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CANOD.pdfCity of Edmonds Critical Area Notice of Decision --Ap-plicant Property Owner: Critical Area File 4: H61 7- A - Permit Number: Site Location: K0 q0 U Parcel Number: oc)o� 3 Project Description: E] Conditional Waiver. No critical area report is required for the project described above. 1, There will be no alteration of a,Critical Area or its required buffer. 2. The proposal is an allowed activity pursuant to ECDC 23.40,220, 23.50.220, and/or 23.80.040. 3. The proposal is exempt pursuant to ECDC 23,40,230. F -I Erosion Hazard. Project is within erosion hazard area. Applicant must prepare an erosion and sediment control plan in compliance with ECDC 18.30. Critical Area Report Required. The proposed project is within a critical area and/or a critical area buffer and a critical area report is required. A critical area report has been submitted and evaluated for compliance with the following criteria pursuant to ECDC 23.40.160: 1. The proposal minimizes the impact on critical areas in accordance with ECDC 23.40, 120, Mitigation sequencing; 2. ,The proposal does not pose an unreasonable threat to the public health, safety, or welfare on or off the development proposal site; 3. The proposal is consistent with the general purposes of this title and the public interest; 4. Any alterations permitted to the critical area are mitigated in accordance with ECDC 23.40.110, Mitigation requirements. 5. The proposal protects the critical area functions and values consistent with the best available science and results in no net loss of critical functions and values; and 6. The proposal is consistent with other applicable regulations and standards. E] Unfavorable Critical Area Decision. The proposed project is not exempt or does not adequately mitigate its impacts on critical areas and/or does not comply with the criteria in ECDC 23.40.160 and the provisions of the City of Edmonds critical area regulations. See attached findings of noncompliance. , Favorable Critical Area Decision. The proposed project as described above and as shown on the attached site plan meets or is exempt from the criteria ih ECDC 23.40.160, Review Criteria, and complies with the applicable provisions of the City of Edmonds critical area regulations. Any subsequent changes to the proposal shall void this decision pending re -review of the proposal, ❑ Conditions. Critical Area specific condition(s) have been applied to the permit number referenced above. See referenced permit number for specific condition(s). 1.4", 0,'A (Y\6,c /M Reviewer Signature Date Appeals: Any decision to approve, condition, or deny a development proposal or other activity based on the requirements of critical area regulations may be appealed according to, and as part of, the appeal procedure, if any, for the permit or approval involved. Revised 12/16/2010 !�eotech7,LicaCT-'7igiii.eei-iii,g . ... .. ..... Wa.tey Resmwces andRe7ned-latio'n F-71 Sustahiabre DeveCoyment Services �eofbgic'Assessnml.ts Associated Earth Sciences, Inc. Serving the Pacific gTorth-west Since 1981 Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report Edmonds, Washington Prepared for Project No, KE080246A April 26, 2013 Associated Ci ces,, Inc. 1E, 111 IU Ell Seri,ing the Pacific Northwest Since I981 April 26, 2013 Project No, KE080246A DJC, Inc. P.O. Box 1508 Mukilteo, Washington 98275 Attention: Mr. Douglas Johnson Subject:. Subsurface Exploration, Geologic Hazard, and Geotechnical Engineering Report TalbotProperty 80XX Cyrus Place Edmonds, Washington Dear Mr. Johnson: We are pleased to present the enclosed copies of the above -referenced report. This report summarizes the results of our subsurface exploration, geologic hazard, and geotechnical engineering studies and offers recommendations for the design and development of the proposed project. This work was originally performed in 2008. We visited the site on April 23, 2013 and observed that site conditions are little changed from what they were when the report was originally prepared. We have updated the recommended seismic design parameters in accordance with the International Building Corte Section 1613. In our opinion, the recommendations presented in this report are appropriate for the current site conditions. We have enjoyed working with you on this study and are confident that the recommendations presented in this report will aid in the successful completion of your project. If you should have any questions or if we can be of additional help to you, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington Jo . Sondrgaard, L.G. , L.E.G. Se i r Prindzpal Geologist JNS/Id - KE080246A3 - Projects1200802461KE\WP Yirklan.d Everett r Tacoma 425-827-7701 425-259-0522 253-722-2992 www.aesgeo.com HIM r! r rNJ r r Prepared for. DJC, Inc. P.O. Box 1508 Mukilteo, Washington 98275 Prepared by, - Associated Earth Sciences, Inc. 9115"' Avenue, Suite 100 Kirkland, Washington 98033 425-827-7701 Fax: 425-827-5424 April 26, 2013 Project No. KE080246A Subsurface Exploration, Geologic Hazard, Talbot Property and Geotechnical Engineering Report Edmonds, Washington Prgiect and Site Conditions 1.0 INTRODUCTION This report presents the results of our subsurface exploration, geologic hazard, and geotechnical engineering study for the proposed construction of a single-family residence. The location of the site is shown on the "Vicinity Map," Figure 1, and the locations of the explorations accomplished for this study are presented on the "Site and Exploration Plan," Figure 2. At this time, it is our understanding that six single-family residences will eventually be constructed. In the event that any changes in the nature, design, or location of the structures are planned, the conclusions and recommendations contained in this report should be reviewed and modified, or verified, as necessary. A geotechnical report is required for this property, based on Section 19.10 of the City of Edmonds Municipal Code for property with slope inclinations exceeding 15 percent and by conditions set forth in the recorded short plats of the property (SP -122 and SP -123). 