HomeMy WebLinkAboutStudies APPLICANT 5/19/2022Geotechnical Investigation
and Seismic Hazard Study
South Hills 3rd Level Reservoir Replacement
Springfield, Oregon
Prepared for:
Springfield Utility Board
Springfield, Oregon
May 16, 2022
Foundation Engineering, Inc.
di h Foundation Engineering, Inc.
Professional Geotechnical Services
Steven Wages, P.E. May 16, 2022
Springfield Utility Board
202 S 18th Street
Springfield, Oregon 97477
South Hills 3rd Level Reservoir Replacement Project No.: 2211098
Geotechnical Investigation and Seismic Hazard Study
Springfield, Oregon
Dear Mr. Wages:
We have completed the requested geotechnical investigation and seismic hazard
study for the above -referenced project. Our report includes a description of our work,
a discussion of the site conditions, a summary of laboratory testing, and a discussion
of engineering analyses. Recommendations for site preparation and foundation design
and construction are also provided.
A seismic hazard study was also completed to identify potential geologic and seismic
hazards and evaluate the effect those hazards may have on the proposed site. The
study fulfills the requirements presented in the 2019 Oregon Structural Specialty
Code (OSSC 2019) for site-specific seismic hazard reports for essential and
hazardous facilities, and major and special -occupancy structures. The 2019 OSSC is
based on the 2018 International Building Code and ASCE 7-16. Results of the study
(provided in Appendix D) indicate there are no geologic or seismic hazards that require
special design consideration or would preclude construction of the proposed
reservoir. The study was completed by Brooke Running, R.G., C.E.G.
There are numerous values in geotechnical investigations that are approximate
including calculated parameters, measured lengths, soil layer depths, elevations, and
strength measurements. For brevity, the symbol "±" is used throughout this report
to represent the words approximate or approximately when discussing these values.
It has been a pleasure assisting you with this phase of your project. Please do not
hesitate to contact us if you have any questions or if you require further assistance.
Sincerely,
FOUNDATION ENGINEERING, INC.
David L. Running, P.E., G.E.
Senior Geotechnical Engineer
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820 NW Cornell Avenue • Corvallis, Oregon 97330 • 541-757-7645
7857 SW Cirrus Drive, Bloo 24 • Beaverton, Oregon 97008 • 503-643-1541
GEOTECHNICAL INVESTIGATION
AND SEISMIC HAZARD STUDY
SOUTH HILLS 3RD LEVEL RESERVOIR REPLACEMENT
SPRINGFIELD, OREGON
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The Springfield Utility Board (SUB) is planning to replace an existing reservoir located
in the south hills of Springfield, east of S. 66" Place. The site location is shown on
Figure 1 A (Appendix A).
The existing site layout is shown on Figure 2A (Appendix A). The existing reservoir
is a 98 -foot diameter, 1.5 MG, concrete tank designated as Reservoir No. 1. It is
proposed to replace Reservoir No. 1 with two smaller, 67 -foot diameter, 0.58 MG,
steel tanks designated as Reservoir No. 2 and Reservoir No. 3. The proposed layout
for the new tanks is shown on Figure 3A (Appendix A). Reservoir No. 2 will be
constructed first and put in service. Then, Reservoir No. 1 will be taken off-line and
demolished and Reservoir No. 3 will be constructed in the existing Reservoir No. 1
footprint. Both new reservoirs will be welded steel tanks, with a finish floor elevation
(FIFE) of EI. 961.50, a maximum operational water surface elevation of EI. 982.75,
and an overflow elevation of EI. 983.75.
SUB is the project owner, Murraysmith is the lead design consultant, and Peterson
Structural Engineers (PSE) is the structural designer. SUB retained Foundation
Engineering, Inc. to conduct a geotechnical investigation for the project.
Foundation Engineering previously completed an investigation for a seismic
evaluation of the existing Reservoir No. 1 in 2013. The investigation included drilling
three exploratory borings at the site to evaluate the subsurface conditions. The
findings of the investigation were presented in a memorandum dated November 19,
2013. Information from that previous investigation was used to supplement the
current investigation. Geotechnical information included in the as -built plans for
Reservoir No. 1 was also utilized.
LOCAL GEOLOGY
Detailed discussions of the local and regional geology, tectonic setting, local faulting,
historical seismicity, seismic hazards, and design earthquakes are included in the
Site-specific Seismic Hazard Study report (Appendix D). References cited in this
section are found in Appendix D. An abbreviated discussion of the local geology is
provided below.
The reservoir site is located on bench on a north -facing slope at the southeast edge
of Springfield where it transitions from the Willamette Valley to the western foothills
of the Western Cascades. The Oregon Department of Geology and Mineral Industries
(DOGAMI) SLIDO and HazVu web viewers indicate the area is mapped as landslide
terrain.
South Hills 3rd Level Reservoir Replacement Mat 18, 2022
Geotechnical Investigation and Seismic Hazard Study 1 Pro act N., 2211098
Springfield. Oregon Springfield Utility Board
A mapped landslide extends across the site with the headscarp located ±800 to
1,200 feet to the south (uphill) and landslide debris extending up to ±3,500 feet to
the north (downhill). A series of smaller scarps are mapped uphill and downhill of the
reservoir site. DOGAMI estimates the landslide to be more than 150 years old. We
completed a reconnaissance of the reservoir site including the slopes immediately
uphill and downhill of the existing and proposed tanks. We did not observe any signs
of recent or active slope instability.
Local geologic mapping indicates the project site and immediate surrounding area is
generally underlain by volcaniclastic rock (Yeats et al., 1996; Hladky and McCaslin,
2006; McClaughry et al., 2010).
The subsurface conditions in our explorations are generally consistent with the
geologic mapping. Colluvial soils were encountered in each of the explorations
extending to depths of up to ±20 feet below the ground surface. Colluvium consists
of material that has been transported downslope and deposited via erosion, creep,
or landslide activity. Based on the terrain, we anticipate the colluvium was deposited
during previous landslide activity. The colluvium is typically underlain by residual soil
(i.e., bedrock that has decomposed in place to the consistency of soil) followed by
tuff, siltstone, sandy siltstone, and silty sandstone.
Details are provided in the Subsurface Conditions section below, cross-sections in
Appendix A, and on the boring logs in Appendix B.
FIELD EXPLORATION
2013 Investigation
We drilled three exploratory borings (BH -1 through BH -3) at the site as part of our
previous investigation on October 9, 2013. BH -2 and BH -3 were drilled adjacent to
Reservoir No. 1 and BH -I was drilled uphill of the reservoir site on Jessica Drive to
provide information to develop a subsurface cross-section. The borehole locations
are shown on Figures 2A and 3A.
Drilling was completed using a truck -mounted, CME 75 drill rig with mud -rotary
drilling and HQ wire -line coring techniques. The borings extended to maximum
depths ranging from ±30.8 to 35 feet. Disturbed samples were obtained in the
borings in conjunction with the Standard Penetration Test (SPT) at 2.5 -foot intervals
to ±15 feet, then at 5 -foot intervals thereafter. The SPT provides an indication of
the density or stiffness of the soil. Continuous, HO -sized coring was completed in
BH -1 from ± 15 to 35 feet, after competent bedrock was encountered.
Upon completion of drilling, BH -1 and BH -2 were backfilled with bentonite chips in
accordance with Oregon Water Resources Department (OWRD) guidelines. The
bentonite backfill was capped with gravel and asphaltic concrete (AC) cold patch in
BH -1, which was drilled on Jessica Drive and with gravel in 1311-3, which was drilled
on the gravel access road adjacent to the tank.
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Geotechnical Investigation and Seismic Hazard Study 2 Preset No.: 2211098
Springfield. Oregon Springfield utility Hoard
A one -inch inside diameter (I.D.) standpipe piezometer was installed in BH -2 to allow
measurement of groundwater levels. The standpipe extends to a depth of ±25 feet
and is slotted from ± 15 to 25 feet. The installation was capped at the ground surface
with a Morris monument set in concrete. After installation, the boring was bailed to
remove the drilling fluid, then allowed to recharge over a period of several days before
measuring.
The explorations were continuously logged during drilling. The final logs (Appendix B)
were prepared based on a review of the field logs, the laboratory test results, and an
examination of the soil and bedrock samples in our office. Photos of the rock core
from BH -1 are also provided in Appendix B.
2021 Investigation
We drilled two exploratory borings (BH -4 and BH -5) adjacent to the proposed
Reservoir No. 2 location on October 27, 2021. The borehole locations are shown on
Figures 2A and 3A.
Drilling was completed using a track -mounted, CME 55 tracked drill rig with
mud -rotary drilling techniques. BH -4 extended to a depth of ±26.5 feet and BH -5
extended to a depth of ±30.4 feet. Both borings terminated in bedrock. Disturbed
SPT samples were obtained in the borings at 2.5 -foot intervals to ±20 feet, then at
5 -foot intervals thereafter.
Upon completion of drilling, the boreholes were backfilled with bentonite chips in
accordance with OWRD guidelines. The bentonite backfill was capped with soil
cuttings in BH -4, which was drilled in an undeveloped area, and with gravel in BH -5,
which was drilled on the edge of the gravel access road.
The explorations were continuously logged during drilling. The final logs (Appendix B)
were prepared based on a review of the field logs, laboratory test results, and an
examination of the soil and bedrock samples in our office.
Previous Explorations by Others
SUB provided as -built plans (latest revision dated August 1982) for the existing
Tank 1 prepared by CH2M Hill, Inc. The plans indicate CH2M Hill dug exploratory
test pits as part of their investigation for the tank. The test pits extended to depths
ranging from ±5 to 12 feet and were dug prior to the site grading for the current
facility. Selected sheets are provided in Appendix B including Sheet 1 (Vicinity Map,
Site Layout, Index to Drawings) which shows the test pit locations and Sheet 2 (Test
Pit Logs, Reservoir Excavation, Roadway Section) which shows the test pit logs. The
locations of the test pits nearest to existing and proposed reservoirs are also shown
on Figures 2A and 3A. Information from the test pits was used to help characterize
the site conditions.
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Geotechnical Investigation and Seismic Hazard Study 3 project No.: 2211098
Springfield, Oregon Springfield Utility Board
The topographic contours shown on Figures 2A and 3A are based on the current
North American Vertical Datum of 1988 (NAVD88). Topographic contours shown on
plan Sheet 1 are based on the older National Geodetic Vertical Datum of 1929
(NGVD29). The ground surface elevations on Sheet 1 may be adjusted to NAVD88
by adding 3.55 feet to the NGVD29 contours.
LABORATORY TESTING
The laboratory testing included moisture content and Atterberg Limits tests to help
classify the soils according to the Unified Soil Classification System (USCS) and
estimate their overall engineering properties. Non -tested samples were visually
classified in accordance with ASTM D 2487 and ASTM D 2488. USCS symbols
shown on the boring logs for untested samples should be considered approximations.
The test results are summarized in Table 1C (Appendix C). The moisture contents
are also shown on the boring logs (Appendix B). The Atterberg limits tests indicate
the colluvium and residual soil that underlie the site have high plasticity with liquid
limits ILLI ranging from 67 to 85, plasticity indices (PI) ranging from 31 to 37, and a
USCS classification of MH.
SUMMARY OF SITE CONDITIONS
Surface Conditions
The existing Reservoir No. 1 (and proposed Reservoir No. 3 location) occupies a cut
bench. There is a gravel access road that extends along the perimeter of the existing
tank. Surface elevations on the bench range from ±EI. 968 on the south (uphill) side
to ±EI. 960 on the north (downhill) side. Photos 1A through 3A (Appendix A) show
the current site conditions.
The proposed Reservoir No. 2 site slopes gently down to the north. Surface
elevations within the proposed tank footprint range from ±EI. 968 on the south
(uphill) side to ±El. 961 on the north (downhill) side. The ground surface in this area
is densely vegetated with grass, weeds, ferns, blackberries, and scattered trees.
Photos 4A and 5A (Appendix A) show the current conditions.
South Hills 3rd Level Reservoir Replacement Mat 16, 2022
Geotechnical Investigation and Seismic Hazard Study 4 Pro ect No.: 2211098
Springfield, Oregon Springfield Utility Board
Subsurface Conditions
The borings encountered subsurface profiles that typically include the following
strata:
• Fill. Fill was encountered in the borings adjacent to Reservoir No. 1 extending
to depths of ±8 feet in BH -2 and ±7 feet in BH -3. The fill was used to backfill
around the lower portion of the tank and to grade the terrain for the access
road. The fill is variable and includes stiff gravelly clay and soft to medium
stiff clay with some sand, and soft to medium stiff clay and silty clay or clayey
silt with trace gravel and scattered cobbles and boulders. The fill is similar in
consistency to the underlying colluvium and was likely generated from onsite
excavations during the construction of Reservoir No. 1.
Fill is also exposed at the ground surface across the eastern portion of the
proposed Reservoir No. 2 location east of BH -4. The surficial fill at this location
consists of silt and clay with gravel to boulder -sized basaltic rock fragments.
Based on the as -built plans, it appears this fill represents material that was
excavated from the Reservoir No. 1 footprint and stockpiled at this location.
Surficial fill was also encountered in BH -1 and BH -5. The fill in BH -1 was
limited to the pavement section (i.e., AC and base rock) on Jessica Drive and
the fill in BH -5 was limited to ±9 inches of silty gravel used to construct the
access road.
• Colluvium. Colluvium (i.e., landslide deposits) was encountered in BH -1
beneath the Jessica Drive pavement, extending to ±7 feet. Adjacent to
Reservoir No. 1, the colluvium was encountered beneath the fill, from ±8 to
30 feet in BH -2 and from ±7 to 20 feet in BH -3. At Reservoir No. 3, the
colluvium extended to ±13.8 feet in BH -4 and ±5 feet in BH -5 -
The colluvium is variable, but primarily consists of stiff to very stiff sandy clay,
sandy silt, or clayey silt with trace to some sand and gravel. Scattered cobble
to boulder -sized rock fragments were observed in the colluvium in BH -2. The
variable nature of the material is typical of colluvial soil.
• Residual Soil. Residual soil (i.e., bedrock decomposed to the consistency of
soil) was encountered beneath the colluvium all borings except BH -2. The
residual soil was observed from ±7 to 10 feet in BH -1, from ±20 to 25 feet
in BH -3, from ± 13.8 to 18.8 feet in BH -4, and from ±5 to 20 feet in BH -5.
