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Report (2) ,,a!-{-/°020/oZ-O60 RECEIVED MAR 28 2012 CITY OF TIGARD BUILDING DIVISION CEO E SG I NZ REPORT OF GEOTECHNICAL ENGINEERING SERVICES Schwindt Dental Office 11445 SW Summerfield Drive Tigard, Oregon For Brandon Schwindt, DMD, PC October 3l, 201 1 GeoDesign Project: SchmidtB-1-01 v:Ars Engineers I Geologists I Environmental Consultants GEODESIGNZ October 31, 201 1 Brandon Schwindt, DMD, PC 11565 SW Durham Road Building F, Suite 100 Tigard, OR 97224 Attention: Dr. Brandon Schwindt Report of Geotechnical Engineering Services Schwindt Dental Office 1 1445 SW Summerfield Drive Tigard, Oregon GeoDesign Project: SchwindtB-1-01 We are pleased to submit this report of geotechnical engineering services for the proposed dental office located at 11445 SW Summerfield Drive in Tigard, Oregon. Our services for this project were conducted in accordance with our proposal dated October 3, 2011. We appreciate the opportunity to be of continued service to you. Please contact us if you have questions regarding this report. Sincerely, GeoDesign, Inc. 'fr . Brett A. Shipton, P.E., G.E. Principal Engineer cc: Mr. Kevin Saxton, Kasa Architects (via email only) Mr. Ken Ackerman, Harper Houf Peterson Righellis, Inc. (via email only) TCM:BAS:kt Attachments One copy submitted(via email only) Document ID:SchwindtB-1-01-1031 1 1-geor.doc ©2011 GeoDesign,Inc. All rights reserved. 15575 SW Sequoia Pkwy•Suite 100 I Portland,OR 97224 I Off 503.968.8787 1 fax S03.9683068 \\I TABLE OF CONTENTS PAGE NO. 1.0 INTRODUCTION 1 2.0 PROJECT UNDERSTANDING 1 3.0 SCOPE OF SERVICES 1 4.0 SITE DESCRIPTION 2 4.1 Surface Conditions 2 4.2 Subsurface Conditions 2 5.0 CONCLUSIONS 3 6.0 SITE DEVELOPMENT RECOMMENDATIONS 3 6.1 Site Preparation 3 6.2 Wet Weather/Wet Soil Grading 4 6.3 Temporary Slopes 4 6.4 Structural Fill 5 6.5 Fill Placement and Compaction 5 6.6 Permanent Cut and Fill Slopes 7 6.7 Erosion Control 7 7.0 FOUNDATION SUPPORT RECOMMENDATIONS 7 7.1 Spread Footings 8 7.2 Slabs on Grade 8 8.0 PERMANENT RETAINING STRUCTURES 9 9.0 GROUNDWATER CONSIDERATIONS 9 9.1 Temporary 9 9.2 Surface 9 9.3 Subsurface 10 9.4 Infiltration System 10 10.0 SEISMIC DESIGN CRITERIA 10 1 1.0 PAVEMENT DESIGN RECOMMENDATIONS 1 1 12.0 INFILTRATION TESTING 11 13.0 OBSERVATION OF CONSTRUCTION 12 14.0 LIMITATIONS 12 FIGURES Vicinity Map Figure 1 Site Plan Figure 2 APPEN DIX Field Explorations A-1 Laboratory Testing Al- Exploration Key Table A-1 Soil Classification System Table A-2 Boring Logs Figures A-1 -A-2 Summary of Laboratory Data Figure A-3 ACRONYMS G EO DESIGN= Schwindt&1-01:103111 1.0 INTRODUCTION GeoDesign, Inc. has prepared this geotechnical engineering report for use in design and construction of the proposed dental office located at 11445 SW Summerfield Drive in Tigard, Oregon. The site is currently occupied by a small office structure and associated paved parking and landscaped areas. Figure 1 shows the site relative to existing topographic features. For your reference, definitions of all acronyms used in this report are presented at the end of this document. 2.0 PROJECT UNDERSTANDING Based on preliminary information provided by Mr. Kevin Saxton of Kasa Architects, Inc., it is our understanding that a new single-story,wood-frame dental office is planned for the site. In addition, stormwater infiltration will also be evaluated as part of the proposed site development. Foundation loads were not available at the time of this report; however,we have assumed column loads of less than 50 kips and floor slab loading less than 100 psf. We have assumed that site cuts and fills will be minimal. 3.0 SCOPE OF SERVICES The purpose of our services was to characterize subsurface conditions and provide geotechnical engineering recommendations for use in design and construction of the proposed development. Specifically,we performed the following tasks: • Reviewed readily available published geologic data and our in-house files for existing information on subsurface conditions in the site vicinity. • Coordinated and managed the field investigation, including private and public utility locates, access preparation, and scheduling of contractors and GeoDesign staff. • Completed a subsurface exploration program that consisted of drilling two borings to a depth of up to 25.5 feet BGS. The borings were drilled using hollow-stem auger drilling techniques. Following completion of drilling, each boring was backfilled with bentonite chips and the surface patched with asphalt,where appropriate. • Classified the materials encountered in the explorations and maintained a detailed log of each exploration. • Conducted infiltration testing in both borings. Infiltration testing was conducted at depths of 2 feet BGS in both borings and at a depth of 10 feet BGS in boring B-1. • Completed laboratory analyses on disturbed and undisturbed soil samples obtained from the explorations as follows: • Eleven moisture content and one dry density tests on selected soil samples • Four grain size analysis on selected soil samples • Provided recommendations for site preparation, grading and drainage, stripping depths, fill type for imported materials, compaction criteria, trench excavation and backfill, use of on-site soils, and wet/dry weather earthwork. G EO DESIGN? 1 SchwindtB-1-01:1031 1 1 • Provided geotechnical engineering recommendations for design and construction of shallow foundations for support of the building. Our recommendations include allowable bearing capacity, estimated settlement, and lateral resistance. • Provided recommendations for preparation of the subgrade for floor slabs. • Recommended design criteria for retaining walls, including lateral earth pressures, backfill, compaction, and drainage. • Provide recommendations for construction of asphalt pavements for on-site access roads and parking areas, including subbase, base course, and asphalt paving thickness. • Provide recommendations for the management of identified groundwater conditions that may affect the performance of structures or pavement. • Provide recommendations for IBC seismic coefficients. • Prepared this report of our explorations, findings, conclusions, and recommendations. 