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Geotech Report 2018.10.20.pdfJJA File#: 18054 I Date: 2018.10.20 8029 238th Street SW Edmonds RUOYUN ZHEN 8029 238th Street SW Edmonds WA 98026 Attn: Mara Moral Re: 8029 238th Street SW Edmonds Parcel: 451900102000 Permit#: PLN20180058 At your request, we have conducted a soils exploration and foundation evaluation for the above mentioned project. The results of this investigation, recommendations, net allowable soil pressures, embedment depth, soil parameters, and total expected settlements have been presented for the site, later in the report. The results of the exploration and analysis indicate that conventional spread and continuous wall footings appear to be the most suitable type of foundation for the support of the proposed structure. Net allowable bearing capacity is suitable for 2,000 psf. Dense, silty sand (till) was found in each location at 2 to 4 feet below the surface. A conventional spread and continuous wall footings appear to be the most suitable type of foundation for the support of the proposed structure. Any infiltration system would need to be considerably deep enough to avoid water gradients across the slowly permeable substratum directing water to the neighboring property to the east. Permeable pavements and infiltration are not recommended per Appendix A of the Edmonds Storm water manual. We recommend connecting to the existing city maintained storm system. We appreciate this opportunity to be of service to you and we look forward to working with you in the future. If you have'any questions concerning this report, the procedures used, or if we can be of any further assistance please call us at (20f) 786-8645. JJA, INC �� o Jason Bell Senior Engineer 37343 O ;� o�J STC.R�G��`� 1L RECEIVED DEC 0 3 2018 DEVELOPMENT SRERVICES COUNTE (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA JJA File#: 18054 I Date: 2018.10.20 8029 238th Street SW Edmonds Table of Contents Table of Contents 2 Investigation Information 3 Introduction 3 Scope: 3 Drilling & Sampling Procedures: 3 Site Information 4 Project Description 4 Landslide hazard area categories 4 Geology of Area: Alderwood-Urban land, 2 to 8 percent slopes 4 Description of Foundation Materials: 5 Geoseismic Setting / Site Class: 5 Liquefaction Potential: 5 Percolation Rate: 6 Foundation Discussion & Recommendations 7 General Notes: 7 Foundation Design Recommendations: 7 Lateral Earth Pressures: 7 Surface and Groundwater Control: 8 Structural Fill: 8 Settlement 8 Slope Impact Analysis& Recommendations: 8 Drainage 9 Conclusion 9 Construction Considerations 11 Earthwork: 1 1 Excavations: Floor Slab -On -Grade: _ Utilities Erosion Control (typical Site Pictures Appendix: Figures 1.0 Site Location 2.0 USGS Soil Map 3.0 County GIS 4.0 Liquefaction and Soil Site Class 5.0 Soil Log 6.0 Bearing Capacity 7.0 Settlement 8.0 Footing Detail 9.0 USGS Seismic Design Summary Report 10.0 Perc Test Results 11.0 Site Plan (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA 11 11 12 12 13 14 JJA File#: 18054 I Date: 2018.10.20 8029 238th Street SW Edmonds Investigation Information Introduction This report presents the results of a soils exploration and foundation analysis for the proposed new construction located at 8029 238th Street SW Edmonds. The subsurface exploration and analysis determines the various soil profile components, the engineering characteristics of the foundation materials and provides criteria for the design engineers and architects to prepare or verify the suitability of the foundation design. This report was requested by Mara Moral. Written authorization to perform this exploration and analysis was provided by Mara Moral. Parcel information, size and legal description are summarized below: Address: 8029 238th Street SW Edmonds WA 98026 Parcel: 451900102000 Legal: FRUITLAND ACRES TO LAKE BALLINGER BLK 001 D-00 S 100FT LOT 20 Lot Size 12,197 SF (0.28 AC) Scope: The scope of this geotechnical report and analysis included; a review of geological maps of the area, review of geologic and related literature, a reconnaissance of the immediate site, subsurface exploration, field and laboratory testing, and an engineering analysis and evaluation of the foundation materials to provide allowable bearing capacity, estimates of settlement, subgrade modulus, lateral earth pressure design values, geotechnical recommendations for site grading including site preparation, subgrade preparation, fill placement criteria, suitability of on -site soils as structural fill, drainage and erosion control measures, as well as an evaluation of landslide and erosion hazards at the site per the Critical Areas regulations. We were not requested to provide an Environmental Site Assessment for this property. Any comments concerning onsite conditions and/or observations, including soil appearances and odors, are provided as general information. Information in this report is not intended to describe, quantify or evaluate any environmental concern or situation. The exploration and analysis of the foundation conditions reported herein are considered sufficient in detail and scope to form a reasonable basis for the foundation design. Any revision in the plans for the proposed structure from those enumerated in this report should be brought to the attention of the soils engineer so that he may determine if changes in the foundation recommendations are required. If deviations from the noted subsurface conditions are encountered during construction, they should also be brought to the attention of the soils engineer. The soils engineer warrants that the findings, recommendations, specifications, or professional advice contained herein, have been promulgated after being prepared according to generally accepted