Highway 99 and Kelly Street TABLE OF CONTENTS PROJECT INFORMATION... 1 FIELD EXPLORATION... 1 SITE CONDITIONS... 2 Surface Conditions:... 2 Subsurface Conditions:... 2 FILL.... 2 Topsoil.... 2 Clay Alluvium.... 2 DISCUSION OF GEOTECHNICAL ISSUES... 2 Weather Conditions:... 2 Site Grading:... 3 Foundations:... 3 Building Pad:... 3 Drainage:... 4 GEOTECHNICAL ANALYSIS... 4 Seismic Design:... 4 Bearing Capacity:... 5 Settlement:... 5 Vehicle Access Areas:... 5 GEOTECHNICAL RECOMMENDATIONS... 6 Materials:... 6 Utilities:... 7 Foundation Design:... 7 Building Site Preparation (Dry Weather):... 7 Foundation/Slab Construction:... 8 Site Preparation- Access Pavements and Parking Areas (Dry Weather):... 9 Site Preparation (Wet Weather):... 10 LIMITATIONS OF THIS REPORT... 10 APPENDIX A APPENDIX B FIGURES TEST PIT LOGS
Page 1 of 11 Highway 99 and Kelly Street PROJECT INFORMATION Bob Grant Construction is assisting with project management for a new commercial building at the southwest corner of Highway 99 and Kelly Street in. We understand that the design for the includes a new wood frame structure fronting Highway 99 and a parking area to the west of the existing alley. The site location is shown on the Vicinity Map (Figure 1), included in Appendix A. The east portion of the parcel is currently covered by asphalt paved areas and gravel surfaced areas. The west portion of the site is grass covered. The parcel is relatively flat with slight slopes from the west down toward the east. The proposed building is expected to consist of a slab on grade structure that is two stories. The structure will be wood framed with relatively light foundation loads. Site grading is expected to consist of minor cuts and fills on the relatively level site with finished grades elevated slightly above the existing grades for the building pad. OGD is providing geotechnical engineering services at the request of Bob Grant Construction for the proposed improvements. Our scope of services was outlined in our proposal dated June 26, 2017. FIELD EXPLORATION The field exploration focused on characterization of the upper soils at the site that will be involved in the proposed foundation excavations. We visited the site on June 28, 2017 to conduct subsurface explorations. During our visit we conducted a brief surface reconnaissance of the proposed development area. The subsurface exploration included digging three test holes using a small track mounted excavator (TP-1 through TP-3). The approximate locations of the test pits are shown on the attached Site Plan (Figure 2, Appendix A). The test pits were advanced to a maximum depth of ±6 feet. The soil profiles in each test pit were logged and samples were collected from some locations. The test pits were backfilled with excavated material and the surface graded relatively smooth. The soil profiles are summarized on the narrative test pit logs attached in Appendix B. Our surface and subsurface observations are summarized in the following sections. SITE CONDITIONS
Page 2 of 11 Surface Conditions: The site includes relatively level to slightly sloping terrain across the parcel. The west portion of the parcel includes grass with some brush that was being removed along the south property line. The proposed building location is to the east and currently includes gravel or asphalt surfaced areas. We understand that previous structures in the area have been demolished. Subsurface Conditions: Subsurface conditions were evaluated using the test pit explorations. The approximate test pit locations are shown on the Site Plan (Figure 2, Appendix A). Ground water was not observed in the test pits. However, we anticipate that surface water perches on the upper soils at the site resulting in relatively shallow water levels during wet weather months. Subsurface conditions observed at the site as part of our field exploration typically included the following strata: FILL. The first two test pits were completed within the proposed building area and include granular fill in the upper 1 to 2 feet of the soil profile. The upper portion of the fill typically consists of sandy gravel. We noted that the fill grades to gravelly clay below a depth of one foot at TP-1. The exploration also