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REVIEWED PLN BLD2020-0865+Geotechnical_Report+8.19.2020_1.21.44_PMLIU & ASSOCIATES, INC. Geotechnical Engineering Engineering Geology Earth Science September 26, 2005 Mr. Bill Ritter 8364 Olympic View Drive Edmonds, WA 98026 Dear Mr. Ritter: BLD2020-0865 RECEIVED Sep 14 2020 CITY OF EDMONDS DEVELOPMENT SERVICES DEPARTMENT Subject: Geotechnical Engineering Study Proposed 3-Lot Short Plat 8364 Olympic View Drive Edmonds, Washington L&A Job No. 5A112 INTRODUCTION We have completed a geotechnical engineering study for the subject plat site, located at the above address in Edmonds, Washington. The general location of the project site is shown on Plate I — Vicinity Map. We understand that the proposed development for the site is to plat it into three single-family residential building lots. The purpose of this study is to characterize the subsurface conditions of the site and provide geotechnical recommendations for grading, slope stabilization, erosion mitigation, surface and ground water drainage control, foundation design and construction, etc., for the proposed development. Presented in this report are our findings and recommendations. 4 PROJECT DESCRIPTION 'y �� 'y�� .. For our use in this study, we were provided with an undated plat plan of the proposed development for the site. According to this plan, the proposed development for the site is to plat it into three single-family residential lots. The existing house on the new Southern Lot will remain, and a new residence will be constructed on each of the two remaining new lots (the Northeast and Northwest lots). The Northeast and Northwest Lots are on a moderate to steep 19213 Kenlake Place NE - Kenmore, Washington 9802RECEIVED Phone (425) 483-9134 - Fax (425) 486-2746 AUG G ' 2010 EXPIRED APPUCATIO"# OLD2018-1030 DEVELODN 7 (NEW) PERMIT# BLD2019-1025 'C���uU�T 8 September 26, 2005 Proposed 3-Lot Short Plat . L&A Job No. 5)A 112 Page 2 hillside. Although design plans for the new residences to be constructed on these lots are not yet available, we anticipate the buildings will be wood -framed structures supported on concrete - walled basement and interior bearing walls, columns and footing foundations. The footprint excavation for these buildings will probably require cuts from a couple to 15 feet deep and possibly less significant fill. SCOPE OF SERVICES Our scope of services for this study comprises specifically the following: 1 Review the geologic and soil conditions at the site based on a published geologic map. 2. Explore the site for subsurface conditions with backhoe test pits to a firm bearing soil stratum or to the maximum depth (about 12 feet) capable by the backhoe used for excavating the test pits, whichever occurs first. 3. Perform necessary geotechnical analyses, and provide geotechnical recommendations for site grading, erosion abatement, slope stabilization, surface and ground water control, and foundation design and construction, based on subsurface conditions encountered in the test pits and results of our geotechnical analyses. 4. Prepare a written report to present our findings, conclusions, and recommendations. SITE CONDITIONS SURFACE CONDITIONS The site is an Y -shaped irregularly tract of land. It is bounded by Olympic View Drive and an g undeveloped city park land to the north, and adjoined by residential developments to the south, east and west. The site is situated on the mid -slope of a broad, moderate to steep, northwesterly - declining hillside. The southern portion of the site where the new South Lot is located has been previously graded into a relatively level bench. The terrain within the new Northeast and LIU & ASSOCIATES, INC. September 26, 2005 .Proposed 3-Lot Short Plat L&A Job No. 5 A 112 Page 3 Northwest Lots of the site generally slopes down northerly to northwesterly at about 15 to 83 percent grade. The steeper portions are mostly along the south sides of these two lots and the eastern half of the Northwest lot. The existing residence on the South Lot is accessed by a paved driveway along the east side of the site. The unpaved area around this existing residence is mostly landscaped with shrubs. The area of the Northeast and Northwest Lots is heavily wooded, dotted by tall, mature evergreen and deciduous trees and covered by dense underbrush. GEOLOGIC SETTING The Geologic Map of the Eastern. Half and Part of the western Half Quadrangles, Washington, by James P. Minard, published by U. S. Geological Survey in 1983, was referenced for the and soil conditions of the lot. According to this publication, the surficial soil units at geologic g and in the vicinity of the lot are mapped as Vashon Till (Qvt) underlain by Advance Outwash (Qva). the 'Puget Sound Lowland has been modified b The geology of g Y the advance and retreat of several glaciers in the past and subsequent deposits and erosion. The latest glacier advanced to the Puget Sound Lowland is referred to as the Vashon Stade of the Fraser Glaciation, which has occurred during the later stages of the Pleistocene Epoch and retreated from the region some 14,500 years ago The Vashon till soil unit is a very dense mixture of unsorted clay, silt, sand, gravel, and scattered cobbles and boulders, often referred to as "hard pan". The Vashon till over the top two to four feet is normally weathered to a medium -dense state, and is moderately permeable and compressible. The underlying fresh till is very dense and practically impervious to stormwater LIU & ASSOCIATES, INCO September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A 112 Page �# infiltration. The Vashon till soil unit, however, was not encountered by the test pits excavated on the site. The advance outwash soil unit underlying the Vashon till is composed of stratified sand and gravel with minor amounts of silt and clay, deposited by ,the meltwater of advancing glacial ice. Due to its generally granular composition, the advance outwash is of moderate permeability and generally drains well. The advance outwash is glacially overridden and is generally dense to very dense in its natural, undisturbed state, except the top 3 to 5 feet where exposed on slopes which may be eroded and weathered to a loose to medium -dense state. The advance outwash deposits can stand in steep cuts or natural slopes for extended period of time when undisturbed. where exposed on slopes of poor vegetation cover and subjected to storm runoff, the advance outwash deposits can be gradually eroded and may slough to a flatter inclination. The advance outwash p g Y Y deposits in their native, undisturbed state can provide very good foundation support with little settlement expected for light to moderate residential structures. SOIL CONDITIONS Subsurface conditions of the .subject site were explored on September 6, 2005, - with six test pits. The test its were excavated with atrack-mounted backhoe to depths from 8.0 to 10.0 feet. The p 1 approximate locations of the test pits are shown on Plate 2 - Site and Exploration Location Plan. The test pits were located with either a tape measure or by visual reference to existing to ra o hic features in the field and on ttopographic to hic survey map, and their locations should be p g p p p considered only accurate to the measuring method used. A g g eotechnical engineer from our office was present during subsurface exploration, who examined the soil and geologic conditions encountered and completed the logs of test pits. Soil samples obtained from each soil unit in the test' pits were visually classified in general LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A 112 Page 5 accordance with United Soil Classification System, a copy of which is presented