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Report (2) r � /'t �! ocr RECEIVE r r r r r c r r o R Beav SW OR 9 Avenue N<<J\ 0 2 2021 Beaverton,oR 97ooa-n72 CITY OF TIGARD p 1 503-641-3478 f 503-644-8034 BUILDING DIVISION June 9, 2017 8970G O OTCOi-INICAL RPT < o 00 cry r� r rc < •,. Tigard-Tualatin School District 6960 SW Sandburg Street Tigard, OR 97223 < Attention: Debbie Pearson/DAY CPM Services, LLC °`° SUBJECT: Geotechnical Investigation 51 T 2 0 2(— 00 0 Z 0 Durham Education Center Tigard, Oregon QD i•f 0 S'W D u Krikft4 RD At your request, GRI completed a geotechnical investigation for the planned improvements at the Durham Education Center in Tigard, Oregon. The Vicinity Map, Figure 1, shows the general location of the site. The purpose of the investigation was to evaluate subsurface conditions at the site and develop geotechnical recommendations for use in the design and construction of the proposed improvements. The investigation included a review of existing geotechnical information for the site and surrounding area, subsurface explorations, laboratory testing, and engineering analyses. As part of our investigation, GRI completed a site- specific seismic-hazard evaluation to satisfy the requirements of the 2012 International Building Code (IBC), which was adopted by the 2014 Oregon Structural Specialty Code (OSSC). This report describes the work accomplished and provides conclusions and recommendations for use in the design and construction of the proposed project. PROJECT DESCRIPTION We understand a new school and parking lot will be constructed at the Durham Education Center under the 2016 Tualatin-Tigard School District Bond Program. The Site Plan, Figure 2, shows the locations of the new school building and parking lot with respect to the existing school building. Based on our review of the 100% Schematic Design Plans, we understand the new building will consist of a two-story, at-grade structure that encompasses approximately 12,740 sq ft. The at-grade level of the structure will generally house classrooms, office space, a commons area, bathrooms, and a kitchen, and the above-grade level will house additional classrooms and bathrooms. Although structural loads for the new building are not currently available, we anticipate the maximum column and wall loads will be less than 200 kips and 4 kips/ft, respectively. We understand the at-grade level of the building will have a finished floor elevation of 162 ft. We anticipate cuts and fills to establish grade across the site will be minimal. We understand a new parking lot will be constructed immediately east of the new building. The parking lot will connect into SW 79th Avenue and consist of a drive lane, parking stalls, and a trash-enclosure area. We anticipate the drive lane and parking stalls will be paved with asphalt concrete (AC) pavement and the trash-enclosure area will be paved with Portland cement concrete (PCC) pavement. We understand water-quality facilities will be constructed south of the new building and parking lot adjacent to SW 79th Avenue and will serve as infiltration facilities to accommodate stormwater runoff. We anticipate the water-quality facilities will consist of shallow swales with overflow pipes that discharge to the sewer. Providing geotechnical,pavement,and environmental consulting services since 7984 SITE DESCRIPTION Gencrzl The noject site is dev3loped with an existing school and auxiliary structure, a paved basketball court and parking lot, and a grass field. The proposed new building will be bordered by SW Durham Road and the existing school on the north, the grass field on the east, SW 79th Avenue on the south, and the existing school anc aax•liz_ry structure on the west. The parking lot will be constructed in the grass field immediately east of the new sc;iool The existing school and auxiliary structure will remain in their current configuration, and the existing parking lot will be removed as part of this project. Review of satellite imagery and our observations at the site indicate the ground surface gently slopes downward from west to east across the site. Geology The site is mantled by soils of the Willamette Silt Formation (Madin, 1990). In general, Willamette Silt is composed of unconsolidated beds and lenses of silt and fine-grained sand. Stratification within this formation commonly consists of 4- to 6-in.-thick beds, although beds up to 10 to 15 ft thick are also common. In some areas, the silt is massive and the bedding is indistinct or nonexistent. The Willamette Silt is brown but typically grades to gray below a depth of about 40 to 50 ft. SUBSURFACE CONDITIONS General Subsurface materials and conditions at the site were investigated on May 22 and 26, 2017, with one boring, designated B-1; one cone penetrometer test (CPT) sounding, designated CPT-1; two dilatometer (DMT) soundings, designated DMT-1 and DMT-2; three hand-augered borings, designated HA-1 through HA-3; and three Kessler Dynamic Cone Penetrometer (DCP) probes, designated DCP-1 through DCP-3. The boring was advanced to a depth of about 91.5 ft, the CPT probe to a depth of 79 ft, the DMT soundings to a depth of about 41 ft, and the hand-augered borings to depths of about 4.5 to 5.5 ft below existing site grades. The DCP probes were completed in the hand-augered boreholes at depths of about 0.5 to 2.5 ft below existing site grades. The approximate locations of the explorations completed for this investigation are shown on Figure 2. Logs of the boring, CPT probe, DMT soundings, and hand-augered borings are provided on Figures 1A through 7A. The field and laboratory programs conducted to evaluate the physical engineering properties of the materials encountered in the explorations are described in Appendix A. The terms and symbols used to describe the materials encountered in the explorations are defined on Tables 1A through 3A and in the attached legend. Sampling Disturbed and undisturbed soil samples were obtained from the boring at 2.5-ft intervals of depth in the upper 15 ft, 5-ft intervals to a depth of 60 ft, and 10-ft intervals below 60 ft. Disturbed soil samples were obtained using a 2-in.-outside-diameter (O.D.) standard split-spoon sampler (SPT). Penetration tests were conducted by driving the samplers into the soil a distance of 18 in. using a 140-lbs hammer dropped 30 in. The number of blows required to drive the SPT sampler the last 12 in. is known as the Standard Penetration Resistance, or SPT N-value. SPT N-values provide a measure of the relative density of granular soils and the relative consistency of cohesive soils. Relatively undisturbed soil samples were collected by pushing a 3-in.- O.D. Shelby tube into the undisturbed soil a maximum of 24 in. using the hydraulic ram of the drill rig. The soil in the Shelby tubes was extruded in our laboratory and Torvane shear strength measurements were recorded on selected samples. CGR1 2 r Pf fr Cr C r C C rC CC r r • P 1 P r P ( r IC r r r P r r f I r P r r r r r r f r CI r r C f CC Cr C C C r r Cr Soils CC r me nrr Cr i?n ha ft C n r8n For the purpose of discussion, the soils disclosed by our investigation h"ae'e beer groped rrtt .e following categories based on their physical characteristics and engineering propectres: ,.;20 ` "Rn Of r rrr fry 1. PAVEMENT ere oee e r er cc 2. FILL e R ® © RReeer r e r r R R e r r, C CCC CC to c C 3. SILT and SAND n n Cant f, f• R C f CCP^ e C C (' CCU` 4. SILT The following paragraphs provide a detailed description of the soil units encountered in the explorations and a discussion of the groundwater conditions at the site. 1. PAVEMENT. Explorations B-1, CPT-1, DMT-1, and DMT-2 were advanced in existing paved areas and encountered approximately 3 in. of AC pavement at the ground surface. The pavement is underlain by about 10 in. of crushed-rock base (CRB) course. 2. FILL. Silt fill was encountered at the ground surface in explorations HA-1 and HA-2 and beneath the pavement in explorations B-1, CPT-1, DMT-1, and DMT-2. The silt fill extends to depths of about 2 to 5 ft below the ground surface and is generally brown to brown mottled gray. The silt fill contains up to a trace of clay, a trace of subangular to subrounded gravel, and a variable amount of fine- to coarse-grained sand ranging from some sand to sandy. Wood debris was present throughout the unit in explorations B-1 and HA-2. The relative consistency of the silt fill is soft to very stiff based on an N-value of 4 blows/ft, CPT tip- resistance values of about 10 to 42 tsf, DMT constrained modulus values of 30 to 540 tsf, and visual observation during hand-auger excavation and is typically medium stiff to stiff. The natural moisture content of the silt fill ranges from 26 to 30%. 3. SILT and SAND. Interbedded layers of silt and sand were encountered at the ground surface in exploration HA-3 and beneath the silt fill in explorations B-1, CPT-1, DMT-1, DMT-2, HA-1, and HA-2. The interbedded layers of silt and sand extend to depths of 55 to 60 ft, and explorations DMT-1, DMT-2, and HA-1 through HA-3 were terminated in the deposit at depths of about 4.5 to 41 ft. The thicknesses of the interbedded layers typically range from about 1 in. to 10 ft; however, layers up to 23 ft thick were encountered in exploration B-1. The soils are generally brown with varying degrees of rust mottling and grade to gray below a depth of 50 ft. In general, the silt has a variable clay content ranging from trace to some clay and contains a variable amount of fine-to medium-grained sand ranging from trace sand to sandy; the sand is fine to medium grained and contains a variable amount of silt ranging from trace silt to silty. The relative consistency of the silt soils is soft to hard based on N-values of 11 to 21 blows/ft, a Torvane shear strength value of 0.3 tsf, CPT tip-resistance values of about 20 to 140 tsf, DMT constrained modulus values of about 80 to 1,060 tsf, and visual observation during hand-auger excavation and is typically medium stiff to a depth of 10 ft and stiff below. The relative density of the sand soils is loose to very dense based on N-values of 11 to 35 blows/ft, CPT tip resistance values of about 30 to 260 tsf, and DMT constrained modulus values of about 275 to 1,500 tsf and is typically medium dense. Using the DCP test results, we estimate the California bearing ratio (CBR) value of the silt soils ranges from 3 to 7%. The natural moisture contents of the silt and sand soils range from 25 to 37% and 20 to 30%, respectively. G ®® A one- dimensional consolidation test was performed on a interbedded silt layer obtained at a depth of 5.5 ft in ex;,lo•at;on 8-1. Test, resuris indicate the silt is overconsolidated and exhibits relatively low comp-esslmity in the preconsolidated range of pressures and moderate compressibility in the normally consolidated range of pressures, see Figure 8A. 4. SILT._ Silt was encountered beneath interbedded layers of silt and sand in explorations B-1 and CPT-1 and extended to the raxirh-um depth explored of 91.5 ft. The silt is gray, has a variable clay content ranging from trace clay toclayey, and contains a variable amount of fine-grained sand ranging from trace to some sand. Organics were encountered in the unit at a depth of 90 ft in exploration B-1. The silt is stiff to hard based on N-values of 11 to 38 blows/ft and CPT tip-resistance values of about 20 to 350 tsf and is typically very stiff. The natural moisture content of the silt ranges from 28 to 49%. Explorations B-1 and CPT-1 were terminated in silt at depths of about 91.5 and 79 ft, respectively. Groundwater Boring B-1 was completed using mud-rotary drilling techniques, which do not allow the measurement of groundwater levels at the time of drilling. Groundwater was not encountered in the hand-augered borings at the time of exploration. Our experience in the project area and review of U.S. Geological Survey (USGS) groundwater data suggest the regional groundwater level occurs at a depth of about 25 ft below the ground surface. We anticipate the local groundwater level typically occurs at a depth of 20 to 25 ft below the ground surface during the normal dry summer and fall months. However, due to the fine-grained soils that mantle the site, it should be anticipated that perched groundwater conditions may approach the ground surface during the wet winter and spring months or during periods of heavy or prolonged precipitation. Infiltration Testing On May 26, 2017, two falling-head infiltration tests, designated I-1 and 1-2, were conducted at depths of about 4 and 5.5 ft, respectively, at the approximate locations shown on Figure 2. The infiltration tests were completed in general accordance with the City of Portland's 2016 Storm water Management Manual(SMM). Details regarding the infiltration testing methods are provided in Appendix A. The unfactored, field- measured infiltration rates recorded at specific depths within a specific soil unit are tabulated below. Test Depth of Average Infiltration Location Infiltration Test,ft Rate,in./hr Soil Classification I-1 4.0 0 SILT 1-2 5.5 0 SILT CONCLUSIONS AND RECOMMENDATIONS General Subsurface explorations completed for this investigation indicate the site is mantled with up to 5 ft of medium-stiff to stiff silt fill underlain by interbedded layers of medium-stiff to stiff silt and medium-dense sand. The interbedded layers of silt and sand extend to depths of 55 to 60 ft and are underlain by very stiff silt. We anticipate the local groundwater level typically occurs at depths of 20 to 25 ft below the ground surface throughout the year; however, perched groundwater may approach the ground surface during the wet winter months and following periods of intense or