1.1 Purpose and Scope The purpose of this study was to provide subsurface data to be utilized in the design and development of the above-mentioned project. Our study included a review of available geologic literature, review of a previous report on the subject property titled "Geologic Reconnaissance Report." prepared on May 30, 2001 by AMSC, excavation of exploration pits, and performing geologic studies to assess the type, thickness, distribution, and physical properties of the subsurface sediments and shallow ground water conditions. Geologic hazard evaluations and engineering studies were also conducted to determine the type of suitable foundation, allowable bearing pressures, anticipated settlements, lateral earth pressures, floor support recommendations, and drainage considerations. This report summarizes our current fieldwork and development recommendations based on our present understanding of the project. 1.2 Authorization Written authorization to proceed with this study was granted by Mr. Douglas Johnson of DJC, Incorporated. Our study was accomplished in general accordance with our scope of work letter, dated April 10, 2008. This report has been prepared for the exclusive use of DJC, Incorporated and their agents for specific application to this project. Within the limitations of scope, schedule; and budget, our services have been performed in accordance with generally accepted geotechnical engineering and engineering geology practices in effect in this area at the April 26, 2013 ASSOCIATED EARTH SCIENCES, INC, JNS11d - KE080246A3 - Projects120080246I KEMIP Page I , fubstnface Exploration, Geologic Hazard, Talbot Property and Geotechnical Engineering Report Edmonds, Washington Proyect and Site Conditions time our report was prepared: No other warranty, express or implied, is made. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the owner, 2.0 PROJECT AND SITE DESCRIPTION The property was located at 8OXX Cyrus Place in Edmonds, Washington. The property was generally sloping from the east down to the west and the southwest. To the south of the project site, there was a steep slope down to Perrinville Creek. The total elevation change across the building lots was on the order of 30 feet. The property had been previously graded, and a private road with underground utilities extended approximately 230 feet south from Cyrus PIace, roughly down the center of the property. There were three lots on the west side of the private road that were relatively flat, and three lots on the east side of the private road that sloped from the east property line down to the road elevation at an inclination of approximately 2.5HAV (Horizontal: Vertical). Based on our field observations and conversations with Mr. Johnson, there had been cuts and fills performed in the previous grading of the site. The cuts occurred mainly on the east side of the project and the fills were placed on the western lots. After the grading was completed, the lots were hydroseeded and. there was good grass cover on the soil. To the south of the project area, there was a slope and ravine down to Perrinville Creek. The slope appeared to range from 1H:lV to 2HAV and was moderately to heavily vegetated with blackberry vines, ferns, and various evergreen and deciduous trees. The property was bordered by Cyrus Place to the north, the Perrinville Creek and slope native growth protection area to the south, and ogler residential properties to the west and east. This report was completed with an understanding of the project based on conversations and site meetings with Mr. Douglas Johnson. Present plans call for six single-family residences to eventually be constructed, one home on each building lot. At this time, the first house will be constructed on the southwest lot. At this time, we do not know when the construction of the other homes will be done. 3.0 SUBSURFACE EXPLORATION Our field study included the excavation of six exploration pits to gain subsurface information about the site. The various types of sediments, as well as the depths where characteristics of the sediments changed, are indicated on the exploration logs presented in the Appendix. The depths indicated on the logs where conditions changed may represent gradational variations between sediment types in the field. Our explorations were approximately located in the field April 26, 2013 ASSOCIATED EARTH SCIENCES, INC. JNVId - KF.O80246A3 - hojecis1200802461KE1 HIP Page 2 Subsurface Exploration, Geologic Hazard, Talbot Property and Geotechnical Engineering Repon Edmonds, Washington Project and Site Conditions by measuring from known site features. The locations of the exploration pits are shown on Figure 2. The conclusions and recommendations presented in this report are based on the six exploration pits.. The number, locations, and depths of the explorations were completed within site and budgetary constraints. Because of the nature of exploratory work below ground, extrapolation of subsurface conditions between field explorations is necessary. It should be noted that differing subsurface conditions may be present due to the random nature of deposition and the alteration of topography by past grading and/or filling. The nature and extent of any variations between the field explorations may not become fully evident until construction. If variations are observed at that time, it may be necessary to re-evaluate specific recommendations in this report and make appropriate changes. 3.1 Exploration Pits The exploration pits were excavated with a track -mounted excavator. The pits permitted direct, visual observation of subsurface conditions. Materials encountered in the exploration pits were studied and classified in the field by an engineering geologist from our firm. All exploration pits were backfilled immediately after examination and logging. Selected samples were then transported to our laboratory for further visual classification and testing, as necessary. 