professional engineering practice in the fields of foundation engineering, soil mechanics and engineering geology. No other warranties are implied or expressed. This investigative report has been prepared for the exclusive use of Evergreen Contracting and retained design consultants thereof. Findings and recommendations within this report are for specific application to the proposed project. All recommendations are in accordance with generally accepted soils and foundation engineering practices. Drilling & Sampling Procedures: The test pits were hand augured. Representative samples were obtained from the pit at various soil intervals. The samples obtained by this procedure were classified in the field by a soils technician, identified according to pit (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA JJA File#: 18054 1 Date: 2018.10.20 8029 238th Street SW Edmonds number and depth, placed in plastic bags to protect against moisture loss and transported to the laboratory for additional testing. The test pits were advanced to 6 feet below the existing ground surface. A site plan was obtained by the architect for the approximate building locations. The test pits were located by the field crew relative to the nearest property corner for orientation and position of the excavations by means of normal taping and pacing procedures. Measurements are presumed to be accurate to within a few feet. After completion, the pits were backfilled with excavated soils and the site cleaned and leveled as required. The types of foundation materials encountered were visually classified and described in detail on the logs provided in the Appendix. Site Information Project Description The purpose of this section is to provide details of the proposed structure. Information was provided by the architect, Atlas Associates. The new construction will be a four unit, multi -story, wood framed, multi -family townhomes. No basements are planned. Conventional spread and column footings and slab -on -grade floors are contemplated. Differential settlements are limited to 3/a inch. The site topography consists is a general slope to the east of 12%. Total vertical relief is 10 feet over 86 feet. The east side of the property is bordered by multi -family residences. The South side is bordered by 238th Street SW and the north and west sides are paved parking lots for the adjacent businesses. Access to the property is from the south off 238`' Street SW. There is an existing wall approximately 4 feet high along the north side and the NW corner adjacent to the parking lot area. There is also a 6 foot wall along the east side adjacent t the existing multi- family residences. There is an existing single family house intended to be demolished. The site vegetation is mostly grass with heavy shrubbery on the north side. There are a few trees on the west side that are intended to stay. The south side has a driveway which will continue to be access to the new structure. The site drainage consists of surface runoff to the east and natural seepage. Landslide hazard area categories The total vertical relief is 10 feet over 86 feet with an average slope of 12% within the property. There is an existing wall along the east side adjacent to the existing multi -family residences. Including the additional elevation drop on the east side, the total vertical relief is 18 feet over 125 feet with an average just under 15%. Geology of Area: Alderwood-Urban land, 2 to 8 percent slopes The geology of the site and surrounding area as taken from the USDA Soil Conservation Service Survey consists of Alderwood-Urban land complex, 2 to 8 percent slopes. Elevation is 50 to 550 feet. This unit is about 60 percent Alderwood gravelly sandy loam and about 25 percent Urban land on till plains. The Alderwood soil formed in glacial till, is moderately deep over a hardpan and is moderately well drained. Typically, the surface layer is very dark grayish brown gravelly sandy loam about 7 inches thick. The upper part of the subsoil is dark yellowish brown and dark brown very gravelly sandy loam about 23 inches thick. The lower part is olive brown very gravelly sandy loam about 5 inches thick. A weakly cemented hardpan is at a depth of about 35 inches. Depth to the hardpan ranges from 20 to 40 inches. Permeability of the Alderwood soil is moderately rapid above the hardpan and very slow through it. Available water capacity is low. A seasonal perched water table is at a depth of 18 to 36 inches from January to March. Runoff is slow, and the hazard of water erosion is slight. The native vegetation is mainly conifers. (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA JJA File#: 18054 1 Date: 2018.10.20 8029 238th Street SW Edmonds Urban land is areas that are covered by streets, buildings, parking lots, and other structures that obscure or alter the soils so that identification is not possible. The Alderwood soil in this unit is used mainly for parks, building sites, lawns, gardens, and woodland. The main limitations of the Alderwood soil for homesites and septic tank absorption fields are the depth to the hardpan and the seasonal perched water table. Onsite waste disposal systems often fail or do not function properly during periods of high rainfall. Drainage is needed if buildings with basements and crawl spaces are constructed. Additions of fertilizer and peat are desirable prior to seeding grass for lawns. This map unit is in capability subclass IVe. Description of Foundation Materials: Typical soil characteristics for glacial till were observed during the investigation. We are in agreement with the USGS description of Alderwood-Urban land for the site and have confirmed the soil type during the subsurface investigation. No water seeps were noted during the site