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20071008113018.pdfo Eno City of Edmonds PLAN REVIEWCOMMENTS BUILDING DIVISION est. } g90 (425) 771-0220 DATE: October 8, 2007 TO: Jerry's Home Repair and Remodel jbbergstrom@aol.com FROM: Jenny Readwin, Plans Ex in RE: Plan Check # 2007-0989 Project: Deck replacement Project Address: 8809 Olympic View Dr. During review of the above noted application, it was found that the following information, corrections, or clarifications are needed. Please redline plans or submit two (2) sets of revised plans/documents (affected sheets only) with a written response to each of the items below to a Permit Coordinator. 1) Please add the following information to the site plan. ■ Topography lines (see attached site plan from previous permit -this can be used as a reference). You may redline plans or resubmit three (3) new site plans scaled no smaller than 1"=20' and one on paper no larger than 8 %2" x 14". 2) Maximum ledger lag screw size and spacing is 318" x 4 %2" at 4" o.c. Revise plans or provide calculations stamped and signed by a Washington State Licensed Professional Engineer for spacing show on the plans. 3) All wood exposed to weather must be pressure treated or naturally decay resistance. Please note on plans. 4) February 8, 2007 a Geotechnical Report was done by HWA GcoSciences, Inc. for an addition to this property. Please provide a supplemental letter from this Geotehcnial Engineer with recommendations for the deck footings or provide new geotechnical report from a different Washington State Licensed Professional Engineer including soil samples for the proposed deck only. "Nothing in this permit approval be interpreted As alloanngor permitting iaaintenance of any currently esiefaa illegal, nonconforming or un rmitW. building, structaure � ne�,_ Cornerbf Fly � or site condition whkh is outside the scope of the Setbacks LqWrea peanut application, regardless of whether such uulding, structure or condition is shown on the Front ' Site.plarl or drawing. Such building, structure or Sides condition may be the subject of a separate enforcement action. Rear D �.�...-. Other APPROVED BY PLANNING 0 WEST N LIaL.c.. ,C -rD elrsT.�;WE �-- -(�-u I `J r i J� STR EET FILE J �I`TJ MA D ,--� 1 AOMw OWNEw .._ rceNAc�rF.l.rrArr;uw[e - -- B4.M 4 WA now OOSPODDD04 ,n11V7IM8Y.Q sicS00000400 T ��G!� �� - TAS90T �AVI9R'AODF770N, 1.OT YS, SBCf{ON 18,;. j� �[�Sr^lti�=^ �. a�wtmmrrf�rrtQAi. nsSw:N:6 nwAW13PC.R - THOMAA En" 6Y8IGNToaO.:;f131 WLWM 220 eAWUM 3at04 WA 96112 206 320.9063 p6oae gwzmN9AYPAGur (wyM&ff-d4Pmw 2124 r(kd Avau4 Soden 100 -- 11 N Semae. WA 98121 206 4434212 pb-- 1 j `✓ IrPULLS) _ TO �.;�� ��UPS - To ' SY'S ! - NOCHMOETO] M.r1M7f 1NGF0OT7A1NT viciWin/ MAP Edmonds area. Washinoton..UnNed Sierra WEST N LIaL.c.. ,C -rD elrsT.�;WE �-- -(�-u I `J r i J� STR EET FILE J �I`TJ MA D HWA GEOSCIENCES INC. LV OltAfQ � F.i�3il:rlf a i'l7i•t'17i.'rif �[1l�INt<: I'17i� :-1 r:rru�t:,�0�: )[. ea��i .�,.'irl��lla� �:1 �t i(.. �,;1 _ ii,t�.S February 8, 2007 HNVA Project No. 2007-000-21, Task 5 Precision Construction Services, Inc. 112.6 8"i Avenue Soul!] Edmonds, WA. 98020 Attn. Mr. Jay LeNvis Subject. GE, OTECHNICaL INVESTIGATION residential Addition 8.09 Olympic View.Drive Edmonds 'Vi'ashingtou 98026 Dear Mr. Lewis: . Al ;_ wii. At your request,14WA GeoSciences Inc. (IIWA.) has iuldertaken and completed a geotechnicalinvestigation within and beyond the footprint of'the proposed. residential. addition at the: subject site at 8809° Olphpic View Drive, in Edmonds, Washington. This investigation has been p:erforrapd in support of application requiied..to obtain a building perinit from the City of Edmonds for the proposed basement floor addition to the existing residence.• For the purposes oftliis investigation HWA performed a rt%liew of the-pertinentgeologic snaps, conducted a site reemmai;;sance to observe local topographic features; excavated 3 shallow hand borings, and conducted 3 DCP'(Dropiveight Cone_Penetrotneter) soundings to delineate site soil conditions within the. footprint of the proposed addition: PROJECT LOCATION T11e. subject property consists of the developed portion of a lot located within the NW '1, Section 18, Tovniship 27 N. and,Range 4 E; situated at municipal.address 8809 Olympic V:iewl)ri re,.in Ednionds,.lVasl rigton (Snohoitrish.