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Report (4) 4.11) • it= *No Q sr3 ! -off (JP) 1p UP zoo , 1 - 00 /C 61111 (I C ,,) te4.345 ... a division of Carlson Testing ‘1111110 I I I I I I I I I Report of Geotechnical Engineering Services I Auditorium Southwest Church of Christ I 9725 Southwest Durham Road Tigard, Oregon I CGT Project: G0302245 I Prepared epa ed fo r I Mr. Gary Lewis Lewis and Van Vleet I 18660 Southwest Boones Ferry Road Tualatin, Oregon 97062 I March 18, 2004 I ci,G°\1 53 I PR 11004 a I eo\ -°\N 0 Goffis (Carlson Geotechnical Main Office Salem Office Bend Office P.O. Box 23814 4060 Hudson Ave., NE P.O. Box 7918 A Division of Carlson Testing, Inc. Tigard, Oregon 97281 Salem, OR 97301 Bend, OR 97708 Geotechnical Consulting Phone (503) 684 -3460 Phone (503) 589 -1252 Phone (541) 330-9155 (Construction Inspection and Related Tests FAX (503) 670-9147 FAX (503) 589 -1309 FAX (541) 330 -9163 I March 18, 2004 I Mr. Gary Lewis Lewis and Van Vleet I 18660 Southwest Boones Ferry Road Tualatin, Oregon 97062 I Report of Geotechnical Engineering Services Auditorium I Southwest Church of Christ 9725 Southwest Durham Road I Tigard, Oregon CGT Project: G0302245 I I Dear Mr. Lewis, Carlson Geotechnical is pleased to submit our report of Geotechnical Engineering Services for I the new auditorium to be constructed at the existing Southwest Church of Christ located at 9725 Southwest Durham Road in Tigard, Oregon. We performed our work in general accordance with our proposal P02972 dated February 10, 2004. I We appreciate the opportunity to work with you on this project. Please call if you have any I questions regarding this report. Sincerely, I Carlson Geotechnical I Brian C. Ranney, G.I.T. I Geotechnical Project Manager Attachments I I I I I TABLE OF CONTENTS I INTRODUCTION 5 PROJECT INFORMATION AND SITE DESCRIPTION 6 Project Information 6 I Regional Geology 6 Site Geology 7 I Earthquake Sources and Seismicity 7 Portland Hills Fault Zone 7 I Gales Creek - Newberg -Mt. Angel Structural Zone 8 Other Mapped and Unmapped Crustal Sources 9 I Intra -Slab Source 9 Cascadia Subduction Zone 9 Earthquake Magnitude 10 I Maximum Credible Earthquake 10 Maximum Probable Earthquake 11 Seismic Shaking 11 I Site Surface Conditions 13 I Site Subsurface Conditions 13 Field Exploration 13 Subsurface Materials 13 I Ground Water 14 Liquefaction Analysis 14 I Laboratory Testing 15 CONCLUSIONS 15 I General 15 I Seismic Hazards 15 Liquefaction Related Ground Failure 15 Landsliding 16 I Tsunami or Seiche Inundation 16 Fault Displacement and Subsidence 16 I I I I RECOMMENDATIONS 16 I Site Preparation 16 Wet Weather Considerations 17 I Structural Fill 18 On -site Materials 18 I Imported Granular Material 18 Shallow Foundations 19 I Bearing Pressure and Settlement 19 Lateral Capacity 19 I Floor Slabs 20 Utility Trenches 20 I Utility Trench Excavation 20 Trench Backfill Material 21 Pavements 21 I Drainage Considerations 22 I Permanent Slopes 22 Seismic Design 22 I OBSERVATION OF CONSTRUCTION 22 I LIMITATIONS 23 REFERENCES 25 1 I I I I I New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 1 INTRODUCTION This report presents the results of our geotechnical investigation for the new auditorium to be ' constructed at the Southwest Church of Christ located at 9725 Southwest Durham Road in Tigard, Oregon. The site location is shown on Figure 1. The purpose of our geotechnical investigation was to evaluate subsurface conditions in order to provide geotechnical recommendations for design and construction. Our scope of work included the following: • Coordinate location of underground utilities. • Advance one cone probe to a maximum depth of 38 feet below ground surface. • Excavate four test pits to depths of up to 10.0 feet bgs. ' • Classify the materials encountered in the explorations by ASTM Visual - Manual Method. • Collect representative soil samples for laboratory testing and to verify our field ' classifications. • Complete two grain size analyses on representative samples collected from the ' explorations in general accordance with ASTM D117 and C136. • Complete moisture content determinations on representative samples collected from the explorations in general accordance with ASTM D2216. ' • Evaluate seismic hazards at the site, including liquefaction, tsunami and estimated peak ground acceleration in accordance with the requirements of Section 1802 of the 1997 Uniform Building Code and the 1998 Oregon Structural Specialty Code Chapter 18, Section 1804. • Provide a discussion of seismic sources and estimated maximum probable earthquakes in the vicinity of the site. • Provide recommendations for site preparation, grading and drainage, stripping depths, fill type for imported materials, compaction criteria, cut and fill slope criteria, trench excavation and backfill, use of on -site soils, and wet/dry weather earthwork. • Provide geotechnical- engineering recommendations for design and construction of shallow spread foundations, including allowable design bearing pressure and minimum footing depth and width. ' • Provide geotechnical engineering recommendations for the design and construction of concrete floor slabs, including an anticipated value for subgrade ' modulus and recommendations for a capillary break and vapor retarder. • Provide recommendations for subsurface drainage of foundations and pavements, if necessary. Carlson Geotechnical Page 5 I I New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 I • Provide recommendations for design pavement sections, including base course and asphalt concrete thicknesses for parking areas and driveways. I • Provide recommendations for the Uniform Building Code (UBC) site coefficient and seismic zone. I • Provide a written report summarizing the results of our investigation. PROJECT INFORMATION AND SITE DESCRIPTION I Project Information I Development will include construction of a 9,000 square foot, single -story wood framed structure with limited repair or installation of associated utilities, pavements and landscaping. I We understand that bearing wall loads and individual column loads will not exceed 2 kips per linear foot (klf) and 50 kips, respectively. We have also assumed that soil - supported ground floor loads will not exceed 250 pounds per square foot (psf). The maximum depth of cuts and fills are I anticipated to be less than 3 feet. Regional Geology I The site is located within the Willamette Valley in Tigard, Oregon. The Willamette Valley was I formed when the volcanic rocks of the Oregon Coast Range, originally formed as submarine islands, were added onto the North American continent. The addition of the volcanic rocks to the North American continent caused inland downwarping, forming a depression in which I various types of marine sedimentary rocks accumulated. Approximately 15 million years ago, these marine sediments were, in turn, covered by Columbia River Basalts that flowed down the Columbia River Gorge and Willamette Valley, as far south as Salem, Oregon. Later uplift and I tilting of these Columbia River Basalts, the Oregon Coast Range, and the western Cascade Range formed the trough -like character of the Willamette Valley that we observe today. During I this same period, local volcanic activity produced the Boring Lavas through several localized vents including Mt. Sylvania, Mt. Scott, and Mt. Tabor. Catastrophic floods later washed into the Willamette Valley approximately 12,000 to 15,000 years ago and deposited fine- grained I sedimentary assemblages mapped throughout the area. I I I Carlson Geotechnical Page 6 ' New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 Site Geology ' The available mapping (Maddin, 1990 indicates that the site is underlain by approximately 60 feet of fine grained Pleistocene aged flood deposits, which are in turn underlain by the basement rocks of the area, the Columbia River Basalts. ' Several northeast trending faults are mapped within a few miles of the site, and one is mapped 9 PP Pp on the site. These faults are defined by offset of a single contact surface such as the Columbia River Basalts. The mapping suggests that these faults do not cut the Pleistocene flood deposits beneath the site. These faults, as well as others that may affect the site, are