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25. RS_Geotechnical_Report_200522_V2.pdf
GEOTECHNICAL REPORT Canopy 4130 Lincoln Avenue NE Renton, Washington Project No. T-7886 Prepared for: Blue Fern Development, LLC Kirkland, Washington March 19, 2019 6th Revision May 18, 2020 5-18-2020 TABLE OF CONTENTS Page No. 1.0 Project Description .......................................................................................................... 1 2.0 Scope of Work ................................................................................................................. 1 3.0 Site Conditions ................................................................................................................ 2 3.1 Surface ................................................................................................................ 2 3.2 Soils .................................................................................................................... 2 3.3 Groundwater ....................................................................................................... 3 3.4 Geologic Hazards ............................................................................................... 3 3.4.1 Erosion Hazard ......................................................................................... 3 3.4.2 Landslide Hazard ...................................................................................... 3 3.4.3 Seismic Hazard ......................................................................................... 3 3.5 Soil Site Class ..................................................................................................... 4 4.0 Discussion and Recommendations .................................................................................. 4 4.1 General................................................................................................................ 4 4.2 Site Preparation and Grading .............................................................................. 4 4.3 Excavations ......................................................................................................... 6 4.4 Foundations ........................................................................................................ 6 4.5 Slab-on-Grade Floors ......................................................................................... 7 4.6 Lateral Earth Pressures ....................................................................................... 7 4.7 Infiltration Facility .............................................................................................. 8 4.8 Drainage.............................................................................................................. 8 4.9 Utilities ............................................................................................................... 9 4.10 Pavements ........................................................................................................... 9 5.0 Additional Services ........................................................................................................ 10 6.0 Limitations ..................................................................................................................... 10 Figures Vicinity Map ....................................................................................................................... Figure 1 Exploration Location Plan .................................................................................................. Figure 2 Protected Slope Layout ....................................................................................................... Figure 3 Typical Slope Key and Bench Detail .................................................................................. Figure 4 Typical Wall Drainage Detail ............................................................................................. Figure 5 Appendices Field Exploration and Laboratory Testing ....................................................................... Appendix A Mounding Analysis ........................................................................................................... Appendix B Geotechnical Report Canopy 4130 Lincoln Avenue NE Renton, Washington 1.0 PROJECT DESCRIPTION The project consists of developing 5 adjoining tax parcels totaling approximately 10.1 acres with 53 single-family homes, stormwater facilities, and associated access and utilities. Based on review of the conceptual site plan, prepared by CORE Design dated February 2019, grading to achieve the building lot and roadway elevations will consist of cuts and fills from 1 to 16 feet. Vertical grade transitions along the perimeter of the site will be supported with reinforced fill rockery walls, Redi-Rock walls, or cut rockery walls. Interior grade transitions will be supported with 2:1 (Horizontal:Vertical) slopes. We anticipate that the structures will be two- to three-story, wood-framed, and constructed either at grade or over a crawl space with relatively light structural loading. We expect that bearing walls will carry loads of 1 to 3 kips per foot and isolated columns will carry maximum loads of 30 to 60 kips. The recommendations in the following sections of this report are based on our understanding of the preceding design features. We should review final design drawings as they become available to verify that our recommendations have been properly interpreted and to supplement them, if required. 2.0 SCOPE OF WORK We completed our site exploration on April 9, 2018 by observing soil and groundwater conditions at 9 test pits excavated to maximum depths of about 11 feet below existing site grades. On April 4, 2019, we supplemented this data by excavating 5 additional test pits to maximum depths of approximately 12 feet below existing site grades. On April 10, 2019 and April 11, 2019, we further supplemented the data by drilling 4 test borings to depths of 30 to 35 feet below current site grades. Using the information obtained from the subsurface exploration and laboratory testing, we performed analyses to develop geotechnical recommendations for project design and construction. Specifically, this report addresses the following: Soil and groundwater conditions. Geologic Hazards per the City of Renton Municipal Code. Seismic Site Class per the 2015 International Building Code (IBC). Site preparation and grading. Slopes and embankments. Excavation Foundation support. Slab-on-grade floors. Infiltration feasibility per 2016 King County Surface Water Design Manual. Rockeries Drainage Utilities Pavements March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 2 It should be noted that recommendations outlined in this report regarding drainage are associated with soil strength, design earth pressures, erosion, and stability. Design and performance issues with respect to moisture as it relates to the structure environment are beyond Terra Associates’ purview. A building envelope specialist or contractor should be consulted to address these issues, as needed. 