-County No. 0094500.000400). The approximatesite location is depicted on Figure 1, tile Project Site & Vicinity. Mali. Based upon the site map provided by Thomas J. Ester (Architect); the new addition will occupy the area nortli of the-existing.garacre and.east of the existing residential 19.730 - 64 itis. suite no structure, as'shown on Figure 2, the Site & Exploration Plan Mali: T:ytuttt'atSii,Wj19Ao3C.7957 Td 425.7711:0306 Fav 425,771271.4`.. j ,n4cv.htiti�geasciences.ca' 1 i February 8, 2007 HWA Project No. 2007-000-21, Task 5 PROPOSED ADDITION As currently proposed, the basement floor addition will. be attached to and extended along the east side of the existing residential structure north of the garage. The addition will consist of a basement level, concrete -wailed, structure supported on a foundation system consisting of cast -in-place concrete strip footings. The proposed addition will be roughly 22 feet long and extend out from the existing residential structure about 16 feet, occupying approximately ±350 square feet according to the site map provided the Architect. SITE OBSERVATIONS The existing residential structure occupies approximately 1,477 square feet (roof coverage) in the south-central portion of an 11,230 square foot lot. Currently, a two car, 456 -square foot, garage is attached along the southeast side of the house, When completed, the addition will occupy the area north of the garage, attaching to the northeast wall of the existing basement level. The house is set into a slope, which is moderately inclined to the southwest at about 15% or less in grade. A low rockery traverses the slope approximately 20 feet north from the existing house at its closest point. The position of this rockery suggests that it was installed to retain fill placed to level the back yard adjacent to the north side of the house. No ground water seeps or surface water erosion features were seen on site, and the existing house showed no apparent signs of settlement or foundation distress. There are no distinct signs of recent or past movement on the hill slope and the upper surface soils along the slope were found to be firm at shallow depth, when probed with a 3 -foot long, 'l2 -inch diameter, steel T -handled bar. GEOLOGY The published geological reap "Composite Geologic Map of the Sno-King Area", prepared by Booth, et al, 2004, shows that the upper plateau north of Puget Drive is underlain by Advance Outwash. Advance Outwash deposits typically consist of dense to very dense, yellowish brown to gray, clean to silty, fine to coarse sand, but may contain gravelly layers at the top and silty layers near the base. Subsequent to deposition, this soil was over-ridden by the advancing glacial front and, therefore, is expected to exhibit low compressibility and very high shear strength. These soils transmit ground water freely and are prone to erosion when denuded of vegetation. SOILS According to the Soil Conservation Map for Snohomish County (NRCS, online web soil survey, 2007), the site is overlain by Alderwood gravelly sandy loam, on 8 to 15 percent 8809 Olympic View Drive. 2 HWA GeoSciences Inc. February 8, 2007 HWA Project No. 2007-000-21, Task 5 slopes. The Alderwood sandy loam soils formed on glacial till plains. The runoff is slow and the erosion hazard is slight for these soils. SITE EXPLORATION On January 22!' , 2007, an HWA geologist conducted a limited shallow hand -exploration program to evaluate near -surface conditions on the site. At that time, 3 hand borings were conducted to depths ranging from 2.5 to 6.2 feet, before refusing on coarse gravel or cobbles. Site soil conditions were noted at each of the hand boring locations, which were selected based on the location of proposed addition as shown on the Site Plan provided by the Architect. The approximate locations of our hand borings are shown on Figure 2, the Site & Exploration Plan Map. Hand boring logs were prepared from our observations, and are presented on Figures 5 through 7. A legend of the terms and symbols used on the exploration logs precedes them as Figure 4. For ease of interpretation of soil conditions on site, Figure 3 provides an inferred geologic cross- section through the proposed development and several of our borings. The straiigraphic contacts shown on the hand boring logs and the cross-section represent the approximate boundaries between soil