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PalmerGeo - RRC Retaining Wall Dsgn Rprt 3-31-2020Rose Ridge Condominiums March 31, 2020 Prepared for: Rose Ridge Condominiums Prepared by: I17A r► LMER mw Geotechnical Consultants, Inc. PO Box 1562, Free/and, WA 98249 www,pa/mergeo,com 360-929-5676 T PALMER eotechnical Consultants, Inc. March 31, 2020 Rose Ridge Home Owners Association c/o Mr. Alex Pierce 21313 76th Avenue West Edmonds, WA 98026 206.650.4165 rpjorgensen3@aol.com RE: Preliminary Geotechnical Report Parcel #: 00875400000100 thru 008754000001200 21317 76th Avenue W. • Edmonds, WA 98026 PGC Project 19011 Dear Mr. Pierce: Palmer Geotechnical Consultants, Inc. (PGC) is pleased to present this geotechnical report regarding proposed improvements at the subject property. This report was prepared in accordance with our proposal dated March 11, 2019. We appreciate the opportunity to be of service to you. If you have questions regarding this report please do not hesitate to call. Sincerely, Palmer Geotechnical Consultants, Inc. Scott Palmer, P.E. President Palmer Geotechnical Consultants, Inc. PO Box 1562, Freeland, WA 98249 360-929-5676 wwww palmergeo, com Table of Contents 1.0 Introduction...........................................................................................................................................1 2.0 Project Description...............................................................................................................................1 3.0 Scope of Services...................................................................................................................................1 4.0 Site Description and Subsurface Conditions......................................................................................1 4.1 Surface Conditions..............................................................................................................................1 4.2 Subsurface Conditions........................................................................................................................ 2 4.3 Groundwater Conditions..................................................................................................................... 3 4.4 Potential Geologic Hazards................................................................................................................. 3 5.0 Conclusions............................................................................................................................................6 6.0 Site Development Recommendations.................................................................................................. 6 6.1 Site Preparation...................................................................................................................................6 6.2 Construction Considerations............................................................................................................... 6 6.3 Erosion Control................................................................................................................................... 7 6.4 Slope Impact Mitigation..................................................................................................................... 7 6.5 Structural Fill......................................................................................................................................9 7.0 Design Recommendations...................................................................................................................10 7.1 Design and Construction Recommendations....................................................................................10 7.2 Alternative Foundations....................................................................................................................11 7.3 Wall Drainage...................................................................................................................................12 7.4 Wall Backfill Soil and Compaction..................................................................................................12 7.5 Site Drainage.....................................................................................................................................13 7.6 Wet weather conditions.....................................................................................................................13 8.0 Seismic Design Criteria......................................................................................................................13 9.0 Construction Observation..................................................................................................................14 10.0 General Comments...........................................................................................................................14 List of Figures: Figure 1: Site Vicinity Figure 2: Exploration Locations Figure 3: Wall Section View Appendices: Appendix A: Exploration Logs Appendix B: Laboratory Testing Appendix C: Slope Profile Appendix D: Design Calculations and Global Stability Palmer Geotechnical Consultants, Inc. PO Box 1562, Freeland, WA 98249 360-929-5676 www, palmergeo, com 1.0 Introduction A geotechnical report has been prepared for the design and construction of proposed improvements at the subject property, located at 21317 76th Avenue W., Edmonds, Washington. The property is identified as parcel number Parcel Numbers 00875400000100 thru 008754000001200 by the Snohomish County Assessor. The property is approximately rectangular in shape and grades gently from the west for the majority of the parcel then descends steeply near the eastern property boundary. Two hollow stem auger borings were completed to 6.0 and 13.0 feet below current site grades. Logs of the borings completed on May 29, 2019 are provided in Appendix A. The purpose of our services was to provide geotechnical recommendations for the design and construction of retaining wall improvements at the site. 2.0 Proiect Description Recently the steep slope at the eastern property boundary experienced distress in the form of slope movement resulting in property damage. Mitigation measures are planned to be constructed at the property near the area of the distress. Specifically, a new wall is planned to be constructed to repair the damage to the slope and existing drainage is to be evaluated. Proposed improvements include installing a laterally anchored soldier pile or pipe pile wall near the top of the existing slope. 3.0 Scope of Services The goal of our scope was to characterize existing conditions of the steep slope in the vicinity of the proposed improvements and provide geotechnical engineering recommendations for use in design and construction of the proposed remediation. 