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Report (2) OFFICE COPY VOID Engineering, Inc. Real-World Geotechnical Solutions Investigation • Design • Construction Support Geotechnical Engineering Report North Dakota Street Subdivision 11375 SW North Dakota Street Tigard, Oregon 97223 GeoPacific Engineering, Inc. Project No. 18-4824 Revised April 30, 2018 14835 SW 72"d Avenue Tel (503) 598-8445 Portland, Oregon 97224 Fax(503) 941-9281 GeoP Inoiteennp Ire Real-World Geotechnical Solutions Investigation • Design • Construction Support TABLE OF CONTENTS List of Appendices List of Figures PROJECT INFORMATION 1 SITE AND PROJECT DESCRIPTION 1 REGIONAL GEOLOGIC SETTING 2 REGIONAL SEISMIC SETTING 2 Portland Hills Fault Zone 2 Gales Creek-Newberg-Mt. Angel Structural Zone 3 Cascadia Subduction Zone 3 FIELD EXPLORATION AND SUBSURFACE CONDITIONS 3 Groundwater and Soil Moisture 4 Pavement Evaluation 4 CONCLUSIONS AND RECOMMENDATIONS 5 Site Preparation Recommendations 5 Engineered Fill 6 Excavating Conditions and Utility Trench Backfill 7 Erosion Control Considerations 7 Wet Weather Earthwork 8 Spread Foundations 9 Drainage 9 Flexible Pavement Design: SW North Dakota Street 10 Flexible Pavement Design: SW North Dakota Street Widening 11 Flexible Pavement Design: SW 114th Place and SW Ellson Lane 12 Wet Weather Construction Pavement Section 13 Seismic Design and Soil Liquefaction 14 Soil Liquefaction 15 UNCERTAINTIES AND LIMITATIONS 15 REFERENCES 16 APPENDIX 18-4824,North Dakota Street Subdivision GRPT GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 ,11 Gee Mc inx Real-World Geotechnical Solutions Investigation • Design •Construction Support List of Appendices Figures Exploration Logs Laboratory Test Results Flexible Pavement Design Photographic Log List of Figures 1 Site Vicinity Map 2 Site Plan and Aerial and Exploration Locations 18-4824,North Dakota Street Subdivision GRPT 1 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 GeoP , lc war=rmai Real-World Geotechnical Solutions Investigation • Design •Construction Support Revised April 30, 2018 Project No. 18-4824 Al Jeck Venture Properties 4230 SW Galewood Street Suite 100 Lake Oswego, Oregon 97035 Email: al(cr�ventureprop.com SUBJECT: GEOTECHNICAL ENGINEERING REPORT 11375 SW NORTH DAKOTA STREET TIGARD, OREGON 97223 PROJECT INFORMATION This report presents the results of a geotechnical engineering study conducted by GeoPacific Engineering, Inc. (GeoPacific) for the above-referenced project. The purpose of our investigation was to evaluate subsurface conditions at the site, and to provide geotechnical recommendations for site development. This geotechnical study was performed in accordance with GeoPacific Proposal No. P-6353, dated January 9, 2018, and your subsequent authorization of our proposal and General Conditions for Geotechnical Services. SITE AND PROJECT DESCRIPTION The subject property is composed of a single parcel and located on the north side of SW North Dakota Street in the City of Tigard, Washington County, Oregon. The property is approximately 2 acres in size and topography is relatively flat with ground elevations ranging from 227 to 231 feet above mean sea level. The site currently has one home near its southern center and vegetation consists numerous trees along the circumference of the property and grass lawn giving way to blackberry bushes in the center. Multiple dilapidated wooden shed type structures, overgrown with brush, were observed in the northern half of the site. It is our understanding that proposed development includes the demolition of the existing house onsite to allow for 8 lots containing single family homes, construction of a stormwater retention pond, and associated underground utilities. We also understand that development will include improvements to SW 114' Place and extension of SW Ellson Lane to connect to SW 114' Place, as well as improvements to the westbound lane of SW North Dakota Street, within the property frontage, if necessary. A grading plan was not provided for our review; however, we anticipate cuts and fill will be less than 4 feet. 18-4824,North Dakota Street Subdivision GRPT GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report Geed Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon REGIONAL GEOLOGIC SETTING The subject site lies within the Willamette Valley/Puget Sound lowland, a broad structural depression situated between the Coast Range on the west and the Cascade Range on the east. A series of discontinuous faults subdivide the Willamette Valley into a mosaic of fault-bounded, structural blocks (Yeats et al., 1996). Uplifted structural blocks form bedrock highlands, while down-warped structural blocks form sedimentary basins. The site is underlain by the Quaternary age (last 1.6 million years) Willamette Formation, a catastrophic flood deposit associated with repeated glacial outburst flooding of the Willamette Valley (Yeats et al., 1996). The last of these outburst floods occurred about 10,000 years ago. These deposits typically consist of horizontally layered, micaceous, silt to coarse sand forming poorly-defined to distinct beds less than 3 feet thick. Regional studies indicate that the thickness of the Willamette Formation in the vicinity of the subject site is approximately 60 feet (Madin, 1990). The fine-grained soils are underlain by the Columbia River Basalt Formation (Madin, 1990). The Miocene aged (about 14.5 to 16.5 million years ago) Columbia River Basalts are a thick sequence of lava flows which form the crystalline basement of the Tualatin Valley. The basalts are composed of dense, finely crystalline rock that is commonly fractured along blocky and columnar vertical joints. Individual basalt flow units typically range from 25 to 125 feet thick and interflow zones are typically vesicular, scoriaceous, brecciated, and sometimes include sedimentary rocks. REGIONAL SEISMIC SETTING At least three major fault zones capable of generating damaging earthquakes are thought to exist in the vicinity of the subject site. These include the Portland Hills Fault Zone, the Gales Creek- Newberg-Mt. Angel Structural Zone, and the Cascadia Subduction Zone. Portland Hills Fault Zone The Portland Hills Fault Zone is a series of NW-trending faults that include the central Portland Hills Fault, the western Oatfield Fault, and the eastern East Bank Fault. These faults occur in a northwest-trending zone that varies in width between 3.5 and 5.0 miles. The combined three faults vertically displace the Columbia River Basalt by 1,130 feet and appear to control thickness changes in late Pleistocene (approx. 780,000 years) sediment (Madin, 1990). The Portland Hills Fault occurs along the Willamette River at the base of the Portland Hills and is about 7.5 miles northeast of the site. The Oatfield Fault occurs along the western side of the Portland Hills and is about 5 miles northeast of the site. The Oatfield Fault is considered to be potentially seismogenic (Wong, et al., 2000). Madin and Mabey (1996) indicate the Portland Hills Fault Zone has experienced Late Quaternary (last 780,000 years) fault movement; however, movement has not been detected in the last 20,000 years. The East Bank Fault occurs along the eastern margin of the Willamette River, and is located approximately 9 miles northeast of the site. The accuracy of the fault mapping is stated to be within 500 meters (Wong, et al., 2000). No historical seismicity is correlated with the mapped portion of the Portland Hills Fault Zone, but in 1991 a M3.5 earthquake occurred on a NW- trending shear plane located 1.3 miles east of the fault (Yelin, 1992). Although there is no definitive 18-4824,North Dakota Street Subdivision GRPT 2 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 . Geotechnical Engineering Report Geo C#Ilc Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon evidence of recent activity, the Portland Hills Fault Zone is assumed to be potentially active (Geomatrix Consultants, 1995). Gales Creek-Newberg-Mt. Angel Structural Zone The Gales Creek-Newberg-Mt. Angel Structural Zone is a 50-mile-long zone of discontinuous, NW- trending faults that lies about 13 miles southwest of the subject site. These faults are recognized in the subsurface by vertical separation of the Columbia River Basalt and offset seismic reflectors in the overlying basin sediment (Yeats et al., 1996; Werner et al., 1992). A geologic reconnaissance and photogeologic analysis study conducted for the Scoggins Dam site in the Tualatin Basin revealed no evidence of deformed geomorphic surfaces along the structural zone (Unruh et al., 1994). No seismicity has been recorded on the Gales Creek Fault or Newberg Fault (the fault closest to the subject site); however, these faults are considered to be potentially active because they may connect with the seismically active Mount Angel Fault and the rupture plane of the 1993 M5.6 Scotts Mills earthquake (Werner et al. 1992; Geomatrix Consultants, 