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REVIEWED RESUB4 BLD2023-0138+Geotechnical_Report+8.14.2023_12.27.42_PM+3723988NELSON GEOTECHNICAL ASSOCIATES. INC. August 14, 2023 Mr. John Weiss VIA Email: jrweiss98020@comcast.net Geotechnical Engineering Evaluation (Update 3) Weiss Residence Retaining Wall Evaluation 1013 — 9t" Avenue South Edmonds, Washington NGA File No. 1415122 17311-135' Ave. N.E. Suite A-500 Woodinville, WA 98072 (425)486-1669 www.nelsongeotech.com Dear Mr. Weiss, This report summarizes the results of our geotechnical engineering evaluation of the existing block retaining walls located at your residence located at 1013 — 9tn Avenue South in Edmonds, Washington, as shown on the Vicinity Map in Figure 1. Our services were completed in general accordance with our services agreement signed by you on November 9, 2022. INTRODUCTION The site is currently occupied by a single-family residence within the central portion of the site. The ground surface within the site generally slopes gently down from the east to the west. We understand that you recently constructed unpermitted modular concrete block retaining walls ranging from approximately 2.5 to 4 feet in overall height within the western portion of the property. The City of Edmonds has requested a geotechnical evaluation to provide stabilization and design recommendations for the retaining wall construction due to the overall height of the retaining walls. SCOPE The purpose of this study is to explore and characterize the surface and subsurface conditions within the vicinity of the existing block retaining walls and provide stabilization and design recommendations for the retaining wall construction due to the overall height of the retaining walls. Geotechnical Engineering Evaluation (Update 3) Weiss Residence Retaining Wall Evaluation Edmonds, Washington Specifically, our scope of services included the following: NGA File No. 1415122 August 14, 2023 Page 2 1. Review available soil and geologic maps of the area as well as other relevant geotechnical information, as provided. 2. Explore the subsurface soil conditions within the vicinity of the retaining wall with hand - tool explorations. 3. Provide our opinion regarding the existing retaining wall construction. 4. Provide recommendations for retaining wall construction and stabilization, as necessary. 5. Provide recommendations for site drainage and erosion control. 6. Document the results of our findings, conclusions, and recommendations in a written geotechnical report. SITE CONDITIONS Surface Conditions The site consists of a roughly rectangular -shaped parcel covering approximately 0.28 acres. The site is occupied by a single-family residence within the central portion of the site. The ground surface within the site generally slopes gently down from the east to the west. The existing retaining wall is located within the very western portion of the property. The property is bordered to the north and east by existing single-family residences, to the south by an access driveway, and to the west by 9th Avenue South. The site is generally vegetated with grass, landscaping plants, and sparse young to mature trees. The existing and proposed site layout is shown on the Site Plan and Proposed Site Plan in Figures 2 and 3, respectively. The existing Allan Block retaining walls are located within the very western portion of the site. The lower wall is approximately 42.0 to 44.0 inches in exposed height with approximately 0 to 1 block being embedded at the toe of the wall. The upper tier retaining wall was approximately 33.0 to 34.0 inches in overall heigh and setback approximately 19.0 to 23.0 inches back from the lower retaining wall. The upper wall blocks were only embedded approximately 1.0 to 2.0 inches. The base of each tier of the retaining wall was supported directly on a thin crushed rock leveling pad. Competent native glacial till soils were observed directly below the crushed rock leveling pad for the lower retaining wall while we observed loose undocumented fill soils below the leveling pad for the upper retaining wall. Backfill for the retaining walls appeared to consist of loose, organic -rich silty sand undocumented fill soils. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation (Update 3) Weiss Residence Retaining Wall Evaluation Edmonds, Washington NGA File No. 1415122 August 14, 2023 Page 3 We understand that an existing rockery retaining wall was left in place behind the tiered retaining walls. Based on probing with a 0.5-inch diameter steel probe rod, it appears that the rockery is likely located approximately 6.0 to 12.0 inches behind the back of the upper retaining wall. We were not able to directly observe the existing rockery due to digging restrictions. We were informed that geogrid-reinforcement and a drainage layer were not utilized for the wall construction. The overall wall heights are shown on Cross -Section A -A' and B-B' in Figures 4 and 5, respectively. We also did not observe surface water in the immediate vicinity of the residence or retaining walls