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BLD20130924_Pfau.pdfCity of Edmonds . . I ritical Area Notice of Decisiou Applicant:( Aq P ul WMF-a Property Owner: Critical Area File &(I�A 16111�1 DO Permit Number: D Site Location:I rtA' v'C� �A/ Parcel Number: 11)(I Project Description: R,6 Of1df6C, (A I 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] 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; : 11-11-11, "zs" . ... ......... S:1 -V Mti2N .... .. . .. . The proposal does not pose an unreasonable threat to the public health, safety, or welfare ' . ... ... on or off the development proposal site; 0 The proposal is consistent with the general purposes of this title and the public interest; 4. v� Any alterations permitted to the critical area are mitigated in accordance with ECDC V 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 vai 6. The proposal is consistent with other applicable regulations and standards. ❑ 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. ❑ Conditions. Critical Area specific condition(s) have been applied to the permit number referenced above. See referenced permit number for specific condition(s). VI (v G4 i I A " --ad ILI Reviewer Si`gnati re 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 . ......... . . HWAGEOSCIENCES INC. U November 6, 2013 HWA Project No. 2012-085-21 Exteriorscapes Inc. 10017 Greenwood Avenue N. Seattle, Washington 98133 Attention: Mr. Cameron Scott Subject: GEOTECHNICAL REPORT ADDENDUM - CRITICAL AREAS WINDY PFAU RESIDENCE 17330 76"' Avenue W Edmonds, Washington Dear Cameron, In regards to City of Edmonds comments pertaining to the permit application for the deck and house reinforcement, we have prepared the following geotechnical report addendum as requested in Item 3 of the Planning Division's letter, dated September 16, 2013, as an addendum to our Geotechnical Report for this project, dated August 26, 2013. Herein we address the geotechnical suitability of deck and fence construction within the erosion and landslide hazard areas and buffers. We understand the deck and fence need to be regarded as "proposed" for purposes of permitting, as these were not constructed with permits. Critical areas criteria are addressed by section, below. ECDC 23.80.070 Per ECDC 23.80.070, the Minimum Buffer for the erosion and landslide hazard areas would be 50 feet. No signs of slope instability were observed above the crest of the slope (boundary of the erosion and landslide hazard areas), such that, in our opinion, a Buffer Reduction to a minimurn of 10 feet would adequately protect the proposed development, adjacent developments and uses, and the subject critical areas. The proposed deck and fence will result in alterations to the erosion and landslide hazard areas. The deck will be constructed at the crest of the slope, mostly within the erosion and landslide hazard areas and partially within the buffer. Disturbance to the ground surface will be minimal. The footings will be Supported with 2 -inch diameter pin piles driven to refusal in dense soils, with a 3,000 pound axial capacity. Lateral support will be 21312 30"' Drive SE SLlitC 110 Bothell, WA 98021-7010 Tel: 425.774,0106 Fax: 425.774,2714 lVivw. hwageo.cir ill November 6, 2013 HWA Project No. 2012-085 provided with Manta Ray (MR -88) anchors at each footing with '/a -inch anchor rods driven at an angle (angle to be determined in final design) into the slope. The deck foundation is designed to withstand potential shallow soil creep or raveling. At the end of construction, the sloping ground beneath the deck will be protected with erosion control matting and mulch. The fence will be constructed just below the crest of the slope (to northwest of deck) with standard construction of wood fence posts set in concrete. In our opinion, the construction activities and long-term presence of the deck and fence per the locations and structural drawings shown in the current plans will not impact the erosion and landslide hazard areas, where constructed within those areas and buffers. In our opinion, the proposed deck and fence will not increase the threat of the erosion and landslide hazards to adjacent properties beyond predevelopment conditions; will not adversely impact other critical areas; are designed so that the erosion and landslide hazards to the deck and fence are mitigated; and are safe as designed and under anticipated conditions. The proposed structures will not increase surface water discharge or sedimentation to adjacent properties beyond pre -construction conditions; will not decrease slope stability on adjacent properties; and will not adversely impact other critical areas. Design Standards: In our opinion, the existing factor of safety for slope stability will not be reduced for the subject property or adjacent properties with construction of the proposed deck and fence. The proposed structures will be clustered at the top of the slope to minimize construction on the slope. Slope contours will not be altered and the deck foundations will be placed to conform to grade at each location in order to conform to existing topography. The proposed locations of the deck and fence at the top of the slope will preserve the majority of the slope and vegetation. The proposed structures will not result in greater risk or a need for increased buffers on neighboring properties. No grading will be conducted for deck and fence construction. Also, the deck and fence will not increase the impervious surface of the lot. Vegetation Retention: No removal of vegetation will be required for construction of the deck and fence. Seasonal Restriction: No clearing will be conducted for this project. Point Discharges: Existing discharge pipes on the slope from roof downspouts and footing drains will be replaced with fused HDPE pipe, discharging beyond the toe of the slope. These will be anchored above the top of the slope and lay on the ground surface down the slope. 