prolonged precipitation. R® 4 • • r re Cr re f r f r rf f f f f e r r , f f f f P F Cr Cr t r f f (ft f f off f f f ✓ f f f f f f f f r f f f f f f f f f In our opinion, foundation support for new structural loads can be provided by conventional ,spread spread and f: ee ° rf mce wall foundations established in firm, undisturbed, native silt orec^orr ted°$truct.FraL f Ij. i fe primary geotechnical considerations associated with construction of the oroposec buildin =anc- associated tee ee eee < ff f( 4 improvements include the presence of fine-grained soils at the ground surface that are extremely sensitive to moisture content, the presence of shallow fill soils, and the potential ef9r shallow, Rerchp1l groundwater conditions. The following sections of this report provide our conclusionsanJ tern reef datibns for use in ✓ f rrf rrf fr f the design and construction of the project. r r f < f f f f e e C r ( Crory Seismic Considerations General. We understand the project will be designed in accordance with the 2012 IBC with 2014 OSSC modifications. For seismic design, the 2012 IBC references the American Society of Civil Engineers (ASCE) document 7-10, titled "Minimum Design Loads for Buildings and Other Structures" (ASCE 7-10). A site- specific seismic-hazard evaluation was completed for the project in accordance with the 2014 OSSC. Details of the site-specific seismic-hazard evaluation and the development of the recommended response spectra are provided in Appendix B. Code Background. The 2012 IBC and ASCE 7-10 seismic hazard levels are based on a Risk-Targeted Maximum Considered Earthquake (MCER), with the intent of including the probability of structural collapse. The ground motions associated with the probabilistic MCER represent a targeted risk level of 1% in 50 years probability of collapse in the direction of maximum horizontal response with 5% damping. In general, these risk-targeted ground motions are developed by applying adjustment factors of directivity and risk coefficients to the 2% probability of exceedance in 50 years, or 2,475-year return period, hazard level (MCE) ground motions developed from the 2014 USGS Unified Hazard Tool. The risk-targeted probabilistic values are also subject to a deterministic limit. The code-based ground-surface MCER-level spectrum is typically developed using the mapped bedrock spectral accelerations, Ss and Si,and corresponding site coefficients, Fa and F",to account for site soil conditions. Site Response. In accordance with Section 20.4.2 of ASCE 7-10, the site is classified as Site Class D, or a stiff-soil site, based on an estimated Vssoof about 900 ft/sec in the upper 100 ft of the soil profile. However, our analysis has identified a potential risk of seismically induced settlement at the site. In accordance with ASCE 7-10, sites with soils vulnerable to failure or collapse under seismic loading should be classified as Site Class F, which requires a site-specific site-response analysis unless the structure has a fundamental period of vibration less than or equal to 0.5 sec. The design response spectrum for sites with structures having a fundamental period of less than or equal to 0.5 sec can be derived using the non-liquefied subsurface profile. For periods greater than 0.5 sec, the code requires a minimum spectral response value equal to 80% of Site Class E. We anticipate the new structure will have a fundamental period of less than 0.5 sec; therefore, the code- based Site Class D conditions are appropriate for design of the structure. The maximum horizontal-direction spectral response accelerations were obtained from the USGS Seismic Design Maps for the coordinates of 45.4038° N latitude and 122.7597° W longitude. The Ss and Si parameters identified for the site are 0.96 and 0.42 g, respectively, for Site Class B or bedrock conditions. To establish the ground-surface MCER spectrum, these bedrock spectral coefficients are adjusted for site class using the short- and long-period site coefficients, Fa and Fv, in accordance with Section 11.4.3 of ASCE 7-10. The design-level response spectrum is calculated as two-thirds of the ground-surface MCER spectrum. G ®0 s • The recommended MCER- and design-level spectral response parameters for Site Class D conditions are tabugated below.and d;ccussed_in turther detail in Appendix B. a2COM AENDED SEISMIC DESIGN PARAMETERS(2012 IBC2014 OSSC) Recommended Seismic Parameter Value 0 0 ` ° Site Class D MCER 0.2-Sec Period 1 07 g Spectral Response Acceleration,SMs MCER 1.0-Sec Period 0.66 g Spectral Response Acceleration,SM, Design-Level 0.2-Sec Period 0.72 g Spectral Response Acceleration, SOS Design-Level 1.0-Sec Period 0.44 g Spectral Response Acceleration, Sol Liquefaction/Cyclic Softening. Liquefaction is a process by which loose, saturated granular materials, such as clean sand and, to a somewhat lesser degree, non-plastic and low-plasticity silts, temporarily lose stiffness and strength during and immediately after a seismic event. This degradation in soil properties may be substantial and abrupt, particularly in loose sands. Liquefaction occurs as seismic shear stresses propagate through a saturated soil and distort the soil structure, causing loosely packed groups of particles to contract or collapse. If drainage is impeded and cannot occur quickly, the collapsing soil structure causes the pore- water pressure to increase between the soil grains. If the pore-water pressure becomes sufficiently large, the inter-granular stresses become small and the granular layer temporarily behaves as a viscous liquid rather than a solid. After liquefaction is triggered, there is an increased risk of settlement, loss of bearing capacity, lateral spreading, and/or slope instability, particularly along waterfront areas. Liquefaction-induced settlement occurs as the elevated pore-water pressures dissipate and the soil consolidates after the earthquake. Cyclic softening is a term that describes a relatively gradual and progressive increase in shear strain with load cycles. Excess pore pressures may increase due to cyclic loading but will generally not approach the total overburden stress. Shear strains accumulate with additional loading cycles, but an abrupt or sudden decrease in shear stiffness is not typically expected. Settlement due to post-seismic consolidation can occur, particularly in lower-plasticity silts. Large shear strains can develop, and strength loss related to soil sensitivity may be a concern. The potential for liquefaction and/or cyclic softening is typically estimated using a simplified method that compares the cyclic shear stresses induced by the earthquake (demand) to the cyclic shear strength of the soil available to resist these stresses (resistance). Estimates of seismically induced stresses are based on earthquake magnitude and peak ground-surface acceleration (PGA). The cyclic resistance of soils is dependent on several factors, including the number of loading cycles, relative density, confining stress, plasticity, natural water content, stress history, age, depositional environment(fabric), and composition. The cyclic resistance of soils is evaluated using in-situ testing in conjunction with laboratory index testing but may also include monotonic and cyclic laboratory strength tests. For sand-like soils, the cyclic resistance is typically evaluated using N-values or CPT tip-resistance values normalized for overburden pressures and corrected for factors that influence cyclic resistance, such as fines content. For clay-like soils, the cyclic G RU 6 . CC CC f f CPC C CC f f r f f l C f f CC C Pf( r f I r f f f f C ( • ( / ( f r f' resistance is typically evaluated using estimates of the undrained(shear strength,,ov erconsolidation ratio (OCR), and sensitivity, or directly from cyclic laboratory tests. ^" C 4%c P f A O 000 ff R ( 6 fec Go c rs r I- re. ce' The potential for liquefaction and/or cyclic softening at the site was evaluated(using the simplified method based on procedures recommended by Idriss and Boulanger (2008)f with subsequent revisions (2014). This method utilizes the PGA to predict the cyclic shear stresses induced kfy the eafth4gUalee.R The;UGS National Seismic Hazard Mapping Project (NSHMP) was used to determine the caltriiiiirigeraiti-griaJCa magnitudes that represent the seismic exposure of the site for the MCEc hazard level. A crustal event on the Portland Hills fault and an event on the Cascadia Subduction Zone (CSZ) were determined to represent the sources of seismic shaking. For our evaluation, we have considered a magnitude Mw 7 crustal earthquake and Mw 9 CSZ earthquake with code-level PGAs (PGAM) of 0.45 and 0.36 g, respectively. We have conservatively assumed a groundwater depth of about 20 ft below the ground surface, which corresponds to the anticipated highest sustained groundwater level at the site. The results of our evaluation indicate there is a potential that zones of the interbedded silt and sand deposit below the groundwater surface at the site could lose strength or liquefy during a code-based earthquake. Based on our analysis, potentially liquefiable soils are present below the ground surface and extend to a depth of about 60 ft. Our analysis indicates the potential for 2 to 3 in. of seismically induced settlement, which may occur during the earthquake and after earthquake shaking has ceased. Conventional geotechnical practice is to assume differential settlements may approach 50% of the calculated total seismic settlement. Discussion of seismically induced building foundation settlement is presented in the Foundation Support section later in this report. Other Seismic Hazards. Based on site topography, the risk of earthquake-induced slope instability and/or lateral spreading is low. The risk of damage by tsunami and/or seiche at the site is absent. The inferred location of the Canby-Mollala Fault is in the general vicinity of the southeastern corner of the site (Personius et al., 2003); however, the USGS does not consider the Canby-Mollala Fault to be an active, contributing source in their Probabilistic Seismic Hazard Analysis (PSHA). The USGS considers the Portland Hills Fault, located about 10 km northeast of the site, to be the closest crustal fault source contributing to the overall seismic hazard at the site. Unless occurring on a previously unmapped or unknown fault, the risk of fault rupture at the site is low. Earthwork General. The fine-grained soils that mantle the site are sensitive to moisture, and perched groundwater may approach the ground surface during the wet winter months. Therefore, it is our opinion earthwork can be completed most economically during the dry summer months, typically extending from June to mid- October. It has been our experience that the moisture content of the upper few ft of silty soils will decrease during extended warm, dry weather. However, below this depth, the moisture content of the soil tends to remain relatively unchanged and well above the optimum moisture content for compaction. As a result, the contractor must use construction equipment and procedures that prevent disturbance and softening of the subgrade soils. To minimize disturbance of the moisture-sensitive silt soils, site grading can be completed using track-mounted hydraulic excavators. The excavation should be finished using a smooth-edge bucket to produce a firm, undisturbed surface. It may also be necessary to construct granular haul roads and work pads concurrently with excavation to minimize subgrade disturbance. If the subgrade is disturbed during construction, soft, disturbed soils should be overexcavated to firm soil and backfilled with structural fill. GRO t If construction occurs during wet ground conditions, granular work pads will be required to protect the ander;),ing silt subgradE. and provide a firm working surface for construction activities. In our opinion, a 12- to 18;ii:thick granular work pad should be sufficient to prevent disturbance of the subgrade by lighter construction equipment and limited traffic by dump trucks. Haul roads and other high-density traffic areas will require a minimum of 18 to 24 in. of fragmental rock, up to 6-in. nominal size, to reduce the risk of subgrad%' cieteroration. The use;of a geotextile fabric over the subgrade may reduce maintenance during construction: I_laal-roads can also be constructed by placing a thickened section of pavement base course and subsequently spreading and grading the excess CRB after earthwork is complete. As an alternative to the use of a thickened section of crushed rock to support construction activities and protect the subgrade, the subgrade soils can be treated with cement. It has been our experience in this area that treating the silt soils to a depth of 12 to 14 in. with about a 6 to 8% admixture of cement overlain by 6 to 12 in. of crushed rock will support construction equipment and provide a good all-weather working surface. Site Preparation. Demolition of the existing improvements within the limits of the proposed building should include removal of existing pavements and underground utilities (if present). The ground surface within all building areas, paved areas, walkways, and areas to receive structural fill should be stripped of existing vegetation, surface organics, and loose surface soils. We anticipate stripping up to a depth of about 4 to 6 in. will likely be required across the majority of the site; however, deeper grubbing may be required to remove brush and tree roots. All demolition debris, trees, brush, and surficial organic material should be removed from within the proposed building and parking-lot footprints. Excavations required to remove existing improvements, brush, and