discussed below. ' Earthquake Sources and Seismicity ' The site is located in tectonically active area that may be affected by crustal earthquakes, intra- slab earthquakes, or large subduction zone earthquakes. Damaging crustal earthquakes in this region may be derived from local sources such as the Portland Hills Fault Zone, the Gales ' Creek - Newberg -Mt. Angel Structural Zone, and several of the unnamed faults located within a few miles of the site. Crustally derived earthquakes typically occur at depths ranging from 15 to 40 km (Geomatrix Consultants, 1995). Intra -slab earthquakes occur within the subducting Juan De Fuca oceanic plate at depths ranging from approximately 40 km to 70 km. Large subduction ' zone earthquakes in this region are derived from the Cascadia Subduction Zone (CSZ). Due to the lack of historical data on large subduction zone earthquakes, a typical depth for the occurrence of subduction zone earthquake was inferred from models presented by Geomatrix Consultants in 1995 and is roughly 10 to 25 km. Portland Hills Fault Zone The Portland Hills Fault Zone is a series of northwest- trending faults located approximately ' 17 miles north of the site. The faults associated with this structural zone vertically displace the Columbia River Basalt Group by 1,130 feet, and appear to control thickness changes in late Pleistocene (approximately 780,000 years) sediment (Madin, 1994). The fault zone extends ' along the eastern margin of the Portland Hills for a distance of 25 miles and has been mapped in the Portland area as a series of inferred faults with no surface expression. Geomorphic lineaments suggestive of Pleistocene deformation have been identified within the fault zone, but none of the fault segments has been shown to cut Holocene (last 10,000 years) deposits (Balsillie and Benson, 1971; Cornforth and Geomatrix Consultants, 1992). The fact that the 1 Madin, 1990. Earthquake Hazard Geology Maps of the Portland Metropolitan Area, Oregon. Ian P. Madin. Oregon Department of Geology and Mineral Industries Open File Report 0 -90 -2. Carlson Geotechnical Page 7 1 New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 ' faults do not cut Holocene sediments is most likely a result of the faulting being related to a time of intense uplift of the Oregon Coast Range during Miocene time, and little to no movement ' along the faults during the Holocene. ' Recent studies of this fault (Wong and Others, 2000) conclude that the Portland Hills Fault is potentially active, based on contemporary seismicity in the vicinity of the fault and seismic reflection data suggesting that the fault cuts late Pleistocene layered strata. Additionally, In May of 2000, while taking magnetic readings to map the fault, an Oregon Department of Geology and Mineral Industries (DOGAMI) geologist observed folded sediment in a retaining wall cut in North Clackamas Park south of Portland. The folded sediments consisted of sand and silt deposited by Pleistocene floods derived from glacial Lake Missoula approximately 12,800 to 15,000 years ago. An investigation of the folded strata by DOGAMI geologist and ' engineering consultants showed that the entire sequence of sediment layers is folded and they concluded that this folding is evidence for an active fault beneath the site, and the fault is either the Portland Hills Fault, or a closely related structure (Madin and Hemphill - Haley, 2001). 1 Gales Creek - Newberg -Mt. Angel Structural Zone ' The Gales Creek - Newberg -Mt. Angel Structural Zone is a 50- mile -long zone of discontinuous, northwest - trending faults located approximately 15 miles to the south - southwest of the site. ' In 1993, Unruh and others modeled the Gales Creek, Newberg, and Mt. Angel faults as separate faults rather than a long, continuous fault zone based on changes in sense of displacement, evidence for discontinuities in the subsurface, different deformation histories, and ' differences in geomorphic expression and seismicity. However, since the faults share a common orientation, and several other studies (Yeats and others, 1996; Nablek and others, 1991) have indicated that these faults may be part of a larger interconnected zone of deformation we have considered these faults as an interconnected structural zone as well. The Gales Creek - Newberg -Mt. Angel Structural Zone is recognized in the subsurface by vertical separation of the Columbia River Basalt and offset seismic reflectors in overlying basin sediments (Yeats et al., 1996; Werner et al., 1992). A geologic study conducted for the Scoggins Dam site in the Tualatin Basin revealed no evidence of deformed geomorphic surfaces along the Gales Creek or Newberg Faults and no seismicity have been recorded on these faults (Unruh, 1994). In contrast, geomorphic surfaces that extend across the Mt. Angel Fault are warped such that they are consistent with uplift on the northeast side of the fault (Unruh et al., 1994). In 1990, a series of small earthquakes ( <M3.5) occurred near the town of Woodburn, and in 1993, an M5.6 earthquake occurred near the town of Scotts Mills (Werner et al., 1992; Geomatrix Consultants, 1995). These seismic events are generally attributed to the Mt. Angel Fault. 1 ' Carlson Geotechnical Page 8 I I New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 I Other Mapped and Unmapped Crustal Sources I Several other crustal sources, including the inferred fault mapped on the site, and numerous unnamed inferred faults mapped within a few miles of the site may be capable of producing damaging earthquakes in the region. However, due to their distance from the site, non - active I classification, their short fault segments, or low probability of activity, we did not elaborate on these sources for this study. I Several crustally derived seismic events have been recorded in areas where no faults are mapped. Recent seismic activity near Kelly Point near the confluence of the Willamette and I Columbia Rivers in Portland, Oregon is an example of seismicity that cannot be correlated to a known fault. This fact is most likely a function of the heavy forestation of western Oregon preventing the direct observation of faults that may occur in those areas. Additionally, most I faulting within the Portland area does not cut the Holocene sediments and is thus difficult to define. Furthermore, the displacement of the Holocene sediments due to ongoing fault I movement in recent geologic time is minor and difficult to observe. Additional geophysical studies may define these unmapped sources in the future. Intra -Slab Source Earthquakes derived from intra -slab sources occur within the subducting Juan De Fuca Plate at I depths ranging from 20 to 40 miles (Geomatrix Consultants, 1995). Approximately 20 miles west of the current coast line is the Cascadia Subduction Zone where the subducting Juan De I Fuca Plate moves eastward (relative to the North American Continent) beneath the North American Plate dipping at an angle of 10 to 20 degrees. As the plate moves farther away from the CSZ, the curvature of the plate increases and causes normal faulting within the oceanic I slab in response to the extensional forces of the down dipping plate. The region of maximum curvature of the slab is where large intra -slab earthquakes are expected to occur, and is located I roughly 30 miles below the Oregon Coast Range. Historically, the seismicity rate within the Juan De Fuca Plate beneath Oregon is very low in northern Oregon and extremely low in southern and central Oregon (Geomatrix Consultants, 1993, 1995). I Cascadia Subduction Zone I The Cascadia Subduction zone is a 680- mile -long zone of active tectonic convergence where oceanic crust of the Juan De Fuca Plate is subducting beneath the North American continent at I a rate of four cm /year (DeMats et al., 1990). Very little seismicity has occurred on the plate interface in historic time, and as a result, the seismic potential of the Cascadia Subduction Zone is a subject of scientific controversy. The lack of seismicity may be interpreted as a period of Carlson Geotechnical Page 9 I New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 quiescent stress buildup between large magnitude earthquakes or as being characteristic of the long -term behavior of