geotechnical investigation report - portland, oregon

Geotechnical Engineering Report Proposed New Academic Building and Student Center Portland Community College - Cascade Campus N. Jessup Street and N. Mississippi Avenue Portland, Oregon Prepared for: Portland Community College Attn: Ms. Rebecca Ocken, Cascade Bond Project Manager 9700 SW Capitol Hwy., Suite 260 Portland, Oregon 97219

April 2, 2012 Project No. 73006.000

Geotechnical Engineering Report Proposed New Academic Building and Student Center Portland, Oregon

April 2, 2012

Project No. 73006.000 i

TABLE OF CONTENTS

1.0 INTRODUCTION ......................................................................................................................... 1 1.1 General ................................................................................................................................ 1 1.2 Purpose and Scope .............................................................................................................. 1

1.2.1 Geologic Map Review .................................................................................................... 1 1.2.2 Subsurface Exploration .................................................................................................. 1 1.2.3 Infiltration Testing ........................................................................................................... 1 1.2.4 Soils Testing ................................................................................................................... 1 1.2.5 Geotechnical Engineering Analysis ................................................................................ 1 1.2.6 Report Preparation ......................................................................................................... 1

1.3 Project Understanding .......................................................................................................... 2 1.4 Field Exploration .................................................................................................................. 2 1.5 Laboratory Testing ............................................................................................................... 3

2.0 SITE CONDITIONS ..................................................................................................................... 3 2.1 Surface Description .............................................................................................................. 3 2.2 Geologic Setting ................................................................................................................... 3 2.3 Subsurface ........................................................................................................................... 4

2.3.1 Soils ................................................................................................................................ 4 2.3.2 Pavement ....................................................................................................................... 4 2.3.3 Flood Deposits ............................................................................................................... 4 2.3.4 Groundwater ................................................................................................................... 4

2.4 Infiltration Testing ................................................................................................................. 5 3.0 CONCLUSIONS AND RECOMMENDATIONS ........................................................................... 5

3.1 Discussion ............................................................................................................................ 5 3.2 Shallow Foundations ............................................................................................................ 6

3.2.1 Footing Preparation ........................................................................................................ 6 3.2.2 Footing Embedment Depths ........................................................................................... 6 3.2.3 Footing Widths / Bearing Pressure ................................................................................. 6 3.2.4 Foundation Static Settlement ......................................................................................... 6 3.2.5 Lateral Resistance .......................................................................................................... 7

3.3 Floor Slabs ........................................................................................................................... 7 3.4 Retaining Structures ............................................................................................................. 7

3.4.1 Drainage ......................................................................................................................... 8 3.4.2 Temporary Shoring ......................................................................................................... 8 3.4.3 Types of Temporary Shoring Walls ................................................................................ 8 3.4.4 Soldier Pile and Lagging ................................................................................................ 9 3.4.5 Soil Parameters for Shoring Design ............................................................................... 9

3.5 Seismic Design Criteria ...................................................................................................... 10 3.6 Pavement Design ............................................................................................................... 10

3.6.1 Asphalt Concrete .......................................................................................................... 10 3.6.2 Portland Cement Concrete ........................................................................................... 11

4.0 CONSTRUCTION RECOMMENDATIONS ............................................................................... 12 4.1 Site Preparation ................................................................................................................. 12

4.1.1 Proofrolling ................................................................................................................... 13 4.1.2 Wet-Weather/Wet-Soil Conditions ................................................................................ 13

4.2 Excavation .......................................................................................................................... 13 5.0 ADDITIONAL SERVICES AND CONSTRUCTION OBSERVATIONS ...................................... 14 6.0 LIMITATIONS ............................................................................................................................ 14 7.0 CLOSING .................................................................................................................................. 15 8.0 REFERENCES .......................................................................................................................... 16


April 2, 2012

Project No. 73006.000 ii

SUPPORTING DATA

Figures

Figure 1 Vicinity Map Figure 2 Site Plan Figure 3 Footing Settlement

Appendix A – Field Explorations

Terminology to Describe Soil Key to Test Pit and Boring Log Symbols Logs for Borings B-1 through B-8

Appendix B – Laboratory Testing

Particle-Size Analysis Test Results

Appendix C – Site-Specific Seismic Analysis

Appendix D – General Construction Information


April 2, 2012

Project No. 73006.000 1

1.0 INTRODUCTION

1.1 General This report presents the results of PBS Engineering and Environmental, Inc. (PBS’) geotechnical engineering investigation and evaluation for the proposed new academic building and student center and buildings with underground parking to be located on the Portland Community College Cascade Campus in Portland, Oregon. These facilities qualify as “Special Occupancy Structures”, in accordance with the 2010 Oregon Structural Specialty Code (OSSC), Chapter 18. The general site location is shown on the Vicinity Map, Figure 1. The locations of the planned new buildings and underground parking and the locations of our explorations are shown on the Site Plan, Figure 2.

1.2 Purpose and Scope The purpose of our services was to develop geotechnical design and construction recommendations in support of the planned new facilities. This was accomplished by performing the following scope of services.

1.2.1 Geologic Map Review Reviewed relevant geologic maps of the site area will be reviewed for information regarding geologic conditions and hazards at or near the site. 1.2.2 Subsurface Exploration Completed eight borings; three within each building footprint and two between the proposed buildings. Seven of the borings were advanced to depths up to 46.5 feet below the ground surface (bgs) and one to depth 71.5 feet bgs. The borings were logged, the presence of groundwater documented, and representative soil samples were collected by a member of our geotechnical staff. 1.2.3 Infiltration Testing As requested, we completed two falling head infiltration tests through the augers at depths of 5.0 and 20.0 feet bgs. 1.2.4 Soils Testing All samples were returned to our laboratory and classified in general accordance with the Unified Soil Classification, Visual-Manual Procedure. Due to the granular nature of the soils, laboratory tests include natural moisture contents and grain-size testing on selected samples as appropriate. 1.2.5 Geotechnical Engineering Analysis Data collected during the subsurface exploration, literature research, and testing were used to develop specific geotechnical design parameters and construction recommendations. 1.2.6 Report Preparation Our Geotechnical Engineering Report summarized the results of our explorations and analyses, including information relating to the following:

Boring logs Laboratory test results Surface and subsurface drainage requirements Earthwork and grading, cut, and fill recommendations


April 2, 2012

Project No. 73006.000 2

Temporary and permanent slope inclinations Structural fill materials and preparation Wet weather/condition considerations Frost penetration Groundwater and infiltration considerations Shallow foundation design recommendations:

Minimum embedment (including frost penetration) Allowable bearing pressure Estimated settlement Sliding coefficient Recommended factors of safety

Retaining wall design recommendations: Lateral earth pressures for embedded wall design including active,

passive, and at-rest earth pressures with recommended factors of safety Allowable bearing pressure Seismic lateral force Sliding coefficient

Seismic design criteria in accordance with the current OSSC Site-specific hazard report for the proposed development Slab and pavement subgrade preparation Pavement design recommendations Lateral earth pressures for use by the contractor in designing temporary

shoring, assumed to be cantilevered soldier pile and lagging

1.3 Project Understanding The development will be located within the area currently occupied by campus parking. The existing parcel is bound to the north by N. Jessup Street, to the west by N. Mississippi Avenue, and to the east by N. Albina Avenue. The proposed project will consist of two, three-story buildings; one each at the north and south ends of the property and each with a footprint on the order of 15,000 square feet. PBS has assumed the buildings will be steel-frame construction. A single level, below-grade parking garage will be constructed beneath and between the new buildings. The parking garage will be concrete slab-on-grade. Embedded building walls will likely be concrete and/or concrete masonry block. The project will also include surrounding pavement surfacing, driveways, and utilities. Site stormwater will be disposed of on the site. Based on conversations with the structural engineer, we understand that building loads (i.e., static dead plus real live loads) are currently preliminary and may be as much as 700 kips for columns and 24 kips per lineal foot for bearing walls. Excavations for the underground parking will be on the order of 12 to 15 feet deep. 1.4 Field Exploration A total of eight (8) borings were drilled to depths between 46.5 and 71.5 feet bgs. Borings were drilled by Western States Soil Conservation of Hubbard, Oregon using mud-rotary drilling techniques. A hollow-stem auger was used to a depth of 20.0 feet bgs in Boring B-5 to facilitate infiltration testing. The approximate test pit boring locations are shown on Figure 2. Dates and depth to which the borings were drilled and sampled are shown in Table 1.


April 2, 2012

Project No. 73006.000 3

Table 1: Boring Drill Dates and Depths

Exploration Date Drilled Depth (feet)

B-1 1/25/2012 46.5

B-2 1/25/2012 46.5

B-3 1/26/2012 71.5

B-4 1/26-27/2012 46.5

B-5 1/27/2012 46.5

B-6 1/30/2012 46.5

B-7 1/31/2012 46.5

B-8 1/30/2012 46.5 The subsurface materials encountered were field classified in general accordance with the Manual-Visual Classification Method (ASTM D 2488) and logged. In the borings, in-situ Standard Penetration Tests (SPT, ASTM D 1586) were performed at 2½- to 5-foot intervals. Disturbed soil samples were collected using a split-spoon sampler and packaged in moisture-tight bags. The borings were backfilled with bentonite chips in accordance with state regulations. The soil samples were re-examined in the laboratory to supplement field classifications. Laboratory testing was performed on selected soil samples. Field exploration methods and Interpreted boring logs are presented in Appendix A – Field Explorations. 1.5 Laboratory Testing Soil samples obtained during our exploration were returned to the laboratory to assist in soil classification and to evaluate the material's general physical properties and engineering characteristics. Due to the relative density and granular nature of site soils, laboratory testing was limited to moisture content and grain-size analyses (sieve and percent passing the No. 200 sieve [P200]). Some of the results of laboratory testing are included on the boring logs. Laboratory testing methods and full test results are presented in Appendix B – Laboratory Testing.

2.0 SITE CONDITIONS

2.1 Surface Description The site is relatively flat with the exception of the existing infiltration facilities located around portions of the parking lot perimeter, which are approximately 4 to 5 feet below the surrounding grade. The site is currently occupied by paved parking areas, landscape islands, infiltration facilities, electronic parking pass kiosks, and light poles. Vegetation at the site includes irrigated lawn, infiltration facility vegetation, landscape bushes, and young deciduous trees. 2.2 Geologic Setting According to published geologic mapping of the site region (Beeson,1990; Madin, 1990), the site is underlain by Quaternary, fine-grained facies flood deposits of fine sands and silt. The fine-grained alluvium is underlain by the coarse-grained facies of the flood deposits consisting of sands and gravels. These flood deposits were deposited from glacial outburst floods of glacial Lake Missoula during the Pleistocene Period. The flood deposits in the area


April 2, 2012

Project No. 73006.000 4

are on the order of 150 feet thick. Gravels of the Troutdale formation are expected below the flood deposits to the bedrock basement of Columbia River Basalt (map unit Tcr) at a depth of approximately 375 feet bgs. 2.3 Subsurface

2.3.1 Soils As discussed in the field explorations section, subsurface conditions at the site were explored by drilling eight borings. Logs summarizing the subsurface conditions encountered in the borings are presented in Appendix A. The soil conditions observed during the subsurface investigation are summarized below. 2.3.2 Pavement All our explorations were drilled in areas covered with asphalt concrete (AC) pavement. The AC was 3 to 4 inches thick and underlain by crushed rock base. The crushed rock base course thickness ranged from 18 to 24 inches over the northern parking area (Borings B-1 through B-6) and ranged from 8 to 12 inches thick in the southern parking area (Borings B-7 through B-8). 2.3.3 Flood Deposits The underlying soils consisted of Alluvium and predominantly sand with variable amounts of silt and gravel. We have separated the Alluvium into three layers.

