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Geotech Report.pdffsrd? ✓ 22, 2016 Mr. Jim Bagby 9131 184th Street Southwest Edmonds, WA 98026 *--ao Z-015- (Y-$�p CI'I'i' COPY REsue Re: Bagby Residence Critical Areas Review 12798-01 Dear Mr. Bagby: JAN 22 2016 BUI101Np DEPARTME►yT CITY ©F EDMONOS This letter presents our findings from a review of the critical areas on and around the Bagby residence, located at 9131 184th Street Southwest in Edmonds, Washington (the site). In a plan review comments letter dated November 24, 2015, the City of Edmonds requested a critical areas review C fence construction project you (the homeowner (AR) for the geologic hazards, stream typing, and buffer determination. The City requested the review include Methods Our review included visiting the site (on January 8, 2016) and reviewing existing information including Washington Department of Natural Resources (WDNR) Forest Practices Application sources, System (FPARS) online stream type ma p on Review Priority Habitat and Species (PHS) on the Web; nohomiishngton DCou County Permit, epartment of Fish h and Wildlife (WDFW) WDNR's Interactive Geologic Map (www.fortress.wa. ov dnr eolo tanning, and Zoning Ma Community Development Code (ECDC); aerial photos; City of Edmonds 'plan reviEdmew c City Code 0TS- T486); and City of Edmonds CAR CRA2015OTL4, dated November 23, 2015. comments (20T5- Background The proposed project consists of constructing a fence at or near the surveyed parcel boundary. The proposed fence along the east side of the property will partially replace an existing chain -link fence at the top of the natural slope and along the top of an existing rock wall. Additional new fence segments are proposed along the remaining borders of the property. Areas of concern for the City include steep slopes near the east and west of the proposed project and a small runoff feature near the southwest boundary of the site, which was flowing both on the day of the Cit ' possible visit. See Attachment 1 for a site plan, Attachment 2 for construction plans, tachmen and our site and At photographs. t 3 for site 190 W Uaylon street. Suite 201 Fdmonds, Washington 98020 rax 4?.5.778.907 Tel 425- 775.4682 A AN Bagby Critical Areas Review January 22, 2016 12r Pa Geologic Hazards comments letter. This section addresses Item 1 of the City's plan review site conditions and the Site Visit Geotechnical Observations. Du uas summarized belowg site visit, we ', existing plan limits of the proposed fence construction, the eastern third of the subject site slopes gradually ■ The associated LiDAR map indicates that approximately 30%. The middle third, where the existing downward from east to west at a grade of app parcel falls away more steeply to the structures are located, is fairly level. The western third of the west at a grade of approximately 35%. hout the site are identified as Alderwood Gravelly sandy loam (15% to 25%slope). As a ■ Soils throu g ult the slopes in excess of 15% are classified as potential erosion hazards and the western slope res , that exceeds 35% is a potential landslide hazard area. ■ We did not observe soil movement or erosion in the project area. Existin Site Data. We reviewed the previously mentioned existing site information to learn Review of g osed construction. We also reviewed WDNR's Interactive about existing conditions and the prop mapped as being within the Geologic Map to determine subsurface soil conditions. The site is Vashon till, of the Frasier Glaciation. Our observations of near -surface soils at the site are Quaternary generally consistent with those indicated on the geologic map. is Hazard Review. We reviewed the ECDC sections defining geologic hazards (23.80.000 ECDC Geolog applicable to the proposed site work, as described below: through 23.80.070) to determine conditions 'de Hazard Areas. In our opinion, the proposed work will not adversely affect the small steep ■ Landslide reasons: slopes in the project area, for the following conditions of the The proposed fence construction would only minimally alter the existing critical area or its buffer.ns of Our observations of the top and toe of existing slope ° not increase loads onithe slopes; work Because of its small footprint, the proposed work would • near the eastern site boundary would replace an existing fence. Hazard. Areas surrounding the proposed construction area are vegetated; maintaining the ■ Erosion Ha r should use standard potential. The construction contracto vegetation well would reduce erosion p Practices (e.g., straw wattles