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Report (81) is ?iso Geotechnical Engineering Re t p SW Atlanta Street Storage Building Tigard, Oregon Dfor IAE Trailblazer Development, LLC JUN 12 2018 June 11, 2018 �I OF TIGARD BUILDING DIVISION • • • • GEOENGINEER Eat.Mr=+11e..wer Geotechnical Engineering Report SW Atlanta Street Storage Building Tigard, Oregon for Trailblazer Development, LLC June 11, 2018 GEOENGINEERS 1200 NW Naito Parkway,Suite 180 Portland, Oregon 97209 503.624.9274 Geotechnical Engineering Report SW Atlanta Street Storage Building Tigard, Oregon File No.23459-001-00 June 11,2016 Prepared for: Trailblazer Development, LLC 333 South State Street,Suite V-144 Lake Oswego, Oregon 97034 Attention:Jeb Koerner Prepared by: GeoEngineers, Inc. 1200 NW Naito Parkway,Suite 180 . 0 PROFF Portland, Oregon 97209 i0 503.624.9274 7 490P r LOR i4ON,(oJ �MeE11)0$ VIVr 0 'ILAN Greg A. Landau, PE, GE � LP" Associate Geotechnical Engineer EXPIRES: 12.3 DMH:GAL: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 INTRODUCTION 1 SCOPE OF SERVICES 1 SITE DESCRIPTION 1 Surface Conditions 1 Site Geology 1 Subsurface Conditions 2 General 2 Soil Conditions 2 Groundwater Conditions 2 CONCLUSIONS 3 EARTHQUAKE ENGINEERING 3 Liquefaction 3 Lateral Spreading 4 Fault Surface Rupture 4 Landslides 4 Seismic Design Information 4 FOUNDATION SUPPORT RECOMMENDATIONS 5 Aggregate Piers 5 Lateral Resistance 6 Footing Drains 6 Construction Considerations 6 Slab-on-Grade Floors 6 Subgrade Preparation 6 Design Parameters 7 Below-Slab Drainage 7 BELOW-GRADE WALLS 8 Permanent Subsurface Walls 8 Other Cast-in-Place Walls 8 Wall Drainage 9 Waterproofing 9 EXCAVATION SUPPORT 10 Excavation Considerations 10 Temporary Cut Slopes 10 Soil Nail Walls 11 Preliminary Design Recommendations 12 Soil Nail Wall Performance 13 Drainage 13 EARTHWORK 13 Clearing and Site Preparation 13 GEOENGINEERS June 11,2018 Page i File No.23459-001-00 Subgrade Preparation 14 Subgrade Protection 14 Structural Fill and Backfill 15 General 15 Use of On-site Soil 15 Imported Select Structural Fill 15 Aggregate Base 15 Retaining Wall Backfill 15 Trench Backfill 16 Fill Placement and Compaction 16 Permanent Cut and Fill Slopes 17 TEMPORARY CONSTRUCTION DEWATERING 17 Sump Pumping 18 Surface Water Drainage Considerations 18 PAVEMENT RECOMMENDATIONS 18 General 18 Drainage 18 Pavement Sections 18 LIMITATIONS 19 REFERENCES 20 LIST OF FIGURES Figure 1.Vicinity Map Figure 2.Site Plan Figure 3. Earth Pressure Diamgrams Temporary Shoring Wall Figure 4. Recommended Surcharge Pressure APPENDICES Appendix A. Field Explorations and Laboratory Testing Figure A-1. Key to Exploration Logs Figures A-2 and A-3. Logs of Borings Figure A-4.Atterberg Limits Test Results Appendix B. Ground Anchor Load Tests and Shoring Monitoring Program Appendix C. Report Limitations and Guidelines for Use GEOENGINEERSI June 11,2018 Page ii File No.23459-001-00 INTRODUCTION GeoEngineers, Inc. (GeoEngineers) is pleased to submit this geotechnical engineering report for the proposed storage building located north of SW Atlanta Street in Tigard, Oregon. The location of the site is shown in the Vicinity Map, Figure 1. The proposed project includes constructing a five-story commercial storage facility, associated pavements and utilities. The site grades from an elevation of approximately 208 feet above mean sea level (MSL) at the north end of the site to approximately 192 feet MSL at the southeast corner of the site. The building will be constructed with a finish floor elevation of 194.5 feet MSL, resulting in maximum cuts up to about 17 feet. A temporary soil nail wall is proposed to retain the excavation and will be replaced by a permanent cast-in-place concrete retaining wall along the north, northeast and northwest portions of the lot. The proposed site layout is shown in relation to existing site features in the Site Plan, Figure 2. SCOPE OF SERVICES Our specific scope of services is detailed in our May 24,2018 proposal to you. Our services were authorized on May 24, 2018. In general our scope of services included: reviewing selected geotechnical information about the site, including the Hardman Geotechnical Services, Inc. (Hardman) geotechnical report for the site dated June 12, 2017 (updated November 29, 2017); exploring subsurface soil and groundwater conditions; collecting representative soil samples; completing relevant laboratory testing and geotechnical analyses; and providing this geotechnical report with our conclusions, findings and design recommendations. SITE DESCRIPTION Surface Conditions The project site encompasses approximately 0.97 acre and is bounded by private commercial properties to the north, east, and west and the SW Atlanta Street right-of-way(ROW)to the south.The site is currently undeveloped. The surface is thickly vegetated with rough field grass and blackberry briars, with scattered deciduous trees and a wooded margin along the southeast property boundary. The site slopes moderately down to the south and east, with elevations ranging from approximately 208 feet MSL at the northeast corner of the site to approximately 192 feet MSL at the southeast corner along the SW Atlanta Street ROW. Site Geology The geology of the site is mapped by the Oregon Department of Geology and Mineral Industries (DOGAMI) Open File Report 0-90-2, Earthquake Hazard Geology Maps of the Portland Metropolitan Area, Oregon (Madin 1990) as mantled by the fine-grained facies of the Pleistocene catastrophic (Missoula) flood deposits.The geologic map shows the site and vicinity underlain by approximately 30 to 50 feet of this fine- grained flood sediment. Our subsurface explorations suggest that the site subsurface conditions generally conform to the published mapping, with some minor exceptions described below. GEOENGINEERS June 11,2018 Page 1 File No.23459-001-00 Subsurface Conditions General The subsurface conditions at the site were evaluated by drilling two geotechnical borings (GEI B-1 and GEI B-2)on May 27, 2018. Borings GEI B-1 and GEI B-2 extended to approximate depths ranging from 311 to 461 feet below the ground surface (bgs). We also reviewed the logs of the two borings and four test pits performed by Hardman in 2017. 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 were taken to GeoEngineers' laboratory for further evaluation. Selected samples were tested for the determination of the fines content, Atterberg limits and moisture/density testing. A description of the laboratory testing and the test results are presented in Appendix A. Soil Conditions In general, subsurface soil conditions consist of a surficial veneer of man-made fill overlying silt and fine sand of the Pleistocene fine-grained catastrophic flood deposits. These units are described in more detail below. FILL GEI B-1 encountered silty soil fill from the ground surface to approximately 3 feet bgs. We did not observe fill soil materials in GEI B-2. All of the Hardman explorations report a mixture of silt fill with gravel, sand and debris from the ground surface to depths ranging between 11 to 3 feet bgs. We also observed a scattering of gravel and concrete debris at the ground surface along the southwestern margins of the site. FINE-GRAINED FLOOD DEPOSITS We encountered fine-grained flood deposits from below the fill (or at the ground surface in GEI B-2)to the maximum depths explored. The upper zone of the flood deposits generally consisted of medium stiff to stiff(occasionally very soft to soft) silt and silt with fine sand; typically, these soils became dark gray below approximately 10 feet bgs. The thickness of this upper zone was highly variable, ranging from 9 feet in GEI B-2 and 16 feet in GEI B-1. Below this upper zone,the flood deposits graded to a complex interlayered or interbedded middle zone of brown to dark gray silt and fine sandy silt, and loose to medium dense (occasionally very loose), dark gray silty fine sand.The thickness of the middle zone ranged from approximately 5 feet in GEI B-Land 10 feet in GEI B-2. Below this middle zone all the explorations encountered a lower zone consisting of stiff to very stiff, dark gray silt,silt with fine sand and lean clay. Groundwater Conditions Groundwater was encountered during drilling in GEI B-1 at approximately 10 feet bgs (elevation 198 feet above MSL) and GEI B-2 at approximately 8 feet bgs (193 feet MSL). Groundwater was also documented in both of Hardman's borings (completed August 25, 2017)and all four test pits (completed May 8, 2017) between 5 and 6 feet bgs. GEOENGINEERS,g June 11,2018 Page 2 File No.23459-001-00 Groundwater may be present at shallower depths in a perched or capillary condition 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. 