3.0 SITE CONDITIONS 3.1 Surface The project site consists of an assemblage of 5 tax parcels totaling approximately 10.1 acres located east of Lincoln Avenue NE and north of NE 40th Street in Renton, Washington. However, our site investigation was limited to the parcel located at 4130 Lincoln Avenue NE and the large parcel located immediately to the north. The approximate site location is shown on Figure 1. The site area explored currently supports a single-family home and a couple of small outbuildings in its southern corner. The remainder of the site is undeveloped and supports a combination of densely forested areas and unforested brush covered areas. Trees at the site consist of a combination of mature coniferous and broadleaf trees. Topography at the site generally falls moderately to steeply from east to west with overall site relief on the order of 145 feet. 3.2 Subsurface In general, the soil conditions observed in the test pits excavated in 2018 and 2019 consisted of 2 to 24 inches of topsoil overlying medium dense to dense sandy silt and silty sand with varying gravel content (weathered till) overlying dense sandy silt, silt with sand, and silty sand with varying gravel content (glacial till) to the terminus of the test pits. There were three exceptions to this general condition. At Test Pits TP-2 and TP-7, we observed two to two- and one-half feet of loose to medium dense inorganic fill overlying the native till soils. At Test Pit TP-8, we observed dense sand to sand with silt underlying the upper approximately six feet of glacial till. At Test Pit TP- 1, underlying the upper topsoil horizon, we observed medium dense to dense sand and sand with silt to the terminus of the test pit. The upper soil conditions observed in the test borings completed at the site were consistent with those observed in the test pits. Underlying the weathered and unweathered till materials, we observed very stiff to hard silt to the termination of the test borings. The till material was observed to depths of 18 to 23 feet below current site grades in Test Borings B-2, B-3, and B-4. Test Boring B-1 did not extend through the till material into the hard silt. The Geologic Map of Surficial Deposits in the Seattle 30’ by 60’ Quadrangle, Washington by J.C. Yount, J.P. Minard, and G.R. Dembroff (1993) indicates that the majority of the site is underlain by Vashon till (Qvt) with Pre- Fraser deposits undifferentiated (Qpf) underlying the westernmost margin of the site near its frontage with Lincoln Avenue NE. The soils observed at depth in our test pits are consistent with the Vashon till mapped unit with the hard silt observed in the test borings consistent with the pre-fraser deposit unit. March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 3 The preceding discussion is intended to be a general review of the soil conditions encountered. For more detailed descriptions, please refer to the Test Pit and Test Boring Logs in Appendix A. 3.3 Groundwater We observed light to moderate, perched groundwater seepage in 10 of the 14 test pits at depths ranging from 1.5 to 9 feet below current site grades. The groundwater seepage was generally noted to flow near the contact between the upper weathered and existing fill soils and the dense to very dense native glacial till. This is typical for sites underlain by glacial till and occurs as a result of rainfall that infiltrates through the upper weathered soil zone and becomes perched on the underlying dense till. The dense till soils have a relatively low permeability that impedes the continued downward migration of the infiltrated rainfall. As a result, groundwater seepage will develop and tend to flow laterally along the contact. Locally, such seepage is referred to as interflow. Scattered across much of the eastern half of the property, we observed areas where groundwater was seeping from the ground surface. In our opinion, these ground seeps are the result of shallow interflow encountering impermeable layers near the ground surface. The occurrence of interflow will fluctuate seasonally with the highest seepage levels occurring during the normally wet winter to late spring months (November to May). Based on the time of year of our exploration, the groundwater observed is likely near the seasonal high levels. 3.4 Geologic Hazards 3.4.1 Steep Slopes Title IV, Chapter 3, Section 4-3-050(G)(5)(a) of the Renton Municipal Code (RMC) defines steep slopes in the following two categories: i. Sensitive Slopes: A hillside, or portion thereof, characterized by: (a) an average slope of 25 percent to less than 40 percent as identified in the City of Renton Steep Slope Atlas or in a method approved by the City; or (b) an average slope of 40 percent or greater with a vertical rise of less than 15 feet as identified in the City of Renton Steep Slope Atlas or in a method approved by the City; (c) abutting an average slope of 25 percent to 40 percent as identified in the City of Renton Steep Slope Atlas or in a method approved by the City. This definition excludes engineered retaining walls. ii. Protected Slopes: A hillside, or portion thereof, characterized by an average slope of 40 percent or greater grade and having a minimum vertical rise of 15 feet as identified in the City of Renton Steep Slope Atlas or in a method approved by the City.” Based on a topographic site plan prepared by CORE Design, there are isolated areas across the site where slope gradients exceed 40 percent over a vertical rise of 15 feet. Therefore, the site does contain protected slopes as defined in item (ii) above. Per the RMC, a building setback of 15 feet must be established between any structures associated with the development and these protected slope areas. A map showing these locations is shown on Figure 3. March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 4 3.4.2 Erosion Hazard Areas Title IV, Chapter 3, Section 4-3-050(G)(5)(c) of the RMC defines erosion hazards in the following two categories: i. Low Erosion Hazard (EL): Areas with soils characterized by the Natural Resource Conservation Service formerly U.S. Soil Conservation Service) as having slight or moderate erosion potential, and a slope less than 15 percent. ii. High Erosion Hazard (EH): Areas with soils characterized by the Natural Resource Conservation Service formerly U.S. Soil Conservation Service) as having severe or very severe erosion potential, and a slope more than 15 percent.” The soils observed within the proposed development area are classified as Alderwood gravelly sandy loam, 8 to 30 percent slopes, Everett very gravelly sandy loam, 8 to 15 percent slopes, Ragnar-Indianola association, sloping and Ragnar-Indianola association, moderately steep by the United States Department of Agriculture Natural Resources Conservation Service (NRCS). With the existing slope gradients, these soils will have a moderate to severe potential for erosion when exposed. Therefore, the site does contain a high erosion hazard area as defined by the RMC. Implementation of temporary and permanent Best Management Practices (BMPs) for preventing and controlling erosion will be required and will mitigate the erosion hazard. As a minimum, we recommend implementing the following erosion and sediment control BMPs prior to, during, and immediately following construction activities at the site. Prevention Limit site clearing and grading activities to the relatively dry months (typically May through September). Limit disturbance to areas where construction is imminent. Locate temporary stockpiles of excavated soils no closer than ten feet from the crest of the slope. Provide temporary cover for cut slopes and soil stockpiles during periods of inactivity. Temporary cover may consist of durable plastic sheeting that is securely anchored to the ground surface or straw mulch. Establish permanent cover over exposed areas that will not be disturbed for a period of 30 days or more by seeding, in conjunction with a mulch cover or appropriate hydroseeding. Containment Install a silt fence along site margins and downslope of areas that will be disturbed. The silt fence should be in place before clearing and grading is initiated. Intercept surface water flow and route the flow away from the slope to a stabilized discharge point. Surface water must not discharge at the top or onto the face of the steep slope. Provide on-site sediment retention for collected runoff. The contractor should perform daily review and maintenance of all erosion and sedimentation control measures at the site. March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 5 3.4.3 Landslide Hazard Areas Title IV, Chapter 3, Section 4-3-050(G)(5)(b) of the RMC defines landslide hazards