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FEB 1 3 2019
CITY GIG RD
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REPORT OF GEOTECHNICAL ENGINEERING SERVICES
Facility Expansion - 6755 SW Sandburg Road
Tigard, Oregon
Gutech
sonttions m ncl
July 4, 2018
GSI Project: reece-18-I-gi
Ge t c
Solutions t nci
July 4, 2018 reece-I8-1-gi
Reece Holdings
ginar(a�ress.us
cc: CIDA;Jennfierecidainc.com
REPORT OF GEOTECHNICAL ENGINEERING SERVICES
Facility Expansion
6755 SW Sandburg Street, Tigard, Oregon
As authorized, herein we present our report of geotechnical engineering services for the proposed
facility expansion/renovation in Tigard, Oregon. This project includes a second story addition to the
existing facility, as well as parking expansion and infiltration evaluation. A retaining wall is planned for
the parking expansion south of the building. We have assumed loads of less than 200 kips for columns,
5ksf for walls and 500 psf for floors. The purpose of our work was to investigate subsurface conditions
and provide geotechnical recommendations for design. Our specific scope of work included the
following:
v Provide principal-level geotechnical project management including client communications,
management of field and subcontracted services, report writing, analyses, and invoicing.
✓ Review previous reports, geologic maps and vicinity geotechnical information as indicators of
subsurface conditions.
✓ Complete a site reconnaissance to observe surface features relevant to geotechnical issues, such as
topography, vegetation, presence and condition of springs, exposed soils and rock, and evidence of
previous grading.
v Identify exploration locations and complete One-Call utility locates for public utilities and a private
locate.
✓ Explore subsurface conditions by advancing up to three CPT probes to depths of up to 30 feet or
refusal with pore pressure testing to evaluate ground water depths, as well as two hand augured
borings to depths of up to 5 feet to visually evaluate near surface soils and for infiltration testing.
✓ Classify and sample materials encountered and maintain a detailed log of the explorations.
v Complete infiltration testing in one boring.
✓ Determine the moisture content of selected samples obtained from the explorations and complete
soil classification testing as necessary.
✓ Provide recommendations for earthwork including site preparation, reuse of existing fill in place or
stabilized or reinstalled, seasonal material usage, compaction criteria, utility trench backfill, slope
inclinations, and the need for subsurface drainage.
✓ Evaluate site liquefaction potential and estimate site deformations and provide qualitative means to
address unsuitable deformations if needed.
✓ Provide recommendations for shallow foundations including suitable soils, stabilization, bearing
pressures, sliding coefficient, and a seismic site class, as well as geotechnical parameters for deep
foundation support for up to one pile type, if needed.
v Provide recommendations for slab support, including a subgrade modulus if needed, underslab rock
thickness and materials, and the need for stabilization.
✓ Provide recommendations for pavements including subgrade preparation and stabilization, and base
rock and asphalt concrete and portland cement concrete thicknesses.
✓ Provide a written report summarizing the results of our geotechnical evaluation
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1112 7"'Street, Oregon City, OR 97045 ph 503.657.3487 fax 503.722.9946
July 4, 2018 reece-I8-1-gi
SITE OBSERVATIONS AND CONDITIONS
Surface Conditions
The property is located at 6755 SW Sandburg Road in Tigard, Oregon as shown on the attached Site
Plan. The site is relatively flat in the present parking and building area, having been cut and filled to its
present condition, with gentle slopes to the south, and a moderate vegetated slope south of the building
with a short wall near its base. A small basalt outcrop is present north of the north parking area. Off-
site to the northeast are MSE wall associated with the 217/ 1-5 interchange. The asphalt concrete on sit
is generally not distressed.
Subsurface Conditions
General— Subsurface conditions at the site were explored on June 25, 2018 by advancing 3 cone
penetrometer explorations (P-I through P-3) to depths near 33 feet in P-2 and P-3 and refusal at 5 feet
in P-1, and 2 hand augers to depths of up to 5 feet. Approximate exploration locations are shown on the
attached Site Plan. Specific subsurface conditions observed at each exploration are described in the
attached Hand Auger Logs and CPT Logs. Conditions were consistent with mapped fine grained
deposits, but with refusal on rock the north. Site pavements ranged from 2.5 to 3.5 inches in thickness
in pre-bored CPT holes, with crushed rock base of 6 to 12 inches.