the subduction zone. A growing body of geologic evidence, however, strongly suggests that prehistoric subduction zone earthquakes have occurred (Atwater, 1992; Carver, 1992; Peterson et al., 1993; Geomatrix Consultants, 1995). This evidence includes: (1) ' buried tidal marshes recording episodic, sudden subsidence along the coast of northern California, Oregon, and Washington; (2) burial of subsided tidal marshes by tsunami wave deposits; (3) paleoliquefaction features; and (4) geodetic uplift patterns on the Oregon coast. Radiocarbon dates on buried tidal marshes indicate a recurrence interval for major subduction zone earthquakes of 250 to 650 years with the last event occurring 300 years ago (Atwater, ' 1992; Carver, 1992; Peterson et al., 1993; GC, 1995). The inferred seismogenic portion of the plate interface is roughly coincident with the Oregon coastline and lies approximately 40 miles west of the site. Earthquake Magnitude Both deterministic and probabilistic methods are generally used to evaluate the seismic hazard at a specific site. The deterministic method, considers the worst -case scenario based on the maximum credible earthquake (the largest earthquake that could be expected to occur) and is used for critical facilities like power plants, hospitals, and hazardous substance storage facilities. The probabilistic method, considers the probability of earthquake occurrence during ' the lifetime of a particular facility, and is more appropriate for residential and commercial development. Both methods involve the choice of a design earthquake that is used to calculate the intensity of ground motion expected at the site. Maximum Credible Earthquake The primary means for estimating the maximum earthquake that a particular fault could generate are empirical relationships between earthquake magnitude and fault rupture length ' (Bonilla et al., 1984). Based on these relationships, the size of historical earthquakes, and the thickness of seismogenic crust in the Willamette Valley, the maximum earthquake magnitude expected from crustal source is M6.0 to M6.6 (Geomatrix Consultants, 1995). Based on the ' likely thin nature of the Juan De Fuca Plate and comparing the historic seismicity along Cascadia with other margins, Geomatrix Consultants (1995) estimated the maximum magnitude ' earthquake for intra -slab sources is M7 to M7.5. Similarly, based on magnitude versus rupture area relationships for subduction zone earthquakes worldwide, the maximum magnitude of a Cascadia Subduction Zone earthquake is estimated to be M8.0 to M9.0 (Geomatrix 1 Consultants, 1995). Carlson Geotechnical Page 10 I I New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 I Maximum Probable Earthquake I Magnitude estimates for the maximum probable earthquake are based largely on the record of historical earthquakes in the region of interest. Table 1 lists earthquakes with magnitudes larger than M4.9 that have occurred in or near Oregon since 1873 (Wong and Bott, 1995). I Table 1 - Historical Earthquakes in Oregon with Magnitudes Greater than M4.9 r Maximum Modified Date Magnitude Location Mercalli Intensity I 1873 M6.75* VIII Crescent City, California 1877 M5.25* VII Portland 1892 M5.0* VI Portland I 1936 M6.1 VII+ Milton - Freewater 1962 M5.5 VII Vancouver - Portland 1968 M5.0 V Adel I 1993 M5.6 VII Scotts Mills 1993 M6.0 VII -VIII Klamath Falls I *Magnitude estimated from Modified Mercalli intensity. Based on the historical record and crustal faulting models of the Willamette Valley region, the I maximum probable earthquake for crustal sources in the vicinity of the subject site is estimated to be M5.75 (Geomatrix Consultants, 1995). Similarly, the maximum probable earthquake for I an intra -slab source on the Cascadia Subduction Zone is estimated to be M7.5 to M7.7. Seismic Shaking I A standard quantitative method of describing ground motion associated with propagating seismic waves is to specify peak ground accelerations (PGA) in bedrock. PGAs are average I values based on empirical attenuation relationships of seismic wave energy with distance from the causative fault. PGAs are expressed as a fraction of the acceleration of gravity (i.e., a I vertical PGA of >1.0 g would throw objects into the air). Table 2 shows the estimated PGA at the subject site for the maximum credible events on the listed faults, based on attenuation relationships developed by and Geomatrix Consultants (1995), on numerical models by Cohee I et al. (1991) and Youngs et al. (1993), and on recent ground shaking maps for the Portland Hills Fault (Wong et al, 2000). 1 I I Carlson Geotechnical Page 11 I I New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 I Table 2 — Estimated Peak Ground Accelerations at "Rock Sites" I Resulting from Maximum Credible Events on Known Faults Moment Epicentral Estimated Peak I Earthquake Source Magnitude (M„,) Distance (miles) Ground Acceleration Portland Hills Fault Zone 6.6 17 0.5 -0.6 g Gales Creek - Newberg -Mt. Angel Fault Zone 6.6 15 0.25 g Infra-Slab 7.5 30 0.30 g I Cascadia Subduction Zone 8.5 40 0.20 g A recent study commissioned by the Oregon Department of Transportation evaluated all known I earthquakes sources in Oregon and formulated probabilistic assessments of expected seismic shaking; based on maximum probable earthquake magnitudes (Geomatrix Consultants, 1995; I Oregon Department of Geology and Mineral Industries, 1996). Table 3 presents the peak bedrock accelerations expected at the subject site (5% dampening), estimated recurrence intervals, and the corresponding probability of occurrence in the next 50 years. I Table 3 — Expected Ground Shaking at "Rock Sites" from Crustal, 1 Plate- Interface, and Intra -slab Earthquake Sources Peak Ground Chance of Modified I Mercalli Intensity Acceleration Recurrence Interval Occurrence in the ( % gravity) Next 50 Years VII+ 0.20 g 500 years 10% I VIII 0.28 g 1,000 years 5% VIII+ 0.38 2,500 years 2% I Another method of describing the intensity of ground shaking associated with an earthquake is the Modified Mercalli intensity scale. This scale is a subjective measure of the affects I experienced by people, man -made structures, and the earth surface. The two largest historical earthquakes in northwestern Oregon, the 1962 M5.5 earthquake near Portland and the 1993 M5.6 earthquake in Scott Mills, generated maximum Modified Mercalli intensities of VII (Wong I and Bott, 1995). The Modified Mercalli intensities predicted for the subject site due to occurrence of maximum probable events is shown in Table 3. An abridged portion of the Modified Mercalli intensity scale, after Bott (1993), is presented in Table 4. I I Carlson Geotechnical Page 12 ' New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 i Table 4 — Abridged Portion of the Modified Mercalli Intensity Scale ' General alarm and everyone runs outdoors. Damage is negligible in buildings of good design VII and construction; slight to moderate in well -built ordinary structures; considerable in poorly built (0.10 to 0.15 g) or badly designed structures; some chimneys broken. Plaster and some stucco fall. Loosened brickwork and roof tiles shake down. Heavy furniture overturns. Stream and cut banks cave. General fright and alarm approaching panic. Damage is slight in specially designed structures; ' VIII considerable in ordinary substantial buildings with partial collapse; great in poorly built (0.25 to 0.30 g) structures. Panel walls thrown out of frame structures. Fall of chimneys, columns, and walls. Heavy furniture is overturned. Branches and tree trunks break off. Liquefied sand mud erupts ' on ground surface. IX General panic. Damage is considerable in specially designed structures; well- designed frame (0.50 to 0.55 g) structures thrown out of plumb; great in substantial buildings, with partial collapse. Buildings 111 shifted off foundations. Conspicuous ground cracking. Underground pipes broken. Site Surface Conditions The site is bordered by paved parking areas to the north, east, and west, and by the existing church building to the south. At the time of our explorations, the site was relatively level and covered with short grass, and sparse deciduous trees and conifers. Site Subsurface Conditions Field Exploration We excavated four test pits on