in the following four categories: i. Low Landslide Hazard (LL): Areas with slopes less than 15 percent. ii. Medium Landslide Hazard (LM): Areas with slopes between 15 percent and 40 percent and underlain by soils that consist largely of sand, gravel, or glacial till. iii. High Landslide Hazards (LH): Areas with slopes greater than 40 percent, and areas with slopes between 15 percent and 40 percent and underlain by soils consisting largely of silt and clay. iv. Very High Landslide Hazards (LV): Areas of known mapped or identified landslide deposits.” The site does contain slopes inclined at greater than 40 percent but does not contain any mapped or identified landslide deposits. Therefore, portions of the site would be considered a High Landslide Hazard (LH) per the RMC. However, during our site reconnaissance, we did not observe evidence of current or historic slope instability such as uniformly back tilted trees, tension cracks, or headscarps. We did observe several areas where groundwater was seeping out of the ground surface. However, in our opinion, these seeps are the result of perched interflow mounding on shallow impermeable obstructions and not indicative of a more significant static groundwater table. Relative Slope Stability In addition to reconnoitering the slope, we completed a slope stability analysis in order to determine if the existing slopes on the site were unstable and to assess the impact of the proposed development. The analyses were performed at locations designated as Cross-Section A-A’, Cross Section B-B’, and Cross Section C-C’ using the computer program Slide 2018. The approximate cross-section locations are shown on Figure 2. Our analysis considered both static and the pseudostatic (seismic) conditions. A horizontal acceleration of 0.3g was used in the pseudostatic analysis to simulate slope performance under earthquake loading. This represents one-half of the Peak Ground Acceleration (PGA) for the site. Based on our field exploration, laboratory testing, and previous experience with similar soil types, we chose the following parameters for our analysis: Table 1 – Slope Stability Analysis Soil Parameters Soil Type Unit Weight (pcf) Friction Angle degrees) Cohesion (psf) New structural fill 120 34 0 – 50 Medium dense silty SAND with gravel (weathered till) 125 34 0 – 50 Dense to very dense silty SAND with gravel (unweathered till) 125 40 150 Very stiff to hard SILT 110 28 750 March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 6 The results of our slope stability analysis, as shown by the lowest safety factors for each condition, are presented in the following table: Table 2 – Slope Stability Analysis Results Based on our analysis, although the slope fits the code criteria of a High Landslide Hazard, the results of our study indicates that they are not at risk of a deep-seated failure in their current state. As such, it is our opinion that the site can be developed as planned as the post construction factors of safety are over the generally required 1.5 for static and 1.1 for seismic. Results of our analysis are attached in Appendix B. Cross Section B-B’ was completed in the area where there is a proposed retaining wall that will regrade a portion of the protected slope in this area. Based on the results of our analysis, the proposed regrading is acceptable from a geotechnical standpoint. 3.4.4 Coal Mine Hazard Areas Title IV, Chapter 3, Section 4-3-050(G)(5)(e) of the RMC defines coal mine hazards in the following three categories: i. Low Coal Mine Hazards (CL): Areas with no known mine workings and no predicted subsidence. While no mines are known in these areas, undocumented mining is known to have occurred. ii. Medium Coal Mine Hazards (CM): Areas where mine workings are deeper than 200 feet for steeply dipping seams, or deeper than 15 times the thickness of the seam or workings for gently dipping seams. These areas may be affected by subsidence. iii. High Coal Mine Hazard (CH): Areas with abandoned and improperly sealed mine openings and areas underlain by mine workings shallower than 200 feet in depth for steeply dipping seams, or shallower than 15 times the thickness of the seam or workings for gently dipping seams. These areas may be affected by collapse or other subsidence.” Based on the City of Renton Sensitive Areas: Coal Mine Hazards Map the site is not located near any coal mine hazards. Therefore, the site would not be classified as a coal mine hazard area per the RMC. Cross Section Minimum Safety Factors Existing Conditions Post Construction A-A’ 2.63 Seismic FS = 1.18) 1.95 Seismic FS = 1.12) B-B’ 2.47 Seismic FS = 1.35) 1.91 Seismic FS = 1.11) C-C’ N/A 1.87 Seismic FS = 1.40) March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 7 3.4.5 Seismic Hazard Areas Title IV, Chapter 3, Section 4-3-050(G)(5)(d) of the RMC defines seismic hazards in the following two categories: i. Low Seismic Hazard (SL): Areas underlain by dense soils or bedrock. These soils generally have site classifications of A through D, as defined in the International Building Code, 2012. ii. High Seismic Hazard (SH): Areas underlain by soft or loose, saturated soils. These soils generally have Site Classifications E or F, as defined in the International Building Code, 2012.” Liquefaction is a phenomenon where there is a reduction or complete loss of soil strength due to an increase in water pressure induced by vibrations. Liquefaction mainly affects geologically recent deposits of fine grained sand that are below the groundwater table. Soils of this nature derive their strength from intergranular friction. The generated water pressure or pore pressure essentially separates the soil grains and eliminates this intergranular friction; thus, eliminating the soil’s strength. Based on the soil and groundwater conditions observed, in our opinion, the potential for soil liquefaction and seismically induced settlement within the native soils is negligible. Therefore, the site would be classified as a Low Seismic Hazard (SL) per the RMC. Based on soil conditions observed in the test pits and our knowledge of the area geology, per Chapter 16 of the 2015 International Building Code (IBC), Site Class D should be used in structural design. 4.0 DISCUSSION AND RECOMMENDATIONS 4.1 General Based on our study, there are no geotechnical conditions that would preclude the planned development. Buildings can be supported on conventional spread footings bearing on competent native soils underlying organic topsoil or on structural fill placed on the competent native soils. Floor slabs and pavements can be similarly supported. We would note that the loose fill material with nested boulders observed at Test Pit TP-2 will be unsuitable for support of new site improvements and should be removed below all structures and pavements. Following removal of the unsuitable fill material, the residential structures can be supported on conventional spread footings bearing on competent native or competent existing fill soils or on structural fill placed and compacted above these competent soils. Pavement and floor slabs can be similarly supported. Most of the native and existing fill soils encountered at the site contain a significant amount of fines and will be difficult to compact as structural fill when too wet. The ability to use native and existing fill soil from site excavations as structural fill will depend on its moisture content and the prevailing weather conditions at the time of construction. If grading activities will take place during winter, the owner should be prepared to import clean granular material for use as structural fill and backfill. The following sections provide detailed recommendations regarding the preceding issues and other geotechnical design considerations. These recommendations should be incorporated into the final design drawings and construction