1995). Cascadia Subduction Zone The Cascadia Subduction Zone is a 680-mile-long zone of active tectonic convergence where oceanic crust of the Juan de Fuca Plate is subducting beneath the North American continent at a rate of 4 cm per year (Goldfinger et al., 1996). A growing body of geologic evidence suggests that prehistoric subduction zone earthquakes have occurred (Atwater, 1992; Carver, 1992; Peterson et al., 1993; Geomatrix Consultants, 1995). This evidence includes: (1) buried tidal marshes recording episodic, sudden subsidence along the coast of northern California, Oregon, and Washington, (2) burial of subsided tidal marshes by tsunami wave deposits, (3) paleoliquefaction features, and (4) geodetic uplift patterns on the Oregon coast. Radiocarbon dates on buried tidal marshes indicate a recurrence interval for major subduction zone earthquakes of 250 to 650 years with the last event occurring 300 years ago (Atwater, 1992; Carver, 1992; Peterson et al., 1993; Geomatrix Consultants, 1995). The inferred seismogenic portion of the plate interface lies roughly along the Oregon coast at depths of between 20 and 40 miles. FIELD EXPLORATION AND SUBSURFACE CONDITIONS Our site-specific explorations for this report were conducted on January 30, 2018 and February 2, 2018. A total of 5 exploratory test pits were excavated with a trackhoe to depths of 11 feet at the approximate locations indicated on Figure 2. It should be noted that test pit locations were located in the field by pacing or taping distances from apparent property corners and other site features shown on the plans provided. As such, the locations of the explorations should be considered approximate. A GeoPacific engineer continuously monitored the excavations and logged the test pits. Soils observed in the explorations were classified in general accordance with the Unified Soil Classification System. During exploration geotechnical conditions such as soil consistency, moisture and groundwater conditions were noted. Logs of test pits are attached to this report. The 18-4824,North Dakota Street Subdivision GRPT 3 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report Gear Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon Dooms ,nt following report sections are based on the conditions observed during our investigation and summarize subsurface materials encountered at the site. 1 Topsoil Horizon: Directly underlying the ground surface in all test pits was a topsoil horizon consisting of dark brown, highly organic SILT (OL-ML). The topsoil horizon was generally loose, contained fine roots throughout, and extended to depths of 8 to 12 inches. A minimal layer of topsoil was observed in test pit TP-4, which was located near the edge of the existing SW Ellson Lane, this area may have been previously stripped at some point during utility installation. A thick layer of topsoil, approximately 18 inches, was observed in test pit TP-5 where the surface soil had appeared to be disturbed and the ground was littered with debris included broken glass and debris. Willamette Formation: Underlying the topsoil horizon in all test pits were fine-grained soils belonging to the Willamette Formation. The light brown SILT (ML) with sand graded to a buff sandy SILT (ML) at depths of 4 to 5 feet and was generally characterized by a medium stiff to very stiff consistency. Subtle to strong orange and gray mottling was observed at varying elevations. Field pocket penetrometer measurements indicate an approximate unconfined compressive strength of 1.0 to 4.0 tons/ft2. In test pits, the sandy SILT extended beyond the maximum depth of our test pit explorations, 11 feet. Groundwater and Soil Moisture On January 30, 2018, groundwater seepage was encountered in test pits TP-2, TP-3, and TP-4 at depths of 4, 8, and 6 feet, respectfully. Experience has shown that temporary storm related perched groundwater within the near surface soils often occur over fine-grained native deposits such as those beneath the site during the wet season and particularly in mottled soils such as were identified in the test pits. It is anticipated that groundwater conditions will vary depending on the season, local subsurface conditions, changes in site utilization, and other factors. Pavement Evaluation As part of our investigation on February 2, 2018, we performed four exploratory pavement cores (RC-1 through RC-4), and an inspection of the condition of the existing asphalt pavement within the proposed development area of SW North Dakota Street and SW 114th Place. The approximate core locations are indicated on Figure 2. During our site visit, we observed some minor cracking of the out 2 feet of existing asphalt on the east edge of SW 114th Place. This is approximately the center line of the proposed widening of SW 114' in association with construction of the subdivision. The existing asphalt pavement surface of SW North Dakota Street was considered to be in good condition and did not display signs of excessive wear. Photos of the cores and existing pavement are provided in the appendix of this report. In the pavement cores of SW North Dakota Street and SW 114th Place, we encountered asphalt pavement over crushed aggregate base rock. Beneath the crushed aggregate we observed subgrade consisting of moist, stiff, brown SILT (ML). At each location we performed strength tests of the subgrade soils using a portable Dynamic Cone Penetrometer (DCP). The DCP values for road core RC-3 were obtained at the shoulder due to the thickness of the base aggregate 18-4824,North Dakota Street Subdivision GRPT 4 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report CeoP 1 Ic Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon inaneen ane encountered. Table 1 summarizes our observations the pavement section in our road core explorations. Table 1 -Summary of Existing Pavement Sections in Exploratory Pavement Cores DCP Average Road Core Asphalt Base Rock Depth Penetration Subgrade Location Thickness Thickness Correlated Designation Interval Per Blow (in) (in) (in) (mm) CBR Value SW North RC-1 Dakota 7.75 3.75 12-43.5 20.25 15 Street SW North RC-2 Dakota 10 3 13-42.5 41.91 25 Street RC-3 SW 114th 2.75 18+ 15-49.5 41.91 4.0 Place SW 114th RC-4 2.5 14.5 19-42.5 16.76 8 Place Based on the results of DCP testing, we estimate that the subgrade exhibits a resilient modulus ranging from 6,000 psi to 37,500 psi. For analysis and design purposes, we conservatively assume that the subgrade exhibits a resilient modulus of 6,000 psi, which correlates to a CBR value of 4, for SW 114th Place and future SW Ellson Lane, and a resilient modulus of 9,000 psi, which correlates to a CBR value of 6, for SW North Dakota Street. DCP calculations are attached to this report. CONCLUSIONS AND RECOMMENDATIONS Our investigation indicates that the proposed development is geotechnically feasible, provided that the recommendations of this report are incorporated into the design and sufficient geotechnical monitoring is incorporated into the construction phases of the project. Site Preparation Recommendations Areas of proposed buildings, new streets, and areas to receive fill should be cleared of vegetation and any organic and inorganic debris. Existing buried structures should be demolished and any cavities structurally backfilled. Inorganic debris and organic materials from clearing should be removed from the site. Existing fill and any organic-rich topsoil should then be stripped from construction areas of the site or where engineered fill is to be placed. The estimated depth necessary for removal of topsoil is approximately 6 to 9 inches — deeper stripping may be necessary to remove large tree roots in isolated areas. The final depth of soil removal will be determined on the basis of a site inspection after the stripping/ excavation has been performed. Stripped topsoil should preferably be removed from the site. Any remaining topsoil should be stockpiled only in designated areas and stripping operations should be observed and documented by the geotechnical engineer or his representative. 