HomeMy WebLinkAboutStudies Applicant 11/9/2023
p: 503-779-2577 | www.branchengineering.com
August 4, 2023
Michelle Martin
Cornerstone Community Housing
PO Box 11923
Eugene, Oregon 97440
RE: GEOTECHNICAL SITE INVESTIGATION – MULTI-UNIT RESIDENTIAL DEVELOPMENT
1875 16TH STREET
SPRINGFIELD, OREGON, 97477
BRANCH ENGINEERING INC. PROJECT NO. 23-291
Pursuant to your authorization, Branch Engineering Inc. (BEI) performed a geotechnical
engineering investigation at the subject site located at 1875 16th Street in Springfield, Oregon, for
a new multi-unit residential development. The accompanying report presents the results of our
site research, field exploration and testing, data analyses, as well as our conclusions and
recommended geotechnical design parameters for the project.
Based on the results of our study, no geotechnical/geologic hazards were identified at the site and
the site is suitable for the planned development provided that the recommendations of this report
are implemented in the design and construction of the project.
Sincerely,
Branch Engineering Inc.
Ronald J. Derrick P.E., G.E. Matthew Renner P.E.
Principal Geotechnical Engineer Construction Engineer
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TABLE OF CONTENTS
1.0 INTRODUCTION .............................................................................................................................. 3
1.1 Project and Site Description 3
1.2 Scope of Work 3
1.3 Site Information Resources 4
2.0 SITE SUBSURFACE CONDITIONS ............................................................................................. 4
2.1 Subsurface Soils 4
2.2 Ground Water 5
2.3 In situ Moisture Content & Soil Shrink/Swell Potential 5
3.0 GEOLOGIC SETTING ...................................................................................................................... 6
3.1 Regional Geology 6
3.2 Site Geology 6
3.3 Seismic and Geologic Hazards 7
4.0 CONCLUSIONS ................................................................................................................................. 7
5.0 RECOMMENDATIONS ................................................................................................................... 8
5.1 Site Preparation, and Foundation Subgrade Requirements 8
5.2 Soil Bearing Capacity 9
5.3 Settlement 9
5.4 Slabs-On-Grade 9
5.5 Site Drainage 9
5.6 Seismic Site Classification 10
5.7 Pavement Design Recommendations 10
5.8 Structural Fill Recommendations 10
6.0 CONSTRUCTION CONSIDERATIONS ..................................................................................... 11
6.1 Wet Weather/Dry Weather Construction Practices 11
6.2 Excavations 11
6.3 Geotechnical Construction Site Observations 12
7.0 REPORT LIMITATIONS ................................................................................................................ 12
FIGURE 1 – Site Vicinity Map
FIGURE 2 – Site Exploration Map
FIGURE 3 – Site Geologic Mapping
APPENDIX A – USCS Soil Description Key, Test Pit Log Summaries, Well Logs, NRCS Soil Survey
APPENDIX B – Geotechnical Specifications
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1.0 INTRODUCTION
The purpose of this work is to establish and present geotechnical engineering criteria and
requirements related to the site and subsurface conditions that may influence the design and
construction of the proposed project. Our field investigation scope of work consisted of a site
reconnaissance with subsurface investigation that occurred on July 17, 2023.
Our scope of work also included pertinent site research activities, engineering data review,
analysis, and preparation of this report.
1.1 Project and Site Description
The subject site consists of three separate tax lots (Tax Lots 1800, 1900, and 2000) that total
approximately 1.26-acres. The site is located at the project coordinates of 44.063401° North
Latitude and 123.000806° West Longitude (see Figure-1, Site Location Map). The three tax lots are
rectangular in shape and share property lines along the long, east-west axis of the parcels. The
site topography is relatively flat with slight slope to south and no abrupt changes in site elevations.
At the time of our visit, one existing single-family residence is present near the center of the site,
with a carport and outbuildings. We understand that the existing residence is vacant. The site
perimeter is fenced with a combination of chain link and wood. Portions of the interior property
lines between the individual tax lots are also fenced. The ground surface was covered with
somewhat overgrown grass and existing vegetation, greenhouses, outbuildings, and composting
equipment indicated that gardening occurred on the site during prior uses.
Review of historical aerial photos of the site location available on Google Earth indicate that the
currently vacant lot on the north side of the site was previously used as small field that was
cultivated for growing crops of vegetables. Prior to 2018 a residence was present on the southern
tax lot included in the site. Our investigation did not determine the presence of any existing septic
tanks which may have been the method of wastewater treatment prior to connection to the city
wastewater system; however, rounded rock was encountered in one of the test pits (TP-3) which
may indicate septic laterals. Clay drain tile pipe was also encountered in the TP-2.
Our understanding of the project is that the existing buildings on the site will be removed and
replaced with multi-unit housing constructed in the central area of the site. Paved parking areas
will be on northern and southern sides of the housing units. Based on a preliminary site plan
provided to BEI the proposed structure is expected to wood framed with line loads not exceeding
2 kips/lf and columns loads less than 15-kips. We are not aware of any basement walls or retaining
walls planned for the site development.
1.2 Scope of Work
Our scope of work included a site reconnaissance and subsurface investigation conducted on July
17, 2023. The subsurface explorations consisted of four test pit excavations advanced to a
maximum depth of 76-inches below ground surface (BGS) at the locations shown on the attached
Figure-2 Site Exploration Map. The soil was visually classified in accordance with the American
Society of Testing and Materials (ASTM) Method D-2488, and representative soil samples were
collected for in-house laboratory in-situ moisture content and shrink/swell potential. Field log
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summaries of the test pit excavations, including field and laboratory test results, are presented in
Appendix A. Also included in Appendix A are copies of nearby well logs from the Oregon
Department of Water Resources online database and the soil survey mapping of the site.