exploration. Organic material was not typical deeper than 2 feet from the existing surface in the investigation. It should be noted that the test pits were placed and sampled by an experienced technician. However, it is sometimes difficult to record changes in stratification within narrow limits. In the absence of foreign substances, it is also difficult to distinguish between discolored soils and clean soil fills. It is recommended that the logs not to be used for estimating quantities due to highly interpretive results. Geoseis`nic Setting / Site Class: Foundation soils on this site are designated Site Class C per the Washington State Department of Natural Resources map. All building structures on this project should be designed per the Code Requirements for such a seismic classification. These types of soils have a shear wave velocity in the range of 1,200 to 2,500 ft/sec. The undrained shear strength is typically greater than 2,000 psf with blow counts greater than 50 blows per foot. Site coefficients are provided by the USGS detailed report provided in the Appendix. (http://earthquake.usgs.gov/desigmnaps/us/application.php) Liquefaction Potential. In our review we found no evidence of liquefaction of the soils in the immediate area from the 1949, 1965 and 2001 earthquakes. Information on the site has been reviewed on Liquefaction Susceptibility Map provided by the Department of Natural Resources rates the site VERY LOW susceptibility to liquefaction. We are in agreement with the provided literature. Liquefaction is when saturated, cohesionless soils are temporarily turned in to a liquid state usually from a seismic event. If ground motion lasts for extended amounts of time, the grain to grain contact shifts and the grain structure can collapse. If the water within the soil cannot flow easily between the grain and out of a collapsing area, the water pressure increases. When pore pressures build up within the soil and exceed the effective contact pressure of the soil, the water can push the soil particles apart. When the particles lose contact with each other, the soil mass can behave like a liquid. If pore pressures are great enough, water may discharge out of the ground like a geyser leaving characteristic signs, such as sand boils. Liquefaction is generally related to; soil characteristics, water table depths and the degree of seismic activity. The results are lower bearing capacities, increased settlement issues, landslides, and lateral spreading to name a few things. Liquefaction potential for this site is provided within the boundaries of the site. Seismic events which affect land masses on a greater scale are beyond the scope of this report. The largest earthquakes in recent history in the Puget Sound Region are the 1949 surface wave (magnitude 7.1) in Olympia, the 1965 Seattle -Tacoma earthquake (magnitude 6.5) and the 2001 (magnitude 6.8). All of the historic liquefaction sites are located in the Duwamish valley in Holocene alluvium (Category I deposits). Liquefaction during the 1949 and 1965 earthquakes were mostly in the form of sand blows and surface cracking which was (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 SPA JJA File#: 18054 1 Date: 2018.10.20 8029 238th Street SW Edmonds substantiated with many eyewitness observers living in the Pacific/Algona area. Broken water lines were reported in Auburn during the 1949 event suggests lateral spreading. Vertical ground water seepage around sewer manholes was also observed in Auburn, but no broken sewer lines were reported. From well records, Osceola deposits are 265 ft below sea level at a site 4 miles north of Auburn. The deposit is found at this depth because the Duwamish valley was an arm of the Puget Sound at that time. An important surface exposure of the Osceola Mudflow in a cut bank of the Puyallup River at Sumner suggests that the mudflow extended in the subsurface to Puyallup. Percolation Rate: We performed the percolation testing in accordance with the applicable EPA standards for a falling head percolation test. The depth of the testing was 5 feet beneath the existing surface. Test hole #1 (TH-1) was used for the perc test. Several tests were run to obtain consistent readings. No safety factor is applied to the perc test values provided. The resulting average was 3.79 min/inch (16.72 inches/hour). Full test results are provided in the Appendix. Knowledge of the engineering characteristics of the foundation materials at the proposed building site was confirmed with a field investigation. Due To the presence of the slowly permeable glacial till at shallow depths, we do not recommend infiltration for this site. (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA JJA File#: 18054 I Date: 2018.10.20 8029 238th Street SW Edmonds Foundation Discussion & Recommendations General Notes: Various foundation types have been considered for the support of the proposed building structure. Two requirements must be fulfilled in the design of foundations. First, the load must be less than the ultimate bearing capacity of the foundation soils to maintain stability; and secondly, the differential settlement must not exceed an amount that will produce adverse behavior of the superstructure. The allowable settlement is usually exceeded before bearing capacity considerations become important; thus, the allowable bearing pressure is normally controlled by settlement considerations. Settlements should not exceed tolerable limits if the following design and construction recommendations are observed. We expect the building to utilize continuous strip foundations for the perimeter and interior footings. Foundation Design Recommendations: On the basis of the data obtained from the site and the test results from the various laboratory