18-4824,North Dakota Street Subdivision GRPT 5 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report GOO i Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon rnolra Inc Any remaining undocumented fills and subsurface structures (tile drains, basements, driveway and landscaping fill, old utility lines, septic leach fields, etc.) should be removed and the excavations backfilled with engineered fill. Once stripping of a particular area is approved, the area must be ripped or tilled to a depth of 12 inches, moisture conditioned, root-picked, and compacted in-place prior to the placement of engineered fill or crushed aggregate base for pavement. Exposed subgrade soils should be evaluated by the geotechnical engineer. For large areas, this evaluation is normally performed by proof-rolling the exposed subgrade with a fully loaded scraper or dump truck. For smaller areas where access is restricted, the subgrade should be evaluated by probing the soil with a steel probe. Soft/loose soils identified during subgrade preparation should be compacted to a firm and unyielding condition, over-excavated and replaced with engineered fill (as described below) or stabilized with rock prior to placement of engineered fill. The depth of over-excavation, if required, should be evaluated by the geotechnical engineer at the time of construction. Engineered Fill All grading for the proposed development should be performed as engineered grading in accordance with the applicable building code at time of construction with the exceptions and additions noted herein. Proper test frequency and earthwork documentation usually requires daily observation and testing during stripping, rough grading, and placement of engineered fill. Imported fill material must be approved by the geotechnical engineer prior to being imported to the site. Oversize material greater than 6 inches in size should not be used within 3 feet of foundation footings, and material greater than 12 inches in diameter should not be used in engineered fill. Engineered fill should be compacted in horizontal lifts not exceeding 8 inches using standard compaction equipment. We recommend that engineered fill be compacted to at least 90% of the maximum dry density determined by ASTM D1557 (Modified Proctor) or equivalent. Field density testing should conform to ASTM D2922 and D3017, or D1556. All engineered fill should be observed and tested by the project geotechnical engineer or his representative. Rocky fill may need to be evaluated by proofrolling and should be placed wet of optimum moisture content. Typically, one density test is performed for at least every 2 vertical feet of fill placed or every 500 yd3, whichever requires more testing. Because testing is performed on an on-call basis, we recommend that the earthwork contractor be held contractually responsible for test scheduling and frequency. Site earthwork will be impacted by soil moisture and shallow groundwater conditions. Earthwork in wet weather would likely require extensive use of cement or lime treatment, or other special measures, at considerable additional cost compared to earthwork performed under dry-weather conditions. 18-4824,North Dakota Street Subdivision GRPT 6 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 J � Geotechnical Engineering Report GeOP ' Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon "!' Excavating Conditions and Utility Trench Backfill All temporary cuts in excess of 4 feet in height should be sloped in accordance with U.S. Occupational Safety and Health Administration (OSHA) regulations (29 CFR Part 1926) or be shored. The existing native soils classify as Type B Soil and temporary excavation side slope inclinations as steep as 1H:1V may be assumed for planning purposes. This cut slope inclination is applicable to excavations above the water table only. Maintenance of safe working conditions, including temporary excavation stability, is the responsibility of the contractor. Actual slope inclinations at the time of construction should be determined based on safety requirements and actual soil and groundwater conditions. Saturated soils and groundwater may be encountered in utility trenches, particularly during the wet season. We anticipate that dewatering systems consisting of ditches, sumps and pumps would be adequate for control of perched groundwater. Regardless of the dewatering system used, it should be installed and operated such that in-place soils are prevented from being removed along with the groundwater. Vibrations created by traffic and construction equipment may cause some caving and raveling of excavation walls. In such an event, lateral support for the excavation walls should be provided by the contractor to prevent loss of ground support and possible distress to existing or previously constructed structural improvements. PVC pipe should be installed in accordance with the procedures specified in ASTM D2321. We recommend that trench backfill be compacted to at least 95% of the maximum dry density obtained by Standard Proctor ASTM D698 or equivalent. Initial backfill lift thickness for a 3/4"-0 crushed aggregate base may need to be as great as 4 feet to reduce the risk of flattening underlying flexible pipe. Subsequent lift thickness should not exceed 1 foot. If imported granular fill material is used, then the lifts for large vibrating plate-compaction equipment (e.g. hoe compactor attachments) may be up to 2 feet, provided that proper compaction is being achieved and each lift is tested. Use of large vibrating compaction equipment should be carefully monitored near existing structures and improvements due to the potential for vibration-induced damage. Adequate density testing should be performed during construction to verify that the recommended relative compaction is achieved. Typically, one density test is taken for every 4 vertical feet of backfill on each 200-lineal-foot section of trench. Erosion Control Considerations During our field exploration program, we did not observe soil types that would be considered highly susceptible to erosion. In our opinion, the primary concern regarding erosion potential will occur during construction, in areas that have been stripped of vegetation. Erosion at the site during construction can be minimized by implementing the project erosion control plan, which should include judicious use of straw bales and silt fences. If used, these erosion control devices should be in place and remain in place throughout site preparation and construction. 18-4824,North Dakota Street Subdivision GRPT 7 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report GeoP Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon ingiftellf111 tac. Erosion and sedimentation of exposed soils can also be minimized by quickly re-vegetating exposed areas of soil, and by staging construction such that large areas of the project site are not denuded and exposed at the same time. Areas of exposed soil requiring immediate and/or temporary protection against exposure should be covered with either mulch or erosion control netting/blankets. Areas of exposed soil requiring permanent stabilization should be seeded with an approved grass seed mixture, or hydroseeded with an approved seed-mulch-fertilizer mixture. Wet Weather Earthwork Soils underlying the site are likely to be moisture sensitive and may be difficult to handle or traverse with construction equipment during periods of wet weather. Earthwork is typically most economical when performed under dry weather conditions. Earthwork performed during the wet-weather season will probably require expensive measures such as cement treatment or imported granular material to compact areas where fill may be proposed to the recommended engineering specifications. If earthwork is to be performed or fill is to be placed in wet weather or under wet conditions when soil moisture content is difficult to control, the following recommendations should be incorporated into the contract specifications. • Earthwork should be performed in small areas to minimize exposure to wet weather. Excavation or the removal of unsuitable soils should be followed promptly by the placement and compaction of clean engineered fill. The size and type of construction equipment used may have to be limited to prevent soil disturbance. Under some circumstances, it may be necessary to excavate soils with a backhoe to minimize subgrade disturbance caused by equipment traffic; • The ground surface within the construction area should be graded to promote run-off of surface water and to prevent the ponding of water; • Material used as engineered fill should consist of clean, granular soil containing less than 5 percent passing the No. 200 sieve. The fines should be non-plastic. Alternatively, cement treatment of on-site soils may be performed to facilitate wet weather placement; • The ground surface within the construction area should be sealed by a smooth drum vibratory roller, or equivalent, and under no circumstances should be left uncompacted and exposed to moisture. Soils which become too wet for compaction should be removed and replaced with clean granular materials; • Excavation and placement of fill should be observed by the geotechnical engineer to verify that all unsuitable materials are removed and suitable compaction and site drainage is achieved; and • Geotextile silt fences, straw waddles, and fiber rolls should be strategically located to control erosion. If cement or lime treatment is used to facilitate wet weather construction, GeoPacific should be contacted to provide additional recommendations and field monitoring. 