specifications. March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 8 4.2 Site Preparation and Grading To prepare the site for construction, all vegetation, organic surface soils, and other deleterious material should be stripped and removed from the site. Surface stripping depths of up to 24 inches should be expected to remove the organic surface soils. In the developed portions of the site, demolition of existing structures should include removal of existing foundations, floor slabs, underground septic systems, and other buried utilities. Abandoned utility pipes that fall outside of new building areas can be left in place provided they are sealed to prevent intrusion of groundwater seepage and soil. Organic topsoil will not be suitable for use as structural fill, but may be used for limited depths in nonstructural areas. As mentioned above, the upper approximately two feet of loose fill material mixed with nested boulders observed at Test Pit TP-2 will need to be removed prior to foundation or pavement construction. We recommend that this material be removed to expose competent native soils and that grade be restored with new structural fill. The fill was noted to be relatively free of organics and would be suitable for reuse as structural fill provided the boulders are removed prior to placement. Removal depths of about two feet should be planned for; however, the actual depth and lateral extents of the unsuitable soils will need to be determined in the field at the time of construction. Once clearing and excavation operations are complete, cut and fill operations can be initiated to establish desired grades. Prior to placing fill, all exposed bearing surfaces should be observed by a representative of Terra Associates, Inc. to verify soil conditions are as expected and suitable for support of new fill. Our representative may request a proofroll using heavy rubber-tired equipment to determine if any isolated soft and yielding areas are present. If excessively yielding areas are observed, and they cannot be stabilized in place by compaction, the affected soils should be excavated and removed to firm bearing and grade restored with new structural fill. Beneath embankment fills or roadway subgrade if the depth of excavation to remove unstable soils is excessive, the use of geotextile fabrics, such as Mirafi 500X, or an equivalent fabric, can be used in conjunction with clean granular structural fill. Our experience has shown that, in general, a minimum of 18 inches of a clean, granular structural fill placed and compacted over the geotextile fabric should establish a stable bearing surface. The native soils encountered at the site contain a sufficient amount of soil fines that will make them difficult to compact as structural fill when too wet or too dry. The ability to use soils from site excavations as structural fill will depend on its moisture content and the prevailing weather conditions at the time of construction. If wet soils are encountered, the contractor will need to dry the soils by aeration during dry weather conditions. Alternatively, the use of an additive such as Portland cement or lime to stabilize the soil moisture can be considered. If the soil is amended, additional Best Management Practices (BMPs) addressing the potential for elevated pH levels will need to be included in the Storm Water Pollution Prevention Program (SWPPP) prepared with the Temporary Erosion and Sedimentation Control (TESC) plan. If grading activities are planned during the wet winter months, or if they are initiated during the summer and extend into fall and winter, the owner should be prepared to import wet weather structural fill. For this purpose, we recommend importing a granular soil that meets the following grading requirements: U.S. Sieve Size Percent Passing 6 inches 100 No. 4 75 maximum No. 200 5 maximum* Based on the 3/4-inch fraction. Prior to use, Terra Associates, Inc. should examine and test all materials imported to the site for use as structural fill. March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 9 Structural fill should be placed in uniform loose layers not exceeding 12 inches and compacted to a minimum of 95 percent of the soil’s maximum dry density, as determined by American Society for Testing and Materials (ASTM) Test Designation D-698 (Standard Proctor). The moisture content of the soil at the time of compaction should be within minus one to plus three percent of its optimum, as determined by this ASTM standard. In nonstructural areas, the degree of compaction can be reduced to 90 percent. 4.3 Excavation All excavations at the site associated with confined spaces, such as utility trenches, must be completed in accordance with local, state, and federal requirements. Based on regulations outlined in the Washington Industrial Safety and Health Act (WISHA), the loose to dense existing fill, sand, and weathered till soils observed at the site would be classified as Type C soils. The dense unweathered glacial till soil would be classified as Type A soil. Accordingly, temporary excavations in Type C soils should have their slopes laid back at an inclination of 1.5:1 Horizontal:Vertical) or flatter, from the toe to the crest of the slope. Side slopes in Type A soils can be laid back at a slope inclination of 0.75:1 or flatter. For temporary excavation slopes less than 8 feet in height in Type A soils, the lower 3.5 feet can be cut to a vertical condition, with a 0.75:1 slope graded above. For temporary excavation slopes greater than 8 feet in height up to a maximum height of 12 feet, the slope above the 3.5-foot vertical portion will need to be laid back at a minimum slope inclination of 1:1. No vertical cut with a backslope immediately above is allowed for excavation depths that exceed 12 feet. In this case, a four-foot vertical cut with an equivalent horizontal bench to the cut slope toe is required. All exposed temporary slope faces that will remain open for an extended period of time should be covered with a durable reinforced plastic membrane during construction to prevent slope raveling and rutting during periods of precipitation. Shallow groundwater seepage may be encountered within excavations particularly during the winter and spring months. In our opinion, the volume of water and rate of flow into the excavation should be relatively minor to moderate and would not be expected to impact the stability of the excavations when completed as described above. Conventional sump pumping procedures along with a system of collection trenches, if necessary, should be capable of maintaining a relatively dry excavation for construction purposes. The above information is provided solely for the benefit of the owner and other design consultants, and should not be construed to imply that Terra Associates, Inc. assumes responsibility for job site safety. It is understood that job site safety is the sole responsibility of the project general contractor. 4.4 Slopes and Embankments All permanent cut and fill slopes should be graded with a finished inclination of no greater than 2:1 (Horizontal: Vertical). Upon completion of grading, the slope face should be appropriately vegetated or provided with other physical means to guard against erosion. Final grades at the top of the slope must promote surface drainage away from the slope crest. Water must not be allowed to flow uncontrolled over the slope face. If surface runoff must be directed towards the slope, the runoff should be controlled at the top of the slope, piped in a closed conduit installed on the slope face, and taken to an appropriate point of discharge beyond the toe. March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 10 All fill placed for embankment construction should meet the structural fill requirements in Section 4.2 of this report. In addition, if the new fills will be placed over existing slopes of 20 percent or greater, the structural fill should be keyed and benched into competent native slope soils. Figure 4 presents a typical slope key and bench configuration. At minimum, a toe drain should be installed in the key cut as shown on Figure 4. Depending on seepage conditions, drains may also be required along individual benches excavated on the slope face. The need for drains along the upper benches will be best determined in the field at the time of construction. 