March 5, 2004 to depths of up to 10.0 feet bgs. We also advanced one cone penetrometer probe (CPT) to 38 feet bgs on March 3, 2004. The ' approximate test pits and CPT locations are shown on Figure 2. A member of CGT's staff logged the soils observed in the test pits in general accordance with the Unified Soil Classification System (USC), collected samples, and performed in -situ testing. We have provided an explanation of the USC classification as Figure 3. Logs of the test pits are presented in the attached Figures 4 through 7, and a log of the CPT is presented as Figure 8. Our laboratory staff visually examined all samples returned to our laboratory in general accordance with the Unified Soil Classification System, in order to refine the field classifications. ' Subsurface Materials ' With the exception of test pit TP -1, our subsurface explorations encountered a three -inch thick loose sand topsoil horizon at the surface that was underlain by stiff sandy silt. The silt graded to sand with varying amounts of silt below 7 feet bgs. Our laboratory testing of this sand Carlson Geotechnical Page 13 1 ' New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 ' indicated that it contains between 19 and 38 percent silt sized particles. In test pit TP -1, below a three -inch thick sand topsoil horizon, we encountered loose gravel fill that extended to 6 inches ' bgs. Below the fill we encountered sandy silt that graded to silty sand below 7 feet bgs, as observed in test pits TP -2 though TP -4. The silty sand extended to the full depths of our explorations, 10.0 feet bgs. The cone penetrometer probe encountered materials similar to those observed in our test pit explorations to the full depth of the probe, 38 feet bgs. The subsurface materials are described in more detail on the attached test pit logs, Figures 4 through 7. . Ground Water ' We did not encounter ground water seepage during our explorations. Water well logs obtained from the Oregon Department of Water Resources indicate that ground water levels in the area range between 10 and 15 feet bgs. We anticipate that ground water levels will fluctuate due to seasonal variations in precipitation, changes in site utilization, or other factors. Additionally the site soils are conducive to the formation of a perched water table. Liquefaction Analysis A wide variety of slope and ground failures can occur in response to intense seismic shaking during large magnitude earthquakes. These failures are usually related to the phenomenon of liquefaction, the process by which water - saturated sediment changes from a solid to a liquid state. Since liquefied sediment may not support the overlying ground, or any structure built thereon, a variety of failures may occur including lateral spreading, landslides ground settlement and cracking, sand boils, oscillation lurching, etc. The conditions necessary for ' liquefaction to occur are: (1) the presence of poorly consolidated, cohesionless sediment; (2) saturation of the sediment by ground water; and (3) an earthquake that produces intense seismic shaking (generally a Richter Magnitude greater than M5.0). In general, older, more consolidated sediment, clayey or gravelly sediment, and sediment above the water table will not liquefy (Youd and Hoose, 1978). Field performance data and laboratory tests indicate that liquefaction occurs predominantly in well - sorted, loose to medium dense (SPT N- values of 0 to 20) sand or silty sand with a mean grain size between 0.8 mm to 0.08 mm (Lee and Fitton, 1968; Seed and Idriss, 1971). We used data obtained from the cone penetrometer probe to analyze liquefaction potential at the site. We modeled groundwater at 9 feet bgs, and considered a maximum peak ground acceleration of 0.6g. Our analysis indicates liquefaction settlement at the site will be on the order of 2 inches during a design level (M6.6) crustal earthquake. Carlson Geotechnical Page 14 I New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 i Laboratory Testing We selected representative samples from those returned to our laboratory for additional testing. We determined water contents in accordance with ASTM D -2216, and completed grain size analysis in general accordance with ASTM C117 and C136. Results of our laboratory testing are included on the attached test pit logs, Figures 4 through 7. CONCLUSIONS General Based on the results of our explorations and analyses, it is our opinion that the proposed structure with the assumed building loads can be supported on shallow spread footings bearing on the stiff silt, the medium dense sand, or on new structural fill that is properly installed during construction. Seismic Hazards ' Based on the available literature, the Portland Hills Fault Zone is judged to be potentially active (Geomatrix Consultants, 1995). Additionally, based on possible deformation of Quaternary (last 1.6 million years) geomorphic surfaces and a spatial association with seismic activity, the Gales ' Creek - Newberg -Mt. Angel Structural Zone is also considered to be potentially active (Geomatrix Consultants, 1995). Although several unnamed faults are mapped in the area, none of these ' faults are considered active. Therefore, the unnamed faults have a low probability of producing a damaging earthquake at the site. Liquefaction - Related Ground Failure Based on our analysis, settlement due to liquefaction during a design level earthquake may be up to 2 inches. Liquefaction will occur at depths below 8 feet bgs; therefore, some of this settlement will be masked by the overlying soils. We anticipate that settlement due to ' liquefaction will be within tolerable limits for the planned structure (less than about once inch), provided that footing subgrades are over excavated and backfilled with compacted structural fill as recommended below. No free faces are present toward which lateral spreading could occur. Historic lateral spread failures which adversely affected man -made structures or resulted in large mass movements ' have tended to occur at sites where a nearby "free face" was present (such as river banks) towards which failure could occur (Seed and Idriss, 1971; Youd and Noose, 1978). However, 1 Carlson Geotechnical Page 15 1 ' New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 ' given the lack of free faces present at the site, the potential for damaging lateral spreading at the site is low. t Landsliding Since no slopes are present on the site, in our opinion, the potential for seismically induced landsliding or slope instability at the site is low. Tsunami or Seiche Inundation ' The site is located more than several miles from any significant body of water; therefore, the potential for tsunami or seiche inundation of the site is low. Fault Displacement and Subsidence Since the fault that is mapped on the site is considered in active, the potential for fault displacement at the site is very low. The following paragraphs present specific geotechnical recommendations for design and construction of the proposed project. ' The following paragraphs present specific geotechnical recommendations for design and construction of the proposed project. ' RECOMMENDATIONS ' Site Preparation Where present, existing topsoil should be stripped and removed from proposed building and ' pavement locations, and for a 5- foot - margin around such areas. Based on our explorations, the depth of stripping of organic topsoil will be on the order of three inches, although greater stripping depths may be required where large trees will be removed. A representative of CGT should provide recommendations for actual stripping /overexcavation depths, based on observations during site stripping. Stripped material should be transported off site for disposal or stockpiled for use in landscaped areas. Silt fences, hay bales, buffer zones of natural growth, sedimentation ponds, and granular haul ' roads should be used as required to reduce sediment transport during construction to acceptable levels. Measures to reduce erosion should be implemented in accordance with Carlson Geotechnical Page 16 I I New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 I Oregon Administrative Rules 340 -41 -006 and 340 -41 -455 and Washington County regulations regarding erosion control. I