18-4824,North Dakota Street Subdivision GRPT 8 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report GeoP ` Project No. 18-4824, North Dakota Street Subdivision,Tigard, Oregon INE=CIM Spread Foundations The proposed residential structures may be supported on shallow foundations bearing on competent undisturbed, native soils and/or engineered fill, appropriately designed and constructed as recommended in this report. Foundation design, construction, and setback requirements should conform to the applicable building code at the time of construction. For maximization of bearing strength and protection against frost heave, spread footings should be embedded at a minimum depth of 12 inches below exterior grade except where footing-to-slope setbacks require deeper embedments. The recommended minimum widths for continuous footings supporting wood-framed walls without masonry are 12 inches for single-story, 15 inches for two-story, and 18 inches for three-story structures. Minimum foundation reinforcement should consist of a No. 4 bar at the top of stem walls, and a No. 4 bar at the bottom of the footings. Concrete slab-on-grade reinforcement should consist of No. 4 bars placed on 24-inch centers in a grid pattern. The anticipated allowable soil bearing pressure is 1,500 lbs/ft2 for footings bearing on competent, native soil and/or engineered fill. A maximum chimney and column load of 30 kips is recommended for the site. The recommended maximum allowable bearing pressure may be increased by 1/3 for short-term transient conditions such as wind and seismic loading. For heavier loads, the geotechnical engineer should be consulted. The coefficient of friction between on-site soil and poured-in-place concrete may be taken as 0.42, which includes no factor of safety. The maximum anticipated total and differential footing movements (generally from soil expansion and/or settlement) are 1 inch and 3/4 inch over a span of 20 feet, respectively. We anticipate that the majority of the estimated settlement will occur during construction, as loads are applied. Excavations near structural footings should not extend within a 1 H:1 V plane projected downward from the bottom edge of footings. Footing excavations should penetrate through topsoil and any loose soil to competent subgrade that is suitable for bearing support. All footing excavations should be trimmed neat, and all loose or softened soil should be removed from the excavation bottom prior to placing reinforcing steel bars. Due to the moisture sensitivity of on-site native soils, foundations constructed during the wet weather season may require over-excavation of footings and backfill with compacted, crushed aggregate. Our recommendations are for house construction incorporating raised wood floors and conventional spread footing foundations. If living space of the structures will incorporate basements, a geotechnical engineer should be consulted to make additional recommendations for retaining walls, water-proofing, undersiab drainage and wall subdrains. After site development, a Final Soil Engineer's Report should either confirm or modify the above recommendations. Drainage The upsiope edge of perimeter footings may be provided with a drainage system consisting of 3-inch diameter, slotted, plastic pipe embedded in a minimum of 1 ft3 per lineal foot of clean, free- draining gravel or uncompacted 3/4"-0 rock. Water collected from the footing drains should be directed into the local storm drain system or another suitable outlet. A minimum 0.5 percent fall 18-4824,North Dakota Street Subdivision GRPT 9 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report GeOP Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon should be maintained throughout the drain and non-perforated pipe outlet. Down spouts and roof drains should not be connected to the foundation drains in order to reduce the potential for clogging. The footing drains should include clean-outs to allow periodic maintenance and inspection. Grades around the proposed structure should be sloped such that surface water drains away from the building. Footing drain recommendations are given to prevent detrimental effects of groundwater on foundations and should not be expected to eliminate all potential sources of water entering a crawlspace. An adequate grade to a low point outlet drain in the crawlspace is required by code. Flexible Pavement Design: SW North Dakota Street We understand that development at the site includes half street improvements to the westbound lane of SW North Dakota Street within the property frontage, if the existing roadway section is not sufficient to support the anticipated traffic loads of a 20-year design life. We analyzed the existing section for a 20-year design life using an Average Daily Traffic Count (ADT) of 5,200 tips per day, derived from data provided by the City of Tigard's traffic data website(Tigard.Maps.arcgis.com). We assume that traffic will primarily consist of light duty residential cars, weekly trash pickups and occasional fire trucks. Founded upon our understanding of anticipated traffic, we assumed an 18- kip ESAL count of 1,317,914 over 20 years, accounting for projected population growth of 3 percent. Table 2 presents our flexible pavement design input factors. Table 2—Flexible Pavement Section Design Input Factors for SW North Dakota Street Input Parameter Design Value 18-kip ESAL Initial Performance Period (20 Years) 1,317,924 Initial Serviceability 4.2 Terminal Serviceability 2.5 Reliability Level 85 Percent Overall Standard Deviation 0.5 Roadbed Soil Resilient Modulus(PSI) 9,000 Structural Number 3.32 Table 3 presents our analyzed section from the existing pavement section at RC-1, with estimated structural coefficients. Pavement design calculations are attached to this report. Table 3—Analyzed Section of Existing Asphalt Pavement of RC-1 Material Layer Section Thickness(in.) Structural Coefficient Asphaltic Concrete(AC) 7.75 0.40 Crushed Aggregate Base 3.75 0.10 Subgrade 12 9,000 PSI Calculated Structural Number 3.48 18-4824,North Dakota Street Subdivision GRPT 10 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report Geed 3 c Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon Based on the observed condition of the asphalt pavement and structural analysis of the existing section, the study area of SW North Dakota Street, within the property frontage, is suitable for supporting the anticipated traffic loads of a 20-year design life. Flexible Pavement Design: SW North Dakota Street Widening We understand that development at the site will also widen the existing SW North Dakota Street within the frontage of the property. We assume that traffic loading for the widening will be the same as that anticipated in Table 2, for the existing lane. Table 4 presents our recommended minimum dry-weather pavement section with estimated structural coefficients. Pavement design calculations are attached to this report. Table 4—Recommended Minimum Dry-Weather Pavement Section for Widening of SW North Dakota Street Material Layer Section Thickness Structural Y (in.) Coefficient Compaction Standard Asphaltic Concrete(AC) 5 0.42 91%/92%of Rice Density AASHTO T-209 Crushed Aggregate Base 95%of Modified Proctor %"-0(leveling course) 2 0.10 AASHTO T-180 Crushed Aggregate Base 95%of Modified Proctor 1'/2%0 12 0.10 AASHTO T-180 Subgrade 12 9,000 PSI 95%of Standard Proctor AASHTO T-99 or equivalent Calculated Structural Number 3.40 The subgrade should be ripped or tilled to a depth of 12 inches, moisture conditioned, root-picked, and compacted in-place prior to the placement of crushed aggregate base for pavement. Any pockets of organic debris or loose fill encountered during ripping or tilling should be removed and replaced with engineered fill (see Site Preparation section). In order to verify subgrade strength, we recommend proof-rolling directly on subgrade with a loaded dump truck during dry weather and on top of base course in wet weather. Soft areas that pump, rut, or weave should be stabilized prior to paving. If pavement areas are to be constructed during wet weather, the subgrade and construction plan should be reviewed by the project geotechnical engineer at the time of construction so that condition specific recommendations can be provided. The moisture sensitive subgrade soils make the site a difficult wet weather construction project. General recommendations for wet weather pavement sections are provided below. During placement of pavement section materials, density testing should be performed to verify compliance with project specifications. Generally, one subgrade, one base course, and one asphalt compaction test is performed for every 100 to 200 linear feet of paving. 