4.0 Site Description and Subsurface Conditions 4.1 Surface Conditions The proposed construction involves twelve parcels identified by the Snohomish County Assessor as parcel number Parcel Numbers 00875400000100 thru 008754000001200. The property is currently developed with an approximately 12-unit multi -family residential building. The parcel generally slopes from 76th Avenue West gently to the east before steeply descending for approximately 10.0 feet near the eastern property boundary. The property is bound on the north, south and east by multi -family residential development. A storm drain is located near the top of 1 the slope near the eastern property boundary. 4.2 Subsurface Conditions For this project we advanced and observed two hollow -stem auger borings utilizing a 3-inch diameter Acker Drill. During advancement soils were classified and logged in accordance with the United Soil Classification System (USCS), bagged and discretely labeled to be transported to the laboratory for supplemental testing. Borings were advanced throughout the slope in the vicinity of the retaining wall and retained slope. Boring B-1 was advanced within the confines of the backyard between the slope crest and the storm drain utility. Boring B-2 was advanced just below the slope crest in the area of distress. Borings were advanced through approximately 2 feet of silty sand before encountering a very dense gravelly sand. Boring B-1 was advanced through 0.3 feet of topsoil that consisted of silty sand with organics. This unit had lawn above and roots throughout and was loose, moist, and dark brown in color. Beneath in B-1 and from the existing ground surface in B-2 a red -brown silty sand that was loose to medium dense and moist was observed. Observed to the maximum depth explored was a gravelly sand with silt that was medium dense becoming very dense, moist, and gray yellow -brown to brown in color. Some orange mottling was observed in the borings beneath the first few feet of silty sand, above the gravelly sand. However, a distinct groundwater surface was not encountered. Groundwater levels are expected to vary with seasonal conditions. See the boring logs in Appendix A for additional information. The Geologic Map of the Edmonds East 7.5-minute Quadrangles, Snohomish County, Washington, published by the Washington State Department of Natural Resources (Schasse, et. al., 2009), maps the site surface geology as two distinct units. The upper bluff from approximately 100 feet west of the slope crest is mapped as Pleistocene Vashon Glacial Till (Qvt). The area near the slope and down the slope is mapped as Pleistocene Vashon Advance (Qva). Qvt is generally described as an overconsolidated and unsorted mixture of clay, silt, sand, pebbles, cobbles, and boulders in varying amounts. The poor sorting reflects mixing of the materials overridden and incorporated in the glaciers. It may include some lenses of stratified material, particularly near the base of the unit. Typically referred to as hard lodgment till, often referred to as "hardpan." The "hardpan" is largely a result of compaction caused by the great weight of the overriding ice; hundreds of meters thick. The till was deposited directly by the ice as it advanced over an eroded, irregular surface of older formations and sediments. In clast composition, the till is similar to both the underlying and overlying deposits, because all were derived from similar sources and partly 2 from each other. Internal drainage is greatly retarded by the unweathered till. Water tends to percolate readily down through the upper, loose, sandy, weathered material, but ponds and moves laterally along the buried, unweathered hardpan surface. Qva is generally described as a thick section of mostly clean, gray, pebbly sand with increasing amounts of gravel higher in the section. Distinctive features of the outwash are its well -developed cross and horizontal stratification, and cut and fill structures. Locally some of these sediments are stained by iron oxide precipitated from ground water. Fine grained sand and some silt are common in the lower part of the unit and also locally occur sparingly in the upper part. The advance outwash was deposited by meltwater flowing from the advancing front of the glacier, partly, at least, by braided streams. Some also was deposited in deltas built in ponded water. The United Stated Department of Agriculture (USDA) maps the site surface soils as Alderwood- Urban land complex in two slope categories with a northeast to southwest trending contact. The Alderwood-Urban land complex, 2 to 8 percent slopes is on the west. The east side of the parcel, including the steep slopes is mapped as Alderwood-Urban land complex, 8 to 15 percent slopes. These units generally consist of gravelly ashy sandy loam in the upper 7 inches with very gravelly ashy sandy loam in the next 28 inches and gravelly sandy loam from 35 to 60 inches. These units exhibit 20 to 40 inches of dense material, are moderately well drained with a depth to water table of 18 to 36 inches and are classified in Hydrologic Soil Group B. Soil conditions encountered in the field consisted of mixtures of sand and silt with varying amounts of gravel, silt, and sand. These conditions are typical of modified and native deposits in the region and are consistent with area geology sources. 4.3 Groundwater Conditions During our exploration, groundwater was not observed in any of our borings. Our scope did not include any conclusive measurement of water level conditions. A direct monitoring program, conducted during the wet months from October to May, should be undertaken if accurate water level conditions are desired. It should be understood that water conditions within the soil column may fluctuate in conjunction with stratigraphic permeability variations during various seasonal conditions. Department of Ecology well logs within the vicinity indicate observed groundwater levels 20 feet below the ground surface on properties at elevations with similar elevation. 4.4 Potential Geologic Hazards As defined by City of Edmonds (COE) 23.80.020 the slope is not an erosion hazard area. Although Alderwood soils are mapped by UDSA at the site, they are mapped as 2 to 8 percent on the west and 8 to 15 percent on the east. The slope is classified as a steep slope and could be a landslide hazard area due the fact that it is a steep slope (greater than 40 percent or 21.8 degrees) for more than 10 feet of elevation change over a 25-foot horizontal run. In addition, it is mapped as a seismic hazard area due to its location within a landslide hazard area. Below we discuss the potential of geologic hazards as defined by COE Chapter 23.80.020. 4.4.1 Erosional Hazard The subject property encompasses the crest of a steep slope along the east property boundary. In accordance with COE 23.80.020.A.1 & 3 the portion of the slope within the subject property is classified as a moderate to severe erosion hazard. While the mapped USDA soils are not classified as 15 to 20 percent, the slope crest, which lies within the boundaries of the subject parcel are calculated at 57.7 percent. The lower slope is located within the confines of the adjacent parcel. During our site visit we observed that the bluff and slope are generally vegetated, though areas of erosion and rilling were observed across the slope face from a recent soil movement event. Additionally, some trees and vegetation were observed to be pistol butted at the slope crest, generally indicating slow movement or creep within the slope face. Grading and clearing activities should be accompanied by appropriate erosion control measures. 