Three falling head infiltration tests were set up during the test pit excavation work, and pre-
saturated. Infiltration testing was conducted the following day on July 18, 2023. Infiltration test
results are presented under a separate cover letter-report delivered.
1.3 Site Information Resources
The following site investigation activities were performed and literature resources were reviewed
for pertinent site information:
Review of the United States Department of the Interior Geological Survey (USGS) Eugene
East Quadrangle Map and Springfield Quadrangle Map, 2014.
Review of Google Earth online aerial photographs of site since 1995.
Four exploratory test pit excavations were advanced on site on July 17, 2023 to a maximum
depth of 76-inches below ground surface (BGS).
Review of the Lane County Area Web Soil Survey, United States Department of Agricultural
(USDA) Natural Resources Conservation Service (NRCS), see Appendix A.
Review of the Department of Geologic and Mining Industries (DOGAMI) Digital Geologic
Map of the Southern Willamette Valley O-10-03, 2010.
Review of DOGAMI online hazard viewer and the Interpretive Map Series IMS-60, Interactive
map of existing landslides in the Eugene-Springfield area.
Review of Oregon Department of Water Resources Well Logs, see Appendix A.
2.0 SITE SUBSURFACE CONDITIONS
The analyses, conclusions, and recommendations contained in this report are based on site
conditions as they presently exist and assume the exploratory borings, presented in Appendix A,
are representative of the subsurface conditions throughout the site. If site development plans
change or during construction, subsurface conditions differ from those encountered in the
exploratory borings, BEI requests that we be informed to review the site conditions and adjust our
recommendations, if necessary.
2.1 Subsurface Soils
Subsurface soil conditions were found to be relatively consistent across the site and generally
consisted of the following:
Topsoil Zone: Stiff, brown CLAY (CL), damp with fine roots, fractured texture consistent
with prior agricultural uses; 14- to 24-inches BGS over,
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Stiff, brown with gray CLAY (CL), damp with mottling/oxidation staining at times; extends
to depths of 28- to 42-inches BGS over,
Stiff to very stiff, light brown CLAY (CL-SC), damp to moist, with fine sand and silt, extends
to depths of 56- to 72-inches over,
Dense, brown, rounded GRAVEL (GP-GC) with clay and fine sand, very slow excavation
progress or practical refusal to mini-excavator, gravels may be partially cemented
As mentioned in the site description above, small amounts of rounded rock and clay tile pipes
were encountered in TP-2 and TP-3. Previously installed drain tile systems and/or wastewater
drainfield(s) may be encountered during site work.
USDA NRCS Web Soil Survey of Lane County Area maps two soil units present on the site; Coburg-
Urban land complex is mapped across most of the site, Malabon-Urban land complex is mapped
on the southwest portion of the site, see attached soil map. The soils are described as alluvial silt
and clay, which is consistent with our site observations.
2.2 Ground Water
No groundwater was encountered in the test pit excavations, which were advanced during the dry
season. Well logs were obtained from the Oregon Water Resources Department online database
from a nearby site to the east. Static groundwater depths were listed between 7.5- and 9-feet in
gravels.
We do not expect that static groundwater will impact the site development; however, perched
lenses of water may be encountered in foundation excavations and may require dewatering
measures. The site subgrade soil is moisture sensitive and will soften with prolonged exposure to
water or precipitation. The likelihood of encountering perched lenses of water will increase during
the wet season through spring, typically late October through May.
2.3 In situ Moisture Content & Soil Shrink/Swell Potential
Moisture content (ASTM D2216) and Free Swell (Holtz and Gibbs) testing was performed on
representative samples of the site soil collected during our field investigation. Results are shown
on Table-1 below, the soil was found to be moderately expansive with moderate to high
shrink/swell potentials noted throughout the soil profile.
Table 1: Lab testing results
Location Depth BGS
(feet)
Moisture
Content (%)
Free
Swell (%) Swell Rating
TP-1 1.6 27 30 Moderate
TP-2 2 25 30 Moderate
TP-2 4 34 25 Moderate
TP-3 2 26 40 High
The recommendations found below in the ‘Building Foundation Subgrade Preparation’ and ‘Wet
Weather/Dry Weather Construction Practices’ sections are intended to mitigate the effects of the
moderate shrink/swell potential of the subgrade soil, provided the recommendations are
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incorporated into the project design and construction, the shrink/swell potential is not anticipated
to impact the proposed development.
3.0 GEOLOGIC SETTING
The following sections describe the regional and local site geology. Our field findings are
consistent with the geologic mapping of the site area by the DOGAMI Digital Geologic Map of the
Southern Willamette Valley O-10-03, 2010.
3.1 Regional Geology
The subject site lies within the southern portion of the Willamette Valley, east of the Coast Range
and west of the Cascade Mountains Provinces. In Oregon, the Willamette Valley is an elongated
basin which narrows at both ends before terminating in the Calapooya Divide to the south and the
Columbia River to the north. The basin is approximately 130 miles long and 40 miles wide. The
valley is drained by the Willamette River and drops from an elevation of approximately 400-feet
at Eugene, to near sea level at the northern end of the basin where the Willamette River drains into
the Columbia River.