trees should be backfilled with structural fill. Organic strippings should be disposed of off site, or stockpiled on site for use in landscaped areas. Following stripping or excavation to subgrade level, the exposed subgrade should be evaluated by a qualified geotechnical engineer or engineering geologist. Proof rolling with a loaded dump truck may be part of this evaluation. Any soft areas or areas of unsuitable material disclosed by the evaluation should be overexcavated to firm material and backfilled with structural fill. Due to the presence of fill soils mantling the site, it should be anticipated some overexcavation of subgrade will be required. Structural Fill. We anticipate minor amounts of structural fill will be placed for this project. We recommend structural fill consist of granular material, such as sand, sandy gravel, or crushed rock with a maximum size of 2 in. Granular material that has less than 5% passing the No. 200 sieve (washed analysis) can usually be placed during periods of wet weather. Granular backfill should be placed in lifts and compacted with vibratory equipment to at least 95% of the maximum dry density determined in accordance with ASTM D698. Appropriate lift thicknesses will depend on the type of compaction equipment used. For example, if hand-operated vibratory-plate equipment is used, lift thicknesses should be limited to 6 to 8 in. If smooth-drum vibratory rollers are used, lift thicknesses up to 12 in. are appropriate, and if backhoe- or excavator-mounted vibratory plates are used, lift thicknesses of up to 2 ft may be acceptable. On-site, fine-grained soils and site strippings free of debris may be used as fill in landscaped areas. These materials should be placed at about 90% of the maximum dry density as determined by ASTM D698. The moisture contents of soils placed in landscaped areas is not as critical, provided construction equipment can effectively handle the materials. GR® r -e ff CC f e' f C f ( f R C I f < f ff f [ f` I f F ^ C f 1 1 I ( fe Utility Excavations. In our opinion, there are three major considerations associated with design and fC � f(�� °Qe fR construction of new utilities. °f of e e tee C P e f C e CCC CC C C G f ( CC to C f f fef Cc 1) Provide stable excavation side slopes or support for trencri sidewalk to minimize`loss of ground. f ff' f:rf f • 60 :e .' f e e e e e e e 2) Provide a safe working environment during construction. e ere C f f n e w e c e o e e o 3) Minimize post-construction settlement of the utility and grbund'�urfacef f f The method of excavation and design of trench support are the responsibility of the contractor and subject to applicable local, state, and federal safety regulation, including the current Occupational Safety and Health Administration (OSHA) excavation and trench safety standards. The means, methods, and sequencing of construction operations and site safety are also the responsibility of the contractor. The information provided below is for the use of our client and should not be interpreted to mean we are assuming responsibility for the contractor's actions or site safety. According to current OSHA regulations, the majority of the fine-grained soils encountered in the explorations may be classified as Type B. In our opinion, trenches less than 4 ft deep that do not encounter groundwater may be cut vertically and left unsupported during the normal construction sequence, assuming trenches are excavated and backfilled in the shortest possible sequence and excavations are not allowed to remain open longer than 24 hr. Excavations more than 4 ft deep should be laterally supported or alternatively provided with side slopes of 1 H:1V (Horizontal to Vertical) or flatter. In our opinion, adequate lateral support may be provided by common methods, such as the use of a trench shield or hydraulic shoring systems. We anticipate the groundwater level will typically occur below the anticipated maximum excavation depth; however, perched groundwater may approach the ground surface during intense or prolonged precipitation. Groundwater seepage, running soil conditions, and unstable trench sidewalls or soft trench subgrades, if encountered during construction, will require dewatering of the excavation and trench sidewall support. The impact of these conditions can be reduced by completing trench excavation during the summer months, when groundwater levels are lowest, and by limiting the depths of the trenches. We anticipate groundwater inflow, if encountered, can generally be controlled by pumping from sumps. To facilitate dewatering, it will be necessary to overexcavate the trench bottom to permit installation of a granular working blanket. We estimate the required thickness of the granular working blanket will be on the order of 1 ft, or as required to maintain a stable trench bottom. The actual required depth of overexcavation will depend on the conditions exposed in the trench and the effectiveness of the contractor's dewatering efforts. The thickness of the granular blanket must be evaluated on the basis of field observations during construction. We recommend the use of relatively clean, free-draining material, such as 2- to 4-in.-minus crushed rock, for this purpose. The use of a geotextile fabric over the trench bottom will assist in trench- bottom stability and dewatering. All utility trench excavations within building and pavement areas should be backfilled with relatively clean, granular material, such as sand, sandy gravel, or crushed rock of up to 11/2-in. maximum size and having less than 5% passing the No. 200 sieve (washed analysis). The bottom of the excavation should be thoroughly cleaned to remove loose materials and the utilities should be underlain by a minimum 6-in. thickness of rosin bedding material. The granular backfill material should be compacted to at least 95% of the maximum dry density ac determined wy ASTM D598 in the upper 5 ft of the trench and at least 92% of this density below a depth of S ,t. The use of hoe-mo'inted vibratory-plate compactors is usually most efficient for this purpose. Flooding or jetting as a means of compacting the trench backfill should not be permitted. Foundatioi support We anticipate tie maximum column and wall loads will be less than 200 kips and 4 kips/ft, respectively. In our opinion, the proposed structural loads can be supported on conventional spread and wall footings in accordance with the following design criteria. As discussed earlier, our analysis indicates 2 to 3 in. of settlement could occur following a code-based seismic event. Based on the thickness of non-liquefiable soil that mantles the site, we estimate the risk of ground manifestation of the seismically induced settlement is generally low. For design purposes, we recommend assuming differential seismic settlement will approach 50% of the calculated total seismic settlement over the length of the building. The 2015 National Earthquake Hazards Reduction Program (NEHRP) document titled "Recommended Seismic Provisions for New Buildings and Other Structures" provides guidance for acceptable limits of seismic differential settlement for different types of structures and different risk categories. In our opinion and based on Table 12.13-3 of 2015 NEHRP, 1 to 1.5 in. of seismic differential settlement over the length of the building is acceptable and consistent with current standards of practice for a life safety performance level. However, the structural engineer should determine if the structure can accommodate the estimated total and differential seismic settlement. Tying the foundations together with a network of grade beams could be considered to help reduce the potential adverse effects associated with differential vertical movement. The grade beams should be designed in accordance with the guidelines presented in the 2015 NEHRP document. All footings should be established in the medium-stiff, native silt that underlies the site. The base of all new footings should be established at a minimum depth of 18 in. below the lowest adjacent finished grade. The footing width should not be less than 24 in. for isolated column footings and 18 in. for wall footings. Excavations for all foundations should be made with a smooth-edge bucket, and all footing subgrades should be observed by a member of GRI's geotechnical engineering staff. Soft or otherwise unsuitable material encountered at foundation subgrade level should be overexcavated and backfilled with granular structural fill. Our experience indicates the subgrade soils are easily disturbed by excavation and construction activities. Due to these considerations, we recommend installing a minimum 3-in.-thick layer of compacted crushed rock in the bottom of all footing excavations. Relatively clean, 3/4-in.-minus crushed rock is suitable for this purpose. Footings established in accordance with these criteria can be designed on the basis of an allowable soil bearing pressure of 2,500 psf. This value applies to the total of dead load and/or frequently applied live loads and can be increased by one-third for the total of all loads: dead, live, and wind or seismic. We estimate the total static settlement of spread and wall footings designed in accordance with the recommendations presented above will be less than 1 in. for footings supporting column and wall loads of up to 200 kips and 4 kips/ft, respectively. Differential static settlements between adjacent, comparably loaded footings should be less than half the total settlement. �� „ • r CC CC Cr CI' C f fr r r r 1 r r f e f r I r • r r Cr( rt I f [ 1 C I r Horizontal shear forces can be resisted partially or completely by frictional forces develop l?gtween the base of the footings and the underlying soil and by soil passive rt" ist£rS;ce.f The total €ri&fiisn [`resistance between the footing and the soil is the normal force times the coeffii:i'vit..pf frict,i4 eetweei ie �ry;I and the base of the footing. We recommend an ultimate value of 0.35 for the coefficient of friction for footings cast on granular material. The normal force is the sum of the vertical forgesr(ijead,load plit red live load). If additional lateral resistance is required, passive earth pressures against emlied4ed foo irl scan fie computed on the basis of an equivalent fluid having a unit weight of 300 pcf. This d igrf f asCiv aarKp.rbssure would be applicable only if the footing is cast neat against undisturbed soil, or if backfill for the footings is placed as granular structural fill. This value also assumes the ground surface in front of the foundation is horizontal, i.e., does not slope downward away from the toe of the footing. Subdrainage/Floor Support To provide a capillary break and reduce the risk of damp floors, slab-on-grade floors established at or above adjacent final site grades should be underlain by a minimum 8 in. of free-draining, clean, angular rock. This material should consist of angular rock such as 11/2-to 3/4-in. crushed rock with less than 2% passing the No. 200 sieve (washed analysis) and should be placed in one lift and compacted to at least 95% of the maximum dry density (ASTM D698) or until well-keyed. To improve workability, the drain rock can be capped with a 2-in.-thick layer of compacted, 3/4-in.-minus crushed rock. In our opinion, it is appropriate to assume a coefficient of subgrade reaction, k, of 175 pci to characterize the subgrade support for point loading with 8 in. of compacted crushed rock beneath the floor slab. In areas where floor coverings will be provided or moisture-sensitive materials stored, it would be appropriate to also install a vapor-retarding membrane. The membrane should be installed as recommended by the manufacturer. In addition, a foundation drain should be installed around the building perimeter to collect water that could potentially infiltrate beneath the foundations and should discharge to an approved storm drain. Pavement Design We anticipate the new parking lot will be subjected primarily to automobile and light truck traffic, with occasional heavy truck traffic. We anticipate the majority of the site will be paved with AC pavement; however, areas subjected to repeated heavy truck traffic, such as trash-enclosure areas, may be paved with PCC pavement. Traffic estimates for the roadways and parking areas are presently unknown. Based on our experience with similar projects and subgrade soil conditions, we recommend the following pavement sections. RECOMMENDED PAVEMENT SECTIONS CRB AC Thickness,in. Thickness,in. Areas Subject to Occasional 12 4 Heavy Truck Traffic Areas Subject to Primarily 8 3 Automobile Traffic and Parking CRB PCC Thickness,in. Thickness,in. Areas Subject to Repeated Heavy Truck Traffic 6 6 (trash-enclosure area) The recommended pavement sections should be considered minimum thicknesses and underlain by a wow, ectexti:e fabric. It s:loilJ be assumed some maintenance will be required over the life of the paverrer..t(15 to 20 ylars). he recommended pavement section is based on the assumption that pavement construction will be accomplished during the dry season and after construction of the building has been completed. If.wet-weather pavement construction is considered, it will likely be necessary to increase the thickness,of CR i o si.pport construction equipment and protect the subgrade from disturbance. The indicate.c1 sc-ct,or,s ara riot,inteF ded to support extensive construction traffic, such as dump trucks and concrete trucks. Pavements subject to construction traffic may require repair. For the above-indicated sections, drainage is an essential aspect of pavement performance. We recommend all paved areas be provided positive drainage to remove surface water and