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HomeMy WebLinkAboutBLD2003-00724 Geotechnical Report t - I I SUBSURFACE EXPLORATION AND I GEOTECHNICAL ENGINEERING REPORT I Weaver Property , Tract 7 Dabob Cove I . 751 Beach Drive Jefferson County, Washington IPrepared for: Bill Weaver - Project No. 030031-002-01 • May 12, 2003 I Aspect Consulting, LLC I . 4, . �, PE7'�'nn I I ' 18802 k�C1STER� :4: ,SIONAL ;' . 9 I a( - EXPIRES 6/22/0 I es A. Peterson John L. Peterson, P.E. Senior Staff Engineer Associate Geotechnical Engineer apeterson@aspectconsulting.com jpeterson@aspectconsulting.com W:\ GEOTECH\030031 Weaver Slide Remediation\030031-002-01 Weaver Geotech Report.doc I - 1 - ' ASPECT CONSULTING l_ ' Contents ' 1 Project Information 1 1.1 Introduction 1 ' 1.1.1 Purpose and Scope 1 1.1.2 Authorization 1 1.2 Project and Site Description 1 ' 1.2.1 Exploration Borings 2 1.3 Subsurface Conditions 3 1.3.1 Stratigraphy 3 1.3.2 Ground Water 4 2 Geologic Hazards and Mitigation 5 I 2.1 Seismic Hazards and Recommended Mitigation 5 2.1.1 Surficial Ground Rupture 5 2.1.2 Liquefaction 5 ' 2.1.3 Ground Motion 6 2.2 Landslide Hazards, Erosion Hazards and Mitigation 6 2.2.1 Rotational Type Landslides 6 ' 2.2.2 Surficial or Debris Landslides 6 2.2.3 Landslide Hazard Mitigation 7 3 Design Recommendations 8 3.1 Site Preparation 8 3.1.1 Clearing and Filling 8 ' 3.1.2 Site Disturbance 8 3.2 Structural Fill 8 3.3 Catchment Wall Recommendation 9 ' 3.3.1 Retaining wall Criteria 9 3.3.2 Drainage Considerations 10 3.3.3 Retaining Wall Drains 10 I 3.4 Project Design and Construction Monitoring 10 Limitations 12 I - PROJECT NO.030031-002-01 • MAY 12, 2003 • i ' ASPECT CONSULTING • List of Figures 1 Vicinity Map 2 Site and Exploration Plan List of Appendices A Boring Logs I II i I I - IIii PROJECT NO. 030031-002-01 • MAY 12, 2003 1 • • M • ASPECT CONSULTING 1 1 Project Information 1 1 .1 Introduction 1 This report presents the results of our subsurface exploration and geotechnical engineering study for the Weaver property located in the Dabob Cove subdivision on the west side of the Toandos peninsula in Jefferson County, Washington. The location of the 1 property is presented on the Vicinity Map, Figure 1. The approximate locations of the subsurface explorations accomplished for this study are presented on the Site and Exploration Plan, Figure 2. In the event that any changes in the nature, design or ' location of the structure are planned, the conclusions and recommendations contained in this report should be reviewed and verified, or modified, as necessary. . 1.1.1 Purpose and Scope The purpose of this study was to provide geotechnical design recommendations to be utilized in the design and development of appropriate landslide remediation/mitigation at ' - the property. Our study included reviewing available geologic literature, drilling six exploration borings, and performing geologic studies to assess the type, thickness, distribution and physical properties of the subsurface sediments and shallow ground water conditions. Geotechnical engineering studies were conducted to formulate 1 retaining wall and drainage recommendations. This geotechnical report summarizes our current field work and offers geologic hazard mitigation and geotechnical engineering ' recommendations based on our present understanding of the project. 1.1.2 Authorization ' Written authorization to proceed with this study was granted by Mr. Bill Weaver on March 5, 2003. Our study was accomplished in general accordance with our revised scope of work proposal dated February 19, 2003. 1 1 .2 Project and Site Description This report was completed with an understanding of the project based on a site plan ' provided by Mr. Weaver, and by our discussions with Mr. Weaver. At the time of our exploration program, the site was occupied by a single-family, wood-frame residence that had been damaged by a landslide. Preliminary plans call for the installation of a landslide mitigation structure to protect the house that is planned to be remodeled. The property is situated on the waterfront along Dabob Bay. The site is an irregular ' rectangle in plan, with property dimensions of approximately 110 feet by approximately 140 feet. The upland portion of the site consisted of a west-facing hillside, with inclinations ranging from 1H:1V (Horizontal:Vertical) to 5H:1V. Overall vertical relief ' of the site was on the order of 100 feet. The low tide line of Dabob Bay formed the west property line. The site was bordered to the north by a private community waterfront i - ' PROJECT NO. 030031-002-01 • MAY 12,2003 1 4111 1110 • ASPECT CONSULTING • park, to the east st by existing homes and to the south by undeveloped, steeply sloping property. Vegetation around the existing residence consisted of grass lawn and landscaped shrubbery. Vegetation on the nearby natural slopes consisted primarily of berry bushes, ' fern and other low ground cover with scattered second- and third-growth fir trees. A landslide occurred in February 1998 above the house that resulted in approximately 50 to 100 cubic yards of slide debris that accumulated east of the house between the house and the toe of the slope. The accumulated slide debris originated from a larger slide upslope of the house and did significant damage to the house structure below. ' Our field study included a surface reconnaissance of the slopes and drilling six exploration borings on the site. The borings were completed adjacent to the existing house and on the slope above the house. The various types of sediments as well as the depths where characteristics of the sediments changed are indicated on the exploration logs presented in the Appendix. The depths indicated on the logs where conditions changed may represent gradational variations between sediment types. Changes logged ' between sample intervals in our borings were interpreted. Soils were classified in general accordance with American Society for Testing and Materials (ASTM)procedure D 2488, y "Standard Practice for Description and Identification of Soils (Visual-Manual ' Procedure)". Our explorations were approximately located in the field by measuring from existing site features shown on the site plan provided Mr. Weaver. • The conclusions and recommendations presented in this report are based on the six exploration borings completed for this study. Because of the nature of exploratory work below ground, extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may be present due to ' the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be ' necessary to re-evaluate specific recommendations in this report and make appropriate changes. ' 1.2.1 Exploration Borings The exploration borings were completed by advancing a 4-inch inside-diameter, hollow- stem auger with a tracked drill