The Upper Alluvium – Loose to medium dense silt with trace to some fine sand to medium dense, silty fine sand. This material was observed in Boring B-3 to an approximate depth 3.0 feet bgs; Boring B-4 to a depth of 5.5 feet bgs; and in Boring B-7 to depth 2.0 feet bgs.

The Middle Alluvium – Medium dense, dark brown-gray, fine to coarse sand

with trace silt. A 2- to 3-foot-thick layer of gravel or sand containing gravel was encountered between depths of 13.0 and 20.0 feet bgs. An approximate 5-foot-thick layer of dense gravel was observed at a depth of 29.0 feet bgs in Boring B-5. This unit was observed in all borings either directly beneath base rock or beneath upper alluvium.

The Lower Alluvium – Interbedded light brown sandy silt, light brown fine

sand, and dark brown-gray, fine to coarse sand. This unit was observed or inferred in Boring B-1 below 39.0 feet bgs; Boring B-2 below an approximate depth of 27.0 feet bgs; Boring B-3 below 48.5 feet bgs; Boring B-4 below 43.5 feet bgs; Boring B-5 below 34.5 feet bgs; Boring B-6 below 34.0 feet bgs; Boring B-7 below 28.0 feet bgs; and Boring B-8 below 34.0 feet bgs.

2.3.4 Groundwater Possible perched zones of groundwater were observed in Boring B-3 at 37.5 feet bgs and in Boring B-5 at 41.0 feet bgs. In addition, shallow wet zones may be present seasonally due to irrigation and infiltration facilities at the site. Nearby well logs (OWRD, 2008) indicate groundwater in the area is at a depth on the order of 150 feet bgs. Regional groundwater mapping by USGS shows groundwater present at depths of approximately 120 to 140 feet bgs.


April 2, 2012

Project No. 73006.000 5

2.4 Infiltration Testing In accordance with the Stormwater Management Manual (COP, 2008; Appendix F2, revised March 2010), PBS completed falling-head infiltration testing in Boring B-5 at depths of 5.0 and 20.0 feet bgs. During the test, the hollow-stem drilling auger was advanced into the soil to the desired test depth. A layer of gravel was placed inside the auger to reduce disturbance of the native material. An initial “soak” was conducted; at both test depths the initial infiltration rate was rapid enough (i.e., 12 inches of water soaked away in less than 10 minutes on two successive tests) precluding the requirement of a prolonged soak period. A small quantity of water was introduced into the auger through a tremie pipe. The height of the water column in the auger was measured initially and at regular timed intervals. Representative soil samples were collected immediately below each infiltration test depth for grain-size distribution analysis. The results of our field infiltration testing are presented in Table 2.

Table 2: Infiltration and Laboratory Test Results

Boring No.

Depth of Infiltration Test

(feet bgs)

Infiltration Rate(1)

(inches/hour)

P200(2)

(% Passing No. 200 Sieve)

Soil Classification

Depth to Groundwater

(feet bgs)

B-5 5.0 140 11 Sand >120

B-5 20.0 > 1,000 5 Sand >120 1 Average in-situ infiltration rate measured in the field. 2 Fines content: material passing the U.S. Standard No. 200 Sieve.

The infiltration rate listed in Table 2 is not a permeability/hydraulic conductivity, but a field-measured rate and does not include correction factors related to long-term infiltration rates. The design engineer should determine the appropriate correction factors to account for the planned level of pre-treatment, maintenance, vegetation, siltation, etc. Field-measured infiltration rates are typically reduced by a minimum factor of 2 to 4 for use in design.

3.0 CONCLUSIONS AND RECOMMENDATIONS

3.1 Discussion We drilled eight borings at various locations across the site. The subsurface conditions consist of alluvial deposits described as loose to medium dense silt with trace to some fine sand to silty fine sand, and medium dense to dense fine to coarse sand observed to the termination depths of 46.5 to 71.5 feet bgs. Significant zones of groundwater were not observed in the borings at the time of our exploration. Wet zones may be present near infiltration or irrigation features seasonally. Our analyses indicate that the risk of liquefaction settlement at the site is low. This is primarily due to the medium dense relative density of site soils and the significant depth to groundwater (i.e., greater than 120 feet). A site-specific seismic hazard study was also conducted in accordance with state regulations for school buildings, and the results are presented in Appendix C – Site-Specific Seismic Analysis. In our opinion, based on the results of this study, seismic design can be completed using the parameters provided by OSSC.

The proposed structure will have one level of underground parking. Medium dense to dense sand was encountered at this depth in each boring. Our current opinion is that the building


April 2, 2012

Project No. 73006.000 6

can be supported on shallow spread footings bearing in the medium dense sand. Building foundations can be proportioned for an allowable bearing pressure of 2,000 to 4,000 pounds per square foot (psf) for building column and perimeter foundation loads (dead plus real live loads) on the order 700 kips and 24 kips per linear foot. The on-site soils can be easily excavated with conventional earthmoving equipment. The depth of excavations will be on the order of 12 to 15 feet bgs. Temporary shoring and/or dewatering may be required for excavations.

3.2 Shallow Foundations

3.2.1 Footing Preparation We recommend that all footing excavations be trimmed neat and footing subgrades carefully prepared. Footing subgrades should be re-compacted to 92 percent of the maximum dry density as determined by the modified Proctor test method (ASTM D1557). PBS should confirm suitable bearing conditions and evaluate all footing subgrades. Observations should also confirm that loose or soft material, organics, unsuitable fill, and old topsoil zones have been removed from footing excavations and concrete slabs on grade. Localized deepening of footing excavations may be required to penetrate any soft, wet, or deleterious materials. If construction occurs during wet weather, we recommend a thin layer of compacted, crushed rock be placed over the footing subgrades to help protect them from disturbance due to foot traffic and the elements. Placement of this rock is the prerogative of the contractor; regardless, the footing subgrade should be in a dense condition prior to pouring concrete. 3.2.2 Footing Embedment Depths We recommend that all footings be founded a minimum of 24 inches below the lowest adjacent grade. The minimum soil frost depth is 18 inches for foundations. The footings should be founded below an imaginary line projecting at a 1H:1V (horizontal to vertical) slope from the base of any adjacent, parallel utility trenches 3.2.3 Footing Widths / Bearing Pressure As discussed above, the building foundations will be on the order of 12 to 15 feet bgs and will be installed on medium dense to dense sand. Continuous wall and isolated spread footings should be at least 18 and 24 inches wide, respectively. Footings should bear on firm native granular soil or structural fill and should be sized using a maximum allowable bearing pressure of 2,000 to 4,000 psf in conjunction with the results presented in Figure 3 – Footing Settlement. The results in Figure 3 are based on a factor of safety of three and one, for bearing capacity and settlement, respectively. These are net bearing pressures. The weight of the footing and overlying backfill can be disregarded in calculating footing sizes. The recommended allowable bearing pressure applies to the total of dead plus long-term-live loads. Allowable bearing pressures may be increased by 1/3 for seismic and wind loads. 3.2.4 Foundation Static Settlement Footings will settle in response to column and wall loads, as well as from the effects of floor live loads. Based on these combined effects and our evaluation of the subsurface conditions, we have estimated static settlement as a function of footing width for three different bearing pressures and presented the results in Figure 3 –


April 2, 2012

Project No. 73006.000 7

Footing Settlement. The structural engineer should select bearing pressures to proportion footings to limit estimated differential settlements between adjacent footings to tolerable magnitudes. 3.2.5 Lateral Resistance Lateral loads can be resisted by passive earth pressure on the sides of footings and embedded walls and by friction at the base of the footings. A passive earth pressure of 300 pounds per cubic foot (pcf) may be used for footings confined by native soils and new structural fills. The allowable passive pressure has been reduced by half to account for the large amount of deformation required to mobilize full passive resistance. Adjacent floor slabs, pavements, or the upper 12-inch depth of adjacent unpaved areas should not be considered when calculating passive resistance. For footings in contact with native granular soils, use a coefficient of friction equal to 0.4 when calculating resistance to sliding. These values do not include a factor of safety.

3.3 Floor Slabs Satisfactory subgrade support for building floor slabs can be obtained from the native granular subgrade prepared in accordance with our recommendations presented in the Site Preparation and/or Wet Weather Construction sections of this report. A minimum 6-inch-thick layer of imported granular material should be placed and compacted over the prepared subgrade. Imported granular material should be composed of crushed rock or crushed gravel that is relatively well-graded between coarse and fine, contains no deleterious materials, has a maximum particle size of 1 inch, and has less than 5 percent by dry weight passing the U.S. Standard No. 200 Sieve. Material recommendations are provided in Appendix D – General Construction Information. For floor slabs supported on subgrades and a base course prepared in accordance with the preceding recommendations, the floor slab may be designed using a modulus of subgrade reaction (k) of 200 pounds per cubic inch (pci). Some moist areas were encountered, but regional groundwater level is more than 120 to 140 feet bgs. The design team should evaluate whether a vapor retarder is needed for confined spaces located below grade. A vapor retarder will reduce the potential for moisture transmission through the floor slabs. Actual selection and design of an appropriate vapor barrier, if needed, should be based on discussions among members of the design team. 3.4 Retaining Structures As discussed above, the proposed structure will include one level of underground parking. This will likely extend to a depth of 12 to 15 feet bgs. For walls allowed to rotate at least 0.005H about the base, where H is the height of the wall, we recommend that an active earth pressure of 36H pcf equivalent fluid unit weight (EFW) be used in design. Where walls are constrained against rotation, we recommend an at-rest earth pressure equal to 60H pcf EFW be used for design. For seismic loading, we recommend using an inverted triangular distribution (seismic surcharge) equivalent to 12H psf. Walls should be designed by applying the active earth pressure in addition to the seismic surcharge or at-rest earth pressures, whichever is greater. If vertical surcharge loads, q, are present within 0.5H of the wall, a lateral surcharge of 0.3q should be applied as a uniform horizontal surcharge active over the full height of the wall. Traffic surcharges can be represented by an additional two feet of equivalent soil


April 2, 2012

Project No. 73006.000 8

depth. These values assume that the wall is vertical and the backfill behind the wall is horizontal. Seismic lateral earth pressures were computed using the Mononobe-Okabe equation. Lateral loads can also be resisted by friction on embedded building walls using a friction coefficient of 0.35 and a normal force equal to the resultant of the active earth pressure. Retaining wall footings should be designed in accordance with the recommendations provided for shallow foundations in Section 3.2.

3.4.1 Drainage Recommended lateral earth pressures assume that walls are fully drained and no hydrostatic pressures develop. A minimum 2-foot-wide zone of free draining material should be installed immediately behind all retaining and embedded building walls. A perforated drain pipe should be installed at the base of the drain rock and routed to a suitable discharge point. Alternatively, the zone of drain rock can be replaced with a prefabricated drain board to provide drainage. Detailed recommendations for retaining wall drainage and backfill are provided in Appendix D.