encountered fill material at the parking area to the west. The fill at the parking lot consists of silty clay with some gravel and debris. The fill extends to a depth of ±1.6 feet below existing grades. Topsoil. The fill is underlain by topsoil, which generally consists of soft to medium stiff clay with some organics. The clay is black to dark grey, dry to moist and has high plasticity. The soft clay topsoil layer is typically 0.5 to 1 foot thick. Clay Alluvium. The upper native soils typically consist of medium stiff clay. The clay has high plasticity and was moist to very moist at the time of our exploration. We anticipate that surface water perches on the clay during wet weather months. The clay becomes stiffer with depth and includes some silt. The high plastic clay extends to the limit of our exploration at the site. DISCUSION OF GEOTECHNICAL ISSUES Weather Conditions: The site is expected to include relatively shallow water levels during wet weather months and into early summer months. In addition, the upper soils have relatively poor permeability. Therefore, surface water will tend to perch in the upper portion of the soil profile. We anticipate that site work will be more difficult during wet weather conditions. Wet weather work is expected to require additional excavation
Page 3 of 11 and haul off volume due to soft, wet soils. Backfill operations, particularly for below grade portions of the site, will also be more difficult and will likely require use of a higher quality, angular stabilization rock. The native subgrade soils at the site are moisture sensitive and will be susceptible to softening and pumping during wet weather conditions. However, we anticipate that during dry weather months, the upper medium stiff, native clay will be adequate to support proposed slabs and pavements. Site Grading: The currently proposed improvements will require only minor site grading on the parcel. We understand that the proposed finished grades at the building pad will be raised approximately 1 foot above existing grades. Finished grades in the parking area will remain close to existing site grades or raised slightly. However, due to the presence of existing soft fill material, we anticipate that the parking area will required excavation depths of ±1.5 feet below existing grades to remove unsuitable materials and expose suitable subgrade soils. Therefore, a relatively thick layer of imported granular fill will be required to support the proposed improvements at the site. Foundations: The proposed structure is expected to be supported by shallow foundations constructed over the medium stiff clay alluvium. The clay has high plasticity and is expected to have moderate shrink/swell movements with seasonal variation in moisture content. Therefore, we have provided recommendations for minimum footing embedment and crushed rock beneath footings and the building slab to minimize seasonal movements. The structure is expected to be supported by a combination of continuous footings and isolated spread footings supporting columns. The footing excavations will need to extend through the upper fill and topsoil to expose firm clay alluvium. Therefore, excavation depths that extend ±3 feet below existing grades will be required. We anticipate that all the shallow foundations will be supported on imported aggregate base fill material that is at least 18 inches thick to provide a working surface and minimize differential settlements. Use of deeper aggregate base may be required to provide a stable surface during wet weather construction. Building Pad: We have assumed that the finished grade of the building pad will be raised slightly above the existing ground level. It may be practical to construct a new leveling pad of compacted aggregate base over the existing granular fill. However, portions of the building pad may include soft fill that requires excavation and replacement. Therefore, a typical aggregate base thickness of ±8 inches over the compacted, approved existing granular fill may be feasible. However, we anticipate that areas of deeper excavation and replacement of the existing fill may be required. This is expected to require off haul and replacement of ±2 feet or more of material.
