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Report (18)
• t • li . . . z CD Emi o r N 02 z PI.' ww con co in gi t, ...:t g 9 0 151 . 0 eq 4+Nl CO >1—, o A � O as p d .41 P4 itO § = W.1 , • U A C , ,., ,,,,, ., O r l T� x - z •IT4 MO o c u l i � oS KJ _r.. .w _. ..........., . ... .ems r. �..� -zu..�U - - � -.W..�.._.�._.�,.____,...,.... ---- �.....�....,..,_.,�.....,.............�,.._........m .........a..................................................- �.._. �.� �...r �.4 ., ,.,..,..,, .....u.. .u......, ._...,,.„ .._...... :. vas... y.._ _.�. . �.. a.,...a ....- { il GEOCON NORTHWEST, INC. GEOTECHNICAL CONSULTANTS 9 P1475-05-01 February 16,2007 Mr.Doug Frey 908 Deborah Road Newberg,Oregon Subject: RED ROCK CREEK TIGARD BUSINESS CENTER TIGARD,OREGON GEOTECHNICAL INVESTIGATION Dear Mr.Frey: In accordance with our proposal number P06-05-150,November 1, 2006,and your authorization,we have performed a geotechnical investigation for the proposed Red Rock Creek Tigard Business Center in Tigard, Oregon. The accompanying report presents the findings of our investigation and our conclusions and recommendations regarding the geotechnical aspects of the proposed construction. Based on the results of this investigation, it is our opinion that the site can be developed as proposed, provided the recommendations of this report are followed. Important geotechnical issues addressed herein include perched/shallow groundwater potential, moderately compressible subsurface soil, deep foundation considerations, shoring and retaining wall evaluation, and grading recommendations for the moisture sensitive native fine-grained soil. It is highly recommended that site grading be completed during the summer months to reduce the potential for increased site preparation costs. If you have questions regarding this report, or if we may be of further service, please contact the undersigned at your convenience. Sincerely, GEOCON NORTHWEST,INCORPORATED �,*,D PR OFFS, cTkNEe '620_ l 18281 9 B an Wavra,P.E. Wesley 'Iaang,P .h:, '.E. - ' Geotechnical Engineer President 01 GO' / '4' (6, 19'6 BJW:AWS �FSCEY Sc*' cc: Mr.James Ponto,Anderson Dabrowski Architects IExPIRATION DATE: 81301 a?, Mr.Brian Lee,PACE Engineers 8283 SW Cirrus Drive 18 Beaverton, Oregon 97008 ■ Telephone (503) 626-9889 • Fax (503) 626-8611 TABLE OF CONTENTS • 1 PURPOSE AND SCOPE 1 2 SITE AND PROJECT DESCRIPTION 1 3 REGIONAL GEOLOGY 2 4 SUBSURFACE EXPLORATION AND CONDITIONS 2 4.1 SITE EXPLORATION 2 4.2 SUBSURFACE CONDITIONS 4 5 SEISMIC HAZARDS 5 5.1 LANDSLIDE HAZARD 5 5.2 CRUSTAL FAULTS 5 5.3 SOIL LIQUEFACTION OR CYCLIC FAILURE POTENTIAL 5 5.4 LATERAL SPREADING 6 5.5 2003 INTERNATIONAL BUILDING CODE SEISMIC DESIGN PARAMETERS 6 6 LABORATORY TESTING 6 7 CONCLUSIONS AND RECOMMENDATIONS 7 7.1 GENERAL 7 7.2 SITE PREPARATION 8 7.3 PROOF ROLLING 10 7.4 FILLS 10 7.5 SURFACE AND SUBSURFACE DRAINAGE 12 7.6 FOUNDATIONS 12 7.7 PERMANENT CUT AND FILL SLOPES 14 7.8 CONCRETE SLABS-ON-GRADE 14 7.9 RETAINING WALLS AND SHORING 15 7.10 UTILITY EXCAVATIONS 16 7.11 PAVEMENT DESIGN 17 8 FUTURE GEOTECHNICAL SERVICES 17 9 LIMITATIONS 18 MAPS AND ILLUSTRATIONS Figure 1,Vicinity Map Figure 2, Site Plan Figure 3,2003 IBC Design Response Spectrum Figure 4,Typical Underslab Drainage Scheme APPENDIX A FIELD INVESTIGATION APPENDIX B LABORATORY TEST RESULTS GEOTECHNICAL INVESTIGATION I PURPOSE AND SCOPE This report presents the results of the geotechnical investigation for the proposed Red Rock Creek Tigard Business Center in Tigard, Oregon. The approximate 4-acre parcel is located at 12625 SW 70th Avenue, which is at the southeast corner of SW 72°d Avenue and SW Dartmouth Street. The purpose of the geotechnical investigation was to evaluate subsurface soil and geologic conditions at the site and, based on the conditions encountered, provide conclusions and recommendations pertaining to the geotechnical aspects of the proposed construction. The scope of the field investigation consisted of a site reconnaissance,review of published geological literature,four exploratory borings,and four dilatometer soundings. A detailed discussion of the field investigation is presented in Section 4 of this report. Laboratory tests were performed on selected soil samples obtained during the investigation to evaluate pertinent physical properties. Appendix B presents a summary of the laboratory test results. The results of laboratory moisture content tests are presented on the exploratory boring logs. The recommendations presented herein are based on analyses of the data obtained during the field investigation, laboratory test results, and our experience with similar soil and geologic conditions. This report has been prepared for the exclusive use of Mr. Doug Frey and his agents, for specific application to this project, in accordance with generally accepted geotechnical engineering practice. This report may not contain sufficient information for purposes of other parties or other uses. 2 SITE AND PROJECT DESCRIPTION The site is currently vacant and is occupied by overgrown grass, trees, brush, and wetlands areas. The wetlands areas exhibited saturated soil and perched water at the ground surface at time of the field investigation. Red Rock Creek extends along the north and northwest boundaries of the property. Private residences extend along the south margin,and a large block retaining wall has been constructed for the property adjacent to the east which forms the east perimeter of the subject site. The topography of the site slopes down to the northwest with maximum elevation of 260 feet at the southeast corner and minimum elevation of 210 feet at the northwest corner. Several piles of rubbish were sporadically located across the property, but evidence to suggest the presence of previous structures at the property was not encountered. Drawings provided by Anderson Dabrowski Architects and project civil engineer,PACE Engineers, indicate the development will include the construction of three single-story buildings, on-grade parking, and SW 70'x' Avenue. Building A will be positioned along the east half of the north ) perimeter, building B at the far west perimeter, and building C at the middle of the south perimeter. The proposed grading plans indicate that the east portion of the site will require excavation to achieve P1475-05-01 -1- February 16,2007 grade while the west section may receive fill on the order of 15 feet. The excavation/fill transition zone extends north/south through proposed buildings A and C. It is understood that the filled • portions of the site will be retained by a retaining structure,and the cut along future SW 70th Avenue will be supported by a shoring structure. Red Rock Creek will be diverted to an underground culvert as part of the overall site development. Due to the City of Tigard building setback criteria, the north wall of Building A and the northwest corner of Building B may be positioned over the culvert. A discussion of deep foundation support in these locations is contained herein. 3 REGIONAL GEOLOGY Based on geologic literature reviewed for the site, the topography of the Tualatin Valley region is characterized by wide, flat lowlands and prominent uplands that are controlled primarily by the folding and faulting of the underlying bedrock. The near-surface geology of the project area consists of Late Pleistocene age deposits of silt and fine-grained sand described as Willamette Silt. These Pleistocene age deposits are characterized by brown to buff,beds and lenses of fine-grained sand,silt and clay. Willamette Silts are slack water fluvial and/or lacustrine deposits resulting from repeated temporary inundation of the Willamette and Tualatin Valleys by Late-Pleistocene glacial outburst floods. These glacial floods originated in the Missoula Valley of Montana, passed through eastern Washington, and followed the Columbia River downstream. When these large floods entered the Portland Basin they flowed up the Willamette River and its tributaries, flooding most of the Willamette and Tualatin Valleys to an approximate elevation of 350 feet MSL. The last of these glacial floods,also thought to be one of the largest,occurred about 12,400 years ago,establishing the minimum age of the silt deposit. The Willamette Valley silt is underlain by the erosional surfaces of older bedrock units including the Troutdale Formation. Well logs on file with Oregon Water Resources Department for the adjacent property to the east indicate the presence of silt which is underlain by andesitic rock at a depth of approximately 15 feet. The site west of the subject property is underlain by silt, sand, and clay to the maximum explored depth of 30 feet 4 SUBSURFACE EXPLORATION AND CONDITIONS 4.1 Site Exploration The subsurface soil conditions at the site were determined based on the literature review, field exploration,and laboratory investigation. The field exploration was completed on December 29th and 30th, 2006, and consisted of four exploratory borings and four dilatometer soundings. The borings were completed using mud rotary drilling techniques to a depth of 31.5 feet below the existing ground surface(bgs). The dilatometer soundings encountered practical refusal at variable depths that ranged from 17 to 33 feet bgs. The subsurface conditions encountered in the borings