tests performed, we recommend that the following guidelines be used for the net allowable soils bearing capacity of 2,000 psf. All footings are required to be a minimum of 18 inches below grade for freeze thaw purposes. Place on native, undisturbed soils. These soils shall be confirmed for bearing capacity and verified by the soils engineer after excavation. The West side will required additional structural fill to get to foundation grade after the organics have been removed. A� We recommend conventional spread and continuous wall footings, at least 24 inches wide. Al Place 6 inches of crushed rock over the compacted native for a leveling course. This wall also assisted in water migration under the footing. Confirm compaction of the native soils and that any excessively loose or soft spots have been removed and replaced with at least 1 foot of suitable structural fill material and compacted to least 95% of the maximum dry density as determined by ASTM D-1557. The footings should be proportioned to meet the stated bearing capacity and/or the current minimum requirements of the current International Building Code. Total settlement should be limited to 1 inch total with differential settlement of/4 inch. In order to minimize the effects of any slight differential movement that may occur due to variations in the characters of the supporting soils and any variations in seasonal moisture contents, it is recommended that all continuous footings be suitably reinforced to make them as rigid as possible. Lateral Earth Pressures: Lateral earth pressures are dependent upon the backfill materials and their configuration and moisture content. Two inch minus sand and gravel mixtures that are free draining are recommended for backfilling walls greater than four feet tall. Any retaining walls or earthen fills anticipated for this project may use the following values for design. Values were obtained by using unit weight of 125 pcf, and phi angle of 30 degrees. Earth Pressure Coefficients Earth Pressure Active, Ka: 0.333 Active: 42 lbs./ft3 At Rest, Ko: 0.500 At Rest: 63 lbs./ft3 Passive, KP: 3.000 Passive: 375 lbs./ft3 Coefficient of Friction: 0.35 (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA JJA File#: 18054 I Date: 2018.10.20 8029 238th Street SW Edmonds Surface and Groundwater Control: Seeps were not encountered at the time the field exploration was conducted. Groundwater is not expected to cause difficulties during the construction of this project. It is recommended that runoff caused by wet weather be directed away from all open excavations. Exterior grades should be sloped away from the structure a minimum of 2% for the at least 10 feet from the structure. A perforated 6 inch PVC perimeter footing drain is recommended. Perimeter footing drains should connect to the storm system separate from the downspout system. Any and all roof drains should be rigid, solid PVC pipe and placed with positive gradient to allow gravity discharge away from the foundation. Roof and surface drains should NOT be connected to footing drains. Mottled soil indicates seasonal soil saturation (alternate oxidizing and reducing conditions). In other words, water flows through this layer periodically creating a saturated soil condition at times and at other times the soil may be dry. This can create soft, saturated areas, problems for basement and septic fields, and poor aeration for landscape plantings. Implementation of perimeter footing drains should alleviate many difficulties associated with these soil conditions. Structural Fill. Structural fill should consist of a 2 inch minus select, clean, granular soil with no more than 10% fines (4200). Suitable structural fill should consist of material that meets one of the following specifications, WSDOT Section 9- 03.9(3) Crushed Surfacing (Base Course Specs), WSDOT Section 9-03.9(3) Crushed Surfacing (Top Course Specs), quarry spalls, or railroad ballast. Material that does not meet one of the specifications should be submitted with sieve analysis results for approval prior to placement. The fill should be placed in lifts not to exceed 12 inches in loose thickness. Each layer of structural fill should be compacted to a minimum density of 95% of the maximum dry density as determined by ASTM designation D-1557. For structural fill below footings, the area of the compacted backfill must extend outside the perimeter of the foundation for a distance at least equal to the thickness of the fill between the bottom of the foundation and the underlying soils. If it is elected to utilize a compacted backfill for the support of foundations, the subgrade preparation and the placing of the backfill should be monitored continuously by a qualified engineer or his representative so that the work is performed according to these recommendations. The use of on -site soils as structural fill is not recommended. Settlement Organic material can compress and result in differential settlement that is detrimental the life and integrity of any foundation. They should be removed prior to the start of any construction. Silty sand layers were encountered beneath the existing topsoil and extended to depths beyond the scope of this investigation. Lines of demarcation represent the approximate boundary between the soil types, but the transition may be gradual. A comparison was made regarding footing width. With all else being equal, a footing width of 1.5 feet exceeds the settlement criteria. Therefore, the minimum recommended footing width is 2 feet. Settlement calculations are included in the Appendix. Slope Impact Analysis& Recommendations: The site averages about 12% slope across the entire property. There were no signs of previous slope instability or failures. The site is stable enough to support the