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Report Geotechnical Engineering Report Pacific Ridge Apartments Tigard, Oregon OO / �� Sq for OV 0 D('0 J.T. Smith Companies <11/ c/o 3J Consulting S` November 20, 2019 r 11,` �►� , . ,. • • GEOENG;NEER Ex Iciece+Trehropr Geotechnical Engineering Report Pacific Ridge Apartments Tigard, Oregon for J.T.Smith Companies c/o 3J Consulting November 20, 2019 GEOENGINEERS 4000 Kruse Way Place Building 3, Suite 200 Lake Oswego, Oregon 97035 503.624.9274 Geotechnical Engineering Report Pacific Ridge Apartments Tigard, Oregon File No.6748-003-00 November 20, 2019 Prepared for: J.T.Smith Companies c/o 3J Consulting, Inc. 9600 SW Nimbus Avenue,Suite 100 Beaverton, Oregon 97008 Attention:Aaron Murphy, PE Prepared by: GeoEngineers, Inc. 4000 Kruse Way Place Bldg. 3,Suite 200 Lake Oswego, Oregon 97035 503.624.9274 4\\��D PR OFFS Tyg ianella, PE ‘5 NGi► 404 Geotechnical Engineer 603 pir irtl�p9•REGON 20° 111 •r• 'RY o$' p, Jul . C.Vela, P' s, PE,GE /O C VET P acipal Geote • ical Engineer EXPIRES: 04/5o/t0 TNG:JCV:cje Disclaimer:Any electronic form,facsimile or hard copy of the original document(email,text,table,and/or figure),if provided,and any attachments are only a copy of the original document.The original document is stored by GeoEngineers,Inc.and will serve as the official document of record. GEOENGINEERS / Table of Contents 1.0 INTRODUCTION 1 2.0 SCOPE OF SERVICES 1 3.0 SITE DESCRIPTION 1 3.1. Surface Conditions 1 3.2. Site Geologic and Landslide Hazard Mapping 2 3.3. Subsurface Conditions 2 3.3.1. General 2 3.3.2. Soil Conditions 2 3.3.3. Groundwater Conditions 3 4.0 INFILTRATION TESTING 3 4.1. Suitability of Infiltration System 5 5.0 CONCLUSIONS 6 6.0 EARTHWORK RECOMMENDATIONS 6 6.1. Site Preparation 6 6.1.1. Stripping 7 6.1.2. Clearing and Grubbing 7 6.2. Subgrade Preparation and Evaluation 7 6.3. Subgrade Protection and Wet Weather Considerations 8 6.4. Soil Amendment with Cement 9 6.5. Dewatering 10 6.6. Shoring 10 6.7. Structural Fill and Backfill 11 6.7.1. General 11 6.7.2. Use of On-site Soil 11 6.7.3. Imported Select Structural Fill 11 6.7.4.Aggregate Base 12 6.7.5. Open-Graded Subbase 12 6.7.6. Open-Graded Base Rock 12 6.7.7. Retaining Wall Backfill 12 6.7.8.Trench Backfill 12 6.8. Fill Placement and Compaction 12 7.0 STRUCTURAL DESIGN RECOMMENDATIONS 13 7.1. Foundation Support Recommendations 13 7.1.1. Foundation Subgrade Preparation 13 7.1.2. Bearing Capacity - Spread Footings 14 7.1.3. Foundation Settlement 14 7.1.4. Lateral Resistance 14 7.2. Footing Drains 14 7.3. Construction Considerations 15 7.4. Slab-on-Grade Floors 15 7.4.1. Subgrade Preparation 15 GEOENGINEERS� November 20,2019 I Page i File No.6748-003-00 7.4.2. Design Parameters 15 8.0 GENERAL STABILITY OF GRADED SLOPES 16 9.0 EXCAVATION SUPPORT AND WALL OPTIONS 17 9.1. Excavation Considerations 17 9.2. Temporary Cut Slopes 17 9.3. Permanent Slopes 18 9.3.1. Slope Drainage 18 9.4. Retaining Walls 19 9.4.1. Concrete Retaining Walls 19 9.4.2. Mechanically Stabilized Earth (MSE)Walls 19 9.4.3. Proprietary Wall Systems 20 9.4.4. Soil Nail Walls 20 9.5. Seismic Design 21 9.5.1. Liquefaction Potential 22 10.0 PAVEMENT RECOMMENDATIONS 22 10.1. Dynamic Cone Penetrometer(DCP)Testing 22 10.2. Drainage 23 10.3.Asphalt Concrete(AC) Pavement Sections 23 10.4. Pervious Pavement Sections 24 10.5. Pervious Pavement Construction Considerations 25 11.0 LIMITATIONS 25 12.0 REFERENCES 26 LIST OF FIGURES Figure 1.Vicinity Map Figure 2.Site Plan APPENDICES Appendix A. Field Explorations and Laboratory Testing Figure A-1. Key to Exploration Logs Figures A-2 through A-5. Logs of Borings Figures A-6 through A-12. Logs of Test Pits Figures A-13 and A-14. Logs of Dynamic Cone Penetrometer Testing Figure A-15.Atterberg Limits Test Results Appendix B.Slope Stability Analysis Figure B-1. Global Stability Figure B-2. Wall 1 Profile Figure B-3. Wall 3 Profile Appendix C. Report Limitations and Guidelines for Use GEOENGINEERS November 20,2019 i Page File No.6748-003-00 r 1.0 INTRODUCTION GeoEngineers, Inc. (GeoEngineers) is pleased to submit this geotechnical engineering report for the proposed Pacific Ridge Apartments development located southeast of the intersection of SW Pacific Highway (OR 99W) and SW Beef Bend Road in Tigard, Oregon. The location of the site is shown in the Vicinity Map, Figure 1. The proposed project includes constructing one, four-story apartment building, associated asphalt-paved parking areas and on-site retaining walls. Current site grades range from an elevation of approximately 310 feet above mean sea level (MSL)at the northeast corner of the site to approximately 245 feet MSL at the southwest corner. The apartment structure is proposed to consist of a tiered floor to be constructed with a finish floor elevation of approximately 269 and 279 feet MSL. Based on grading exhibits prepared by 3J Consulting, Inc. (3J),dated October 29,2019,cuts and fills at the site are generally 5 feet or less, but with isolated areas of site cuts up to approximately 10 feet within the lower tier(southwestern portion) of the proposed building footprint and up to 12 feet for wall construction. Various wall types are being considered as part of site development, including cast in place walls, gravity block walls, and geogrid reinforced counterfort and panel or segmented block walls. The proposed site layout is shown in relation to existing site features in the Site Plan, Figure 2. 2.0 SCOPE OF SERVICES Our specific scope of services is detailed in our June 28, 2019 proposal to you. Our services were authorized on July 2, 2019. In general our scope of services included: reviewing selected geotechnical information about the site; performing a geologic reconnaissance; exploring subsurface soil and groundwater conditions; collecting representative soil samples; performing infiltration testing in general accordance with City of Tigard standards;completing relevant laboratory testing and geotechnical analyses; and providing this geotechnical report with our conclusions, findings and design recommendations. As discussed with the project team, borings for widening along OR 99W were removed from the original scope, and a third infiltration test, additional test pit explorations, and site clearing to access the boring locations were added to the original scope. 3.0 SITE DESCRIPTION 3.1. Surface Conditions The project site encompasses an approximate 2.87-acre parcel located on the lower eastern slopes of Bull Mountain on the east side of OR 99W, an isolated prominence near the edge of the Tualatin Valley in the Tigard, Oregon metropolitan area. The property is bound by undeveloped property to the north, developed apartment structures on the uphill side to the east,a church building and associated parking lots and drive areas to the south, and OR 99W to the west. The parcel is currently undeveloped, and slopes moderately steeply down to the south and west. The slope is thickly vegetated, with a second-growth canopy over a dense Northwest understory. While on site, we observed scattered debris in several areas, including the remains of temporary campsites. GEOENGINEERS� November20,2019 I Page 1 File No.6748-003-00 3.2. Site Geologic and Landslide Hazard Mapping The geology of the site is mapped by Madin (1990)as mantled by the fine-grained facies of the Pleistocene catastrophic(Missoula)flood deposits below 250 feet MSL and igneous basalt of the Columbia River Basalt Group (CRBG) above that elevation. Our subsurface explorations suggest that, instead, the entire site is mantled by silty and fine sandy flood deposits, with decomposed to weathered basalt at depth. Existing landslides and landslide features for the site and vicinity are mapped by Burns et al. (2011), and the landslide susceptibility in Burns et al. (2016). No active, recent, or dormant landslides are mapped on site by Burns et al.(2011). During our field investigation we did not observe surficial features characteristic of landsliding, such as concave scarps or depressions in the hillside, sunken or bulging soil slopes, "hummocky"topography, and anomalous vegetation or drainage patterns. Burns et al. (2016) maps the south- and southwest-facing slopes of Bull Mountain as "moderately" susceptible to landsliding, the second-lowest of a four-tier rating system from "low"to "very high" hazard. This rating is likely due to the regional slope gradient rather than site-specific soil or slope conditions. 3.3. Subsurface Conditions 3.3.1.General The subsurface conditions at the site were explored by drilling four geotechnical borings (B-1 to B-4) and excavating seven test pits(TP-1 to TP-7)on October 8 and 9, 2019 The borings were drilled to approximate depths ranging from 171 to 261/2 feet below the ground surface (bgs), while the test pits extended from 8 to 11 feet bgs. Infiltration testing was performed in three of the test pits at a depth of approximately 51/2 to 7 feet bgs. The approximate locations of the explorations completed at the site are shown in Figure 2. The logs of GeoEngineers explorations completed for this study are presented in Appendix A. Soil samples were obtained during drilling and excavation were taken to GeoEngineers' laboratory for further evaluation. Selected samples were tested for determination of moisture content, Atterberg limits and moisture/density testing. A description of the laboratory testing and the test results are presented in Appendix A. 3.3.2.Soil Conditions In general, subsurface soil conditions consist of a surficial layer consist of silt and fine sand of the Pleistocene fine-grained catastrophic flood deposits to depths ranging between 12 to more than 261/2 feet bgs. In some explorations we encountered a mixture of gravel, silt, and sand beneath the upper silt and fine sand that we interpret to be the weathered basalt and basalt decomposition products of the CRBG that underlies the Bull Mountain uplands.These units are described in more detail below. 3.3.2.1.FINE-GRAINED FLOOD DEPOSITS We encountered fine-grained flood deposits from the ground surface to depths ranging from 12 feet bgs in B-3 to more than 25 feet bgs,and in B-4 at which depth these deposits were still present.The flood deposits generally consist of yellow-brown to brown, soft to very stiff(predominantly stiff) massive silt and silt with fine sand. As noted, B-4 did not penetrate the full thickness of the flood deposits. B-1 through B-3 penetrated between 12 and 201/2 feet of silty flood deposit soils before encountering CRBG materials. GEOENGINEERS_O November 20,2019 I Paget File No.6748-003 00 �r► 3.3.2.2.WEATHERED TO DECOMPOSED COLUMBIA RIVER BASALT(CRB) We encountered soils we interpret as the decomposition products of the CRBG bedrock below the fine- grained deposits in B-1 through B-3 to the maximum depths explored. This material was typically brown, gray-brown, or gray, dense to very dense, silty to clayey gravel with sand that graded with depth to angular basalt rock fragments with sand, silt and clay. Borings B-2 and B-3 encountered practical refused on hard, relatively intact basalt at 25 feet bgs and 17 feet bgs, respectively. 3.3.3.Groundwater Conditions Groundwater was not encountered during drilling, although soil conditions in B-4 suggest that the seasonal or perched groundwater may be encountered at or just below 25 feet bgs at the lower elevations along the northwest portions of the site. Test pits and borings further up the slope, or in the eastern and southern portions of the site, did not encounter indications of groundwater to the maximum depths explored.Snyder (2008) maps groundwater more than 100 feet bgs near the base of the slope. Groundwater may be present at shallower depths in a perched condition on harder underlying layers as it moves downslope during wet times of the year or during extended periods of wet weather. Groundwater conditions at the site are expected to vary seasonally due to rainfall events and other factors not observed in our explorations. 4.0 INFILTRATION TESTING As requested by the project team, we conducted three on-site infiltration tests to assist in evaluation of the site for stormwater infiltration design at the exploration locations as shown in Figure 2 at depths of 51/2 to 7 feet bgs. Washington County's LIDA Handbook does not contain specified testing procedures but references several different methods described by other local jurisdictions. On site testing was conducted using the open pit falling head method in general accordance with the procedures outlined in Chapter 2 of the City of Portland 2016 Stormwater Management Manual. Our general procedure included excavating an approximately 2-foot-square test pit to the specified depth using a tracked excavator. Test excavations were filled with clean water to approximately 1 foot above the soil at the bottom of the test pit. The initial fill of water did not drain into the soil within ten minutes, so the water level was maintained, and the soil allowed to saturate overnight. The levels were checked, and the test pits were refilled the following morning to 12 inches above the soil in the bottom of the test pits. The drop-in water level was measured during three, hour-long iterations. Field test results are summarized in Table 1. GEOENGINEERS November 20,2019 1 Page3 File No.6748-003 00 TABLE 1. FIELD MEASURED INFILTRATION RESULTS Infiltration Depth USCS Material Field Measured Infiltration Ratel Test No. Location feet Type(feet) YP (inches/hour) TP-5/IT-1 See Site Plan 6 ML/CL 0.0 TP-6/IT-2 See Site Plan 51/2 ML/CL 1.5 TP-7/IT-3 See Site Plan 7 ML/CL 0.0 Notes: 1 Appropriate factors should be applied to the field-measured infiltration rate, based on the design methodology and specific system used. USCS=Unified Soil Classification System The infiltration rate shown in Table 1 represents a field-measured infiltration rate.The rate summarized for IT-1 and IT-3 indicates 0.0 inches per hour because minimal to no infiltration (drop in water levels) was observed during the testing period. Similar tests that are performed during drier times of the year in similar soils may yield field-measured rates of 1 to 3 inches per hour, but do not necessarily reflect the conditions when these facilities are to perform (during rain events in the wet times of the year). Field measurements are limited to accuracy of equipment employed to conduct the test.Actual long-term infiltration rates of the on-site soils are likely greater than 0.0 inches per hour if measured out over very long time frames (much longer than the time frames prescribed in the testing standards. A field-measured rate of zero inches per hour generally indicates infiltration less than 0.05 to 0.08 inches per hour, which is about the limit of the field measuring equipment. In addition,field-measured rates represent a relatively short-term infiltration rate,and factors of safety have not been applied for the type of infiltration system being considered, or for variability that may be present across large areas in the on-site soil. In our opinion,and consistent with the state of the practice, correction factors should be applied to this measured rate to reflect the localized area of testing relative to the field sizes. Appropriate correction factors should also be applied by the project civil engineer to account for long-term infiltration parameters. From a geotechnical perspective, we recommend a factor of safety (correction factor) of at least 2 be applied to the field infiltration values to account for potential soil variability with depth and location within the area tested. In addition, the stormwater system design engineer should determine and apply appropriate remaining correction factor values, or factors of safety, to account for repeated wetting and drying that occur in this area, degree of in-system filtration, frequency and type of system maintenance, vegetation, potential for siltation and bio-fouling, etc., as well as system design correction factors for overflow or redundancy, and base and facility size. The actual depths, lateral extent and estimated infiltration rates can vary from the values presented above. Field testing/confirmation during construction is often required in large or long systems or other situations where soil conditions may vary within the area where the system is constructed. The results of this field testing might necessitate that the infiltration locations be modified to achieve the design infiltration rate. The infiltration flow rate of a focused stormwater system like a drywell or small infiltration box or pond typically diminishes over time as suspended solids and precipitates in the stormwater further clog the void spaces between the soil particles or cake on the infiltration surface or in the engineered media. The serviceable life of an infiltration media in a stormwater system can be extended by pre-filtering or with on- GEOENGINEERS ) November 20,2019 I Page 4 File No.6748-003-00 going accessible maintenance.Eventually, most systems will fail and will need to be replaced or have media regenerated or replaced. We recommend that infiltration systems include an overflow that is connected to a suitable discharge point. Also, infiltration systems can cause localized, high groundwater levels and should not be located near basement walls, retaining walls, or other embedded structures unless these are specifically designed to account for the resulting hydrostatic pressure.Infiltration locations should not be located on sloping ground, unless it is approved by a geotechnical engineer, and should not be infiltrated at a location that allows for flow to travel laterally toward a slope face, such as a mounded water condition or too close to a slope face that could cause instability of the slope. 