on' Plate 3. Detailed descriptions of soil units encountered during site exploration are presented in the test pit logs on Plates 4 through 6. The test pits revealed that the site is mantled by a layer of loose, organic topsoil, from 0.8 to 2.7 feet thick. The topsoil is underlain by a layer of weathered soils of light -brown, loose to medium -dense, silty fine sand with a trace of .gravel, from. 1.6 to 3.5. feet thick. Underlying this layer of weathered soils is a brown -gray to light -brown to light -gray advance outwash deposit of medium -dense, gravelly, clean to slightly silty, fine to medium sand with occasional cobble, from 1.8 to 3.2 feet thick. This medium -dense advance outwash deposit is underlain to the depths explored by a light -gray advance outwash deposit of dense, gravelly, fine to coarse sand. GROUNDWATER CONDITION Groundwater was not encountered in any of the test pits. The advance outwash deposits underlying the site are of moderately high permeability, and would allow stormwater I to seep Y g through. Stormwater infiltrating into the advance outwash deposits would perch and accumulate over an underlying impervious silt and clay layer at greater depth. We expect little impact on the proposed development by this deeper groundwater. DISCUSSION! AND RECOMMENDATIONS GENERAL Based on the soil conditions encountered in our subsurface explorations, it is our opinion that the site is suitable for the proposed development from the geotechnical engineering viewpoint, provided that the recommendations in this report are fully implemented and observed during construction. The topsoil, loose weathered soils and soils in the root zone should be completely stripped within the driveways, the building pads and where the subgrade soils are to support LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A 112 Page 6 structural or traffic load. The medium -dense to dense advance outwash soils are of fair to moderately high shear strength and can provide good foundation support to the driveways and the new buildings to constructed on the site. Conventional footing foundations placed on or into the underlying medium -dense to dense advance outwash soils may be used for supporting the new buildings to be constructed on the site. Structural fill, if required for site grading, should be constructed over the underlying medium -dense to dense advance outwash soils following the stripping of surficial unsuitable soils. GRADING SEASON Due to the sensitive nature of the steep slopes within the site, we recommend that grading and foundation construction work for the residence be carried out and completed in the dryer period from April 1 to October 30 of the year. The site should be stabilized with proper drainage and erosion control measures in place beyond this dry season grading period. GEOLOGIC HAZARDS AND REMEDIATION Landslide Hazards The subject site is underlain at shallow depth by medium -dense to dense advance, outwash soils of fair to moderately -high shear strength. The advance outwash deposits are quite permeable, and the impervious silty soils normally underlying the advance outwash soil unit is not exposed within the site. Therefore, seepage of groundwater out of slopes from the interface of the advance outwash deposits and the underlying silty soil unit should not occur within the site. The competent advance outwash soils underlying the site and little potential of groundwater seepage within the site would make it unlikely for deep-seated landslide to occur within the site. LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A. Job No. SA 112 Page 7 Erosion Hazard The surficial topsoil axed loose weathered soils over the steeper portion of the site can be easily eroded when stripped of vegetation cover and overly saturated. Prolonged erosion can lead to soil sloughing and shallow, skin -type mudflows on the steeper portion of the site. To mitigate erosion potential, the vegetation cover outside of construction limits should not be disturbed. Concentrated stormwater should not be discharged onto the ground anywhere within the site. Spoil soils and yardwaste should not be disposed of within the site. Storm runoff over impervious surfaces, such as roofs and paved driveways, should be captured with underground drain line systems tied to roof downspouts and by catch basins installed in driveways, and should be tightlined to discharge collected water into a storm sewer or a suitable stormwater disposal facility. Unpaved, disturbed ground within the site should be re -vegetated as soon as possible to provide erosion protection. Once the drainage control measures for the roadway and houses are in place after the completion of the proposed development, the amount of surface runoff and near -surface groundwater flow will be reduced, which would further reduce soil erosion and enhance site stability. Seismic Hazard The Puget Sound region is in an active seismic zone. The lot is underlain by medium -dense to I dense advance outwash soils of fair to moderately high shear strength. There is a lack of continuous, extensive, static groundwater table at shallow depth under the lot. Therefore the potential for seismic hazards, such as deep-seated landslides, liquefaction, lateral soil spreading, to occur on the site should be minimal. The proposed building, however, should be designed for seismic forces induced by strong earthquakes. Based on the soil conditions encountered by the test pits, it is our opinion that Seismic Use .Group I and Site Class D should be used in the seismic design of the proposed residences in accordance with the 2003 international Building Code (IBC). LIU & ASSOCIATES, INC. I S September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A 112 Page 8 SITE PREPARATION AND GENERAL GRADING Site preparation for the proposed development should include clearing and grubbing within construction limits. Topsoil, loose weathered soils, and unsuitable soils in the root zone should be completely stripped within the driveways, the building pads of the proposed buildings and in other areas subject to traffic and structural loads. The exposed soils should be compacted to a non -yielding state with a vibratory compactor and proof -rolled with a piece of heavy earthwork equipment operated on the site. The on -site soils contain a high percentage of fines and are sensitive to moisture. A layer of clean quarry spalls should be placed over excavated areas and areas of frequent traffic, as required, to protect the subgrade soils from disturbance by construction traffic. Silt fences should be erected along the downslope boundaries of the site to prevent sediments being transported by storm runoff onto adjoining properties or the street. The bottom edge of the silt fence should be embedded in a trench and ballasted with crushed rock or gravel. EXCAVATION AND FILL SLOPES Under no circumstance should excavation slopes be steeper than the limits specified by local, state and federal safety regulations if workers have to perform construction work in excavated areas. Unsupported temporary cuts greater than 4 feet in height should be no steeper than 1- 1/4H:1 V in the surficial topsoil and loose weathered soils, and no steeper than 1 H:1 V in the underlying medium -dense to dense advance outwash soils. Permanent cuts should be no steeper than 21 /2H:1 V in the surficial topsoil and loose weathered soils, and no steeper than 2H:1 V in the underlying medium -dense to dense advance outwash soils. The soil units and the stability of cut slopes should be observed and verified by a geotechnical engineer during excavation. LIU & AS50CIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A112 Page 9 Permanent fill embankments required