4.0 SUBSURFACE CONDITIONS Subsurface conditions at the project site were inferred from the field explorations accomplished. for this study, visual reconnaissance of the site, review of geologic literature, and previous projects completed in the vicinity. As shown on the field logs, fill soils and natural deposits of Vashon advance outwash sediments were encountered in the exploration pits. Minor amounts of sod and topsoil were encountered at the surface. Review of a geologic map of the area titled Composite Geologic Map of the Sno-King Area, Draft, Central Puget Lowland, Washington, by Booth, Cox, Troost, and Shimel, (2004), indicates that the area of the subject site is underlain by Vashon lodgement till deposits. It also indicates the presence of Vashon advance outwash sediments nearby to the east and south of the project site. The Vashon advance outwash sediments mapped nearby correlate with our interpretation of the sediments encountered on the site. Though our findings are different from the map reviewed, our interpretation of the sediments observed correlates with the Vashon-age stratigraphic column. Our interpretations differ due to the smaller scale, more detailed focus of this site-specific study. The following section presents more detailed subsurface information. April 26, 2013 ASSOCIATED EARTH SCIENCES, INC. JNS/1d - KE080246A3 - ProjecIA200802461 KE1111P Page 3 Subsurface Exploration, Geologic Hazard, Talbot Property and Geotechnical Engineering Report Edmonds, Washington Project and Site Conditimis 4.1 Stratigraphy Sod/Topsoil Sod and topsoil were encountered in all of the exploration pits, except for EP -5, performed at the surface to a maximum depth of approximately 4 inches. The topsoil is composed of organic matter from the sod combined with the weathered surface of the fill and native soils. FillSoils Fill soils were encountered in all of the exploration pits, except EP -5. The fill soils typically consisted of loose to medium dense, moist to wet, light brown to gray sand, with some gravel and organic material. The sources of the fill soils are presumed to be a combination of regraded soils and the cut soils from the eastern lots. Due to the inconsistent relative density, thickness, and composition of the fill soils, the fill soils are not suitable for support of structures or future structural fills. Vashon Advance Ounvash — Qva Vashon advance outwash was encountered at the ground surface in EP -5, and underlying the fill soils in our other exploration pits. These sediments consist of medium dense to dense, moist, light brown to gray, fine to coarse sand with gravel and trace silt. This material was deposited from high-energy streams carrying sediments at the front of the advancing glacier. These sediments typically have a high ,infiltration rate and, except for the pockets of clean, fine sand, have good resistance to erosion. The Vashon advance outwash sediments were glacially consolidated by being overridden by the Vashon glacial ice subsequent to deposition. The medium dense Vashon advance outwash sediments are suitable for foundation support. 4.2 Hydrology There was no significant shallow ground water or seepage observed in any of the exploration pits performed for this study. The fill soils encountered in EP -6 were more wet than soils encountered in the other explorations, but it is our opinion that this was due to the lower relative density of the fill soils encountered. Based on the permeable nature of the native sediments encountered and the outcrops of Vashon advance outwash sediments observed in the Perrinville Creek ravine to the south of the project, we do not anticipate that groundwater will be encountered during excavation and construction of the homes. April 26, 2013 ASSOCIATED EARTH SCIENCES, INC. JN.511d - KE080246113 - ProjerW200802461ME IVP page 4 Subsurface Eyploration, Geologic Hazard, Talbot Property and Geotechnical Engineering Report Edmonds, Washington Project and Site Conditions 4.3 SCS Soil Classification Upon review or the soil maps at the USDA Natural Resource Conservation Service website, the subject property is mapped as Everett gravelly sandy loam, 15 to 25 percent slopes (EvD). Based on our site reconnaissance and subsurface exploration, we are in agreement with the referenced soil classification. The Everett -series soils are derived from glacial outwash parent material and the erosion potential is considered to be moderate to severe. April 26, 2013 ASSOCIATED EARTH SCIENCES, INC. JNSI(d - KE080246,43 - Projects1200802461KEMP Page 5 Substaface Exploration, Geologic Hazard, Talbot Property and Geotechnical Engineer=ing Report Edmonds, 'Washington Geologic Hazards and Mitigations 5.0 SEISMIC HAZARDS AND RECOMMENDED MITIGATION Earthquakes occur in the Puget Lowland with great regularity. The vast majority of these events are small and are usually not felt. However, large earthquakes do occur as evidenced by the February 28, 2001, 6.8 -magnitude event; the 1965, 6.5 -magnitude event; and the 1949, 7.2 -magnitude event. The 1949 earthquake appears to have been the largest in this area during recorded history. Based on the soils underlying the property and our field reconnaissance, it is our opinion that the property is not a seismic hazard area, as defined by City of Edmonds Municipal Code 23.80.020C. The remainder of this section discusses typical seismic -related geologic hazards. The seismic hazards relevant to the planned development are primarily the potential for seismic shaking. Mitigation of the potential for seismic hazards will be to verify that all structures, including retaining walls, are designed and constructed in accordance with the seismic parameters set forth in the applicable building codes. Generally, . there are four types of potential geologic hazards associated with large seismic events 1) surficial ground rupture, 2) seismically induced landslides, 3) liquefaction, and 4) ground motion. The potential for each of these hazards to adversely impact the proposed project is discussed below. 