water within the base course. This will be particularly important in cut sections or at low points within the paved areas, such as at catch basins. Effective methods to prevent saturation of the base course materials include providing weep holes in the sidewalls of catch basins, subdrains in conjunction with utility excavations, and separate trench drain systems. To ensure quality materials and construction practices, we recommend the pavement work conform to Oregon Department of Transportation standards. Prior to placing base course materials, all pavement areas should be proof rolled with a fully loaded, 10-cy dump truck. Any soft areas detected by the proof rolling should be overexcavated to firm ground and backfilled with compacted structural fill. Provided the pavement section is installed in accordance with the recommendations provided above, it is our opinion the site-access areas will support infrequent traffic by an emergency vehicle having a gross vehicle weight (GVW) of up to 75,000 lbs. For the purposes of this evaluation, "infrequent" can be defined as once a month or less. On-Site Disposal of Stormwater The unfactored, field-measured infiltration rate for the silt soils that mantle the site is 0 inJhr; therefore, it is our opinion the near-surface silt soils do not meet the requirements for on-site stormwater disposal. DESIGN REVIEW AND CONSTRUCTION SERVICES We welcome the opportunity to review and discuss construction plans and specifications for this project as they are being developed. In addition, GRI should be retained to review all geotechnical-related portions of the plans and specifications to evaluate whether they are in conformance with the recommendations provided in our report. To observe compliance with the intent of our recommendations, our design concepts, and the plans and specifications, we are of the opinion that all construction operations dealing with earthwork and foundations should be observed by a GRI representative. Our construction-phase services will allow for timely design changes if site conditions are encountered that are different from those described in our report. If we do not have the opportunity to confirm our interpretations, assumptions, and analyses during construction, we cannot be responsible for the application of our recommendations to subsurface conditions different from those described in this report. LIMITATIONS This report has been prepared to aid the architect and engineer in the design of this project. The scope is limited to the specific project and location described herein, and our description of the project represents CIIR ® ,� s C r r f r r r r r C r f F f f f r F e r C r ✓ eef rr f P r r free re , r elf ( r If f f r r f f r P t rr r rett merrur our understanding of the significant aspects of the project relevrr t tc he �e gn poi,�Si ik3n of the new foundations and floors. In the event any changes in the design a'd loca=.corf of the j o;�0t elements as err Cr f rfoutlined in this report are planned, we should be given the opportunity to review the changes and modify or reaffirm the conclusions and recommendations of this report in weritc ting i=r r t rr rr r r rr r err C f r Y f C r r The conclusions and recommendations submitted in this report:are bas dror etne Bata dbtained from the explorations made at the locations indicated on Figure 2 and other sources ofeinformation discussed in this report. In the performance of subsurface investigations, specific information is obtained at specific locations at specific times. However, it is acknowledged that variations in soil conditions may exist between exploration locations. This report does not reflect any variations that may occur between these explorations. The nature and extent of variation may not become evident until construction. If during construction subsurface conditions differ from those encountered in the explorations, we should be advised at once so that we can observe and review these conditions and reconsider our recommendations where necessary. Please contact the undersigned if you have any questions. Submitted for GRI, •<(- ?G)PROFFSL9ioZ ce444 k, 18281 9 —12-44 N 6 qN 16 t 99 tieFSLEy$ 9P`46 Renews 06-2018 Wesley Spang, Ph.D, PE, GE Nicholas M. Hatch, PE Principal Project Engineer This document has been submitted electronically. References Idriss, I.M., and Boulanger, R.W., 2008, Soil liquefaction during earthquakes: Earthquake Engineering Research Institute, EERI MNO-12. Idriss, I. M., and Boulanger, R.W., 2014, CPT and SPT based liquefaction triggering procedures: Department of Civil & Environmental Engineering,College of Engineering, University of California at Davis, Report No. UCD/CGM-14/01. Madin, I.P.,1990, Earthquake-hazard geology maps of the Portland metropolitan area: Oregon Department of Geology and Mineral Studies,Open-File Report 90-02. Personius,S. F., Dart, R. L., Bradley, Lee-Ann,and Haller, K.M., 2003,Map and data for Quaternary faults and folds in Oregon: U.S. Geological Survey Open-File Report 03-095. U.S.Geological Survey(USGS),Unified hazard tool,Conterminous U.S.2014(v4.0x),accessed 5/30/17 from USGS website: https://earthquake.usgs.gov/hazardslinteractive/. G R® ,3 P. PP fP Pr err r r r P t P t f f P f r I f f f E r r f f t f f r r 5 �� Jeff f l t I f r f r 1( J f}J� i i - SW EDGEWOOD ST r � 1. �' - , t \� c a: , `.�� ..J - - � ?i•so 1v-' _4.r r / CRek DR • t • 1Cr t �. rt, SWMEADOWS/ "� F o N! ,SW ONITA-RD 1,` i -- BONITA=RD '�'EY LNG, r-a„1 / i�t) I/ ST �? _.t' �.� CJ:/� v- r (;, �.� �� ( -.i,� � ) , ,) A //'i / SW PINEBROp/1 r / P -F`t er— Nr —'.t c I fI/; ;F� i r-:/ ; (, � i r � C C (%Zj 1 I/1 V` r , - {' 1.- -• /�i [ , ""'• ._.� , BURMA RD t. 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A .1, 1``' l ,�vt` SW KENNY ST Z � m- .� l'%�/SW KINGFISHEq • ': ��,aJ '$ _r,-t. \50 �=-� W al V �< 1 _ c��^ .Ya uts Bicycle ands _1- _ / j -.I destnan Bridge �' j I a J ,WinonayLem m i st o I _ Rive -grove,, W / „ a - Ir t i.5 MCEWAN RD I r� i 11 < 'try. A C T_ m .N Tuatatm 5, - , �c'1/ t f _ a _, Communrt y� 7� ! 1® �►� .r l n- C1�c5 GI _, --City Park'Bo t• mRa p ',1';„.1 /�/ f 1• '^,a�-. I OVf:. . o lie ve 1�� O l� APART vy /. ! � (} �( jli ^ i'> 1 �Ir _i ��,' / �! f.�'I �_',.5 / a�i.,'\Jy 1��,� TIT .A 11i A rill' USGS TOPOGRAPHIC MAP BEAVERTON OREG.(2014) LAKE OSWEGO,OREG.(2014) 0 1/2 1 MILE 1 GI, fl TIGARD TUALATIN SCHOOL DISTRICT 23J j� DURHAM CENTER VICINITY MAP yy P IV V . —_. - _ o 0 0 o a c to u ' SW DURHAM ROAD-__ _ _ ___ o e a a o o n n n a0 (10 , I ( 1 1 — i • o y t �i1 I { 41\ . ! Lim BEIiI SCHOOL D .. 1 't A , Il 1,, �, -HA•P10CP•2 NEW PARKING LOT HA•11 DCP-1❑ ^t,(+-� ..'�' r 1 ? "' �� II�I' 1I., •Il I. 1 il q rrA„ c, li 9 1 \ F' J g 11 DI ,1 III ,9 : ,•E I ! y� 11 1 S i Pk4 '3,A t I t..). a T I i - I s a -'' 1 Y `e''l I 'p a �yy _ ._ I �nl. fib"":. II, �,. I• � 1 I_ �1_. _ .5� 'V'^d' A �� +4 �'�.� (I� V HA3IDCP�I,� .0 r.','' t_.,...., S BORING COMPLETED BYGRI q (MAY 26,2011 C I I ..L _ F < fi< -0 T n: . I I 7 1 [rnr1nr Y ' HANUAUGERED BORING AND DYNAMIC CONE PENETROMETER PROBE A4 II, ' t I �. rE 11 !� i - COMPLETED B01�RI ( 11 _, 'x 1A P •TMY < IE•a I 11;,,.•" 7/ '/ INFILTRATION TEST COMPLETED BY GRI J i NI .K +Y. >.. —,,..� E,' (MAY 26,2017E F S ' < 1 ". . f h ' ! 11 " (ONE PENETRATION TEST COMPLETED BY GRI r (MAY 22,2017) < ,,,,1 DRATOMETER COMPLETED BYGRI IMAY 22,20171 1j s f 1-I 9� SITE PLAN FROM FILE BY BORA ARCHITECTS,INC.,DATED APRIL 21,2017 - taa / \ 11 C 5 `i - o so too Fr .s.1.' / __ rt y: 1 I I � 1 ry I1 j,'•., ,r. r' L ' , 1 ( I , 1 I 11' I ' ,.,;...,I - - - ' 1 J II I m , \,4- Elio © TICARD TUALATIN SCHOOL DISTRICT �( il 1 ' DURHAM EDUCATION CENTER i _ - tir �9 A. — �1 ,�!'I� f SITE PLAN 1 I is I, t 1 Z; - 1 ' I .I IUNE 2017 JOB NO.5970-G FIG.2 • • r CC CC CC CCP C Cr r C r I C r f- C r C r I. f f of re f r r €f f f I f f r r f f f f f r r r (r f r C Cr C CC() COC CC ()R Cr. or r C C CrCC APPENDIX A e r C r Cer er. CCC (Cr CfG C C(f IrG FIELD EXPLORATIONS AND LABORATORY TESTING CCC err C C CC CC C c tern C e f. n r C C e C C C f C C C (CO COf (C C C FIELD EXPLORATIONS C C 0 C C C e 000 C CCC C C. C C C CO Subsurface materials and conditions at the site were investigated on May 22 and 26, 2017, with one boring, designated B-1; one cone penetrometer test (CPT) sounding, designated CPT-1; two dilatometer (DMT) soundings, designated DMT-1 and DMT-2; and three hand-augered borings, designated HA-1 through HA-3. The explorations were completed at the approximate locations shown on the Site Plan, Figure 2. Logs of the boring, CPT probe, DMT soundings, and hand-augered borings are provided on Figures 1A through 7A. The field exploration work was coordinated and documented by an experienced member of GRI's geotechnical engineer staff, who maintained a log of the materials and conditions disclosed during the course of work. Borings One boring, designated B-1, was advanced to a depth of about 91.5 ft below existing site grades. The boring was completed with mud-rotary drilling techniques using a track-mounted drill rig provided and operated by Holocene Drilling, Inc., of Puyallup, Washington. Disturbed and undisturbed soil samples were obtained from the borings at 2.5-ft intervals of depth in the upper 15 ft, 5-ft intervals to a depth of 60 ft, and 10-ft intervals below 60 ft. Disturbed soil samples were obtained using a standard split-spoon sampler (SPT). The outside diameter of the SPT sampler is 2 in. Penetration tests were conducted by driving the sampler into the soil a distance of 18 in. using a 140-lbs hammer dropped 30 in. The number of blows required to drive the SPT sampler the last 12 in. is known as the Standard Penetration Resistance, or N-value. N-values provide a measure of the relative density of granular soils and relative consistency of cohesive soils. Samples obtained from the boring were placed in airtight jars and returned to our laboratory for further classification and testing. In addition, relatively undisturbed samples were collected by pushing a 3-in.-outside-diameter(O.D.) Shelby tube into the undisturbed soil a maximum distance of 24 in. using the hydraulic ram of the drill rig. The soil exposed in the end of the Shelby tube was examined and classified in the field. After classification, the tube was sealed with rubber caps and returned to our laboratory for further examination and testing. A log of the boring is provided on Figure 1A. The log presents a descriptive summary of the various types of materials encountered in the boring and notes the depths at which the materials and/or characteristics of the materials change. To the right of the descriptive summary, the numbers and types of samples are indicated. Farther to the right, N-values are shown graphically, along with the natural moisture contents and Torvane shear strength values, where applicable. The terms and symbols used to describe the materials encountered in the borings are defined in Table 1A and the attached legend. Electric Cone Penetration Test One electric CPT probe, designated CPT-1, was advanced to a depth of about 79 ft using a truck-mounted CPT rig provided and operated by Oregon Geotechnical Explorations, Inc., of Keizer, Oregon. During the CPT, a steel cone is forced vertically into the soil at a constant rate of penetration. The force required to cause penetration at a constant rate can be related to the bearing capacity of the soil immediately min surrounding the point of the penetrometer cone. This force is measured and recorded every 8 in. In addition 6-the cone measurements, measurements are obtained of the magnitude of force required to force a friction sleeve, attached above the cone, through the soil. The force required to move the friction sleeve can be related to the undrained shear strength of fine-grained soils. The dimensionless ratio of sleeve friction to poirt bearing capacity,pro.rdes an indicator of the type of soil penetrated. The cone-penetration resistance and_slee","e.frvtion can be ;used to evaluate the relative consistency of cohesionless and cohesive soils, respectively. In addition, -a piezometer fitted between the cone and the sleeve measures changes in water pressures as the probe is advanced and can also be used to measure the depth of the top of the groundwater table. The probe was also operated using an accelerometer fitted to the probe, which allows measurement of the arrival time of shear waves from impulses generated at the ground surface. This allows calculation of shear-wave velocities for the surrounding soil profile. A log of the electric CPT probe is provided on Figure 2A and presents a graphical summary of the tip resistance, local (sleeve) friction, friction ratio, pore pressure, and soil behavior type (SBT) index. The types of soils encountered within the probe are shown graphically along the right side of the figure. The terms used to describe the soils encountered in the probe are defined in Table 2A. Shear-wave velocity measurements for the probe are shown on Figure 3A. Dilatometer Test Two DMT soundings, designated DMT-1 and DMT-2, were advanced to a depth of about 41 ft using a truck-mounted CPT rig provided and operated by Oregon Geotechnical Explorations, Inc., of Keizer, Oregon. DMT soundings provide additional geotechnical information to characterize the subsurface materials. The dilatometer test is performed by pushing a blade-shaped instrument into the soil. The blade is equipped with an expandable membrane on one side that is pressurized until the membrane moves horizontally into the surrounding soil. Readings of the pressures required to move the membrane to a point flush with the blade (Po— pressure) and 1.1 mm into the surrounding soil (Pi —pressure) are recorded. The test sequence was performed at 8-in. intervals to obtain a comprehensive soil profile. A material index (ID), horizontal stress index (Ko), and dilatometer modulus (ED) are obtained directly from the dilatometer data. The constrained modulus (M) is then obtained from the dilatometer data. The dilatometer test results are summarized on Figures 4A and 5A. The results show the dilatometer pressure readings (Po, P,) and three dilatometer- derived parameters: horizontal stress index (Ko), material index (lo), and constrained modulus (M). The terms used to describe the materials encountered in the sounding are defined in Table 3A. Hand-Augered Borings Three hand-augered borings, designated HA-lthrough HA-3, were advanced to depths of about 4.5 to 5.5 ft using a 4-in.