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REVIEWED PLN_Geotech ReportGroup Northwest, Inc. March 4, 2021 Mr. David Jenkins 18914 — 94th Ave W Edmonds, WA 98020 djseaandski@aol.com Subject: GEOTECHNICAL REPORT — CRITICAL AREAS REPORT PROPOSED ADDITION AND DECK 18914 — 94TH AVE W EDMONDS, WASHINGTON Dear Mr. Jenkins: Geolechnical Engineers, Geologists & Environmental Specialists G-5362 In accordance with our January 15, 2021 contract with you we have prepared the following geotechnical report — critical areas report for the proposed development. SITE AND PROJECT DESCRIPTION The project site consists of a developed residential lot at the subject address as shown on the attached Plate 1- Vicinity Map. An existing one-story home with daylight basement is located near the central portion of the lot as shown on the attached Plate 2 — Topographic Survey. The house has a main floor level deck at the north side of the house. The subject site is mostly flat at the east side of the lot. At the north and west sides of the existing development there are gentle to moderate inclination west and northwest -facing slopes. Based upon our review of the Edmonds GIS we understand that the following potential geologically critical areas are mapped for the west portion of the lot and at the adjacent west property: Severe Erosion Hazard 15-40% and Landslide Hazard 40%. GEO Group Northwest has been provided with a development plan for the proposed addition and deck prepared by Alexandra Immel Residential Design and attached herein as Plate 3 — Site Plan. The plan indicates that a new deck is proposed at the west side of the residence. We understand that this deck will be at the main floor level. The plan also notes that a main floor level addition will be added at the southeast building corner. 13705 Bel -Red Road, Bellevue, Washington 98005 Phone 425/649-8757 • Fax 425/649-8758 March 4, 2021 G-5362 Geotechnical Report — 18914 — 941h Ave W, Edmonds, WA Page 2 GEOLOGIC CONDITIONS The geologic map' for the site indicates that the subject lot is underlain by Quaternary aged Vashon Till (Qvt) and Advance Outwash (Qva). The till deposit consists of a mixture of gravel, silt and sand which was overridden by glacial ice during the most recent period of glaciation. The outwash soils reportedly consist of predominately sand and gravel which was deposited by flowing meltwater as glaciers advanced into the region during the last period of glaciation. SUBSURFACE CONDITIONS GEO Group Northwest explored the subsurface soil and groundwater conditions by advancing three hand-augered borings labeled HA-1 through HA-3 at the site on February 11, 2021. The borings were located approximately as shown on the attached Plate 2 — Topographic Survey and Plate 3 — Site Plan. Soils encountered at the borings HA-1 and HA-2 consist of medium dense to dense sandy SILT with varying amounts of gravel/cobbles (topsoil) overlying dense silty SAND and sandy SILT with varying amounts of gravel (till) at a depth of around 8-inches below ground surface (bgs). Soils encountered at the boring HA-3 consist of medium dense sandy SILT (topsoil) overlying loose to medium dense sandy SILT and silty SAND with occasional gravel, apparent fill, at a depth of 9-inches bgs. Underlying the apparent fill at a depth of 29-inches is dense gravelly fine sandy SILT (till) at the HA-3 location. The borings were advanced to the following depths: HA- 1 = 24-inches, HA-2 = 32-inches, HA-3 = 35-inches. The observed underlying dense soils appear to match the description for glacially consolidated Vashon Till (Qvt). Groundwater seepage was not encountered at the boring locations. It is important to note that seepage levels may vary dependent upon the time of year and changes in surrounding development conditions. The results of our subsurface investigation are shown on the attached Appendix A — Hand- Augered Boring Logs & USCS Soil Legend. 