Report (65) .
Geotechnical Engineering Report
SW Atlanta Street Storage Building
Tigard, Oregon ° ,ICE COPY
forg' CE1VEDTrailblazer Development, LLC
June 11, 2018 OCT 2 9 2018
CITY OF TIGARD
IILDING DIVISION
• • GEOENGINEERS
•
Geotechnical Engineering Report
SW Atlanta Street Storage Building
Tigard, Oregon
111
for
Trailblazer Development. LLC
June 11, 2018
GEOENGINEERS
1200 NW Naito Parkway, Suite 180
Portland, Oregon 97209
503.624.9274
•
o
• Geotechnical Engineering Report
SW Atlanta Street Storage Building
Tigard, Oregon
File No. 23459-001-00
June 11, 2016
Prepared for:
Trailblazer Development, LLC
333 South State Street,Suite V-144
Lake Oswego, Oregon 97034
Attention:Jeb Koerner
Prepared by:
GeoEngineers, Inc.
1200 NW Naito Parkway,Suite 180 0.V) PRO
Portland, Oregon 97209
503.624.9274 �(4, 77490P
/7,-41
ZOLOOJ
EEt 0 COQ
lLAN LP
Greg A. Landau, PE, GE
Associate Geotechnical Engineer EXPIRES: 1 .1_ i
DMH:GAL:cje
Disclaimer:Any electronic form,facsimile or hard copy of the original document(email,text,table,and/or figure),if provided,and any attachments are only a copy
of the original document.The original document is stored by GeoEngineers,Inc.and will serve as the official document of record.
4111
GEOENGINEERS
• Table of Contents
INTRODUCTION 1
SCOPE OF SERVICES 1
SITE DESCRIPTION 1
Surface Conditions 1
Site Geology 1
Subsurface Conditions 2
General 2
Soil Conditions 2
Groundwater Conditions 2
CONCLUSIONS 3
EARTHQUAKE ENGINEERING 3
Liquefaction 3
Lateral Spreading 4
Fault Surface Rupture 4
Landslides 4
Seismic Design Information 4
FOUNDATION SUPPORT RECOMMENDATIONS 5
Aggregate Piers 5
Lateral Resistance 6
Footing Drains 6
Construction Considerations 6
Slab-on-Grade Floors 6
Subgrade Preparation 6
Design Parameters 7
Below-Slab Drainage 7
BELOW-GRADE WALLS 8
Permanent Subsurface Walls 8
Other Cast-in-Place Walls 8
Wall Drainage g
Waterproofing 9
EXCAVATION SUPPORT 10
Excavation Considerations 10
Temporary Cut Slopes 10
Soil Nail Walls 11
Preliminary Design Recommendations 12
Soil Nail Wall Performance 13
Drainage 13
EARTHWORK 13
• Clearing and Site Preparation 13
GEOENGINEERS� June 11,2018 Page i
He No.23459-001-00
Subgrade Preparation 14
Subgrade Protection 14
•
Structural Fill and Backfill 15
General 15
Use of On-site Soil 15
Imported Select Structural Fill 15
Aggregate Base 15
Retaining Wall Backfill 15
Trench Backfill 16
Fill Placement and Compaction 16
Permanent Cut and Fill Slopes 17
TEMPORARY CONSTRUCTION DEWATERING 17
Sump Pumping 18
Surface Water Drainage Considerations 18
PAVEMENT RECOMMENDATIONS 18
General 18
Drainage 18
Pavement Sections 18
LIMITATIONS 19
REFERENCES 20
LIST OF FIGURES •
Figure 1. Vicinity Map
Figure 2. Site Plan
Figure 3. Earth Pressure Diamgrams Temporary Shoring Wall
Figure 4. Recommended Surcharge Pressure
APPENDICES
Appendix A. Field Explorations and Laboratory Testing
Figure A-1. Key to Exploration Logs
Figures A-2 and A-3. Logs of Borings
Figure A-4. Atterberg Limits Test Results
Appendix B. Ground Anchor Load Tests and Shoring Monitoring Program
Appendix C. Report Limitations and Guidelines for Use
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• INTRODUCTION
GeoEngineers, Inc. (GeoEngineers) is pleased to submit this geotechnical engineering report for the
proposed storage building located north of SW Atlanta Street in Tigard, Oregon. The location of the site is
shown in the Vicinity Map, Figure 1.
The proposed project includes constructing a five-story commercial storage facility, associated pavements
and utilities. The site grades from an elevation of approximately 208 feet above mean sea level (MSL) at
the north end of the site to approximately 192 feet MSL at the southeast corner of the site. The building
will be constructed with a finish floor elevation of 194.5 feet MSL, resulting in maximum cuts up to about
17 feet. A temporary soil nail wall is proposed to retain the excavation and will be replaced by a permanent
cast-in-place concrete retaining wall along the north, northeast and northwest portions of the lot. The
proposed site layout is shown in relation to existing site features in the Site Plan, Figure 2.
SCOPE OF SERVICES
Our specific scope of services is detailed in our May 24,2018 proposal to you. Our services were authorized
on May 24, 2018. In general our scope of services included: reviewing selected geotechnical information
about the site, including the Hardman Geotechnical Services, Inc. (Hardman) geotechnical report for the
site dated June 12, 2017 (updated November 29, 2017); exploring subsurface soil and groundwater
conditions; collecting representative soil samples; completing relevant laboratory testing and geotechnical
analyses; and providing this geotechnical report with our conclusions, findings and design
• recommendations.
SITE DESCRIPTION
Surface Conditions
The project site encompasses approximately 0.97 acre and is bounded by private commercial properties
to the north, east, and west and the SW Atlanta Street right-of-way(ROW)to the south.The site is currently
undeveloped. The surface is thickly vegetated with rough field grass and blackberry briars, with scattered
deciduous trees and a wooded margin along the southeast property boundary.The site slopes moderately
down to the south and east, with elevations ranging from approximately 208 feet MSL at the northeast
corner of the site to approximately 192 feet MSL at the southeast corner along the SW Atlanta Street ROW.
Site Geology
The geology of the site is mapped by the Oregon Department of Geology and Mineral Industries (DOGAMI)
Open File Report 0-90-2, Earthquake Hazard Geology Maps of the Portland Metropolitan Area, Oregon
(Madin 1990) as mantled by the fine-grained facies of the Pleistocene catastrophic (Missoula) flood
deposits.The geologic map shows the site and vicinity underlain by approximately 30 to 50 feet of this fine-
grained flood sediment. Our subsurface explorations suggest that the site subsurface conditions generally
conform to the published mapping, with some minor exceptions described below.
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Subsurface Conditions •
General
The subsurface conditions at the site were evaluated by drilling two geotechnical borings(GEI B-1 and GEI
B-2)on May 27, 2018. Borings GEI B-1 and GEI B-2 extended to approximate depths ranging from 311/2 to
461/2 feet below the ground surface (bgs). We also reviewed the logs of the two borings and four test pits
performed by Hardman in 2017. The approximate locations of the explorations completed at the site are
shown in Figure 2. The logs of GeoEngineers explorations completed for this study are presented in
Appendix A.
Soil samples were obtained during drilling and were taken to GeoEngineers' laboratory for further
evaluation. Selected samples were tested for the determination of the fines content, Atterberg limits and
moisture/density testing. A description of the laboratory testing and the test results are presented in
Appendix A.
Soil Conditions
In general, subsurface soil conditions consist of a surficial veneer of man-made fill overlying silt and fine
sand of the Pleistocene fine-grained catastrophic flood deposits. These units are described in more detail
below.
FILL
GEI B-1 encountered silty soil fill from the ground surface to approximately 3 feet bgs. We did not observe
fill soil materials in GEI B-2. All of the Hardman explorations report a mixture of silt fill with gravel, sand
1111 and debris from the ground surface to depths ranging between 11/2 to 3 feet bgs. We also observed a
scattering of gravel and concrete debris at the ground surface along the southwestern margins of the site.
FINE-GRAINED FLOOD DEPOSITS
We encountered fine-grained flood deposits from below the fill (or at the ground surface in GEI B-2)to the
maximum depths explored.
The upper zone of the flood deposits generally consisted of medium stiff to stiff (occasionally very soft to
soft) silt and silt with fine sand; typically, these soils became dark gray below approximately 10 feet bgs.
The thickness of this upper zone was highly variable, ranging from 9 feet in GEI B-2 and 16 feet in GEI B-1.
Below this upper zone, the flood deposits graded to a complex interlayered or interbedded middle zone of
brown to dark gray silt and fine sandy silt, and loose to medium dense (occasionally very loose), dark gray
silty fine sand. The thickness of the middle zone ranged from approximately 5 feet in GEI B-1 and 10 feet
in GEI B-2. Below this middle zone all the explorations encountered a lower zone consisting of stiff to very
stiff, dark gray silt,silt with fine sand and lean clay.
Groundwater Conditions
Groundwater was encountered during drilling in GEI B-1 at approximately 10 feet bgs (elevation 198 feet
above MSL) and GEI B-2 at approximately 8 feet bgs (193 feet MSL). Groundwater was also documented
in both of Hardman's borings (completed August 25, 2017)and all four test pits(completed May 8, 2017)
between 5 and 6 feet bgs.
•
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• Groundwater may be present at shallower depths in a perched or capillary condition during wet times of
the year or during extended periods of wet weather. Groundwater conditions at the site are expected to
vary seasonally due to rainfall events and other factors not observed in our explorations.
CONCLUSIONS
Based on our explorations, testing and analyses, it is our opinion that the site is generally suitable for the
proposed development from a geotechnical engineering standpoint, provided the recommendations in this
report are included in design and construction. A summary of the primary geotechnical considerations is
provided below. The summary is presented for introductory purposes only and should be used in
conjunction with the complete recommendations presented in this report.
■ Liquefaction-induced settlement is anticipated during the design level earthquake. We estimate
approximately 6 to 8 inches of liquefaction induced settlement during this event. Supporting the
structures on aggregate piers, as recommended, will mitigate for this liquefaction-induced settlement.
■ Groundwater was encountered at an elevation of approximately 193 to 198 feet MSL during our
explorations.
■ Permanent drainage measures should be incorporated into the design of below-grade walls and below
slabs-on-grade.
as On-site near surface soils generally consist of silt. The silt will become significantly disturbed from
earthwork occurring during periods of wet weather, or when the moisture content of the soil is more
• than a few percentage points above optimum. Wet weather construction practices will be required
unless earthwork occurs during the dry summer months(typically mid-July to mid-September).