-diameter hand auger provided and operated by GRI. Disturbed soil samples were obtained from the hand-augered boreholes at about 2-to 2.5-ft intervals of depth. Samples obtained from the hand- augered borings were examined in the field, and representative portions were saved in plastic jars for further examination and physical testing in our laboratory. Logs of the hand-augered borings are provided on Figures 6A and 7A. Each log presents a descriptive summary of the various types of materials encountered in the hand-augered boring and notes the depths at which the materials and/or characteristics of the materials change. To the right of the descriptive summary, • • r rr rr fr CCP C rr r C F r r F r F ft r r F e r r r r r r F Fitt r f Cl t F P r F r ! F r the numbers and types of samples are indicated. Farther to thright,,the natural nmoistueebntent values are shown graphically. The terms and symbols used to describe thf mate4alsrencou r0A'.in the hand- augered r PrP rrr augered borings are defined in Table 1A and the attached legenrd.r. rr err Dynamic Cone Penetrometer Probes O C C CPC t C CC PC f C ry 6 P 0 ( II r C C CCPCCC Three Dynamic Cone Penetrometer (DCP) probes, designated DC2P-1 fthra heT C01, vie%e completed in the hand-augered boreholes at depths of about 0.5 to 2.5 ft using ar Kessler dynamic cone penetrometer manufactured by KSE Testing Equipment. The DCP tests were completed in accordance with ASTM D6951 by driving a 5/8-in.-diameter steel rod with a cone tip into the soil using a 17.6-lbs sliding hammer dropped a fixed height of 22.6 in. The number of blows required to drive the probe approximately 5 cm (2 in.) was recorded to depths ranging from 938 to 950 mm (3 to 3.1 ft). The DCP blow counts were used to estimate a California bearing ratio (CBR) value for the in-situ subgrade. Infiltration Testing Falling-head infiltration tests were completed at the site on May 26, 2017, in general conformance with the City of Portland's 2016 Stormwater Management Manual using the encased falling-head method outlined in Section 2.3.6 of the manual. The falling-head infiltration tests, designated I-1 and 1-2, were conducted in boreholes at depths of about 4 and 5.5 ft, respectively, below existing site grades at the approximate locations shown on Figure 2. The I-1 and 1-2 boreholes were drilled to the selected depths using a hand- operated 4-in.-O.D. auger and a 6.25-in.-inside- diameter (I.D.) hollow-stem auger, respectively. A PVC pipe was seated firmly into the base of the hand-augered borehole and the hollow-stem auger was embedded about 1 ft below the drilled depth of the boring. The PVC pipe and hollow-stem auger were filled with water to a height of approximately 1 ft above the drilled depth. After soaking, infiltration testing was conducted by reestablishing the water level in the PVC pipe and auger to the target height and recording the drop in water level over 1 hr or until the water completely drained, whichever occurred first. Where necessary, the infiltration test was repeated until consecutive tests showed little or no change in the infiltration rate. The average unfactored, field-measured infiltration rate for the silt soils that mantle the site is 0 in./hr. LABORATORY TESTING General The samples obtained from the borings were examined in our laboratory, where the physical characteristics of the samples were noted and the field classifications modified where necessary. At the time of classification, the natural moisture content of each sample was determined. Additional testing included analyses of Torvane shear strength, dry unit weight, and one- dimensional consolidation. A summary of the laboratory test results has been provided in Table 4A. The following sections describe the testing program in more detail. Natural Moisture Content Natural moisture content determinations were made in conformance with ASTM D2216. The results are summarized on Figures 1A, 6A, and 7A and in Table 4A. Torvane Shear Strength The approximate undrained shear strength of the fine-grained soils was determined using a Torvane shear device. The Torvane is a hand-held apparatus with vanes that are inserted into the soil. The torque G Ril A_� required C!frii,the soil in shear around the vanes is measured using a calibrated spring. The results of the Torvane s#:tear-strength tests are summarized on Figure 1A. Undisturbed Unit Weight The unit weight, or density, of undisturbed soil samples was determined in the laboratory in conformanc e with A>T,M;DD29.47. The results are summarized on Figure 1A and in Table 4A. One-Dimensional Consolidation A one- dimensional consolidation test was performed in conformance with ASTM D2435 on a relatively undisturbed soil sample extruded from a Shelby tube. This test provides data on the compressibility of underlying fine-grained soils, necessary for settlement studies. The test results are summarized on Figure 8A in the form of a curve showing percent strain versus applied effective stress. The initial dry unit weight and moisture content of the sample are also shown on the figure. G.R E A-4 F r A re r r e r r e r r C C C ! r C PVC C C r r r tr r ter a C C t r r C. I Table 'IA CC rec. e r C r e 0 r r . e GUIDELINES FOR CLASSIFICATION OF SOIL r ( < < e r ere ree r e cc cc i Description of Relative Density for G nulir S6il e e r ^C . r e e C r e s f 1 f C r e f ( < Standard Penetration Resistance' (C Relative Density (N-values),blows per ft very loose 0-4 loose 4- 10 medium dense 10-30 dense 30-50 very dense over 50 Description of Consistency for Fine-Grained (Cohesive)Soils Standard Penetration Torvane or Resistance(N-values), Undrained Shear Consistency blows per ft Strength,tsf very soft 0-2 less than 0.125 soft 2-4 0.125-0.25 medium stiff 4-8 0.25-0.50 stiff 8- 15 0.50-1.0 very stiff 15-30 1.0-2.0 hard over 30 over 2.0 Grain-Size Classification Modifier for Subclassification Boulders: Primary Constituent Primary Constituent >12 in. SAND or GRAVEL SILT or CLAY Cobbles: Adjective Percentage of Other Material(by weight) 3-12 in. trace: 5- 15 (sand,gravel) 5-15 (sand,gravel) Gravel: some: 15-30(sand,gravel) 15-30(sand,gravel) 1/4-3/4 in. (fine) sandy,gravelly: 30-50(sand,gravel) 30-50(sand,gravel) 3/4-3 in. (coarse) Sand: trace: <5 (silt,clay) No.200-No.40 sieve(fine) Relationship of clay and No.40-No. 10 sieve(medium) some: 5-12 (silt,clay) silt determined by No. 10-No.4 sieve(coarse) silty, clayey: 12-50(silt, clay) plasticity index test Silt/Clay: pass No. 200 sieve TabI.2A: CONE PENETRATION TEST (CPT) CORRELATIONS COHESIVE SOILS Cone-T=p Resistance,tsf Consistency <5 Very Soft 5 to 15 Soft to Medium Stiff 15 to 30 Stiff 30 to 60 Very Stiff >60 Hard COHESIONLESS SOILS Cone-Tip Resistance,tsf Relative Density <20 Very Loose 20 to 40 Loose 40 to 120 Medium 120 to 200 Dense >200 Very Dense Reference Kulhawy, F.H.,and Mayne,P.W., 1990,Manual on estimating soil properties for foundation design: Electric Power Research Institute,EL-6800. f ff CC fr frr C. Cr C f r f f C t r r ( r C. re e f F • f " C C' C CCC err r' 4r ( r Table 3A: SOIL CHARACTERiZ TI iN BASED ON MARCHETTI FLAT-PLATE DILATOMETER TEST tee crc r C Cr rr r R f r ! f C f C CfeP P[C Cr C r Description of Consistency for Fine-GrainOd(C14.16i e);Sdil ; r" Soil Type"' CH, CL ML, MH DMT Constrained Modulus(Mohr),tsf Consistency Ip2)< 0.6 0.6 <ID2)< 1.8 Very Soft 0-30 0- 50 Soft 30-60 50- 100 Medium Stiff 60- 100 100-200 Stiff 100- 175 200-375 Very Stiff 175 + 375 + Description of Relative Density for Granular Soils Soil Type SM, SC SP, SW DMT Constrained Modulus(Mohr),tsf Relative Density 1.8 <lo m< 3.3 3.3 <Io2' Very Loose 0-75 0- 100 Loose 75 - 150 100-200 Medium Dense 150-300 200-425 Dense 300-550 425-850 Very Dense 550 + 850 + 1) Unified Soil Classification System 2) ID = Material Index Table 4A `NUMMARY OF LABORATORY RESULTS Sample Information Atterberg Limits Moisture Dry Unit Liquid Plasticity Fines Location Sample 13 th,f. .1evation,ft Content,% Weight,pcf Limit,% Index, % Content, °10 Soil Type B-1 S-1 '.5: n — 28 — — — — FILL S-2 5.2 — 29 — — — 63 SILT S-2 6.3 — 28 94 — — — SILT 5-3 7.0 — 30 — — — 50 Silty SAND S-4 10.5 — 23 100 — — — Silty SAND S-5 12.0 — 25 — — — — SAND S-6 15.0 — 20 — — — 18 SAND S-7 20.0 — 25 — — — — SAND S-8 25.0 — 29 — — — 17 SAND S-9 30.0 — 37 — — — — SILT S-10 35.0 — 27 — — — — SILT S-11 40.0 — 26 — — — — SAND S-12 45.0 — 27 — — — 34 SAND 5-13 50.0 — 25 — — — — Silty SAND S-14 55.0 — 28 — — — 88 SILT S-15 60.0 — 34 — — — — SILT S-16 70.0 — 32 — — — — Clayey SILT S-17 80.0 — 37 — — — — SILT S-18 90.0 — 49 — — — — SILT HA-1 S-1 1.5 — 26 — — — — FILL S-2 4.0 — 29 — — — — SILT HA-2 S-1 1.5 — 30 — — - — FILL S-2 5.0 — 25 — — — 71 SILT HA-3 S-1 2.0 — 26 — — — — SILT S-2 5.0 — 28 — — — — SILT room • rr rr Cr r• r r e r e r r r f , r r BORING AND TEST PIT LOG I R;END : r r f , r` SOIL SYMBOLS SAMPLER GYMBOLS r rrr rrr Pr rr rr rf Symbol Typical Description Symbol : : ` r :Sairrplef 1144rri tion LANDSCAPE MATERIALS T 2.0-in. O.D. split-spoon sampfler and Standard la,,.. ,..,++ 1 Penetration Test with recovery(ASTM D1586) FILL eryel ietupu sa pjertrrith;re&Query fASTM D?587)- r r r C r I r ( CI(' rrr rr r r GRAVEL; clean to some silt,clay, and sand 0 �rtt.PO.=D rspiitep&o spirpler with recovery I (ASTM D3550) M1Sandy GRAVEL; clean to some silt and clay Grab Sample rlSilty GRAVEL; up to some clay and sand Rock core sample interval 7. � f. �� Clayey GRAVEL; up to some silt and sand Sonic core sample interval SAND;clean to some silt, clay,and gravel ? Geoprobe sample interval t `t Gravelly SAND;clean to some silt and clay "'' � INSTALLATION SYMBOLS . ;{ Silty SAND; up to some clay and gravel Symbol Symbol Description Phj Clayey SAND; up to some silt and gravel El Flush-mount monument set in concrete ® SILT; up to some clay,sand, and gravel 111 Concrete,well casing shown where applicable iiIGravelly SILT; up to some clay and sand %I Benoapplicable itseal,well casing shown where Sandy SILT; up to some clay and gravel `;_; Filter pack, machine-slotted well casing shown where applicable DIClayey SILT; up to some sand and gravel ;' Grout, vibrating-wire transducer cable shown where applicable ® CLAY; up to some silt, sand, and gravel • Vibrating-wire pressure transducer .44 Gravelly CLAY; up to some silt and sand I 1-in.-diameter solid PVC 7 Sandy CLAY; up to some silt and gravel 1-in.-diameter hand-slotted PVC goSilty CLAY; up to some sand and gravel Grout, inclinometer casing shown where applicable V PEAT FIELD MEASUREMENTS BEDROCK SYMBOLS Symbol Typical Description Symbol Typical Description a Groundwater level during drilling and date measured ,, +++ BASALT I Groundwater level after drilling and date o measured 5 .-� MUDSTONE �j Rock core recovery(%) SILTSTONE L- Rock quality designation (RQD, %) g — SANDSTONE a 0 W SURFACE MATERIAL SYMBOLS W Symbol Typical Description J 0• II Asphalt concrete PAVEMENT a Co ■ Portland cement concrete PAVEMENT z ¢ n Crushed rock BASE COURSE z N r Cr rr cc o c r r 00 C r Pr OCCOB tf, f, P Q c r r r r r Err r r r r et i p CLASSIFICATION OF MATERIAL p ii (SLOW;PER ,OQT `,r rr.°� U I- . o • MOISTURE CONTENT, g w w O ❑ FINES CONTENT,% a a_ ¢ ii a 3 F LIQUID LIMITn% r C c c c 9OMMENTS AND w a r~n o 1—P` TI LI ICIrT,% r r ND!'re� a � p r A�D.T't?NAL TESTS o co Surface Elevation:Not Available o z �ii cl m 0 ( ( 50 ,` : 1K: Asphalt concrete PAVEMENT(3 in.)over crushed d a e s rock BASE COURSE(10 in.) ,-- 1.1 ve SILT,some fine-to coarse-grained sand,trace clay : - and subangular to subrounded gravel,brown, 2 �■ medium stiff,contains wood debris(Fill) s-1 1 '� d ( ( 3 ■�:` �s r a c r SILT,some fine-to medium-grained sand,trace 5.0 II o so — clay,brown,stiff to very stiff S-2 Dry Density=94 pcf ? Silty SAND,brown,medium dense,fine to medium 7 0 4 _11IF ''r.:.': grained S-3 5 LIs 10, — 3€ --basalt cobble encountered at 11 ft sa Dry Density=100 pcf - :A.: --some silt below 12 ft s _15 S5 6 s 114 15— S5 4 10 20 1 S-7 I 9 19 I I m S-8 6 0 8 e — I I 1 c. 1 w 30='1 30.0 o SILT,trace fine-grained sand,brown,stiff, r 4 _11 r E — interbedded with 1-to 2-in.-thick layers of fine-to s-s 1 7 1. medium-grained sand with trace to some silt / w _ I 1 i 1 1 Z 35— —very stiff below 35 ft 6 21 f — s-10 1 9 12 —o J 0 z — E 0 :0 — 0—40 (CONTINUED NEXT PAGE) 0 0.5 1.0 Logged By:A.Strahler Drilled by:Holocene Drilling Inc. • TORVANE SHEAR STRENGTH,TSF Date Started:5/26/17 Coordinates:Not Available • UNDRAINED SHEAR STRENGTH,TSF Drilling Method: Mud Rotary Hammer Type:Auto Hammer Equipment: Diedrich D-50 Track-Mounted Drill Rig Weight:Drop 140 in. BORING B-1 Hole Diameter: 5 in. Drop:30 in. Fnnrnv Rat in'NnI Availably `7 A BLOWS PER FOOT p CLASSIFICATION CF MATERIAL O ' - z • MOISTURE CONTENT,% LL 0 LL w w o ❑ FINES CONTENT,% _ = a a a U LIQUID LIMIT,% COMMENTS AND a o c a - < < oLLI ~�PLASTIC LIMIT,% ADDITIONAL TESTS o o o f rf'cs Elciatic.l:Not;,veils:)le 0 z co co m 0 50 100 =;/'`EANO;tace silt,Loyal r ottled',1.3',;MaCliam dense, 4110 11 251 S-11 1 13 — fine grained 12 _ :: ° 45—:.;:;' —some silt,fine-to coarse-grained sand 6 28 interbedded with 1-to 2-in.