2012-085 AR.doc 2 HWA GEOSCIENCES INC. November 6, 2013 HWA Project No. 2012-085 ECDC 23.40.240 Regarding unauthorized alterations to the erosion and landslide critical areas: As noted above, the proposed deck and fence will not reduce slope stability or increase erosion and thus the hazards are not increased relative to the predevelopment condition. Also, the risk of personal injury resulting from the alterations will be eliminated by the geotechnical and structural design and construction. The erosion and landslide hazard areas have been improved by the removal of invasive vegetation and replacement with erosion control matting and native vegetation. Should you have any questions, or if we may be of further service, please call. Sincerely, HWA GEOSCIENCES INC. Brad W. Thurber, L.G., L.E.G. Senior Engineering Geologist Bryan K. Hawkins, P.E. Senior Geotechnical Engineer 2012-085 AR.doc 3 HWA GEOSCIENCES INC. October 25, 2013 Windy Pfau 1733076 1hAvenue VV Edmonds, VVAS8O26 RE: Stream Classification for Edmonds Property Dear Ms. Pfau: This letter summarizes my findings on critical areas at your property in Edmonds, Snohomish County, Washington. This O.68-acveproperty (Parcel #27O4O7OO4O14OO)islocated ot1733O7GmAvenueVV. It is my understanding that proposed reinforcement of a cleck on your property may impact critical areas. In order to obtain building permits from the City of Edmonds, you need to know the classification and buffer width for a stream near the construction site. The results of a background review and site reconnaissance that | conducted are described below. (i,' V �mv") The background review of existing information on this property includes but is not limited to: Snohomish County property records, City ofEdmonds critical area maps, Snohomish County critical area maps, architectural drawings prepared by Exteriorscapes, a letter from the City of Edmonds Planning Division, and aerial photographs. | also reviewed the City of Edmonds Municipal Code for critical areas (Title 23—Natural Resources to determine if there are any land use restrictions on this property (City of Edmonds 2013a). The critical areas identified by the City of Edmonds that I address in this letter include: wetlands, fish and wildlife habitat conservation areas, and geologically hazardous areas. | did not address critical areas such as, critical aquifer recharge areas and frequently flooded areas. The Exteriorscapesdrawing indicates this irregularly-shaped property measures approximately 163 feet wide and 178 feet long (29,730 square feet). The southwest corner of the property is bisected by a strearn (Terrace Creek) that flows from southeast to northwest (City of Edmonds 2013b). This stream continues northwest onto adjacent properties and eventually discharges into the Puget Sound approximately 1,50Ofeet downstream. The pmpe�Ys|op�so������the ��mm�he��o���'range from -195 feet at the eastern edge to145feet a1the southwest corner. The Snohomish County critical area map indicates there are portions of the slope steeper than 33% (Snohomish County 2013), while the City of Edmonds topographic map indicates the slope is greater than 40% (City of Edmonds 2013b). The City ofEdmonds Municipal Code (Chapter 23.8D.O2O)would classify this as a landslide hazard area (City ofEdmonds 2018a). The proposed deck reinforcements are located near the top of this steep slope approximately - 8Ofeet from the toe ofthe slope. G8fS/kAMBVKKONME07ALSERVk3S 937NVV96mStreet, Seattle, WA 98117 (20E) 794-K520 doug@greshamenviro ��m��IT Edmonds stream classification October 25, 2023 I conducted a site reconnaissance of the property on October 23, 2013 to evaluate critical areas such as wetlands, fish and wildlife conservation areas, and geologically hazardous areas. The steep slope between the deck and toe of slope has recently undergone restoration that involved removing invasive species, preventing erosion by staking down jute matting, and planting native shrub and herbaceous species. I located the stream near the southwest property corner and approximated the property lines onthe north and east sides (see attached oketoh\. Terrace Creek has a wetted width that ranges from 2 to 6 -feet for an average of 3 feet, and a depth averaging 2inches. The fish habitat types mainly consist of low gradient riffle and lateral scour pools, and the average channel gradient is2%. There isabundant woody debris inthe channel that functions asweirs, bridges, and lateral logs. The Substrate ranges from cobbles tosilt with sand and small gravel dominating. The banks are incised I to 3 feet and vary from low banks to nearly vertical walls that confine the channel. There were some floodplain benches where woody debris confines the channel. There are also depositional areas where the channel widens