to support structural or traffic loads should be constructed with compacted structural fill placed over proof -rolled, undisturbed, medium -dense to dense advance outwash soils after the unsuitable surficial soils are stripped. Permanent fill to be placed on slopes steeper than 20 percent grade should be retained structurally. Sloping ground exceeding 15 percent grade over which fill is to be placed should be benched with vertical steps no more than 4 feet high after stripping in of unsuitable surficial soils. The slope of permanent fill embankments should be no steeper than 2H:1V. Upon completion, the sloping face of permanent fill embankments should be thoroughly compacted to a non -yielding state with a hoe -pack. The above recommended cut and fill slopes are under the assumption that groundwater seepage will not be encountered during construction. If encountered, the construction work should be immediately halted and the slope stability re-evaluated. The slopes may have to be flattened and other measures . taken to stabilize the slopes. Storm runoff should not be allowed to flow uncontrolled over the top of cut or fill slopes. Permanent cut slopes or fill embankments should be seeded and vegetated as soon as possible for erosion protection and long-term stability, and should be covered with clear plastic sheets, as required, to protect them from erosion by stormwater until the vegetation is fully established. STRUCTURAL FILL pp Structural fill is the fill that supports structural or traffic load. Structural fill should consist of . clean soils free of organic and other deleterious substances and with particles not larger than four inches. Structural fill should have a moisture content within one percent of its optimum moisture content at the time of placement. The optimum moisture content is the water content in the soils that enable the soils to be compacted to the highest dry density for a given compaction effort. LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A112 . Page 10 ' The on -site advance outwash soils contain a high percentage of fines, and may be used as structural fill only under fair weather condition when their moisture content can be controlled to close to optimum moisture content. Imported material for structural fill should be clean, free - draining, granular soils containing no more than 5% by weight finer than the No. 200 sieve based on the fraction of the material passing No. 4 sieve, and should have individual particles not larger than four inches. Imported structural fill should be stockpiled and covered separately from the on -site soils. Structural fill should be placed in lifts no more than 10 inches thick in loose state, with each lift compacted to a minimum percentage of the maximum dry density determined by ASTM D 1557 ' : (Modified Proctor Method) as follows: Application % of Maximum Dry Density Within building pads 95% Roadway/driveway subgrade 95% for top 2 feet and 90% below Retaining wall backfill 90%. Utility trench backfill 95% for top 4 feet and 90% below BUILDING SETBACK The purpose of building setback from the top or toe or an overly steep portion of a slope is to establish a safe buffer such that if a slope failure should occur the stability of the structure can be maintained and damages to the structure minimized. To maintain stability of the buildings to be construction on the new Northeast and Northwest Lots, we recommend that the buildings be set back at least 20 feet from the crest or toe or any portion of .40% or steeper slopes. Reinforced concrete r soldier pile retaining walls may be used to regrade the round and enhance stability o nc, o p g y g g LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A 112 Page 11 . .11 of 40% or steeper slopes. If retaining walls are used, the proposed building should be set back no less than 10 feet from the retaining walls. The buildings should be. also be set back sufficiently such that an imaginary plane drawing from the edge of the footing foundations to the toe of slopes 40% or steeper should be no steeper than. 3H:IV. Also, the footing foundations within 30 feet of the toe or top or any .portion of 40% or. steeper slopes should be embedded at least 1.5 foot into the medium -dense to dense advance outwash soils. The footprint bearing soils should be verified by a geotechnical engineer after the ekcavation of the building footprints are completed. DEBRIS 'V'4lA.LLS If retaining walls are not constructed to enhance the stability of the steep slopes uphill of the proposed new buildings, we recommend that the uphill -side basement galls of the buildings be extended at least 3 feet above their adjacent finish grade to serve as debris blocking walls in case a mudflow should occur on the uphill steep slope. The combined basement/debris walls should be designed in accordance with the recommendations in the BASEMENT AND RETAINING WALLS section of this report. BUILDING FOUNDATIONS Conventional footing foundations may be used for supporting the buildings to be constructed on the site. The footingfoundations should be laced on or into the underlying, medium -dense to p dense advance outwash soils, or on structural fill constructed over these undisturbed competent basal soils. water should not be allowed to accumulate in excavated footing trenches. Disturbed soils in footing trenches should be completely removed down to firm native soils prior to pouring concrete for the footings. The sandy advance outwash soils can be easily disturbed by construction traffic. To protect the footing bearing soils, a 6-inch-minimum layer of 2-inch- acted crushed rock should be laced over *the bearing soils. The footing foundations minus comp p may then be poured over the crushed rock base. LIU & ASSOCIATES, INCO September 26, 2005 Proposed 3-Lot Short Plat . L&A Job No. 5 A 112 Page 12 If the above recommendations are followed, our recommended design criteria for footing foundations are as follows: • The allowable soil bearing pressure for footing foundations, including dead and live loads should be no greater than 2� 500 p pp sf if supported on undisturbed medium -dense to g dense native soils and no greater than 2,000 psf if supported on structural fill placed over firm undisturbed soils. The footing bearing soils should be verified on -site by a geotechnical - engineer after the footing trenches are excavated and before the footings poured. • The minimum depth to bottom of perimeter footings below adjacent final exterior grade should be no less than 18 inches. The minimum depth to bottom of the interior footings below top of floor slab should be no less than 12 inches. • The minimum width should be no less than 16 inches for continuous footings, and no less than 24 inches for individual footings. A one-third increase in the. above recommended allowable soil bearing pressure may be used when considering short-term, transitory, wind or seismic loads. For footing foundations designed and constructed per recommendations above, we estimate that the maximum total post - construction settlement of the buildings should be 3/4 inch or less and the differential settlement across building width should be 1/2 inch or less. Lateral loads on buildings can be resisted by the friction force between the foundations and the subgrade soils or the passive earth pressure acting on the- below -grade portion of the foundations. g p For the latter, the foundations must be poured "neat" against undisturbed soils or backfilled with a clean compacted p , acted structural fill. We recommend that an equivalent fluid density of 300 cf(pounds er cubic foot) for the passive earth pressure be used for lateral (EFD) p p resistance. The above pressure ressure assumes that