■ Floor slabs having 125 pounds per square foot(psf) loads or less can be supported on aggregate base
placed on native medium stiff or firmer silt.
▪ Standard pavement sections prepared as described in this report will suitably support estimated traffic
loads.
EARTHQUAKE ENGINEERING
Liquefaction
Liquefaction refers to the condition when vibration or ground shaking, usually from earthquake forces,
results in the development of excess pore pressures in saturated soils with subsequent loss of strength in
the soil deposit affected. In general,soils that are susceptible to liquefaction include very loose to medium
dense clean to silty sands and low plasticity silts. For liquefaction to occur, soils must be saturated.
Liquefaction usually results in ground settlement and loss of bearing capacity, resulting in settlement of
structures that are supported on foundations within or above the liquefied soils.
The evaluation of liquefaction potential is a complex procedure and is dependent on numerous site
parameters, including soil grain size, soil density, site geometry, static stress and the design ground
acceleration. Typically, the liquefaction potential of a site is evaluated by comparing the cyclic stress
• ratio (CSR), which is the ratio of the cyclic shear stress induced by an earthquake to the initial effective
overburden stress, to the cyclic resistance ratio (CRR), which is the soils resistance to liquefaction.
GEOENGINEERS Jne 1.1 2018 P6ge'
Estimation of the CSR and the CRR were completed using empirical methods(Youd,et al.2001). Estimated •
ground settlement resulting from earthquake-induced liquefaction was analyzed using empirical
procedures based on correlations from the SPT results (Tokimatsu and Seed, 1987; Ishihara and
Yoshimine, 1992).
The liquefaction analyses are based on the 2015 International Building Code (IBC) (2 percent chance of
exceedance in 50 years, or 2,475-year event) which corresponds to a peak ground acceleration (PGA) of
0.41g and a magnitude of 9.0. Based on our explorations, soils at the site are potentially liquefiable.
Without ground improvement, we estimate approximately 6 to 8 inches of liquefaction induced settlement
during the design earthquake.
Lateral Spreading
A body of soft, liquefiable soil located near a steep or vertical slope is typically subject to failure towards
the unsupported ("free face") slope during an earthquake. This "lateral spreading" is usually related to
liquefaction of the underlying soils and flow-like movement towards the unsupported face and is typically
more severe where the free face is high,steep and the site soils more highly liquefiable. Lateral spreading
is not expected to be a concern due to the lack of steep slope or free face.
Fault Surface Rupture
The closest mapped fault to the site possibly capable of surface rupture is the northwest-to-southeast
trending Canby-Molalla Fault with its inferred extension approximately 1.6 miles northeast of the site
(Personius 2002). No faults are mapped as crossing the site,and the potential for site fault surface rupture
is, therefore, very low. •
Landslides
It is our opinion that landsliding as a result of strong ground shaking is unlikely at this site because of the
relatively gentle site topography.
Seismic Design Information
For preliminary design purposes, we recommend using the procedure outlined in the 2015 IBC and the
2014 Oregon Structural Specialty Code (OSSC). The parameters provided in Table 1 are based on the
conditions encountered during our subsurface exploration program and should be used in preparation of
response spectra for the proposed structures.
•
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TABLE 1.SEISMIC DESIGN PARAMETERS
• 2015 IBC Parameter Recommended Value
Soil Profile Type D/F1
Short Period Spectral Response Acceleration,Ss(percent g) 0.98
1-Second Period Spectral Response Acceleration,Si(percent g) 0.42
Seismic Coefficient, FA 1.11
Seismic Coefficient, Fv 1.58
Note:
1 In accordance with American Society of Civil Engineers(ASCE)7-10,Site Class F soils vulnerable to potential failure or collapse under
seismic loading,such as liquefiable soils,may be classified in accordance with Section 20.3,without regard for liquefaction,provided
the structure under design has a fundamental period of vibration equal or less than 0.5 seconds.
FOUNDATION SUPPORT RECOMMENDATIONS
We understand building loads are on the order of 715 kips for column loads and 9 kips per lineal foot(klf)
for wall loads. These loads are dead plus live loads.
Due to the liquefiable soils and relatively high building loads, we recommend the building be supported on
shallow foundations supported on aggregate piers.
Aggregate Piers
IllShallow spread footings supported on aggregate piers will provide high bearing capacity and reduced
settlement by creating a stiff soil subgrade. Aggregate piers should also be designed to mitigate for
liquefaction. Ground improvement methods can consist of the Rammed Aggregate Pier® (RAP) System
constructed by GeoPier Foundation Company or Vibro PiersTM constructed by Hayward Baker.
Aggregate pier systems are typically designed and constructed by the specialty contractor to a performance
specification. They should submit a ground improvement design that has been completed and stamped by
a registered professional engineer with experience in such projects. We recommend that GeoEngineers
review the design on behalf of the Owner, although the specialty contractor will retain responsibility for the
design and construction of the ground improvements to the specified performance criteria.
We anticipate that the aggregate piers would extend from footing subgrade to approximately 25 to 30 feet
bgs. They should be designed to meet the final bearing capacity and settlement tolerances provided by the
structural engineer. The specialty contractor would provide final design and in-house quality control for the
piers. We recommend that GeoEngineers provide construction quality assurance for the owner during the
construction process.
The bearing capacity of the aggregate pier-improved subgrade would be determined by the specialty
contractor. We typically see a bearing capacity of approximately 5,000 to 6,000 psf in soil similar to those
at the site that have been improved with aggregate piers.
Aggregate piers will mitigate for liquefaction induced settlement within the improvement zone.
•
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Lateral Resistance •
Lateral loads on footings can be resisted by passive earth pressures on the sides of footings and by friction
on the bearing surface. We recommend that passive earth pressures be calculated using an equivalent
fluid unit weight of 300 pounds per cubic foot(pcf)for foundations confined by native medium stiff or stiffer
silt and 350 pcf if confined by a minimum of 2 feet of imported granular fill.
We recommend using a friction coefficient of 0.35 for foundations placed on the native medium stiff or
stiffer silt, or 0.50 for foundations placed on a minimum 2-foot-thickness of compacted crushed rock.The
passive earth pressure and friction components may be combined provided the passive component does
not exceed two-thirds of the total.
The passive earth pressure value is based on the assumptions that the adjacent grade is level and static
groundwater remains below the base of the footing throughout the year. The top 1 foot of soil should be
neglected when calculating passive lateral earth pressures unless the adjacent area is covered with
pavement.The lateral resistance values do not include safety factors.
Footing Drains
We recommend that perimeter footing drains be installed around the buildings at the base of the exterior
wall footings. The perimeter drains should be provided with cleanouts and should consist of at least
4-inch-diameter perforated pipe placed on a 3-inch bed of, and, surrounded by 6 inches of drainage
material enclosed in a non-woven geotextile fabric such as Mirafi 140N (or approved equivalent)to prevent
fine soil from migrating into the drain material. We recommend that the drainpipe consist of either heavy-
wall solid pipe (SDR-35 PVC or equal) or rigid corrugated smooth interior polyethylene pipe (ADS N-12 or •
equal). We recommend against using flexible tubing for footing drainpipes.Where permanent below-grade
walls are cast against temporary shoring, the wall drainage should be connected to the footing drain. The
perimeter drains should be sloped to drain by gravity,if practicable,to a suitable discharge point, preferably
a storm drain. We recommend that the cleanouts be covered and be placed in flush-mounted utility boxes.
Water collected in roof downspout lines must not be routed to the footing drain lines.
Construction Considerations
Immediately prior to placing concrete,all debris and loose soils that accumulated in the footing excavations
during forming and steel placement must be removed. Debris or loose soils not removed from the footing
excavations will result in increased settlement.
We recommend that all completed footing excavations be observed by a representative of our firm prior to
placing reinforcing steel and structural concrete. Our representative will confirm that the bearing surface
has been prepared in a manner consistent with our recommendations and that the subsurface conditions
are as expected.
Slab-on-Grade Floors
Subgrade Preparation
The exposed subgrade should be evaluated after site grading is complete. Proof-rolling with heavy,
rubber-tired construction equipment should be used for this purpose during dry weather and if access for
this equipment is practical. Probing should be used to evaluate the subgrade during periods of wet weather •
or if access is not feasible for construction equipment.The exposed soil should be firm and unyielding and
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without significant groundwater. Disturbed areas should be recompacted if possible or removed and
replaced with compacted structural fill.
Design Parameters
Conventional slabs may be supported on-grade, provided the subgrade soils are prepared as recommended
in the "Subgrade Preparation" section above. We recommend that the slab be founded on either
undisturbed medium stiff or stiffer silt or on structural fill placed over this material. For slabs designed as
a beam on an elastic foundation, a modulus of subgrade reaction of 150 pounds per cubic inch (pci) may
be used for subgrade soils prepared as recommended.
A minimum 6-inch-thick layer of crushed rock Aggregate Base material should be placed over the prepared
subgrade as a capillary break. Aggregate Base material placed directly below the slab should be 3/4-inch
maximum particle size or less. Concrete slabs constructed as recommended will likely settle less than
1 inch under static conditions. Concrete slabs that are not supported on ground improved with aggregate
piers are susceptible to liquefaction induced settlement. We recommend that concrete slabs be jointed
around columns to allow the individual structural elements to settle differentially.
Below-Slab Drainage
Groundwater could accumulate below the proposed building floor slabs since the building will be cut into
soils where groundwater exists. To help mitigate potential build-up of groundwater below the slabs, we
recommend that the concrete slabs-on-grade be provided with under drainage to collect and discharge
potential groundwater from below the slabs. This can be accomplished by installing a 4-inch-diameter,
4111 heavy-wall perforated collector pipe in a shallow trench placed below the capillary break gravel layer.
Perforated pipe should have two rows of 1/2-inch holes spaced 120 degrees apart and at 4 inches on center.
The trench should measure about 1-foot-wide by 1.5-feet-deep and should be backfilled with clean 3/8-inch
pea gravel or an alternative approved by GeoEngineers. The drainage material should be wrapped with a
nonwoven geotextile filter fabric,such as Mirafi 14ON. For design,the perforated drainage pipes should be
centered longitudinally below the building and can be connected to the perimeter footing drain pipe.
If connected to the footing drain system,the invert of the underdrain pipe should be higher than the invert
of the footing drain pipe where they connect.
The collector pipe should be sloped to drain and discharge into the stormwater collection system to convey
the water off site.The pipe should also incorporate cleanouts, if possible.The cleanouts could be extended
through the foundation walls to be accessible from the outside or could be placed in flush-mounted access
boxes cast into the floor slabs.The civil engineer should develop a conceptual foundation drainage plan for
GeoEngineers to review.