Residual soil may also be present above the bedrock in BH -2, but it was not
encountered within the selected sampling intervals.
The residual soil includes very stiff to hard sandy clay or clayey silt with some
sand. Relict sandstone texture was observed in samples of the residual soil in
BH -4 and BH -5.
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Geotechnical Investigation and Seismic Hazard Study 5 Proiect No.: 2211096
Springfield, Oregon Springfield Utility Hoard
Bedrock. Bedrock was encountered in each of the borings at ± 10 feet in BH -1 ,
at ±30 feet in BH -2, at ±25 feet in BH -3, at ± 18.8 feet in BH -4, and at ±20
feet in BH -5. The bedrock includes tuff, siltstone, sandy siltstone, and silty
sandstone. The bedrock is decomposed to slightly weathered at the surface
and generally becomes less weathered with depth. The rock hardness ranges
from extremely weak (RO) to very weak (R1). The rock typically becomes less
weathered and harder with depth. The siltstone core from BH -1 from ±25 to
35 feet indicates the rock has very close to moderately close, planar to
irregular, rough, open joints. Rock Quality Designation (ROD) values in the rock
core ranged from ±82 to 90 percent consistent with good quality.
The test pit logs provided in the as -built drawings by CH2M Hill typically describe
silty clay with basalt boulders or basalt boulders in a silty clay or silty sand matrix.
From the description and depths indicated in the logs, we expect these soils
correspond with the colluvium encountered in the recent borings. TP -4 indicated
weathered siltstone from ±4 to 12 feet. No further description of the siltstone was
provided. Based on its depth, this material may be consistent with the material we
are classifying as residual soil.
We developed three cross-sections across the site utilizing topographic data and the
subsurface information from the borings. The cross-section locations are shown on
Figures 2A and 3A. The cross-sections are shown on Figures 4A through 6A
(Appendix A).
Groundwater
Mud -rotary drilling precluded an accurate measurement of the groundwater in the
borings at the time of drilling. The piezometer in BH -2 was used to evaluate the
groundwater levels at the site. Groundwater measurements taken on October 16 and
November 7, 2013, and on October 27, 2021, are summarized in Table 1.
Table 1. Groundwater Depths and Elevations (BH -2)
Date
Groundwater Depth
(ft)
Groundwater Elevation
(ft)
11/16/13
23.2
944.5
11/7/13
16.0
951.7
10/27/21
16.4
951.3
The lower groundwater reading (±23.2 feet) was taken during a period of relatively
dry weather, while the higher groundwater readings (±16 feet and 16.4 feet) were
taken after several days of moderate rain. The available data suggests a significant
rise in the water table can occur in response to moderate rainfall.
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Geotechnical Investigation and Seismic Hazard Study 6 Project No.: 2211098
Springfield, Oregon Springfield Utility Board
DISCUSSION
Reservoir No. 2
Reservoir No. 2 will be a welded steel tank with a diameter of 67 feet, a FFE of
EI. 961.50, a maximum operational water surface elevation of EI. 982.75, and an
overflow elevation of EI. 983.75. The tank will have a 1/,inch thick steel floor plate
and a perimeter ring footing. No interior column footings will be required. A minimum
of 2 feet of compacted crushed rock will be placed beneath the floor and a minimum
of 1 foot of compacted crushed rock will be placed beneath the perimeter footing.
The current ground surface elevations within the planned footprint of the tank and
perimeter access road range from ±EI. 961 to ±EI. 970. Site grading for Reservoir
No. 2 will require excavations extending up to ± 10 feet below the current site grades
to allow for construction of the perimeter access road and a granular building pad
supporting the tank.
Based on the available information, we anticipate the excavations will encounter
surficial fill followed by colluvium or residual soil. The fill will likely consist of a
mixture of fine-grained soil and sand to boulder -sized rock fragments. The required
excavations will remove the fill and terminate in colluvium or residual soil comprised
of predominantly clayey silt with some sand. SPT N -values recorded in the colluvium
and residual soil correlate to medium stiff to very stiff consistency, however, these
N -values were recorded in soil having moisture contents above 40%. Fine-grained
soils with high moisture contents are typically sensitive to disturbance and develop
pore water pressure when penetrated by a split -spoon sampler, resulting in low SPT
N -values. Therefore, we anticipate the SPT N -values underestimate the soil strength
and the colluvium and residual soil are generally stiff to very stiff.
Reservoir No. 3
Reservoir No. 3 be a welded steel tank with the same general configuration as
Reservoir No. 2 including a FFE of EI. 961 .50, a maximum operational water surface
elevation of El, 982.75, and an overflow elevation of EI. 983.75. Reservoir No. 3 will
have a Y inch thick steel floor plate and a perimeter ring footing. No interior column
footings will be required.
Reservoir No. 3 will be located within the existing Reservoir No. i footprint. Reservoir
No. 1 has a 98 -foot diameter and a FFE of 956.75. Reservoir No. 1 will be partly
demolished with the removal of the roof, interior support columns, and the portion
of the perimeter wall that extends above -grade. The buried portion of the perimeter
wall and the floor slab will remain in place. The as -built plans for Reservoir No. 1
indicate the existing floor slab is typically 6 inches thick, transitioning to a 16 -inch
thick by 4 -foot wide perimeter footing. The plans also indicate the floor slab and
perimeter footing are underlain by at least 1 foot of compacted granular fill.
South Hills 3rd Level Reservoir Replacement Mat 16, 2022
Geotechnical Investigation and Seismic Hazard Study 7 Project No., 2211096
Springfield. Oregon Springfield Utility Board
Holes will be made in the existing floor slab to allow for drainage and compacted
crushed rock will be placed over the floor slab to grade the terrain beneath the new
tank. The crushed rock between the new tank floor will be up to 4.25 feet thick.
Cut Slopes
No retaining walls are currently planned. The site grading will require a permanent
cut slope on the south side of Reservoir No. 2. Based on the terrain and the soil
conditions, we recommend grading permanent cut slopes at 2(H):1 (V) or flatter. The
site should he graded to drain surface water away from the tanks. All cut and fill
slopes should be seeded as soon as practical to allow time to establish vegetation
before the wet winter and spring months.
Temporary cut slopes for the project should be made in accordance with OR OSHA
standards. We anticipate the colluvium and residual soil will correspond to an
OR-OSHA Class B soil due to its stiffness and plasticity. OR-OSHA recommends a
maximum temporary cut slope of 1(H):1(V) in Class B soil. The soil may degrade
when exposed to rainfall. Therefore, suitable cut slopes in these soils will have to be
confirmed in the field at the time of construction.
Construction Timing
The colluvium and residual soil are predominantly fine-grained and will be
moisture-sensitive. These materials will be susceptible to softening and erosion when
wet. Therefore, we recommend completing the earthwork in dry summer months
(typically mid-June through the end of September). Completing the earthwork during
this period will also allow time to establish vegetation on the cut slopes before the
wet season.
ENGINEERING ANALYSIS
Seismic Design
A detailed seismic hazard study was completed for the site and the findings are
summarized in Appendix D. The study concluded there are no seismic hazards that
would preclude construction of the proposed reservoirs, provided the earthwork is
completed as recommended herein.
Site Response Spectra. We developed site response spectra for the site in accordance
with AWWA D1OO-11 Section 13.2.7. The AWWA D1OO-11 site response is
separated into components with an impulsive component representing the structure
with 5% damping and a convective component with 0.5% damping representing the
fluid contents.
Based on the interpreted cross-sections, we anticipate the new tanks will be
underlain by stiff to very stiff colluvium and residual soil followed by relatively
shallow bedrock. We have concluded the subsurface conditions correspond most
closely to an AWWA Site Class C.
South Hills 3rd Level Reservoir Replacement Mat 16, 2022
Geotechnical Investigation and Seismic Hazard Study 8 Project No., 2211098
Springfield, Oregon Springfield Utility Board
AWWA D100-11 references ASCE 7-05 for seismic design. Seismic design in
ASCE 7-05 utilizes USGS 2002 seismic maps. For our evaluation of the tank site,
we used the updated USGS 2014 maps referenced in ASCE 7-16 and OSSC 2019
to provide the spectral accelerations consistent with the current building codes.
Risk -targeted maximum considered earthquake (MCER) spectral accelerations on
bedrock were obtained using modified USGS 2014 maps with 2% probability of
exceedance in 50 years (i.e., a ±2,475 -year return period). The modifications
include factors to adjust the spectral accelerations to account for directivity and risk.
We also used the USGS 2014 maps to determine maximum considered earthquake
(MCE) spectral accelerations on bedrock for a 10% probability of exceedance in
50 years (i.e., a ±475 -year return period), in case it is needed for design.
The bedrock spectral accelerations were multiplied Fe and Fv values selected from
ASCE 7-16 Tables 11-4-1 and 11-4-2 to calculate spectral accelerations at the
ground surface. The AWWA D100-11 site response spectra for 2% probability of
exceedance in 50 years are shown on Figure 7A (Appendix A). The site response
spectra for 10% probability of exceedance in 50 years are shown on Figure 8A
(Appendix A).
Vertical Accelerations. Design vertical acceleration (Av) may be calculated as 0.14Sos
based on AWWA D100-11 Section 13.5.4.3, using Sus from Figure 7A.
Liquefaction. Liquefiable soils typically consist of saturated, loose sands and
non -plastic or low plasticity silt (i.e., a PI of less than 8). Our borings indicate the
site is underlain by predominantly stiff to very stiff soil with medium to high plasticity.
These soils are not susceptible to liquefaction. Therefore, there is no liquefaction
hazard at the site.
Slope Stability Analysis. Because the site is located within mapped landslide
topography, we completed slope stability analysis to address potential instability
concerns. The analyses were completed for Cross -Sections A -A' and C -C' shown on
Figures 4A and 6A. We did not complete analysis for Cross -Section B -B' because
that cross-section is not aligned with the direction of movement of the original
landslide. Also, the subsurface conditions on Cross -Section B -B' are similar to the
other cross-sections.
Both static and seismic conditions were analyzed. Strength parameters for the soil
units were estimated from available correlations based on SPT N -values, laboratory
tests, and visual classifications. Typical strength tests (e.g., direct shear or triaxial
shear) were not practical based on the variable nature of the colluvium and residual
soil. Strength parameters were assigned to the colluvium, residual soil, and bedrock,
as well as an assumed thin soil layer at the interface between the colluvium and
residual soil.
South Hills 3rd Level Reservoir Replacement Mat 18, 2022
Geotechnical Investigation and Seismic Hazard Study 9 Project No.: 2211098
Springfield, Oregon Springfield Utility Board
Reduced strength parameters were assumed for this interface layer because previous
movement is expected to have occurred along this interface. Strength parameters
were not assigned to the surficial fill because this material is limited in extent. The
strength parameters vary slightly for static and seismic conditions. For static
analysis, the soil strength was modeled using internal friction angles (�) and no
cohesion (c) assuming drained loading conditions. For seismic analysis, an apparent
cohesion was added for the colluvium and residual soil to account for the soil
response to dynamic loading.
Groundwater conditions for the analysis were based, in part, on the groundwater
measurements from the piezometer in BH -2 and an estimation of the upper -bound
and average groundwater levels. We assumed the phreatic surface would
approximately follow the estimated slope of the bedrock surface. For static loading
conditions, we assumed the phreatic surface would correspond to a depth of
±10 feet at BH -2. We anticipate this groundwater level represents an upper -bound
condition. For seismic loading, we assumed the phreatic surface would correspond
to a depth of ±15 feet at BH -2. We anticipate this depth will represent an average
groundwater condition during the winter and spring.
Seismic conditions were simulated using pseudo -static analysis. For pseudo -static
analysis, a design horizontal acceleration (kh) of one-third to one-half of the estimated
peak ground surface acceleration (Aa) is typically used. The reduction accounts for
the non -rigid nature of the soil and the fact the peak ground acceleration only exists
for a short period of time and does not necessarily align perpendicular to the slope
(Kramer, 1996). For the analysis, we assumed a kh value of 0.1 Big corresponding to
0.5As. Aa was calculated by multiplying the estimated peak bedrock acceleration for
a 2% in 50 -year return interval (0.308) by a site amplification factor (FPGA) of 1.2,
assuming a Site Class C soil classification.
The program SL/DE 5.0 was used to complete the two-dimensional stability analysis
utilizing Bishop, Janbu, and Spencer methods. Circular and block failure modes were
analyzed. The circular failure search was limited to areas where a slope failure could
impact the reservoirs. The block failure search focused on the zone extending
beneath the reservoirs and assumed a failure surface approximately following the
interface between the colluvium and residual soil (i.e., along the failure surface of
the previous landslide). For Reservoir No. 2, a nominal uniform pressure of
1,500 lbs/foot2 (psf) was applied on the ground surface within the tank footprint to
represent the dead load imparted by the water and the structure. For Reservoir No. 3,
a nominal uniform pressure of 2,000 psf was applied on the ground surface within
the tank footprint to represent the dead load imparted by the water, the structure,
and the crushed rock used to backfill beneath the structure.
South Hills 3rd Level Reservoir Replacement Mat 16, 2022
Geotechnical Investigation and Seismic Hazard Study 10 Project Nri 2211098
Springfield, Oregon Springfield Utility Board
The output from the analyses is presented in Appendix E. A factor of safety (FS) of
at least 1.5 is typically required for static conditions where slope stability can affect
a critical facility. A FS of at least 1 .1 is typically required for seismic conditions. For
all cases, the results indicate FS values greater than 1 .5 for critical failure surfaces
that would impact the new tanks. The relatively high FS values are due to the
stiffness of the colluvium and residual soil, the relatively shallow bedrock depth, and
the relatively level bedrock surface.
Bearing Capacity
For Reservoir No. 2, we calculated an ultimate bearing capacity for the ring footing
assuming the footing will bear on 1 foot of compacted crushed rock underlain by
foundation soil with a 0 of 28 degrees and c of 200 psf. The calculations indicate an
ultimate bearing capacity of 9,000 psf. This value corresponds to an allowable
bearing pressure of 3,000 psf with a typical factor of safety of 3. A one-third
increase in the allowable bearing pressure (i.e., 4,000 psf) may be used in evaluating
short-term seismic loads.