5.1 Surficial Ground Rupture Generally, the largest earthquakes that have occurred in the Puget Sound area are sub -crustal events with epicenters ranging from 50 to 70 kilometers in depth. For this reason, no surficial faulting or earth rupture resulting from deep, seismic activity has been documented, to date, in the area of the subject site. Therefore, it is our opinion, based on existing geologic data, that the risk of surface rupture impacting the proposed project is low, and no mitigations are necessary. 5.2 Seismically Induced Landslides Due to the medium dense subsurface conditions and the absence of adverse ground water conditions, the potential for seismically induced slope failures on the site is considered low to moderate. The critical area buffer and building setback limit, stated in the following section April 26, 2013 ASSOCIATED EARTH SCIENCES, INC. MINN KE080246A3 - Projecls1200802461M WP page 6 Subsurface Exploration, Geologic Hazard, Talbot Property and Geotechnical Engineering Report Edmonds, Washington Geologic Hazards and Mitigations titled "Landslide Hazard Area and Mitigation," are suitable for mitigation of seismically induced landslides, as well. 5.3 Liquefaction Liquefaction is a condition where loose, saturated, typically sandy soils lose shear strength when subjected to high intensity, cyclic loads, such as occur in earthquakes. The resulting reduction in strength can cause differential foundation settlements and slope failures. Loose, saturated, fine-grained sand that cannot dissipate the buildup of pore water pressure is the predominant type of sediment subject to liquefaction. Due to the medium dense, well -graded soils encountered in our exploration pits and the absence of adverse ground water conditions, the liquefaction potential of this site is very low, and no mitigations are necessary. 5A Ground Motion The guidelines presented in the 2012 International Building Code (IBC) Section 1613 should be used in the seismic design of the project. The USES Earthquake Hazards Program website (http://earthquake.usgs.gov/hazmaps/) was used to determine interpolated probabilistic ground motion values in percent of gravity (g) for an event with a return period of 2 percent exceedence in 50 years. Using the website, the project area was submitted using latitude and longitude for mapped spectral accelerations of Ss = 1.299 for short periods (0.2 seconds) and Si = 0.51 for a 1 -second period. Based on the results of our subsurface exploration and our estimation of soil properties at depth utilizing available geologic data, Site Class "C" in conformance with Chapter 20 of ASCE may be used. These values correspond to site coefficients Fa = '1.0 and FY = 1.37 in conformance with IBC Tables '1613.3.3(1) and 1613.3.3(2), respectively. 6.0 LANDSLIDE HAZARDS AND MITIGATION The native growth protection area easement (NGPA/E) and ravine down to Perrinville Creek along the south side of the property meets the criteria for. a landslide hazard area, as defined by the City of Edmonds Municipal Code 23.$0.020B. This slope ranged from approximately IH;IV to 2H: IV in steepness, and the vertical elevation from the top of the slope to Perrinville Creek ranges from approximately 60 to 150 feet. The slope was moderately to heavily vegetated with blackberry vines, ferns, and various evergreen and deciduous trees. There were topographic features associated with ancient slump failures on portions of the slope. These features include headscarps, slump blocks, and blocky, hummocky character below the April 26, 2013 ASSOCIATED EARTH SCIENCES, INC. JNS11d - KE080246A3 - Projects1200802461KE11VP page 7 Subsinjace Etploration, Geologic Hazard, Talbot Property and Geotechnical Engineering Report Edmonds, Washington Geologic Hazards and Mitigations headscarps. Though the topography shows signs of past slope movement, there were no signs of recent slope movement. Mature trees, up to approximately 2 feet in diameter, were present on the slope. These trees were growing straight and the trees present did not have bent trunks. Since this slope area will not be disturbed in the future grading, and the structures to be constructed will be founded on medium dense or denser, native Vashon advance outwash sediments, it is our opinion that the minimum critical area buffer of 10 feet should be applied to the top of the slope. The minimum building setback limit of 15 feet from this buffer should be applied, to result in an effective building setback from the top of the slope of 25 feet. It is our opinion that the application of this buffer and building setback limit mitigates the landslide hazard area adjacent to the property. 7.0 EROSION HAZARD AREA AND MITIGATION The native growth protection area easement (NEPA/E) and ravine down to Perrinville Creek along the south side of the property meet the criteria for an erosion hazard area, as defined by the City of Edmonds Municipal Code 23.80.020A. The NGPA/E area is underlain by Everett - series soils, with slopes ranging from approximately 0 to 50 percent. During our slope reconnaissance, we did not observe signs of surface -water -related erosion. We presume that this is because of the highly permeable nature of the native soils and that there are not any point source discharges from the flatter areas above the slope. Surface and roof runoff from the houses to be constructed should be collected and routed to the previously installed storm system. There are storm water sewer stub -outs on each lot. All yard drains, roof drains and footing drains should be tied into the storm system. Further details on the various drains are provided in the "Drainage Considerations" section of this report. We also recommend that the slope area be left undisturbed and vegetated, which are terms of the native growth protection area easement designation. In combination with the surface drainage control and non- disturbance, the minimum critical area buffer and building setback Iimit, as described in the preceding section, will mitigate the erosion hazard area. In addition to the surface drainage control, non -disturbance measures, and application of buffers and setbacks for the slope area, a Temporary Erosion and Sediment Control Plan (TESCP) will need to be implemented during construction to mitigate turbid construction runoff and