If no special waterproofing measures are taken, leaks and/or seepage may occur in localized areas of the
below-grade portion of the building, even if the recommended wall drainage and below-slab drainage
provisions are constructed. If leaks or seepage is undesirable, below-grade waterproofing should be
specified. A vapor barrier should be used below slab-on-grade floors located in occupied portions of the
buildings, such as retail space or equipment/storage space. Specification of the vapor barrier requires
consideration of the performance expectations of the occupied space, the type of flooring planned and
other factors and is typically completed by other members of the project team.
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BELOW-GRADE WALLS •
Permanent Subsurface Walls
Permanent below-grade walls constructed adjacent to temporary soil nail walls should be designed for the
same earth pressures (including surcharge pressures, were applicable, as the adjacent temporary wall).
Permanent below-grade walls constructed adjacent to temporary soil nail walls should be designed for the
earth pressures shown in Figure 3, Soldier Pile Wall with Multiple Levels of Tiebacks. Permanent below-
grade walls should also include a seismic load acting over the height of the wall equal to 7H psf, where H
is the height of the wall in feet. Other surcharge loads, such as from foundations, construction equipment
or construction staging areas,should be considered on a case-by-case basis, as shown in Figure 4.We can
provide the lateral pressures from these surcharge loads as needed.
The soil pressures recommended above assume that wall drains will be installed to prevent the buildup of
hydrostatic pressure behind the walls,as described below in the "Excavation Support"section of this report
and tied to permanent drains to remove water to suitable discharge points.
Other Cast-in-Place Walls
Lateral earth pressures for design of below-grade walls and retaining structures which are not adjacent to
temporary shoring walls should be evaluated using an equivalent fluid density of 35 pcf provided that the
walls will not be restrained against rotation when backfill is placed. If the walls will be restrained from
rotation, we recommend using an equivalent fluid density of 55 pcf. Walls are assumed to be restrained if
top movement during backfilling is less than H/1000,where H is the wall height.These lateral soil pressures
assume that the ground surface behind the wall is horizontal. If the ground surface within 5 feet of the wall 1111
rises at an inclination of 2H:1V (horizontal to vertical) or steeper, the walls should be designed for lateral
pressures based on equivalent fluid densities of 50 and 80 pcf, respectively, for unrestrained and
restrained conditions. These lateral soil pressures do not include the effects of surcharges such as floor
loads, traffic loads or other surface loading. Surcharge effects should be included as appropriate. Below-
grade walls for buildings should also include seismic earth pressures. Seismic earth pressures should be
determined using a rectangular distribution of 7H in psf, where H is the wall height.
If vehicles can approach the tops of exterior walls to within half the height of the wall, a traffic surcharge
should be added to the wall pressure. For car parking areas,the traffic surcharge can be approximated by
the equivalent weight of an additional 1 foot of soil backfill (125 psf) behind the wall. For delivery truck
parking areas and access driveway areas, the traffic surcharge can be approximated by the equivalent
weight of an additional 2 feet (250 psf) of soil backfill behind the wall. Other surcharge loads, such as
from foundations, construction equipment or construction staging areas, should be considered on a
case-by-case basis, as shown in Figure 4. Positive drainage should be provided behind below-grade walls
and retaining structures as discussed in "Drainage Considerations"section of this report.
These recommendations are based on the assumption that all retaining walls will be provided with
adequate drainage. The values for soil bearing, frictional resistance and passive resistance presented
above for foundation design are applicable to retaining wall design. Walls located in level ground areas
should be founded at a depth of 18 inches below the adjacent grade.
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GEOENGINEERS .10.e 11.2018 Page 8
�Eti�_zsasyoa:-oo
• Wall Drainage
Drainage behind the permanent below-grade walls constructed adjacent to temporary shoring walls is
recommended to consist of a combination of drainage material located behind the facing of the temporary
soil nail shoring walls(where present)and drainage placed between the temporary shoring wall (soldier pile
or soil nail)and the permanent below grade wall.The drainage material should be connected to weep pipes
that extend through the permanent below grade building walls at the footing elevation. The weep pipes
through the permanent below grade wall should be spaced no more than 12 feet on center and should be
hydraulically connected to the sump. These weep pipes may be designed for a hard connection to the
perimeter drains discussed above in the "Below-Slab Drainage"section of this report.
Prefabricated geocomposite drainage material, such as Mirafi G100TM, Miradrain® 6000 or approved
equivalent, should be used where drainage material is required either as strips behind the temporary
shoring wall, or as full coverage drainage panels located between the temporary shoring wall and the
permanent below grade walls. The drainage material should be installed on the excavation side of the
temporary shoring wall with the fabric adjacent to the temporary shoring wall. The weep pipes constructed
near the base of each strip of drainage material placed behind temporary soil nail walls should be
hydraulically connected to the drainage material placed between the temporary and permanent below
grade walls.
In areas where temporary cut slopes are used,and conventional cast-in-place techniques are used to build
the below grade walls, a conventional footing drain should be located on the outside of the building. The
footing drain should be constructed consistent to drains recommended for cast-in-place walls, below.
Positive drainage should be provided behind cast-in-place retaining walls by using free draining wall
drainage material with perforated pipes to discharge the collected water.The zone of wall drainage material
should be 2 feet wide and should extend from the base of the wall to within 2 feet of the ground surface.
The wall drainage material should be covered with 2 feet of less permeable material, such as the on-site
silt that is properly moisture conditioned and compacted.A geotextile separator should be placed between
the wall drainage material and overlying cover soil.
A 4-inch-diameter perforated drain pipe should be installed within the free-draining material at the base of
each wall. We recommend using either heavy-wall solid pipe(SDR-35 PVC)or rigid corrugated polyethylene
pipe (ADS N-12 or equal). We recommend against using flexible tubing for the wall drain pipe. The footing
drain recommended above in the "Footing Drains" section can be incorporated into the bottom of the
drainage zone and used for this purpose.
The pipes should be laid with minimum slopes of one-quarter percent and discharge into the stormwater
collection system to convey the water off site. The pipe installations should include a cleanout riser with
cover located at the upper end of each pipe run. The cleanouts could be placed in flush-mounted access
boxes. Collected downspout water should be routed to appropriate discharge points in separate pipe
systems.
Waterproofing
The recommendations in this section are provided to reduce the potential for buildup of hydrostatic
• pressures behind below grade walls and hydrostatic uplift forces below building slabs. If no special
waterproofing measures are taken, leaks or seepage may occur in localized areas of the below-grade
GEOENGINEERS June 11.2018 Page 9
File No.23459-001-00
portion of the building, even if the recommended wall drainage and below-slab drainage provisions are
111 constructed. If leaks or seepage is undesirable, below-grade waterproofing should be specified.
A waterproofing consultant should be contracted to provide recommendations for below-grade
waterproofing for this project.
EXCAVATION SUPPORT
We understand that excavations may range from 7 to 17 feet below site grades.The subsurface conditions
support use of temporary cut slopes and soil nail walls for temporary excavation support.Soil nails will likely
need additional measures,such as vertical elements,to control face stability.
The following sections provide geotechnical design and construction recommendations for soil nail walls.
The soil nail wall design should take into account the soft silt soils. It will likely be necessary to implement
vertical elements in the upper portion of the soil nail wall in areas where fill or soft soils are present.
Additionally, vertical elements can be used to control deflections of the shoring system provided that they
extend full depth. Full depth vertical elements (extending at least 5 feet below the planned bottom of
excavation elevation)should be considered where heavy construction surcharges are anticipated, or where
deflection tolerances are lower to protect adjacent improvements. The need for vertical elements or other
measures should be evaluated by the shoring designer during design of the shoring system.
Because soil nails will extend into private property, easements will be required.
The following sections provide design information for temporary cut slopes and soil nail walls. •
Excavation Considerations
Based on the material encountered in our subsurface explorations, it is our opinion that conventional
earthmoving equipment in proper working condition should be capable of making necessary general
excavations.
The earthwork contractor should be responsible for reviewing this report, including the boring logs,
providing their own assessments,and providing equipment and methods needed to excavate the site soils
while protecting subgrades.
Temporary Cut Slopes
For planning purposes,temporary unsupported cut slopes more than 4 feet high may be inclined at 1H:1V
maximum steepness within the medium stiff or stiffer silt soils. Temporary cuts within the fill and soft to
very soft silt soils may be cut at a maximum inclination of 11/2H:1V. If significant seepage is present on the
cut face then the cut slopes may have to be flattened. However, temporary cuts should be discussed with
the geotechnical engineer during final design development to evaluate suitable cut slope inclinations for
the various portions of the excavation.
The above guidelines assume that surface loads such as traffic, construction equipment, stockpiles or
building supplies will be kept away from the top of the cut slopes a sufficient distance so that the stability
of the excavation is not affected. We recommend that this distance be at least 5 feet from the top of the •
GEOENGINEERS� June 11.2018 Page 10
Pile No.23459-001-00
cut for temporary cuts made at 1H:1V or flatter and less than 10 feet high, and no closer than a distance
IIIequal to one half the height of the slope for cuts more than 10 feet high.
Temporary cut slopes should be planned such that they do not encroach on a 1H:1V influence line projected
down from the edges of nearby or planned foundation elements. New footings planned at or near existing
grades and in temporary cut slope areas for the lower level should extend through wall backfill and be
embedded in native soils.
Water that enters the excavations must be collected and routed away from prepared subgrade areas. We
expect that this may be accomplished by installing a system of drainage ditches and sumps along the toe
of the cut slopes. Some sloughing and raveling of the cut slopes should be expected. If excessive
groundwater is observed while making cuts, then alternative groundwater control systems will be
necessary,such as well points or wells.Temporary covering,such as heavy plastic sheeting with appropriate
ballast, should be used to protect these slopes during periods of wet weather. Surface water runoff from
above cut slopes should be prevented from flowing over the slope face by using berms, drainage ditches,
swales or other appropriate methods.
If temporary cut slopes experience excessive sloughing or raveling during construction, it may become
necessary to modify the cut slopes to maintain safe working conditions. Slopes experiencing problems can
be flattened, regraded to add intermediate slope benches, or additional dewatering can be provided if the
poor slope performance is related to groundwater seepage.
Soil Nail Walls
• The soil nail wall system consists of drilling and grouting rows of steel bars or"nails" behind the excavation
face as it is excavated and then covering the face with reinforced shotcrete. The placement of soil nails
reinforces the soils located behind the excavation face and increases the soil's ability to inhibit a mass of
soil from sliding into the excavation. It may be necessary to utilize vertical elements, post-tensioned nails
and/or temporary cut slopes in areas where looser soils are present and/or where wall deflections must be
limited to protect existing improvements.