4.5 Foundation Support The buildings can be supported on conventional spread footing foundations bearing on competent native soils or on structural fills placed above competent native soils. As noted above, the existing loose fill material observed in Test Pit TP-2 would not be suitable for support of building foundations. Foundation subgrade should be prepared as recommended in Section 4.2 of this report. Perimeter foundations exposed to the weather should bear a minimum depth of 1.5 feet below final exterior grades for frost protection. Interior foundations can be constructed at any convenient depth below the floor slab. The native soils that will be exposed at the expected foundation elevations are moisture sensitive and will be easily disturbed by normal construction activity when wet. As a measure to protect the soils from disturbance during construction, consideration should be given to placing a four-inch thick layer of clean crushed rock or lean mix concrete over the foundation subgrade to serve as a working surface. Foundations obtaining support on competent native soil or on new structural fill can be dimensioned for a net allowable bearing capacity of 2,500 pounds per square foot (psf). For short-term loads, such as wind and seismic, a one-third increase in this allowable capacity can be used. With structural loading as anticipated and this bearing stress applied, estimated total and differential settlements are expected to be less than one-half inch. For designing foundations to resist lateral loads, a base friction coefficient of 0.35 can be used. Passive earth pressures acting on the side of the footing can also be considered. We recommend calculating this lateral resistance using an equivalent fluid weight of 350 pcf. We recommend not including the upper 12 inches of soil in this computation because they can be affected by weather or disturbed by future grading activity. This value assumes the foundation will be constructed neat against competent native soil or backfilled with structural fill as described in Section 4.2 of this report. The values recommended include a safety factor of 1.5. 4.6 Floor Slab-on-Grade Slab-on-grade floors may be supported on subgrade prepared as recommended in Section 4.2 of this report. Immediately below the floor slab, we recommend placing a four-inch thick capillary break layer composed of clean, coarse sand or fine gravel that has less than three percent passing the No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting of the floor slab. March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 11 The capillary break layer will not prevent moisture intrusion through the slab caused by water vapor transmission. Where moisture by vapor transmission is undesirable, such as covered floor areas, a common practice is to place a durable plastic membrane on the capillary break layer and then cover the membrane with a layer of clean sand or fine gravel to protect it from damage during construction, and to aid in uniform curing of the concrete slab. It should be noted that if the sand or gravel layer overlying the membrane is saturated prior to pouring the slab, it will not be effective in assisting uniform curing of the slab and can actually serve as a water supply for moisture bleeding through the slab, potentially affecting floor coverings. Therefore, in our opinion, covering the membrane with a layer of sand or gravel should be avoided if floor slab construction occurs during the wet winter months and the layer cannot be effectively drained. We recommend floor designers and contractors refer to the current American Concrete Institute (ACI) Manual of Concrete Practice for further information regarding vapor barrier installation below slab-on-grade floors. 4.7 Lateral Earth Pressures for Wall Design The magnitude of earth pressures developing on below-grade walls and retaining walls will depend on the quality and compaction of the wall backfill. We recommend placing and compacting wall backfill as structural fill, as described in Section 4.2 of this report. To prevent overstressing the walls during backfilling, heavy construction machinery should not be operated within five feet of the back of the wall. Wall backfill in this zone should be compacted with hand-operated equipment. To prevent hydrostatic pressure development, wall drainage must also be installed. A typical wall drainage detail is shown on Figure 5. All drains should be routed to the storm sewer system or other approved point of controlled discharge. With drainage properly installed, we recommend designing unrestrained walls for an active earth pressure equivalent to a fluid weighing 35 pounds per cubic foot (pcf). For restrained walls, an additional uniform load of 100 psf should be added to the 35 pcf. To account for typical traffic surcharge loading, the walls can be designed for an additional imaginary height of two feet (two-foot soil surcharge). For evaluation of wall performance under seismic loading, a uniform pressure equivalent to 8H psf, where H is the height of the below-grade portion of the wall should be applied in addition to the static lateral earth pressure. These values assume a horizontal backfill condition and that no other surcharge loading, sloping embankments, or adjacent buildings will act on the wall. If such conditions exist, then the imposed loading must be included in the wall design. Friction at the base of foundations and passive earth pressure will provide resistance to these lateral loads. Values for these parameters are provided in Section 4.5 of this report. 4.8 Infiltration Feasibility In our opinion, the native soils observed at the site would not be suitable for support infiltration facilities. The site is underlain by relatively impermeable glacial till soils and exhibited shallow perched groundwater seepage. These are all indicators of a poorly-drained soil formation. Therefore, we recommend that development stormwater be routed to a conventional storm system for disposal. March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 12 4.9 Rockeries As noted above, some of the vertical grade transitions may be supported using rockery walls. A rockery is not intended to function as an engineered structure to resist lateral earth pressures as a conventional retaining wall system does. Rockeries should only be used to face soil formations that are inherently stable and can stand in a near-vertical exposure without lateral support. The primary function of the rockery is to cover the stable exposed soil face to reduce the potential for erosion. We recommend limiting cut rockeries to a height of ten feet when placed again competent native soils and limiting fill rockeries to a height of four feet where placed against unreinforced structural fill. Where buildings will be constructed above and adjacent to all rockery construction, the foundations should be lowered to prevent surcharge loading on the rockery. Foundation depths should provide for a theoretical 1:1 influence line extending from the footing edge to pass beneath the rockery base. The structural fill should be overbuilt and then cut back prior to constructing the rockery. This will provide a more competent and stable soil face behind the rockery. Where buildings or roadways will be constructed above the rockeries, the rockeries should be constructed using geotextile reinforcing. We can complete the designs for a reinforced rockery wall, if requested. A rockery design has been completed and is in a separate design package. 