Page 4 of 11 Drainage: The site improvements will require construction of a perimeter foundation drain around the new building. The site includes upper soils consisting of high plastic clay. Therefore, we anticipate that a perched water condition will develop at the site during wet portions of the year. We understand that the new building will primarily surrounded by pavements associated with the parking lot. Therefore, we anticipate that the finished grading surrounding the structure be sloped to promote surface drainage away from the structure. We have assumed that all site drainage would be collected and transmitted to the storm system. GEOTECHNICAL ANALYSIS OGD has conducted geotechnical analysis of the foundation soils for design of the new foundations. Our work is briefly summarized below. Seismic Design: The average soil conditions in the upper ±100 feet beneath the proposed development area are expected to include medium stiff grading to stiff clay with variable silt. Therefore, we believe that use of a site class D is appropriate for seismic design. In our opinion, the spectral accelerations and attenuation relationships provided in the 2014 OSSC are appropriate for seismic design of the new structure. We recommend using the General Procedure of OSSC, Section 1613 to develop parameters for seismic design of the structure. The stiff clay soils are not expected to have a significant risk of liquefaction at the site. Peak ground accelerations and spectral accelerations (on rock) were determined for design using 2% probability of exceedence in 50 years (i.e., ±2,475 year return interval). The USGS modeling considers a variety of seismic sources including crustal and subduction zone earthquakes. However, the principal sources of the design ground motion is due to a large magnitude (M w 8.3 to 9.0) earthquake along the Cascadia Subduction Zone along the Pacific coast and a shallow crustal earthquake. The 2014 OSSC design parameters are summarized in Table. 1. Site Class Table 1. Seismic Design Parameters Ss S1 SMS SM1 SDS SD1 D 0.93 0.47 1.05 0.72 0.70 0.48
Page 5 of 11 Bearing Capacity: We conducted bearing capacity analysis for the anticipated foundation loads for the new structure. We understand that the loads for the structure will be relatively light and may be as great as 3 kips/linear foot for continuous footings and as great as 50 kips for spread footings. The lightly loaded footings may be constructed over the upper medium stiff clay using an allowable bearing pressure of 2,000 psf. The bearing pressure may be increased to 2,500 psf when considering short-term (i.e., wind or seismic) loads. All continuous footings should have a minimum width of 16 inches. Isolated spread footing foundations should have a minimum dimension of 24 inches. Our analysis assumed that all footings would be underlain by a nominal ±18 inches of compacted crushed rock that extends a minimum of 12 inches beyond the limits of the footing. The base of all footings should be embedded 2 feet below finished grades. The footings should be designed using an ultimate subgrade friction coefficient of 0.4 for foundations constructed on compacted crushed rock. A factor of safety of 1.5 is appropriate for this coefficient to minimize relative movements when considering long-term loads. Passive pressures against the sides of the footings may be estimated using an equivalent fluid density of 300 pcf assuming the footings will be backfilled with compacted granular fill. Settlement: Settlement analysis was completed for the anticipated footings based on the typical soil profile. Our analysis considered the assumed foundation loads over spread and continuous footings constructed ±2 feet below existing site grades. Our analysis suggests that post-construction settlements of ½ inch should be assumed for the new foundations. Vehicle Access Areas: We have conducted a brief review of subgrade conditions for areas that will be used for vehicle access at the west portion of the site. We have assumed that the parking and vehicle access areas will be excavated and the crushed rock section placed for use for site access and staging during upcoming wet weather months. The parking and paving areas will require excavation of the upper soft clay fill and soft organic topsoil resulting in a relatively thick layer of aggregate base. The pavement areas should be excavated to expose firm subgrade soils. We anticipate that the subgrade will consist of high plastic clay that may be wet at the time of the work. Therefore, we recommend that a separation geotextile be used with an initial lift of 12 to 18 inches of crushed rock. We anticipate that a total aggregate base thickness of at least 24 inches will be required to support wet weather operations. The required excavation depths may result in even greater thickness of crushed rock in some areas.
