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CANOD.pdfCity of Edmonds Critical Area Notice of Decision Applicant: C_ C Property Owner: Critical Area File #: Pen -nit Number: c) Site Location: Parcel Number: 0 Project Description: [ Conditional Waiver. No critical area report is required for the project descri4eYabove ofiq 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. ❑ 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. V, ❑ 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 in 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. E] Conditions. Critical Area specific condition(s) have been applied to the permit number referenced above. See referenced permit number for specific condition(s). Reviewer Signature Appeals: Any decision to approve, condition, or deny a development proposal or other activity based on the requirements of critical area regrilations may be appealed according to, and as part of, the appeal proc.edure, if any, for the permit or approval involved, Revised 12/16/2010 a n 4i �6..- ,7 O II � �, � o 2 rt"poo",, W O p cp N U O b N g� _O oZm �m � tl�I e3mmN a m iII �I U bo p 2 O �� Q�CC:111111 Q a n 4i �6..- ,7 O II ra til �1 � � o 2 rt"poo",, W O a n 4i �6..- ,7 � o 2 p cp N U O b N Q O 2 iII �I U bo p 2 O w Q z Z w ¢ � p w p �w Oi � W II II II II N C3U a n 4i �6..- ,7 Geotechnical Engineer Geolo; Environmental Scientik Construction Monitorii GEOTECHNICAL ENGINEERING STUD) PROPOSED SINGLE-FAMILY RESIDENCES 1035 MAIN STREET DMONISS, WASHINGTON ES -3380 ,t iia �r i Geotechnical Engineer Geolo; Environmental Scientik Construction Monitorii GEOTECHNICAL ENGINEERING STUD) PROPOSED SINGLE-FAMILY RESIDENCES 1035 MAIN STREET DMONISS, WASHINGTON ES -3380 ,t iia June 23, 2014 .i . . .�� . .. y �. i.. Kyle R. >. y. .. Campbell, \e /P.E. . Principal GEOTECHNICAL ENGINEERING STUDY PROPOSED SINGLE-FAMILY RESIDENCES STREET . MAIN » »»» 2a»$».... #? WASHINGTON 24yCI Earth Solutions NW ».« th 1805-136 face Northeast, Suite 201 Bellevue, . . \\;»°«!la< !!.!S Phone: 425-449-47 04 » 426-449-47 �>. � :!6633 °■ Toll Free: + a Geotechnical Sepwices Are Performed for Specific Purposes, Persons, and Projects Geotechnical engineers structure their services to meet the specific needs of their clients. A geotechnical engineering study conducted for a civil engi- neer may not fulfill the needs of a construction contractor or even another civil engineer. Because each geotechnical engineering study is unique, each geotechnical engineering report is unique, prepared solelyfor the client. No one except you should rely on your geotechnical engineering report without first conferring with the geotechnical engineer who prepared it. And no one — not even you —should apply the report for any purpose or project except the one originally contemplated. Read II Repopt Serious problems have occurred because those relying on a geotechnical engineering report did not read it all. Do not rely on an executive summary Do not read selected elements only. Geotechnical Engineeringuart is Based on Unique Set of P110jee peclf a Factors Geotechnical engineers consider a number of unique, project -specific fac- tors when establishing the scope of a study. Typical factors include: the client's goals, objectives, and risk management preferences; the general nature of the structure involved, its size, and configuration; the location of the structure on the site; and other planned or existing site improvements, such as access roads, parking lots, and underground utilities. Unless the geotechnical engineer who conducted the study specifically indicates oth- erwise, do not rely on a geotechnical engineering report that was: ® not prepared for you, ® not prepared for your project, ® not prepared for the specific site explored, or ® completed before important project changes were made. ® elevation, configuration, location, orientation, or weight of the proposed structure, ® composition of the design team, or ® project ownership. As a general rule, always inform your geotechnical engineer of project changes --even minor ones—and request an assessment of their impact. Geotechnical engineers cannot accept responsibility or liability for problems that occur because their reports do not consider developments of which they were not informed. Subsurface Conditions Can Change A geotechnical engineering report is based on conditions that existed at the time the study was performed. Do not rely on a geotechnical engineer- ing report whose adequacy may have been affected by: the passage of time; by man-made events, such as construction on or adjacent to the site; or by natural events, such as floods, earthquakes, or groundwater fluctua- tions. Always contact the geotechnical engineer before applying the report to determine if it is still reliable. A minor amount of additional testing or analysis could prevent major problems. Most Geotechnical Findings Ape Ppolossional Opinions Site exploration identifies subsurface conditions only at those points where subsurface tests are conducted or samples are taken. Geotechnical engi- neers review field and laboratory data and then apply their professional judgmeht to render an opinion about subsurface conditions throughout the site. Actual subsurface conditions may differ—sometimes significantly— from those indicated in your report. Retaining the geotechnical engineer who developed your report to provide construction observation is the most effective method of managing the risks associated with unanticipated conditions. Typical changes that can erode the reliability of an existing geotechnical engineering report include those that affect: A Report'sc a ns Ape Not Final ® the function of the proposed structure, as when it's changed from a Do not overrely on the construction recommendations included in your parking garage to an office building, or from a light industrial plant report. Those recommendations are not final, because geotechnical engi- to a refrigerated warehouse, neers develop them principally from judgment and opinion. Geotechnical engineers can finalize their recommendations only by observing actual subsurface conditions revealed during construction. The geotechnical engineer who developed your report cannot assume responsibility or liability for the report's recommendations if that engineer does not perform construction observation. Geotechnical Engineeping Repopt Is Subject t Misinterpretation Other design team members' misinterpretation