4.4.2 Landslide Hazard PGC conducted a visual reconnaissance of the slope along the east boundary of the study area to observe existing surface processes as related to the proposed site improvements. During our visit, as safe access allowed, conditions were assessed and catalogued using hand measurements, visual estimations, visual mapping of salient surface features, photo documentation, and field evaluation of slope conditions. Indications of past and ongoing surface raveling were noted, including geomorphic features and vegetation patterns. City of Edmonds maps the project area as a steep slope. The site elevation at the west boundary of 761h Avenue W is approximately 415 feet above mean sea level (AMSL). While the east property boundary is at 400 feet AMSL. The toe of the slope lies at 370 feet AMSL. The crest of the slope is moderately vegetated with some mature evergreen and deciduous trees. A fence is constructed near the eastern property boundary near the slope crest. Vegetation consisting of some deciduous trees and blackberries were observed on the slope face. Areas of the slope face exhibited exposed soils due to movement within the slope face. Trees were observed 4 to be at angles ranging from near vertical to off -vertical. Pistol butting was observed on some trees across the face and at the slope crest, where undercutting of the vegetation was also observed. Pistol butting, reclined tree angles and undercutting at the slope crest indicate ongoing erosion or creep during growth. The parcel slopes from 76th Avenue W to the east third of the parcel at angles between 0 and 2 degrees. The east third of the parcel slopes at 7 to 9 degrees to the slope crest. The portion of the steep slope slopes is at an inclination of 30 degrees, while the rest of the slope face slopes is at angles between 41 and 47 degrees. The toe of the slope runs out at 31 degrees becoming 17 degrees to the parking area. Subsurface soils within the property were observed to consist of silty sand with varying amounts gravel and clay overlying gravelly sand with varying amounts of silt. Due to hazardous conditions within the slope face, the slope profile in Appendix D was approximated from the Snohomish County Assessor's website, therefore actual slope conditions may vary. 4.4.3 Seismic Hazard The subject property does not contain mapped faults. A lidar photo review does not suggest linear or faultic features and no such features were observed during our site visit. Although, the site is located within the Southern Whidbey Fault Zone with an inferred, Class B fault trending northwest to southeast at the southwest corner of the property, though we do not believe the proposed improvements or existing drainage features will exacerbate the conditions associated with the nearby fault. Based on our findings, we believe the risk of fault rupture at the ground surface within the confines of the subject property to be low. The site is underlain by a thin layer of soil composed of silty sand overlying gravelly sand with varying amounts of silt. This soil gradation is not prone to liquefaction and the risk of damage due to liquefaction is mapped by the Liquefaction Susceptibility Map of Snohomish County, Washington (Palmer, 2004) as very low on the west three-quarters and very low to low on the east quarter. The site is not mapped in a Tsunami Inundation or Tsunami Evacuation Zone. We believe the risk of Tsunami at the site to be quite low or negligible. 4.4.4 Other Geologic Hazards The site is not near any known volcanoes and is located outside the volcanic arc of the Cascade Range. The site is mapped outside known Lahar Deposits. During our site visit we did not observe any indications of rock fall or mud flows. We did not observe any signs of differential settlement at the subject property. 5 There is not any known present or historic mining in the area. Additionally, we did not observe evidence of any adits, shafts or other mine workings during our site visit. 5.0 Conclusions Based on our review of available data, soil conditions encountered during exploration, laboratory testing, and our analysis, we believe the site is suitable for the proposed improvements. Installation of the retaining wall and associated drainage will not decrease slope stability or pose an unreasonable threat to persons or property on or off site. The lower slope should be planted with root anchoring vegetation as described in Table 1 or through the consultation of a landscape architect. Additionally, existing drainage should be inspected to ensure no breaks or leaks are present. The proposed retaining wall construction should be appropriately designed utilizing the recommendations set forth below. 6.0 Site Development Recommendations 6.1 Site Preparation Initial grading shall include the removal of all vegetation within proposed construction areas. The actual depth of stripping should be reviewed by the Project Geotechnical Engineer of Record at the time of construction, with expected minimum stripping depths of approximately 1.0 to 2.0 feet. Stripping depths within native soils could vary from the recommended stripping depths to approximately 2.0 to 3.5 feet if a significant amount of time lapses from the writing of this report. All vegetation, trees and roots larger than 1/-inch diameter or any accumulation of organic matter that will result in an organic content of more than 3 percent should be removed and not used as engineered fill. Roots larger than 1/a-inch diameter should not be disced into the soils. These materials should be raked and hand-picked, as necessary, to ensure proper removal of organic materials. Any areas proposed for structural fill should be relatively level with appropriately prepared subgrade soils. Stripping depths should be anticipated to be between 2.0 and 2.5 feet Below Present Grade (BPG). 6.2 Construction Considerations The near -surface fine-grained soil at the project site is easily disturbed during wet weather and may become difficult to work with. Haul roads and staging area improvements will be necessary for support of construction traffic during the rainy season or when the moisture content of the 6 subgrade soil begins to elevate, generally within a few percentage points above optimum. If not carefully executed, site preparation and excavation activities can create extensive soft areas. Earthwork should be planned and executed to minimize subgrade disturbance if site improvements are performed during wet weather months. The thickness of the haul roads and staging areas should be selected by the contractor. Haul roads subjected to repeated construction traffic may require a minimum of 18 inches of imported granular material. For light staging areas, 12 inches of imported granular material may be required. We recommend that imported granular material for haul roads and staging areas consist of durable crushed rock that is well graded with less than 8 percent by dry weight passing the U.S. Standard No. 200 sieve. 