between the work area temporary erosion and sedimentation control poff-site urin construction activities that expose bare soil, as nee long Ite m eros on off o and slopes) during turbid water. After construction, landscape restoration would likely prevent MrN as Bagby Critical Areas Review January 22, 2016 12798-01 Page 3 ■ Seismic Hazards. We did not observe subsurface conditions such as shallow groundwater in loose clean sand that would lead to liquefaction. In addition, the site subsurface geology is mapped as Vashon Till, which is typically dense and therefore less susceptible. In our opinion, liquefaction hazards do not apply to this site. At any rate, ECDC 23.80.040 allows fences in seismically hazardous zones. Stream Typing and Buffer Determination A very small runoff feature near the southwest boundary of the site was identified on the day of the site visit. The source of this feature is not visible, but is likely nearby stormwater runoff from 184th Street SW, rain gutters, and drainage lines. The runoff feature terminates underground near the western Bagby property boundary. Local topography suggests that during storm events the feature may contribute to another water feature near Olympic View Drive, but the Bagby runoff feature is not visible in the approximately 650 feet between the Bagby property and Olympic View Drive. The Bagby runoff feature only contains water after large precipitation events. It is not mapped by WDNR, WDFW PHS on the Web, or Snohomish County Permit, Planning, and Zoning Map. Considering this information, we believe the runoff feature is a collection area where stormwater runoff occasionally settles, not a regulated stream. Conclusions Our geologic and geotechnical evaluation indicates that the proposed project will not alter the existing small steep slopes if basic construction practices and precautions are followed. This project should not result in increased landslide hazard or erosion hazard. Seismic hazards are not applicable. Our stream investigation found that the water feature on the site is generated from stormwater runoff and is not a regulated stream. Use of This Report Work for this project was performed, and this letter prepared, in accordance with professional practices generally accepted at the time our work was performed for work of similar nature done in the same or similar localities and under similar conditions. This letter is intended for the exclusive use of the property owner for specific application to the referenced site. This analysis applies only to the proposed project described above. New analyses and permits must be obtained for any alterations or for any MrW as Bagby Critical Areas Review 12798-01 January 22, 2016 Page 4 future projects on the site. This letter was prepared in general accordance with our proposal dated January 11, 2016. It is not a legal opinion. No other warranty, express or implied, is made. Sincerely, HART CROWSER, INC. G JIM SHANNON Fisheries and Wetland Scientist Attachments: Attachment 1 Site Plan Attachment 2 Design Plan Supplied by Homeowner Attachment 3 Site Photographs AARON WISHER, LG Senior Project Geologist R:\NOTEBOOKS\1279801_Bagby Critical Areas Review\Dellverables\Letters\Critical Areas Review Letter.docx ATTACHMENT Site Plan As12798-01 m.wcpOmf_vA January 22, 2016 k k x k \ x x i 1 x kx / % .. x X /. / ♦ ` \ 1 i N N 1 x i • 1 a° j + x X ccDIX IX �.X Ix se,...e rave e,,l, ro,gnalcmhe. Genr_ve ra,Insla, ce.g,apm—, t CNES/Airbus DS, USDA USGS AEX Get—pping, A—g-. IGN. IGP, s.visslouo, and Ilse { GIS User Cb--ty — waterteahue (unregulated) ... - ••- • • • • C drain — stormwaterIme,(approx) x — x proposed fenceline 1 parcel boundary —f asphalt • rock wall ATTACHMENT 2 Design Plan Supplied by Homeowner � 12798-01 IVLRTCROWWA January 22, 2016 ATTACHMENT A — FENCE PLOT PLAN PROPERTY OWNER — James Bagby & Mary VanCitters-Bagby PROPERTY ADDRESS — 9131 1841" St. SW, Edmonds, WA 98026 PARCEL NUMBERS — 27041800201100, 00565600101700 PROJECT DESCRIPTION — Six (6) foot chain link fence to be constructed in two phases. Phase 1 (to be completed upon permit approval) — east property line. Phase 2 (to be completed Summer 2016) — remaining property lines with automatic gate over driveway. f tt/Y-.,e. ` k \ /2S- A IVY x� vx\� I �C2K iLA�� ' N° x s I� � K I A`re_ I�PI;RT`/ L1rJE -- fY� ' F6�c.t zr N6- f�r.Hs I F- - -- - - - - — -- - ATTACHMENT 3 Site Photographs A 12798-01 FOR January 22, 2016 Hart Crowser 12798-01 Looking north toward carport and slightly downslope. 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