The allowable bearing pressures provided above may also be used for the design of
Reservoir No. 3. We anticipate the allowable bearing pressures will be conservative
for Reservoir No. 3 because the ring footing for that structure will be underlain by a
thicker section of granular fill and the Reservoir No. 1 floor slab, which will help
spread the foundation load.
Settlement
Reservoir No. 3. The maximum operational water level in Reservoir No. 3 will
approximately match the operational water surface elevation in the original tank
(Reservoir No. 1). The net increase in bearing pressure beneath the new tank is
estimated to bet205 psf due to the weight of the steel floor and the thickened
granular fill section under the floor. The existing Reservoir No. 1 floor slab that will
remain in place beneath the new tank will also help distribute the load. For these
conditions, we anticipate the total foundation settlement will be less than % inch
and the differential settlement between the center and edges of the new tank floor
will be Y. inch or less.
Reservoir No. 2. The net increase in vertical stress for Reservoir No. 3 will be higher.
We calculated a net increase of ±885 psf beneath the center of the floor to account
for the removal of an average of 6 feet of existing fill and colluvium and the addition
of 2 feet of crushed rock, a A -inch thick steel floor plate, and 21.25 feet of water.
We assumed the perimeter ring footing will be 2.5 feet wide with a dead load in the
range of 1,500 to 2,000 psf.
We completed settlement analysis for Reservoir No. 3 using the computer program
Settle3D. We assigned a range of compressibility parameters for the colluvium and
residual soil based on our previous experience with similar stiff to very stiff soil. The
underlying bedrock was assigned a low compressibility.
South Hills 3rd Level Reservoir Replacement Mat 16, 2022
Geotechnical Investigation and Seismic Haeard Study 11 Pmjei No.: 2211098
Springfield, Oregon Springfield Utility Board
Our analysis indicates the total settlement may be up to ± 1 inch with up to ± % inch
of differential settlement between the center and edges of the tank. The calculations
indicate most of the settlement is due to the weight of the water rather than the
weight of the structure. Therefore, most of the settlement is expected to occur during
or shortly following the initial filling of the tank. Some long-term, post-construction
settlement (i.e., creep) should also be expected.
Staging the initial filling of the tank may be used to help the structure adjust to the
total and differential settlement. If this approach is selected, we recommend initially
filling the tank only halfway and monitoring settlements for a period of at least
2 weeks. If the rate and magnitude of settlement are confirmed to be close to or
below the estimated values and the pattern of settlement is relatively uniform, the
tank may be filled relatively quickly. Otherwise, we recommend filling the tank in
stages while monitoring the settlement.
Sliding Coefficient and Passive Resistance for Footings
The footings and tank floors will bear on compacted crushed rock. For sliding
analysis, we recommend using a coefficient of friction of 0.5 between the base of
the concrete and the crushed rock.
Passive resistance of the backfill in front of the buried footings was calculated as an
equivalent fluid density equal to y'Kp, where y is the unit weight of the backfill and
Kip is the passive earth pressure coefficient. We anticipate the footings for Reservoir
No. 2 will be backfilled with compacted crushed rock surrounded by medium stiff
colluvium or residual soil. For these conditions, we calculated the passive pressure
on the footings assuming an average y of 120 pcf (lbs./ft) and an average � of
34 degrees. The calculations indicate the ultimate passive resistance may be
modeled using an equivalent fluid density of ±420 pcf.
We anticipate the ring footing for Reservoir No. 3 will be backfilled with compacted
crushed rock extending at least 10 feet beyond the edges of the tank. For these
conditions, we calculated the passive pressure on the footings assuming a y of
130 pcf and a 0 of 38 degrees. The calculations indicate the ultimate passive
resistance may be modeled using an equivalent fluid density of ±550 pcf.
The passive resistance may be combined with the sliding resistance at the base of
the footings to evaluate the overall lateral resistance, however, the sliding and
ultimate passive resistances will develop with different displacements. The sliding
resistance will develop with very small transitional movement. Development of the
ultimate passive resistance on the footings may require a lateral displacement
corresponding to 1 % of the buried footing height.
South Hills 3rd Level Reservoir Replacement Mat 16, 2022
Gecnechnical Investigation and Seismic Hazard Study 12 Protect No.: 2211098
Springfield. Oregon Springfield Utility Board
DESIGN AND CONSTRUCTION RECOMMENDATIONS
Design and construction recommendations are provided in the following sections.
We recommend contractors be provided a copy of this report to review the site
conditions and recommendations for site preparation and foundation construction.
The construction recommendations provided below assume earthwork will occur
during dry weather. These recommendations will need to be modified if the work is
completed during wet weather.
General Earthwork
1. Select Fill as defined in this report should consist of % or 1 -inch minus,
clean (i.e., less than 5% passing the #200 U.S. Sieve), well -graded,
angular crushed rock. We should be provided a gradation sheet for this
material for approval prior to delivery to the site.
2. Drain Rock should consist of % to 11/,inch, clean (less than 2% passing
the #200 sieve), open -graded, angular, crushed quarry rock. Other
gradations may be acceptable, provided the rock is durable and free
draining. We should be provided a gradation sheet for this material for
approval prior to delivery to the site.
3. Separation Geotextile should be a non -woven or non -woven geotextile
with Mean Average Roll Value (MARV) strength properties meeting the
requirements of an AASHTO M 288-17 Class 2 Separation Geotextile
with a maximum AOS of 0.6 mm (max average roll value) and a
permittivity greater than 0.05 sec'. We should be provided a
specification sheet on the selected geotextile for approval prior to delivery
to the site.
4. Subsurface Drainage Geotextile should be a non -woven geotextile with
Mean Average Roll Value (MARV) strength properties meeting the
requirements of an AASHTO M 288-17 Class 3 Subsurface Drainage
Geotextile, with a maximum AOS of 0.22 mm (max average roll value)
and a permittivity greater than 0.1 sec'. We should be provided a
specification sheet on the selected geotextile for approval prior to delivery
to the site.
5. Compact all fill in loose lifts not exceeding 12 inches. The lift thickness
should be reduced to 6 inches where light or hand -operated equipment is
used. Compact all fill to a minimum of 95% relative compaction. The
maximum dry density of ASTM D 698 should be used as the standard for
estimating relative compaction. The moisture content of the fill should be
adjusted to within ±2% of its optimum value prior to compaction. Field
density tests should be run frequently to confirm adequate compaction of
the fill.
South Hills 3rd Level Reservoir Replacement Mat 16, 2022
Geotechnical Investigation and Seismic Hazard Study 13 Project No.: 2211098
Springfield, Oregon Springfield Utility Board
Foundation Design and Construction
6. Design the tanks using the seismic design parameters and response
spectra shown on Figures 7A and 8A.
7. Design the footings using an allowable bearing pressure of 3,000 psf.
This value may be increased by one-third for transient loads. The
allowable bearing pressure assumes the footings will bear on at least
1 foot of compacted Select Fill underlain by stiff soil.
S. For Reservoir No. 2, assume the total foundation settlement will be less
than 1 inch and the differential settlement will be %4 inch or less.
9. For Reservoir No. 3, assume the total foundation settlement will be less
than Y� inch and the differential settlement will be % inch or less.
10. Use a coefficient of sliding friction of 0.5 between the bottom of the
footings and the compacted Select Fill and a coefficient of sliding friction
of 0.4 between the bottom of the steel floors and the compacted Select
Fill. The ultimate passive resistance for the buried ring footing at Reservoir
No. 2 may be calculated using an equivalent fluid density of 420 pcf. The
ultimate passive resistance for the buried ring footing at Reservoir No. 3
may be calculated using an equivalent fluid density of 550 pcf. Assume
sliding friction will develop with very little movement, but a lateral
displacement of up to 1 % of the buried footing height will be required to
mobilize the ultimate passive resistance.
Foundation Preparation
Reservoir No. 2
11. Strip the existing ground as required to remove roots and organics. The
typical stripping depth is expected to be ±4 inches. Deeper stripping and
grubbing depths will be required where trees are encountered. Dispose of
all strippings outside of construction areas.
12. Excavate the tank area as required to provide a minimum of 2 feet of
Select Fill beneath the floor and 1 foot of Select Fill beneath the ring
footing. The excavation of the ring footing would extend at least 1 foot
beyond the edges of the footing. We recommend completing the final
excavation using an excavator equipped with a smooth-edged bucket to
reduce subgrade disturbance. All loose or disturbed soil should be
removed prior to backfilling.
13. Use Select Fill to backfill the tank excavation. Place and compact the fill
in lifts as recommended in Item 5.
South Hills 3rd Level Reservoir Replacement Mat 16, 2022
Geotechnical Investigation and Seismic Hazard Study 14 Project No.: 2211098
Springfield, Oregon Springfield Utility Board
14. Grade the area surrounding the tank to promote runoff away from the
foundation. Surface runoff should be collected by swales or a French
drain and directed away from the tank. Concentrated runoff should not
be directed onto native slopes.
Reservoir No. 3
15. Demolish the roof, interior columns, and above -grade walls of the existing
tank. Existing interior columns should be cut off at least 2 feet below the
bottom of the new floor. Drill or punch several holes in the existing floor
slab to allow for drainage. Haul all construction debris off site.
16. Use Select Fill to backfill inside the existing reservoir footprint as required
to grade for the new ring footing and floor. Place and compact the fill in
lifts as recommended in Item 5.
17. Grade the area surrounding the tank to promote runoff away from the
foundation. Surface runoff should be collected by sweles or a French
drain and directed away from the tank. Concentrated runoff should not
be directed onto native slopes.
Access Road
Reservoii No. 2
18. Excavate the access road subgrade to accommodate a minimum of
12 inches of Select Fill. Compact the subgrade surface to mitigate any
surface disturbance. Proof -roll the subgrade using a loaded, 10 -yd' dump
truck or other heavy construction vehicle approved by Foundation
Engineering prior to placing the Select Fill. Soft or pumping subgrade
identified during the proof -roll may be moisture -conditioned and
recompacted, or overexcavated and replaced with compacted Select Fill
and proof -rolled again.
19. We recommend providing a Separation Geotextile beneath the Select Fill
to reduce the risk of subgrade intrusion into the base rock. The Separation
Geotextile should be laid flat over the subgrade and pulled tight to remove
wrinkles. A minimum of ±2 feet of overlap should be provided between
adjacent rolls of the Separation Geotextile. The geotextile should be
overlapped in the direction the fill will be placed to reduce the risk of
separation. Place a minimum of 12 inches of Select Fill over the
Separation Geotextile to construct the base rock section. Compact the
Select Fill as recommended in Item 5.
South Hills 3rd Level Reservoir Replacement Mat 16, 2022
Geotechnical Investigation and Seismic Hazard Study 15 Project No.: 2211098
Springfield Oregon Springfield Utility Board
Reservoir No. 3
20. The perimeter access road for Reservoir No. 3 will be located within the
footprint of Reservoir No. 1. We recommend backfilling the Reservoir
No. 1 footprint using Select Fill placed and compacted as recommended
in Item 5. A Separation Geotextile is not required at this location.
Cut and Fill Slopes
21. Temporary cut slopes should be excavated or shored in accordance with
OR OSHA recommendations.
22. We anticipate the medium stiff to stiff colluvium and residual soil will
correspond to an OR OSHA Type B soil. OSHA recommends excavating
temporary cut slopes no steeper than 1 (H):1 (V) in Type B soil. The soil
may degrade when exposed to rainfall. Therefore, the appropriate soil
type and suitable temporary cut slopes will have to be confirmed in the
field at the time of construction.
23. The permanent cut slope on the south side of the tanks should be graded
at 2(H):1(V) or flatter. Fill slopes should also be graded no steeper than
2(H):I M.
24. Soil that is left exposed on slopes will also be susceptible to raveling and
erosion. Therefore, following construction, all exposed ground surfaces
should he vegetated as soon as practical so that a mature vegetation cover
is in place prior to the onset of wet weather. Residual soil exposed in the
cut slopes may be relatively sterile for growing vegetation. Therefore, it
may be necessary to dress the finished surfaces with topsoil or use an
appropriate fertilizer and erosion control blanket to help establish
vegetation. We assume specific recommendations of the type of vegetation
will be provided by others.
Drainage
A perimeter foundation drain is not required around the tanks if the site is adequately
graded to direct surface water away from the foundations. However, a perimeter
drain may be desirable for leak detection, if so, the system should be built as
described below. These recommendations may also be used for constructing a French
drain to intercept surface runoff.
25. The foundation drain, if needed, should consist of a 6 -inch diameter,
perforated HDPE or PVC pipe. The flowline of the pipe should be set at
least 12 inches below the bottom of the floor. The pipe should be bedded
in at least 4 inches of Drain Rock and backfilled to within 6 inches of the
ground surface with Drain Rock. The mass of Drain Rock should be
wrapped in a Subsurface Drainage Geotextile that laps at least 12 inches
at the top.
South Hills Srd Level Reservoir Replacement Mat 16, 2022
Gap achurical Investigation and Seismic Hazard Study 16 Project No.: 2211098
Springfield, Oregon Springfield Utility Board
26. Provide clean -outs at appropriate locations for future maintenance of the
drainage system.
27. Discharge the water from the drain system away from the tank in a
manner that will not cause local erosion or ponding at the outlet of the
drainpipe.
DESIGN REVIEW/CONSTRUCTION OBSERVATION/TESTING
We should be provided the opportunity to review all drawings and specifications that
pertain to site preparation and foundation construction. Site preparation will require
field confirmation of the subgrade conditions beneath the tanks. That confirmation
should be done by a Foundation Engineering representative. Mitigation of any
subgrade pumping will also require engineering review and judgment. Frequent field
density tests should be run on all engineered fill.
VARIATION OF SUBSURFACE CONDITIONS, USE OF THIS REPORT, AND WARRANTY
The analysis, conclusions, and recommendations contained herein assume the
subsurface profiles observed in the borings and test pits are representative of the
site conditions. The above recommendations assume we will have the opportunity
to review final drawings and be present during construction to confirm the assumed
soil and groundwater conditions in the excavations. No changes in the enclosed
recommendations should be made without our approval. We will assume no
responsibility or liability for any engineering judgment, inspection, or testing
performed by others.
This report was prepared for the exclusive use of the Springfield Utility Board and
their design consultants for the South Hills 3rd Level Reservoir Replacement project
in Springfield, Oregon. Information contained herein should not be used for other
sites or for unanticipated construction without our written consent. This report is
intended for planning and design purposes as described herein. Contractors using
this information to estimate construction quantities or costs do so at their own risk.