types; actual transitions may be more gradual. The hand auger borings at the locations of HH -1, HH -2, were supplemented by utilizing a Dropweight Cone Penetrometer (DCP) to check relative soil density/strength conditions. The DCI' consists of a steel extension shaft assembly, with a SO degree hardened steel cone tip attached to one end, which is driven into the subsoil by means of a sliding drop hammer. The base diameter of the cone is 20mm. The diameter of the shaft is 8mm less than that of the cone to ensure that at shallow penetration depths the resistance to penetration is exerted on the cone alone. The DCP is driven by repeatedly dropping an 8 kg sliding hammer fiom a height of 575 mm. The depth of cone penetration was measured after each hammer drop and the soil shear strength is reported in terms of the DCP index. The DCP index is based on the average penetration depth resulting fiom 1 blow of the 8 kg hammer and is reported as millimeters per blow (mm/blow). The data obtained from the DCP tests was correlated to approximate Standard Penetration Testing (SPT) blows per foot, in order to evaluate the strength of the subgrade soils. The DCP data is plotted on the appropriate Hand Boring Logs in Appendix A. In addition, a third DCP sounding was conducted without an associated hand auger boring, and is designated DCP-3 and is presented on Figure 8. SOIL PROFILE Typically, the near surface soils observed in the hand borings consisted of loose to median dense fill soils overlying weathered and unweathered glacial outwash soils. The soil conditions are described briefly as follows: Topsoil: At the surface at the location of all the hand borings, topsoil consisting of loose, dark brown, silty sand with gravel, containing abundant organic material, was encountered. The topsoil layer encountered ranged from 0.25 to 0.33 feet in thickness. 8809 Olympic View Drive. 3 HWA GeoSciences Inc. FebLuaiy 8, 2007 HWA Project No. 2007-000-21, Task 5 Fill: -Below the topsoil layer in all hand borings, and at the surface in DCP-3, fill was encountered, consisting of loose to medium dense, brown, silty sand with gravel, rootlets, woody debris and charcoal pieces. This soil unit was only fully penetrated in.HH-2 where it was about 5.5 feet thick. The other hand borings were terminated due to refusal on coarse gravel or cobbles and did not fully penetrate the fill. At the location of DCP-3, native soil was encountered at an approximate depth of 9.5 below the existing ground surface. Apparently the fill thickens to the south along the alignment explored on site. Advance Outwash — Advance Outwash soils, consisting of dense, yellow brown, fine to medium sand with gravel was encountered below the fill at an approximate depth of 5.7 feet in HH -2. DCP refusal, presumably in dense native soils, occurred at a depth of 9.5 feet below the existing ground surface, in DCP-3. The thickness of this unit is unknown as it was too deep to fully penetrate with hand tools. We expect that the depth to dense sand increases somewhat from north to south due to the amount of filling required to level those areas near the adjacent property to the east and the on-site gauge. GROUND WATER Ground water seepage was not observed in any of the hand borings. However, it is anticipated that ground water conditions will vary depending on the season, variation in local subsurface conditions, and other factors. During wet season periods, it is possible that ground water may become perched on the surface of the low permeability deposits at other locations of this site. GEOLOGIC HAZARDS In accordance with the criteria contained in the City of Edmonds Code, Title 23 -Natural Resources; Chapter 23.80 -- Geologically Hazardous Areas, the subject site is not within an area designated as a potential erosion or landslidelsteep slope or seismic hazard. The existing native soils consist of soils that were indirectly glacially consolidated, and are dense. Present site development plans do not include any modification of the steep slope portion of the existing hillslope, and will not extend significantly beyond the present footprint to the north. CONCLUSIONS AND RECOMMENDATIONS General In summary, the soil conditions within the portion of the site proposed for the addition consist of dense, granular, glacial outwash soils, overlain by loose to medium dense fill and topsoil layers at least 5. to 9 feet thicic. The actual depth to dense, native, sands at other locations within the footprint of the addition will need to be verified in the field 8809O.Iympic View Drive. 