during our site visit on December 13, 2022. Subsurface Conditions Geology: The geologic units for this area are shown on the Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles, Washington, by Minard, J.P., (USGS, 1983). The site is mapped as Vashon glacial till (Qvt) mapped nearby. Glacial till is described as a non -sorted, compact diamict of silt, sand, and sub -rounded to well-rounded clasts. Our explorations generally encountered undocumented fill soils underlain by brown -gray to gray, silty fine to medium sand with varying amounts of gravel consistent with the description of glacial till deposits at depth. Explorations: The subsurface conditions within the site were explored on December 13, 2022 by completing four hand auger explorations within the site extending to depths of 2.0 and 4.0 feet below the existing ground surface. The approximate locations of our explorations are shown on the Site Plan in Figure 2. A geologist from Nelson Geotechnical Associates, Inc. (NGA) was present during the explorations, collected samples of the soils encountered, and maintained a log of the explorations. The soils were visually classified in general accordance with the Unified Soil Classification System, presented as Figure 6. The logs of the explorations are presented as Figure 7. We present a brief summary of the subsurface conditions in the following paragraph. For a detailed description of the subsurface conditions, the exploration logs should be reviewed. At the surface of all of our hand auger explorations, we encountered approximately 0.1 to 0.8 feet of surficial crushed rock and/or topsoil. Underlying the surficial gravel and/or topsoil in Hand Augers 1 and 2 along the base of the lower retaining wall tier, we encountered dense to very dense, brown -gray to gray silty fine to medium sand with gravel that we interpreted as native glacial till soils. Below the surficial gravel and/or topsoil in Hand Augers 3 and 4 along the base of the upper retaining wall tier, we encountered approximately 1.9 feet of loose, organic - rich silty fine to medium sand with gravel that we interpreted as undocumented fill soils underlain by dense to very dense, brown -gray to gray silty fine to medium sand with gravel that we interpreted as native glacial till soils. All of the hand auger explorations were terminated within the native glacial till deposits at depths in the range of 2.0 to 4.0 feet below the existing ground surface. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation (Update 3) Weiss Residence Retaining Wall Evaluation Edmonds, Washington NGA File No. 1415122 August 14, 2023 Page 4 Hydrogeologic Conditions We encountered slight groundwater seepage within Hand Augers 1 and 2 at depths of approximately 0.2 and 0.3 feet below the existing ground surface, respectively. We interpreted this to be perched groundwater located just below the crushed rock leveling pad for the retaining wall. 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 precipitation. We would expect the amount of perched water to decrease during drier times of the year and increase during wetter periods. CONCLUSIONS AND RECOMMENDATIONS General It is our opinion from a geotechnical standpoint that the recently constructed block walls within the western portion of the property were not adequately installed and/or engineered, due to a combination of several factors: lack of adequate drainage measures behind the walls, lack of geogrid reinforcement, supporting the upper wall on unsuitable fill material, inadequate wall toe embedment, inadequate horizontal separation between the two tiers, and placement of unsuitable fill behind the walls. We also did not observe drainage system components, such as drainpipes and drain rock layers behind the retaining walls. Our explorations encountered up to 2.0 feet of loose undocumented fill soils that are not suitable as structural fill immediately behind the lower retaining wall and supporting the upper retaining wall. Multi -tiered retaining wall systems need to have an engineered design and need to utilize geogrid reinforcement to support the backfill material. We understand that an engineered design was not used in the construction of the walls. We recommend removing all of the concrete block retaining walls and associated loose soils and reconstructing the retaining wall system with the provided design. The new geogrid-reinforced fill walls could be constructed using the existing Allan Block retaining wall blocks. Loose native and undocumented fill soils are interpreted to be located behind the existing retaining walls and is not suitable for structural fill. We recommend that the base of the new wall blocks and reinforced fill area be supported directly on competent native soils. The base of the new walls should be embedded a minimum of 6-inches below the finished ground surface and supported directly on the competent native glacial till soils encountered at shallow depths. Due to tight site constraints between the western property line and the existing buried rockery, we recommend that the existing two tiers be replaced with one, single -tier wall with sloping ground above. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation (Update 3) Weiss Residence Retaining Wall Evaluation Edmonds, Washington NGA File No. 1415122 August 14, 2023 Page 5 Based on our understanding of the proposed retaining wall height restrictions and calculations, the wall should be no greater than 3.0 feet in exposed height in addition to the recommended 6-inch embedment. This is discussed further in the Wall Design and Construction Recommendations subsection of this letter. Due to the tight site constraints and the substantial amount of fill material that will need to be removed from the wall and reinforced fill area prior to construction of the new wall, we stress that implementing proper planning and construction staging techniques will be key to achieving a successful outcome. NGA should be retained to review project plans prior to construction and should be retained to observe wall construction to verify wall installation is being performed in accordance with the plans and our recommendations provided in this report. All residence drains including roof, driveway, footing, and yard drains along with drains associated with the proposed wall construction should be thoroughly investigated and directed to flow into an approved system. Temporary and Permanent Slopes Temporary cut slope stability is a function of many factors, including the type and consistency of soils, depth of the cut, surcharge loads adjacent to the excavation, length of time a cut remains open, and the presence of surface water or groundwater. It is exceedingly difficult under these variable conditions to estimate a stable, temporary, cut slope angle. Therefore, it should be the responsibility of the contractor to maintain safe slope configurations since they are continuously at the job site, able to observe the soil and groundwater conditions encountered and able to monitor the nature and condition of the cut slopes. The following information is provided solely for the benefit of the owner and other design consultants and should not be construed to imply that Nelson Geotechnical Associates, Inc. assumes responsibility for job site safety. Job site safety is the sole responsibility of the project contractor. For planning purposes, we recommend that temporary cuts in the on -site soils be no steeper than 2 Horizontal to 1 Vertical (2H:1V). If significant groundwater seepage or surface water flow were encountered, we would expect that flatter inclinations would be necessary. We recommend that cut slopes be protected from erosion. The slope protection measures may include covering cut slopes with plastic sheeting and diverting surface runoff away from the top of cut slopes. We do not recommend vertical slopes for cuts deeper than four feet if worker access is necessary. We recommend that cut slope heights and inclinations conform to appropriate OSHA/WISHA regulations. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation (Update 3) Weiss Residence Retaining Wall Evaluation Edmonds, Washington NGA File No. 1415122 August 14, 2023 Page 6 Permanent cut and fill slopes should be no steeper than 2HAV. However, flatter inclinations may be required in areas where loose soils are encountered. If permanent slopes steeper than 2HAV are created, we would anticipate such slope(s) to require on -going maintenance. Permanent slopes should be planted and the vegetative cover should be maintained until it is established. We should review plans and visit the site to evaluate excavations for this project. Geogrid-Reinforced Block Wall Design and Construction Due to tight site constraints between the western property line and the existing buried rockery, we recommend that the wall be one, taller single -tier wall with sloping ground above. Based on our calculations, the wall should be no greater than 3.0 feet in overall exposed height. The base of the wall should be embedded a minimum of 6-inches. We have provided a wall design for a single wall system with an individual tier exposed height of up to 3.0 feet with the existing Allan Block wall blocks. We recommend that wall be reconstructed utilizing geogrid reinforced backfill. The wall detail and design parameters along with construction notes are shown on Figure 8. Allan Block wall calculations are provided in Appendix A. We have assumed that the retained fill zones will consist of crushed rock material compacted to structural fill specifications. We understand that the fill will be placed level behind the walls and extending back into the reinforced fill zone. As indicated on the detail, the drainage system should be installed along the base of the blocks. The block facing should consist of the on -site Allan Block concrete blocks. The block facing should be placed on a minimum of 6-inch-thick crushed rock leveling pads placed over competent native glacial till soils, or structural fill material prepared under the supervision of NGA. We recommend that the wall and reinforced -fill subgrade be extended down to expose