rig operated under subcontract to Aspect Consulting, LLC ' on April 1 and 2, 2003. During the drilling process, samples were obtained at generally 5-foot depth intervals. The borings were continuously observed and logged by a geological engineer from our firm. The exploration logs presented in the Appendix are based on the field logs, drilling action, and inspection of the samples secured. Disturbed but representative samples were obtained from the soil borings using the I Standard Penetration Test procedure in accordance with ASTM test method D-1586. This test and sampling method consists of driving a standard 2-inch outside-diameter split-barrel sampler a distance of 18 inches into the soil with a 140-pound hammer free- ' falling a distance of 30 inches. The number of blows for each 6-inch interval is recorded and the number of blows required to drive the sampler the final 12 inches is used to calculate the Standard Penetration Resistance ("N")or blow count. The resistance, or N- I „ 111 2 PROJECT NO. 030031-002-01 • MAY 12, 2003 • 1 � • ASPECT CONSULTING value,provides a measure of the relative de nsity of granular soils or the relative consistency of cohesive soils; these values are shown on the attached boring logs. The 1 samples obtained from the split-barrel sampler were classified in the field and representative portions placed in watertight containers. The samples were then transported to our laboratory for further visual classification and laboratory testing, as ' necessary. 1 .3 Subsurface Conditions 1 Subsurface conditions at the project site were inferred from the field explorations accomplished for this study, visual reconnaissance of the site and vicinity, and review of 1 applicable geologic literature. The site is characterized by a complex history of landslide activity both prehistoric and recent. In addition to the slide activity that has affected the existing house, evidence of an adjacent,unrelated prehistoric slide was encountered in the 1 southern borings EB-4 and EB-6. "In place"soils encountered below the most recent landslide activity consisted of prehistoric slide debris that was not active during the most recent landslide. The prehistoric slide activity is expressed in the overall topography of ' - the drainage basin that makes up Dabob Cove. As shown on the boring logs, fill soils from road construction were encountered in borings EB-3, EB-4,and EB-6. The fill soils consisted primarily of loose,silty sand and ' gravel or sandy silt and gravel with variable amounts of organic material. Recent slide debris was encountered in EB-1, EB-2, EB-4, EB-5 and EB-6. The recent slide debris consisted primarily of very loose sand with varying amounts of silt and gravel, or soft, 1 moist silt. All borings, except EB-1 and EB-2, encountered prehistoric slide debris below the recent slide debris. The older slide deposits consisted of both stiff to hard, silt and medium dense to dense sand. The older slide debris was underlain by medium dense to ' very dense brown sand in borings EB-1, EB-2,EB-3, and EB-5. These sediments were interpreted as pre-Fraser age, non-glacial outwash sediments. These sediments were encountered to the total explored depths of 16.5 feet in EB-1 and EB-2, 31.5 feet in EB-3, ' 41 feet in EB-5. The following section presents more detailed subsurface information organized from the upper(youngest)to the lower(oldest) sediment types. 1.3.1 Stratigraphy Fill Road fill was encountered in borings EB-3, EB-4, and EB-6. Thickness was 3 feet in ' EB-4 and 4 feet in EB-3 and EB-6. As noted on the exploration logs, the fill soils consisted of loose silty sand and gravel, or very stiff sandy silt and gravel. The fill is the ' result of historic, as well as recent earthmoving and road construction for the access driveway to the residence and the community park. Recent Slide Deposits ' Recent slide deposits were encountered in borings EB-1, EB-2, EB-4, EB-5, and EB-6. Thickness was 3 feet in EB-1 and E2-2, and 8 feet in EB-6. As noted on the exploration logs, the recent slide deposits consisted primarily of very loose to loose sand with I . variable amounts of silt and gravel, and soft to very stiff silt. The slide debris encountered in the upper several feet of EB-1 and EB-2 consisted of a localized debris I - PROJECT NO. 030031-002-01 • MAY 12, 2003 3 I • ASPECT CONSULTING i _ flow that accumulated behind the existing house. The slide debris originated as a semi- . intact block/blocks that translated and rotated down slope. The debris then cascaded over Ia"bench" formed by harder, prehistoric slide debris that remained in place. A combination of ground water seepage and availability of moving soil at the bench above the house and below the access road resulted in the slurry-type debris flow that impacted I the house. The upper, semi-intact slide mass moved approximately 5 feet vertically and approximately 10 feet horizontally before coming to rest in its current position. I Older Slide Deposits Older slide deposits were encountered below the recent slide deposits in all borings, except EB-1,EB-2, and EB-3. These soils consisted of medium dense to very dense sand I and medium stiff to hard silt. These sediments were deposited as a result of prehistoric landslide activity that occurred at an unknown time in the past. The sediments were disturbed but exhibited stronger general soil properties than the more recent slide debris I above. The prehistoric slide debris is consistent with large-scale topographic features of the area that suggest repeated,historic movement in the area. Characterization of the regional landslide activity and extent of the prehistoric slide debris was beyond the scope Iof study for slide mitigation related to the existing house. Pre-Fraser Non-Glacial Sediments Intact,pre-Fraser age,non-glacial outwash sand was encountered in all borings, except EB-4. This stratum continued to the entire depth explored in each boring where encountered. The soil consisted of medium dense to very dense, light brown sand with I trace amounts of silt and gravel. This stratum can be seen in the hill behind the waterfront parking area north of the subject site. These sediments appeared to be in-place and not appear to have been effected by past slide activity. However,the contact with I this geologic unit and the overlying prehistoric slide debris was not readily discernible from the collected samples. Due to the complexity of the landslide environment at the site, it is probable that portions of this unit have also been affected by prehistoric I landslide activity. 