4 HWA GeOSciences Inc. February 8, 2007 HWA Project No. 2007-000-21, Task 5 during construction. In our opinion, the dense native sand will provide adequate bearing for the residential foundation system. Excavation and Temporary Shoring Requirements Preparation for construction of conventional foundations will require the excavation and removal of all undocumented fill beneath proposed footing and slab areas. Based on the results of our investigation, these excavations will be at least 5 feet deep or greater and require lay backs and/or shoring to protect workers and existing structures in accordance with Part N of WAC (Washington Administrative Code) 296-155. The fill materials at the site classify as Type C soil. Unsupported excavations in Type C soils must be inclined no steeper than 1'/211: 1V (horizontal to vertical). Flatter slopes may be required where ground water seepage occurs. We expect shoring will be required along the east side of the excavation to protect the adjacent property and underpinning on the south to protect the existing garage foundation. Temporary slopes should be protected from erosion, as necessaty, by covering the cut face with well -anchored plastic sheets. Maintenance of safe working conditions, including temporary excavation stability, is the responsibility of the contractor. Based on the soil conditions observed in our explorations, we anticipate that the on-site soils can be excavated with conventional equipment such as backhoes and loaders. Foundations Design Considerations: The proposed structure may be supported on footings bearing directly on dense native soils, or either properly compacted structural fill consisting of compacted crushed rock base course, meeting the requirements specified in WSDOT Standard Specification Section 9-03.9(3), or controlled density fill (CDF; 1 -sack concrete mix) placed over dense native soils. The advantage of using CDF backfill is that once excavations are made to bearing soils, backfilling can occur immediately, with minimal shoring and no workers in open excavations or trenches with steep back slopes. The recommended compaction level for crushed rock base course placed under footing and slab levels is 95% Modified Proctor maximum dry density (per ASTM D1557). Exterior strip footings bearing on native dense sand may be proportioned for an allowable bearing pressure of 3, 000 psf. This may be increased by 1/3 for short-term loads such as wind and seismic effects. Exterior footings should be founded at least 18 inches below the lowest adjacent finished grade, and interior footings should be founded at least 12 inches below the lowest adjacent finished grade. We recommend strip footings be a minimum of 18 inches wide and interior spread footings be a minimum of 24 inches in the smallest dimension — these recommendations may govern footing design. Alternatively, if excavation of the existing fill is not desired, then the structure could be founded on a pin pile (small diameter steel pipe pile) and grade beam foundation system s that would transfer wall loads directly to bearing soils and support the slab should the fill settle in the future. 8809 Olympic View Drive. 5 HWA GeoSciences Inc. February 8, 2007 HWA Project No. 2007-040-21, Task 5 Construction Considerations: Footing excavations should be trimmed neat and the excavation bottoms should be carefully prepared in order to minimize the amount of over -excavation required. The ground surface where structural fill, foundations, or slabs are to be placed should be proof -rolled, or suitably probed. This procedure will help determine the presence and approximate extent of any soft or unstable areas. Proof- rolling roofrolling or probing should be performed under full-time observation of an HWA representative. Any soils that cannot be adequately recompacted should be over - excavated and the unsuitable materials removed and replaced with compacted structural fill to a depth that will provide a stable base. Over -excavation and compaction of the structural fill should extend outward from the edge of the footing a lateral distance of at least two feet. We recommend that HWA be retained