1 "Geologic Map of the Edmonds East and Part of the Edmonds West Quadrangles", USGS, Minard, 1983. GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 941h Ave W, Edmonds, WA Page 3 EDMONDS GEOLOGIC HAZARDS — CRITICAL AREAS EVALUATION Based upon our review of the City of Edmonds GIS the subject site is mapped as having a known or suspect erosion and landslide hazards. The Edmonds Municipal Code defines Erosion Hazards and Landslide Hazards as Critical Areas — Geologically Hazardous Areas. Erosion Hazard The Edmonds Code defines Erosion Hazard Areas per the following: 23.80.020 Designation of specific hazard areas. A. Erosion Hazard Areas. Erosion hazard areas are at least those areas identified by the U.S. Department of Agriculture's Natural Resources Conservation Service as having a "moderate to severe, " "severe, " or "very severe" rill and inter -rill erosion hazard. Erosion hazard areas are also those areas impacted by shoreland and/or stream bank erosion. Within the city of Edmonds erosion hazard areas include: 1. Those areas of the city of Edmonds containing soils that may experience severe to very severe erosion hazard. This group of soils includes, but is not limited to, the following when they occur on slopes of 15 percent or greater: a. Alderwood soils (15 to 25 percent slopes); b. Alderwood/Everett series (25 to 70 percent slopes); c. Everett series (15 to 25 percent slopes); 2. Coastal and stream erosion areas which are subject to the impacts from lateral erosion related to moving water such as stream channel migration and shoreline retreat; 3. Any area with slopes of 15 percent or greater and impermeable soils interbedded with granular soils and springs or ground water seepage; and 4. Areas with significant visible evidence of ground water seepage, and which also include existing landslide deposits regardless of slope. We have reviewed the online USDA Web Soil Survey with regard to erosion susceptibility at the subject site. The mapped site soils are Alderwood gravelly sandy loam and Alderwood-Everett GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 94th Ave W, Edmonds, WA Page 4 gravelly sandy loam, with the former being the majority (90%). These soils are described has having a low erosion risk with K factors for the whole soil unit ranging from 0.05 to 0.1. Per the site topographic survey the maximum slope inclination at the site for a minimum run of 25-feet (min. 10-ft vertical relief) is 46 percent from the horizontal and this slope area is at the northwest portion of the lot. The west and northwest facing slopes at the west and northwest yard area range from 23 to 46 percent with the northern half of this slope area having an average inclination of 44 percent and the southern half having an average inclination of around 25 percent. The overall maximum height of the west site slopes is 12-feet. Our slope inclinations noted here include the vertical relief due to existing landscaping rockeries. The site qualifies as having Alderwood series soil with slope inclination in the range specified within the Code to qualify as an Erosion Hazard Area. Based upon our site investigation the subject site does not meet the criteria for items #2, 3 or 4 pertaining to Erosion Hazard classification. At the time of our subsurface investigation we observed the current slope conditions at the site. We did not observe signs of recent erosion or landsliding such as bare soil areas, scarps, slumps or set -downs. Site soils consist of primarily silty SAND and sandy SILT with varying amounts of gravel. Based upon our site investigation the site is not particularly prone to erosion risks. The erosion risks for the proposed development are low. The erosion risks at the steep slope area are moderate. However, no development or alteration is proposed at the steep slope area. We recommend that the erosion risks related to the proposed addition and deck development are mitigated by implementing standard erosion control Best Management Practices (BMPs) and that the recommendations contained herein are properly implemented. Erosion hazard mitigation for the temporary construction condition is recommended to include the installation and maintenance of filter fabric fences (silt fences) at the downhill side of the work area and the placement of silt socks at the nearest catchbasin which has the potential to collect site surface water, if any basins are located within 50-feet of the work area and are located downhill from the work area. For the permanent condition we recommend that erosion risks are mitigated by restoring the ground surface with hardscape or by planting and maintaining appropriate drought - tolerant native vegetation. GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 94th Ave W, Edmonds, WA Page 5 Provided that our erosion hazard mitigation recommendations are properly implemented and maintained during and following the proposed development it is the opinion of GEO Group Northwest that the proposed development: 1. Will not increase the threat