4.0 SITE DESCRIPTION 4.1 SURFACE CONDITIONS The site is located immediately northwest of the intersection of SW Durham Road and SW Summerfield Drive in Tigard, Oregon. The site includes a small structure occupied by a real estate agency located within the central portion of the site and is surrounded by a landscaped area, which includes several large trees and a concrete pond. A small asphalt parking area is located north of the existing structure. The site is primarily surrounded by commercial development to the north,west, and south and residential development to the east. Topography of the site slopes upward from north to south across the site with elevations ranging from 186 to 191 feet above MSL. 4.2 SUBSURFACE CONDITIONS We explored site subsurface conditions by drilling two borings (B-1 and B-2)to a maximum depth of approximately 25.5 feet BGS. Figure 2 shows the approximate boring locations. The exploration logs and results of our laboratory testing program are provided in the Appendix. Boring B-1 was completed within the landscaped area on the southeast corner of the site and encountered an approximate 4-inch-thick root zone. Boring B-2 was completed in the asphalt- paved parking lot on the northwest corner of the site and encountered 2.5 inches of AC underlain by 16 inches of base rock. In general, subsurface conditions beneath the root zone and asphalt section consist of silt with varying amounts of sand and clay to the total depths explored of 25.5 feet BGS. The silt is generally stiff to medium stiff in the upper 10.0 to 15.0 feet. It becomes soft to very soft to depths ranging between 15.0 and 22.0 feet BGS. The site was observed to be medium stiff at a depth of 25.0 feet BGS. We observed groundwater at depths on the order of 10 to 12 feet BGS in the borings. The depth to groundwater will fluctuate in response to seasonal changes, changes in topography, irrigation, and other factors not observed in this study. G EO DESIGN= 2 SchwindtB-1-01:1 031 1 1 5.0 CONCLUSIONS Based on our review of available information, the results of our explorations, and the laboratory testing and analyses, it is our opinion that the site can be developed as proposed. Our • geotechnical engineering recommendations for use in design and construction of the proposed development are provided in subsequent sections of this report. • The proposed structures can be supported on spread footings bearing on the underlying native silt or on structural fill overlying firm site soils. • The existing structure and concrete pond and trees will be demolished and removed as part of the new development. These areas will require backfill with structural fill. • The site soils are sensitive to moisture and are easily disturbed when at a moisture content that is above optimum. The subgrade should be protected from construction traffic. The following sections present general recommendations based on evaluation of results from geotechnical investigation and our understanding of the proposed project. 6.0 SITE DEVELOPMENT RECOMMENDATIONS 6.1 SITE PREPARATION Demolition includes removal of the existing pavements, concrete curbs, abandoned utilities, and any subsurface elements from previous development. Demolished material should be transported off site for disposal. Excavations remaining from removing basements (if present) foundations, utilities, and other subsurface elements should be backfilled with structural fill • where below planned site grades. The bottoms of the excavations should be excavated to expose firm subgrade before filling. The sides of the excavations should be cut into firm material and sloped a minimum of 1%ZH:1V. Utility lines abandoned under new structural components should be completely removed and backfilled with structural fill. Soft soil encountered in utility line excavations should be removed and replaced with structural fill. The existing root and topsoil zones should be stripped and removed from all proposed structural fill, pavement, and improvement areas and for a 5-foot margin around such areas. Based on the results of our explorations, we observed a 4-inch-thick root zone within the landscaped portion of the site. Greater stripping depths may be required to remove localized zones of loose or organic material during construction. The actual stripping depth should be based on field observations at the time of construction. Stripped material should be transported off site for disposal or used in landscaped areas. Existing trees and shrubs should be removed from all pavement and improvement areas. In addition, root balls should be grubbed out to the depth of the roots,which could exceed 3 feet BGS. Depending on the methods used to remove the root balls, considerable disturbance and loosening of the subgrade could occur during site grubbing. We recommend that soil disturbed during grubbing operations be removed to expose firm, undisturbed subgrade. The resulting excavations should be backfilled with structural fill. G EODESIGNz 3 SchwindtB-1-01:10311 1 A member of our geotechnical staff should observe all exposed subgrades after stripping and site cutting have been completed to determine if there are areas of unsuitable or unstable soil. Our representative should observe a proofroll with a fully loaded dump truck or similar heavy, rubber- ' tire construction equipment to identify soft, loose, or unsuitable areas. Areas that appear to be too wet and soft to support proofrolling equipment should be evaluated by probing and prepared in accordance with the recommendations for wet weather construction presented in the"Wet Weather/Wet Soil Grading" section of this report. 