Our services do not include any survey or assessment of potential surface
contamination or contamination of the soil or groundwater by hazardous or toxic
materials. We assume those services, if needed, have been completed by others.
Our work was done in accordance with generally accepted soil and foundation
engineering practices. No other warranty, expressed or implied, is made.
South Hills 3rd Level Reservoir Replacement
Geotechnical Investigation and Seismic Hazard Study
Springfield, Oregon
REFERENCES
AASHTO, 2017, Geosynthetic Specification for Highway Applications, American
Association of State Highway Transportation Officials (AASHTO), M288-17,
June 2017.
ASCE, 2017, ASCE 7-16: Minimum Design Loads and Associated Criteria for
Buildings and Other Structures, American Society of Civil Engineers (ASCE),
ISBN 978-0-7844-7996-4.
ASTM, 2011, Standard Test Method for Classification of Soils for Engineering
Purposes (Unified Soil Classification System, USCS): American Society of
Testing and Materials (ASTM) International, ASTM Standard D2487, DO]:
10.1520/D2487-11, 11 p.
ASTM, 2009, Standard Test Method for Description and Identification of Soils
(Visual -Manual Procedure): American Society of Testing and Materials (ASTM)
International, ASTM Standard D2488, DOI: 10.1520/D2488 -09A, 11 p.
AWWA, 2011, Welded Carbon Steel Tanks for Water Storage, Q1004 1): American
Water Works Association (AWWA), July 1, 2011.
DOGAMI, 2020, SLIDO (Statewide Landslide Information Database for Oregon)
Viewer, SLIDO-4.2: Oregon Department of Geology and Mineral Industries
(DOGAMI), website: http://www.oregongeology.com/sub/slido/index.htm,
updated October 30, 2020, accessed November 2021.
IBC, 2018, International Building Code: International Code Council, Inc.,
Sections 1613 and 1803.3.
Kramer, S.L., 1996, Geotechnical Earthquake Engineering, Published by Prentice Hall
OSSC, 2019, Oregon Structural Speciality Code (OSSC): Based on the International
Code Council, Inc., 2018 International Building Code (IBC), Sections 1613 and
1803.
OR -OSHA, 2011, Oregon Administrative Rules, Chapter 437,
Division 3 - Construction, Subdivision P - Excavations: Oregon Occupational
Safety and Health Division (OR -OSHA), 1926.650,
www.osha.orlpdf/rules/division3/div3.pdf.
South Hills 3rd Level Reservoir Replacement Mat 1
Geotechnical Investigation and Seismic Hazard Study 18 Pro ect No.::
Springfield, Oregon Springfield Utili
di hk
Appendix A
Figures and Site Photos
Foundation Engineering, Inc.
Professional Geotechnical Services
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c a�
SITE
\ \ L I
SCALE IN FEET
NOTE:
BASE MAP OBTAINED FROM THE USGS WEBSITE (https://ngmdb.usgs.gov). 0 1000 2000 4000
Foundation Engineering Inc. VICINITY MAP FIGURE NO.
Professional Geotechnical Services
PROJECT NO. DATE DRAWN BY SOUTH HILLS 3RD LEVEL RESERVOIR REPLACEMENT 1A
22nass ocr zozi MLM SPRINGFIELD, OREGON
ID' PUE
.A' —
APPROX LOC
A)3AND 12' W _ --4� _ _ _ �i OF EXIST W
H
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c i -`. – — -- v
SBH 311��I�-
13
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FSE IVO_2\ 3RD LEVEL RES NO. 1
IN P-5 98' DIA
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EXIST PARTIALLY BURIED,
PRE -STRESSED CONC RES
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A A Cross -Section Location �:d` vIT,tA��,. �f V �-'
SCALE IN FEET
0 2D 40 80
NOTES: IIIII ���I EXISTING SITE LAYOUT AND EXPLORATIONS FIGURE NO.
1. EXPLORATION LOCATIONS WERE ESTABLISHED REFERENCING EXISTING LANDMARKS AND ARE APPROXIMATE. JIVUII IUW4 Foundation Engineering, Inc.
2. SEE REPORT FOR A DISCUSSION OF SUBSURFACE CONDITIONS. Professional Geotechnical Services
3. BASE MAP WAS PROVIDED BY MURRAYSMITH. PROJECT No. DATE: DRAWN BY: SOUTH HILLS 3RD LEVEL RESERVOIR REPLACEMENT 2A
4. CROSS-SECTIONS A -A' AND C -C' EXTEND NORTH OFF OF THE PAGE. SEE FIGURE 3A FOR NORTHERN EXTENTS.
22tto9s Mar ts, zazz MLM SPRINGFIELD, OREGON
LEGEND
BH -1 - Foundation Engineering Boring
9 TP -4 - CH2M Hill Test Pit
A -A' - Cross -Section Location
NOTES:
1. EXPLORATION LOCATIONS WERE ESTABLISHED REFERENCING EXISTING LANDMARKS AND ARE APPROXIMATE.
2. SEE REPORT FOR A DISCUSSION OF SUBSURFACE CONDITIONS.
3. BASE MAP WAS PROVIDED BY MURRAYSMITH.
4. CROSS-SECTIONS A -A' AND C -C' EXTEND SOUTH OFF OF THE PAGE. SEE FIGURE 2A FOR SOUTHERN EXTENTS.
BH -1
SCALE IN FEET
0 20 40 80
A
Ar
PROPOSED RES. 3
)090
995 EXISTING RES. 1
j
990 \
985
980
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some Minn. tram b some
945 xE1. 0440 �Ity CLAY ace allays clur
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(w odium)
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930 d"r o Ekmmnly waak (RC) TUFF
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925
920
SCALE IN FEET
0 15' 30' 60'
NOTES:
1. CROSS-SECTION A-A' BASED ON SURVEY BY MURRAYSMITH. IOW
��pp����,, CROSS-SECTION A-A'
�L FOUriCI&ilOri Engineering, Inc.
FIGURE NO.
2.
SEE FIGURES 2A AND 3A FOR LOCATION OF CROSS-SECTION A-A'. aiiiiii
Protes9i0i Ob016C119I191 Services
3.
SEE REPORT FOR A DISCUSSION OF SUBSURFACE CONDITIONS. PROJECT NO. DATES DRAWN eY'. SOUTH HILLS 3RD LEVEL RESERVOIR REPLACEMENT
��
4.
SYMBOL-? - DENOTES THE ASSUMED SOIL1BEDROCK CONDITIONS BETWEEN EXPLORATION LOCATIONS.
2211098 mAY 18, zozz yi SPRINGFIELD, OREGON
C
C'
SCALE IN FEET
0 15' 30' 60'
NOTES:
1. CROSS-SECTION C -C' BASED ON SURVEY BY MURRAYSMITH,
2. SEE FIGURES 2A AND 3A FOR LOCATION OF CROSS-SECTION C -C'.
3. SEE REPORT FOR A DISCUSSION OF SUBSURFACE CONDITIONS.
4. SYMBOL -? - DENOTES THE ASSUMED SOILIBEDROCK CONDITIONS BETWEEN EXPLORATION LOCATIONS.
PROPOSED RES 2
BH Jessica Drive
1000
-t
(ke1. 892.61
995
/
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Very 6411 assay SILT. some sand
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935
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930
aELsalm
925
920
SCALE IN FEET
0 15' 30' 60'
NOTES:
1. CROSS-SECTION C -C' BASED ON SURVEY BY MURRAYSMITH,
2. SEE FIGURES 2A AND 3A FOR LOCATION OF CROSS-SECTION C -C'.
3. SEE REPORT FOR A DISCUSSION OF SUBSURFACE CONDITIONS.
4. SYMBOL -? - DENOTES THE ASSUMED SOILIBEDROCK CONDITIONS BETWEEN EXPLORATION LOCATIONS.
M
0.8
0.7
N 0.6
c
O
� 0.5
a
� 0.4
1j 0.3
N
ON
0.1
a
t r r
-I
T
1-
AWWA Response Spectrum
Convective Components - I
r
AMA Response Spectrum _
Impulsve Components
2 4 6 8 10 12
Period (seconds)
Notes:
1. The Design Response Spectra are based on the General Procedure in AW WA D100-11
Section 13.2. 7 with a 2% probability of exceedenee in 50 years.
2. The following parameters were used for the impulsive component response spectrum:
Site Class= C Damping = 5%
Ss= 0.63 Fe= 1.25 Srns= 0.78 Sas— 0.52
S, = 0.36 F,= 1.50 Su, = 0.54 Sm = 0.36
3. Sc and S, values indicated in Note 2 are USES 2014 risk -targeted MCE spectral
accelerations available from Ifflua utaismicmaps.oM.
4. F, and F„ rere selected from ASCE 7-16 Tables 11.4-1 and 11.4-2 based on the
Ss and Si values. Sus and Sm values include a 213 reduction on Sues and Sun as
discussed in AWWA D100-11 Section 13.2.7.
5. The response spectrum for the convective components was calculated based on
AW WA Di 00-11 Eq. 13-12.
6. Site location is: Latitude 44.0347, Longitude -122.9097.
FIGURE 7A
AWWA D100-11 SITE RESPONSE SPECTRA
2% Probability of Exceedence in 50 years
South Hills 3rd Level Reservoir Replacement
Springfield, Oregon
Project No.: 2211098
0.6
0.5
3
0.1
0.0
mse Spectrum
Components
AVrWA Response Spectrum
Impuleve Components
0 2 4 6 8 10 12
Period (seconds)
Notes:
1. The Design Response Spectra are based on the General Procedure in AV VA D100-11
Section 13.2.7 with a 10% probability of exreedence in 50 years.
2. The follovdng parameters were used for the impulsive component response spectmm
Site Class = C Damping = 5%
Se = 0.26 F, = 1.30 S.- 0.33
St= 0.13 F„= 1.50 Sx,= 0.20
3. Ss and S, values indicated in Nate 2 are USGS 2014 MCE spectral accelerations
corrected for directivity available from httpslf:seismicmaps.org.
4. F, and F, were selected from ASCE 7-16 Tables 11.4-1 and 11.4-2 based on the
Ss and S, values.
5. The response spectrum for the convective eemponents was calculated based on
AVMA D100-11 Eq. 13-12.
6. Site location is: Latitude 44.0347; Longitude -122.9097.
FIGURE 8A
AWWA D100-11 SITE RESPONSE SPECTRA
10% Probability of Exceedence in 50 years
South Hills 3rd Level Reservoir Replacement
Springfield, Oregon
Project No.: 2211098
Foundation Engineering, Inc.
South Hills 3rd Level Reservoir Replacement
Project No.: 2201098
Photo 1A. Existing surface conditions south of Reservoir No. 1 looking east.
Photo 2A. Existing surface conditions west of Reservoir No. 1 looking northeast.
Foundation Engineering, Inc.
South Hills 3rd Level Reservoir Replacement
Project No.: 2201098
Photo 3A. Existing surface conditions north of Reservoir No. 1 looking east.
Photo 4A. Existing surface conditions at the proposed Reservoir No. 2
location looking southeast.
Foundation Engineering, Inc.
South Hills 3rd Level Reservoir Replacement
Project No.: 2201098
Photo 5A. Existing surface conditions at the proposed Reservoir No. 2
location looking southwest.
Ah
Professional
Geotechnical
Services
Appendix B
As -Built Plans, Boring Logs,
and Rock Core Photos
Foundation Engineering, Inc.
DISTINCTION BETWEEN FIELD LOGS AND FINAL LOGS
A field log is prepared for each exploration by our field representative. The log contains information
concerning sampling depths and the presence of various materials such as gravel, cobbles, and fill, and
observations of groundwater. It also contains our interpretation of the soil conditions between samples.
The final logs presented in this report represent our interpretation of the contents of the field logs and the
results of the sample examinations and laboratory test results. Our recommendations are based on the
contents of the final logs and the information contained therein and not on the field logs.
VARIATION IN SOILS BETWEEN EXPLORATIONS
The final log and related information depict subsurface conditions only at the specific location and on the
date indicated. Those using the information contained herein should be aware that soil conditions at other
locations or on other dates may differ. Actual foundation or subgrade conditions should be confirmed by
Foundation Engineering during construction.
TRANSITION BETWEEN SOIL OR ROCK TYPES
The lines designating the interface between soil, fill or rock on the final logs and on subsurface profiles
presented in the report are determined by interpolation and are therefore approximate. The transition
between the materials may be abrupt or gradual. Only at boring or test pit locations should profiles be
considered as reasonably accurate and then only to the degree implied by the notes thereon.
SAMPLE AND TEST SYMBOLS
SS -3-4 C - Pavement Core Sample
Sample Number CS - Rock Core Sample
Exploration Number OS -Oversize Sample (3 -inch O.D. split -spoon)
Sample Type S - Grab Sample
SH - Thin-walled Undisturbed Sample
Top of Sample Attempt SS - SPT Sample (2 -inch O.D. split -spoon)
Recovered Portion
• Standard Penetration Test resistance equals the number
Unrecovered Portion of blows a 140 lb. weight falling 30 in. is required to drive a
standard split -spoon sampler 1 ft. Practical refusal is
SH SS Bottom of Sample Attempt equal to 50 or more blows per 6 in. of sampler penetration.
• Water Content (%)
FIELD SHEAR STRENGTH TEST GROUNDWATER
Shear strength measurements on test pit side walls, Groundwater Location
blocks of soil or undisturbed samples are typically —
made with Towers or Field Vane shear devices. (1/3121) Date of Measurement
Values reported as undrained shear strength (S,) in tsf.
TYPICAL SOIL/ROCK SYMBOLS
® Concrete
® Silt
Basalt
® Organics
Sand
Sandstone
® Clay
Gravel
Siltstone
SII h Foundation Engineering, Inc.
Professional Geotechnical Set -vices
UNIFIED SOIL CLASSIFICATION SYMBOLS
G - Gravel
W - Well Graded
S - Sand
P - Poorly Graded
M - Silt
L - Low Plasticity
C - Clay
H - High Plasticity
Pt - Peat
O - Organic
EXPLORATION LOG KEY
IMPORTANT INFORMATION AND SYMBOLS
Explanation of Common Terms Used in Soil Descriptions
Field Identification
Cohesive Soils
Granular Soils
SPT-
Sr** (tsf)
Term
SPT"
Term
Easily penetrated several inches by fist.