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. ■ Liquefaction-induced settlement is anticipated during the design level earthquake. We estimate approximately 6 to 8 inches of liquefaction induced settlement during this event. Supporting the structures on aggregate piers, as recommended, will mitigate for this liquefaction-induced settlement. ■ Groundwater was encountered at an elevation of approximately 193 to 198 feet MSL during our explorations. ■ Permanent drainage measures should be incorporated into the design of below-grade walls and below slabs-on-grade. ■ On-site near surface soils generally consist of silt. The silt will become significantly disturbed 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 unless earthwork occurs during the dry summer months (typically mid-July to mid-September). ■ 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. ■ Standard pavement sections prepared as described in this report will suitably support estimated traffic loads. EARTHQUAKE ENGINEERING • Liquefaction Liquefaction refers to the condition when vibration or ground shaking, usually from earthquake forces, results in the development of excess pore pressures in saturated soils with subsequent loss of strength in the soil deposit affected. In general,soils that are susceptible to liquefaction include very loose to medium dense clean to silty sands and low plasticity silts. For liquefaction to occur, soils must be saturated. Liquefaction usually results in ground settlement and loss of bearing capacity, resulting in settlement of structures that are supported on foundations within or above the liquefied soils. The evaluation of liquefaction potential is a complex procedure and is dependent on numerous site e parameters, including soil grain size, soil density, site geometry, static stress and the design ground acceleration. Typically, the liquefaction potential of a site is evaluated by comparing the cyclic stress ratio (CSR), which is the ratio of the cyclic shear stress induced by an earthquake to the initial effective overburden stress, to the cyclic resistance ratio (CRR), which is the soils resistance to liquefaction. GEOENGINEERS June 11,2018 Page3 File No.23459-001-00 Estimation of the CSR and the CRR were completed using empirical methods(Youd,et al.2001). Estimated ground settlement resulting from earthquake-induced liquefaction was analyzed using empirical procedures based on correlations from the SPT results (Tokimatsu and Seed, 1987; Ishihara and Yoshimine, 1992). The liquefaction analyses are based on the 2015 International Building Code (IBC) (2 percent chance of exceedance in 50 years, or 2,475-year event) which corresponds to a peak ground acceleration (PGA) of 0.41g and a magnitude of 9.0. Based on our explorations, soils at the site are potentially liquefiable. Without ground improvement, we estimate approximately 6 to 8 inches of liquefaction induced settlement during the design earthquake. Lateral Spreading A body of soft, liquefiable soil located near a steep or vertical slope is typically subject to failure towards the unsupported ("free face") slope during an earthquake. This "lateral spreading" is usually related to liquefaction of the underlying soils and flow-like movement towards the unsupported face and is typically more severe where the free face is high,steep and the site soils more highly liquefiable. Lateral spreading is not expected to be a concern due to the lack of steep slope or free face. Fault Surface Rupture The closest mapped fault to the site possibly capable of surface rupture is the northwest-to-southeast trending Canby-Molalla Fault with its inferred extension approximately 1.6 miles northeast of the site (Personius 2002). No faults are mapped as crossing the site,and the potential for site fault surface rupture is,therefore,very low. Landslides It is our opinion that landsliding as a result of strong ground shaking is unlikely at this site because of the relatively gentle site topography. Seismic Design Information For preliminary design purposes, we recommend using the procedure outlined in the 2015 IBC and the 2014 Oregon Structural Specialty Code (OSSC). The parameters provided in Table 1 are based on the conditions encountered during our subsurface exploration program and should be used in preparation of response spectra for the proposed structures. GEOENGINEERS� June 11,2018 Page 4 File No.23459-001-00 TABLE 1.SEISMIC DESIGN PARAMETERS 2015 IBC Parameter Recommended Value Soil Profile Type D/F1 Short Period Spectral Response Acceleration,Ss(percent g) 0.98 1-Second Period Spectral Response Acceleration,Si(percent g) 0.42 Seismic Coefficient, FA 1.11 Seismic Coefficient, Fv 1.58 Note: 1 In accordance with American Society of Civil Engineers(ASCE)7-10,Site Class F soils vulnerable to potential failure or collapse under seismic loading,such as liquefiable soils,may be classified in accordance with Section 20.3,without regard for liquefaction,provided the structure under design has a fundamental period of vibration equal or less than 0.5 seconds. FOUNDATION SUPPORT RECOMMENDATIONS We understand building loads are on the order of 715 kips for column loads and 9 kips per lineal foot(klf) for wall loads. These loads are dead plus live loads. Due to the liquefiable soils and relatively high building loads, we recommend the building be supported on shallow foundations supported on aggregate piers. Aggregate Piers Shallow spread footings supported on aggregate piers will provide high bearing capacity and reduced settlement by creating a stiff soil subgrade. Aggregate piers should also be designed to mitigate for liquefaction. Ground improvement methods can consist of the Rammed Aggregate Pier® (RAP) System constructed by GeoPier Foundation Company or Vibro PiersTM constructed by Hayward Baker. Aggregate pier systems are typically designed and constructed by the specialty contractor to a performance specification. They should submit a ground improvement design that has been completed and stamped by a registered professional engineer with experience in such projects. We recommend that GeoEngineers review the design on behalf of the Owner, although the specialty contractor will retain responsibility for the design and construction of the ground improvements to the specified performance criteria. We anticipate that the aggregate piers would extend from footing subgrade to approximately 25 to 30 feet bgs. They should be designed to meet the final bearing capacity and settlement tolerances provided by the structural engineer. The specialty contractor would provide final design and in-house quality control for the piers. We recommend that GeoEngineers provide construction quality assurance for the owner during the construction process. The bearing capacity of the aggregate pier-improved subgrade would be determined by the specialty contractor. We typically see a bearing capacity of approximately 5,000 to 6,000 psf in soil similar to those at the site that have been improved with aggregate piers. Aggregate piers will mitigate for liquefaction induced settlement within the improvement zone. GEOENGINEERS_ci June 11,2018 Page 5 File No.23459-001-00 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 300 pounds per cubic foot(pcf)for foundations confined by native medium stiff or stiffer silt and 350 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 2-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 do not include safety factors. Footing Drains We recommend that perimeter footing drains be installed around the buildings at the base of the 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 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. 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. Slab-on-Grade Floors 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 GEOENGINEERS June 11,2018 Page 6 File No.23459-001-00 without significant groundwater. Disturbed areas should be recompacted if possible or removed and replaced with compacted structural fill. Design Parameters Conventional slabs may be supported on-grade,provided the subgrade soils are prepared as recommended in the "Subgrade Preparation" section 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 150 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. Below-Slab Drainage Groundwater could accumulate below the proposed building floor slabs since the building will be cut into soils where groundwater exists. To help mitigate potential build-up of groundwater below the slabs, we recommend that the concrete slabs-on-grade be provided with under drainage to collect and discharge potential groundwater from below the slabs. This can be accomplished by installing a 4-inch-diameter, heavy-wall perforated collector pipe in a shallow trench placed below the capillary break gravel layer. Perforated pipe should have two rows of 1/2-inch holes spaced 120 degrees apart and at 4 inches on center. The trench should measure about 1-foot-wide by 1.5-feet-deep and should be backfilled with clean 3/s-inch pea gravel or an alternative approved by GeoEngineers. The drainage material should be wrapped with a nonwoven geotextile filter fabric,such as Mirafi 140N. For design,the perforated drainage pipes should be centered longitudinally below the building and can be connected to the perimeter footing drain pipe. If connected to the footing drain system,the invert of the underdrain pipe should be higher