3.4.2 Temporary Shoring Temporary construction excavation and site safety are the sole responsibility of the contractor who also is solely responsible for the means, methods, and sequencing of construction operations. We are providing the following information only as a service to our client for planning purposes by their design team. Under no circumstances should the information provided herein be interpreted to mean that PBS is assuming responsibility for construction site safety or the contractor's activities; such responsibility is not being implied and should not be inferred. Current plans include construction of a single story of underground parking underneath both buildings and the area between the buildings. The base elevation of the underground parking is assumed to be at a depth 12 to 15 feet bgs. Due to the planned location of parking garage walls, there is not sufficient room to safely slope the excavation without impacting perimeter streets. As a result, we recommend only using shoring that provides continuous support; open cuts will not be allowed. Although permanent groundwater was not encountered in our explorations, zones of perched water may be present and may rise in response to wet weather. The shoring design must take this in to account. 3.4.3 Types of Temporary Shoring Walls Based on conversations with the design team, we understand that temporary shoring will likely be used for excavation support. A wide variety of shoring systems are available. We recommend the contractor be responsible for selecting the appropriate shoring and dewatering systems. In our opinion, due to the relatively close proximity of the planned parking garage walls to surrounding surface streets, it may not be feasible to use tied back shoring systems such as anchored soldier pile and lagging walls or soil nails, as the anchors and soil nails would extent into the right-of-way (ROW). It may be possible to obtain permission to install temporary anchors or soil nails into/under the surrounding City


April 2, 2012

Project No. 73006.000 9

ROW if one of these systems is selected. However, with an excavation depth of 12 to 15 feet bgs, cantilevered shoring is likely feasible. 3.4.4 Soldier Pile and Lagging Cantilevered soldier pile and lagging walls are generally constructed using steel H-piles placed into augered holes drilled at intervals along the wall alignment. The holes are then backfilled with structural concrete (below the depth of embedment) and weak concrete (lean mix, controlled density fill (CDF), etc.). The soil in front of the wall is excavated from the top down. As the soil is exposed, the weak concrete is chipped away and lagging is fitted between the steel H-piles. Lagging may be inserted behind the flanges or attached to the face of the flanges. The lagging usually consists of wood planks or steel plates. The soil is temporarily supported by arching between adjacent steel H-piles until the lagging is installed. However, soft/loose soils can slough into the excavation until the lagging is installed and soil is in contact with the lagging. Please note that the potential settlement of the soil behind temporary shoring is highly dependent on the contractor’s approach to constructing the wall, and some additional risk is thereby incurred. 3.4.5 Soil Parameters for Shoring Design The soil parameters commonly used for the design of temporary excavation shoring are soil unit weight “”, soil internal friction angle “”, and soil cohesion “c”. The soil parameters recommended for use in the excavation shoring design are presented on Table 3. Passive resistance can be applied over 2 times the pier diameter below the base of the excavation. Passive resistance should be neglected over the top 12 inches of embedment.

Table 3: Soil Parameters for Shoring Design

Soil Material

Unit Weight

(pcf)

Friction Angle

(degrees)

Cohesion c

(psf)

Lateral Earth Pressure Coefficient

Ka (active)

Kp* (passive)

KO (at-rest)

Loose to M. Dense Sand (0 – 10 ft.)

120 32 0 0.30 3.3 0.50

M. Dense Sand

(10 – 70 ft.) 120 34 0 0.28 3.8 0.47

* Passive lateral earth pressure coefficients have been reduced by a factor of 2 to account for the amount of deflection required to engage full passive pressures.

The lateral earth pressure coefficient, Ka (active), Kp (passive), and KO (at rest) provided in Table 4, are based upon the assumptions that the ground surface behind the shoring walls and the bottom of the excavation are flat surfaces. The designer must consider an adequate surcharge load on the wall to account for adjacent construction and vehicular traffic. The designer must also use appropriate factors of safety. The lateral earth pressure distribution used to design the wall is dependent


April 2, 2012

Project No. 73006.000 10

upon the allowable lateral soil deformation and settlement, and the lateral restraint used. If no lateral yield is allowed, then at-rest pressure distribution should be used. The shoring design should consider and identify the design criteria to be used.

3.5 Seismic Design Criteria We understand the seismic design criteria for this project will be based on the 2010 OSSC, Section 1615. We completed a site-specific seismic analysis as presented in Appendix C of this report. As discussed in Appendix C, 2010 OSSC spectra can be used. The seismic design criteria, in accordance with the 2010 OSSC, are summarized in Table 4.

Table 4: OSSC 2010 Seismic Design Parameters

Short Period 1 Second

Maximum Credible Earthquake Spectral Acceleration Ss = 0.97 g S1 = 0.34 g

Site Class D

Site Coefficient Fa = 1.11 Fv = 1.72

Adjusted Spectral Acceleration SMS = 1.08 g SM1 = 0.58 g

Design Spectral Response Acceleration Parameters SDS = 0.72 g SD1 = 0.39 g

Design Spectral Peak Ground Acceleration 0.29 g

3.6 Pavement Design 3.6.1 Asphalt Concrete We understand that site pavements may consist of both asphalt concrete (AC) and portland cement concrete (PCC) pavements that will be localized and limited to driveways and access areas around the building perimeters. These pavement sections should be limited to on-site pavements and should not be used to restore city streets. Recommendations for loading both AC and PCC pavements were developed using the American Association of State Highway and Transportation Officials (AASHTO) design methods. AC pavements were evaluated using a pavement design life of 20 years and a truck factor of 0.6 equivalent single-axle load (ESAL) per truck. Heavy construction traffic on pavements or partial pavement sections (such as base rock over the prepared subgrade) may exceed the design loads and could potentially damage or shorten the life of the pavements. Therefore, we recommend the contractor take appropriate measures to protect the base rock and pavement during construction. Pavement subgrades should be evaluated and prepared in accordance with the Site Preparation and Wet Weather sections of this report. Our pavement recommendations are based on the following assumptions:

20 year design life A resilient modulus of 7,500 pounds per square inch (psi) was assumed for

the site soils


April 2, 2012

Project No. 73006.000 11

A resilient modulus of 25,000 psi was estimated for the base rock An initial and terminal serviceability index of 4.2 and 2.5, respectively The reliability and standard deviation of 85 percent and 0.45, respectively A structural coefficient of 0.42 and 0.12 for the asphalt and base rock,

respectively Site traffic was assumed to include 15 trucks per day for heavy duty

pavement and 5 trucks per day for standard duty pavement If any of these assumptions are incorrect, our office should be contacted and provided with the appropriate information so that the pavement designs can be revised. Our pavement design recommendations are summarized in Table 5. The following pavement design was completed in accordance with the procedures in the AASHTO Pavement Design Guide and the parameters indicated above.

Table 5: Minimum Pavement Sections

Traffic Loading (ESALs)

AC (inches)

Base Rock (inches)

Standard Duty 3.0 6.0 Heavy Duty 3.0 8.0

The asphalt cement binder should be PG 70-22 Performance Grade Asphalt Cement according to ODOT SS 00744.11 – Asphalt Cement and Additives. The AC should consist of ½-inch hot mix asphalt. The minimum lift thicknesses should be 2.0 inches. The AC should conform to ODOT SS 00744.13 and 00744.13 and be compacted to 91 percent of Rice Density of the mix, as determined in accordance with ASTM D 2041. 3.6.2 Portland Cement Concrete We understand that PCC pavements will be used in the parking garage and may be used for localized access to the new buildings. We have used a design life of 30 years for design of PCC pavements. This is longer than for AC pavements due to the costs associated with repair over the life of the pavement. The subgrade under PCC pavement areas should be prepared as recommended above for AC pavement. We recommend that the PCC section for the pavement areas consist of 6 inches of PCC over 6 inches of base rock. The structural engineer should check the recommended concrete thickness for the dead load of the trucks in the truck loading ramp using a subgrade modulus of 350 pci in addition to performing final reinforcement design. Longitudinal and transverse joint spacing should not exceed 12 feet and 15 feet, respectively. AASHTO evaluation of PCC pavement section thicknesses was completed using the parameters and values in the following table. Our analysis was based on the use of joint reinforced concrete pavement (JRCP) with the use of dowels as load transfer devices and no tied shoulders. The following additional assumptions were used.


April 2, 2012

Project No. 73006.000 12

Changes in these assumptions will affect the corresponding design pavement section.

30-year design life Initial and terminal serviceability index of 4.5 and 3.0, respectively Reliability and standard deviation of 90 percent and 0.39, respectively Modulus of subgrade reaction on Base Rock = 350 pci Modulus of rupture of concrete = 600 psi Concrete pavement should have a minimum 28 day compressive strength of

4,000 psi Aggregate interlock joints No concrete shoulders 219,000 ESALs;. this corresponds with up to 20 trucks per day with a truck

factor of 1.0 over the design life of the pavement The recommended PCC pavement sections presented below are contingent on the following recommendations being implemented during construction.

Adequate drainage should be provided at the surface such that the subgrade soils are not allowed to become saturated by infiltration of surface runoff.

Concrete slumps should be from 3 to 4 inches. The concrete should be properly cured in accordance with Portland Cement Association (PCA) recommended procedures and vehicular traffic should not be allowed for 3 days (automobile traffic) or 7 days (truck traffic).

To help offset shrinkage, concrete pavement may be reinforced with at least No. 3 bars, 24 inches on-center, each way or 6x6-W2.0xW2.0 wire mesh (located 1/3 of the slab thickness from the top of the slab).

Construction joint spacing should not exceed 12 feet. Over-finishing of concrete pavements should be avoided. Typically, a broom

or burlap drag finish should be used. 4.0 CONSTRUCTION RECOMMENDATIONS

4.1 Site Preparation We estimate excavations on the order of 12 to 15 feet extending over the entire existing parking area will be necessary at the site to constructed the underground parking garage. The existing surface features such as pavements curbs, sidewalks, etc. will therefore, be demolished and removed from the site. Stripped vegetation and topsoil should be transported off-site for disposal. Demolition should include removal of existing improvements throughout the project site, including remnant foundation elements. Underground utility lines, vaults, basement walls and underground tanks should be removed. The voids resulting from removal of these should be backfilled with compacted structural fill. Before filling, the base of these excavations should be excavated to firm subgrade to allow for uniform compaction.

Materials generated during demolition of existing improvements should be transported off-site or stockpiled in areas designated by the owner. Asphalt, concrete, gravel fill, and base rock materials may be crushed and recycled for use as general fill. Such recycled materials should meet the criteria described in Appendix D – Structural Fill section of this report.


April 2, 2012

Project No. 73006.000 13

4.1.1 Proofrolling Following stripping/excavation and prior to placing fill, pavement, or building improvements, the exposed subgrade should be evaluated by proofrolling. The subgrade should be proofrolled with a fully loaded dump truck or similar heavy, rubber-tire, construction equipment to identify soft, loose, or unsuitable areas. We recommend that PBS be retained to observe the proofrolling. Soft or loose zones identified during the field evaluation should be compacted to an unyielding condition or be excavated and replaced with structural fill, as discussed in Appendix D – Structural Fill section of this report...

4.1.2 Wet-Weather/Wet-Soil Conditions Due to the presence of silt soils near the surface in some of our explorations, construction equipment may have difficulty operating on the near-surface soils during or after extended wet periods or when the moisture content of the surface soil is more than a few percentage points above optimum. Soils that have been disturbed during site-preparation activities, or soft or loose zones identified during probing or proofrolling, should be removed and replaced with compacted structural fill. Protection of the subgrade is the responsibility of the contractor. Construction of granular haul roads during wet weather can help reduce disturbance of site soils. The thickness of the granular material for haul roads and staging areas will depend on the amount and type of construction traffic. Typically a 12- to 18-inch-thick layer of imported granular material is sufficient for light staging areas. For haul roads and areas with repeated heavy construction traffic, this should be increased to at least 18 to 24 inches. The actual thickness of haul roads and staging areas should be based on the contractors approach to site development and the amount and type of construction traffic. The imported granular material should be placed in one lift over the prepared, undisturbed subgrade and compacted using a smooth-drum, non-vibratory roller. A geotextile fabric should be used to separate the subgrade from the imported granular material in areas of repeated construction traffic.

