASTM D1586-84.
Relative Density Term SPT N -value
Veryloose 0-4
Loose 5-10
Medium dense 11-30
Dense 31-50
Very dense > 50
aTable A-2
�. Key To
PBS
aNmSAMPLING
Test Pit and
Boring Log Symbols
DESCRIPTIONS
Hd P� o C
m a
~ Fa n rn a" 6
.o h� mF - Z °
a
or.oc
dF¢
�CQ CSN b Qty ^ l �j° OCo,4N
4 W
`C�Q¢`
.g°
,N
h0 Z 2 , 0
} N T
LOG GRAPHICS
Soil and Rock Sampling Symbols
Instrumentation Detail
.r Litholo Boundary:
gy ry�
- - - — a Ground Surface
separates distinct units
d Sample
Well Cap
a (i.e., Fill, Alluvium,
Bedrock)at Recovery
Sample
Well Seal
approximate depths
Interval
Well Pipe
z° inciated
Piezometer
° Soil -type or Material -type
777 Change Boundary: separates soil VWe11Screen
N
_ - = and material changes within the Sampler
g
Piezometer
_-_-_ same lithographic unit at Type
LM,
approximate depth indicated
Bottom of Hole
Geotechnical Testing Acronym Explanations
PP Pocket Penetrometer
HYD
Hydrometer Gradation
TOR Torvane
SIEV
Sieve Gradation
DCP Dynamic Cone Penetrometer
DS
Direct Shear
ATT Atterberg Limits
DD
Dry Density
PL Plasticity Limit
CBR
California Bearing Ratio
LL Liquid Limit
RES
Resilient Modulus
PI Plasticity Index
VS
Vane Shear
P200 Percent Passing US Standard No, 200 Sieve
logs
Below ground surface
OC Organic Content
MSL
Mean Sea Level
CON Consolidation
HCL
Hydrochloric Acid
UC Unconfined Compressive Strength
Details of soil and rack classification systems are available on request. Rr 02=7
RIDGEVIEW GARDENS
TEST PIT TP -1
NGFIELD, OREGON
(PROJECT
PBS NUMBER:
APPROX. TEST PIT TP -1 LOCATION:
(See Site Plan)
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Lat 44.04]030 Long: -122.941314
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i
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-
c
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PIP
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4.0
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d .
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a
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COMPLETED: 9/092020 EXCAVATION METHOD: Case 500 with 24' Becket Page t at
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GRAVEL FILL (18 inches)
Is
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20
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PP
PP-45isf
PP
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3.5
4.0
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PP
PP C5 isf
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s.o
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LOOOEDBY:Eii,vt EXCAVATED BV: Dan J. Fischer Excavating, Inc. FIGURE 4
COMPLETED: 91022020 EXCAVATION METHOD. Case 580 With 26' Bo&nt P'. t a1
RIDGEVIEW GARDENS
TEST PIT TP -5
SPRINGFIELD, OREGON
PBS PROJECT NUMBER:
APPROX. TEST PR Fl.S) CATION:
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LOGGED BY: D. Elbert EXCAVATED BY. Dan J. Fischer &mv bng, Inc FIGURE A5
COMPLETED:&022828 EXCAVATION METHOD: Case 580 with 24" Bucket page 101
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TEST PIT TP -6
SPRINGFIELD, OREGON
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P200=60%
O
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ss
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-
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RIDGEVIEW GARDENS
TEST PIT TP-7
SPRINGFIELD, REGON
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PBS PROJECT15.002 BER:
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Y
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ab
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moist
PP
PP=4.5bar
4.0
PP
PP=4.5V
becomes sandy
PM
P200=85%
^; Gray to brown, well-graded GRAVEL
5.5
Inercranon leafing wrnpletea at a reel Egs
(GW-GM) with silt and sand; non-plastic;
50
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PZW
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w
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COMPLETED: 9XV2020 EXCAVATION METHOD: Case 580 wat 24"Bucket Paget mt
RIDGEVIEW GARDENS
TEST PIT TP$
OREGON
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PBS PROJECT NUMBER:
APPROX. TEST PIT TP -8 LOCATION
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MATERIAL DESCRIPTION
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mSTADC
COMMEWS
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0 5D 100
GRAVEL FILL (18 inches)
s
1
15
Hard, brown, lean CLAY (CL) with sand;
20
medium plasticity; fine to medium sand;
moist
PP
PP=4.51sf
��
•:
PP
PP 4.5 of
4.0
PP
PP=4.5Ist
.-
Gray to brown, silty GRAVEL (GM) with
4s
..
sand; fine to coarse sand; Me to coarse,
..
rounded gravel; moist
�y
6.0
�;
0.0
_
Gray, well -graded GRAVEL (GW-(Wwith
6'0
silt, sand, and cobbles; non -plastic; fine
sand; fine to coarse, rounded gravel; moist
i'
10.0
i
11'0
Final depth 11.0 feet bgs; test pit backfilled
with excavated material to existing ground
surface. Groundwater not encountered at
120
time of exploration.