to comply with City of Edmonds regulations. Upon request, Associated Earth Sciences, Inc, (AESI) can recommend which best management practices (BMPs) should be used in the TESCP, help field -fit the BMPs selected for maximum effectiveness, and perform. field inspections to assess BMP performance and to provide maintenance recommendations. These field inspections may be required by the City of Edmonds for TESC compliance. April 26, 2013 ASSOCIATED EARTH SCIENCES, INC. JNSgd - KE080246A3 Projeris1200802461KE1 ii'P Page 8 Subsitiface Exploration, Geologic Hazard, Talbot Property acid Geotechnical Engineering Report Ednnonds, Washington Design Recommeltdations 8.0 INTRODUCTION Our exploration indicates that, from a geotechnical standpoint, the property is suitable for the proposed development, provided the risks discussed are accepted and the recommendations contained herein are properly followed. Any fill soils encountered will need to be evaluated during the grading of the property to determine whether the fill can be excavated and recompacted for structural support or removed from the site. The bearing strata of Vashon advance outwash sediments was relatively shallow in our exploration pits and will provide suitable support for structural fills and building foundations. Conventional spread footing foundations constructed to bear on medium dense or denser natural sediment or on approved structural fill soil may be utilized to provide foundation support. Previously placed fill soils are not suitable for foundations support. Based on our conversations with Mr. Johnson, it is our understanding that present plans call for construction of homes with full basements on the lots that have existing fills, and that footings will be placed directly on native soils. 9.0 SITE PREPARATION The site has been previously graded and site preparation for home construction should be straightforward and minimal. Structural fills may be placed on native Vashon advance outwash sediments. Existing fill soils are not suitable for structural support or support of future fill soils. Depending on their organic content, existing fill soils may be removed and recompacted as structural fill. In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction. For estimating purposes, however, we anticipate that temporary, unsupported cut slopes in the medium dense, Vashon advance outwash sediments may be planned at a maximum slope of 1H:1V. Unsupported cut slopes in the loose fill soils may be planned at a maximum slope of 1.5H: IV. As is typical with earthwork operations, some sloughing and raveling may occur, and cut slopes may have to be adjusted in the field. Fill soils, though prone to caving, will typically stay open long enough to install temporary shoring for trenching operations. In addition, WISHAIOSHA regulations should be followed at all times. As a standard, permanent slopes in structural fill should not exceed a 2H:1V inclination. Permanent slopes in landscaping fill should be limited to 3H:lV. The existing fill soils that April 26, 2013 ASSOCIATED EARTH SCIENCES, INC. 1NS/1d - KE080246A3 - Projects120080246tKEt 1W Page 9 Subsurface Exploration, Geologic Hazard, Talbot Property and Geotechnical Engineering Report Edmonds, Washington Design Recommendations were encountered in EP -6, near the south end of the site should be graded to a maximum of a 3H: IV slope for the final grade of the project. 10.0 STRUCTURAL FILL Due to the topography of the site and proposed driveway improvements, structural fill will be necessary to establish desired grades. All references to structural fill in this report refer to subgrade preparation, fill type, placement, and compaction of materials, as discussed in this section. If a percentage of compaction is specified under another section of this report, the value given in that section should be used. After overexcavation/stripping has been performed to the satisfaction of the geotechnical engineer/engineering geologist, the upper 12 inches of exposed ground should be recompacted to a firm and unyielding condition. Fill placed on slopes greater than 5H: IV must be benched into the native soils. The benches should be at least 2 feet deep and wide enough to allow compaction equipment to operate. Once the subgrade has been recompacted, structural fill can be placed to the desired grades. Structural fill is defined as non-organic soil, acceptable to the geotechnical engineer, placed in maximum 8 -inch loose lifts with each lift being compacted to 95 percent of the modified Proctor maximum density using American Socieo, for Testing and Materials (ASTM):D 1557 as the standard. The top of the compacted fill should extend horizontally outward a minimum distance of 3 feet beyond the location of the perimeter footings or pavement edge before sloping down at an angle of 2H: IV. The contractor should note that any proposed fill soils must be evaluated by AESI prior to their use in fills. This would require that we have a sample of the material 72 hours in advance to perform a Proctor test and determine its field compaction standard. Soils in which the amount of fine-grained material (smaller than the No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture -sensitive. Use of moisture -sensitive soil in structural fills should be limited to favorable dry weather and dry subgrade conditions. The on-site soils did not contain significant amounts of silt and will not be moisture -sensitive. If fill is placed during wet weather or if proper compaction cannot be obtained, a select, import material consisting of a clean, free -draining gravel and/or sand should be used. Free -draining fill consists of non-organic soil with the amount of fine-grained material limited to 5 percent by weight when pleasured on the minus No. 4 sieve fraction. A representative from our firm should inspect the stripped subgrade and be present during placement of structural fill to observe the work and perform a representative number of in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses and any problem areas may be corrected at that time. It is important to understand April 26, 2013 ASSOCIATED EARTH SCIENCES, INC, JNS11d - KE030246A3 - Projects1200802461W IVP Page 10 Substaface Exploration, Geologic Hazard, Talbot Properly, mxd Geotechnical Engirteerhig Report Ednioiids, Washington Design Reconiniemtatioits that taking random compaction tests on a part-time basis will not assure uniformity or acceptable performance of a fill. As such, we are available to aid the owner in developing a suitable monitoring and testing frequency. 