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BLD REVIEWED BLD2020-1386+Geotechnical_Report+12.18.2020_5.32.25_PM+1955988NELSON GEOTECHNICAL ASSOCIATES. INC. September 16, 2020 Mr. Ryan Rotmark 17512 — 71" Avenue West Edmonds, WA 98026 Geotechnical Engineering Evaluation Rotmark Property Slope Stabilization and Retaining Wall 17512 — 715t Avenue West Edmonds, Washington NGA Project No. 1184120 17311-13511 Ave. N.E. Suite A-500 Woodinville, WA 98072 (425) 486-1669 www.nelsongeotech.com Dear Mr. Rotmark, This report summarizes the results of our geotechnical engineering investigation and evaluation of the proposed slope stabilization and retaining wall located at 17512 — 71s' Avenue West in Edmonds, Washington, as shown on the Vicinity Map in Figure 1. INTRODUCTION The purpose of this study is to explore and characterize the site's surface and subsurface conditions and to provide geotechnical recommendations for the proposed site improvements. Our services were completed in general accordance with our proposal signed by you on July 15, 2020. The site is currently occupied by an existing single-family residence within the gently sloping upper central portion of the site. A steep west -facing slope is located below and to the west of the existing residence and yard area, and extends down from the gently sloping upper bench area to the western property line and the neighboring property to the west. The slope is heavily vegetated with underbrush and trees. We understand that you have observed some settlement within the top of slope area throughout the years. We understand that you desire to improve the slope conditions to reduce the potential future impact to your residence and backyard and have requested a geotechnical evaluation be performed evaluating the slope conditions and providing recommendations for stabilizing the steep slope area utilizing a light retaining wall structure. The existing site conditions are shown on the Site Plan in Figure 2. Geotechnical Engineering Evaluation Rotmark Property Slope Stabilization and Retaining Wall Edmonds, Washington NGA File No 1184120 September 16, 2020 Page 2 SCOPE The purpose of this study is to explore and characterize the site subsurface conditions, and provide our opinions and recommendations regarding the existing slope stability and proposed retaining wall. Specifically, our scope of services included the following: 1. Review available soils and geologic maps of the area. 2. Explore the subsurface soil and groundwater conditions within the site with two up to 30 feet deep borings, using a limited -access track -mounted drill rig. The drill rig was subcontracted by NGA. 3. Map the conditions on the slope and evaluate current slope stability conditions and perform shallow hand explorations, as needed. 4. Provide recommendations for improving slope stability, including the use of light retaining structures, erosion control systems, and drainage improvements. 5. Provide recommendations for long term slope maintenance. 6. Document the results of our explorations, findings, conclusions, and recommendations in a written geotechnical report. SITE CONDITIONS Surface Conditions The site consists of an irregular -shaped parcel covering approximately 0.31 acres. The site is occupied with an existing single-family residence within the central portion of the property. The property is bordered to the north, south and west by existing residential properties, and to the east by 71s' Avenue West. The ground surface within the upper eastern and central portion of the property is relatively level to gently sloping down from east to the west. A steep west -facing slope descends from the upper yard area immediately west of the residence to the lower western property line and neighboring properties at gradients in the range of 18 to 32 degrees (32 to 62 percent) as shown on Cross Sections A -A' and B-B' in Figures 3 and 4, respectively. The overall vertical relief of the steep slope area is up to approximately 20 feet. The site is vegetated with grass, landscaping plants, underbrush and young to mature trees. We observed some indications of minor erosion and settlement within the exposed soils on the steep slope below and to the west of the residence; however, we did not observe any indications of deep-seated landslides within or in the vicinity of the subject site during our site visit on August 19, 2020. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No 1184120 Rotmark Property Slope Stabilization and Retaining Wall September 16, 2020 Edmonds, Washington Page 3 Subsurface Conditions Geology: The Geologic map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington (MF-1541), by James P. Minard, (USGS, 1983) was reviewed for this site. This geologic map indicates the location of the subject property is underlain by Vashon till (Qvt). Vashon till typically consists of a concrete -like mixture of relatively equal parts of silt, sand, and gravel. Our explorations generally encountered surficial undocumented fill soils underlain by silty fine to medium sand with gravel that we interpreted as native glacial till soils. Explorations: The subsurface conditions within the site were explored on August 19, 2020 by drilling three borings to depths in the range of 5.5 to 16.5 feet below the existing ground surface using a track - mounted, limited -access drill rig. The approximate locations of our explorations are shown on the Schematic Site Plan in Figure 2. A geologist from Nelson Geotechnical Associates, Inc. (NGA) was present during the explorations, examined the soils and geologic conditions encountered, obtained samples of the different soil types, and maintained logs of the explorations. A Standard Penetration Test (SPT) was performed on each of the samples during drilling to document soil density at depth. The SPT consists of driving a 2-inch outer - diameter, split -spoon sampler 18 inches using a 140-pound hammer falling 30 inches. The number of blows required to drive the sampler the final 12 inches is referred to as the "N" value and is presented on the boring logs. The N value is used to evaluate the strength and density of the deposit. The soils were visually classified in general accordance with the Unified Soil Classification System presented in Figure 5. The logs of our borings are attached to this letter and presented as Figures 6 through 8. We present a brief summary of the subsurface conditions in the following paragraph. For a detailed description of the subsurface conditions, the boring logs should be reviewed. At the surface of each of our borings, we generally encountered approximately 2.5 to 7.0 feet of loose, dark brown to gray silty fine to medium sand with varying amounts of gravel and organics that we interpreted as undocumented fill soils. Underlying the fill soils within each of our explorations, we encountered dense to very dense, gray silty fine to medium sand with gravel that we interpreted as native glacial till soils. The borings met refusal within the native glacial till soils at depths in the range of 5.5 to 15.5 feet below the existing ground surface. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No 1184120 Rotmark Property Slope Stabilization and Retaining Wall September 16, 2020 Edmonds, Washington Page 4 Hydrologic Conditions Groundwater seepage was not encountered in our explorations. If groundwater were to be encountered during construction, we would interpret it to be perched water. Perched water conditions may occur on the site during periods of wet weather. Perched water occurs when surface water infiltrates through less dense, more permeable soils and accumulates on top of underlying, less permeable soils. Perched water does not represent a regional groundwater "table" within the upper soil horizons. Perched water tends to vary spatially and is dependent upon the amount of rainfall. We would expect the amount of perched water to decrease during drier times of the year and increase during wetter periods. SENSITIVE AREA EVALUATION Seismic Hazard The 2018 International Building Code (IBC) seismic design section provides a basis for seismic design of structures. Since medium dense or better native glacial till soils were generally encountered underlying the site at depth, the site conditions best fit the IBC description for Site Class D. Table 1 below provides seismic design parameters for the site that are in conformance with the 2018 IBC, which specifies a design earthquake having a two percent probability of occurrence in 50 years (return interval of 2,475 years), and the 2008 USGS seismic hazard maps. Table 1— 2018 IBC Seismic Design Parameters Site Class Spectral Acceleration Spectral Acceleration Site Coefficients Design Spectral at 0.2 sec. (g) at 1.0 sec. (g) Response SS S1 Parameters Fa Fv Sys Sol D 1.305 0.512 1.000 1.500 0.870 0.512 The spectral response accelerations were obtained from the USGS Earthquake Hazards Program Interpolated Probabilistic Ground Motion website (2008 data) for the project latitude and longitude. Hazards associated with seismic activity include liquefaction potential and amplification of ground motion. Liquefaction is caused by a rise in pore pressures in a loose, fine sand deposit beneath the groundwater table. It is our opinion that the competent native glacial till soils interpreted to underlie the site have a low potential for liquefaction or amplification of ground motion. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No 1184120 Rotmark Property Slope Stabilization and Retaining Wall September 16, 2020 Edmonds, Washington Page 5 The competent glacial till soils interpreted to form the core of the site slope are considered stable with respect to deep-seated slope failures. However, the loose surficial soils and undocumented fill on and near the sloping portions of the site have the potential for shallow sloughing failures during seismic events. Such events should not affect the proposed retaining wall, slope stabilization measures and existing residence provide the design recommendations in this letter are incorporated into the overall site stabilization. Landslide Hazard/Slope Stability The criteria used for evaluation of landslide hazards include soil type, slope gradient, and groundwater conditions. A steep west -facing slope is located below and to the west of the residence that descends from an upper yard area to the lower western portion of the property at gradients in the range of 18 to 32 degrees (32 to 62 percent) as shown on Cross Sections A -A' and B-B' in Figures 3 and 4, respectively. The overall height of the steep slope below and to the west of the residence is up to approximately 20 feet. We did not observe significant evidence of past deep-seated slope instability along the subject slope during our site visit, however we did observe indications of erosion and settlement of the exposed surficial soils along the top of the steep slope area. Our explorations and observations indicate that the core of the steep slope consists primarily of dense glacial till soils at depth. Inclinations up to 32 degrees on the slope indicate high strength and internal friction angle within the underlying soils. Relatively shallow failures as well as surficial erosion are natural processes and should be expected on these slopes especially within the loose surficial soils and the undocumented fill soils on the slopes. It is our opinion that while there is potential for on -going sloughing, soil creep, and shallow failures within the loose surficial and undocumented fill soils on the steep slope as has been observed throughout the years, there is not a significant potential for deep- seated rotational slope failures under current site conditions. Investigating and improving the existing residence drainage systems, as well as proper site grading and the construction of the proposed retaining wall as recommended in this report should help improve and maintain current stability conditions within the site. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No 1184120 Rotmark Property Slope Stabilization and Retaining Wall September 16, 2020 Edmonds, Washington Page 6 CONCLUSIONS AND RECOMMENDATIONS General Based on our explorations and observations of the current conditions in the vicinity of the top of slope area, it is our opinion that the proposed installation of a pin pile retaining wall along the top of the steep slope below the residence is feasible from a geotechnical standpoint. Due to the presence of loose undocumented fill soils along the top of the steep slope area, it is also our opinion that these soils may experience continued settlement and/or shallow failures potentially impacting the adjacent yard area and ultimately the residence and existing utilities especially during a seismic event if the proposed retaining wall is not constructed to support the top of slope area. Additionally, it is imperative that the existing residence drainage systems are investigated and improved, as needed, such that all stormwater is accounted for and is tightlined to the base of the steep slopes or an approved point of discharge. In our opinion, construction of the proposed retaining wall should aid in stabilizing the top of slope area and limit potential impacts associated with potential slope movements on the yard area and residence structure. Due to site constraints, and based on our explorations and site observations, we recommend the use of a "light" retaining wall to protect and support the top of the slope area, along with erosion control and drainage systems to be utilized below the new retaining wall. We have provided recommendations for design and installation of a new pipe pile wall with timber lagging along the top of the steep slope. We understand that the anticipated exposed wall height may be up to eight feet. Due to the exposed height of the wall we anticipate grouted tie -back anchors will be needed to support lateral loads. We have also provided recommendations for improvements on the slope below the wall to lessen the potential for future sliding on the slope within the vicinity of the retaining wall. Detailed recommendations regarding the proposed retaining wall design and installation have been included in the following subsections of this report. The surficial soils encountered on this site are considered moisture -sensitive and may disturb easily when wet. To lessen the potential impacts of construction and to reduce cost overruns and delays, we recommend that construction take place during the drier summer months if possible. If construction takes place during the rainy months, additional expenses and delays should be expected. These extra expenses could include additional erosion control and temporary drainage measures to protect the proposed development area including placement of a blanket of rock spalls to protect exposed subgrades, and the need for importing all-weather materials for structural fill. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No 1184120 Rotmark Property Slope Stabilization and Retaining Wall September 16, 2020 Edmonds, Washington Page 7 All construction operations and drainage improvements planned as part of this project should be planned and completed in a manner that enhances the stability of the steep slope, not reduces it. Any excavation spoils generated during site improvements should not be stockpiled on site but rather promptly hauled away. Also, all current and future runoff generated within the site should be collected and routed to a permanent discharge location at the bottom of the slope, or to an approved drainage system. Under no circumstances should water be allowed to concentrate or flow uncontrollably over the site slopes. The vegetation cover on the slope should be evaluated for compatibility with desired slope stability conditions, and a vegetation management plan should be devised to enhance slope stability. The proposed retaining wall and the slope should be monitored on an on -going basis after construction especially during the wet season for any signs of instability, and corrective actions promptly taken should any signs of instability be observed. Lawn clippings and any other household trash or debris should never be cast over the slope. Any future plans for structures near the slope or modifications to the slope should be specifically evaluated by NGA and approved by the City of Edmonds. Retaining Wall Design and Construction The proposed new retaining wall should consist of 3-inch square driven steel tubing or 2-inch pin piles bridged using pressure -treated timber lagging. We understand that the proposed retaining wall will be designed as a cantilever wall but will likely need to incorporate tieback anchors consisting of grouted anchors. The new retaining wall should generally be located along the top of the steep slope below and to the west of the existing residence. The final location, extent and heights of the wall should be determined by your structural engineer based on a topographic survey. However, we recommend that the exposed portion of the wall not exceed eight feet in height. The cross section detail of the proposed retaining wall is shown on the Schematic Pin Pile Retaining Wall Detail in Figure 9. The retaining wall should be designed by an experienced structural engineer licensed in the State of Washington. We understand that existing sewer utility pipes associated with the neighboring property to the north and the subject property are located within the vicinity of the proposed retaining wall and slope improvements. We understand that these sewer utilities trend in a north to south direction within the yard area to the west of the residence and then descend to an existing manhole structure along the base of the steep slope within the southwest corner of the property. We recommend that the structural engineer and contractor accurately locate and confirm the location of the existing sewer line utilities prior to finalizing the design and installation of the proposed retaining wall. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No 1184120 Rotmark Property Slope Stabilization and Retaining Wall September 16, 2020 Edmonds, Washington Page 8 We recommend that the 3-inch square tubing or 2-inch pin piles be galvanized extra strong (Schedule 80) steel pipe sections driven into place using a hand-held, 140-pound jackhammer or larger. The piles should be spaced at a maximum distance of four feet, and should be embedded a minimum of 5 feet into the competent native glacial till soils. Based on our explorations, we anticipate minimum embedment depths of the piles to range from 10 to 20 feet below the existing ground surface. Piles that do not meet this minimum embedment criterion should be rejected, and replacement piles should be driven after consulting with the structural engineer on the new pile locations. Our explorations encountered loose undocumented fills underlain by native glacial till deposits at depth within the proposed retaining wall location. If large particles or debris are present within the fill, there is a possibility that this material may obstruct some piles at shallow depths. There should be contingencies in the budget and design for additional/relocated piles to replace piles that may be obstructed by debris in the fill. In addition to the minimum recommended embedment into the native material, the piles should be driven to a refusal criterion of less than one inch of movement during 60 seconds of continuous driving. The wall lagging should be embedded a minimum of 12 inches into the finished slope face. Metal plates should be welded to the back of the pin piles to allow a connection for the timber lagging. We recommend that the voids behind the wall be backfilled with 2-inch clean crushed rock up to the top of the retaining wall. For the 2-inch crushed rock, the shoring wall should be designed to resist a lateral load resulting from a fluid with a unit weight of 45 pounds per cubic foot (pcf). These loads should be applied across the pile spacing above the excavation line. We recommend that all lateral pressures be transferred to tieback anchors. A uniform surcharge of 8H should be applied to the wall design to account for seismic loading, where H is the exposed height of the wall. We should be retained to review final plans, observe test pile installation prior to finalizing design, monitor installation of the piles, and evaluate pile refusal. Tiebacks General: We recommend that these systems consist of drilled, grouted tiebacks anchors due to the very dense nature of the native glacial till soils likely to be encountered. We recommend that one of the anchors be tested to a minimum of 200 percent of the design loads to confirm design values. We recommend that measurements be made by the contractor in the field at the time of tieback installation to verify that tiebacks do not encounter any existing structures or underground utilities. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No 1184120 Rotmark Property Slope Stabilization and Retaining Wall September 16, 2020 Edmonds, Washington Page 9 No -Load Zone: The anchor portion of all tiebacks must be located a sufficient distance behind the wall face to develop resistance within a stable soil mass. We recommend the anchorage be obtained behind an assumed no-load zone. The no-load zone is defined by a line extending horizontally from the base of the wall back towards the residence a distance of five feet. The line should then extend up from the base elevation at an angle from the horizontal of 60 degrees. We expect that some undocumented fill may exist beyond the no-load zone. We therefore recommend that the anchors be a minimum of 20 feet long. We recommend that we monitor soil conditions during anchor installation in order to evaluate adequate penetration into competent soils. Soil Design Values: The tiebacks will likely terminate in glacial soils below and behind the walls. For use in design of the anchors, we estimate an allowable grout to soil adhesion of 2000 pounds per square foot (psf) for anchors terminated within the native glacial soils. We recommend that we review anchor design and proposed installation methods. We should also observe anchor installation and testing. Tieback Installation and Testing: The contractor should be responsible for using equipment suited for the site conditions. We do not recommend the use of open -hole methods for the purpose of installing the tiebacks due to the potential for soil caving. Secondary grouting to increase soil adhesion may be used; however, if secondary grouting is used, the anchors should be tested using the methods outlined for the performance testing. One anchor should be performance tested to 200 percent of the anchor design capacity. The performance test should consist of cyclic loading in increments of 25 percent of the design load, as outlined in the Federal Highways Administration (FHA) report No. FHWA/RD-82/047. The test location should be determined in the field, based on soil conditions observed during anchor installation. All other tiebacks should be proof -tested to at least 130 percent of design capacity. Wall Drainage and Slope Improvements We recommend that after the pin piles are installed, a 4-inch perforated PVC pipe be placed behind the base of the wall and extended through the face of the retaining wall to aid in drainage through the wall. The pipe should be surrounded by a minimum of one foot of drain rock and the drain rock entirely wrapped in a heavy-duty filter fabric prior to the placement of the crushed rock backfill. The drain should be tightlined into the existing drain system or independently down to the base of the slope and adequately anchored to the slope. If tightlined to the base of the slope we recommend utilizing a 4-inch HDPE pipe terminating at a dispersion tee placed on a splash pad consisting of 2- to 4-inch quarry spalls. The backfill should be carefully placed as to not disturb or damage the tieback anchoring system. We should be retained to evaluate the crushed rock placement during construction. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No 1184120 Rotmark Property Slope Stabilization and Retaining Wall September 16, 2020 Edmonds, Washington Page 10 The areas along the top of the slope below the proposed wall should be improved, as needed by gently re -grading the over-steepened/loosened areas, removing the vegetative cover, compacting the exposed surface to a non -yielding condition, placing suitable erosion control systems on the prepared areas, and re -vegetating with deep-rooted drought -resistant plants. The actual improvement methods for these areas will be highly depended on the conditions encountered during construction. We should work with your contractor to determine the best course of action at the time of construction. We recommend that the exposed soil be covered with heavy duty jute netting. The jute netting should be staked at the top of the slope with 2- to 3-foot long metal rebar that has a metal "T" welded to the end. The mat should be staked to the surface every five feet. After the matting is placed, we recommended that deep-rooted vegetation be planted on the slope and grass seed be placed to re- establish vegetation growth. The vegetation should be maintained until established. We recommend a mixture of 25% each