6.3 Erosion Control The on -site soil is susceptible to erosion. Thus, we recommend that all efforts are made to limit construction during periods of wet weather. However, if construction occurs during wet weather, erosion control measures should be implemented prior to construction and all steep slopes should be covered with straw matting or loose straw and that all slope surfaces be planted as soon as practical to minimize erosion. Surface water runoff should be collected and directed away from slopes to prevent water from running down the slope face. Erosion control measures such as truck tire washers and temporary detention and settling basins should be used in accordance with local and state ordinances. 6.4 Slope Impact Mitigation Additionally, the following general recommendations should be implemented to reduce long-term erosion potential at the project site and maintain existing conditions for site slope stability: 1. Minimize the volume and velocity of water that travels toward and down the slope face. 2. To avoid accelerating slope erosion and mass wasting due to human activity refrain from the following; a) Adding side -cast debris to the slopes b) Using heavy construction equipment on or near steep slopes. If necessary, appropriate benching of the slope in small increments should be implemented. c) Excavating near adjacent steep slope crests, toes or on the slope face d) Placing loads of excavated soil near the slope crest 3. Prior to construction, silt fences and/or a continuous line of straw bales should be placed downslope of the construction area. Inhibit the placement of heavy construction equipment, construction materials, or native and imported soils from being placed within close proximity to any erosion control devices. Suitable temporary erosion and sediment 7 control measures should be implemented at the construction site prior to, during and immediately after ground disturbance occurs. Areas upslope and with minimal vegetation should be protected from erosion via a blanket of straw or rolled erosion control product (RECP) if site work is not continuous in the vicinity and prior to reseeding or re -vegetation. 4. At the completion of the project, all disturbed or removed vegetation should be repaired and maintained until established. Surface water should not be allowed to concentrate or traverse the slope during or after the construction phase of the project. Outlets for all drainage pipes should terminate in an energy dissipating device such as a T or through the use of rip -rap. Similarly, concentrated drainages should be captured in closed pipe systems and routed down slope to appropriate outfalls. 5. Avoid clearing of existing vegetation outside the construction area, especially on or near to the existing slopes, unless approved by a qualified professional. Any cleared or loose topsoil should be covered to minimize downslope movement. 6. Grading or excavation of soils during construction should be accompanied by grass reseeding and re -vegetation as the project is completed. 7. Care should be given to species selection regarding mature height of planted/reseeded vegetation to avoid adverse wind/storm damage to the slope. Species with a mature height of 15 feet or more should be avoided on the slope face or within 10 feet of the crest. According to "Slope Stabilization and Erosion Control Using Vegetation" (Myers, 1993) Table 1 below highlights vegetation that provide increased slope impact mitigation. Table 1. Slope Stabilizing Vegetation Common Name Botanical Name Deciduous/Evergreen Mature Height (ft) Vine Maple Acer cricinatum Deciduous 10+ Oceanspray Holodiscus discolor Deciduous 10+ Willow Salix spp. Deciduous 10+ Snowberry Symphoricarpos albus Deciduous 3+ Rose Rose spp. Deciduous 2-10 Salmonberry Rubus spectabilis Deciduous To 12 Salal Gaultheria shallon Evergreen To 4 Oregon grape Mahonia spp. Evergreen To 6 Red huckleberry Vaccinium parvifolium Deciduous To 12 Evergreen Vaccinium ovatum Evergreen To 8 Serviceberry Amelanchier alnifolia Deciduous 12+ 8 If extensive site landscaping or replanting is considered in the future, an approved and qualified licensed professional should be consulted prior to implementation. 6.5 Structural Fill Structural fill includes fill proposed for use beneath foundations, slabs, pavements, any other areas intended to support structures, or within the influence zones of structures. Structural fill shall be free of organic matter and other deleterious material and, in general, should consist of a maximum particle size no larger than 3 inches in diameter. Recommendations for suitable fill material are provided in the following sections. 6.5.1 On -Site Native Soil The on -site native soil consisting of gravelly sand with varying amounts of silt may be suitable for use as structural fill. Based on our experience and laboratory testing, the on -site soil will be sensitive to small changes in moisture content and may be difficult, if not impossible, to compact adequately during wet weather or when its moisture content is more than a few percentage points off optimum. Therefore, this soil may require extensive drying if it is used as structural fill. We recommend using imported granular material for structural fill if the moisture content of the on - site soil cannot be reduced. 6.5.2 Imported Granular Material PGC assumes the contractor will utilize material for the improvements as recommended by the manufacturer. However, if additional fill is necessary for any proposed structures, PGC recommends imported material be used as structural fill. Imported structural fill material should conform to Section 9-03.14(2), Select Borrow, Section 9-03.9(3) Crushed Surfacing Base Course or Crushed Surfacing Top Course as outlined in the most recent edition of the State of Washington Department of Transportation Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT Standard Specifications), or approved equal verified by the geotechnical engineer of record. Trenches and other areas proposed for the waterline should be backfilled utilizing material that conforms to Section 9-03.12(3) Gravel Backfill for Pipe Zone Bedding as outlined in the most recent edition of WSDOT Standard Specifications. All granular material must be durable such that there is no degradation of the material during and after installation as structural fill. The percentage of fines can be increased to 12 percent if the fill is placed during dry weather and provided the fill material is moisture conditioned, as necessary, for proper compaction. The material should be placed in lifts with a maximum uncompacted E thickness of 8 inches and compacted to not less than 95 percent of the maximum dry density, as determined by ASTM D 1557. During the wet season or when wet subgrade conditions exist, the initial lift should have a maximum thickness of 15 inches and should be compacted by rolling with a smooth -drum, non -vibratory roller. 