competent native glacial till soils. The wall and reinforced fill areas should also be graded to level benches prior to wall and reinforced fill construction. A drainage blanket of 12 inches of free -draining clean crushed rock should be placed between the blocks and the retained fill zone. The block cavities should also be filled with the crushed rock. A rigid, perforated drainpipe embedded in a minimum of 1-foot of pea gravel and wrapped in a filter fabric should be placed at the bottom of the drainage blanket. The drain should be sloped to drain into a permanent discharge. Mirafi 3XT geogrid (or equivalent) is recommended in the wall designs. The geogrid should be cut to the recommended lengths, attached to the blocks as recommended by the manufacturer, and extended back into the reinforced fill zone. The grid should be pulled tight before the fill is placed over the geogrid. Care should be taken not to damage the geogrid by operating construction equipment on the exposed grid, or by allowing large rocks to be placed directly on the grid. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation (Update 3) Weiss Residence Retaining Wall Evaluation Edmonds, Washington NGA File No. 1415122 August 14, 2023 Page 7 All fill placed in the retained fill zone behind the retaining walls should be placed as structural fill. Structural fill, by definition, is placed in accordance with prescribed methods and standards and is monitored by an experienced geotechnical professional or soils technician. Field monitoring procedures would include the performance of a representative number of in -place density tests to document the attainment of the desired degree of relative compaction. The fill subgrade should consist of native medium dense or better native soil compacted to a non -yielding condition. The fill subgrade should consist of level benches. Structural fill behind the wall should consist of crushed rock material. The material should have no more than 10 percent by weight of the portion passing the US #200 Sieve. We should be retained to evaluate proposed fill material prior to construction. Following subgrade preparation, placement of structural fill may proceed. All fill placements should be accomplished in uniform lifts up to eight inches thick. Each lift should be spread evenly and be thoroughly compacted prior to placement of subsequent lifts. All structural fill should be compacted to a minimum of 95 percent of the material's maximum dry density. Maximum dry density, in this report, refers to that density as determined by the ASTM D 1557 Compaction Test procedure. The moisture content of the soils to be compacted should be within about two percent of optimum so that a readily compactable condition exists. It may be necessary to over -excavate and remove wet soils in cases where drying to a compactable condition is not feasible. All compaction should be accomplished by equipment of a type and size sufficient to attain the desired degree of compaction. Site Drainage If ground water seepage is encountered or if excessive rainfall occurs during construction of specific aspects, we recommend that the contractor slope the bottom of the excavations and direct the water to ditches and small sump pits. The collected water can then be directed to a suitable discharge point. We also recommend that all residence downspouts and yard drains be investigated to understand where they are directed. If any irrigation systems are located above the wall, they should also be abandoned and removed. We recommend that all of the existing roof, footing, yard, and driveway drains associated with the residence be tightlined to flow into an approved system. NGA should be retained to evaluate the drainage systems as they are investigated and constructed. NELSON GEOTECHNICAL ASSOCIATES, INC. Geotechnical Engineering Evaluation (Update 3) Weiss Residence Retaining Wall Evaluation Edmonds, Washington NGA File No. 1415122 August 14, 2023 Page 8 USE OF THIS REPORT NGA has prepared this report for Mr. John Weiss and his agents, for use in the planning and design of the slope stabilization project on this site only. This report is a specific evaluation of the observed soil settlement and related distress, and the existing concrete block retaining walls. 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 report for consideration in design. There are possible variations in subsurface conditions between the explored and unexplored areas and also with time. Our report, 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. We recommend that NGA be retained to review final plans prior to construction. We also recommend that NGA be retained to provide monitoring and consultation services during construction 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 earthwork and foundation installation activities comply with contract plans and 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 report 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 (Update 3) Weiss Residence Retaining Wall Evaluation Edmonds, Washington NGA File No. 1415122 August 14, 2023 Page 9 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. 