4.10 Drainage Surface Final exterior grades should promote free and positive drainage away from the site at all times. Water must not be allowed to pond or collect adjacent to foundations or within the immediate building areas. We recommend providing a positive drainage gradient away from the building perimeters. If this gradient cannot be provided, surface water should be collected adjacent to the structures and disposed to appropriate storm facilities. Subsurface We recommend installing perimeter foundation drains adjacent to shallow foundations. The drains can be laid to grade at an invert elevation equivalent to the bottom of footing grade. The drains can consist of four-inch diameter perforated PVC pipe that is enveloped in washed pea gravel-sized drainage aggregate. The aggregate should extend six inches above and to the sides of the pipe. Roof and foundation drains should be tightlined separately to the storm drains. All drains should be provided with cleanouts at easily accessible locations. 4.11 Utilities Utility pipes should be bedded and backfilled in accordance with American Public Works Association (APWA) or the local jurisdiction specifications. As a minimum, trench backfill should be placed and compacted as structural fill, as described in Section 4.2 of this report. As noted, depending on the soil moisture when excavated most inorganic native soils on the site should be suitable for use as backfill material during dry weather conditions. However, if utility construction takes place during the wet winter months, it will likely be necessary to import suitable wet weather fill for utility trench backfilling. March 19, 2019 6th Revision May 18, 2020 Project No. T-7886 Page No. 13 4.12 Pavement Pavement subgrade should be prepared as described in the Section 4.2 of this report. Regardless of the degree of relative compaction achieved, the subgrade must be firm and relatively unyielding before paving. The subgrade should be proofrolled with heavy rubber-tire construction equipment such as a loaded 10-yard dump truck to verify this condition. The pavement design section is dependent upon the supporting capability of the subgrade soils and the traffic conditions to which it will be subjected. For the parking areas, with traffic consisting mainly of light passenger vehicles with only occasional heavy traffic, and with a stable subgrade prepared as recommended, we recommend the following pavement sections: Two inches of hot mix asphalt (HMA) over four inches of crushed rock base (CRB). Three- and one-half inches full depth HMA. The paving materials used should conform to the Washington State Department of Transportation (WSDOT) specifications for ½-inch class HMA and CRB. Long-term pavement performance will depend on surface drainage. A poorly-drained pavement section will be subject to premature failure as a result of surface water infiltrating into the subgrade soils and reducing their supporting capability. For optimum pavement performance, we recommend surface drainage gradients of at least two percent. Some degree of longitudinal and transverse cracking of the pavement surface should be expected over time. Regular maintenance should be planned to seal cracks when they occur. 5.0 ADDITIONAL SERVICES Terra Associates, Inc. should review the final design drawings and specifications in order to verify that earthwork and foundation recommendations have been properly interpreted and implemented in project design. We should also provide geotechnical service during construction to observe compliance with our design concepts, specifications, and recommendations. This will allow for design changes if subsurface conditions differ from those anticipated prior to the start of construction. 6.0 LIMITATIONS We prepared this report in accordance with generally accepted geotechnical engineering practices. No other warranty, expressed or implied, is made. This report is the copyrighted property of Terra Associates, Inc. and is intended for specific application to the Canopy project in Renton, Washington. This report is for the exclusive use of Blue Fern Development, LLC and its authorized representatives. The analyses and recommendations present in this report are based on data obtained from the subsurface exploration conducted on-site. Variations in soil conditions can occur, the nature and extent of which may not become evident until construction. If variations appear evident, Terra Associates, Inc. should be requested to reevaluate the recommendations in this report prior to proceeding with construction. 2018 Microsoft Corporation © 2018 HERE SITE Environmental Earth Sciences Terra Associates, Inc. Consultants in Geotechnical Engineering Geology and Figure 1 VICINITY MAP 0 2000 4000 APPROXIMATE SCALE IN FEET REFERENCE: https://www.bing.com/maps ACCESSED 4/19/18 Proj.No. T-7886 Date: MAY 2020 RENTON, WASHINGTON CANOPY Proj.No. T-7886 Date: MAY 2020 RENTON, WASHINGTON CANOPY Environmental Earth Sciences Terra Associates, Inc. Consultants in Geotechnical Engineering Geology and TYPICAL SLOPE KEY AND BENCH DETAIL Figure 4 NOT TO SCALE 6' (MIN.) 2 1 EXISTING SLOPE TOE NOTES: 1)STRUCTURAL FILL SHALL BE COMPACTED TO A MINIMUM OF 95% OF ASTM D 698 MAXIMUM DRY DENSITY VALUE. TOE OF NEW FILL EMBANKMENT KEYWAY 6' (MIN.) 2' (MIN.) 1 1 STRUCTURAL FILL SEE NOTE 1) TYPICAL SLOPE BENCH CLEARED AND STRIPPED NATIVE GROUND 1 1 2)DRAINS SHALL CONSIST OF 6" DIA. PERFORATED PVC PIPE ENVELOPED IN 1 cu ft OF 3/4" WASHED GRAVEL. DRAIN PIPE SHALL BE DIRECTED TO KEYWAY DRAIN SEE NOTE 2) THE STORM DRAIN SYSTEM OR APPROVED POINT OF DISCHARGE. SEE NOTE 3) 3)ADDITIONAL BENCHES AND BENCH DRAINS MAY BE REQUIRED BASED ON FIELD EVALUATION BY THE GEOTECHNICAL ENGINEER. 12" COMPACTED STRUCTURAL FILL EXCAVATED SLOPE SEE REPORT TEXT FOR APPROPRIATE INCLINATIONS) SLOPE TO DRAIN 12" MINIMUM 3/4" MINUS WASHED GRAVEL 3" BELOW PIPE 12" OVER PIPE 4" DIAMETER PERFORATED PVC PIPE SEE NOTE 6"(MIN.) NOT TO SCALE NOTE: MIRADRAIN G100N PREFABRICATED DRAINAGE PANELS OR SIMILAR PRODUCT CAN BE SUBSTITUTED FOR THE 12-INCH WIDE GRAVEL DRAIN BEHIND WALL. DRAINAGE PANELS SHOULD EXTEND A MINIMUM OF SIX INCHES INTO 12-INCH THICK DRAINAGE GRAVEL LAYER OVER PERFORATED DRAIN PIPE. Environmental Earth Sciences Terra Associates, Inc. Consultants in Geotechnical Engineering Geology and TYPICAL WALL DRAINAGE DETAIL Figure5Proj.No. T-7886 Date: MAY 2020 RENTON, WASHINGTON CANOPY Project No. T-7886 APPENDIX A FIELD EXPLORATION AND LABORATORY TESTING Canopy Renton, Washington On April 9, 2018, we completed our site exploration by observing soil conditions at 9 test pits. On April 4, 2019, we supplemented this data by observing soil conditions at 5 additional test pits. On April 10, 2019 and April 11, 2019, we supplemented this data by observing soil conditions at 4 test borings drilled to depths of 31.5 to 36.5 feet below current site grades. The test pits were excavated using a track-mounted mini-excavator and trackhoe to maximum depths of about 12 feet below existing site grades. Test Pit and Test Boring locations were determined in the field by measurements from existing site features and with a handheld GPS using coordinates obtained from Google Earth. The approximate locations of the test pits and test borings are shown on the attached Exploration Location Plan, Figure 2. Test Pit and Test Boring Logs are attached as Figures A-2 through A-19. A geotechnical engineer from our office conducted the field exploration. Our representative classified the soil conditions encountered, maintained a log of each test pit, obtained representative soil samples, and recorded water levels observed during excavation. During drilling, soil samples were obtained in general accordance with ASTM Test Designation D-1586. Using this procedure, a 2-inch (outside diameter) split barrel sampler is driven into the ground 18 inches