18-4824,North Dakota Street Subdivision GRPT 11 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 ...4441004, Geotechnical Engineering Report CSO Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon fnpneertns lac Flexible Pavement Design: SW 114th Place and SW Ellson Lane We understand that development at the site will widen the existing SW 114th Place and extend SE Ellson Lane to connect to SW 114th Place. We assume that traffic will primarily consist of local • traffic to the homes these streets provide access to and will include light duty residential cars, weekly trash and recycling pickups, and occasional fire trucks. We assumed an 18-kip ESAL count of 63,362 over 20 years, accounting for projected population growth. Table 5 presents our flexible pavement design input factors. Table 5—Flexible Pavement Section Design Input Factors for SW 114th Place and SW Ellson Lane Input Parameter Design Value 18-kip ESAL Initial Performance Period (20 Years) 63,362 Initial Serviceability 4.2 Terminal Serviceability 2.5 { Reliability Level 85 Percent Overall Standard Deviation 0.5 Roadbed Soil Resilient Modulus(PSI) 6,000 Structural Number 2.34 Table 6 presents our recommended minimum dry-weather pavement section with estimated structural coefficients. Pavement design calculations are attached to this report. Table 6—Recommended Minimum Dry-Weather Pavement Section for SW 114th Place and SW Ellson Lane Material Layer Section Thickness Structural Y (in.) Coefficient Compaction Standard 91%/92%of Rice Density Asphaltic Concrete(AC) 3.5 0.42 AASHTO T-209 Crushed Aggregate Base 95%of Modified Proctor '/:'-0(leveling course) 2 0.10 AASHTO T-180 Crushed Aggregate Base 95%of Modified Proctor 1'/z'-0 8 0.10 AASHTO T-180 Subgrade 12 6,000 PSI 95%of Standard Proctor AASHTO T-99 or equivalent Calculated Structural Number 2.47 The subgrade should be ripped or tilled to a depth of 12 inches, moisture conditioned, root-picked, and compacted in-place prior to the placement of crushed aggregate base for pavement. Any pockets of organic debris or loose fill encountered during ripping or tilling should be removed and replaced with engineered fill (see Site Preparation section). In order to verify subgrade strength, we recommend proof-rolling directly on subgrade with a loaded dump truck during dry weather and on top of base course in wet weather. Soft areas that pump, rut, or weave should be stabilized prior to paving. 18-4824,North Dakota Street Subdivision GRPT 12 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report GeoP Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon , If pavement areas are to be constructed during wet weather, the subgrade and construction plan should be reviewed by the project geotechnical engineer at the time of construction so that condition specific recommendations can be provided. The moisture sensitive subgrade soils make the site a difficult wet weather construction project. General recommendations for wet weather pavement sections are provided below. During placement of pavement section materials, density testing should be performed to verify compliance with project specifications. Generally, one subgrade, one base course, and one asphalt compaction test is performed for every 100 to 200 linear feet of paving. Wet Weather Construction Pavement Section This section presents our recommendations for wet weather pavement section and construction for new pavement sections at the project. These wet weather pavement section recommendations are intended for use in situations where it is not feasible to compact the subgrade soils, due to wet subgrade soil conditions, and/or construction during wet weather. Based on our site review, we recommend a wet weather section with a minimum subgrade deepening of 6 inches to accommodate a working subbase of additional 11/2'-0 crushed rock. Geotextile fabric, Mirafi 500x or equivalent, should be placed on subgrade soils prior to placement of base rock. In some instances, it may be preferable to use Special Treated Base (STB) in combination with overexcavation and increasing the thickness of the rock section. GeoPacific should be consulted for additional recommendations regarding use of STB in wet weather pavement sections if it is desired to pursue this alternative. Cement treatment of the subgrade may also be considered instead of overexcavation. For planning purposes, we anticipate that treatment of the onsite soils would involve mixing cement powder to approximately 6 percent cement content and a mixing depth on the order of 12 to 18 inches. With implementation of the above recommendations, it is our opinion that the resulting pavement section will provide equivalent or greater structural strength than the dry weather pavement section currently planned. However, it should be noted that construction in wet weather is risky and the performance of pavement subgrades depend on a number of factors including the weather conditions, the contractor's methods, and the amount of traffic the road is subjected to. There is a potential that soft spots may develop even with implementation of the wet weather provisions recommended in this letter. If soft spots in the subgrade are identified during roadway excavation, or develop prior to paving, the soft spots should be overexcavated and backfilled with additional crushed rock. During subgrade excavation, care should be taken to avoid disturbing the subgrade soils. Removals should be performed using an excavator with a smooth-bladed bucket. Truck traffic should be limited until an adequate working surface has been established. We suggest that the crushed rock be spread using bulldozer equipment rather than dump trucks, to reduce the amount of traffic and potential disturbance of subgrade soils. 18-4824,North Dakota Street Subdivision GRPT 13 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report Geer '`'MI Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon 11110 '!11111111 Pi Care should be taken to avoid overcompaction of the base course materials, which could create 1 pumping, unstable subgrade soil conditions. Heavy and/or vibratory compaction efforts should be I applied with caution. Following placement and compaction of the crushed rock to project 1 specifications (95 percent of Modified Proctor), a finish proof-roll should be performed before 1 paving. The above recommendations are subject to field verification. GeoPacific should be on-site e during 1 I construction to verify subgrade strength and to take density tests on the engineered fill, base rock and asphaltic pavement materials. Seismic Design and Soil Liquefaction The Oregon Department of Geology and Mineral Industries (Dogami), Oregon HazVu: 2018 Statewide GeoHazards Viewer indicates that the site is in an area where severe ground shaking is anticipated during an earthquake (Dogami HazVu, 2018). Structures should be designed to resist earthquake loading in accordance with the methodology described in the 2015 International Building Code (IBC) with applicable Oregon Structural Specialty Code (OSSC) revisions (current 2014). We recommend Site Class D be used for design per the OSSC, Table 1613.5.2 and as defined in ASCE 7, Chapter 20, Table 20.3-1. Design values determined for the site using the USGS (United States Geological Survey) 2018 Seismic Design Maps Summary Report are summarized in Table 7 and are based upon existing soil conditions. Table 7 - Recommended Earthquake Ground Motion Factors (2010 ASCE-7) Parameter Value Location (Lat, Long), degrees 45.439361, -122.793813 Probabilistic Ground Motion Values, 2% Probability of Exceedance in 50 yrs Mean Peak Ground Acceleration 0.456 g Short Period, S5 0.969 g 1.0 Sec Period, Si 0.423 g Soil Factors for Site Class D: Fa 1.113 F„ 1.577 SDs = 2/3 x Fa x Ss 0.718g SD1 = 2/3 X Fv x Si 0.445 g Seismic Design Category D 18-4824,North Dakota Street Subdivision GRPT 14 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report C ' . 6eoP Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon Enulncennu.Inc Soil Liquefaction The Oregon Department of Geology and Mineral Industries (DOGAMI), Oregon HazVu: 2018 Statewide GeoHazards Viewer indicates that the site is in an area considered to be at moderate risk for soil liquefaction during an earthquake. Soil liquefaction is a phenomenon wherein saturated soil deposits temporarily lose strength and behave as a liquid in response to ground shaking caused by strong earthquakes. Soil liquefaction is generally limited to loose, sands and granular soils located below the water table, and fine-grained soils with a plasticity index less than 15. The site was observed to be underlain by medium stiff to very stiff, fine-grained soils which displayed moderate plasticity, located above the static groundwater table. Based upon the results of our study, it is our opinion that the risk of soil liquefaction during a seismic event at the subject site should be considered to be low to moderate. UNCERTAINTIES AND LIMITATIONS We have prepared this report for the owner and his/her consultants for use in design of this project only. The conclusions and interpretations presented in this report should not be construed as a warranty of the subsurface conditions. Experience has shown that soil and groundwater conditions can vary significantly over small distances. Inconsistent conditions can occur between explorations that may not be detected by a geotechnical study. If, during future site operations, subsurface conditions are encountered which vary appreciably from those described herein, GeoPacific should be notified for review of the recommendations of this report, and revision of such if necessary. Within the limitations of scope, schedule and budget, GeoPacific executed these services in accordance with generally accepted professional principles and practices in the fields of geotechnical engineering and engineering geology at the time the report was prepared. No warranty, express or implied, is made. The scope of our work did not include environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous or toxic substances in the soil, surface water, or groundwater at this site. We appreciate this opportunity to be of service. Sincerely, PROF E� F�`P�O GEOPACIFIC ENGINEERING, INC. r•w 147 • OREGON vv�N23 \ 4 ,Fik'S D.';M�4 V 7 6' -. EXPIRES:06/30/20li Michael T. Baker James D. Imbrie, G.E., C.E.G. Geotechnical Staff Principal Geotechnical Engineer 18-4824,North Dakota Street Subdivision GRPT 15 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 Geotechnical Engineering Report Cede me Project No. 18-4824, North Dakota Street Subdivision, Tigard, Oregon .