the backfill is level or inclines upward away p LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A 112 Page 13 from the foundations for a horizontal distance at least twice the depth of the foundations below the final grade. A coefficient of friction of 0.60 between the foundations and the subgrade soils may be used. The above soil parameters are unfactored values, and a proper factor of safety should be used in calculating the resisting forces against lateral loads on the buildings. BASEMENT AND RETAINING WALLS Basement walls restrained horizontally at the top are considered unyielding and should be designed for a lateral soil pressure under the at -rest condition; while retaining walls free to move at the top should be designed for active lateral soil pressure. we recommend that a lateral soil pressure of 45 and 70 pcf EFD be used for the design of foundation walls with level/descending backslope and rising backslope, respectively; and 35 and 55 pcf EFD for retaining walls with level/descending backslope and rising backslope, respectively. To counter the active soil or at - rest pressure, a passive lateral soil pressure of 350 pcf EFD may be used, except that the passive pressure within the top 12 inches of the finish subgrade should be ignored. The above passive pressure assumes that the backfill is level or inclines upward away from the walls. The above lateral soil pressures are under the assumption that groundwater behind the walls is fully drained. To resist against sliding, the friction force between the footings and the subgrade soils may be calculated based on a coefficient of friction of 0.60. The above soil parameters are ultimate values, and factors of safety should be used in the design of the basement and retaining proper walls against sliding and overturning failures. Basement walls or retaining walls may be supported on footing foundations seated on or into the underlying very -dense fresh till or very - hard transitional beds soils, with an allowable soil bearing pressure not to exceed 3,000 psf. A vertical drainage blanket consisting of at least 12-inch-thick free -draining pea gravel or washed gravel should be placed against foundation and retaining walls to prevent accumulation of groundwater behind and buildupof hydrostatic pressure against the walls. The remaining LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5 A 112 Page 14 backfill should consist of structural fill constructed per recommendations in the STRUCTURAL FILL section of this report. The top 12 inches of backfill should consist of compacted, clean, on - site soils. The backfill material for the foundation and retaining walls should be compacted with a hand -operated compactor. Heavy compaction equipment should not be allowed closer to the walls than a horizontal distance equal to the wall heights. A footing drain, as -recommended in the DRAINAGE CONTROL section of this report, should also be provided for foundation and retaining walls. SLAB -ON -GRADE FLOORS Slab -on -grade floors, if used, should be placed on firm subgrade prepared as outlined in the SITE PREPARATION AND GENERAL EARTHWORK and the STRUCTURAL FILL sections of this report. Where moisture controls critical, th.e slab -on -grade floors should be placed on a capillary break which is in turn placed on the compacted subgrade. The capillary break should P ry consist of a minimum four -inch -thick layer of clean, free -draining, 7/8-inch crushed rock, containingno more than 5 percent by weight passing the No. 4 sieve. A vapor barrier, such as a 6-mil y p ma plastic membrane, be placed over the capillary break, as required, to keep moisture from migrating upwards. PAVED DRIVEWAYS e of paved driveways is critically related to the conditions of the underlying subgrade . Performance p y y . ' end that the subgrade soils within the driveways be treated and prepared as soils. We recommend described to the SITE PREPARATION AND GENERAL EARTHWORK section of this report. placing Prior to lacin base material, the subgrade soils should be compacted to a non --yielding state _ orn actor and roof -rolled with a piece of heavy construction equipment, with a vibratory roller compactor p such as a fully -loaded . aded dump truckAn areas with excessive weaving or deflection should be y over -excavated and re -compacted or laced with a structural fill or crushed rock placed and pactereplaced LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A 112 Page 15 compacted in * accordance with the recommendations provided in the STRUCTURAL FILL section of this report. We recommend that an 4-inch-thick minimum, compacted; crushed rock base (CRB), consisting of 7/8-inch-minus crushed rock, be used for the roadways. The crushed rock or sub. grade base should be topped with 2-inch asphalt heated base (ATB) topped by 1-1/2-inch-thick Class B asphalt concrete (AC). DRAINAGE CONTROL Building Footprint Excavation Groundwater is not expected within depth of excavation for the construction of the proposed buildings. If encountered, the bottom of building footprint excavation should be sloped and ditches excavated along the bases of the cut banks to direct runoff and groundwater into a sump pit from which water can be pumped into a nearby storm sewer. The inlet of the storm sewer should be covered by a filter sack to keep sediments from entering the storm sewer system. A layer of 2-inch crushed rock should be placed over undisturbed subgrade soils support y ing ;. footings and on -grade slabs, as required, to protect the. soils from disturbance by construction i traffic. Surface Drainage Water should not be allowed to stand in any areas where footings, slabs, or pavement is to be constructed. Final site grades should allow storm runoff to flow away from the building. We recommend the finish ground be sloped at a gradient of 3 percent minimum fora distance of at least 10 feet away from the building, except in the areas to be paved. LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A 112 Page 16 Runoff over Impervious Surfaces Storm runoff over impervious surfaces, such as roofs and paved driveways, should be collected by underground drain line systems connected to downspouts and by catch basins installed in the driveways. Stormwater thus collected should be tightlined to discharge into a storm sewer or a suitable stormwater disposal facility. Sufficient numbers of cleanouts at strategic locations should be provided to the underground drain line systems to allow for periodical cleaning of the drain lines. Footing Drains A subdrain should be installed around the perimeter footings of the proposed houses and along the base of retaining walls. The subdrains should consist of a 4-inch-minimum-diameter, perforated, rigid, drain pipe, laid a few inches below bottom of the building perimeter footings or retaining gall footings. The trenches and the drain- lines should have a sufficient gradient to g Y generate flow b gravity. The drain lines should be embedded in washed gravel completely wrapped in non -woven filter fabric to within about 12 inches of finish grade. The remaining trenches may be backfilled with clean on -site soils. Sufficient numbers of cleanouts at strat y egic locations should be provided to the footing drain lines to allow for their periodical cleaning and Water collected b the footing drains should be tightlined, separately from the roof maintenance.y g and surface stormwater drain systems, to discharge into a storm sewer. i RISK EVALUATION STATEMENT The site is 'underlain by medium -dense to dense advance outwash soils at shallow depth. These it to moderately -high shear stren th and have good resistance against deep-seated soils are of fair g slope failures. The key to maintain