proposed construction within the recommendations made herein. We do not anticipate that the proposed new construction will have any off -site impacts. Landslide hazard areas are classified into categories which reflect past activity and the potential for future landslide activity based on an analysis of slope instability. The city of Edmonds planning department has determined in a preliminary design review letter dated October 12, 2018 (Critical areas checklist file #CRA20180183) that (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA JJA File#: 18054 1 Date: 2018.10.20 8029 238th Street SW Edmonds "Portions of the site contain slopes that exceed 15-percent and meet the definition of Erosion Hazard. The steepest portion of the site occurs at the northeast corner, just beyond the property boundary. While this slope exceeds a 40%-slope, it does not have a vertical rise of 10 feet or greater; therefore, it does not meet the definition of Landslide Hazard." We are in agreement with the city planner's determination. No landslide hazard area exists on site. Drainage The east side of the property contains slopes greater than 15% with a portion of the NE corner exceeding 40%. However, it does not have a vertical rise of 10 feet or greater; therefore, it does not meet the definition of Landslide Hazard. Roof infiltration and dispersion was reviewed per Appendix A of the Edmonds Storm water manual. Roof BMP infeasibility criteria for full dispersion include: 1. The slope of the flow path or dispersal area is steeper than 15 percent for any 20-foot reach of the flow path. 2. A 65 to 10 ratio of forested or native vegetation area to impervious area cannot be achieved. 3. A minimum forested or native vegetation flow path length of 100 feet (25 feet for sheet flow from a nonnative pervious surface) cannot be achieved 4. Flow paths for adjacent dispersion devices cannot be sufficiently spaced to prevent overlap of flows in the flow path areas. 5. For splash blocks, a vegetated flow path at least 50 feet in length from the downspout to the downstream property line, structure, stream, wetland, slope over 15 percent (unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system), or other impervious surface is not feasible. Roof BMP infeasibility criteria for infiltration include: 1. There is not at least 3 feet or more of permeable soil from the proposed final grade to the seasonal high groundwater table or other impermeable layer. 2. Within 50 feet of the top of slopes greater than 15 percent (unless a geotechnical assessment and soils report is prepared addressing the potential impact of the proposed system). BMP infeasibility criteria for other hard surfaces: 1. Sheet flow dispersion for flat to moderately sloped areas- at least a 10-foot-wide vegetation buffer for dispersion of the adjacent 20 feet of contributing surface cannot be achieved. A permeable pavement may be feasible, however an overflow system connected to the city maintained storm system should be considered. Also, the bottom of the drainage system is still likely to be at least 4 feet higher than the existing surface grade of the property to the east. Therefore, roof and drainage runoff or is likely to flow to the east, either on the surface or below grade in the infiltration gallery. Any infiltration system would need to be considerably deep enough to avoid water gradients across a slowly permeable substratum directing water to the neighboring property to the east. We recommend connecting to the existing city maintained storm system. Conclusion On site soils are suitable for a 2,000 psf foundation. Place footings on native, undisturbed soil. A conventional spread and continuous wall footings appear to be the most suitable type of foundation for the support of the proposed structure. Any infiltration system would need to be considerably deep enough to avoid water gradients across a slowly permeable substratum directing water to the neighboring property to the east. Permeable pavements and infiltration are not recommended due to slow permeability of on site soils. In addition, infiltration and dispersion is not feasible per the storm water Manual Appendix A. (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA JJA File#: 18054 I Date: 2018.10.20 8029 238th Street SW Edmonds When the plans and specifications are complete, or if significant changes are made in the character or location of the proposed structures, a consultation should be arranged to review them regarding the prevailing soil conditions. Then, it may be necessary to submit supplementary recommendations. It is recommended that the services of our firm be engaged to test and evaluate the soil conditions during the construction phase of the project. The design values and recommendations made herein are valid only insomuch as they are followed during the construction phase. Additionally, monitoring and testing during the construction phase needs be performed to verify the subgrade conditions and that suitable materials are used and that they are properly placed and compacted. While the recommendations are considered sufficient in detail for the construction of the proposed project, there are many alternative methods of construction which are available. We can discuss various other options for construction at your request. (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA JJA File#: 18054 I Date: 2018.10.20 8029 238th Street SW Edmonds Construction Considerations Earthwork: Excessively organic top soils generally undergo high volume changes when subjected to loads. This is detrimental to the behavior of pavements, floor slabs, structural fills and foundations placed upon them. It is recommended that excessively organic top soils be removed and wasted or stockpiled for later