4.1. Suitability of Infiltration System Successful design and implementation of stormwater infiltration systems and whether a system is suitable for a development depend on several site-specific factors. Stormwater infiltration systems are generally best suited for sites having sandy or gravelly soil with saturated hydraulic conductivities greater than 2 inches per hour. Sites with silty or clayey soil, including sites with fine sand,silty sand or gravel that has a high percentage of silt or clay in the matrix or sites with relatively shallow underlying decomposed rock (residual soil) are generally not well suited for development using infiltration exclusively for stormwater disposal. Soil that has fine-grained matrices is susceptible to volumetric change and softening during wetting and drying cycles. Fine-grained soil also has large variations in the magnitude of infiltration rates because of bedding and stratification that occurs during alluvial deposition that often have thin layers of less permeable or impermeable soil within a larger layer. Local groundwater conditions also significantly affect the capacity to infiltrate from a stormwater system. Sites with shallow groundwater can result in groundwater mounding. A hydraulic gradient that reaches the level of water in the soil immediately drops to zero and local groundwater will rise and mound and the infiltration rate slows dramatically, resulting in overflows or system flooding (failure). Groundwater mounding can also negatively impact structures, slopes or other areas adjacent to the stormwater infiltration facility. Typically, we do not recommend using infiltration systems where groundwater is less than 10 feet below the bottom of the proposed system unless the host soil is very permeable and consistently graded and will not cause mounding. Some jurisdictions require a minimum of 5 or 10 feet between high groundwater conditions and the bottom of proposed facilities. Depending on the size of the project,adjacent features such as streams that can source water to a system instead of allowing it to drain and on-site soil infiltration capacities, there may be conditions where even a 10-foot separation between the level of groundwater and the base of the infiltration system may not be sufficient. Considering the underlying generally medium stiff,fine-grained soil conditions, on-site infiltration will likely be minimal during wet times of the year and infiltration may cause mounding of groundwater if areas of perched water are present in the area. We do not recommend stormwater infiltration be used as the exclusive method of stormwater management and recommend an overflow be a part of system design. On- site infiltration systems should be considered as having only marginal potential for success based on the conditions observed. GEOENGINEERS..„0 November 20,2019 I Page 5 He No.6748-003-00 5.0 CONCLUSIONS Based on our explorations, testing and analyses, it is our opinion that the site is generally suitable for the proposed development from a geotechnical engineering standpoint, provided the recommendations in this report are included in design and construction. A summary of the primary geotechnical considerations is provided below. The summary is presented for introductory purposes only and should be used in conjunction with the complete recommendations presented in this report. • Groundwater was not encountered during our explorations, but based on our experience and our observations, perched groundwater may be present during periods of persistent rainfall. • The upper silty and clayey soils at the site will likely become disturbed by construction traffic from earthwork occurring during periods of wet weather or when the moisture content of the soil is more than a few percentage points above optimum. Wet weather construction practices will be required, except during the dry summer months. • On-site soils may be reused as structural fill; however, the material is very moisture sensitive and will likely not be suitable for reuse except during the driest of summer months. On-site material will be practically unworkable as structural fill during the wet season or when prolonged wet weather persists. In general,the most persistent wet weather in the area occurs from early October to mid-May. • Floor slabs having 125 pounds per square foot(psf) loads or less can be supported on aggregate base placed on native medium stiff or firmer silt. • Proposed structures can be satisfactorily supported on continuous and isolated shallow foundations supported on the stiff native soils or on structural fill that extends to native soil. • Standard pavement sections prepared as described in this report will suitably support estimated traffic loads. in Configuration of permanent slopes should consider final use (landscape areas or unmaintained) and construction conditions (fill or cut slopes) when determining site grades. • Retaining wall design will require consideration of required depth of embedment of the wall,stability of wall type to support graded slopes, and global stability of the wall and slope system as a whole, which will depend on slopes above and below wall locations and potential for tiered grading. • Installation of deep utilities may encounter less weathered or unweathered underlying rock depending on final grading and required invert elevations. 6.0 EARTHWORK RECOMMENDATIONS 6.1. Site Preparation Initial site preparation and primary earthwork operations will include, stripping and grubbing, and grading the site to create a level building pad and graded areas for parking and drives. In addition,some preliminary work may include excavation for final utilities and wall foundations. Although not anticipated, if present, all existing utilities in proposed earthwork construction areas should be identified prior to excavation. Live utility lines identified beneath proposed structures should be relocated. Abandoned utility lines beneath structures should be completely removed or filled with grout in GEOENGINEERS November20,2019 I Page 6 File No.6748-003-00 order to reduce potential settlement of new structures. Soft or loose soil encountered in utility line excavations should be removed and replaced with structural fill where it is located within structural areas. Debris materials generated during demolition of existing improvements or relocation of utilities should be transported off site for disposal. Existing voids and new depressions created during site preparation, and resulting from removal of existing utilities,or other subsurface elements,should be cleaned of loose soil or debris down to firm soil and backfilled with compacted structural fill. Disturbance to a greater depth should be expected if site preparation and earthwork are conducted during periods of wet weather. 6.1.1.Stripping Areas to receive fill,structures or pavements should be cleared of vegetation and stripped of topsoil. Based on our observations at the site,we estimate that the depth of stripping will generally be on the order of 8 to 12 inches. We anticipate the majority of the open brush and grass-covered areas will require stripping depths of up to 12 inches with increased depths in areas of thicker vegetation. Tree-covered areas are discussed below. Greater stripping depths may be required to remove localized zones of loose or organic soil. The actual stripping depth should be based on field observations at the time of construction.Stripped material should be transported off site for disposal unless otherwise allowed by project specifications for other uses such as landscaping. Clearing and grubbing recommendations provided below should be used in areas where moderate to heavy vegetation are present, or where surface disturbance from prior use has occurred. 6.1.2.Clearing and Grubbing Where thicker vegetation is present, more extensive site clearing will be required to remove site vegetation, including thick grass, shrubs and trees that are designated for removal. Following clearing, grubbing and excavations up to several feet will be required to remove the root zones of thick shrubs and trees. Deeper excavations, up to 5 or 6 feet may be required to remove the root zones of large trees. In general, roots larger than s/z inch in diameter should be removed. Excavations to remove root zones should be done with a smooth-bucket to minimize subgrade disturbance. Portions of the site are heavily vegetated and previously buried roots may be present, even in the current grassy areas of the site. Grubbed materials should be hauled off site and properly disposed unless otherwise allowed by the project specifications for other uses such as landscaping, stockpiling or on-site burning. Existing voids and new depressions created during demolition, clearing, grubbing or other site preparation activities,should be excavated to firm soil and backfilled with Imported Select Structural Fill.Greater depths of disturbance should be expected if site preparation and earthwork are conducted during periods of wet weather. 6.2. Subgrade Preparation and Evaluation Upon completion of site preparation activities,exposed subgrades should be proof-rolled with a fully loaded dump truck or similar heavy rubber-tired construction equipment where space allows to identify soft, loose or unsuitable areas. Probing may be used for evaluating smaller areas or where proof-rolling is not practical. Proof-rolling and probing should be conducted prior to placing fill, and should be performed by a representative of GeoEngineers who will evaluate the suitability of the subgrade and identify areas of yielding that are indicative of soft or loose soil. If soft or loose zones are identified during proof-rolling or GEOENGINEERS November 20,2019 I Pagel File No.6748-003.00 probing, these areas should be excavated to the extent indicated by our representative and replaced with structural fill. As discussed in Section 6.7 of this report,the native fine-grained,silty soil can be sensitive to small changes in moisture content and will be difficult, if not impossible,to compact adequately during wet weather.While tilling and compacting the subgrade is the economical method for subgrade improvement, it will likely only be possible during extended dry periods and following moisture conditioning of the soil.As discussed further in this report,cement amendment is an option for conditioning the soil for use as structural fill when drying the soil is not feasible. During wet weather, or when the exposed subgrade is wet or unsuitable for proof-rolling, the prepared subgrade should be evaluated by observing excavation activity and probing with a steel foundation probe. Observations, probing and compaction testing should be performed by a member of our staff.Wet soil that has been disturbed due to site preparation activities or soft or loose zones identified during probing should be removed and replaced with compacted structural fill. 6.3. Subgrade Protection and Wet Weather Considerations The upper fine-grained soils at the site are highly susceptible to moisture. Wet weather construction practices will be necessary if work is performed during periods of wet weather. If site grading will occur during wet weather conditions, it will be necessary to use track-mounted equipment, load material into trucks supported on gravel work pads and employ other methods to reduce ground disturbance. The contractor should be responsible to protect the subgrade during construction reflective of their proposed means and methods and time of year. Earthwork planning should include considerations for minimizing subgrade disturbance. The following recommendations can be implemented if wet weather construction is considered: av The ground surface in and around the work area should be sloped so that surface water is directed to a sump or discharge location. The ground surface should be graded such that areas of ponded water do not develop. Measures should be taken by the contractor to prevent surface water from collecting in excavations and trenches. Measures should be implemented to remove surface water from the work area. • Earthwork activities should not take place during periods of heavy precipitation. Iv Slopes with exposed soils should be covered with plastic sheeting or similar means. • The site soils should not be left uncompacted and exposed to moisture. Sealing the surficial soils by rolling with a smooth-drum roller prior to periods of precipitation will reduce the extent to which these soils become wet or unstable. • Construction activities should be scheduled so that the length of time that soils are left exposed to moisture is reduced to the extent practicable. ▪ Construction traffic should be restricted to specific areas of the site, preferably areas that are surfaced with working pad materials not susceptible to wet weather disturbance such as haul roads and rocked staging areas. • When on-site fine-grained soils are wet of optimum, they are easily disturbed and will not provide adequate support for construction traffic or the proposed development.The use of granular haul roads GEOENGINEERSI November 20,2019 i Page Fie No,6748-003-00 and staging areas will be necessary for support of construction traffic.Generally,a 12-to 16-inch-thick mat of imported granular base rock aggregate material is sufficient for light staging areas for the building pad and light staging activities, but is not expected to be adequate to support repeated heavy equipment or truck traffic.The granular mat for haul roads and areas with repeated heavy construction traffic should be increased to between 18 and 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. a During periods