6.2 WET WEATHER/WET SOIL GRADING The surficial silty soils at the site are easily disturbed during the wet season and when they are moist. If not carefully executed, site preparation, utility trench work, and roadway excavation can create extensive soft areas and significant subgrade repair costs can result. If construction is planned when the surficial silty soils are wet or may become wet, the construction methods and schedule should be carefully considered with respect to protecting the subgrade to reduce the need to over-excavate disturbed or softened soil. The project budget should reflect the recommendations below if construction is planned during wet weather or when the surficial soils are wet. If construction occurs when silty,wet soils are present, site preparation activities may need to be accomplished using track-mounted excavating equipment that loads removed material into trucks supported on granular haul roads. The thickness of the granular material for haul roads and staging areas will depend on the amount and type of construction traffic. Generally, a 12-to 18-inch-thick mat of imported granular material is sufficient for light staging areas and the basic building pad but is generally not expected to be adequate to support heavy equipment or truck traffic. The granular mat for haul roads and areas with repeated heavy construction traffic typically needs to be increased to between 18 to 24 inches. The actual thickness of haul roads and staging areas should be based on the contractor's approach to site development and the amount and type of construction traffic. The imported granular material should be placed in one lift over the prepared, undisturbed subgrade and compacted using a smooth-drum, non-vibratory roller. In addition, a geotextile fabric should be placed as a barrier between the subgrade and imported granular material in areas of repeated construction traffic. The imported granular material and the geotextile fabric should meet the specifications in the"Structural Fill" section of this report. 6.3 TEMPORARY SLOPES Where construction slopes are possible, excavation side slopes less than 10 feet high should be no steeper than 1 Y2H:1 V, provided groundwater is not present. If slopes greater than 10 feet high are required, GeoDesign should be contacted to make additional recommendations. We recommend a minimum horizontal distance of 5 feet from the edge of the existing improvements to the top of the temporary slope. All cut slopes should be protected from erosion by covering them during wet weather. If sloughing or instability is observed, the slope should be flattened or the cut supported by shoring. Excavations should be made in accordance with applicable OSHA and state regulations. While this report describes certain approaches to excavation and dewatering, the contractor should be G EO DESIGN= 4 SchwindtB-1.01:1031 1 1 responsible for selecting excavation and dewatering methods, monitoring the excavations for safety, and providing shoring, as required to protect personnel and adjacent utilities and structures. 6.4 STRUCTURAL FILL Structural fill includes fill beneath foundations, slabs, pavements, any other areas intended to support structures, or within the influence zones of structures. Structural fill should be free of organic matter and other deleterious materials and, in general, should consist of particles no larger than 3 inches in diameter. Recommendations for suitable fill materials are provided in the following sections. 6.4.1 On-site Soil The on-site native soils will be suitable for use as structural fill only if they can be moisture conditioned. Based on our experience, the on-site silty soils are sensitive to small changes in moisture content and may be difficult to compact adequately during wet weather or when their moisture content is more than a few percentage points above optimum. If the aggregate base beneath the pavement can effectively be separated from the underlying silt, it will be suitable for use as structural fill. 6.4.2 Select Granular Fill Granular material for use as structural fill should be pit-or quarry-run rock, crushed rock, or crushed gravel and sand that is fairly well graded between coarse and fine and has less than 5 percent by dry weight passing the U.S. Standard No. 200 Sieve. Granular fill used during - periods of prolonged dry weather may have up to 10 percent passing the U.S. Standard No. 200 Sieve, provided it is properly moisture conditioned. 6.4.3 Pipe Bedding Utility trench backfill for bedding and in the pipe zone should consist of well-graded granular material with a maximum particle size of% inch and less than 5 percent by dry weight passing the U.S. Standard No. 200 Sieve or as required by the pipe manufacturer. 6.4.4 Crushed Rock Crushed rock will be required as base material for floor slabs and pavements as specified. Crushed rock fill should consist of imported clean, durable, crushed, angular rock that meets the requirements of the pertinent sections of this report. 6.5 FILL PLACEMENT AND COMPACTION Fill soils should be compacted at a moisture content that is near optimum. The maximum allowable moisture content varies with the soil gradation and should be evaluated during construction. Fill and backfill material should be placed in uniform, horizontal lifts and compacted with appropriate equipment. The maximum lift thickness will vary depending on the material and G EO DESIGN? 5 SchwindtB-1-01:10311 1 compaction equipment used but should generally not exceed the loose thicknesses provided in Table 1. Fill material should be compacted in accordance with the compaction criteria provided in Table 2. Table 1. Recommended Uncompacted Lift Thickness Recommended Uncompacted Lift Thickness (inches) Compaction Equipment Granular and Crushed Crushed Rock Silty Soils Rock Maximum Maximum Particle Particle Size<_ 1Y2 inches Size > 1%2 inches Hand Tools: Plate Compactors and 4 to 8 4 to 8 Not Recommended Jumping Jacks Rubber-Tire Equipment 6 to 8 10 to 12 6 to 8 Light Roller 8 to 10 10 to 12 8 to 10 Heavy Roller 10 to 12 12 to 18 12 to 16 Hoe Pack Equipment 12 to 16 18 to 24 12 to 16 Table 1 is based on our experience and is intended to serve only as a guideline. The information provided in this table should not be included in the project specifications. Table 2. Compaction Criteria Compaction Requirements in Structural Zones _ • Percent Maximum Dry Density Fill Type Determined by ASTM D 1557 0 to 2 Feet Below > 2 Feet Below Pipe Zone Subgrade Subgrade (percent) (percent) (percent) Area Fill 95' 92 Aggregate Bases 95 95 Trench Backfill 95' 92 902 Retaining Wall Backfill 9513 92' 1. May be reduced to 92 percent if native soils are used. 2. Or as recommended by the pipe manufacturer. 