stability of the site is to maintain stable temporary cut slopes and to have q proper ro and adequate erosion and drainage control during and after construction. It is p p our opinion that if the recommendations in the report are fully implemented and observed during e the completion of the development, the areas disturbed by construction construction and after p p . LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A 112 Page 17 will remain stable and will not increase the potential for soil movement. In our opinion, the risk of damage to the proposed development and from the development to adjacent properties from soil instability should be minimal. LIMITATIONS been prepared for the specific application to this project for the exclusive use by This report has p p p pp P J Mr. Bill Ritter, and his associates, representatives, consultants and contractors. We recommend that this report, in its entirety, be included in the project contract documents for the information of the contractors for their estimating and bidding purposes. The conclusions and prospective inter interpretations in this report, however, should not be construed as a warranty of the subsurface p conditions. The scope of this study does not include services related to construction safety precautions and our recommendations are not intended to direct the contractor's methods, techniques, sequences or procedures, except as specifically described in this report for design considerations. Our recommendations and conclusions are based on the geologic and soil conditions encountered in the test borings, and our experience and engineering judgment. The conclusions and recommendations *are professional opinions derived in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. No warranty, expressed or implied, is made. The actual subsurface conditions of the site may vary from those encountered by the test pits. The nature and extent- of such variations may not become evident until construction starts. If variations app ear then we should be retained to re-evaluate the recommendations of this report, and to verify or modify them in writing prior to proceeding further with the construction. LIU & ASSOCIATES, INC. September 26, 2005 Proposed 3-Lot Short Plat L&A Job No. 5A 112 Page 18 CLOSURE We are leased to be of service to you on this project. Please feel free to call us if you have any p Y p J questions regarding this report or need further consultation. S4 WAS ONAL g 3irci COMES 7 / 17 /7, � Six plates attached Yours very truly, LIU &ASSOCIATES, INC. J. S. (Julian) Liu, Ph.D., P.E. Consulting Geotechnical Engineer LIU & ASSOCIATES, INC. ITT & ASSOCIATES,--_------_._.__._._ _ APR Geotechnicai En ineerin • --`-- • ---- ""'------- - ---- -2 �-- --�- •---_-_._..- _-••-. _ _.. • _ --- - --- 9 9 Engineering Geology Earth •--—.---------------- _____ ._.. __----------- ---- ---- -= -----= __..—..___.: Science-- - - April 14, 02006 Mr. Dili Ritter 8364 Olympic View Drive Edmonds., WA g8026 Dear r. Ritter: Subiect: Addendurn No. 1 to 9;26/2005 Geotechnieal Report On -Site Stori`nwater In iltraLion I rent hes Proposed 3-Lot Short Flat 01 8364 01y111pxc View Drive Edmonds. Washington L&A Job No. SA l 12 Six test pits were excavated on the subject plat site. The test its encountered 0.8 to 17 fee t et c�f- loose organic topsoil undo ria n by a layer of weathered soils of litrbht-brown. loose to medium - dense, silty fine sand with « trace of gravel, from 1.6 to 3:5 feet thick. UnderlY inn this laver of i eathered sails are: advance outwash sand deposits of brown-txra to Ii �l�t- r 'cr _ . y b own to li�lit giav niedlLIM-dense. gravelly. clean to slightly Silt', tine: to nie'dium sand with occasional cobble, from 1.8 to 3.? iect thick, and light --gray advance 0Lttwash deposit of dense, rravel!v, fine to coarse sand. GroundwItter was not encotinte:red by any of the test pits excavated u to 10 feet.deep. . � P p n:. ad-vanc e )Lltwash deposit of cleLan. fin., to coars,. sand. vvilth various ain;ount of gravw!, underlying the site at depths f l-on1 3.2 to 6.0 feet below existing ground surface is of high b penueabi l ity. The Soil Surve of Snohon-tish C ounto• Area of Washington. pubs ished .b in U. S. 1 y Department of Agriculture in cooperation with W.ashinbton State. -Department of Natur al Resources and -Washington State University Agriculture Research Center, was also referenced for the surficial soil unit at the subject site. According to this publication, the advance outwash sand deposit at the; subject site is also classified as Everett G"ravelly Sandy Loam with the Soil 19213 Keniake Place NE Kenmore, Washington 98028 Phone (425) 483-9134 Fax (425) 486-2746 April 14, 2006 Addendum No. I to 9/26/2005 Geotechnical Report Proposed -Trot Short Plat L&A .lob No. 5 A I 1 Page 2 . Conservation Services (SCS) Classification System. Table 14 of the above publication lists the permeability Of thiS soil unit at a depth from 6 to 60 inches below grade to be from 6 to 20 i h p (inches per hour). C�LIi• experience of this soil unit in the neighborhood of the sub'ect site . .1 indicates its in-sita in -filtration rate to be in the range from 20 to 40 ip h. It is, therefore, feasible to List infiltration trenches to dispose stookwater into the growid oil site. We recommend a design infiltration rate of 5.0 iph (including a factor of safety of at least 4.0) be used for• the design of infiltration trenches. • Infiltration trenches should be located on the downhill of the houses to be constructed on the lots. 'they should be setback at least 10 feet f•roni the houses and ) feet from proper tines. Our l p y recornniendations for design and constr•UCtion of the iji iltration trenches are shown can Plate 1 attac;lied hereto. "rhe bottom of infiltration trenches, s110LIld be excavated at least 6 inches into the Underlying. clean, light -brown to Iight-gray, advance outwash sand deposit. The Soils at bottom of infiltration trenches s110ulcl be verified by a ocotec:hnical engineer. file side walls of the trenches should be lined with a laver of non-ivoti-en filter fabric, and the trenches backfilled with clean washed p gi-a��el to within ab�llit 2 inches of the finished grade. A 4-inch perforated PVC pipe through which stormwatcr is to be dispersed into the g€� round should be set level in the gravel fill of each infiltration trench. The perforated PVC pipes should beset as high as possible in the trenc:lies to have maxinlUm separation Irons the winter high groundwater table, but should have at least 18 inches of soil/gravel cover over the perforated pipes. The top p of the gravel fill should also be covered with filter tabr•ic:. The renia ire i ng trenches may be back i i l led with o*n-site clean soi Is. We are pleased to he of service to you on this project. Please feel tree to call Lis if you have any gLle.StiOns regarding this report or need further consultation. LIU & ASSOCIATES, INC. April 14, 2006 Addendum No. I to 9/26,12005 Geotechnical Report Proposed 3-Lot Short Plat L&A.Job No. 5A I I? age One plate attached Yours very truly, I-JU & ASSOCIATES, INC. S. (Julian) Liu, Ph.D., P.f-,. Consulting Geotechnical Engineer LiU & ASSOCIATES, INC. qt �L oC —z 1�1 0-- •' 2 CLO > a- •' �o a �A 7A Oq o� v • - - , • ,r 9 O � o �� o ;� aD�J40 � �00 c �q 41 0-0 1100 V �' • i oil • iQ a 0 *oo ' • i Qe `1 .. log I* o •o c .oV •t 3 o U t� L • �Q o 0:a Ono • o.. 47 a o 1 • O , ovamp -' Ili 1 =1 I� Its 1S t t-�� _ Q <� �— � J V Ofl� �1 Vf .....� . TYPICAL SECTION - INFILTRATION TRENCHES LIU & ASSOCIATES, INC. BILL RITTER 3-LOT SHORT PLAT 8364 OLYMPIC VIEW DRIVE Geotechnical Engineering - Engineering Geology • Earth Science EDMON DS , WAS H I NGTON JOB NO. 5A112 DATE 4/14/2006 PLATE 1 LIU ASSOCIATES, INC*. CnieE00 Sdiso4eerng0dgY. -h NOVOMber 26, 2.012 Mr, Bin Mier :83-64-:01yulpic", Vie* Dnvc .F,drnon&�A 99026 Doar Nwk, RiAer: Subj-evV, A.d endum'Na.