0-2
x0.125
Very Soft
0-4
Very Loose
Easily penetrated several inches bythumb.
2-4
0.125-0.25
Soft
4-10
Loose
Can be penetrated several inches by thumb with
moderate effort.
4-3
0.25-0.50
Medium Stiff
10-30
Medium Dense
Readily indented by thumb but penetrated only with
ffo
grantert.
8-15
0.50-1.0
Stiff
30-50
Dense
Readily indented by thumbnail.
15-30
1.0-2.0
Very Stiff
>50
Very Dense
Indented with difficulty by thumbnail.
> 30
> 2.0
Hard
' SPT N -value in blows per foot (bpr)
' Untrained shear strength
Term
Soil Moisture Field Description
Dry
Absence of moisture. Dusty. Dry to the touch.
Damp
Soil has moisture. Cohesive soils are below plastic limit and usually moldable.
Moist
Grains appear darkened. but no visible water. Silt/clay will clump. Sand will bulk. Soils are often at or near plastic
Can be rolled into a thread with some difficulty.
limit.
15-30
Visible water on larger grain surfaces. Sand and mhesionless silt exhibit dilatancy. Cohesive sail can be readily
Wet
remolded. Soil leaves wetness on the hand when squeezed. Soil is wetter than the optimum moisture content and
Easily rolled and re -rolled into thread.
above the plastic limit.
Term
PI
Plasticity Field Test
Nan -plastic
0-3
Cannot be rolled into a thread at any moisture.
Lew Plasticity
3- 15
Can be rolled into a thread with some difficulty.
Medium Plasticity
15-30
Easily rolled into thread.
High Plasticity
> 30
Easily rolled and re -rolled into thread.
Term
Soil Structure Criteria
Stratified
Alternating layers at least''/. inch thick.
Laminated
Alternating layers less than 'A inch thick.
Fissured
Contains shears and partings along
planes of weakness.
Slickensided
Palings appear glossy or striated.
Blecky
Breaks along surfaces into smaller lumps
or blocks. Slickensides may be visible.
Lensed
Contains pockets of different soils.
Term
Soil Cementation Criteria
Weak
Breaks under light finger pressure.
Moderate
Breaks under hard finger pressure.
Strong
Wit not break with finger pressure.
Foundation Engineering, Inc.I EXPLORATION LOG KEY
Professional Geotechnical Services COMMON SOIL DESCRIPTION TERMS
Explanation of Common Terms Used in Rock Descriptions
Field Identification
Weathering Field Identification
UCS (psi)
Strength
Hardness
Rock mass is generally fresh. Discontinuities are stained and may contain clay. Some discoloration in rock fabric.
Mcderatedly
Significant portions of rock show discoloration and weathering effects. Crystals are dull and show visible chemical
Weathered
(ODOT)
Indented by thumbnail.
R0
'100
Extremely Weak
Extremely Soft
Crumbles under firm blows with geological hammer.
Decomposed
Rock mass is completely decomposed. Original rock' fabric' maybe evident (relict texture). Maybe reduced ideal l
Wide
with hand pressure.
Can be peeled by a packet knife.
R1
100- 1,000
Very Weak
Very Soft
Can be peeled by a pocket knife with difficulty, shallow indentations
made by firm blow with geological hammer.
R2
1,000-4,000
Weak
Soft
Cannot be scraped or peeled with a pocket knife, specimen can be
fractured with a single blow of geological hammer.
R3
4,000-8,000
Medium Strang
Medium Hard
Specimen requires more than one blow of geological hammer to
R4
8,000-16,000
Strong
Hand
fracture it.
Specimen requires many blows ofgeological hammer to fracture it.
R5 1
116,000 1
Very Strong
Very Hard
Term (ODOT)
Weathering Field Identification
Fresh
Crystals are bright. Discontinuities may show some minor surface staining. No discoloration in rock fabric.
Slightly Weathered
Rock mass is generally fresh. Discontinuities are stained and may contain clay. Some discoloration in rock fabric.
Mcderatedly
Significant portions of rock show discoloration and weathering effects. Crystals are dull and show visible chemical
Weathered
alteration. Discontinuities are stained and may contain secondary mineral deposits.
Highly Weathered
Rock can be excavated with geologist's pick. All discontinuities exhibit secondary mineralization. Complete
(Predominately
discoloration of rack fabric. Surface of core is friable and usually pitted due to washing out of highly altered minerals
Decomposed)
by drilling water.
Decomposed
Rock mass is completely decomposed. Original rock' fabric' maybe evident (relict texture). Maybe reduced ideal l
Wide
with hand pressure.
Spacing (metric)
Spacing (imperial)
Spacing Term
Bedding/Foliation
<6 cm
<2 in
Very Close
Very Thin (Laminated)
6cm-30 cm
2in-1ft
Close
Thin
30 cm -90 can
lit-3ft
Moderately Close
Medium
90 cm-3.Om
311-101
Wide
Thick
> 3.0 in
> 10 it
Very Wide
Very Thick (Massive)
Vesicle Term Volume
Some vesicles
5-25%
Highly vesicular
25-50%
Scoriaceous
> 50%
Stratification Term
Description
Lamination
< 1 can(0.4 in) thick beds
Fissile
Preferred break along laminations
Parm,
Prepared break parallel to bedding
Foliation
Metamorpic layering and segregation of minerals
RQD %
Designation
RQD %
Designation
0-25
Very Poor
75-90
Good
11
25-50
Poor
g0-100
Excellent
50-75
Fair
Rock Quality Designation (RQD) is the
cumulative length of intact rock core pieces 4
inches or longer (excluding breaks caused by
drilling and handling) divided by run length,
expressed as a percentage.
AWWII Foundation Engineering, Inc. I EXPLORATION LOG KEY
Professional Geotechnical Services COMMON ROCK DESCRIPTION TERMS
Depth
Soil and Rock Description
May.
♦ SPT, 0 Moisture, %
Baokgg/
and
Log
Samples
N -Value
InstallationsI
Feat
comments
Depth
Rewvery ® RQD., %
Water Table
992.63
992.9
0 50 1a0
%ASPHALTIC CONCRETE (+5 incM1es).
993.2
Capped with
1
1 Dense CRUSHED GRAVEL, (xT'ncbes); grey, damp, I
..
951 a
AC cold
2
Bi-inch_minus (base rock).
t0
-
patch and
_ _J
CLAY to sandy gravel; brown,
Son
-
♦ •
gravel
3
andsanin ained,SILT,trace
iron and manganese -stained, damp to moist, metlium
SS1-1
tt
Barldilled
4
to coarse sang fine, subangulargravel,
to
(colluvium).ne
(colluvium),
bentonite
5
SS1-2
�f
chips
6
7,
____________
985.6
Very stiff clayey SILT; lighlgrey, iron and
7,6
L
e
manganesestained, damp, medium plasticity,
SS1-3
24
(residual soil).
9
10
_____ ________________
Exbemelyweak(RD) TUFF; light grey antl
9926
100
SS1-0
�....
-
14,
11
iron -stained, decomposed.12
3
Y
13
6S1-5
66.
14
15
__ _ ____ _ ___
-
9]]6
•
Extremely weak(RO)sandy SILT3TONE; greyto
150
SS -16
48
16
brown, ironslained. decomposed, fine to coarse sand.
_
1]
_
18
_-
19
20
Blu"my and highly to moderately weathered below
—
SS1a
5
21
±20 feet.
—_
-
22
_
23
_-
24
=
25
Very weak (RI), slightly weathered to fresh, very dose
8S1 -e
;301
3,
26
to moderately dose, planar to irregular, and open
—
csvl
joints below ±25 feet.
27
28
29
_
30
CS -1-2
31
32
_
33
—_
34
—_
35
—
957,6
BOTTOM OF BORING
35.0
Project No.. 21 31 02 8-1 01 Boring Log: 131-1-1
Surface Elevation: 992.6 feet (Approx.) Springfield Utility Board (SUB)
Date of Boring October 9, 2013 South Hills Reservoir
A h Foundation Engineering, jne. Springfield, Oregon
MW Page 1 of 1
Depth
Soil and Rock Description
Elev.
• SPT, @ Molsture,%
Backfill/
and
Log
Samples
N-Value
Installadorer
Feer
Comments
Depth
Recovery ® RQD.,%
Water Table
05000
Soft t0 medium stiff silty CLAY to clayey SILT, some
90
Morris
1
and, trace to some gravel, scattered cobbles and
monument
boulders; brown to red-brown, iron and
set in
2
manganese-stained, moist, medium plasticity, fine to
concrete
3
coarse, subangularmavel, (fill).
562-1
6
Bentonite
4
chips
s
s2
s
1-inch I.D.
7
PVC
8
— — --_— --___
9597
562-3
Very stiff t0 hard clayey SILT,me sand, trace to
sa
e 0
9
some gravel, scattered cobbles and boulders; brown
to grey, iron and manganese-stained, moist, medium
10
to high plasticity, fine to coarse sand, fine to coarse,
5624
'�
'g
11
subangular gravel,(colluNum).
t18-inch diameter boulder encountered from x11 to
12
12.5 feet.
13
SSF2 5
1
14
Col
15-IF
silicaa sand
6z�
fig: "�
16
Ground
17
water level
19
0.010
20
5627
,3 41
-:
machine slat
21
screen
22
23
24
Ground
water level
26
y I.
(10-i6-13)
sze
46
:._
28
-
.....
....
27
Bentonite
28
chips
29
30
________________
9377
Extremely weak (ROJ SILTSTCTIN blueyrey, slightly
30.0
562-9
! ifi
weathered.
93s:
30.8
BOTTOM OF BORING
Project No.. 2131028-101 Boring Log: BH-2
Surface Elevation: 967.7 feet (Approx.) Springfield Utility Board (SUB)
Date of Baring: October 9, 2013 South Hills Reservoir
I hk Foundation Engineering, Inc. Springfield, Oregon
qiw page 1 of 1
Depth
Soil and Rock Description
Eley.
A SPT, • Moisture, %
Backfill/
and
Log
Samples
N -Value
Installations/
Feef
Comments
Depth
0 Recovery ® RQD.,%
Water Table
96066
a 50 100
Loose to medium dense CRUSHED GRAVEL, grey,
959.9
Capped With
1
idirmid, t1.5 inchminus, (fll) (±g inches). I
0.8
gravel
2
Stiff gravelly CLAY, some sang brown to grey, moist_
medium plasticity, fine to coarse sang fine tocoarse,
3
subangular gravel, (fill).
Sss-f
�3
s56]
BacIled
q
____ __ ____ ____
Soft CLAY, some sang brown iron -With
stained, moist,
4,0
bentonite
5
medium plasticity, fine to coarse sand (fill).
p
SS3-2
chips
6
953 ]
Stiff to very srH sandy CLAY, trace gravel; brawn to
] o
8
light grey, iron and manganese -stained, moist,
SS- -3
15
medium plasticity, fine to coarse sand, fine,
9
subangulargravel,(colluviom).
0
SS -34
g
11
12
13
S&3-5
g
14
5
3535
g
16
17
18
19
20 --\Fry
_
'ronstaineh,
9 0.]
--
_
stili sandy CLAY; light grey damp
20o
SS3-7
�1 _
21
low plasticity, fine to coarse sand (residual soil).
22
23
24
25
______
935.7
Eremelyweak(RO) TUFF; light grey grading to
256
SS39
y
D"
26
blue-grey,iron-stained, decomposed to highly
Q_,>
weathered.
27
28
29
j r
30
t
Ss9
69
31
9292
BOTTOM OF BORING
a1 s
Project No.2131028-101 Boring Log: BHJ
Surface Elevation: 960.7 feet (Approx.) Springfield Utility Board (SUB)
Date of Boring: October 9, 2013 South Hills Reservoir
'gFoundation Engineering, Inc. Springfield, Oregon
7 Page 1 of 1
Depth
Soil and Rack Description
Eley.
♦ SPT, • Moisture, 4
Ba d,fifll
and
Log
Samples
N -Value
Installations/
Fast
Comments
Depth
t] Recovery ® Ron., 'A
Water Table
966
6 50 00
Medium stiff to stiff clayey SILT, some sand (MHT
oo
Capped with
1
brown and iron and manganese -stained, moist, high
cuttings
plasticity, fine to coarse sand -sized rock fragments,
2
(colluvium).
3
55-14
to -
Backfilled
with
4
Orange -brown and iron and manganese -stained below
_
bentonite
5
t5 feet.
...6 y.
chips
s54 2
6
7
8
S54-3
:3
9
10
_ _ _ _ ____ _ __
Medium stiff to stiff clayey SILT, some sand and
9560
16.0
SS44
�,
;7
•
11
gravel (MH); mange -brown and iron and
manganese -stained, moist, medium plasticity, fine to
12
coarse sand, fine to subangular gravel -sized rock
13
fragments, (colluvium).
14
Very s[iR [a hard clayey SILT, some santl (MH);
952.2
13.a
15
yellowish brown and manganese -stained, damp to
;,.
49
moist, medium to high plasticity, fire sand, (residual
SS4-5
23
16
soil).
17
18
554-7
19
-- — — -- ---
EMremely weak to very weak (RO to R1) cantly
_
90].2
16.8
20
SILTSTONE; grey, slightly weathered, fine volcanic
—
sand.
21
_
22
23
24
_
5
i6
549
26
_
9395
BOTTOM OF BORING
265
Project No.: 2211098 Boring Log: BH -4
surface Elevation: 966.0 feet (Approx.) Springfield Utility Board (SUB)
Date of Boring: October 27, 2021 South Hills 3rd Level Reservoir Replacement
k Foundation Engineering, Inc. Springfield, Oregon
� Page 1 of 1
Depth
Soil and Rock Description
Elev
♦ SPT. 0 Mandate, -1,
Backfill)
and
Log
Samples
IN -value
installatiorisl
Feet
Comments
Depth
El Recovery ® RQD.,%
Water Table
952
0 50 100
Loose to medium dense silty GRAVEL (GM); grey,
1
961.2
Capped with
1
moist, low plasticity silt, fine to coarse angular gravel, I
his
gravel and
2
I(fiIQ. _— — --_ ---- —J
cuttings
m
Soft to metlium stiff clayey SILT, soe santl (MHj;
3
orange -broom and iron and manganese -stained,
S&S -1
g-
Backfilled
moist, high plasticity, fine to medium santl-sizetl rock
with
4
fragments. (colluvium).
bentonite
5
-- -- _-- —___—_
9570
chips
Very stiff clayey SILT, some sm (914T yellowish
s o
S%2
�9
6
brawn and iron and manganese -stained, moist,
medium to high plasticity, fine sand, (residual soil).