of the geological hazard to adjacent properties beyond predevelopment conditions; 2. Will not adversely impact other critical areas; 3. Are designed so that the hazard to the project is eliminated or mitigated to a level equal or less than pre -development conditions, and 4. Are certified as safe as designed and under anticipated conditions, by a qualified engineer or geologist licensed in the State of Washington. Landslide Hazard The Edmonds Code defines Landslide Hazard Areas per the following: 23.80.020 Designation of specific hazard areas. B. Landslide Hazard Areas. Landslide hazard areas are areas potentially subject to landslides based on a combination of geologic, topographic, and hydrologic factors. They include areas susceptible because of any combination of soil, slope (gradient), slope aspect, structure, hydrology, or other factors. Within the city of Edmonds potential landslide hazard areas include: 1. Areas of ancient or historic failures in Edmonds which include all areas within the earth subsidence and landslide hazard area as identified in the 1979 report of Robert Lowe Associates and amended by the 1985 report of GeoEngineers, Inc., and further discussed in the 2007 report by Landau Associates; 2. Coastal areas mapped as class u (unstable), uos (unstable old slides), and urs (unstable recent slides) in the Department of Ecology Washington coastal atlas; 3. Areas designated as quaternary slumps, earthflows, mudflows, or landslides on maps published by the United States Geological Survey or Washington State Department of Natural Resources; GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 941h Ave W, Edmonds, WA Page 6 Simple Slope Calculation The slope calculation guidance shall be used to determine the toe and top of%slope for slopes that are potentially landslide hazard areas or potentially erosion hazard areas. Toe and top of landslide hazard areas (generally slopes of 40% or greater) delineated where incline reverses or diminishes to <40%over at least 10 feet of horizontal distance. Toe and top of erosion hazard areas (generally slopes 15-40%) delineated where incline reverses or diminishes to <15%over .f Im �f 1nfootMh.,ri—.tnl .I i,+.nro <40%slop hazard are slope (em area) over min 10 ft 10, Top of Slope v (Vertical Rise) %Slope= x100% H (Horizontal Run) Note: Steps, gradient changes, and incline reversals or breaks below percent slopes derini ng landslide hazard areas (40%) and erosion hazard areas (15%) shall be included as part ofthe larger slope. Figure 1 4. Any slope of 40 percent or steeper that exceeds a vertical height of 10 feet over a 25 foot horizontal run. Except for rockeries that have been engineered and approved by the engineer as having been built according to the engineered design, all other modified slopes (including slopes where there are breaks in slopes) meeting overall average steepness and height criteria should be considered potential landslide hazard areas); 5. Any slope with all three of the following characteristics: a. Slopes steeper than 15 percent; b. Hillsides intersecting geologic contacts with a relatively permeable sediment overlying a relatively impermeable sediment; and c. Springs or ground water seepage; GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 941h Ave W, Edmonds, WA Page 7 6. Any area potentially unstable as a result of rapid stream incision or stream bank erosion; 7. Any area located on an alluvial fan, presently subject to, or potentially subject to, inundation by debris flow or deposition of stream -transported sediments; and 8. Any slopes that have been modified by past development activity that still meet the slope criteria. GEO Group Northwest is aware of the Meadowdale area earth subsidence hazard area and the subject site is not located within this area. Based upon the DOE coastal atlas online mapping the subject site is located in an area which is mapped as "stable". GEO Group Northwest is not aware of any mapping by the USGS or WA DNR denoting the subject site as containing slumps, earthflows, mudflows or landslides. GEO Group Northwest did not find evidence of springs or seeps at the property at the time of our subsurface investigation. We also did not observe the presence of slope movement indicators such as bare earth, soil cracks, slump blocks, hillocky ground or bare soils areas. Based upon our subsurface investigation the underlying soils at the subject site consist of dense and competent glacial till soils. In