4.2 Excavation Soils at the site consist of loose to dense sand with variable amounts of silt and gravel and some sloughing and caving should be anticipated. Excavation of the soils encountered can be accomplished using conventional earthwork equipment. Trench cuts should stand relatively vertical to a depth of approximately 4 feet bgs, provided no groundwater seepage is present in the trench walls. Open excavation techniques may be used in the sand and gravel, provided the excavation is configured in accordance with the Occupational Safety and Health Administration (OSHA) requirements, groundwater seepage is not present, and with the understanding that some sloughing may occur. The trenches should be flattened if sloughing occurs or seepage is present. Groundwater was not observed during our field investigation. However, if shallow groundwater is observed during construction, use of a trench shield or other approved temporary shoring is recommended for cuts that extend below groundwater seepage or if vertical walls are desired for cuts deeper than 4 feet bgs. If dewatering is used, we recommend that the type and design of the dewatering system be the responsibility of the contractor, who is in the best position to choose systems that fit the overall plan of operation.


April 2, 2012

Project No. 73006.000 14

All excavations should be made in accordance with applicable OSHA and State regulations. The contractor is responsible for adherence to the OSHA requirements.

5.0 ADDITIONAL SERVICES AND CONSTRUCTION OBSERVATIONS

In most cases, other services beyond completion of a geotechnical report are necessary or desirable to complete the project. Occasionally, conditions or circumstances arise that require the performance of additional work that was not anticipated when the geotechnical report was written. PBS offers a range of environmental, geological, geotechnical, and construction services to suit the varying needs of our clients. PBS should be retained to review the plans and specifications for this project before they are finalized. Such a review allows us to verify that our recommendations and concerns have been adequately addressed in the design. Satisfactory earthwork performance depends on the quality of construction. Sufficient observation of the contractor's activities is a key part of determining that the work is completed in accordance with the construction drawings and specifications. We recommend that PBS be retained to observe general excavation, stripping, fill placement, footing subgrades, and/or installation of drilled shafts or piles. Subsurface conditions observed during construction should be compared with those encountered during the subsurface explorations. Recognition of changed conditions requires experience; therefore, qualified personnel should visit the site with sufficient frequency to detect whether subsurface conditions change significantly from those anticipated. 6.0 LIMITATIONS

This report has been prepared for the exclusive use of the addressee, and their architects and engineers for aiding in the design and construction of the proposed development and is not to be relied upon by other parties. It is not to be photographed, photocopied, or similarly reproduced, in total or in part, without the expressed written consent of the Client and PBS. It is the addressee's responsibility to provide this report to the appropriate design professionals, building officials and contractors to ensure correct implementation of the recommendations. The opinions, comments, and conclusions presented in this report are based upon information derived from our literature review, field explorations, laboratory testing, and engineering analyses. Conditions between, or beyond, our exploratory borings may vary from those encountered. It is possible that soil, rock, or groundwater conditions could vary between or beyond the points explored. If soil, rock, or groundwater conditions are encountered during construction that differ from those described herein, the client is responsible for ensuring that PBS is notified immediately so that we may reevaluate the recommendations of this report. Unanticipated soil and rock conditions and seasonal soil moisture and groundwater variations are commonly encountered and cannot be fully determined by merely taking soil samples or soil borings. Such variations may result in changes to our recommendations and may require that additional expenses to attain a properly constructed project. Therefore, we recommend a contingency fund to accommodate such potential extra costs. The scope of services for this subsurface exploration and geotechnical report did not include environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous substances in the soil, surface water, or groundwater at this site.


April 2, 2012

Project No. 73006.000 15

If there is a substantial lapse of time between the submission of this report and the start of work at the site, if conditions have changed due to natural causes or construction operations at or adjacent to the site, or if the basic project scheme is significantly modified from that assumed, it is recommended that this report be reviewed to determine the applicability of the conclusions and recommendations. Land use, site conditions (both on- and off-site), or other factors may change over time and could materially affect our findings. Therefore, this report should not be relied upon after three years from its issue, or in the event that the site conditions change. 7.0 CLOSING

We appreciate the opportunity to provide our geotechnical investigation services to you and trust that this report meets your needs at this time. Please contact us if you have any questions regarding this report. Sincerely, PBS Engineering + Environmental

Ryan White, PE, GE Senior Geotechnical Engineer

Arlan H. Rippe, PE, GE, D.GE Chief Geotechnical Engineer


April 2, 2012

Project No. 73006.000 16

8.0 REFERENCES

Beeson, M. H., Tolan, T. L., Madin, I. P., (1991). [Map]. Geologic Map of the Portland Quadrangle,

Multnomah and Washington Counties, Oregon, and Clark County Washington. Oregon Department of Geology and Mineral Industries. Geologic Map Series (GMS) 75.

COP (City of Portland, Environmental Services, Clean River Works). (2008, August 1). Stormwater

Management Manual (Revision 3). Accessed from City of Portland web site: http://www.portlandonline.com/shared/cfm/image.cfm?id=55741

Madin, I. P. (1990). [Map]. Earthquake-hazard geology maps of the Portland metropolitan area,

Oregon. Oregon Department of Geology and Mineral Industries. Open File Report 0-90-2. ODOT SS. (2008). Oregon Standard Specifications for Construction, Volume 2. Salem, OR: Oregon

Department of Transportation. OSSC. (2010). Oregon structural specialty code. OWRD (1991). Oregon Water Resource Department. Accessed April 2008 from the Oregon Water

Resource Department web site: http://apps2.wrd.state.or.us/apps/gw/well_log/Default.aspx.

FIGURES

ryanw

Text Box

APR 2012

PROJECT #

DATE

APR 2012

73006.000FIGURE

3PCC CASCADE – ACADMEIC & STUDENT CENTER BUILDINGSPORTLAND, OREGON

FOOTING SETTLEMENT

APPENDIX A Field Explorations


April 2, 2012

Project No. 73006.000 A-1

APPENDIX A – FIELD EXPLORATIONS

A1.0 GENERAL

We explored subsurface conditions at the project site by advancing eight borings between January 25 and 31, 2012. The locations of the borings, designated Borings B-1 through B-8, are shown on Figure 2. The procedures and techniques used to advance the borings, collect samples, and other field techniques are described in detail in the following paragraphs. Unless otherwise noted, all soil sampling and classification procedures followed applicable ASTM standards.

A2.0 BORINGS

A2.1 Drilling

The borings were advanced to depths varying from 46.5 to 71.5 feet bgs with a truck-mounted drill rig provided and operated by Western States Soil Conservation. Borings were advanced primarily using rotary drilling techniques with bentonite drilling mud. Drilling mud was used to maintain stability in the hole. Boring B-5 was advanced to a depth of 20 feet bgs using hollow-stem augers to allow for infiltration testing. The borings were observed by an engineering geologist from PBS who located the general areas for drilling and maintained a detailed log of the subsurface conditions and materials encountered during the course of the work. A2.2 Sampling

Disturbed soil samples were taken in the borings at selected depth intervals. The samples were obtained using a standard 2-inch outside diameter (OD), split-spoon sampler following procedures prescribed for the Standard Penetration Test (SPT). Using the SPT, the sampler is driven 18 inches into the soil using a 140-pound. hammer dropped 30 inches. The number of blows required to drive the sampler the last 12 inches is defined as the standard penetration resistance, or N-value. The N-value provides a measure of the relative density of granular soils such as sands and gravels, and the consistency of cohesive soils such as clays and silts. The disturbed soil samples were examined by the PBS engineering geologist and then sealed in plastic bags for further examination and physical testing in our laboratory. One relatively undisturbed sample was collected in the Boring B-3. The sample was obtained in a 3-inch OD, thin-wall Shelby tube by hydraulically pushing the tube into the undisturbed soil at the bottom of the bore hole. The soils exposed at the ends of the tubes were examined and classified. After field classification, the ends of the tubes were sealed to help preserve the natural moisture of the sample. The sealed tube was returned to our laboratory for physical testing.

A2.3 Logs of Borings

The logs of the borings are presented in Appendix A. The logs show the various types of materials that were encountered in the borings and the depths where the materials and/or characteristics of these materials changed, although the changes may be gradual. Where material types and descriptions changed between samples, the contacts were interpreted. The types of samples taken during drilling, along with their sample identification number, are shown to the right of the classification of materials. Standard penetration resistances (N-values) and natural water (moisture) contents are shown further to the right. Measured groundwater levels and the dates of the readings are plotted in the column to the right. The groundwater levels are only for the dates shown and probably vary from time to time during the year.


April 2, 2012

Project No. 73006.000 A-2

A3.0 MATERIAL DESCRIPTION

Initially, soil samples were classified visually in the field. Consistency, color, relative moisture, degree of plasticity, and other distinguishing characteristics of the soil samples were noted. Afterwards, the samples were re-examined in the PBS laboratory, various standard classification tests were conducted, and the field classifications were modified where necessary. The terminology used in the soil classifications and other modifiers are defined in Attachment A, Terminology Used to Describe Soil.

Terminology Used to Describe Soil 1 of 2

Soil Descriptions Soils exist in mixtures with varying proportions of components. The predominant soil, i.e., greater than 50 percent based upon total dry weight, is the primary soil type and is capitalized in our log descriptions, e.g., SAND, GRAVEL, SILT or CLAY. Lesser percentages of other constituents in the soil mixture are indicated by use of modifier words in general accordance with the Visual-Manual Procedure (ASTM D2488-93). “General Accordance” means that certain local and common descriptive practices have been followed. In accordance with ASTM D2488, group symbols (such as GP or CH) are applied on that portion of the soil passing the 3-inch (75mm) sieve based upon visual examination. The following describes the use of soil names and modifying terms used to describe fine- and coarse-grained soils. Fine - Grained Soils (More than 50% fines passing 0.074 mm, #200 sieve) The primary soil type, i.e. SILT or CLAY is designated through visual – manual procedures to evaluate soil toughness, dilatency, dry strength, and plasticity. The following describes the terminology used to describe fine - grained soils, and varies from ASTM 2488 terminology in the use of some common terms.

Primary soil NAME, adjective and symbols Plasticity

Description Plasticity Index (PI)

SILT ML & MH

CLAY CL & CH

ORGANICSILT & CLAY

OL & OH

SILT Organic SILT Non-plastic 0 - 3 SILT Organic SILT Low plasticity 4 - 10

Clayey SILT Silty CLAY Organic clayey SILT Medium Plasticity >10 – 20 Clayey SILT CLAY Organic silty CLAY High Plasticity >20 – 40 Clayey SILT CLAY Organic CLAY Very Plastic >40

Modifying terms describing secondary constituents, estimated to 5 percent increments, are applied as follows:

Description % Composition Trace sand, trace gravel 5% - 10% With sand; with gravel 15% - 25%

Sandy, or gravelly 30% - 45% Borderline Symbols, for example CH/MH, are used where soils are not distinctly in one category or where variable soil units contain more than one soil type. Dual Symbols, for example CL-ML, are used where two symbols are required in accordance with ASTM D2488. Soil Consistency. Consistency terms are applied to fine-grained, plastic soils (i.e., PI > 7). Descriptive terms are based on direct measure or correlation to the Standard Penetration Test N-value as determined by ASTM D1586-84, as follows.