11.0 FOUNDATIONS Spread footings may be used for building support, when founded on medium dense, native soils or structural fill placed, as previously discussed. To limit differential settlements between footings that bear on both structural fill and medium dense to dense, native soils, we recommend that an allowable bearing pressure of 2,000 pounds per square foot (psf) be utilized for design purposes, including both dead and live loads. An increase of one-third may be used for short-term wind or seismic loading. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection; interior footings require only 12 inches burial. However, all footings must penetrate to the prescribed bearing stratum, and no footing should be founded in or above loose, organic, or existing fill soils. It should be noted that the area bounded by lines extending downward at lH:lV from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM:D 1557. In addition, a 1.5H:1V line extending down from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus, footings should not be placed near the edge of steps or cuts in the bearing soils. Anticipated settlement of footings founded on medium dense, native soils or approved structural fill should be less than 1 inch. However, disturbed soil not removed from footing excavations prior to footing placement could result in increased settlements. All footing areas should be inspected by AESI prior to placing concrete to verify that die design bearing capacity of the soils has been attained and that construction conforms to the recommendations contained in this report. Such inspections may be required by the governing municipality. Perimeter footing drains should be provided as discussed under the "Drainage Considerations" section of this report. 12.0 LATERAL WALL PRESSURES All backfill behind walls or around foundation units should be placed as per our recommendations for structural fill and as described in this section of the report. Horizontally backfilled walls that are free to yield laterally at least 0.1 percent of their height may be designed using an equivalent fluid pressure equal to 35 pounds per cubic foot (pco, Fully restrained, horizontally backfilled, rigid walls that cannot yield should be designed for an April 26, 2013 ASSOCIATED EARTH SCIENCES, INC, AWN - KE080246A3 - Projects1200802461 KERP Page 11 SubsuiJace Exploration, Geologic Hazard, Talbot Property and Geotechnical Engineering Report Edmonds, Washington DesignRecommendations equivalent fluid of 50 pcf. If roadways, parking areas, or other areas subject to vehicular traffic are adjacent to walls, a surcharge equivalent to 2 feet of soil should be added to the wall height in determining lateral design forces. Walls that retain sloping backfill at a maximum angle of 2H:1V should be designed using an equivalent fluid pressure of 55 pef for yielding conditions and 75 pef for fully restrained conditions. The lateral pressures presented above are based on the conditions of a uniform, drained backfill consisting of on-site, alluvial sediments compacted to 90 percent of ASTM:D 1557. A higher degree of compaction is not recommended, as this will increase the pressure acting on the wall. Surcharges from adjacent footings, heavy construction equipment, or sloping ground must be added to the above values. Footing drains should be provided for all retaining walls as discussed under the "Drainage Considerations" section of this report. 12.1 Passive Resistance and Friction Factor Lateral loads can be resisted by friction between the foundation and the natural sediments or supporting fill soils, and/or by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with compacted structural fill to achieve the passive resistance provided below. We recommend the following allowable design parameters: Passive equivalent fluid = 250 pef Coefficient of friction = 0.35 13.0 FLOOR SUPPORT We anticipate that the single-family homes that are built in the future will utilize a combination of slab -on -grade floors and structural/crawl space -type floors. Slab -on -grade floors should be constructed to bear on structural fill or pre -rolled, medium dense, native soils. The floors should be cast atop a minimum of 4 inches of washed pea gravel to act as a capillary break where moisture migration through the slabs is to be controlled. The slab should also be protected from dampness by an impervious vapor retarder. American Concrete Institute (ACI) recommendations should be followed for all concrete placement. In areas that structural/crawl space -type floors are used, the exposed soil in crawl spaces should be covered with a membrane, and the crawl spaces should be suitably ventilated to reduce the potential for excess moisture vapor. April 26, 2013 ASSOCIATED EARTH SCIENCES, INC. MPH - KFO80246A3 - Projei-W20 802461KEMP Page 12 Subsurface Exploration, Geologic Hazard, Talbot Property mid Geotechnical Engineering Report Edmonds, 44raslihigton Design Reconimendations 14.0 DRAINAGE CONSIDERATIONS All retaining and perimeter footing walls should be provided with a drain at the footing elevation. Drains should consist of rigid, perforated, polyvinyl chloride (PVC) pipe surrounded by washed pea gravel or drain rock. The level of the perforations in the pipe should be set approximately 2 inches below the bottom of the footing and should be constructed with sufficient gradient to allow gravity discharge away from the building. In addition, all retaining walls should be lined with a minimum, 12 -inch -thick, washed gravel blanket provided over the full height of the wall that ties into the footing drain. Roof and surface runoff should not discharge into the footing drain system, but should be handled by a separate, rigid, tightline drain. In planning, exterior grades adjacent to walls should be sloped downward away from the structure to achieve surface drainage. All roof, footing, and yard drains should be connected to the existing storm water sewer system. There are stub -outs on each lot that were installed in the previous construction phase of the project. 