Soil nail walls are typically constructed using the following sequence:
1. Install vertical elements (where necessary) into vertical drilled holes and grout each hole with lean
concrete.
2. Excavate the soil at the wall face to between 1 and 3 feet below the row of soil nails to be installed.
Depending upon the soil conditions at the wall face, the excavation may be completed with a vertical
cut or with berms(native or fill).
3. Drill, install and grout soil nails.
4. Excavate berm, if present, located within about 3 feet below the elevation of the soil nail.
5. Place drainage strips,steel wire mesh and/or reinforcing bars in front of the excavated soil.
6. Install shotcrete and place steel plates and nuts over the soil nails.
7. Complete nail pullout capacity testing on approximately one out of every 20 nails in an installed row.
8. Repeat steps two through seven for each row of nails located below the completed row.
GEOENGINEERS� June 11,2018 Page 11
He Na 23459-00100
Vertical elements may be used to improve face stability of the site soils or to act as a cantilever wall to meet •
nail clearance requirements where buried utilities are present.Vertical elements typically consist of vertical
steel beams placed in drilled holes located along the wall alignment and backfilled with lean concrete.
Soil nails typically consist of #6 to #12 threaded steel bars (3/4- to 1/-inch-diameter). The steel bars
are placed in 4- to 8-inch-diameter holes drilled at angles typically ranging from 10 to 25 degrees
below horizontal. Centralizers are used to center the steel bars in the holes. Once the steel bars are
installed,the holes are grouted using cement grout or concrete.
The soils typically are required to have an adequate standup time (to allow placement of the steel wire
mesh and/or reinforcing bars to be installed and the shotcrete to be placed).Soils that have short standup
times are problematic for soil nailing and may require the use of vertical elements.
Preliminary Design Recommendations
Soil nail wall design should be completed by the specialty contractor. We recommend the following for
preliminary design and cost estimating purposes:
■ Vertical elements (where necessary) installed at approximately 6 feet on center.
■ A soil nail grid pattern of about 6 feet by 6 feet.
■ A soil nail length ranging up to the wall height (but not less than 10 feet), inclined at about 15 to
20 degrees from the horizontal.
■ A preliminary allowable load transfer of 1.0 kips/foot for fill and soft silt, and 1.5 kips per foot for •
medium stiff silt soils for 6-to 8-inch-diameter grouted nails.
■ Strips of drainage material installed behind the shotcrete to relieve hydrostatic pressures. Additional
drainage provisions may be necessary if significant groundwater is encountered during the excavation.
Soft silt may affect the soil nail design. Typically,the soil nail spacing is tighter or the soil nails are longer,
or both, where low strength soils are present.
Difficulties associated with face stability and standup time may be experienced during construction in the
site soils. Soft silt soils and soils in areas with groundwater seepage may exhibit shorter standup times.
Spalling and raveling of the cut face may occur at these locations during soil nail wall installation.
Construction techniques used to mitigate spalling and raveling include:
■ Flash coating the cut face with 2 to 4 inches of shotcrete immediately after the cut face is excavated
to final line and the drainage material is installed.This typically provides enough standup time to allow
for the installation of the reinforcing steel and final shotcrete.
■ Excavating in half-height(2-to 3-foot) lifts, rather than full-height(6-foot) lifts.
■ Excavating leaving a 1H:1V earth berm in front of the wall.The soil nails are installed by drilling through
the soil berm. The soil berm is then removed to allow for installation of the drainage material and
reinforcing steel and shotcrete.
s Shortening the length of wall drilled and shotcreted using a staggered excavation approach.
■ Installing closely spaced vertical soil nails or small steel beams (vertical elements) along the wall •
alignment.
GEOENGINEERS june 11.2018 Page 12
Contractors experienced in the soil nailing method should be able to mitigate significant spalling and
raveling conditions.Contractors should also be prepared to use techniques to address problems that occur
because of caving soils.The contractor should be made responsible for the safety of the shoring system.
Soil Nail Wall Performance
A soil nail wall is a passive shoring system that requires deflections for load to be applied to the soil nails.
We recommend that the soil nail be designed such that average wall deflections are limited to 1 inch and
ground surface settlements behind the wall are less than about 1 inch. Where existing structures are
located within 10 feet of the shoring wall, the soil nail wall should be designed to limit deflections to less
than 1/2 inch. The deflections and settlements are usually highest at the excavation face and decrease to
negligible amounts beyond a distance behind the wall equal to the excavation height. Wall deflections can
be reduced by post-tensioning the upper row(s) of soil nails. Localized deflections may exceed the above
estimates and may reflect local variations in soil conditions (such as around abandoned side sewers) or
may be the result of the workmanship used to construct the wall.
Monitoring of the shoring system should be completed as described in Appendix B, Ground Anchor Load
Tests and Shoring Monitoring Program.
Drainage
A suitable drainage system should be installed to prevent the buildup of hydrostatic groundwater pressures
behind the soil nail walls. Drainage behind soil nail walls typically consists of prefabricated geocomposite
drainage strips, such as Mirafi G100TM, installed vertically between the soil nails. The drainage strips are
typically a minimum of 16 inches wide and extend the entire height of the wall. Horizontal drainage strips
may also be used in areas where perched groundwater is observed or for other reasons. We recommend
that drainage strips be connected to a tightline pipe installed along the base of the wall and routed to a
suitable discharge point as described above in the "Below-Grade Walls"section of this report.
EARTHWORK
The on-site soils contain a high percentage of fines(material passing the U.S.standard No. 200 sieve)that
are extremely moisture-sensitive and susceptible to disturbance, especially when wet. Ideally, earthwork
should be undertaken during extended periods of dry weather when the surficial soils will be less
susceptible to disturbance and provide better support for construction equipment. Dry weather
construction will help reduce earthwork costs. If earthwork will occur from October through May,we suggest
that a contingency be included in the project schedule and budget to account for increased earthwork
difficulties.
Trafficability is not expected to be difficult during dry weather conditions and if groundwater is controlled in
excavations. However, the native soils will be susceptible to disturbance from construction equipment
during wet weather conditions or if groundwater seepage is not controlled adequately. Even in the summer
months pumping and rutting of the exposed native soils under equipment loads will occur.
Clearing and Site Preparation
411 Areas to receive fill, structures or pavements should be cleared of vegetation and stripped of topsoil.
Clearing should consist of removal of all debris, trees, brush and other vegetation within the designated
GEOENGINEERS June 11.2018 Page 13
File No.23459-001 00
clearing limits. The topsoil materials could be separated and stockpiled for use in areas to be landscaped. •
Debris should be removed from the site, but organic materials could be chipped/composted and also
reused in landscape areas, if desired.
We anticipate that the depth of stripping will range from 2 to 8 inches across the site.Stripping depths may
be greater in some areas, particularly where trees and large vegetation have been removed.Actual stripping
depths should be determined based on field observations at the time of construction.The organic soils can
be stockpiled and used later for landscaping purposes or may be spread over disturbed areas following
completion of grading. If spread out,the organic strippings should be placed in a layer less than 1-foot-thick,
should not be placed on slopes greater than 3H:1V and should be track-rolled to a uniformly compacted
condition. Materials that cannot be used for landscaping or protection of disturbed areas should be
removed from the project site.
Grubbing should consist of removing and disposal of stumps, roots larger than 1-inch-diameter and matted
roots.Grubbed materials should be completely removed from the project site.All depressions made during
the grubbing activities to remove stumps and other materials should be completely backfilled with properly
placed and compacted structural fill.
Subgrade Preparation
Upon completion of site preparation activities, the exposed subgrade should be proof-rolled with a fully
loaded dump truck or similar heavy rubber-tired construction equipment to identify soft, loose or unsuitable
areas. Proof-rolling should be conducted prior to placing fill and should be observed by a representative of
GeoEngineers who will evaluate the suitability of the subgrade and identify areas of yielding that are
indicative of soft or loose soil. If soft or loose zones are identified during proof-rolling, these areas should
be excavated to the extent indicated by our representative and replaced with Imported Select Structural Fill
as defined in this report.
During wet weather, or when the exposed subgrade is wet or unsuitable for proof-rolling, the prepared
subgrade should be evaluated by observing excavation activity and probing with a steel foundation probe.
Observations, probing and compaction testing should be performed by a member of our staff.Wet soil that
has been disturbed due to site preparation activities or soft or loose zones identified during probing,should
be removed and replaced with Imported Select Structural Fill as defined in this report.
Subgrade Protection
Site soils contain significant fines content (silt and clay) and will be highly sensitive and susceptible to
moisture and equipment loads. The exposed subgrade soils can deteriorate rapidly in wet weather and
under equipment loads.
The contractor should take necessary measures to prevent site subgrade soils from becoming disturbed or
unstable. Construction traffic during the wet season should be restricted to specific areas of the site,
preferably areas where a working pad has been constructed.
Protecting the existing soils with a thin layer of crushed rock will not be adequate during the wet season
and the subgrade will still deteriorate under equipment loads. If wet weather construction is planned,
consideration should be given to protecting the exposed subgrade areas with a thick section of crushed •
rock underlain by a geotextile separator.
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File No.23459-001-00
Structural Fill and Backfill
General
Materials used to support building foundations, floor slabs, hardscape, pavements and any other areas
intended to support structures or within the influence zone of structures are classified as structural fill for
the purposes of this report.
All structural fill soils should be free of debris, clay balls, roots, organic matter, frozen soil, man-made
contaminants, particles with greatest dimension exceeding 4 inches and other deleterious materials. The
suitability of soil for use as structural fill will depend on the gradation and moisture content of the soil. As
the amount of fines in the soil matrix increases, the soil becomes increasingly more sensitive to small
changes in moisture content and achieving the required degree of compaction becomes more difficult or
impossible. Recommendations for suitable fill material are provided in the following sections.
Use of On-site Soil
As described in the "Subsurface Conditions" section, the on-site surface soil consists of silt. On-site soils
can be used as structural fill, provided the material meets the above requirements, although due to
moisture sensitivity, this material will likely be unsuitable as structural fill during most of the year. If the
soil is too wet to achieve satisfactory compaction, moisture conditioning by drying back the material will be
required. If the material cannot be properly moisture conditioned,we recommend using imported material
for structural fill.
• An experienced geotechnical engineer from GeoEngineers should determine the suitability of on-site soil
encountered during earthwork activities for reuse as structural fill.