Page 6 of 11 We anticipate that a nominal asphalt thickness of 3 inches would be acceptable for the new pavements that will be used primarily for car parking and vehicle access with occasional delivery truck traffic. GEOTECHNICAL RECOMMENDATIONS Based on our observations of the soils and our understanding of the proposed development OGD believes that it will be practical to construct the improvements using conventional construction techniques. Geotechnical recommendations are provided in the following sections. Materials: 1. Aggregate base as defined in this report should consist of ¾ or 1-inch minus, well graded crushed rock. The rock should be relatively clean with less than 5% (by weight) passing the #200 sieve. 2. Stabilization rock, if required, should consist of clean, angular, 3-inch crushed rock. Stabilization rock should contain less than 2% (by weight) passing the #200 sieve. Use of an open-graded rock may be required for the initial lift of fill during wet weather conditions. 3. Unsuitable site fill consists of existing fill materials, soft organic topsoil and the soft high plastic clay soils that are expected in required excavations across the site. The excavated materials are unsuitable for use as fill at the site and should be hauled from the parcel. 4. Compact all aggregate base and stabilization rock to 95% relative compaction. The maximum dry density of ASTM D 698 should be used as the standard for evaluation of relative compaction. Placement and compaction of structural fill should be completed using loose lifts no greater than 8 inches thick, unless specified otherwise. Field density testing and observation of placement and compaction procedure should be conducted on all structural fill to document proper compaction at regular intervals throughout the work. 5. Subgrade beneath foundations, pavements and the building pad should be evaluated and approved by the engineer prior to placement of structural fill or aggregate base. Proof rolling of the subgrade in the building pad should be completed to delineate areas of the existing fill material that require excavation and replacement. Proof rolling of the parking lot subgrade may not be practical if wet subgrade conditions are present. Subgrade conditions should be visually confirmed during the work. Wet weather construction will require more frequent evaluation of subgrade conditions encountered as the work progresses.
Page 7 of 11 Utilities: 6. Provide shoring for all trench excavations greater than 4 feet below grade. Anticipate that minor caving of trench sidewalls may occur, even in shallow excavations, particularly in areas of upper fill and soft clay topsoil. 7. Dewatering of trenches may be required, particularly during winter and spring months. Use of slightly deeper excavation and stabilization of the bottom of the trenches may also be required in wet conditions. Foundation Design: 8. Design all lightly loaded foundations (continuous wall footings and isolated column footings) using an allowable bearing capacity of 2,000 psf. The bearing capacity may be increased to a maximum of 2,500 psf when considering short-term (i.e., wind or seismic) loads. This evaluation assumes that footing preparation and placement of compacted aggregate base will be conducted as recommended. 9. Provide a minimum footing width of 16 inches for continuous footings and 24 inches for isolated column footings. Place the base of all footings at least 2 feet below the finished grade or paved surfaces. 10. Provide a minimum of 18 inches of compacted aggregate base beneath the footings. The excavation and associated aggregate base backfill should extend laterally 12 inches beyond the footing limits. 11. Provide for foundation drainage at the perimeter of the structure. The drain should consist of a 3 or 4 inch diameter perforated pipe that is backfilled with at least 12 inches of drain rock. The entire mass of drain rock should be wrapped in a drainage geotextile. Building Site Preparation (Dry Weather): Recommendations for building site preparation conducted during dry weather months are provided below. 12. Building pad preparation should be completed to allow placement of ±8 inches of imported aggregate base over the existing granular fill. The existing granular fill surface should be proof rolled using a loaded dump truck to identify areas, such as the test pits, that require deeper excavation and replacement with aggregate base. The proof roll should be observed by the engineer to determine areas that require deeper excavation. 13. Areas of deeper excavation should be completed to remove all existing fill material and organic topsoil from beneath the proposed building pad. We
Page 8 of 11 anticipate that the required excavation will extend ±2 to 2.5 feet below existing grades. 14. Structural fill should be placed and compacted in lifts over the approved subgrade. The structural fill should be compacted using multiple passes of a vibratory smooth drum roller. 15. Place the structural fill in loose lifts no greater than 8 inches thick. Use of a ±16 inch thick initial lift may be required to protect the subgrade in deeper excavation areas during placement and compaction. The fill material should be moisture conditioned to within ±2% of optimum moisture content at the time of placement and compaction. Compact the fill to 95% relative compaction according to ASTM D 698. All structural fill should be documented at regular intervals throughout placement and compaction. Field density testing should be completed at several locations across the fill area every ±12 vertical inches of fill. In addition, periodic observations of the fill material and placement and compaction method should be made throughout the work. Foundation/Slab Construction: 16. Foundation excavations extending through the building pad fill should be extended into the medium stiff native clay. All foundation excavations should be conducted using an excavator equipped with a smooth bucket to minimize disturbance to the foundation soils. 17. Footing excavations should extend at least ±3.5 feet below finished site grades to allow placement of the required aggregate base and provide adequate footing embedment. Footing subgrade soils should be verified by the engineer at the time of construction. 18. Place and compact a minimum of 18 inches of aggregate base in two lifts beneath all foundations. The aggregate base beneath footings should extend laterally ±12 inches beyond the limits of the footing. 19. Construct a perimeter foundation drain around the new structure that includes a perforated 3 or 4 inch diameter drain pipe with the flow line near the footing level. The foundation drain should be bedded in drain rock and include at least 12 inches of drain rock cover over the pipe. The entire mass of drain rock should be wrapped in a drainage geotextile. 20. After completion of all plumbing and electrical trenching in the building pad the aggregate base should be finish graded and compacted. 21. Install a vapor barrier beneath the slab on grade building per the manufacturer s recommendations.