general, these soils are relatively stable due to their well - consolidated condition. Alluvial fan soils are not located at the site. Loose to medium dense soils, if located overlying the dense soils at the steep slopes located at the northern half of the west yard area present a relatively low risk of soil movement. Our site investigation indicates that the competent and stable till soils are at relatively shallow depth at the investigation locations. Additionally, we did not observe groundwater seepage or surface water drainage concerns at the subject site. Therefore, based upon our site investigation it is our opinion that the northwest steep slopes (40% or steeper) at the site may qualify as a Landslide Hazard area, however, the risk of landsliding at this area is low and is not anticipated to change as a result of the proposed development. Risks related to landsliding at the steep slope area can be mitigated by maintaining native drought tolerant vegetation at steep slope areas, preventing the placement of fills or other structural loads on top of loose overlying soils at steep slopes and the proper routing of drainage away from steep slope areas. No development, alterations or impacts are proposed for the steep slope Landslide Hazard area discussed herein. The proposed west deck appears to be located at least 20-feet from the northwest steep slope area which has a maximum slope height of 12-feet. We recommend that the combined minimum buffer and setback from the top of the steep slope area to the proposed GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 94th Ave W, Edmonds, WA Page 8 development area is at minimum 10-feet. The buffer area at the top of the steep slope is recommended to be maintained with native drought tolerant vegetation and irrigation systems are not recommended at the steep slope area or within the buffer. SEISMIC DESIGN CRITERIA Based upon the subsurface investigation it is our opinion that the overlying 100-foot thickness of soils at the project site may be characterized as Site Class C soil (Very Dense Soil and Soft Rock) and may be designed accordingly for seismic loads per the IBC. According to an online Seismic Hazard tool the seismic coefficients are as follows: SS = 1.283g S1= 0.503g CONCLUSIONS AND RECOMMENDATIONS Based upon our subsurface investigation the proposed development is acceptable for the subject site soil conditions. We recommend that the footings for the new deck and addition are constructed to bear on top of the underlying competent medium dense to very dense glacially consolidated site soils or compacted structural fills placed on top of the competent soils. Based upon our investigation the competent soils are anticipated at standard footing depths at the southeast addition. However, at the west proposed deck area some over -excavation may be necessary to remove apparent overlying loose fills. If loose soils are encountered at the footing subgrades then over -excavation and replacement with compacted structural fill is recommended. We recommend that all foundation subgrades and compacted structural fills are approved by GEO Group Northwest at the time of construction, prior to foundation pour(s), in order to confirm compliance with the geotechnical recommendations. We recommend that the following recommendations and design parameters be incorporated into the design for the development. Site Preparation and General Earthwork The proposed development areas should be stripped and cleared of surface vegetation, organic soils (topsoil) and loose soils. Silt fences should be installed around areas disturbed by construction activity to prevent sediment -laden surface runoff from being discharged off -site. Exposed soils that are subject to GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 94th Ave W, Edmonds, WA Page 9 erosion should be compacted and covered with plastic sheeting. Stockpiled soils should be covered with plastic sheeting if work is done during wet weather in order to mitigate off -site sedimentation risks. Temporary Excavation Slopes and Permanent Slopes Under no circumstances should temporary excavation slopes be greater than the limits specified in local, state and national government safety regulations. Temporary cuts greater than four feet in height should be sloped at an inclination no steeper than 1H:1V (Horizontal:Vertical) in the overlying loose to medium dense site soils. If seepage is encountered at the building pad excavations, then