of the following vegetation: Snowberry (Symphoricarpos albus), Nootka rose (Rosa nutkana), Ocean Spray (Holodiscus discolor), and Oregon -grape (Manhonia nervosa). We should be retained to review and comment on the slope vegetation plan and observe the slope repairs. We also recommend that all residence downspouts and yard drains be investigated to understand where they are directed. At a minimum, we recommend that all residence downspouts and yard drains along with the proposed retaining wall drain be tightlined and directed to discharge to an approved location. USE OF THIS REPORT NGA has prepared this report for Mr. Ryan Rotmark and his agents, for use in the planning and design of the retaining wall and slope stabilization measures on this site only. This letter is a specific evaluation of the proposed timber retaining wall and steep slopes and should not be considered an evaluation of the entire site or the existing residence. There is potential for failures to continue to occur on the slope near and below the wall. This potential can be reduced by maintaining the drainage systems and refraining from casting any material what so ever over the slope. Irrigation systems near the new wall should be avoided. The scope of our work does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractors' methods, techniques, sequences, or procedures, except as specifically described in our letter for consideration in design. There are possible variations in subsurface conditions between the explored and unexplored areas and also with time. Our letter, conclusions, and interpretations should not be construed as a warranty of subsurface conditions. A contingency for unanticipated conditions should be included in the budget and schedule. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation NGA File No 1184120 Rotmark Property Slope Stabilization and Retaining Wall September 16, 2020 Edmonds, Washington Page 11 All people who own or occupy homes on hillsides should realize that landslide movements are always a possibility. The homeowner should periodically inspect the slope, especially after a winter storm. If distress is evident, a geotechnical engineer should be contacted for advice on remedial/preventative measures. The probability that landsliding will occur is substantially reduced by the proper maintenance of drainage control measures at the site (the runoff from the roofs should be led to an approved discharge point). Therefore, the homeowner should take responsibility for performing such maintenance. Consequently, we recommend that a copy of our letter be provided to any future homeowners of the property if the home is sold. We recommend that NGA be retained to review project plans prior to construction and to monitor wall repairs. These additional services are intended to confirm that the conditions encountered are consistent with those indicated by the explorations, to provide recommendations for design changes should the conditions revealed during the work differ from those anticipated, and to evaluate whether or not construction activities comply with specifications. We should be contacted a minimum of one week prior to construction activities and could attend pre -construction meetings if requested. Within the limitations of scope, schedule and budget, our services have been performed in accordance with generally accepted geotechnical engineering practices in effect in this area at the time this letter was prepared. No other warranty, expressed or implied, is made. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the owner. • • • NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation Rotmark Property Slope Stabilization and Retaining Wall Edmonds, Washington NGA File No 1184120 September 16, 2020 Page 12 It has been a pleasure to provide service to you on this project. If you have any questions or require further information, please call. Sincerely, NELSON GEOTECHNICAL ASSOCIATES, INC. Lee S. Bellah, LG Project Geologist Khaled M. Shawish, PE Principal LSB:KMS:sg Nine Figures Attached NELSON GEOTECHNICAL ASSOCIATES, INC. VICINITY MAP Not to Scale t ' 65th PI S'N Lynnwood n 's� Meadowdale Playfields 0 0 D y Q Wastewater Treatment _ ® Deb the Dog Walker Q Meadowdale 1681h St SW Residential Locks Middle School Meadowda Meadowdale High School Q Neighborho D Edmonds WA Park IBM ^a � . :. s• sr( °t Project Sitev` 1 bnt Rn Superior Fibers Q 174th S1 SW } Saint Thomas Q O More Parish nwh 51 SW 176th St svr Colorific Porcelain F^ V g £ t Cedar Park eb 119h St SW 10 Christian School 0 Southwest County Park 18M S1 SW 1801h 3 s, SW Q cvleND a m Crossway Fellowship e .10 G P -. 