After site radin , and prior to excavation for footings, a representative from CGT should I 9 9 P 9 P observe the existing site subgrades to identify areas of excessive yielding. The subgrade should be evaluated by proof rolling with a fully loaded dump truck. If areas of soft soil or excessive yielding are identified, the material should be excavated and replaced with I compacted materials as recommended for structural fill. Areas that appear too soft and wet to support proof rolling equipment should be prepared in accordance with recommendations for I wet weather construction given below. Wet Weather Considerations I The site soils contain silt, and may be susceptible to disturbance during wet weather. Trafficability of the site soils may be difficult and significant damage to subgrade soils could I occur if earthwork is undertaken without proper precautions at times when the exposed soils are more than a few percentage points above optimum moisture content. I For construction that occurs during the wet season, the site preparation activities may need to be accomplished using track - mounted equipment, loading removed material into trucks I supported on granular haul roads, or other methods to limit soil disturbance. A qualified geotechnical engineer should evaluate the subgrade during excavation by probing rather than proof rolling. Soils that have been disturbed during site preparation activities, or soft or loose I areas identified during probing should be removed and replaced with structural fill. I Haul roads subjected to repeated heavy construction traffic will require a minimum of 18 inches of imported granular material. Twelve inches of imported granular material should be sufficient for light staging areas. The imported granular material should consist of crushed rock that is t well - graded between coarse and fine, contains no unsuitable materials or particles larger than 4 inches, and has less than 5 percent by weight passing the U.S. Standard No. 200 Sieve. The I imported granular material should be placed in one lift over the prepared, undisturbed subgrade and compacted using a smooth -drum, nonvibratory roller. I We recommend that a geotextile be placed as a barrier between the subgrade and imported fill in areas of repeated construction traffic. The geotextile should have a minimum Mullen burst I strength of 250 pounds per square inch for puncture resistance and an apparent opening size (AOS) between the U.S. No. 70 and No. 100 Sieves. I I Carlson Geotechnical Page 17 1 ' New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 Structural Fill On -site Materials Use of the on -site silt as structural fill may be difficult because it is sensitive to small changes in moisture content and is difficult, if not impossible, to adequately compact during wet weather. Our laboratory testing indicates that the moisture content of the on -site silt is likely higher than the optimum moisture content needed for satisfactory compaction. Therefore, moisture conditioning (drying) should be expected in order to achieve adequate compaction. When used as structural fill, the on -site silt should be placed in lifts with a maximum thickness of 8 inches and compacted to not less than 92 percent of the materials maximum dry density, as determined by ASTM D -1557. Fill should be tested for compaction every two vertical feet as the fill is being placed. Use of the on site sand as structural fill is unlikely since it is located roughly 7 feet bgs. It may also be difficult to compact due to its high silt content. However, if the sand is used for structural fill, moisture conditioning should be expected in order to achieve adequate compaction. Based on our laboratory testing, we anticipate that the material will need to be dried in order to achieve ' compaction. When used as structural fill, the on -site sand should be placed in lifts with a maximum thickness of 8 inches and compacted to not less than 92 percent of the materials ' maximum dry density, as determined by ASTM D -1557. Fill should be tested for compaction every two vertical feet as the fill is being placed. If the on -site soils cannot be properly moisture - conditioned, we recommend using imported granular material for structural fill. ' Imported Granular Material t Imported granular structural fill should consist of angular pit or quarry run rock, crushed rock, or crushed gravel and sand that is fairly well - graded between coarse and fine particle sizes. The fill should contain no organic matter or other deleterious materials, have a maximum particle ' size of 3 inches, and have less than 5 percent passing the U.S. No. 200 Sieve. The percentage of fines can be increased to 12 percent of the material passing the U.S. No. 200 Sieve, if placed during dry weather and provided the fill material is moisture - conditioned, as necessary, for proper compaction. The material should be placed in lifts with a maximum uncompacted thickness of 12 inches and be compacted to not less than 95 percent of the maximum dry ' density, as determined by ASTM D -1557. During the wet season or when wet subgrade conditions exist, the initial lift thickness should be increased to 24 inches and should be Carlson Geotechnical Page 18 I ' New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 compacted by rolling with a smooth -drum, nonvibratory roller. The fills should be testes for compaction every two vertical feet as the fill is being placed. Shallow Foundations We recommend that spread footings be founded on the stiff silt, the medium dense sand, or on new structural fill that is properly installed during construction. We recommend that all spread footings have a minimum width of 24 inches, and the base of the footings be founded at least 24 inches below the lowest adjacent grade. Continuous wall footings should have a minimum width of 18 inches and be founded a minimum of 18 inches below the lowest adjacent grade. ' Excavations near foundation footings should not extend within a 1 H:1 V (horizontal to vertical) plane projected from the bottom of the footings. For footings founded on the medium dense sand, we recommend over excavating the upper two feet of the subgrade soils and recompacting to a minimum of 95% ASTM D1557. Bearing Pressure and Settlement Footings founded as recommended should be proportioned for a maximum allowable soil bearing pressure of 2,500 psf. This bearing pressure is a net bearing pressure and applies to the total of dead and long -term live loads, and may be increased by 1/3 when considering seismic or wind loads. For the recommended design bearing pressure, total settlement of footings is anticipated to be less than 1 inch. Differential settlements should not exceed 1/2-inch. Lateral Capacity ' We recommend using a passive pressure of 250 pounds per cubic foot (pcf) for design, for footings confined by the stiff silt, the medium dense sand, or by new structural fill. In order to ' develop these capacities, concrete must be poured neat in excavations, the adjacent grade must be level, and the static ground water must remain below the base of the footing ' throughout the year. Adjacent floor slabs, pavements, or the upper 12- inch -depth of adjacent, unpaved areas should not be considered when calculating passive resistance. ' A coefficient of friction equal to 0.32 may be used when calculating resistance to sliding for the silt. When calculating resistance to sliding for the on site sands, we recommend using a friction coefficient equal to 0.35. Carlson Geotechnical Page 19 1 ' New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 ' Floor Slabs Satisfactory subgrade support for building floor slabs supporting up to 250 psf area loading can be obtained from the stiff silt, the medium dense sand, or new structural fill when prepared in accordance with the recommendations presented in the "Site Preparation" section of this report. A minimum 6- inch -thick layer of crushed rock should be placed over the prepared subgrade to assist as a capillary break. A subgrade modulus of 175 pounds per cubic inch can be used for the design of the floor slab. Floor slabs constructed as recommended will likely settle less than A -inch. We recommend that slabs be jointed around columns and walls to permit slabs