than the invert of the footing drain pipe where they connect. The collector pipe should be sloped to drain and discharge into the stormwater collection system to convey the water off site.The pipe should also incorporate cleanouts, if possible.The cleanouts could be extended through the foundation walls to be accessible from the outside or could be placed in flush-mounted access boxes cast into the floor slabs.The civil engineer should develop a conceptual foundation drainage plan for GeoEngineers to review. If no special waterproofing measures are taken, leaks and/or seepage may occur in localized areas of the below-grade portion of the building, even if the recommended wall drainage and below-slab drainage provisions are constructed. If leaks or seepage is undesirable, below-grade waterproofing should be specified. A vapor barrier should be used below slab-on-grade floors located in occupied portions of the buildings, such as retail space or equipment/storage space. Specification of the vapor barrier requires consideration of the performance expectations of the occupied space, the type of flooring planned and other factors and is typically completed by other members of the project team. GEOENGINEERS June 11,2018 Page 7 File No.23459-001-00 BELOW-GRADE WALLS Permanent Subsurface Walls Permanent below-grade walls constructed adjacent to temporary soil nail walls should be designed for the same earth pressures (including surcharge pressures, were applicable, as the adjacent temporary wall). Permanent below-grade walls constructed adjacent to temporary soil nail walls should be designed for the earth pressures shown in Figure 3, Soldier Pile Wall with Multiple Levels of Tiebacks. Permanent below- grade walls should also include a seismic load acting over the height of the wall equal to 7H psf, where H is the height of the wall in feet. Other surcharge loads,such as from foundations, construction equipment or construction staging areas,should be considered on a case-by-case basis,as shown in Figure 4.We can provide the lateral pressures from these surcharge loads as needed. The soil pressures recommended above assume that wall drains will be installed to prevent the buildup of hydrostatic pressure behind the walls,as described below in the "Excavation Support"section of this report and tied to permanent drains to remove water to suitable discharge points. Other Cast-in-Place Walls Lateral earth pressures for design of below-grade walls and retaining structures which are not adjacent to temporary shoring walls should be evaluated using an equivalent fluid density of 35 pcf provided that the walls will not be restrained against rotation when backfill is placed. If the walls will be restrained from rotation, we recommend using an equivalent fluid density of 55 pcf. Walls are assumed to be restrained if top movement during backfilling is less than H/1000,where H is the wall height.These lateral soil pressures assume that the ground surface behind the wall is horizontal. If the ground surface within 5 feet of the wall rises at an inclination of 2H:1V(horizontal to vertical) or steeper, the walls should be designed for lateral pressures based on equivalent fluid densities of 50 and 80 pcf, respectively, for unrestrained and restrained conditions. These lateral soil pressures do not include the effects of surcharges such as floor loads, traffic loads or other surface loading. Surcharge effects should be included as appropriate. Below- grade walls for buildings should also include seismic earth pressures. Seismic earth pressures should be determined using a rectangular distribution of 7H in psf, where H is the wall height. If vehicles can approach the tops of exterior walls to within half the height of the wall, a traffic surcharge should be added to the wall pressure. For car parking areas,the traffic surcharge can be approximated by the equivalent weight of an additional 1 foot of soil backfill (125 psf) behind the wall. For delivery truck parking areas and access driveway areas, the traffic surcharge can be approximated by the equivalent weight of an additional 2 feet (250 psf) of soil backfill behind the wall. Other surcharge loads, such as from foundations, construction equipment or construction staging areas, should be considered on a case-by-case basis, as shown in Figure 4. Positive drainage should be provided behind below-grade walls and retaining structures as discussed in "Drainage Considerations"section of this report. These recommendations are based on the assumption that all retaining walls will be provided with adequate drainage. The values for soil bearing, frictional resistance and passive resistance presented above for foundation design are applicable to retaining wall design. Walls located in level ground areas should be founded at a depth of 18 inches below the adjacent grade. GEOENGINEER_ June 11,2018 Page 8 File No.23459-001-00 Wall Drainage Drainage behind the permanent below-grade walls constructed adjacent to temporary shoring walls is recommended to consist of a combination of drainage material located behind the facing of the temporary soil nail shoring walls(where present)and drainage placed between the temporary shoring wall (soldier pile or soil nail)and the permanent below grade wall.The drainage material should be connected to weep pipes that extend through the permanent below grade building walls at the footing elevation. The weep pipes through the permanent below grade wall should be spaced no more than 12 feet on center and should be hydraulically connected to the sump. These weep pipes may be designed for a hard connection to the perimeter drains discussed above in the "Below-Slab Drainage"section of this report. Prefabricated geocomposite drainage material, such as Mirafi G100TM, Miradrain® 6000 or approved equivalent, should be used where drainage material is required either as strips behind the temporary shoring wall, or as full coverage drainage panels located between the temporary shoring wall and the permanent below grade walls. The drainage material should be installed on the excavation side of the temporary shoring wall with the fabric adjacent to the temporary shoring wall.The weep pipes constructed near the base of each strip of drainage material placed behind temporary soil nail walls should be hydraulically connected to the drainage material placed between the temporary and permanent below grade walls. In areas where temporary cut slopes are used,and conventional cast-in-place techniques are used to build the below grade walls, a conventional footing drain should be located on the outside of the building. The footing drain should be constructed consistent to drains recommended for cast-in-place walls, below. Positive drainage should be provided behind cast-in-place retaining walls by using free draining wall drainage material with perforated pipes to discharge the collected water.The zone of wall drainage material should be 2 feet wide and should extend from the base of the wall to within 2 feet of the ground surface. The wall drainage material should be covered with 2 feet of less permeable material, such as the on-site silt that is properly moisture conditioned and compacted.A geotextile separator should be placed between the wall drainage material and overlying cover soil. A 4-inch-diameter perforated drain pipe should be installed within the free-draining material at the base of each wall.We recommend using either heavy-wall solid pipe (SDR-35 PVC)or rigid corrugated polyethylene pipe (ADS N-12 or equal). We recommend against using flexible tubing for the wall drain pipe. The footing drain recommended above in the "Footing Drains" section can be incorporated into the bottom of the drainage zone and used for this purpose. The pipes should be laid with minimum slopes of one-quarter percent and discharge into the stormwater collection system to convey the water off site. The pipe installations should include a cleanout riser with cover located at the upper end of each pipe run. The cleanouts could be placed in flush-mounted access boxes. Collected downspout water should be routed to appropriate discharge points in separate pipe systems. Waterproofing The recommendations in this section are provided to reduce the potential for buildup of hydrostatic pressures behind below grade walls and hydrostatic uplift forces below building slabs. If no special waterproofing measures are taken, leaks or seepage may occur in localized areas of the below-grade GEOENGINEERS June 11,2018 Page 9 File No.23459-001-00 portion of the building, even if the recommended wall drainage and below-slab drainage provisions are constructed. If leaks or seepage is undesirable, below-grade waterproofing should be specified. A waterproofing consultant should be contracted to provide recommendations for below-grade waterproofing for this project. EXCAVATION SUPPORT We understand that excavations may range from 7 to 17 feet below site grades.The subsurface conditions support use of temporary cut slopes and soil nail walls for temporary excavation support.Soil nails will likely need additional measures,such as vertical elements,to control face stability. The following sections provide geotechnical design and construction recommendations for soil nail walls. The soil nail wall design should take into account the soft silt soils. It will likely be necessary to implement vertical elements in the upper portion of the soil nail wall in areas where fill or soft soils are present. Additionally, vertical elements can be used to control deflections of the shoring system provided that they extend full depth. Full depth vertical elements (extending at least 5 feet below the planned bottom of excavation elevation)should be considered where heavy construction surcharges are anticipated,or where deflection tolerances are lower to protect adjacent improvements.The need for vertical elements or other measures should be evaluated by the shoring designer during design of the shoring system. Because soil nails will extend into private property, easements will be required. The following sections provide design information for temporary cut slopes and soil nail walls. 