of geotechnical engineering reports has resulted in costly problems, Lower that risk by having your geo- technical engineer confer with appropriate members of the design team after submitting the report. Also retain your geotechnical engineer to review perti- nent elements of the design team's plans and specifications. Contractors can also misinterpret a geotechnical engineering report. Reduce that risk by having your geotechnical engineer participate in prebid and preconstruction conferences, and by providing construction observation. Do Not Redpaw the Engineer's logs Geotechnical engineers prepare final boring and testing logs based upon their interpretation of field logs and laboratory data, To prevent errors or omissions, the logs included in a geotechnical engineering report should never be redrawn for inclusion in architectural or other design drawings. Only photographic or electronic reproduction is acceptable, butrecognize that separating logs from the report can elevate risk. Give Compactors Complete Repopt and Guidance Some owners and design professionals mistakenly believe they can make contractors liable for unanticipated subsurface conditions by limiting what they provide for bid preparation. To help prevent costly problems, give con- tractors the complete geotechnical engineering report, but preface it with a clearly written letter of transmittal. In that letter, advise contractors that the report was not prepared for purposes of bid development and that the report's accuracy is limited; encourage them to confer with the geotechnical engineer who prepared the report (a modest fee may be required) and/or to conduct additional study to obtain the specific types of information they need or prefer. A prebid conference can also be valuable. Be sure contrac- tors have sufficient time to perform additional study. Only then might you be in a position to give contractors the best information available to you, while requiring them to at least share some of the financial responsibilities stemming from unanticipated conditions. Read- Responsibility Ppovislons Closely Some clients, design professionals, and contractors do not recognize that geotechnical engineering is far less exact than other engineering disci- plines. This lack of understanding has created unrealistic expectations that have led to disappointments, claims, and disputes. To help reduce the risk of such outcomes, geotechnical engineers commonly include a variety of explanatory provisions in their reports. Sometimes labeled "limitations" many of these provisions indicate where geotechnical engineers' responsi- bilities begin and end, to help others recognize their own responsibilities and risks. Read these provisions closely. Ask questions, Your geolechnical engineer should respond fully and frankly. ovipmntl Concerns Ape Not Coveped The equipment, techniques, and personnel used to perform a geoenviron- mental study differ significantly from those used to perform a geotechnical study. For that reason, a geotechnical engineering report does not usually relate any geoenviron mental findings, conclusions, or recommendations; e.g., about the likelihood of encountering underground storage tanks or regulated contaminants. Unanticipated environmental problems have led to numerous project failures. If you have not yet obtained your own geoen- vironmental information, ask your geotechnical consultant for risk man- agement guidance. Do not rely on an environmental report prepared for someone else. Obtain Professional Assistance To Deal with Mold Diverse strategies can be applied during building design, construction, operation, and maintenance to prevent significant amounts of mold from growing on indoor surfaces. To be effective, all such strategies should be devised for the express purpose of mold prevention, integrated into a com- prehensive plan, and executed with diligent oversight by a professional mold prevention consultant. Because just a small amount of water or moisture can lead to the development of severe mold infestations, a num- ber of mold prevention strategies focus on keeping building surfaces dry. While groundwater, water infiltration, and similar issues may have been addressed as part of the geotechnical engineering study whose findings are conveyed in -this report, the geotechnical engineer in charge of this project is not a mold prevention consultant; none of the services per- formed in connection with the geotechnical engineer's study were designed or conducted for the purpose of mold preven- tion. Proper implementation of the recommendations conveyed in this report will not of itself he sufficient to prevent mold from growing in or on the structure involved. Rely, on Your ember GeoteChfiCial gine p fop Additional Assistance Membership in ASFE/The Best People on Earth exposes geotechnical engineers to a wide array of risk management techniques that can be of genuine benefit for everyone involved with a construction project. Confer with you ASFE-member geotechnical engineer for more information. ASFE The best Peeeia on Enrtd 8811 Colesville Road/Suite G106, Silver Spring, MD 20910 Telephone: 301/565-2733 Facsimile: 301/589-2017 e-mail: info@asfe.org www.asfe.org Copyright 2004 by ASFE, Inc. Duplication, reproduction, or copying of this document, in whole or in part by any means whatsoever, is strictly prohibited, except with ASFEs specific written permission. Excerpting, quoting, or otherwise extracting wording from this document is permitted only with the express written permission ofASFE, and only for purposes of scholarly research or book review. Only members of ASFE may use this document as a complement to or as an element of a geotechnical engineering report. Any other firm, individual, or other entity that so uses this document without being an ASFE member could be committing negligent or intentional (fraudulent) misrepresentation. IIGER06045.OM June 23, 2014 ES -3380 Echelbarger Investments, LLC 4001 —198th Street Southwest Lynnwood, Washington 98036 Attention: Mr. Todd Echelbarger Dear Mr, Echelbarger: Sb��l�iorrrs Earth Solutions NW 11C Geotechnical Engineering ® Construction Monitoring ® Environmental Sciences Earth Solutions NW, LLC (ESNW) is pleased to present this report titled "Geotechnical Engineering Study, Proposed Single -Family Residences, 1035 Main Street, Edmonds, Washington". Based on the results of our study, construction of the proposed