15.0 PROJECT DESIGN AND CONSTRUCTION MONITORING At the time of this report, site grading, structural plans, and construction methods have not been finalized. We are available to provide additional geotechnical consultation as the project design develops and possibly changes from that upon which this report is based. We recommend that AESI perform a geotechnical review of the pians prior to final design completion. In this way, our earthwork and foundation recommendations may be properly interpreted and implemented in the design. We are also available to provide geotechnical engineering and monitoring services during construction, The integrity of the foundation depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Some of these monitoring services may be required by the City of Edmonds as conditions of your construction permits. Construction monitoring services are not part of this current scope of work. If these services are desired, please let us know and we will prepare a cost proposal. April 26, 2013 ASSDCIA7ED EARTH SCIENCES; INC. rhSIld-Kcoso246,4s-Projects 12oo$o24r1KERP Page 13 Subsurface Exploration, Geologic Hazard, Talbot Property and Geotechnical Engineering Report Edmonds, Washington Design Recommendations We have enjoyed working with you on this study and are confident that these recommendations will aid in the successful completion of your project. If you should have any questions or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Kirkland, Washington qq t t, k 1 U Jon,# . Sondegaard, L.G., L.E.G, Matthew A. Miller, P.E. Seri, r Principal Geologist Principal Engineer Attachments: Figure 1 Vicinity Map Figure 2: Site and Exploration Plan Appendix: Exploration Logs April 26, 2013 ASSOCIATED EARTH SCIENCES, INC. JNSIN-KF080246A3-Projects1200802461KE1};'P Page 14 miullli" 11 1p, 14"l -A uv4uu() x � � \ I 0 0 EM� UJ k - EM� Classifications of soils in this report are based on visual field and/or laboratory observations, which include density/consistency, moisture condition, grain size, and Plasticity estimates and should not be construed to imply field or laboratory testing unless presented herein. Visual -manual and/or laboratory classification methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System. rn Associated Earth Sciences, Inc. U t EXPLORATION LOG KEY FIGURE Al O b °o ° Well -graded gravel and Terms Describing Relative Density and Consistency . ° o a ° a GW 9 ravel with sand, little to t�1 Density SPT blows/foot _ c o no fines Very Loose 0 to 4 Coarse - W >. 2 tQ > O (a U e �n n o° ° ° O O ° Poorly graded gravel Loose 4 to 10 Grained Sails Medium Dense 10 to 30 Test Symbols Y U5 w0 V vl ° o° o ° o°oro GP and gravel with sand, Dense 30 to 50 .. 0 d ° o o little to no fines Very Dense >50 G =Grain Size M = Moisture Content t2?blows/foot 0 o c p°°fl Consistency SPT A= Atterberg Limits Z c U) ° c -o Silty gravel and silty Very Soft 0 to 2 C= Chemical o GM gravel with sand Fine- Soft 2 to 4 DD = Dry Density a) a, '2o 42 = d = 0 Grained Soils Medium Stiff 4 to 8 K = Permeability v stiff 8 to 15 01 Clayey gravel and Very Stiff 15 to 30 a NiGC clayey gravel with sand Hard >30 N > 2 Component Definitions oWell-graded sand and Descriptive Term Size Range and Sieve Number r ;: sand with gravel, little Boulders Larger than 12' t° LL ter.•: •_.•;• to no fines Cobbles 3' to 12" Gravel 3' to No. 4 (4.75 mm) N @ >ee Poorly -graded sand Coarse Gravel 3° to 3/4" vi °> 0 —' N w sP and sand with gravel, Fine Grave) 3/4' to No, 4 (4.75 mm) m little t0 no fines Sand No. 4 (4,75 mm) to No. 200 (0.075 mm) Z Coarse Sand No. 4 (4.75 mm) to No. 10 (2.00 mm) d) Silty sand and Medium Sand No. 10 (2.00 mm) to No. 40 (0.425 mm) 0 N I SM silty sand with Fine Sand No. 40 (0,425 mm) to No. 200 (0,075 mm) C) a � gravel Silt and Clay Smaller than No. 200 (0:075 mm) Nl sc Clayey sand and clayey sand with gravel (3) Estimated Percentage Moisture Content Dry Absence Percentage by - of moisture, Component Weight dusty, dry to the touch Trace <5 Slightly Moist - Perceptible moisture Silt, sand silt, ravel) silt, Y y ML silt with sand of gravel r Few 5 to 10 Little 15 to 25 Moist -Damp but no visible N With Non -primary coarse water constituents: > 15% Very Moist - Water visible but Clay of low to medium "t U v / plasticity; silty, sandy, or Fines content between not free draining N J / CL gravelly clay, lean clay 5% and 15/o Wet -Visible free water, usually from below table N water a 5 -_ Organic clay or silt of low Symbols T 's— = OL plasticity Blows/6" or Sampler portion of 6' Cement grout `o �I Type / surface seal Elastic silt, clayey silt, silt with micaceous or 2 0 f Sampler Type ' OD Description Bentonite MH Split -Spoon N <+� seal N diatomaceous fine sand or silt Sam ler 3.0" ODS Split -Spoon Sampler p p p p - • ;;• Filler packvrith m o (SPT) 3,25" OD Split -Spoon Ring Sampler t,i ; :- :• blank casing section Clay of high plasticity, m° -Q N U o -o °' CH sand or ravel) clay, fat Y gravelly y Bulk sample -' 3.0" OD Thin -Wall Tube Sampler Screenedcasin 9 c= E clay with sand or ravel Y g .