The Willamette River Valley in the area of the subject site is believed to be heavily influenced by
historic hydrology, including the movement and sediment deposition of the McKenzie, Middle, and
Coast Forks of the Willamette Rivers. The site is in an alluvial terrace between the McKenzie and
Middle Fork of the Willamette channels. During the last deglaciation and the resulting termination
of the Last Glacial Maximum in North America, the Willamette Valley was cyclically flooded by
catastrophic breaks in the ice dams of Glacial Lake Missoula. Occurring repeated times over an
approximately 2,000-year period between 13,000 to 15,000 ago, these flood events filled the valley
to an elevation of 350- to 400-feet, mostly to the north of the subject site, before retreating, causing
sequences of upward fining deposits of silt and clay that may or may not still be present in areas
depending on erosion by subsequent fluvial actions. Much of these deposits have since become
developed and urbanized.
3.2 Site Geology
The DOGAMI O-10-03 Geologic Map of the Southern Willamette Valley maps the site geologic unit
as Terrace and Fan Deposits (Quaternary), which are described as deeply dissected, unconsolidated
to semi-consolidated deposits of gravel, sand, silt, and clay that form upper alluvial terraces along
the Willamette, Coast Fork of the Willamette, McKenzie, Calapooia, South Santiam, and North
Santiam Rivers and a number of tributary streams draining the Cascades. The unit forms broad,
dissected fans between the confluence of the Willamette and McKenzie Rivers. The site geologic
unit description is consistent with our field findings.
Nearby well logs from a site approximately 800-feet east of the subject site list gravels underlying
fine grain silt to a depth of 20-feet BGS, with the depth of the fine grail soil logged as 5-feet, which
is consistent with our field observations and the site geologic mapping.
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3.3 Seismic and Geologic Hazards
OSSC 2019 (1803.5.11) required criteria for hazards the geotechnical investigation shall address
for seismic site class designations C through F are listed below. Our recommended seismic site
classification may be found in Section 5.6 below.
Slope Instability: The site is mapped as having low susceptibility to shallow and deep
landslides by the Statewide Landslide Information Database for Oregon (SLIDO). No
landslides are mapped on the site, or in locations that may impact the site. No slopes are
present on the site that are capable of producing landslides. In our opinion, the risk of
landslides impacting the site is low.
Liquefaction: The DOGAMI HazVu map does not indicate any potential for liquefaction on
site in the event of seismic activity in the area. Loose, granular soils with a low fine-grained
soil content and a recent depositional history are especially vulnerable to liquefaction. No
zones of loose sand were observed during site explorations that would be likely to
experience liquefaction during a significant seismic event. In our opinion, the risk of
liquefaction to the proposed development is low.
Expected Earthquake Shaking: The site is mapped within the zone of strong shaking in the
event of a large earthquake event that would typically be associated with Cascadia
Subduction Zone (CSZ) off the Oregon coastline. In the event of a smaller, non-CSZ
earthquake event, the site is similarly mapped within a zone of strong shaking.
Surface Displacement Due to Faulting or Seismically Induced Lateral Spreading or Lateral
Flow: There are no known faults on the site and the closest faults are not known to be
active. There are no abrupt changes in ground elevation on or near the site that would
present a potential for lateral spreading to occur during a seismic event. Additionally,
there are no soil types observed in onsite explorations or in nearby well logs that would
be susceptible to later spread or lateral flow. Therefore, surface displacement due to
faulting or seismically induced lateral spreading is not expected to occur at the site.
Tsunami/seiche: The nearest significant body of water to the site is the McKenzie River,
located approximately 1.0-miles to the north, which poses no risk of a seiche or tsunami
to the subject site.
4.0 CONCLUSIONS
Based on our field observations, subsurface explorations, and data analyses, we conclude that the
site is geologically and geotechnically suitable for the proposed development provided that the
recommendations of this report are incorporated into the design and construction of the project.
Our investigation did not reveal any specific site features or subsurface conditions that would
impede the site development as proposed.
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5.0 RECOMMENDATIONS
The following sections present site-specific recommendations for site preparation, drainage,
foundations, utility excavations, and slab/pavement design. General material and construction
specifications for the items discussed herein are provided in Appendix B.
5.1 Site Preparation and Foundation Subgrade Requirements
The following recommendations are for earthwork in the building foundation areas and private
parking areas. Earthwork shall be performed in general accordance with the standard of practice
as generally described in Appendix J of the Uniform Building Code and as specified in this report.
All areas intended to directly or laterally support structures, roadways, or pavement areas shall
be stripped of vegetation, organic soil, unsuitable fill, existing structures, foundations, and/or
other deleterious material such as moisture softened exposed soil. Strippings shall be removed
from the site or reserved for use in landscaping or non-structural areas. In areas of any existing
trees, vegetation, or undocumented fill, the required depth of site clearing/stripping may be
increased.
The subsurface conditions observed in our site investigation borings are consistent; however, the
explorations only represent those specific locations on the site. Should soft or unsuitable soils
extend to a depth greater than that described herein, or areas of distinct soil variation be
discovered, this office shall be notified to perform site observation and additional excavation may
be required.
Building Foundation Subgrade Preparation
In areas of building foundations, we recommend removing the existing topsoil zone, described in
the test pit logs as 14- to 24-inches in thickness to subgrade soil consisting of clay that is free of
organics, and a medium stiff to stiff consistency. At the time of our investigation, the site soil
consistency was influenced by hot and dry seasonal conditions. During the wet season, or spring,
the clay soil is expected to at softer consistencies than encountered during our investigation. We
recommend scheduling a site visit with the Geotechnical Engineer of Record (GER) during
foundation excavation to confirm the suitability of the subgrade soil for structural fill placement.