1 washi� �e �9r\ a 2883 I LEE S. BELLAH Lee S. Bellah, LG Senior Geologist 8.11.2023 Khaled M. Shawish, PE Principal LSB:KMS:dy Attachments: Eight Figures Appendix A NELSON GEOTECHNICAL ASSOCIATES, INC. VICINITY MAP Not to Scale D Hummingbird R z z z Hill Park o Edmonds Ferry Terminal Frances Anderson Center Edmonds Edmonds QDriftwood Players St J Dayton St Edmonds Library a T Ben St n Main St Maple St a Maple St 4 _ Yost Pool m � Alder St ui �' Alder St Alder St JBeck Ln Walnut St s Shelleberger = Holly or ' cedar St a / I�Barkada Ecllnonds Spruce St _Edmonds City Park —, Harvey Homes NW Laurels, 'pine St I Pine St Pine Street Playfield m m a n� y 104 CA N _ Fir St PINE -.PARK a NEIGHBORHOOD �k `m Elm 51 Puget-P-owenW'ashing Pi 5 2' Birch St \ �s rz r °p Maple Way � D 1A1 Intlt Si Project Site m a Pi S! `m 8 a Emerald City Cash For Cars V Main St - W _ s _:7ffe L 7 Yost Park Tennis and Pickleball Courts Sinbon Techwoicgies West sSOWdoinway 215i"St SW n m Q S $ � n 216th St SW f f 217th St SW 217th St SW Renaissance Acacia Group Home II go Plastering, Inc Iglesia Cristiana Cristo Vlve 220th St SW 220th St SW Westgate o 3: co Elementary School a n `m 4 o Rye W Edmonds, WA Project Number 1415122 Weiss Residence Retaining Walls IIELSOt1 GEOTECHIIICAL ASSOCIATES, Inc No. Date Revision By cK s 1 1/27/23 Original LSB LSB m J Figure 1 Vicinity MapW Woodinville Office Wenatchee Office 311-135th Ave. NE, A-500 05 Palouse St Woodinville, WA 98072 Wenatchee, WA 98801 y 7 ww.nelsongeotech.com (425) 486-1669 / Fax 481-2510 (509) 665-7696 / Fax: 665-7692 b U Site Plan i IL T VI I �JGL.JJ , m N N c N � II °° I fro' � 12.2' ,� ,� i I 11.4' N CD'� -- �v N 88'5241 " W 148.52' { WOOD FENCE- WOOD FENCE i -- ' END FENCE 0.1 '(N) A A-4AOF PROPERTY LINE I 0.5' OVERLAP A_1 SEE AIL 'A' cn J T (D - �0 I a o '\\ HOUSE LOT AREA D cu m Existing 12,321 SF �� Residence 27032500109200 Cr. c / 1 a Q ` U I B r1, -2 B l/ -r T HA-3 ASPHALT M I s M I DETAIL 'A' aN' !30 d2 I � � � • Cn v, ter, , O o m \ 1 cmn T -- N 30.00' M ---- - ----- ---- --- RIM=3z4.93 1 s= CB I N N 88'52 55" W 148.50' v n IE 6" RCP(S)=323.03 Existing Block Retaining Walls z 0 LEGEND N W � — — Property line 0 20 40 d N HA-1 A A' Approximate location _�_ Number and approximate Scale: 1 inch = 20 feet W W Reference: of cross-section location of hand auger Site plan based on a t000araohic survey dated 12/22/22 and oreoarec by Pacific Coast Survevs. Inc. r w 0 C:\Users\LeeBellah\Nelson Geotechnical Associates, Inc\Nelson Geotechnical Associates, Inc - Company\2022 NGA Project\14151-22 Weiss Res Retaining Walls Edmonds\Drafting\SP.dwg Proposed Site Plan C Z IE 4"" CPP=322.99 W N 3 I IL.L - � ® i °� "• ' + , W FENCE ,1.4' N WOOD FENCE -,� — ° <.' ND FENCE 0.1 N ® 0.5' OVERLAP 4 4 o A m SEE DETAIL 'A' n O �. icn Q D N J t.D CD o Existing LOT AREA (n 0 m Residence 12,321 SF IW. 27032500109200 ® ° a W N Lu "-A ASPHALT r� r7'1 ' `` lI �— DETAIL 'A'Cn <: N O IDmo Cn M — a r7'1 30.00' o In T ^ E 6 RCP S =323.0 Approximate Location of Proposed Block Retaining Wall z 0 m N W � 0 20 40 d N O 7 Scale: 1 inch = 20 feet W Cn Reference: Site plan based on a t000araDhic survev dated 12/22/22 and DreDarec by Pacific Coast Survevs. Inc. r w 0 C:\Users\LeeBellah\Nelson Geotechnical Associates, Inc\Nelson Geotechnical Associates, Inc - Company\2022 NGA Project\14151-22 Weiss Res Retaining Walls Edmonds\Drafting\Proposed SP.dwg 0. A AN -n _ 1 ^^ CD CD N N Cr West East m I I 20 20 Existing Buried Rockery (approximate) n CD Existing Block Walls �. cn CD CD CQ 15 15 =BCD R D 0 Sidewalk cn D (D 0 10 10 > w 9th Ave S 3 HA-4 Undocumented m } 5 Q Fill HA-1 Qvt 5 a�a to , �= Nv am 0 Cn m 0 0 s IM 0 5 10 15 20 25 Distance (feet) Exploration Z m W fD Hand Auger Designations HA-1 o � Groundwater Level ---> 1 NOTES: During Exploration 1) Stratigraphic conditions are interpolated between Geologic Contact ---> ? — —? 2) the explorations. Actual conditions may vary. Elevations are arbitrary. m p0 (approximate) Reference: Cross Section is based on field measurements using a hand-held clinometer and 100-ft tape measure. W C:\Users\LeeBellah\Nelson Geotechnical Associates, Inc\Nelson Geotechnical Associates, Inc - Company\2022 NGA Project\14151-22 Weiss Res Retaining Walls Edmonds\Drafting\CS.dwg -n 1 ^ C. V1 Z CD N cn N 3 Cr m n � 0 m ccnn cn cn m ;U v cQ cn 0 0. a) CD W—=3 po Cn m B B' West I I East I I 20 F Existing Buried Rockery (approximate) 15 Existing Block Walls Sidewal A Lu 9th Ave S HA-3 3 Undocumented m 5 HA-2 Qvt Fill r Q a s cn can O T> o N a m 0 cI� m 0 C'7 I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I s 5 10 15 20 25 .M 0 C') 0 Distance (feet) Exploration T � v J N W fD Hand Auger Designations HA-1 o � 20 15 10 9 0 Groundwater Level NOTES: During Exploration 1) Stratigraphic conditions are interpolated between the explorations. Actual conditions may vary. m Geologic Contact ? — —? 