single-family residential structures at the subject site is feasible from a geotechnical standpoint. Based on the results of our study, the proposed residential structures can be supported on a conventional foundation system bearing on competent native soil, recompacted native soil, or structural fill. Competent soils suitable for support of foundations should be encountered at depths of about four to six feet below existing grades across the majority of the site. Slab -on - grade floors should be supported on dense native soil, re -compacted native soil, or structural fill. Where loose, organic or other unsuitable materials are encountered at or below the footing subgrade elevation, the material should be removed and replaced with structural fill, as necessary. This report provides a geologically hazardous areas assessment, and recommendations for foundation subgrade preparation, foundation and retaining wall design parameters, drainage, the suitability of the on-site soils for use as structural fill, and other geotechnical recommendations. The opportunity to be of service to you is appreciated. If you have any questions regarding the content of this geotechnical engineering study, please call. Sincerely, Henry T. right, E.I.T. Staff En Ineer 18015 - 1361h Place N.E., Suite 201 ® Bellevue, WA 98005 ® (425) 449-4704 ® FAX (425) 449-471"1 11JURMOINIONVIOR • • < • - • • • MU,41 - . • 0 • • ........ ... • Earth Solutions NW, LLC Plate 1 Vicinity Map Plate 2 Boring Location Plan [-"'-late 4 Footing Drain Detail Appendix A Subsurface Exploration Boring Logs Nppendix B Laboratory Test Results Grain Size Distribution Earth Solutions NW, LLC •I 1.11P PROPOSED SINGLE-FAMILY RESIDENCES 1035 MAIN STREET EDMONDS, WASHINGTON • This geotechnical engineering study was prepared for the proposed single-family residential structures to be constructed at 1035 Main Street in Edmonds, Washington. To complete the scope of services detailed in our proposal PES -3380 dated May 5, 2014, we performed the following: ® Subsurface exploration and characterization of soil and groundwater conditions by advancing a boring adjacent to the toe of the steep slope to the north of the property; ® Laboratory testing of soil samples obtained during subsurface exploration; ® Engineering analyses and recommendations for the proposed development, and; ® Preparation of this report. The following documents and/or resources were reviewed as part of our report preparation; Geologic . • of • • and Part of • • •s West Quadrang Washington, prepared by James P. Minard, dated 1983; Critical Areas Reconnaissance -•• - Number`A1 X11 NorthCRA20140022, prepared by City of Edmonds; • a •s Earth Subsidence « • Landslide Hazard Area « Report, prepared by Landau Associates, dated March 14, 2007, and; • • • ••- .• - 1=16 110111 201I.V011.11210EM2112M Earth Solutions NW, LLC Echelbarger Investments, LLC June 23, 2014 Based on the site plan provided to us, the existing single-family residential structure and associated outbuildings will be demolished and two new single-family residential structures will be constructed. We anticipate grading activities will include cuts and fills to establish the planned building alignments. Based on the existing grades, we estimate cuts to establish building pad and foundation subgrade elevations will be on the order of up 10 to 12 feet. However, grading plans were not available at the time this report was prepared. Site improvements will also include underground utility installations. At the time this report was prepared, specific building load values were not available. However, we anticipate the proposed. residential structures will consist of relatively lightly loaded wood framing supported on conventional foundations. Based on our experience with similar developments, we estimate wall loads on the order of two kips per linear foot and slab -on -grade loading of 150 pounds per square foot (psf). If the above design assumptions are incorrect or change, ESNW should be contacted to review the recommendations in this report. ESNW should review the final design to verify the geotechnical recommendations provided in this report have been incorporated into the plans. The subject site located at 1035 Main Street in Edmonds, Washington, as illustrated on the Vicinity Map (Plate 1). The site consists of two residential tax parcels (Snohomish County parcel numbers 0434204003000 and 0434204002800) totaling approximately 0.28 acres of land area. The property is currently developed with a single-family residence and associated improvements. The majority of the site is relatively level with a gentle west descending slope. Based on site observation and review of the referenced critical areas reconnaissance report, a south descending slope with a gradient in excess of 50 percent is located to the north of the site. Vegetation within the steep slope area consists of mature trees, saplings, and ivy groundcover. The subject site is bordered to the north, east, and west by residential structures and to the south by Main Street, The Boring Location Plan (Plate 2) illustrates the approximate limits and local topography of the property. As part of the subsurface exploration, a boring was advanced adjacent to the toe of the steep slope area to the north of the site for purposes of assessing soil and groundwater conditions. The boring was advanced to a depth of 26.5 feet below existing grade. Please refer to the boring logs provided in Appendix A for a more detailed description of the subsurface conditions. Soil conditions observed at the boring location consisted of loose to very dense silty sar% (Unified Soil Classification SM) and poorly graded sand (SP) advance outwash deposits. Overall soil relative density increased with depth. Earth Solutions NW, LLC Echelbarger Investments, LLC June 23, 2014 According to the referenced geologic map, the subject site is underlain by advance outwash (Qva) deposits. Soil conditions observed at the boring location were generally consistent with advance outwash deposits. The National Resources Conservation Service (MRCS) Web Soil Survey indicates the site soils consist of Alderwood-Everett gravelly sandy loam. The soil conditions observed at the boring location were generally consistent with the NRCS soil mapping. Groundwater seepage was observed during our fieldwork on May 30, 2014 at a depth of approximately five and one-half feet below existing grades, which