Following excavation to the subgrade soil described above, we recommend placing compacted
aggregate with a minimum thickness of 12-inches under foundations. The placement of compacted
aggregate shall extend a minimum of 12-inches horizontally outward from the edges of foundation
footings. The compacted aggregate shall be placed in accordance with the engineered fill
recommendations in Section 5.8 below.
If any abandoned septic tanks, wastewater drain-field laterals, or other previously installed
underground items are encountered in foundation excavations they should be removed, and
replaced with compacted aggregate. Abandoned septic tanks may be partially demolished,
perforated, and filled with compacted aggregate in-place.
In order to minimize moisture fluctuations that could exacerbate the shrink/swell potential of the
subgrade soil, the subgrade shall be covered with structural fill in a timely manner upon
excavation. Once exposed, the soil moisture of the subgrade shall be monitored so that it remains
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consistent. At the time of the aggregate placement the subgrade soil shall not be allowed to dry or
be exposed to extremely dry conditions, nor shall water be allowed to pond on the exposed surface.
5.2 Soil Bearing Capacity
If foundation areas are prepared as described in Section 5.1 of this report, footings founded on
firm, unyielding soils and underlain by a minimum of 12-inches of compacted crushed aggregate
will provide an allowable bearing capacity of 2,000 psf. The placement of any compacted aggregate
under footings shall extend a minimum of 1-feet horizontally beyond footing perimeters or the
thickness of the aggregate, whichever is greater. This bearing pressure may be increased by 1/3
for short term loading, such as wind or seismic events.
Conventional spread and strip footings are suitable for the proposed building and we recommend
that column and line loads are distributed evenly to mitigate the potential for differential
settlement. At the time of this report, we are not aware of any walls requiring lateral earth
pressures for design. If retaining walls, or tall basement walls are planned, retaining wall design
parameters may be given based on the locations, depth of the walls and the type of soil, or backfill
to be retained.
5.3 Settlement
Following the building pad preparation above, with the plastic clay removed down to the very stiff
red-brown material the total settlement is estimated to be less than ¾-inch with differential
settlements being less than ½-inch between equivalently loaded footings over spans of 20-feet or
less.
5.4 Slabs-On-Grade
After preparation of the subgrade as described in Section 5.1, those areas to be overlain by interior
concrete slabs or vehicle pavement/slabs shall be underlain by a minimum of 12-inches of
compacted granular material. A clean, free draining aggregate is recommended beneath structural
slabs.
Although not a structural element and not part of BEI review, due to the shrink/swell potential of
the near surface site soil, the project designer/contractor may consider increasing the typical
thickness of aggregate below exterior concrete flatwork to reduce the potential for seasonal
movement that is commonly visible for flatwork adjacent to foundations.
5.5 Site Drainage
Based on preliminary site plan drawings, and measured infiltration rates provided to BEI we expect
a stormwater plan to be engineered for the project. Falling head infiltration tests were conducted
in three of the test pit locations, the infiltration results, and field data have been transmitted to
the report addressee under a separate cover.
Alteration of existing grades for the proposed development will likely change drainage patterns.
Slopes next to adjacent properties shall be graded away or blocked from flow so as to not adversely
affect them with surface runoff. Perimeter landscape and hardscape grades shall be sloped away
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from the foundations and water shall not be allowed to pond adjacent to footings during or after
construction.
5.6 Seismic Site Classification
Based on our findings in our subsurface explorations and nearby well logs, a Site Class C (Table
20.3-1 ASCE 7-16) is recommended for the site, based on the consistency and depth of the
underlying dense gravels. See the above Section 3.3 Seismic and Geologic Hazards for more
detailed seismic information.
5.7 Pavement Design Recommendations
Based on a correlated California Bearing Ratio of 3 for the site soil, we recommend the following
for new AC pavement installation in parking areas and light vehicle routes. A minimum pavement
thickness of 3 inches of AC over a minimum of 12 inches of compacted aggregate base rock and
that the AC thickness be increased to 4 inches in areas of heavier traffic, such as refuse truck
routes or delivery vehicles. Prior to placement of base rock any soft clay soil, wet soil, or organic
soil shall be removed from the pavement subgrade. This may require excavation to depths greater
than above recommended pavement section below finish grades.
The pavement recommendations discussed above are designed for the type of vehicle use on the
site after construction completion, not for construction vehicle traffic which is generally heavier,
occurs over a short time, and impacts the site before full pavement sections are constructed. The
construction traffic may cause subgrade failures and the site contractor should consider over-
building designated haul routes through the site to mitigate soft areas at the time of final paving.
Pavement subgrades shall be observed and proof-rolled prior to placement of base rock, provided
moisture conditions allow for truck traffic, and the base rock shall be compacted to at least 90%
of the material’s maximum dry density as determined by AASHTO T-180/ASTM D-1557 (modified
Proctor). BEI recommends using a geotextile separation fabric between the subgrade and subbase
rock. The base rock shall be tested to measure compliance with this compaction standard prior to
placement of asphalt concrete.
5.8 Structural Fill Recommendations
All engineered fill placed on the site shall consist of homogenous material and shall meet the
following recommendations.
The recommended compaction level for crushed aggregate and soil fill is 90% of the
maximum dry density as determined by ASTM D-1557 (modified Proctor).
Prior to placement onsite, the aggregate or soil to be used shall be approved by the GER.
If no recent Proctor curve (moisture-density relationship) is available for the material, a
material sample will be required for testing to determine the maximum dry density and
optimum moisture content of the aggregate or fill material. Use of the onsite soils for fill
will require careful moisture conditioning and appropriate compaction equipment
selection. Compaction of clayey soils during the wet season (November through May) will
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be difficult, if not impossible, to achieve due to insitu moisture contents being
significantly higher than optimum moisture contents.