-2to.91 16/,. "' eta cad. epOrd- Critical -Ai-eas Rtpor( ' 3 t' Sh. on at - L Ni 83 64" 0 Y. 1.4- Monds; NV4s. toni. L&A Job No, 5A] 1..2. is re projtct p sen o. ucal A hni tbr the ia6b ed u ills: addendmt to dur'9126/2005. gwleo ca�-I.repor h deECDC21-80:.0-70. T---. e - rep in areas ort aocordanic e NNvun e E d' Moods e P1 to 4 '1 g.jr .Y -.PU.Dq-.d' M...g. jot'S La ts A and I B are locrated S to I .Led Iree _t sin. ect PrOF, tv i b (pipbfll-) Wit GI W. tiv uth -M -c-a-ted. f h ip. cr�w mm iterthem (downh'11) In tb� viside -e �is wtil. -em-Ir nc v u -.e - x1s. m on-, Lot C the, propertyr. We und"ersMud b - e t* 1 9 resid me. tto be kip d .6ii roach. off'. Lot-s-A and.. BAO d Accordi+gtoo -X Lands ldEro§i' ou. Arvass., 'Efich. 0. TietZe an " a uniidew 15 1/o jg The gil"Ou n-d- abo h -is. mos. q in Liat C e t rr L A. waite.g. hk. its n4ftwest, j&' f slope 40% ov r sOut meddlehalf of`i ot A,'t ending: 00m 4 9 A*e - xcept:a. 0' .) o 40% giraCUp de gmedde or steeper, wA the area mmstivy-10f6l j.,ortheList. comer and. 'Thbdd.dle ..of --the lot-whic h--are. .'i B. is. genw y(r.veen1% arid 4nd stce.ner e twrrnofLoera side.. ww. e - 40% or A -e Cr 'go Nw.,st comer. and. ItS. D-Orth cn.. ar of with smaller areas at its. uth 98,028 19i1+ll'KOnlake'Plate NE. Kenmore." - - Wr - 4. - M A, fax : .��i�6) 486-2746'Phone'-(.426) 4.834-134 Fax_. 2 NU ber t 20 1 Addendum No. .2 to 9.42,61200.5 GeOtechnical RePOrt Proposed 3'W-*.ShorI. Plat L&.. Job N. SAI-12 Page 2 tt-h-e new re-Mdznm�o be g -a ioss S-CeCl.tm ve refbretced.dra .s pr"euted '-m thelbo -&o-Vpecss wou- Id ha�ost -of. thc. surfik".W...., ANrcuker. ib. rc-oviedcmutbel0W. thsurface o L6d B efouded on-Ievel b6nc.-hes 4ej� s; Tc.mmAd fththm' � 4n.4 p o.e .0 erosimn- d slide hazards Gf t Ite. buildifig. paid -is and, ..-u�,,,.redueethw aM back.6f the hou 119 on. thm si-te. U. 11&r t.h. ..e. AtwIp-pe'd c:o.nd6ifi6­ fi. Th� bascinent/foundation -vva sts. 4U Adhie ve. requWMAd f�ctb :i� Solt, pMS 1 - to reIateral. howe_VCT� 4hould P.-adcqqa�ely de'S*tui;0 V 50 vert-unvi1pan. W 4V, g -e ".ennn- -of th ge . .01 1. M-ica[ test ere excavate. 4 oti. t1w subijept. site -for: bu - SIX pits w jor topsoil. underlai-n -by g. ]ayer *7 f t. . I perty. These test pio0se ts encountered 0.8 -to w.7 ee of Pr-0 VC of'Iyeathend soils of fight-brow.m., loolse to. medjumrdtnse: ty sand'vm'h- a -a e Of Zm1, and. t ed are a., si. avier r— fmm 1 .6 t61.6--ft�f-thick. y. fine to B&mgr - n1jad+ ufn-,--&nS. clean. to. ghtly- de�omts* .-of ."bro N.vn-*g.. -a to ay., g-- T a silt Y d ra. sam Ight,0y. dense, g M. LS to 3 .2 f -t t. .1m. e L. and- -1 Lediu. ve -U - -occasion cobble, fro d. Groundmaiter'NOS h.0t encount­r..red b�4 4ny ofthetPst hep.t.h.., , Vier . - exp sana, to fine to. coam t CaNa-e. ..p 4pp. n *y" fret P. easily- M_ oderately high to high pc=cdbUit.Nr and would AII.ow stormwate 9/Z IZ0.0 -MuMim I if Ihe recommen. ons va our -hazard of ft site should be' refor �pms.mn. The - �Ontr `nd re - e -e - t on are. IUIIY ag. p c- .0.1 g (a. port -,for gradin& eromon rm. m. geotedhical re, ptio 4L unpleme * jed- dbs.&ved duflng and. -follo*in OMPICt"On. Of COnstn' n and IOU A layer, CIS I by'4. ally,: 8'=...dy dep * it on the uaf�,hce of. "the unde-d-yin. g fule- so-fi. W A the. -sody k. , -ter, pe.rc -Saor infi-Itradi.h., Sudace "rhe perched gr.ounNvaterAoudflowilateraly downd-u. aj()ng. the -k Pe cat bbm --s of -the underly-ing i--ine�-gram-ed dep-o-Sit. G. koun-dw-u-t-eis. would. eme-r-ge.1.0s LT[i 8z A,5S{3CIATF, TNC' November 26,2012 Addendum No. 2 to 9/2612005 Geotechnical Report Proposed .-Lot Short Plat L&A Job No. 5A 112 Page 3 where flie underlying fme-grained deposit is exposed, The per ched. gmundwater would accumulate and nke and build up sec .ale pressure substantially in the Net winter months. When the Pro I and the above the seepage zone. gressive groundwater see -page would erode sail in crosion gpts to the point the soil mass in and above. the seepage zone can no longer sustain its slouhing and slide -%rould. occur, This is how most slides occur in the coastal and steep w 1 gilt. g. sloped. areas i'n, the Ptiget Sound region. Since the test, pits was excavated to 10 feet deep;cmd did not encountered any. fine-grained soil., groundwater seepage should not occur within the property of and slide hazard of the propert�v should be minimal. Under the developed condition stormwatcr 'th vh ., stonn sewer systems whic over impervioul.; Stirfaces will be, collected and drained. awaywl do would reduce stonnwater seeping inter wid re * arpin groundtO the v ch 9 -Wrater under the Site. , %�W Therefore, stability of the lots Should. 'be enha iced under the developed condition. -1-he Puget Sound re.aion is in an acu"Ve seisinic zone.. The lots are underlain at shallow M d:epth *by medium-densc to dense advance outwash deposits of -moderately high to higli stslope faflures. Therefore, seisinic hazards. shear strength witb high resi'stance ascrain such as landsfides and lateral soil spreading., should be minimal 'as Iona as the site the grading. erosion ='ti.gafion.. drainage wntrol and re-iregctafion measures recommended in oux- 9/2-6/200-5 awotechnical report are fully implemented md observed during and follo-wing completion of construction.* Lique-facti• on is another forn, of seisr i st susceptible to n- c hazard., 17-he type- of Soil mO liquefaction during a strong earthquake. is saturated, loose,. fine sand- to silty fine sand deposits under a hi,o,,h groundwater conditi-on., Such loose deposits. Nvb.cn subjected to $trung .round. steal g, can be densified and decrease in volume. if groundwater in such. LIU &ASSOCIATES, INC* November 26, 2012 Addendum No. 2 to -9/2612005 Geotechni cal Report Proposed 3-Lot. Short Plat L& k Job No. 05A.1 12 PaL,i-e- 4 deposits is unable to drain quickly, pore water presst a m.* would increase, en pore. water pressure continues to build u�by prolongedground shaking,., a Oquick.." condition will be reached vN&e.n the pore water Pressure equals the e5ective overburden soil Pressure at some depths. Under this eonditlontbe. sand dposlt�111 tum. into a liquid wash. dosnder..lyina C state and loss. its load bearing Capacity. The sanc�v advance out the site, however are of high penneability. Water can dram' quicklv in these -deposits and buildupof pore waterpressure will unl ikely to occur M' these deposits. Also..., there is fl, absence of an extensive groundwater stable under the site ;,xt shallow depth. Therefore, the liquefaction hazard ofthesite should also be. mM*='.aI. 014 . Based on the above -discuss1" it is our oPIL"on at .6M th 1. Minimum buffer does not apply as the houses to be developed on Lots A and B woaid be founded orl level benches step-cut below the steep. slopes and with the steep slopes eliminated wittu"n the house building pads.. The houses should be able to maintain stabilit,vr as long as the basement/foundations walls on the back- and the howses themselvcs 'JU (T fal - res. m. desi�med -with adequate. factors of safety against sliding and overturnin, . 2. Alteration of the ero-sion or landslide hazard are -as frorn the proposed development will beyond p re - I -to ad-jacent PT W, not mereotse surficee water discharge or sed"ment -Werdes, is and '11not will not decr -case slope stability on. adjacent propertie� , - NVI developed conditions. U1 oar adverswal,y •impact other crifical areas as long as the recommendations " 9/ 2 6 t2. 