Imported Select Structural Fill
Select imported granular material may be used as structural fill. The imported material should consist of
pit or quarry run rock, crushed rock or crushed gravel and sand that is fairly well-graded between coarse
and fine sizes (approximately 25 to 65 percent passing the U.S. No. 4 sieve). It should have less than
5 percent passing the U.S. No. 200 sieve. During dry weather, the fines content can be increased to a
maximum of 12 percent.
Aggregate Base
Aggregate base material located under floor slabs and pavements, and crushed rock used in footing
overexcavations should consist of imported clean,durable, crushed angular rock.Such rock should be well-
graded, have a maximum particle size of 1 inch and have less than 5 percent passing the U.S. No. 200
sieve (3 percent for retaining walls). In addition, aggregate base shall have a minimum of 75 percent
fractured particles according to American Association of State Highway and Transportation Officials
(AASHTO)TP-61 and a sand equivalent of not less than 30 percent based on AASHTO T-176.
Retaining Wall Backfill
Fill placed to provide a drainage zone behind retaining walls should meet the general requirements above
and consist of free-draining sand and gravel or crushed rock with a maximum particle size of 3/4 inch and
• less than 3 percent passing the U.S. No. 200 sieve.
GEOENGINEERs June 11,2018 Page 15
He No.23459-001-00
Trench Backfill •
Backfill for pipe bedding and in the pipe zone should consist of well-graded granular material with a
maximum particle size of 3/4 inch and less than 5 percent passing the U.S. No. 200 sieve. The material
should be free of organic matter and other deleterious materials. Further,the backfill should meet the pipe
manufacturer's recommendations. Above the pipe zone, Imported Select Structural Fill may be used as
described above.
Fill Placement and Compaction
Structural fill should be compacted at moisture contents that are within 2 percent of the optimum moisture
content as determined by ASTM International (ASTM) Standard Practices Test Method D 1557 (Modified
Proctor).The optimum moisture content varies with gradation and should be evaluated during construction.
Fill material that is not near the optimum moisture content should be moisture conditioned prior to
compaction.
Fill and backfill material should be placed in uniform, horizontal lifts and compacted with appropriate
equipment. The appropriate lift thickness will vary depending on the material and compaction equipment
used. Fill material should be compacted in accordance with Table 2, below. It is the contractor's
responsibility to select appropriate compaction equipment and place the material in lifts that are thin
enough to meet these criteria. However, in no case should the loose lift thickness exceed 18 inches.
TABLE 2.COMPACTION CRITERIA
Compaction Requirements •
Fill Type Percent Maximum Dry Density Determined by
ASTM Test Method D 1557 at±3%of Optimum Moisture
0 to 2 Feet Below Subgrade >2 Feet Below Subgrade Pipe Zone
Fine-grained soils(non- 95 92
expansive)
Imported Granular, maximum 95 95
particle size < 11/4 inch
Imported Granular, maximum
particle size 11/4 inch to 4 inches
n/a(proof-roll) n/a (proof-roll)
(3-inch maximum under building
footprints)
Retaining Wall Backfill* 92 92
Nonstructural Zones 90 90 90
Trench Backfill 95 90 90
Note:
*Measures should be taken to prevent overcompaction of the backfill behind retaining walls. We recommend placing the zone of
backfill located within 5 feet of the wall in lifts not exceeding about 6 inches in loose thickness and compacting this zone with hand-
operated equipment such as a vibrating plate compactor and a jumping jack.
A representative from GeoEngineers should evaluate compaction of each lift of fill. Compaction should be
evaluated by compaction testing, unless other methods are proposed for oversized materials and are
approved by GeoEngineers prior to fill placement. These other methods typically involve procedural •
placement and compaction specifications together with verifying requirements such as proof-rolling.
GEOENGINEERS June 11.2018 Page 16
File No.23459-001-00
Permanent Cut and Fill Slopes
IPWe recommend that permanent slopes be constructed at inclinations of 2H:1V or flatter. Fill slopes should
be blended into existing slopes with smooth transitions. To achieve uniform compaction, we recommend
that fill slopes be overbuilt slightly and subsequently cut back to expose well compacted fill.
To reduce erosion, newly constructed slopes should be planted or hydroseeded shortly after completion of
grading. Until the vegetation is established,some sloughing and raveling of the slopes should be expected.
This may necessitate localized repairs and reseeding. Temporary covering, such as clear heavy plastic
sheeting, jute fabric or erosion control blankets (such as American Excelsior Curlex 1 or North American
Green SC150) could be used to protect the slopes during periods of rainfall.
If seepage is encountered at the face of permanent or temporary slopes, it will be necessary to flatten the
slopes or install a subdrain to collect the water. We should be contacted to evaluate such conditions on a
case-by-case basis.
TEMPORARY CONSTRUCTION DEWATERING
Groundwater levels observed at the time of drilling indicates that groundwater will likely be encountered
during construction.The contractor should plan for groundwater control consisting of sumps and pumps to
complete the excavations. Surface water from rainfall will likely contribute significantly to the volume of
water that needs to be removed from the excavation during construction and will vary as a function of
season and precipitation. If significant groundwater seepage is observed during site excavations a more
411 robust dewater system may be needed such as well points or deep wells. It may be beneficial to have the
contractor excavate a test trench in the center of the site to observe groundwater flow conditions and
excavation stand-up time prior to commencing the mass excavation.
The temporary dewatering system should be designed to maintain the groundwater level at least 3 feet
below the foundation subgrade elevation until such time that the engineer determines that the permanent
underslab drainage system is completely constructed, all foundations and underground utilities are
installed and the permanent underslab drainage system is functioning properly.
In our opinion,the contractor should be responsible for designing and installing the appropriate dewatering
system needed to complete the work.Appropriate discharge points should be designated by the contractor.
Also, the contractor will need to obtain the necessary discharge permits from the regulatory agencies. We
recommend the details of the dewatering system be reviewed by GeoEngineers prior to construction. This
will allow us to evaluate if the designs are consistent with the intent of our recommendations and to provide
supplemental recommendations in a timely manner.
Other dewatering issues that must be addressed include disposal of water and backup power.
We anticipate that water removed from excavations will be diverted into the existing storm sewer system.
A permit will be required to do this.Water sampling prior to and during dewatering may also be required as
a part of the permit.
The following sections discuss sump pumping. Recommendations for well points and deep wells are not
• included in this report but can be provided if needed.
GEOENGINEERS� June 11,2018 Page 17
He No.23459-00]-00
Sump Pumping
This dewatering method involves removing water that has seeped into an excavation by pumping from a 4111
sump that has been excavated at one or more locations in an excavation. Drainage ditches that lead to the
sump are typically excavated along the excavation sidewalls at the base of an excavation. The excavation
for the sump and discharge drainage ditches should be backfilled with gravel or crushed rock to reduce the
amount of erosion and associated sediment in the water pumped from the sump. In our experience, a
slotted casing or perforated 55-gallon drum that is installed in the sump backfill provides a suitable housing
for a submersible pump.Surface water from rainfall will likely contribute significantly to the volume of water
that needs to be removed from the excavation during construction and will vary as a function of season
and precipitation.
Surface Water Drainage Considerations
All paved and landscaped areas should be graded so that surface drainage is directed away from the
proposed buildings to appropriate catch basins.
Water collected in roof downspout lines must not be routed to the footing drain lines or subsurface drain
lines. Collected downspout water should be routed to appropriate discharge points in separate pipe
systems.
PAVEMENT RECOMMENDATIONS
General
Pavement subgrades should be prepared in accordance with the "Earthwork" section of this report. The
design of the recommended pavement sections is based on an assumed California Bearing Ratio of 3. Our
pavement design is based on an estimated traffic volume for this facility of 200 cars and up to 1 truck per
day.
Heavy construction traffic has not been considered in our pavement design;therefore,we assume that the
pavements will be constructed at the end of the project after heavy construction vehicles,such as concrete
trucks and construction material delivery trucks, will no longer access the site. Construction traffic should
not be allowed on new pavements. If this is not the case,we will have to re-design the pavements for those
heavier loading conditions.
Drainage
Long-term performance of pavements is influenced significantly by drainage conditions beneath the
pavement section. Positive drainage can be accomplished by crowning the subgrade with a minimum
2 percent cross slope and establishing grades to promote drainage.
Pavement Sections
Based on the estimated traffic data and our analyses, our recommended pavement sections are presented
in Table 3.
•
GEOENGINEERS� June 11,2018 Page 18
File No.23459-001.-00
TABLE 3. RECOMMENDED PAVEMENT SECTIONS
Minimum PCC Minimum Asphalt Minimum Aggregate Base
Thickness Thickness Thickness
(inches) (inches) (inches)
5 - 6
3.5 8
The aggregate base course should conform to the "Aggregate Base" section of this report and be
compacted to at least 95 percent of the maximum dry density determined in accordance with AASHTO
T-180/ASTM Test Method D 1557.
The asphalt concrete (AC) pavement should conform to Section 00745 of the most current edition of the
Oregon Department of Transportation (ODOT) Standard Specifications for Highway Construction. The Job
Mix Formula should meet the requirements for a /-inch Dense Graded Level 2 Mix. The AC binder should
be PG 64-22 grade meeting the ODOT Standard Specifications for Asphalt Materials. AC pavement should
be compacted to 91.0 percent of the Maximum Theoretical Unit Weight (Rice Gravity) as determined by
AASHTO T-209.
PCC pavement sections should be Class 4000 3/4-inch-minus with minimum 28-day flexural strength of
600 pounds per square inch (psi). Class 4000 indicates a design compressive strength of 4,000 psi.
• The recommended pavement sections assume that final improvements surrounding the pavement will be
designed and constructed such that stormwater, groundwater or excess irrigation water from landscape
areas does not infiltrate below the pavement section into the crushed base.
LIMITATIONS
We have prepared this report for the exclusive use of Trailblazer Development, LLC and their authorized
agents and/or regulatory agencies for the proposed storage facility located on SW Atlanta Street in Tigard,
Oregon.
This report is not intended for use by others,and the information contained herein is not applicable to other
sites. No other party may rely on the product of our services unless we agree in advance and in writing to
such reliance.
Within the limitations of scope,schedule, and budget, our services have been executed in accordance with
generally accepted practices in the area at the time this report was prepared. No warranty or other
conditions, express or implied, should be understood.
Please refer to Appendix C titled "Report Limitations and Guidelines for Use" for additional information
pertaining to use of this report.
•
GEOENGINEERS June 11.2018 Page 19
File No.23459-001-00
REFERENCES
International Code Council. 2015. 2015 International Building Code.