Compaction shall be measured by on site testing with a nuclear densometer (ASTM D-
6938), or sand cone method (ASTM D-1556) on structural fill with thicknesses in excess
of 12-inches. If compaction testing is not feasible for any onsite or imported material due
to factors such as oversize rock content or variable material, proof rolls with a fully
loaded 10 cubic yard haul-truck or equivalent equipment shall be observed at regular
intervals. Any observed areas of excessive yielding or rutting will require removal and
replacement with granular fill or moisture conditioning and recompaction.
The structural fill shall be moisture conditioned to within +/- 2% of optimum moisture
content and compacted in lifts with loose thicknesses not exceeding 8-inches. Periodic
visits to the site to verify lift thickness, source material, and compaction effort shall be
conducted by the GER, or designated representative, and documented.
Utility trenches excavated to depths below the top of the subgrade elevation shall be
backfilled with approved material and compacted to at least 90% of the maximum dry
density.
6.0 CONSTRUCTION CONSIDERATIONS
The following sections pertain to work on the site specific to construction practices.
6.1 Wet Weather/Dry Weather Construction Practices
The native clay soils, if left exposed to prolonged precipitation, will become saturated and soften.
Subgrade soil that will be below foundations, slabs, and pavement shall be covered with compacted
aggregate in a timely manner after excavation to minimize moisture fluctuations.
Construction during the wet season may require special drainage considerations, such as covering
of excavations, pumping to mitigate standing water in footing excavations, or over-excavation of
moisture softened soils. Water shall not be allowed to pond in foundation or other structural areas.
Construction traffic routes will also be more susceptible to “pumping” and rutting during the wet
season and may require thicker rock sections.
6.2 Excavations
We expect excavations into the fine-grained surficial soils to stand near-vertical to depths of at
least 5-feet BGS except in areas of near surface fill which may require removal of loose material
from the upper portions of excavations. The site soils are classified as OSHA Type A for the upper
5-feet of the site soil profile, below the depth of the gravels encountered in the test pit excavations
the soil is classified as OSHA Type C, and thus, heavy equipment or stored materials should not
be placed within 10-feet of open excavations
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6.3 Geotechnical Construction Site Observations
Periodic site observations by a geotechnical representative of BEI are recommended during the
construction of the project; the specific phases of construction that should be observed are shown
below in Table 1:
Table 1:
Recommended Construction Phases to be Observed by the Geotechnical Engineer
At completion of subgrade excavation
Subgrade observation by the geotechnical
engineer before aggregate and geogrid (if
applicable) placement.
Imported fill material Observation of material or information on
material type and source.
Placement or Compaction of fill material Observation by geotechnical engineer or test
results by qualified testing agency.
7.0 REPORT LIMITATIONS
This report has presented BEI’s site observations and research, subsurface explorations,
geotechnical engineering analyses, and recommendations for the proposed site development. The
conclusions in this report are based on the conditions described in this report and are intended
for the exclusive use of the Cornerstone Community Housing and their designated representatives
for use in design and construction of the development described herein. The analysis and
recommendations may not be suitable for other structures or purposes.
Services performed by the geotechnical engineer for this project have been conducted with the
level of care and skill exercised by other current geotechnical professionals in this area. No
warranty is herein expressed or implied. The conclusions in this report are based on the site
conditions as they currently exist and it is assumed that the limited site locations that were
physically investigated generally represent the subsurface conditions at the site. This report
represents our findings and should site development or site conditions change, or if a substantial
amount of time goes by between our site investigation and site development, we reserve the right
to review this report for its applicability and adjust our recommendations. If you have any
questions regarding the contents of this report, please contact our office.
SCALE: NOT TO SCALE
NOTE: MAP BY LANE COUNTY GIS, 2023
FIGURE-1
07-17-2023
PROJECT NO. 23-291
SITE VICINITY MAP - CORNERSTONE HOUSING
1875 16th STREET, SPRINGFIELD, OREGON
SITE LOCATION
SCALE: NOT TO SCALE
FIGURE-1
07-17-2023
PROJECT NO. 23-291
