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HomeMy WebLinkAboutR_Stream Study_20171129_v2 November 29, 2017 AOA-5029 Jim Dalpay Dalpay Properties LLC 4033 NE Sunset Boulevard Renton, WA 98059 SUBJECT: Standard Stream Study for Dalpay Short Plat (LUA17-000234) Parcel 042305-9032, Renton, WA (Revised) Dear Jim: We have updated this stream study for the subject project to address the required encroachment into the stream buffer for the Lot 1 access drive. Background On December 14, 2015 a wetland and stream reconnaissance was conducted on the subject property utilizing the methodology outlined in the May 2010 Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (Version 2.0). One stream (Stream 1) was identified and delineated within a small ravine that traverses the central portion of the property. No wetlands were identified on the site. Stream 1 Stream 1 is a tributary to Honey Creek, which is identified as a Type Np stream per the City of Renton (COR) mapping. The stream on the subject property is not mapped on the COR mapping. Stream 1 drains from north to south through a ravine dominated by a coniferous forest that includes Douglas fir (Pseudotsuga menziesii), western red cedar (Thuja plicata), Oregon grape (Mahonia sp.), holly (Ilex sp.), Himalayan blackberry (Rubus armeniacus), sword fern (Polystichum munitum), and English ivy (Hedera helix). Jim Dalpay November 29, 2017 Page 2 Stream 1 was identified as a Class 4 stream as part of a previous short plat associated with the subject property. As part of the previous application, Stream 1 and the adjacent slopes were placed within a Native Growth Protection Easement (Recording No. 20050927003163). It is my understanding that the stream dries out during the summer months and would therefore be considered a Type Ns stream per the current City of Renton classification system. City of Renton Mapping The new stream delineation has been surveyed and is depicted on the survey drawing. Type Ns streams in the City of Renton currently require a standard 50-foot buffer plus 15-foot building setback from the ordinary high water of the stream adjacent new development per RMC 4-3-050.G.2 (Figure 1). When a required stream buffer falls within a protected slope or very high landslide hazard area, the stream buffer width must extend to the boundary of the protected slope or very high landslide hazard area (as determined by the geotechnical consultant). Proposed Project The proposed project consists of a 4-lot Short Plat. Access to Lots 2-4 in the southeast portion of the site would be from Redmond Court NE to the east and would be constructed outside of all applicable buffers. Jim Dalpay November 29, 2017 Page 3 Lot 1 Stream Buffer Crossing Access to Lot 1 would be provided by the continuation of Redmond Place NE, which currently terminates along the northern property boundary. There is no other viable alternative access point available for Lot 1. The proposed driveway must unavoidably impact 860 s.f. of the historically cleared outer buffer of the stream. As depicted on the tree survey, there are no significant trees that would be impacted as part of the driveway construction and the impacted buffer is not located on a sensitive slope. Stream buffer crossings associated with transportation crossings such as driveways are required to meet all of the conditions outlined in RMC 4-3-050.J.2.a (below). a. Criteria for Administrative Approval of Transportation Crossings in Stream/Lake or Buffer Areas: Construction of vehicular or non-vehicular transportation crossings may be permitted in accordance with an approved stream/lake study subject to the following criteria: i. The proposed route is determined to have the least impact on the environment, while meeting City Comprehensive Plan Transportation Element requirements and standards in RMC 4-6-060; and There is no other access driveway location for Lot 1 that would have less impact on the stream buffer. The only other potential access to Lot 1 would be to cross the forested ravine and stream from the south. This potential crossing would have significantly greater impacts to the stream buffer and would require both culverting the stream at the crossing and traversing the steep slope. It is my understanding that the driveway as proposed is consistent with the City Comprehensive Plan Transportation Element requirements and standards in RMC 4- 6-060. ii. The crossing minimizes interruption of downstream movement of wood and gravel; and The driveway would cross the buffer only and would not require any work within the stream channel or adjacent ravine that could potentially interrupt the downstream movement of wood and gravel within the riparian corridor. Furthermore, the proposed crossing does not require the removal of any significant trees from the buffer. iii. Transportation facilities in buffer areas shall not run parallel to the water body; and The proposed driveway crossing would enter Lot 1 and immediately turn west toward the proposed residence to avoid running parallel to the stream corridor. Jim Dalpay November 29, 2017 Page 4 iv. Crossings occur as near to perpendicular with the water body as possible; and The proposed crossing of the buffer has been designed to impact the least amount of buffer area as possible. Upon entering Lot 1, the driveway would turn west and be as perpendicular as feasible to the riparian corridor. v. Crossings are designed according to the Washington Department of Fish and Wildlife Fish Water Crossing Design Guidelines, 2013, and the National Marine Fisheries Service Guidelines for Salmonid Passage at Stream Crossings, 2000, as may be updated, or equivalent manuals as determined by the Administrator; and There is no proposed crossing of the stream channel and this condition is not applicable. vi. Seasonal work windows are determined and made a condition of approval; and Although no work associated with the buffer crossing would occur on the slope or within the stream channel, the condition is noted as it may apply to conditions of the required Temporary Erosion Control Plan (TESCP) for the development proposal. vii. Mitigation criteria of subsection L of this Section are met. Mitigation for the impact of the 860 s.f. of degraded and historically cleared buffer would occur through the preservation of 860 s.f. of additional forested replacement buffer located adjacent to Lot 2. The buffer area to be impacted was entirely cleared by 2005 and does not currently provide any significant stormwater storage, water quality protection, or habitat functions to the stream corridor. The proposed buffer replacement area is currently forested and would increase the size of the protected habitat corridor over existing conditions. The additional buffer area will also provide increased physical and visual screening to riparian corridor from the development and will allow for increased potential of large woody debris recruitment. Since the buffer replacement area is already forested, no buffer plantings are proposed and the maintenance and monitoring requirements associated within mitigation site per RMC 4-3-050.L are not applicable. Jim Dalpay November 29, 2017 Page 5 2005 Aerial photo showing Lot 1 cleared as part of construction to north If you have any questions regarding the stream study, please give me a call. Sincerely, ALTMANN OLIVER ASSOCIATES, LLC John Altmann Ecologist Attachment PROJECT DRAWN DATE SCALE REVISED Landscape Architecture AOA Environmental Planning &Office (425) 333-4535 PO Box 578Carnation, WA 98014Fax (425) 333-4509 Altmann Oliver Associates, LLC 5029-MIT-02-19-17.dwg L L 4 / 2 7 / 2 0 1 6 4 / 2 7 / 2 0 1 6 L L 4 / 2 7 / 2 0 1 6 L L 4 / 2 7 / 2 0 1 6