use. It is recommended that the final exposed subgrade be inspected by a representative of the soils engineer. This inspection should verify that all organic material has been removed. Any soft spots or deflecting areas should be removed to sound bearing and replaced with structural fill down to 1 feet below bottom of concrete footing. Once the existing soils are excavated to the design grade, proper control of the subgrade conditions (i.e., moisture content) and the placement & compaction of new fill (if required) should be maintained by a representative of the soils engineer. The recommendations for structural fill presented within this report, can be utilized to minimize the volume changes and differential settlements that are detrimental to the behavior of footings, and floor slabs. Enough density tests should be taken to monitor proper compaction. For structural fill beneath building structures one in -place density test per lift for every 1,000 ft2 is recommended. In parking and driveway areas this can be increased to two tests per lift for every 1,000 W. Excavation equipment may disturb the bearing soils and loose pockets can occur at bearing levels that were not disclosed by the test pit. For this reason, it is recommended that the bottoms of the excavations be compacted in - place by vibratory compactors. The upper 12 inches should be re -compacted to achieve an in -place density of not less than 95% of the maximum dry density as determined by ASTM D-1557. Excavations: Shallow excavations required for construction of foundations that do not exceed four feet in depth may be constructed. Side slopes are likely to slough to a 1:1 ratio. For deep excavations, the soils present cannot be expected to remain in position. These materials can be expected to fail, and collapse into any excavation thereby undermining the upper soils materials. This is especially true when working at depths near the water table. Proper care must be taken to protect personnel and equipment. Care must be taken so that all excavations made for the foundations are properly backfilled with suitable material compacted according to the procedures outlined in this report. Before the backfill is placed, all water and loose debris should be removed from these excavations. This information is provided for planning purposes. It is our opinion that maintaining safe working conditions is the responsibility of the contractor. Jobsite conditions such as soil moisture content, weather condition, earth movements and equipment type and operation can all affect slope stability. All excavations should be sloped or braced as required by applicable local, state and federal requirements. Floor Slab -On -Grade: Before the placing of concrete floors or pavements on the site, or before any floor supporting fill is placed, the organic, loose or obviously compressive materials must be removed. The subgrade should then be verified by the geotechnical engineer or his representative that all soft or deflecting areas have been removed. Areas of excessive yielding should be excavated and backfilled with structural fill. Any additional fill used to increase the elevation of the floor slab should meet the requirement for structural fill. Structural fill should be placed in layers of not more than 12 inches in thickness, at moisture contents at or above optimum, and compacted to a minimum density of 95% of the maximum dry density as determined by ASTM designation D-1557. (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA JJA File#: 18054 I Date: 2018.10.20 8029 238th Street SW Edmonds A granular mat should be provided below the floor slabs. This should be a minimum of four inches in thickness and properly compacted. The mat should consist of sand or sand and gravel mixture with non -plastic fines. All material should pass a % inch sieve and contain less than 10% passing the #200 sieve. Groundwater can be expected at shallower depths during the winter months. A moisture barrier, such as visqueen or plastic sheeting, should be placed beneath all floor slabs that are within a foot of the water table, as determined during excavation. Utilities There are existing utilities on site. Care should be taken to avoid disruption or breakage of water, power, sewer, gas, cable, phone and any other utility that may exist. Call 811 prior to excavation to have utilities marked. Erosion Control (typical) 1. The implementation of these ESC plans and the construction, maintenance, replacement, and upgrading of these ESC facilities is the responsibility of the owner/ESC supervisor until all construction is approved. 2. During the construction period, ESC facilities shall be upgraded as needed for unexpected storm events and modified to account for changing site conditions (e.g., additional sump pumps, relocation of ditches and silt fences, etc.). 3. The ESC facilities shall be inspected daily by the applicant/ESC supervisor and maintained to ensure continued proper functioning. Written records shall be kept of weekly reviews of the ESC facilities during the wet season (Oct. 1 to April 30) and of monthly reviews during the dry season (May 1 to Sept. 30). 4. Any areas of exposed soils, including roadway embankments, that will not be disturbed for two days during the wet season or seven days during the dry season shall be immediately stabilized with the approved ESC methods (e.g., seeding, mulching, plastic covering, etc.). 5. Any area needing ESC measures not requiring immediate attention shall be addressed within fifteen (15) days. 6. The ESC facilities on inactive sites shall be inspected and maintained a minimum of once a month or within forty-eight (48) hours following a storm event. 