likely represents perched groundwater. Seepage should be expected in site excavations. Groundwater seepage rates and elevations fluctuate depending on many factors, including precipitation duration and intensity, the time of year, and soil conditions. In general, groundwater elevations and flow rates are higher during the winter, spring and early summer months. As part of this geotechnical engineering study, the referenced chapter of the Edmonds City Code was reviewed. Per the Edmonds City Code requirements, the following topics related to development plans and site conditions are addressed. During our fieldwork, we performed a visual slope reconnaissance across the steep slope area to the north of the site. The main focus of our reconnaissance was to identify signs of instability or erosion hazards along the site slopes. The typical instability indicators include features such as head scarps, tension cracks, hummocky terrain, groundwater seeps along the surface and erosion features such as gulleys and rills. During the slope reconnaissance, no signs of recent, large scale erosion or slope instability were observed. The slope is vegetated with mature trees, saplings, and ivy groundcover. In general, based on the slope reconnaissance, stability of the steep slope to the north of the property can be characterized as good. I-WIM•- a _ With respect to landslide hazard areas, section 23,80,020 of the Edmondsii^ dlandslide hazard areas as "areas potentially subject to landslides based on a combination of geologic, topographic, and hydrologic factors, They include areas susceptible because of any combination of bedrock, soil, slope (gradient), slope aspect, structure, hydrology, or other factors. Within the city of Edmonds, landslide hazard areas specifically include: efines Earth Solutions NW, LLC Echelbarger Investments, LLC June 23, 2014 1. Areas of ancient or historic failures in Edmonds which include all areas within the earth subsidence and landslide hazard area as identified in the 1979 report of Robert Lowe Associates and amended by the 1985 report of GeoEngineers, Inc.; 2. Any area with a slope of 40 percent or steeper and with a vertical relief of 10 feet or more except areas composed of consolidated rock; 3. Any area potentially unstable as a result of rapid stream incision or stream bank erosion; and 4. Any area located on an alluvial fan, presently subject to, or potentially subject to, inundation by debris flow or deposition of stream -transported sediments." Based on site observation and the referenced critical areas reconnaissance report, a south - descending steep slope with gradient in excess of 50 percent is located to the north of the subject property. Per the above definition of landslide hazard areas, the steep slope to the north of the subject property classifies as a landslide hazard area based on a slope gradient of 40 percent or steeper with a vertical relief of 10 feet or more. The proposed development will not alter the landslide hazard area. • With respect to erosion hazard areas, section 23.80.020 of the Edmonds City Code defines erosion hazards as "at least those areas identified by the U.S. Department of Agriculture's Natural Resources Conservation Service as having a "moderate to severe", "severe", or "very severe" rill and inter -rill erosion hazard. Erosion hazard areas are also those areas impacted by shoreland and/or stream bank erosion. Within the city of Edmonds, erosion hazard areas include: Those areas of the city of Edmonds containing soils that may experience severe to very severe erosion hazard. This group of soils includes, but is not limited to, the following when they occur on slopes of 15 percent or greater: a. Alderwood soils (15 to 25 percent slopes); b. Alderwood/Everett series (25 to 70 percent slopes); c. Everett series (15 to 25 percent slopes); slopesf. Any area with percent or greater and impermeable soils intwith granular soils and springs or ground water seepage; and erbedded 3. Areas with significant visible evidence of ground water seepage, and which also include existing landslide deposits regardless of slope." Earth Solutions NK LLC Echelbarger Investments, LLC ES -3380 June 23, 2014 Page 5 As previously indicated, the on-site soils are generally consistent with Alderwood-Everett gravelly sandy loam. Based on the Edmonds City Code definition, the steep slope area to the north of site classifies as an erosion hazard area. The proposed development will not alter the erosion hazard area. The proposed development will involve demolition of the existing single-family residential structure and associated outbuildings and construction of two new single-family residential structures. Based on the referenced site plans, the grading will involve cuts and fills to establish level building pada areas. Based on the information provided to us, the proposed development will not impact the landslide hazard and erosion hazard area and adjacent properties. Based on the results of our study, in our opinion, the proposed development will not increase the threat of the geological hazard to adjacent properties beyond predevelopment conditions and will not adversely impact other critical areas. Minimum Buffer anduildin etback Based on the results of our study and our understanding of the proposed development, in our opinion, the proposed development should incorporate a minimum no -disturbance buffer of 10 feet and a minimum building setback of 15 feet from the landslide hazard area. Based on the results of our study, in our opinion, construction of the proposed residential structures at the subject site is feasible from a geotechnical standpoint. The primary geotechnical considerations associated with the proposed development include foundation support, temporary excavations, retaining walls, and the suitability of the on-site soils for use as structural fill. The proposed structures can be supported on conventional spread and continuous foundations bearing on undisturbed competent native soil, recompacted native soil, or structural fill. Competent soils suitable for support of foundations should be encountered at depths of approximately four to six feet below existing grades across the majority of the site. Slab -on - grade floors should be supported on dense native soil, re -compacted native soil, or structural fill. Organic material exposed at subgrade elevations must be removed below design elevation and grades