0 0 5 ge. otechnical report are fully implemented and observed ding and following completion of consitruction. •pment of this prof ect should com-ply Based on our review of the. civ*l des"gn plans, develo with design standards. in compliance ard areas. should be 4. Removal and. re -vegetation. in. erosion mid slide hazz Nvi th the recommendations In our 9/26/2005 geotechnic al report. Lru & assoctATEs, INC* November 26, 20-1.2 Addendum N-0. 2. to 9,126Le,)005 Geotechnical Report Proposed '..'"Lot Short Plat L&A Job No. 5*A 11. 2 Pace 5 anng gand foundation construct" 5. Cie , I rading ion. . A ould be carried out and completed from May 1 " to October I" of each ye4r. The . erosion mitigation and drainage control recommendations in out 9026/2005 geoteclu-iical- report should be compliedv%9'th and in place under operating conditions beyond the. above grading season. 6. Point discharge of stomiwirater sliould. not be allowed within the property.. Stonnmirater collected over imperv'ous surfaces of the development should be tiehtline-d to discharge 01 a . V mto an existmv. storms sewer or into infiltiwation trenches installed in the- gently sloped areas at the base of the slope. We are pleased to be of service to you on this project. Please feel free to contact us if you have any ques6ons m&*Lu.-ding this report or need further consultaion. t Yours very truly, LTU I "'.S OCIAT I N C J. S.. (Julian) Litt. Ph,D., P.E. Consulting Ge-otechnical Engineer LIU & INC.q LIU & ASSOCIATES, INC* Geatmhnical Engineering Eng-ineedng Geology June 26*2013 I Mr.. Bill. Ritter 8364 Olympic View Drive Edmonds, WA 984?G . Dear Mr. Ritter: Subject: Access Road Retaim qa.., Wall 3-Lot Short Plat 8364 Olympic View Drive Edmonds, Wasliingbjn L&A. Job No. 5-MI 2' INTRODUCTION Earth Scienoe We undersitand that an access road is to be waded to provide access upward from Olympic Vie-vv Drive to the lots of -the subject development project. This access road will require cutting into the slope on the Uph-111 Side and filling over the slope on the downhiil side of the road. NVe also understand that the cut bank and fill embankment fruM. Mad ,Vadi-n,jz,' will be supported by retaining walls. Presented in this report ire our recomn-iendations for the desip. of the access road retan"fing wa �l�. N,EVTEW OF -SUBSURFACE CONDITIONS Previously, we complete-d a geo-technical en. gincering study for this deve1ppment -:Pr -ct "th our findings of flie site conditions and geotee zal. recommendatiOnS presented in a wi Proposed 3.1wot Plat, 8364 Olympi - -C Vl' Ov, re ort. t"Iled '"Geotechnical Engineerinv studN p Drive, Fdmonds.- Wa�hinigyton," dated 9/26/2005. Our recommendations for the. access road retailim'_g walls are based on the subsurface condition's presented M* that report. Six 19213 Kenlake Place NE a Kenmore., Washington 98028 Phone. (425j 483=9134 a Fax. (425) 486..*2746 June 26, 2.013 Access Road Retain i ng Wal 1.5 — Ritter Short. Plat L&A Job No. 5A 11.2 Page 2 test pits we excavated on the site had encountered loosiz topsoil and silty flne Sand to about 3.5 to 5.0 feet deep, underlain by -medium-dense to dense ad-%rrance outwash deposiis of grdvelly fine to coarse sand. Growidwater was not encountered by the test pits DESCRIPTION OF RETAINING WALLS The retaining wall. on the uphill side of ac-cess road is To support a cut into the slope and this retainincr wall will be firom about 1.0 to 13.0 feet tall. The retaining wall on -the do-%-► .hil.l. side of the access road, will be supporting, fill and will be about 1.0 -to 3.0 feet RECOMMENDATIONS General The uphill retaining wall will b:e -up to 1.3 feet tall. Construdidn of conventional cast -in - place reinforced concrete wall or precast cast bl nek wall for the up'hill retaining wall would require over excavation of 10 to 1.2 feet behind the face of this wall. for ex*tcnded wall tboting. of the cast-T*.n-place concrete wall and for placement of gea�rid- reinforGe ent mesh in the wall backfill. 'IEs would cause extensive disturbance to the site. Therefore.,we recommend the uphill retaining wall ble consisting of a soldi - er pile wall. i0ich would require minini al excavation and cause little disturbance to the site. The downhill retaini-ng wall Will be up to 3 feet -tall and this wall may be a soldier pile gall or a precast -concrete block wal I. LIU &ASSOCIATES, INC. June '16, 7013 Access Road Retaining- Wal.1.5*1 —.Ritter-Sao r-t- Plat Page: 3, Soldie*r Pite-WAII A soldierpi to wa]] is. consisted of discrete soldier piles -vviitli tim''be r - boards :logged b constmeted with. steel beams ctwe'-en, the-- pile s to re-tain'' c'.ir'di bank. 'The- 'Soldier piles are.' inkrted m*- drilled hole's,fifled with con'cket . e. The.soldier Piles. 6-re MUNT.. sp. a'ce d at gence . iiwldi.i fe-backs. The b-but cet 6 f&n.-cie'nters'.. Ile. se.r. pile' wall ma'y,* be :ontilever o -.r' w#h fl. purpose'. of fie -backs- is to pro"vi*de. -ad di.Uonal lateral -force resistance. to the. wall., ror permanent s.pldier pile walls, such -m5-.-the subject. uphill wall,. the dn'lled. holes 'in the toe enibednient Of the soldic'r . piles should- be backfilled wig structural concrete With a . COMP.ressive strength off­Z.000 psi ut`2 8. da�►fs -and withlean mix (1 /2 sa*c'k of cemenlper Cubic - Yard- sand-C'-e-Tiient. ix) . ab.ove the soldicr* gille bedin.-ent.. Design. Soil Pressure . ia.gra r' Our reronimendadons -for the deign -of the %,61dierpile wall, either cantilever or with one level o--ti-*e�-baanchorsare. shown on Plate. I Design Soil Pr'cssur ]CI.tagram. f'ck- ,, XW t om e wal �r�avera-gofUt Cderm*!g�.the slope. behind thevall. that- mes. i-maiv --ft -th*-` Hat'e a -Do nod f�� an 'active soil hill r*etaininc01%grade.we reconu-nend. theup wall be dds'l* AI '61en Mtn ity). 11,-e actilr.e. toil pressure -may be pressure of 50 (equiv. W th '.EY.D. over - the toe eihb dnien of -e co teed by.' a passive: -sail pre5sure.pf 425, dv h sand deposit. soldier , 'iles. as t e soldier piles Will be.. toeincy dense'into, a. a ance oun-vas P These soil: pressures are It ate es. 'For the dekgn of'somier piles, the+ active soil -uimvalu ev tn . .on pres,c,;ure- should be appli-ed on one pfle-spacing above'die road I 'rant.. the wall and on onve pressure. to bye. appli.ed on pile toe e pilc'-widffi� elo b-W''; Nlivfle' the . passi embedment S'hou]-d be the less'er of onc ameter. The sold.i.er pile-s acmcy. and 2.5 pile -di P pile. E all. if in cantilever form. should be designed f r a nukininn-,n faaoil ssafetv of 1.65 W, LIU &ASSOCIATES,INC. � , June '.26.. 20,13 Access Road..Retaim"npa Walls —.-Ritter Short. Plat.. Pagre. 4 agat.n. st: slid- 'ing and overturnin -failures . - If wl"th one tee e* I of tieirbackn .aehors,tha.-soldier, He wall should be anal�7Led under service load -with. the pfle toe. embedi-nent deter.miued. at equ, flibrium of lateral. -forces and: tum*lnz moments. Fiatctorofsafetyisto be included in tfie wall bey increasing ' m this bedment bv -40%. toe em a.. Tieback AnCchbrs `Tti-e-back ahors shouldbeds to deve-:1op, an ultimate pullout resistance At least 'he nc*''igned M load at. the s- mr ice load level'.. '11e.1ical anchors. niaNr he used. as lie- 1.65 ti' es the anchor a, assemblies of back. anchors -for -the uph-111 retain.m. wall.. H-eli'c.,ci-.Ianchor*s.are compor5ed.*o.f. a. lead. section and. extension bats tbat.- Can b-e. SCrew M.dt-a- -slanted an,g-1e into. the gr..Qu.nd with a rdta'ting drill hi;a:d*. Th-ev Are com'merciacllv available :from A. B.. Chance., Camp=v and o*the'rs'. -flie lead sections are made* of single or multj'ple steet hefic'al fliahts �-Avelded onto a s. - steel bar. quare Sion b.var tain head. t _kt S Into e grouhd o t w the en Ilie 1ea�d sections are to be advanced ` to th coh it*. ' bars -added until the lead sections. are seated .int'0 -den-se Ads ane at as deposCapable tim Gut cj1paciv%ir of helical anchors -op". .8'require ut� -cap -ev d. pull-o The ul ate, pull'' de of d in a( h U1 C i s closet rc.14ted to. the Ov7pe. of so-H. the a*nchofs ate ns'talled , into. and t e torque req r -d V to turn and adva,nee the, fielical ter assemblies info- the soils,. We estimate. a. hell"Cal anchor with. -an S.