Consistency Term

SPT N-value Unconfined Compressive Strength Tons/ft2 kPa

Very soft Less than 2 Less than 0.25 Less than 24 Soft 2 – 4 0.25 - 0.5 24 - 48

Medium stiff 5 – 8 0.5 - 1.0 48 – 96 Stiff 9 – 15 1.0 - 2.0 96 – 192

Very stiff 16 – 30 2.0 - 4.0 192 – 383 Hard Over 30 Over 4.0 Over 383

Very soft Less than 2 Less than 0.25 Less than 24

Note: For SILT with low to non-plastic behavior, (i.e., PI < 7) a relative density description is applied.

Terminology Used to Describe Soil 2 of 2

Soil Descriptions Coarse - Grained Soils (less than 50% fines) Coarse-grained soil descriptions, i.e., SAND or GRAVEL, are based on that portion of materials passing a 3-inch (75mm) sieve. Coarse-grained soil group symbols are applied in accordance with ASTM D2488 based upon the degree of grading, or distribution of grain sizes of the soil. For example, well graded sand containing a wide range of grain sizes is designated SW; poorly graded gravel, GP, contains high percentages of only certain grain sizes. Terms applied to grain sizes follow.

Material Particle Diameter

Inches Millimeters Sand (S) 0.003 - 0.19 0.075 - 4.8

Gravel (G) 0.19 - 3.0 4.8 - 75

Additional Constituents Cobble 3.0 - 12 75 - 300 Boulder 12 - 120 300 - 3050

Rock Block >120 >3050 The primary soil type is capitalized, and the amount of fines in the soil are described as indicated by the following examples. Other soil mixtures will provide similar descriptive names.

Example: Coarse-Grained Soil Descriptions with Fines

5% fines 10% fines (Dual Symbols) 15% to 45% fines

GRAVEL with trace silt: GW or GP GRAVEL with silt, GW-GM Silty GRAVEL: GM SAND with trace clay: SW or SP SAND with clay, SP-SC Silty SAND: SM

Additional descriptive terminology applied to coarse-grained soils follow.

Coarse-Grained Soil Containing Secondary Constituents

Clean < 5% fines With sand or with gravel 15% - 25% sand or gravel

Sandy or gravelly 30% - 45% sand or gravel With cobbles; with boulders Any amount cobbles or boulders.

Additional terms may be used to describe amount including abundant, scattered.

Cobble and boulder deposits may include a description of the matrix soils, as defined above. Relative Density terms are applied to granular, non-plastic soils based on direct measure or correlation to the Standard Penetration Test N-value as determined by ASTM D1586-84.

Relative Density Term SPT N-value

Very loose 0 - 4 Loose 4 - 10

Medium dense 10 - 30 Dense 30 - 50

Very dense > 50

Key To Test Pit and Boring Log Symbols

SAMPLING DESCRIPTIONS1

SPT

Drive

Sam

pler

Stan

dard

Pen

etra

tion

Test

ASTM

D 1

586

Shel

by T

ube

Push

Sam

pler

ASTM

D 1

587

Spec

ializ

ed D

rive

Sam

pler

s

(Det

ails

Note

d on

Log

s)Sp

ecia

lized

Dril

l or P

ush

Sam

pler

(Det

ails

Note

d on

Logs

)

Gra

b Sa

mpl

e

Rock

Cor

ing

Inte

rval

Scre

en

(Wat

er o

r Air

Sam

plin

g)

Wat

er L

evel

Dur

ing

Drilli

ng/E

xcav

atio

nW

ater

Lev

el A

fter

Drilli

ng/E

xcav

atio

n

LOG GRAPHICS

Geotechnical Testing/Acronym Explanations

PP Pocket Penetrometer SIEV Sieve GradationSC Sand Cone DD Dry DensityDCP Dynamic Cone Penetrometer ATT Atterberg LimitsSP Static Penetrometer CBR California Bearing RatioTOR Torvane OC Organic ContentCON Consolidation RES Resilient ModulusDS Direct Shear VS Vane ShearP200 Percent Passing U.S. Standard No. 200 Sieve HCL Hydrochloric AcidUC Unconfined Compressive Strength kPa kiloPascalPL Plasticity Limit GPS Global Positioning SystemPI Plasticity Index bgs Below ground surfaceLL Liquid Limit MSL Mean Sea LevelHYD Hydrometer Gradation

Environmental Testing/Acronym Explanations

bgs Below ground surface ATD At Time of DrillingCA Sample Submitted for Chemical Analysis NS No SheenPID Photoionization Detector Headspace Analysis SS Slight SheenPPM Parts Per Million MS Moderate SheenND Not Detected HS High Sheen

1Note: Details of soil and rock classification systems are available on request. Rev. 04/29/09

Observed contact between soil or rock units (at depths indicated)

Inferred contact between soil or rock units(at approximate depths indicated) Sampler

Type

Sample Recovery Sample

Interval

Instrumentation Detail Sampling SymbolsSoil and Rock

Well Pipe

Piezometer

Piezometer

Ground Surface

Well Cap

Bottom of Hole

Soil

or R

ock

Type

s

Well Seal

Well Screen

0.00.3

2.0

39.0

40.0

44.0

46.5

Intermittent rocky drilling

Rocky drilling at 21 ft bgs

Slight chatter, 25 ft - 30 ft

Light chatter 30 ft - 35 ft

Driller reports soft, smoothdrilling 39 ft - 40 ft

ASPHALT CONCRETE (4 inches thick)BASE ROCK (20 inches thick)Medium dense, dark brown-gray, fine tocoarse SAND with trace silt; dry,subangular (Missoula Flood Deposits)

trace fine gravel, thinly laminated1.5"-thick light brown fine sand layer,dampincreasing gravel content

with some fine to coarse gravel

becomes damp to moist

becomes moist to wet

becomes very dense

with no gravel

Stiff, gray-brown sandy SILT; damp,nonplasticDense, light brown-gray, fine SAND withtrace silt; damp, thin (approx. 3/4" thick)layer of fine to medium sand

Dense, interbedded light brown-gray fineSAND with trace silt, micaceous; andbrown-gray fine to medium SAND withtrace silt; dampFinal depth 46.5 ft bgs, groundwater notobserved

DYNAMIC CONE PENETROMETER

BLOW COUNT

DE

PT

H INSTALLATION ANDCOMMENTS

CORE REC%RQD% MOISTURE CONTENT %

BORING BIT DIAMETER: 3-7/8 inchLOGGING COMPLETED: 1/25/12

TE

ST

ING

MATERIAL DESCRIPTION

PBS PROJECT NUMBER:73006.000

PCC CASCADE NEW ACADEMIC BUILDING & STUDENT CENTER

PORTLAND, OREGON

BORING METHOD: Mud RotaryDRILLED BY: Western States Soil Conservation, Inc. LOGGED BY: B. Portwood

DEPTHFEET

BORING B-11310 Main St.Vancouver, WA 98660Phone: (360) 690-4331Fax: (360) 696-9064

Lat 45°33'50.30"N, Long 122°40'32.51"WAPPROX. BORING B-1 LOCATION:

SA

MP

LE T

YP

E &

INT

ER

VA

L

GR

AP

HIC

LOG

HAMMER EFFICIENCY: 78.1

BO

RIN

G L

OG

73

006_

B1-

8_03

1612

.GP

J D

AT

AT

MP

L.G

DT

PR

INT

DA

TE

: 3/

16/1

2:R

SD

SS

-1S

S-2

SS

-3S

S-4

SS

-5S

S-6

SS

-7S

S-8

SS

-9S

S-1

0S

S-1

1S

S-1

2S

S-1

3

0 50 100

0 50 1000.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

12

15

23

27

27

27

19

26

25

74

20

39

30

0.00.3

1.8

27.0

30.5

38.0

43.0

46.5

Driller reports 12 - 18" layersof sand to sand with gravel

ASPHALT CONCRETE (4 inches thick)BASE ROCK (18 inches thick)Medium dense, dark gray-brown, fine tocoarse SAND with trace silt and finegravel; moist (Flood deposits)

with some fine to coarse gravel, damp

becomes dense

wilth trace to some silt, trace to some fineto coarse gravel, dry to damp, silt matrix

with trace silt, moist to wet

becomes medium dense, trace to somesilt, damp to moist

Medium dense, light brown-gray fineSAND with trace silt; damp

Medium dense, dark brown-gray, fine tocoarse SAND with trace to some fine tocoarse gravel and trace silt; damp

1-inch-thick layer of medium dense, lightbrown, sandy SILT at top of sample

Medium dense, light gray-brown, fineSAND with trace silt; damp, grades finerwith depth within sample

Medium dense, light brown fine SANDwith trace silt; damp, grades coarser withdepth within sample, finely laminated

Final depth 46.5 ft bgs, groundwater notobserved


BLOW COUNT

DE

PT




TE

ST

ING




PORTLAND, OREGON


DEPTHFEET



SA

MP

LE T

YP

E &

INT

ER

VA

L

GR

AP

HIC

LOG


BO

RIN

G L

OG

73

006_

B1-

8_03

1612

.GP

J D

AT

AT

MP

L.G

DT

PR

INT

DA

TE

: 3/

16/1

2:R

SD

SS

-1S

S-2

SS

-3S

S-4

SS

-5S

S-6

SS

-7S

S-8

SS

-9S

S-1

022

-11

0 50 100

0 50 1000.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

17

24

32

32

33

21

16

27

30

22

26

0.00.3

1.8

3.0

17.5

20.0

48.5

01/26/12 Possible perchedzone

Very rocky drilling, 11' - 11.5'

Driller reports no gravel, 31.5'- 35'

ASPHALT CONCRETE (4 inches thick)BASE ROCK (18 inches thick)Loose to medium dense brown SILT withtrace sand; damp, non-plastic (Flooddeposits)Loose, dark brown-gray fine to coarseSAND with trace fine gravel and silt;moist, angular to subangular

becomes dense; gravel grades fine tocoarse

becomes medium dense, damp

Medium dense, dark brown-gray, fine tocoarse GRAVEL with some sand andtrace silt; moist, subrounded tosubangularMedium dense, dark gray-brown, fine tocoarse SAND with trace to some fine tocoarse gravel and trace silt; damp tomoist, sand is angular, gravel issubangular to subrounded

becomes dense

becomes medium dense, no gravel, moistto wet

becomes wet

becomes fine to medium sand, no gravel,moist

Interbedded, dense, light brown, (cont.)