and dilatometer P1475-05-01 -2- February 16,2007 soundings were recorded on the subsurface logs that are located in Appendix A at the end of this report. The approximate locations of the explorations are shown in Figure 2,Site Plan. 4.1.1. Dilatometer Test The dilatometer test provides a rational, cost-effective method to determine engineering parameters for the design of earthworks and structural foundations. It is particularly useful in silts and sands that can be difficult to sample or test by other methods. The DMT is performed in situ by pushing a blade-shaped instrument into the soil. The blade is equipped s ! with an expandable membrane on one side that is pressurized until the membrane moves horizontally into the surrounding soil. Readings of the pressure required to move the membrane to a point that is flush with the blade(A—pressure)and to a point 1.1 mm into the surrounding soil (B—pressure) are recorded. The pressure is subsequently released and, in permeable soils below the groundwater table,a pressure reading is recorded as the membrane returns to the flush position (C — pressure). The test sequence is performed at 0.2-meter intervals to obtain a comprehensive soil profile. A material index (ID), a horizontal stress index(KD)and a dilatometer modulus(ED)are obtained directly from the dilatometer data. Marchetti (1980) developed a soil classification system based on the material index. According to this system, soils with ID values less than 0.35 are classified as clay. Soils classified as sand have an ID value greater than 3.3. Material index values between 0.35—3.3 indicate silty clay to silty sand soils. Empirical relationships between the horizontal stress index and the coefficient of lateral earth pressure (K,) have been developed by Lunne et al. (1990) for clays and by Schmertmann (1983) for uncemented sands. While Lunne's method makes use of dilatometer data exclusively,Schmertmann utilizes both DMT and cone penetration data to estimate K . Since the DMT is strain-controlled, the measured difference between the B-pressure and A- pressure readings (corrected for membrane stiffness) and cavity expansion theory, can be used to directly measure the soil stiffness. Assuming a Poisson's ratio, the dilatometer modulus is correlated to shear modulus,Young's modulus,and constrained modulus. Four dilatometer soundings completed at this site were advanced to depths ranging from 17 to 33 feet below the ground surface, where refusal was encountered. A member of Geocon Northwest's engineering staff recorded pressure readings every eight inches along the length of the sounding. 4.1.2. Borings Four borings were advanced to a depth of 31.5 feet bgs using a CME-75 track mounted drill rig equipped with mud rotary drilling capabilities. A member of Geocon Northwest's P1475-05-01 -3- February 16,2007 • geotechnical engineering staff logged the subsurface conditions encountered within the boring. Standard penetration tests (SPT) were performed in the boring by driving a 2-inch outside diameter split spoon sampler 18 inches into the bottom of the boring, in general accordance with ASTM D I586. The number of blows required to drive the sampler the last 12 of the 18 inches(blow count)are reported on the boring log located in Appendix A at the end of this report. Disturbed bag samples were obtained from SPT testing. Service providers • subcontracted by Geocon Northwest completed the borings. • 4.2 Subsurface Conditions The subsurface exploration is assumed to be representative of the subsurface conditions across the site; however, it is possible that some local variations and possible unanticipated subsurface conditions exist. Based on the conditions observed during the reconnaissance and field exploration, the subsurface conditions, in general,consisted of the following: ORGANIC TOPSOIL—An initial layer of approximately 12 to 24 inches of organic topsoil was present across the majority of the site. The topsoil will require stripping in all planned structural and pavement areas. Unsuitable organic soil may locally extend to depths exceeding 2 feet,particularly where existing trees or large shrubs will be removed. Perched water was encountered across the entire site within the organic topsoil layer at a depth less than 12 inches. CLAYEY SILT TO SILTY CLAY—Medium stiff,wet,dark brown/dark gray/rust,mottled clayey silt to silty clay was encountered below the organic topsoil to depths ranging from 5 to 10-feet bgs. The mottling is an indicator of periodic saturation due to perched or shallow groundwater. Moisture contents of this deposit were in excess of 30 percent and will require substantial drying operations to achieve the optimum moisture content for compaction which is expected to range from 15 to 20 percent. SILT — In general, soft to stiff, saturated, brown/gray, silt with varying amounts of fine- grained sand and clay were encountered below the clayey silt to silty clay to depths ranging from 23 to 30-feet bgs. The soil consistency was soft in borings B-1 (12 to 24-feet bgs)and B-2 (15 to 23-feet bgs) with a standard penetration test blowcount value (N-value) of 2. Atterberg limits tests completed on samples retrieved from this layer had liquid limit values ranging from 28 to 30 and plasticity index ranging from 1 to 3 which characterizes the soil as having very low plasticity. SILTY CLAY — Beneath the silt in borings B-2 and B-4, a layer of very stiff, saturated, gray/light green, silty clay with seams of completely weathered gravel was encountered between 23 and 31.5-feet bgs.Blowcount values ranged from 16 to 20. CEMENTED SILT—A hard,moist,light brown cemented fine-grained sandy silt formation was encountered in borings B-1,B-2,and B-3 at the terminal depth of 30 to 31.5-feet bgs. P1475-05-01 -4- February 16,2007 GROUNDWATER—Saturated conditions due to either perched or static groundwater were observed at depths of 6 to 12 inches bgs. Perched or shallow groundwater should be anticipated during the majority of the year, particularly during periods of prolonged wet weather. • 5 SEISMIC HAZARDS 5.1 Landslide Hazard Due to the gently rolling topography across the site,the landslide hazard is considered negligible. A discussion regarding potential slope/wall instability at the east perimeter of the site during grading is presented in subsequent sections of this report. 5.2 Crustal Faults Based on the literature review,there are no identified faults mapped within the boundaries of the site or within adjacent properties.Evidence was not encountered during the field investigation to suggest the presence of faults within the property. The potential for fault displacement and associated ground subsidence at the site is considered remote. 5.3 Soil Liquefaction or Cyclic Failure Potential Liquefaction can cause aerial and differential settlement, lateral spreading, loss of bearing capacity, and sudden loss in soil strength. Soils prone to liquefaction are typically loose, saturated sands and, to a lesser degree, silt. Cyclic failure can result in similar hazards to those of liquefaction, but is a phenomena related to low-strength, fine-grained silt and clay soils. When ground shaking commences, the low-strength saturated soils tend to generate excess pore water pressures. The degree of excess pore water pressure generation is largely a function of the magnitude and duration of the ground shaking,as well as the density or consistency of the soil. The sandy soils at the subject site were evaluated for liquefaction potential in accordance with the procedures presented in NCEER, 1997,while the cyclic failure potential of the fine grained deposits were assessed using procedures outlined by Boulanger and ldriss, 2004. The liquefaction resistance of the soils was assessed using methods based on the SPT blow counts and grain size distribution data obtained during the geotechnical field and laboratory investigation. The undrained shear strength of the fine-grained deposits were evaluated using the results of the dilatometer soundings. The seismically induced shear stresses at the site were assessed through the use of a standard-of-practice simplified empirical procedure. The analyses were conducted using the 2003 IBC design Ievel earthquakes which consisted of a moment magnitude 6 for the crustal source, moment magnitude 7 for the intraslab zone,and a moment magnitude 8.5 for a subduction zone event. Peak ground surface ( ) acceleration values of 12%, 19%, and 30% gravity (0.12g, 0.19g, and 0.30g) were used for the subduction zone, intraslab zone,and crustal earthquakes,respectively. P1475-05-01 -5- February 16,2007 Based on the results of our analyses,the liquefaction potential at the site is considered remote due to the lack of sand deposits within the subsurface profile.However, an approximate 5-foot layer of soft to medium stiff silt initially encountered throughout the site at depths ranging from approximately 10 to 15 feet had a factor of safety against cyclic failure near 1.0 and may experience softening due to earthquake-induced shear strains. Due to the limited thickness of the soil layer, the effects of this softening on building foundations is anticipated to be minor and will not affect the building's life safety. Settlement of the zone of cyclic softening will occur after earthquake shaking has ceased. According to very preliminary research presented by Boulanger and Idriss, a factor of safety against cyclic failure of 1 corresponds to about 3 percent shear strain. The results of the analysis indicate a maximum settlement of I to 2 inches may occur due to the design level earthquake loading. 