1.3.2 Ground Water I Ground water was encountered in EB-4 and EB-6 at the time of our field study. The depth to ground water in the exploration borings was measured at the time of drilling and ranged from approximately 11.5 feet in EB-4 to 15 feet in EB-6. At the time of drilling, I seepage was noted in the roadway near the borings, and a shallow ravine with flowing water was located south of the property outside the inferred current slide area. The ground water levels in the area will likely respond rapidly to precipitation, due to the I relatively high permeability of the sand encountered. Ground water seepage at the contact between the recent slide debris and the older underlying sediments was likely a primary driving factor for the recent slide activity. The January and February 1999 slides I • , occurred after several months of prolonged heavy precipitation. Increased ground water volumes and seepage are a direct result of precipitation. In addition to precipitation rates and duration, fluctuations in ground water levels will occur due to the time of the year, I . site usage, irrigation tidal influence and other factors such as off-site usage and water supply systems in the area. Seepage may also occur at random depths and locations in the non-uniform fill soils. U I 4 PROJECT NO. 030031-002-01 • MAY 12, 2003 1 • r ASPECT CONSULTING 2 n Geologic Hazards and Mitigation g g o ' The following discussion of potential geologic hazards is based on the geologic, surface and ground water conditions observed. Specific hazards addressed include landslide seismic and erosion hazards. 2.1 Seismic Hazards and Recommended Mitigation Earthquakes regularly occur in the Puget Lowland. The vast majority of these events are small and usually not felt. However, large earthquakes do occur, as evidenced by the 1949, 7.2-magnitude event, the 1965, 6.5-magnitude event, and the recent 2001, 6.8- ' magnitude event. The 1949 earthquake appears to have been the largest in this area during recorded history. Generally, there are three types of potential geologic hazards associated with large seismic events at the site: 1) surficial ground rupture, 2) liquefaction, and 3) ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. Seismically induced landslides are discussed under the landslide hazard portion of this report. 2.1.1 Surficial Ground Rupture The nearest known, active fault trace to the project is the Seattle fault, although other north-south trending fault structures are likely located in the Hood Canal region that have not been fully characterized. Recent studies by the U.S. Geological Survey(e.g., Johnson et al., 1994, Origin and Evolution of the Seattle Fault and Seattle Basin, Washington, Geology, v. 22, p.71-74 and Johnson et al., 1999, Active Tectonics of the Seattle Fault ' and Central Puget Sound Washington-Implications for Earthquake Hazards, Geological Society of America Bulletin, July 1999, v. 111, n. 7, p. 1042-1053) suggest that the trace of an east-west trending thrust fault may project approximately 12 miles southeast of the project site in the vicinity of Bremerton. The trace of this fault can be seen south of Blakely Harbor on Bainbridge Island. According to the U.S. Geological Survey studies, the latest movement of this fault was about 1,100 years ago, resulting in about 20 feet of ' surficial displacement. This displacement can presently be seen in the form of raised, wave-cut beach terraces along Alki Point in West Seattle and Restoration Point at the south end of Bainbridge Island. The recurrence interval of movement along these fault systems is still unknown, although it is hypothesized to be on the order of several thousand years. Due to the suspected long recurrence interval, the distance from the fault, the potential for surficial ground rupture as a result of faulting is considered low during the expected life of the structure. ' 2.1.2 Liquefaction The recent and prehistoric landslide deposits in EB-4, EB-5, and EB-6 have a moderate to high potential for liquefaction (the temporary transformation of sediment into a fluid mass during seismically induced shaking) due to their disturbed, loose state, relatively 1 - ' PROJECT NO. 030031-002-01 • MAY 12, 2003 5 ASPECT CONSULTING s low silt content and poten tial tial for ground water seepage and accumulation. Elsewhere, the density and/or silt content of the soils are sufficiently high that liquefaction potential is ' low. Liquefaction hazard increases in loose sandy soils with increases in ground water levels. 2.1.3 Ground Motion Based on the site stratigraphy encountered and visual reconnaissance of the site, it is our 1 opinion that earthquake damage to the proposed structure, if founded on a suitable bearing stratum, would likely be caused by the intensity and magnitude of horizontal ground acceleration associated with the event. Structural design of the building should follow current UBC standards and take into consideration stress caused by seismically induced earth shaking. The site would be characterized in the UBC by a Seismic Zone Factor Z=0.30 and Soil Profile= Sc. 2.2 Landslide Hazards, Erosion Hazards and Mitigation The landslide that has affected the site was a rotational/translational landslide and a resulting debris flow. Discussions of these types of slides are presented below. - _ 2.2.1 Rotational Type Landslides The majority of the slide above the house consisted of a semi-intact, rotational/translational landslide. While not observed directly in our explorations, the slide likely moved along a gently curved or irregular shear surface. The slide transported ' approximately 500 to 1,000 cubic yards over the bench above the house,where it was deposited as a debris flow against the house. The majority of the slide remained semi- intact and stopped shortly after initial movement. The active, semi-intact slide debris is at risk for moving in the future under similar triggering conditions. The overall topography of the Dabob Cove property consists of a prominent ravine with a ' series of relatively flat benches indicative of a large, deep-seated rotational landslide during prehistoric time. With the exception of the current slide area and resulting damage, we saw no evidence of active rotational landslides elsewhere on the site. ' 2.2.2 Surficial or Debris Landslides The slide debris that impacted the house was essentially a surficial slide debris as the toe ' of the upper larger slide moved over the bench behind the house. Surficial slides commonly result from a significant increase in the moisture content within the upper colluvium layer on slopes. Increased moisture typically results from periods of extended, ' heavy precipitation, ground water seepage or concentrated surface water discharge onto a slope. As moisture increases, unit weight of the soil increases and shear strength within the soil decreases. Once shear strength is reduced relative to the force of gravity acting Ion the soil, rapid downslope movement of the affected soil and underlying