Our explorations in undeveloped areas south of the building consisted of two hand augers. Each of
these explorations encountered roughly 12 inches of rooty brown silt topsoil developed in silt fill that
extended to depths of at least 3 to 4 feet where refusal was met on cobbles or boulders or rock.
Explorations in paved areas were done with CPT probes. P-I was done near a rock outcrop that is off
pavement to the north, and met refusal on rock at 5.5 feet in depth. P-2 and P-3 encountered shallow
fills then medium stiff silt to depths of 12 to 17 feet. Tip resistance in the upper silt generally ranged
from 7 to 30 tsf. This material is moderately over-consolidated with a moderate compressibility and is
moisture sensitive to disturbance from construction traffic in the wet season. The lower silt generally
had tip resistance ranging from 40 to 150 tsf. This material has a low compressibility.
Laboratory Testing— Laboratory testing in samples from the hand augers resulted in moisture contents
generally from 19% to 24% in the silt fill, with one shallow sample at 6%. Results of moisture content
testing are provided in the attached Moisture Contents.
Groundwater— We did not observe groundwater seepage in the hand augers. Back-calculated water
levels from pore pressure dissipation testing in P-2 was 8 feet below the ground surface. However, due
to the low permeability of the silt soils, perched ground water conditions could exist at shallower
depths during wet periods and during the wet season. Mapping (USGS 2007) indicates ground water
levels in the area are 20-40 feet in depth.
Infiltration Testing—We completed double ring configuration standpipe falling-head infiltration tests in
the southern portion of the site in HA-2 as summarized in the following table. Testing was conducted
after an initial wetting period and measurements were taken over time. Geotechnical recommendations
for infiltration rate are provided in the Infiltration section of this report.
Test Pit Soil Tested Unfactored rate (in3/hr/in2) *
HA-2@ 3 ft Silt with trace clay <0.1*
*this value is unfactored and not to be used for design
2/8
1112 7Th Street Oregon City, OR 97045 ph 503.657.3487 fax 503.722.9946
July 4, 2018 reece-18-I-gi
CONCLUSIONS AND RECOMMENDATIONS
General
Based on the results of our explorations and analyses, it is our opinion that the site can be developed as
proposed following the recommendations herein. The proposed new structural loads within the limits
herein can be supported on shallow spread footings. Construction for new parking areas in wet
conditions versus dry will require more extensive working blankets and haul roads and subgrade
stabilization/protection. Our geotechnical engineering recommendations are provided in the following
sections.
Site Preparation
General- Prior to earthwork construction, new pavement and new building and wall areas of the site
must be prepared by removing any existing structures, utilities, and any loose surficial or undocumented
fill. Any excavation resulting from the aforementioned preparation must be brought back to grade with
structural fill. Site preparation for earthwork will also require the removal of the root zone and topsoil
from all pavement, building, hard-scaping and fill areas.
Root balls from trees and shrubs may extend several feet and grubbing operations can cause
considerable subgrade disturbance. All disturbed material must be removed to undisturbed subgrade
and backfilled with structural fill. In general, roots greater than one-inch in diameter must be removed
as well as areas of concentrated smaller roots.
Stabilization and Soft Areas-After stripping, we must be contacted to evaluate the exposed
subgrade. This evaluation can be done by proof rolling in dry conditions or probing during wet
conditions. Soft areas will require over-excavation and backfilling with well graded, angular crushed
rock compacted as structural fill, overlying a separation geosynthetic such as a Propex Geotex 601 or
equivalent. A geogrid may also be required, such as a Tensar BSXQ 2020 or equivalent punched and
drawn geogrid.
Working Blankets and Haul Roads - Construction equipment must not operate directly on the
subgrade, as it is susceptible to disturbance and softening. Rock working blankets and haul roads placed
over a geosynthetic in a thickened advancing pad can be used to protect subgrades. We recommend
that sound, angular, pit run or crushed basalt with no more than 6 percent passing a#200 sieve be used
to construct haul roads and working blankets, overlying the preceding separation geosynthetic.