using a 140-pound hammer free falling a height of 30 inches. The number of blows required to drive the sampler 12 inches after an initial 6-inch set is referred to as the Standard Penetration Resistance value or N value. This is an index related to the consistency of cohesive soils and relative density of cohesionless materials. N values obtained for each sampling interval are recorded on the Boring Logs, Figures A-16 through A-19. All soil samples were visually classified in accordance with the Unified Soil Classification System (USCS) described on Figure A-1. Representative soil samples obtained from the test pits were placed in closed containers and taken to our laboratory for further examination and testing. The moisture content of each sample was measured and is reported on the individual Test Pit Logs. Grain size analyses were performed on selected samples. The results of the grain size analyses are shown on Figures A-20 and A-21. Environmental Earth Sciences Terra Associates, Inc. Consultants in Geotechnical Engineering Geology and MAJOR DIVISIONS LETTER SYMBOL TYPICAL DESCRIPTION GRAVELS More than 50% of coarse fraction is larger than No. 4 sieve Clean Gravels (less than 5% fines) GW Well-graded gravels, gravel-sand mixtures, little or no fines. GP Poorly-graded gravels, gravel-sand mixtures, little or no fines. Gravels with fines GM Silty gravels, gravel-sand-silt mixtures, non-plastic fines. GC Clayey gravels, gravel-sand-clay mixtures, plastic fines. SANDS More than 50% of coarse fraction is smaller than No. 4 sieve Clean Sands less than 5% fines) SW Well-graded sands, sands with gravel, little or no fines. SP Poorly-graded sands, sands with gravel, little or no fines. Sands with fines SM Silty sands, sand-silt mixtures, non-plastic fines. SC Clayey sands, sand-clay mixtures, plastic fines. SILTS AND CLAYS Liquid Limit is less than 50% ML Inorganic silts, rock flour, clayey silts with slight plasticity. CL Inorganic clays of low to medium plasticity. (Lean clay) OL Organic silts and organic clays of low plasticity. SILTS AND CLAYS Liquid Limit is greater than 50% MH Inorganic silts, elastic. CH Inorganic clays of high plasticity. (Fat clay) OH Organic clays of high plasticity. HIGHLY ORGANIC SOILS PT Peat. COARSE GRAINED SOILSMore than 50% material largerthan No. 200 sieve sizeFINE GRAINED SOILSMore than 50% material smallerthan No. 200 sieve sizeDEFINITION OF TERMS AND SYMBOLS COHESIONLESSCOHESIVE Standard Penetration Density Resistance in Blows/Foot Very Loose 0- 4 Loose 4-10 Medium Dense 10- 30 Dense 30-50 Very Dense >50 Standard Penetration Consistancy Resistance in Blows/ Foot Very Soft 0-2 Soft 2-4 Medium Stiff 4-8 Stiff 8-16 Very Stiff 16-32 Hard >32 2" OUTSIDE DIAMETER SPILT SPOON SAMPLER 2.4" INSIDE DIAMETER RING SAMPLER OR SHELBY TUBE SAMPLER WATER LEVEL (Date)Tr TORVANE READINGS, tsf Pp PENETROMETER READING, tsf DD DRY DENSITY, pounds percubicfootLLLIQUIDLIMIT, percent PI PLASTIC INDEX N Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A-2 T- 7886 AJD Renton, Washington Grass April 9, 2018 Goodwin Assemblage LOG OF TEST PIT NO. TP-1 78 Feet 8 Feet N/A 1 2 3 Dark brown silty SAND, fine to medium, moist, frequent organics. (SM) (TOPSOIL)Brown grading to tan SAND with silt, fine to medium, moist. (SP-SM)Gray-brown SAND, fine to medium, moist becoming wet below 8 feet, interbedded with scattered gravel layers, occasional boulder to 18 inches in diameter. (SP)Test pit terminated at approximately 10.5 feet.Light groundwater seepage observed at 8 feet. Loose Medium Dense Medium Dense to Dense 7. Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 A-3 T- 7886 AJD Renton, Washington Grass April 9, 2018 Goodwin Assemblage LOG OF TEST PIT NO. TP-2 124 Feet 2 Feet N/A 1 2 FILL: Brown silty SAND with gravel mixed with boulders, fine to coarse sand, fine to coarse gravel,moist. (SM)Brown silty SAND, fine to medium, moist, weakly cemented in places, mottled.SM) (Weathered Till)Gray silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist, moderately cemented. (SM) (Glacial Till)Test pit terminated at approximately 8 feet.Light perched groundwater seepage observed at 2 feet.Loose Medium Dense Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 A-4 T- 7886 AJD Renton, Washington Blackberries April 9, 2018 Goodwin Assemblage LOG OF TEST PIT NO. TP-3 162 Feet 2 Feet N/A 1 2 Dark brown silty SAND, fine to medium, moist, frequent organics. (SM) (TOPSOIL)Brown silty SAND to silty SAND with gravel, fine to medium sand, fine gravel, wet.SM) (Weathered Till)Gray silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist, moderately cemented. (SM) (Glacial Till)Test pit terminated at approximately 9 feet.Light perched groundwater seepage observed at 2 feet. Medium Dense Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A-5 T- 7886 AJD Renton, Washington Blackberries April 9, 2018 Goodwin Assemblage LOG OF TEST PIT NO. TP-4 190 Feet 2 Feet N/ A 1 2 3 4 Dark brown silty SAND, fine to medium, wet, frequent organics. (SM) (TOPSOIL)Brown silty SAND to sandy SILT, fine to medium sand, wet becoming moist below 2.5 feet, mottled. (SM/ML) (Weathered Till)Gray and brown SILT with sand, fine to medium sand, moist. (MH) (Glacial Till)Test pit terminated at approximately 10 feet.Light perched groundwater seepage observed at 2 feet.Loose Medium Dense Stiff Very Stiff 14. 7 26. Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 A-6 T- 7886 AJD Renton, Washington Blackberries April 9, 2018 Goodwin Assemblage LOG OF TEST PIT NO. TP-5 158 Feet 6 Feet N/A 1 2 4 inches of ORGANIC TOPSOIL)Red-brown grading to tan silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist,interbedded with scattered sand seams, weakly cemented in places, mottled.SM) (Weathered Till)Gray silty SAND to sandy SILT, fine to medium sand, moist, moderately cemented.SM/ML) (Glacial Till)Test pit terminated at approximately 8.5 feet.Light perched groundwater seepage observed at 6 feet. Medium Dense Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 A-7 T- 7886 AJD Renton, Washington Grass Forest Duff Goodwin Assemblage LOG OF TEST PIT NO. TP-6 124 Feet N/A N/A 1 10 inches of ORGANIC TOPSOIL)Brown and gray silty SAND, fine to coarse, moist, moderately cemented. (SM) (Glacial Till)Test pit terminated at approximately 8 feet. No groundwater Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 A-8 T- 7886 AJD Renton, Washington Grass April 9, 2018 Goodwin Assemblage LOG OF TEST PIT NO. TP-7 130 Feet N/ A N/A 1 2 3 4 inches of ORGANIC TOPSOIL)FILL: Brown silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist, trace organics. (SM)Tan and gray silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist to wet.SM) (Weathered Till)Gray silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist, moderately cemented. (SM) (Glacial Till)Test pit terminated at approximately 8.5 feet.No groundwater seepage observed. Medium Dense Dense 23. Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A-9 T- 7886 AJD Renton, Washington Brush April 9, 2018 Goodwin Assemblage LOG OF TEST PIT NO. TP-8 192 Feet 6. 5 Feet N/A 1 2 Dark brown silty SAND, fine to medium, wet, frequent organics. (SM) (TOPSOIL)Gray silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist, mottled.SM) (Glacial Till)Gray SAND with silt, fine to medium, scattered gravel, wet. (SP-SM)Test pit terminated at approximately 11 feet.Light to moderate perched groundwater seepage observed at 6.5 feet.Loose Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A-10 T- 7886 AJD Renton, Washington Brush April 9, 2018 Goodwin Assemblage LOG OF TEST PIT NO. TP-9 194 Feet 1. 5 Feet N/A 1 2 10 inches of ORGANIC TOPSOIL)Brown silty SAND, fine to coarse, moist to wet, mottled, weakly cemented in places below 2 feet.SM) (Weathered Till)Gray-brown silty SAND to sandy SILT, fine to medium sand, moist, scattered fine gravel, weakly cemented. (SM/ML) (Glacial Till)Test pit terminated at approximately 10 feet.Light perched groundwater seepage observed at 1. 