SITE EXPLORATION MAP - CORNERSTONE HOUSING
1875 16th STREET, SPRINGFIELD, OREGON
INDICATES APPROXIMATE
LOCATION OF
TEST PIT
LEGEND
TP-1
IT-1
INDICATES APPROXIMATE
LOCATION OF
INFILTRATION TEST
TP-1
TP-2
TP-3
TP-4
IT-1
IT-2
IT-3
SCALE: NOT TO SCALE
FIGURE-3
07-17-2023
PROJECT NO. 23-291
APPROX. SITE
LOCATION
NOTE: GEOLOGIC MAP OPEN-FILE REPORT O-10-03, GEOLOGY OF THE SOUTHERN WILLAMETTE VALLEY BY DOGAMI, 2010
SITE GEOLOGIC MAPPING - CORNERSTONE HOUSING
1875 16th STREET, SPRINGFIELD, OREGON
APPENDIXAPPENDIXAPPENDIXAPPENDIX AAAA
Test PitTest PitTest PitTest Pit Log Summaries, Well Logs, and Log Summaries, Well Logs, and Log Summaries, Well Logs, and Log Summaries, Well Logs, and NRCS NRCS NRCS NRCS
SoilSoilSoilSoil SurveySurveySurveySurvey
Depth1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 GraphicMaterial Description
Stiff, brown-dark brown CLAY (CL), dry with fine roots (Topsoil Zone)
Stiff, brown-gray mottled CLAY (CH), damp
Very stiff, light brown CLAY (CL), damp with trace fine sand
Dense, brown, rounded GRAVEL (GP) with clay, damp, refusal to mini-
excavator, possibly cemented SampleS-1
BAG Pocket Pen. (tsf)Free SwellMoisture Content: ⊗
PL and LL: ⬤━∎
Borehole ID: TP-1
Sheet 1 of 1
Client:Cornerstone Housing Project Name:Cornerstone on 16th Street
Project Number:23-291 Project Location:1875 16th Street, Springfield, Oregon
Date Started:Jul 17 2023 Completed:Jul 17 2023 Logged By:MWR Checked By:RJD
Drilling Contractor:Latitude:44.063401 Longitude:-122.000806 Elevation:
Drilling Method:Test Pit Excavation Ground Water Levels
Equipment:Rubber Tracked Mini-Excavator
Hammer Type:
Notes:
10 20 30 40 50 60 70 80 90
Depth1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 GraphicMaterial Description
Stiff, dark brown CLAY (CL), dry with fine roots (Topsoil Zone)
Stiff, black-orange mottled CLAY (CH), damp, oxidation staining
Very stiff, light brown CLAY (CL), damp with trace fine sand
Dense, brown, rounded GRAVEL (GP) with clay, damp, refusal to mini-
excavator, possibly cemented SampleS-1
BAG
S-2
BAG Pocket Pen. (tsf)4.00 Free SwellMoisture Content: ⊗
PL and LL: ⬤━∎
Borehole ID: TP-2
Sheet 1 of 1
Client:Cornerstone Housing Project Name:Cornerstone on 16th Street
Project Number:23-291 Project Location:1875 16th Street, Springfield, Oregon
Date Started:Jul 17 2023 Completed:Jul 17 2023 Logged By:MWR Checked By:RJD
Drilling Contractor:Latitude:44.063401 Longitude:-122.000806 Elevation:
Drilling Method:Test Pit Excavation Ground Water Levels
Equipment:Rubber Tracked Mini-Excavator
Hammer Type:
Notes:
10 20 30 40 50 60 70 80 90
Depth1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 GraphicMaterial Description
Stiff, brown-dark brown CLAY (CL), dry with fine roots (Topsoil Zone)
Stiff, brown-gray CLAY (CH) with silt, damp
Very stiff, light brown CLAY (CL), damp with trace fine sand
Dense, brown, rounded GRAVEL (GP) with clay, damp, refusal to mini-
excavator, possibly cemented SampleS-1
BAG Pocket Pen. (tsf)4.50 Free SwellMoisture Content: ⊗
PL and LL: ⬤━∎
Borehole ID: TP-3
Sheet 1 of 1
Client:Cornerstone Housing Project Name:Cornerstone on 16th Street
Project Number:23-291 Project Location:1875 16th Street, Springfield, Oregon
Date Started:Jul 17 2023 Completed:Jul 17 2023 Logged By:MWR Checked By:RJD
Drilling Contractor:Latitude:44.063401 Longitude:-122.000806 Elevation:
Drilling Method:Test Pit Excavation Ground Water Levels
Equipment:Rubber Tracked Mini-Excavator
Hammer Type:
Notes:
10 20 30 40 50 60 70 80 90
Depth1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 GraphicMaterial Description
Stiff, dark brown CLAY (CL), dry with fine roots (Topsoil Zone)
Stiff, brown-gray CLAY (CH), damp
Very stiff, light brown CLAY (CL) with silt and trace fine sand, damp SamplePocket Pen. (tsf)4.50 Free SwellMoisture Content: ⊗
PL and LL: ⬤━∎
Borehole ID: TP-4
Sheet 1 of 1
Client:Cornerstone Housing Project Name:Cornerstone on 16th Street
Project Number:23-291 Project Location:1875 16th Street, Springfield, Oregon
Date Started:Jul 17 2023 Completed:Jul 17 2023 Logged By:MWR Checked By:RJD
Drilling Contractor:Latitude:44.063401 Longitude:-122.000806 Elevation:
Drilling Method:Test Pit Excavation Ground Water Levels
Equipment:Rubber Tracked Mini-Excavator
Hammer Type:
Notes:
10 20 30 40 50 60 70 80 90
Soil Map—Lane County Area, Oregon
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/27/2023
Page 1 of 348788304878850487887048788904878910487893048789504878970487899048790104878830487885048788704878890487891048789304878950487897048789904879010499860499880499900499920499940499960499980500000
499860 499880 499900 499920 499940 499960 499980 500000
44° 3' 51'' N 123° 0' 6'' W44° 3' 51'' N122° 59' 59'' W44° 3' 45'' N
123° 0' 6'' W44° 3' 45'' N
122° 59' 59'' WN
Map projection: Web Mercator Corner coordinates: WGS84 Edge tics: UTM Zone 10N WGS84
0 45 90 180 270
Feet
0 10 20 40 60
Meters
Map Scale: 1:984 if printed on A portrait (8.5" x 11") sheet.
Soil Map may not be valid at this scale.