-thick layers of silt below S12 I 14 I] 45 ft 14 I 1 — I I 50— ,..'.....*.. —silty,gray,dense below 50 ft T 12 135 S-13 -IL 16 ---# . 19 1 — I 55—'v- 55.0 SILT,some fine-grained sand,trace clay,gray,very �t4 i 8 26 — stiff 15 t 1 . . — 1 60— --some clay below 60 ft 8 _�7. di S-15 1 12 15 IT L 1.. I' I 1 1 ,p- 65— 1 5 — I 0 — 1 U — I, I a 70- —clayey,trace fine-grained sand,stiff below 70 ft 4 11 1 o S-i6 I 4 o 7 I I Lii J _ J t Z I 0 75 / 3 ?1O HL 9—a0 (CONTINUED NEXT PAGE) 0 0.5 1.0 • TORVANE SHEAR STRENGTH,TSF ■ UNDRAINED SHEAR STRENGTH,TSF G R BORING B-1 • • • r re re rr e ( r• e r r e r e c c e. a: e, r. rrr r r rr err CLASSIFICATION OF MATERIAL zo a A. LOWPEROF t o d > z • MOISTURE CONTENT,% z w w ElFINES CONTENT,% a s UOUIDLIMITr% r%o 0 n`�� AL COMMENTS AND TESTS w w ¢ ¢ —1 r P41TIh'LIMl ,% ` c o c9 Surface Elevation:Not Available o z mom 0 50 r 10 `r `'` SILT,some clay,trace fine-grained sand,gray,hard 8 e°e r 4 S-17 12 26 re* is a c . oe. rr C f r r P r r CC rc( `E r r Ca ! r:'•�' r r r J n _'—.r; r e 65— I 1 _ I — 1 90— --very stiff,contains organics below 90 ft 5 �1s i s-18 B . (5/26/2017) 91.5 11 95 100- r- 105- 0 c� — w g - ✓ 110- 0 W _ 2 115— H 3 0 2 _0 ir -120 0 0.5 1.0 • TORVANE SHEAR STRENGTH,TSF ■ UNDRAINED SHEAR STRENGTH,TSF G RD BORING B-1 Poi P1 , tsf I Kp M, tsf 0 5 10 15 20 25 0.1 1 10 0 10 20 30 40 0 400 800 1,200 1,600 0 1 1 1 1 111 I I 1 1 1 I I I 1 I I 1 1 I 1 I 11 1- r 11 1 1 I 1 1 1 1 1 ' I I I L1 0— r Po —— • r r� .--� 10 A —0 15 •—_ r r, 21 20 f • t -A r' 0 25 A •__ x K. r 30 r___-r • A, 35 r 411 ____A _ i 40 _ ti' 45 GRD DILATOMETER SOUNDING - DMT-1 JUNE 2017 JOB NO. 5970-G FIG. 4A Pp, P, ,tsf I K0 M, tsf 0 5 10 15 20 25 0.1 1 10 0 10 20 30 40 0 400 800 1,200 1,:00 0 I I I I ! I I I I I I I I I ITIT 1 1 1 1111I1 I I I I1111 I I I I I I I ITT I1 I I I I I I I III I , I Po 5 • P, _,„,_____._____.________ A_ 15 20 _ Alk in 25 r___ _ CL'Aiia 30 35 a'J",> 40 a _ etaeo. 0 0 .-too a © e a 45 oa a la.,..00 a +na, alaee , a ,,, , am ,, ,, 9 a a is , an-,,, a e 1 ,,,,,,,a rea 9e n ��,„ G R �.. „„m,> > .,.oeo DILATOMETER SOUNDING DMT-2 JUNE 2017 JOB NO. 5970-G FIG. 5A CLASS'FI('ATION OF MATERIAL a • MOISTURE CONTENT,% 1— of I— z 0 FINES CONTENT,% u v LL w w LIQUID LIMIT,% 1 �- COMMENTS AND _ _ I- a a PLASTIC LIMIT, a m m ADDITIONAL TESTS o 0 I _ 8 0 50 100 HA-1 Surface Elevation:Not Available 0 50 100 • SILT,some fine-to coarse-grained sand,trace subangular • to subi ourx:eJ gravel,brown,n1~oiun i stid 4-in.-thick heevilj'rooted zcae at the(,round surface(Fill) s 1 ® ! • o - _ t SILT,trace to some fine-to medium-grained sand,brown 2.5 J mottled rust,medium stiff I --trace to some clay below 4 ft - - I 4.5 S-2 ® •� 5_ (5/26/2017) 10- 0 0.5 1.0 • TORVANE SHEAR STRENGTH,TSF Logged By: A.Strahler Excavated by: GRI Equipment: Hand Auger Date Started: 5/26/17 Coordinates: Not Available I Note: See Legend for Explanation of Symbols HA-2 Surface Elevation:Not Available 0 50 100 Sandy SILT,trace subangular to subrounded gravel,brown mottled gray,stiff,fine-to coarse-grained sand,contains organics,4-in.-thick heavily rooted zone at the ground S1 ® • Organics=13% surface(Fill) J •2.0 SILT,some fine-grained sand,trace clay,brown mottled i rust,medium stiff I r. 1 1 1 0 cs 5— S2 El • 0 5 _ (5/26/2017) 5.5 f W I10 - O F. 0 0,5 1.0 0 • TORVANE SHEAR STRENGTH,TSF 0 J s Logged By: A.Strahler Excavated by: GRI Equipment: Hand Auger ca Date Started: 5/26/17 Coordinates: Not Available I Note: See Legend for Explanation of Symbols MEM BORINGS • • • r Cr •Pf •r ter f f( f C ( r t r r C (CI' rt ( C r CLASSIFICATION OF MATERIAL a 0C alOISTURE,CON4N1,P-% `(` r r - z 0 FINES CONTENT,% _ = z w J r { LIQUID LIMIT,°k COMMENTS AND 13- a 2 PLA57SIC LIMIT,% f1DpIT$CNAL TESTS n r.r a c9 a g u¢i 0 :- n ® r rr 100 r.< , Pre Con rec. c (CC HA-3 Surface Elevation:Not Available 0 50 100 SILT,some fine-to medium-grained silt,trace clay,brown, soft to medium stiff,4-in.-thick heavily rooted zone at the "°' •P r _d e P r ground surface o ( c rr --medium stiff below 3 ft I — I 5— --some clay below 5 ft I (5/26/2017) 5.5 S-2 ® � 10- 0 0.5 1.0 • TORVANE SHEAR STRENGTH,TSF Logged By: A.Strahler Excavated by: GRI Equipment: Hand Auger Date Started: 5/26/17 Coordinates: Not Available I Note: See Legend for Explanation of Symbols F- a a 3 Ceffin BORINGS l G 0` CG I 5 10 Z I- F" 15 20 25 10 100 0.01 0.1 1 STRESS,TSF Initial Location Sample Depth,ft Classification Xi,pcf MC, % 8 • B-1 S-2 5.5 SILT, some fine-to medium-grained sand,trace clay, brown 92 30 r CC w G RO 0 4 CONSOLIDATION TEST • P .°r . Cr r f r err f r r f. . err f r e r r r f f 5 ! rI S r (ncr f f I ( r ( t q • R r r APPENDIX B e ref. rcr rr rI fr ( r ( pre e re e e n e ref er SITE-SPECIFIC SEISMIC-HAZARD STI fDY� Feb r ; ( a rrr err r cc, rrr GENERAL eee fee r e ee ee ( () r e o e e f r GRI completed a site-specific seismic-hazard study for the proposed neu,buisdirfg dt grfi4 Clikh4 Education Center in Tigard, Oregon. The purpose of our study was to evaluate the potentials seismic hazards associated with regional and local seismicity. The site-specific seismic-hazard evaluation is intended to meet the requirements of the 2014 Oregon Structural Specialty Code (OSSC), which is based on the 2012 International Building Code (IBC). Seismic design in accordance with the 2012 IBC is based on the American Society of Civil Engineers (ASCE) 7-10 document, titled "Minimum Design Loads for Buildings and Other Structures." Our work was based on the potential for regional and local seismic activity as described in the existing scientific literature and the subsurface conditions at the site as disclosed by the subsurface explorations completed for this project. Specifically, our work included the following tasks: 1) A detailed review of available literature, including published papers, maps, open-file reports, seismic histories and catalogs, works in progress, and other sources of information regarding the tectonic setting, regional and local geology, and historical seismic activity that might have a significant effect on the site. 2) Compilation and evaluation of subsurface data collected at and in the vicinity of the site, including classification and laboratory analyses of soil samples. This information was used to prepare a generalized subsurface profile for the site. 3) Identification of the potential seismic events (earthquakes) appropriate for the site and characterization of those events in terms of a generalized design event. 4) Office studies based on the generalized subsurface profile and the generalized design earthquake resulting in conclusions and recommendations concerning: a) specific seismic events that might have a significant effect on the site, b) the potential for seismic energy amplification and liquefaction or soil-strength loss at the site, and c) site-specific acceleration response spectra for design of the seismic retrofit and building addition. This appendix describes the work accomplished and summarizes our conclusions and recommendations. Geologic Setting On a regional scale, the site is located at the northern end of the Willamette Valley, a broad, gently deformed, north-south-trending topographic feature separating the Coast Range to the west from the Cascade Mountains to the east. The site is located approximately 75 km inland from the Cascadia Subduction Zone (CSZ), an active plate boundary along which remnants of the Farallon plate (the Gorda, Juan de Fuca, and Explorer plates) are being subducted beneath the western edge of the North American GRD Q , plate. The subduction zone is a broad, eastward-dipping zone of contact between the upper portion of the suu•iuccirg slats of the Ciorzla,Juan de Fuca, and Explorer plates and the overriding North American plate, as s:),Dwii on the`Tec tonic Sting Summary, Figure 1 B. On a local scale, the site is located in the Tualatin Basin, a large, well-defined, southeast-trending structural basin bouncec by high•ang;e, northwest-trending, right-lateral, strike-slip faults considered to be seisme genic. -Ft* g84iog c units in the area are shown on the Regional Geologic Map, Figure 2B. The distribution of nearby Quaternary faults is shown on the Local Fault Map, Figure 3B. Information regarding the continuity and potential activity of these faults is lacking due largely to the scale at which geologic mapping in the area has been conducted and the presence of thick, relatively young, basin-filling sediments that obscure underlying structural features. Other faults may be present within the basin, but clear stratigraphic and/or geophysical evidence regarding their location and extent is not presently available. Additional discussion regarding crustal faults is provided in the Local Crustal Event section below. Because of the proximity of the site to the CSZ and its location within the Tualatin Basin, three distinctly different sources of seismic activity contribute to the potential for the occurrence of damaging earthquakes. Each of these sources is generally considered to be capable of producing damaging earthquakes. Two of these sources are associated with the deep-seated tectonic activity related to the subduction zone; the third is associated with movement on the local, relatively shallow structures within and adjacent to the Tualatin Basin. Subsurface and Geologic Conditions. The site is mantled by soils of the Willamette Silt Formation (Madin, 1990). In general, Willamette Silt is composed of unconsolidated beds and lenses of silt and fine-grained sand. Stratification within this formation commonly consists of 4-to 6-in.-thick beds, although beds up to 10 to 15 ft thick are also common. In some areas, the silt is massive and the bedding is indistinct or nonexistent. The Willamette Silt is brown but typically grades to gray below a depth of about 40 to 50 ft. Seismicity General. The geologic and seismologic information available for identifying the potential seismicity at the site is incomplete, and large uncertainties are associated with estimates of the probable magnitude, location, and frequency of occurrence of earthquakes that might affect the site. The available information indicates the potential seismic sources that may affect the site can be grouped into three independent categories: subduction zone events related to sudden slip between the upper surface of the Juan de Fuca plate and the lower surface of the North American plate, subcrustal events related to deformation and volume changes within the subducted mass of the Juan de Fuca plate, and local crustal events associated with movement on shallow, local faults within and adjacent to the Tualatin Basin. Based on our review of currently available information, we have developed generalized design earthquakes for each of these categories. The design earthquakes are characterized by three important properties: size, location relative to the subject site, and the peak horizontal bedrock accelerations produced by the event. In this study, earthquake size is expressed by the moment magnitude (Mw); location is expressed as the closest distance to the fault rupture, measured in kilometers; and peak horizontal bedrock accelerations are expressed in units of gravity (1 g = 32.2 ft/sec2 = 981 cm/sec2). G R H R_, YF rr' Ir f f r p f fr r '. f I' (� p . • t fff rr r t E t , r r t r t t ( r C < e r ` Subduction Zone Event. The last interplate earthquake on the CSZ occurfed in January 1700.E Geological studies show that great megathrust earthquakes have occurred repeafedly`if rthe past 7r60Q mrs5Wwater et al., 1995; Clague, 1997; Goldfinger et al., 2003; and Kelsey , 4, „2044 aid ge4 4tI rstudies (Hyndman and Wang, 1995; Savage et al., 2000) indicate rate of strain accumulation consistent with the assumption that the CSZ is locked beneath offshore northern Cadiierrrige OJregop, Washington, and southern British Columbia (Fluck et al., 1997; Wang et al., 2001). NuFrerovs eolckieatal?idrgf?ophysical studies suggest the CSZ may be segmented (Hughes and Carr, 1980; 141 avta¢0A¢icilaN.4on, 1985; Guffanti and Weaver, 1988; Goldfinger, 1994; Kelsey and Bockheim, 1994; Mitchell et al., 1994; Personius, 1995; Nelson and Personius, 1996; Witter, 1999), but the most recent studies suggest that for the last great earthquake in 1700, most of the subduction zone ruptured in a single Mw 9.0 earthquake (Satake et al., 1996; Atwater and Hemphill-Haley, 1997; Clague et al., 2000). Published estimates of the probable maximum size of subduction zone events range from moment magnitude Mw 8.3 to >9.0. Numerous detailed studies of coastal subsidence, tsunamis, and turbidites yield a wide range of recurrence intervals, but the most complete records (>4,000 years) indicate average intervals of 350 to 600 years between great earthquakes on the CSZ (Adams, 1990; Atwater and Hemphill-Haley, 1997; Witter, 1999; Clague et al., 2000; Kelsey et al., 2002; Kelsey et al., 2005; Witter et al., 2003). Tsunami inundation in buried marshes along the Washington and Oregon coast and stratigraphic evidence from the Cascadia margin support these recurrence intervals (Kelsey et al., 2005; Goldfinger et al., 2003). The U.S. Geological Survey (USGS) probabilistic analysis assumes four potential locations for the location of the eastern edge of the earthquake rupture zone, shown on Figure 4B. The 2008 USGS mapping effort indicates three rupture scenarios are assumed to represent these interface events: 1) Mw9.0±0.2 events that rupture the entire CSZ every 500 years, 2) Mw 8.3 to 8.7 events with rupture zones that occur on segments of the CSZ and occur over the entire length of the CSZ during a period of about 500 years, and 3) Mw 8.0 