Page 9 of 11 Site Preparation- Access Pavements and Parking Areas (Dry Weather): Recommendations for site preparation of pavement areas conducted in the summer months are provided below. 22. Pavements should be constructed during dry weather to the extent practical. The pavement sections recommended herein are not intended to support heavy construction traffic. 23. The subgrade should be evaluated to identify any areas of fill, soft soils or unsuitable material. We have assumed that the pavement areas would be excavated to the required subgrade elevation with the pavement section constructed over firm, relatively undisturbed clay. The excavation work is expected to require removal of all the existing soft, high plastic clay fill material. Therefore, excavation depths of 1 to 2 feet below existing grades are expected throughout the pavement improvements. 24. The excavation should be completed using an excavator equipped with a smooth bucket to minimize disturbance to the subgrade. Areas of soft subgrade, organics or unsuitable materials will require deeper excavation. The exposed subgrade should be observed and approved by the engineer prior to placement of aggregate base. Do not allow construction traffic on the subgrade soils. 25. The approved subgrade should be covered with a separation geotextile prior to rock placement. Place and compact the required aggregate base section over the approved subgrade as soon as practical. We anticipate that a thickened initial lift of aggregate base would be placed to assist in minimizing the risk of subgrade disturbance or pumping. The initial 16 to 18 inches of aggregate base should be placed and compacted prior to allowing truck traffic operating on the structural fill surface. The aggregate base should be moisture conditioned to near optimum moisture content and compacted using a large, smooth drum, vibratory compactor. Subsequent lifts of aggregate base should be placed and compacted as recommended. Field density testing should be conducted on the compacted aggregate base to confirm adequate compaction. 26. We anticipate that a minimum of 24 inches of aggregate base will be provided beneath paved parking areas based on the thickness of the existing fill material. The required thickness of the aggregate base will depend on the construction schedule, anticipated construction traffic, and soil conditions at the time of the work. We anticipate that some areas of thicker aggregate base will be required due to the required excavation depth to remove the existing fill material.