Working blankets must be at least 12 inches thick, and haul roads at least 18 inches thick. If the
preceding geogrid is used these can be reduced to 9 inches and 14 inches, respectively. The preceding
thicknesses are the minimum recommended. Subgrade protection is the responsibility of the contractor
and thicker sections may be required based on subgrade conditions during construction and type and
frequency of construction equipment.
Earthwork
Fill—The on-site fine grained soil, and silt fill that has all organics and unsuitable debris removed, can be
used for structural fill if properly moisture conditioned. Use of this material will not be feasible during
wet conditions. Even during dry summer conditions the on-site soils will require drying by scarification
and frequent mixing in thin lifts. Once moisture contents are within 3 percent of optimum, the material
must be compacted to at least 92 percent relative to ASTM D 1557 (modified proctor) using a tamping
3/8
1 112 7°Street, Oregon City, OR 97045 ph 503.657.3487 fax 503.722.9946
July 4, 2018 reece-l8-I-gi
foot type compactor. Fill must be placed in lifts no greater than 10 inches in loose thickness. In addition
to meeting density specifications, fill will also need to pass a wheel roll using a loaded dump truck, water
truck, or similar wheel load equipment.
In wet conditions, fill must be imported granular soil with less than 6 percent fines, such as clean
crushed or pit run rock. This material must also be compacted to 95 percent relative to ASTM D 1557.
Trenches— Utility trenches may encounter ground water seepage and caving must be expected where
seepage is present, including flowing conditions if sandy soils are present. Shoring of utility trenches will
be required for depths greater than 4 feet and where groundwater seepage is present. We recommend
that the type and design of the shoring system be the responsibility of the contractor,who is in the best
position to choose a system that fits the overall plan of operation.
Depending on the excavation depth and amount of groundwater seepage, dewatering may be necessary
for construction of underground utilities. Flow rates for dewatering are likely to vary depending on
location, soil type, and the season during which the excavation occurs. The dewatering systems, if necessary,
must be capable of adapting to variable flows.
Pipe bedding must be installed in accordance with the pipe manufacturers' recommendations. If
groundwater is present in the base of the utility trench excavation,we recommend overexcavating the trench
by 12 to 18 inches and placing trench stabilization material in the base. Trench stabilization material must
consist of well-graded, crushed rock or crushed gravel with a maximum particle size of 4 inches and be free of
deleterious materials. The percent passing the U.S.Standard No.200 Sieve must be less than 5 percent by
weight when tested in accordance with ASTM C 117.
Trench backfill above the pipe zone must consist of well graded, angular crushed rock or sand fill with
no more than 7 percent passing a#200 sieve. Trench backfill must be compacted to 92 percent relative
to ASTM D-1557, and construction of hard surfaces, such as sidewalks or pavement, must not occur
within one week of backfilling.
Infiltration
Design - Based on the results of our testing and analyses, infiltration rates in the silt unit are very low
and infiltration is not feasible.
Seismic Design
General- In accordance with the International Building Code (IBC) as adapted by State of Oregon
Structural Specialty Code (SOSSC) and based on our explorations and experience in the site vicinity, the
subject project should be evaluated using the parameters associated with Site Class D.
Liquefaction and Lateral Spreading- Liquefaction can occur in loose, saturated, non-plastic soils.
Strong shaking, such as that experienced during earthquakes, causes the densification and subsequent
settlement of these soils and high pore pressures which weaken the soil. Our analyses indicate that site
soils are not susceptible to liquefaction.
4/8
1112 7"' Street, Oregon City, OR 97045 ph 503.657.3487 fax 503.722.9946
July 4, 2018 reece-I8-1-gi
Shallow Foundations
Existing foundation dimensions are not known, but the pressures herein can be used to evaluate existing
and new footings. For any new foundations, or widened foundations, topsoil, undocumented fill soils,
and till zone soils must be removed from beneath all new foundations. This material may be present
below existing fills or at the surface. Based on the preceding anticipated structural loads, the proposed
structure can be supported on shallow spread foundations bearing in the native medium stiff or stiffer
inorganic silt below any unsuitable fill or on properly constructed structural fill based in native soils.