restored with structural fill. Where loose, organic or other unsuitable materials are encountered at or below the footing subgrade elevation, the material should be removed and replaced with structural fill, as necessary. This study has been prepared for the exclusive use of Echelbarger Investments, LLC and his representatives. No warranty, expressed or implied, is made. This study has been prepared in a manner consistent with the level of care and skill ordinarily exercised by other members of the profession currently practicing under similar conditions in this area. Earth Solutions NW, LLC Echelbarger Investments, LLC ES -3380 June 23, 2014 Page 6 Based on the referenced site plans and given the existing topography, we anticipate grading for the project will involve cuts of up to 10 to 12 feet to establish building pad and foundation subgrade alignments. Silt fencing and temporary erosion control measures should be placed along the perimeter of the site prior to beginning grading activities. Temporary construction entrances, consisting of at least six inches of quarry spalls can be considered in order to minimize off-site soil tracking and to provide a temporary road surface, Silt fences should be placed along the margins of the property. Interceptor swales and a temporary sediment pond may be necessary for control of surface water during construction. Erosion control measures should conform to the Washington State Department of Ecology (DOE) and City of Edmonds standards. In -Situ Soils From a geotechnical standpoint, the soils encountered at the boring location are generally suitable for use as structural fill. However, successful use of the on-site soils will largely be dictated by the moisture content of the soils at the time of placement and compaction. The site soils were generally in a moist to wet condition at the time of the exploration on May 30, 2014. Based on the conditions encountered during our fieldwork, the site soils will generally have a moderate sensitivity to moisture. During periods of dry weather, the on-site soils should generally be suitable for use as structural fill, provided the moisture content is at or near the optimum level at the time of placement. Successful placement and compaction of the on-site soils during periods of precipitation will be difficult. If the on-site soils cannot be successfully compacted, the use of an imported soil may be necessary. Imported soil intended for use as structural fill should consist of a well -graded granular soil with a moisture content that is at or near the optimum level. During wet weather conditions, imported soil intended for use as structural fill should consist of a well -graded granular soil with a fines content of 5 percent or less defined as the percent passing the Number 200 sieve, based on the minus three-quarter inch fraction. Structural Fill Structural fill is defined as compacted soil placed in foundation, slab -on -grade, and roadway areas. Fills placed to construct permanent slopes and throughout retaining wall and utility trench backfill areas are also considered structural fill. Soils placed in structural areas should be placed in loose lifts of 12 inches or less and compacted to a relative compaction of 90 percent, based on the laboratory maximum dry density as determined by the Modified Proctor Method (ASTM D-1557). For soil placed in utility trenches underlying structural areas, compaction requirements are dictated by the local city, county, or utility district, and in general are specified as 95 percent relative compaction. The upper 24 inches of foundation subgrade areas and the upper 12 inches of slab -on -grade and pavement subgrade areas should be compacted to a relative compaction of at least 95 percent. Earth Solutions NW, LLC Echelbarger Investments, LLC June 23, 2014 The Federal Occupation Safety and Health Administration (OSHA) and the Washington Industrial Safety and Health Act (WISHA) provide soil classification in terms of temporary slope inclinations. Based on the. soil conditions encountered at the boring location, the loose to medium dense native soils encountered in the upper approximately four to six feet of the boring location and where fill and/or groundwater seepage is exposed are classified as Type C by OSHA/WISHA. Temporary slopes over four feet in height in Type C soils must be sloped no steeper than 1.51-1:1V (Horizontal:Vertical). Medium dense to dense native soils encountered below approximately four to six feet where no groundwater seepage is exposed would be classified as Type B by OSHA/WISHA. Temporary slopes over four feet in height in Type B soils must be sloped no steeper than 1 H:1V. The presence of perched groundwater may cause caving of the temporary slopes due to hydrostatic pressure. ESNW should observe site excavations to confirm the soil type and allowable slope inclination are appropriate for the soil exposed by the excavation. If the recommended temporary slope inclination cannot be achieved, temporary shoring may be necessary to support excavations. Permanent slopes should maintain a gradient of 2H:1V, or flatter, and should be planted with vegetation to enhance stability and to minimize erosion. A representative of ESNW should observe temporary and permanent slopes to confirm the slope inclinations are suitable for the exposed soil conditions, and to provide additional excavation and slope recommendations, as necessary. Based on the results of our study, the proposed residential structures can be supported on conventional spread and continuous footings bearing on competent native soil, recompacted native soil, or structural fill. Based on the soil conditions encountered at the boring location, competent native soils suitable for support of foundations should be encountered at depths of about four to six feet below existing grades. Where loose or unsuitable soil conditions are observed at foundation subgrade elevations, compaction of the soils to the specifications of structural fill, or overexcavation and replacement with granular structural fill will be necessary. Organic material exposed at foundation subgrade elevations must be removed and grades restored with structural fill. Provided •structuresbesupported as described above, following parameterscan it used for design of the new foundations: Allowable soil bearingcapacity2,500 •: o Passive earth pressure 300 pcf (equivalent fluid) v Coefficient of friction 0.40 • the allowable soilbearing capabe assumed forshort-term • seismic loading conditions. Earth Solutions NW, LLC Echelbarger Investments, LLC ES -3330 June 23, 2014 Page 3 With structural loading as expected, total settlement in the range of one inch is anticipated, with differential settlement of about one-half inch. The majority of the settlements should occur during construction, as dead loads are applied. The 2012 IBC recognizes ASCE for seismic site class definitions. If the project will be permitted under the 2012 IBC, in accordance with Table 20.3-1 of ASCE, Minimum Design Loads for Buildings and Other Structures, Site Class D, should be used for design. In our opinion, the site is not susceptible to liquefaction. The soil relative density and the absence of an established shallow groundwater table is the primary basis for this opinion. Slab -on -grade floors should be supported on a firm and unyielding subgrade consisting of competent native soil or at least 12 inches of structural fill. Unstable or yielding areas of the subgrade should be recompacted or overexcavated and replaced with suitable structural fill prior to construction of the slab. A capillary break consisting of a minimum of four inches of free -draining crushed rock or gravel should be placed below the slab. The free -draining material should have a fines content of 5 percent or less defined as the percent passing the Number 200 sieve, based;on the minus three-quarters inch fraction. In areas where slab moisture is undesirable, installation of a vapor barrier below the slab should be considered. If used, the vapor barrier should consist of a material specifically designed to function as a vapor barrier and should be installed in accordance with the manufacturer's specifications. If retaining walls will be utilized, they should be designed to resist earth pressures and applicable surcharge loads. The following parameters can be used for retaining wall design: ® Active earth pressure (yielding condition) ® At -rest earth pressure (restrained condition) ® Traffic surcharge (passenger vehicles) ® Passive earth pressure ® Coefficient of friction ® Seismic surcharge . *Where H equals retained height Earth Solutions NW, LLC 35 pcf 50 pcf 70 psf (rectangular distribution) 300 pcf 0.40 6H* (active) 12H* (at -rest condition) Echelbarger Investments, LLC ES -3380 June 23, 2014 page 9 Where sloping or other surcharge conditions will be present, supplement recommendations and design earth pressure values should be provided by ESNW. Drainage should be provided behind retaining walls such that hydrostatic pressures do not develop. If drainage is not provided, hydrostatic pressures should be included in the wall design. Retaining walls should be backfilled with free -draining material that extends along the height of the wall, and a distance of at least 18 inches behind the walla The upper one foot of the wall backfill can consist of a less permeable soil, if desired. A perforated drain pipe should be placed along the base of the wall, and should be connected to an approved discharge location. A typical retaining wall drainage detail is provided as Plate 3. ®rainm Groundwater seepage was observed during our fieldwork on May 30, 2014 at a depth of approximately five and one-half feet below existing grades, which likely represents perched groundwater. Seepage should be expected in site excavations, particularly in the winter, spring and early summer months. Temporary measures to control groundwater seepage and surface water runoff during construction will likely involve passive elements such as interceptor trenches and sumps, as necessary. Surface water should not be allowed to runoff over sloped areas and should not be allowed to pond near the top of sloped areas or retaining structures, Surface grades must be designed to direct water away from buildings. The grade adjacent to buildings should be sloped away from the buildings at a gradient of at least 2 percent for a horizontal distance of ten feet. In our opinion, perimeter footing drains should be installed at or below the invert of the building footings. A typical footing drain detail is provided on Plate 4 of this report. WHO Trench Support andBackfill In our opinion, the soils observed at the boring location are generally suitable for support of utilities. In general, the soils observed at the boring location should be suitable for use as structural backfill in the utility trench excavations, provided the soil is at or near the optimum moisture content at the time of placement and compaction. Moisture conditioning of the soils may be necessary at some locations prior to use as structural fill. Utility trench backfill should be placed and compacted to the specifications of structural fill provided in this report, or to the applicable requirements of the City of Edmonds. Pavement Sections The performance of site pavements is largely related to the condition of the underlying subgrade. To ensure adequate pavement performance, the subgrade should be in a firm and unyielding condition when subjected to proofrolling with a loaded dump truck. Structural fill in pavement areas should be compacted to the specifications detailed in the Site Preparation and Earthwork section of this report. It is possible that soft, wet, or otherwise unsuitable subgrade areas may still exist after base grading activities. Areas of unsuitable or yielding subgrade conditions may require remedial measures such as overexcavation and replacement with structural fill or thicker crushed rock sections prior to pavement. Cement treatment of the subgrade soil can also be considered for stabilizing pavement subgrade areas. Earth Solutions NW, LLC Echelbarger Investments, LLC ES -3380 June 23, 2014 Page 10 For relatively lightly loaded pavements subjected to automobiles and occasional truck traffic, the following sections can be considered for preliminary design: ® Two inches of hot mix asphalt (HMA) placed over four inches of crushed rock base (CRIB), or; ® Two inches of HMA placed over three inches of asphalt treated base (ATB). The HMA, CRIB and ATB materials should conform to WSDOT specifications. LIMITATIONS The recommendations and conclusions provided in this geotechnical engineering study are professional opinions consistent with the level of care and skill that is typical of other members in the profession currently practicing under similar conditions in this area. A