Loading...
HomeMy WebLinkAboutFinal Shoreline Mit Plan(5-31-22) Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 1 SHORELINE MITIGATION PLAN FOR Asdourian Remodel 3901 Lake Washington Boulevard N City of Renton, WA Wetland Resources, Inc. Project #20102 Prepared By Wetland Resources, Inc. 9505 19th Avenue SE, Suite 106 Everett, WA 98208 (425) 337-3174 Prepared For Northwest Architectural LLC Attn: Bruce Sinkey 19705 SW 65th Ave Tualatin, OR 97062 May 10, 2022 Revision: May 31, 2022 Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 2 TABLE OF CONTENTS 1.0 PROPOSED PROJECT ...................................................................................................................3 1.1 PROJECT LOCATION ........................................................................................................................... 3 1.2 LANDSCAPE SETTING ......................................................................................................................... 4 1.3 SITE DESCRIPTION ............................................................................................................................. 5 1.4 PROJECT DESCRIPTION ...................................................................................................................... 6 2.0 SHORELINE/CRITICAL AREAS NARRATIVE ...............................................................................7 3.0 ECOLOGICAL FUNCTIONS ..........................................................................................................7 4.0 REGULATORY CONSISTENCY ....................................................................................................7 5.0 SHORELINE MITIGATION PLAN .................................................................................................9 5.1 ALTERNATIVES ANALYSIS .................................................................................................................. 9 5.2 IMPACT EVALUATION ....................................................................................................................... 10 6.0 USE OF THIS REPORT ..............................................................................................................11 7.0 REFERENCES ............................................................................................................................12 Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 3 1.0 PROPOSED PROJECT 1.1 PROJECT LOCATION The project occurs on King County Tax Parcel 3342700070. This is a .31-acre parcel, located at 3901 Lake Washington Boulevard North in the City of Renton. Access to the property is from the east via Lake Washington Boulevard North. The Public Land Survey System Locator is Section 32, Township 24N, Range 5E, WM. Site-Scale Vicinity Map Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 4 1.2 LANDSCAPE SETTING Basin: Puget Sound Sub-Basin: Water Resource Inventory Area (WRIA) 8 – Cedar River/Renton River Watershed: Lake Washington Watershed Shoreline Designation: Shoreline Residential Landscape-Scale Vicinity Map (Google Earth) Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 5 The study area is located on the east shore of Lake Washington, the second-largest natural lake in Washington State with a total surface area of over 22,000 acres. The lake is approximately 20 miles in total length, with an average width of 1.5 miles (Kerwin, 2001). Lake Washington is highly developed along much of the approximately 50 miles of lake shoreline. 1.3 SITE DESCRIPTION The subject property is immediately surrounded to the north and south by high-intensity residential development, to the east by Lake Washington Boulevard North and to the west and north by Lake Washington. An existing house, driveway, and deck cover the majority of the property. Between the house and the shoreline of the lake, the backyard is covered entirely by a large deck. Two small, vegetated areas are located on the site, including a maple tree on the northern side of the house and ivy under the deck, adjacent to the ordinary high watermark. Development along the lake’s shoreline is limited to the existing rock bulkhead, deck, and dock. The face of the bulkhead clearly defines the ordinary high water mark (OHWM) of Lake Washington. No vegetation is present waterward of the OHWM and no aquatic vegetation or lake-fringe wetlands were observed. Beach substrate consists of sorted sand and large cobble pieces on a moderate grade. This is consistent with a high-energy shoreline. No other habitat features were observed on or in the vicinity of the subject property. Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 6 Bing Maps Bird’s Eye View 1.4 PROJECT DESCRIPTION The applicant proposes to add additional elevation to the dwelling story entirely within the boundary of the existing impervious surfaces. There will be no increase in impervious surfaces or shoreline impact resulting from this development proposal. The footprint of the first and second floor of the structure will change slightly and will be no closer to the shoreline than existing improvements. The proposed improvements will encroach approximately 382 square feet within the required 25-foot setback, but not beyond the footprint impervious surfaces. All existing overwater structures (dock) will remain, but the segment parallel to the shoreline will have its decking replaced to allow for the passage of light. Given no vegetation removal will occur, impervious surfaces will not increase, and improvements will be behind (landward) of the existing primary structure first-floor footprint, no net loss of shoreline ecological function will occur. Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 7 2.0 SHORELINE/CRITICAL AREAS NARRATIVE Lake Washington, a Type S water, is the only aquatic critical area located on and near the subject property. This segment of Lake Washington is designated as Shoreline Residential by the City of Renton. Except for minor landscaping and ivy under the existing deck, the subject property lacks vegetation. Generally, the surface area of the site is dominated by existing impervious surfaces including the house and driveway. No other Critical Areas are located on or immediately adjacent to the subject property. 