Footings must be embedded at least 18 inches below the lowest adjacent, exterior grade. Footings can
be designed for an allowable net bearing pressure of 3,000 psf when founded as recommended. The
preceding bearing pressure can be increased to 5,000 psf for temporary wind and seismic loads.
Continuous footings should be no less than 18 inches wide, and pad footings should be no less than 24
inches wide. Resistance to lateral loads can be obtained by a passive equivalent fluid pressure of 400 pcf
against suitable footings, ignoring the top 12 inches of embedment, and by a footing base friction
coefficient of 0.38. Properly founded footings are expected to settle less than a total of I inch, with less
than '/Z inch differentially.
If footing construction is to occur in wet conditions, a few inches of crushed rock should be placed at
the base of footings to reduce subgrade disturbance and softening during construction.
Slabs
Floor slab loads up to 500 psf are expected to induce less than one inch of settlement. The structural
engineer should confirm the existing floor slabs are structurally suitable to support expected loads. A
minimum of 12 inches of clean, angular crushed rock with no more than 5 % passing a#200 sieve is
recommended as underslab rock for any new slabs. Increased rock thicknesses and stabilization may be
required for construction in wet conditions and where used as a working blanket or haul road per the
Stabilization section in this report. Prior to slab rock placement the subgrade will need to be
evaluated by us by probing or observing a proof rolling using a fully loaded truck. Underslab rock must
be compacted to 92 % compaction relative to ASTM D 1557, and must be proof rolled as well. In
addition, any areas contaminated with fines must be removed and replaced with clean rock. If the base
rock is saturated or trapping water, this water must be removed prior to slab placement.
Floor Moisture - For any new slabs, a properly installed and protected vapor flow retardant can reduce
slab moistures. If moisture sensitive floor coverings or operations are planned, we recommend a vapor
barrier be used. Typically a reinforced product or thicker product (such as a 15 mil STEGO wrap or
equivalent) can be used. Experienced contractors using special concrete mix design and placement have
been successful placing concrete directly over the vapor barrier which overlies the rock. This reduces
the issue of water trapped in the rock between the slab and vapor barrier, which otherwise requires
removal. In either case, slab moisture must be tested/monitored until it meets floor covering
manufacturer's recommendations.
Retaining Walls
General-The following recommendations are based on the assumptions that (I) Walls are
conventional concrete cantilever walls (2) Wall backfill consists of level, well-drained, angular, granular
material, (3) Walls are less than 10 feet in height, and (4) No surcharges such as stockpiled soil or
equipment are placed within 10 feet of the wall.
5/8
1112 7th Street Oregon City, OR 97045 ph 503.657.3487 fax 503.722.9946
July 4, 2018 reece-18-1-gi
Walls restrained against rotation should be designed using an equivalent fluid pressure of 50 pcf. Walls
not restrained against rotation should be designed using an equivalent fluid pressure of 30 pcf. Seismic
design for roughly one inch of deflection (Based on NCHRP 6-I I and NCHRP 12-70; Anderson 2008
and 0.4g PGA), can be evaluated for an apparent cohesion of 200 psf and internal friction angle of 30
degrees in the retained silt for a seismically induced rectangular wall pressure of II H (to determine if
this controls wall design or the preceding static condition).
These forces can be resisted by passive pressure at the toe of the wall using an equivalent fluid pressure
of 350 pcf(this should exclude the top 12 inches of embedment) and friction along the base using a
friction coefficient of 0.35. Wall foundations should be designed as recommended herein for shallow
foundations.
Backfill- Retaining walls should be backfilled with clean, imported, granular soil with less than 6 percent
fines, such as clean sand or rock. This material should also be compacted to a minimum of 92 percent
relative to ASTM D-1557 (modified proctor). Within 3 feet of the wall, backfill should be compacted to
not more than 90 percent relative to ASTM D-I 557 using hand-operated equipment. Retaining
structures typically rotate and displace up to I percent of the wall height during development of active
pressures behind the wall. We therefore recommend that construction of improvements adjacent to
the top of walls be delayed until approximately two weeks after wall construction and backfill.