* !� REFERENCES Atwater, B.F., 1992, Geologic evidence for earthquakes during the past 2,000 years along the Copalis River, southern coastal Washington: Journal of Geophysical Research,v. 97,p. 1901-1919. Carver, G.A., 1992, Late Cenozoic tectonics of coastal northern California:American Association of Petroleum Geologists-SEPM Field Trip Guidebook, May, 1992. Gannet, M.W., and Caldwell, R. R., 1998, Generalized Geologic Map of the Willamette Lowland, U.S. Department of the interior, U.S. Geological Survey, 1998. Geomatrix Consultants, 1995, Seismic Design Mapping, State of Oregon: unpublished report prepared for Oregon Department of Transportation, Personal Services Contract 11688,January 1995. Goldfinger, C., Kulm, L.D.,Yeats, R.S.,Appelgate, B, MacKay, M.E.,and Cochrane, G.R., 1996,Active strike-slip faulting and folding of the Cascadia Subduction-Zone plate boundary and forearc in central and northern Oregon: in Assessing earthquake hazards and reducing risk in the Pacific Northwest, v. 1: U.S. Geological Survey Professional Paper 1560, P.223-256. Ma, L., Madin, I.P., Duplantis, S., and Williams, K.J., 2012, Lidar-based Surficial Geologic Map and Database of the 1 Greater Portland, Oregon, Area, Clackamas, Columbia, Marion, Multnomah,Washington, and Yamhill Counties, Oregon, and Clark County,Washington, DOGAMI Open-File Report 0-12-02 Mabey, M.A., Madin, I.P., and Black G.L., 1996, Relative Earthquake Hazard Map of the Lake Oswego Quadrangle, Clackamas, Multnomah and Washington Counties, Oregon: Oregon Department of Geology and Mineral Industries Madin, I.P., 1990, Earthquake hazard geology maps of the Portland metropolitan area, Oregon: Oregon Department of Geology and Mineral Industries Open-File Report 0-90-2, scale 1:24,000, 22 p. Oregon Department of Geology and Mineral Industries, Statewide Geohazards Viewer, www.oregongeology.org/hazvu. Peterson, C.D., Darioenzo, M.E., Burns, S.F., and Burris,W.K., 1993, Field trip guide to Cascadia paleoseismic evidence along the northern California coast: evidence of subduction zone seismicity in the central Cascadia margin: Oregon Geology,v. 55, p. 99-144. United States Geological Survey, USGS Earthquake Hazards Program Website (earthquake.usgs.gov). Unruh,J.R.,Wong, I.G., Bott,J.D., Silva,W.J.,and Lettis,W.R., 1994, Seismotectonic evaluation: Scoggins Dam, Tualatin Project, Northwest Oregon: unpublished report by William Lettis and Associates and Woodward Clyde Federal Services,Oakland, CA,for U. S. Bureau of Reclamation, Denver CO (in Geomatrix Consultants, 1995). Werner, K.S., Nabelek, J., Yeats, R.S., Malone, S., 1992, The Mount Angel fault: implications of seismic-reflection data and the Woodburn, Oregon, earthquake sequence of August, 1990: Oregon Geology,v. 54, p. 112-117. Wong, I. Silva,W., Bott, J.,Wright, D., Thomas, P., Gregor, N., Li., S., Mabey, M., Sojourner,A., and Wang,Y., 2000, Earthquake Scenario and Probabilistic Ground Shaking Maps for the Portland, Oregon, Metropolitan Area; State of Oregon Department of Geology and Mineral Industries; Interpretative Map Series IMS-16 Yeats, R.S., Graven, E.P.,Werner, K.S., Goldfinger, C., and Popowski, T., 1996, Tectonics of the Willamette Valley, Oregon: in Assessing earthquake hazards and reducing risk in the Pacific Northwest,v. 1: U.S. Geological Survey Professional Paper 1560, P. 183-222, 5 plates, scale 1:100,000. Yelin,T.S., 1992,An earthquake swarm in the north Portland Hills(Oregon): More speculations on the seismotectonics of the Portland Basin:Geological Society of America, Programs with Abstracts, v. 24, no. 5, p. 92. 18-4824,North Dakota Street Subdivision GRPT 16 GEOPACIFIC ENGINEERING, INC. Version 2,April 30,2018 CeoP Engineering,Inc, Real-World Geotechnical Solutions Investigation • Design • Construction Support FIGURES 14835 SW 72"d Avenue Tel (503) 598-8445 Portland, Oregon 97224 Fax (503) 941-9281 14835 SW 72nd Avenue Geop 'f Portland, Oregon 97224 VICINITY MAP Engineering,Inc. Tel: (503) 598-8445 Fax: (503)941-9281 1 a t y ,..,..{.v, t ..,."tea Y _ .n ..j t t ; ,, , , 1 ,,,,, , , , HOME ,)rr._...7-s -,-r:...!r JJ r ' do; •i 1 ' '' ''') , ' 1,1ffir r- I ' ""•...) i / ' > '/f/ l� 4 V J 1. - Z: . _.- gip , � \\e , �!•• ' • .: k' _,...; , k7 A NI1 $ u' "^f (ct i :,�1 / Bradt ttobiTiso r nt<arcrie SUBJECT SITE f v. 1 r. C'er, . . ..,,DP.'+mac _ � 99 : �, ., ii� \ } � ';�54tsol" •J I fr i K . • 1 P� I • t Pr 1. .�11 '• •• .'.+ _. hY ,2_:.. Fes.. >; ji ,' :,,,•v �, :� .Z', • � �"., r Nr N11. . • i ,, •,� NORTH )1/// ,< .. - - ., t r j.. ` 'x,�,�/ TiBa,•, t ♦ . - J • l w • g 7� / • 1�• '• d? �,i lea ? ems 5.{V —F- - F<- 'i SI A Date: 1.31.2018 Legend Approximate Scale 1 in =2,000 ft Drawn by: MTB Base maps: U.S. Geological Survey 7.5 minute Topographic Map Series, Beaverton,Oregon Quadrange, 1961 (Photorevised 1984). Project: 11375 SW North Dakota Street I Project No. 18-4824 FIGURE 1 Tigard, Oregon I GeoP Engineering,Inc. Real-World Geotechnical Solutions Investigation • Design •Construction Support EXPLORATION LOGS 14835 SW 72"d Avenue Tel (503) 598-8445 Portland, Oregon 97224 Fax (503) 941-9281 - 14835 SW 72nd Avenue eoPacific Portland, Oregon 97224 TEST PIT LOG En,1 nesting Inc. Tel: (503) 598-8445 Fax: (503)941-9281 Project: North Dakota Subdivision Project No. 18-4824 Tigard, Oregon Boring No. TP-1 U) a 0 0 L C N o E o 0 3.0 Material Description C U) H 0 m Soft, highly organic SILT (OL), dark brown, numerous tree roots and leaf litter, moist [Topsoil] 1 Medium stiff to stiff, SILT (ML), light brown, friable, numerous tree roots, moist to 1.0 damp [Willamette Formation] 2 2.5 Stiff, SILT (ML)with sand, light brown, faint gray and orange mottling, micaceous, 3 2.0 damp [Willamette Formation] 4 4.0 5 Grades Stiff, sandy SILT (ML) to a light buff color, blocky structure 6 7 8 9 10 11 Boring Terminated at 11 feet. No Groundwater Encountered. LEGEND o Date Drilled: 1.30.2018 oo,000tn ed o Logged By: MTB , — d Surface Elevation: 230 feet Bag Sample Split-Spoon Shelby Tube Sample Seepage Static Water Table Water Bearing Zone J 7 Nry 14835 SW 72nd Avenue GeoPacific Portland,Oregon 97224 TEST PIT LOG 1 Engineering,Inc. Tel: (503)598-8445 Fax: (503)941-9281 I Project: North Dakota Subdivision 18-4824Boring Tigard, Oregon Project No. No.TP-2 ii a o 0 a� s ~ Q at N aJ � C O) o 2 Material Description p m o � o aai Cl) ~ U m Soft, highly organic SILT (OL), dark brown, numerous tree and plant roots, moist [Topsoil] Medium stiff to stiff, SILT (ML), light brown, friable, numerous tree roots in the upper 1 1.0 18 inches, moist to damp [Willamette Formation] 2 3.0 Medium stiff to stiff, SILT (ML)with sand, light brown, faint gray and orange mottling, 3 11,000 3.5 26.8 micaceous, damp [Willamette Formation] ' 4 1.0 4O Grades to Stiff, sandy SILT (ML), light brown to buff color, blocky structure, moist 5 6 7 8-- 9 10 i 11 . Boring Terminated at 11 feet. Perched groundwater encountered at 4 feet. Visually estimated at approximately 1/4 gallons per minute LEGEND _ Date Drilled: 1.30.2018 loot. de4 Logged By: MTB 1,000 — u Surface Elevation:227 feet Bag Sample Split-Spoon Shelby Tube Sample Seepage Static Water Table Water Bearing Zone ./' c1_ 14835 SW 72nd Avenue GeoP cific Portland, Oregon 97224 TEST PIT LOG Engineering.Inc. Tel: (503)598-8445 Fax: (503)941-9281 Project: North Dakota Subdivision Project No. 18-4824 BoringNo.TP-3 Tigard, Oregon a • mo 0 °' °' a. n Material Description w o C� m � O 2 0 m co U Soft, highly organic SILT (OL), dark brown, numerous tree plant roots, moist[Topsoil] Soft to medium stiff, SILT (ML), light brown, friable, some grass and blackberry roots in 1 1.0 the upper 18 inches, moist to damp [Willamette Formation] 2 1.0 Stiff, SILT (ML)with sand, light brown, faint gray and orange mottling, micaceous, 