vegetation occurs. The slide at the site was not a typical surficial landslide in that the source material was not the typical near-surface weathered soil layer. The impact of the fast- ' moving slide debris caused the structural damage to the house and accumulated to a depth of approximately 8 feet against the east wall of the house. The slide debris then flowed south and west around the house where it came to rest. 1 6 PROJECT NO.030031-002-01 • MAY 12, 2003 • • „„„„ w • ASPECT CONSULTING Given the available source of slide debris above the house, the risk of future surficial landslides and future damage to structures is high. Additionally, the risk of damage to ' site slopes and the existing access road and driveway to the beach park is also considered high. ' 2.2.3 Landslide Hazard Mitigation The risk of damage to the existing residence structure from landslide activity can be mitigated through installation of a passive retaining wall structure or catchment wall in conjunction with partial regarding of the area and performing drainage improvements. An active retaining wall system upslope of the house was considered but due to the complexity of the landslide terrain, and resulting length and depth of a proposed active restraint retaining wall, this alternative was not cost-effective and subsequently was not considered feasible. ' Erosion Hazards and Mitigation The slope above the existing residence, where most of the construction activity will take ' place, possesses high erosion potential. To mitigate and reduce the erosion hazard and potential for off-site sediment transport, we recommend the following: 1. Surface water should not be allowed to flow across the site over unprotected surfaces. 2. All storm water from the impermeable surfaces, including roadways and roofs, should be tightlined to approved drainage areas or storm water conveyance system and not be directed into the site surface soils. ' 3. Areas stripped of natural vegetation during construction should be replanted as soon as possible or otherwise protected. ' 4. Silt fences should be placed and maintained around the perimeter of the proposed construction areas throughout the entire construction phase of the project until ' permanent landscaping and storm water transport facilities have been installed. 5. Soils that are to be reused around the site should be stored in such a manner as to reduce erosion from the stockpile. Protective measures may include, but are not ' necessarily limited to, covering with plastic sheeting, the use of low stockpiles in flat areas, or the use of hay bales and/or additional silt fences around pile perimeters. 6. Provisions of the Jefferson County Grading and Drainage standards should be used on the site. I I PROJECT NO. 030031-002-01 • MAY 12, 2003 7 • ' ASPECT CONSULTING • • 3 Design Recommendations 1 3.1 Site Preparation 1 Those portions of the existing house and foundations that are not part of the proposed project should be removed. Any buried utilities that are to be abandoned should be removed or relocated if they are under building areas. The resulting depressions should ' be backfilled with structural fill, as discussed under Section 3.2, Structural Fill. 3.1.1 Clearing and Filling Site preparation of planned building and driveway areas should include removal of all trees, brush, debris and any other deleterious material. Organic topsoil should be removed and the remaining roots grubbed. Areas where loose surficial soils exist due to ' - grubbing operations should be considered as fill to the depth of disturbance and treated as subsequently recommended for structural fill placement. The upper 12 inches of the soils that will be exposed, as a result of stripping and grubbing should be recompacted to a firm and non-yielding condition. This recompacted fill will serve primarily as a working surface during construction. Loose to very loose sandy and gravelly soils were present in the existing surficial debris ' on the site. Because the densities of these soils are variable, random soft pockets may exist and the depth and extent of stripping can best be determined in the field by the geotechnical engineer. ' 3.1.2 Site Disturbance The on-site fill and slide debris deposit soils contain areas with a high percentage of fine- grained material (silt) or organic matter, which makes them moisture-sensitive (subject to disturbance when wet). The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened. If disturbance occurs, ' the softened soils should be removed and the area brought to grade with structural fill. Consideration should be given to protecting access and staging areas with an appropriate cover of crushed rock. 3.2 Structural Fill ' Structural fill will be necessary to establish desired grades,particularly in areas where unsuitable loose soils have been removed, such as in the vicinity of the proposed retaining wall and residence construction. All references to structural fill in this report refer to subgrade preparation, fill type, placement and compaction of materials as discussed in this section. Different percentages of compaction may be specified in other sections of this report for other purposes. 8 PROJECT NO. 030031-002-01 • MAY 12, 2003 • e • ASPECT CONSULTING 111- After overexcavation/stripping have been completed, the upper 12 inches of exposed pp p ground should be recompacted to 90 percent of the Modified Proctor maximum density using ASTM D 1557 as the standard. If the subgrade contains too much moisture, adequate recompaction may be difficult or impossible to obtain and should probably not be attempted. In lieu of recompaction, the area to receive fill can be blanketed with ' washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. The use of washed rock or quarry spalls should be considered for areas where filling activity may take place where periodic and/or cyclic inundation may occur during 1 high tide. After recompaction of the exposed ground is tested and approved, or a free-draining rock ' course is laid, structural fill may be placed to attain desired grades. Structural fill is defined as non-organic soil, acceptable to the geotechnical engineer,placed in maximum 8-inch-thick, loose,horizontal lifts with each lift being compacted to 95 percent of the Modified Proctor maximum density using ASTM D-1557 as the standard. The contractor should note that any proposed fill soils must be evaluated by Aspect Consulting prior to their use in fills. This would require that we have a sample of the ' material 48 hours in advance to perform a Proctor test and determine its field compaction standard. Soils in which the amount of fine-grained material (smaller than No. 200 sieve) is greater than approximately 5 percent(measured on the minus No. 4 sieve size) should ' be considered moisture-sensitive. Use of moisture-sensitive soil in structural fills should be limited to favorable, dry weather conditions. The on-site fill and slide debris deposit soils contained variable amounts of silt, and while considered moisture-sensitive, may be ' suitable for use as structural fill,provided they can be demonstrated to compact and perform well. If fill is placed during wet weather or if proper compaction cannot be obtained, a select import material consisting of free-draining gravel and/or sand should be ' used. Free-draining fill consists of non-organic soil with the amount of fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve fraction. 