International Code Council. 2014. 2014 Oregon Structural Specialty Code.
Ishihara and Yoshimine. 1992. "Evaluation of Settlements in Sand Deposits Following Liquefaction During
Earthquakes,"Soils and Foundations, 32(1), pp. 173-188.
Madin, I.P. 1990. Earthquake Hazard Geology Maps of the Portland Metropolitan Area, Oregon: DOGAMI
Open File Report 0-90-2, 14 pages, 8 plates, 1:24,000 scale.
Occupational Safety and Health Administration (OSHA).Technical Manual Section V: Chapter 2,
Excavations: Hazard Recognition in Trenching and Shoring:
httb://www.osha.gov/dts/osta/otm/otm v/otm v 2.html.
Personius. 2002. Fault number 716, Canby-Molalla fault, in Quaternary fault and fold database of the
United States: U.S. Geological Survey website, httb://earthauakes.usgs.gov/hazards/afaults,
Accessed 6/7/2018.
Tokimatsu and Seed. 1987. "Evaluation of Settlements in Sands Due to Earthquake Shaking,"Journal of
Geotechnical Engineering,ASCE, 113 (GT8), pp. 861-878.
Youd, et al. 2001. "Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998
NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of Soils,"Journal of Geotechnical111
and Geoenvironmental Engineering,ASCE, October 2001, pp. 817-833.
•
GEOENGINEERS1 June 11,2018 Page 20
File No.23459-001-00
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•
APPENDIX A
Field Explorations and Laboratory Testing
•
•
• APPENDIX A
FIELD EXPLORATIONS AND LABORATORY TESTING
Field Explorations
Soil and groundwater conditions at the site were explored on May 27, 2018 by completing two borings at
the approximate locations shown in the Site Plan, Figure 2. The borings were advanced using a trailer-
mounted drill rig owned and operated by Dan Fischer Excavating.
The drilling was continuously monitored by an engineering geologist from our office who maintained
detailed logs of subsurface explorations, visually classified the soil encountered and obtained
representative soil samples from the borings. Representative soil samples were obtained from each boring
at approximate 21/2-to 5-foot-depth intervals using either:(1)a 1-inch, inside-diameter,standard split spoon
sampler;or(2)a 2.4-inch, inside-diameter,split-barrel ring sampler(Dames& Moore [D&M]).The samplers
were driven into the soil using a 140-pound hammer, free-falling 30 inches on each blow. The number of
blows required to drive the sampler each of three, 6-inch increments of penetration were recorded in the
field.The sum of the blow counts for the last two, 6-inch increments of penetration is reported on the boring
logs as the ASTM D 1556 Standard Penetration Test(SPT) N-value. The N-value for D&M samples has been
reduced by approximately 50 percent from the field readings to roughly correlate with the SPT N-values.
Recovered soil samples were visually classified in the field in general accordance with ASTM D 2488 and
the classification chart listed in Key to Exploration Logs, Figure A-1. Logs of the borings are presented in
Figures A-2 and A-3. The logs are based on interpretation of the field and laboratory data and indicate the
depth at which subsurface materials or their characteristics change,although these changes might actually
• be gradual.
Laboratory Testing
Soil samples obtained from the explorations were visually classified in the field and in our laboratory using
the USCS and ASTM classification methods. ASTM Test Method D 2488 was used to visually classify the
soil samples, while ASTM D 2487 was used to classify the soils based on laboratory tests results. Moisture
content tests were performed on selected samples in general accordance with ASTM D 2216, moisture-
density tests in general accordance with ASTM D 7263 and fines content tests in general accordance with
ASTM D 1140. Two Atterberg limits test were performed in accordance with ASTM D 4318. Results of the
laboratory testing are presented in the appropriate exploration logs at the respective sample depths and
the Atterberg limits results in Figure A-4 in this appendix.
•
GEOENGINEERSi June 11,2018 Page A-1
Pile No.23459-001-00
SOIL CLASSIFICATION CHART ADDITIONAL MATERIAL SYMBOLS
MAJOR DIVISIONS SYMBOLS TYPICAL SYMBOLS TYPICAL
GRAPH LETTER DESCRIPTIONS GRAPH LETTER DESCRIPTIONS
o� U <
III CLEAN GRAVELS .30 GW WELL-GRADED GRAVELS,GRAVEL-
GRAVEL �� SAND MIXTURES AC Asphalt Concrete
AND
GRAVELLY (LITTLE OR NO Ewes) o 0 0 0 o c POORLY-GRADED GRAVELS, A V A
SOILS O o o GP GRAVEL-SAND MIXTURES /\/A j/A CC Cement Concrete
o /�/y//�
COARSE c i• GM SILTY GRAVELS,GRAVEL-SAND-
GRAVELS WITH m SIL7 MIXTURES
GRAINED MORE THAN Wu FINES X11 ,'. CR Crushed Rock/
SOILS OF COARSE •FRACTION RETAINED , • Quarry Spalls
ON NO.4 SIEVE (APPRECIABLE AMOUNT CAEYIGAS,GRAVEL-SAND-
• • •
OF FINES) o/oGC J I, J I, J
, 0 I, 0 I, SOD Sod/Forest Duff
SW WELL-GRADED SANDS,GRAVELLY
CLEAN SANDS SANDS
MORE THAN 50% SAND °
RETAINED ON AND (LITTLE ORNO FINES) a TS Topsoil
NO.200 SIEVE SANDY SP POORLY-GRADED SANDS,GRAVELLY
SAND ...
SOILS
MORE THAN 50% SANDS WITH SM SILTY SANDS,SAND-SILT MIXTURES
OF COARSE FINES I. Groundwater Contact
FRACTION PASSING
ON NO.4 SIEVE
(APPRECIABLE AMOUNT S`. CAYETUYRES SANDS,SAND-CLAY . Measured groundwater level in exploration,
OF FINES
—
well,or piezometer
INORGANIC SILTS,ROCK FLOUR,
I ML CLAYEY SILTS WITH SLIGHT —
PLASTICITY C Measured free product in well or piezometer
INORGANIC CLAYS OF LOW TO
SILTS AND LIQUID LIMIT CL CLAYS, PLASTICAYS,SIAVELLY Graphic Log Contact
FINE CLAYS LESS THAN 50 LEAN CLAYS Y CLAYS,SILTY CLAYS,
GRAINED
SOILS ORGANIC SILTS AND ORGANIC SILTY Distinct contact between soil strata
j OL CLAYS OF LOW PLASTICITY
/ Approximate contact between soil strata
MORE THAN 50% INORGANIC SILTS,MICACEOUS OR
PASSING MH DIATOMACEOUS SILTY SOILS
NO.200 SIEVE Material Description Contact
SILTS AND LIQUID LIMIT GREATERINORGANIC CLAYS OF HIGH
CLAYS THAN 50 CH PLASTICITY Contact between geologic units
____ Contact between soil of the same geologic
i OH MEDIIUM TO HIGH PLLASTICITYF unit
III
HIGHLY ORGANIC SOILS `N`""J` PT PEAT,HUMUS,SWAMP SOILS WITH
HIGH ORGANIC CONTENTS Laboratory/ Field Tests
NOTE: Multiple symbols are used to indicate borderline or dual soil classifications %F Percent fines
%G Percent gravel
Sampler Symbol Descriptions AL Atterberg limits
CA Chemical analysis
2.4-inch I.D.split barrel CP Laboratory compaction test
CS Consolidation test
X Standard Penetration Test(SPT) DD Dry density
II Shelby
Direct shear
Shelby tube HA Hydrometer analysis
Piston MC Moisture content
MD Moisture content and dry density
II
Direct Push Mohs Mohs hardness scale
OC Organic content
Bulk or grab PM Permeability or hydraulic conductivity
PI Plasticity index
Continuous Coring PP Pocket penetrometer
SA Sieve analysis
TBlowcount is recorded for driven samplers as the number of u UnconfinedTricol compressioncompression
blows required to advance sampler 12 inches(or distance noted). VS Vane
See exploration log for hammer weight and drop. VS shear
Sheen Classification
"P"indicates sampler pushed using the weight of the drill rig.
NS No Visible Sheen
"WOH"indicates sampler pushed using the weight of the SS Slight Sheen
hammer. MS Moderate Sheen
HS Heavy Sheen
NOTE:The reader must refer to the discussion in the report text and the logs of explorations for a proper understanding of subsurface conditions.
Descriptions on the logs apply only at the specific exploration locations and at the time the explorations were made;they are not warranted to be
representative of subsurface conditions at other locations or times.
fa I 1
Key to Exploration Logs
GEOENGINEERS ( ` FigureA-1
Rev 06/2017
SSW
End Total 315 Logged By JLL Driller Dan Fischer DrillingDrilling Hollow-stem Au
Drilled 5/27/2018 5/27/2018 Depth(ft) Checked By GAL Auger
Surface Elevation(ft) 214 Hammer Rope&Cathead Drilling Paul Bunyan Trailer
Vertical Datum NAVD88 Data 140(lbs)/30(in)Drop Equipment
Latitude 45.437 System OR Decimal Degrees See"Remarks"section for groundwater observed
0 Longitude -122.7548 Datum WGS84(feet)
Notes: D&M N-value reduced 50%to approximate SPT N-value
FIELD DATA
E o MATERIAL
a2 Z J `° DESCRIPTION 47,
a o REMARKS
o as ;_� Q. o � 80 oc
W 0 O ce m U H o o5 2U LLU
0
ML Dark brown silt with trace sand,occasional gravel and
- - - fine roots to 8 inches,low to moderate plasticity -
(very soft,moist)(fill)
- /
�tio ML Brown silt with trace sand,low plasticity(very soft,
moist) -
- 5 v 2 0 1 -
o° -
- 10I I 12 9 2
- - MD;AL Becomes gray-brownand stiff,with occasional layers — 35 DD=87 pcf;AL(LL=30,PL=27,P1=3)
of sandy silt Groundwater observed at 10 feet during drilling
- o
o
ry - - Dark gray sandy silt,massive(stiff,wet) - 30
• ,I 15 —\ / 10 13 3 - _' X
o�_ _ 10 10 4 - 37 51 DD=84 pcf
MD;%F —
0 0p
_ti -
E'- 20 �, ML/SM — Interbedded dark gray fine sandy silt and silty fine — 35 69
o \/ 10 2 F sand with occasional dark brown fibrous organic
wi
/y\ - matter,rapid to very rapid dilatancy(soft to very -
5 loose,wet)
c?_ _ 6 7 f 31 80
N MD;%F •' _ DD-_
85pcf
o
ML Dark gray silt with fine sand,low plasticity to
S_
25 \/ 12 13 —
non-plastic(very rapid dilating(stiff,wet) 84
,9 /x\ %F
0
d
z
L,
w_,,,b
g
_X
26 $ - _ 28
2 MC
0
0;
0
0
0
0
m
9 Note:See Figure A-1 for explanation of symbols.
S Coordinates Data Source:Horizontal approximated based on USGS Topo.Vertical approximated based on USGS Topo.