temporary slopes should have inclinations of no steeper than 2H:1 V.. We recommend that permanent graded slopes shall be sloped no steeper than 3H:1 V unless faced by a rockery and that any fills placed at the areas where inclinations are steeper than 4H:1 V are compacted to meet the structural fill compaction requirements. Structural Fill All fill material used to achieve design site elevations below the building areas and below non - structurally supported slabs, parking lots, sidewalks, driveways, and patios, should meet the requirements for structural fill. During wet weather conditions, material to be used as structural fill should have the following specifications: 1. Be free draining, granular material containing no more than five (5) percent fines (silt and clay -size particles passing the No. 200 mesh sieve); 2. Be free of organic material and other deleterious substances, such as construction debris and garbage; 3. Have a maximum size of three (3) inches in diameter. All fill material should be placed at or near the optimum moisture content. The optimum moisture content is the water content in soil that enables the soil to be compacted to the highest dry density for a given compaction effort. Based upon our subsurface investigation the overlying site soils consist of silty soils which are moisture sensitive and fine-grained. These soils are not recommended to be placed as structural fill due to the difficulty of achieving the compaction criteria. It may be possible to use the native GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 94th Ave W, Edmonds, WA Page 10 soils for structural fills if they are to be placed during dry summer months if they can be adequately dried and compacted, however, drying the material and re -placing it may require significant space and may also take more time then replacement with an import. Alternatively, it may be beneficial and more efficient to import a granular fill material meeting the specifications noted above, especially if work is to be performed during a period of wet weather. Structural fill should be placed in thin horizontal lifts not exceeding ten inches in loose thickness. Structural fill under building areas (including foundation and slab areas) and behind earth reinforced retaining walls (segmental block retaining walls and geo-grid reinforced rockery walls), should be compacted to at least 92 percent of the maximum dry density, as determined by ASTM Test Designation D-1557-91 (Modified Proctor). Structural fill under driveways, parking lots and sidewalks should be compacted to at least 90 percent maximum dry density, as determined by ASTM Test Designation D-1557-91 (Modified Proctor). Fill placed within 12-inches of finish grade should meet the 92% requirement. We recommend that GEO Group Northwest, Inc., be retained to evaluate the suitability of structural fill material and to monitor the compaction work during construction for quality assurance of the earthwork. Spread Footing Foundations The proposed new addition and deck foundations may consist of conventional spread footings bearing on top of the underlying medium dense to dense competent glacially consolidated site soils or on compacted structural fill which is placed and compacted on top of the competent soils. The footings should not be constructed on top of loose fills. Loose soils present settlement related risks to the foundations. Based upon the subsurface investigation it is anticipated that the competent soils may be present at typical shallow foundation depths except potentially at the west deck footing locations. We recommend that where loose soils are encountered at the footing subgrades that these areas are over -excavated to expose the underlying competent medium dense to dense glacially consolidated soils. Compacted structural fill may then be placed and compacted in the over -excavated area in order to fill the over -excavated area to the proposed footing subgrade level. Structural fills should be placed and compacted in accordance with the Structural Fill section of this report. We recommend that all foundation subgrades are approved by GEO Group Northwest at the time of construction, prior to the foundation pour, in order to confirm that the subgrades consist of the competent soils and that they have been properly prepared. GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 941h Ave W, Edmonds, WA Page 11 Individual spread footings may be used for supporting columns and