warranty is not expressed or implied. Variations in the soil and groundwater conditions observed at the boring location may exist, and may not become evident until construction. ESNW should reevaluate the conclusions in this geotechnical engineering study if variations are encountered. ESNW should have an opportunity to review the final design with respect to the geotechnical recommendations provided in this report. ESNW should also be retained to provide testing and consultation services during construction. Earth Solutions NW, LLC Reference: Snohomish Map 454 By The The Rand MCN, 32nd Editic NORTH A7 �hlb- NOTE: This plate may contain areas of color. ESNW cannot be Drwn. GLSDate 06/19/2014 Proj. No. 3380 responsible for any subsequent misinterpretation of the information Checked HTW Date June 2014 Plate 1 resulting from black & white reproductions of this plate. I I I I 210 i I I I I I I 220 AH EY . MAIN STREET • ► to B-1—�— Approximate Location of ESNW Boring, Proj. No. ES -3380, May 2014 Subject Site Existing Building NOTE: The graphics shown on this plate are not intended for design purposes or precise scale measurements, but only to illustrate the approximate test locations relative to the approximate locations of existing and / or proposed site features. The information illustrated is largely based on data provided by the client at the time of our study. ESNW cannot be responsible for subsequent design changes or interpretation of the data by others. NOTE: This plate may contain areas of color. ESNW cannot be responsible for any subsequent misinterpretation of the information resulting from black & white reproductions of this plate. 1 210 0 15 30 60 1 "=30' MWM IN Q Scale in Feet Drwn. GLS Date 06/19/2014 Proj. No. 3380 Checked HTW Date June 2014 Plate 2 - IE II r 18" Min. o o - 0 0 o 0 0�0�'0 o ..° o o B 00 o °o0 oo0 0 o 0 0 0 0 0 0 0° 0 0 0 o0 0 o��yy�o 0 o 0 000-0 0 0 0 o O V o 00 0 0 ° o O 0 o ° °o o. 0 o o o 0,op �o � o 0 0 000 00 o o0 0�0 0 0 0o 0 c ( Oo o 0 o 0 0 0 o 0 0 00 0o Oo 0o p° oo o ° o 0 0o 00000. oo o° o 0 6 0 00 0 00 0 o p 00 O o o 0 o 0 0 0 0 OoOp 00 o oo 0 o ° o0 o 0 o O o 0 00 oo000 00 00o00 �o 0 a o 0 0000 o Oo o o o 0 o 0 sJ�.1s o Free Draining Backfill should consist of soil having less than 5 percent fines. Percent passing #4 should be 25 to 75 percent. e Sheet Drain may be feasible in lieu of Free Draining Backfill, per ESNW recommendations. ® Drain Pipe should consist of perforated, rigid PVC Pipe surrounded with 1" Drain Rock. 0 0 o 00 Free Draining Structural Backfill ' 1 inch Drain Rock Structural Fill \ Perforated Drain Pipe (Surround In Drain Rock) SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING RETAINING WALL DRAINAGE DETAIL 1035 Main Street Edmonds, Washington Drwn. GLS Date 06/23/2014 Proj. No. 3380 Checked HTW Date June 2014 Plate 3 Perforated Rigid Drain Pipe (Surround with 1" Rock) Do NOT tie roof downspouts to Footing Drain. ® Surface Seal to consist of 12" of less permeable, suitable soil. Slope away from building. Surface Seal; native soil or other low permeability material. 1" Drain Rock SCHEMATIC ONLY - NOT TO SCALE NOT A CONSTRUCTION DRAWING Drwn. GLS Date 06/23/2014 Proj. No. 3380 Checked HTW Date June 2014 Plate 4 � ::•. .Y. i The subsurface conditions at the site were explored by advancing one boring at the approximate locations illustrated on Plate 2 of this report. The boring logs are provided in this Appendix. The subsurface exploration was completed on May 30, 2014. The boring was advanced to a maximum depth of 26.5 feet below existing grades. Logs of the boring advanced by ESNW are presented in Appendix A. The final logs represent the interpretations of the field logs and the results of laboratory analyses. The stratification lines on the logs represent the approximate boundaries between soil types. In actuality, the transitions may be more gradual. Earth Solutions NW, LLC Earth Solutions NWLLC SOIL CLASSIFICATION CHART DUAL SYMBOLS are used hJindicate borderline soil classifications, The discussion in the text of this report is necessary for a proper understanding of the nature SYMBOLS, TYPICAL MAJOR DIVISIONS GRAPH, LETTER DESCRIPTIONS CLEAN OIL. WELL -GRADED GRAVELS, GRAVEL - GRAVEL GRAVELS 01111 111 GW SAND MIXTURES, LITTLE OR NO AND FINES GRAVELLY SOILS (LITTLE OR NO FINES GP POORLY -GRADED GRAVELS, GRAVEL SAND MIXTURES, - LIT TLE OR NO FINES COARSE GRAINED GRAVELS WITH 0. No GM SILTY GRAVELS, GRAVEL - SAND - SOILS MORE THAN 50% FINES SILT MIXTURES OF COARSE 0M. 0 FRACTION RETAINED ON NO. 4 SIEVE (APPRECIABLE GC CLAYEY GRAVELS, GRAVEL - SAND - AMOUNT OF FINES) CLAY MIXTURES CLEAN SANDS SW WELL -GRADED SANDS, GRAVELLY MORE THAN 50% SAND SANDS, LITTLE OR NO FINES OF MATERIAL IS AND LARGER THAN SANDY NO. 200 SIEVE SOILS OR NO FINES) SID POORLY -GRADED SANDS, GRAVELLY SAND, LITTLE OR NO SIZE (LITTLE sm SILTY SANDS, SAND - SILT SANDS WITH MORE THAN 50% FINES MIXTURES OF COARSE FRACTION PASSING ON NO. 4 SIEVE (APPRECIABLE sc CLAYEY SANDS, SAND - CLAY AMOUNT OF FINES) MIXTURES INORGANIC SILTS AND VERY FINE ML SANDS, ROCK FLOUR, SILTY OR CLAYEY FINE SANDS OR CLAYEY SILTS WITH SLIGHT PLASTICITY SILTS INORGANIC CLAYS �F LC7W TO FINE LIQUID LIMIT AND CL MEDIUM PLASTICITY, GRAVELLY GRAINED LESS THAN 50 CLAYS CLAYS, SANDY CLAYS, SILTY SOILS I CLAYS, LEAN CLAYS OL ORGANIC SILTS AND ORGANIC SILTY CLAYS OF LOW PLASTICITY MORE THAN 50% INORGANIC SILTS, MICACEOUS OR OF MATERIAL IS MH DIATOMACEOUS FINE SAND OR SMALLER THAN SILTY SOILS NO. 200 SIEVE SIZE SILTS LIQUID LIMIT ANb CH INORGANIC CLAYS OF HIGH GREATER THAN 50 CLAYS PLASTICITY OH ORGANIC CLAYS OF MEDIUM TO HIGH PLASTICITY, ORGANIC SILTS HIGHLY ORGANIC SOILS PT PEAT, HUMUS, SWAMP SOILS WITH L' HIGH ORGANIC CONTENTS DUAL SYMBOLS are used hJindicate borderline soil classifications, The discussion in the text of this report is necessary for a proper understanding of the nature =Earth Solutions NW BORING ®1 1805 - 136th Place N.E., Suite 201 k' Bellevue %A/.shin ton 98005 PAGE 1 OF 2 9 Telephone: 425-449-4704 � m Fax: 425-449-4711 SP CLIENT _Echelba-rger_Investments, LLC ._., , , .. , SS PROJECT NAME . 1035 MainStreet _, PROJECT NUMBER 3380_...___..._..