of wet weather, concrete should be placed as soon as practical after preparation of the footing excavations. Foundation bearing surfaces should not be exposed to standing water. If water collects in the excavation, it should be removed before placing structural fill or reinforcing steel. Subgrade protection for foundations consisting of a lean concrete mat may be necessary if footing excavations are exposed to extended wet weather conditions. During wet weather, or when the exposed subgrade is wet or unsuitable for proof-rolling, the prepared subgrade should be evaluated by observing excavation activity and probing with a steel foundation probe. Observations, probing and compaction testing should be performed by a member of our staff.Wet soil that has been disturbed due to site preparation activities or soft or loose zones identified during probing should be removed and replaced with compacted structural fill. 6.4. Soil Amendment with Cement As an alternative to the using Imported Select Structural Fill material for wet weather structural fill, an experienced contractor may be able to amend the on-site soil with portland cement concrete(PCC)to obtain suitable support properties. It is often less costly to amend on-site soils than to remove and replace soft soils with imported granular materials. Single pass tilling depths for cement amendment equipment is typically 18 inches or less. However, multiple tilling passes may be required to adequately blend in the cement with the soils and to sufficiently process the soils. It may also be necessary to place the recommended cement quantities in multiple passes between tilling passes, which requires intermediate compaction. The contractor should be responsible for selecting the means and methods to construct the amended soil without disturbing exposed subgrades.We recommend low ground-pressure(such as balloon-tired)cement spreading equipment be required.We have observed other methods used for spreading that have resulted in significant site disturbance and high remedial costs. For example,we have observed amendment efforts to use a spreader truck equipped with road tires pulled by track-mounted equipment that resulted in significant disturbance to the work area and required re-working large areas of cement-amended product at additional expense. Areas of standing water, or areas where traffic patterns are concentrated and disturbing the subgrade,will also create a need for higher amounts of cement to be applied and additional tilling for better mixing and cement hydration prior to final compaction. Successful use of soil amendment depends on the use of correct mixing techniques, the soil moisture content at the time of amendment and amendment quantities. Specific recommendations, based on exposed site conditions,for soil amending can be provided, if necessary. However,for preliminary planning purposes, it may be assumed that a minimum of 5 percent cement(by dry weight, assuming a unit weight of 100 pounds per cubic foot[pcf])will be sufficient for improving on-site soils. Treatment depths of 12 to GEOENGINEERS November 20,2019 = Page 9 Pile No.6748 003 00 16 inches are typical (assuming a seven-day unconfined compressive strength of at least 80 pounds per square inch [psi]), although this may be adjusted in the field depending on site conditions. Soil amending should be conducted in accordance with the specifications provided in Oregon Structural Specialty Code (OSSC) 00344 (Treated Subgrade). We recommend a target strength for cement-amended soils of 80 psi. The amount of cement used to achieve this target generally varies with moisture content and soil type. It is difficult to predict field performance of soil-to-cement amendment due to variability in soil response and we recommend laboratory testing to confirm expectations. However,for preliminary design purposes,4 to 5 percent cement by weight of dry soil can generally be used when the soil moisture content does not exceed approximately 20 percent. If the soil moisture content is in the range of 20 to 35 percent, 5 to 7 percent by weight of dry soil is recommended. The amount of cement added to the soil should be adjusted based on field observations and performance. PCC-amended soil is hard and has low permeability;therefore,this soil does not drain well nor is it suitable for planting. Future landscape areas should not be cement amended, if practical, or accommodations should be planned for drainage and planting. Cement amendment should not be used if runoff during construction cannot be directed away from adjacent low-lying wet areas, and active waterways and drainage paths. When used for constructing pavement, staging or haul road subgrades, the amended surface should be protected from abrasion by placing a minimum 4-inch thickness of base rock material (Aggregate Base/ Aggregate Subbase). To prevent strength loss during curing, cement-amended soil should be allowed to cure for a minimum of four days prior to placing the base rock. The base rock typically becomes contaminated with soil during construction. Contaminated base rock should be removed and replaced with clean base rock in pavement areas to meet the required thickness(es) in Section 10.0 to this report. It is not possible to amend soil during heavy or continuous rainfall. Work should be completed during suitable weather conditions. 6.5. Dewatering As discussed in Section 3.3.3 of this report, groundwater was not encountered in our explorations and is expected to be typically below the anticipated excavation depth. Excavations that extend into saturated/wet soils should be dewatered. Sump pumps are expected to adequately address groundwater encountered in shallow excavations. In addition to groundwater seepage and upward confining flow, surface water inflow to the excavations during the wet season can be problematic. Provisions for surface water control during earthwork and excavations should be included in the project plans and should be installed prior to commencing earthwork. 6.6. Shoring All trench excavations should be made in accordance with applicable Occupational Safety and Health Administration (OSHA) and state regulations. Site soils within expected excavation depths typically range from medium stiff to stiff silt. In our opinion, native soils are generally OSHA Type B, provided there is no seepage and excavations occur during periods of dry weather. Excavations deeper than 4 feet should be shored or laid back at an inclination of 1H:1V(horizontal to vertical)for Type B soils. Flatter slopes may be necessary if workers are required to enter. Excavations made to construct footings or other structural GEOENGINEERS November20,2019 I Page 10 File No.6748-003-00 elements should be laid back or shored at the surface as necessary to prevent soil from falling into excavations. Shoring for trenches less than 6 feet deep that are above the effects of groundwater should be possible with a conventional box system.Slight to moderate sloughing should be expected outside the box.Shoring deeper than 6 feet or below the groundwater table should be designed by a registered engineer before installation. Further,the shoring design engineer should be provided with a copy of this report. In our opinion, the contractor will be in the best position to observe subsurface conditions continuously throughout the construction process and to respond to the soil and groundwater conditions. Construction site safety is generally the sole responsibility of the contractor,who also is solely responsible for the means, methods and sequencing of the construction operations and choices regarding excavations and shoring. Under no circumstances should the information provided by GeoEngineers be interpreted to mean that GeoEngineers is assuming responsibility for construction site safety or the contractor's activities; such responsibility is not being implied and should not be inferred. 6.7. Structural Fill and Backfill 6.7.1.General Materials used to support building foundations, floor slabs, hardscape, pavements and any other areas intended to support structures or within the influence zone of structures are classified as structural fill for the purposes of this report. All structural fill soils should be free of debris, clay balls, roots, organic matter, frozen soil, man-made contaminants, particles with greatest dimension exceeding 4 inches and other deleterious materials. The suitability of soil for use as structural fill will depend on the gradation and moisture content of the soil. As the amount of fines in the soil matrix increases, the soil becomes increasingly more sensitive to small changes in moisture content and achieving the required degree of compaction becomes more difficult or impossible. Recommendations for suitable fill material are provided in the following sections. 6.7.2.Use of On-site Soil On-site near surface soil consists of native brown silt. On-site soils can be used as structural fill, provided the material meets the above requirements,although due to moisture sensitivity,this material will likely be unsuitable as structural fill during most of the year. If the soil is too wet to achieve satisfactory compaction, moisture conditioning by drying back the material will be required. If the material cannot be properly moisture conditioned,we recommend using imported material for structural fill. An experienced geotechnical engineer from GeoEngineers should determine the suitability of on-site soil encountered during earthwork activities for reuse as structural fill. 6.7.3.Imported Select Structural Fill Select imported granular material may be used as structural fill. The imported material should consist of pit or quarry run rock, crushed rock, or crushed gravel and sand that is fairly well-graded between coarse and fine sizes (approximately 25 to 65 percent passing the U.S. No. 4 sieve). It should have less than 5 percent passing the U.S. No. 200 sieve. During dry weather, the fines content can be increased to a maximum of 12 percent. GEOENGINEERS November 20,2019 I Page 11 File No.6748-003-00 6.7.4.Aggregate Base Aggregate base material located under floor slabs and pavements and crushed rock used in footing overexcavations should consist of imported clean,durable, crushed angular rock.Such rock should be well- graded, have a maximum particle size of 1 inch and have less than 5 percent passing the U.S. No. 200 sieve (3 percent for retaining walls). In addition, aggregate base shall have a minimum of 75 percent fractured particles according to American Association of State Highway and Transportation Officials (AASHTO)TP-61 and a sand equivalent of not less than 30 percent based on AASHTO T-176. 6.7.5.Open-Graded Subbase Open-graded subbase material for permeable pavements should consists of durable, angular (fractured) fine to course gravel stone with negligible sand and fines content. Material meeting gradational criteria for ASTM International (ASTM)Standard Practices No. 2 should be suitable. 6.7.6.Open-Graded Base Rock Open-graded base rock material for permeable pavements should consist of durable, angular (fractured) fine gravel with sand and negligible fines content. Material meeting gradation criteria for open-graded aggregate in Section 02630.11 of the Oregon Department of Transportation (ODOT) Standard Specifications or ASTM No. 57 should be suitable. 6.7.7.Retaining Wall Backfill Fill placed to provide a drainage zone behind retaining walls should meet the general requirements above and consist of free-draining sand and gravel or crushed rock with a maximum particle size of 3/4 inch and less than 3 percent passing the U.S. No. 200 sieve. 6.7.8.Trench Backfill Backfill for pipe bedding and in the pipe zone should consist of well-graded granular material with a maximum particle size of 3/4 inch and less than 5 percent passing the U.S. No. 200 sieve. The material should be free of organic matter and other deleterious materials. Further,the backfill should meet the pipe manufacturer's recommendations. Above the pipe zone, Imported Select Structural Fill may be used as described above. 6.8. Fill Placement and Compaction Structural fill should be compacted at moisture contents that are within 3 percent of the optimum moisture content as determined by ASTM Test Method D 1557 (Modified Proctor). The optimum moisture content varies with gradation and should be evaluated during construction. Fill material that is not near the optimum moisture content should be moisture conditioned prior to compaction. Fill and backfill material should be placed in uniform, horizontal lifts and compacted with appropriate equipment. The appropriate lift thickness will vary depending on the material and compaction equipment used. Fill material should be compacted in accordance with Table 2 below. It is the contractor's responsibility to select appropriate compaction equipment and place the material in lifts that are thin enough to meet these criteria. However, in no case should the loose lift thickness exceed 18 inches. GEOENGINEERS November20,2019 1 Page 12 File No.6748-003-00 TABLE 2.COMPACTION CRITERIA Compaction Requirements Percent Maximum Dry Density Determined by ASTM Test Method D 1557 at±3%of Optimum Moisture Fill Type 0 to 2 Feet Below Subgrade >2 Feet Below Subgrade Pipe Zone Fine-grained soils 92 92 (non-expansive) Imported Granular, maximum particle size 95 95 < 11/4 inch Imported Granular, maximum particle size 11/4 inch to 4 inches n/a (proof-roll) n/a (proof-roll)(3-inch maximum under building footprints) Retaining Wall Backfill* 92 92 -- Nonstructural Zones 90 90 90 Trench Backfill 95 90 90 Notes: *Measures should be taken to prevent overcompaction of the backfill behind retaining walls.We recommend placingthe zone of backfill located within 5 feet of the wall in lifts not exceeding about 6 inches in loose thickness and compacting this zone with hand-operated equipment such as a vibrating plate compactor and a jumping jack. A representative from GeoEngineers should evaluate compaction of each lift of fill. Compaction should be evaluated by compaction testing, unless other methods are proposed for oversized materials and are approved by GeoEngineers during construction. These other methods typically involve procedural placement and compaction specifications together with verifying requirements such as proof-rolling. 7.0 STRUCTURAL DESIGN RECOMMENDATIONS 7.1. Foundation Support Recommendations Proposed structures can be satisfactorily founded on continuous wall or isolated column footings supported on firm native soils or on structural fill placed over native soils. Exterior footings should be established at least 18 inches below the lowest adjacent grade.The recommended minimum footing depth is greater than the anticipated frost depth. Interior footings can be founded a minimum of 12 inches below the top of the floor slab. Isolated column and continuous wall footings should have minimum widths of 24 and 18 inches, respectively. We have assumed that the maximum isolated column loads will be on the order of 40 kips, wall loads will be 2 kips per linear foot(klf)or less and floor loads for slabs on grade will be 100 psf or less for the proposed development. If design loads exceed these values, we should be notified as our recommendations may need to be revised. 