strip footings for bearing walls. Our recommended minimum design criteria for foundations bearing on the medium dense to dense competent glacial till site soils or on compacted structural fill placed on top of these soils are as follows: Allowable bearing pressure, including all dead and live loads Medium dense to dense glacially consolidated soils = 2,000 psf Compacted structural fill on top of the medium dense to dense competent native soils = 2,000 psf - Minimum depth to bottom of perimeter footing below adjacent final exterior grade = 18 inches - Minimum width of wall footings = 16 inches Minimum lateral dimension of column footings = 24 inches - Estimated post -construction settlement = 1/4 inch A one-third increase in the above allowable bearing pressures can be used when considering short-term transitory wind or seismic loads. Lateral loads can also be resisted by friction between the foundation and the supporting compacted fill subgrade or by passive earth pressure acting on the buried portions of the foundations. For the latter, the foundations must be poured "neat" against the existing undisturbed soil or be backfilled with a compacted fill meeting the requirements for structural fill. Our recommended parameters are as follows: - Passive Pressure (Lateral Resistance) 350 pcf equivalent fluid weight for compacted structural fill 350 pcf equivalent fluid weight for native dense soil. - Coefficient of Friction (Friction Factor) 0.35 for compacted structural fill 0.35 for native dense soil GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 94th Ave W, Edmonds, WA Page 12 Drainage Considerations We recommend that subsurface drains (footing drains) be installed at the perimeter of continuous spread footings and tightlined to an approved discharge point or stormwater system. Footing drains should consist of a four -inch minimum diameter, perforated, rigid PVC drain pipe laid at the bottom of the footing with a gradient sufficient to generate flow. The footing drain line should be bedded on and surrounded with drain rock or other appropriate, free -draining, granular material. The drain rock should be wrapped in a layer of geotextile fabric such as Mirafi 18ON or equivalent. After the footing drains are installed, the excavation should be backfilled with compacted structural fill material. Under no circumstances should roof downspout drain lines be connected to the footing drainage system. All roof downspouts should be separately tight lined to an appropriate storm -water discharge point. We recommend that sufficient cleanouts be installed at strategic locations in each of the drainage systems to allow for periodic maintenance of and clearing of possible future blockages. ADDITIONAL SERVICES We recommend that GEO Group Northwest Inc. be retained to perform a general plan review of the final design and specifications for the proposed development to verify that the earthwork and foundation recommendations have been properly interpreted and implemented in the design and in the construction documents. We also recommend that GEO Group Northwest Inc. be retained to provide monitoring and testing services for geotechnically-related work during construction. This is to observe compliance with the design concepts, specifications or recommendations and to allow design changes in the event subsurface conditions differ from those anticipated prior to the start of construction. We anticipate that geotechnical construction monitoring inspections may be necessary for the following construction tasks: 1. Foundation subgrade preparation and verify bearing conditions; 2. Structural fill placement and compaction; LIMITATIONS This report has been prepared for the specific application to this site for the exclusive use of Mr. David Jenkins and his authorized representatives. Any use of this report by other parties is solely at that party's own risk. GEO Group Northwest, Inc. March 4, 2021 G-5362 Geotechnical Report — 18914 — 941h Ave W, Edmonds, WA Page 13 Our findings and recommendations stated herein are based on field observations, our experience and judgement. The recommendations are our professional opinion derived in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area and within the budget constraint. No warranty is expressed or implied. In the event that soil conditions not anticipated in this report are encountered during site development, GEO Group Northwest, Inc., should be notified and the above recommendations