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. 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. Temporary cuts within the fill and soft to very soft silt soils may be cut at a maximum inclination of 11 H:1V. 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 GEOENGINEERS. June 11,2018 Page 10 Ale No.23459-001-00 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. Water that enters the excavations must be collected and routed away from prepared subgrade areas. We expect that this may be accomplished by installing a system of drainage ditches and sumps along the toe of the cut slopes. Some sloughing and raveling of the cut slopes should be expected. If excessive groundwater is observed while making cuts, then alternative groundwater control systems will be necessary,such as well points or wells.Temporary covering,such as heavy plastic sheeting with appropriate ballast, should be used to protect these slopes during periods of wet weather. Surface water runoff from above cut slopes should be prevented from flowing over the slope face by using berms, drainage ditches, swales or other appropriate methods. If temporary cut slopes experience excessive sloughing or raveling during construction, it may become necessary to modify the cut slopes to maintain safe working conditions.Slopes experiencing problems can be flattened, regraded to add intermediate slope benches, or additional dewatering can be provided if the poor slope performance is related to groundwater seepage. Soil Nail Walls The soil nail wall system consists of drilling and grouting rows of steel bars or"nails" behind the excavation face as it is excavated and then covering the face with reinforced shotcrete. The placement of soil nails reinforces the soils located behind the excavation face and increases the soil's ability to inhibit a mass of soil from sliding into the excavation. It may be necessary to utilize vertical elements, post-tensioned nails and/or temporary cut slopes in areas where looser soils are present and/or where wall deflections must be limited to protect existing improvements. Soil nail walls are typically constructed using the following sequence: 1. Install vertical elements (where necessary) into vertical drilled holes and grout each hole with lean concrete. 2. Excavate the soil at the wall face to between 1 and 3 feet below the row of soil nails to be installed. Depending upon the soil conditions at the wall face, the excavation may be completed with a vertical cut or with berms (native or fill). 3. Drill, install and grout soil nails. 4. Excavate berm, if present, located within about 3 feet below the elevation of the soil nail. 5. Place drainage strips,steel wire mesh and/or reinforcing bars in front of the excavated soil. 6. Install shotcrete and place steel plates and nuts over the soil nails. 7. Complete nail pullout capacity testing on approximately one out of every 20 nails in an installed row. 8. Repeat steps two through seven for each row of nails located below the completed row. GEoENGINEERS,g June 11,2018 Page 11 File No.23459-001-00 Vertical elements may be used to improve face stability of the site soils or to act as a cantilever wall to meet nail clearance requirements where buried utilities are present.Vertical elements typically consist of vertical steel beams placed in drilled holes located along the wall alignment and backfilled with lean concrete. Soil nails typically consist of #6 to #12 threaded steel bars (3/4- to 1%-inch-diameter). The steel bars are placed in 4- to 8-inch-diameter holes drilled at angles typically ranging from 10 to 25 degrees below horizontal. Centralizers are used to center the steel bars in the holes. Once the steel bars are installed,the holes are grouted using cement grout or concrete. The soils typically are required to have an adequate standup time (to allow placement of the steel wire mesh and/or reinforcing bars to be installed and the shotcrete to be placed).Soils that have short standup times are problematic for soil nailing and may require the use of vertical elements. Preliminary Design Recommendations Soil nail wall design should be completed by the specialty contractor. We recommend the following for preliminary design and cost estimating purposes: ■ Vertical elements (where necessary) installed at approximately 6 feet on center. ■ A soil nail grid pattern of about 6 feet by 6 feet. ■ A soil nail length ranging up to the wall height (but not less than 10 feet), inclined at about 15 to 20 degrees from the horizontal. ■ A preliminary allowable load transfer of 1.0 kips/foot for fill and soft silt, and 1.5 kips per foot for medium stiff silt soils for 6-to 8-inch-diameter grouted nails. ■ Strips of drainage material installed behind the shotcrete to relieve hydrostatic pressures. Additional drainage provisions may be necessary if significant groundwater is encountered during the excavation. Soft silt may affect the soil nail design. Typically,the soil nail spacing is tighter or the soil nails are longer, or both, where low strength soils are present. Difficulties associated with face stability and standup time may be experienced during construction in the site soils. Soft silt soils and soils in areas with groundwater seepage may exhibit shorter standup times. Spalling and raveling of the cut face may occur at these locations during soil nail wall installation. Construction techniques used to mitigate spalling and raveling include: ■ Flash coating the cut face with 2 to 4 inches of shotcrete immediately after the cut face is excavated to final line and the drainage material is installed.This typically provides enough standup time to allow for the installation of the reinforcing steel and final shotcrete. ■ Excavating in half-height(2-to 3-foot) lifts, rather than full-height(6-foot) lifts. ■ Excavating leaving a 1H:1V earth berm in front of the wall.The soil nails are installed by drilling through the soil berm. The soil berm is then removed to allow for installation of the drainage material and reinforcing steel and shotcrete. ■ Shortening the length of wall drilled and shotcreted using a staggered excavation approach. ■ Installing closely spaced vertical soil nails or small steel beams (vertical elements) along the wall alignment. GEoENGINEERSIZ) June 11,2018 Page 12 File No.23459-001-00 Contractors experienced in the soil nailing method should be able to mitigate significant spalling and raveling conditions.Contractors should also be prepared to use techniques to address problems that occur because of caving soils.The contractor should be made responsible for the safety of the shoring system. Soil Nail Wall Performance A soil nail wall is a passive shoring system that requires deflections for load to be applied to the soil nails. We recommend that the soil nail be designed such that average wall deflections are limited to 1 inch and ground surface settlements behind the wall are less than about 1 inch. Where existing structures are located within 10 feet of the shoring wall, the soil nail wall should be designed to limit deflections to less than 1 inch. The deflections and settlements are usually highest at the excavation face and decrease to negligible amounts beyond a distance behind the wall equal to the excavation height.Wall deflections can be reduced by post-tensioning the upper row(s) of soil nails. Localized deflections may exceed the above estimates and may reflect local variations in soil conditions (such as around abandoned side sewers) or may be the result of the workmanship used to construct the wall. Monitoring of the shoring system should be completed as described in Appendix B, Ground Anchor Load Tests and Shoring Monitoring Program. Drainage A suitable drainage system should be installed to prevent the buildup of hydrostatic groundwater pressures behind the soil nail walls. Drainage behind soil nail walls typically consists of prefabricated geocomposite drainage strips, such