7.1.1.Foundation Subgrade Preparation We recommend loose or disturbed soils resulting from foundation excavation be removed before placing reinforcing steel and concrete. Foundation bearing surfaces should not be exposed to standing water. If GEOENGINEERS_g November20,2019 I Page 13 File No.6748-003-00 water infiltrates and pools in the excavation, the water, along with any disturbed soil, should be removed before placing reinforcing steel. A thin layer of crushed rock can be used to provide protection to the subgrade from weather and light foot traffic. Compaction should be performed as described in Section 6.8. We recommend GeoEngineers observe all foundation excavations before placing concrete forms and reinforcing steel in order to determine that bearing surfaces have been adequately prepared and the soil conditions are consistent with those observed during our explorations. 7.1.2.Bearing Capacity-Spread Footings We recommend conventional footings be proportioned using a maximum allowable bearing pressure of 2,500 psf if supported on medium stiff or stiffer native silt or structural fill bearing on these materials. The recommended bearing pressure applies to the total of dead and long-term live loads and may be increased by one-third when considering earthquake or wind loads. This is a net bearing pressure. The weight of the footing and overlying backfill can be ignored in calculating footing sizes. 7.1.3.Foundation Settlement Foundations designed and constructed as recommended are expected to experience settlements of less than 1 inch. Differential settlements of up to one half of the total settlement magnitude can be expected between adjacent footings supporting comparable loads. 7.1.4.Lateral Resistance Lateral loads on footings can be resisted by passive earth pressures on the sides of footings and by friction on the bearing surface. We recommend that passive earth pressures be calculated using an equivalent fluid unit weight of 220 pcf for foundations confined by native medium stiff or stiffer silt and 300 pcf if confined by a minimum of 2 feet of imported granular fill. We recommend using a friction coefficient of 0.35 for foundations placed on the native medium stiff or stiffer silt, or 0.50 for foundations placed on a minimum 1-foot thickness of compacted crushed rock. The passive earth pressure and friction components may be combined provided the passive component does not exceed two-thirds of the total. The passive earth pressure value is based on the assumptions that the adjacent grade is level and static groundwater remains below the base of the footing throughout the year. The top 1 foot of soil should be neglected when calculating passive lateral earth pressures, unless the adjacent area is covered with pavement. The lateral resistance values include a safety factor of approximately 1.5. 7.2. Footing Drains Because of potential for near-surface water from uphill sources to be present during wet times of the year, we recommend that perimeter footing drains be installed around the buildings at the base of exterior wall footings. The perimeter drains should be provided with cleanouts and should consist of at least 4-inch-diameter perforated pipe placed on a 3-inch bed of, and, surrounded by 6 inches of drainage material enclosed in a non-woven geotextile fabric such as Mirafi 14ON (or approved equivalent)to prevent fine soil from migrating into the drain material. We recommend that the drainpipe consist of either heavy- wall solid pipe (SDR-35 PVC or equal) or rigid corrugated smooth interior polyethylene pipe (ADS N-12 or equal). We recommend against using flexible tubing for footing drainpipes. Where permanent below-grade GEOENGINEERS November2O,2019 9 Page 14 File No.6748-003-00 walls are cast against temporary shoring,the wall drainage should be connected to the footing drain. The perimeter drains should be sloped to drain by gravity,if practicable,to a suitable discharge point, preferably a storm drain.We recommend that the cleanouts be covered and be placed in flush-mounted utility boxes. Water collected in roof downspout lines must not be routed to the footing drain lines. 7.3. Construction Considerations Immediately prior to placing concrete,all debris and loose soils that accumulated in the footing excavations during forming and steel placement must be removed. Debris or loose soils not removed from the footing excavations will result in increased settlement. We recommend that all completed footing excavations be observed by a representative of our firm prior to placing reinforcing steel and structural concrete. Our representative will confirm that the bearing surface has been prepared in a manner consistent with our recommendations and that the subsurface conditions are as expected. 7.4. Slab-on-Grade Floors 7.4.1.Subgrade Preparation The exposed subgrade should be evaluated after site grading is complete. Proof-rolling with heavy, rubber-tired construction equipment should be used for this purpose during dry weather and if access for this equipment is practical. Probing should be used to evaluate the subgrade during periods of wet weather or if access is not feasible for construction equipment.The exposed soil should be firm and unyielding and without significant groundwater. Disturbed areas should be recompacted if possible or removed and replaced with compacted structural fill. 7.4.2.Design Parameters Conventional slabs may be supported on-grade,provided the subgrade soils are prepared as recommended in Section 7.4.1 above. We recommend that the slab be founded on either undisturbed medium stiff or stiffer silt or on structural fill placed over this material. For slabs designed as a beam on an elastic foundation, a modulus of subgrade reaction of 125 pounds per cubic inch (pci) may be used for subgrade soils prepared as recommended. A minimum 6-inch-thick layer of crushed rock Aggregate Base material should be placed over the prepared subgrade as a capillary break. Aggregate Base material placed directly below the slab should be 3/4-inch maximum particle size or less. Concrete slabs constructed as recommended will likely settle less than 1 inch under static conditions. Concrete slabs that are not supported on ground improved with aggregate piers are susceptible to liquefaction induced settlement. We recommend that concrete slabs be jointed around columns to allow the individual structural elements to settle differentially. Due to the presence of fine-grained soils, moisture should be expected at the subgrade surface. Where moisture vapor emission through the slab must be minimized,a vapor retarding membrane or vapor barrier below the slab should be considered. GEOENGINEERS November20,2019 i Page 15 File No.6748-003-00 8.0 GENERAL STABILITY OF GRADED SLOPES We conducted a general stability analyses to assess global stability of the existing slope at the site and to aid in evaluating the feasibility of the proposed grading plan that might include a two-tiered wall system along the east portion of the site. It is our understanding that site grading plans are being revised to include 2H:1V permanent slopes above and below a single wall and eliminating the initially proposed tier system. Our initial analysis included a single wall configuration. Slope stability analyses were performed using SLOPE/W software, provided by Geo-Slope International Ltd.The program identifies the sliding surface with the lowest factor of safety (FS) for a given set of input parameters, including topography, subsurface conditions, soil properties, and water table elevation and/or pore water pressure. Graphical results of the slope stability analyses are included in Appendix B. The stability of a given failure surface is reported as a FS, which is the ratio of resisting forces to driving forces.Generally,a FS greater than 1.0 indicates that the resisting forces are greater than the driving forces and the slope should be stable. FS less than 1.0 indicate that the driving forces are greater than resisting forces and a landslide could occur.A FS of between 1.3 and 1.5 is generally considered suitable for slopes under static(non-seismic)conditions. Based on our experience, a static FS of 1.3 is a suitable minimum FS for repair of unstable slopes, particularly where critical structures are not involved.Slopes that are expected to remain stable under dynamic conditions (earthquake loads) should be designed to maintain a FS of at least 1.1 under seismic conditions. All stability analyses for this study were conducted for static (non- seismic) conditions. Slope geometry was provided to us by 3J based on potential site grading and proposed wall sections being considered at the site. Our stability analysis included various sections along the proposed wall profile, and a global stability cross section running through the middle of the site (northeast to southwest). Our model of the subsurface conditions consists of a medium stiff silt/clay with a unit weight of 110 pcf , a friction angle of 28 degrees, and a cohesion of 100 psf. Soil parameters were developed through a combination of laboratory testing, our experience with similar materials. Figure B-1 presents the failure surface and a FS of approximately 2.8 during analysis of the global stability analysis (existing conditions) a section of the site.The proposed site grading does not present a high risk to the existing stability of the slope. Stability analysis were also conducted for various wall sections in the southeast corner of the site. Figures B-2 and B-3 present the results of the failure surfaces and factor of safety ranging from approximately 1.0 to 1.1 for proposed two-tiered wall sections. This indicates that wall design will require deeper extension of reinforcement to provide a higher level of stability. The relatively low factor of safety also indicates that the temporary support condition during construction may not be adequate and will require the wall designer to consider special construction methods depending on the final wall configuration. The results summarized in this report are not for a specific wall type or system and are intended as a general characterization of proposed wall configurations. The wall designer should account not only for the local stability of the wall system being designed but also for designing a wall system that will provide a sufficient global stability of the overall graded site and wall configuration. Our analyses are not a part of final wall design and separate analyses by the wall designer should be conducted as a part of their design. GEOENGINEERS November20,2019 I Page 16 File No.6748-003 00 9.0 EXCAVATION SUPPORT AND WALL OPTIONS Based on discussions with the project team, a variety of wall types are being considered as a result of proposed height and space restrictions along the east (uphill) portion of the site. Tied-back or restrained wall systems may be cost prohibitive in a tiered configuration and constructing tiered walls as reinforced earth walls with counterfort and panel facing or with segmented blocks may be impractical with limited space. Wall options discussed with the project team include restrained walls such as soil nail or tied-back walls, tiered lock and load or gravity block walls, hilfiker retaining walls, and permanent cut slopes or a combination of graded slopes and a single-height wall. 9.1. Excavation Considerations Based on the material encountered in our subsurface explorations, it is our opinion that conventional earthmoving equipment in proper working condition should be capable of making necessary general excavations. The earthwork contractor should be responsible for reviewing this report, including the boring logs, providing their own assessments, and providing equipment and methods needed to excavate the site soils while protecting subgrades. 9.2. Temporary Cut Slopes For planning purposes,temporary unsupported cut slopes more than 4 feet high may be inclined at 1H:1V maximum steepness within the medium stiff or stiffer silt soils. If significant seepage is present on the cut face then the cut slopes may have to be flattened. However, temporary cuts should be discussed with the geotechnical engineer during final design development to evaluate suitable cut slope inclinations for the various portions of the excavation. The above guidelines assume that surface loads such as traffic, construction equipment, stockpiles or building supplies will be kept away from the top of the cut slopes a sufficient distance so that the stability of the excavation is not affected. We recommend that this distance be at least 5 feet from the top of the cut for temporary cuts made at 1H:1V or flatter and less than 10 feet high, and no closer than a distance equal to one half the height of the slope for cuts more than 10 feet high. Temporary cut slopes should be planned such that they do not encroach on a 1H:1V influence line projected down from the edges of nearby or planned foundation elements. New footings planned at or near existing grades, and in temporary cut slope areas for the lower level, should extend through wall backfill and be embedded in native soils. The stability and safety of cut slopes depend on a number of factors, including: ■ The type and density of the soil. • The presence and amount of any seepage. ■ Depth of cut. • Proximity and magnitude of the cut to any surcharge loads, such as stockpiled material,traffic loads or structures. ■ Duration of the open excavation. GEOENGINEERS November20,2019 i Page 17 File No.6748-003-00 auwruiKfaxeurateina++a.ixa ' .. , — .... .. — ,. - • Care and methods used by the contractor. We recommend that stability of the temporary slopes used for construction be the responsibility of the contractor,since the contractor is in control of the construction operation and is continuously at the site to observe the nature and condition of the subsurface. If groundwater seepage is encountered within the excavation slopes, the cut slope inclination may have to be flatter than 1.5H:1V. However, appropriate inclinations will ultimately depend on the actual soil and groundwater seepage conditions exposed in the cuts at the time of construction. It is the responsibility of the contractor to ensure that the excavation is properly sloped or braced for worker protection, in accordance with applicable guidelines. To assist with this effort,we make the following recommendations regarding temporary excavation slopes: • Protect the slope from erosion with plastic sheeting for the duration of the excavation to minimize surface erosion and raveling. of Limit the maximum duration of the open excavation to the shortest time period possible. is Place no surcharge loads (equipment, materials, etc.)within 10 feet of the top of the slope. More restrictive requirements may apply depending on specific site conditions, which should be continuously assessed by the contractor. If temporary sloping is not feasible based on site spatial constraints, excavations could be supported by internally braced shoring systems, such as a trench box or other temporary shoring. There are a variety of options available. We recommend that the contractor be responsible for selecting the type of shoring system to apply. 9.3. Permanent Slopes If the width of the entrance can be reduced or shifted to the west in the southwest corner of the site, permanent slopes may be an option in place of retaining walls or in combination with a shorter retaining wall below a cut slope. Permanent cut or fill slopes should not exceed a gradient of 2H:1V. Where access for landscape maintenance is desired, we recommend a maximum gradient of 3H:1V. Fill slopes should be overbuilt by at least 12 inches and trimmed back to the required slope to maintain a firm face. To reduce erosion, newly constructed slopes should be planted or hydroseeded shortly after completion of grading. Until the vegetation is established,some sloughing and raveling of the slopes should be expected. This may necessitate localized repairs and reseeding. Temporary covering, such as clear heavy plastic sheeting,jute fabric or erosion control blankets (such as American Excelsior Curlex 1 or North American Green SC15O) could be used to protect the slopes during periods of rainfall. 