6
Relict sandstone texture below 9.5 feet.
sSs-3
I A6
i -
9
10
_.
SSs4
Ag�
11
Hard below 110.5 feet.
12
13
Light be. below±12.5 feet.
SSS -s
53
14
15
SS -5.6i6
16
17
18
19
Bluegrey and sandy below+19 feet.
20
______________________....
9420
Extremely weak (ROJ silty SANDSTONE: bto" and
zoo
SSs]
8
1
21
iron-absned, moderately weathered, fine to medium
volcanic sand.
-
22
23
24
25
--------------------
..:
9370
..-.
Very weak (R1) santly SILTSTONE; grey to dark
25.0
sss-s
26
blue -grey, slightly weathered, fine to medium volcanic
_—
sand.
27
28
29
_
30-
931 s
SS9
BOTTOM OF BORING
-5
30.4
Project
No.. 2211098
Boring Log:
BH
Surface
Elevation: 962.0 feet (Approx.)
Springfield
Utility
Board (SUB)
Date of
Boring: October 27, 2021
South Hills
Springfield,
3rd Level
Oregon
Reservoir Replacement
AhFoundation
Engineering, Inc.
Page 1 of
Foundation Engineering, Inc.
South Hills V Level Reservoir
Project No.: 2211098
Photo 1 B. BH -1 Box 1 (25.0 to 33.0 feet)
Photo 2B. BH -1 Box 2 (33.0 to 35.0 feet)
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. ZBS'
( TES/p�WERE EM>l`HT6'J dJ CK!EMGEF H./S3
% lw q ./OKN MERE 555 OnCKF W/TNA L fT 4'MKET
S THE ca lw W WE INT£RryO, `%er N SGG TYrYS AS
S. % 0.1"OU SEE vw A,~ or/ I GRryC;ViJG
4 AS WRTER WAS .6 . W ANY TEST P/T ¢TI!£T THAN
TP -/O.. ..VARTd T/ONS AR£ EXPECTED
5 THE LGGS S3IOW SUBSURFACE CaVO/TYONS ONLY AT T]/E
T/ME ANO PLACE THE TEST A/ WEPE IMDE.
TEST P/T LOGS
R£an
EX/sT/
G,(bUNZ,C
EX/ST.`NG—. /f/� �yE_ OG3FF-TFZa ��iy
GROUND -• _--.� _
9'M/N GAYER QE -c"AAN CAPER OF
9U/PF/IG'E COVRGE-� LR/IVEC EASE COURSE
OTE:
Y SAME TH/CKNESS OG SURfMC/NG pIJ RLL
GRgVELLEO PREAs
ROACWAY SELT/ON
SECT/ON B\
K?S /
4
G a G s
CH2A1UHILL
aR Lw'a
MOTES:
1. CLEAR ALL GROUND WITHIN THE NORTH AND SOUTH
CLEARING LIMITS EXCEPT FOR TREES LARGER THAN fi'
DIAMETER WHICH AREWESTERLV OF THE PROPOSED WEST
FENCE LINE AND OUTSIOETHEROAOWAV.
2 EXGAVATETHERESERVOIR AREATOTHELINESANDGRADES
SHOWN. THE EXCAVATED MATERIAL SHALL BE STOCKPILED
OFF SITE PER SPECIFICATIONS AND AS OIPEGTE'J BY THE
ENGINEER.
N04THERGY
cLEgR/NG G/M/T
T'SVP OV`
sLO
SLOPE AS RC ---
q WD SOUTH
OF. SERVWR
RESERV01,f EXCAVATION PLAN
�x20._px
RECORD DRAWINGS
iu Ecapo opxwlu¢s XAVE6EEU GRE.I,gm. IN PART. ONI
♦HE BMIN OF WFpgME➢ON COMPrtm BV OTHEPS MEV Aq4
TOAEHIESEM M.ETAN, EFWTWCATION
IYGE IX COMPON¢NT Nap YINNEP OF GONAquCTION HE
-SWIEp INLL NW BE pETPoNSNpOLGpaq ApY EppaRi Op
ao°ohiwlxlCCs. HNVE aEEII FppATm INTO 1NE
iS MG
SPRINGFIELD IITILITV REGERNO. I TEST PIT LOGS, RESERVOIR EXCAVATION/
ORRO
SPRIN.NS O, OPFGOx ROADWAY SECTION
AS '
O
a9
L
'
H4sfCT CA/LLIPAS
.a✓o aevpvres
eN59LT 6CULL1'A5'
ov.' •R/o G.ea�Nlcr
40°
t1j.41t? �.•LSEES
Vi
.wo ceGANlas
y'�p
JC
'b
OgSAGT B¢ULGE4S
-
6g5yGT BOVLQ�ES NJ /J
®AA S/LT, 1C 1 MATP/Y
j
SNA S/LTY CLAY A.Mix
SILJY CLHY ✓H%�!k
S
YY
4�
I
CRV%M
.Q
SILTY C[hY
't
7tT eOL/LL1FR5
/p _
'
U, III,
VATU 3'O/A.
. ZBS'
( TES/p�WERE EM>l`HT6'J dJ CK!EMGEF H./S3
% lw q ./OKN MERE 555 OnCKF W/TNA L fT 4'MKET
S THE ca lw W WE INT£RryO, `%er N SGG TYrYS AS
S. % 0.1"OU SEE vw A,~ or/ I GRryC;ViJG
4 AS WRTER WAS .6 . W ANY TEST P/T ¢TI!£T THAN
TP -/O.. ..VARTd T/ONS AR£ EXPECTED
5 THE LGGS S3IOW SUBSURFACE CaVO/TYONS ONLY AT T]/E
T/ME ANO PLACE THE TEST A/ WEPE IMDE.
TEST P/T LOGS
R£an
EX/sT/
G,(bUNZ,C
EX/ST.`NG—. /f/� �yE_ OG3FF-TFZa ��iy
GROUND -• _--.� _
9'M/N GAYER QE -c"AAN CAPER OF
9U/PF/IG'E COVRGE-� LR/IVEC EASE COURSE
OTE:
Y SAME TH/CKNESS OG SURfMC/NG pIJ RLL
GRgVELLEO PREAs
ROACWAY SELT/ON
SECT/ON B\
K?S /
4
G a G s
CH2A1UHILL
aR Lw'a
MOTES:
1. CLEAR ALL GROUND WITHIN THE NORTH AND SOUTH
CLEARING LIMITS EXCEPT FOR TREES LARGER THAN fi'
DIAMETER WHICH AREWESTERLV OF THE PROPOSED WEST
FENCE LINE AND OUTSIOETHEROAOWAV.
2 EXGAVATETHERESERVOIR AREATOTHELINESANDGRADES
SHOWN. THE EXCAVATED MATERIAL SHALL BE STOCKPILED
OFF SITE PER SPECIFICATIONS AND AS OIPEGTE'J BY THE
ENGINEER.
N04THERGY
cLEgR/NG G/M/T
T'SVP OV`
sLO
SLOPE AS RC ---
q WD SOUTH
OF. SERVWR
RESERV01,f EXCAVATION PLAN
�x20._px
RECORD DRAWINGS
iu Ecapo opxwlu¢s XAVE6EEU GRE.I,gm. IN PART. ONI
♦HE BMIN OF WFpgME➢ON COMPrtm BV OTHEPS MEV Aq4
TOAEHIESEM M.ETAN, EFWTWCATION
IYGE IX COMPON¢NT Nap YINNEP OF GONAquCTION HE
-SWIEp INLL NW BE pETPoNSNpOLGpaq ApY EppaRi Op
ao°ohiwlxlCCs. HNVE aEEII FppATm INTO 1NE
iS MG
SPRINGFIELD IITILITV REGERNO. I TEST PIT LOGS, RESERVOIR EXCAVATION/
ORRO
SPRIN.NS O, OPFGOx ROADWAY SECTION
Appendix C
Laboratory Testing
Foundation Engineering, Inc.
Professional Geotechnical Services
Foundation Engineering, Inc.
South Hills 3rd Level Reservoir Replacement
Pro act No.: 2211098
Table 1 C. Moisture Contents (ASTM D 2216) and Atterberg Limits (ASTM D 4318)
Sample
Number
Sample
Depth
(ft)
Moisture
Content
(%)
Atterberg Limits
USCS
Classification
LL
PL
PI
SS -3-4
10.0 - 11.5
58.4
48
37
MH
SS -4-1
2.5-4.0
38.9
34
31
MH
SS -4-2
5.0- 6.5
43.3
P67
SS -4-3
7.5 - 9.0
41.9
SS -4-4
10.0- 11.5
54.0
SS -4-5
12.5 - 14.0
65.4
SS -4-6
15.0- 16.5
54.4
SS -4-7
17.5 - 19.0
43.9
SS -5-1
2.5 - 4.0
43.1
SS -5-2
5.0-6.5
64.4
SS -5-3
7.5 -9.0L45.
78
47
31
MH
SS -5-4
10.0- 11.5SS-5-5
12.5 - 14.0SS-5-6
15.0- 16.5
di Ek
Appendix D
Seismic Hazard Study
Foundation Engineering, Inc.
Professional Geotechnical Services
SEISMIC HAZARD STUDY
SOUTH HILLS 3RD LEVEL RESERVOIR REPLACEMENT
SPRINGFIELD, OREGON
INTRODUCTION
This seismic hazard study was completed to identify potential geologic and seismic
hazards and evaluate the effect those hazards may have on the proposed project. The
study fulfills the requirements presented in the 2019 Oregon Structural Specialty Code
(OSSC), Section 1803 for site-specific seismic hazard reports for essential and
hazardous facilities and major and special -occupancy structures (OSSC, 2019). The
2019 OSSC is based on the 2018 International Building Code and ASCE 7-16.
The following sections provide a discussion of the local and regional geology, seismic
and tectonic setting, earthquakes, and seismic hazards. A detailed discussion of the
subsurface conditions at the project location, including exploration logs, is provided in
the main report.
The project site currently has an existing 98 -foot diameter concrete reservoir tank
designated as Reservoir No. 1. A proposed, new, 57 -foot diameter steel
tank (designated as Reservoir No. 2) is planned to the west of Reservoir No. 1. Once
Reservoir No. 2 is built, Reservoir No. 1 will be demolished and a new reservoir
(designated as Reservoir No. 3) will be built in its place. Reservoir No. 3 will be a
67 -foot diameter steel tank consistent with Reservoir No. 2. This report is focused on
the area that will include Reservoir No. 2 and Reservoir No. 3.
LITERATURE REVIEW
We reviewed available geologic, seismic, and hazard publications and maps to
characterize the local and regional geology and evaluate relative seismic hazards at the
site. We also reviewed information from geotechnical and seismic hazard
investigations previously conducted by Foundation Engineering for Reservoir No. 1 and
the South Hills 4th Level Reservoir located upslope. As -built plans for Reservoir No. 1
were also reviewed.
Regional Geology
Springfield is located within the eastern edge of the Southern Willamette Valley, which
is a broad, north -south -trending basin separating the Coast Range to the west from
the Cascade Range (Western and High Cascade Ranges) to the east. The project site
is along the western foothills of the Western Cascades where it transitions to the
southern extent of the Willamette Valley.
At the western margin of Oregon is the Cascadia Subduction Zone (CSZ). The CSZ is
a converging, oblique plate boundary where the Juan de Fuca oceanic plate is being
subducted beneath the western edge of the North American continental plate
(Geomatrix Consultants, 1995). The CSZ extends from central Vancouver Island, in
British Columbia, Canada, through Washington and Oregon to Northern California
in the United States (Atwater, 1970). The movement of the subduction zone has
South Hills 3rd Level Reservoir Replacement November 23, 2021
Seismic Hazard Study 1 Project No.: 2211098
Springfield, Oregon Springfield Utility Board
resulted in accretion, folding, faulting, and uplift of oceanic and other sediments on
the western margin of the North American plate.
In the early Eocene (±55 million years ago), the present location of the Willamette
Valley was part of a broad continental shelf extending west from the Western
Cascades beyond the present coastline (Orr and Orr, 1999). Basement rock underlying
most of the north -central portion of the Valley includes the Siletz River Volcanics (early
to middle Eocene, ±50 to 58 million years old), which erupted as part of a submarine
oceanic island -arc (Bela, 1979; Yeats at al., 1996). The thickness of the basement
volcanic rock is unknown; however, it is estimated to be ±3 to 4 miles thick (Yeats
at al., 1996).
The island -arc collided with, and was accreted to, the western margin of the
converging North American plate near the end of the early Eocene. Volcanism
subsided and a forearc basin was created and infilled to the south with marine
sediments of the Eugene Formation and terrestrial sedimentary and volcanic deposits
of the Fisher Formation and Little Butte Volcanics throughout the late Eocene and
Oligocene (Orr and Orr, 1999; Wiley, 2008). These sediments typically overlie but are
also interbedded with younger Tertiary volcanics in the Springfield area.
After emerging from a gradually shallowing ocean, the marine sediments and volcanic
formations were covered by the terrestrial Columbia River Basalt (CRB). The CRIB
poured through the Columbia Gorge from northeastern Oregon and southeastern
Washington and spread as far south as Salem, Oregon (± 17 to 10 million years ago,
middle to late Miocene) (Tolan et al., 2000). Uplift and folding of the Coast Range
and the Western Cascades during the late Miocene formed the trough-like
configuration of the Willamette Valley (Orr and Orr, 1999; O'Connor at al., 2001;
Wiley, 2008; McClaughry et al., 2010).
Following the formation of the Willamette Valley, thick layers of Pliocene gravel filled
the Southern Valley (McClaughry at al., 2010). The deposits were then incised by the
Willamette River, forming alluvial terraces. In the Pleistocene (±1.6 million to
10,000 years ago), the Central and Southern Valley was refilled with fan -delta gravel,
originating from the melting glaciers in the Cascade Range. The Willamette and
McKenzie Rivers in the Springfield area incised deeply into the fan -delta deposits during
the Quaternary and deposited recent alluvium adjacent to the river banks and along
major tributaries (Madin and Murray, 2006).