3. Should be reduced to 90 percent within a horizontal distance of 3 feet from the retaining wall. 6.5.1 Area Fills Imported fill placed to raise site grades should be placed on a prepared subgrade that consists of firm, inorganic site soils or compacted fill. The fill material should be placed in uniform horizontal lifts and compacted to the recommended minimum density provided in Table 2. C EO DFSIGN? 6 SchwindtB-1-01:1031 1 1 6.52 Aggregate Bases Aggregate base materials under foundations and floor slabs should be placed on a prepared subgrade that consists of firm, inorganic, native soils or compacted fill. Aggregate base material should be placed in uniform horizontal lifts and compacted to the recommended minimum density provided in Table 2. 6.5.3 Trench Backfill Trench backfill in structural areas should consist of select granular fill or crushed rock as described in the"Structural Fill" section of this report and be compacted to the minimum density provided in Table 2. Pipe bedding and fill in the pipe zone should be compacted to the minimum density presented in Table 2 or as recommended by the pipe manufacturer. 6.5.4 Retaining Wall Backfill Retaining wall backfill should be compacted to the recommended minimum density provided in Table 2, except that fill within 3 horizontal feet of the wall should be placed in uniform horizontal lifts and compacted to a lesser density of 90 percent of the maximum density as determined by ASTM D 1557 to reduce the effect of compaction-induced stresses against the retaining wall. Settlement of up to 1 percent of the wall height commonly occurs immediately adjacent to retaining walls as the walls rotate and develop lateral active earth pressures. Consequently, we recommend that flatwork (slabs, sidewalks, or pavement) placed adjacent to retaining walls be postponed at least four weeks following wall construction, unless survey data indicates that settlement is complete prior to that time. 6.6 PERMANENT CUT AND FILL SLOPES - Permanent cut and fill slopes in the site soils should be inclined no steeper than 2H:1 V. Buildings, access roads, and pavements should be set back a minimum of 5 feet from the crest of any such slopes. • 6.7 EROSION CONTROL The on-site soils are moderately susceptible to erosion. Consequently,we recommend that slopes be covered with an appropriate erosion control product if construction occurs during periods of wet weather. We recommend that all slope surfaces be planted as soon as practical to minimize erosion. Surface water runoff should be collected and directed away from slopes to prevent water from running down the slope face. Erosion control measures such as straw bales, sediment fences, and temporary detention and settling basins should be used in accordance with local and state ordinances. 7.0 FOUNDATION SUPPORT RECOMMENDATIONS Based on the results of our subsurface exploration program and geotechnical analysis, the planned structure may be supported by continuous wall and isolated column footings founded on the underlying native medium stiff to very stiff silt or on structural fill overlying firm site soils. Our recommendations for use in foundation design and construction are provided in the following sections. G EO DESIGNy 7 schwindtB-1-01:10311 1 7.1 SPREAD FOOTINGS 7.1.1 Bearing Capacity All footings 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 50 percent when considering seismic or wind loads. The weight of the footing and any overlying backfill can be ignored in calculating footing loads. We recommend that isolated column and continuous wall footings have minimum widths of 24 and 18 inches, respectively. The bottom of exterior footings should be founded at least 18 inches below the lowest adjacent grade. Interior footings should be founded at least 12 inches below the top of the floor slab. The recommended minimum footing depth is greater than the anticipated frost depth. We recommend that a qualified geotechnical engineer or geotechnical field technician evaluate all footing subgrades prior to construction of forms or placement of reinforcing steel and concrete. We recommend that 2 to 4 inches of compacted crushed rock be placed over the exposed subgrade to reduce disturbance to the silty subgrade soils during construction of forms and placement of reinforcing steel if construction occurs during wet weather. 7.1.2 Lateral Resistance Lateral loads can be resisted by passive earth pressure on sides of the footings and by friction on the base of the footings. We recommend a friction coefficient of 0.45 for computing the friction capacity of building foundations that bear on the gravel fill or compacted crushed rock and 0.35 for footings bearing on the native soils. An equivalent fluid unit weight of 350 pcf is recommended to compute passive earth pressure acting on footings constructed in direct contact with compacted structural fill or native soils. This value is based on the assumptions that the adjacent confining structural fill or native soils are level and that groundwater remains below the base of the footing. The top 1 foot of soil should be neglected when calculating lateral earth pressures unless the foundation area is covered with pavement or is inside a building. 7.1.3 Settlement Shallow foundations with real bearing pressures less than 2,500 psf should experience post- construction settlements of less than 1 inch. Differential settlements of up to one-half of the total settlement magnitude can be expected between adjacent footings with similar loads. We expect that settlement will occur during construction as loads are applied. 