5.4 Lateral Spreading Lateral spreading is a liquefaction related seismic hazard that may adversely impact some sites. Areas subject to lateral spreading are underlain by liquefiable sediments and are sites that slope or are • flat sites adjacent to an open face. Due to the gently sloping topography and lack of open face adjacent to the site, the potential lateral spreading hazard is considered negligible. Furthermore, it is our opinion that potential lateral movements due to cyclic softening of the fine-grained deposits will be substantially less than the magnitude of the vertical strain potential that was discussed in the previous paragraph. 5.5 2003 International Building Code Seismic Design Parameters The structures will be designed in accordance with the 2003 International Building Code (IBC). A soil characteristic called "Soil Profile Type" is used to account for the effect of the underlying soil conditions on bedrock motion. Based on the subsurface conditions encountered during the field investigation, Geocon Northwest's previous geotechnical engineering work in the site vicinity, and the geological literature reviewed for the site, it is estimated that the material in the upper 100 feet, determined in accordance with the procedures outlined in IBC Section 1615 "Site Categorization Procedure", has an average blowcount (N) value between 15 and 50 and an average shear wave velocity between 600 and 1200 feet per second. The preceding criteria characterizes the site as Soil Profile Type D. It is recommended that the 2003 International Building Code seismic factors and coefficients given in Table 1 at the end of this report be used for seismic design. Figure 3, shown at the end of this report,illustrates the design response spectrum. 6 LABORATORY TESTING Laboratory testing was performed on selected soil samples to evaluate moisture content, gradation, consolidation characteristics,and plasticity. Visual soil classification was performed both in the field and laboratory, in general accordance with the Unified Soil Classification System. Moisture content determinations (ASTM D2216) were performed on soil samples to aid in classifying the soil. Grain size analyses were performed on selected samples using procedures ASTM D1140 and ASTM D422. • The plasticity index was determined in general accordance with ASTM D4318. Consolidation testing was completed in general accordance with ASTM D2435. Moisture contents are indicated on the P1475-05-01 -6- February 16,2007 boring logs and are located in Appendix A of this report. Other laboratory test results for this project are summarized in Appendix B. 7 CONCLUSIONS AND RECOMMENDATIONS 7.1 General 7.1.1 It is our opinion that the proposed construction of the Red Rock Creek Tigard Business Center project is geotechnically feasible, provided the recommendations of this report are followed. 7.1.2 The primary geotechnical concern associated with the project development is the consolidation of the moderately compressible soils when subjected to the planned fill surcharge. Settlement analyses were completed for the fills anticipated for each of the three structures. The results indicate settlements of 1 to 2 inches within building A, 2 to 4 inches within building B, and 0.5 to 1-inch within building C. Monitoring of the settlement in fill locations is recommended to determine when the majority of primary consolidation has occurred prior to the construction of the buildings. Analyses and experience with similar soils indicate that surcharge-induced settlement should be near complete after approximately 90 to 150 days. 7.1.3 The placement of structural fill should completed in staged intervals to prevent a bearing capacity failure of the low-strength fine-grained soil below the site. Recommendations for • fill construction are provided in Section 7.4.4. 7.1.4 Red Rock Creek will be diverted to an underground culvert as part of the overall site development. Due to the City of Tigard building setback criteria,the north wall of Building A and the northwest corner of Building B may be positioned over the culvert. The building may not be supported on a shallow foundation that is positioned above or near the underground culvert. A discussion of potential foundation support in these locations is contained herein. 7.1.5 Retaining walls and shoring will be required around the majority of the property,the types of which have not yet been finalized. The retaining structures along the north, south, and west perimeters will retain structural fill soils and, potentially be subject to surcharging from building foundations. Retaining walls in these locations may consist of a mechanically stabilized earth (MSE) wall, or a cast in place concrete retaining wall. An excavation is planned adjacent to the proposed SW 70th Avenue alignment. It is our opinion that the shoring structure must provide active restraint during excavation to prevent instability issues with the large block retaining wall on the east property margin. A shoring wall with soldier piles and pretensioned tie-back elements is recommended. 7.1.6 The existing organic topsoil layer is unsuitable for structural foundation or pavement support. Recommendations for site stripping and fill removal in structural locations are provided herein. Stripping depths exceeding 12 inches are likely. P1475-05-01 -7- February 16,2007 7.1.7 Recommendations regarding drainage and vapor retarders are provided in subsequent sections of this report. Perched water was present at a depth of less than 12 inches at the time of the field investigation. Recommendations for underslab drainage in building pads located at or below the existing ground surface are provided. Underslab drainage is not recommended in locations where the building pad is founded on structural fill above the existing ground surface elevation. 7.1.8 Instability of excavations below the groundwater surface should be anticipated. Excavations made below the groundwater surface should be sloped or shored in conformance with OSHA regulations. Shoring systems are typically contractor designed. 7.1.9 Wet weather construction techniques should be anticipated during the majority of the year due to the presence of the moisture sensitive, near-surface soils. Recommendations for wet weather construction are provided in subsequent sections of this report. It is recommended that the project budget include costs for wet weather site preparation, regardless of the time of year construction is scheduled to occur. Extra costs associated with wet weather construction may include overexcavation of soft soils, geotextile separator fabric, crushed rock backfill,and use of crushed rock for structural fills. 7.2 Site Preparation 7.2.1 Prior to beginning construction, the areas of the site to receive fill, footings or pavement should be stripped of vegetation, topsoil, non-engineered fill, previous subsurface improvements, debris, and otherwise unsuitable material, down to firm native soil. The majority of the site is anticipated to be underlain by at least 12 inches of organic topsoil which will require stripping prior to construction. Additional removal and recompaction/replacement should be anticipated within the areas currently occupied by large trees to provide a stable subgrade. Excavations made to remove previous subsurface improvements should be backfilled with structural fill per Section 7.4 of this report. 7.2.2 Staging areas and haul roads specifically constructed to accommodate anticipated construction loading must be installed by the contractor to minimize future overexcavation of deteriorated subgrade soil. All concrete slab-on-grade and pavement sections presented in the following sections of this report do not include an allowance for construction traffic.Past experience suggests that 18 inches of rock underlain by a geotextile separator fabric typically provides adequate work pad/haul road thickness. The recommended design sections may be "overbuilt"to obtain the necessary working thickness and subsequently reduced to the design section for possible cost savings in lieu of overexcavation of suitable subgrade soil. Alternatively, the working surface may be incorporated into the final design. Recommendations for.wet weather haul roads and working pads should be implemented in areas of the site that will experience significant construction traffic. t 7.2.3 Moisture contents of near-surface soils were significantly wet of optimum at the time of the field investigation. Due to the moisture sensitive nature of the near-surface soils, it is recommended that earthwork-related construction take place during dry weather. Feb 16,2007 P1475-05-0I -8- m�T , • I _ Recommendations for both dry weather and wet weather site preparation are provided in the following sections. Wet weather is defined as any time of year that adequate moisture control cannot be obtained. Increased costs, associated with subgrade stabilization, • should be anticipated regardless of the time of year of construction. 