to observe footing excavations, and placement and compaction of structural fill prior to pouring concrete. Assuming construction is performed as recommended herein, we estimate that the total and differential settlements for foundations will be less than 1 -inch and Y2 -inch, respectively. An important component of ensuring stability of the on-site slopes is the provision of adequate surface and subsurface drainage to prevent water buildup in the slope deposits. To help facilitate this, footing drains should be installed around the perimeter of all exterior foundation walls and tied into an appropriate offsite disposal system. Seismic Considerations Should it be necessary for a development of this type to design for seismic conditions, we anticipate that the new structure would be designed in accordance with the 2403 International Building Code (IBC) standards. In this regard, for seismic design, the site is considered Site Class C, as described in Section 1615.1 of the 2403 IBC. For the site location, the design maximum considered spectral response acceleration at short periods, SS, is 1.26g. The design maximum considered spectral response acceleration 1 second period, Si, is 0.43g. Soil liquefaction is a phenomenon wherein loose, saturated, granular deposits temporarily lose strength and behave as a liquid in response to earthquake shaking. Based on our observation of relatively dense material at or close to the base of the hand borings and the apparent absence of regional ground water at shallow depths, we consider the potential for seismic liquefaction on the site to be negligible. Hence, seismically induced liquefaction instability is not considered to be an issue for this site. Erosion Control during Construction Best Management Practices (BMP's) as described in City of Edmonds Code must be followed. These measures include an erosion control plan brat addresses, limiting activity during wet periods, placement of a silt retention system on the eastern side of the 8809 Olympic View Drive. 6 HWA GeoSeiences Inc. February 8, 2407 HWA Project No. 2407-000-21, Task 5 property, and proper disposal or recompaction of any material that is disturbed on the site. CONDITIONS AND LIMITA`T'IONS We have prepared this letter report for Precision Construction, Inc., and the property owner Mr. Jay Lewis, for use in construction and pennitting of the proposed basement addition on the subject lot. Experience has shown that soil and ground water conditions can vary significantly over small distances. Inconsistent conditions can occur between explorations and may not be detected by a geotechnical study. The scope of work did not include environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous substances in the soil, surface water, or ground water at this site. HWA does not practice or consult in the field of safety engineering. We do not direct the contractor's operations and we cannot be responsible for the safety of personnel other than our own on the site; the safety of others is the responsibility of the contractor. The contractor should notify the owner if any of the recommended actions presented herein are considered unsafe. O.O We appreciate the opportunity to be of service. If you have any questions regarding this report, please do not hesitate to contact me at (425) 774-0146. Sincerely, HWA GEOSaENCES INC. Steven E. Greene, L.E.G. Vice President/Senior Engineering Geologist 8809 Olympic View Drive. 7 HWA GeoSciences Inc. February 8, 2007 HWA Project No. 2007-000-21, Task 5 Attachments: Figure 1: Project Site Location and Vicinity Map Figure 2: Site Plan & Proposed Addition Location Figure 3: Geologic Cross -Section A -A' Figure 4: Legend of Symbols and Terms Figure 5: Log of HH -1 Figure 6: Log of HH -2 Figure 7 Log of HH -3 Figure 8 Log of DCP-3 REFERENCES Booth, D.B, Cox, B.F., Troost, K.G., a S. A. Shi;nel, 2004, Composite Geologic Map of the Sno-King Area, University of Washington, Seattle Area Geologic Mapping Project. City of Edmonds, 2000, Title 23 -Natural Resources; Chapter 23.80 --- Geologically ,Hazardous Areas. International Code Council (ICC), 2003 International Building Code. MRCS, 1983, Soils Map of Snohomish County Area, WA661 (on-line version) WSDOT, 2044, Standard Specifications for Road, Bridge, and Municipal Construction, M41-10. 8809 Olympic View Drive. 8 HVA GeoSciences Inc.