should be re-evaluated. If there are any questions please do not hesitate to contact us. Sincerely, GEO GROUP NORTHWEST, INC. Adam Gaston Project Engineer Cf�/q� yJ *AS �► � T M O 2p114 O IONAL William Chang, P.E. Principal Attachments: Plate 1 — Vicinity Map Plate 2 — Topographic Survey Plate 3 — Site Plan Appendix A — Hand-Augered Boring Logs and USCS Soil Legend GEO Group Northwest, Inc. Chris SolilhWeal CounV Park I-W Crosswis) E Park Cyphers Jeannette A United States Postal Service 9 in Seaview Park Off -leash ©Lynndade DugArea Hull Park Brandon Maldonado 9 Seaview 45 dernentairy School PEARINVILLE 19 is 4 AW. &Edrn.r d O11 A 98020 P;jrk T 9 As-sociales Maggie Lawrerce 9 Portofino 1, Restaurant & Bar Edmonds Sovonlh-Day Adyiuntim Church V Royal India Lyn%vo<A Pizza Flu, 7 Grace Lo1hr-ran Church QFC 19611, �l sw 9 'F'1'r`rn0Pn4v'iry School I'"inwood Ice Ctrwn Maplewood all VICINITY MAP Group Northwest, Inc. 18914 - 94TH AVE W 13705 Bel -Red Rd, Bellevue, WA 98005 Phone 425/649-8757 FAX 425/649-8758 EDMONDS, WASHINGTON Email info@geogroupnw.com SCALE: NTS DATE: 2-12-21 1 MADE: AG JOB NO.: G-5362 PLATE: 1 1 SCALE IN FEET * SYMBOLS MONUMENT IN CASE M BB@BEHBBQfl15 MAPLE TREE LEfT = EDGE OF ASPIIALr FOUND SURVEY MARKER AS NOTED F nR TREE RIGHT OF MY GE MW MO 1•} CONIFER TREE C CEDAR TREE - - RIGHT OF WAY (Ury BOUNDARY L E DECIDUOUS TREE HEM HEMLOCK TREE A DHA SURVEY CONTROL _R R_ FEND: LAW B BIRCH TREE — - - - 0---- 0— (R OAS Me SHRUB/RHODWODRpI OI CHMY WEE ---- E ---- E — IR p21D POET! LOE I� POWER/TELETYIdE AWCWH BOX DEC DECDUOUS TREE ----E----CE— OIEMEAB POER LIE ® CAS METER SSMH SANITARY SEVER NIANHOE ---- T - - - - T— (NC1MMM O=KffBA7K W LBE Iti GAS VALVE CB STOBU DRAIN r4M H BASIN ---- ----S)— S1=1 WE { CULVERT E NV141T E(EVATXW --------� mcemmmm $NN � A YARD LIGHT -- R---- R— (008010M WER WE O ST'IM CATCH 943M BOT P.A. morma1 slwicnw PLAN= Q SANITARY SEER MANHOLE AREA SeD71 / M METER METER / a 4 POREN POE / enf Q 1TOL7aRY / / o PA eo6'V~- / /' / ✓ / / e'a r ✓ /� PA I a // // c - �/ PATH 'DEC / % / // Q aEOK 9WK / PA f / p ° ®// l % PA I HA-3 p O°"C PADGlum 94TH AVENUE W. TAM )W BAB 12 ENT FFMsmw �FLOW N ASAO.BOB aEYr2BB.0• tl amir b �rw xv PA PA x Ionra I I I I Ir OUFA(L jII NOr LOCATED I uI ` f l R �l mK T E NW 2=0 � ES2=6h I bOT ...Ma-Ar_To a4• MIT ' I Q I I PA Au ME ! {° EA11 -�E----E�'~ Q PA QsraB4��s� *� E ASFU4LT \ owl£ -v Q FMW NM WE af1V X an SE OMWER TRACT 64 "T s I 8�I to �� to III ' A539YAI.T I I INBK I (I 1 1 ANT 1-710 N' RM 2',JEDB E N 247.0 to (I I ESH471� E E 247.4 1 I I I OIMBM BO w�TI to I I -�� / 3 � 00 I Ti WAKE II f BASED UPON THE TOPOGRAPHIC SURVEY BY DUANE HARTMAN AND ASSOCIATES, I-28-21. F if / 00 ASPHALT DINE ` LANDSu �HAZAR EA PER CITY& J EDMONDGIS MAPSj40%-) SINGLE FAMILY RESIDENCE 15914941h Ave W. Edmonds. WA98020 00434600006403 / / I °°"°°" HA-1 / r `-------------------------- r � N I f } ® 1 f I 1 \ 1 1 1 I 1 I 1 I 1 I 1 I 1 I � I � I I I I I I I I I I I I I I I I / I I I / I BASED UPON THE SITE PLAN FOR "HUTT PARK" BY ALEXANDRA IMMEL RESIDENTIAL DESIGN, 1-11-2021. APPENDIX A HAND-AUGERED BORING LOGS & USCS SOIL LEGEND G-5362 LEGEND OF SOIL CLASSIFICATION AND PENETRATION TEST UNIFIED SOIL CLASSIFICATION SYSTEM (USCS) MAJOR DIVISION GROUP TYPICAL DESCRIPTION LABORATORY CLASSIFICATION CRITERIA SYMBOL WELL GRADED GRAVELS, GRAVEL -SAND Cu = (D60 / D10) greater than 4 CLEAN Gyy MIXTURE, LITTLE OR NO FINES Cc = (D302) / (D10 ` D60) between 1 and 3 GRAVELS DETERMINE PERCENTAGES OF GRAVELS (little or no GP POORLY GRADED GRAVELS, AND GRAVEL- GRAVEL AND SAND NOT MEETING ABOVE REQUIREMENTS (More Than Half fines) SAND MIXTURES LITTLE OR NO FINES FROM GRAIN SIZE COARSE- Coarse Grains DISTRIBUTION ATTERBERG LIMITS BELOW GRAINED SOILS Larger Than No. 4 CURVE Sieve) DIRTY GM SILTY GRAVELS, GRAVEL -SAND -SILT MIXTURES CONTENT "A" LINE. GRAVELS OF FINES or P.I. LESS THAN 4 EXCEEDS ATTERBERG LIMITS ABOVE (with some GC CLAYEY GRAVELS, GRAVEL -SAND -CLAY "A" LINE. fines) MIXTURES COARSE GRAINED SOILS ARE or P.I. MORE THAN 7 CLASSIFIED AS SANDS WELL GRADED SANDS, GRAVELLY SANDS, FOLLOWS: Cu 2(D60 / D10) greater than 6 CLEAN SW LIITLE OR NO FINES Cc = (D30 ) / (D10 ` D60) between 1 and 3 SANDS (More Than Half More Than Half Coarse Grains (little or no SP POORLY GRADED SANDS, GRAVELLY SANDS, < 5 % Fine Grained: NOT MEETING ABOVE REQUIREMENTS by W eight Larger Smaller Than No. fines ) LITTLE OR NO FINES GW, GP, SW, SP Than No. 200 4 Sieve) ATTERBERG LIMITS BELOW Sieve DIRTY SM SILTY SANDS, SAND -SILT