and has a lower slope. | flagged the ordinary high water mark of Terrace Creek near the southwest property corner using lath stakes and ribbon labeled OHVVM-1through 12. Vegetation within the riparian area ofthe stream includes tree, invasive, shrub, and herbaceous species (see Table 1for a plant list). The trees near the stream include red alder, big leaf maple, Douglas fir, western red cedar, and western hemlock. Invasive species inthe riparian area include Himalayan blackberry, cherry laurel, holly, and English ivy. The shrub layer includes sa|nonnberry,red huckleberry, andsa|ai The herbaceous species include lady fern, sword fern, nettles, skunk cabbage, creeping buttercup, and pig0y'back-p|ant. Plants that have been installed on the slope as part of the slope stabilization and restoration include native shrub and herbaceous species. These shrubs include rhododendron, vine rnap\e,red osier ~ dogwood, redwood, red elderberry, wax myrtle, and Pacific willow. The herbaceous species include sword fern, lupine, and grasses. Some invasive species have started colonizing this restored slope such asbindweed and foxglove. The City of Edmonds Municipal Code (Chapter 23.90.010.A) classifies four types of streams as fish and wildlife habitat conservation areas. Terrace Creek isnot identified asoshoreline wfthe state (Type S)or enadnonnousfish bearing stream (Type F). The City ofEdmonds Municipal Code (Chapter 33.9D.O10.A\ makes a distinction between non-anadromous fish bearing streams that have perennial (Np) or seasonal (Ns) flow. Based on observations made during the site visit, I believe Terrace Creek is a perennial stream. According to the City of Edmonds Municipal Code (Chapter 23.90.040.D), Type Np waters require a5O-6ontbuffer. All of the proposed construction involved with reinforcing the deck Should occur outside this 50' stream buffer. There should be no short.-terrn construction impacts to Terrace Creek because no riparian 6RES/IA&YBVV09O0MfJVlAlSERVICES Windy Pfau Edmonds stream classification Page October 25, 2013 vegetation would becleared and storm water runoff from the construction area would be stopped by the jute matting and other best management practices. Long-term impacts toTerrace Creek from stabilizing the slope and restoring the plant community are beneficial. The removal ofinvasive blackberry onthis slope and planting of native shrub and herbaceous species will improve the riparian habitat. We recommend additional restoration of the riparian area along Terrace Creek inorder to improve wildlife habitat. |fyou have any questions regarding these findings, please contact nneatCK)G>794-4S2D. Sincerely, w Doug Gresham Professional Wetland Scientist Gresham Environmental Services Enclosure G82SHAM ENVIRONMENTAL SERVICES Windy Pfau Edmonds stream classification Page 4 October 25, 2013 Table 1 List of Plant Species Observed on the Pfau Property Stratum Scientific Name Common Name WISa Acer macrophylium Bigleaf maple FACU Ainus rubra Red alder FAC Tree Pseudotsuga menziesii Douglas fir FACU Thuja plicata Western red cedar FAC Tsuga heterophylla Western hemlock FACU Acer circinatum Vine maple FAC Cornus sericea Red osier dogwood FACW Gaultheria shallon Salal FACU Ilex aquifolium Holly FACU Morelia colifornica Wax myrtle FACW Shrub Prunus lourocerasus Cherry laurel NI Rhododendron macrophyllum Pacific rhododenron NI Rubus spectabilis Salmonberry FAC Salix lucida Pacific willow FACW Sambucus racemosa Red elderberry FACU Sequoia sempervirens Redwood NI Vaccinium parvifolium Red huckleberry UPL Hedera helix English ivy NI Vine Rubus armeniacus Himalayan blackberry FACU Rubus ursinus Trailing blackberry FAC Athyriumfilix-femina Lady fern FAC Herb Convolvulus arvensis Bindweed NI GRESIIAM ENVIRONMENTAL SERVICES 937 NW 96th Street, Seattle, WA 98117 (206) 794-4520 doug@greshamenvironmental.com Windy Pfau Edmonds stream ckosif/ozbonOctober 25, 2013 Page Table 1 List of Plant Species Observed on the Pfau Property Stratum Scientific Name Common Name WISa Digitalis purpurea Foxglove FACU Lupinus latifolius Lupine FAC Herb Ranunculus repens Creeping buttercup FACW Tolmiea menziesii Piggy -back plant FAC Urtica dioica Stinging nettle FAC a Wetland indicator status based on USCOE 2012 is defined as: obligate wetland (013L), facultative wetland (FACW), facultative (FAC), facultative upland (FACU), and not indicated (NI). City ofEdmonds. 2013m. Edmonds Municipal Code, Title 23--Natuna|Resources. Obtained from City of Edmonds. 2013b. City of Edmonds critical area maps. Obtained from website: Snohomish County. 2013. Snohomish County critical area and property map. Obtained from website: IdexjArn GRfSHAMENVIRONMENTAL SERVICES Windy Pfau Edmonds stream classification 2E October 25, 2013 Photo 1—Steep slope between Terrace Creek and house looking north. Photo 2—Terrace Creek looking upstream at low gradient riffle habitat. GRESHAM ENVIRONMENTAL SERVICES 937 NW 96111 Street, Seattle, WA 981.17 (206) 794-4520 doug@greshamenvit-onmental.com Windy Pfau Edmonds stream classification z= October 25, 2013 Photo 3—Terrace Creek looking downstream at sediment deposition area. Photo 4—Terrace Creek looking downstream at confined channel caused by log. GRESHAM ENVIRONMENTAL SERVICES 937 NW 96th Street, Seattle, WA 98117 (206) 794-4520 doug@greshamenvironmental.com Figure 1, Sketch of Pfau property showing Terrace Creek.