3 3.0 damp [Willamette Formation] 4 2.0 Grades to Stiff sandy SILT (ML), light brown to buff color, blocky structure, moist 5 100to 26.5 1,000 6 7 8 aee 9 10 Grades to strong gray mottling Boring Terminated at 10.5 feet. 11 Perched groundwater encountered at 8.5 feet. Visually estimated at less than 1/4 gallons per minute LEGEND _ Date Drilled: 1.30.2018 looto111 did o Logged By: MTB 1,000 d Surface Elevation: 230 feet Bag Sample Split-Spoon Shelby Tube Sample Seepage Static Water Table Water Bearing Zone °g "> 14835 SW 72nd Avenue GeoP k ffi me Portland, Oregon 97224 TEST PIT LOG Engineering,Inc. Tel: (503)598-8445 Fax: (503)941-9281 Project: North Dakota Subdivision Project No. 18-4824 BoringNo.TP-4 Tigard, Oregon a ^ c T a. E o 0 F ci N o 20. Material Description p o to ~ U m Soft, highly organic SILT (OL), dark brown, numerous tree and plant roots, moist [Topsoil] Medium stiff to stiff, SILT (ML), light brown, friable, moist to damp [Willamette 1 1.25 Formation] 2 3.25 Medium stiff to stiff, SILT (ML)with sand, light brown, faint gray and orange mottling, 3 2.0 micaceous, damp [Willamette Formation] 4 4.0 Grades to Stiff, sandy SILT (ML), light brown to buff color, blocky structure, moist 5 6 did 7 8- 9 10 11 Boring Terminated at 10.5 feet. Perched groundwater encountered at 6 feet. Visually estimated at approximately 1/4 gallons per minute LEGEND - Date Drilled: 1.30.2018 too to d ed o Logged By: MTB 1,000 Surface Elevation: 227 feet Bag Sample Split-Spoon Shelby Tube Sample Seepage Static Water Table Water Bearing Zone 14835 SW 72nd Avenue GeoPacific Portland,Oregon 97224 TEST PIT LOG ineineeriniInc. Tel: (503)598-8445 Fax: (503)941-9281 Project: North Dakota Subdivision Project No. 18-4824 BoringNo. TP-5 Tigard, Oregon a Cr N a,a o .o w Material Description p mE o o a20, Cl) ~ U m Soft, highly organic SILT (OL), dark brown, numerous tree roots and leaf litter, garbage debris and numerous glass bottles, moist [Topsoil] 1 0.5 Soft to medium stiff, SILT (ML), light brown, friable, moist to damp [Willamette 2 0.5 Formation] Stiff, SILT(ML)with sand, light brown, faint gray and orange mottling, micaceous, 3 3.5 damp [Willamette Formation] 4 3.0 Grades to Stiff, sandy SILT (ML), light brown to buff color, blocky structure 5 6 7 8 9 10 11 Boring Terminated at 11 feet. No Groundwater Encountered. LEGEND o d eea LoggedDate By:Drille :MTB1.30.2018 100 to 1,000 4 Surface Elevation:227 feet Bag Sample Split-Spoon Shelby Tube Sample Seepage Static Water Table Water Bearing Zone CeoP En(neeting.Inc. Real-World Geotechnical Solutions Investigation • Design •Construction Support LABORATORY TEST RESULTS 14835 SW 72"d Avenue Tel (503) 598-8445 Portland, Oregon 97224 Fax(503) 941-9281 LIQUID AND PLASTIC LIMITS TEST REPORT 60 Dashed line indicates the approximate upper limit boundary for natural soils 50 G�o�0� x 40 -_ - w 0 U 30 co 20 o<Ov 10— � f7C Mi��f MLorOI MH or OH 0 0 10 20 30 40 50 60 70 80 90 100 110 LIQUID LIMIT 33.6 33.2 32.8 32.4 H 32 z �31.6— - cc Q 31.2-- 30.8 30.4 -- - 30 29.6 5 6 7 8 9 10 20 25 30 40 NUMBER OF BLOWS MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS • Silt with Sand 31.7 27.3 4.4 98.8 74.4 ML Project No. 18-4824 Client: Venture Properties Remarks: Project: North Dakota Subdivision Location:TP-2 Sample Number: S18-047 Depth: 3' GEOPACIFIC ENGINEERING, INC. Figure Tested By: SJC F____.... . _ 1 Particle Size Distribution Report c • c tD O o o C C \ C . O V i a 9 �k i 100 MN - 6 nC q OO 0j I I I •I 90 F.. 10 1 • 70 -30 m w n Z 60 40 m Z Z 50 50 n w p 0_ 40 60 x LU 11. m 30 4 70 73 20 y 80 I I I I 10 i 90 i 0 100 100 10 1 0.1 0.01 0.001 GRAIN SIZE-mm. y.+3" %Gravel I Sand I Fines Coarse Fine Coarse Medium Fine Slit Clay 0.0 0.0 0.0 0.0 1.2 24.4 74.4 TEST RESULTS Material Description Opening Percent Spec.* Pass? Silt with Sand Size Finer (Percent) (X=Fail) .75 100.0 .5 100.0 Atterberg Limits(ASTM D 4318) .375 100.0 PL= 27.3 LL= 31.7 PI= 4.4 .25 100.0 #4 100.0 Classification #10 100.0 USCS(D 2487)= ML AASHTO(M 145)= A-4(3) #20 99.5 Coefficients #40 98.8 D90= 0.1220 D85= 0.1028 060= #100 94.7 D50= 030= D15= #200 74.4 D10= Cu= Cc= Remarks Moisture 26.8% Date Received: Date Tested: 1/31/2018 Tested By: SJC Checked By: Title: (no specification provided) Location:TP-2 Date Sampled: 1/30/2018 Sample Number:S18-047 Depth:3' GEOPACIFIC Client: Venture Properties Project: North Dakota Subdivision 1 ENGINEERING, INC. Project No: 18-4824 Figure LIQUID AND PLASTIC LIMITS TEST REPORT 60 Dashed line indicates the approximate upper limit boundary for natural soils 50— /' /OGoo � wx 40 — — 0 z U 30 F cn J a- 20 — ot0- G'' 10 /.Z4'• / MLorOL MHorOH 0 I • 0 10 20 30 40 50 60 70 80 90 100 110 LIQUID LIMIT 32.6 32.2 -- 31.8 31.4 F- z H 31 z S30.6- - cc Q 30.2 29.8 29.4 29 28.6 5 6 7 8 9 10 20 25 30 40 NUMBER OF BLOWS MATERIAL DESCRIPTION LL 1 PL PI %<#40 %40200 USCS • Sandy Silt 29.9 29.6 0.3 99.8 66.4 ML r Project No. 18-4824 Client: Venture Properties Remarks: Project: North Dakota Subdivision II f Location:TP-3 li Sample Number: S18-048 Depth:5' fiji r GEOPACIFIC ENGINEERING, INC. fi Figure I Tested By: SJC 11 Particle Size Distribution Report . G 0 o c c c . E S�ECC yob 0 (o 0 (o o a !D Ol N '- 1 6 �V 5 5 # ik it 5 100 �1 0 I I I I 90 - 10 I I 1 I I I I I 80 a 20 1 70 30 m W n Z 60 40 m ti Z Z 50 ' 50 0 W p I 40 I -60 x W W 0 m 30 70 70 I I I I I I I I 1 I 1 I I I I 1 I I I I I I I 1 I I I 1 I 1 20 I _ I I I I I 1 I I I I - 80 10 -- --90 0 100 100 10 1 0.1 0.01 0.001 GRAIN SIZE-mm. %+3" %Gravel %Sand %Fines Coarse Fine Coarse Medium Fine Silt Clay 0.0 0.0 1 0.0 0.0 0.2 33.4 66.4 TEST RESULTS Material Description Opening Percent Spec.* Pass? Sandy Silt Size Finer (Percent) (X=Fall) .75 100.0 1 .5 100.0 Atterberg Limits(ASTM D 4318) 1 .375 100.0 PL= 29.6 LL= 29.9 PI= 0.3 1 .25 100.0 #4 I 100.0 Classification #10 1 100.0 USCS(D 2487)= ML AASHTO(M 145)= A-4(0) #20 100.0 Coefficients A #40 99.8 D90= 0.1438 D85= 0.1218 D60= #200 91.1 66.4 D50 D30= D15= 10= Cu= Cc= Remarks Moisture 26.5% Date Received: Date Tested: 1/31/2018 Tested By: SJC Checked By: Title: * (no specification provided) Location:TP-3 Date Sampled: 1/30/2018 Sample Number: S18-048 _ Depth:5' - G E O PACIFIC Client: Venture Properties Project: North Dakota Subdivision ENGINEERING, INC. Project No: 18-4824 Figure_ A -...0..lemi GeoPacitic Engineering,Inc. Real-World Geotechnical Solutions Investigation • Design •Construction Support FLEXIBLE PAVEMENT DESIGN 14835 SW 72"d Avenue Tel (503) 598-8445 Portland, Oregon 97224 Fax (503) 941-9281 ============_========.==ta== DARWin(tm) - Pavement Design A Proprietary AASHTOWARE(tm) Computer Software Product Flexible Structural Design Module Project Description 17-4824 - Existing Westbound North Dakota Flexible Structural Design Module Data 18-kip ESALs Over Initial Performance Period: 1, 317, 924 Initial Serviceability: 4 .2 Terminal Serviceability: 2.5 Reliability Level (%) : 85 Overall Standard Deviation: .5 Roadbed Soil Resilient Modulus (PSI) : 9, 000 Stage Construction: 1 Calculated Structural Number: 3.32 Specified Layer Design Layer: 1 Material Description: 1/2-0 Dense Asphalt Structural Coefficient (Ai) : .4 Drainage Coefficient (Mi) : 1 Layer Thickness (Di) (in) : 7.75 Calculated Layer SN: 3.10 Layer: 2 Material Description: Existing Crushed Rock Structural Coefficient (Ai) : .1 Drainage Coefficient (Mi) : 1 Layer Thickness (Di) (in) : 3.75 Calculated Layer SN: .38 Total Thickness (in) : 11.50 Total Calculated SN: 3.48 Simple ESAL Calculation Initial Performance Period (years) : 20 Initial Two-Way Daily Traffic (ADT) : 5,200 Heavy Trucks (of ADT) FHWA Class 5 or Greater: 3 Number of Lanes In Design Direction: 1 Percent of All Trucks In Design Lane (%) : 100 Percent Trucks In Design Direction (%) : 50 Average Initial Truck Factor (ESALs/truck) : 1.8 Annual Truck Factor Growth Rate (%) : 0 Annual Truck Volume Growth Rate (%) : 3 Growth: Simple Total Calculated Cumulative Esals: 1,317, 924 s—cas t===.=s:=as- =xansaaaa asaa=s sasn=s===*..