14.0
°
50
1a°
LOGGED 6Y: 0. Eibed EXCAVATED W. Dan J. Fischer Excavating. Inc. FIGURE AB
COMPLETED: 91OV2020 EXCAVATION METHOD: Case 580 with 24' Bucket Pagel d1
Appendix B
Laboratory Testing
Geotechnical Engineering Report Ridgeview Gardens
Ridgeview Gardens, LLC Springfield, Oregon
Appendix B: Laboratory Testing
B1 GENERAL
Samples obtained during the field explorations were examined in the PBS laboratory. The physical
characteristics of the samples were noted and field classifications were modified where necessary. During the
course of examination, representative samples were selected for further testing. The testing program for the
soil samples included standard classification tests, which yield certain index properties of the soils important
to an evaluation of soil behavior. The testing procedures are described in the following paragraphs. Unless
noted otherwise, all test procedures are in general accordance with applicable ASTM standards. "General
accordance" means that certain local and common descriptive practices and methodologies have been
followed.
B2 CLASSIFICATION TESTS
82.1 Visual Classification
The soils were classified in accordance with the Unified Soil Classification System with certain other
terminology, such as the relative density or consistency of the soil deposits, in general accordance with
engineering practice. In determining the soil type (that is, gravel, sand, silt, or clay) the term that best
described the major portion of the sample is used. Modifying terminology to further describe the samples is
defined in Table A-1, Terminology Used to Describe Soil, in Appendix A.
B2.2 Moisture (Water) Contents
Natural moisture content determinations were made on samples of the fine-grained soils (that is, silts, clays,
and silty sands). The natural moisture content is defined as the ratio of the weight of water to dry weight of
soil, expressed as a percentage. The results of the moisture content determinations are presented on the
exploration logs in Appendix A and on Figure B2, Summary of Laboratory Data, in Appendix B.
B2.3 Atterberg Limits
Atterberg limits were determined on select samples for the purpose of classifying soils into various groups for
correlation. The results of the Atterberg limits test, which included liquid and plastic limits, are plotted on
Figure B1, Atterberg Limits Test Results, and on the exploration logs in Appendix A, where applicable.
B2.4 Grain -Size Analyses (P200 Wash)
Washed sieve analyses (P200) were completed on samples to determine the portion of soil samples passing
the No. 200 Sieve (i.e., silt and clay). The results of the P200 test results are presented on the exploration logs
in Appendix A and on Figure B2, Summary of Laboratory Data, in Appendix B.
ON PBS B-1 PBS Project 73 15.002
ATTERBERG LIMITS TEST RESULTS
PBS
5050 MAIN STREET
PBS PROJECT NUMBER:
SPRINGFIELD, OREGON
73415.002
Si
TEST METHOD: ASTM D4318
24.1
60
30
50
9
CH
wOH
"A"
LINE
40
X
z
z_
U 30
Q
CL or C
L
J
a
20
MH
rrOH
10
LL ML
ML 'r OL
0
0 10 20 30 40 50 60 70 80 90 100 110
LIQUID LIMIT
w
`3
F
EXPLORATION
SAMPLE
SAMPLE
NATURAL MOISTURE
PERCENT PASSING
LIQUID
B
KF/
NUMBER
NUMBER
DEPTH
CONTENT
NO. 40SIEVE
PLASTIC
PUISTICITY
(FEET)
(PERCENT)
(PERCENT)
LIMIT
LIMIT
INDEX
�i
E
n
R
FIGURE Bi
Page t off
•
TPi
Si
3.0
24.1
NA
30
21
9
���
SUMMARY OF LABORATORY DATA
RINGFEMAIN
SP5050
LD,O OREGON
PBS PRO415002 NUMBER:
SAMPLE INFORMATION
EXPLORATION SAMPLE SAMPLE ELEVATION
NUMBER NUMBER DEPTH IFEEp
(FEET)
MOISTURE
CONTENT
(PERCENT)
DRY
DENSITY
(PCF)
SIEVE
ATTERBERG LIMITS
GRAVEL
(pERCENt)
SAND
(PERCENT)
P200
(PERCENT)
LIQUID
LIMB
(PERCENT)
PLASTIC
LIMB
(PERCENT)
PLASTICITY
INDEX
(PERCENT)
TP-1
S-1
2
15.2
TP-2
&1
2.5
16.5
TP-2
S-2
5.5
9.4
3
TPJ
S-1
2
15.0
TP4
Si
3
24.1
30
21
9
TPS
S1
3
25.2
TP6
S-1
3.5
15.2
60
TP-7
&1
3.5
16.9
TP-]
S-2
5
20.5
65
TP-8
S-1
2.5
1].2
FIGURE B2
Pagel a1