7.2.4 Dry Weather Construction Native soil subgrades in pavement and structural areas that have been disturbed during stripping, cutting, or demolition operations should be scarified to a depth of at least eight- inches. The scarified soil should be moisture conditioned as necessary to achieve the proper moisture content,then compacted to at least 92%of the maximum dry density as determined by ASTM D 1557. Minimum compaction for the 8 inches immediately underlying pavement sections should be 95%. Even during dry weather it is likely that most areas of the subgrade will become soft or may"pump,"particularly in poorly drained areas. Soft or wet areas that cannot be effectively dried and compacted should be prepared in accordance with Section 7.2.5. 7.2.5 Wet Weather Construction During wet weather, defined as whenever adequate soil moisture control is not possible, it may be necessary to install a granular working blanket to support construction equipment and provide a firm base on which to place subsequent fills and pavements. Commonly, the working blanket consists of a bank run gravel or pit run quarry rock (six to eight inch maximum size with no more than 5% by weight passing a No. 200 sieve). A member of Geocon Northwest's engineering staff should be contacted to evaluate the suitability of the material before installation. The working blanket should be installed on a stripped subgrade in a single lift with trucks end-dumping off an advancing pad of granular fill. It should be possible to strip most of the site with careful operation of track-mounted equipment. However, during prolonged wet weather, or in particularly wet locations, operation of this type of equipment may cause excessive subgrade disturbance. In some areas fmal stripping and/or cutting may need to be accomplished with a smooth-bucket trackhoe, or similar equipment, working from an advancing pad of granular fill. After installation, the working blanket should be compacted by a minimum of four complete passes with a moderately heavy static steel drum or grid roller. It is recommended that Geocon Northwest be retained to observe granular working blanket installation and compaction. The working blanket must provide a firm base for subsequent fill installation and compaction. Past experience indicates that about 18 inches of working pad is normally required. This assumes that the material is placed on a relatively undisturbed subgrade prepared in accordance,with the preceding recommendations. Areas used as haul routes for heavy construction equipment or construction staging areas may require a work pad thickness of two feet or more. P1475-05-01 -9- February 16,2007 In particularly soft areas, a heavy-grade, non-degradable geotextile fabric installed on the subgrade may reduce the thickness of working blanket required. The fabric should have a minimum puncture resistance of 80 pounds and a minimum Mullen Burst strength of 300 psi. Construction practices can affect the amount of work pad necessary. By using tracked equipment and special haul roads,the work pad area can be minimized. The routing of dump trucks and rubber tired construction equipment across the site can require extensive areas and thicknesses of work pad. Normally, the design, installation and maintenance of a work pad are the responsibility of the contractor. Cement treatment may be a suitable alternative for construction traffic or wet-weather subgrade stabilization at this site. Successful cement treatment is dependent upon moisture content of the subgrade soils,cement percentage,weather conditions at the time of treatment, depth of treatment, and adequate mixing and compaction of the soil and cement. Past experience indicates that approximately 5%to 8%cement by weight,tilled to a depth of 12 to 14 inches, is typically sufficient to produce an acceptable subgrade. It is generally recommended that cement amended soil be compacted within a four-hour window. It is recommended that cement treated soils have a three-day,unconfined compressive strength of 250 psi. Cement treatment design is typically the responsibility of the contractor. The high soil moisture content may require multiple cement treatment operations. 7.3 Proof Rolling 7.3.1 Regardless of which method of subgrade preparation is used (i.e., wet weather or dry weather), it is recommended that, prior to on-grade slab construction, the subgrade or granular working blanket be proof-roIled with a fully-loaded 10- to 12-yard dump truck. Areas of the subgrade that pump, weave, or appear soft or muddy should be scarified, dried and compacted, or overexcavated and backfilled with structural granular fill per Section 7.4. If a significant length of time passes between fill placement and commencement of construction operations,or if significant traffic has been routed over these areas,the subgrade should be similarly proof-rolled before slab construction. It is recommended that a member of our geotechnical engineering staff observe the proof-roll operation. 7.4 Fills 7.4.1 Structural fills should be constructed on a subgrade that has been prepared in accordance with the recommendations in Section 7.2 of this report. Structural fills should be installed in horizontal lifts not exceeding approximately eight inches in thickness and should be compacted to at least 92%of the maximum dry density for the native soils,95%for imported granular material, and should be within 2% of the optimum moisture content. Compaction l ) should be referenced to ASTM D1557 (Modified Proctor). The compaction criteria may be reduced to 85%in landscape,planter,or other non-structural areas. P1475-05-01 -10- February 16,2007 7.4.2 During dry weather when moisture control is possible, structural fills may consist of native material, free of topsoil, debris and organic matter,which can be compacted to the preceding specifications. However, if excess moisture causes the fill to pump or weave, those areas should be scarified and allowed to dry. The soil should then be recompacted,or removed and backfilled with compacted granular fill as discussed in Section 7.2 of this report. Past experience suggests that the native soil has a maximum dry density ranging from 110 to 115 lbs/ft 3 at an optimum moisture content between 15 and 20 percent. Moisture contents of the near surface native soil were typically greater than 30 percent at the time of the field investigation. Extensive drying of the native soil will be required if used as structural fill during construction. 7.4.3 During wet-weather grading operations, Geocon Northwest recommends that fills consist of well-graded, angular, granular soils (sand or sand and gravel) that do not contain more than 5%material by weight passing the No. 200 sieve. In addition, it is usually desirable to limit this material to a maximum of six inches in diameter for future ease in the installation of utilities. 7.4.4 The site is underlain by relatively low-strength, moderately compressible soil. Current grading plans indicate the fills up to 15 feet high will be placed along the west margin of building B. The depth of fill decreases to the east with the excavation/fill transition zone extending north/south through proposed buildings A and C. The fill placement will create excess pore water pressure and,in turn,decreased strength in the underlying soil. To prevent — a failure of the soil during fill construction, it is recommended that piezometers and settlement cells be installed prior to the commencement of grading operations. The piezometers will used to monitor excess porewater pressure and settlement cells to evaluate both total and time-rate of consolidation. It our opinion that both monitoring devices are essential for successful fill construction and to mitigate the potential for a bearing capacity failure. 7.4.5 Preliminary analyses indicate that a maximum of 8 feet of fill may initially be placed without a bearing failure. Settlement and pore pressure measurements should be evaluated to determine when approximately 80 percent of consolidation has occurred prior to additional fill placement. 7.4.6 Settlement analyses were completed for the fills planned for each of the three structures. The results indicate settlements of 1 to 2 inches within building A,2 to 4 inches within building B, and 0.5 to 1-inch within building C. Monitoring of the settlement in fill locations is recommended to ensure the majority of primary consolidation has occurred prior to the construction of the buildings. 7.4.7 The results of our engineering analyses indicate that the structural fill-induced settlement should be near completion after approximately 90 to 150 days. Our experience with previous surcharges in the Willamette Valley has shown that evaluating the time rate of surcharge settlement from laboratory testing is extremely difficult. This difficulty arises from the small dimension and uniformity of laboratory test samples compared to the larger dimensions and P1475-05-01 -11 - February 16,2007 non-uniformity of native soil(particularly with respect to drainage conditions). The time rate of surcharge settlement may be modified as settlement and piezometer data is interpreted during construction. 