7.2 SLABS ON GRADE A modulus of subgrade reaction of 120 pci can be used for design of the floor slabs provided the subgrade is prepared in accordance with the recommendations presented in this section. The native soils are non-expansive, so heave is not anticipated beneath the floor slab. We recommend that the floor slab be supported on at least 6 inches of imported granular material to aid as a capillary break and to provide uniform support. The imported granular material should be placed and compacted as previously recommended for aggregate bases. G EO DESIGN= 8 SchwindtB-1-01:103111 Vapor barriers beneath floor slabs are typically required by flooring manufactures to maintain the warranty on their products. In our experience, adequate performance of floor adhesives can be achieved by using a clean base rock(less than 5 percent fines) beneath the floor slab with no vapor barrier. In fact,vapor barriers can frequently cause moisture problems by trapping water - beneath the floor slab that is introduced during construction. If a vapor barrier is used, water should not be applied to the base rock prior to pouring the slab and the work should be completed during extended dry weather so that rainfall is not trapped on top of the vapor barrier. Selection and design of an appropriate vapor barrier, if needed, should be based on discussions among members of the design team. We can provide additional information to assist you with your decision. 8.0 PERMANENT RETAINING STRUCTURES Permanent retaining structures free to rotate slightly around the base should be designed for active earth pressures using an equivalent fluid unit weight of 35 pcf. This value is based on the assumption that(1)the walls will not be restrained against rotation, (2)the backfill is level, (3)the backfill consists of granular material, (4)the backfill is drained, and(5)the wall is less than 10 feet in height. If retaining walls are restrained against rotation during backfilling, they should be designed for an at-rest earth pressure of 55 pcf. Seismic lateral forces can be calculated using a dynamic force equal to 6.5 H2 pounds per linear foot of wall, where H is the wall height. The seismic force should be applied as a distributed load with the centroid located at 0.6H from the wall base. Footings for retaining wall should be designed in as recommended for shallow foundations. Drains consisting of a perforated drainpipe wrapped in a geotextile filter should be installed behind exterior walls. The pipe should be embedded in a zone of coarse sand or gravel containing less than 2 percent by dry weight passing the U.S. Standard No. 200 Sieve and should outlet to a suitable discharge. 9.0 GROUNDWATER CONSIDERATIONS 9.1 TEMPORARY During grading at the site, the contractor should be made responsible for temporary drainage of surface water as necessary to prevent standing water and/or erosion at the working surface. During rough and finished grading of the building site, the contractor should keep all footing excavations and building pads free of water. 9.2 SURFACE The finished ground surface around structures should be sloped away from their foundations at a minimum 2 percent gradient for a distance of at least 5 feet. Downspouts or roof scuppers should discharge into a storm drain system that that carries the collected water to an appropriate stormwater system. Trapped planter areas should not be created adjacent to structures without providing means for positive drainage(i.e., swales or catch basins). CEO DESIGN? 9 SchwindtB-1-01:10311 1 9.3 SUBSURFACE Due to the shallow depth to groundwater at the site, we recommend that footing drains be installed. Footing drains should consist of a filter fabric-wrapped, drain rock-filled trench that extends at least 12 inches below the lowest adjacent grade(i.e., slab subgrade elevation). A perforated pipe should be placed at the base to collect water that gathers in the drain rock. The drain rock and filter fabric should meet the specifications outlined in the "Structural Fill"section of this report. The discharge for the footing drain should not be tied directly into the stormwater drainage system, unless mechanisms are installed to prevent backflow. 9.4 INFILTRATION SYSTEM Infiltration values are provided in the"Infiltration Testing"section of this report. The values have been factored to account for potential site variability and the limited number of tests performed but has not been factored for design. This value should be factored by the civil designer during design to account for the system size, the degree of long-term maintenance and influent/pre- treatment control, as well as the potential for long-term clogging due to siltation and bio-buildup, depending on the proposed length, location, and type of use of infiltration facility. 10.0 SEISMIC DESIGN CRITERIA Seismic design is prescribed by the 2010 SOSSC and the 2009 IBC. Table 3 presents the site design parameters prescribed by the 2009 IBC for the site. Table 3. IBC Seismic Design Parameters Parameter Short Period 1 Second Period (T==0.2 second) (T, = 1.0 second) Maximum Considered Earthquake Spectral Acceleration, S Sz° 0.92 g S = 0.33 g Site Class D Site Coefficient, F F a= 1.134 F 1.735 Adjusted Spectral Acceleration,SN SM5= 1.04 g SM, = 0.58 g Design Spectral Response S =0.69 g Sp =0.39 g Acceleration Parameters, Sp � Design Peak Ground Acceleration, Sam 0.28 g Liquefaction is caused by a rapid increase in pore water pressure that reduces the effective stress between soil particles to near zero. Granular soils,which rely on interparticle friction for strength, are susceptible to liquefaction until the excess pore pressures can dissipate. In general, loose, saturated sand soils with low silt and clay contents are the most susceptible to liquefaction. Silty soils with low plasticity are moderately susceptible to liquefaction under relatively higher levels of ground shaking. Based on our experience in the site vicinity, the risk of liquefaction under design levels of ground shaking is considered low. G EO DESIGN= 10 SchwindtB-1.01:1031 11 11.0 PAVEMENT DESIGN RECOMMENDATIONS The pavement subgrade should be prepared in accordance with the previously described site preparation, construction considerations, and structural fill recommendations. Our pavement - recommendations assume that traffic at the site will consist of light-weight passenger vehicles and delivery trucks. Our pavement recommendations are based on an assumed California bearing ratio value of 3 for the pavement subgrade and a design life of 20 years. In access roadways and areas trafficked by trucks,we recommend a pavement section consisting of a minimum of 3.5 inches of AC pavement underlain by a minimum of 10.0 inches of crushed base rock. A pavement section of 2.5 inches of AC over 8.0 inches of aggregate base can be used in paved areas that will be exposed to passenger car traffic only. In addition, we recommend that a geotextile separation layer be placed on the subgrade and under the crushed rock base in access and truck traffic areas to prevent migration of the silt up into the base course. The geotextile should meet the requirements previously presented. The AC should be Level 2, 1/2-inch, dense HMAC according to OSSC 00745 (Hot Mixed Asphalt Concrete)and compacted to 91 percent of maximum specific gravity of the mix, as determined by ASTM D 2041. Minimum lift thickness for 1/2-inch HMAC is 2.0 inches. Asphalt binder should be performance graded and conform to PG 64-22. The base rock should meet the specifications for aggregate base rock provided in the"Structural Fill" section of this report. The pavement subgrade should be prepared in accordance with the"Site Preparation" and - "Structural Fill" sections of this report. The top 12 inches of subgrade below the pavement should be compacted to at least 92 percent of the maximum dry density, as determined by ASTM D 1557, or until proofrolling with a fully loaded dump or water truck indicates an unyielding, non-pumping subgrade is present. Construction traffic should be limited to non-building, unpaved portions of the site or haul roads. Construction traffic should not be allowed on new pavements. If construction traffic is to be allowed on newly constructed road sections, an allowance for this additional traffic will need to be made in the design pavement section. 12.0 INFILTRATION TESTING Infiltration tests were conducted in borings B-1 and B-2 located on the northwestern and southeastern areas of the site. Infiltration testing was conducted in general accordance with the City of Portland Bureau of Environmental Services Stormwater Management Manual (revised February 1, 2010). Table 4 presents a summary of infiltration test results and fines content determinations. The exploration logs and particle-size analyses are presented in the Appendix. G EO DESIGN? 11 SchwindtB-1-01:10311 1 Table 4. Infiltration Test Results Depth Observed Fines Content' Exploration (feet BGS) Infiltration Rate (percent) (inches/hour) 8-1 2 2.9 70 B-1 10 2.2 66 —_ B-2 2 6 62 1. Fines content: material passing the U.S.Standard No.200 Sieve The infiltration rates provided in table above are measured rates and are unfactored. Correction factors should be applied to the measured infiltration rates by the civil engineer during design to account for the degree of long-term maintenance and influent/pre-treatment control, as well as the potential for long-term clogging due to siltation and buildup of organic material, depending on the proposed length, location, and type of infiltration facility. We recommend GeoDesign be retained to observe the installation of the infiltration system and confirm that subsurface conditions are consistent with those encountered during our explorations. If the stormwater infiltration system does not have a redundant overflow system,we also recommend GeoDesign conduct confirmation infiltration testing at the base of the proposed system. 13.0 OBSERVATION OF CONSTRUCTION Satisfactory earthwork and foundation performance depends to a large degree on the quality of construction. Subsurface conditions observed during construction should be compared with • those encountered during the subsurface explorations. Recognition of changed conditions often requires experience; therefore, qualified personnel should visit the site with sufficient frequency to detect whether subsurface conditions change significantly from those anticipated. In addition, 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. 14.0 LIMITATIONS We have prepared this report for use by the Dr. Brandon Schwindt, DMD, PC and his consultants. The data and report can be used for estimating purposes, but our report, conclusions, and interpretations should not be construed as a warranty of the subsurface conditions and are not applicable to other sites. Soil explorations indicate soil conditions only at specific locations and only to the depths penetrated. They do not necessarily reflect soil strata or water level variations that may exist between exploration locations. If subsurface conditions differing from those described are noted during the course of excavation and construction, re-evaluation will be necessary. The site development plans and design details were not finalized at the time this report was prepared. When the design has been finalized and if there are changes in the site grades or [DESIGN= 12 SchwindtB-1-01:1031 1 1 location, configuration, design loads or type of construction for the buildings, the conclusions and recommendations presented may not be applicable- If design changes are made, we should be retained to review our conclusions and recommendations and to provide a written evaluation or modification. 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. • • We appreciate the opportunity to be of continued service to you. Please call if you have questions concerning this report or if we can provide additional services. Sincerely, ,->;' PROF4- GeoDesign, Inc. 1;':? 73 1 r \ .0A7GON 3. Cac cia C. Miller, P.E., G.E. a ''' Senior A sociate Engineer . .' ../ Brett . S 1• .n, P. .,G.E. Principal Engineer G EO DESIG N= 13 SchwindtB-1-01:103111 FIGURES S „"r•(:..,,„,,,0', ,� "p j..F F* f' 4 r K W "f i .o' •.+y�emu- rc ` w , : � } ♦ M r .--4."1' r ,�� s� Zr }� ,r }, '$ v,.„ t S4+' Ya � �.• i ”r V M r • Z . n _ 1„ �C,�� .. 1.-4,,;„-,;:o.