2) Elevations are arbitrary. p0 (approximate) W Reference: Cross Section is based on field measurements using a hand-held clinometer and 100-ft tape measure. \Users\LeeBellah\Nelson Geotechnical Associates. Inc\Nelson Geotechnical Associates. Inc - Comoanv\2022 NGA Proiect\14151-22 Weiss Res Retainina Walls Edmonds\Drafting\CS.dwa 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 OF COARSE FRACTION SILTY GRAVEL 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 CH 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 IIELSOn GEOTECHnICAL No. Date Revision By cK 1415122 Weiss Residence Retaining Walls B ASSOCIATES, inc 1 1/27/23 Original LSB LSB Figure 6 Soil Classification Chart Woodinville Office Wenatchee Office 311-135th Ave. NE, A-500 105 Palouse St. Woodinville, WA 98072 Wenatchee, WA 98801 ww.nelsongeotech.com (425) 486-1669 / Fax: 481-2510 (509) 665-7696 / Fax: 665-7692 LOG OF EXPLORATION DEPTH (FEET) USCS SOIL DESCRIPTION HAND AUGER ONE 0.0 - 0.1 CRUSHED ROCK 0.1 - 2.0 SM BROWN -GRAY TO GRAY SILTY FINE TO MEDIUM SAND WITH GRAVEL (DENSE TO VERY DENSE, MOIST) SAMPLE WAS COLLECTED AT 1.5 FEET SLIGHT GROUNDWATER SEEPAGE WAS ENCOUNTERED AT 0.2 FEET CAVING WAS NOT ENCOUNTERED HAND AUGER WAS COMPLETED AT 2.0 FEET ON 12/13/22 HAND AUGER TWO 0.0 - 0.7 DARK BROWN SILTY SAND WITH GRAVEL AND ORGANICS (VERY LOOSE, MOIST TO WET) (UNDOCUMENTED FILL) 0.7 - 0.8 CRUSHED ROCK 0.8 - 2.0 SM BROWN -GRAY TO GRAY SILTY FINE TO MEDIUM SAND WITH GRAVEL (DENSE TO VERY DENSE, MOIST) SAMPLES WERE NOT COLLECTED SLIGHT GROUNDWATER SEEPAGE WAS ENCOUNTERED AT 0.3 FEET CAVING WAS NOT ENCOUNTERED HAND AUGER WAS COMPLETED AT 2.0 FEET ON 12/13/22 HAND AUGER THREE 0.0 - 0.1 CRUSHED ROCK 0.1 - 2.0 DARK BROWN SILTY SAND WITH GRAVEL AND ORGANICS (VERY LOOSE, MOIST TO WET) (UNDOCUMENTED FILL) 2.0-4.0 SM BROWN -GRAY TO GRAY SILTY FINE TO MEDIUM SAND WITH GRAVEL (DENSE TO VERY DENSE, MOIST) SAMPLES WERE NOT COLLECTED GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED CAVING WAS NOT ENCOUNTERED HAND AUGER WAS COMPLETED AT 4.0 FEET ON 12/13/22 HAND AUGER FOUR 0.0 - 0.1 CRUSHED ROCK 0.1 - 2.0 DARK BROWN SILTY SAND WITH GRAVEL AND ORGANICS (VERY LOOSE, MOIST TO WET) (UNDOCUMENTED FILL) 2.0-4.0 SM BROWN -GRAY TO GRAY SILTY FINE TO MEDIUM SAND WITH GRAVEL (DENSE TO VERY DENSE, MOIST) SAMPLES WERE NOT COLLECTED GROUNDWATER SEEPAGE WAS NOT ENCOUNTERED CAVING WAS NOT ENCOUNTERED HAND AUGER WAS COMPLETED AT 4.0 FEET ON 12/13/22 LSB:KMS NELSON GEOTECHNICAL ASSOCIATES, INC. FILE NO 1415122 FIGURE 7 SPECIFICATIONS FOR REINFORCED FILL WALL General 1. The contractor shall have an approved set of plans and specifications on site at all times during the construction of the wall. The wall layout is the responsibility of the contractor. 2. Nelson Geotechnical Associates (NGA) should observe and monitor the construction of the wall. 3. Mirafi 3XT geogrid or equivalent shall be used for this project. All geogrid and facing materials shall be approved by NGA prior to installation. 4. The contractor may use longer geogrid lengths than the design sections for ease of construction. The geogrid lengths may not be shorter unless approved by NGA. Subgrade Preparation 1. The block and reinforced zone subgrade should be prepared by removing surficial organics and loose soil to expose competent native soils as approved by NGA. 2. A generally level bench with a minimum width equal to the design length of the geogrid is required for placement of the reinforced fill. 3. The excavation shall be cleaned of all loose material and protected, as necessary, from construction traffic to maintain the intergrity of the subgrade. 4. The base of the excavation should be deep enough to satisfy a minimum embedment based on the total wall height as shown in the table below. 5. The wall facing and reinforced fill shall be supported on a minimum of 6-inches of crushed rock. Geogrid Placement 1. The reinforcement shall be rolled out, cut to length, and laid at the proper elevation, location, and orientation. Orientation of the reinforcement is of extreme importance since geogrids vary in strength with roll direction. The contractor shall be responsible for the correct orientation of the geogrid. 2. Geogrid shall be placed at the location and elevations shown on the plans. The geogrid length is measured from the back of the block wall. 3. Prior to placing the fill, the geogrid shall be pulled to remove the slack and stretched by hand until taut and free of wrinkles. Existing Buried Rockery (appr��*�' Filter fabric to be Allan Block placed between topsoil wall batter and wall rock from vertical Clean Crushed Fill Placement Exposed 1. Structural fill, consisting of granular import soils or on -site material no greater than 3 inches in size, would then be placed upon the wall height geogrid. If larger rock is used in the fill, additional layers of geogrid may need to be used in the reinforcement. The contractor shall 3.0ft Max prevent damage to the geogrid by placing the first lift of structural fill with at least a 1-foot thickness. NGA shall approve the material for use as reinforced fill, before placement. 