Local Geology
The reservoirs are located on bench on a north -facing slope at the southeast edge of
Springfield. The project site located is down slope (north) from the newly constructed
South Hills 4th Level Reservoir and Jessica Drive.
Local geologic mapping and cross-sections indicate the project site and immediate
surrounding area is generally underlain by volcaniclastic bedrock (Yeats at al., 1996;
Hladky and McCaslin, 2006; McClaughry et al., 2010). Landslide deposits have been
mapped in the vicinity of the site and are shown on the Oregon Department of Geology
and Mineral Industries (DOGAMI) SLIDO and HazVu web viewers.
South Hills 3rd Level Reservoir Replacement November 23, 2021
Seismic Hazard Study 2 Project No.: 2211096
Springfield, Oregon Springfield Utility Board
The subsurface conditions in our explorations are generally consistent with the
geologic mapping. Colluvial soils were encountered in each of the explorations
extending to depths of up to ±20 feet below the ground surface. Colluvium consists
of material that has been transported downslope and deposited via erosion, creep, or
landslide activity. Based on the terrain, we anticipate the colluvium was likely
deposited as a result of previous landslide activity. The colluvium consists of
predominantly sandy clay, sandy silt, or clayey silt with sand to boulder -sized basaltic
rock fragments. Basaltic cobble and boulder -sized rock fragments were observed in
the cut slope on the south side of Reservoir No. 1 and in the fill stockpiled on the
proposed Reservoir No. 2 site. We anticipate the stockpiled fill was excavated from
the Reservoir No. 1 site. Colluvium including cobble to boulder -sized rock fragments
was also encountered in our previous test pits and boring completed up slope for the
new South Hills 4th Level reservoir. The colluvium is typically underlain by residual
soil (i.e., bedrock that has decomposed in place to the consistency of soil) followed
by tuff, siltstone, sandy siltstone, and silty sandstone.
A boring (ES9) and accompanying shear wave velocity log were completed near
70th Street and Ivy Street (±2,000 feet southeast of the site) in 1996 by DOGAMI.
This boring was part of a shear wave velocity study of the Eugene -Springfield area
(Wang at al., 1998). Subsurface conditions at ES9 included fill and landslide deposits
(colluvium) followed by vitric tuff below ±18.5 feet. The recorded shear wave
velocities at ES9 included 387 feet/second Ift/s) extending to ±8 feet, 1,092 ft/s in
the colluvium extending to ± 18.5 feet, and 1,989 ft/s in the vitric tuff to ±29.5 feet
(Wang at al., 1998). The shear wave velocities at ES9 should be fairly comparable to
the South Hills 3rd Level Reservoir site.
Details are provided in the Subsurface Conditions section of the main report,
cross-sections in Appendix A, and on the boring logs in Appendix B.
Seismic Setting and Local Faulting
We completed a literature review of faults to evaluate the seismic setting and identify
the potential seismic sources. The US Geological Survey (USGS) website includes an
interactive deaggregation tool, which allows evaluation of the contribution of the
various seismic sources to the overall seismic hazard (USGS, 2014). The USGS
interactive deaggregation indicates the seismic hazard at the site is dominated by the
CSZ (USGS, 2014). Crustal faults also represent a potential seismic hazard.
A discussion of these earthquake sources is provided below.
Cascadis Subduction Zone /CSZ/. The site is ± 120 miles east of the surface expression
of the CSZ and the subduction zone extends beneath the site at an estimated depth
of about 31 miles. The CSZ is a converging, oblique plate boundary where the Juan
de Fuca plate is being subducted beneath the western edge of the North American
plate. It is estimated the average rate of subduction of the Juan de Fuca plate under
the North American plate is ±37 mm/year northeast, based on Pacific and Mid -Ocean
Ridge velocities, geodetic studies of convergence, and magnetic anomalies of the Juan
de Fuca plate (Personius and Nelson, 2006; DeMets et al., 2010). The CSZ extends
±700 miles from central Vancouver Island in British Columbia, Canada, through
Washington and Oregon to Northern California (Atwater, 1970).
South Hills 3m! Level Reservoir Replacement November 23, 2021
Seismic Hazard Study 3 Pm2ct No., 2211098
Springfield, Oregon Springfield Utility Board
Crustal Fauns. Crustal faults are fractures within the North American plate. Numerous
faults are presented on local and regional geologic maps. However, not all faults are
considered to be active. Because the historical earthquake record is so short, active
faults are identified by geologic mapping and seismic surveys.
The USGS has defined four fault classifications based on evidence for displacement
within the Quaternary (<1.6 million years) in their US fault database (Palmer, 1983;
Personius et al., 2003). The fault classes are defined as follows:
• Class A - Faults with geologic evidence supporting tectonic movement in the
Quaternary known or presumed to be associated with large -magnitude
earthquakes.
• Class 8 - Faults with geologic evidence that demonstrates the existence of a
fault or suggests Quaternary deformation, but either: 1) the fault might not
extend deep enough to be a potential source of significant earthquakes or 2) the
current evidence is too strong to confidently classify the fault as a Class C but
not strong enough to classify it as a Class A.
• Class C - Faults with insufficient evidence to demonstrate 1) the existence of
a tectonic fault, or 2) Quaternary movement or deformation associated with
the feature.
• Class D - Geologic evidence indicates the feature is not a tectonic fault or
feature.
Class A and B faults are included in the USGS fault database and interactive fault map.
USGS considers 17 features in Oregon to be Class C faults (USGS, 2006a), including
Harrisburg anticline located ±21 miles northwest of the site. The USGS does not
consider any features in Oregon as Class D (USGS, 2006a).
Local geologic maps indicate no crustal faults mapped beneath the site (Yeats at al.,
1996; Hladky and McCaslin, 2006). The site is located between approximate to
concealed crustal faults that have been mapped less than 1 mile of the site (Hladky
and McCaslin, 2006). However, none of the nearby faults show any evidence of
movement in the last ± 1.6 million years (Palmer, 1983; Geomatrix Consultants, 1995;
Personius et al., 2003; USGS, 2006a).
Six potentially active Quaternary Class A and B crustal fault zones have been mapped
by the USGS within ±50 miles of the site (Palmer, 1983; Geomatrix Consultants,
1995; Personius at al., 2003; USGS, 2006a). These faults are listed in Table 1 D.
Figure 1 D shows the approximate surface projection locations of these faults.
South Hills 3rd Level Reservoir Replacement November 23, 2021
Seismic Hazard Study 4 Pro act No.: 2211098
Springfield, Oregon Springfield Utility Board
Table 1 D. USGS Class A and Class B Crustal Faults
within a± 50 -mile Radius of the Site 11(
i9 Fault data based on Persodus at al., 2003 and USGS, 2006a and b.
Isl Distance and direction from site to nearest surface projection of the crustal fault.
isl Quaternary time period defined at <1.6 million years based on the 1983 Geologic Time Scale (Palmer, 1983).
Historic Earthquakes
Available information indicates the CSZ is capable of generating earthquakes along the
inclined interface between the two plates (interface) and within the descending Juan
de Fuca plate (intraplate) (Weaver and Shedlock, 1996). The fault rupture may occur
along a portion or the entire length of the CSZ (Weaver and Shedlock, 1996).
CSZ Interface Earthquakes. The estimated maximum magnitude of a CSZ interface
earthquake is up to a moment magnitude (Mw) 9.3 (Petersen et al., 2014). No
significant interface (subduction zone) earthquakes have occurred on the CSZ in
historic times. However, several large -magnitude (>M —8.0, M = unspecified
magnitude scale) subduction zone earthquakes are thought to have occurred in the
past few thousand years. This is evidenced by tsunami inundation deposits, combined
with evidence for episodic subsidence along the Oregon and Washington coasts
(Peterson et al., 1993; Atwater of al., 1995).
Numerous detailed studies of coastal subsidence, tsunami, and turbidite deposits have
been conducted to develop a better understanding of CSZ earthquakes. The studies
include investigations of turbidite deposits in the offshore Cascadia Basin that were
used to help develop a paleoseismic record for the CSZ and estimate recurrence
intervals for interface earthquakes (Adams, 1990; Goldfinger at al., 2012). Study of
offshore turbidites from the last ±10,000 years suggests the return period for
South Hills 3rd Level Reservoir Replacement November 23, 2021
Seismic Hazard Study 5 Project No.: 2211098
Springfieltl, Oregon Springfield Utility Board
Approximate
Approximate
Last Known
Fault Name
Fault
Distance and
Slip Rate
and Class
Number
Length
Directien from Site
Deformation
(a)
larval
(miles)
(miles) (21
(Yeats)
Upper Willamette
863
±27
±33 BE
<1.6 million
<0.20
River IBI
Owl Creek (A)
870
±9
±34 N -NW
<750,000
<0.20
Corvallis (B)
869
±25
±41 NW
<1.6 million
<0.20
Unnamed faults
862
±17
±44 S -SW
<750,000
<0.20
near Sutherlin (B)
White Branch
1809
±11
±46 E
<750,000
<0.20
fault zone (A)
Salem-Eola Hills
719
±20
±50 N
<1.6 million
<0.20
homocline (A)
i9 Fault data based on Persodus at al., 2003 and USGS, 2006a and b.
Isl Distance and direction from site to nearest surface projection of the crustal fault.
isl Quaternary time period defined at <1.6 million years based on the 1983 Geologic Time Scale (Palmer, 1983).
Historic Earthquakes
Available information indicates the CSZ is capable of generating earthquakes along the
inclined interface between the two plates (interface) and within the descending Juan
de Fuca plate (intraplate) (Weaver and Shedlock, 1996). The fault rupture may occur
along a portion or the entire length of the CSZ (Weaver and Shedlock, 1996).
CSZ Interface Earthquakes. The estimated maximum magnitude of a CSZ interface
earthquake is up to a moment magnitude (Mw) 9.3 (Petersen et al., 2014). No
significant interface (subduction zone) earthquakes have occurred on the CSZ in
historic times. However, several large -magnitude (>M —8.0, M = unspecified
magnitude scale) subduction zone earthquakes are thought to have occurred in the
past few thousand years. This is evidenced by tsunami inundation deposits, combined
with evidence for episodic subsidence along the Oregon and Washington coasts
(Peterson et al., 1993; Atwater of al., 1995).
Numerous detailed studies of coastal subsidence, tsunami, and turbidite deposits have
been conducted to develop a better understanding of CSZ earthquakes. The studies
include investigations of turbidite deposits in the offshore Cascadia Basin that were
used to help develop a paleoseismic record for the CSZ and estimate recurrence
intervals for interface earthquakes (Adams, 1990; Goldfinger at al., 2012). Study of
offshore turbidites from the last ±10,000 years suggests the return period for
South Hills 3rd Level Reservoir Replacement November 23, 2021
Seismic Hazard Study 5 Project No.: 2211098
Springfieltl, Oregon Springfield Utility Board
interface earthquakes varies with location and rupture length. That study estimated
an average recurrence interval of ±220 to 380 years for an interface earthquake on
the southern portion of the CSZ, and an average recurrence interval of ±500 to
530 years for an interface earthquake extending the entire length of the CSZ
(Goldfinger et al., 2012). Older, deep-sea cores have been re-examined more recently,
and the findings may indicate greater Holocene stratigraphy variability along the
Washington coast (Atwater et al., 2014). Additional research by Goldfinger for
the northern portion of the CSZ suggests a recurrence interval of ±340 years for the
northern Oregon Coast (Goldfinger et al., 2016). The most recent CSZ interface
earthquake occurred ±321 years ago (January 26, 1700) (Nelson et al., 1995; Satake
at al., 1996).
CSZlntraplate Earthquakes. Intraplate (Intraslab or Wadati-Benioff Zone) earthquakes
occur within the Juan de Fuca plate at depths of ±28 to 37 miles (Weaver and
Shedlock, 1996). The maximum estimated magnitude of an intraplate earthquake is
about Mw 7.5 (Petersen et al., 2014). The available record for intraplate earthquakes
in Oregon is limited. The available data indicates a Mb = 4.6 (compressional body
wave magnitude) event occurred in 1963, located ±23 miles east of Salem at a depth
of ±29 miles (Barnett et al., 2009). Based on its depth, this earthquake may be
considered an intraplate event. The Puget Sound region of Washington State has
experienced three intraplate events in the last ±72 years, including a surface wave
magnitude (M.) 7.1 event in 1949 (Olympia), a Ms 6.5 event in 1965 (Seattle/Tacoma)
(Wong and Silva, 1998), and a Mw 6.8 event in 2001 (Nisqually) (Dewey et al., 2002).
Crustal Earthquakes. Crustal earthquakes dominate Oregon's seismic history. Crustal
earthquakes occur within the North American plate, typically at depths of ±6 to
12 miles. The estimated maximum magnitude of a crustal earthquake in the
Willamette Valley and adjacent physiographic regions is about Mw 7.0 (Petersen et al.,
2014). Only two historic crustal events in Oregon have reached Richter local
magnitude (ML) 6 (the 1936 Milton-Freewater ML 6.1 earthquake and the
1993 Klamath Falls Mi 6.0 earthquake) (Wong and Bott, 1995). The majority of
Oregon's larger crustal earthquakes are in the Mi 4 to 5 range (Wong and Bott, 1995).
Table 2D summarizes earthquakes with a M of 4.0 or greater or Modified Mercalli
Intensity (MMI) of V or greater, that have occurred within a ±50 -mile radius of
Springfield in the last ±188 years (Johnson et al., 1994; USGS, 2013). Note that the
referenced earthquake catalogs are a composite of different earthquake catalogs and
seismic networks; therefore, data errors may exist. Complete historic earthquake
records may not yet be included in the referenced earthquake catalogs. Therefore, it
is possible some earthquakes may not be included in Table 2D.
South Hills 3rd level Reservoir Replacement November 23, 2021
Seismic Hazard Study 6 Project No.: 2211098
Springfield, 01.1.1 Springfield Utility Board
Table 2D. Historic Earthquakes Within a ± 50 -mile Radius of Springfield "1
Year
Month
Day
Hour
Minute
Latitude
Longitude
Depth
(miles)
Magnitude or
Intensity (1)
1921
02
25
20
00
44.4
-122.4
unknown
MMI — v
1942
05
13
01
52
44.5
-123.3
unknown
MMI = v
1961
08
19
04
56
44.7
-122.5
unknown
M = 4.5
2015
07
04
15
42
44.1
-122.8
5.0
Me = 4.1
I The site is located at Latitude 44.034716, Longitude -122.909738.
of M = unspecified magnitude, Mb =compressional body wave magnitude, M, = primary coda magnitude, Mr = local Richter
magnitutle, and MMI = Modified Memalli Intensity at or near epicenter.