Page 10 of 11 Site Preparation (Wet Weather): Recommendations for paving and building site preparation conducted during wet weather months are provided below. 27. Construction access will need to be established from the existing paving. Construction traffic should not be allowed on the granular fill section until the total thickness is 2.5 feet or greater. Excavation and structural fill placement may need to be suspended during periods of heavy rainfall at the site. 28. All subgrade excavation should be completed using an excavator equipped with a smooth bucket in a manner to minimize subgrade disturbance throughout the work. No construction traffic should be allowed on the clay subgrade. 29. The subgrade conditions should be evaluated by the engineer throughout the work. All site excavations will need to be conducted to provide a minimum granular fill thickness of 2.5 feet. A thicker rock section may be required in some areas depending on the thickness of the existing fill and subgrade conditions. We anticipate that required excavations during wet weather months will result in a typical rock section of 3 to 3.5 feet to support the improvements. 30. The initial 18 inch thick lift of granular fill should consist of stabilization rock that is placed and compacted over a separation geotextile over the approved subgrade. 31. Use of a dewatering sump will be required throughout the work to control water levels within the rock fill. The excavation work may require installation and pumping from several of these temporary sumps as the work progresses across the site. 32. Aggregate base should be placed and compacted in lifts over the initial lift of stabilization rock. The aggregate base should be compacted using multiple passes of a vibratory smooth drum roller. Do not allow truck traffic on the rock until the total thickness is 2.5 feet. LIMITATIONS OF THIS REPORT The analysis, conclusions and recommendations contained herein are based on the assumption that the soil conditions and ground water levels encountered in the test pits are representative of overall site conditions. The above recommendations assume that we will be present during construction to confirm the assumed foundation and subgrade conditions. We will assume no responsibility or liability for any engineering judgment, inspection or testing performed by others.
Page 11 of 11 Our work was performed for the exclusive use by Bob Grant Construction and their design consultants for the proposed at Highway 99 and Kelly Street in. OGD performed our work in accordance with generally accepted professional geotechnical engineering practices in similar locations. Our services do not include any survey or assessment of potential contamination or contamination of the soil or ground water by hazardous or toxic substances. No other warranty, expressed or implied, is made.
Highway 99 and Kelly Street Appendix A Figures OGD Consulting, PC Serving Oregon Geotechnical Design and Consulting Needs
Figure 1. Vicinity Map Long Timber Brewing Highway 99 and Kelly Street 2017 Google 1000 ft N
Figure 2. Site Plan Long Timber Brewing Highway 99 and Kelly Street 2017 Google 100 ft N
Highway 99 and Kelly Street Appendix B Test Pit Logs OGD Consulting, PC Serving Oregon Geotechnical Design and Consulting Needs
Page 1 of 3 Highway 99 and Kelly Street APPENDIX B NARRATIVE TEST PIT SUMMARIES Logged on June 28, 2017 Test Pit: TP-1 Depth (feet) Material Description Notes/Sampling 0.0 to 0.9 Medium dense sandy GRAVEL; grey, dry to slightly moist, 1 minus crushed and rounded gravel, (fill). 0.9 to 1.9 Medium stiff gravelly CLAY with some sand; grey, moist, high plasticity clay, (fill). 1.9 to 2.4 Soft, organic CLAY; black, moist, high plasticity, (topsoil). 2.4 to 4.7 Medium stiff CLAY; grey, very moist, high plasticity. 4.7 to 6.0 Stiff silty CLAY; grey, moist, medium to high plasticity. Gravel at surface. No ground water infiltration noted. Appendix B
Page 2 of 3 Test Pit: TP-2 Depth (feet) Material Description Notes/Sampling 0.0 to 0.9 Medium dense sandy GRAVEL with some silt; grey, dry to slightly moist, ¾ inch minus over 3-inch quarry rock, (fill). 0.9 to 1.9 Soft to medium stiff CLAY with some organics; dark grey, moist, high plasticity, (topsoil). 1.9 to 4.0 Medium stiff CLAY; grey, moist, high plasticity. 4.0 to 4.5 Medium stiff silty CLAY; grey, moist, medium to high plasticity. Gravel at surface No ground water infiltration noted. Appendix B
Page 3 of 3 Test Pit: TP-3 Depth (feet) Material Description Notes/Sampling 0.0 to 1.6 Medium stiff silty CLAY with some gravel and scattered debris; brown, dry, medium plasticity clay, (fill). 1.6 to 2.5 Medium stiff CLAY with organics; dark grey, dry to slightly moist, high plasticity, (topsoil). 2.5 to 3.5 Medium stiff CLAY with some silt; grey, moist, high plasticity. Grass at surface. Debris includes occasional asphalt fragments. No ground water infiltration noted. Appendix B