and foundations to settle differentially. ' Base rock material placed directly below the slab should be 3 /4 inch maximum or less. If the ' base rock is 3/8 inch or larger, the surface of the rock should be filled with sand just prior to concrete placement in order to reduce the lateral restraint on the bottom of the concrete during curing. We recommend placing a capillary break, consisting of at least 6 inches of coarse granular material having less than 5 percent passing the U.S. Standard No. 200 sieve, to protect against moisture. Where moisture vapor emission through the slab must be minimized, (e.g. impervious floor coverings, storage of moisture sensitive materials directly on the slab surface, etc), a vapor retarding membrane or vapor barrier below the slab should be considered. Factors such as cost, special considerations for construction, floor coverings, and end use suggest that the decision regarding a vapor retarding membrane or vapor barrier be made by the architect and owner. ' Utility Trenches Utility Trench Excavation Trench cuts should stand near vertical to a depth of approximately 4 feet in the silt or sand provided no ground water seepage is observed in the sidewalls. If seepage is encountered that ' undermines the stability of the trench, or caving of the sidewalls is observed during excavation, the sidewalls should be flattened or shored. ' Trench dewatering may be required to maintain dry working conditions if the invert elevations of the proposed utilities are below the ground water level. Pumping from sumps located within the trench will likely be effective in removing water resulting from seepage. If ground water is present at the base of utility excavations, we recommend placing trench stabilization material consisting of 1 foot of well - graded gravel, crushed gravel, or crushed rock with a minimum Carlson Geotechnical Page 20 1 ' New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 t particle size of 4 inches and less than 5 percent passing the U.S. Standard No. 4 Sieve at the base of the excavation. The material should be free of organic matter and other deleterious ' material and should be placed in one lift and compacted until well- keyed. t While we have described certain approaches to the trench excavation, it is the contractor's responsibility to select the excavation and dewatering methods, to monitor the trench excavations for safety, and to provide any shoring required to protect personnel and adjacent ' improvements. All trench excavations should be in accordance with applicable OSHA and state regulations. ' Trench Backfill Material Trench backfill for the utility pipe base and pipe zone should consist of well - graded granular material containing no organic material or other deleterious material, have a maximum particle size of % -inch, and have less than 8 percent passing the U.S. Standard No. 200 Sieve. Backfill for the pipe base and within the pipe zone should be placed in maximum 12- inch -thick lifts and compacted to not less than 90 percent of the maximum dry density, as determined by ' ASTM D -1557 or as recommended by the pipe manufacturer. Backfill above the pipe zone should be placed in maximum 12- inch -thick lifts and compacted to not less than 92 percent of ' the maximum dry density, as determined by ASTM D -1557. Trench backfill located within 2 feet of finish subgrade elevation should be placed in maximum 12- inch -thick lifts and compacted to not less than 95 percent of the maximum dry density, as determined by ASTM D -1557. Pavements We recommend a pavement section of 3 inches of asphaltic concrete over 8 inches of aggregate base be used in planned paved areas. The design of the recommended pavement section is based on an assumed California Bearing Ratio (CBR) of 3 and on the assumption that construction will be completed during an extended period of dry weather. This design is also based on an assumed traffic loading of up to 200 passenger cars and 3 trucks per day. ' Increased base rock section may be required in wet conditions to support construction traffic and protect the subgrade. Asphalt concrete should conform to Section 00745 of the 2002 Edition — Standard Specifications for Highway Construction, Oregon Department of Transportation, for light -duty ' asphalt concrete. Aggregate base should conform to Section 02630 of the same specifications. Place aggregate base in one lift and compact to not less than 95 percent of the maximum dry density, as determined by ASTM D -1557. Carlson Geotechnical Page 21 ' New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 ' Drainage Considerations We recommend that subsurface drains be connected to a tightline leading to the storm drain. Pavement surfaces and open space areas should be sloped such that the surface water runoff is collected and routed to suitable discharge points. We recommend that the ground and paved ' surfaces adjacent to the buildings be sloped to drain away from the buildings. Permanent Slopes We do not anticipate that new permanent slopes will be constructed during development. If new ' permanent slopes are constructed, they should not exceed 2H:1V. Adjacent on -site and off -site structures and surfacing should be located at least 5 feet from the top of slopes. Footings should have a minimum set back of 5 feet between the face of the slope and the outer edge of the footing. Excavations should not extend within a 1 H:1 V line projected from the bottom outside edge of the footings. Seismic Design ' The site is located in Seismic Zone 3 of the 1997 Uniform Building Code. Based on our understanding of the subsurface conditions, the UBC soil profile that best characterizes the site is "S We recommend using a seismic coefficient of C = 0.36 and C 0.54 for site conditions corresponding to the amplification of an SD soil profile. ' OBSERVATION OF CONSTRUCTION Satisfactory pavement and earthwork performance depends to a large degree on the quality of ' construction. Sufficient observation of the contractor's activities is a key part of determining that the work is completed in accordance with the construction drawings and specifications. Subsurface conditions observed during construction should be compared with those encountered during subsurface explorations, and recognition of changed conditions often requires experience. We recommend that qualified personnel visit the site with sufficient frequency to detect whether subsurface conditions change significantly from those observed to date and anticipated in this report. We recommend that site stripping, rough grading, foundation and pavement subgrades, and placement of engineered fill are observed by the project geotechnical engineer or their ' representative. Because observation is typically performed on an on -call basis, we recommend that the earthwork contractor be held contractually responsible for scheduling observation. Carlson Geotechnical Page 22 ' New Auditorium — Southwest Church of Christ Tigard, Oregon March 18, 2004 ' LIMITATIONS ' We have prepared this report for use by the owner /developer and other members of the design and construction team for the proposed development. The opinions and recommendations contained within this report are not intended to be, nor should they be construed as a warranty of subsurface conditions, but are forwarded to assist in the planning and design process. We have made observations based on our explorations that indicate the soil conditions at only those specific locations and only to the depths penetrated. These observations do not necessarily reflect soil types, strata thickness, or water level variations that may exist between explorations. If subsurface conditions vary from those encountered in our site exploration, CGT should be alerted to the change in conditions so that we may provide additional geotechnical ' recommendations, if necessary. Observation by experienced geotechnical personnel should be considered an integral part of the construction process. The owner /developer is responsible for insuring that the project designers and contractors implement our recommendations. When the design has been finalized, we recommend that the design and specifications be reviewed by our firm to see that our recommendations have been ' interpreted and implemented as intended. If design changes are made, we request that we be retained to review our conclusions and recommendations and to provide a written modification or verification. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in ' design. Within the limitations of scope, schedule, and budget, our services have been executed in ' accordance with the generally accepted practices in this area at the time this report was prepared. No warranty or other conditions express or implied, should be understood. 1 Carlson Geotechnical Page 23 New Auditorium - Southwest Church of Christ Tigard, Oregon March 18, 2004 We appreciate the opportunity to serve as your geotechnical consultant on this project. Please contact us if you have any questions. Sincerely, CARLSON GEOTECHNICAL Brian C. Ranney, G.I.T. Geotechnical Staff ' r IN -cv #1564i %-` - ; EX" 2 - Jeanne M. Niemer, P.E. Principal Geotechnical Engineer ' Attachments: Figures 1 through 18 Doc ID: P: \GEOTECH \PROJECTS\2003 Projects \Head Start of Yamhill County \Geotechnical Report.doc 1 r I Carlson Geotechnical Page 24 i REFERENCES Atwater, B.F., 1992. Geologic evidence for earthquakes during the past 2,000 years along the Copalis River, southern coastal Washington: Journal of Geophysical Research, v. 97, p. 1901 -1919. Balsillie, J.J. and Benson, G.T., 1971. Evidence for the Portland Hills fault: The Ore Bin, Oregon Dept. of Geology and Mineral Industries, v. 33, p. 109 -118. ' Bonilla, 1984. Bonilla, M.G., R. K. Mark, and J.J. Lienkaemper, 1984, Statistical relations among earthquake magnitude, surface rupture length, and surface fault displacement: Bulletin of the Seismological Society of America, V. 74, p. 2379 -2411. Carver, G., 1992. Late Cenozoic tectonics of coastal northern California: American Association of Petroleum Geologists -SEPM Field Trip Guidebook, May, 1992. ' Cohee et al 1991. Cohee, B.P., Somerville, P.G., and Abrahamson, N.A., 1991, Simulated ground motions for hypothetical Mw = 8 earthquakes in Washington and Oregon: Bulletin of the Seismological Society of America, v. 81, p. 28 -56. Conforth and Geomatrix Consultants, 1992. Seismic hazard evaluation, Bull Run dam sites ' near Sandy, Oregon: unpublished report to City of Portland Bureau of Water Works. DeMets, C., Gordon, R.G., Argus, D.F., Stein, S., 1990. Current plate motions: Geophysical Journal International, v. 101, p. 425 -478. Geomatrix Consultants, 1993. Seismic margin Earthquake For the Trojan Site: Final ' Unpublished Report For Portland General Electric Trojan Nuclear Plant, Rainier, Oregon, May 1993. Geomatrix Consultants, 1995. Seismic Design Mapping, State of Oregon: unpublished report prepared for Oregon Department of Transportation, Personal Services Contract 11688, January 1995. Lee, K.L. and Fitton, J.A., 1968. Geotechnical Aspects of Earthquake Engineering, a compilation of notes prepared by T.S. Vinson and S.E. Dickenson, Dept. of Civil ' Engineering, Oregon State University, Corvallis, November, 1992. ' Madin, 1994. GMS -60, Geology of the Damascus Quadrangle, Clackamas and Multnomah Counties, Oregon Department of Geology and Mineral Industries. ' Madin and Hemphill - Haley, 2001: The Portland Hills Fault at Rowe Middle School. Oregon Geology V63 p47 ' Nablek and others, 1991. Nablek, J., A. Ttrehu, G. Lin, G. Vernon, and J. Orcutt, 1991. Samson; preliminary results fro the onshore broadband array (abs): Eos, American Geophysical Union, v 72., n. 44, p. 302. ' Peterson, C.D., Darioenzo, M.E., Burns, S.F., and Burris, W.K., 1993. Field trip guide to Cascadia paleoseismic evidence along the northern California coast: evidence of subduction zone seismicity in the central Cascadia margin: Oregon Geology, v. 55, p. ' 99 -144. Seed, H.B., and Idriss, I.M., 1971. Simplified procedure for evaluating soil liquefaction potential: Journal of Soil Mechanics and Foundation Division, proceedings of the American Society of Civil Engineers, v. 97, p. 1249 -1273. Unruh, J.R., Wong, I.G., Bott, J.D., Silva, W.J., and Lettis, W.R., 1994. Seismotectonic evaluation: Scoggins Dam, Tualatin Project, Northwest Oregon: unpublished report by William Lettis and Associates and Woodward Clyde Federal Services, Oakland, CA, for U.S. Bureau of Reclamation, Denver, CO (in Geomatrix Consultants, 1995). Walker and MacLeod, 1991. Geologic Map of Oregon. United States Department of the Interior., United States Geological Survey, 1991. Werner, K.S., Nabelek, J., Yeats, R.S., Malone, S., 1992. The Mount Angel fault: implications of seismic - reflection data and the Woodburn, Oregon, earthquake sequence of August, 1990: Oregon Geology, v. 54, p. 112 -117. ' Wong et al, 2000. Wong, I. Silva, W. Bott, J., Wright, D., Thomas, P., Gregor, N., Li, S., Mabey, M., Sojourner, A., Wang, Y. IMS -15. Earthquake Scenario and Probabilistic Ground Shaking 1 11 Maps for the Portland, Oregon, Metropolitan area. Portland hill Fault M6.8 Earthquake, Peak Horizontal Acceleration at the Ground Surface. Yeats and others, 1996. Geologic Map of the Northern Willamette Valley, Marion, 9 P Y, 1 Multnomah, Polk, Tillamook, Washington, and Yamhill Counties, Oregon. United States Department of the Interior, United States Geological Survey, 1996. Yeats et al, 1996: Yeats, R.S., Graven, E.P., Werner, K.S., Goldfinger, C., and Popowski, T., 1996. Tectonics of the Willamette Valley Oregon: in Assessing earthquake hazards and ' reducing risk in the Pacific Northwest, v. 1: U.S. Geological Survey Professional Paper 1560, p. 183 -222, 5 plates, scale 1:100,000. ' Yelin, T.S., 1992. An earthquake swarm in the north Portland Hills (Oregon): More speculations on the seismotectonics of the Portland Basin: Geological Society of America, ' Programs with Abstracts, v. 24, no. 5, p. 92. Youd, T.L., and Hoose, S.N., 1978. Historic ground failures in northern California triggered by ' earthquakes: U.S. Geological Survey Professional Paper 993, 117 p. Youngs et al. 1993 Youngs, R. R., S. -J. Chiou, W.L. Silva, and J. R. Humphery, 1993, Strong ' ground motion attenuation relationships for subduction zone earthquakes based on empirical data and numerical modeling (abs.): Seismological Research Letters, v. 64 p.18. 1 1 1 1 I SOUTHWEST CHURCH OF CHRIST I SITE LOCATION e /i "�. R 1 j3 . -. . ? : t 'r; , y rCi rr ... ( J y � TM `' jjj , ° •. .• • ? ,�,.•�� rt` '� f ,! ` r i Al§s, - r.r.' = :;t4401,151?" 011 !1 - • i j i, ..�...� ,. I . � (''�f.L -- I t1a 44' p g y � � T' .der ' • - - .,,,-.,,?„ I r �!. r � t x i1 � �•� ! A�'i1�.11i •11�� -- _. /,.._ • .A/I a w ` r _ 1 . •y, .""` _ L a�. � d' ;g i • / — /•. •`� II ?r te. . M I _ _ } 1 � J � _ - t Y ` r` y tt'4.*`'ti' \ ,/ .! _ - a w N� l - l ip . + r P � #3 ' I J j / i ! , ° // I ; k _ „ : '' � ;:. I : , + q� I f ' s I 0 1 W , 1 ° X07; ,�� , �x 1 'X ' J 4i lj.. 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I ICI I ; I ` !: ".:-.111-2- � r i . . • t re . ,• T r G r ! t I — _ �: g A I - , * `• - m SOUTHWEST CHURCH OF CHRIST r 1 \ /I"' �-" - : 1}; Q f r i - i , � J SITE PLAN 3 f �< 1 II `/ II � , •. a Ir't r i t I! I ir, te r, . ` \ f- t. .L I ,,i �III I ;1 CPT -1 I ,1I; - , � 1, E XISTING PAVED I , .1 �. : '1: ---- -- • .. - I — ` h i PARKING r.. l i �(' I I`li I � ; •� III 6.1111WNN = — - ._. 1 . 03/10/04 FIGURE 2 1' � / } III` i 1: ;:: _� • I � � , , � � I 1 : 1 1 • F'�: /` ; -i, , -•. I CGT JOB NUMBER i -< T t r • TP -3 -- - PROPOSED ADDITION f \� / r te ,!r.•4 TP-4 —` •� / 1 \ � , I / G0402245 -.e. 1 \` I ... I I I 1 ` T I ,, • I `I a' ) A .• 1 _ I ,� _ LEGEND • r -+= ( r ; ` - � ` ' fl `- •^- r -'- ' *' j 1 •r Location of test pit explorations y1 1 ° ' I `; .t ~ rl 1 L ) t y �� t a ! , w r C 1,' . - •, i 1 1-x' , I • . 'I r-, • U--� ,:p ( - •q . ...ft, ft7 ✓.