as Mirafi G100TM, installed vertically between the soil nails. The drainage strips are typically a minimum of 16 inches wide and extend the entire height of the wall. Horizontal drainage strips may also be used in areas where perched groundwater is observed or for other reasons. We recommend that drainage strips be connected to a tightline pipe installed along the base of the wall and routed to a suitable discharge point as described above in the "Below-Grade Walls"section of this report. EARTHWORK The on-site soils contain a high percentage of fines(material passing the U.S.standard No.200 sieve)that are extremely moisture-sensitive and susceptible to disturbance, especially when wet. Ideally, earthwork should be undertaken during extended periods of dry weather when the surficial soils will be less susceptible to disturbance and provide better support for construction equipment. Dry weather construction will help reduce earthwork costs.If earthwork will occur from October through May,we suggest that a contingency be included in the project schedule and budget to account for increased earthwork difficulties. Trafficability is not expected to be difficult during dry weather conditions and if groundwater is controlled in excavations. However, the native soils will be susceptible to disturbance from construction equipment during wet weather conditions or if groundwater seepage is not controlled adequately. Even in the summer months pumping and rutting of the exposed native soils under equipment loads will occur. Clearing and Site Preparation Areas to receive fill, structures or pavements should be cleared of vegetation and stripped of topsoil. Clearing should consist of removal of all debris, trees, brush and other vegetation within the designated GEOENGINEERS June 11,2018 Page 13 File No.23459-D01-00 clearing limits.The topsoil materials could be separated and stockpiled for use in areas to be landscaped. Debris should be removed from the site, but organic materials could be chipped/composted and also reused in landscape areas, if desired. We anticipate that the depth of stripping will range from 2 to 8 inches across the site.Stripping depths may be greater in some areas,particularly where trees and large vegetation have been removed.Actual stripping depths should be determined based on field observations at the time of construction.The organic soils can be stockpiled and used later for landscaping purposes or may be spread over disturbed areas following completion of grading. If spread out,the organic strippings should be placed in a layer less than 1-foot-thick, should not be placed on slopes greater than 3H:1V and should be track-rolled to a uniformly compacted condition. Materials that cannot be used for landscaping or protection of disturbed areas should be removed from the project site. Grubbing should consist of removing and disposal of stumps, roots larger than 1-inch-diameter and matted roots. Grubbed materials should be completely removed from the project site.All depressions made during the grubbing activities to remove stumps and other materials should be completely backfilled with properly placed and compacted structural fill. Subgrade Preparation Upon completion of site preparation activities, the exposed subgrade should be proof-rolled with a fully loaded dump truck or similar heavy rubber-tired construction equipment to identify soft, loose or unsuitable areas. Proof-rolling should be conducted prior to placing fill and should be observed 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, these areas should be excavated to the extent indicated by our representative and replaced with Imported Select Structural Fill as defined in this report. 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 Imported Select Structural Fill as defined in this report. Subgrade Protection Site soils contain significant fines content (silt and clay) and will be highly sensitive and susceptible to moisture and equipment loads. The exposed subgrade soils can deteriorate rapidly in wet weather and under equipment loads. The contractor should take necessary measures to prevent site subgrade soils from becoming disturbed or unstable. Construction traffic during the wet season should be restricted to specific areas of the site, preferably areas where a working pad has been constructed. Protecting the existing soils with a thin layer of crushed rock will not be adequate during the wet season and the subgrade will still deteriorate under equipment loads. If wet weather construction is planned, consideration should be given to protecting the exposed subgrade areas with a thick section of crushed rock underlain by a geotextile separator. GEOENGINEERS1j. June 11,2018 Page 14 File No.23459-001-00 Structural Fill and Backfill 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. Use of On-site Soil As described in the "Subsurface Conditions" section, the on-site surface soil consists of 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. 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. 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. 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. GEOENGINEERS June 11,2018 Page 15 File No.23459-001-00 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. Fill Placement and Compaction Structural fill should be compacted at moisture contents that are within 2 percent of the optimum moisture content as determined by ASTM International (ASTM) Standard Practices 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. TABLE 2.COMPACTION CRITERIA Compaction Requirements Fill Type Percent Maximum Dry Density Determined by ASTM Test Method D 1557 at±3%of Optimum Moisture 0 to 2 Feet Below Subgrade >2 Feet Below Subgrade Pipe Zone Fine-grained soils(non- expansive) 95 92 Imported Granular, maximum 95 95 particle size< 11/4 inch -- Imported Granular, maximum particle size 11/4 inch to 4 inches (3-inch maximum under building n/a (proof roll) n/a (proof roll) footprints) Retaining Wall Backfill* 92 92 --- Nonstructural Zones 90 90 90 Trench Backfill 95 90 90 Note: *Measures should be taken to prevent overcompaction of the backfill behind retaining walls. We recommend placing the 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 prior to fill placement. These other methods typically involve procedural placement and compaction specifications together with verifying requirements such as proof-rolling. GEOENGINEERY June 11,2018 Page 16 File No.23459-001-00 Permanent Cut and Fill Slopes We recommend that permanent slopes be constructed at inclinations of 2H:1V or flatter. Fill slopes should be blended into existing slopes with smooth transitions. To achieve uniform compaction, we recommend that fill slopes be overbuilt slightly and subsequently cut back to expose well compacted fill. 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 SC150) could be used to protect the slopes during periods of rainfall. 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. TEMPORARY CONSTRUCTION DEWATERING Groundwater levels observed at the time of drilling indicates that groundwater will likely be encountered during construction.The contractor should plan for groundwater control consisting of sumps and pumps to complete the excavations. Surface water from rainfall will likely contribute significantly to the volume of water that needs to be removed from the excavation during construction and will vary as a function of season and precipitation. If significant groundwater seepage is observed during site excavations a more robust dewater system may be needed such as well points or deep wells. It may be beneficial to have the contractor excavate a test trench in the center of the site to observe groundwater flow conditions and excavation stand-up time prior to commencing the mass excavation. The temporary dewatering system should be designed to maintain the groundwater level at least 3 feet below the foundation subgrade elevation until such time that the engineer determines that the permanent underslab drainage system is completely constructed, all foundations and underground utilities are installed and the permanent underslab drainage system is functioning properly. In our opinion,the contractor should be responsible for designing and installing the appropriate dewatering system needed to complete the work.Appropriate discharge points should be designated by the contractor. Also, the contractor will need to obtain the necessary discharge permits from the regulatory agencies. We recommend the details of the dewatering system be reviewed by GeoEngineers prior to construction. This will allow us to evaluate if the designs are consistent with the intent of our recommendations and to provide supplemental recommendations in a timely manner. Other dewatering issues that must be addressed include disposal of water and backup power. We anticipate that water removed from excavations will be diverted into the existing storm sewer system. A permit will be required to do this.Water sampling prior to and during dewatering may also be required as a