7.4.8 The time rate of settlement may be accelerated using wick (strip) drains if the construction schedule does not allow for the settlement time estimate. Wick drains are typically spaced 7 to 10 feet on center and would extend down to a depth of approximately 30 feet. The wick drains provide a shorter drainage path and significantly increases the time rate of settlement. It is estimated that the installation of wick drains would reduce the time rate of settlement at the site by 50%to 75%. 7.5 Surface and Subsurface Drainage 7.5.1 During site contouring,positive surface drainage should be maintained away from foundation and pavement areas. Additional drainage or dewatering provisions may be necessary if soft spots, springs,or seeps are encountered in subgrades or cut slopes. Where possible, surface runoff should be routed independently to a storm water collection system. Surface water should not be allowed to enter subsurface drainage systems. 7.5.2 Due to the proximity of groundwater to the surface, an underslab drainage system is recommended for those locations where slab-on-grade subgrade elevations will be at or below the existing surface elevation. An underslab drainage system is not recommended in fill locations where slab on grade elevations will be greater than existing grade. It is typically recommended that the underslab drainage system consist of 4-inch diameter PVC perforated pipe placed within granular fill at 15-foot centers beneath the building footprint. The granular fill should consist of a minimum 8-inch thick layer of crushed rock or gravel with less than 5%by weight passing the No. 200 sieve. The PVC pipe should be wrapped with a geotextile filter fabric. Figure 4 presents a cross-section of the underslab drainage system. Final design of the underslab drainage system should be completed by the project civil engineer,with consultation from Geocon Northwest. 7.5.3 Drainage systems should be sloped to drain by gravity to a storm sewer or other positive • outlet. 7.5.4 Drainage and dewatering systems are typically designed and constructed by the contractor. Failure to install necessary subsurface drainage provisions may result in premature foundation or pavement failure. 7.6 Foundations 7.6.1 Spread and perimeter foundation support for proposed structures may be obtained from the near-surface, non-organic native soil, or from structural fill installed in accordance with our previous recommendations. If unsuitable fill soils,or soft, saturated soil are encountered at 1. footing elevation, the unsuitable soils should be removed to firm soil. If these unforeseen conditions are encountered, a member of Geocon Northwest's engineering staff should be contacted to evaluate the suitability of the material before installation. Overexcavation P1475-05-01 -12- February 16,2007 should be expected in cut locations across the site due to the potential for perched water near the existing ground surface. 7.6.2 Red Rock Creek will be diverted to an underground culvert as part of the overall site development. Due to the City of Tigard building setback criteria,the north wall of Building A and the northwest corner of Building B will likely be positioned over the culvert. The building may not be supported on a shallow foundation that is located within a horizontal distance equal to the depth of the pipe(1H:IV). Potential deep foundation schemes that may be feasible would include helical anchors, augercast piles,driven pipe, or driven H-piles. A deep foundation using an open-hole installation system is not preferred given the presence of near surface saturated soil and the potential for caving or"necking"of the borehole. Geocon Northwest should be contacted for deep foundation design recommendations as the building layout and project plans are finalized. 7.6.3 The following shallow foundation recommendations are based on maximum anticipated column and wall loads of 150 kips and 4 kips/foot, respectively. Furthermore, it was assumed that site grading will be limited to maximum cuts of 5 feet. Geocon Northwest should be consulted for potential modifications to the following recommendations if either of these assumptions are not correct. 7.6.4 Spread and perimeter footings should be at least 18 inches wide and should extend at least 18 inches below the lowest adjacent pad grade. Foundations having these minimum dimensions that are founded on firm soils or engineered fill may be designed for an allowable soil bearing pressure of 2,000 pounds per square foot(psf). If unsuitable soils are encountered at footing elevation,the unsuitable soils should be overexcavated and replaced with compacted structural fill per the recommendation of Geocon Northwest during construction. 7.6.5 A minimum of 12 inches of compacted crushed rock should be placed beneath footings located in cut locations of buildings A and C due to the presence of near surface soft, saturated soil. Deeper rock sections may be locally required. 7.6.6 Foundation subgrades that are anticipated to be exposed to inclement weather prior to concrete placement should be protected to guard against future over-excavation of unsuitable soil. 7.6.7 Gravel or lean concrete may need to be placed in the bottom of the footing excavations to reduce soil disturbance during foundation forming and construction during wet weather. 7.6.8 The allowable bearing pressure given above may be increased by one-third for short term transient loading,such as wind and seismic forces. 7.6.9 Lateral loads may be resisted by sliding friction and passive pressures. A base friction of 40% of the vertical load may be used against sliding. An equivalent fluid weight of 300 pcf may be used to evaluate passive resistance to lateral loads. 7.6.10 Foundation settlements for the loading conditions expected for this project are estimated to be less than one inch, with not more than one-half inch occurring as differential settlement. P1475-05-01 -13- February 16,2007 These values assume that site cuts will be less than 5 feet. This settlement is only attributed to the aforementioned building loads and does not include the estimated settlement that will occur below planned structural fills. It is recommended that building construction commence once primary consolidation has been complete due to the structural fill placement. 7.6.11 Geocon Northwest, Inc. recommends that foundation drains be installed at or below the elevation of perimeter footings to intercept potential subsurface water that may migrate under { the building area. 7.7 Permanent Cut and Fill Slopes 7.7.1 New permanent cut slopes should be sloped no steeper than 2H:1 V. These values assume that the slopes will be protected from erosion and that significant drainage will not occur over the face of the slope. They further assume that no loads will be imposed within a horizontal distance of one-half of the slope height measured from the top of the slope face. Cut slopes should be constructed with a smooth bucket excavator to minimize subgrade disturbance. Slope drainage may be required if springs, seeps,or groundwater are encountered. 7.7.2 Excavation should not be completed in the vicinity of the block retaining wall at the east perimeter of the property without the employment of an active shoring system as described in Section 7.9. 7.7.3 If permanent fills are placed in areas where ground slopes exceed 5H:1 V,the fills should be keyed and benched into existing native, undisturbed non-organic soil. Fill slopes should be obtained by placing and compacting material beyond the design slope and then excavating back to the desired grade or by other means that will result in a dense,compacted sloped face. Filled slopes should not be graded steeper than 2H:1 V. The face of the fill slope should be protected from erosion by applying vegetation or other approved erosion control material as soon as practicable after construction. Fill compaction should be as stated in Section 7.4. If slopes higher than ten feet above the original grade are proposed,Geocon Northwest should be contacted to evaluate slope stability conditions. 7.8 Concrete Slabs-on-Grade 7.8.1 Subgrades in floor slab areas should be prepared in accordance with Section 7.2 of this report. Floor slab areas should be proof-rolled with a fully loaded 10-to 12-yard dump truck to detect areas that pump,weave,or appear soft or muddy. When detected these areas should be overexcavated and stabilized with compacted granular fill. 7.8.2 A minimum six-inch thick layer of compacted 3/4-inch minus material should be installed over the prepared subgrade to provide a capillary barrier and to minimize subgrade disturbance during construction. The crushed rock or gravel material should be poorly graded, angular, and contain no more than 5%by weight passing the No.200 Sieve. The thickness of crushed rock should be increased to 12 inches in cut locations where slab on grade subgrade elevation will be less than existing grade. The underslab drainage system is only recommended in P1475-05-01 -14- February 16,2007 planned cut locations where finished subgrade elevation will be at or lower than existing grade. 