__...._ _._ _.. PROJECT LOCATION Edmonds Washington_, , ------- DATE STARTED _5/30/14 COMPLETED 5/30/14. GROUND ELEVATION 205 ft_ HOLE SIZE DRILLING CONTRACTOR Boretec SS GROUND WATER LEVELS: DRILLING METHOD _ HSAAT MC = 23.10% TIME OF DRILLING --- LOGGED BY HTW CHECKED BY HTW AT END OF DRILLING – NOTES BramblesAFTER DRILLING — Wy o SM 55 100 11(355-18 MC = 27.20% a_ a? o m o> TESTS p MATERIAL DESCRIPTION Q W 0 0 Brown silty SAND, loose to medium dense, damp to moist 15 ~ SS 100 20-50/5" MC = 19.90% z SM ' � m SP SS 100 5-4-4 MC = 25.40% SM (8) Fines = 8.60% SS 100' 6-8-10 MC = 23.10% (18) Fines = 4.00% SM 55 100 11(355-18 MC = 27.20% 15 ~ SS 100 20-50/5" MC = 19.90% z � m w z . _20 Black poorly graded SAND with silt, loose, wet [USDA Classification: gravelly SAND] -moderate seepage .. Brown silty SAND, medium dense, wet [USDA Classification: SAND] poorly graded SAND, very dense, moist to wet Earth Solutions NW BORING ®1 1805 - 136th Place N.E., Suite 201 r r Bellevue, ashington 98005 PAGE 2 OF 2 Telephone: 425-449-4704 Fax: 425-449-4711 CLIENT Echelbarger Investments LLC; PROJECT NAME 1035 Main Street - --- - PROJECT NUMBER 3380 PROJECT LOCATION _drnpnds,_WgshEngtpn_ ._ W o �w � ��D n~ i � > O � Q TESTS ° O MATERIAL DESCRIPTION aV ¢z o moz Uj 20, Gray poorly graded AND, very dense, moist to wet (continued) SS 100 19-50 MC = 21.40% SP - z3it7 1z,0 Gray silty SAND, very dense, wet 25 SM _ 16-36 MC 22.00% [USDA Classification: loamy SAND] SS 100 50/3" Fines = 23.70% 26.5,:. ._ ..-:. 178.5 Boring terminated at 26.5 feet below existing grade. Groundwater seepage encountered at 5.5 feet during drilling. Boring backfilled with bentonite. Bottom of hole at 26.5 feet. v `m O U` Z_ 0 D. O M M 1`yJ' a H x m w T., • .. • Earth Solutions NW, LLC Earth Solutions NW GRAIN SIZE DISTRIBUTIOW 1805 -136th Place N ' E., Suite 201 Bellevue, WA 98005 Telephone: 425-284-3300 CLIENT nher Investment LLC PROJECT NAME 7 1035 Edmonds PROJECT NUMBER ES -3380— — — PROJECT LOCATION Edmonds — - - --------------- GRAIN SIZE IN MILLIMETERS GRAVEL SAND COBBLES ---G--oa-We— fine coarse -medium �ne SILT ORCLAY - - — - ------- Specimen Identification Classification LL PL P1 Cc Cu 0 B-1 6.0ft. USDA: Black Gravelly Sand. USCS: SP-SM1with Gravel. 1.00 6.49 zt am B-1 7.6ft. USDA: Brown Sand. USCS: SM. A- B-1 25.0ft. USDA: Gray Loamy Sand. USCS: SM. Specimen Identification D100 D60 D30 D10 %Silt %Clay B-1 5.Oft. 19 0.69 0.232 0.091 8.6 . ........... B-1 7.6ft. 9.5 0.241 0.167 14.0 Uf 23.7 A B-1 26.0ft. 4.76 0.228 0.148 Echelbarger Investments, 4001 — 198" Street Southwest Lynnwood, Washington 9:1 Earth Solutions NK LLC ti ur N M, Echelbarger Investments, LLC 4001 _ 198th Street Southwest, Suite 2 Lynnwood, Washington 98036 Subject: Response to Comments City of Edmonds — Plan Review Comments #2 1036 and 1037 Main Street Edmonds, Washington Reference: City of Edmonds Plan Review Comments #2 Project # 2014-0380 and 2014-0381 July 21, 2014 Insight Engineering Co. Site Plans March 31, 2014 Earth Solutions NW, LLC Geotechnical Engineering Study ES -3380, June 23, 2014 Dear Mr. Echelbarger: Earth Solutions NW LLC • Geotechnical Engineering • Construction Monitoring 1, Environmental Sdem�es As requested, Earth Solutions NW, LLC (ESNW) has prepared this letter addressing the referenced City of Edmonds Development Services Department review comments memo. The referenced documents have been reviewed in preparation of this letter. The comments pertinent to the geotechnical aspects of the project are provided below, 'followed by our responses. City of Edmonds Comment I — Geotechnical report: Thank you for submitting the Earth Solutions report dated June 23, 2014. It was rioted in the report that the geotech had not had the opportunity to review the associated grading plans; please have Earth Solutions review the grading and TESC plan (Sheet C2) and the associated drainage and utility plan (Sheet Cl). 180." - 1.36111 Place N1, Suile 201 1 Bellevue, VVA ()8005 9 (42.10 149-4704 1 FAX AX 1119-1711 Echelbarger Investments, LLC July 30, 2014 Because the proposed 4' retaining wall will be constructed in a critical area or buffer, it must be designed by a licensed engineer. Submit section and elevation views for the wall along with design calculations and a letter from the engineer as identified in Building Division Handout T�1362. ESNW Response — Based on our review of the grading and drainage plans, the geotechnical recommendations have been appropriately incorporated into the final plans. Based on review of the most current plans, a small segment of the proposed gravity block wall is proposed within the 15 -foot structure setback. The height of the wall will be up to one to two feet within the 15 - foot structure setback, In this respect, from a geotechnical standpoint, the small segment ol wall proposed within the 15 foot setback will have a negligible impact on the critical area and associated buffer. A". CornerStone gravity wall design is provided as an attachment. We trust this response to City of Edmonds review comments meets your current needs. Should. you have questions, or if additional information is required., please call. 9= Henry T. Wright, E.I.T. Staff Engineer Attachment: CornerStone Gravity Wall Design o�40 A Co,,, le .1001, Raymond A. Coglas, P.E. Principal Earth Solutions NK LLG aw. _�,....,..� V Out W"Fur 31C C1881) tatt 0.ro�rla t a003) II r oqd r is tM tr`R7J� at iiet 4.6r Max (ra�r CrIAHj!or)Cutl&ruc 11I .,, r Fa gb :r (tech To Confia 'a) Dam p1pe r �a t w k ,"rYPICAL GRAVITY WALL DETAIL (4.67" N - To - .stale Reinforced t.mtn t' a r;taaat't tae e::t mp aeWtect to a r'wa7rlaaar.traa of 96% of me maximum rRy rtensR . as deta=:rmaulr„td by ASTM D1557. The undstulue content of the backfill material p1or to and M,,i ng compaction shaH be JAUS, Of raMUS 3,Of the tatrnataaaa alf'Asture deet. The waH ta'aeatings sttaalt be observed by the Gpotect°aaa caat tmngiiunr,t. r ¢;:gra rM fl,W - tan Tt-.,s rang of the ar"ompaact t.t taacKfM shaH be peffoa rent by the t: weer at least ()'IPYW e Cw a ely two hth; of 1.,ackf fl t„Y0r`Ar"ra ent aaW"td coM"tltt:ta°Achon. q��y6�'�^:�ppa"a 0 app q��¢8'at�tl'a'1gpMgm, kY¢&�.9n�ig�g�,�t^'�f^y assurance �@.ry��ic Mvw�'mM, Y0.,.a�g'l�r`�t rM'�'t.":Wta.�.wW,,Q,p�d:, td::t@'+.y,grl/a''yat".��atG vr"pV��"w•" ;F p1 �grBy"4*�µrv,�"i�:6.�wt�pQ^%:'�n,,p.�d`�uk�4 i,,,,ir;&gd backfill 6tµ-strO it..�l,,. MR.,��rkIca.Atio of demIn pa,N'M aaaR,�,',tew 's, and observation l.apion ��f C t,. 1 SW.4a.atrfi()0.1 dt.W fjt,. neral at a':C;ua"rat: h ante wffl,a'ta ""s8gn ri u`aMavings aa ,41 s pecM'tVcadorn > N IA AS (401"0- ". ra��° roto r vity all 1035 Main Street Ile Edmonds, Washington ' t u urr ttt� Date 1129/2014 t�roj thio. 3380.01 •y'�"t.) Crib t . � w*ed HTW Plate �