7. At no time shall more than one (1) foot of sediment be allowed to accumulate within a catch basin. All catch basins and conveyance lines shall be cleaned prior to paving. The cleaning operation shall not flush sediment -laden water into the downstream system. 8. Stabilized construction entrances and roads shall be installed at the beginning of construction and maintained for the duration of the project. Additional measures, such as wash pads, may be required to ensure that all paved areas are kept clean for the duration of the project. 9. Any permanent flow control facility used as a temporary settling basin shall be modified with the necessary erosion control measures and shall provide adequate storage capacity. (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA Site Pictures View looking north at frontage View looking west behind existing house JJA File#: 18054 I Date: 2018.10.20 8029 238th Street SW Edmonds orl , View looking east behind existing house View looking west behind existing house (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA JJA File#: 18054 1 Date: 2018.10.20 8029 238th Street SW Edmonds Appendix: Figures 1.0 SITE LOCATION 2.0 USGS SOIL MAP 3.0 CoUNTYGIS 4.0 LIQUEFACTIONAND SOIL SITE CLASS 5.0 SOIL LOG 6.0 BEARING CAPACITY 7.0 SETTLEMENT 8.0 FOOTING DETAIL 9.0 USGS SEISMIC DESIGN SUMMARY REPORT 10.0 PERC TEST RESULTS 11.0 SITE PLAN (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 PPA :31 st St S'. Holly Ln V 00 rcry [+ a fe Ln D Q M 2341h St S."; 234th P1 SW ZE 0o ?36th St SW A s n 8029 238th rD Street Southwest 238th St SW 238th St SWs ti 240th St SW Burlington Q II AutoGroup p 99 205th St SW St 1 St The Home Depot St co Wholesale Q St Math ay -Ballinger Park 2©1st St ON S D E: 242nd 5t SW -,1 D m 104) Ballinger Commons Apartments } Wi 7C` Edmou Islanc c D (D z M Not to Scale Zhen Townhome 8029 238th Street SW SITE LOCATION Edmonds WA 98026 Parcel: 451900102000 Date: 2018.10.20 A.1.0 File#: 18054 JJA -- (206) 786-8645 -- office(&,,JJAinc.biz -- PO Box 181 Auburn WA 98071 Alderwood-Urban land complex, 2 to 8 percent slopes. The Alderwood soil is moderately deep over a hardpan and is moderately well drained. It formed in glacial till. Typically, the surface layer is very dark grayish brown gravelly sandy loam about 7 inches thick. The upper part of the subsoil is dark yellowish brown and dark brown very gravelly sandy loam about 23 inches thick. The lower part is olive brown very gravelly sandy loam about 5 inches thick. A weakly cemented hardpan is at a depth of about 35 inches. Depth to the hardpan ranges from 20 to 40 inches. Permeability of the Alderwood soil is moderately rapid above the hardpan and very slow through it. Available water capacity is low. A seasonal perched water table is at a depth of 18 to 36 inches from January to March. Runoff is slow, and the hazard of water erosion is slight. Zhen Townhome 8029 238th Street SW Edmonds WA 98026 Parcel: 451900102000 Not to Scale USGS SOIL TYPE Date: 2018.10.20 A.2.0 File#: 18054 JJA -- (206) 786-8645 -- ofiice(u)_IJAinc.biz -- PO Box 181 Auburn WA 98071 4 Q Landslide Hazard Area 40% ❑ Severe Erosion Hazard 15%-40% ❑ Erosion Hazard Areas 15%-40% Zhen Townhome 8029 238th Street SW Edmonds WA 98026 Parcel: 451900102000 Not to Scalel COUNTY GIS MAP Date: 2018.10.20 A.3.0 File#: 18054 JJA -- (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 EXPI.ANM ION ® Licl❑craetionsusceptibility.lrIGH F1Liquel'acticot sttsccptihflity. 410UGRA1'E to HIGH L.iquelaction suaecptibilhy.1O[)IeR1Cl E LiquAtetion susceptibility; LOW to MODERATE Liqunracniortsuscrptil+i3ity: LOW Liqurlaction titncrpuhilin' VERY LOW to LOW Liquefaction susceptibility: VERY LOW LIQUEFACTION SUSECEPTIBILITY EXPLANATION ® site class F taalc-:t>ecti%c un—�+e•fili wamu Site class L sty class n it) r ao F 4.4 71 Site class r) Sitc class C to U Site class C z Site class B to C ao ❑ Site class B SITE CLASS Zhen Townhome 8029 238th Street SW Edmonds WA 98026 Parcel: 451900102000 Not to Scale LIQUEFACTION SUSECEPTIBILITY --------------- ---------------------- SITE CLASS I)atc: 2018.10.20 A.4.0 File#: 18054 JJA -- (206) 786-8645 -- office(a),JJAinc.biz -- PO Box 181 Auburn WA 98071 Excavation Date: 2018.10.20 Boring ID: TH-1 Total depth (ft): 6 Project Name: 8029 238th Street SW Technician: JB Surface Elevation (ft): 430 Sample Method: Hand Excavated SPT: NA Sample 0 y _ Description / Notes Topsoil 1 Brown, medium dense, gravelly sandy loam 2 SM-GP 3 4 Tan, sandy loam with gravel, dense 5 No water visible End test pit 6 Excavation Date: 2018.10.20 Boring ID: TH-2 Total depth (ft): 6 Project Name: 8029 238th Street SW Technician: JB Surface Elevation (ft): 430 Sample Method: Hand Excavated SPT: NA Sample � a 0 Description / Notes o QJ o p V 3 Topsoil 1 Brown, medium dense, gravelly sandy loam 2 SM-GP 3 Tan, sandy loam with gravel, dense 4 No water visible End test pit 5 6 Then Townhome 8029 238th Street SW SOIL LOG Edmonds WA 98026 Parcel: 451900102000 Date: 2018.10.20 A.5.0 File#: 18054 JJA -- (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 Given: Strip Footin In -situ density, 7 at = 125 pcf dry density, y = 125 pcf footing depth, Df = 2 ft depth of water table, Dw = 10 ft Factor of Safety = 3 Sketch: Surface Grade Df Determine: Cohesion, C = 0 psf Width, B = 2.00 ft Length, L = 20.00 ft Phi angle, = 30 degrees R = 0 degrees Dw 0 No groundwater within 2x footing depth 19 B Allowable Bearing Capacity (psf) for Footing size, B Solution: quit = c Nc Fcs Fcd Fci + q Nq Fqs Fqd Fqi + 0.5 g B Ng Fgs Fgd Fgi (Meyerhof) Table 3.4 Nc = 30.10 Nq = 18.38 Ng = 22.38 (Vesic) 30.10 18.38 18.06 (Brinch Hansen) 30.10 18.38 15.65 (Meyerhoo Shape Factors Depth Factors Inclination Factors Fcs = 1.061 Fcd = 1.400 Fci = Fqi = 1.000 Fqs = 1.058 Fqd = 1.289 Fgs = 0.960 Fgd = 1.000 Fgi = 1.000 Complete) q�tt = 0 + 6,264 + 2,685 = q It = 