part of the permit. The following sections discuss sump pumping. Recommendations for well points and deep wells are not included in this report but can be provided if needed. GEOENGINEERS June 11,2018 Page 17 File No.23459-001-00 Sump Pumping . This dewatering method involves removing water that has seeped into an excavation by pumping from a sump that has been excavated at one or more locations in an excavation. Drainage ditches that lead to the sump are typically excavated along the excavation sidewalls at the base of an excavation. The excavation for the sump and discharge drainage ditches should be backfilled with gravel or crushed rock to reduce the amount of erosion and associated sediment in the water pumped from the sump. In our experience, a slotted casing or perforated 55-gallon drum that is installed in the sump backfill provides a suitable housing for a submersible pump.Surface water from rainfall will likely contribute significantly to the volume of water that needs to be removed from the excavation during construction and will vary as a function of season and precipitation. Surface Water Drainage Considerations All paved and landscaped areas should be graded so that surface drainage is directed away from the proposed buildings to appropriate catch basins. Water collected in roof downspout lines must not be routed to the footing drain lines or subsurface drain lines. Collected downspout water should be routed to appropriate discharge points in separate pipe systems. PAVEMENT RECOMMENDATIONS General Pavement subgrades should be prepared in accordance with the "Earthwork" section of this report. The design of the recommended pavement sections is based on an assumed California Bearing Ratio of 3. Our pavement design is based on an estimated traffic volume for this facility of 200 cars and up to 1 truck per day. Heavy construction traffic has not been considered in our pavement design;therefore,we assume that the pavements will be constructed at the end of the project after heavy construction vehicles,such as concrete trucks and construction material delivery trucks,will no longer access the site. Construction traffic should not be allowed on new pavements. If this is not the case,we will have to re-design the pavements for those heavier loading conditions. 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. Pavement Sections Based on the estimated traffic data and our analyses,our recommended pavement sections are presented in Table 3. GEOENGINEERS June 11,2018 Page 18 File No.23459-001-00 TABLE 3. RECOMMENDED PAVEMENT SECTIONS Minimum PCC Minimum Asphalt Minimum Aggregate Base Thickness Thickness Thickness (inches) (inches) (inches) 5 - 6 3.5 8 The aggregate base course should conform to the "Aggregate Base" section of this report and be compacted to at least 95 percent of the maximum dry density determined in accordance with AASHTO T-180/ASTM Test Method D 1557. The asphalt concrete (AC) pavement should conform to Section 00745 of the most current edition of the Oregon Department of Transportation (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 binder should be PG 64-22 grade meeting the ODOT Standard Specifications for Asphalt Materials. AC pavement should be compacted to 91.0 percent of the Maximum Theoretical Unit Weight (Rice Gravity) as determined by AASHTO T-209. PCC pavement sections should be Class 4000 3/4-inch-minus with minimum 28-day flexural strength of 600 pounds per square inch (psi). Class 4000 indicates a design compressive strength of 4,000 psi. The recommended pavement sections assume that final improvements surrounding the pavement will be designed and constructed such that stormwater, groundwater or excess irrigation water from landscape areas does not infiltrate below the pavement section into the crushed base. LIMITATIONS We have prepared this report for the exclusive use of Trailblazer Development, LLC and their authorized agents and/or regulatory agencies for the proposed storage facility located on SW Atlanta Street in Tigard, Oregon. 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. GEOENGINEER1c) June 11,2018 Page 19 File No.23459-001-00 REFERENCES International Code Council. 2015. 2015 International Building Code. International Code Council. 2014. 2014 Oregon Structural Specialty Code. Ishihara and Yoshimine. 1992. "Evaluation of Settlements in Sand Deposits Following Liquefaction During Earthquakes,"Soils and Foundations, 32(1), pp. 173-188. 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: http://www.osha.gov/dts/osta/otm/otm v/otm v 2.html. Personius. 2002. Fault number 716, Canby-Molalla fault, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, httpV/earthquakes.usgs.gov/hazards/ofaults, Accessed 6/7/2018. Tokimatsu and Seed. 1987. "Evaluation of Settlements in Sands Due to Earthquake Shaking,"Journal of Geotechnical Engineering,ASCE, 113 (GT8), pp.861-878. Youd, et al. 2001. "Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of Soils,"Journal of Geotechnical and Geoenvironmental Engineering,ASCE, October 2001, pp. 817-833. GEoENGINEERS June 11,2018 Page 20 File No.23459-001-00 N W W Z Z rWn V isv nrugger]c D L < y • r. -.. SW Taylors Fern/Rd'Z CO `w SW Evelyn St $ SW Wiibard St 3 SW Huber St SW Radcliff St SW Alfred St — n As SWEImwcd`, shingtoc fluare j2y Mall r' SW Lehmann SC - o Sly -40 or 3 V a �t then g,Park n Dr f `a Markhar f tt Grove - SW Coral St v__ S W 4 Ditkinson Parts - St c-.ete.•r t. entura Dr rt d WE '-SV t Must St 'SW L..,us>St m a w > 3 > METZGER r a v a t `Q s d is $ eyta Dr Wr x Sr sme-=r,ry a ,SW Mapleieaf St 1 3 3 3 pasad tiil h. ,W is:k ' z _. SW OakStS:^r. `1,, v c. f-,F' L�'f anEHwp s--- SW Pine St �''"' n VILLA RIDGE:, e. ,' SWSprureSt --- SW Spruce St Z e.r ¢ Ca 3 i n s v © fJ i; 3 tt s a L ♦ Pnt Gaod Camnwnity It ` Lasser patlK f (ry�v 4yNa*.,r j, .a - h Sct ca ,4 rn R nG ' z D S,, ' pr 0,44 r'n63a rd i'atk a c▪ 3{n Tigard w ' wAi Galer tt a a 7,g.d Tran 1 Ccmxr a t° z SF,>. .` > 5 C. a q M v QNyr Oak Creek Elementary ed El-..ent.ry _ Srhooi a Melrose St Mr,Scharr ,* t nton Or canna::eek€ark �Cn pe 'y ,.. SW Varna SI -. o0 3 Nest, R ,fZ Fan (e.ek Pa'a C I't"gs {9 r �. 4.;" • s 2 , GrA e. e;" (al.,,y Creek Grxnway e kruse ci Way. 4rrtse>P r Kr u_r 8 sw McDnn,iC St S.r RcDon,c1 St E W ti N 0w\ r w'i ' . o .LTi ml..E LTJ Vancouver `�/�'' yS Camas ' Forest Grove Portland 2,000 0 2,000 g > 4 min mi ,--i Oregon City Feet 0 , a• Notes: Vicinity Map 2 1.The locations of all features shown are approximate. O• 2.This drawing is for information purposes.It is intended to assist in SW Atlanta St. Storage Building • showing features discussed in an attached document.GeoEngineers,Inc. (77• 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 this communication. rn LC) d- m Data Source:Mapbox Open Street Map,2016 G EO E N G I N E E R Figure 1 m N Projection:NAD 1983 UTM Zone TON a N W W Z cc Z W tWn V 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 May 27, 2018 by completing two borings at the approximate locations shown in the Site Plan, Figure 2. The borings were advanced using a trailer- mounted drill rig owned and operated by Dan Fischer Excavating. The drilling was continuously monitored by an 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 soil samples were obtained from each boring at approximate 21/2-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 D 1556 Standard Penetration Test(SPT) N-value. The N-value for D&M samples has been reduced by approximately 50 percent from the field readings to roughly correlate with the SPT N-values. 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 and A-3.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 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-4 in this appendix. GEOENGINEERS� June 11,2018 Page A-1 File No.23459-001-00 SOIL CLASSIFICATION CHART ADDITIONAL MATERIAL SYMBOLS MAJOR DIVISIONS SYMBOLS TYPICAL SYMBOLS TYPICAL GRAPH LETTER DESCRIPTIONS GRAPH LETTER DESCRIPTIONS o"Uc CLEAN GRAVELS o3° GW WELL-GRADED GRAVELS,GRAVEL- GRAVEL D SAND MIXTURES AC Asphalt Concrete AND 0 o GRAVELLY (LITTLE OR NO ONES) o ° c POORLY-GRADED GRAVELS, SOILS 0 o o GP GRAVEL-SAND MIXTURES '/\/\//\ O I O I C �i�A�ii� CC Cement Concrete COARSE GRAVELS WITH m SILTY GRAVELS,GRAVEL-SAND- GRAINED MORE THAN 50% if• GM SILT MIXTURES SOILS OF COARSE FINES I •'. • CR Crushed Rock/ FRACTION RETAINED . ON NO.4 SIEVE (APPRECIABLEOF FINES)AMOUNT o GC CLAYEY GRAVELS GRAVEL-SAND- • �' Quarry Spalls CLAY MIXTURES 0 ii 0 i/ 0 i 0 I, SOD Sod/Forest Duff WELL-GRADED SANDS,GRAVELLY CLEAN SANDS SW SANDS MORE THAN 50% SAND c NO.200 SIEVE SAND ANDY (LITTLE OR NO FINES) oo SPTS Topsoil POORLY-GRADED SANDS,GRAVELLY SOILS SAND Z,^,^:^::::',;. : MORE THAN50% SANDS WITH I SM SILTY SANDS,SAND-SILT MIXTURES OF COARSE FINES Groundwater Contact FRACTION PASSING ON NO.4 SIEVE //7/ (APPR EOFCIARLFINES YE;MOUNT SC XTEYR SNDS,SAND-CLAY . Measured groundwater level in exploration, well,or piezometer INORGANIC SILTS,ROCK FLOUR, ML CLAYEY SILTS WITH SLIGHT PLASTICITY Measured free product in well or piezometer j SILTS AND / INORGANIC CLAYS OF LOW