3.3 Catchment Wall Recommendation Based on the slope and access conditions at the site,a catchment wall built along the east ' wall of the proposed remodeled house will provide protection against future, similar landslide activity. This section of the report presents preliminary design considerations and criteria that should be considered in the design of the retaining wall. ' 3.3.1 Retaining wall Criteria The proposed location of the catchment wall at the back wall of the house would likely result in the wall footings bearing on the in-situ soils encountered in the area in our exploration borings. For design purposes,we recommend a maximum allowable soil bearing capacity of 3,000 pounds per square foot(psf) on properly prepared subgrade ' . soil. Subgrade preparation and backfill should be performed in accordance with the - recommendations presented in the Section 3.2, Structural Fill. In order to minimize the retaining wall height and required lateral design forces, we recommend incorporating a minimum 10-foot-wide,relatively flat area upslope of the wall, between the wall and the toe of the slope, to act as a run-out/catchment area. The PROJECT NO. 030031-002-01 • MAY 12, 2003 • 9 1 , ASPECT CONSULTING •• 410 0 go ... i- ' _ run-out area will also facilita te the removal of debris when necessary. Utilizing a 10- foot-wide run-out/catchment area, the wall should extend a minimum of 12 feet above Igrade level in order to accommodate the volume of material capable of being mobilized. The exposed portions of walls subject to impact loading should be designed to withstand a dynamic earth pressure of 90 pounds per cubic foot(pcf) to resist the impact of the Ilandslide, and a static equivalent fluid pressure of 60 pcf over the full height of the wall. These two loads would not occur simultaneously. A passive resistive footing pressure of 350 pcf can be utilized if the concrete is poured "neat" against the native soil. If re- Icompacted fill is used for resistance, a value of 250 pcf can be utilized. Any material which accumulates against the wall must be removed as soon as possible to Iprovide continuing protection for any subsequent event. 3.3.2 Drainage Considerations I Ground water occurrence and surface drainage within the landslide area is complex due to repeated movement and repositioning of potential confining layers. Ground water drainage is not considered an alternative due to the anticipated high cost and limitations I on the potential success of installing a ground water drainage system in the slide area. However, to further reduce the effect occurrence of landslide activity, we recommend a comprehensive surface water drainage plan be implemented for the roadway and the slide I . area in general. The existing culvert below the access road must be maintained in proper operating conditions. Under no circumstances should this culvert be allowed to overflow. Drainage improvements should include redirecting surface water from the upper road I area above the slide to a suitable discharge point near the beach, adequate storm flow ditches on the upslope side of the road and erosion control and energy dissipating outfall structures where appropriate. French drains may also be considered above the slide area I to the east to reduce the amount of near-surface ground water flow from entering the slide area. I 3.3.3 Retaining Wall Drains The retaining wall should be provided with drainage at the ground surface. Drains should consist of grading the soil behind the retaining wall with sufficient gradient to allow I gravity discharge from the center of the wall out to both ends. Roof and surface runoff from the residence should not discharge into the foundation drain system but should be handled by a separate,rigid tightline system routed to an appropriate discharge point. In I planning, exterior grades adjacent to walls should be sloped downward away from the structure to achieve surface drainage. If grades do not allow gravity flow of the foundation drains into the existing system, a sump may be required. I3.4 Project Design and Construction Monitoring At the time of this report, site grading, structural plans, and construction methods had not I _ been finalized. We are available to provide additional geotechnical consultation as the project design develops and possibly changes from that upon which this report is based. We recommend that Aspect Consulting perform a geotechnical review of the plans prior I . to final design completion. In this way, our earthwork and foundation recommendations may be properly interpreted and implemented in the design. I - 10 PROJECT NO. 030031-002-01 • MAY 12, 2003 • • ASPECT CONSULTING '-- We are also available to provide geotechnical engineering and monitoring services during construction. The integrity of the foundation depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Construction monitoring services are not part of this current scope of work. If these services are ' desired,please contact us and we will prepare a cost proposal. • 1 1 1 1 1 - PROJECT NO. 030031-002-01 • MAY 12, 2003 11 • ASPECT CONSULTING • 1_. Limitations 1 Work for this project was performed and this report prepared in accordance with generally accepted professional practices for the nature and conditions of work completed in the same or similar localities, at the time the work was performed. It is intended for the 1 exclusive use of Bill Weaver for specific application to the referenced property. This report does not represent a legal opinion. 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I •• �J! lY r(S �+!: 'r\... saa1k. 4+' .t, 0 ZM, / 4 f t v[ ,, ,/F .t'•" • 1 i' 1` .. ii 1 1 s 1 z1 .. } v1 I t". / i 1i.