5 feet. Medium Dense Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A-11 T-7886 MJX Renton, Washington Grass & brush April 4, 2019 Canopy LOG OF TEST PIT NO. TP-101 N/A 4.5 Feet N/A Black silty SAND with gravel, fine sand, fine to coarse gravel, moist, numerous organics, scattered cobbles. (SM) (Organic TOPSOIL)Reddish-brown SAND with silt and gravel, fine to medium sand, fine to coarse gravel, moist,scattered roots, scattered rootlets, trace cobbles. (SM)Gray sandy SILT with gravel, fine to medium sand, fine to coarse gravel, moist, mottled,interbedded sand with silt seams. (ML)Gray silty SAND with gravel, fine to medium sand, fine to coarse gravel, moist, trace cobbles, occasional boulder, weak cementation. (SM)Bluish-gray silty SAND, fine to coarse sand, moist, trace gravel, stratified silt and sand with silt layers. (SM)Test pit terminated at approximately 12 feet.Light perched groundwater seepage observed at approximately 4. 5 feet.No caving observed.Loose to Medium Dense Medium Dense Stiff Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A-12 T- 7886 MJX Renton, Washington Grass April 4, 2019 Canopy LOG OF TEST PIT NO. TP-102 N/A 4 & 9 Feet 3 to 5 Feet 10 inches ORGANIC TOPSOIL)Gray sandy SILT with gravel, fine to coarse sand, fine to coarse gravel, moist to wet, mottled, trace cobbles. (ML)6-inch layer of grayish-brown SAND with silt.Gray silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist to wet, slightly mottled, trace cobbles, occasional rootlet, weak to moderate cementation. (SM)6-inch layer of gray SAND with silt observed.Test pit terminated at approximately 11 feet.Light perched groundwater seepage observed at approximately 4 and 9 feet.Minor caving observed from approximately 3 to 5 feet. Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A-13 T- 7886 MJX Renton, Washington Blackberries April 4, 2019 Canopy LOG OF TEST PIT NO. TP-103 N/ A N/A N/ A 8 inches ORGANIC TOPSOIL)Gray silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist, scattered rootlets,trace roots, trace cobbles, occasional sand inclusion, weak to moderate cementation. (SM)Test pit terminated at approximately 10 feet.No groundwater seepage observed.No Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A-14 T- 7886 MJX Renton, Washington Brush April 4, 2019 Canopy LOG OF TEST PIT NO. TP-104 NA 1 & 6 Feet 1 to 7 Feet Black silty SAND with gravel, fine sand, fine to coarse gravel, moist to wet, numerous organics, scattered cobbles. (SM) (Organic TOPSOIL)Gray sandy SILT with gravel, fine to medium sand, fine to coarse gravel, moist, mottled, trace rootlets, trace cobbles. (ML)1-foot layer of gray SILT observed.Gray SAND with silt to silty SAND, fine to medium sand, moist to wet. (SP-SM/SM)Gray silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist, trace cobbles, weak to moderate cementation. (SM)Test pit terminated at approximately 10 feet.Light perched groundwater seepage observed at approximately 1 feet.Moderate perched groundwater seepage observed at approximately 6 feet.Moderate caving observed from approximately 1 to 7 feet.Loose to Medium Dense Medium Stiff Medium Sample No.Depth (ft)PROJECT NAME: PROJ. NO: LOGGED BY:LOCATION: DATE LOGGED:APPROX. ELEV: DEPTH TO CAVING: FIGURE DEPTH TO GROUNDWATER: SURFACE CONDITIONS: Description Consistency/Relative Density W (%)interpreted as being indicative of other locations at the site.NOTE: This subsurface information pertains only to this test pit location and should not be 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 A-15 T- 7886 MJX Renton, Washington Grass April 4, 2019 Canopy LOG OF TEST PIT NO. TP-105 N/ A N/A N/ A 10 inches ORGANIC TOPSOIL)Brown silty SAND with gravel, fine to medium sand, fine to coarse gravel, moist, scattered roots,trace cobbles. (SM)Gray sandy SILT, fine to medium sand, moist, mottled, trace gravel, trace cobbles. (ML)Gray silty SAND with gravel, fine to coarse sand, fine to coarse gravel, moist, trace cobbles, weak to moderate cementation. (SM)Test pit terminated at approximately 10 feet.No groundwater seepage observed. No caving observed. Medium Figure No. Project:Project No: Logged By:Driller: Location:Approx. Elev: Client: Relative Density Consistency/ Soil Description SPT (N) Blows/foot 10 30 50 Date Drilled: Depth to Groundwater: Sample IntervalDepth (ft)MoistureContent (%)pertains only to this boring location and should not be interpeted as being indicative of NOTE: This borehole log has been prepared for geotechnical purposes. This information other areas of the site 0 5 10 15 20 25303540A-16LOG OF BORING NO. B-1 Canopy T- 78864/10/ 19 BSBoreTecBlue FernDevelopmentRenton, Washington 90 Feet25 Feet 19 50/ 5" 50/ 4"77 45 69 Medium Dense Very Dense Dense Very Dense 8 inches TOPSOIL)Tan silty SAND with gravel, fine to medium sand, fine to coarse gravel, moist. (SM)Gray/tan silty SAND with gravel, fine to medium sand, fine to coarse gravel, mosit to wet. (SM)At 20 feet observed interbedded coarse sand layers.At 25 feet becomes fine sand and fine gravel.Test boring terminated at 31.5 feet.Groundwater observed at 25 feet. 18.2 16.9 21.7 Figure No. Project:Project No: Logged By:Driller: Location:Approx. Elev: Client: Relative Density Consistency/ Soil Description SPT (N) Blows/foot 10 30 50 Date Drilled: Depth to Groundwater: Sample IntervalDepth (ft)MoistureContent (%)pertains only to this boring location and should not be interpeted as being indicative of NOTE: This borehole log has been prepared for geotechnical purposes. This information other areas of the site 0 5 10 15 20 25303540A-17LOG OF BORING NO. B-2 Canopy T- 78864/11/ 19 BSBoreTecBlue FernDevelopmentRenton, Washington 150 FeetN/ A 27 68 63 34 20 34 Medium Dense Very Dense Very Stiff 12 inches TOPSOIL)Tan/brown silty SAND with gravel, fine to medium sand, fine to coarse gravel, moist. (SM)Tan silty SAND with gravel, fine to medium sand, fine to coarse gravel, moist to wet. (SM) Gray SILT, moist. (ML)Test boring terminated at 31.5 feet. No groundwater seepage observed. 14.1 12.5 17.3 16.1 Figure No. Project:Project No: Logged By:Driller: Location:Approx. Elev: Client: Relative Density Consistency/ Soil Description SPT (N) Blows/foot 10 30 50 Date Drilled: Depth to Groundwater: Sample IntervalDepth (ft)MoistureContent (%)pertains only to this boring location and should not be interpeted as being indicative of NOTE: This borehole log has been prepared for geotechnical purposes. This information other areas of the site 0 5 10 15 20 25303540A-18LOG OF BORING NO. B-3 Canopy T- 78864/11/ 19 BSBoreTecBlue FernDevelopmentRenton, Washington 168 FeetN/ A 47 73 78 47 32 25 27 Dense Very Dense Very Stiff to Hard 12 inches TOPSOIL)Gray/tan silty SAND with gravel, fine to medium sand, fine to coarse gravel, moist. (SM) Gray SILT, moist. (ML)Test boring terminated at 36.5 feet. No groundwater seepage observed. 9.9 12. 7 17. 3 18 21.8 Figure No. Project:Project No: Logged By:Driller: Location:Approx. Elev: Client: Relative Density Consistency/ Soil Description SPT (N) Blows/foot 10 30 50 Date Drilled: Depth to Groundwater: Sample IntervalDepth (ft)MoistureContent (%)pertains only to this boring location and should not be interpeted as being indicative of NOTE: This borehole log has been prepared for geotechnical purposes. This information other areas of the site 0 5 10 15 20 25303540A-19LOG OF BORING NO. B-4 Canopy T- 78864/11/ 19 BSBoreTecBlue FernDevelopmentRenton, Washington 174 FeetN/ A 14 50/ 5" 23 5 73 38 Medium Dense Very Dense Very Stiff Medium Stiff Hard 12 inches TOPSOIL)Gray/tan silty SAND with gravel, fine to medium sand, fine to coarse gravel, moist. (SM)Gray sandy SILT, fine sand, moist, interbedded with some coarse sand, some gravel. (ML) Gray SILT, moist. (ML)Test boring terminated at 31.5 feet. No groundwater seepage observed. 15.0 14.4 12.6 18.3 APPENDIX B SLIDE 2018 GRAPHICAL OUTPUT