0 ,r
m`"� Log of Boring GE! B-1
Project: SW Atlanta Street Storage Building
GEO E N G I N E E R S Project Location: Tigard,Oregon
Figure A-2
Project Number: 23459-001-00 Sheet 1 of 1 ,
auft
End Total 46.5 Logged By JLL Driller Dan Fischer DrillingDrilling Hollow stem Auger ,
Drilled 5/27/2018 5/27/2018 Depth(ft) Checked By GAL Method
Surface Elevation(ft) 206 Hammer Rope&Cathead Drilling Paul Bunyan Trailer
Vertical Datum NAVD88 Data 140(lbs)/30(in)Drop Equipment
Latitude 45A367 System OR Decimal Degrees See"Remarks"section for groundwater observed
.
Longitude -122.755 Datum WGS84(feet)
Notes: D&M N-value reduced 50%to approximate SPT N-value
• I
e v
FIELD DATA
SE s MATERIAL REMARKS
o o
° za, to J DESCRIPTION
> OCD a). N OU 3 E, N O N =�c „„c
co
W 0 c cr m U H 0 00 2 U E U
0
oh ML Dark brown silt with trace sand and rootlets to 10
- - - inches,low plasticity(soft,moist) -
5 —
00 X 16 9 1 Becomes mottled brown and light gray,stiff
Becomes wet Groundwater observed at 8 feet during drilling
- ,.'-**-:----
SM/ML Interbedded dark gray silty fine sand and sandy silt,
10 \ / 6 •2 — low plasticity to non-plastic,massive to horizontal — 38 61
—yoh X �F _ laminations(loose to medium stiff,wet)
\/ 14 8 3
ID SM — Dark graysiltyfine sand,massive,rapid dilatancy(very 15 ( ry — 29 26 pcf
3—ya° I I 8 4
MD;%F loose to loose,wet) DD=95
0
z
o- X 14 2 5 - Becomes very loose -
8,, ML Dark gray silt with fine sand,massive,low plasticity
w- 20 ¢ — (medium stiff,wet) — 32 94
_Ci�' I I 6 8
L'J %F
-
"- -
i,
Fl
- - - Dark gray silt to sandy silt,massive,low plasticity(stiff, -
,, moist)
,- 7 25 10 15
0
0
z
�0 30 \/ 10 17 $ Becomes very stiff
— 27 AL(LL=32,PL=25,PI=7)
0
0
LZ:'V
Z- 35— — —
Note:See Figure A-1 for explanation of symbols.
S Coordinates Data Source:Horizontal approximated based on USGS Topo.Vertical approximated based on USGS Topo.
0 a♦ i
Log of Boring GEI B-2
Project: SW Atlanta Street Storage Building
G EO E N G I N E E R 5 l Project Location: Tigard,Oregon Figure A-3
o o' Project Number: 23459-001-00 Sheet 1 of 2 ,
I V
FIELD DATA
C EMATERIAL
0 o REMARKS
DESCRIPTION
L j > C7
C L O.- 92 C
m �- ' 0]_p N N (6 O N C C •
W O U NC7 U �U iio
35 \ � 12 24 9
—ti
—
- - / CL Dark gray lean clay,massive,low to moderate
plasticity(very stiff,moist) -
co
X12 17 10 — —
—
ML/CL Dark gray and brown mottled silt to lean clay,low
plasticity(stiff,moist)
- 45 x
12 11 %
0�
•
„,
0
0
0
•
Log of Boring GEI B-2(continued)
Project: SW Atlanta Street Storage Building
G EO E N G I N E E R / Project Location: Tigard,Oregon Figure A-3
o _.fir Project Number: 23459-001-00 Sheet 2 of 2 ,
• •
PLASTICITY CHART
60
•
50
CH or OH
w 40
N 30 •
a J.*.` OH or MH
20
•
/CL or OL
•
10 -
CL-ML �. ML or OL
0
0 10 20 30 40 50 60 70 80 90 100
LIQUID LIMIT
Moisture Liquid Plasticity
Boring Depth Content Limit Index
Symbol Number (feet) (%) (%) (%) Soil Description
o • B-1 10 35 30 3 Dark brown silt(ML)
❑ B-2 30 27 32 7 Gray silt(ML) Atterberg Limits Test Results
SW Atlanta Street Storage Building
Tigard, Oregon
o Note:This report may not be reproduced,except in full,without written approval of GeoEngineers,Inc. Test results are applicable
only to the specific sample on which they were performed,and should not be interpreted as representative of any other
m samples obtained at other times,depths or locations,or generated by separate operations or processes. (E C E N G I N E E R S Figure A-4
The liquid limit and plasticity index were obtained in general accordance with ASTM D 4318.
N
•
APPENDIX B
Ground Anchor Load Tests and
Shoring Monitoring Program
•
• APPENDIX B
GROUND ANCHOR LOAD TESTS AND SHORING MONITORING PROGRAM
Ground Anchor Load Testing
The locations of the load tests shall be approved by the Engineer and shall be representative of the field
conditions. Load tests shall not be performed until the ground anchor grout and shotcrete wall facing,where
present, have attained at least 50 percent of the specified 28-day compressive strengths.
Where temporary casing of the unbonded length of test ground anchors is provided, the casing shall be
installed to prevent interaction between the bonded length of the ground anchor and the casing/testing
apparatus.
The testing equipment shall include two dial gauges accurate to 0.001 inch, a dial gauge support, a
calibrated jack and pressure gauge, a pump and the load test reaction frame. The dial gauge should be
aligned within 5 degrees of the longitudinal ground anchor axis and shall be independently supported from
the load frame/jack and the shoring wall. The hydraulic jack, pressure gauge and pump shall be used to
apply and measure the test loads.
The jack and pressure gauge shall be calibrated by an independent testing laboratory as a unit. The
pressure gauge shall be graduated in 100 pounds per square inch (psi) increments or less and shall have
a range not exceeding twice the anticipated maximum pressure during testing unless approved by the
Engineer. The ram travel of the jack shall be sufficient to enable the test to be performed without
repositioning the jack.
The jack shall be independently supported and centered over the ground anchor so that the ground anchor
does not carry the weight of the jack. The jack, bearing plates and stressing anchorage shall be aligned
with the ground anchor. The initial position of the jack shall be such that repositioning of the jack is not
necessary during the load test.
The reaction frame should be designed/sized such that excessive deflection of the test apparatus does not
occur and that the testing apparatus does not need to be repositioned during the load test. If the reaction
frame bears directly on the shoring wall facing, the reaction frame should be designed to not damage the
facing.
Verification Tests
Prior to production ground anchor installation,at least two ground anchors for each soil type shall be tested
to validate the design pullout value. All test ground anchors shall be installed by the same methods,
personnel, material and equipment as the production anchors. Changes in methods, personnel, material
or equipment may require additional verification testing as determined by the Engineer. At least two
successful verification tests shall be performed for each installation method and each soil type.The ground
anchors used for the verification tests may be used as production ground anchors if approved by the
Engineer.
The allowable ground anchor load should not exceed 80 percent of the steel ultimate strength.
•
GEOENGINEERS June 11.2018 Page B-1
File No.23459001-00
Ground anchor design test loads should be the design loads specified on the shoring drawings.Verification
IIItest tiebacks shall be incrementally loaded and unloaded in accordance with the following schedule:
Load Hold Time Load Hold Time
Alignment Load (AL) Until Stable 0.75DL Until Stable
0.25 Design Load (DL) Until Stable 1.0DL Until Stable
AL Until Stable 1.25DL Until Stable
0.25DL Until Stable 1.5DL 10 Minutes
0.5DL Until Stable AL Until Stable
AL Until Stable 0.25DL Until Stable
0.25DL Until Stable 0.5DL Until Stable
0.5DL Until Stable 0.75DL Until Stable
0.75DL Until Stable 1.0DL Until Stable
AL Until Stable 1.25DL Until Stable
0.25DL Until Stable 1.5DL Until Stable
0.5DL Until Stable 1.75DL Until Stable
0.75DL Until Stable AL Until Stable
1.0DL Until Stable 0.25DL Until Stable
AL Until Stable 0.5DL Until Stable
0.25DL Until Stable 0.75DL Until StableIII
0.5DL Until Stable 1.0DL Until Stable
0.75DL Until Stable 1.25DL Until Stable
1.0DL Until Stable 1.5DL Until Stable
1.25DL Until Stable 1.75DL Until Stable
AL Until Stable 2.0DL 10 Minutes
0.25DL Until Stable AL Until Stable
0.5DL Until Stable
The alignment load shall be the minimum load required to align the testing apparatus and should not
exceed 5 percent of the design load.The dial gauge should be zeroed after the alignment load is applied.
Proof Tests
The allowable ground anchor load should not exceed 80 percent of the steel ultimate strength.
III
GEOENGINEERS June 11 2018 Page B-2
Fue[4:2.,,.:+-OD7-0G
• Ground anchor design test loads should be the design loads specified on the shoring drawings. Proof test
tiebacks shall be incrementally loaded and unloaded in accordance with the following schedule:
Load Hold Time
AL Until Stable
0.25DL Until Stable
0.5DL Until Stable
0.75DL Until Stable
1.0DL Until Stable
1.33DL 10 minutes
AL Until Stable
The alignment load shall be the minimum load required to align the testing apparatus and should not
exceed 5 percent of the design load. The dial gauge should be zeroed after the alignment load is applied.
Depending upon the ground anchor deflection performance,the load hold period at 1.33DL(tiebacks) may
be increased to 60 minutes. Ground anchor movement shall be recorded at 1, 2, 3, 5, 6 and 10 minutes
during the load hold period. If the ground anchor deflection between 1 and 10 minutes is greater than
0.04 inches, the 1.33DL load shall be continued to be held for a total of 60 minutes and deflections
recorded at 20, 30, 50 and 60 minutes.
Test Ground Anchor Acceptance
41111 A test ground anchor shall be considered acceptable when:
1. For tieback verification tests, a tieback is considered acceptable if the creep rate is less than
0.04 inches per log cycle of time between 1 and 10 minutes,and the creep rate is linear or decreasing
throughout the creep test load hold period.