MAP LEGEND MAP INFORMATION
Area of Interest (AOI)
Area of Interest (AOI)
Soils
Soil Map Unit Polygons
Soil Map Unit Lines
Soil Map Unit Points
Special Point Features
Blowout
Borrow Pit
Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
Landfill
Lava Flow
Marsh or swamp
Mine or Quarry
Miscellaneous Water
Perennial Water
Rock Outcrop
Saline Spot
Sandy Spot
Severely Eroded Spot
Sinkhole
Slide or Slip
Sodic Spot
Spoil Area
Stony Spot
Very Stony Spot
Wet Spot
Other
Special Line Features
Water Features
Streams and Canals
Transportation
Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
The soil surveys that comprise your AOI were mapped at
1:20,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL:
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: Lane County Area, Oregon
Survey Area Data: Version 21, Mar 13, 2023
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Jun 12, 2019—Jun
19, 2019
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Soil Map—Lane County Area, Oregon
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/27/2023
Page 2 of 3
Map Unit Legend
Map Unit Symbol Map Unit Name Acres in AOI Percent of AOI
32 Coburg-Urban land complex 1.0 24.6%
76 Malabon-Urban land complex 3.1 75.4%
Totals for Area of Interest 4.1 100.0%
Soil Map—Lane County Area, Oregon
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/27/2023
Page 3 of 3
Lane County Area, Oregon
32—Coburg-Urban land complex
Map Unit Setting
National map unit symbol: 2369
Elevation: 100 to 1,300 feet
Mean annual precipitation: 30 to 60 inches
Mean annual air temperature: 50 to 55 degrees F
Frost-free period: 160 to 235 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Coburg and similar soils:55 percent
Urban land:30 percent
Minor components:4 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Coburg
Setting
Landform:Stream terraces
Landform position (three-dimensional):Tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Loamy alluvium over clayey alluvium
Typical profile
H1 - 0 to 18 inches: silty clay loam
H2 - 18 to 53 inches: silty clay
H3 - 53 to 65 inches: fine sandy loam
Properties and qualities
Slope:0 to 3 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Moderately well drained
Capacity of the most limiting layer to transmit water
(Ksat):Moderately high (0.20 to 0.57 in/hr)
Depth to water table:About 18 to 30 inches
Frequency of flooding:None
Frequency of ponding:None
Available water supply, 0 to 60 inches: High (about 11.0 inches)
Interpretive groups
Land capability classification (irrigated): 2w
Land capability classification (nonirrigated): 2w
Hydrologic Soil Group: C
Ecological site: R002XC006OR - Stream Terrace Group
Forage suitability group: Moderately Well Drained < 15% Slopes
(G002XY004OR)
Map Unit Description: Coburg-Urban land complex---Lane County Area, Oregon
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/27/2023
Page 1 of 2
Other vegetative classification: Moderately Well Drained < 15%
Slopes (G002XY004OR)
Hydric soil rating: No
Description of Urban Land
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 8
Hydric soil rating: No
Minor Components
Conser
Percent of map unit:4 percent
Landform:Stream terraces
Hydric soil rating: Yes
Data Source Information
Soil Survey Area: Lane County Area, Oregon
Survey Area Data: Version 21, Mar 13, 2023
Map Unit Description: Coburg-Urban land complex---Lane County Area, Oregon
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/27/2023
Page 2 of 2
Lane County Area, Oregon
76—Malabon-Urban land complex
Map Unit Setting
National map unit symbol: 238t
Elevation: 300 to 650 feet
Mean annual precipitation: 40 to 60 inches
Mean annual air temperature: 52 to 54 degrees F
Frost-free period: 165 to 210 days
Farmland classification: Farmland of statewide importance
Map Unit Composition
Malabon and similar soils:50 percent
Urban land:45 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Malabon
Setting
Landform:Terraces
Landform position (three-dimensional):Tread
Down-slope shape:Linear
Across-slope shape:Linear
Parent material:Silty and clayey alluvium
Typical profile
H1 - 0 to 12 inches: silty clay loam
H2 - 12 to 42 inches: silty clay
H3 - 42 to 60 inches: clay loam
Properties and qualities
Slope:0 to 3 percent
Depth to restrictive feature:More than 80 inches
Drainage class:Well drained
Capacity of the most limiting layer to transmit water
(Ksat):Moderately high (0.20 to 0.57 in/hr)
Depth to water table:More than 80 inches
Frequency of flooding:None
Frequency of ponding:None
Available water supply, 0 to 60 inches: High (about 11.4 inches)
Interpretive groups
Land capability classification (irrigated): 1
Land capability classification (nonirrigated): 1
Hydrologic Soil Group: C
Ecological site: R002XC006OR - Stream Terrace Group
Forage suitability group: Well drained < 15% Slopes
(G002XY002OR)
Other vegetative classification: Well drained < 15% Slopes
(G002XY002OR)
Map Unit Description: Malabon-Urban land complex---Lane County Area, Oregon
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/27/2023
Page 1 of 2
Hydric soil rating: No
Description of Urban Land
Interpretive groups
Land capability classification (irrigated): None specified
Land capability classification (nonirrigated): 8
Hydric soil rating: No
Data Source Information
Soil Survey Area: Lane County Area, Oregon
Survey Area Data: Version 21, Mar 13, 2023
Map Unit Description: Malabon-Urban land complex---Lane County Area, Oregon
Natural Resources
Conservation Service
Web Soil Survey
National Cooperative Soil Survey
7/27/2023
Page 2 of 2
APPENDIX B:
Recommended Earthwork Specifications
GEOTECHNICAL SPECIFICATIONS
General Earthwork
1. All areas where structural fills, fill slopes, structures, or roadways are to be constructed shall be
stripped of organic topsoil and cleared of surface and subsurface deleterious material, including
but limited to vegetation, roots, or other organic material, undocumented fill, construction debris,
soft or unsuitable soils as directed by the Geotechnical Engineer of Record. These materials shall
be removed from the site or stockpiled in a designated location for reuse in landscape areas if
suitable for that purpose. Existing utilities and structures that are not to be used as part of the
project design or by neighboring facilities, shall be removed or properly abandoned, and the
associated debris removed from the site.