8,949 psf (Vesic) Complete) q,,It = 0 + 6,264 + 2,168 = q It = 8,431 psf (Brinch Hansen) Complete) q„it = 0 + 6,264 + 1,878 = q It = 8,142 psf (Meyerhof) Average of 3, using all soil factors and the applied safety factor q allowable = 2,983 p5 Not to Scale Zhen Townhome ESTIMATED 8029 238th Street SW BEARING CAPACITY Edmonds WA 98026 Parcel: 451900102000 Date: 2018.10.20 A.6.0 File#: 18054 JJA -- (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 I CONTINUOUS WALL (Terzaghi Method) CONTINUOUS WALL (Terzaghi Method) Unit Weight of Soil, in lbs/ft'= 125 Average Corrected SPT N-value= 15 Total Load (load, footing, soil) in kips= 2 Soil Internal Friction Angle (from Fig. 9-9)= 30 General or local shear (determine for Fig.9-9)= Ng (using above results and figure 9-7)= 18.38 N, (using above results and Figure 9-7)= 22.38 Nc (using figure 9-7)= 30.10 Unconfined Compressive Strength, Cohesion (kips/so=�.J Cohesion of Soil= 0 Embedment Depth, in feet= 2 Footing Width (square), in feet= 1.5 Ultimate Bearing Capacity (lbs/ft)= 6,693 Actual Bearing from Total Load (lbs/fe)= 889 F., Against Bearing Capacity Failure (>3.0)= 7.53 Unit Weight of Soil, in lbs/cf= 125 Average Corrected SPT N-value= 15 Total Load (load, footing, soil), in kips= 2 Soil Internal Friction Angle (from Fig. 9-9)= 30 Ng (using above results and figure 9-7)= 18.38 N„ (using above results and Figure 9-7)= 22.38 N, (using figure 9-7)= 30.10 Unconfined Comp. Strength, Cohesion (kips/sf)=� Unit Cohesion= 0 Embedment Depth, in feet= 2 Footing Width, in feet= 2 Ultimate Bearing Capacity (lbs/ft2)= 7,393 Actual Bearing from Total Load Qbs/ft2)= 500 Fs Against Bearing Capacity Failure (>3.0)= 14.79 SETTLEMENT CHECK (for sand and SPT values only) Maximum Settlement on Dry Sand= 0.09 feet Maximum Settlement on Dry Sand= 0.06 feet 1.02 inches 0.71 inches Zhen Townhome SETTLEMENT 8029 238th Street SW CALCULATIONS Edmonds WA 98026 Parcel: 451900102000 Date: 2018.10.20 A.7.0 File#: 18054 JJA -- (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 Ground surface Footing Depth: 1S inches subgrade Compaction 9= 15.0 in min I I I_I I I -I required for met Al1owableBearing: 2,000 PSF freeze thaw -I I Perimeter Footing Drain 24.0in III- erferated, 6 inch pipe -III 12 _0 in m b _Q in (tip) min (n-p) Crushed Rack (ABC) for 14-•eling 2,000 PSF q ive Be Nataring (Approx): Zhen Townhome 8029 238th Street SW Edmonds WA 98026 Parcel: 451900102000 Not to Scale FOOTING DETAIL Date: 2018.10.20 A.8.0 File#: 18054 JJA -- (206) 786-8645 -- office0JJAinc.biz -- PO Box 181 Auburn WA 98071 WuSGS Design Maps Summary Report User -Specified. Input Building Code Reference Document 2012/2015 International Building Code (which utilizes USGS hazard data available in 2008) Site Coordinates 47.783320N, 122.34201°W Site Soil Classification Site Class C - "Very Dense Soil and Soft Rock" Risk Category I/II/III POUT GPI VAILE RESERVA-VON Lynnwood Edmonds' r� MountlakeTe ce• Bothell ��R 7 frl,'iDlSON 99 .; � REsfRVATlou .Indianola 'Shoreline Nut+vc 'Suquamish K pRr l E7pORI USGS-Provided Output N Mc c Z Ss = 1.262 g %s = 1.262 g SDs = 0,841 g S,, : 0.493 g SN>< = 0.644 g SDl = 0.429 g For information on how the SS and S1 values above have been calculated from probabilistic (risk -targeted) and deterministic ground motions in the direction of maximum horizontal response, please return to the application and select the'2009 NEHRP" building code reference document. MCE6 Response Sperlrum IA; 1� I.I7 UPF nkl u,77r A v.� /Uwi•A 4LY. U Li Ct#1 'im 0-M 0,W1 QW UM JO) t-V IAU 440 Imu :fir Fsa*A T Isv ? Zhen Townhome 8029 238th Street SW Edmonds WA 98026 Parcel: 451900102000 Design RusponseSpeMin a.� bNl 072 s>'a 0.54 413Pr kl r p�tlC 00? 4UU UA0 i11, UAti Off! u2m ltJlA I.2U 1W 1A0 tM Im 11ml,mi, T 4MV) USGS SEISMIC DESIGN DATA Date: 2018.10.20 A.9.0 File#: 18054 JJA -- (206) 786-8645 -- office@JJAinc.biz -- PO Box 181 Auburn WA 98071 Test pit - 2nd trial Test pit - 3rd trial Time Distance Pere Rate Time Distance Pere Rate Time Distance Pere Rate Minutes inches in/min Minutes inches in/min Minutes inches in/min 0.0 12.00 0.0 10.00 0.0 10.50 1.0 12.50 0.50 1.0 10.50 0.50 1.0 11.00 0.50 2.0 13.25 0.75 2.0 11.00 0.50 2.0 11.50 0.50 5.0 14.50 0.42 5.0 12.00 0.33 5.0 12.75 0.42 10.0 16.00 0.30 10.0 13.25 0.25 10.0 13.75 0.20 15.0 17.25 0.25 15.0 14.00 0.15 15.0 15.00 0.25 20.00 18.00 0.15 20.0 15.25 0.25 20.0 16.00 0.20 Average: 0.37 in/min Average: 0.25 in/min Average: 0.22 in/min Steady Rate 2.68 min/in Steady Rate 4.07 min/in Steady Rate 4.62 min/in Average of Three: 0.28 in/min 3.79 min/in (No Safety Factor Applied) 16.72 inch/hr 0.06 hr/inch A 19.00 17.00 15.00 WIC %AIII; GX1I1; 0.0 5.0 10.0 15.0 20.0 25.0 Time (Minutes) Zhen Townhome 8029 238th Street SW PERC TEST RESULTS Edmonds WA 98026 Parcel: 451900102000 Date: 2018.10.20 A.10.0 File#: 18054 JJA -- (206) 786-8645 -- office(t�,JJAinc.biz -- PO Box 181 Auburn WA 98071 LEGAL: Address: 8029 238th Street SW Edmonds WA 98026 Parcel: 451900102000 Legal: FRUITLAND ACRES TO LAKE BALLINGER BLK 001 D-00 S 100FT LOT 20 Lot Size 12,197 SF (0.28 AC) .y i''�' .,T _ BNARt:DPARICING i•iZ��st; I T � N 88°3715' W' +-420L= W/ SE 1 0 ` L -,�,�: c. tip IJNR C1 ` 4 5, avil r UNIT 03 .FOOT PRiN1 "Ro SF J TOTAL AREA 1.343 SF- Tl-I-1 PEPC�f GARFIGEBASEIAENT6QO�SF. r: T i gkE_432 4.0 1't' 'UNIT82 / U 47.0 ft: Ic 1 C C ` .ifjnT 1 > .1 / 120.00' ✓1''` -- - - - - 14 IEJI� l 238TH ST F�IJ�. 40 Y, E:< p Date: 10-20-2018 z Dwg#:18054 37343 Designed by: JB r'FFJ�oC/gTEQ ����$` Drawn by: JB p �A l E V REV I DATE I NOTES A.11.0 SITE PLAN SCALE 1" = 20 FT RUOYUN THEN 8029 238th Street SW Edmonds WA 98026 Parcel# 451900102000 PO Box 181 AuburnWA 98071' (206) 786-S645' ofice®JJAinc.biz Geotechnical Engineering Special Inspections Materials Testing Construction Inspections