Drainage
General-We recommend installing perimeter foundation drains around all new exterior foundations.
The surface around the building perimeter must be sloped to drain away from the building. As stated
previously, our retaining wall recommendations are based on fully drained conditions. All retaining walls
must include a drain constructed as described in the following section.
Foundation and Wall Drains - Foundation and retaining wall drains should consist of a two-foot wide
zone of drain rock encompassing a 4-inch diameter perforated pipe, all enclosed with a non-woven filter
fabric. The drain rock should have no more than 2 percent passing a #200 sieve and should extend to
within one foot of the ground surface. The geosynthetic should have an AOS of a#70 sieve, a minimum
permittivity of 1.0 sec-I, and a minimum puncture resistance of 80 pounds (such as a Propex Geotex 601
or approved equivalent). For walls a composite drain board such as an Amerdrain 500/520 could be
used above the footing drain for wall drainage. In either case one foot of low permeability soil (such as
the on-site silt) should be placed over the fabric at the top of the drain to isolate the drain from surface
runoff.
Pavement
Asphalt Concrete - At the time of this report we did not have specific information regarding the type
and frequency of expected traffic. We therefore developed new asphalt concrete pavement thicknesses
for areas exposed to passenger vehicles only and areas exposed to up to 5 trucks per day based on a
20-year design life with 3-to 5-axle trucks. We assumed that the average truck will consist of a panel-
type delivery truck or 3-axle truck. Traffic volumes can be revised if specific data is available. In general,
the existing site pavements have this capacity.
6/8
1112 71 Street, Oregon City, OR 97045 ph 503.657.3487 fax 503.722.9946
July 4, 2018 reece-18-1-gi
Our pavement analyses is based on AASHTO methods and subgrade of structural fill or undisturbed
medium stiff or better native silt having a resilient modulus of 6,000 psi and prepared as recommended
herein. We have also assumed that roadway construction will be completed during an extended period
of dry summer weather. The results of our analyses based on these parameters are provided in the
table below.
Traffic 18k ESAL's AC (inches) CR (inches)
Passenger Vehicle Only - 3 6*
Up to 5 Trucks Per Day 29,000 3 8*
* Increased rock thicknesses and stabilization will be required for construction in working
blankets and hauls roads and during wet conditions per the Stabilization section in this report.
The thicknesses listed in the above table are the minimum acceptable for construction during an
extended period of dry weather in the dry season. Increased rock thicknesses and stabilization will be
required for construction in working blankets and hauls roads and during wet conditions per the
Stabilization section in this report. Crushed rock must conform to ODOT base rock standards and
have less than 6 percent passing the#200 sieve. Asphalt concrete must be compacted to a minimum of
91 percent of a Rice Density.
Portland Cement Concrete -We developed PCC pavement thicknesses at the site for the assumed
one-way traffic levels as shown in the table below. Each of these sections is based on AASHTO
methods with no reduction for wander and a composite modulus of subgrade reaction of 350 pci
(AASHTO Figure 3.3 with Mr = 6,000 psi and 6 inches crushed rock base). Other parameters include
4,000 psi compressive strength portland cement concrete (PCC), and plain jointed concrete without
load transfer devices or tied concrete shoulders. PCC pavements over trench backfill should not be
placed within one week of fill installation unless survey data indicates that settlement of the backfill is
complete.
Traffic I8k ESALS PCC (inches) CRB (inches)
Up to 5 Trucks Per Day 233,000 6 6
Subgrade Preparation -The pavement subgrade must be prepared in accordance with the Earthwork
and Site Preparation recommendations presented in this report. All pavement subgrades must pass a
wheel roll prior to paving. Soft areas must be repaired per the preceding Stabilization section.