7.0 Desi2n Recommendations The site is generally underlain by silty sand overlying gravelly sand with varying amounts of fines. Locations with a higher fines content will be difficult to work with in extreme dry or wet conditions. We understand that a soldier pile wall with horizontal anchors will be installed to reinforce the existing slope along the west side of the property. We recommend that the following parameters shown on Table 2 below are utilized for design and construction of the structures. Table 2. Soil Bearing Pressures Bearing Capacity 2,000 psf Active — Free to Rotate 34 Active — At Rest 53 Passive 210 Sliding .38 7.1 Design and Construction Recommendations Though no designs or plans were available at the time of this report, we understand that the anticipated design will consist of piles and lagging with horizontal anchors. Pile diameter should consist of either 2- or 3-inch piles. We recommend that if 2-inch piles are utilized that they consist of schedule 80 steel with a total capacity of 6 kips. For 3-inch piles we recommend that they consist of schedule 80 steel with a total capacity of 12 kips. Piles should be driven to suitable refusal, with refusal criteria determined by the pile contractor and approved by the geotechnical engineer based upon the driving hammer size and weight. Care should be taken to ensure piles are sufficiently embedded into dense soils, with an anticipated depth between 10 and 15 feet below finished grade. PGC recommends that during pile driving a representative is onsite to verify adequate pile depth and refusal are met. to For lateral anchors, we recommend a minimum diameter of 3 inches consisting of schedule 80 steel. Embedment should be anticipated between 5.0 and 10.0 feet and driven to suitable refusal criteria as determined by the pile contractor and approved by PGC. The outermost 3.0 feet should be ignored. 7.2 Alternative Foundations For the proposed improvements to be supported on pin (or "pipe") piles, we recommend a minimum diameter of 2 inches, with an outside diameter of 2.375 inches consisting of schedule 80 steel. Embedment should be anticipated between 5.0 and 10.0 feet below existing ground. Piles shall be driven to suitable refusal criteria as determined by the pile contractor and approved by PGC. PGC recommends that during the driving of the piles a representative of our firm is onsite to verify adequate shaft depth and suitable refusal conditions are met. If the proposed improvements are to be supported by lateral anchors, we recommend a minimum pin pile diameter of 3 inches consisting of schedule 80 steel. Embedment should be anticipated between 5.0 and 10.0 feet and driven to suitable refusal criteria as determined by the pile contractor and approved by PGC. The outermost 3.0 feet should be ignored. 7.2.1 Axial Capacity for Pin Piles The piles should be galvanized steel pipe, driven with a suitable hammer to the refusal criteria shown on Table 4 below. Table 4. Pin Pile Underpinning Refusal Criteria 11 Minimum I Allowable Axial Pipe Diameter Hammer Size Refusal Compressive Load (inches) Wall Thickness (pounds) Criteria' (kips)' 2 Schedule 80 90 60 6.0 3 Schedule 80 400 25 12.0 1. Refusal is defined as less than 1-inch of penetration in "X" seconds under constant driving. 2. Allowable load to be verified by load tests in accordance with ASTM D1143 "quick load test." 7.2.2 Lateral Capacity for Pin Piles Based on the conditions encountered during our exploration we expect the pin piles to be driven into dense sand and gravel, and to meet refusal in glacial till. For the purposes of design, we recommend that the top 3 feet of each pile is ignored for lateral capacity. However, below this depth we recommend that 60 pounds and 100 pounds per foot of pile for 2-inch and 3-inch 11 respectively in the dense sand unit is used for lateral capacity. Additionally, a reaction force of 2,000 pounds and 4,000 pounds for 2-inch and 3-inch piles may be used for design for piles driven to refusal. This reaction force may be increased by one third for short-term wind and seismic effects. 7.3 Wall Drainage To facilitate drainage behind the wall we recommend a 4-inch diameter Schedule-40 PVC pipe is encapsulated in a minimum of 12-inch thick drain aggregate set behind the wall. The wall drain should be installed with sufficient fall to drain into the existing stormwater system at the lowest point possible. Drain aggregate should also extend up the extent of the wall height maintaining a minimum of 12-inch thickness. Drain aggregate should conform to WSDOT Standard Specification 9-03.12(4) Gravel Backfill for Drains or 9-03.12(5) Gravel Backfill for Drywells, be 3/a-inch washed crushed rock with less than 5 percent by weight passing the No. 200 U.S. Sieve or an approved equal. Drain aggregate should be compacted to an unshifting and unyielding condition. We recommend placement of a filter fabric between drain aggregate and backfill soil, taking care during placement to limit contamination of drain aggregate. Filter fabric suitable for use should conform to WSDOT Standard Specification 9-33.2(1) Table 3 for Geotextile for Separation or approved equal. An alternative to the PVC drain is to utilize Mirro Drain 6000 drainage composite or approved equal. Drain aggregate and filter fabric behind the wall should conform to the specifications above. 7.4 Wall Backfill Soil and Compaction Imported granular fill as defined in Section 6.5.1 or 2 should be used for wall backfill provided it is free of organics, deleterious material or pieces larger than 6-inches in linear dimension. To prevent excessive lateral pressures over -compaction should be avoided. However, improperly compacted backfill may exhibit excessive settlement with time. We recommend smaller hand - operated or walk -behind equipment be used to perform compaction within 5 feet of the wall. Since this equipment is lighter, we recommend that backfill is placed in 6- to 8-inch thick loose lifts, prior of passing of hand -operated or walk -behind equipment. Compaction effort should begin near the wall and propagate away from the wall with each pass of the equipment. 12 7.5 Site Drainage Footing drains and downspouts should be inspected to ensure they are properly functioning, and no cracks or breaks are present. Retaining wall drainage should be installed such that there is sufficient fall from the placement of the drain into the existing stormwater system located near the proposed retaining wall in the existing pavement. PGC recommends ensuring that the connections are watertight and sealed and annual inspection and maintenance of the length of pipe occurs. Additionally, care should be taken to ensure that the drainage and stormwater facilities are not damaged during construction and are sufficient to carry the proposed runoff. 