„-f, ^� -'---1 9f • w :. • • kap q }, T Lai V cc EL • LT_O I - C _ r. ,,,,lie _ • 8■■ 1. 41..`""" .to,,,,,,,, ,..*- - . — ' ':c' • G ih 1/110^ N a m • ji IWO aim 0 . ji ii 0 2000 4000 - v VICINITY MAP BASED ON AERIAL x PHOTOGRAPH OBTAINED FROM r A NI ' 1 '. I I 0 f3, GOOGLE EARTH PROS ;!:_` pt ��' (SCALE IN APPROXIMATE FEET)iii v -v . i G EODESIGNz SCHWINDTB-1-01 VICINITY MAP m °A 15575 Sequoia Parkway-Suite 100 E Portland 8787 Fax 97224 503 SCHWINDT DENTAL OFFICE c y Off 503.968.8787 Fax 503.968.3068 OCTOBER 201 1 TIGARD, OR FIGURE 1 it iL: Primed fly aday I Print Date.10/31/2011 10.27.37 AM File Name\\geodeslgn.local\FilesV obs\SNSchwindt8\Schswnd18.1\SchwlndtB-I-01\Figures\CAD\SehwvndtB 1.01-SPOI.dwg I Layout.FIGURE 2 I / i I ( \ 1.1 �0;r I I �a- c) n n I\ r) I I m m�l ni / / I 'I‘ i 1 01 /0I, -__ f�C 5 L I I P m a,Gll 44714c m, I I , 1 c; (-, `' 1�I 2V2 ' . - I— �LEB! LE), BEAR acs I ���n ° �' ) r� 1 1 c, -/ C I x \ ^+ 1 t7 c-L n • I 1 l\ IF—N41-N— 'l I d, 1 'r1)1 I / xl I A -i} II I I"// i i to_ \ N 1 1 I tI I '➢v 2 c \K mac" y ;I �, �1 �} I\ v p \ 1 IG O / 1 i y n Lk''D f � I c &); \ / • z2N __ ) n I I c g'c-3 '1, I I J o I,v _ n Z I I L- ` / to _ N ; 1- F'60]1 '.----I `'x' 0 0..8►� _ _._ _ > I I —G ------ c _! G is Cgam \ i / J % I I i 1 cc � 1 m 0 c, c /• �� on CI-'-' --"-- c % �/ ./1 I �O ,I Cox �/ I 5C rT1z ��--t' Q NN // I 00 S 1--I SW SUMMERFIELD DRIVE .6 I I r N. CCy / \n N En r i2< a D 11 f, \ l lr U7? i z r Fn Cl w Z sm D-. o A =Z O 1 F In tn0 n - O r �Z m Fv Z oO 2 'o w F m m r.l z .[-, .7.:p O • A O 0 MI 0 CO eR ®DESIGNW SCHWINDT8-1-01 SITE PLAN Off soe 9Noland OR 97,4 elose OCTOBER 2011 SCHWINDT DENTAL OFFICE FIGURE 2 as DM Fa.SDI 96 TIGARD,OR APPENDIX APPENDIX FIELD EXPLORATIONS GENERAL We explored subsurface conditions in the project area by drilling two borings (B-1 and B-2) to a maximum depth of 25.5 feet BGS. Figure 2 shows the approximate exploration locations. The borings were drilled on October 10, 2011 by Dan J. Fischer Excavation, Inc. of Forest Grove, Oregon. The exploration locations were located in the field pacing from survey existing site features. This information should be considered accurate only to the degree implied by the methods used. A member of our geotechnical staff observed the explorations. We obtained representative samples of the various soils encountered in the explorations for geotechnical laboratory testing. Classifications and sampling intervals are shown in the exploration logs included in this appendix. SOIL SAMPLING Soil samples were obtained from the borings using the following method: • Standard penetration tests were performed in general conformance with ASTM D 1 586. The sampler was driven with a 140-pound automatic trip hammer free-falling 30 inches. The number of blows required to drive the sampler 1 foot, or as otherwise indicated, into the soils is shown adjacent to the sample symbols on the exploration logs. Disturbed samples were obtained from the split barrel for subsequent classification and index testing. SOIL CLASSIFICATION The soil samples were classified in accordance with the"Exploration Key"(Table A-1)and "Soil Classification System" (Table A-2), which are included in this appendix. The exploration logs indicate the depths at which the soils or their characteristics change, although the change actually could be gradual. If the change occurred between sample locations, the depth was interpreted. Classifications and sampling intervals are shown in the exploration logs included in this appendix. • LABORATORY TESTING CLASSIFICATION The soil samples were classified in the laboratory to confirm field classifications. The laboratory classifications are included on the exploration logs if those classifications differed from the field classifications. G EODESIGN? A-1 SchwindtB-1-01:103111 MOISTURE CONTENT We tested the natural moisture content of selected samples obtained from the explorations in general accordance with ASTM D 2216. The natural moisture content is a ratio of the weight of the water to soil in a test sample and is expressed as a percentage. The moisture contents are - included on the exploration logs presented in this appendix. GRAIN-SIZE TESTING Grain-size testing was completed on four selected sample. The results of the grain-size testing are included on the exploration logs presented in this appendix. DESIGN A-2 SchwindtB-1-01:10311 1 SYMBOL SAMPLING DESCRIPTION Location of sample obtained in general accordance with ASTM D 1 586 Standard Penetration Test with recovery Location of sample obtained using thin-wall Shelby tube or Geoprobe® sampler in general accordance with ASTM D 1 587 with recovery Location of sample obtained using Dames & Moore sampler and 300-pound hammer or pushed with recovery N Location of sample obtained using Dames & Moore and 140-pound hammer or pushed with recovery N Location of sample obtained using 3-inch-O.D. California split-spoon sampler and 140-pound hammer NLocation of grab sample Graphic Log of Soil and Rock Types .•,�"• / Observed contact between soil or 0 Rock coring interval •.• ,. / rock units(at depth indicated) V Water level during drilling Inferred contact between soil or rock units (at approximate depths indicated) Water level taken on date shown —- .t., —o GEOTECHNICAL TESTING EXPLANATIONS ATT Atterberg Limits PP Pocket Penetrometer CBR California Bearing Ratio P200 Percent Passing U.S. Standard No. 200 CON Consolidation Sieve DD Dry Density RES Resilient Modulus DS Direct Shear SIEV Sieve Gradation HYD Hydrometer Gradation TOR Torvane MC Moisture Content UC Unconfined Compressive Strength MD Moisture-Density Relationship VS Vane Shear OC Organic Content kPa Kilopascal P Pushed Sample ENVIRONMENTAL TESTING EXPLANATIONS CA Sample Submitted for Chemical Analysis ND Not Detected P Pushed Sample NS No Visible Sheen PID Photoionization Detector Headspace SS Slight Sheen Analysis MS Moderate Sheen ppm Parts per Million HS Heavy Sheen G EO DESIGN? EXPLORATION KEY TABLE A-1 15575 SW Sequoia Parkway-Sone 100 Portland OR 97224 Off 503.968.8787 Fax 503.968.3068 RELATIVE DENSITY -COARSE-GRAINED SOILS Relative Density Standard Penetration Dames&Moore