LIMITATIONS AND OBSERVATION DURING CONSTRUCTION
We have prepared this report for use by Reece Holdings and the design and construction teams for this
project only. The information herein could be used for bidding or estimating purposes but must not be
construed as a warranty of subsurface conditions. We have made observations only at the
aforementioned locations and only to the stated depths. These observations do not reflect soil types,
strata thicknesses, water levels or seepage that may exist between observations. We must be consulted
to observe all foundation bearing surfaces, subgrade stabilization, proof rolling of slab and pavement
subgrades, installation of structural fill, subsurface drainage, and cut and fill slopes. We must be
consulted to review final design and specifications in order to see that our recommendations are
7/8
1 112 7"Street Oregon City, OR 97045 ph 503.657.3487 fax 503.722.9946
July 4, 2018 reece-1 8-1-gi
suitably followed. If any changes are made to the anticipated locations, loads, configurations, or
construction timing, our recommendations may not be applicable, and we must be consulted. The
preceding recommendations must be considered preliminary, as actual soil conditions may vary. In
order for our recommendations to be final, we must be retained to observe actual subsurface
conditions encountered. Our observations will allow us to interpret actual conditions and adapt our
recommendations if needed.
Within the limitations of scope, schedule and budget, our services have been executed in accordance
with the generally accepted practices in this area at the time this report was prepared. No warranty,
expressed or implied, is given.
We appreciate the opportunity to work with you on this project and look forward to our continued
involvement. Please call if you have any questions.
Sincerely,
--14) -------44-------- 4 . t PROF
Don Rondema, MS, PE, GE ;:-
Principal VI
4140
' W rng _. 1
Attachments — Site Plan, Guidelines for Classification, Hand Auger Logs, CPT Logs, Moisture Contents.
818
1112 7d' Street Oregon City, OR 97045 ph 503.657.3487 fox 503.722.9946
•
• '
Geotech Solutions / CPT-P1 / 6577 SW Sandburg st . Tigard
OPERATOR: OGE DMM
CONE ID: DPG1323
HOLE NUMBER: CPT-P1
TEST DATE: 6/26/2018 11:52:26 AM
TOTAL DEPTH: 5.577 ft
SPT N60 SBT Tip (Qc) Sleeve (Fs) FR (Fs/Qc) PP (U2)
(UNITLESS) (UNITLESS) (tsf) (tsf) (%) (psi)
1 0 100 0 12 0 60C C '/ 0 0 _5 _
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® 3 clay 6 sandy silt to clayey s . 9 sand 11 12 sand to clayey sand (*)
*SBT/SPT CORRELATION: UBC-1983
Geotech Solutions 1 CPT-P2 16577 SW Sandburg st. Tigard
OPERATOR:OGE DMM
CONE ID:DPG1323
HOLE NUMBER:CPT-P2
TEST DATE:6/26/2018 10:08:02 AM
TOTAL DEPTH:32.808 ft
SPT N60 SBT Tip(Qc) Sleeve(Fs) FR(Fs/Qc) PP(U2)
(UNITLESS) (UNITLESS) (tsf) (tsf) (%) (psi)
0 0 80 0 12 0 200 0 6 0 7 -10 20
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®3 day a6 sandy silt to clayey silt W 9 sand ®12 sand to clayey sand(*)
`SBT/SPT CORRELATION: UBC-1983
, •
Geotech Solutions / CPT-P3 / 6577 SW Sandburg st . Tigard
OPERATOR: OGE DMM
CONE ID: DPG1323
HOLE NUMBER: CPT-P3
TEST DATE: 6/26/2018 12:09:27 PM
TOTAL DEPTH: 32.808 ft
SPT N60 SBT Tip (Qc) Sleeve (Fs) FR (Fs/Qc) PP (021
(UNITLESS) (UNITLESS) (tsf) (tsf) (%) (psi)
0 a 80 0 12 0 140 0 8 0 8 -10 40
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® 2 organic material ■ 5 clayey silt to silty c? 6 sand to silty sand ,';k. 11 very stiff fine grained (*)
■ 3 clay ® 6 sandy silt to clayey s 9 sand $ 12 sand to clayey sand (*)
*SBT/SPT CORRELATION: UBC-1983
Exploration Depth,ft Moisture Content
HA-1 2.0 6%
HA-1 4.0 27%
HA-2 2.0 19%
HA-2 4.0 24%
Ge,o chh MOISTURE CONTENTS
Solutions I ncl reece-18-01-gi
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July 7, 2018 reece-18-1-cros
Reece Holdings; ginar_@ress.us
cc: CIDA;Jennfiercidainc.com
ADDENDUM TO REPORT OF GEOTECHNICAL ENGINEERING SERVICES
MSE Retaining Walls
6755 SW Sandburg Street, Tigard, Oregon
As requested this letter summarizes our report addendum (report dated july 4, 2018) for MSE retaining
wall design parameters at the project. We understand a Lock and Load wall is planned for the parking
area expansion, and have assumed walls are less than 10 feet in height (and in total combined height if
tiered walls are used). The walls are to be designed by others. The following criteria are recommended
for wall design:
• Wall base layers must be embedded at least I foot below erosion protected grades, with toe
slopes no greater than 4H:I V for at least 5 feet horizontally below the toe.