7.6 Wet weather conditions If unstable conditions are encountered due to wet weather, windrowing or mixing with dry materials may be required. In some cases, a sacrificial lift of unsuitable material may need to be used to cap the fill, and removed later to continue fill process during more suitable weather conditions. 8.0 Seismic Design Criteria The Liquefaction Susceptibility Map of Snohomish County (Palmer et al., 2004) indicates that there is a very low potential (Site Class C) for liquefaction on the west three-quarters of the property. The remaining east quarter, including the steep slope is mapped as very low to low (Site Class C to D). All structures should be designed according to criteria outlined by the latest edition, at the time of construction, of the International Code Council° for Site Class C. Seismic design is prescribed by the 2015 IBC. Table 3 below presents the site design parameters prescribed by the USGS Earthquake Hazards Program, Seismic Design Tool, using the 2015 IBC parameters for the site. Table 3. Seismic Design Parameters Parameter Short Period 1 Second Period (Ts = 0.2 second) (Ti = 1.0 second) Spectral Acceleration, S (MCE) SS = 1.272 g S I = 0.497g Site Class C Spectral Acceleration Parameters, SM (MCE) SMs = 1.272 g SMi = 0.647 g Design Spectral Acceleration Parameters, SD SDs = 0.848 g SM = 0.432 g Site Coefficient, F Fa = 1.000 F,, = 1.303 13 9.0 Construction Observation We recommend that PGC is retained to review final design plans and to ensure conformance with our recommendations. Satisfactory earthwork and foundation performance depends to a large degree on the quality of construction. Subsurface conditions observed during construction should be compared with those encountered during the subsurface explorations. Recognition of changed conditions often requires experience; therefore, qualified personnel should visit the site with sufficient frequency to detect whether subsurface conditions conform or have changed significantly from those anticipated. 10.0 General Comments The analysis and recommendations presented in this report are based upon the data obtained from our exploration locations, available public records, and from other information and sources discussed in this report. This report does not reflect variations that may occur between known data points, across the site, or due to the modifying effects of construction or weather. The nature and extent of such variations may not become evident until construction begins or is completed. Should variations appear that differ from the data and recommendations contained within this report, PGC should be immediately notified so that further evaluation and supplemental recommendations can be provided. PGC is not responsible for ensuring that other members of the project team implement our recommendations. The scope of our services does not include services related to construction safety precautions or dewatering operations. Our recommendations are not intended to direct the contractor's methods, techniques, sequences or procedures, except as specifically described in our report for consideration in design. Within the limitations of scope, schedule, and budget, our services have been executed in accordance with the generally accepted practices. This report has been prepared for the exclusive use of our client and their representatives for specific application to the project discussed and has been prepared in accordance with generally accepted geotechnical engineering practices in this area at the time this report was prepared. This report may not be relied upon by third parties or for other sites. No warranties, either expressed or implied, are intended or made. Site safety and dewatering requirements are the responsibility of others. In the event that changes in the nature, design, or location of the project as outlined in this report are planned, the conclusions and recommendations contained in this report shall not be considered valid unless PGC reviews the changes and either verifies or modifies the conclusions of this report in writing. 14 If you have questions concerning this report, please feel free to contact me at 360-929-5676. Sincerely, Palmer Geotechnical Consultants, Inc. Scott A. Palmer, P.E. -2020 15 Figure 1: Site Vicinity sa, Lyrlden Maple Falls ® ® Glacl of ys remdale sss d MI Shuksan v peening 9 Mr Baker Q North Bellingham Mt. cascades L.— (sand Baker-Sno4ualmle National Park Ross Lake hound National Forest National Newnalem Recreation Island a Area COricrese MalI11 C-R10[in� Adacottes I alend 5edm-Weogey Barlinglon Rockport Fidalgo IsfarM 0 saa G'rill MI eman Y a tonne Lake Chelan C Lake National Raareal'on 0 Cmanaugh Manslold Area Oak ❑so Q 5lanwaod paninglon Coopevd'e Camalro Island Al Wceme Glacier Peak 9 Pon Townsend Grande Frills Ver1o1 Sllvenon 9edal Pars Marysville ® n Nadiock-Imndale Whidbey O Island Ewell Pon wdlaw '�` © 5nahamiah Mwroe Gold sar Okanogan -Wenatchee dcen` Lynnwoo ® Inaex National Forest O gaols orhell Baring Wellington Coles comer ,qrd It,=J Skykamieh Scenm on Redm Sea6 Bainhrdge ( Seatt _ Leavenwodh Bremerton QQ �� Issaquah Siroqual Cashmere ® Rent n North ben eel€a.r SeaTac vaahanIsland ��'+ Go ale I wJI& ' Sid L ynnxll k Edmonds Ci)mrnu r}I[y Cl V.il 1 .l.'llh SE 9W 9w K.-.:y `+I '. it 2 �aCR1191 � I= LA p*** Figure: G PA LMERRose Ridge Condominiums chnical Consultants, In, Edmonds, WA 1 Figure 2: Exploration Locations it igure: PALMERRose Ridge Condominiums Not to Scale 2 Edmonds, WA Not to be Used for Construction Geotechnical Consultants, IncI I I Figure 3: Wall Section DRAIN ROCK AGGREG TAREG TA E RETAINED SOIL FILTER FABRIC APPROX. EXIST'G 0o STORM DRAIN LOC. 3° ° o 9 FEET BEHIND PROPOSED WALL (Varies) 0 0 0 0 00°� APPROX EXIST'G STORM DRAIN LOC. 3 TO 5 FT ABOVE ANCHOR (4 ft typ) MR-4 MANTA RAY ANCHOR 12-FOOT LONG 3/4-IN ALL THREAD 15 DEG MIN. TO 25 DEG MAX. 4x12 PRESSURE ,ATED TIMBER 2-INCH SCHEDULE 80 PIPE PILE C 1 Ox20 CHANNEL WALER TO RESTRAIN PIN PILES 0000 ° 0 ° ° 4" PVC DRAIN PIPE ° CONNECTED TO EXISTING STORMWATER SYSTEM 4 /fq 11 DEPTH TBD DRIVEN TO 5 TO 10 FEET BELOW WALL p*** Figure: G **PA LMER Rose Ridge Condominiums wall Section View Not to Scale Date: 03.06.2020 Not to be C Geotechnical Consultants, Inc. Edmonds, WA By: S. Palmer Used for Construction 3 Appendix A: Exploration Logs B-1, SAMPLE DATA SOIL PROFILE Exploration Method: Hollow Stem Auger o Ground Surface Elev: Approx 400' AMSL _ > c N -0 ', _ O E c � N CU C — 0 (D cn U) ino 3 (U C) L CO to ii Z3 M ( Q � d U U U co ( Z) SOIL DESCRIPTION z (6 0 o- � a N s 0 (0.0 - 0.3) TOPSOIL SM silty SAND with organics, lawn above and roots throughout, loose, moist. DARK BROWN 1' (0.3 - 2.0) silty SAND, loose, moist. RED -BROWN sm 2' (2.0 - 6.0) gravelly SAND with trace silt, very dense, damp. BROWN 6 3' SPT 9.1 41 SP 5' SPT 50/1" 3.3 48.5 49.3 2.2 50/5" 6' Refusal at 6.0 feet BPG. No Groundwater Encountered. 