====scsss-«-^^_ • DARWin(tm) - Pavement Design A Proprietary AASHTOWARE(tm) Computer Software Product Flexible Structural Design Module GeoPacific Engineering, Inc. 14835 SW 72nd Avenue Portland, OR 97224 Michael T. Baker Project Description 17-4824 - Widening of North Dakota Street Flexible Structural Design Module Data 18-kip ESALs Over Initial Performance Period: 1, 317, 924 Initial Serviceability: 4 .2 Terminal Serviceability: 2.5 Reliability Level (%) : 85 Overall Standard Deviation: .5 Roadbed Soil Resilient Modulus (PSI) : 9,000 Stage Construction: 1 Calculated Structural Number: 3.32 Specified Layer Design Layer: 1 Material Description: 1/2-0 Dense Asphalt Structural Coefficient (Ai) : .4 Drainage Coefficient (Mi) : 1 Layer Thickness (Di ) (in) : 5.00 Calculated Layer SN: 2.00 Layer: 2 Material Description: 3/4-0 Crushed Rock Structural Coefficient (Ai) : .1 Drainage Coefficient (Mi) : 1 Layer Thickness (Di) (in) : 2.00 Calculated Layer SN: .20 Layer: 3 Material Description: 1.5-0 Crushed Rock Structural Coefficient (Ai) : .1 Drainage Coefficient (Mi) : 1 Layer Thickness (Di) (in) : 12.00 Calculated Layer SN: 1.20 Total Thickness (in) : 19.00 Total Calculated SN: 3.40 Simple ESAL Calculation Initial Performance Period (years) : 20 Initial Two-Way Daily Traffic (ADT) : 5, 200 Heavy Trucks (of ADT) FHWA Class 5 or Greater: 3 Number of Lanes In Design Direction: 1 Percent of All Trucks In Design Lane (%) : 100 Percent Trucks In Design Direction (%) : 50 , Average Initial Truck Factor (ESALs/truck) : 1 .8 Annual. Truck Factor Growth Rate (%) : 0 Annual Truck Volume Growth Rate (%) : 3 Growth: Simple Total Calculated Cumulative Esals: 1, 317, 924 li DARWin(tm) - Pavement Design A Proprietary AASHTOWARE(tm) Computer Software Product Flexible Structural Design Module GeoPacific Engineering, Inc. 14835 SW 72nd Avenue Portland, OR 97224 Michael T. Baker Project Description 17-4824 - SW 114th Place and SW Ellson Lane New Pavement Section Flexible Structural Design Module Data 18-kip ESALs Over Initial Performance Period: 63, 362 Initial Serviceability: 4.2 Terminal Serviceability: 2.5 Reliability Level (%) : 85 Overall Standard Deviation: .5 Roadbed Soil Resilient Modulus (PSI) : 6, 000 Stage Construction: 1 Calculated Structural Number: 2.34 Specified Layer Design Layer: 1 Material Description: 1/2-0 Dense Asphalt Structural Coefficient (Ai) : .42 Drainage Coefficient (Mi) : 1 Layer Thickness (Di) (in) : 3.50 Calculated Layer SN: 1.47 Layer: 2 Material Description: 3/4-0 Crushed Rock Structural Coefficient (Ai) : . 1 Drainage Coefficient (Mi) : 1 Layer Thickness (Di) (in) : 2.00 Calculated Layer SN: .20 Layer: 3 Material Description: 1.5-0 Crushed Rock Structural Coefficient (Ai) : .1 Drainage Coefficient (Mi) : 1 Layer Thickness (Di) (in) : 8.00 Calculated Layer SN: .80 Total Thickness (in) : 13.50 Total Calculated SN: 2.47 Simple ESAL Calculation Initial Performance Period (years) : 20 Initial Two-Way Daily Traffic (ADT) : 250 % Heavy Trucks (of ADT) FHWA Class 5 or Greater: 3 Number of Lanes In Design Direction: 1 Percent of All Trucks In Design Lane (%) : 100 Percent Trucks In Design Direction (%) : 50 , Average Initial Truck Factor (ESALs/truck) : 1.8 Annual Truck Factor Growth Rate (o) : 0 Annual Truck Volume Growth Rate (o) : 3 Growth: Simple Total Calculated Cumulative Esals: 63, 362 GeoPacific Engineering, Inc. Real-World Geotechnical Solutions 14835 SW 72nd Avenue Tel(503)598-8445 Investigiation,Design,Construction Support Portland,Oregon 97224 Fax(503)941-9281 Dynamic Cone Penetrometer(DCP)/California Bearing Ratio(CBR)Correlation Project:North Dakota Subdivision Date:2.2.2018 Existing A/C Thickness:7.75 Test:RC-1 Project No.18-4824 Collector:MTB Existing Base Aggregate Thickness:3.75 Location:Westbound North Dakota 30ft W of E Prop Line Subgrade:SILT Notes:Location on Figure 2 Length of shaft I Height(from ref)at start Depth below ground at start Length of shaft Height(from ref)at start Depth below ground at start cm cm cm in in in 132.08 101.6 30.48 52 40 12 Blows Height(from ref)in Height(from ref)cm Depth(below ground)cm Depth(inches below ground) Depth(feet below ground) mm/blow CBR 5 38.75 98.43 33.66 13.25 1.10 6.35 40 5 37.75 95.89 36.20 14.25 1.19 5.08 50 5 36.25 92.08 40.01 15.75 1.31 7.62 30 5 34 86.36 45.72 18.00 1.50 11.43 20 5 31.5 80.01 52.07 20.50 1.71 12.70 16 5 28.5 72.39 59.69 23.50 1.96 15.24 14 5 21.5 54.61 77.47 30.50 2.54 35.56 5 5 16.25 41.28 90.81 35.75 2.98 26.67 7 5 13.25 33.66 98.43 38.75 3.23 15.24 14 5 10.75 27.31 104.78 41.25 3.44 12.70 18 5 8.5 21.59 110.49 43.50 3.63 11.43 20 Average 14.55 15 This table for DCP measurements recorded in inches Measurements are after each blow. Mm/blow is difference between previous and current blow Dynamic Cone Penetrometer(DCP)/California Bearing Ratio(CBR)Correlation It Project:North Dakota Subdivision Date:2.2.2018 Existing NC Thickness: 10 Test:RC-2 Project No.18-4824 Collector:MTB Existing Base Aggregate Thickness:3 Location:Westbound North Dakota 50ft E of W Prop Line Subgrade:SILT Notes:Location on Figure 2 Length of shaft I Height(from ref)at start Depth below ground at start Length of shaft Height(from ref)at start Depth below ground at start cm cm cm in in in 132.08 99.06 33.02 52 39 13 Blows Height(from ref)in Height(from ref)cm Depth(below ground)cm Depth(inches below ground) Depth(feet below ground) mm/blow CBR 5 38 96.52 35.56 14.00 1.17 5.08 50 5 37.5 95.25 36.83 14.50 1.21 2.54 100 5 37 93.98 38.10 15.00 1.25 2.54 100 5 36.5 92.71 39.37 15.50 1.29 2.54 100 5 35.25 89.54 42.55 16.75 1.40 6.35 35 5 34.75 88.27 43.82 17.25 1.44 2.54 100 5 33 83.82 48.26 19.00 1.58 8.89 25 5 31.5 80.01 52.07 20.50 1.71 7.62 30 5 29.5 74.93 57.15 22.50 1.88 10.16 20 5 27.5 69.85 62.23 24.50 2.04 10.16 20 5 25.5 64.77 67.31 26.50 2.21 10.16 20 5 23 58.42 73.66 29.00 2.42 12.70 16 5 21 53.34 78.74 31.00 2.58 10.16 20 5 18.75 47.63 84.46 33.25 2.77 11.43 20 5 15.25 38.74 93.35 36.75 3.06 17.78 11 f 5 12 30.48 101.60 40.00 3.33 16.51 12 5 9.5 24.13 107.95 42.50 3.54 12.70 16 Average 8.82 25 1 11 18-4824 DCP Data 1 GeoPacific Engineering,Inc. GeoPacific Engineering, Inc. Real-World Geotechnical Solutions 14835 SW 72nd Avenue Tel(503)598-8445 Investigiation,Design,Construction Support Portland,Oregon 97224 Fax(503)941-9281 ) Dynamic Cone Penetrometer(DCP)/California Bearing Ratio(CBR)Correlation !, Project:North Dakota Subdivision Date:2.2.2018 Existing A/C Thickness:2.75 Test:RC-3 Project No.18-4824 Collector:MTB Existing Base Aggregate Thickness:18+ 1 Location:Center of 114th Place Cul-de-sac at edge of pave Subgrade:SILT Notes:Location on Figure 2 1 Length of shaft i Height(from ref)at start Depth below ground at start Length of shaft Height(from ref)at start Depth below ground at start CM cm cm in in in 1 132.08 119.38 12.7 52 47 5 1 Blows Height(from ref)in Height(from ref)cm Depth(below ground)cm Depth(inches below ground) Depth(feet below ground) mm/blow CBR :1 5 37 93.98 38.10 15.00 1.25 50.80 3.6 5 23 58.42 73.66 29.00 2.42 71.12 2.5 1 17 43.18 88.90 35.00 2.92 152.40 1.1 1 14 35.56 96.52 38.00 3.17 76.20 2.3 1 12 30.48 101.60 40.00 3.33 50.80 3.6 1 10 25.40 106.68 42.00 3.50 50.80 3.6 1 8 20.32 111.76 44.00 3.67 50.80 3.6 ) 1 6.5 16.51 115.57 45.50 3.79 38.10 5 1 5 12.70 119.38 47.00 3.92 38.10 5 1 3.5 8.89 123.19 48.50 4.04 38.10 5 1 2.5 6.35 125.73 49.50 4.13 25.40 8 Average 58.42 3.1 e Average at Subgrade Elevation 46.04 4 1 ) ) i� Dynamic Cone Penetrometer(DCP)/California Bearing Ratio(CBR)Correlation j Project:North Dakota Subdivision Date:2.2.2018 Existing A/C Thickness:2.5 Test:RC-3 Project No.18-4824 Collector:MTB Existing Base Aggregate Thickness: 17 !J Location:Center of 114th Place 75ft N of N.Dakota St. Subgrade:SILT Notes:Location on Figure 2 i Length of shaft I Height(from ref)at start Depth below ground at start Length of shaft Height(from ref)at start Depth below ground at start cm cm cm in in in 132.08 83.82 48.26 52 33 19 Blows Height(from ref)in Height(from ref)cm Depth(below ground)cm Depth(inches below ground) Depth(feet below ground) mm/blow CBR It kf 1 32 81.28 50.80 20.00 1.67 25.40 8 1 31 78.74 53.34 21.00 1.75 25.40 8 I 1 30.5 77.47 54.61 21.50 1.79 12.70 16 1 29.5 74.93 57.15 22.50 1.88 25.40 8 1 28.5 72.39 59.69 23.50 1.96 25.40 8 1 27.75 70.49 61.60 24.25 2.02 19.05 11 1 26.75 67.95 64.14 25.25 2.10 25.40 8 1 25.75 65.41 66.68 26.25 2.19 25.40 8 1 24.5 62.23 69.85 27.50 2.29 31.75 6 'f 1 23.25 59.06 73.03 28.75 2.40 31.75 6 1 22 55.88 76.20 30.00 2.50 31.75 6 1 20.75 52.71 79.38 31.25 2.60 31.75 6 1 19.5 49.53 82.55 32.50 2.71 31.75 6 1 18 45.72 86.36 34.00 2.83 38.10 5 1 17.25 43.82 88.27 34.75 2.90 19.05 11 1 16.5 41.91 90.17 35.50 2.96 19.05 11 1 15.5 39.37 92.71 36.50 3.04 25.40 8 1 14.75 37.47 94.62 37.25 3.10 19.05 11 1 14 35.56 96.52 38.00 3.17 19.05 11 1 13.25 33.66 98.43 38.75 3.23 19.05 11 5 9.5 24.13 107.95 42.50 3.54 19.05 11 Average 24.80 8 li ii 18-4824 DCP Data 2 GeoPacific Engineering,Inc. CeoPacific Engineering,Inc. Real-World Geotechnical Solutions Investigation • Design •Construction Support PHOTOGRAPHIC LOG 14835 SW 72nd Avenue Tel (503) 598-8445 Portland, Oregon 97224 Fax (503) 941-9281 r _4/j .J CeoPácitIc Engineering,Inc, Real-World Geotechnical Solutions Investigation • Design • Construction Support I ra i • 4 il , '4 '‘.... ' ,, e, 1 f it . w �'f1 iiiit ,. li , , te"i"! ii Y.. \ I 1 1 1 1 i f Test Pit TP-1 Page 1 ../ty ,041 MI CeoP , !fie Engineering,Ilnc. Real-World Geotechnical Solutions Investigation • Design •Construction Support c 'Fa ,.y i. i I I Test Pit TP-2 A t ti hi i I Ii fi Page 2 I i 1 ! ,..0;00,011,,,, 11 CeoP 'fie 1 Engineering.inc. a Real-World Geotechnical Solutions 1 ? Investigation • Design •Construction Support 1 1 i a Y �[ E 4' "'y+ , .0 -01 - . L N `Yin , . ".F i'yt k, • w Y +++rrrrrr ,y . • . f y , ' .,`s..`,w fit,:! r+ _ .� a fob p .� / , .. ixi~ �,,;g��ypryryry{t i e ` w Test Pit TP-5 Page 3 404(", GeoPeitic Engineering,Inc. 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