2. Structural fill should have parameters equal to or better than those listed below as design parimeters for the reinforced wall fill. The reinforced fill soil should have no more than 15 percent passing the number 200 sieve. NGA may allow a higher silt content based on review of the wall design and proposed fill materials. 3. Soil density tests should be performed as designated by NGA. 4. Fill soils in the wall area shall be compacted to at least 95 percent of the Maximum Dry Density (MDD) as determined by ASTM D-1557. 5. The soil shall be placed in relatively uniform horizontal lifts not exceeding 8 inches in thickness. The lift thickness shall not exceed the manufacturer's recommended depth for the compactive device used on the project. 6. If a fence or rail is planned along the top of the wall, the layout of any support posts should by determined prior to constructing the Min. 6ir wall. Any foundation forms or Sonotubes should be installed at the post locations during placement of the reinforced fill to allow for later Embed placement of the fence posts without excavation in the reinforced fill. Depth Drainage 1. A specific drainage system is shown on the plans. Alternative drains can be used based on conditions found in the field and the material used within the reinforced zone. Changes to the drainage system should be approved by NGA. 2. A drainage blanket 12 inches in width should be installed directly behind the keystone block facing and shall consist of 3/4-inch clean crushed rock. All of the drainage materials shall have a fines content no greater than 5 percent passing the number 200 sieve. A 4-inch rigid perforated pipe embedded in a minimum of one foot of pea gravel or washed rock and wrapped with filter fabric should be installed at the bottom of the drainage blanket and be sloped to drain to an approved outlet. 3. Surface water shall not be allowed to collect in or near the reinforced fill zone during or after construction. 4. Suitable clean -outs should be installed every 50 feet for drain maintenance, but a minimum of two clean -outs should be utilized. Design Parameters Reinforced Wall Fill: 36 degrees, 0 PSF, 120 PCF Retained Soil: 36 degrees, 0 PSF, 120 PCF Foundation Soil: 36 degrees, 0 PSF, 120 PCF External Stability of Wall Minimum Factor of Safety against Base Sliding: 1.5 Minimum Factor of Safety against Overturning: 2.0 Minimum Factor of Safety against Bearing Capacity: 2.0 Internal Stability of Wall Minimum Factor of Safety on Geogrid Strength: 1.5 Minimum Factor of Safety on Geogrid Pullout: 1.5 Soil-Geogrid Interaction Coefficient: 1.0 Percent Coverage of Geogrid: 100 Percent Seismic 0.20g peak ground acceleration. Inspection Wall construction shall be periodically monitored by NGA. Allan Block unit Finished grade 6 in (150 mm) (min) Finished grade 3 max 1 � Geogrid length an unyielding state and approved by NGA 4 in (100 mm) toe drain pipe vented to daylight *Not To Scale Total Wall Number of Geogrid Height Geogrid Length** Geogrid Height Above Leveling Pad / (feet) Layers (feet) Geogrid Type (feet) 3.0 2 3.0 0.65 1.94 3XT* 3XT *3XT: Mirafi 3XT Geogrid, or equivalent ** Geogrid length measured from face of block Retained soil Y m U CO m W J C 0 A m o � m c 0 6 z CZ o� lo o�� d>a C arm cc d�Im- 3 m- ILU N I-- W ® ~ W C o N N N C:J wm� CN O Z a X N da3Lo C* Q. C L = 0 >Cn a a rn O C O M:Q �7oa W� N C� 0 (1) (1) U = N 4) C) U - N _C m of CE C 70 c6 (3) Q 0 j � O c a) rr �'Q M. S� of wn rlc �G E N =5 C 00 35215 w Z Ln GIST$, V~ sSjONAL N I LL 8.14.2023 O E 0 0 0 o 3 APPENDIX A Allan Block Software Retaining Wall Design Calculations AB Classic Section 0 of 0 Base Information Base Width: 2 ft Base Depth: 0.5 ft Base From Toe: 0.5 ft Allan Block Disclaimer Allan Block provides this software as a service for Its clients. The sole purpose of this software Is to assist engineers In the design of mechanically stabilized retaining walls. The software uses evaluation techniques and engineering principles found In the Allan Block Engineering Manual. (Refer to R0900 and supporting references,) It is [he responsibility of Me engineer of remM [o determine the Propriety and accuracy of input parameters and to review and verify the correctness of the results. ALIAN BLOCK CORPORATION, ITS LICENSEES OR AGENTS DO NOT ASSUME ANY LIABILRY OR RESPONSIBILITY FOR DAMAGES WHICH MAY RESULT FROM THE USE OR MISUSE OF THIS SOFTWARE. This software only considers internal, I —I and intemal compound stability (ICS) of the reinceco ford mposite mass. The intemal compound stability calculations are limited m on evaluation zone above the base material and back no further than 2 * H or He + L, whichever is greater. This program DOES NOT address global stabilty, defined as soil stability below the base material end beyond the limits for intemal compound stability. Global Stability should be evaluated to determine if the overall site is stable. It is fie responslblllty of the owner to ensure the global stablllty Is analyzed. The engineer of record must evaluate the project site for props water management and all potential modes of failure within the segmental retaining well evaluation zone. The geotechnical engineering