7.8.3 A subsurface drainage system is recommended due to the potential for shallow groundwater during the winter months. It is recommended that the underslab drainage system consist of 4-inch diameter PVC perforated pipe placed within granular fill at 15-foot centers beneath the building footprint. The granular fill should consist of a minimum 8-inch thick layer of crushed rock or gravel with less than 5%by weight passing the No.200 sieve. The thickness of granular fill is in addition to the 12 inches recommended in Section 7.8.2 The PVC pipe should be wrapped with a geotextile filter fabric. Figure 4 presents a cross-section of the underslab drainage system. 7.8.4 A modulus of subgrade reaction of 125 pci is recommended for design. 7.8.5 The fine-grained near-surface soils at the site have high natural moisture contents and low permeability. These characteristics indicate that high ground moisture may develop under floor slabs during the life of the project. This moisture condition, coupled with differential temperatures and humidity between the subgrade soils and the building interior,can create a differential in vapor pressure between the above- and below-slab environments. The resulting water vapor pressure differential will force migration of moisture through the slab. This migration can result in the loosening of flooring materials attached with mastic, the warping of wood flooring,and in extreme cases,mildewing of carpets and building contents. To retard the migration of moisture through the floor slab, Geocon Northwest recommends installing a 10-mil polyethylene vapor retarding membrane below the concrete slab. Care should be exercised to ensure that any moisture accumulation on the vapor retarder surface, from either construction activities or precipitation, should be removed prior to the concrete pour. A concrete mix of low water/cement ratio (i.e. less than 0.48) is recommended. • Thorough curing of the concrete,using water when possible,should be provided. 7.9 Retaining Walls and Shoring 7.9.1 The information presented in the following section is a general discussion of retaining walls and shoring that may be utilized at the site. Geocon Northwest should be contacted for specific design recommendations as project plans are finalized and the following discussion may be modified accordingly. 7.9.2 Retaining wall support in locations of the site that will be filled above existing grade will likely be accomplished using a mechanically stabilized earth (MSE) retaining wall or, less likely, a cast-in-place concrete cantilever retaining wall. The latter is not as likely due to expected height of the retaining structure, lateral soil pressure to resist, fill soil settlement, and potential surcharge from the new buildings. Several MSE wall-types are possible, the majority of which are designed as a proprietary system. The MSE wall construction may be (' ) complicated by the interference of geogrid reinforcing with underground footings and utilities for the buildings. The construction of the walls will need to be in accordance with the recommendations provided in Section 7.4 to prevent a bearing capacity failure. Additional P1475-05-01 - 15- February 16,2007 t rock may need to be placed below retaining wall footings for subgrade stabilization. Geocon Northwest should be contacted to provide consultation for retaining structures as project plans become finalized. 7.9.3 Shoring support of the proposed cut along the east property margin should be accomplished using a soldier pile and tieback system. This system provides active restraint to limit wall movements, due to the tensioning of tiebacks prior to excavating below the current tieback level. Limiting wall movements and limiting the removal of soil buttressing the existing block retaining wall at the east property margin is critical in maintaining the stability of this wall. Soil nail excavation support is a system that consists of installing steel bars into the retained soil to provide an in-place"retaining wall"that resists the lateral soil pressures. A soil nail structure is a passive excavation support system as no tensioning of the steel bars(soil nails) is typically performed before excavating to the next level. The soil nail system develops resistance due to excavation-induced soil movements which mobilize soil-structure interaction within the soil nail mass. It is our opinion that a soil nail wall would not provide the degree of stability and restraint as that of a soldier pile and tieback system and may compromise the stability of the existing block retaining wall. 7.10 Utility Excavations 7.10.1 Based on the subsurface explorations,difficult excavation characteristics are not anticipated within the upper fine-grained soils. Perched groundwater was encountered less than 12 inches below the existing ground surface and may created trench instability issues. Utility trench bottoms will likely require stabilization with rock and geotextile fabric. 7.10.2 Excavations deeper than four feet, or those that encounter groundwater, should be sloped or shored in conformance with OSHA regulations. Shoring systems are typically contractor designed. Caving of trench sidewalls should be anticipated below the groundwater surface. 7.10.3 It is likely that perched groundwater will be encountered in the near surface soil during periods of wet-weather. Therefore, excavation dewatering may be necessary if substantial flow of groundwater is encountered. Dewatering systems are typically designed and installed by the contractor. 7.10.4 Utilities should be bedded in sand within one conduit diameter in all directions,prior to the placement of coarser backfill. Trench backfill should be lightly compacted within two diameters or 18 inches, whichever is greater, above breakable conduits. The remaining backfill,to within 12 inches of finished grade, should be compacted to 92%of the maximum dry density as determined by ASTM D1557. In structural areas, the upper foot of backfill should be compacted to 95%of the maximum dry density. The moisture content at the time of compaction should be within 2%of optimum. P1475-05-01 -16- February 16,2007 7.11 Pavement Design 7.11.1 Near surface soil samples were evaluated to determine pavement design parameters. A CBR of 3 at 95% compaction and a resilient modulus of 4,500 psi were assumed for pavement design. 7.11.2 If possible, construction traffic should be limited to unpaved and untreated roadways, or • specially constructed haul roads. If this is not possible, the pavement design should include an allowance for construction traffic. Construction staging areas and haul roads specially designed to accommodate anticipated construction loading must be installed by the contractor to minimize future overexcavation of deteriorated subgrade soil. Past experience suggests 18 inches of rock underlain by a geotextile separator fabric typically provides adequate work pad/haul road thickness. The recommended sections may be "overbuilt" to obtain the necessary working thickness and subsequently reduced to the design section for possible cost savings in lieu of overexcavation of suitable subgrade soil. Alternatively, the working surface maybe incorporated into the final design. 7.11.3 Alternate pavement designs for both asphalt and portland cement concrete(pcc)are presented in Tables 2 and 3. Pavement designs have been prepared in accordance with accepted AASHTO design methods. A range of pavement designs for various traffic conditions is provided in the tables. The designs assume that the top eight inches of pavement subgrade will be compacted to 92% of ASTM D-1557. Specifications for pavement and base course should conform to current Oregon State Department of Transportation specifications. Additionally, the base rock should contain no more than 5% by weight passing.a No. 200 Sieve, and the asphaltic concrete should be compacted to a minimum of 91% of ASTM D2041.A geotextile fabric should be placed below the base rock. 7.11.4 Pavement sections were designed using AASHTO design methods, with an assumed reliability level(R)of 90%. Terminal serviceability of 2.0 for asphaltic concrete,and 2.5 for portland cement concrete were assumed. The 18 kip design axle loads are estimated from the number of trucks per day using State of Oregon typical axle distributions for truck traffic and AASHTO load equivalency factors, and assuming a 20 year design life. The concrete designs were based on a modulus of rupture equal to 550 psi, and a compressive strength of 4000 psi. The concrete sections assume plain jointed or jointed reinforced sections with no load transfer devices at the shoulder. 8 FUTURE GEOTECHNICAL SERVICES The analyses, conclusions and recommendations contained in this report are based on site conditions as they presently exist, and on the assumption that the subsurface investigation locations are representative of the subsurface conditions throughout the site. It is the nature of geotechnical work for soil conditions to vary from the conditions encountered during a normally acceptable geotechnical investigation. While some variations may appear slight, their impact on the performance of the proposed improvements can be significant. Therefore, it is recommended that Geocon Northwest be retained to observe portions of this project relating to geotechnical engineering, including site P1475-05-01 -17- February 16,2007 preparation, grading, and compaction. This will allow correlation of observations and findings to actual soil conditions encountered during construction and evaluation of construction conformance to • the recommendations put forth in this report. A copy of the plans and specifications should be forwarded to Geocon Northwest so that they may be evaluated for specific conceptual, design, or construction details that may affect the validity of the recommendations of this report. The review of the plans and specifications will also provide the opportunity for Geocon Northwest to evaluate whether the recommendations of this report have been appropriately interpreted. 