TO LIQUID LIMIT l CL MEDIUM PLASTICITY,GRAVELLY Graphic Log Contact FINE CLAYS LESS THAN 50 l/ LEAN CLAYS YCLAYS,SILTY CLAYS, GRAINED SOILS ORGANIC SILTS AND ORGANIC SILLY Distinct contact between soil strata OL CLAYS OF LOW PLASTICITY MORE THAN 50% INORGANIC SILTS,MICACEOUS OR / Approximate contact between soil strata PASSING Mn DIATOMACEOUS SILTY SOILS NO.200 SIEVE Material Description Contact SILTS AND CLAYS LIQUID LIMIT GREATER CH INORGANIC CLAYS OF HIGH Contact between geologic units THAN 50 PLASTICITY g g ORGANIC CLAYS AND SILTS OF —— Contact between soil of the same geologic OH MEDIUM TO HIGH PLASTICITY unit HIGHLY ORGANIC SOILS ' PT PEAT,HUMUS,SWAMP SOILS WITH HIGH ORGANIC CONTENTS Laboratory/ Field Tests �Mn NOTE: Multiple symbols are used to indicate borderline or dual soil classifications %F Percent fines %G Percent gravel Sampler Symbol Descriptions AL Atterberg limits CA Chemical analysis 2.4-inch I.D.split barrel CP Laboratory compaction test CS Consolidation test Standard Penetration Test(SPT) DD Dry density IIIDS Direct shear Shelby tube HA Hydrometer analysis Piston MC Moisture content MD Moisture content and dry density IIDirect Push Mohs Mohs hardness scale OC Organic content IIIBulk or grab PM Permeability or hydraulic conductivity PI Plasticity index I Continuous Coring PP Pocket penetrometer SA Sieve analysis on Blowcount is recorded for driven samplers as the number of TX TriaxialUnconfined cecompression UC acompression blows required to advance sampler 12 inches(or distance noted). VS Vane shear See exploration log for hammer weight and drop. "P"indicates sampler pushed using the weight of the drill rig. Sheen Classification NS No Visible Sheen "WOW 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. I ` Key to Exploration Logs GEOENGINEERS FigureA-1 , / Rev 06/2017 I • Start End Total Logged By JLL Drilling ` Drilled 5/27/2018 5/27/2018 Depth(ft) 31.5 Checked By GAL Driller Dan Fischer Drilling Method Hollow-stem Auger Surface Elevation(ft) 214 Hammer Rope&Cathead Drilling Paul Bunyan Trailer Vertical Datum NAVD88 Data 140(lbs)/30(in)Drop Equipment Latitude 45.437 System OR Decimal Degrees See'Remarks"section for groundwater observed Longitude -122.7548 Datum WGS84(feet) Notes: D&M N-value reduced 50%to approximate SPT N-value • I I V FIELD DATA I CO s MATERIAL REMARKS o o C 2 o z J DESCRIPTION O L j 7 u, ,1i3 -Uc L Q„- J G C 16 O v - O- 3 N N.o. 2'C') > a N N O ,3 as y ,- O .o c W 0 CC CO o cn as H 0 0 U §3 li U 0 ML Dark brown silt with trace sand,occasional gravel and - - fine roots to 8 inches,low to moderate plasticity - (very soft,moist)(fill) - - o ML Brown silt with trace sand,low plasticity(very soft, —`L,' - - moist) - 5 /V 2 0 1 - o -, _ — 1012 9 2 Becomes gray-brown and stiff,with occasional layers — 35 DD=87 pcf;AL(LL=30,PL=27,PI=3) MD;AL - of sandy silt - Groundwater observed at 10 feet during drilling 0 -10 - - Dark gray sandy silt,massive(stiff,wet) - 30 15X10 — — 13 3 ao10 10 4 37 51 DD=84pcf - A MD;%F - 20 -: ML/SM — Interbedded dark gray fine sandy silt and silty fine — 35 69 E \/ 10 2 F sand with occasional dark brown fibrous organic - /x\ - matter,rapid to very rapid dilatancy(soft to very loose,wet) _ 6 7 C _ 31 80 DD=85 pcf 8_ O mo;%F ML Dark gray silt with fine sand,low plasticity to - 25 X12 13 7 % — nonplastic(very rapid dilating(stiff,wet) — 84 - F ',n 0 P,y40 - - - 30 \I 26 $ — — 28 z _ X MC 0 0 0 0 a z Note:See Figure A-1 for explanation of symbols. 8 Coordinates Data Source:Horizontal approximated based on USGS Topo.Vertical approximated based on USGS Topo. 8' i 5! Log of Boring GEI B-1 Project: SW Atlanta Street Storage Building " G EO E N G I N E E R S Project Location: Tigard,Oregon Figure A-2 Project Number: 23459-001-00 Sheet 1 of 1 ii i Start End. Total 5 Logged By JLL Driller Dan Fischer Drilling Drilling Hollow-stem Auger Drilled 5/27/2018 5/27/2018 Depth(ft) Checked By GAL Method Surface Elevation(ft) 206 Hammer Rope&Cathead Drilling Paul Bunyan Trailer Vertical Datum NAVD88 Data 140(lbs)/30(in)Drop Equipment Latitude 45.4367 System OR Decimal Degrees See'Remarks"section for groundwater observed Longitude -122.755 Datum WGS84(feet) Notes: D&M N-value reduced 50%to approximate SPT N-value i , V FIELD DATA o N z o c. MATERIAL a o REMARKS A? DESCRIPTION - B .G N a• N bD .2 t > > of c .c a.(7) aci ami N a '6 U N• E N PP O N N� N l W ❑ c cc m U Pn- C7 0U 2U it8 0 g ML Dark brown silt with trace sand and rootlets to 10 iz -I' - - inches,low plasticity(soft,moist) - o S \/ 16 9 1 Becomes mottled brown and light gray,stiff - - Becomes wet Groundwater observed at 8 feet during drilling - - ---- ML Interbedded dark SM/ gray silty fine sand and sandy silt, 1.0 • — low plasticity to non-plastic,massive to horizontal — 38 61 y9h x12 6 %F - laminations(loose to medium stiff,wet) - _\/ 14 8 3 - _ SM — Darkgraysiltyfine sand,massive,rapid dilatancy(very• ( ry — 29 26 yao 8 4 MD%F - loose to loose,wet) DD=95 pcf o' zi- - - _X 14 2 5 - Becomes very loose - N, ML Dark gray silt with fine sand,massive,low plasticity w- 20 — (medium stiff,wet) — 32 94 6 8 5 y$0 %F _52-: o- - 0 0 z)_ - - Dark gray silt to sandy silt,massive,low plasticity(stiff, - moist) - 250 0 \/ 10 15 7 — — 0 - 0 0,- - _tiA<0 30 \/ 10 17 Aa Becomes very stiff 27 AL(LL=32,PL=25,PI=7) o_ I o 0 0 w a P-. `% Note:See Figure A-1 for explanation of symbols. 8 Coordinates Data Source:Horizontal approximated based on USGS Topo.Vertical approximated based on USGS Topo. a• , N, , 5 Log of Boring GEI B-2 Project: SW Atlanta Street Storage Building . G EOENGINEER Project Location: Tigard,Oregon Figure A-3 Project Number: 23459-001-00 Sheet 1 of 2 , FIELD DATA w — o MATERIAL C 2 z J DESCRIPTION REMARKS UO L+' (>3 L a —N U C Q co.N 3 N N N N N d p E V) @ O o o g. cc m U co F C7 C7 U U U ii U 35 12 24 9 '\o X CL Dark gray lean clay,massive,low to moderate plasticity(very stiff,moist) 40 /X\\/ 12 17 10 6 ML/CL Dark gray and brown mottled silt to lean clay,low - plasticity(stiff,moist) - 45 60 V12 11 S 7,17 c� C, vt 1 Log of Boring GEI B-2(continued) Project: SW Atlanta Street Storage Building G EO E N G I N E E R S Project Location: Tigard,Oregon Figure A-3 Project Number: 23459-001-00 Sheet 2 of 2 PLASTICITY CHART 60 • • 50 • • • CH or OH z 40 • • • 30 U) 0_ `?(• OH or MH 20 • .•• CLorOL 10 CL-ML ML or OL •0 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 c B-1 10 35 30 3 Dark brown silt(ML) I=1 B-2 30 27 32 7 Gray silt(ML) Atterberg Limits Test Results r a a LZ SW Atlanta Street Storage Building ',E1 w Tigard, Oregon a si 4 Note:This report may not be reproduced,except in full,without written approval of GeoEngineers,Inc. Test results are applicable - only to the specific sample on which they were performed,and should not be interpreted as representative of any other m GEC NEI ESR samples obtained at other times,depths or locations,or generated by separate operations or processes. Figure A-4 N The liquid limit and plasticity index were obtained in general accordance with ASTM D 4318. APPENDIX B Ground Anchor Load Tests and Shoring Monitoring Program APPENDIX B GROUND ANCHOR LOAD TESTS AND SHORING MONITORING PROGRAM Ground Anchor Load Testing The locations of the load tests shall be approved by the Engineer and shall be representative of the field conditions. Load tests shall not be performed until the ground anchor grout and shotcrete wall facing,where present, have attained at least 50 percent of the specified 28-day compressive strengths. Where temporary casing of the unbonded length of test ground anchors is provided, the casing shall be installed to prevent interaction between the bonded length of the ground anchor and the casing/testing apparatus. The testing equipment shall include two dial gauges accurate to 0.001 inch, a dial gauge support, a calibrated jack and pressure gauge, a pump and the load test reaction frame. The dial gauge should be aligned within 5 degrees of the longitudinal ground anchor axis and shall be independently supported from the load frame/jack and the shoring wall. The hydraulic jack, pressure gauge and pump shall be used to apply and measure the test loads. The jack and pressure gauge shall be calibrated by an independent testing laboratory as a unit. The pressure gauge shall be graduated in 100 pounds per square inch (psi) increments or less and shall have a range not exceeding twice the anticipated maximum pressure during testing unless approved by the Engineer. The ram travel of the jack shall be sufficient to enable the test to be performed without repositioning the jack. The jack shall be independently supported and centered over the ground anchor so that the ground anchor does not carry the weight of the jack. The jack, bearing plates and stressing anchorage shall be aligned with the ground anchor. The initial position of the jack shall be such that repositioning of the jack is not necessary during the load test. The reaction frame should be designed/sized such that excessive deflection of the test apparatus does not occur and that the testing apparatus does not need to be repositioned during the load