MIXTURES > 12% Fine Grained: CONTENT OF "A" LINE SANDS GM, GC, SM, SC FINES with P.I. LESS THAN 4 5 to 12% Fine EXCEEDS DS ATTERBERG LIMITS ABOVE (with some SC CLAYEY SANDS, SAND -CLAY MIXTURES Grained: use dual "A" LINE fines) symbols with P.I. MORE THAN 7 SILTS Liquid Limit INORGANIC SILTS, ROCK FLOUR, SANDY SILTS (Below A -Line on < 50% ML OF SLIGHT PLASTICITY 60 Plasticity Chart, PLASTICITY CHART A -Line Liquid Limit INORGANIC SILTS, MICACEOUS OR FINE-GRAINED Negligible FOR SOIL PASSING 50 SOILS Organic) > 500� MH DIATOMACEOUS, FINE SANDY OR SILTY SOIL NO. 40 SIEVE o CH or OH INORGANIC CLAYS OF LOW PLASTICITY, X 40 CLAYS Liquid Limit CL GRAVELLY, SANDY, OR SILTY CLAYS, CLEAN 0 (Above A -Line on < 30 % CLAYS Z Placticity Chart, 30 Liquid Limit INORGANIC CLAYS OF HIGH PLASTICITY, FAT Negligible H Organic) > 500� CH CLAYS U CL or OL 20 � More Than Half Q / by Weight Liquid Limit ORGANIC SILTS AND ORGANIC SILTY CLAYS OF o_ MH or OH Smaller Than No. ORGANIC SILTS <50% OL LOW PLASTICITY 10 - / ML 200 Sieve & CLAYS 7 L_M �Lj (Below A -Line on 4 Placticity Chart) Liquid Limit OH ORGANIC CLAYS OF HIGH PLASTICITY 0 > 50% 0 10 20 30 40 LIQUID 0 60 70 80 90 100 110 LIMIT (%) HIGHLY ORGANIC SOILS Pt PEAT AND OTHER HIGHLY ORGANIC SOILS SOIL PARTICLE SIZE GENERAL GUIDANCE OF SOIL ENGINEERING PROPERTIES FROM STANDARD PENETRATION TEST (SPT) U.S. STANDARD SIEVE FRACTION Passing Retained SANDY SOILS SILTY & CLAYEY SOILS Sieve S1Ze Sieve S1Ze Blow Relative Friction Blow Unconfined (mm) (mm) Counts Density Angle Description Counts Strength Description SILT / CLAY #200 0.075 N % 0, degree N qu, tsf SAND 0-4 0 -15 Very Loose < 2 < 0.25 Very soft FINE #40 0.425 #200 0.075 4-10 15 - 35 26 - 30 Loose 2-4 0.25 - 0.50 Soft MEDIUM #10 2 #40 0.425 10-30 35 - 65 28 - 35 Medium Dense 4-8 0.50 -1.00 Medium Stiff COARSE #4 4.75 #10 2 30-50 > 50 65 - 85 85 -100 35 - 42 38 - 46 Dense Very Dense 8 - 15 15 - 30 1.00 - 2.00 2.00 - 4.00 Stiff Very Stiff GRAVEL FINE 19 #4 4.75 > 30 > 4.00 Hard COARSE 76 19 _ Group Northwest, Inc. COBBLES 76 mm to 203 mm BOULDERS > 203 mm Geotechnical Engineers, Geologists, & Environmental Scientists ROCK FRAGMENTS >76mm 13240 NE 20th Street, Suite 10 Bellevue, WA 98005 Phone (425) 649-8757 Fax (425) 649-8758 PLATE Al ROCK >0.76 cubic meter in volume HAND AUGERED BORING NO: HA-1 LOGGED BY AG LOG DATE: 2/11/2021 DEPTH ft. USCS SOIL DESCRIPTION SAMPLE No. Water % OTHER TESTS/ COMMENTS ML Dark brown fine sandy SILT with some cobbles and roots, moist, medium dense to dense (planter surfacing and topsoils _ _ _ _ _ _ _ _ _ _ _ _ SM/ Tan silty SAND with some gravel becoming gray gravelly sandy ML SILT, moist, dense (TILL) Probe 0.5" 2 Probe 0.5" Total depth of boring = 24" bgs (below ground surface) 3 No groundwater seepage observed 4 5 6 7 LOGGED BY AG HAND AUGERED BORING NO: HA-2 LOG DATE: 2/11/2021 DEPTH ft. USCS SOIL DESCRIPTION SAMPLE No. Water % OTHER TESTS/ COMMENTS ML Dark brown fine sandy SILT, moist, medium dense to dense (topsoil) --- ---- -------------------------------------------------- SM/ Tan gravelly silty SAND becoming gray fine sandy SILT with 2 ML occasional gravel, moist, dense (TILL) Probe 1-2" Probe 1" Probe 0.5" 3 Probe 0.5" Total depth of boring = 32" bgs (below ground surface) No groundwater seepage observed 4 5 6 7 Group Northwest, Inc. Geotechnical Engineers, Geologists, & Environmental Scientists HAND AUGERED BORING LOG PROPOSED ADDITION AND DECK 18914 - 94TH AVE W EDMONDS, WA HAND AUGERED BORING NO: HA-3 LOGGED BY AG LOG DATE: 2/11/2021 DEPTH ft. USCS SOIL DESCRIPTION SAMPLE No. Water % OTHER TESTS/ COMMENTS ML Dark brown sandy SILT, moist, medium dense (topsoil) 1 ---- SM/ ------------------------------------------------ Tan and brown sandy SILT and silty SAND with occasional gravel, Probe 12" ML moist, loose (apparent fill) Probe 6-10" 2 ............................................................ -- ---- -------------------------------------------------- Probel2" 3 ML Gray gravelly fine sandy SILT, moist, dense (TILL) Probe 1" Total depth of boring = 35" bgs (below ground surface) 4 Auger refusal due to dense/gravel at 35" bgs Dense competent soils below 29" bgs No groundwater seepage observed 5 6 7 HAND AUGERED BORING NO: 11•zKHa•11-yd DEPTH ft. USCS SOIL DESCRIPTION SAMPLE No. Water % OTHER TESTS/ COMMENTS 1 2 3 4 5 6 7 Group Northwest, Inc. Geotechnical Engineers, Geologists, & Environmental Scientists HAND AUGERED BORING LOG PROPOSED ADDITION AND DECK 18914 - 94TH AVE W EDMONDS, WA