9 LIMITATIONS Unanticipated soil conditions are commonly encountered during construction and cannot always be determined by a normally acceptable subsurface exploration program. The recommendations of this report pertain only to the site investigated and are based upon the assumption that the soil conditions do not deviate from those disclosed in the investigation. If variations or undesirable conditions are encountered during construction, or if the proposed construction will differ from that anticipated herein, Geocon Northwest, Inc. should be notified so that supplemental recommendations can be given. This report is issued with the understanding that the owner, or his agents, will ensure that the information and recommendations contained herein are brought to the attention of the architect and engineer for the project and incorporated into the plans. The findings of this report are valid as of the present date. However, changes in the conditions of a property can occur with the passage of time,whether they are due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appropriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Therefore, the conclusions and recommendations provided in this letter are subject to review should such changes occur. If you have any questions regarding the information herewith, or if you desire further information, please contact the undersigned at(503)626-9889. GEOCON NORTHWEST,INC. it, . AV/----- If'::\ i 6--1- - ."-/ ___ Bryan Wavra,P.E. Wesle pang, .D.,P.E. Project Engineer President P1475-05-01 -18- February 16,2007 REFERENCES Boulanger,R.W.,and Idriss,I.M.,2004, "Evaluating the Potential for Liquefaction or Cyclic Failure of Silts and Clays," Report No. UCD/CGM-04/01, Center for Geotechnical Modeling, Department of Civil & Environmental Engineering College of Engineering University of California at Davis. Ishihara, K., 1985, "Stability of Natural Deposits During Earthquakes", Proceedings, 11th International Conference on Soil Mechanics and Foundation Engineering,Vol. 1, pp. 321- 376. National Center For Earthquake Engineering Research, 1997,"Proceedings of the NCEER Workshop on Evaluation of Liquefaction Resistance of Soils,"Technical Report NCEER 97-0022. Seed, H.B., and Idriss, I.M., 1982 Ground Motions and Soil Liquefaction During Earthquakes, Earthquake Engineering Research Institute Table 1: 2003 IBC Seismic Design Recommendations Seismic Variable Recommended Value Site Class D MCE short period spectral response 1.14 accel.,SMS MCE 1-second period spectral 0.61 response accel.,SMl 5%damped short period spectral 0.76 response accel.,SDs 5%damped 1-second period 0.41 spectral response accel., SD1 Table 2: Asphalt Concrete Pavement Design Approximate Approximate Number of Trucks Number of 18 Sip Asphalt Concrete Crushed Rock Base per Day Design Axle Load Thickness(inches) Thickness(inches) (each way) (1000) Auto Parking 10 2.5 8 5 22 3.0 8 10 44 3.0 10 15 66 3.5 10 25 110 4.0 10 50 220 4.0 12 100 440 4.5 12 150 660 5.0 13 Table 3:Portland Cement Concrete Pavement Design Approximate Approximate Number of Trucks Number of 18 Kip P.C.C. Crushed Rock Base per Day Design Axle Load Thickness(inches) Thickness(inches) (each way) (1000) 25 110 6.0 6 50 220 7.0 6 100 440 8.0 6 150 660 8.5 6 200 880 8.5 6 250 1100 9.0 6 (.) • 1 _ 9'0451' sr f sY BIRCH yr = .. s N ' �' �I , ®T I'S z A F 'RY i5_-RD •,Th!g BiRLH N 4 p, i SV EYEEY @ 1, Sp / y 2 1?'�.r Z;"x o`RINGSnM< +w 4n&m E s Y a ¢ ` R • �_ S �Sh,a cu,,.... 'VW +9i CLnARCRE5 1' 1< ST. ..1 - gsa t.;kAt>,rt ySW HUBS• ST u a• aui: sr r. Bq y`C sw 7 ,, . , ,. v wDC PPS c -- . a• , . ET ST I;;•S A coEA71 !ALFRED tc g 'l SN RfD MIUI n '`...'i 6z0C 2• fi Q swa� aaa3e•,�,BC[i0 < E „➢7of ,� tea' ' �� >� � sw-, ss�{�'M � ,v s3oo� i + i.,-.••„i 9100 �5 BBt)0 S7 a -w „..',+:1.1-,, J�s: S� /F' .cr✓ //(11 T Ir.a ISN LE WH ST ) Sw ST �r r 4 g! \4 '�'r 0 ! c 920Qy.;c dfak '�`` f'�'' °d'. a '¢ 1 9� r i . `f �!,' ~ - j�g'.'� R'' //��+{I^ V, Sw LAR[H 1 ..3 !.T r Y.• t .0 < M �”rSii CORAL ST 'V i SW LANDAU SM V Y� y 1, s n` ,a 'r 5T =� a E1I�: � _ mh `. 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NO SCALE 1 , GEOCON _ SITE VICINITY N O R T H W E S T MAP RED ROCK CREEK (M GEOTECHNICAL CONSULTANTS TIGARD BUSINESS CENTER 1 --'.' 8283.SW CIRRUS DRIVE BEAVERTON, OREGON 97008! TIGARD,OREGON PHONE: (503) 626-9889 FAX: (503) 626-8611 BJW I RSS I I DSK I DOOOD 1 February 2007 P1475-05-01 i G_ . . fl RED ROCK CREEK-TIGARD BUSINESS CENTER I , . TIGARD, OREGON i 1 i ..._____I ; 4 4y.1. 1..:.; allOy;;:riCs.;.; 41::..M.A".....1.,•,/t7r ;;!..,..4.11;.:4.11.1.0■ ; tc•e;:re•....,10....Volcv.e..‘,1,,e•Qi..,,i,., — --.::4'....WM— , ' ——.... _i....„....,...,., -..-1, ,..--, ..-,...:.4,- - -..o.....1._„.........-_-.1r.-._-_,.........-_,,-.--......_-....,..........-0- 1--7 7,crf S.W. $4 DARTMOUTH SinaT 4 — —I ‘ ' 4 miL... .miiii■temommiiiiir=m 1:.•—_L.;._: ... 0..;:: -,-- . - - vl 1' ,,,,,-4.gowisivaii"..17.77/;.,1,1.nsmt slaw(cr am If.Pe*Mr.18.-4,;23.T4M.W.,a, 2.-I..• . v, . 01 A _ B-3 6 —, 1:-1( .. )1 , , . ...._ , k , :..1.;1 t C.-.3 7 '0 1 1 1 1i 1 ! l ( 1 i 1 1 n 1 I 1 I L A : ------- (',ig.LliI.F 4-fI.l,'.„•-4 ')o':;■I''1 , f• . -- -- ...... _ ___• ,„ ,.... 1 . i -,.i.-------i C ! 1-‘ _... __ .. _ I NO SCALE I = , _\;".- ,_-_-_--- •,! 1 t ,-- • 1 `C -7-- 5i I 1 ill = - -- t ;b: GEOCON LEGEND I is, 1 i 1 1 .7::1.•• A --- ..— Q. PPROX.LOCATION OF BORING I t I 1 , — -.- — * II:. D-4, t APPROX.LOCATION OF DILATOMETER t ti 1 ..... 1 OS I. will -----. I■• :I.: I I I 1 i i I , '-.'s. 7iiiiillr) r 'f--- I._. •_____ __ ,,,,,,v,„.-1.-.1,:nry ig n..71I M.A.CE2n1..?1,1.:7:...,!,..-•-• , I S bi, ELAIHIRSr 81?707 , !A, ,eC_Mrgi;It ozi83Ikge,timmerama. , t.,---,,n , 1.— GEOCON .. ___........._ ____. ........... __, 17H: -'..;, 1 i NOILTEWHST, INC. I i 1 I 1 I I 1 I GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS i i I 8283 SW CIRRUS DRIVE.BEAVERTON,OREGON 97608.5997 PHONE 503 626-9889-FAX 503 626-8611 PROJECT NO.P1475-05-01 SITE PIA" FIGURE 2 IN DATE 2/16/2007 P1476-03-01 JIG2_11W/RS5 1 i J 2003 International Building Code Design Response Spectrum Red Rock Creek 0.9 Tigard Business Center 0.8 0.7 a, ° 0.6 m a, I :: l d 0 3 5%of Critical Damping a Q. N 0.2 - 0.1 0 - 0 0.5 1 1.5 2 2.5 3 3.5 4 Period (s) • Figure 3 i • • o CONCRETE-SLAB.ON GRADE - • " , 6" ° 3/4"-O" CRUSHED.-ROCK a • . Q• • • L <lz a , ' • ° 3/4"-0" CRUSHEDROCK. : T 4�.PVC PIPE . .Q . .4. 4. 4"- PVC PIPE '''. SOIL SUBGRADE NOT TO SCALE UNDERSLAB DRAINAGE SYSTEM RED ROCK CREEK TIGARD BUSINESS CENTER 2116/2007 P1475-05-01 FIGURE 4 4) pqcp EN 0 . W E S T GEOTECHNICAL CONSULTANTS 8270 SW NIMBUS AVENUE-BEAVERTON, OREGON 97008 PHONE 503 626-9889 - FAX 503 626-8611 APPENDIX A FIELD INVESTIGATION The subsurface soil conditions at the site were determined based on the literature review, field exploration,and laboratory investigation. The field exploration was completed on December 29th and 30th, 2006, and consisted of four exploratory borings and four dilatometer soundings. The borings were completed using mud rotary drilling techniques to a depth of 31.5 feet below the existing ground surface(bgs). The dilatometer soundings encountered practical refusal at variable depths that ranged from 17 to 33 feet bgs. The subsurface conditions encountered in the borings and dilatometer soundings were recorded on the subsurface logs that are located in Appendix A at the end of this report. The approximate locations of the explorations are shown in Figure 2,Site Plan. Disturbed bag samples were collected and returned to the laboratory for further testing. A member of Geocon Northwest's geotechnical engineering staff logged the subsurface conditions encountered. Subsurface logs of the conditions encountered are presented in the following pages. Both solid and dashed contact lines indicated on the logs are inferred from soil samples and drilling characteristics and should be considered approximate. i 1 1 I PROJECT NO. P1475-05-01 } w BORING B '[ o�r. w DEPTH SAMPLE _I > SOIL a. Z FEET NO. = Z CLASS ELEV.(MSL.) 240' DATE COMPLETED 12-29 2006 y o a IC-J3 Z J =O (USCS) W ce m d O cc EQUIPMENT CME MUD ROTARY d Q MATERIAL DESCRIPTION 0 lista= Approximately 12 tp 24-inches of organic TOPSOIL - � -Perched water encountered at time of drilling - 2 _ Io�� CLl1v11. Soft,saturated,brown gray,mottled Silty CLAY to Clayey SILT - B1-1 - 2 31.4 4 - 401 — - - B 1-2 IPO� ML Stiff,moist to wet,brown/gray,mottled Clayey SILT with some 10 31.8 - 6 - 1041 fine-grained sand _ g - B1-3 - 9 34.9 I/4/ -Becomes saturated,color includes black rust seams - 10 - - B1-4 5 37.2 - 0 -Medium stiff,saturated,light brownhust,mottled fine-grained sandy - - ' - _ _ silt with some clay _ 12 - ML Soft,saturated,gray,SILT with varying amounts of fine-grained sand - B1-4.5 I and clay SHELBY 37.3 14 - - • - B1-5 I 2 16 - - i 18 - - 20 = B1-6 I _ 2 35.5 22 - - t 24 - - - BI-7 IF � CL/ML Medium still;saturated,gray,Silty CLAY to Clayey SILT - 5 42.7 - 26 = - 28 - 0,, 1/� - _ �� _ 30 - B1-8 I ML Hard,moist,lightbrown,cemented fine-grained Sandy SILT - 54 32.2 , BORING TERMINATED AT 31 i4 FEET Perched water encountered at 6-inches Figure A-1, P7475-05A5.GPJ Log of Boring B 1, Page 1 of 1 1. p SAMPLE SYMBOLS m°•SHELBY TUBE _.