to 8.2 events that rupture only segments of the CSZ every 500 years (Petersen et al., 2008). The assumed distribution of earthquakes is shown on the Assumed Magnitude-Frequency Distribution, Figure 5B. This distribution assumes the larger Mw 9.0 earthquakes likely occur more often than each of the smaller segmented ruptures, as also indicated by the USGS deaggregation for the site. Therefore, for our deterministic analysis, we have chosen to represent the subduction zone event by a design earthquake of Mw 9.0 at a focal depth of 30 km and rupture distance of 75 km. This corresponds to a sudden rupture of the whole length of the Juan de Fuca-North American plate interface with an assumed rupture zone due west of the site. Based on an average of the attenuation relationships published by Atkinson and Macias (2009), Zhao et al. (2006), and Abrahamson et al. (2015), a subduction zone earthquake of this size and location would result in a peak horizontal bedrock acceleration of approximately 0.21 g at the site. Subcrustal Event. There is no historical record of significant subcrustal, intraslab earthquakes in Oregon. Although both the Puget Sound and northern California region have experienced many of these earthquakes in historical times, Wong (2005) hypothesizes that due to subduction zone geometry, geophysical conditions, and local geology, Oregon may not be subject to intraslab earthquakes. In the Puget Sound area, these moderate to large earthquakes are deep (40 to 60 km) and over 200 km from the deformation front of the subduction zone. Offshore along the northern-California coast, the earthquakes are shallower (up to 40 km) and located along the deformation front. Estimates of the probable size, location, and frequency of subcrustal events in Oregon are generally based on comparisons of the CSZ with active convergent plate margins in other parts of the world and on the historical seismic record for the region surrounding Puget Sound, where significant events known to have occurred within the subducting G R® Q , Juan de Fuca plate have been recorded. Published estimates of the probable maximum size of these events rang troll rrgmera r agr,itudr Mw 7.0 to 7.5. The 1949, 1965, and 2001 documented subcrustal ear{ wi,kes in the Puget',Sour d area correspond to Mw 7.1, 6.5, and 6.8, respectively. Published information regarding the location and geometry of the subducting zone indicates a focal depth of 50 km is probable (Weaver and Shedlock, 1989). We have chosen to represent the subcrustal event by a design earthgaaceoc n,agnirude 730 at a focal depth of 50 km and a rupture distance of 63 km. Based on the attenuaation rcla:icns:ups .ubli hed by Youngs et al. (1997) and Abrahamson et al. (2015), a subcrustal earthquake of this size and location would result in a peak horizontal bedrock acceleration of approximately 0.17 g at the site. Local Crustal Event. Sudden crustal movements along relatively shallow, local faults in the Portland area, although rare, have been responsible for local crustal earthquakes. The precise relationship between specific earthquakes and individual faults is not well understood since few of the faults in the area are expressed at the ground surface and the foci of the observed earthquakes have not been located with precision. The history of local seismic activity is commonly used as a basis for determining the size and frequency to be expected of local crustal events. Although the historical record of local earthquakes is relatively short(the earliest reported seismic event in the area occurred in 1920), it can serve as a guide for estimating the potential for seismic activity in the area. Based on fault mapping conducted by the USGS (Personius et al., 2003), the inferred location of the Canby-Mollala Fault is in the general vicinity of the southeastern corner of the site. However, the USGS does not consider the Canby-Mollala Fault to be an active, contributing source in their Probabilistic Seismic Hazard Analysis (PSHA). Based on our review of the USGS deaggregations for the site (U.S. Geological Survey, 2014), the Portland Hills Fault is the closest crustal fault identified as a hazard to the site. The inferred location of the Portland Hills Fault is approximately 10 km from the site, and the fault has a characteristic earthquake magnitude of Mw = 7. A crustal earthquake of this size would result in a peak horizontal bedrock acceleration of approximately 0.45 g at the site based on an average of the next generation attenuation (NGA) ground-motion relations published by Boore et al. (2014), Campbell and Bozorgnia(2014), and Chiou and Youngs (2014). Summary of Deterministic Earthquake Parameters In summary, three distinctly different types of earthquakes affect seismicity in the project area. Deterministic evaluation of the earthquake sources using recently published attenuation ground-motion relations provides estimates of ground response for each individual earthquake type. Unlike probabilistic estimates, these deterministic estimates are not associated with a relative hazard level or probability of occurrence and simply provide an estimate of the ground-motion parameters for each type of fault at a given distance from the site. The basic parameters of each type of earthquake are as follows: Average Earthquake Attenuation Relationships Rupture Focal Peak Bedrock Peak Bedrock Source for Deterministic Spectra Magnitude,Mw Distance,km Depth,km Acceleration,g Acceleration,g Subduction Zone Atkinson and Boore,2003 9.0 75.0 30 0.14 Atkinson and Macias,2009 9.0 75.0 30 0.18 Zhao et al.,2006 9.0 75.0 30 0.23 0.21 Abrahamson et al.,2015 9.0 75.0 30 0.29 Subcrustal Youngs et al.,1997 7.0 63.0 50 0.10 0.17 1 1 \ I Q n • P re- r e : rr , r cr Average Earthquake Attenuation Relationships Rupture , 0cal<<' Peak Bed..Q. PeOk Ptdrock Source for Deterministic Spectra Magnitude,M. Distance,km Dephh,kre r, Accreoferatio)1;g,. ff ele:rgon,g Abrahamson et al.,2015 7.0 62.0 °. r;r r�4.24 f f f Local Crustal Campbell and Bozorgnia,2014 7.0 10.0 NA 0.54 Chiou and Youngs,2014 7.0 10.0 Tr, ecc c 0.40. cc re 0.45 Boore et al. (2014) 7.0 10.0 tfA r `ce0• fi `eeo e e c e e r c e r e- e tee r c C ( , , C Probabilistic Considerations The probability of an earthquake of a specific magnitude occurring at a given location is commonly expressed by its return period, i.e., the average length of time between successive occurrences of an earthquake of that size or larger at that location. The return period of a design earthquake is calculated once a project design life and some measure of the acceptable risk that the design earthquake might occur or be exceeded are specified. These expected earthquake recurrences are expressed as a probability of exceedance during a given time period or design life. Historically, building codes have adopted an acceptable risk level by identifying ground acceleration values that meet or exceed a 10% probability of exceedance in 50 years, which corresponds to an earthquake with an expected recurrence interval of 475 years. Previous versions of the IBC developed response spectra based on ground motions associated with the Maximum Considered Earthquake (MCE), which is generally defined as a probabilistic earthquake with a 2% probability of exceedance in 50 years (return period of about 2,500 years) except where subject to deterministic limitations (Leyendecker and Frankel, 2000). The recent 2012 IBC develops response spectra using a Risk-Targeted Maximum Considered Earthquake (MCER), which is defined as the response spectrum expected to achieve a 1% probability of building collapse within a 50-year period. The design-level response spectrum is calculated as two-thirds of the MCER ground motions. Since the MCER earthquake ground motions were developed by the USGS to incorporate the targeted 1% in 50 years risk of structural collapse based on a generic structural fragility, they are different than the ground motions associated with the traditional MCE. Although site response is evaluated based on the MCER, it should be noted that seismic hazards, such as liquefaction and soil strength loss, are evaluated using the Maximum Considered Earthquake Geometric Mean (MCEG) peak ground acceleration (PGA), which is more consistent with the traditional MCE. The 2012 IBC design methodology uses two mapped spectral acceleration parameters, Ss and Si, corresponding to periods of 0.2 and 1.0 sec to develop the MCER earthquake. The Ss and Si parameters for the site located at the approximate latitude and longitude coordinates of 45.4038°N and 122.7597°W are 0.96 and 0.42 g, respectively. Estimated Site Response The effect of a specific seismic event on the site is related to the type and quantity of seismic energy delivered to the bedrock beneath the site by the earthquake and the type and thickness of soil overlying the bedrock at the site. A ground-motion hazard analysis was completed to estimate this site-specific behavior in accordance with Section 21.2 of ASCE 7-10. The ground-motion hazard analysis consisted of four significant components: 1) estimation of bedrock response using recently developed attenuation relationships (deterministic evaluation), 2) estimation of bedrock response using the 2014 USGS-based PSHA (probabilistic evaluation), 3) comparison of the deterministic and probabilistic bedrock-response CiRA r spectra to determine the controlling spectrum, and 4) development of recommended response spectra for thenu-hazard'eves: The,follq,wing paragraphs describe the details of the ground-motion hazard analysis. To estimate the deterministic''bedrock-response spectrum, recently developed attenuation relationships were used to evaluate bedrock ground motions at the site. Based on our review of the USGS OGO deagg-egatfors (U.S. Geological Survey, 2014), crustal seismicity and an event on the CSZ represent the largesi o so rce3 to tie seismic hazard at the site. Considering this, we have chosen to estimate the deterministic bedrock response using 84th-percentile ground motions from the following two earthquake scenarios: 1) a Mw 7.0 crustal earthquake at a distance of 10 km from the site and 2) a Mw 9.0 subduction zone earthquake at a distance of 75 km from the site. The same attenuation relationships outlined in the deterministic section were used to evaluate the crustal and subduction earthquake response. The resulting deterministic bedrock-response spectra are shown on Figure 6B and indicate crustal seismicity controls the hazard at the site. The deterministic MCER bedrock spectrum is taken as the larger of the 84th-percentile ground motions and the deterministic lower limit. The probabilistic bedrock- response spectrum was acquired through the use of the USGS Interactive Deaggregation (U.S. Geological Survey, 2014). The deaggregation was evaluated for a 2% in 50 years probability over a period range of PGA to 5 sec. In accordance with Section 21.2 of ASCE 7-10, the site-specific bedrock MCER response spectrum is taken as the lesser of the probabilistic and deterministic MCER bedrock motions. Figure 6B demonstrates the probabilistic bedrock spectrum is the lesser of the spectra. The site is classified as Site Class D, or a stiff-soil site, based on the average Vs3o of 900 ft/sec in accordance with Section 20.3 of ASCE 7-10. Corresponding short-and long-period adjustment factors Fa and Fv of 1.12 and 1.58, respectively, were used to develop the probabilistic Site Class D MCER response spectrum. We recommend using the Site Class D MCER and design response spectra shown on Figure 7B for design of the new structure. Seismic Hazards Liquefaction/Cyclic Softening. The results of our evaluation indicate there is a potential that zones of the interbedded silt and sand deposit below the groundwater surface at the site could lose strength or liquefy during a code-based earthquake. Based on our analysis, potentially liquefiable soils are present below the ground surface and extend to a depth of about 60 ft. Our analysis indicates the potential for 2 to 3 in. of seismically induced settlement, which may occur during the earthquake and after earthquake shaking has ceased. Other Hazards. Based on site topography, the risk of earthquake-induced slope instability and/or lateral spreading is low. The risk of damage by tsunami and/or seiche at the site is absent. The inferred location of the Canby-Mollala Fault is in the general vicinity of the southeastern corner of the site (Personius et al., 2003); however, the USGS does not consider the Canby-Mollala Fault to be an active, contributing source in their PSHA. The USGS considers the Portland Hills Fault, located about 10 km northeast of the site, to be the closest crustal fault source contributing to the overall seismic hazard at the site. Unless occurring on a previously unmapped or unknown fault,the risk of fault rupture at the site is low. Gi DL • r Cr fr Cr Cr r r r PC f f f f f f f f: tie f f et f f f f f VC f f CC( f f f f f f. f r { f f f F f It f f f r f f f CONCLUSIONS C The 2012 IBC design methodologyuses two spectral res ons aeriFneeteF , Ss gti Si p�o,.i s ondin to g P P P �, � � r�G' r 4 P g periods of 0.2 and 1.0 sec to develop the MCER response spec t 4m,,Jhe Si par e_ers for the site are 0.96 and 0.42 g, respectively. The results of the ground-motion hazard analysis indicate the 2012 IBC Site Class D spectrum provides an appropriate estimate of the fsperal facceleratbonLat the site. We recommend use of the Site Class D design spectrum shown on Fiurei7B Corr desiarr of t15elew structure at roc eff to o e the site. r e f e r f f fi f e c Ott/ r Cr CO CC References Abrahamson, N.A., Gregor, N., and Addo, K., 2015, BC hydro ground motion prediction equations