firm contacted by the owner should provide a full global stablllty opinion of the slte Including the eff— on the segmental retaining wall. AB Walls to -ins DEFAULT values for all data inputs that the user MUST change or verify as appropriate for the p ,—rwise noted by the engineer of record. It is also recommended that on independent assessment of the foundation soil for settlement potential and wall defl-ions for the proposed s[rutture be pertormed. Changes in the subsoil conditinns are not included in this software. These additional potential failure modes should be evaluated by the engineer of record pnor to initiating well on —co- and may require site Inspettlon by the on -site soils engineer. All Installations must conform to the Allan Block Spec Book. (Refer to Ro9o1). MathCAD files for hand <alcul,tlons to support the software's consideration of internal, I —el and Inte—1 c,mp,u,d stabiltty of the reinforced composite mass are provided in the AS Resources Drop Down Menu. These files are to be —fig— so that the engineer of record can evaluate the output of the software. Individual equations may be altered at the discretion of the engineer of rewrd. Geogrid Information: 2 x Miragrid 3XT @ 3 ft Number Of Geogrid 2 Wall Design Variables AB Classic Total Panel Heiqht 3.23 ft 0.646 ft Angle of Setback 6 Deq. Depth of Block 0.98 ft Lenqth of Block 1.47 ft Safety Factors Static External Actual Slidinq 5.18 >= 1.5 Actual Overturninq 10.55 >= 2 Safety Factors Seismic External Peak Ground Acceleration = 0.2 Actual Slidinq 3.48 >= 1.125 Actual Overturninq 6.35 >= 1.5 Infill Soil Friction Anqle 36 Deq. Unit WT 120 pcf Retained Soil Friction Anqle 36 Dec. Unit WT 120 pcf Foundation Soil Friction Anqle 36 Dec. Unit WT 120 pcf Cohesion 0 psf Bearing Capacity Factor of Safety 22.01 Sigma_ult - 10173.85 psf Sigma_max - 462.22 psf Internal Compound Stability ics not calculated Wall Rock Requirements Variable Depth Height Depth Bottom 2.58 ft 1 ft 8.14. I hereby certity that these calculations were prepared by me or under my direct supervision and that I am a duly licensed engineer certified and responsible for the content of these calculations. Signature: Engineer: License #: Date: M V) N U N V) s4 -r fa a) L m N a M N i N N z =5 Z 00 L U O Z U v m— w rn� 'O^ U f0 O Ln +� a � a 0 Pacle #: 1 v 21.0.27 Wall Design Variables Kai = Active Earth Pressure Coefficient Infill = 0.235 Setback = 90 - Beta Angle = 6.62 Deg. Kar = Active Earth Pressure Coefficient Retained = 0.238 Wf = Weight of Facing = 407.86 plf H = Wall Height = 3.23 ft Wt = Total Weight = 1261.77 plf He = Effective Height = 3.95 ft Fa = Active Force = 221.94 plf He_i = Effective Height = 3.47 ft Fav = Vertical Force = 90.27 plf i = Slope = 18 Deg. Fah = Horizontal Force = 202.75 plf i_int = Effective Slope = 17.21 Deg. Fr = Resistance Force = 1051.1 plf i_ext = Effective Slope = 18 Deg. Internal Design Calculations (Static) Section: 0 Geogrid Number Geogrid Elevation ft Geogrid Length ft Tensile Force plf Allowable Load plf Factor Safety Factor Safety Factor Safety Efficiency Overstress Pullout Block Pullout Soil 2A 1.94 3 60.91 1332.67 32.82 31.6 4.42 4.57 lA 0.65 3 93.76 1332.67 21.32 21.98 7.16 7.04 Geoqrid Leqend A - Miragrid 3XT B - Miragrid 5XT C - Miragrid 7XT Min. Lenqth of Geoqrid 3 ft 8. I hereby certity that these calculations were prepared by me or under my direct supervision and that I am a duly licensed engineer certified and responsible for the content of these calculations. Signature: Engineer: License #: Date: V) N U N U7 L U r0 N L CO N N M N i N N Z E Z L N 00 U O Z U c: 71 N = N 'O^ U r0 O In +� a � a 0 Paqe #: 2 v 21.0.27 Wall Design Variables Ao = Specified Horizontal Peak Ground Acceleration = 0.2 d1 = Allowable Lateral Deflection Internal = 3 in d2 = Allowable Lateral Deflection External = 3 in Kaei = Dynamic Earth Pressure Coefficient Infill = 0.3 Kaer = Dynamic Earth Pressure Coefficient Retained = 0.3 Khi = Horizontal Seismic Coefficient Internal = 0.08 Khr = Horizontal Seismic Coefficient Retained = 0.08 DFdyn = Dynamic Earth Force = 60.17 DFdynh = Dynamic Earth Force Horizontal = 54.97 DFdynv = Dynamic Earth Force Vertical = 24.47 Pir = Seismic Internal Force = 49.78 plf Hir = Seismic Internal Force Location = 1.63 ft Internal Design Calculations (Seismic) Section: 0 Geogrid Number Geogrid Elevation ft Geogrid Length ft Tensile Force plf Allowable Load plf Factor Safety Factor Safety Factor Safety Efficiency Overstress Pullout Block Pullout Soil 2A 1.94 3 107.46 2635.05 26.97 17.91 1.74 4.08 lA 0.65 3 121.39 2635.05 23.88 16.98 5.12 4.61 Geoqrid Leqend A - Miragrid 3XT B - Miragrid 5XT C - Miragrid 7XT Min. Lenqth of Geoqrid 3 ft ;O M. S o a 35215 sv 'GIs TV' Q G~ 8.14.2023 ssIONAL I hereby certity that these calculations were prepared by me or under my direct supervision and that I am a duly licensed engineer certified and responsible for the content of these calculations. Signature: Engineer: License #: Date: 3 w M � N N N (n CO L N � M E J O Z E Z L 00 a0 U O Z U c: N = N 'O^ U r6 O In +� a 0� a a) 0 Paqe #: 3 v 21.0.27