Sampler Dames&Moore Sampler Resistance (140-pound hammer) (300-pound hammer) Very Loose 0- 4 0- 11 0-4 Loose 4- 1 0 1 1 -26 4- 10 Medium Dense 10- 30 26- 74 10- 30 Dense 30- 50 74- 120 30-47 Very Dense More than 50 More than 120 More than 47 CONSISTENCY- FINE-GRAINED SOILS Consistency Standard Penetration Dames&Moore Sampler Dames&Moore Sampler Unconfined Compressive Resistance (140-pound hammer) (300-pound hammer) Strength(tsf) Very Soft Less than 2 Less than 3 Less than 2 Less than 0.25 Soft 2 -4 3 -6 2 - 5 0.25 -0.50 Medium Stiff 4 -8 6- 12 5 -9 0.50- 1.0 Stiff 8- 15 12 -25 9- 19 1.0- 2.0 Very Stiff 15 - 30 25 -65 19- 31 2.0-4.0 Hard More than 30 More than 65 More than 31 More than 4.0 PRIMARY SOIL DIVISIONS GROUP SYMBOL GROUP NAME CLEAN GRAVELS GW or GP GRAVEL GRAVEL (< 5%fines) (more than 50%of GRAVEL WITH FINES GW-GM or GP-GM GRAVEL with silt (mo core haraction (z 5%and 5 12%fines) GW-GC or GP-GC GRAVEL with clay COARSE GRAINED retained on GRAVELS WITH FINES GM silty GRAVEL SOILS No.4 sieve) (> 12%fines) GC clayey GRAVEL GC-GM silty,clayey GRAVEL (more than 50% CLEAN SANDS retained on SAND (<5%fines) SW or SP SAND No. 200 sieve) (50%or more f SANDS WITH FINES SW-SM or SP-SM SAND with silt (5 more o c 0%or mor o (Z 5%and_< 12%fines) SW-SC or SP-SC SAND with clay passing SM silty SAND SANDS WITH FINES No.4 sieve) (> 12%fines) SC clayey SAND SC-SM silty, clayey SAND ML SILT FINE-GRAINED CL CLAY SOILS Liquid limit less than 50 CL-ML silty CLAY (50%or more SILT AND CLAY OL ORGANIC SILT or ORGANIC CLAY passing MH SILT No. 200 sieve) Liquid limit 50 or CH CLAY greater OH ORGANIC SILT or ORGANIC CLAY HIGHLY ORGANIC SOILS PT PEAT MOISTURE ADDITIONAL CONSTITUENTS CLASSIFICATION Secondary granular components or other materials Term Field Test such as organics,man-made debris,etc. Silt and Clay In: Sand and Gravel In: Percent Percent dry very low moisture, Fine-Grained Coarse- Fine-Grained Coarse- dry to touch Soils Grained Soils Soils Grained Soils damp,without < 5 trace trace < 5 trace trace moist visible moisture _ 5 - 12 minor with 5 - 15 minor minor wet visible free water, > 12 some silty/clayey 15 - 30 with with usually saturated > 30 sandy/gravelly sandy/gravelly G EO DESIGN? SOIL CLASSIFICATION SYSTEM TABLE A-2 15575 SW Sequoia Parkway Suite 100 Portland OR 97224 Off 503.968.8787 Fax 503.968.3068 Z 0= u w •BLOW COUNT INSTALLATION AND 1 Z J COMMENTS DEPTH u <0_ a •MOISTURE CONTENT% = MATERIAL DESCRIPTION >'-u I— g FEET o w w Q ®RQD% =CORE REC% w H IA 188.5 0 50 100 —o.o Stiff, brown mottled orange/black SILT (ML), minor clay and sand,trace organics; dry to moist, low plasticity (4- - _ inch-thick root zone). 2.5— ! 10 P200=70% P200 5.0— r becomes brown,with sand, trace clay; moist at 6.0 feet • 7.5— becomes sandy at 7.5 feet becomes medium stiff, brown, some 7 clay, minor sand; medium plasticity at IL A • 8.0 feet lo.o— becomes light brown, sandy at 10.0 feet P200 • P200-66% 12.5- becomes soft; wet at 12.0 feet Groundwater estimated at I 4 12.0 to 16.0 feet 15.0 ■ • 17.5— 169.5 - Very soft to soft, brown, sandy SILT 190 20.0— (ML), trace clay; wet, nonplastic to low plasticity, rapid dilatancy. P200 ♦ • P200=52'/ I- m 22.5— o - r _ o becomes medium stiff at 24.0 feet z r • d 25.0— 163.0 - Exploration completed at a depth of 25.5 25.5 feet. z - a• 27.5— 2 _ w u _ a. u - O0 30.0 0 50 100 0 I- DRILLED BY Dan J.Fischer Excavating,Inc. LOGGED BY:CLR COMPLETED:10/10/11 z = BORING METHOD:hollow-stem auger(see report text) BORING BIT DIAMETER:3.5-inch z G EODESIGN? SCHWINDTB-1-01 BORING B-1 15575 SW Sequoia Parkway-Suite 100 SCHWINDT DENTAL OFFICE FIGURE A-1 m Portland OR 97224 OCTOBER 2011 Off 503.968.8787 Fax 503.968.3068 TIGARD,OR z o = u w BLOW COUNT INSTALLATION AND DEPTH u ¢a z a •MOISTURE CONTENT% COMMENTS = MATERIAL DESCRIPTION >w FEET w O w Q ®RQD% 177]CORE REC% w I— IA • —0.0 u 186.5 0 SO 100 yo ASPHALT CONCRETE(2.5 inches). f 10 23 - AGGREGATE BASE(16 inches). 185.0 Stiff, brown mottled black SILT with 1.5 2.5— sand (ML),trace clay; moist, low 10 P200-62% - plasticity. P200 • • becomes medium stiff, brown, sandy at 7 — 4.0 feet 5.0 S 7.5 becomes wet at 7.5 feet r • 10.0- _ Groundwater estimated at 10.0 feet 175,0 Soft, brown and gray SILT with sand 11.5 12.5— (ML), minor clay; wet, medium plasticity, 4 = rapid dilatancy. A • 15.0— - - becomes medium stiff, sandy at 16.0 11 feet r 18 inches of heave 17.5- 20.0 166.5 Exploration completed at a depth of 20.0 20.0 feet. I- Y 22.5— o 0 z z a 25.0- a H O u - z 0• 27.5- 0 W ✓ _ u - N • 30.0 0 50 100 0 DRILLED BY:Dan J.Fischer Excavating,Inc. LOGGED BY:CLR COMPLETED:10/10/11 z = BORING METHOD:hoow-stem auger(see report text) BORING BIT DIAMETER:3.5-inch GEODESIGN? SCHWINDTB-1-01 BORING B-2 z E 15575 SW Sequoia Parkway-Suite 100 SCHWINDT DENTAL OFFICE Portland OR 97224 OCTOBER 2011 FIGURE A-2 Off 503.968.8787 Fax 503.968.3068 TIGARD,OR SAMPLE INFORMATION SIEVE ATTERBERG LIMITS MOISTURE DRY - EXPLORATION SAMPLE ELEVATION CONTENT DENSITY GRAVEL SAND P200 LIQUID PLASTIC PLASTICITY NUMBER DEPTH (FEET) (PERCENT) (PCF) (PERCENT) (PERCENT) (PERCENT) LIMIT LIMIT INDEX (FEET) (PERCENT) (PERCENT) (PERCENT) B-1 2.0 186.5 14 70 B-1 4.0 184.5 23 • B-1 8.0 180.5 27 B-1 10.0 178.5 33 66 B-1 16.0 172.5 26 B-1 20.0 168.5 34 52 B-1 24.0 164.5 33 B-2 2.0 184.5 29 62 B-2 4.0 182.5 29 B-2 8.0 178.5 38 B-2 12.0 174.5 34 O z Z K 0. u z O w V a u O m H z Z x N (^ CEODESIGNZ SCHWINDTB-1-01 SUMMARY OF LABORATORY DATA 15575 SW Sequoia Parkway Suite I00 SCHWINDT DENTAL OFFICE m Portland OR 97224 OCTOBER 2011 FIGURE A-3 5 Off 503.968.8787 Fax 503.968.3068 TIGARD,OR ACRONYMS ACRONYMS AC asphalt concrete ASTM American Society for Testing and Materials BGS below ground surface g gravitational acceleration (32.2 feet/second) H:V horizontal to vertical HMAC hot mixed asphalt concrete IBC International Building Code MSL mean sea level OSHA Occupational Safety and Health Administration OSSC Oregon Standard Specifications for Construction (2008) pcf pounds per cubic foot pci pounds per cubic inch psf pounds per square foot SOSSC State of Oregon Structural Specialty Code ®DESIGNY SchwindtB-1-01:1031 11