182nd St SW Q c 'N;:nd St SYt 3 t+ m _ United States G � b Service ® i`33ld VI SWPostal P Seaview Park © The Hook aco 4 ,h y1 s'A' Seafood Broiler z 186th St SW a r a Seaview ; 1e7th St sw s s a Itary School P E R R I N V I L L E 0 ~ ^ 188th St SW � 111atn PI Sty pr 0' j Lynndale Park CO PennyLn J as 789thPls(y ° �( Picnic Shelter 189thp/ $ n > 190th St SW SW A Edmonds, WA ® Village Market Q176th St SW Maple Park Lutheran Church = t No Arir frig K ao 0 PetSmart N r a Y Project Number NELSON GEOTECHNICAL No. Date Revision By CK o Rotmark Property Slope NGA ASSOCIATES, INC. 1184120 Stabilization & Retaining Wall 1 8/27/20 Original DPN ABR GEOTECHNICAL ENGINEERS & GEOLOGISTS E Figure 1 Vicinity Map W°35thAv..NE,°e EastWenat°yLanehee 2 17311-135[h Ave. NE, A-500 552fi Industry Lane, it2 a J Woodinville, WA 98072 East Wenatchee, WA 98802 (425) 486-16691 Fax:481-2510 ww-lsongeotech—, (509) 665-76961 Fax: 665-7692 = 0 _ z CD N) o 3 CT CD Cn CD 3 a T� V 9 0 CD CD m v ��.Cn m v m 0o Z a -) ^ Z m z yr � Z mo m O Z 3 N Y m m� N2 6)) n Z 0 a N r LEGEND ,Z — — Property line V C1 0 m B-1 o Number and approximate v <_ location of boring 0 3 Schematic Site Plan Iw -1 A A' Approximate location Z W of cross-section D 0 CO X Reference: Site plan based on field measurements, observations, and aerial parcel map review. .... 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Ain. ffi ..ire A,— D 00 0 A nine UNIFIED SOIL CLASSIFICATION SYSTEM GROUP MAJOR DIVISIONS GROUP NAME SYMBOL CLEAN GW WELL -GRADED, FINE TO COARSE GRAVEL COARSE- GRAVEL GRAVEL GP POORLY -GRADED GRAVEL GRAINED MORE THAN 50 % GRAVEL GM SILTY GRAVEL OF COARSE FRACTION RETAINED ON SOILS NO.4 SIEVE WITH FINES GC CLAYEY GRAVEL SAND CLEAN SW WELL -GRADED SAND, FINE TO COARSE SAND SAND SP POORLY GRADED SAND MORE THAN 50 % RETAINED ON MORE THAN 50 % NO. 200 SIEVE OF COARSE FRACTION SAND SM SILTY SAND PASSES NO. 4 SIEVE WITH FINES SC CLAYEY SAND FINE - SILT AND CLAY ML SILT INORGANIC GRAINED LIQUID LIMIT CL CLAY LESS THAN 50 % SOILS ORGANIC OL ORGANIC SILT, ORGANIC CLAY SILT AND CLAY MH SILT OF HIGH PLASTICITY, ELASTIC SILT INORGANIC MORE THAN 50 % PASSES LIQUID LIMIT CH CLAY OF HIGH PLASTICITY, FAT CLAY NO. 200 SIEVE 50 % OR MORE ORGANIC OH ORGANIC CLAY, ORGANIC SILT HIGHLY ORGANIC SOILS PT PEAT NOTES: 1) Field classification is based on visual SOIL MOISTURE MODIFIERS: examination of soil in general accordance with ASTM D 2488-93. Dry - Absence of moisture, dusty, dry to the touch 2) Soil classification using laboratory tests is based on ASTM D 2488-93. Moist - Damp, but no visible water. 3) Descriptions of soil density or Wet - Visible free water or saturated, consistency are based on usually soil is obtained from interpretation of blowcount data, below water table visual appearance of soils, and/or test data. Project Number NELSON GEOTECHNICAL No. Date Revision By CK 1184120 Rotmark Property Slope NGA ASSOCIATES, INC. Stabilization & Retaining Wall GEOTECHNICAL ENGINEERS & GEOLOGISTS 1 8/27/20 Original DPN ABR Figure 5 Soil Classification Chart W°35thAv..NE,°e Ea=1We"at°yLanehee 2 [h Ave. NE, A-500 Industry Lane, st W 88 Woodinville, WA 98072 East Wenatchee, WA 98802 Weed (425) 486-1669 / F_ 481-2510 www. nelsongeotech.con, (509) 665-7696 1 Fax: 665-7692 BORING LOG B-1 Approximate Ground Surface Elevation: ?? Soil Profile Sample Data Penetration Resistance - 0) 10 20 30 40 50 50+ 0) c(Blows/foot �5 H Piezometer Installation - Description p `— 0 a o 0-0 3� _ c a) Q B w o Ground Water Data Moisture Content C J o ;_ � o m U E � � s (Percent - ■) p (Depth in Feet) C7 U) � 0 10 20 30 40 50 50+ m J Dark brown to gray, silty fine to medium sand with gravel and trace organics (very loose to loose, moist) FILL 4 ' 5 ................................................... 5 4 1 Light brown, silty fine to medium sand with gravel and — trace iron -oxide staining (very loose to loose, moist) -becomes gray, medium dense i 28 ' 10 ........................................ .......... 10 becomes very dense, no iron -oxide staining 50-4 ' SM —,.: .. 1 50-5 15 .................................................... 15 Boring met refusal at 15.5 feet below existing grade on 8/19/20. Groundwater seepage was not encountered during drilling. 20 .................................................... 20 25 .................................................... 25 LEGEND C Solid PVC Pipe Concrete M Moisture Content 0 Slotted PVC Pipe Bentonite A Atterberg Limits Depth Driven and Amount Recovered G Grain -size Analysis with 2-inch O.D. Split -Spoon Sampler Monument/ Cap Native Soil DS Direct Shear to Piezometer PP Pocket Penetrometer Readings, tons/ft Depth Driven and Amount Recovered 0 Silica Sand p * Liquid Limit P Sample Pushed with 3-inch Shelby Tube Sampler + Plastic Limit 1 Water Level T Triaxial NOTE: Subsurface conditions depicted represent our observations at the time and location of this exploratory hole, modified by engineering tests, analysis and judgement. They are not necessarily representative of other times and locations. We cannot accept responsibility for the use or interpretation by others of information presented on this log. Project Number NGEOTECHNICAL No. Date Revision By CK Rotmark Property Slope ASSOCIATES,NELSON AINC. NGA 1184120 Stabilization &Retaining Wall Boring Log GEOTECHNICAL ENGINEERS & GEOLOGISTS � a/2�/Zo Original DPN ABR Figure 6 Wo einville Office East Wenatchee Office 17311-135th Ave. NE, A-500 5526 l.dustry Lane, #2 Woodinville, WA 98072 East Wenatchee, WA 98802 PaPagel of 1 q (425) 486-16691 Fax:481-2510—.nelsongeotech.com 509) 665-7696 /Fax: 6fi5-7fi92 BORING LOG B-2 Approximate Ground Surface Elevation: ?? Soil Profile Sample Data Penetration Resistance 0) c(Blows/foot - 0) 10 20 30 40 50 50+ �5 H Piezometer Installation - Description p `— 0 a o 0-0 3� _ c a) Q B w o Ground Water Data Moisture Content C J o ;_ � o m U E � � s (Percent - ■) p (Depth in Feet) C7 U) � 0 10 20 30 40 50 50+ m J Dark brown to brown, silty sand with organics (loose, moist) FILL) 5 ' -becomes light brown, loose to medium dense, trace 5 ......... .................. ......... ........ 