• Walls must be battered back 1 H:I OV or flatter.
• Grid zone fill must consist of angular, well-graded crushed rock with no more than 6% fines
compacted to 95% of ASTM D-1557 or until suitably dense as determined by our geotechnical
engineer.
• The design angle of internal friction used for the preceding grid zone rock must be no more
than 38 degrees, with a unit weight of 125 pcf.
• Drainage against the wall face units must conform to the manufacturers specifications.
• Wall foundation soils must consist of a rebuilt crushed rock pad at least 6 inches thick bearing
on undisturbed native silt soils or GSI observed structural fill based on native soils.
• We must be provided the wall design for review and external stability analyses.
• Foundations above walls must be located no closer than a I H:1 V projection up from the nearest
wall grid.
The Limitations of our report apply. Please contact us if you have any questions.
Sincerely, �����OT
-141— •
tB,1Itt .+ �
Don Rondema, MS, PE, GE
Principal
UI
1112 7th Street Oregon City, OR 97045 ph 503.657.3487 fax 503.722.9946
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Test Pit# Depth (ft) Soil Description
Explorations completed on June 25,20I8 with a hand auger.
HA-I Location: S of building to East.
Surface conditions: grass, ivy.
0—2 Medium stiff, light brown, SILT FILL with some roots; dry.
2—4 Medium stiff, brown SILT FILL; moist.
3 ft becomes with trace sand.
4 refusal on rock? Or boulder?
No caving. No seepage.
HA-2 Location: S of building to west.
Surface conditions: ivy.
0— 1.5 Medium stiff, light brown, SILT FILL with some roots; dry.
1.5—3 Medium stiff, brown SILT FILL; moist
3 ft becomes with trace sand.
3 refusal on rock? Or boulder?
No caving. No seepage.
Double ring configuration cased hole falling head infiltration test at 2 feet.
Ge t c HAND AUGER LOGS
Solutions I nci reece-l8-I-gi
GUIDELINES FOR CLASSIFICATION OF SOIL
Description of Relative Density for Granular Soil
Standard Penetration Resistance
Relative Density
(N-values) blows per foot
very loose 0-4
loose 4- 10
medium dense 10- 30
dense 30- 50
very dense over 50
Description of Consistency for Fine-Grained (Cohesive) Soils
Standard Penetration Torvane
Consistency Resistance (N-values) Undrained Shear
blows per foot Strength,tsf
very soft 0-2 less than 0.125
soft 2-4 0.125 -0.25
medium stiff 4 - 8 0.25 - 0.50
stiff 8- 15 0.50- 1.0
very stiff 15 - 30 1.0- 2.0
hard over 30 over 2.0
Grain-Size Classification
Description Size
Boulders 12-36 in.
Cobbles 3 - 12 in.
Gravel '/+ - 3/4 in. (fine)
3/4- 3 in. (coarse)
Sand No. 200- No.40 Sieve (fine)
No.40 - No. 10 sieve (medium)
No. 10 - No.4 sieve (coarse)
Silt/Clay Pass No. 200 sieve
Modifier for Subclassification
Percentage of Other
Adjective
Material In Total Sample
Clean/Occasional 0- 2
Trace 2- 10
Some 10- 30
Sandy, Silty, Clayey, etc. 30-50