2. Upon completion of site stripping and clearing, the exposed soil and/or rock shall be observed by
the Geotechnical Engineer of Record or a designated representative to assess the subgrade
condition for the intended overlying use. Pits, depressions, or holes created by the removal of root
wads, utilities, structures, or deleterious material shall be properly cleared of loose material,
benched and backfilled with fill material approved by the Geotechnical Engineer of Record
compacted to the project specifications.
3. In structural fill areas, the subgrade soil shall be scarified to a depth of 4 -inches, if soil fill is used,
moisture conditioned to within 2% of the materials optimum moisture for compaction, and
blended with the first lift of fill material. The fill placement and compaction equipment shall be
appropriate for fill material type, required degree of blending, and uncompacted lift thickness.
Assuming proper equipment selection, the total uncompacted thickness of the scarified subgrade
and first fill lift shall not exceed 8-inches, subsequent lifts of uncompacted fill shall not exceed 8-
inches unless otherwise approved by the Geotechnical Engineer of Record. The uncompacted lift
thickness shall be assessed based on the type of compaction equipment used and the results of
initial compaction testing. Fine-grain soil fill is generally most effectively compacted using a
kneading style compactor, such as a sheeps-foot roller; granular materials are more
effectively compacted using a smooth, vibratory roller or impact style compactor.
4. All structural soil fill shall be well blended, moisture conditioned to within 2% of the material’s
optimum moisture content for compaction and compacted to at least 90% of the material’s
maximum dry density as determined by ASTM Method D-1557, or an equivalent method. Soil fill
shall not contain more than 10% rock material and no solid material over 3 -inches in diameter
unless approved by the Geotechnical Engineer of Record. Rocks shall be evenly distributed
throughout each lift of fill that they are contained within and shall not be clumped together in such
a way that voids can occur.
5. All structural granular fill shall be well blended, moisture conditioned at or up to 3% above of the
material’s optimum moisture content for compaction and compacted to at least 9 0% of the
material’s maximum dry density as determined by ASTM Method D-1557, or an equivalent
method. 95% relative compaction may be required for pavement base rock or in upper lifts of the
granular structural fill where a sufficient thickness of the fill section allows for higher compaction
percentages to be achieved. The granular fill shall not contain solid particles over 2-inches in
diameter unless special density testing methods or proof-rolling is approved by the Geotechnical
Engineer of Record. Granular fill is generally considered to be a crushed aggregate with a fracture
surface of at least 70% and a maximum size not exceeding 1.5-inches in diameter, well-graded
with less than 10%, by weight, passing the No. 200 Sieve.
6. Structural fill shall be field tested for compliance with project specifications for every 2-feet in
vertical rise or 500 cy placed, whichever is less. In-place field density testing shall be performed
by a competent individual, trained in the testing and placement of soil and aggregate fill
placement, using either ASTM Method D-1556/4959/4944 (Sand Cone), D-6938 (Nuclear
Densometer), or D-2937/4959/4944 (Drive Cylinder). Should the fill materials not be suitable for
testing by the above methods, then observation of placement, compaction and proof-rolling with a
loaded 10 cy dump-truck, or equivalent ground pressure equipment, by a trained individual may
be used to assess and document the compliance with structural fill specifications.
Utility Excavations
1. Utility excavations are to be excavated to the design depth for bedding and placement and shall
not be over-excavated. Trench widths shall only be of sufficient width to allow placement and
proper construction of the utility and backfill of the trench.
2. Backfilling of a utility trench will be dependent on its location, use, depth, and utility line material
type. Trenches that are required to meet structural fill specifications, such as those under or near
buildings, or within pavement areas, shall have granular material strategically compacted to at
least the spring-line of the utility conduit to mitigate pipeline movement and deformation. The
initial lift thickness of backfill overlying the pipeline will be dependent on the pipeline material,
type of backfill, and the compaction equipment, so as not to cause deflection or deformation of the
pipeline. Trench backfill shall conform to the General Earthwork specifications for placement,
compaction, and testing of structural fill.
Geotextiles
1. All geotextiles shall be resistant to ultraviolet degradation, and to biological and chemical
environments normally found in soils. Geotextiles shall be stored so that they are not in direct
sunlight or exposed to chemical products. The use of a geotextile shall be specified and shall meet
the following specification for each use.
Subgrade/Aggregate Separation
Woven or nonwoven fabric conforming to the following physical properties:
Minimum grab tensile strength ASTM Method D-4632 180 lb
Minimum puncture strength (CBR) ASTM Method D-6241 371 lb
Elongation ASTM Method D-4632 15%
Maximum apparent opening size ASTM Method D-4751 No. 40
Minimum permittivity ASTM Method D-4491 0.05 s-1
Drainage Filtration
Woven fabric conforming to the following physical properties:
Minimum grab tensile strength ASTM Method D-4632 110 lb
Minimum puncture strength (CBR) ASTM Method D-6241 220 lb
Elongation ASTM Method D-4632 50%
Maximum apparent opening size ASTM Method D-4751 No. 40
Minimum permittivity ASTM Method D-4491 0.5 s-1
Geogrid Base Reinforcement
Extruded biaxially or triaxially oriented polypropylene conforming to the following physical properties:
Peak tensile strength
lb/ft
Tensile strength at 2% strain
ASTM Method D-6637
ASTM Method D-6637
925
300
lb/ft
Tensile strength at 5% strain
ASTM Method D-6637
600
lb/ft Flexural Rigidity ASTM Method D-1388 250,000 mg-cm
Effective Opening Size ASTM Method D-4751 1.5x
rock size