test. If the reaction frame bears directly on the shoring wall facing, the reaction frame should be designed to not damage the facing. Verification Tests Prior to production ground anchor installation,at least two ground anchors for each soil type shall be tested to validate the design pullout value. All test ground anchors shall be installed by the same methods, personnel, material and equipment as the production anchors. Changes in methods, personnel, material or equipment may require additional verification testing as determined by the Engineer. At least two successful verification tests shall be performed for each installation method and each soil type.The ground anchors used for the verification tests may be used as production ground anchors if approved by the Engineer. The allowable ground anchor load should not exceed 80 percent of the steel ultimate strength. GEOENGINEERS� June 11,2018 Page B-1 File No.23459-001-00 Ground anchor design test loads should be the design loads specified on the shoring drawings.Verification test tiebacks shall be incrementally loaded and unloaded in accordance with the following schedule: Load Hold Time Load Hold Time Alignment Load(AL) Until Stable 0.75DL Until Stable 0.25 Design Load (DL) Until Stable 1.0DL Until Stable AL Until Stable 1.25DL Until Stable 0.25DL Until Stable 1.5DL 10 Minutes 0.5DL Until Stable AL Until Stable AL Until Stable 0.25DL Until Stable 0.25DL Until Stable 0.5DL Until Stable 0.5DL Until Stable 0.75DL Until Stable 0.75DL Until Stable 1.0DL Until Stable AL Until Stable 1.25DL Until Stable 0.25DL Until Stable 1.5DL Until Stable 0.5DL Until Stable 1.75DL Until Stable 0.75DL Until Stable AL Until Stable 1.0DL Until Stable 0.25DL Until Stable AL Until Stable 0.5DL Until Stable 0.25DL Until Stable 0.75DL Until Stable 0.5DL Until Stable 1.0DL Until Stable 0.75DL Until Stable 1.25DL Until Stable 1.0DL Until Stable 1.5DL Until Stable 1.25DL Until Stable 1.75DL Until Stable AL Until Stable 2.0DL 10 Minutes 0.25DL Until Stable AL Until Stable 0.5DL Until Stable The alignment load shall be the minimum load required to align the testing apparatus and should not exceed 5 percent of the design load.The dial gauge should be zeroed after the alignment load is applied. Proof Tests The allowable ground anchor load should not exceed 80 percent of the steel ultimate strength. GEOENGINEER_ June 11,2018 Page B-2 File No.23459-001-00 • Ground anchor design test loads should be the design loads specified on the shoring drawings. Proof test tiebacks shall be incrementally loaded and unloaded in accordance with the following schedule: Load Hold Time AL Until Stable 0.25DL Until Stable 0.5DL Until Stable 0.75DL Until Stable 1.0DL Until Stable 1.33DL 10 minutes AL Until Stable The alignment load shall be the minimum load required to align the testing apparatus and should not exceed 5 percent of the design load. The dial gauge should be zeroed after the alignment load is applied. Depending upon the ground anchor deflection performance,the load hold period at 1.33DL(tiebacks) may be increased to 60 minutes. Ground anchor movement shall be recorded at 1, 2, 3, 5, 6 and 10 minutes during the load hold period. If the ground anchor deflection between 1 and 10 minutes is greater than 0.04 inches, the 1.33DL load shall be continued to be held for a total of 60 minutes and deflections recorded at 20,30, 50 and 60 minutes. Test Ground Anchor Acceptance A test ground anchor shall be considered acceptable when: 1. For tieback verification tests, a tieback is considered acceptable if the creep rate is less than 0.04 inches per log cycle of time between 1 and 10 minutes,and the creep rate is linear or decreasing throughout the creep test load hold period. 2. For proof tests,a ground anchor is considered acceptable if the creep rate is less than 0.04 inches per log cycle of time between 1 and 10 minutes or less than 0.08 inches per log cycle of time between 6 and 60 minutes,and the creep rate is linear or decreasing throughout the creep test load hold period. 3. The total movement at the maximum test load exceeds 80 percent of the theoretical elastic elongation of the unbonded length. 4. Pullout failure does not occur. Pullout failure is defined as the load at which continued attempts to increase the test load result in continued pullout of the test ground anchor. Acceptable proof-test ground anchors may be incorporated as production ground anchors provided that the unbonded test length of the ground anchor hole has not collapsed and the test ground anchor length and bar size/number of strands are equal to or greater than the scheduled production ground anchor at the test location. Test ground anchors meeting these criteria shall be completed by grouting the unbonded length, as necessary. Maintenance of the temporary unbonded length for subsequent grouting is the contractor's responsibility. GEOENGINEERS June 11,2018 Page B-3 File No.23459-001-00 The Engineer shall evaluate the verification test results. Ground anchor installation techniques that do not satisfy the ground anchor testing requirements shall be considered inadequate. In this case,the contractor shall propose alternative methods and install replacement verification test ground anchors. The Engineer may require that the contractor replace or install additional production ground anchors in areas represented by inadequate proof tests. Shoring Monitoring Preconstruction Survey A shoring monitoring program should be established to monitor the performance of the temporary shoring walls and to provide early detection of deflections that could potentially damage nearby improvements. We recommend that a preconstruction survey of adjacent improvements, such as streets, utilities and buildings, be performed prior to commencing construction. The preconstruction survey should include a video or photographic survey of the condition of existing improvements to establish the preconstruction condition,with special attention to existing cracks in streets or buildings. Optical Survey The shoring monitoring program should include an optical survey monitoring program. The recommended frequency of monitoring should vary as a function of the stage of construction,as presented in the following table. Construction Stage Monitoring Frequency During excavation and until wall movements have stabilized Twice weekly During excavation if lateral wall movements exceed 1 inch and until wall Daily movements have stabilized After excavation is complete and wall movements have stabilized,and before the Weekly floors of the building reach the top of the excavation Monitoring should include vertical and horizontal survey measurements accurate to at least 0.01 feet. A baseline reading of the monitoring points should be completed prior to beginning excavation.The survey data should be provided to GeoEngineers for review within 24 hours. For shoring walls, we recommend that optical survey points be established along the top of the shoring walls and at the curb line behind the shoring walls. The survey points along the top of the shoring wall should be spaced every 25 feet for soil nail walls and adjacent buildings.The points on the curb lines should be spaced approximately 25 feet apart. GeoEngineers recommends that a survey monitoring plan be developed for GeoEngineers' review prior to establishing the survey points in the field. If lateral wall movements are observed to be in excess of/ inch between successive readings or if total wall movements exceed 1 inch,construction of the shoring walls should be stopped to determine the cause of the movement and to establish the type and extent of remedial measures required. GEOENGINEERS June 11,2018 "" Page B-4 File No.23459-001-00 APPENDIX C Report Limitations and Guidelines for Use 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 Trailblazer Development, LLC for the SW Atlanta Street Storage Building 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 Trailblazer Development dated May 24, 2018 (authorized May 24, 2018) 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 SW Atlanta Street Storage Building project located north of SW Atlanta Street 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: ■ not prepared for you, ■ not prepared for your project, ■ not prepared for the specific site explored, or ■ 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; 1 Developed based on material provided by GBA,GeoProfessional Business Association;www.geoprofessional.org. GEOENGINEERSI June 11,2018 Page C-1 File No.23459-001-00 elevation,configuration, location, orientation or weight of the proposed structure; 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 GEOENGINEERS_g June 11,2018 Page C-2 File No.23459-001-00 0 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 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: ■ 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. GEOENGINEERS June 11,2018 Page C-3 File No.23459-001-00 Have we delivered World Class Client Service? Please let us know by visiting www.geoengineers.com/feedback. GEOENGINEERS'