7' 8' 9' 10' 11' 12' 13' 0 ** Log. of: AV G PALMER Roseridge Condominiums C Geotechnical Consultants, Inc. Edmonds, WA B-1 B -2 SAMPLE DATA SOIL PROFILE Exploration Method: Hollow Stem Auger o Ground Surface Elev: Approx 400' AMSL _ > c N -0 ', _ O E c � N CU C — 0 (D cn U) ino 3 (U C) L ii Z3 M ( Q � d (6 U U U co ( Z) SOIL DESCRIPTION z 0 o- � a N s 0' (0.0 - 1.8) silty SAND, medium dense, damp to moist. RED -BROWN 1 SM 2' (1.8 - 13.0) gravelly SAND with some silt, medium dense becoming very dense with depth. GRAY YELLOW -BROWN SPT 14 5.8 31.2 59.5 9.3 3' 4' 51 33 SPT 7.1 23.3 66.0 10.7 6' 7' SP SM 8' 9' 10' 58 SPT 8.4 25.6 63.1 11.2 11' 12' ' 50/6" 13' sPT 8.1 Refusal at 13.0 feet BPG. No Groundwater Encountered. ** Log of: AV G PALMER Roseridge Condominiums C Geotechnical Consultants, Inc. Edmonds, WA B-2 Appendix B: Laboratory Testing Unified Soils Classification System G jPALMER SP C Geotechnical Consultants, Inc. DateTested: 6/5/2019 D(lo)= 0.176 mm % Gravel = 48.5% Coeff. of Curvature, CC = 0.38 Sample #: 13-1 Dl301= 0.726 mm % Sand = 49.3% Coef£ of Uniformity, CU = 44.98 Depth: 5.0-5.1 D(go)= 7.935 mm % Silt & Clay = 2.2% Fineness Modulus= 4.70 Project Roseridge Liquid Limit= 0.0% Plastic Limit-- 0.0% Plasticity Index-- 0.0% Actual Interpolated Cumulative Percent Cumulative Percent Grain Size Distribution Sieve Size Specs FSpecs US Metric Passing Passing Max Min 100.0% T_..._..._...7T-T .F T_.i._.T_...T..._...T..._..._..._.1.T.T-T T...r...T..._.i._..._.i._..._..._...rT.T..r.i._i.._.i._...r..._...r..._..._... 1 6.00" 150.00 100.0% 100.0% 0.0% 4.00" 100.00 100.0% 100.0% 0.0% 3.00" 75.00 100.0% 100.0% 0.0% 90.0% ♦! r i..a...t...a..._.1_... 1_..._..._...4.14...� 1_. i.___ .1_...t..._...t........._.i.1.14..t...I...t..._.i._..._.i._..._..._...Il.t..-.i._i.._.i._...I..._...I..._..._... 0.9 2.50" 63.00 100.0% 100.0% 100.0% 0.0% i i i i i i i i i i i i i i i i i i ll ! ! ill!! ! ! ! Hill!! ! ! ! !IIIII ! ! 2.00" 50.00 100.0% 100.0% 100.0% 0.0% ill ! ! ! ! ! ! ! ! ! ! ! ! ! ill ! ! ! ! ! ii 1.75" 45.00 100.0% 100.0% 0.0% 80.0% ill i i i Hill!! ! ! ! !IIIII ! ! t1...r+-i +-...t.._...t.._..._..._.;.tt-t t..t..t.._.i._..._.!._..._..._...ttt.r.._.._t._...t.._...t.._..._... 0.8 III I I I I I I I I I I I I Hill 11 1 1 1.50" 37.50 100.0% 100.0% 0.0% 1.25" 31.50 100.0% 100.0% 0.0% 70.0% ! ! ! ! ! ! ! ! 0.7 1.00" 25.00 100.0% 100.0% 100.0% 0.0% i i i i ? l l l l i i i i i i i i i i i i i Hill i i i 1 ! ! ! Hill!! ! ! ! 7/8" 22.40 91.3% 100.0% 0.0% ! ! ! Hill ! ! ! ! ! 3/4" 19.00 79.9% 79.9% 100.0% 0.0% 60.0% !..a...1...a..._.i_..._.i_..._..._...i.i.L.i_.i._.i_...i..._...4..._..._..._.414..4...4...4..._.i._..._.i._..._..._...ii.i...i._i.._.i._...4..._...4..._..._... 0.6 5/8" 16.00 74.9% 100.0% 0.0% �1 IIIII i i i !il ii i i i iiiiii i t I iiiiii l l I III *I IIII IIII 1/2" 12.50 69.1% 100.0% 0.0% 'y ,III III I I I I I ',I I I I �I I I IIII I I I I I IIII I I I I I 3/8" 9.50 64.2% 64.2% 100.0% 0.0% s3 50.0% �i..i...7......_.t_..._.t_..._..._...-.t�..t.1_.._...T..._...T..._..._..._.i.t.t�..t...t..t..._.i._..._.i._..._..._...tt.t...i._i.._.i._...r..._...r..._..._... 0.5 i IL 11 1 i i i 11 i i 1 i i 1/4" 6.30 55.6% 100.0% 0.0% o III .III HillIIII #4 4.75 51.5% 51.5% 100.0% 0.0% 40.0% L.1.....1.._. _..._. _..._..._...1.1i_ . _._. _......_...1....._..._.. .. i...i ......_j._..._i._..._..._...Hi Hill 1._1._._......_......_..._... 0 .4 #8 2.360 44.4% 100.0% 0.0% ill i i i i i Hill i i ! #10 2.000 43.3% 43.3% 100.0% 0.0% ° ♦iiiiii #16 1.180 34.7% 100.0% 0.0% 30.0%,.....+......_.,_..._.,_..._..._...:.,...F.,_.,._.,_...t..._...t..._..._..._.,.+.a...t..t..._.;._..._.;._..._..._...+;.t...;._;.._.;._...+..._...+..._..._... 0.3 Ai►� l #20 0.850 31.3% 100.0% 0.0% III I I I I I III I I I I I IIII I I I I I IIII I I I I I #30 0.600 28.7% 100.0% 0.0% 20.0% ! ! �t! ! l l ! ! ! ri........�..._.1_..._. 1_..._..._....r1...r.1_:i._.1_... t..._... t..._..._..._.i.fi.l�..t...fi...t... ..._.i._..._..._...tl.t..r.i._1.._.i._...fi..._...fi..._... _... 0.2 #40 0.425 26.9% 26.9% 100.0% 0.0% � I I I I ] i i i 1111 I l i i 11111 1 i I♦ I 11111 1 i i i #50 0.300 18.4% 100.0% 0.0% i i 11 1 1 1 Hill 1 1 ! ! #60 0.250 15.0% 100.0% 0.0% 10.0% .LI..1..1...1.._.1_..._.1_..._..._....11..L.1_.I._.1_...1..._...1..._..._..._.I.1.11..1... L... 1... _.I._..._.,.._..._...11.1..L.I._I.._.I._...L..._...L..._..._... 0.1 #80 0.180 10.2% 100.0% 0.0% #100 0.150 0 8.2/° 0 8.2/0 0 100.0% o 0.0% 0.0% iiiiii iiiiii I�'�II l 0 10 1 0.1 0.01 #140 0.106 4.7% 100.0% 0.0% 100 #170 0.090 3.4% 100.0% 0.0% Particle Size (mm) #200 0.075 2.2% 2.2% 100.0% 0.0% Unified Soils Classification System C**PALMER SP-SM Geotechnical Consultants, Inc. DateTested: 6/5/2019 D(10)= 0.091 nun % Gravel = 31.2% Coeff. of Curvature, CC = 0.82 Sample #: B-2 D(30)= 0.415 nun % Sand = 59.5% Coeff. of Uniformity, CO = 25.44 Depth: 2.5-3.0 D(60)= 2.306 mm % Silt & Clay = 9.3% Fineness Modulus= 3.86 Project Roseridge Li uid Limit= 0.0% Plastic Limit= 0.0% Plasticity Index= 0.0% Actual Interpolated Cumulative Percent Cumulative Percent Grain Size Distribution Sieve Size Specs Specs US Metric Passing Passing Max Min 100.0% -- 1 6.00" 150.00 100.0% 100.0% 0.0% --- - - -- - --- 4.00" 100.00 100.0% 100.0% 0.0% 3.00" 75.00 100.0% 100.0% 0.0% 90.0% - 0.9 2.50" 63.00 100.0% 100.0% 100.0% 0.0% 2.00" 50.00 100.0% 100.0% 100.0% 0.0% 1.75" 45.00 100.0% 100.0% 0.0% 80.0% -- 0.8 - --- - - -- - --- 1.50" 37.50 100.0% 100.0% 0.0% 1.25" 1.00" 31.50 25.00 100.0% 100.0% 100.0% 100.0% 100.0% 0.0% 0.0% 7/8" 22.40 96.7% 100.0% 0.0% 3/4" 19.00 92.3% 92.3% 100.0% 0.0% 60.0% -- 0.6 - --- - -- - --- 5/8" 16.00 88.3% 100.0% 0.0% 01 c 1/2" 12.50 83.5% 100.0% 0.0% vo 3/8" 9.50 79.5% 79.5% 100.0% 0.0% a 50.0% a -- 0.5 - --- - - - --- 1/4" 6.30 72.3% 100.0% 0.0% #4 4.75 68.8% 68.8% 100.0% 0.0% 40.0% - 0.4 - - .......... #8 2.360 60.2% 100.0% 0.0% #10 2.000 58.9% 58.9% 100.0% 0.0% LL #16 1.180 44.2% 100.0% 0.0% 30.0% -- 0.3 - --- - - --=... - --- #20 0.850 38.3% 100.0% 0.0% #30 0.600 33.8% 100.0% 0.0% 20.0% -- 0.2 - --- - - -- --- #40 0.425 30.7% 30.7% 100.0% 0.0% #50 0.300 22.5% 100.0% 0.0% #60 0.250 19.2% 100.0% 0.0% 10.07C -- 0.1 - --- - - -- - --- #80 0.180 14.6% 100.0% 0.0%IL #100 0.150 12.6% 12.6% 100.0% 0.0% 0.0% 0 10 1 0.1 #140 0.106 10.7% 100.0% 0.0% 100 0.01 #170 #200 0.090 0.075 9.3% 10.0% 9.3% 100.0% 100.0% 0.0% 0.0% Particle Size (mm) see k�„ Unified Soils Classification System G jPALMER SP-SM C Geotechnical Consultants, Inc. DateTested: 6/5/2019 D(lo)= 0.070 mm % Gravel = 23.3% Coeff. of Curvature, CC = 0.83 Sample #: B-2 Dl301= 0.295 mm % Sand = 66.0% Coef£ of Uniformity, CU = 21.29 Depth: 5.0-6.0 D(60)= 1.492 mm % Silt & Clay = 10.7% Fineness Modulus= 3.32 Project Roseridge Liquid Limit= 0.0% Plastic Limit-- 0.0% Plasticity Index-- 0.0% Actual Interpolated Cumulative Percent Cumulative Percent Grain Size Distribution Sieve Size Specs FSpecs US Metric Passing Passing Max Min 100.0% -.T_..._..._...T.r,...r-.T_.i._.T_...T..._...T..._..._..._.I.T.T-T T...r...T..._.i._..._.i._..._..._...rT.T..r.i._i.._.i._...r..._...r..._..._... 1 6.00" 150.00 100.0% 100.0% 0.0% 4.00" 100.00 100.0% 100.0% 0.0/o ° III I I I I ,I IIII I I I I I IIII I I I I I IIII I I I I I 3.00" 75.00 100.0% 100.0% 0.0% 90.0% ` r i..a...a...a..._.1-..._.L_..._...i.ia....1_.i._.1_...a..._...a..._..._..._.14.14..a...1...a..._.i._..._.i._..._..._...Il.a...i._i.._l._...1..._...1..._..._... 0.9 �� 2.50" 63.00 100.0% 100.0% 100.0% 0.0% ! ! ! ! 