(( 1 I J4 ^�I i♦t17�/ 1s 11l 81I �I I' r ....4 ' Ig 'Camp Hirmoir%i.r „e �y-),(( � 27 /({fix IS=, ��� ' I' I Aspect Vicinity Map °,rE 05/12/03 PROJECT NO. ® p consulting °Faro ° 030031 IN-DEPTH PERSPECTIVE EO RFC ' Weaver Landslide Remediation A , °°yMs FIGURE NO. 179 Madrane Lane North 811 First Avenue 7N80 Bainbridge Island,WA 98110 Seattle,WA 98104 (208)780-9370 (208)-328-7443 Dabob Cove I-. • • Beach Park Parking Area 111 _ Upland Bluff I I I (1H 1V) Hood Canal \ \\ Existing Houses - Top of L4bc I Beach Slope Garage Exposed Headscarp - Toe of�' = 1 Beach _ Slope ` t EB { `. I EB-5' Existing \ ' Damaged House -' ` \ �� �k/-.., Top of ;. r f , Slope \ \ Surficial - 'r X `\\ > \1 ✓ ` {EBB 6 Slide Debris z\ / ; j�x, \x ; ). ` /"r , f�EB-4 Translational/Rotatio :I Slide Area / Pre-slide I Road Location Existing I Access Road Legend I EB-1 Boring Location CD Slide Area i 0 60 120 1 u u Il Feet I Site and Exploration Plan °E5e 05/12/03 PROJECT NO $ IN-DE tconsulting ar 030031 IN-DEPTH PERSPECTIVE eerto RFC Weaver Landslide Remediation `MS FIGURE NO. I 179 Madrona Lane North 811 Flrsl Avenue#480 e2aIZ909 Vond,WA 910 Sa06W Dabob Cove, Washington n • APPENDIX A i Boring Logs • o Well graded gravel and Terms Describing Relative Density and Consistency -- ` 'n GW gravel with sand, little to (2) ,� u, 0000t Density SPT blows/foot ono Cr) no fines Very Loose 0 to 4 - m112 e Q°o°Q Coarse Loose 4 to 10 Poorly-graded gravel Grained Soils i o a) w o 0 o 0 0 GP Medium Dense 10 to 30 It u, o °°°°° and gravel with sand, Test Symbols o little to no fines Dense 30 to 50 I N vo 0 0 0 0°o Very Dense >50 G =Grain Size d o c r°2° M = Moisture Content Consistency SPT(2)blows/foot A=AtterbergLimits °° o c Silty gravel and silty ° 2 •2 Coo°( GM gravel with sand Fine- Soft Soft 0 to 2 C =Chemical o 0 0 0 0 Grained Soils Soft 2 to 4 DD= Dry Density m o cr if) �� Medium Stiff 4 to 8 K=Permeability t . I Stiff 8 to 15 N �'��..�. Clayey gravel and Very Stiff 15 to 30 o > '� .j GC clayey gravel with sand Hard >30 0 ," Component Definitions L (3 I o Well graded sand and Descriptive Term Size Range and Sieve Number SW sand with gravel, little Boulders Larger than 12" LO N y .'.'.'.•.' d•..... to no fines Cobbles 3"to 12" o LL • Gravel 3"to No.4(4.75 mm) al Poorly graded sand 'o o Coarse Gravel 3"to 3/4" II ° in vn SP and sand with gravel, Fine Gravel 3/4"to No.4(4.75 mm) I 1v o . little to no fines 1.T2oo` z Sand No.4(4.75 mm)to No.200(0.075 mm) g Coarse Sand No.4(4.75 mm)to No. 10(2.00 mm) Silty sand and Medium Sand No. 10(2.00 mm)to No.40(0.425 mm) m p° CO�N SM silty sand with Fine Sand No.40(0.425 mm)to No.200(0.075 mm) II o ° a C U C . gravel Silt and Clay Smaller than No.200(0.075 mm) n_- Sc Clayey sand and (3)Estimated Percentage Moisture Content al clayey sand with gravel co Component Percentage by Dry-Absence of moisture, // Weight dusty,dry to the touch I Trace <5 Slightly Moist Perceptible Silt, sandy silt, gravelly silt, P > ,o ML silt with sand or gravel Few 5 to 10 moisture a, ° Little 15 to 25 Moist-Damp but no visible • CO r With -Non-primary coarse water 0o 1° rn Clayof low to medium constituents: > 15% �, v y j Very Moist Water visible but ,j L j CL plasticity; silty, sandy,or -Fines content between not free draining ° -0 j gravelly clay, lean clay 5%and 15% Wet-Visible free water,usually I - _ _ from below water table a - 7= Organic clay or silt of low Symbols _— OL plasticityy �' Blows/6"or I 0 __ Sampler Type \ portion of 6" N Cement grout ` / surface seal ° Elastic silt, clayey silt, silt yp j Sampler Type 2.0"OD o P yp with micaceous or ,5 seal ° diatomaceous fine sand or silt Sampler 'I' 3.0"OD Split-Spoon Sampler in w (SPT) - Filter pack with 'o o 3.25'OD Split Spoon Ring Sampler (4) :. :.:blank casing 11 rn Q o Clay of high plasticity, t° sandyor gravellyclay,fat Bulk sample Q::_:•_section I a) m = CH 3.0"OD Thin-Wall Tube Sampler • _'=.Screened casing m E clay with sand or gravel .•:or H droti (including Shelby tube) with filter ack o •° Grab Sample P m - 5 ii/i% 2.• End cap c o' ;iii/ Organic clay or silt of o Portion not recovered I L` J //;/7 OH medium to high t1) = !ii/ii, Percentage by dry weight (4) Depth i�/ii� plasticity (2) p of groundwater i, (SPT)Standard Penetration Test T (ASTM D 1586) 1 ATD At time of drilling 0 �, Peat, muck and other (s) Q Static water level(date) In General Accordance with I _ = m'o PT highly organic soils Standard cs) Practice for Description Combined USCS symbols used for and Identification of Soils(ASTM D-2488) fines between 5%and 15% Classifications of soils in this report are based on visual field and/or laboratory observations,which include density/consistency,moisture condition,grain size,and -plasticity estimates and should not be construed to imply field or laboratory testing unless presented herein.Visual-manual and/or laboratory classification methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System. IA - ec consuttinfg FIGURE 11,1 r-,:>T;,1rrr,4r=E,:r.VE Exploration Log Key 179 Madrone Lane North Tel:(206)780-9370 A- I Bainbridge Island,WA 98110 Fax:(206)780-9438 { AS 2Ctconsuttin Exploration IN-DEPTH PERSPEtaTIVE ig Project Number III gig) Exploration Number Sheet 030031 EB-1 1 of 1 Name Weaver Slide Remediation Ground Surface Elevation(ft) 0 IProject _, Location Dabob Bay,WA; Datum Driller/Equipment Davies Drilling/Hollow stem auger,8"OD,3-1/4"ID Date Start/Finish 4/1/2003-4/1/2003 - Hammer Weight/Drop 140 lb/30" Hole Diameter(in) 8" I This log is part of the report prepared by Aspect Consulting,LLC for the named project and should be read together only with tha report for o = a r o complete interpretation. This summary applies only to the location of m E s n o.- this exploration and at the time of exploration. Subsurface conditions m c 3, Blows/Foot I S @ T may change at this location with the passage of time. The data v oco p T 0 v) presented are a simplification of actual conditions encountered. m° m DESCRIPTION a 0 10 20 30 40 S-1 RECENT SLIDE DEBRIS 1 Ij • 3"Very loose,wet,brown,fine to medium SAND (SP) 1 A Soft,moist,gray SILT,few sand,trace organics (ML) 1 I FRASIER PRE-VASHON OUTWASH I 5'-6'Alternating hard-dense,moist,gray and brown SILT and SAND;some horizontal laminations in silt (SP/ML) 6'-6.5'Hard,moist,reddish-brown SANDY SILT,trace gravel (ML) I 5 18 S 2 25 50-5" 50+A I • - I Very dense,moist,light brown fine to coarse SAND,trace fine gravel;sand predominantly fine to medium (SP) I — 10 S r/ -3 _ 7 26 50+A • 42 I • I — 15 24 S 4 I 34 47 50+♦ / .l O • Bottom of boring at 16.5 feet. Backfilled with bentonite chips and cuttings. I - 0o N m_ d ❑- J c Q 3 Sampler Type(ST): Lab tests: ix O No Recovery A-Atterberg Limit o P-Permeability Logged by: JAP I o 2"OD Split Spoon Sampler M-Moisture Approved by: RFC a U 3"OD Dames&Moore Split-Spoon Ring Sampler Z Static Water Level Figure No. A-2 a T. Water Level at time of drilling(ATD) 1 ,,, Exploration As0 • 0 pectconsulting g • IN-DEPTH PERSPECTIVE Project Number Exploration Number Sheet 030031 EB-2 1 of 1 Name Weaver Slide Remediation Ground Surface Elevation(ft) 0 IProject __ Location Dabob Bay,WA; Datum Driller/Equipment Davies Drilling/Hollow stem auger,8"OD,3-1/4"ID Date Start/Finish 4/1/2003-4/1/2003 Hammer Weight/Drop 140 lb/30" Hole Diameter(in) 