Seismic events in Oregon were not comprehensively documented until the 1840s
(Wong and Bott, 1995). Earthquake epicenters located in Oregon from the late 1920s
to 1962 were limited due to the number of and the distance between seismographs,
the number of recording stations, and uncertainty in travel times. Therefore,
information recorded during that time suggests only earthquakes with magnitudes
>5 would be recorded in Oregon (Bela, 1979). Oregon State University (OSU) likely
had the first station installed in 1946, and the first modern seismograph was installed
at OSU in 1962 (Wong and Bott, 1995; Barnett at al., 2009). According to Wong and
Batt (1995), seismograph stations sensitive to smaller earthquakes (ML <4 to 5) were
not implemented in northwestern Oregon until 1979 when the University of
Washington expanded their seismograph network to Oregon. The local Richter
magnitude (ML) of events occurring prior to the establishment of seismograph stations
have been estimated based on correlations between magnitude and MMI. Some
discrepancy exists in the correlations.
Table 3D summarizes distant, strong earthquakes felt in the Springfield area (Noson at
al., 1988; Bott and Wong, 1993; PNSN, 1993; Stover and Coffman, 1993; Wong and
Bott, 1995; PNSN, 2001). None of these events caused significant, reportable damage
in Springfield or surrounding area.
Heplacement
Seismic Hazard Study
Springfield, Oregon
Table 3D. Distant Earthquakes Felt in the Springfield Area
Earthquake
Modified Memalli Intensities
(MMI)
2001 Nisqually, Washington
II to III
1993 Klamath Falls, Oregon
IV
1993 Scotts Mills, Oregon
IV
1965 Seattle - Tacoma, Washington
I to IV
1962 Portland, Oregon
I to IV
1961 Lebanon/Albany, Oregon
IV
1949 Olympia, Washington
IV
1873 Crescent City, California
V
Seismic and Geologic Hazards
Section 1803.6.1 of the OSSC 2019 requires the evaluation of risks from a range of
seismic hazards including landslides, earthquake -induced landslides, liquefaction and
lateral spread, seismic -induced settlement or subsidence, fault rupture, earthquake -
induced flooding and inundation, and local ground motion amplification (OSSC, 2019).
We have developed conclusions regarding the seismic hazards based on the subsurface
profiles encountered in the explorations completed at the project site. The conclusions
are also based on our knowledge of the site geology, a review of previous geotechnical
and seismic studies performed at the site and in the vicinity, and available geologic
hazard maps (including information available from DOGAMO.
DOGAMI has completed geologic and seismic hazard studies, which include Lane
County and Eugene -Springfield (Black at al., 2000; Burns et al., 2008; Calhoun et al.,
2018), and provides online hazard information through HazVu, LiDAR, and SLIDO
viewers (DOGAMI, 2018, 2O20a, b). The above-mentioned maps and viewers refer
to some, but do not cover all of the seismic hazards. The information available from
DOGAMI is only considered a guide and does not have precedence over site-specific
evaluations. In the following sections, information from the available seismic hazard
maps is provided along with our site-specific evaluations for comparison.
The relative earthquake hazard is based on the combined effects of ground shaking
amplification and earthquake -induced landslides with a range in hazard from Zone A
(highest hazard) to Zone D (lowest hazard). The relative earthquake hazard in the
vicinity of the Reservoirs is mapped as Zone B (intermediate to high hazard) likely due
to the Reservoirs being located in an area mapped as existing landslide deposits (Black
et al., 2000; Hladky and McCaslin, 2006).
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Landslides and Earthquake-Mduced Landslides. DOGAMI references including SLIDO
and HazVu web viewers indicate the area is mapped as landslide terrain (Hladky and
McCaslin, 2006; Calhoun at al., 2018; DOGAMI, 2018, 20206). A mapped landslide
extends across the site with the headscarp located ±800 to 1,200 feet to the south
(uphill) and landslide debris extending up to ±3,500 feet to the north (downhill). A
series of smaller scarps are mapped uphill and downhill of the reservoir site. DOGAMI
estimates the mapped landslide to be more than 150 years old (Calhoun at al., 2018).
LiDAR imagery shows relatively smooth, gentle to moderate slopes for most of the site
(DOGAMI, 2020a).
We completed a reconnaissance of the reservoir site including the slopes immediately
uphill and downhill of the existing and proposed tanks. We did not observe any signs
of recent or active slope instability. We understand Reservoir No. 1 was built in 1981
and no landslide related issues have impacted Reservoir No. 1 to date.
Any development within hillside terrain includes inherent risk of slope instability,
particularly hillside terrain with mapped landslide topography. However, no recent or
on-going active slope instability features were observed during the exploration phase.
The existing and proposed reservoirs are sited on a relatively wide bench that is
underlain by predominantly stiff to hard soil and shallow bedrock that has a relatively
flat surface. Based on our observations, soil and rock conditions, and the results of the
slope stability analysis (discussed in the main report), we believe the risk of landslides
or earthquake -induced landslides (with design -level earthquake loads) occurring at the
site is low. Investigating the potential for movement on the large, mapped slide
extending downhill and uphill of the site is a complex and uncertain process and is not
within the scope of this investigation.
Liquefaction, Settlement, and Lateral Spread. Soil liquefaction occurs when loose,
saturated cohesionless soil experiences a significant loss of strength during strong
ground shaking. The strength loss is associated with rapid densification of the soil
and corresponding development of high pore water pressure, which can lead to the
soil behaving like a viscous fluid. Liquefiable soils typically consist of saturated, loose,
clean sand and non -plastic to low plasticity silt with a plasticity index (PI) typically less
than 8. The colluvium and residual soil underlying the site are comprised of
predominantly fine-grained soil with medium to high plasticity. These soils are not
susceptible to liquefaction. Therefore, we have concluded there is no liquefaction hazard
at the project site. The DOGAMI hazard report and HazVu site indicate liquefaction
susceptibility is moderate in the project area (Burns at al., 2008; DOGAMI, 2018).
Lateral spread is a liquefaction -induced hazard, which occurs when soil or blocks of
soil are displaced down slope or toward a free face (such as a riverbank) along a
liquefied layer. The lateral spread hazard does not exist at the site due to the absence
of a liquefaction hazard.
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Subsidence. Ground subsidence is a regional phenomenon resulting from a large
magnitude CSZ earthquake. It occurs because the subduction of the oceanic crust
beneath the continental crust compresses the continental crust and pushes it upward.
Prior to the earthquake, the continental crust is held in this position by friction at the
CSZ interface. When the earthquake occurs, that frictional bond breaks allowing
the continental crust to drop.
The subsidence hazard map included in the Oregon Resilience Plan (OSSPAC, 2013),
indicates the ground subsidence in the Springfield area during a Me 9 CSZ earthquake
could be up to 1 foot. Ground subsidence cannot be mitigated. Therefore, it should
be assumed the site and surrounding area could drop by up to 1 foot during a large
magnitude CSZ earthquake.
Fault Rupture. The risk of fault rupture is expected to be low due to the lack of known
active crustal faulting beneath the site (Personius at al., 2003; Hladky and Mc Caslin,
2006; USGS, 2OO6b, a; McClaughry et al., 2010). The closest potentially active
(Class A) crustal fault is the Owl Creek fault, which is ±34 miles north-northwest of
the site.
Tsunami/Seiche/Earthouake-Induced Flooding. Tsunami are waves created by a large-
scale displacement of the sea floor due to earthquakes, landslides, or volcanic
eruptions (Priest, 1995). Tsunami inundation is not applicable to this site because
Springfield is not on the Oregon Coast. Seiche (the back and forth oscillations of a
water body during a seismic event) is also not a local hazard due to the absence of
large bodies of water near the site.
According to HazVu, there is no localized flood potential for the Effective FEMA
100 -year flood at or near the site (DOGAMI, 2018). Earthquake -induced flooding
related to the failure of other structures (e.g., dams) or shallow groundwater and
subsidence does not apply to the site.
Local Ground Motion Ampli>ication. Ground motion amplification is the influence of a
soil deposit on the earthquake motion. As seismic energy propagates up through the
soil strata, the ground motion is typically increased (i.e., amplified) or decreased
(i.e., attenuated) to some extent.
The site is underlain by medium stiff to hard colluvium and residual soil followed by
relatively shallow bedrock. Based on the site conditions, we have concluded the
amplification hazard is relatively low and is consistent with an OSSCIIBC Site Class C
(i.e., very dense soil and soil rock). The DOGAMI hazard studies indicate the
amplification susceptibility for the site is low (NEHRP Site Class B) (Black et al., 2000;
Burns at al., 2008). Although the amplification hazard is low, the site is expected to
experience strong ground shaking during a CSZ earthquake due to its proximity to the
CSZ (DOGAMI, 2018). See the main report for more discussion on the site response.
South Hills Set Level Reservoir Replacement November 23, 2021
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SEISMIC DESIGN
Design Earthquakes
The OSSC 2019, Section 1803.3.2.1, requires the design of structures classified as
essential or hazardous facilities and of major and special occupancy structures to
address, at a minimum, the following earthquakes:
Crustal: A shallow crustal earthquake on a real or assumed fault near the site
with a minimum Mw 6.0 or the design earthquake ground motion
acceleration determined in accordance with the OSSC 2019
Section 1613.
Intraplate: A CSZ intraplate earthquake with Mw of at least 7.0.
Interface: A CSZ interface earthquake with a Mw of at least 8.5.
The design maximum considered earthquake ground motion maps provided in the
OSSC 2019, are based on modified (risk -targeted) 2014 maps prepared by the USGS
for an earthquake with a 2% probability of exceedance in 50 years (i.e., a
±2,475 -year return period) for design spectral accelerations (USGS, 2014). The
modifications include factors to adjust the spectral accelerations to account for
directivity and risk.
The 2014 USGS maps were established based on probabilistic studies and include
aggregate hazards from a variety of seismic sources. The USGS interactive
deaggregation for a 2,475 -year return period indicates the seismic hazard at the site
is dominated by the CSZ. The principal seismic sources comprising at least 5% of the
overall hazard are summarized in Table 4D. Crustal earthquakes were included in
the studies; however, the crustal earthquakes are not listed in Table 4D because each
of the individual crustal sources represent less than 5% of the overall hazard at the
site.
Table 4D. Principal Seismic Sources based on USGS (2014)
Seismic Hazard Maps
Source
Mean Moment
Magnitude, W
Mean Source -to -Site
Distance, R (km)
Percent Contribution
CSZ Megathrust Interface
9.10
74.5
±41.3
CSZ Megathrust Interface
8.92
125.0
±18.2
CSZ Megathrust Interface
8.83
137.2
±4.7
CSZ Megathrust Interface
8.73
74.1
±3.9
South Hills 3rd Level Reservoir Replacement November 23, 2021
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Springfield, Oregon Springfield Utility Board
The earthquake magnitudes and source -to -site distances used to generate the
2014 USGS maps satisfy the requirements of OSSC 2019. Seismic design parameters
are discussed in the Site Response Spectra section of the main report. AWWA
D100-11 design response spectra are shown on Figures 7A and 8A (Appendix A).
CONCLUSION
Based on the findings presented herein, it is our opinion there are no geologic or seismic
hazards that would preclude the design and construction of the proposed reservoirs.
This site-specific seismic hazard investigation for the South Hills 3rd Level Reservoir
Replacement, Springfield, Oregon, was prepared by Brooke Running, R.G., C.E.G.
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Springfield, Oregon Springfield Utility Board
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South Hills Sid Level Reservoir Replacement November 23, 2021
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1. PORTION OF MAP BASED ON MAP OF QUATERNARY FAULTS AND FOLDS IN OREGON
FERSONIUS ET AL., 2003).
2. SEE SITE-SPECIFIC SEISMIC HAZARD STUDY FOR A DISCUSSION OF LOCAL FAULTING.
3. FAULTS: 9719 = SALEM-EOLA HILLS HOMOCLINE; #862 = UNNAMED FAULTS NEAR SUTHERLIN;
#863 = UPPER WILLAMETTE RIVER; 4869 = CORVALLIS; #870 = OWL CREEK; #1809 = WHITE
BRANCH FAULT ZONE.
4. MAP IS NOT TO SCALE.
MAP LEGEND:
— Nmol'ena l<1o,DDoyearal«aoeuav glatletlon l<ls ocg r,aral-,
nohlsbnc vii 13,000
3 In Gregor 10eale
— LID.. matarytu1d0.0DDrears pcet perultlmele glaolallml
— Late and mleme DaelemarY (a50 US raanl
— groura lµ undmarenualae (<,,pba.coo rear)
—fa aawnurt (age«odgm Uncertain)
SLIP RATE TRACE
al�e5mmseer Mosey rent—us at map anile
—100 mu --- Metal dlewntruoua at map Selo
05lrear 0-10 aul --- I. -a or coreoul,l'
— <o.mnuyea
STRUCTURE TYPEy RELATED FEAT1IEs
I Normal or nigh- aril, reverse fault
Shop -slip Fault
FrrmraW
—{— MOcllnel bid
�— Syrollrel fad
—I— MmoonnaRad
j Faull sectlar metkm
irl egress
/ Plenary trilateral sped
Primanent liver of stream
I ntelmltlent deer or dream
arR Pelmenent or rearn Thus lark,
DETNLED STUDY Sl LES
�, Trani elle
all Super. Ione ewer alt
aW Foundation Engineering, Inc.
QUARTERNARY CRUSTAL FAULT MAP
FIGURE NO.
Professlonal Geotechnical Services
SOUTHERN WILLAMETTE VALLEY
PROJECT No.
DATE
LRAM BY,
SOUTH HILLS 3RD LEVEL RESERVOIR REPLACEMENT
1D
2211098
Nay. zz, 2021
ekR
SPRINGFIELD, OREGON
Ahk
Appendix E
Slope Stability Analysis
Foundation Engineering, Inc.
Professional Geotechnical Services
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