11 ! ! ! ! ! ! ! 11 ! i i i i Hill i i i i i iiiiii 2.00" 50.00 100.0% 100.0% 100.0% 0.0% ! ! l 1.75" 45.00 100.0% 100.0% 0.0% 80.0% ii,'!i r1..1...t...1..._.f_..._.f_..._..._....11..._.1._.1_...}..._...}..._..._..._.itt-tt...t..t..._.1._..._.1._..._..._...t{.t..r.I._I.._.I._...t.._...t.._..._... 0.8 III I I I I I 111 1� I I I IIII I I I I I IIII I I I I I 1.50" 1.25" 37.50 31.50 100.0% 100.0% 100.0% 100.0% 0.0% 0.0% III l III ! HillHill IIII! i ! i !!!ii ! ! i ! !!!!! ! 1.00" 25.00 100.0% 100.0% 100.0% 0.0% 70.0%0,7 ..i......!!!!...! ', • 7/8" 22.40 96.1% 100.0% 0.0% III I I I I I I I I I I I I I I I I I I I I I IIII I I I I I 3/4" 19.00 91.1% 91.1% 100.0% 0.0% 60.0% P 4-4-4--.1_..._.1_..._..._...!.is...-.i_.i._.i__i14..4...4...4..._.1._..._.1._..._..._...41.4..i-.i._i.._.1._...4..._...i..._..._... 0.6 5/8" 16.00 89.2% 100.0% 0.0% �1 1/2" 12.50 87.0% 100.0% 0.0% y III I I I I I III I I I I I I I I I I I I IIII I I I I I 3/8" 9.50 85.1% 85.1% 100.0% 0.0% p 50.0% t-i 7 r.�--T r----- n ri-i-T 7 "Y"""- Y� ""Y" r 7 i---i rtr rI i i r- r - --- 0.5 iiiii ] HIII I IL I I 1/4" 6.30 79.4% 100.0% 0.0% � III I i i i i 'I I I i i I i i II i i i i i I Ii i 1 1 1 i i i #4 4.75 76.7% 76.7% 100.0% 0.0% 40.0% L.........._.1_..._.1_..._..._..._.li_I._.1_......_...i..._..._..._i.i.i i..i...i... _!._..._I._..._..._...il...i l._L._I._...i..._...i..._..._... 0.4 i i i i i i #8 2.360 68.6% 100.0% 0.0% #10 2.000 67.3% ° 67.3/0 o 100.0% 0 0.0% #16 1.180 55.5% 100.0% 0.0% 30.0%,.....+......_.+_..._.+_..._..._...:.+...F.+_.,._.+_...+..._...+..._..._..._.,.+.+�..+...+...+.._� ..._.;._..._..._...++.+...;._;.._.;._...+..._...+..._..._... 0. c 3 I l i I i i I I III I I I I I I I I I I I I I` I IIII I l i I I #20 #30 0.850 0.600 50.7% 47.1% 100.0% 100.0% 0.0% 0.0% 20.0% ri 7 t 7--1 1- - - r7 rr-i -1 t 1-- ittt-T r t i- rtrri i i -t- t - - 02 #40 0.425 44.6% 44.6% 100.0% 0.0% III l III IIII I♦ IIII #50 0.300 30.5% 100.0% 0.0% #60 0.250 24.9% 100.0% 0 0.0 % 10.0% LI..1.1...1.._.1_..._.1_..._..._....11..L.1_.I._.1_..1..._..1..._..._..._.I.1.11.1...L..1..._.j._..._.j._..._..._...ill:.i._i.._.i._...i..._...i..._..._... 0.1 #80 0.180 17.1% 100.0% 0.0% i i i Hill i i i i i Hill i i i i i Hill i i i i i i i i i i i i i #100 0.150 13.7% 13.7% 100.0% 0.0% 0.0% ill i i i i i Hill i i i i i Hill i i i i i 0 10 1 0.1 0.01 #140 0.106 11.9% 100.0% 0.0% 100 #170 0.090 11.3% 100.0% 0.0% Particle Size (mm) #200 0.075 10.7% 10.7% 100.0% 0.0% Unified Soils Classification System G jPALMER SP-SM C Geotechnical Consultants, Inc. DateTested: 6/5/2019 D(lo)= 0.067 mm % Gravel = 25.6% Coeff. of Curvature, CC = 5.38 Sample #: B-2 D(30)= 0.957 mm % Sand = 63.1% Coef£ of Uniformity, CU = 38.06 Depth: 10.0-11.1 D(60)= 2.546 mm % Silt & Clay = 11.2% Fineness Modulus= 4.10 Project Roseridge Liquid Limit= 0.0% Plastic Limit-- 0.0% Plasticity Index-- 0.0% Actual Interpolated Cumulative Percent Cumulative Percent Grain Size Distribution Sieve Size Specs FSpecs US Metric Passing Passing Max Min 100.0% T.r,...r-.T_.i._.T_...T..._...T..._..._..._.i.T.T-T T...T- T..._.i._..._.i._..._..._...rT.T..r.i._i.._.i._...r..._...r..._..._... 1 �i 6.00" 150.00 100.0% 100.0% 0.0% 4.00" 100.00 100.0% 100.0% 0.0% iiiii i i •`i iiiiii i i i iiiiii i i i iiiiii i i i 3.00" 75.00 100.0% 100.0% 0.0% 90.0% r I..a...a...a..._.1-..._.���..._...a.la....1-.i._.1-...a..._...a..._..._..._.i.1.1�..a...I...a..._.i._..._.i._..._..._...Il.a...i._i.._.i._...I..._...I..._..._... 0.9 2.50" 63.00 100.0% 100.0% 100.0% 0.0% ° iiiii iiiiii 2.00" 50.00 100.0% 100.0% 100.0% 0.0% ♦iiiiii I I I 1.75" 45.00 100.0% 100.0% 0.0% 80.0% r1..1...t..1..._.{_..._.{_..._..._...T.t i-i-t-...t.._...t.._..._..._.i.t.t-t t..t...t.._.i._..._.._..._..._...tt.t.N._i.._.i._...t..._...t..._..._... 0.8 1.50" 37.50 100.0% 100.0% 0.0% III I I I I I ',I I,� I I I I III I I I I I I III I I I I I I 1.25" 31.50 100.0% 100.0% 0.0% Ilk 1 70.0% 0,7 1.00" 25.00 100.0% 100.0% 100.0% 0.0% 7/8" 22.40 95.8% 100.0% 0.0% iiiiii 3/4" 19.00 90.3% 90.3% 100.0% 0.0% 60.0% -1 a-4-.a-._.i_..._.1_..._..._...!.ia...-.i_.i._.i_...�.....�..._..._..._.i.i.14..I...i...1..._.i._..._.i._..._..._i..._...i... _... _... 0.6 !!!!! i i i ',iiiii i!♦� iiiiii ! i i iiiiii i i i 5/8" 16.00 88.2% 100.0% 0.0% t71 1/2° 12.50 85.8% 100.0% 0.0% 3/8" 9.50 83.6% 83.6% 100.0% 0.0% y s350.0%.....7......_.t_..._.t_..._..._...-.1�...ri j i...7..._...7....._..._..Y.t�..7...t...7..._.._..._.._..._..._...tt.7...._.._.._...t..._...t..._..._... 0.5 IL 1/4" 6.30 77.4% 100.0% 0.0% ° iii i i i i i Hill i i i i i #4 4.75 74.4% 74.4% 100.0% 0.0% 40.0% 1 1.1..1...i.._.l_..._.l_..._..._...1.1 ._ .l_I._.l_...1..._...1..._... Ill..1...i...1..._I._..._I._..._..._...il.l..l 1._I.._I._...i..._...i..._..._... 0.4 -iiiiii i i i iiiii i i i #8 2.360 58.8% 100.0% 0.0% 1 I I I I Hill I I I I I ♦:i:::: #10 2.000 56.4% 56.4% 100.0% 0.0% ° ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! iiiii i i i !iiiii i i i iiiii i i i Hill ii i i i #16 1.180 35.6% 100.0% 0.0% 30.0% ,.....+......_.+_..._.+_..._..._...:.+...F.+_.,._.+_...+..._...+..._..._. _..+4..44...+..._.,._..._.,._..._..._...++.+..4.;._,.._.,.t. ._...._...+..._..._... 0.3 #20 0.850 27.3% 100.0% 0.0% #30 0.600 20.9% 100.0% 0.0% 20.0% t-i 7 t 7..._ t r..._..._ 11 r t_.I._ t t I - i t t� t -1- -1- ttrr i i i t.. t ._... _... 0 2 #40 0.425 16.5% 16.5% 100.0% 0.0% !! i Hill I I I i I #50 0.300 14.3% 100.0% 0.0%♦��♦��� LI..1.1...1.._.1_..._.1_..._..._....11..L.1_.I._.1_..1..._..1..._..._..._.I.1.11.1...L..1..._.I._..._.I._..._..._...t,.i..i.I._I.._.I._...L..._...L..._..._... #60 0.250 13.4% 100.0%0.0% 0 0.0 % 10.0% 0.1 #80 0.180 12.1% 100.0% 0.0% i i i Hill i i i i i Hill i i i i i iii i i i i i Hill i i i i #100 0.150 11.6% 11.6% 100.0% 0.0% 0.0% i i i i i i i i i i i i i i i 0 10 1 0.1 0.01 #140 0.106 11.4% 100.0% 0.0% 100 #170 0.090 11.3% 100.0% 0.0% Particle Size (mm) #200 0.075 11.2% 11.2% 100.0% 0.0% Appendix C: Slope Profile 0 o° QVt a EXISTING BUILDINGS PROPOSED PIPE -PILE RETAINING WALL 9. 10' \ 70 3 14' EXISTING 47 s' FENCE 41° 10 31�17' \ NIEGHBORING PROPERTY \ Qva k *** Slope Profile * PA\MERRose Ridge Condominiums Not to Scale A -A' Geotechnical Consultants, Inc. Edmonds, WA Not to be Used for Construction Date: 06.27.19 By., M. Hallam Appendix D: Design Calculations and Global Stability SOIL PARAMETERS Ym = 125 pcf (P'=(p=30 CONFIRM ANCHOR SPACING 3 FT OVERTURNING MOT = 2Y(HZ)KA\3)( WHERE KA = tan' 145 — � I = 0.333 =-125(52)0.333 G) = 867 MRESIsr = T cos B(HT) = 805.5(3) = 2,416.3 ft • lbs MRESIST = 2,416 FpSpr= =2.8>2.0 MOT 867 OK� T ANCHOR SPACING = 7 FEET ANCHOR CAPACITY T= 7 T _ 6,000 cos 20 _ 805.5 lbs 7 SLIDING R = 520.3 T = 805.5 RESIST T _ 805.5 _ Fossrrns = DRIVE R 520.3 — 1.5 >_ 1.5 O j Silty Sand Unit Weight: 120 PCF Cohesion: 0 PSF Phi: 30 Glacially Consolidated Soils Unit Weight: 130 PCF Cohesion: 1500 PSF Phi: 45 Rose Ridge Condominiums Prior to Improvements Factor of Safety < 1.0 Approx. Fence Location 119 Silty Sand Unit Weight: 120 PCF Cohesion: 0 PSF Phi: 30 Glacially Consolidated Soils Unit Weight: 130 PCF Cohesion: 1500 PSF Phi: 45 Rose Ridge Condominiums With New Wall Factor of Safety 4.5