= (including Shelby tube) orHydrotip with filter pack _y Grab Sample End cap c a %iii Organic clay or silt of o Portion not recovered LL % „ if � 0 OH medium to high til t4) Percentage by dry weight Depth of ground water plasticity (2) (SPT) Standard Penetration TestY ATD = At time of drilling t3) (ASTM D-1586) Q Static water level (date) In General Accordance with > Peat, muck and other a) N a,'o w PT highly organic soils Standard Practice for Description ts) Combined USCS symbols used for to O and Identification of Soils (ASTM D-2488) fines between 5% and 15% Classifications of soils in this report are based on visual field and/or laboratory observations, which include density/consistency, moisture condition, grain size, and Plasticity estimates and should not be construed to imply field or laboratory testing unless presented herein. Visual -manual and/or laboratory classification methods of ASTM D-2487 and D-2488 were used as an identification guide for the Unified Soil Classification System. rn Associated Earth Sciences, Inc. U t EXPLORATION LOG KEY FIGURE Al O b III • _. is IIIi w m a 0 Talbot Property Edmonds, WA a t� Associated Earth Sciences, Inc. Project Na. KE080246A a Logged by; ALG F Approved by; RAP r, to a P Wig''; 4/15/08 U Y This log is part of the reportprepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be read together with that report for complete interpretation, This summary a only to the location of this trench at the plies time of excavation. Subsurface conditions may change at this location with the passage of time. The data presented are Q a simplfication of actual conditions encountered. DESCRIPTION Fill Loose, moist, gray, fine to medium SAND, with gravel, some roots and organic material. 1 Sod remnant at 1.6 to 2 feet; also old curtain drain for berm (washed rock trench). 2 Vashon Advance Outwash Medium dense, moist, light brown, fine to medium SAND, with some gravel. 3 4 5 6 7 Bottom of exploration pit at depth 7 feet 8 9 10 11 12 13 14 I m a 0 Talbot Property Edmonds, WA a t� Associated Earth Sciences, Inc. Project Na. KE080246A a Logged by; ALG F Approved by; RAP r, to a P Wig''; 4/15/08 U Y CL This log is part of the reportrepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be read together with that report complete interpretation. This summary applies only to the location of this trench at the time Subsurface conditions may change at this location with the passage of time. The data presented are o of excavation. a simpffication of actual conditions encountered. DESCRIPTION Fill Loose, moist, gray, fine to medium SAND, with roots and some brown organic topsoil. 2 3 4 @4 to 5 feet: Stump remnant/topsoil. 5 Loose, moist, brown -black, fine to medium SAND, with organic silt and wood debris. 6 7 Vashon Advance Outwash Loose to medium dense, moist, orange light brown, fine to medium SAND, with gravel and some 8 silt, 9 Becomes gray at 9 feet. 10 Bottom of exploration pit at depth 10 feet 11 12 13 14 Logged by: ALG Approved by: RAP §*Z1611 I A Eel HW 'lull, Associated Earth Sciences, Inc. r Project No. KE080246A 4/15/08 MOM NIMMM E v o This log is part of the reportprepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be read together with that report for complete interpretation. This summary applies only to the location of this trench at the time of excavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplfication of actual conditions encountered. DESCRIPTION Fill Sod, 1 Loose to medium dense, light brown gray, fine to medium SAND, with gravel. 2 3 4 5 ----------------------------------------------------- Native Topsoil Loose, moist, black brown, organic SILT. 6 ----------------- — ----------------- Vashon Advance Outwash 7 8 Medium dense, moist, orange brown to gray, fine to medium SAND, with gravel. 9 Bottom of exploration pit at depth 9 feet 10 11 12 13 14 Associated Earth ScieIlces, Inc. Logged by: ALG E0� � c Approved by: RAP r? ' .- j < Ko Project No. KE080246A 4/15108 0 o This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be read together with that report for complete interpretation. This summary appplies only to the location of this trench at the time of excavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simpification of actual conditions encountered. DESCRIPTION Fill Sod. 1 Loose, moist, brown, fine to medium SAND, with silt and gravel, some large cobbles (-12 inches). 2 3 4 Sod/topsoil remnant. _ _____________________ .------_----__—_ J ----------- — — Vashon Advance Qutwash 5 Medium dense, moist, light brown, fine to medium SAND, with gravel. Some pockets of fine sand. 6 7 8 9 10 Bottom of exploration pit at depth 9.5 feet 11 12 13 14 m 0 0 N Talb®t Property Edmonds, Associated Earth Sciences, Inc. Logged by: ALG Approved by: RAP H1 R Project No. KE080246A 4/15/08 : -5 v o This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be read together with that report for complete interpretation. This summary applies only to the location of this trench at the time of excavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplfication of actual conditions encountered. DESCRIPTION Top of exploration pit approximately 8 feet above street (existing cut). Medium dense, moist, light brown, fine to medium SAND, with gravel. (8 feet above street level) 7 ---------------- ------------------- Vashon Advance Outwash 6 Medium dense, moist, light brown, fine to medium SAND, with gravel. Some orange mottling of gravel surfaces and matrix around gravels. (6 feet above street level). 5 4 Medium dense, moist, light brown gray, fine to medium SAND, with gravel and silt. (4 feet above street level) 3 2 1 p Street grade. Bottom of exploration pit at street grade. 1 A fresh out into an existing cut slope, logged in feet above road grade (top of pit = 8 feet above road grade). -2 -3 -4 -5 -6 0 0 N Talbot Property d Edmonds, WA a Associated Earth Sciences, Inc, project No, KE080246A N Logged by: ALG i Approved by: RAP�t a€,, # 4/15108 Q This log is part of the reportprepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be read together with that report for complete interpretation. This summary applies only to the location of this trench at the time of excavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplfication of actual conditions encountered. DESCRIPTION Fill 1 2 Loose, moist to wet, fine to medium SAND, with gravel. 3 4 6 Seams of gray SAND at 5 feet - sampled. 6 7 Loose to medium dense, moist to wet, light brown, fine to medium SAND, with gravel. $ — _ — — -------------- Fili/Vashon Advance Outwash g Refusal due to caving. r Bottom of exploration pit at depth 9 feet 10 11 12 13 14 I Associated Earth Sciences, Inc. Logged by: ALG aFApproved by: RAP � �- $"• . �s�� ��a Project No. KE080246A 4115/08