-.:{ 'IV Z r' r ., •y ��.. C-�a, r_� , • ; • `y Location of cone penetrometer probe i ... _ ^ ;rw�= '�' CPT -1 SW 98TH AVENUE Scale 1 inch = 50 feet 0 50 100 I All locations are app roximate. I Site plan provided by Lewis and Van Vleet, Inc . The drawing has been reproduced and modified by CGT staff. I GP CARLSON GEOTECHNICAL Tif A DIVISION OF CARLSON TESTING INC. I 503- 684•3460 P.O. BOX 23814 TIGARD, OR. 97281 I I I SOIL CLASSIFICATION CRITERIA AND TERMINOLOGY Classification of Terms and Content USCS Grain Size NAME : MINOR Constituents (12 -50 %); MAJOR Fines < #200 (.075 mm) Constituents ( >50 %); Slightly (5 -12 %) Sand Fine #200 - #40 (.425 mm) Relative Density or Consistency Medium #40 - #10 (2 mm) Color Coarse #10 - #4 (4.75) Moisture Content Gravel Fine #4 - 0.75 nch I Plasticity Coarse 0.75 inch - 3 inches Trace Constituents (0 -5 %) Cobbles 3 to 12 inches; Other: Grain Shape, Approximate gradation, scattered <15% est., Organics, Cement, Structure, Odor.... numerous >15% est. Geologic Name or Formation: (Fill, Willamette Silt, Till, Boulders > 12 inches Alluvium,...) Relative Density or Consistency Granular Material Fine - Grained (cohesive) Materials I SPT SPT Torvane tst Pocket Pen tsf Manual Penetration Test N -Value Density N -Value Shear Strength Unconfined Consistency <2 <0.13 >0.25 Very Soft Easy several inches by fist 0 - 4 VeryLoose 2 - 4 0.13 - 0.25 0.25 - 0.50 Soft Easy several inches by thumb I 4 -10 Loose 4 - 8 0.25 - 0.50 0.50 - 1.00 Medium Stiff Moderate several inches by thumb 10 - 30 Medium Dense 8 - 15 0.50 -1.00 1.00 - 2.00 Stiff Readily indented by thumb 30 50 Dense 15 - 30 1.00 - 2.00 2.00 - 4.00 Very Stiff Readily indented by thumbnail >50 Very Dense >30 >2.00 >4.00 Hard Difficult by thumbnail I Moisture Content Structure Dry: Absence of moisture, dusty, dry to the touch Stratified: Alternating layers of material or color >6 mm thick Damp: Some moisture but leaves no moisture on hand Laminated: Alternating layers < 6 mm thick Moist: Leaves moisture on hand Fissured: Breaks along definate fracture planes Wet: Visible free water, likely from below water table Slickensided: Striated, polished, or glossy fracture planes I Plasticity Dry Strength Dilatancy Toughness Blocky: Cohesive soil that can be broken down into small angular lumps which resist further breakdown ML Non to Low Non to Low Slow to Rapid Low, can't roll Lenses: Has small pockets of different soils, note thickness CL Low to Med. Medium to High None to Slow Medium Homogeneous: Same color and appearance throughout I MH Med to High Low to Medium None to Slow Low to Medium CH Med to High High to V. High None High Unified Soil Classification Chart (Visual - Manual Procedure) (Similar to ASTM Designation D - 2488) Major Divisions Group Typical Names t Symbols Coarse Gravels: 50% Clean GW Well graded gravels and gravel -sand mixtures, little or no fines Grained or more Gravels GP Poorly - graded gravels and gravel -sand mixtures, little or no fines Soils: retained on Gravels GM Silty gravels, gravel- sand -silt mixtures I More than the No. 4 sieve with Fines GC Clayey gravels, gravel- sand -clay mixtures 50% retained Sands: more Clean SW Well- graded sands and gravelly sands, little or no fines on No. 200 than 50% Sands SP Poorly- graded sands and gravelly sands, little or no fines sieve passing the Sands SM Silty sands, sand -silt mixtures No. 4 Sieve with Fines SC Clayey sands, sand -clay mixtures I Fine - Grained ML CL Inorganic silts, rock flour, clayey silts Soils: Silt and Clays Inorganic clays of low to medium plasticity, gravelly clays, sandy clays, lean clays 50% or more Low Plasticity Fines OL Organic silt and organic silty clays of low plasticity Passes No. MH Inorganic silts, clayey silts I 200 Sieve Silt and Clays High Plasticity Fines CH OH Inorganic days of high plasticity, fat clays Organic clays of medium to high plasticity Highly Organic Soils _ PT Peat, muck, and other highly organic soils I - I p` . Carlson Geotechnical P.O. Box 23814 CGT Job No. G0402245 Figure 3 503.684.3460 Tigard, Oregon 97281 I 1 SOUTHWEST CHURCH OF CHRIST Logged by: Brian Ranney Date Excavated: 03/05/04 Location: See Figure 2 Surface Elevation: Unavailable N W C 1 C 2°' a s ~ ' . g o. o a v z E ° 0 7 ' Material Description a co o 0 DU ' — SM \Very soft dark brown silty SAND TOPSOIL, moist; 3" root zone. _ GW \Loose gray sandy GRAVEL FILL, moist 1 2 ' 0 ML Stiff light brown sandy SILT, moist I — 1.5 2 1.0 — 2.0 3— 1.5 orange -gray mottled below 3 feet — 1.0 4— 1.5 S -1 30 ' 5 ' 6- 7— S -2 ® 31 SM ' — Stiff light brown silty SAND, moist 8 38 percent passing U.S. #200 sieve 9 10= Test pit terminated at 10.0 feet 11 12— ' 13= 14 - ' 15 ' 16— NOTE: No ground water seepage or caving observed during excavation. ' 17 Job No. G0402245 Log of Test Pit 1 Figure: 4 ' Carlson Geotechnical - P.O Box 23814 - Tigard. Oregon 97281 - 684 -3460 - Fax 670 -9147 503.884.348 SOUTHWEST CHURCH OF CHRIST ' Logged by: Brian Ranney Date Excavated: 03/05/04 ' Location: See Figure 2 Surface Elevation: Unavailable ' t oe m wQ EE o m y o a c" co z' L. Cog Material Description r 10 C7 n cg � o ' — 0.25 SM \ Very soft dark brown silty SAND TOPSOIL, moist; 3" root zone. 1— 0.5 ML Medium dense to dense light brown sandy SILT, moist — 1.5 2 1.0 abundant roots to 2 feet bgs — 0.5 ' 3— 2 orange -gray mottled below 3 feet — 2.0 4 2.0 ' 5 - ' 6= 7- - SM Medium dense light brown SAND with silt, moist 8 ' 9 wet below 9 feet S -1 ® 30 19 percent passing U.S. #200 sieve ' 10= Test pit terminated at 10.0 feet 11— ' 12— 13^ 14— I 15— ' 16— NOTE: No ground water seepage or caving observed during excavation. 17 ' Job No. G0402245 Log of Test Pit 2 Figure: 5 ' Carlson Geotechnical - P.O. Box 23814 - Tigard, Oregon 97281 - 684 -3460 - Fax 670 -9147 5 03.684 -3 SOUTHWEST CHURCH OF CHRIST Logged by: Brian Ranney Date Excavated: 03/05/04 ' Location: See Figure 2 Surface Elevation: Unavailable m _o m E� a� m m ( ° • g m a z E o ` m o �W Material Description o a � o D U - 0.25 SM \ Very soft dark brown silty SAND TOPSOIL, moist; 3" root zone. 1— 0.5 ML Stiff light brown sandy SILT, moist — 1.0 2— 1.0 — 1.0 orange -gray mottled below 2.5 feet bgs 3— 1.0 — 2.0 very stiff below 4 feet 4 1.0 5— S -1 61 31 6= 7— ' SM Medium dense light brown SAND with silt, moist 8 9— ' 10- Test pit terminated at 10.0 feet 11--- ' 12— ' 13= 14— ' 15 ' 16— NOTE: No ground water seepage or caving observed during excavation. II 17 - - Job No. G0402245 Log of Test Pit 3 Figure: 6 ' Carlson Geotechnical - P.O. Box 23814 - Tigard, Oregon 97281 - 684 -3460 - Fax 670 -9147 503 - 684 -3480 SOUTHWEST CHURCH OF CHRIST ' Logged by: Brian Ranney Date Excavated: 03/05/04 ' Location: See Figure 2 Surface Elevation: Unavailable g o m 2 w I L m m c n z o ro Material Description 0 d ( 0 2 c co 0 U — 0.5 SM Very soft dark brown silty SAND TOPSOIL, moist; 3" root zone. 1 — 1.0 ML Stiff light brown sandy SILT, moist — 1.0 abundant roots to one foot 2— 1.0 2.5 I 3— 3.0 orange -gray mottled below 3.0 feet bgs — 2.0 4 1.0 5 Test pit terminated at 5.0 feet 6- g 9 ' 10 11- ' 12— ' 13 14 15 16— NOTE: No ground water seepage or caving observed during excavation. 17 Job No. G0402245 Log of Test Pit 4 Figure: 7 `` ® 503- 6843460 Carlson Geotechnical - P.O. Box 23814 - Tigard, Oregon 97281 - 684 -3460 - Fax 670 -9147 ' [ Subsurface Technologies O perator: W.MCC / A.MEE CPT Date/Time: 03-04 -04 10:38 Sounding: SND619 Location: CPT1 SW CH 0 CHR 1 Cone Used: 683 TC Job Number: G0402245 I Tip Resistance Local Friction Friction Ratio Pore Pressure Duff PP Ratio Soil Behavior Type* Qt (Ton/ff ^2) Fs (Ton /ff ^2) Fs /Qt ( %) Pw (psi) (Pw- Ph) /Qt ( %) Zone: UBC -1983 0 200 0 5 0 5 -20 100 20 100 0 12 0 I I I I I I I I I I I I I I I 1 1 V I I I V I I I ■u I 1 1 I I I I I I , ! ! ; 1 I I 1[111 11111 11 1 I ' 1 ! l l l J1111 II I li 1 , 1111 11 1111,11 1 I i 1 i 1 I 1 - 11 l 1 ! 1 1 1 1 1 1 1 I 1 ! 1 ! 1 ! 1 ! { I t 1 ! 1 i 1 I 1 I i' 1 1 i I ! : i`! j I I ! 1 7 - -1 1 I HI 1 ! 1 I-1 - - i 1 I ! 1 1I I Lpth ` 1 tl ', i — --4—+-+-4-1 - 11 f (ft) j 1 i 1 I 1 III j i 1 I 1 II I 25 t ; T _ r - - -,1-1---1---1- I 1 I I 1 1 1 ! 1 1 i I . li i I ! I I j I I I r ! ! 1 I ! it 1 ! ! 1 I 1 11111 : • I ( 1 I l I i I ! II ! 1 ' I ' % i! u 1 ' 1 '11 • 1 1 1 ,I 11 I l I ' 1 I I!, 1 I ! l { [I I ! '1 1 y iii! - 1 —. ( -- —N A I . I I I ; I .... t I Ill 35 — ! r 1 1 1 I I H I ,I I I 1 ' 1 1 , 1 I 1 1 .I 1 1 11 1 I IHII 1 "" 40 i! I I i 1 1 i 1 1 1 1 i'" I Maximum Depth = 39.04 feet Depth Increment = 0.328 feet 1 sensitive fine grained • 4 silty clay to clay • 7 silty sand to sandy silt • 10 gravelly sand to sand I • 2 organic material • 5 clayey silt to silty clay 8 sand to silty sand • 11 very stiff fine grained ( *) •• 3 clay • 6 sandy silt to clayey silt 9 sand • 12 sand to clayey sand ( *) Soil behavior type and SPT based on data from UBC -1983 1 FIGURE 8