9.3.1.Slope Drainage If seepage is encountered at the face of permanent or temporary slopes, it will be necessary to flatten the slopes or install a subdrain to collect the water. We should be contacted to evaluate such conditions on a case-by-case basis. GEOENGINEERS November20,2019 s Page 18 File No.6748-003-00 9.4. Retaining Walls 9.4.1.Concrete Retaining Walls Retaining structures free to rotate slightly around the base should be designed for active earth pressures using an equivalent fluid unit weight(efp)of 40 pcf when the ground surface extends level behind the wall equal to a distance of at least twice the height of the wall,and 65 pcf for an inclined slope of 2H:1V above the wall. For lesser slopes between flat and 2H:1V, the efp can be linearly interpolated between the recommended values. The efp value is based on the following assumptions. • The walls will not be restrained against rotation when the backfill is placed. • Walls are 12 feet or less in total wall support height. ott The backfill within 2 feet of the wall consists of free-draining granular materials. • Grades above the top of the walls are no steeper than a 2H:1V slope. at Total wall heights are determined based on a level front slope from the base of the wall. • Hydrostatic pressures do not develop, and drainage will be provided behind the wall. Seismically induced lateral forces on permanent below-grade building walls can be calculated using a dynamic force equal to 9H psf, where H is the wall height. This seismic force should be applied with the centroid located at 0.6H from the wall base. These values assume that the wall is vertical and unrestrained and the backfill behind the wall is horizontal. For site retaining walls, seismic lateral earth pressures should be computed as a part of retaining wall design using the Mononobe-Okabe equation or another method appropriate to the selected wall system. Retaining walls, including foundation walls that are restrained against rotation during backfilling, should be designed for an at-rest equivalent fluid unit weight of 58 pcf when the ground surface extends level behind the wall equal to a distance of at least twice the height of the wall,and 80 pcf for an inclined slope of 2H:1V above the wall. For lesser slopes between flat and 2H:1V,the efp can be linearly interpolated between the recommended values. Surcharge loads applied closer than one-half of the wall height should be considered as uniformly distributed horizontal pressures equal to one-third of the distributed vertical surcharge pressure. Footings for retaining walls should be designed as recommended for shallow foundations. Backfill should be placed and compacted as recommended for structural fill. Re-evaluation of our recommendations will be required if the retaining wall design criteria for the project vary from these assumptions. We recommend that GeoEngineers be retained to review the retaining wall design to confirm that it meets the requirements in our report. The retaining wall designer should perform global stability analysis of the proposed wall. 9.4.2.Mechanically Stabilized Earth(MSE)Walls MSE wall design, including determination of bearing resistance values, should be based on the soil parameters presented in Table 3. GEOENGINEERS November20,2019 I Page 19 File No.6748-003 00 TABLE 3. MSE WALL DESIGN PARAMETERS A Material Unit Weight,y Friction Angle, Cohesion,c (pcf) (degrees) (psf) Reinforced Zone Fill 130 38 0 Retained Soil (Native or New Fill) 110 28 100 Foundation Soil 110 28 100 The reinforced zone behind the MSE wall should be backfilled with retaining wall backfill as specified in Section 6.7 of this report. The retained and foundation soil zones should consist of undisturbed in-situ native soil or new engineered fill. Where traffic loads are located within a horizontal distance from the top of the wall equal to one-half the wall height, the lateral earth pressure should be increased by a surcharge load equal to 2 feet of soil (assuming a soil density of 125 pcf). For overturning and sliding analysis, this surcharge should only be applied behind the reinforced soil zone. The long-term design strength of any geotextile required for the wall should be equal to or greater than the maximum tensile force. Unless manufacturer specific reduction factors are applied during the design, the ultimate tensile strength of the geosynthetic selected should be reduced by a factor of 7 to account for creep, installation damage, and chemical and biological degradation. The foundation excavations for MSE walls should extend a minimum of 18 inches below lowest adjacent grade and should be lined with a minimum 6-inch-thick layer of compacted, imported granular material. A minimum 4-inch-diameter, perforated collector pipe should be embedded at the base of the wall and should discharge at an appropriate location away from the base of the wall. The discharge pipe(s) should not be tied directly into stormwater drain systems, unless measures are taken to prevent backflow into the wall drainage system. Settlements of up to 1 percent of the wall height commonly occur immediately adjacent to the wall, as the wall rotates and develops active lateral earth pressures. Consequently, we recommend that construction of flat work adjacent to retaining walls be postponed at least 4 weeks after backfilling of the wall, unless survey data indicate that settlement is complete prior to that time. 9.4.3.Proprietary Wall Systems Proprietary wall systems such as Hilfiker Walls or Reinforced Earth Company (RECO) Walls, or specialty systems such as those provided by Geostabilization International (GSI) may also be suitable for support of proposed site grades. Wall design for proprietary systems is generally provided by the wall supplier/contractor. Proprietary wall system design should also be required to include global stability analyses as part of their design and not defer that portion of design to the project design team. 9.4.4.Soil Nail Walls On-site subsurface conditions are generally suitable for construction of soil nail walls. A soil nail wall system will likely need vertical elements as part of structural design. The need for vertical elements or other measures should be evaluated by the wall designer during design of the shoring system. GEOENGINEERS November 20,2019 1 Page 20 File No.8748-003-00 Soil nail wall systems consist of drilling and grouting rows of steel bars or"nails" behind an excavation face as it is excavated and then covering the face with reinforced shotcrete. Placement of soil nails reinforces the soils located behind the wall face and creates a surface and connection point for a wall face. Soil nail wall design should include a global stability analysis for the final graded configuration and not be deferred to the project team. 9.5. Seismic Design Parameters provided in Table 4 are based on the conditions encountered during our subsurface exploration program and the procedure outlined in the 2015 International Building Code (IBC). Some jurisdictions are beginning to adopt the 2018 IBC, which references the 2016 Minimum Design Loads for Buildings and Other Structures(American Society of Civil Engineers[ASCE] 7-16). Per ASCE 7-16 Section 11.4.8,a ground motion hazard analysis or site-specific response analysis is required to determine the design ground motions for structures on Site Class D sites with Si greater than or equal to 0.2g. For this project,the site is classified as Site Class D with an Si value of 0.393g;therefore,the provision of 11.4.8 applies. Alternatively, the parameters listed in Table 5 below may be used to determine the design ground motions if Exception 2 of Section 11.4.8 of ASCE 7-16 is used. Using this exception, the seismic response coefficient (Cs) is determined by Equation (Eq.) (12.8-2) for values of T <_ 1.5Ts, and taken as equal to 1.5 times the value computed in accordance with either Eq. (12.8-3) for IL >_ T > 1.5T5 or Eq. (12.8-4) for T > TL, where T represents the fundamental period of the structure and Ts=0.763 sec. If requested, we can complete a site-specific seismic response analysis which might provide somewhat reduced seismic demands from the parameters in Table 5 and the requirements for using Exception 2 of Section 11.4.8 in ASCE 7-16. The reduced values will likely not be significant enough to warrant the additional cost of further evaluation if designing to the 2018 IBC. We recommend seismic design be performed using the values noted in Table 4 or Table 5 below depending on the version of the IBC used for design. TABLE 4. MAPPED 2015 IBC SEISMIC DESIGN PARAMETERS Parameter Recommended Value' Site Class D Mapped Spectral Response Acceleration at Short Period (Ss) 0.956 g Mapped Spectral Response Acceleration at 1 Second Period (Si) 0.42 g Site Modified Peak Ground Acceleration(PGAM) 0.453 g Site Amplification Factor at 0.2 second period (Fe) 1.117 Site Amplification Factor at 1.0 second period (Fv) 1.58 Design Spectral Acceleration at 0.2 second period (Sos) 0.712 g Design Spectral Acceleration at 1.0 second period (Soi) 0.442 g Note: =Parameters developed based on Latitude 45.410937° and Longitude-122.792869°using the ATC Hazards online tool. GEOENGINEERS November 20,2019 I Page 21 File No.6748-003.00 TABLE 5. MAPPED 2018 IBC SEISMIC DESIGN PARAMETERS Parameter Recommended Valuel,2 Site Class D Mapped Spectral Response Acceleration at Short Period(Ss) 0.846 g Mapped Spectral Response Acceleration at 1 Second Period (Si) 0.393 g Site Modified Peak Ground Acceleration(PGAM) 0.469 g Site Amplification Factor at 0.2 second period (Fa) 1.161 Site Amplification Factor at 1.0 second period (Fv) 1.907 Design Spectral Acceleration at 0.2 second period (Sos) 0.655 g Design Spectral Acceleration at 1.0 second period (Sol) 0.500 g Note: 1 Parameters developed based on Latitude 45.410937°and Longitude-122.792869°using the ATC Hazards online tool. 2 These values are only valid if the structural engineer utilizes Exception 2 of Section 11.4.8(ASCE 7-16). 9.5.1.Liquefaction Potential Liquefaction is a phenomenon caused by a rapid increase in pore water pressure that reduces the effective stress between soil particles to near zero. The excessive buildup of pore water pressure results in the sudden loss of shear strength in a soil. Granular soil, which relies on interparticle friction for strength, is susceptible to liquefaction until the excess pore pressures can dissipate.Sand boils and flows observed at the ground surface after an earthquake are the result of excess pore pressures dissipating upwards, carrying soil particles with the draining water. In general, loose, saturated sand soil with low silt and clay contents is the most susceptible to liquefaction. Low plasticity, silty sand may be moderately susceptible to liquefaction under relatively higher levels of ground shaking. As discussed in Section 3.3.3 of this report, groundwater was not encountered during drilling within the upper 25 feet bgs at the site and is not anticipated within the upper 100 feet bgs. The site soils below the groundwater table on site are expected to consist of CRBG and are not prone to liquefaction during the design level earthquake. Accordingly, lateral spreading or liquefaction induced deformations are not expected. 10.0 PAVEMENT RECOMMENDATIONS 10.1. Dynamic Cone Penetrometer(DCP)Testing We conducted DCP tests in general accordance with ASTM D 6951 to estimate the subgrade resilient modulus(MR)at each test location as shown in Figure 2.We recorded penetration depth of the cone versus hammer blow count and terminated testing at depths of approximately 44 inches below the existing ground surface. We plotted depth of penetration versus blow count and visually assessed regions where slopes of the data were relatively constant using equation from the Oregon Department of Transportation (ODOT) Pavement Design Guide to estimate the moduli using a conversion coefficient, Cr= 0.35.Table 6 lists our estimate of the subgrade resilient modulus at each test location based on data obtained in the upper 18 inches below the upper topsoil. Field data are summarized in Figures A-13 and A-14. GEoENGiNEERs November 20,2019 ? Page 22 File No.6748 003-00 TABLE 6.ESTIMATED SUBGRADE RESILIENT MODULI BASED ON DCP TESTING Boring Number Estimated Resilient Modulus (psi) DCP-1 5,600 DCP-2 7,600 10.2. Drainage Long-term performance of pavements is influenced significantly by drainage conditions beneath the pavement section. Positive drainage can be accomplished by crowning the subgrade with a minimum 2 percent cross slope and establishing grades to promote drainage. 10.3. Asphalt Concrete(AC) Pavement Sections Pavement subgrades should be prepared in accordance with Section 6.0 of this report. Our pavement recommendations assume that traffic at the site will consist of occasional truck traffic and passenger cars. We do not have specific information on the frequency and type of vehicles that will use the area; however, we have based our design analysis on traffic consisting of two heavy trucks per day to account for delivery- and service-type vehicles and passenger car traffic for the heavy-duty pavement sections, and passenger car traffic only for the light-duty pavement sections. Our pavement recommendations are based on the following assumptions: ■ The on-site soil subgrade below proposed fill placed to raise site grades or below aggregate base sections has been prepared as described in Section 6.1 of this report, and observations indicate that subgrade is in a firm and unyielding condition. ■ A resilient modulus of 20,000 psi was estimated for base rock prepared and compacted as recommended. a A resilient modulus of 5,600 psi was estimated for firm in-place soils or structural fill placed on firm native soils for the proposed parking lot. a Initial and terminal serviceability indices of 4.2 and 2.5, respectively. • Reliability and standard deviations of 85 percent and 0.45, respectively. a Structural coefficients of 0.41 and 0.10 for the asphalt and base rock, respectively. ■ A 20-year design life. If any of the noted assumptions vary from project design use, our office should be contacted with the appropriate information so that the pavement designs can be revised or confirmed adequate. The recommended minimum pavement sections are provided in Table 7 below. GEOENGINEERS November 20,2019 I Page 23 File No.6748-003-00 TABLE 7. RECOMMENDED AC PAVEMENT SECTIONS Minimum Asphalt Minimum Aggregate Section Thickness Base Thickness (inches) (inches) Light Duty 3 6 (general automobile parking areas) Heavy Duty (drive aisles and heavy delivery areas) 3.5 8 The aggregate base course should conform to Section 6.7.4 of this report and be compacted to at least 95 percent of the maximum dry density (MDD) determined in accordance with AASHTO T-180/ASTM Test Method D 1557. The AC pavement should conform to Section 00745 of the most current edition of the ODOT Standard Specifications for Highway Construction. The Job Mix Formula should meet the requirements for a 1/2-inch Dense Graded Level 2 Mix. The AC should be PG 64-22 grade meeting the ODOT Standard Specifications for Asphalt Materials. AC pavement should be compacted to 91.0 percent at Maximum Theoretical Unit Weight(Rice Gravity) of AASHTO T-209. The recommended pavement sections assume that final improvements surrounding the pavement will be designed and constructed such that stormwater or excess irrigation water from landscape areas does not infiltrate below the pavement section into the crushed base. 10.4. Pervious Pavement Sections Pervious pavements are typically incorporated into development projects in order to capture stormwater from developed (impervious) areas developed by paving or structures and allowing it to seep into the ground.The pavement structure includes a layer of porous asphalt over open-graded base rock over open- graded subbase over native subgrade. The open-graded base rock and subbase provide stormwater storage for given design level events and must support design traffic levels as well. Based on our discussions with the project team, pervious pavements are being considered for sidewalks adjacent to OR 99W. Pavement subgrades should be prepared in accordance with Section 6.0 of this report. Our pavement recommendations assume that traffic on pervious pavements will consist solely of pedestrian traffic. General infiltration of a porous pavement section will be limited by the lower infiltration capacity of silt soils on site. Proposed porous asphalt pavement section is provided in Table 8 below. TABLE 8. PERMEABLE ASPHALT PAVEMENT SECTIONS Porous Asphalt Open Graded Base Open-Graded Subbase Rock(Choker Rock) Pavement Thickness Thickness Thickness (inches) (inches) (inches) Sidewalks (Pedestrian traffic only) 2.5 3.0 5.0 GEOENGINEERS November 20,2019 I Page 24 File No.6748 003-00 The porous AC pavement should conform to Section 00743 of the most current edition of the ODOT Standard Specifications for Highway Construction. The minimum thickness provided above are based on structural calculations; the civil engineer should evaluate the minimum thicknesses for storage capacity. We recommend a geotextile fabric be placed as a barrier between the prepared subgrade and the imported base rock section to minimize migration of fines and provide additional support to the overlying pavement structure. We recommend that the drainage type geotextile under permeable pavements meet criteria in Table 02320-1 for "Drainage Geotextile, Type 2," of the ODOT Standard Specifications for Highway Construction. 