BLOW COUNT

DE

PT




TE

ST

ING




PORTLAND, OREGON


DEPTHFEET



SA

MP

LE T

YP

E &

INT

ER

VA

L

GR

AP

HIC

LOG


BO

RIN

G L

OG

73

006_

B1-

8_03

1612

.GP

J D

AT

AT

MP

L.G

DT

PR

INT

DA

TE

: 3/

16/1

2:R

SD

SH

-1S

S-2

SS

-3S

S-4

SS

-5S

S-6

SS

-7S

S-8

SS

-9S

S-1

0S

S-1

1S

S-1

2

0 50 100

0 50 1000.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

5

45

16

24

20

21

39

39

23

18

22

58.5

71.5

fine SAND with trace silt; moist, dilatant;and medium dense, dark gray-brown, fineto medium SAND; moist; and mediumdense, light brown sandy SILT; moist

Dense to very dense, dark brown-gray,fine to coarse SAND with trace silt; moist,sand is subangular to angular

with trace fine gravel, moist to wet

becomes medium dense to dense

Final depth 71.5 ft bgs, possible perchedgroundwater at approx. 37.5 ft bgs


BLOW COUNT

DE

PT




TE

ST

ING




PORTLAND, OREGON


DEPTHFEET


(continued)


SA

MP

LE T

YP

E &

INT

ER

VA

L

GR

AP

HIC

LOG


BO

RIN

G L

OG

73

006_

B1-

8_03

1612

.GP

J D

AT

AT

MP

L.G

DT

PR

INT

DA

TE

: 3/

16/1

2:R

SD

SS

-13

SS

-14

SS

-15

SS

-16

SS

-17

0 50 100

0 50 10050.0

55.0

60.0

65.0

70.0

75.0

80.0

85.0

90.0

95.0

100.0

32

17

50

39

30

0.00.3

1.8

4.0

43.5

46.5

Lost all mud; pumped grout totry to seal off formationovernight

Continuing slow mud loss

ASPHALT CONCRETE (3 inches thick)BASE ROCK (18 inches thick)Light brown SILT with sand (Flooddeposits)

Very loose, brown fine SAND with tracesilt; wet, grading to medium dense, darkbrown-gray, fine to coarse SAND withtrace silt; moist

with trace fine to coarse gravel


becomes dense, damp

with some fine to coarse gravel to gravellySAND with trace silt

Dense, brown-gray, fine to coarse SANDwtih trace silt; moist

Final depth 46.5 ft bgs, groundwater notobserved


BLOW COUNT

DE

PT




TE

ST

ING




PORTLAND, OREGON


DEPTHFEET



SA

MP

LE T

YP

E &

INT

ER

VA

L

GR

AP

HIC

LOG


BO

RIN

G L

OG

73

006_

B1-

8_03

1612

.GP

J D

AT

AT

MP

L.G

DT

PR

INT

DA

TE

: 3/

16/1

2:R

SD

SS

-1S

S-2

SS

-3S

S-4

SS

-5S

S-6

SS

-7S

S-8

SS

-9S

S-1

0S

S-1

1

0 50 100

0 50 1000.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

19

15

25

27

30

44

24

21

28

28

37

0.00.3

2.3

29.0

34.5

45.5

46.5

01/27/12 Perched zone

P200 = 11%Infiltration test at 5.0 ft bgs

P200 = 1%

P200 = 5%Infiltration test at 20.0 ft bgs;switched to mud rotary aftertest completionDriller reports cobbles at 21.5ft bgs; lost mudVery rocky drilling, 24 ft - 30 ftbgsP200 = 1%

Driller reports formationchange at 34.5 ft bgs

ASPHALT CONCRETE (3 inches thick)BASE ROCK (24 inches thick)

Loose to medium dense, dark brown-grayfine to coarse SAND with trace fine graveland silt; damp, sand is angular tosubangular, gravel is subrounded (Flooddeposits)

becomes moist

with sparse cobbles to 4" diam. in cuttings

becomes damp

grades to some fine to coarse gravel

becomes moist

with occasional cobbles

grades coarser

Dense, gray, sandy GRAVEL with somecobbles and trace silt; moist to wet,subrounded, sand is subangular

Medium dense, light brown-gray, fine tomedium SAND with trace silt; moist towet, sand is subrounded to rounded

becomes wet

Medium dense, light gray-brown, fineSAND with trace silt; dampFinal depth 46.5 ft bgs, perched zone at41 ft bgs

P200SIEV

P200

P200SIEV

P200


BLOW COUNT

DE

PT



BORING BIT DIAMETER: 8-inchLOGGING COMPLETED: 1/27/12

TE

ST

ING




PORTLAND, OREGON

BORING METHOD: Hollow-Stem AugerDRILLED BY: Western States Soil Conservation, Inc. LOGGED BY: B. Portwood

DEPTHFEET



SA

MP

LE T

YP

E &

INT

ER

VA

L

GR

AP

HIC

LOG


BO

RIN

G L

OG

73

006_

B1-

8_03

1612

.GP

J D

AT

AT

MP

L.G

DT

PR

INT

DA

TE

: 3/

16/1

2:R

SD

DM

-1S

S-2

SS

-3S

S-4

SS

-5D

M-6

SS

-7S

S-8

SS

-9S

S-1

0S

S-1

1

0 50 100

0 50 1000.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

46

22

17

26

29

45

23

40

26

21

26

0.00.3

1.8

34.0

46.5

Chatter at 12 ft bgs

Cobbles at 18.5 ft bgs

Steadily losing mud, 25 ft - 30ft bgs

Smooth drilling, 40 ft - 45 ftbgs

ASPHALT CONCRETE (3 inches thick)BASE ROCK (18 inches thick)Medium dense, dark brown-gray fine tocoarse SAND with trace silt; moist to wet(Flood deposits)

with trace fine gravel, damp



becomes dense, grades coarser

becomes medium dense, moist to wet,predominantly coarse sand

becomes dense

becomes medium dense

Medium dense, brown to brown-gray, fineSAND with trace silt; damp, no gravel

becomes dense

Final depth 46.5 ft bgs, no groundwaterobserved


BLOW COUNT

DE

PT




TE

ST

ING




PORTLAND, OREGON


DEPTHFEET



SA

MP

LE T

YP

E &

INT

ER

VA

L

GR

AP

HIC

LOG


BO

RIN

G L

OG

73

006_

B1-

8_03

1612

.GP

J D

AT

AT

MP

L.G

DT

PR

INT

DA

TE

: 3/

16/1

2:R

SD

SS

-1S

S-2

SS

-3S

S-4

SS

-5S

S-6

SS

-7S

S-8

SS

-9S

S-1

0S

S-1

1

0 50 100

0 50 1000.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

21

23

26

29

44

19

37

29

29

23

32

0.00.31.0

2.0

28.0

46.5

ASPHALT CONCRETE (4 inches thick)BASE ROCK (8 inches thick)Light brown sandy SILT (Flood deposits)Loose to medium dense, dark brown-gray,fine to coarse SAND wtih trace silt; moist,sand is angular to subangular

becomes medium dense to dense withtrace fine gravel; damp to moist; gravel issubrounded to subangular

becomes predominantly coarse sand

Interbedded medium dense, light brownfine SAND with trace silt; damp, fewlayers of medium to coarse sand; andmedium dense, dark brown-gray fine tocoarse SAND; damp

Final depth 46.5 ft bgs, no groundwaterobserved


BLOW COUNT

DE

PT




TE

ST

ING




PORTLAND, OREGON


DEPTHFEET



SA

MP

LE T

YP

E &

INT

ER

VA

L

GR

AP

HIC

LOG


BO

RIN

G L

OG

73

006_

B1-

8_03

1612

.GP

J D

AT

AT

MP

L.G

DT

PR

INT

DA

TE

: 3/

16/1

2:R

SD

SS

-1S

S-2

SS

-3S

S-4

SS

-5S

S-6

SS

-7S

S-8

SS

-9S

S-1

0S

S-1

1

0 50 100

0 50 1000.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

30

29

21

27

20

23

15

19

26

27

30

0.00.3

1.3

34.0

46.5

Rocky drilling, 14' - 15'

Driller reports gradual mudloss

ASPHALT CONCRETE (4 inches thick)BASE ROCK (12 inches thick)Medium dense, brown to brown-gray, fineto coarse SAND with trace silt; moist(Flood deposits)


becomes dense, trace to some fine tocoarse gravel, damp to moist

with trace to some cobbles

becomes medium dense, no cobbles

with some fine to coarse gravel

becomes gravelly

becomes fine to coarse SAND with tracegravel and silt

Interbedded medium dense, gray-brown,fine to medium SAND with trace silt, damp

becomes dense

Final depth 46.5 ft bgs; groundwater notobserved


BLOW COUNT

DE

PT




TE

ST

ING




PORTLAND, OREGON


DEPTHFEET



SA

MP

LE T

YP

E &

INT

ER

VA

L

GR

AP

HIC

LOG


BO

RIN

G L

OG

73

006_

B1-

8_03

1612

.GP

J D

AT

AT

MP

L.G

DT

PR

INT

DA

TE

: 3/

16/1

2:R

SD

SS

-1S

S-2

SS

-3S

S-4

SS

-5S

S-6

SS

-7S

S-8

SS

-9S

S-1

0S

S-1

1S

S-1

2S

S-1

3

0 50 100

0 50 1000.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

50.0

15

18

24

33

49

23

26

17

24

24

25

25

36

APPENDIX B Laboratory Tests


April 2, 2012

Project No. 73006.000 B-1

APPENDIX B – LABORATORY TESTS

B1.0 GENERAL

The samples that were obtained during the field explorations were examined in PBS’ laboratory. The physical characteristics of the samples were noted and the field classifications were modified where necessary. During the course of the examination, representative samples were selected for further testing. The laboratory testing program adopted for this investigation included a variety of tests to provide data for the various engineering studies. The testing program on the soil samples included standard classification tests, which consisted of visual examination, moisture contents, and grain-size analyses. The classification tests yield certain index properties of the soils important to an evaluation of soil behavior. The testing procedures and results of the tests are presented in the following paragraphs. Unless noted otherwise, all test procedures followed applicable ASTM standards. B2.0 CLASSIFICATION TESTS

B2.1 Visual Classification

The soils were classified in accordance with the Unified Soil Classification System with certain other terminology, such as the relative density or consistency of the soil deposits, in general accordance with engineering practice. In determining the soil type (that is, gravel, sand, silt or clay) the term which best described the major portion of the sample was used. Modifying terminology to further describe the samples is defined in Appendix A, Terminology Used to Describe Soil and detailed laboratory test results are presented in the Summary of Laboratory Data.

B2.2 Moisture (Water) Contents

Natural moisture content determinations were made on all samples of the fine-grained soils (that is, silts, clays, and silty sands). The natural moisture content is defined as the ratio of the weight of water to dry weight of soil, expressed as a percentage. The results of the moisture content determinations are presented in Appendix A on the logs of the borings and are tabulated on the Summary of Laboratory Data.

B2.3 Grain-Size Analyses

Mechanical grain-size analyses (wet sieve) were conducted on selected soil samples to determine their grain-size distribution. In addition, a No. 200 wash (P200) was completed on samples to determine the portion of soil samples passing the No. 200 sieve (i.e. silt and clay). The results of the mechanical grain-size analyses and P200 testing are presented in Appendix B.