for subduction earthquakes, Earthquake Spectra In-Press. Adams, J., 1990, Paleoseismicity of the Cascadia subduction zone: Evidence from turbidites off the Oregon-Washington margin: Tectonics,vol.9,no.4,pp.569-583. Atkinson, G.M., and Boore, D.M., 2003, Empirical ground motion relations for subduction zone earthquakes and their application to Cascadia and other regions:Seismological Research Letters,vol.93,no.4,pp. 1703-1729. Atkinson,G.M.,and Macias,M.,2009, Predicted ground motions for great interface earthquakes in the Cascadia Subduction Zone: Bulletin of the Seismological Society of America,vol.99, no.3,pp.1552-1578. Atwater, B.F., and Hemphill-Haley, E., 1997, Recurrence intervals for great earthquakes of the past 3,500 years at northeastern Willapa Bay,Washington:U.S.Geological Survey Professional Paper 1576,p. 108. Atwater, B.F., Nelson, A.R., Clague, J.J., Carver, G.A., Yamaguchi, D.K., Bobrowsky, P.T., Bourgeois, J., Darienzo, M.E., Grant, W.C., Hemphill-Haley, E., Kelsey, H.M.,Jacoby, G.C., Nishenko,S.P., Palmer, S.P., Peterson, C.D., and Reinhart, M.A., 1995, Summary of coastal geologic evidence for past great earthquakes at the Cascadia subduction zone: Earthquake Spectra. Boore, D.M., Stewart, J.P, Seyhan, E., and Atkinson, G.M., 2014, NGA-West2 equations for predicting PGA, PGV, and 5% damped PSA for shallow crustal earthquakes: Earthquake Spectra,August 2014,vol. 30, no. 3, pp. 1057-1085. Campbell, K. W., and Bozorgnia, Y., 2014, NGA-West2 ground motion model for average horizontal components of PGA, PGV, and 5%damped linear acceleration response spectra:Submitted to Earthquake Spectra. Chiou, B. S.J., and Youngs, R. R., 2014, Update of the Chiou and Youngs NGA model for the average horizontal component of peak ground motion and response spectra:Submitted to Earthquake Spectra. Clague,J.J., 1997, Evidence for large earthquakes at the Cascadia subduction zone: Reviews of Geophysics,vol.35,no.4,pp.439- 460. Clague, J.J., Atwater, B.F., Wang, K., Wang, Y., and Wong, I., 2000, Penrose conference report-Great Cascadia earthquake tricentennial:GSA Today,vol. 10,no. 11,pp. 14-15. Fluck, P., Hyndman, R.D., and Wang, K., 1997, Three-dimensional dislocation model for great earthquakes of the Cascadia subduction zone:Journal of Geophysical Research,vol. 102,no.B9,pp.20539-20550. Goldfinger, C., 1994, Active deformation of the Cascadia Forearc-Implications for great earthquake potential in Oregon and Washington,Oregon State University, unpublished dissertation. Goldfinger, C., Nelson, C.H., and Johnson, J.E., 2003, Holocene earthquake records from the Cascadia subduction zone and northern San Andreas fault based on precise dating of offshore turbidites:Annual Review of Earth and Planetary Sciences 31,pp. 555-577. Guffanti, M., and Weaver, C.S., 1988, Distribution of Late Cenozoic volcanic vents in the Cascade Range-Volcanic arc segmentation and regional tectonic considerations:Journal of Geophysical Research,vol.93,no.B6,pp.6513-6529. Hughes,J.M.,and Carr,M.J., 1980,Segmentation of the Cascade volcanic chain:Geology,vol.8,pp. 15-17. Hyndman, R.D., and Wang, K., 1995,The rupture zone of Cascadia great earthquakes from current deformation and the thermal regime:Journal of Geophysical Research,vol. 100,no.B11, pp.22133-22154. Kelsey, H.M., and Bockheim, J.G., 1994, Coastal landscape evolution as a function of eustasy and surface uplift rate, Cascadia margin,southern Oregon:Geological Society of America Bulletin,vol. 106,pp.840-854. Kelsey, H.M., Witter, R.C.,and Hemphill-Haley, E., 2002, PI.-boundary earthquakes and tsunamis of the past 5500 yr,Sixes River estuary,southern Oregon:Geological Society of America Bulletin,vol. 114,no. 3,pp.298-314. G R N R_, 4 Kelsey, H.M., Nelson, A.R., Hemphill-Haley, E.,and Witter, R.C.,2005,Tsunami history of an Oregon coastal lake reveals a 4600 yr record of great earthquakes on the Cascadia subduction zone:GSA Bulletin,vol. 117,pp. 1009-1032. Leyendecker, E.'/.., and Frankel;A.C., 2000, Development of maximum considered earthquake ground motion maps_Earthquake Spectrepy.ol. 16,nD. 1. Madin,I.P.,1990, Earthquake-hazard geology maps of the Portland metropolitan area:Oregon Department of Geology and Mineral Studies Open-File Report 90-02. Mitchell, C.E., Vi,iccnt,,P. Weldor, R.,. III, end Richards, M.A., 1994, Present-day vertical deformation of the Cascadia margin, Pacific Plortk'e t, l nitcd Stat.s:Journal of Geophysical Research,vol.99,no. B6,pp. 12257-12277. Nelson, A.R., aria Personius, S.F.., 1996, Great-earthquake potential in Oregon and Washington-An overview of recent coastal geologic studies and their bearing on segmentation of Holocene ruptures, central Cascadia subduction zone, in 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,vol.1,pp.91-114. Personius, S.F., 1995, Late Quaternary stream incision and uplift in the forearc of the Cascadia subduction zone,western Oregon: Journal of Geophysical Research,vol. 100,no. B10,pp.20193-20210. Personius,S. F., Dart, R. L.,Bradley,Lee-Ann,and Haller,K.M.,2003,Map and data for Quatemary faults and folds in Oregon: U.S.Geological Survey Open-File Report 03-095. Petersen,M. D.,Frankel,A. D., Harmsen,S. C.,Mueller,C.S., Haller, K.M.,Wheeler, R. L.,Wesson, R. L.,Zeng,Y., Boyd, O.S., Perkins, D. M., Luco, N., Field, E. H.,Wills, C.J.,and Rukstales, K.S., 2008, Documentation for the 2008 update of the United States National Seismic Hazard Maps: U.S.Geological Survey Open-File Report 2008-1128. Satake, K., Shimazaki, K., Tsuji, Y., and Ueda, K., 1996, Time and size of a giant earthquake in Cascadia inferred from Japanese tsunami records of January 1700: Nature,vol.379,pp.246-249. Savage,J.C.,Svarc,J.L.,Prescott,W.H.,and Murray,M.H.,2000, Deformation across the forearc of the Cascadia subduction zone at Cape Blanco,Oregon:Journal of Geophysical Research,vol. 105,no.B2,pp.3095-3102. U.S.Geological Survey,2014,Unified hazard tool lookup by latitude,longitude,accessed 04/11/17 from USGS website: https://earthquake.usgs.gov/hazards/interactivel. Wang, Y., He, J., Dragert, H., and James, T.S., 2001, Three-dimensional viscoelastic interseismic deformation model for the Cascadia subduction zone:Earth,Planets and Space,vol.53,pp.295-306. Weaver, C.S., and Shedlock, K.M., 1989, Potential subduction, probable intraplate and known crustal earthquake source areas in the Cascadia Subduction Zone:U.S.Geological Survey Open-File Report 89-465,pp. 11-26. Weaver,C.S.,and Michaelson,C.A., 1985,Seismicity and volcanism in the Pacific Northwest-Evidence for the segmentation of the Juan de Fuca PI.:Geophysical Research Letters,vol. 12,no.4,pp.215-218. Witter, R.C., 1999, Late Holocene Paleoseismicity, tsunamis and relative sea-level changes along the south-central Cascadia subduction zone,southern Oregon: University of Oregon,unpublished Ph.D dissertation,pp. 178. 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G R_ R-R '1$ 130°Q 126° 122°W (4 11 52°N PORTLAI.D NORTH AMERICA Coastline Dar sl Cascades PLATE Range Ark. A British -_ Columbia 1 1 1 - r 1. i r Rr 1245 1241 1231 123.0 122.5 1220 121.5 A /EXPLORERe , LONGITUDE PLATE Vancouver_- fi�iA� �,,��vv.a \ p A DISTANCE IN KM Crustal faults �� aY` "" (q is A 4Q° 10. 30. 50. 70. 90. 110. 130. 150. 170 I1�90I.� L210. 230 250. 270. 290. 01 dif Seattle to. D o e : L'. T' 1:>�!v •- a 10. e • �w 1 (y fr a T e v ° .l`,,�,':�� e p ° v,O O e / es 00 D CP ° ° mn •'. .4 °° North America Plate Q / r; Washington $p, O 12 6 Plate Crustal �' D JUAN DE FUCA n r Interface °e^de�, seismicity _ 'gym �� PLATE p ? PonlandQ ? 70, Lea prate 70. L 1.1 L° 90. Intresleb 7 �1earthquakes _90. 0 d B/an� U Q 44° t I0. 110. �&y R Oregon �pn® c gi A 130. iJO. rg PACIFIC PLATE �, d ___- 150 150. a 1 r 1 1 r 1 p8 -- fete 124.0 123A 123.0 122.5 122.0 12'I.0 , e / GORDA A LON011UOE co PLATE California A ,0 1, , DEFORMATION '^ * a 8) EAST-WEST CROSSSECDON THROUGH WESTERN OREGON AT THE LATITUDE Of PORTLND,SHOWING THESE7SMIC "'^ 0 200 km Mendocino Fault ky l�CyyN O; 40° SOURCES CONSIDERED IN THE 5ITESPECIFICSEISMIC HAZARD STUDY WIODIFIED FROM GEOMATRIX,1995) ^ ? i � A^ R '3 1 , , 1 9 # ^ 9R AI TECTONIC MAP Of PACIFIC NORTHWEST,SHOWING ORIENTATION AND EXTENT OF CASG1gA •, SUBDIICFION ZONE MODIFIED FROM ORAGERT AND OTHERS,1994) ^ T , ,^ "' ©'FrasiI ^ ' , TECTONIC SETTING SUMMARY JUNE 2017 JOB NO.5970G FIG.18 • \ Kelso MAP EXPLANATION `•\ �� y ,� + TIME OF MOST RECENT SURPRL£RIIPNRE STRUCTURE TYPE AND ROAMS FEATUPE5 ul' r d r \ ,,min W\1 — Balsam Is10.000 ysemla peel past 9ledelon 915 COS years:IS ke1'. �— Normal o,n41v194 revere hue tFGearhott - L I mmzonemwresmwmle �-- rinse-Rpew \r y lee WelmreN l<1a41 atcp mnulemele9la]atgnl TeuMte,q rt n, ' d v. — Sae and mtlEle Oualnuryf OM MO years.PAte1 —I— AneditMl kN 781 i \ — — Oealemen.ameeremlemn �- \. FS — class B smmere Mae a wlgm uncertain, + Mgl¢Imlmle 7 0�\ -jOS 1 SLIP HATE '— Plunge dl,elycndlad 1 l 25 mMYea / Fault section maser ach1781-0e +A"i ``•j`718 \ — lo5ommya.r r r 8 St.Helens — OTI ammyem oETMleesTuov slrEs I A2mmnNr Ill' s TKM1i,see / o C') Suertucwn zomseely NN TRACE la '6 !V continuo. sa �e ..-� RAFHIC FEATURES ��. �,^�r•' ^t \\580 Mostly sawnl noa Imes _ IN.Nm nglomyE 87 mP o a �J' e 'ft" r 1 1 7 . Inrenmamt,mMm P aewm n� P ry 81" , . q' Vancouver Into Ayer or 'af `N`e r y enMnentaser entLM ..✓' V� 714 ITva e LAi n 3 t _ 880 8'4 T FAULT NUMBER NAME OF STRUCTURE ' rT a!E, {�+_• f% A\ 1 war SLY c �'> Forest Grove "� — 8'' "• .876 to n 714 HELVETIA FAULT ,_ t �,� •' n\\ 875\ ',r ;+E BFAVERTON FAULT 1�8 a +„ ., j,`y Hillsboro t878ti 77165 EANBYMOLALIAFAULT 1882. t"`,.r{'1', vAv t. ", ., -,3 879 868E ,�y ,a*` 868 11 k A d yA` 718 715 �� b �7% AA' yg . '• 718 NEWEEKGFAUU 718 GALES CREEK HILSHOMOCU ,. v+ . !1 Ty �y g, � � yt 719 SALEM-EDLA HILLS HQNOCDNE 781 Gr «t+'r I '\\ vN Portland a - 864 CLACKAMAS RIVER FAULT ZONE ••� / Tt,y. SITE ei4 879 I yi,3 p,. 867 EAGLE CREEK THRUST FAULT 1 T Sd7ina ' Mr% .717 ,y , ,y""�sIM 86B BULL RUN THRUST FAULT rr Area Of \�.&'"�,,,'(yjD 872 WALDO HILLS FAULT T,a, 1`Newberg Portland map r are ��Lggq''+++ �'� 873 MOUNT ANGEL FAULT Jr,.se 874 ATFIEL FAULT McMinnville Canby'T P„, Z #a ". 876 EAST FAULT o , Dayton "- s� qr 876 FAST BANK FAULT o 761-3 � 877 ass slit ND HILLIrttIsss ere-o Woodburn 'Morella aM r.. 878 s�N LE CRE FAULT s ,�_ n Sheridan Amity Jr :e, �" •�y- 879AAIASCUSTICKLE CREC#FAULT ROVE 880 y ^`t a.,-wN �n y o r e s1A IAKEUATLZ•s s s 'o Ye..A `-., 881 s TILIAM�OKBAY FAULT ZORIE `l A 0 3 , 1 d b 8 t •'`. . Silverton e`,,873 h^"� •Doss 1 1-" ' :t .° FR[MFN1II�,S.F.,ANDD pp]t POFQUATtRNAVY FAULISAND } • NADS IN OREGON,l l OPR03095.s e,, o " . Dallas 719y Salem 7 x} e F ooso sss o Independence i ti 872, ' "+" '� \ 864 - ;,_I ',� "<884 ... '4 Monmouth. `x t'ay5"" x.' \ 8! e s©s e® 70s 20 M'AEg- �n - Z 671Staylon -•"�".,w'„Y "• o e o o s o n9 `,4- 4 is 4 a qp 5 _ _ {�`"" ;, s o 0 o'y•s s KIL01�1ETER osoomo Mill City yr+ `4* r T e5. a 8.wa- o o L. -_ lirye wU'Fi.,,.: - _�,.r„ .u, � ^*.. .,,,.,,y T, +` .+ ®®� e a s o a o •. d o 0 LOCAL FAULT MAP IUNE 2017 JOB NO.5970G FIG.38 -,yY-- 48 N f dus :a : . _ . � • t , • , ,,' ashington - .,. • ; • . , n 4 : : a s Fi' - 4 Arw yea: 4 a y 46°N - , I FIGURE 21. LOCATION OF THE EASTERN EDGE OF EARTHQUAKE RUP... TURE ZONES ON THE CASCADIA SUBDUCTION ZONE FOR THE VARIOUS MODELS USED IN THIS STUDY RELATIVE TO THE SURFICIAL EXPRESSION >>"� OF THE TRENCH:TOP,BASE OF THE ELASTIC ZONE;MID,MIDPOINT OF 44`N THE TRANSITION ZONE;BOTTOM,BASE OF THE TRANSITION ZONES; BASE,BASE OF THE MODEL THAT ASSUMES RUPTURES EXTEND TO ABOUT 30 KILOMETERS DEPTH.FIGURE PROVIDED BY RAY WELDON. t 'r . VJ 1 42 N 4 a:?t; t ',�f 3 L A i a lsj.=-,i top ggggf f1 .. mid xf F bottom 1 base s a 5 trench 26`W 124°W 122°W FROM: PETERSEN,MD,FRANKEL,AD,HARMSEN,SC, AND OTHERS,2008,DOCUMENTATION FOR THE 2008 UPDATE OF THE UNITED STATES NATIONAL SEISMIC HAZARD MAPS:US GEOLOGICAL SURVEY,OPEN FILE REPORT 2008-1128 G RQ ASSU vVED RUPTURE ATIONS (CASCADIA SUBDUCTIONLOC ZONE) e re Cr Cr' C f r f Cr frt- I r r I r r C r' t r r Cr tr I r rf r r r r cr r r r f` rrr C Cr C frf. ref rr f et f. C f t r f r R or( Cr r tr t fff frf ^fP r rCf tCE" err e'er C C Cr CC f I f R f f f C f f 0.0009 f r f, C r r r t, f r r CPf9 14I !C R r r r C I f I err C err C r C r CC . 0.0008 —_ 0.0007 - LJJ 0.0006 --- _ 0 0.0005 - w CC a 0.0004 a 0.0003 0.0002 - 0.0001 0 7.8 8 8.2 8.4 8.6 8.8 9 9.2 9.4 MOMENT MAGNITUDE Figure 22. Magnitude-frequency distribution of the Cascadia subduction zone. FROM: PETERSEN,M,FRANKEL,A,HARMSEN,S, AND OTHERS,2008,DOCUMENTATION FOR THE 2008 UPDATE OF THE UNITED STATES NATIONAL SEISMIC HAZARD MAPS:US GEOLOGICAL SURVEY,OPEN FILE REPORT 2008-1128 G RO ASSUMED MAGNITUDE-FREQUENCY DISTRIBUTION (CASCADIA SUBDUCTION ZONE) Deterministic Bedrock Response Spectrum r Based on Portland Hills Fault Hazard 2.0 / (84th Percentile Ground Motions) 1.8 VI lDeterministic Lower Limit Response Spectrum 1.6 I 1.4 I I Probabilistic Bedrock Response Spectrum Based on 2% in 50-Year Hazard r 1 (USGS 2014 Deaggregation) o L i 1.2ID i u !_ Q M V / Deterministic Bedrock Response Spectrum II Based on Subduction Zone Hazard 0.8 (84th Percentile Ground Motions) 0.6 9 \ \ 0.4 N 0.2 0.0 - 0 1 2 3 4 Period, T, seconds G ®II DETERMINISTIC VS PROBABILISTIC BEDROCK RESPONSE SPECTRA (5%DAMPING) P r re re or P r r r re e r ( r t e r e f cc (. r f f If If I r e e r r4 r P rr err e'er re er rr f (r• C r f rrf f C ffr e ( r f f f r r rrr e z r e( r C r c It a err' 1.2 r- ref CCe f a+ Fr CC f ( I (' r P ( ( ( f r f 4 fee ec( f (e Y 4 < f C f ! ( r ( f ( (It C ( ( ( r ( 1.0 0.8 00 c , Recommended MCER Response Spectrum L d a C.) 0.6 ro d a J.") / Recommended Design Response Spectrum 0.4 l! 0.2 0.0 --_ 0 1 2 3 4 Period,T, seconds G ©fl DESIGN AND RECOMMENDED RESPONSE SPECTRA (5%DAMPING)