10.5. Pervious Pavement Construction Considerations The long-term performance of pervious pavements is reliant upon proper design, installation and long-term maintenance. As a result, we recommend that the contractor supplying and installing the pervious pavement has at least three years successful experience installing pervious pavements. In addition,at least one test panel should be constructed and reviewed prior to installation of the entire area of pervious pavements, or a project site should be visited where successful installation and performance of a project constructed by the supplier can be observed by the project team. Subgrade beneath pervious pavements is typically graded to be relatively flat(less than 3 percent slope)to prevent uneven ponding of water within the storage aggregate.Subgrade beneath the pervious pavement section should be sloped sufficiently to drain away from standard AC sections or otherwise routed to suitable drainage, so as not to allow infiltrating water to migrate into the standard AC section base rock that might compromise performance. During preparation,subgrade should be cut from the edges, not trafficked by heavy machinery,and remain in an uncompacted state. Irrespective,the subgrade may be proof-rolled with a fully loaded dump truck or water truck to identify soft or pumping areas. Soft areas, or areas that are excessively compacted by construction equipment,should be removed and replaced by additional storage aggregate. Landscaping areas that are adjacent to pervious pavements should be designed to prevent run-off from washing over the pavements, otherwise sediment can clog the pervious materials. During and after construction, stockpiles of landscaping materials (i.e., topsoil, bark dust, etc.) and construction materials (i.e., sand, gravel, etc.)should not be placed on the pervious pavements. Extreme care should be taken to prevent trafficking of muddy construction equipment over pervious pavements. Regular maintenance of porous pavements should consist of periodic cleaning by vacuuming and flushing with high volume water at low pressures. We note that sweeping is not an effective method for cleaning of pervious pavements. In fact, available information indicates that sweeping may decrease the permeability of pervious pavements by clogging pores. In addition,blowing sands commonly occurring in the project area should be regularly washed off of pervious pavements to maintain intended performance. 11.0 LIMITATIONS We have prepared this report for the exclusive use of J.T.Smith Companies,3J and their authorized agents and/or regulatory agencies for the proposed Pacific Ridge Apartment Development located on SW Pacific Highway(OR 99W) in Tigard, Oregon. GEOENGINEERS November20,2019 I Page 25 File No.6748-003-00 This report is not intended for use by others,and the information contained herein is not applicable to other sites. No other party may rely on the product of our services unless we agree in advance and in writing to such reliance. Within the limitations of scope,schedule,and budget, our services have been executed in accordance with generally accepted practices in the area at the time this report was prepared. No warranty or other conditions, express or implied, should be understood. Please refer to Appendix C titled "Report Limitations and Guidelines for Use" for additional information pertaining to use of this report. 12.0 REFERENCES Burns, W.J., I.P. Madin and K.A. Mickelson. 2011. Landslide inventory maps of the Beaverton quadrangle, Washington County, Oregon: Oregon Department of Geology and Mineral Industries, Interpretive Map Series IMS-34, 5 plates, 1:8,000 scale. Burns, W.J., K.A. Mickelson and I.P. Madin. 2016. Landslide susceptibility overview map of Oregon: Oregon Department of Geology and Mineral Industries Open-File Report 0-16-02, 48 p. 1 pl., 1:750,000 scale. International Code Council. 2014. 2014 Oregon Structural Specialty Code. International Code Council. 2015. 2015 International Building Code. International Code Council. 2018. 2018 International Building Code. Madin, I.P. 1990. Earthquake Hazard Geology Maps of the Portland Metropolitan Area, Oregon: DOGAMI Open File Report 0-90-2, 14 pages, 8 plates, 1:24,000 scale. Occupational Safety and Health Administration (OSHA). Technical Manual Section V: Chapter 2, Excavations: Hazard Recognition in Trenching and Shoring: htto://www.osha.gov/dts/ostajotm/otm v/otm v 2.html. Snyder, D.T., 2008, Estimated Depth to Ground Water and Configuration of the Water Table in the Portland, Oregon Area: U.S. Geological Survey, Scientific Investigations Report 2008-5059, 52p. 3 plates. GEOENGINEERS� November 20,2019 Page 26 nie No.6748-003-00 O -L") cc W W Z l7 Z W O W 0 .01,y444. 7 srcdxaHeB e..x y fi, � s � � sp. 4�- ,y '" tit, ...mfia ��r p e �e ''',, r „ P,i g Y e e sw Albert;.SA > a� ' SW 44'es SE pr cf� tame Crtfit PAPA 47M , J° „ i4r444 Sy 4 tY SYk`a'3ru St. i ' � t..*vc trr SWHaltpwta �' <v+ta� t Ws 3, `a ', `S' ` e a9N f.m rtr;yve.r,it 'e * ` �. Se.' Aca»npi,;s ' S *h a Ji C a,N a `' r`. ski 5 i �. ft . SW Comde St•,a.., SW GtovrUr St , .. SW^ Mttycnatd 5a ,... 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Ae*t 64y(di 64444 �'`. ` nnti DI „ t'e=1k rt , Sxrser EOYrttM t+xrn,* eriG at i, A }w.1arUr, 4 ,p Sa*m.tWdtwitp trar ?tiiurvk 'l F kA .+ taw*nwe' N3, g 7e SA DaMa n>_ e, SW 6.4.41 4rry 646 SW User neyres Rai �4` King City F ,„. 0<+i crr*h c5e*te+ugry , , n a RiaetW t=t-.m a > t" ,. x ti,c.a>t A4nafatp 4uz;E+rwst z 51W Rer,r SC '� ^^tagard Nair Scngryh ES Sir 7 so-wavved/4< s Tub Pr trae �,f��.` v��aeare ,Syt q,tchr,Rd <r sxror.v,r ...i¢ h.,r fi *u* * i .4 x l p le+ Ravi.r*r ¢ ra =, g v it h h}, SVd H,�2*11Yaxtai 8 j m ' °3. <j/ m t a* A*adu*font 6 ye.-' r u>x.*x*w uwrote ram. ,.; .8 cn N o tv , 1 �,� › W i�1 E V'anc0uver .r - ,, ,Cafds «g w forest Grove'. "Portland : ' S 2,000 0 2,000 Oregon City Feet i > M(Minnviiie s Notes: Vicinity Map 1.The locations of all features shown are approximate. m 2.This drawing is for information purposes.It is intended to assist in Pacific Ridge Apartments o showing features discussed in an attached document.GeoEngineers,Inc. . cannot guarantee the accuracy and content of electronic files.The master Tigard, Oregon file is stored by GeoEngineers,Inc.and will serve as the official record of o i this communication.o /� o Figure 1 GEOENGINEERS ! Data Source:Mapbox Open Street Map,2016 -..r CD m Projection:NAD 1983 UTM Zone 10N a a• r. • 1 , 1 V i '.*'.jillr *' / I , , , \_yl 0 is', . ;,...\,, \ , \ , :P-4 --,,,„„ ,...,,, B-3 N\ \\ \°,}. NNip 04 IP " -, \\. ,,i. NNN....\-... it •. N \\\' ,\,\,\ \‘‘‘ •. TP 3 y ilit‘ \ -. ' '• - 410. 4 \ , „ i 1 N i TP-7/-IT-3 '-,it. ,-. . , 414,60 • q'tr\ - ''•% \ '' ', \ 44e -, \,44,..#, 4%11111410%. 0,s � ___.\ _ \ -_, t __, 5° ..A \ i ' -\.. \ 10 4 1 'P17 -t 'S'" 1Ck& ‘4, \ , A \ • 7 , .„ ;t ' TP-1'/DCP-1 TP-2/DaC 2 TP-6/IT_2 , ' -5%IT- r . T P, 1 B-1 \ >. ._,, : .\ \ '2' ' 4 - -.. ,. -,. ,ra _ , . , , , s , \ .,2 _., . , , , , . ,,5 11111111 ....ittr.—mege,.., ..,,.... givingnikikk \ ',,, tJ r^ t __ ttnn 1 1 —� , : ,� 1. ] _..... .-.�(\� . • Z t 3 1 -- -�.,. �► --------- -- -- -- --- ------ ------ - - ---` - \ter----' 0111k in \ A \',. • , _.`, t . i .�r,a c :, Legend ed 4- Boring Number and Approximate Location n ti Icontent //—� I content r•� ' -wpm Inr '1�Y Tact Pit Niimhar anti Annrnvimata I nratinn GEOENGINEERS APPENDIX A Field Explorations and Laboratory Testing APPENDIX A FIELD EXPLORATIONS AND LABORATORY TESTING Field Explorations Soil and groundwater conditions at the site were explored on October 8 and 9, 2019 by completing seven test pits (TP-1 to TP-7) and four borings (B-1 to B-4), three infiltration tests (IT-1 to IT-3) and two dynamic cone penetrometer tests(DCP-1 and DCP-2) at the approximate locations shown in the Site Plan, Figure 2. The test pits were excavated using a tracked excavator, and the borings were advanced using a track- mounted drill rig; both pieces of equipment were owned and operated by Western States Drilling, Inc. The excavation and drilling were continuously monitored by an engineer or engineering geologist from our office who maintained detailed logs of subsurface explorations,visually classified the soil encountered and obtained representative soil samples from the borings. Representative samples from the test pits were collected from the sidewalls at depths above 4 feet bgs, and from the excavation spoil for deeper depths. Representative soil samples were obtained from each boring at approximate 21 -to 5-foot-depth intervals using either: (1)a 1-inch, inside-diameter,standard split spoon sampler; or(2)a 2.4-inch, inside-diameter, split-barrel ring sampler(Dames&Moore[D&M]).The samplers were driven into the soil using a 140-pound hammer, free-falling 30 inches on each blow. The number of blows required to drive the sampler each of three, 6-inch increments of penetration were recorded in the field. The sum of the blow counts for the last two, 6-inch increments of penetration is reported on the boring logs as the ASTM International (ASTM)Test Method D 1556 Standard Penetration Test (SPT) N-value. The approximate N-values for D&M samples were converted to SPT N-values using the Lacroix-Horn Conversion [N(SPT) = (2*N1*W1*H1)/(175*D1*D1*L1), where N1 is the non-standard blowcount,W1 is the hammer weight in pounds (140), H1 is the hammer drop height in inches (30), D1 is the non-standard sampler outside diameter in inches(3.23), and L1 is the length of penetration in inches (12)]. Recovered soil samples were visually classified in the field in general accordance with ASTM D 2488 and the classification chart listed in Key to Exploration Logs, Figure A-1. Logs of the borings are presented in Figures A-2 through A-5 and logs of the test pits are presented in Figures A-6 through A-12. The logs are based on interpretation of the field and laboratory data and indicate the depth at which subsurface materials or their characteristics change, although these changes might actually be gradual. Laboratory Testing Soil samples obtained from the explorations were visually classified in the field and in our laboratory using the Unified Soil Classification System (USCS)and ASTM classification methods.ASTM Test Method D 2488 was used to visually classify the soil samples, while ASTM D 2487 was used to classify the soils based on laboratory tests results. Moisture content tests were performed on selected samples in general accordance with ASTM D 2216, moisture-density tests in general accordance with ASTM D 7263 and fines content tests in general accordance with ASTM D 1140. Two Atterberg limits test were performed in accordance with ASTM D 4318. Results of the laboratory testing are presented in the appropriate exploration logs at the respective sample depths and the Atterberg limits results in Figure A-15 in this appendix. GEOENGINEERS November 20,2019:. Page A-1 File No.6748-003-00 SOIL CLASSIFICATION CHART ADDITIONAL MATERIAL SYMBOLS MAJOR DIVISIONS SYMBOLS TYPICAL SYMBOLS I TYPICAL • GRAPH LETTER DESCRIPTIONS GRAPH LETTER DESCRIPTIONS ovU < CLEAN GRAVELS 0 5O ° GW SAND MIIXXTUREBRAVELS,GRAVEL- AC Asphalt Concrete GRAVEL ) r\ AND 0 0 0 GRAVELLY (LITTLE OR NO FINES) o o c GP POORLY-GRADED GRAVELS, 1\/\//\, CC SOILS o o GRAVEL-SAND MIXTURES '/\/\//\ Cement Concrete COARSE GRAVELS WITH c a GM SILTY GRAVELS,GRAVEL-SAND - GRAINED MORE THAN 50% FINES SILT MIXTURES Crushed Rock/ SOILS OF COARSE CR Quarry Spalls FRACTION RETAINED ON NO.4 SIEVE (APPRECIABLE AMOUNT C GC warms,GRAVEL SAND OF FINES) „/ CLAY MIXTURES J f, J I, J 8 a \„ (, SOD Sod/Forest Duff SW SANDS RADED SANDS,GRAVELLY CLEAN SANDS MORE THAN 50% SAND RETAINED ON (LITTLE OR NO FINES) TS Topsoil Na200SIEVE AND SANDY SP SANDLY GRADED SANDS,GRAVELLY SOILS MORE THAN 50% SANDS WITH SM SILTY SANDS,SAND-SILT MIXTURES OF COARSE FINES Groundwater Contact FRACTION PASSING ON NO.4 SIEVE (APPR E AMOUNT /� SC MXTURE$NDS,SAND-CLAY - Measured groundwater level in exploration, OF FIN OF FINES) l well,or piezometer INORGANIC SILTS,ROCK FLOUR, ML P ETIYCSILTS WITH SLIGHT ITY 7 Measured free product in well or piezometer INORGANIC CLAYS OF LOW TO SILTS AND / MEDIUM PLASTICITY,GRAVELLY CLAYS LIQUID LIMIT /! CL CLAYS,SANDY CLAYS,SILTY CLAYS, Graphic Log Contact FINE LESS THAN 50 !