-M.'ch and a. 10-inch. helices advanced the underlying. dense advan-ce ias't fo O't of penetration ourw ash de. -Posit at an avmgc torque of 2. 500 foot-pounds fort e should, be able to develop. -an ultimate pull-out capa*e,ity of 2-5 kips per anchor. When. cat. 75%; of the omplet d, stress -tested. then locked aff C , the helical anchors should -e stress -tested. b de.5.ig*n . anchor -load against walers Mounted on the -soldi;rpiles-. LIU &ASSOCIATES, INC. June 2.6. 2013 Access Road Retaining Walls —River Short Plat L&A Job No.. 5,Al 12 pkee 5 Refical Anchor Testing IEach helical anchor should be proof-testcd to 165% of its design service loads (P). An initial seatm'�eload of 1.000 pounds should be applied to the helical anchors to remove Cow - slack fi-am the me-hor assemblies. The. test load should *beappli-ed in 0.33.E increments up to 1.65P and record the corresponding movement of anchor .head at each load level. The anchor head movement shall be measured with a dial Page accurate to 0.001 inch affixed on an unyieldin.,gy reference point. The 1.6 5P load level of th-e perform. ance tests should be held for 10 minutes with the imchor head. movement -recorded at every, 1, 2, 3. 5 and 10 mi-nutes. The anchor tests will be acceptable if the creep rate of the anchors do not exceed 0.080 M*'c..b ove-r the 10 Miffiftutes time. After completion of tests, the helical anchors should. be locked. off against the walers at 75% off"the r desian. load.. Long. -Tern Corrosion Protection The exposed portion of the Steel members of the soldier piles plus one foot embedment in. concrete IM should he sandblasted and coated with prote di - ve paint for long-term choirs and emoston. protection.. The Healers, if used, should also be coated. The helical an. accessories shall be galvanized fors .long-term corrosion protecti-oyn.* The timber laggina boards should be of treated -wood suditable for outdoor and soil contact use for Protection acramst deca-�.'. M 01 Timber Lagging Boards Design and, Installation. Timber lagging boards, may be deli gned for one half of the above recommended active. soil pressure to account fog- soil arching effect between -the soldier piles. After soldier piles are completed, excavation f6r rading of accessroad should proceed. Timber- LIU &ASSOCIATES, INC* June 26, 2013 Access,Road Ret��ning Wa11s — Ritter Shirt Plat T,&A Job No, SA112 Page fi lagging boards are installed as exca'vation i3roaresses downward. Timber boards should extend at least one foot below the road surface. A lzever of icon -woven filter fabric, such as N rafi. .14UNS or equal, should be tacked onto the back of the lagging boards. The lagging boards should bye shimmed to leave a 1/4-inch gap betwee i the boards. The fabric liner and the gaps would all water behind the wall to bleed out while keeping poll in place. Voids behind the b-oards should be filled w .1 to bc ol with clean. onsito sand soi rodded down to a fight contact with X e lagginer boards. C CLOSURE We are pleased to be of service to 'you on thi's projiect. Please feel free to call -us if Vou have any- questions regarding this report. One plate attached Yaurs very truly, LIU* & ASSOCTA S. INC. J .'s. i liars) sI ( Lim., Ph.D., P.E. Cons.u. Itina G e-ote ei cal Engineer LIU &ASSOCIATES, INC. H u Lili &ASSOCIATES, INC. 4nee..fi Geotethoical Eng-.1 .11,g - Engineering Geology - Earth 56ehce: SOIL PRESSURE DIAGRAM SOLDIER PILE; WALL. m- RITTER SHORT PLAT 8364 C LY'M:PIC VIEW DRIVE EDMONDS, I/VASHINGTO�i FOWN0. 5A .112 DoATE 6/26/2-0-1-3 PLATE I LIU & ASSOCIATES, MC. Geatechnical Engineering Engineering Geology Earth Sdence August 27, 2013 Mr-. Bill Ritter 8364 Olympic View Drive Edmonds., WA 98026 Dear eft. Ritter: Subject.- Geaiechnical Design. Plans Review Ritter Short. Plat 8364 Olympic View Drive Edmonds, Washington L&A Job; No. 5A1 12 Puns: Review We have Completed a geotechnical review of the design plans for the subject project. It is our opinir on that the design plans are in compliance with the recommendations inour 6" 9/26/200D. geotechnical report. Drive wa Retaining Wall De We recommended a soldier pile wall to retain the cut bank required for grading of the proposed drivcwky and presented our recommendations of design soil parameters and static lateral sod pressure for the design of this wall in our 6��'.�6/2013 letter report. To c 'der seismic loading on the wall, an inverted triangular distribution soil pressure onsl diagram should be applied on the -wall, in addition to the static soil pr.essure. The. pressure di.agrarn should have a m . 4 pressure of 13.5H (considering the hackslo rising av,raLy from the Nvall) at the top of the wall, where H is the expose d height cif he all, reducing linearly down to zero at the base of the wall. "nie factor of safe ry can be reduced to 1.15 against sliding and L25 against over' tuming. when considerm'g seismi V c 19-213 Ken -lake Place NE 6 Kenmore, Washington 918028 Phone (425) 4834134 a Fax (425) d86-z74s r. August 27, 2013 Ritter Short Plat L&A Job No. 5A 112 Page 2 loading.. For se-iismic diesign the allowable stresses of the structural elements ofAhe wall may be increased. by one third. Please contact us if you bavc questions. 0; Yours very truly, Lru sOC1a LINC, INC J. S. (Julian.) Liu, Pb.D.t P.E. Consul.ting Geotec+nical Engineer LIiT &ASSOCIATES, INC* LIU& ASSOCIATES, INC. Geotechnical Engineering Engineering Geology Earth Science August 16, 2417 Mr. Joe Smeby Omega Engineering, Inc. 2707 Wetmore Avenue Everett, WA 98201 Dear Mr. Smeby: Subject: Design Plans Review Ritter Short Plat 8364 Olympic View Drive Edmonds, Washington L&A Job No. 5A112 At your request, we have completed a geotechnica.l review of the design plans for the subject project. It is our opinion that the design plans are substantially in complia nce with the recommendations in our 9/26/2005 eotechnic g al report and subsequent correspondences. Cut banks in suriicial loose sand soil in excavation for detention ' ion pipe installation may cave suddenly. Therefore, cut banks should be stabilized with• shoring blocks during construction. Yours very truly, LRJ & ASSOCIATES, INC. J. S. (Julian) Liu, Ph.D., P.E. Principal 19213 Kenlake Place NE a Kenmore, Washington 98028 Phone (425) 483-9134 Fax (425) 486-2746 - LIU ASSOCIATES9 INC. Geotechnical Engineering Engineering Geology. Earth Science October 2, 2017 Mr. Joe Smeby Omega Engineering, Inc. 2707 Wetmore Avenue' Everett, WA 98201 Dear Mr. Smeby: Subject: Design Plans Review Ritter ShortPlat 8364 Olympic View Drive Edmonds, Washington I.&A Job No. 5A112 At your request, we have completed a geotechnical review of the design. plans, including Vegetation Management Plan, prepared .by Omega Engineering, Inc.,. for the subject project. It is our opinion that the. design plans are substantially in compliance with the recommendations in ..our 9/26/2005 geotechnical report and subsequent correspondences. The Vegetation Management Plan is also' -acceptable. Cut banks in surficial loose sand soil in excavation for detention pipe installation may cave suddenly. Therefore, cut banks should be stabilized with shoring blocks during construction. . .Please contact us if you. have questions. 19213 Kenlake Place NE - Kenmore, Washington 98028 Ph -one (425) 483-9134 Fax (425) 486--2746 October 2, 2017 Ritter Short Plat L&A Job No. SA 112 Page 2 Yours very truly, LIU &ASSOCIATES, INC. J. S. (Julian) Liu, Ph.D., P.E. Principal LIU & ASSOCIATES, INC.