8" I This log is part of the report prepared by Aspect Consulting,LLC for the named project and should be read together only with that report for E r o complete interpretation. This summary applies only to the location of °'E a a..0 this exploration and at the time of exploration. Subsurface conditions .c ` Blows/Foot o T E >, may change at this location with the passage of time. The data v°o oio I 0 presented are a simplification of actual conditions encountered. co m m DESCRIPTION a 10 10 20 30 40 S-1 RECENT SLIDE DEBRIS 1 1 I / 2 Soft,moist,gray and brown mottled SANDY SILT with GRAVEL,trace 2 organics (ML) I FRASIER PRE-VASHON OUTWASH I Dense,moist,light brown fineSAND,trace coarse gravel,trace silt (SP) 5 p S-2 14 19 21 A . - O • I • - 10 S 3 •N • ,7 10 o gravel,faint horizontal laminations 19 28 • I • — 15 S-4 -Very dense,reddish staining 16'-16.5' 8 21 I % 35 50+♦ Q -g- Bottom of boring at 16.5'. Backfilled with bentonite chips and cuttings. • N T N • o- J N Q 3 Sampler Type(ST): Lab tests: M 0 No Recovery A-Atterberg Limit °m P-Permeability Logged by: JAP ® 2"OD Split Spoon Sampler M-Moisture Approved by: RFC a U 3"OD Dames&Moore Split-Spoon Ring Sampler Q Static Water Level Figure No. A-3 a 1 Water Level at time of drilling(ATD) • is I , AS 1ectconsuttin Exploration Lig IN-DEPTH PERSPECTI 9 Project Number Exploration Number Sheet 030031 EB-3 1 of 2 - Project Name Weaver Slide Remediation Ground Surface Elevation(ft) 15 -. Location Dabob Bay,WA; Datum Driller/Equipment Davies Drilling/Hollow stem auger,'8"OD,3-1/4"ID Date StarUFinish 4/1/2003-4/1/2003 ' Hammer Weight/Drop 140 lb/30" Hole Diameter(in) 8" I This log is part of the report prepared by Aspect Consulting,LLC for the named project and should be read together only with tha report for a L 3 c E complete his exploration interpretation. the timsummary of exploratioln. Subsurface location t c N Blows/Foot I S E >, may change at this location with the passage of time. The data °o oic p T C7 cn presented are a simplification of actual conditions encountered. m°m m DESCRIPTION ¢ 0 10 20 30 40 S-1 • ROAD FILL/RECENT SLIDE DEBRIS 8 • 1 12 , O Very stiff,moist,brown and gray SANDY SILT and GRAVEL (MLG) to • I 1 FRASIER PRE-VASHON OUTWASH Medium dense,moist,light brown fine to medium SAND,trace silt;faint 5 7 s-2 . horizontal laminae (SP) 6 11 16 • • I • I - 10 S-3 -Dense 14 _ p 21 • I I I — 15 / S-4 "Wet at 15.5',sand predominantly fine $ 1 s 26 • I - - 0 a • o- J Iin - '-' Sampler Type(ST): Lab tests: "' O No Recovery A-Atterberg Limit o P-Permeability Logged by: JAP a 2"OD Split Spoon Sampler M-Moisture Approved by: RFC d U 3"OD Dames&Moore Split-Spoon Ring Sampler Static Water Level Figure No. A-4 Q 1 Water Level at time of drilling(ATD) • • Iult Exploration Ltg AspectconS Ing Project Number Exploration Number • Sheet IN-DEPTH PERSPECTIVE 030031 EB-3 2 of 2 Project Name Weaver Slide Remediation Ground Surface Elevation(ft) 15 Location Dabob Bay,WA; Datum Driller/Equipment Davies Drilling/Hollow stem auger,8"OD,3-1/4"ID Date Start/Finish 4/1/2003-4/1/2003 ' Hammer Weight/Drop 140 lb/30" Hole Diameter(in) 8" I This log is part of the report prepared by Aspect Consulting,LLC for the named project and should be read together only with that report for E �, L o complete interpretation. This summary applies only to the location of a�E Y a a E this exploration and at the time of exploration. Subsurface conditions .c 3= Blows/Foot S E `` > may change at this location with the passage of time. The data �'0 o o o T c9 Cl) presented are a simplification of actual conditions encountered. m°m m DESCRIPTION a 0 10 20 30 40 j S-5 •Very dense,moist,light gray-brown,fine to medium,horizontal orange tl banding 21'-21.5' 33 50+. • I ` • 25 % S-6 : "Sand predominantly fine24 11 50 50+A I 1 • - 30 r/ 11 S7 39 50+. I ±, Bottom of boring at 31.5'. Backfilled with bentonite chips and cuttings. I I — 35 I - • 0 T 0 I i?- CO CC 3 Sampler Type(ST): Lab tests: cr O No Recovery A-Atterberg Limit Logged o P-Permeability 99 b Y JAP I ® 2"OD Split Spoon Sampler M-Moisture Approved by: RFC a U 3"OD Dames&Moore Split-Spoon Ring Sampler Static Water Level Figure No. A-4 a Y. Water Level at time of drilling(ATD) • i 1 As ectconsultin Exploration Lag �,N-DEPTH PERSPECTIvyE Project Number Exploration Number Sheet 030031 EB-4 1 of 2 Project Name Weaver Slide Remediation Ground Surface Elevation(ft) 25 I_, Location Dabob Bay,WA; Datum Driller/Equipment Davies Drilling/Hollow stem auger, 8"OD,3-1/4"ID Date Start/Finish 4/1/2003-4/1/2003 Hammer Weight/Drop 140 lb/30" Hole Diameter(in) 8" I This log is part of the report prepared by Aspect Consulting, LLC for the named proj�ect and should be read together only with that report for C' -a n a� complete his exe loration andtat the timsummary of exa loratiolnSSubsurface location �ond lions t E N E p p a 3_ Blows/Foot 0 S E '>n >, may change at this location with the passage of time. The data ;U o oio I p T c 0 cn presented are a simplification of actual conditions encountered. o m 0,DESCRIPTION a 0 10 20 30 40 S-1 "0 ROAD FILL b I 0 g° Loose,moist to wet,brown and black SILTY SAND and GRAVEL 2 O 0 (SM-GM) • Oo O0 J L RECENT SLIDE DEBRIS I - Loose, moist,mottled gray,brown and tan SILTY SAND,few organics (SM) I - 5 S2 4 A . 6 O PREHISTORIC SLIDE DEBRIS I Loose,wet, light brown fine to medium SAND (SP) 10 r S-3 3 2 g4 I I I 15 7-7 S-4 . •Medium dense, light gray-brown 4 I 6 9 I • - m a I • ao o- i w 3 Sampler Type(ST): Lab tests: it 0 No Recovery A-Atterberg Limit o — P-Permeability Logged by: JAP cco ® 2"OD Split Spoon Sampler M-Moisture Approved by: RFC I a 3"OD Dames&Moore Split-Spoon Ring Sampler Static Water Level Figure No. A-5 a T. Water Level at time of drilling(ATD) • r Exploration L'Sg • Aspectconsulting Project Number Exploration Number Sheet IN-DEPTH PERSPECTIVE 030031 EB-4 2 of 2 • Project Name Weaver Slide Remediation Ground Surface Elevation(ft) 25 • Location Dabob Bay,WA; Datum Driller/Equipment Davies Drilling/Hollow stem auger,8"OD,3-1/4"ID Date Start/Finish 4/1/2003-4/1/2003 Hammer Weight/Drop 140 lb/30" Hole Diameter(in) 8" I This log is part of the report prepared by Aspect Consulting LLC for the named project and should be read together only with that report fpr a)E a n E complete his exe loratio pandtat the time of exploration. Subsurface location t p p ° N Blows/Foot S ,, may change at this location with the passage of time. The data m ao o m I p T c9 v) presented are a simplification of actual conditions encountered. m° m DESCRIPTION < 0 10 20 30 40 S-5 b 13 16 A • • 25 % S 6 13 13 A o Very stiff,moist,gray and light brown mottled SILT (ML) I I 30 v S-7 -Gray,blocky,block ,fractured 7 3 I Bottom of boring at 31.5'. Backfilled with bentonite chips and cuttings. I I 35 I _ I • o a o J N I _ Sampler Type(ST): Lab tests: O No Recovery A-Atterberg Limit Logged o — P-Permeability 99 by: JAP I ® 2"OD Split Spoon Sampler M Moisture Approved by: RFC a U 3"OD Dames&Moore Split-Spoon Ring Sampler Static Water Level Figure No. A-5 a 1 Water Level at time of drilling(ATD) • ! I 'ilk AS ectconsultjn Exploration Mt ._ 9 Project Number Exploration Number Sheet IN-DEPTH PERSPECTIVE 030031 EB-5 1 of 2 Project Name Weaver Slide Remediation Ground Surface Elevation(ft) 37 Location Dabob Bay,WA; Datum Driller/Equipment Davies Drilling/Hollow stem auger,8"OD,3-1/4"ID Date Start/Finish 4/1/2003-4/2/2003 Hammer Weight/Drop 140 lb/30" Hole Diameter(in) 8" I This log is part of the report prepared by Aspect Consulting,LLC for the named project and should be read together only with that report for E = m r o complete interpretation. This summary applies only to the location of °'E w a a this exploration and at the time of exploration. Subsurface conditions r o c. Blows/Foot aai S E i >, may change at this location with the passage of time. The data s--0 o CO I p T ct/3 0 m presented are a simplification of actual conditions encountered. m° co a o 10 20 30 40 S-1 RECENT SLIDE DEBRIS 1-12" I 0 Very loose,moist,light gray fine to medium SAND (SP) ,113 ;iI i. t • • I — 5 S2 1 ♦ 2 O i -i—Soft,moist,light gray-brown SILT,trace sand;blocky (ML) 1 r- 10 S3 2 1 ice! ! .•! %• •i. ?i WIT — 15 S-4 •Light brown grading to gray,fractured,slickensides e, 2 lImi i 1 re Si -b be; ftI — ' ,20 ` � S-5 PREHISTORIC SLIDE DEBRIS k 14 A / .- Hard,moist,olive gray �s oto gray SILT;fractures,slickensides (ML) :� 23 N O ��. �. 1 O i16 j- V ix W 41' le Q �r Sampler Type(ST): Lab tests: cn O No Recovery A-Atterberg Limit o — P-Permeability Logged by: JAP m ® 2"OD Split Spoon Sampler M-Moisture Approved by: RFC I a U 3"OD Dames&Moore Split-Spoon Ring Sampler a Static Water Level Figure No. A-6 a 1 Water Level at time of drilling(ATD) • • AS eCtconsuttin Exploration L'6g ". g Project Number Exploration Number Sheet IN-DEPTH PERSPECTIVE 030031 EB-5 2 of 2 Project Name Weaver Slide Remediation Ground Surface Elevation(ft) 37 I.- Location Dabob Bay,WA; Datum Driller/Equipment Davies Drilling/Hollow stem auger,8"OD,3-1/4"ID Date Start/Finish 4/1/2003-4/2/2003 Hammer Weight/Drop 140 lb/30" Hole Diameter(in) 8" I This log is part of the report prepared by Aspect Consulting,LLC for the named project and should be read together only with that report for aci = a t o complete interpretation. This summary applies only to the location of °'E a a E this exploration and at the time of exploration. Subsurface conditions t c '' Blows/Foot S > may change at this location with the passage of time. The data ;--o oco I p T m (7 rn presented are a simplification of actual conditions encountered. m° m te DESCRIPTION < 0 10 20 30 40 S-6 •Gray 50-5" 501 • Ii FRASIER PRE-VASHON OUTWASH Very dense,moist,light brown fine to medium sand (SP) 1- 30 I. —, ss S 7 $: 50-6" 50+♦ 4 • is •• I • 35 �r 26 I S-8 •Horizontal laminae a 50-6^ 50+A ., k 1. • T�: MP re 40 S {:• 9 :5os" 50+A 26 Bottom of boring at 41'. Backfilled with bentonite chips and cuttings to 10'. Placed 1.25"PVC 10-slot screen 10'-5', 1.25"PVC blank 5'-surface. I 8-12 silica sand filter pack 11'-4'. Cuttings to surface. I r 45 0 0 a- N m I •• u uj J- co ce '--' Sampler Type(ST): Lab tests: cc O No Recovery A-Atterberg Limit o 77 — P-Permeability Logged by: JAP 2"OD Split Spoon Sampler M-Moisture Approved by: RFC a IF 3"OD Dames&Moore Split-Spoon Ring Sampler Q Static Water Level Figure No. A-6 a 1 Water Level at time of drilling(ATD) 0 QSp@Ctconsulting I ExplOraOn L lit -- IN-DEPTH PERSPECTIVE Project Number Exploration Number Sheet 030031 EB-6 1 of 2 Project Name Weaver Slide Remediation Ground Surface Elevation(ft) 31 I • Location Dabob Bay,WA; Datum Driller/Equipment Davies Drilling/Hollow stem auger,8"OD,3-1/4"ID Date Start/Finish 4/2/2003-4/2/2003 Hammer Weight/Drop 140 lb/30" Hole Diameter(in) 8" 1 This log is part of the report prepared by Aspect Consulting,LLC for the c named project and should be read together only with that report for t -a a a E complete his exploration interpretation. the timsummary of exploratioln. Subsurface conditions t g 3 Blows/Foot 0° S E m >, may change at this location with the passage of time. The data m-0 o o I o T IA C9 rn presented-are a simplification of actual conditions encountered. m° m DESCRIPTION a 0 10 20 30 40 • S-1 0 0 FILL 3 I I 4 O - loose,moist,light brown SILTY SAND with GRAVEL;roots (SM-GM) - • 3 OI _ . CrC . 7 1- Op o PREHISTORIC SLIDE DEBRIS I :• 5 Medium dense,moist, light gray-brown,fine to medium SAND,trace silt 5 S-2 (SP) 13 • O 14 i - I- Very stiff,moist,light gray-brown SILT;blocky,fractured (ML) - rs 1 — 10 S-3 i 3 16 I I- FRASIER PRE-VASHON OUTWASH1.1 I Dense,wet, light gray,fine to medium SAND (SP) 1 L 15 • IL I 7 S-4 L ,5 I • 16 O I — • 1 r 20 % S-5 •Medium dense,trace gravel 6 15 S - 6- m m I - o o _ J- - • co — 1 - W Sampler Type(ST): Lab tests: 3 A-Atterberg Limit o O No Recovery P-permeability Logged by: JAP co ® 2"OD Split Spoon Sampler M-Moisture Approved by: RFC 1 a U 3"OD Dames&Moore Split-Spoon Ring Sampler Static Water Level Figure No. A_7 1 Water Level at time of drilling(AID) • 1 ExploraYon La I %Aspectconsulting Project Numberall Exploration Number Sheet IN-DEPTH PERSPECTIVE 030031 EB-6 2 of 2 I . • Project Name Weaver Slide Remediation Ground Surface Elevation(ft) 31 Location Dabob Bay,WA; Datum Driller/Equipment Davies Drilling/Hollow stem auger,8"OD,3-1/4"ID Date Start/Finish 4/2/2003-4/2/2003 Hammer Weight/Drop 140 lb/30" Hole Diameter(in) 8" I This log is part of the report prepared by Aspect Consulting,LLC for the c named project and should be read together only with that report for m o E complete his exploration interpretation. the timsummary of exploration. Subsurface location r E 3. Blows/Foot p aai S E `L >, may change at this location with the passage of time. The data m o o I p T 0 v) presented are a simplification of actual conditions encountered. m° in DESCRIPTION a 0 10 20 30 40 S-6 'Very dense — r 1 I 0A 50+21 30 I • — 30 7 S 7 •Dense - - 9 Z 25 I - ° - • Very stiff,moist,olive grading to gray SILT,trace sand;silt blocky, fractured (ML) "'_ t — 35 S-8 � 9 18 ♦ 1 1. I A 40 2 S-9 •Gray 10 A I O 13 Z6 Bottom of boring at 41.5'. Backfilled with cuttings to 33'. Placed 1.25"PVC blank 40'-32', 1.25"PVC 10-slot screen 32'-22', 1.25" PVC blank 22'-surface. 8-12 silica sand filter pack 33'-19'. Bentonite pellets and chips 19'-16.5'. Cuttings to surface. — 45 I _ a - f a c_ 0 J- y x a_ — I � Sampler Type(ST): Lab tests: it No Recovery A-Atterberg Limit Lo ed o — P-Permeability 99 b Y JAP 03 ® 2"OD Split Spoon Sampler M-Moisture Approved by: RFC a 3"OD Dames&Moore Split-Spoon Ring Sampler Static Water Level Figure No. A-7 a 1 Water Level at time of drilling(ATD)