• STANDARD PENETRATION TEST II(...DRIVE SAMPLE(UNDISTURBED) `.c j .- ...DISTURBED OR BAG SAMPLE IQ...• CHUNK SAMPLE X...WATER TABLE OR SEEPAGE NOTE: THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. R IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES. GEOCON I , PROJECT NO. P1475-05-01 i } w BORING B 2 g wZZ� Wo - DEPTH 0 Q SOIL Q Z 0- j Z 1 IN SAMPLE F p 2 CLASS FEET NO. J o (USCS> ELEV.(MSL.) _ 241' _ _ DATE COMPLETED 12-29-2006 z x m Q a g O LLI cc EQUIPMENT CME MUD ROTARY o g MATERIAL DESCRIPTION I - (1 Approximately 12 to 24-inches of organic TOPSOIL Oliftisi -Perched water encountered at time of drilling - allistipag - 2 Medium stiff,wet,dark brown/dark gray,mottled Silty CLAY to B2-1 I CLMII Clayey SILT - 5 30.1 B2-2 1 ^—ML Stiff;moist to wet,light brown/rust/light gray,mottled Clayey SILT 10 30.0 - 6 - 11110� with a trace of fine-grained sand - - - - - g - B2-3 - 11 32.6 - - I/11/ Becomes saturated,color includes blackhvst seams - 1 _ _ 01 - 10 - B2-4 // - 7 34.5 I ��0 -Medium stiff';saturated,light brown/rust,mottled fine-grained sandy - 12 - silt with some clay - 7 - - -� J ML Soft to medium stiff,saturated,gray,SILT with varying amounts of - 14 - fine-grained sand and clay - - - B2-5 I - 4 34.5 ')I - 16 - - _ -1 - B2-5.5 I SHELBY -_ t8 -- _ .( i 20 - B2-6 I - 2 40.5 Soft,saturated,gray,fine-grained sandy silt with some clay - 22 - - CL Stiff to very stiff,saturated,gray,Silty CLAY with interlayers of - 24 - completely weathered gravel - 20 31.5 :: B27 l�- - � - - 30 - -- -- - B2-8 ML Hard,moist,light brown,cemented fine-grained Sandy SILT 23 24.2- BORING TERMINATED AT 31'/11' t Perched water encountered at 6-inches Figure A-2, P147505.01.GPJ Log of Boring B 2, Page 1 of 1 I SAMPLE SYMBOLS m...SHELBY TUBE 13...STANDARD PENETRATION TEST .-.DRIVE SAMPLE(UNDISTURBED) ' ` :• ...DISTURBED OR BAG SAMPLE Io...CHUNK SAMPLE t...WATER TABLE OR SEEPAGE NOTE: THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES. GEOCON PROJECT NO. P1475-05-01 >-. W BORING B 3 _o t= W DEPTH p0 Q SOL ~ co.r SAMPLE 1.1 w p p CLASS cn FEET Na. m j (uses) ELEV.(MSL.) 229' DATE COMPLETED 12-29-2006 Z us p °a o z zi O wctm o MO CC EQUIPMENT CME MUD ROTARY n. • MATERIAL DESCRIPTION 0 ;;• •• g Approximately 12 to 24-inches of organic TOPSOIL - •• .• . -Perched water encountered at time of drilling - 2 - 001 CLJML Medium stiff,wet,dark brown/dark gray/rust,mottled Silty CLAY to A B3-1 Clayey SILT - 4 31.4 4 _ / - B3-2 p 9 30.9 6 - I. pr -Becomes stiff --^ ---- - - ML Stiff,saturated,light gray/light brown/rust,mottled Clayey SILT with 8 _ B3-3 e 1 fine-grained sand _ 10 33.6 1 D - B3-4 SHELBY 44.6 . - — ---- 12 - ML Medium stiff,saturated,dark gray/black,SILT with fine sand/caly - - B3-4.5 [ and organics - 4 84.9 14 - -6-inch seam of woody debris and additional decayed organics - - H3-5 - 5 48.2 16 - -Medium stiff,saturated,gray,silt with fine-grained sand and clay, trace organics 18 - - 20 - B3-6 1 - 11 34.6 Stiff;saturated,gray,silt with fine-grained sand,clay and trace organics 22 - - 24 - - B3-7 r 4 34.7 26 - L -Becomes soft to medium stiff,no organics - 28 - - 30 - B3-8 ;.4.-' Hard,moist,dark gray,weathered rock or gravel(no sample recovery) 50/2'- - Lg L� BORING TERMINATED AT 311/2 PEET Perched water encountered at 6-inches Figure A-3, P1476.05-01.GPJ Log of Boring B 3, Page 1 of 1 ( } SAMPLE SYMBOLS W._SHELBY TUBE (a...STANDARD PENETRATION TEST I...DRIVE SAMPLE(UNDISTURBED) -. ...DISTURBED OR BAG SAMPLE ❑...CHUNK SAMPLE X•..WATER TABLE OR SEEPAGE NOTE:THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES. GEOCON t PROJECT NO. P1475-05-01 BORING B 4 0 ^ W U7 F to^ DEPTH SAMPLE SOIL a Z LL Z 0 0 CLASS ELEV. K FEET NO. S (uses) (MSL.) 215' DATE COMPLETED 12-29-2006 N a 4 ri I.0 z C Zcem o 2O X EQUIPMENT CME MUD ROTARY a MATERIAL DESCRIPTION - 0 — Approximately 12 to 24-inches of organic TOPSOIL spasm -Perched water encountered at time of drilling — - 2 _ 1071 CL/MI. Stiff,wet,dark brown/dark gray,mottled Silty CLAY to Clayey SILT _ _ B4-1 — 8 29.8 —- 4 — °y — B4-2 ok 12 31.2 _ g -Stiff,moist,light brown/brown/light gray,mottled silty clay to clayey — Pr silt — 8 — B4-3 1001 - 13 28.9 00; -Color Change to gray- 10 134-4 ML , Stiff,saturated,gray,fine-grained Sandy SILT with a trace of organics 8 41.5 — 12 — B4-4.5 SHELBY 38.7 — 14 — — B4-5 I 8 37.7 — 16 — — — 18 — — ML Soft to medium stiff,saturated,gray,SILT with fine-grained sand _ 20 — B4-6 I — 3 35.4 — 22 — — 24 — B4-7 I SHELBY 32.6 - 26 CL Very stiff,saturated,light gray/light green,Silty CLAY ^J _ 28 _ _ - 30 — B4-8 16 28,7 BORING TERMINATED AT 313i 1'�1 Perched water encountered at 6-inches Figure A-4, P1475-05-01.GPJ Log of Boring B 4, Page 1 of 1 SAMPLE SYMBOLS m..SHELBY TUBE El...STANDARD PENETRATION TEST I„.DRIVE SAMPLE(UNDISTURBED) .. ...DISTURBED OR BAG SAMPLE Li...CHUNK SAMPLE y...WATER TABLE OR SEEPAGE NOTE THE LOG OF SUBSURFACE CONDITIONS SHOWN HEREON APPLIES ONLY AT THE SPECIFIC BORING OR TRENCH LOCATION AND AT THE DATE INDICATED. IT IS NOT WARRANTED TO BE REPRESENTATIVE OF SUBSURFACE CONDITIONS AT OTHER LOCATIONS AND TIMES. GEOCON I .• • • Red Rock Creek Tigard Business Center - Dilatometer Sounding #1 Dilatometer Values 0.1 1 10 100 1000 10000 a ef e, l i . i 1 - (-----.2.____ aaa 10 :t. 1 ■ 20 , ir i � Modulus(tsf) - - Kd — —Id L 25 ) i J / . , r :.1 30 K.... _ ) I Red Rock Creek Tigard Business Center • Dilatometer Sounding #2 Dilatometer Values 0.1 1 10 100 1000 10000 0 • %a • I. J ‘ S • `� ` 5 ' `1 •I. • f f ■ ■ 10 - i I,.. ) `■ ." -#4 , i .) 15 C r a.-.+ _r r r 4 a �` .. CD I o •#, 20 �� •'• 1 c,... + 25 r ..> �',� Modulus (tsf) _ <S !; - -- Kd 1ll •. 3 r — —Id 30 `' • +. n 35 L t 1 i -a . f i 1 1 Red Rock Creek Tigard Business Center Dilatometer Sounding #3 I Dilatometer Values • 0.1 1 10 100 1000 i 0 • 1 • • . ...s �. so- s j t"'" la.. i �, r 1 15 _ • S.• r c �. 20 �'^'� i +. i L 001 1 r Zr~ ~ •. 25 i 30 N. Modulus(tsf) - - - Kd — —Id f"..-- 35 i . - • I Red Rock Creek Tigard Business Center Dilatometer Sounding #4 Dilatometer Values 0.1 1 10 100 1000 - a - 2- rr /i ar 1 a . 4 — ` \ r 1 + j , s ( , I i .. i g i 1 O 10 ) �.' ti . 12 r.. ` ,+"ti i ar . 14 — ..` . i 0,- t f.. i 16 \.� Modulus(tsf) / .e - - Kd • — —Id (� 18- (i L F APPENDIX B LABORATORY TESTING Laboratory tests were performed in accordance with generally accepted test methods of the American Society for Testing and Materials(ASTM)or other suggested procedures. Selected soil samples were tested for their moisture content and gradation. Moisture contents are indicated on the boring logs in Appendix A. The results of the remaining laboratory tests performed are presented in following pages. TABLE B-1 SUMMARY OF PLASTICITY INDEX TEST RESULTS ASTM D43I8 Sample Depth Liquid Plastic Plasticity USCS Number (ft} Limit Limit Index Classification B1-5 15-16.5 29 27 2 ML B2-5.5 17-19 28 26 2 ML B3-7 25-26.5 28 27 1 ML B4-7 24-26 30 27 3 ML 0 Consolidation Test(ASTM D 2435) ! l Project Tigard Business Center Boring Number B2-5.5 Project Number P1475-05-01 Sample Number 5.5 Description of Soil Gray Silt Depth of Sample 17-19 Initial Final Moisture Content _ 32.8 24.5 Void Ratio 0.64 0.48 Tigard Business Park Consolidation Test B4-7 Depth=25 feet 0.6500 - 0.6000 • • 0.5500 - - 9 b i 0.5000 0.4500 — - - - 0.4000 - 1000 10000 100000 pressure(psf) • L • • Consolidation Test(ASTM D 2435) Project Tigard Business Center Boring Number B4-7 Project Number P1475-05-01 Sample Number 7 Description of Soil Gray Silt Depth of Sample 24-26 Initial Final Moisture Content 34.9 29.5 Void Ratio 0.83 0.64 Tigard Business Park Consolidation Test B4-7 Depth=25 feet 0.8500 - 0.8000 0.7500 0.7000 O ea e3 • 0.6500 0.6000 • 0.5500 • 0.5000 1000 10000 100000 pressure(psf) Grain Size Distribution (ASTM D1140 and D 422) Tigard Business Center Sample B1-5 Depth= 15 feet GRAVEL I SAND I SILT I CLAY 100 -- r - — 1 1 1 1 1 II 1 80 I b4 3 60 PI , a t 40 g 1 N i I 1 e I 20 _ . 1 1 a it t s 0 1 , , • i ' 1 l i 1 100 10 1 0.1 0.01 0.001 Grain size(mm) • f i� - • Grain Size Distribution(ASTM D1140 and D 422) . Tigard Business Center Sample B2-5.5 Depth= 15 feet I—"—GRAVEL I SAND I SILT 1 CLAY 100 1 - -, 1 I I 1 80 - I I 1 I . I I +' . to .n I I i ' I a w \\ I 0 40 1 i 1 R.1 1 1 I a 20 - - I I i a I 0 ' I , J . . I ' I . . . . 100 10 1 0.1 0.01 0.001 Grain size(mm) I I • I ■ to Grain Size Distribution (ASTM D1140 and D 422) Tigard Business Center Sample B3-7 Depth= 25 feet I GRAVEL I SAND I SILT , CLAY 100 1 I I I I I I 80 I I — 1 I 1 I I I • i I I I 1 .0.- 60 I _ I 3 i I I I �.. _ .I — . -I . ai EI 1 G I I U 40 _ 1 s. I 1 0a) 1 I 1 20 , 1 1 1 1 1 1 1 1 1 1 V 1 1 1 ■ I I ,• , 1 1 1 I 100 10 1 0.1 0.01 0.001 Grain size(mm) I I I • Grain Size Distribution (ASTM D1140 and D 422) Tigard Business Center Sample B4-7 Depth= 25 feet GRAVEL I SAND I SILT I CLAY I 100 --- . I , 80 - ' ' . , , an 60 .. t. 0 40 U . a ' • • I , 20 ' ' 100 10 1 0.1 0.01 0.001 Grain size(mm)