/ LEAN CLAYS GRAINED SOILS ORGANIC SILTS AND ORGANIC SILTY Distinct contact between soil strata OL CLAYS OF LOW PLASTICITY I / Approximate contact between soil strata MORE THAN 50% I PASSING MH NORGANIC SILTS,MICACEOUS OR DIATOMACEOUS SILTY SOILS NO.200 SIEVE Material Description Contact SILTS AND LIQUID LIMIT GREATER CH INORGANIC CLAYS OF HIGH Contact between geologic units CLAYS THAN 50 PLA/d STICITY _ Contact between soil of the same geologic ORGANIC CLAYS AND SILTS OF unit OH MEDIUM TO HIGH PLASTICITY HIGHLY ORGANIC SOILS , """N` PT PEAT,HUMUS,SWAMP SOILS WITH Laboratory Field Tests HIGH ORGANIC CONTENTS Laboratory fines NOTE: Multiple symbols are used to indicate borderline or`dual soil classifications %F Percent gravel Percent g gravel AL Atterberg limits Sampler Symbol Descriptions CA Chemical analysis CP Laboratory compaction test II (I 2.4-inch I.D.split barrel CS Consolidation test M DD Dry density W Standard Penetration Test(SPT) DS Direct shear HA Hydrometer analysis III Shelby tube MC Moisture content I Piston MD Moisture content and dry density Mohs Mohs hardness scale Direct-Push OC Organic content PM Permeability or hydraulic conductivity III Bulk or grab PI Plasticity index PL Point lead test Continuous Coring PP Pocket penetrometer SA Sieve analysis TX Triaxial compression Blowcount is recorded for driven samplers as the number of UC Unconfined compression blows required to advance sampler 12 inches(or distance noted). VS Vane shear See exploration log for hammer weight and drop. Sheen Classification "P"indicates sampler pushed using the weight of the drill rig. NS No Visible Sheen "WOH"indicates sampler pushed using the weight of the SS Slight Sheen hammer. MS Moderate Sheen HS Heavy Sheen NOTE:The reader must refer to the discussion in the report text and the logs of explorations for a proper understanding of subsurface conditions. Descriptions on the logs apply only at the specific exploration locations and at the time the explorations were made;they are not warranted to be representative of subsurface conditions at other locations or times. Keyr to Exploration Logs GEOENGINEERS Figure A-1 IT,...,A7 Mf14 n Start End Total Logged By JLL Drilling Drilled 10/9/2019 10/9/2019 Depth(ft) 26.5 Checked By TNG Driller Western States Method Mud Rotary Surface Elevation(ft) Hammer Autohammer Drilling Geoprobe 7822DT Track Vertical Datum Undetermined Data g p 140(Ibs)/30(in)Drop Equipment Easting(X) 516236.88 System Northing(Y) 50285555.57 Datum WGS84(feet) Groundwater not observed at time of exploration Notes: D&M N-Values reduced using LaCroix-Horn conversion to approximate SPT N-Values HELD DATA E E to MATERIAL > Z J DESCRIPTION REMARKS O O L O N m L O.N fiLl 0 ML Dark brown silt with duff and organic material to - _ organic silt,roots to 10 to 12 inches,occasional _ roots to 2 feet(soft,moist)(topsoil) - ML - Yellow-brown silt,trace fine sand,massive(medium - $ 1 stiff to stiff,moist)(fine-grained flood deposits)x 12 5 72 11 MO Becomes stiff 25 DD=86 pcf _` / 10 6 3 - /�/\ Becomes medium stiff 10 — — 12 4 r b Becomes soft to medium stiff 32 DD=89 pcf 3 - - 0 0 15 X 16 3 5 Becomes soft z U W - - tJ 7 20 %F DD=102 pcf c 13 6 22 65 - MD % CL _ Yellow-brown gray and gray-brown gravelly clay, , / angular weathered basalt gravels in yellow-brown N - / clay matrix(stiff,moist)(decomposed Columbia _ N / River basalt) N 2 S 25 z \/ 24 7 Becomes gray-brown with occasional black and red 13 � / brown staining,strong relict volcanic rock texture, very stiff 0 0 0 0 0 m v Note:See Figure A-1 for explanation of symbols. o Coordinates Data Source:Horizontal approximated based on Google Earth.Vertical approximated based on Google Earth. F 0 Log of Boring B-1 Project: Pacific Ridge Apartments G EO E N G I N E S RS Project Location: Tigard,Oregon Figure A-2 Project Number: 6748-003-00 Sheet 1 of 1 Start Total 25 25 Logged By JLL Driller Western States Drilling Mud Rotary Drilled 10/9/2019 10/9/2019 Depth(ft) Checked By TNG Method Surface Elevation(ft) Undetermined Hammer Autohammer Drilling Geoprobe 7822DT Track Vertical Datum J . Data 140(Ibs)/30(in)Drop Equipment Easting(X) 576248.14 System WGS84(feet) Groundwater not observed at time of exploration Northing(Y) 5028600.55 Datum Notes: D&M N-Values reduced using LaCroix-Horn conversion to approximate SPT N-Values ` FIELD DATA t i o MATERIAL REMARKS 0 w 0 J u DESCRIPTION dUUo m N \ w by ., c,_` c c .@ L O (n U Q = N yN Oa. N U 30 m N N O OW O G m m U t F co � (..1 (20 §U iiO 0 ML Dark brown organic silt to silt with organic matter, _ roots and duff(soft,moist)(topsoil) _ ML _ Brown with light gray mottling silt,trace sand,massive _ (very stiff,moist)(fine-grained flood deposits) 1 / 12 16 1 21 X MC 5 \ 14 15 2 +V/y� Becomes yellow-brown,stiff X 12 19 3 _ 1 Becomes very stiff 10 X 14 11 4 Becomes brown,occasional subrounded fine H _ gravel-sized rock fragments,stiff _ ML Gray with brown mottling,occasional black streaking _ silt with fine to medium sand,strong relict volcanic _ 0 rock texture(very stiff,moist)(decomposed Columbia River basalt) _ 15 iV/y\ /X16 26 5 - z 6 U O - W 20 _ixi 65/11" 6 "ML/GM Gray to brown and black sandy silt with gravel-sized weathered to decomposed basalt fragments to -- silty gravel and angular basalt gravel in sandy silt matrix(hard and very dense,moist) vi iii - 0 u 25 �\ 0 n`�/2J `li 7 _ S z 0 i, 0 m m Note:See Figure A-1 for explanation of symbols. o Coordinates Data Source:Horizontal approximated based on Google Earth.Vertical approximated based on Google Earth. Log of Boring B•2 Project: Pacific Ridge Apartments �a E®ENGINEER 5 Project Location: Tigard,Oregon Figure A-3 Project Number: 6748-003-00 Sheet 1 of 1 Start E0d Total Logged By JLL Drilling Drilled 10/9/2019 10/9/2019 Depth(ft) 17.25 Checked By TNG Driller Western States Method Mud Rotary Surface Elevation(ft) Hammer Autohammer Drilling Geoprobe 7822DTTrack Vertical Datum Undetermined Data g p 140(Ibs)/30(in)Drop Equipment Fasting(X) 516242.93Syst Northing(Y) 5028673.67 uat m WGS84(feet) Groundwater not observed at time of exploration Notes: D&M N-Values reduced using LaCroix-Horn conversion to approximate SPT N-Values FIELD DATANI E °° MATERIAL CD °' ° z i co DESCRIPTION REMARKS (0 r > O 0 U C .0 O.!— 5 C C N ti N N p m E R O w t 2 S W CC CO U (1)H C7 0 0 8 E U 0 ML Dark brown sift with organic material,roots and duff - _ (soft,moist)(topsoil) _ _ ML - Light brown silt,occasional gray discoloration,trace _ fine sand and occasional roots(medium stiff, J 14 13 3 _ moist)(fine-grained flood deposits) _ i7 LL=36;PL=24;PI=12 X AL 5 ` / 10 11 2 —— ABecomes stiff _I 14 22 3 - - 20 DD=92 pcf MD Becomes brown,trace to occasional fine gravel sized _ rock fragments,very stiff _ 10 x — — 16 18 4 - Becomes dark brown,occasional fine to medium sand Gc Black and brown clayey gravel,angular basalt fragments in brown clay matrix(very dense,moist) _ (decomposed Columbia River basalt) 3 - - _ z 15—TlIl 3 75/5" 5 — — o' o - - a 0 0/2" , 6 / _ 0 w C u 0 a 0 z 0 F 0 0 Note:See Figure A-1 for explanation of symbols. 0` Coordinates Data Source:Horizontal approximated based on Goode Earth.Vertical approximated based on Google Earth. Log of Boring B-3 Fl Project: Pacific Ridge Apartments : G EO E N G I N E E R Sii7 Project Location: Tigard,Oregon o Project Number: 6748-003-00 Figure 4 Sheet 1 off 1 . End Toil 25.5 Logged By JLL Driller Western States Drilling Mud Rotary Drilled 10/9/2019 10/9/2019 Depth(ft) Checked By TNG Method Surface Elevation(ft) Hammer Autohammer Drilling Geoprobe 7822DTTrack l Vertical Datum Undetermined Data 140(lbs)/30(in)Drop Equipment Easting(X) 516198.91 System WGS84(feet) Groundwater not observed at time of exploration Northing(Y) 5028681.51 Datum Notes: D&M N-Values reduced using LaCroix-Horn conversion to approximate SPT N-Values v FIELD DATA E o MATERIAL M REMARKS fn z J 0 DESCRIPTION a, O• — To N v N tip U @ L >O N , O- a.. N N y N >• a N V 33 co. E N ° O N 92 W o cc m U (O - (3 (0 U 2 U LE Co o OL Dark brown organic silt,many fine roots and duff(soft, _ moist)(topsoil) ML Yellow-brown with gray discoloration silt,trace fine - - sand,massive(stiff,moist)(fine-grained flood - I14 11 D deposits) 25 DD=85 pcf 5 \ / 16 10 2 X Becomes yellow brown 16 10 3 26 OD=92 pcf MC — 10 14 7 4 Trace to occasional fine sand,medium stiff 3 u 0 15 1 18 4 5 Becomes soft to medium stiff a' _ _ z i O _ U' m 20 X 18 13 6 Becomes brown,occasional red-brown mottling,stiff, z grades to gray 0 0 X 7 r 25 Becomes very dark gray,occasional subangular gravel-size basalt fragments,medium stiff r 0 is g 0 0 F Note:See Figure A-1 for explanation of symbols. 8 Coordinates Data Source:Horizontal approximated based on Goode Earth.Vertical approximated based on Goode Earth. o ♦ Log of Boring B-4 a Project: Pacific Ridge Apartments G EO E N G I N E E RS r Project Location: Tigard,Oregon Figure A 5 Project Number: 6748-003-00 Sheet 1 of 1 Date 10/9/2019 Total 8 Logged By NPVW Excavator Western States Groundwater not observed Excavated Depth(ft) Checked By TNG Equipment Youmen PC40 Excavator Caving not observed Surface Elevation(ft) Undetermined Easting(X) 516172.9 Coordinate System Vertical Datum Northing(Y) 5028581.8 Horizontal Datum WGS84(f ) SAMPLE ti a) o o MATERIAL o w Z J CO DESCRIPTION o REMARKS bD N M V L C C L d j C C j O. 7 N N .3 O' Ul N N O N a.C N W 0 F� (n 1— CDU U 2 O ii 8 ML Dark brown silt with organic matter,roots and duff(soft,moist) .1— _ (topsoil) - 2 I I 5-i / PP=0.25 tsf at 1 z feet CL Brown lean clay with trace fine sand(medium stiff to stiff,moist) ( 3— _ (fine-grained flood deposits) - — PP=2.5 tsf at 3 feet 42 - 21 AL(LL=43;PL=23;PI=22) y Mc / PP=4.0 tsf at 4 feet ! fj 5_ AL _ I - Becomes light brown with fine sand,stiff 1,A8 T S3 7— — 8 11 S4 '1-', w )22 w' w u m i2 0 z 0 )11 0 cC r z 0 i2 0 0 0 m e Notes:See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 1/2 foot. 8 Coordinates Data Source:Horizontal approximated based on Google Earth.Vertical approximated based on Google Earth. , 6 Log of Test Pit TP-1 i Project: Pacific Ridge Apartments Project Location: Tigard,Oregon GEOENGINEERS Figure A6 ' Project Number: 6748-003-00 Sheet 1 of 1 Date Total Logged By NPVW Excavator Western States Groundwater not observed Excavated 10/9/2019 Depth(ft) 8 Checked By TNG Equipment Youmen PC40 Excavator Caving not observed • Surface Elevation(ft) Undetermined Easting(X) 516214.74 Coordinate System WGS84(feet) Vertical Datum Northing(Y) 5028575.12 Horizontal Datum SAMPLE 92 o o MATERIAL e REMARKS c z DESCRIPTION v O NbO O 'C N L C C 0- „C C C 152. @ N E O O g iLLg w o H Ern- C7 L.,CJ ML Brown silt,roots up tot-inch(soft,moist)(topsoil) — s-1 PP=0.25to0.75 tsf at11feet 2 _ ML Light brown silt with occasional sand and fine roots(1/8 inch)(stiff, moist)(fine-grained flood deposits) _ PP=2.0 to 2.5 tsf at 21/2 feet 3- 4--II 52 PP=3 to4tsf at 4feet 5— 6--n - s-3 7— - 8 II S-4 ti 0 0) k- Notes:See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 1/2 foot. s Coordinates Data Source:Horizontal approximated based on Google Earth.Vertical approximated based on Google Earth. Log of Test Pit TP-2 ,,r� Project: Pacific Ridge Apartments G EO E N G I N E E R S f Project Location: Tigard,Oregon Figure A-7 Project Number: 6748-003-00 Sheet 1of 1 EDate xcavated 10/9/2019 TotalDept (ft) 10.5 Logged By NPVW Excavator Western States Groundwater not observed Checked By TNG Equipment Youmen PC40 Excavator Caving not observed Surface Elevation(ft) Undetermined Easting(X) 516224.08 Coordinate System WGS84 feet Vertical Datum Northing(Y) 5028631.85 Horizontal Datum ( ) • J SAMPLE a) o s MATERIAL Z J DESCRIPTION o REMARKS O . N pq V V y�- L c - c L O_ ,n N N y n N Ei/i O(0 O N Nc c W O F-- cr) C7 C0 U �U it U ML Brown silt with large roots(medium stiff,moist)(topsoil) — 2 I I S1 PP=0.5to1.0tsfat1'/zfeet 3— ML _ Light brown silt with occasional sand(stiff,moist)(fine-grained flood _ deposits) PP=3 tsf at 3 feet 4— PP=3.5 tsf at 4feet 5-1-1 5-2 6— Becomes very stiff 7- 8 I I S-3 PP=4.5tsft71/zfeet 9— 10 — s-4 ae ti 0 m c� 0 u r 0 Notes:See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to lh foot. coo Coordinates Data Source:Horizontal approximated based on Google Earth.Vertical approximated based on Google Earth. Log of Test Pit TP-3 Project: Pacific Ridge Apartments GEO E N G I N E E RS Project Location: Tigard,Oregon Figure A-8 Project Number: 6748-003-00 Sheet 1 of 1 Date al Lotogged By NPVW Excavator Western States Groundwater not observed Excavated 10/9/2019 TDeepth(ft) 9•5 Checked By TNG Equipment Youmen PC40 Excavator Caving not observed 1 Surface Elevation(ft) Undetermined Easting(X) 516214.58 Coordinate System WGS84(feet) Vertical Datum Northing(Y) 5028663.93 Horizontal Datum v SAMPLE a MATERIAL REMARKS in z J DESCRIPTION O• — bD N GO U '— '5+ati aa'i L C C a a-- N..+ N.+ C T,C f!) O C N a) N to N N O O §U it U w 0 H in H 0 0 U ML Brown silt with trace sand and heavy roots up to 1-inch(soft,moist) f— (topsoil) - s-1 Mt _ Light brown silt with occasional sand(stiff,moist)(fine-grained flood _ PP=0 to 0.5 tsf at 11feet 2 deposits) PP=3.5tsfat21feet 3— 4--n 9 PP=4.5tsfat4feet Mc 5- 6— Becomes very stiff - 7— - - 5-3 _ PP=4.5 tsf at 71 feet B - 9—T� _ I 5-4 U O cp' ~I O O O N Z O ''' Z Z O (a O O O V Notes:See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 1/2 foot. 8 Coordinates Data Source:Horizontal approximated based on Google Earth.Vertical approximated based on Google Earth. a Log of Test Pit TP-4 a, Project: Pacific Ridge Apartments GProject Location: Tigard,Oregon EOENGINEERS Figure A-9 Project Number: 6748-003-00 Sheet 1 of 1 Date 10/8/2019 Total 7 5 Logged By JLL/NPVW Excavator Western States Groundwater not observed Excavated Depth(ft) Checked By TNG Equipment Youmen PC40 Caving not observed Surface Elevation(ft) Undetermined Easting(X) 516208.87 Coordinate System Vertical Datum Northing(Y) 5028565.29 Horizontal Datum WGS84(feet) SAMPLE o o MATERIAL 0 co�' z J CO DESCRIPTION o REMARKS O �. to N tjp U U t C C Q C C > a o d �m a) 0 0 2 O N c d o W F v7H 0 O U O ML Dark brown silt,tree roots to 6 to 8 inches,occasional duff,organic — _ material(soft,moist)(topsoil) p— j MLCL Grades to yellow-brown silt to lean clay(medium stiff,moist) _ (fine-grained flood deposits) s— a— Becomes stiff 5— 6 S-1 IT-1 performed at 6 feet bgs;see report text for details LL,O O U' O r z 0 u i Notes:See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 1/2 foot. o Coordinates Data Source:Horizontal approximated based on Google Earth.Vertical approximated based on Google Earth. • Log of Test Pit TP-5 Project: Pacific Ridge Apartments Project Location: Tigard,Oregon GEO NGINEERS,>,E r FigureA10 Project Number: 6748-003-00 Sheet 1 of 1 Logged By JLL/JPVW Excavator Western States Groundwater not observed Excavated 10/8/2019Date pth(ft) 11 Checked By TNG Equipment Youmen PC40 Excavator Caving not observed Surface Elevation(ft) Undetermined Easting(X) 516188.85 Coordinate System WGS84(feet) Vertical Datum Northing(Y) 5028576.77 Horizontal Datum F SAMPLE MATERIAL REMARKS C Z DESCRIPTION o CDe _ av @ C C Q �'a yr. O C A O C a) a) N (0 a, N 2 ) §U LL U ill ❑ h- cn F- o o U Mr Dark brown silt,low plasticity,fine roots to 6 to 8 inches,organic _ __ material,duff(soft,moist)(topsoil) 1 % MT CT Grades to yellow-brown silt to lean clay(medium stiff,moist) 2— _ (fine-grained flood deposits) - 3- 5— IT-2 performed at 51/2 feet bgs;see report text for 6— 5-1 details 7— j 8- 9- 10— 11— — ,32 0 a u 0 0 a a a Notes:See Figure A-1 for explanation of symbols. 9 The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to 1/2 foot. m Coordinates Data Source:Horizontal approximated based on Google Earth.Vertical approximated based on Google Earth. Log of Test Pit TP-6 72, Project: Pacific Ridge Apartments G EO E N G I N E E R S rProject Location: Tigard,Oregon Figure A-11 a Project Number: 6748-003-00 Sheet 1 of 1 • , Date Total Logged By JLL/JPVW Excavator Western States Groundwater not observed Excavated 10/8/2019 Depth(ft) 10.5 Checked By TNG Equipment Youmen PC40 Excavator Caving not observed Surface Elevation(ft) Undetermined Easting(X) 516172.29 Coordinate System WGS84(feet) Vertical Datum Northing(Y) 5028603.47 Horizontal Datum ♦ SAMPLE o o MATERIAL 0 ( z J ro DESCRIPTION _ REMARKS C C L .