0

10

20

30

40

50

60

70

80

90

100

0.0010.010.11101001,000

PARTICLE-SIZE ANALYSIS TEST RESULTS

U.S. STANDARD SIEVE NUMBERS (ASTM E11)

FINE

GRAVEL SAND FINES

D10(MM)

D5(MM)

GRAVEL(PERCENT)

16.3

7.5

1.4

3.6

0.6

2.1 0.09

5.0

10.0

20.0

25.0

KEYEXPLORATION

NUMBER

CLAYBOULDERS

SAMPLE DEPTH(FEET)

D60(MM)

SAND(PERCENT)

FINES(PERCENT)

D30(MM)

D50(MM)

MOISTURE CONTENT(PERCENT)

3/4"

2.1

4.8 0.5

65

55

11

8

5

5

10 2003" 1 1/2" 1003/8" 404 16 30 50

PARTICLE-SIZE (MM)

PE

RC

EN

T F

INE

R B

Y W

EIG

HT

B-5

B-5

B-5

B-5

COBBLESFINECOARSE COARSE MEDIUM SILT

TEST METHOD: ASTM C136


1310 Main St.Vancouver, WA 98660Phone: (360) 690-4331Fax: (360) 696-9064 PORTLAND, OREGON

PCC CASCADE NEW ACAD BLDG & STUDENT CTR

PARTICLE-SIZE ANALYSIS 73006 PCC CASCADE NEW ACAD BLDG AND STUDENT CTR.GPJ PBS_DATATMPL.GDT PRINT DATE: 2/28/12:RSD

APPENDIX C Site-Specific Seismic Hazard Analysis

Geotechnical Investigation Report Proposed Academic Building and Student Center Portland, Oregon

April 2, 2012

Project No. 73006.000 C-1

APPENDIX C – SITE-SPECIFIC SEISMIC HAZARD ANALYSIS

C1.0 INTRODUCTION

This appendix presents the results of PBS’ seismic site hazard report for the proposed new Academic Building and Student Center. The new building will be located on the south side of N. Jessup Street between N. Mississippi Avenue and N. Albina Avenue in Portland, Oregon. The site location relative to surrounding physical features is shown on Figure 1. These facilities qualify as “Special Occupancy Structures,” in accordance with 2010 OSSC, Chapter 18. A site-specific seismic hazard analysis is therefore required and was conducted in general accordance with Section 1803.7. C2.0 SITE CONDITIONS

C2.1 Geologic Setting

According to published geologic mapping of the site region (Beeson et. al, 1990), the site is underlain by Quaternary fine-grained facies flood deposits of fine sands and silt. In some areas the fine-grained alluvium is underlain by coarse-grained facies of the flood deposits consisting of sands and gravels. These flood deposits were deposited from the glacial outburst floods of glacial Lake Missoula during the Pleistocene. The flood deposits in the area are on the order of 100 feet thick. Gravels of the Troutdale Formation are expected below the flood deposits to the bedrock basement of Columbia River Basalt at a depth of approximately 375 feet bgs. C2.2 Subsurface Conditions

PBS explored subsurface conditions by drilling eight (8) borings to depths between 46.5 to 71.5 feet bgs. Details of our field explorations and subsurface conditions are provided in Sections 2.3 of the Geotechnical Engineering Report. The interpreted geologic profile, shown in Table C-1 below, is based on our explorations and review of geologic maps of the area.

Table C-1: Estimated Geologic Profile

Profile Depth (feet)

GEOLOGIC UNIT

Shear Wave Velocity

(feet per second)

0 to 10 Loose to medium dense, sand with interbeds of silt (Missoula Flood Deposits)

600 - 800

10 to 100 Medium dense to dense, fine to coarse sand (Missoula Flood Deposits)

800 - 1,200

100 to 375 Very dense, gravel (Troutdale Formation) 1,500 - 2,000

>375 Basalt (Columbia River Basalt) >2,500

C2.3 Groundwater Conditions

Possible perched zones were observed in Boring B-3 at 37.5 feet bgs, and in Boring B-5 at 41.0 feet bgs. Groundwater was not observed in the other borings at the time of our exploration. Nearby well logs (OWRD, 2008) indicate groundwater in the area is on the order of 150 feet bgs.


April 2, 2012


C3.0 SEISMICITY

C3.1 Historic Seismicity

Information on the historical record of Oregon earthquakes dates back to approximately 1841. Prior to 1900, approximately 30 earthquakes were recorded. Several hundred earthquakes were recorded in the state since 1900, especially since the 1980s when the University of Washington established a recording station. Catalogues of earthquake events are available from Berg and Baker (1963); Johnson, et al. (1994); and Wong, et al. (2000). Also provided is a summary of Oregon earthquakes.

Oregon as a region has a relatively low to medium record of historical seismicity. Clusters of earthquakes are recorded in the Klamath Falls region (Magnitude [M] = 6.0), northeast Oregon (M = 5.0 Umatilla and M = 6.5 Milton Freewater), and the Portland-Northern Willamette Valley (M = 5.6 Mount Angel).

C3.2 Seismic Sources

There are several types of seismic sources in the Pacific Northwest which are outlined below (Wong & Silva, 2006). Volcanic sources beneath the Cascade Range are not considered further in this study; since they rarely exceed about M = 5.0 in size and, thus, are not considered to pose a significant ground-shaking hazard to the project site.

C3.2.1 Cascadia Subduction Zone – Interface Earthquakes

The Cascade Subduction Zone (CSZ) megathrust represents the boundary between the subducting Juan de Fuca tectonic plate and the overriding North American tectonic plate. Recurrence intervals for subduction zone earthquakes are based on studies of the geologic record. Based on these studies, recurrence interval estimates have been generated ranging from about 300 to 600 years. Geologic evidence suggests the most recent earthquake occurred in January 1700, probably ruptured much of the approximately 1,200-kilometer length of the CSZ, and was estimated at M = 7.0 to 9.0. The OSSC recommends using a minimum M = 8.5, which likely corresponds to a 10 percent chance of being exceeded in 50 years. A magnitude M = 9.0 event likely corresponds to a 2 percent chance of being exceed in 50 years. The horizontal distance from the edge of the CSZ megathrust, located offshore from Portland, is approximately 150 kilometers (km) with an uncertainty of ±50 km (Wong & Silva, 2000).

C3.2.2 Intraslab Earthquakes

A number of researchers have noted the complete absence of intraslab seismicity in Western Oregon (Ludwin et al., 1991; Rogers et al., 1996). With the possible exception of 1873 Richter Magnitude 6.75 Crescent City Earthquake, no moderate to large intraslab earthquakes have occurred in the CSZ from south of Puget Sound to Cape Mendocino. These earthquakes are postulated to have a deep focus of 40 to 70 km in the subducted Juan de Fuca Plate (Wong, 2005), and theoretical magnitudes of up to 7.8. These earthquakes are expected to have epicenters for 50 to 100 km from the site. The 2010 OSSC recommends evaluating a minimum M = 7. C3.2.3 Crustal Earthquakes and Faults

Due to their proximity, the crustal faults are possibly the most significant seismic sources in the Portland metropolitan area. There are at least 55 faults or fault zones in northwest Oregon and southwest Washington (within 200 km of Portland). However, recorded seismicity due to crustal sources in the site vicinity, is relatively


April 2, 2012


limited with only a few recorded earthquakes exceeding M = 5 in the Portland Region. Studies (Yelin & Patton, 1991) of small earthquakes in the region indicate most crustal earthquake activity is occurring at depths of 10 to 20 km. The three most important faults in the site vicinity include the East Bank Fault, Portland Hills Fault, and the Oatfield Fault. The nearest mapped fault is the East Bank Fault which is located approximately 1.6 km southwest of the site and consists of a northwest-trending fault (Madin, 1990; Geomatrix, 1995). The East Bank Fault is not listed as active or potentially active (Geomatrix, 1995; Wong, 2000). The Portland Hills Fault is located approximately 4 km to the southwest of the site and consists of a northwest-trending fault (Madin, 1990; Geomatrix, 1995). The Portland Hills Fault is not listed as active or potentially active (Geomatrix, 1995; Wong, 2000).The Oatfield Fault is located less than 8 km southwest of the site. The resulting peak ground acceleration (PGA) for a 10 percent probability of exceedance in 50 years is 0.19g. The fault zones within this vicinity are listed in Table C-2.

Table C-2: Faults Within the Site Vicinity

Fault Zone Name

Proximity to Site (Surface projection in km)

East Bank 1.6

Portland Hills 4.1

Oatfield 7.7

East Bank Fault: “The East Bank fault lies in the Portland basin. The fault lies a few km east of and generally runs parallel to the Portland Hills fault, which forms the southwestern margin of the basin. No fault scarps on surficial Quaternary deposits have been described along the fault, and the fault is mapped as buried by latest Pleistocene Missoula flood deposits.” (Personius, 2002) Portland Hills Fault: “The Portland Hills fault is mapped along the northeastern margin of the Tualatin Mountains (Portland Hills) and the southwestern margin of the Portland basin. The crest of the Portland Hills is defined by the northwest-striking Portland Hills anticline. Displacement on the Portland Hills fault is poorly known and controversial. No fault scarps on surficial Quaternary deposits have been described along the fault, but some geomorphic and geophysical evidence suggest Quaternary displacement.” (Personius, 2002) Oatfield Fault: “The Oatfield fault forms northeast-facing escarpments in volcanic rocks of the Miocene Columbia River Basalt Group in the Tualatin Mountains and northern Willamette Valley. No fault scarps on surficial deposits have been described, but exposures in a light-rail tunnel showing offset of Boring Lava across the fault indicate Quaternary displacement.” (Personius, 2002)


April 2, 2012


C4.0 SEISMIC HAZARDS

Based on our subsurface exploration, literature review, analysis, and experience, a summary of the seismic hazards at the site are as follows:

Earthquake-Induced Landslides – The proposed development is in an area with relatively flat site topography and relatively deep groundwater elevation. The risk of landslides at the site is low and we do not consider earthquake-induced landslides to be a significant hazard at this site.

Liquefaction/Settlement – Based on a review of the Relative Seismic Hazard Map for the

Portland Metro Area (DOGAMI IMS-1), the site is located in an area of low relative liquefaction hazard. The site is noted as having potentially liquefiable sediments if the groundwater were to rise seasonally (DOGAMI GMS-79).

Our analyses indicate that the risk of liquefaction settlement at the site is low. This is primarily due to the medium dense relative density of site soils and relatively deep depth to groundwater.

Fault Surface Rupture – The nearest mapped fault zone is more than 1 km from the site. As

such, the risk of fault rupture at the project site is low.

Tsunami Inundation/Seiche/Subsidence – The site is inland and elevated away from

tsunami inundation and subsidence zones and away from large bodies of water that may develop seiches. Accordingly, tsunami or seiche events do not represent a seismic hazard to the site.

Amplification – Based on a review of the Relative Seismic Hazard Map for the Portland

Metro Area (DOGAMI IMS-1), the site is located in an area with a high relative amplification of PGA. Site amplification is further classified in DOGAMI GMS-79 as ranging from approximately 1.4 to 1.8.


April 2, 2012


C5.0 REFERENCES

Atwater, B. F., et al. (1995). Summary of Coastal Geologic Evidence for past Great Earthquakes at

the Cascadia Subduction Zone. Earthquake Spectra, 11. p. 1-18 EERI. Berg, J.W., & Baker, C. D. (1963). Oregon Earthquakes: 1841 – 1958. Seismological Society of

America Bulletin, v. 53. p. 95-108. Boore, D.M., et al. (1993). Estimation of response spectra and peak accelerations from Western

North American Earthquakes: An interim report. Open File Report 93-509, USGS Reston, Virginia. 72 pp.

Geomatrix Consultants. (1995). Seismic Design Mapping, State of Oregon. Prepared for Oregon

Department of Transportation of Salem, Oregon. Project No. 2442. Johnson, J. D., et al. (1994). Earthquakes Database for Oregon: 1833 – 10/25/1993. Oregon

Department of Geology and Mineral Industries. Open File Report O-94-04. Ludwin, R. S., Weaver, C. S., & Crosson, R. S. (1991). Seismicity of Washington and Oregon.

(Slemmons, D.B., Engdahl, E.R., Blackwell, E., and Schwartz, D., eds.). Neotectonics of North America, Decade of North American Geology, GSMV-1. Geological Society of America. p. 77-98.

Mabey, M. A., Madin, I. P., Youd, T. L., and Jones, C. F. (1993). [Map]. Earthquake Hazard Maps of

the Portland Quadrangle, Mulnomah and Wahington Counties, Oregon, and Clark County Washington. Oregon Department of Geology and Mineral Industries. Geologic Map Series (GMS) 79.