5 organics 10 ' Gray, silty fine to medium sand with gravel and trace iron -oxide staining (very dense, wet) SM 50-3 -becomes moist, with no iron-ox'de stainina 50-6 10 .................................................... 10 Boring met refusal at 10.5 feet below existing grade on 8/19/20. Groundwater seepage was not encountered during drilling. 15 .................................................... 15 20 .................................................... 20 25 .................................................... 25 LEGEND C Solid PVC Pipe Concrete M Moisture Content 0 Slotted PVC Pipe Bentonite A Atterberg Limits Depth Driven and Amount Recovered G Grain -size Analysis with 2-inch O.D. Split -Spoon Sampler Monument/ Cap Native Soil DS Direct Shear to Piezometer PP Pocket Penetrometer Readings, tons/ft Depth Driven and Amount Recovered 0 Silica Sand p * Liquid Limit P Sample Pushed with 3-inch Shelby Tube Sampler + Plastic Limit 1 Water Level T Triaxial NOTE: Subsurface conditions depicted represent our observations at the time and location of this exploratory hole, modified by engineering tests, analysis and judgement. They are not necessarily representative of other times and locations. We cannot accept responsibility for the use or interpretation by others of information presented on this log. Project Number NGEOTECHNICAL No. Date Revision By CK Rotmark Property Slope ASSOCIATES,NELSON AINC. NGA 1184120 Stabilization &Retaining Wall Boring Log GEOTECHNICAL ENGINEERS & GEOLOGISTS � a/2�/Zo Original DPN ABR Figure 7 Wo einville Office East Wenatchee Office 17311-135th Ave. NE, A-500 55261ndustry Lane, #2 Woodinville, WA 98072 East Wenatchee, WA 98802 PaPagel of 1 q (425) 486-16691 Fax:481-2510—.nelsongeotech.com 509) 665-7696 /Fax: 6fi5-7fi92 BORING LOG B-3 Approximate Ground Surface Elevation: ?? Soil Profile Sample Data Penetration Resistance 0) c(Blows/foot - 0) 10 20 30 40 50 50+ �5 H Piezometer Installation - Description p `— 0 a o 0-0 3� _ c a) Q B w o Ground Water Data Moisture Content C J o ;_ � o m U E � � s (Percent - ■) p (Depth in Feet) C7 U) � 0 10 20 30 40 50 50+ m J Light brown, silty sand with organics (loose, moist) (FILL) 50 5 ' Gray, silty fine to medium sand with gravel (very dense, wet) SM ,. 50 6 5 ................................................... 5 Boring met refusal at 5.5 feet below existing grade on 8/19/20. Groundwater seepage was not encountered during drilling. 10 .................................................... 10 15 .................................................... 15 20 .................................................... 20 25 .................................................... 25 LEGEND C Solid PVC Pipe Concrete M Moisture Content 0 Slotted PVC Pipe Bentonite A Atterberg Limits Depth Driven and Amount Recovered G Grain -size Analysis with 2-inch O.D. Split -Spoon Sampler Monument/ Cap Native Soil DS Direct Shear to Piezometer PP Pocket Penetrometer Readings, tons/ft Depth Driven and Amount Recovered 0 Silica Sand p * Liquid Limit P Sample Pushed with 3-inch Shelby Tube Sampler + Plastic Limit 1 Water Level T Triaxial NOTE: Subsurface conditions depicted represent our observations at the time and location of this exploratory hole, modified by engineering tests, analysis and judgement. They are not necessarily representative of other times and locations. We cannot accept responsibility for the use or interpretation by others of information presented on this log. Project Number NGEOTECHNICAL No. Date Revision By CK Rotmark Property Slope ASSOCIATES,NELSON AINC. NGA 1184120 Stabilization &Retaining Wall Boring Log GEOTECHNICAL ENGINEERS & GEOLOGISTS � a/2�/Zo Original DPN ABR Figure 8 Wo einville Office East Wenatchee Office 17311-135th Ave. NE, A-500 55261ndustry Lane, #2 Woodinville, WA 98072 East Wenatchee, WA 98802 PaPagel of 1 q (425) 486-16691 Fax:481-2510—.nelsongeotech.com 509) 665-7696 /Fax: 6fi5-7fi92 Schematic Pin Pile Wall Detail Not to Scale U—. „-- Grouted Anchor Tieba (as need( -------------•-•---•-_ ------VI "A Project Number 1184120 Rotmark Property Slope Stabilization and Retaining Wall Schematic Pin Pile Wall NELSON GEOTECHNICAL ASSOCIATES, INC. NGA GEOTECHNICAL ENGINEERS & GEOLOGISTS No. Date Revision By CK 1 8/27/20 Original LSB 2 KMS C7 Z Figure 9 Detail W°°"in°ille Office East Wenatchee Office 17311-135th Ave. NE, A-500 5526 Industry Lane, M2 Woodinville, WA 98072 East Wenatchee, WA 98802 O (425) 486-1669 / Fax:481-2510 www. nele°ng-tech—, (509) 665-7696 / Fax: 665-7692 Z