� C Q - Q 7 y „d y y N N O c v c W H (n1_ (i 0U 28 u o ML Dark brown silt,roots to 6 inches,organic material and duff(soft, 1— —— moist)(topsoil) ML-CL Yellow-brown silt to lean clay(medium stiff,moist)(fine-grained flood 2— _ deposits) - 3— - 4— 5 — 6— / y _ - 7 IT-3 performed at 7 feet bgs;see report text for details 8 9— 0 - 10— 0 U' (W'J r Q Notes:See Figure A-1 for explanation of symbols. The depths on the test pit logs are based on an average of measurements across the test pit and should be considered accurate to l foot. Coordinates Data Source:Horizontal approximated based on Google Earth.Vertical approximated based on Google Earth. Log of Test Pit TP-7 ,91 Project: Pacific Ridge Apartments GEO E N G I N E E R S Project Location: Tigard,Oregon Figure A-12 Project Number: 6748-003-00 Sheet 1 of 1 Soil Texture wn silt with organic matter(roots)(topsoil) an clay with trace fine sand 50 40 30 Depth below ground Cumulative Cummulative Penetration per Penetration Hammer blow 20 3tive blows surface penetration Penetration blow set per blow factor DCP Index DCP Index CBR Mu CBR= 1 for 8-kg 2 for of 15 1 8 (in) (mm) (in) (in) (in) 4.6-kg hammer in/blow mm/blow % psi CC- OD 10 2 9.2 30,0 1.2 1.2 0.59 2 1.18 30.00 6 4554 _ 4 8.5 62.5 2.5 1.3 0.64 2 1.28 32.50 6 4414 t 7 9.9 100.0 3.9 1.5 0.49 2 0.98 25.00 8 4890 10 11.1 130.0 5.1 1.2 0.39 2 0.79 20.00 10 5334 5 13 12.3 160.0 6.3 1.2 0.39 2 0.79 20.00 10 5334 4 16 13.9 200.0 7.9 1.6 0.52 2 1.05 26.67 7 4768 3 19 14.7 220.0 8.7 0.8 0.26 2 0.52 13.33 16 6248 24 16.2 260.0 10.2 1.6 0.31 2 0.63 16.00 13 5819 2 29 17.8 300.0 11.8 1.6 0.31 2 0.63 16.00 13 5819 34 19.6 345.0 13.6 1.8 0.35 2 0.71 18.00 11 5558 39 21.2 385.0 15.2 1.6 0.31 2 0.63 16.00 13 5819 44 22.9 430.0 16.9 1.8 0.35 2 0.71 18.00 11 5558 1 49 24.9 480.0 18.9 2.0 0.39 2 0.79 20.00 10 5334 1 2 3 4 5 10 15 20 31 54 26.5 520.0 20.5 1.6 0.31 2 0.63 16.00 13 5819 DCP INDEX,mm/blow 59 28.0 560.0 22.0 1.6 0.31 2 0.63 16.00 13 5819 69 32.4 670.0 26.4 4.3 0.43 2 0.87 22.00 9 5140 (after Webster et al.,1992) 74 34.0 710.0 28.0 1.6 0.31 2 0.63 16.00 13 5819 Webster,S.L.,Grau,R.H.,and Williams,T.P.(1992).Description and application of c 79 36.7 780.0 30.7 2.8 0.55 2 1.10 28.00 7 4678 penetrometer.Department of the Army Waterways Equipment Station,No.GL-92-3. 84 39.5 850.0 33.5 2.8 0.55 2 1.10 28.00 7 4678 89 42.2 920.0 36.2 2.8 0 55 2 1.10 28.00 7 4678 Cumulative Blows 94 44.6 980.0 38.6 2.4 0.47 2 0.94 24.00 8 4968 0 50 f ♦ , ♦ 10 ),-- -_..._ ____......_�. Gal • t.. U ♦ -. C15 + - .._-._ ...._. ...._-♦ C ♦ O L ♦i 20 __ ___-.. .._ _.___._..- • C { i d t 25 jO. - d > $ ., 30 i--_.�._-_..._ �....._..__-.._ -_......... ...._.._._.._ .___. +++ -__.._.__._. E } 7 40 45 I Soil Texture - wn silt with organic matter(roots)(topsoil) wn silt with occasional sand 50 40 30 Depth below ground Cumulative Cummulative Penetration per Penetration Hammer blow 20 3tive blows surface penetration Penetration blow set per blow factor DCP Index DCP Index CBR M, CBR= 1 for 8-kg 2 for o 15 # (in) (mm) (in) (in) (in) 4.6-kg hammer in/blow mm/blow % psi if 1 9.2 30.0 1.2 1.2 1.18 2 2.36 60.00 3 3475 m 10 - UN. 3 8.8 70.0 2.8 1.6 0.79 2 1.57 40.00 5 4071 6 9.9 100.0 3.9 1.2 0.39 2 0.79 20.00 10 5334 - 9 11.1 130.0 5.1 1.2 0.39 2 0.79 20.00 10 5334 5 - - 12 12.3 160.0 6.3 1.2 0.39 2 0.79 20.00 10 5334 4 - 15 12.9 175.0 6.9 0.6 0.20 2 0.39 10.00 22 6990 3 18 14.1 205.0 8.1 1.2 0.39 2 0.79 20.00 10 5334 23 15.1 230.0 9.1 1.0 0.20 2 0.39 10.00 22 6990 2 28 15.8 250.0 9.8 0.8 0.16 2 0.31 8.00 28 7625 33 16.4 265.0 10.4 0.6 0.12 2 0.24 6.00 39 8531 38 17.0 280.0 11.0 0.6 0.12 2 0.24 6.00 39 8531 43 17.4 290.0 11.4 0.4 0.08 2 0.16 4.00 62 9992 1 53 18.2 310.0 12.2 0.8 0.08 2 0.16 4.00 62 9992 1 2 3 4 5 10 15 20 3 63 19.8 350.0 13.8 1.6 0.16 2 0.31 8.00 28 7625 DCP INDEX,mm/blow 73 21.0 380.0 15.0 1,2 0.12 2 0.24 6.00 39 8531 83 22.9 430.0 16.9 2.0 0.20 2 0.39 10.00 22 6990 (after Webster et al.,1992) 93 24.9 480.0 18.9 2.0 0.20 2 0.39 10.00 22 6990 Webster,S.L.,Grau,R.H.,and Williams,T.P.(1992).Description and application of t 103 28.0 560.0 22.0 3.1 0.31 2 0.63 16.00 13 5819 penetrometer.Department of the Army Waterways Equipment Station,No.GL-92-3. 113 29.4 595.0 23.4 1.4 0.14 2 0.28 7.00 33 8033 123 30.4 620.0 24.4 1.0 0.10 2 0.20 5.00 48 9159 133 32.0 660.0 26.0 1.6 0.16 2 0.31 8.00 28 7625 Cumulative Blows 0 50 100 150 143 33.0 685.0 27.0 1.0 0.10 2 0.20 5.00 48 9159 0 __-._ _ .___ 153 33.8 705.0 27.8 0.8 0.08 2 0.16 4.00 62 9992 163 35.3 745.0 29.3 1.6 0.16 2 0.31 8.00 28 7625 S -♦ 1 173 35.9 760.0 29.9 0.6 0.06 2 0.12 3.00 85 11179 • ♦ • 183 36.9 785.0 30.9 1.0 0.10 2 0.20 5.00 48 9159 193 37.9 810.0 31.9 1.0 0.10 2 0.20 5.00 48 9159 n 10 }--- -♦♦- 203 38.9 835.0 32.9 1.0 0.10 2 0.20 5.00 48 9159 m f ♦♦ L • 213 40.8 885.0 34.8 2.0 0.20 2 0.39 10.00 22 6990 u 15 r ♦ -..-- • ----..._.. _.-. - ------- ._.._.__"..__-._._.... 223 41.6 905.0 35.6 0.8 0.08 2 0.16 4.00 62 9992 233 42.6 930.0 36.6 1.0 0.10 2 0.20 5.00 48 9159 13 243 44.2 970.0 38.2 1.6 0.16 2 0.31 8.00 28 7625 ` I 20 ----- ----__.__ _ ___. iii c • ♦ . v ' d 25 f --.....------+ -. _ ♦ d j ♦ ♦ > I ♦ m 30 '.. __....___.-_.._ .__._...- _..._...._....�.__�.._. _ • • E . ✓• 35 . - f i i F PLASTICITY CHART 1 60 , • • • • 50 -• • CH or OH ix 40 • • PP 30 a J'• 0 OH or MH 20 • ' CLorOL 10 CL-ML M.or OL 0 ii r 0 10 20 30 40 50 60 70 80 90 100 LIQUID LIMIT Moisture Liquid Plasticity Boring Depth Content Limit Index Symbol Number (feet) (%) (%) (%) Soil Description • 6-3 2.5 17 36 12 Yellow-brown.silt(ML) ❑ TP-1 4 21 43 22 Yellow-brown lean clay(CL) Atterberg Limits Test Results li Pacific Ridge Apartments Lil 0. Tigard, Oregon 0 Note:This report may not be reproduced,except in full,without written approval of GeoEngineers,Inc. Test results are applicable m only to the specific sample on which they were performed,and should not be interpreted as representative of any other G c samples obtained at other times,depths or locations,or generated by separate operations or processes. EOENGINEES R p� Figure A-15 r- The liquid limit and plasticity index were obtained in general accordance with ASTM D 4318. APPENDIX B Slope Stability Analysis 4 Name:Pacific Ridge Apartments_Global Stability 2.739 File Name:Tigard Apts Global Stability_existing.gsz Method:Spencer Date:11/14/2019 310— 300 Name:Madam stiff silt/clay _ Model:Moh Cwlomb t90 Unit Weight:110 pcf Cohesion':100 psf zeo— Phi':28° 270— 290— 250— 0 10 20 30 40 50 00 70 00 00 100 110 120 130 110 150 100 170 130 100 200 210 220 230 210 250 200 270 200 290 300 310 320 330 340 350 300 370 300 390 400 410 420 430 440 450 Firyl ira R- Name: Pacific Ridge Apartments_Wall 1 File Name: Tigard Apts Wall 1 .gsz Method: Spencer Date: 11/1/2019 i I 290 1.020 • Approximate exisiting ground surface 280 270 260 , .,' Name: Soft to medium stiff silt/cla: Model: Mohr-Coulomb Unit Weight: 110 pcf 25o Cohesion': 100 psf 0 10 20 30 40 50 60 70 Phi': 28 ° . Figure B-2 Name: Pacific Ridge Apartments_Wall 3 File Name: Tigard Apts Wall 3.gsz Method: Spencer Date: 11 /14/2019 290 •1 .134 Approximate exisiting ground surface 280 ■ Name: Medium stiff silt/cla 270 Model: Mohr-Coulomb Unit Weight: 110 pcf Cohesion': 100 psf 260 Phi': 28 ° 250 0 10 20 30 40 50 60 70 Figure B APPENDIX C Report Limitations and Guidelines for Use { f})3I 6 APPENDIX C REPORT LIMITATIONS AND GUIDELINES FOR USE1 This appendix provides information to help you manage your risks with respect to the use of this report. Read These Provisions Closely It is important to recognize that the geoscience practices (geotechnical engineering, geology and environmental science) rely on professional judgment and opinion to a greater extent than other engineering and natural science disciplines,where more precise and/or readily observable data may exist. To help clients better understand how this difference pertains to our services, GeoEngineers includes the following explanatory"limitations" provisions in its reports. Please confer with GeoEngineers if you need to know more about how these "Report Limitations and Guidelines for Use" apply to your project or site. Geotechnical Services Are Performed for Specific Purposes, Persons and Projects This report has been prepared for J.T. Smith Companies, 3J for the Project specifically identified in the report.The information contained herein is not applicable to other sites or projects. GeoEngineers structures its services to meet the specific needs of its clients. No party other than the party to whom this report is addressed may rely on the product of our services unless we agree to such reliance in advance and in writing. Within the limitations of the agreed scope of services for the Project, and its schedule and budget, our services have been executed in accordance with our Agreement with J.T. Smith Companies dated June 28, 2019 (authorized July 2, 2019)and generally accepted geotechnical practices in this area at the time this report was prepared. We do not authorize, and will not be responsible for,the use of this report for any purposes or projects other than those identified in the report. A Geotechnical Engineering or Geologic Report is Based on a Unique Set of Project-Specific Factors This report has been prepared for the Pacific Ridge Apartment Development Project located east of SW Pacific Highway(OR 99W) in Tigard,Oregon.GeoEngineers considered a number of unique, project-specific factors when establishing the scope of services for this project and report.Unless GeoEngineers specifically indicates otherwise, it is important not to rely on this report if it was: a not prepared for you, a not prepared for your project, a not prepared for the specific site explored, or a completed before important project changes were made. For example, changes that can affect the applicability of this report include those that affect: ■ the function of the proposed structure; a elevation, configuration, location, orientation or weight of the proposed structure; 1 Developed based on material provided by GBA,GeoProfessional Business Association;www.geoprofessional.org. GEOENGINEERs November 20,2019 `. Page C-i File No.6748-003-00 R ^ If changes occur after the date of this report, GeoEngineers cannot be responsible for any consequences of such changes in relation to this report unless we have been given the opportunity to review our interpretations and recommendations. Based on that review, we can provide written modifications or confirmation,as appropriate. Environmental Concerns Are Not Covered Unless environmental services were specifically included in our scope of services, this report does not provide any environmental findings, conclusions, or recommendations, including but not limited to, the likelihood of encountering underground storage tanks or regulated contaminants. Subsurface Conditions Can Change This geotechnical or geologic report is based on conditions that existed at the time the study was performed. The findings and conclusions of this report may be affected by the passage of time, by man-made events such as construction on or adjacent to the site, new information or technology that becomes available subsequent to the report date, or by natural events such as floods, earthquakes, slope instability or groundwater fluctuations. If more than a few months have passed since issuance of our report or work product,or if any of the described events may have occurred, please contact GeoEngineers before applying this report for its intended purpose so that we may evaluate whether changed conditions affect the continued reliability or applicability of our conclusions and recommendations. Geotechnical and Geologic Findings Are Professional Opinions Our interpretations of subsurface conditions are based on field observations from widely spaced sampling locations at the site.Site exploration identifies the specific subsurface conditions only at those points where subsurface tests are conducted or samples are taken. GeoEngineers reviewed field and laboratory data and then applied its professional judgment to render an informed opinion about subsurface conditions at other locations. Actual subsurface conditions may differ, sometimes significantly, from the opinions presented in this report. Our report, conclusions and interpretations are not a warranty of the actual subsurface conditions. Geotechnical Engineering Report Recommendations Are Not Final We have developed the following recommendations based on data gathered from subsurface investigation(s). These investigations sample just a small percentage of a site to create a snapshot of the subsurface conditions elsewhere on the site. Such sampling on its own cannot provide a complete and accurate view of subsurface conditions for the entire site.Therefore,the recommendations included in this report are preliminary and should not be considered final. GeoEngineers' recommendations can be finalized only by observing actual subsurface conditions revealed during construction. GeoEngineers cannot assume responsibility or liability for the recommendations in this report if we do not perform construction observation. We recommend that you allow sufficient monitoring, testing and consultation during construction by GeoEngineers to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes if the conditions revealed during the work differ from those anticipated, and to evaluate whether earthwork activities are completed in accordance with our recommendations. Retaining GeoEngineers for construction observation for this project is the most effective means of managing the risks associated with unanticipated conditions. If another party performs GEOENGINEERS November 20,2019 Page C-2 File No.6748-003-00 field observation and confirms our expectations, the other party must take full responsibility for both the observations and recommendations. Please note, however, that another party would lack our project- specific knowledge and resources. A Geotechnical Engineering or Geologic Report Could Be Subject to Misinterpretation Misinterpretation of this report by members of the design team or by contractors can result in costly problems. GeoEngineers can help reduce the risks of misinterpretation by conferring with appropriate members of the design team after submitting the report, reviewing pertinent elements of the design team's plans and specifications, participating in pre-bid and preconstruction conferences, and providing construction observation. Do Not Redraw the Exploration Logs Geotechnical engineers and geologists prepare final boring and testing logs based upon their interpretation of field logs and laboratory data.The logs included in a geotechnical engineering or geologic report should never be redrawn for inclusion in architectural or other design drawings. Photographic or electronic reproduction is acceptable, but separating logs from the report can create a risk of misinterpretation. Give Contractors a Complete Report and Guidance To help reduce the risk of problems associated with unanticipated subsurface conditions, GeoEngineers recommends giving contractors the complete geotechnical engineering or geologic report, including these "Report Limitations and Guidelines for Use."When providing the report,you should preface it with a clearly written letter of transmittal that: is advises contractors that the report was not prepared for purposes of bid development and that its accuracy is limited; and ■ encourages contractors to confer with GeoEngineers and/or to conduct additional study to obtain the specific types of information they need or prefer. Contractors Are Responsible for Site Safety on Their Own Construction Projects Our geotechnical recommendations are not intended to direct the contractor's procedures, methods, schedule or management of the work site. The contractor is solely responsible for job site safety and for managing construction operations to minimize risks to on-site personnel and adjacent properties. Biological Pollutants GeoEngineers' Scope of Work specifically excludes the investigation, detection, prevention or assessment of the presence of Biological Pollutants. Accordingly, this report does not include any interpretations, recommendations, findings or conclusions regarding the detecting, assessing, preventing or abating of Biological Pollutants, and no conclusions or inferences should be drawn regarding Biological Pollutants as they may relate to this project.The term "Biological Pollutants" includes, but is not limited to, molds,fungi, spores, bacteria and viruses, and/or any of their byproducts. A Client that desires these specialized services is advised to obtain them from a consultant who offers services in this specialized field. GEOENGINEERSg November 20,2019 Page C-3 File No.6748 003-00