Mabey, M. A., Black, G, Madin, I. P., Meier, D., Youd, T. L., Jones, C., and Rice, B., (1997) [Map],

Relative Earthquake Hazard Map of the Portland Metro Region, Clackamas, Multnomah, and Washington Counties, Oregon. Oregon Department of Geology and Mineral Industries. Interpretive Map Series (IMS) 1.

Madin, I. P. (1990). Earthquake-Hazard Geology Maps of the Portland Metropolitan Area, Oregon.

Oregon Department of Geology and Mineral Resources. Open File Report 0-90-2. NCEER (National Center for Earthquake Engineering Research). (2001, October). Liquefaction

resistance of soils: Summary report from the 1996 NCEER and 1998 NCEER/NSF workshops on evaluation of liquefaction resistance of soils. Journal of Geotechnical and Geoenvironmental Engineering.

O’Connor, J. E., Sarna-Wojcicki, A., Wozniak, K. C., Polette, D. J., & Fleck, R. J. (2001). Origin,

extent, and thickness of Quaternary geologic units in the Willamette Valley, Oregon. U.S. Geological Survey Professional Paper 1620.

OWRD (Oregon Water Resources Department). (1991). Accessed on May 2008 from website:

http://apps2.wrd.state.or.us/apps/gw/well_log/Default.aspx.


April 2, 2012


Personius, S.F., compiler (2002). Quaternary fault and fold database of the United States: U.S. Geological Survey website, http://earthquakes.usgs.gov/regional/qfaults, accessed 02/28/2012 10:30 AM.

Peterson, C. P., Kulm, L. D., & Gray, J. J. (1986). Geologic map of the ocean floor off Oregon and

the adjacent continental margin. Oregon Department of Geology and Mineral Industries. Geological Map Series GMS-42.2.

Rogers, A. M., Walsh, T. J., Kockelman, W. J., & Priest, G. R. (1996). Earthquake hazards in the

Pacific Northwest: An overview. (Rogers, A. M., Walsh, T. J., Kockelman, W. J., and Priest, G. R., eds.) Assessing earthquake hazards and reducing risk in the Pacific Northwest. U.S. Geological Survey Professional Paper 1560. p. 1-67.

USGS (U.S. Geological Survey). (2007). Accessed May 2008 from the U.S. Geological Survey

website: http://earthquake.usgs.gov/regional/qfaults/or/slm.html. USGS (U.S. Geological Survey). (2007). Earthquake hazards program: Conterminous states

probabilistic maps and data. Wong, I., et al. (2000). Earthquake scenario and probabilistic ground shaking maps for the Portland,

Oregon, metropolitan area. State of Oregon Department of Geology and Mineral Industries, IMS 16. 11 Sheets, scale 1:62,500.

Yelin, T. S. & Patton, H. J. (1991, February). Seismotectonics of the Portland, Oregon Region.

Bulletin of the Seismological Society of America, 81:1. pp. 109-130. Youngs, R. R., et al. (1988). Near field ground motions on rock for large subduction earthquakes,

proceedings, earthquake engineering and soil dynamics II: Recent advances in ground motion evaluations. GSP 20. New York: ASCE. pp. 445-462.

APPENDIX D

General Construction Information


April 2, 2012

Project No. 73006.000

D-1

APPENDIX D – GENERAL CONSTRUCTION INFORMATION

D1.0 STRUCTURAL FILL

Structural fills should be placed over subgrade, which has been prepared in conformance with the “Site Preparation” and “Wet-Weather/Wet-Soil Considerations” sections of this report. A wide range of material may be used as structural fill; however, all material used should be free of organic matter or other unsuitable materials and should meet the specifications provided in the 2008 Oregon Standard Specifications for Construction, Oregon Department of Transportation (ODOT SS), Section 00330 – Earthwork, depending on the application. A brief characterization of some of the acceptable materials and our recommendations for their use as structural fill is provided below.

D1.1 Borrow Material

Borrow material for general structural fill construction should meet the requirements set forth in ODOT SS 00330.12 – Borrow Material. When used as structural fill, native soils should be placed in lifts with a maximum uncompacted thickness of approximately 8 inches and compacted to not less than 92 percent of the maximum dry density, as determined by ASTM D 1557. If suitable common borrow material is not available, use of selected general backfill as specified in ODOT SS 00330.13 – Selected General Backfill should be considered. D1.2 Selected Granular Backfill

Selected granular backfill used during periods of wet weather for structural fill construction should meet the specifications provided in ODOT SS 00330.14 – Selected Granular Backfill. Selected granular backfill should be placed in lifts with a maximum uncompacted thickness of 8 to 12 inches and be compacted to not less than 92 percent of the maximum dry density, as determined by ASTM D 1557. Selected Stone backfill (ODOT SS 00330.15) and Stone Embankment Material (ODOT SS 00330.16) can also be used for the construction of general structural fill. However, we recommend that the larger size material (>6 inches) should be placed in the deeper portions of the fill and should not be used within 2 feet of the pavement subgrade. Considerations should also be given to the future excavation of utilities through this material, since it is relatively difficult to excavate through larger-size material. D1.3 Trench Backfill

Pipe bedding placed to uniformly support the barrel of pipe should meet specifications provided in ODOT SS 00405.12 – Pipe Zone Bedding. The pipe zone that extends from the top of the bedding to at least 8 inches above utility lines should consist of material prescribed by ODOT SS 00405.13 – Pipe Zone Material. The pipe zone material should be compacted to at least 90 percent of the maximum dry density, as determined by ASTM D 1557, or as required by the pipe manufacturer. Under pavements, paths, slabs, or beneath building pads, the remainder of the trench backfill should consist of well-graded granular material with less than 10 percent by weight passing the U.S. Standard No. 200 Sieve, and should meet standards prescribed by ODOT SS 00405.14 – Trench Backfill, Class B or D. This material should be compacted to at least 92 percent of the maximum dry density, as determined by ASTM D 1557 or as required by the pipe manufacturer. The upper 2 feet of the trench backfill should be compacted to at least 95 percent of the maximum dry density, as determined by ASTM D 1557. Controlled


April 2, 2012


D-2

low-strength material (CLSM), ODOT SS 00405.14 – Trench Backfill, Class E, can be used as an alternative. Outside of structural improvement areas (e.g., pavements, sidewalks, or building pads), trench material placed above the pipe zone may consist of general structural fill materials that are free of organics and meet ODOT SS 00405.14 – Trench Backfill, Class A. This general trench backfill should be compacted to at least 90 percent of the maximum dry density, as determined by ASTM D 1557 or as required by the pipe manufacturer or local jurisdictions. D1.4 Stabilization Material

Stabilization rock should consist of pit or quarry run rock that is well-graded, angular, crushed rock consisting of 4- or 6-inch-minus material with less than 5 percent passing the U.S. Standard No. 4 Sieve. The material should be free of organic matter and other deleterious material. ODOT SS 00330.16 – Stone Embankment Material can be used as a general specification for this material with the stipulation of limiting the maximum size to 6 inches. D1.5 Retaining Wall Backfill

Backfill material placed behind retaining walls and extending a horizontal distance of 0.5H, where H is the height of the retaining wall, should consist of granular material meeting ODOT SS 00510.12 – Granular Wall Backfill which recommends ODOT SS 02630.11 – Open-Graded Aggregate. We recommend the granular wall backfill be separated from general fill, native soil, and/or topsoil using a geotextile fabric that meets the requirements provided in ODOT SS 02320.10 – Geosynthetics, Acceptance, and ODOT SS 02320.20 – Geotextile Property Values, Table 02320-1 for separation geotextile. The geotextile should be installed in conformance with ODOT SS 00350.00 – Geosynthetic Installation. The wall backfill should be compacted to a minimum of 92 percent of the maximum dry density, as determined by ASTM D 1557. However, backfill located within a horizontal distance of 3 feet from the retaining walls should only be compacted to approximately 90 percent of the maximum dry density, as determined by ASTM D 1557. Backfill placed within 3 feet of the wall should be compacted in lifts less than 6-inches thick using hand-operated tamping equipment (such as jumping jack or vibratory plate compactors).

D1.6 Granular Drain Backfill Material

Backfill in a 2-foot zone against the back of retaining walls should consist of granular drain rock meeting the specifications provided in ODOT SS 00430.11 – Granular Drain Backfill Material. The granular drain rock should be wrapped in a geotextile fabric that meets the specifications provided in ODOT SS 02320.10 Geosynthetics, Acceptance, and ODOT SS 02320.20 – Geotextile Property Values, Table 02320-1 for drainage geotextile. The geotextile should be installed in conformance with ODOT SS 00350.00 – Geosynthetic Installation. D1.8 Aggregate Base Rock

Aggregate base rock below asphalt concrete pavements should be clean, crushed rock or crushed gravel. The base aggregate should contain no deleterious materials, meet specifications provided in ODOT SS 02630.10 – Dense-Graded Aggregate, and have less than 5 percent by weight passing the U.S. Standard No. 200 Sieve. The aggregate base


April 2, 2012


D-3

rock should be compacted to at least 95 percent of the maximum dry density, as determined by ASTM D 1557.

D1.9 Recycled Concrete, Asphalt, and Base Rock

Asphalt pavement, concrete, and base rock from the existing site parking lot can be re-used in structural fills provided no particles greater than 6 inches are present and no hazardous or deleterious material is present. It also must be thoroughly mixed with soil, sand, or gravel such that there are no voids between the fragments. The recycled material should generally conform to ODOT SS 00330.12 – Borrow Material. This material should be approved by the engineer before use.

D2.0 TEMPORARY SLOPES

Current plans do not include permanent slopes and excavation for the basement parking garage will likely require shoring. For temporary cut slopes up to 10 feet tall may be inclined at 2H:1V. Access roads and pavements should be located at least 5 feet from the top of temporary slopes. Surface water runoff should be collected and directed away from slopes to prevent water from running down the face of the slope. These excavations should be made in accordance with applicable OSHA and State regulations. The contractor is responsible for adherence to the OSHA requirements.


April 2, 2012


D-4

TABLE D-1: OREGON STATE STANDARDS FOR CONSTRUCTION (ODOT SS)

The Contractor should refer to the following 2008 Oregon Standard Specifications for Construction (ODOT SS, 2008) with regard to backfill materials and geosynthetics. Local or municipal standards may also apply. The Contractor should check with the jurisdictional permitting office to determine applicability of local or municipal standards. ODOT SS 00330.12 – Borrow Material ODOT SS 00330.13 – Selected General Backfill ODOT SS 00330.14 – Selected Granular Backfill ODOT SS 00330.16 – Stone Embankment Material ODOT SS 00350.00 – Geosynthetic Installation ODOT SS 00350.40 – Geosynthetic Construction, General Requirements ODOT SS 00405.12 – Pipe Zone Bedding ODOT SS 00405.13 – Pipe Zone Material ODOT SS 00405.14 – Trench Backfill ODOT SS 00430.11 – Granular Drain Backfill Material ODOT SS 00510.12 – Granular Wall Backfill ODOT SS 00744.03 – Reclaimed Asphalt Pavement (RAP) Material ODOT SS 00744.11 – Asphalt Cemented and Additives ODOT SS 02320.10 – Geosynthetics, Acceptance ODOT SS 02320.20 – Geotextile Property Values ODOT SS 02630.10 – Dense-Graded Aggregate ODOT SS 02630.11 – Open-Graded Aggregate

geotechnical investigation report - portland, oregon

Documents