2. For proof tests,a ground anchor is considered acceptable if the creep rate is less than 0.04 inches per
log cycle of time between 1 and 10 minutes or less than 0.08 inches per log cycle of time between
6 and 60 minutes,and the creep rate is linear or decreasing throughout the creep test load hold period.
3. The total movement at the maximum test load exceeds 80 percent of the theoretical elastic elongation
of the unbonded length.
4. Pullout failure does not occur. Pullout failure is defined as the load at which continued attempts to
increase the test load result in continued pullout of the test ground anchor.
Acceptable proof-test ground anchors may be incorporated as production ground anchors provided that the
unbonded test length of the ground anchor hole has not collapsed and the test ground anchor length and
bar size/number of strands are equal to or greater than the scheduled production ground anchor at the
test location. Test ground anchors meeting these criteria shall be completed by grouting the unbonded
length, as necessary. Maintenance of the temporary unbonded length for subsequent grouting is the
contractor's responsibility.
GEOENGINEERS June 11.2018 Page B-3
File No.233459-001-00
The Engineer shall evaluate the verification test results. Ground anchor installation techniques that do not •
satisfy the ground anchor testing requirements shall be considered inadequate. In this case,the contractor
shall propose alternative methods and install replacement verification test ground anchors.
The Engineer may require that the contractor replace or install additional production ground anchors in
areas represented by inadequate proof tests.
Shoring Monitoring
Preconstruction Survey
A shoring monitoring program should be established to monitor the performance of the temporary shoring
walls and to provide early detection of deflections that could potentially damage nearby improvements.
We recommend that a preconstruction survey of adjacent improvements, such as streets, utilities and
buildings, be performed prior to commencing construction. The preconstruction survey should include a
video or photographic survey of the condition of existing improvements to establish the preconstruction
condition, with special attention to existing cracks in streets or buildings.
Optical Survey
The shoring monitoring program should include an optical survey monitoring program. The recommended
frequency of monitoring should vary as a function of the stage of construction,as presented in the following
table.
Construction Stage Monitoring Frequency
During excavation and until wall movements have stabilized Twice weekly
During excavation if lateral wall movements exceed 1 inch and until wall
Daily
movements have stabilized
After excavation is complete and wall movements have stabilized,and before the Weekly
floors of the building reach the top of the excavation
Monitoring should include vertical and horizontal survey measurements accurate to at least 0.01 feet.
A baseline reading of the monitoring points should be completed prior to beginning excavation.The survey
data should be provided to GeoEngineers for review within 24 hours.
For shoring walls, we recommend that optical survey points be established along the top of the shoring
walls and at the curb line behind the shoring walls. The survey points along the top of the shoring wall
should be spaced every 25 feet for soil nail walls and adjacent buildings.The points on the curb lines should
be spaced approximately 25 feet apart. GeoEngineers recommends that a survey monitoring plan be
developed for GeoEngineers' review prior to establishing the survey points in the field. If lateral wall
movements are observed to be in excess of 1/2 inch between successive readings or if total wall movements
exceed 1 inch,construction of the shoring walls should be stopped to determine the cause of the movement
and to establish the type and extent of remedial measures required.
•
GEOENGINEERS_g June 11.2018 Page B-4
•
APPENDIX C
Report Limitations and Guidelines for Use
•
•
• APPENDIX C
REPORT LIMITATIONS AND GUIDELINES FOR USE1
This appendix provides information to help you manage your risks with respect to the use of this report.
Read These Provisions Closely
It is important to recognize that the geoscience practices (geotechnical engineering, geology and
environmental science) rely on professional judgment and opinion to a greater extent than other
engineering and natural science disciplines, where more precise and/or readily observable data may exist.
To help clients better understand how this difference pertains to our services, GeoEngineers includes the
following explanatory"limitations" provisions in its reports. Please confer with GeoEngineers if you need to
know more about how these "Report Limitations and Guidelines for Use" apply to your project or site.
Geotechnical Services Are Performed for Specific Purposes, Persons and Projects
This report has been prepared for Trailblazer Development, LLC for the SW Atlanta Street Storage Building
project specifically identified in the report.The information contained herein is not applicable to other sites
or projects.
GeoEngineers structures its services to meet the specific needs of its clients. No party other than the party
to whom this report is addressed may rely on the product of our services unless we agree to such reliance
in advance and in writing. Within the limitations of the agreed scope of services for the Project, and its
schedule and budget, our services have been executed in accordance with our Agreement with Trailblazer
Development dated May 24, 2018 (authorized May 24, 2018) and generally accepted geotechnical
practices in this area at the time this report was prepared.We do not authorize,and will not be responsible
for, the use of this report for any purposes or projects other than those identified in the report.
A Geotechnical Engineering or Geologic Report is Based on a Unique Set of Project-Specific
Factors
This report has been prepared for the SW Atlanta Street Storage Building project located north of SW Atlanta
Street in Tigard, Oregon. GeoEngineers considered a number of unique, project-specific factors when
establishing the scope of services for this project and report. Unless GeoEngineers specifically indicates
otherwise, it is important not to rely on this report if it was:
▪ not prepared for you,
■ not prepared for your project,
■ not prepared for the specific site explored, or
■ completed before important project changes were made.
For example, changes that can affect the applicability of this report include those that affect:
• the function of the proposed structure;
• i Developed based on material provided by GBA,GeoProfessional Business Association;www.geoprofessional.org.
GEOENGINEERS June 11,2018 Page C-1
File Ne 23459-001-00
is elevation, configuration, location, orientation or weight of the proposed structure; •
If changes occur after the date of this report, GeoEngineers cannot be responsible for any consequences
of such changes in relation to this report unless we have been given the opportunity to review our
interpretations and recommendations. Based on that review, we can provide written modifications or
confirmation, as appropriate.
Environmental Concerns Are Not Covered
Unless environmental services were specifically included in our scope of services, this report does not
provide any environmental findings, conclusions, or recommendations, including but not limited to, the
likelihood of encountering underground storage tanks or regulated contaminants.
Subsurface Conditions Can Change
This geotechnical or geologic report is based on conditions that existed at the time the study was performed.
The findings and conclusions of this report may be affected by the passage of time, by man-made events
such as construction on or adjacent to the site, new information or technology that becomes available
subsequent to the report date, or by natural events such as floods, earthquakes, slope instability or
groundwater fluctuations. If more than a few months have passed since issuance of our report or work
product,or if any of the described events may have occurred, please contact GeoEngineers before applying
this report for its intended purpose so that we may evaluate whether changed conditions affect the
continued reliability or applicability of our conclusions and recommendations.
Geotechnical and Geologic Findings Are Professional Opinions •
Our interpretations of subsurface conditions are based on field observations from widely spaced sampling
locations at the site.Site exploration identifies the specific subsurface conditions only at those points where
subsurface tests are conducted or samples are taken. GeoEngineers reviewed field and laboratory data
and then applied its professional judgment to render an informed opinion about subsurface conditions at
other locations. Actual subsurface conditions may differ, sometimes significantly, from the opinions
presented in this report. Our report, conclusions and interpretations are not a warranty of the actual
subsurface conditions.
Geotechnical Engineering Report Recommendations Are Not Final
We have developed the following recommendations based on data gathered from subsurface
investigation(s). These investigations sample just a small percentage of a site to create a snapshot of the
subsurface conditions elsewhere on the site. Such sampling on its own cannot provide a complete and
accurate view of subsurface conditions for the entire site.Therefore,the recommendations included in this
report are preliminary and should not be considered final. GeoEngineers' recommendations can be
finalized only by observing actual subsurface conditions revealed during construction. GeoEngineers
cannot assume responsibility or liability for the recommendations in this report if we do not perform
construction observation.
We recommend that you allow sufficient monitoring, testing and consultation during construction by
GeoEngineers to confirm that the conditions encountered are consistent with those indicated by the
explorations, to provide recommendations for design changes if the conditions revealed during the work
differ from those anticipated, and to evaluate whether earthwork activities are completed in accordance •
GEOENGINEERS June 11,2018 Page C-2
File No.23459-001-00
• with our recommendations. Retaining GeoEngineers for construction observation for this project is the most
effective means of managing the risks associated with unanticipated conditions. If another party performs
field observation and confirms our expectations, the other party must take full responsibility for both the
observations and recommendations. Please note, however, that another party would lack our project-
specific knowledge and resources.
A Geotechnical Engineering or Geologic Report Could Be Subject to Misinterpretation
Misinterpretation of this report by members of the design team or by contractors can result in costly
problems. GeoEngineers can help reduce the risks of misinterpretation by conferring with appropriate
members of the design team after submitting the report, reviewing pertinent elements of the design team's
plans and specifications, participating in pre-bid and preconstruction conferences, and providing
construction observation.
Do Not Redraw the Exploration Logs
Geotechnical engineers and geologists prepare final boring and testing logs based upon their interpretation
of field logs and laboratory data.The logs included in a geotechnical engineering or geologic report should
never be redrawn for inclusion in architectural or other design drawings. Photographic or electronic
reproduction is acceptable, but separating logs from the report can create a risk of misinterpretation.
Give Contractors a Complete Report and Guidance
To help reduce the risk of problems associated with unanticipated subsurface conditions, GeoEngineers
recommends giving contractors the complete geotechnical engineering or geologic report, including these
1111 "Report Limitations and Guidelines for Use."When providing the report,you should preface it with a clearly
written letter of transmittal that:
a advises contractors that the report was not prepared for purposes of bid development and that its
accuracy is limited; and
■ encourages contractors to confer with GeoEngineers and/or to conduct additional study to obtain the
specific types of information they need or prefer.
Contractors Are Responsible for Site Safety on Their Own Construction Projects
Our geotechnical recommendations are not intended to direct the contractor's procedures, methods,
schedule or management of the work site. The contractor is solely responsible for job site safety and for
managing construction operations to minimize risks to on-site personnel and adjacent properties.
Biological Pollutants
GeoEngineers' Scope of Work specifically excludes the investigation, detection, prevention or assessment
of the presence of Biological Pollutants. Accordingly, this report does not include any interpretations,
recommendations, findings or conclusions regarding the detecting, assessing, preventing or abating of
Biological Pollutants, and no conclusions or inferences should be drawn regarding Biological Pollutants as
they may relate to this project.The term "Biological Pollutants" includes, but is not limited to, molds,fungi,
spores, bacteria and viruses, and/or any of their byproducts.
• A Client that desires these specialized services is advised to obtain them from a consultant who offers
services in this specialized field.
GEOENGINEERLQ June 11.2018 Page C-3
File No,23459-001-00
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