3.0 ECOLOGICAL FUNCTIONS Based on the City of Renton’s Revised Draft Shoreline Inventory and Analysis, Parametrix 2010, The majority of Lake Washington’s shoreline is urban residential with large commercial and industrial development located within the City of Renton at the south end of the lake. Analysis of aerial photos indicates that in 1999, approximately 59 percent of the vegetation cover adjacent to the shoreline was lawn/garden, with slightly less than 20 percent natural shrub-scrub, forested, or herbaceous habitat. Approximately 67 percent of the shoreline in the City of Renton is bulkheaded. Nearshore and riparian habitat along Lake Washington shoreline is severely altered in the reach containing the subject parcel and within the surrounding neighborhood. Residential development, including bulkheads, docks, paved areas, and landscaped yards has adversely modified most of the Lake Washington shoreline habitat. However, many of these shoreline areas continue to provide shallow water habitat at the toe of bulkheads, and some locations that do not have bulkheads. Narrow docks perpendicular to the shorelines do not appear to impede shoreline migration of young Chinook, but the fish appear to migrate around wider structures where they occur in shallow water (Parametrix 2010). The site, which is located within Reach D identified in the Parametrix 2010 report, is no exception to the general characteristics of the lake. The rock bulkhead deflects wave energy, which can cause erosion that leads to deeper water along the shoreline. High-energy/deepwater shorelines do not provide refuge opportunities for migrating fish. Bulkheads also prevent the establishment of riparian vegetation, which provides cover and forage opportunities for juvenile salmon. The absence of overhanging vegetation and the presence of the nearshore dock limits the ecological value for migrating fish. The existing impervious surface also limits the establishment of native vegetation, reducing the overall ecological value of this shoreline. Overall, the site provides a low level of shoreline ecological function 4.0 REGULATORY CONSISTENCY RMZ 4.10.095 (F)(2) states “Lawfully constructed single-family homes, their appurtenances, and impervious area built or installed before the adoption of the Shoreline Master Program (October 24, 2011) shall be considered conforming if alteration is consistent with the compliance standards below: For a Moderate Alteration - An alternate mitigation proposal prepared by a qualified professional and approved by the Administrator that would provide at least equal protection of ecological functions and processes as the full required* setback and buffer. Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 8 *The full buffer/setback as required in RMC 4-3-090D7a, Shoreline Bulk Standards, or as modified under RMC 4- 3-090F1, Vegetation Conservation. The Applicant is proposing an alternative mitigation plan that does not involve removing structures to reestablish the 25-foot setback but does propose re-decking the portion of the dock paralleling the entire shoreline of the site. This directly aligns with the opportunities for enhancement described below and will provide a significant lift in the shoreline ecological function over reestablishing the 25-foot setback. 4.1.1 Opportunities for Enhancement/ Analysis Mitigation Options The City of Renton’s Draft Shoreline Inventory and Analysis (Parametrix 2010) identifies multiple opportunities for maintaining and enhancing the ecological functions of the shoreline areas in Reach D. These opportunities are listed below and are the basis for developing the enhancement recommendations within this mitigation plan. An analysis of the proposed options is provided below in Italics. • Restoring shallow water habitat to facilitate young salmon rearing and to include: shallower shoreline depths and slope, greater substrate composition mix, and alteration or replacement of bulkheads, to (a) sloped with shallow depths, or (b) composed of logs or riprap, and (c) excluding concrete, riprap, or sheet pile exposed below the OHWM (which eliminates the shallow water habitat). In its existing condition the depth of water at the toe of the bulkhead is relatively shallow (less than 3 feet), is relatively low gradient, and is composed of native cobble and gravel material. LWD is not present and given the narrowness of the lot and private shoreline recreation uses placement is not feasible. This mitigation opportunity is not suitable for this lot. • Replanting native shoreline vegetation overhanging at the shoreline edge to provide shading, refuge habitat and enhanced prey resources (insects) for young salmon and other fish, isolation of grass areas from the shoreline, and reduction of need for fertilizers and pesticides. Much of the lot is currently comprised of impervious surfaces and is not available for enhancement. The only feasible location is under the dock where English Ivy is currently growing. This area has limited soil for planting and light availability is marginal. It is unlikely any beneficial native species would survive/thrive under the existing deck. • Limiting the total number of docks, the number of docks in shallow water (0-3 feet), and the number and size of piles supporting over-water structures. The existing dock paralleling the shoreline is the primary access point to the main dock extending perpendicular to the shoreline and therefore this dock cannot be reasonably removed. • Upgrading to grated docks (or other means) to reduce potential predation and facilitate shoreline migration of young salmon. The applicant is proposing to install grading on the nearshore dock paralleling the shoreline. This proposal is consistent with the City of Renton Shoreline Inventory and Analysis document, has the greatest likelihood of success overall of any recommended mitigation options, provides a lift in nearshore fish habitat, and limits the disruption of the existing uses of the shoreline area by the applicant. Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 9 • Augmenting density of woody debris at the shoreline and embedding it, to provide refuge habitat for young salmon and reduce habitat for smallmouth bass (Micropterus dolomieu) prey. Augmenting LWD along the existing shoreline is not feasible given the width of the property, lack of access for importing material, and the potential impact on existing recreational uses of this parcel. 5.0 SHORELINE MITIGATION PLAN The applicant is proposing to maintain the footprint of the existing impervious surfaces and not increase the degree of impact. Approximately 382 square of improvements are proposed outside of the footprint of the existing house, but within the footprint of existing impervious surfaces. However, to increase the shoreline ecological function of the site and provide equivalent or better shoreline function than the standard 25-foot setback the applicant is proposing to replace the decking material on the nearshore dock paralleling the shoreline. Replacing this solid board decking with grated material such as Fibergrate® / Chemgrate®: Aetna Plastics will allow a significant amount of light penetration providing an increase in nearshore fish habitat along the shoreline under the dock. As discussed in City of Renton’s Draft Shoreline Inventory and Analysis (Parametrix 2010), upgrading the decking material on docks has a direct benefit on salmonid populations in Lake Washington by reducing predation and helping facilitate the migration of young salmon. This will provide a significant improvement over the existing condition of the site or of a potential redevelopment of the site that maintains the 25-foot setback for the residential structure and preserves the existing dock with its solid board decking. 5.1 ALTERNATIVES ANALYSIS RMC 25.06.020(1) requires that mitigation for environmental impacts be applied in the following order. The applicant’s response immediately follows each sequencing principle (as indented, italicized text). Avoidance Avoiding the impact altogether by not taking a certain action or parts of an action; The applicant is proposing to remodel the existing house in a location that is no closer to the lake than the existing first floor of the primary structure. This work will be entirely constructed over the top of existing impervious surface and will not involve removing any vegetation, or temporary or permanent impacts to natural buffer or setback areas. This is the only feasible location for the improvement since it involves building over the existing impervious surfaces on a small waterfront lot. Minimization Minimizing impacts by limiting the degree or magnitude of the action and its implementation by using appropriate technology or by taking affirmative steps to avoid or reduce impacts; Impact minimization will be achieved in the following ways: • The house has been designed to be built over the existing footprint of the existing impervious surfaces and will be no closer to the lake; • BMPs will be implemented, and the existing structure will minimize the potential for sedimentation to the lake; and • Materials selection does not include wood treated with toxic compounds. Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 10 Rectification Rectifying the impact by repairing, rehabilitating, or restoring the affected environment; The affected environment in this case is the buffer zone that is entirely covered with impervious surfaces. Rectification is not practical for this project because repair, rehabilitation, and restoration could only be achieved by, for example, removing the existing house. No opportunities for rectification are known to exist for this project. Reduction Reducing or eliminating the impact over time by preservation and maintenance; The proposed structure will be regularly maintained and preserved by the Homeowner, to reduce the frequency of short-term impacts associated with repair/replacement actions. Compensation Compensating for the impact by replacing, enhancing, or providing substitute resources or environment; Approximately 250 square feet of decking material on the existing dock will be replaced with Fibergrate® / Chemgrate®: Aetna Plastics or a similar material to allow for the passage of light and the increase of fish habitat. 5.2 IMPACT EVALUATION (a) Identification, by characteristics and quantity, of the resources (stream, lake) and corresponding functional values found on the site; Lake Washington, a Type S water, is the only critical area located on the site. Given the existing developed nature of the subject property, the ecological function provided by the on-site buffer is limited (refer to the ecological function section of this report). (b) Evaluation of alternative locations, design modifications, or alternative methods of development to determine which option(s) reduce(s) the impacts on the identified resource(s) and functional values of the site; This is a narrow waterfront single-family lot, alternative locations for the proposed remodel are not feasible. If the proposed addition location were modified, it’s likely that the overall impervious surfaces and impact would be similar. (c) Determination of the alternative that best meets the applicable approval criteria and identify significant detrimental impacts that are unavoidable; The entirety of the site is currently developed and covered with impervious surfaces; no detrimental impacts will occur from this proposal. (d) Evaluation of the cumulative impacts on the system, to the extent that the site resources and functional values are part of a larger natural system such as a watershed; No cumulative impacts will occur from this project. If the site is not redeveloped, the existing house and associated improvements, including the solid board dock will remain in their existing footprint. Redevelopment of the site provides an opportunity to reduce the impact rather than creating a cumulative impact. (e) Evaluation, for shorelines regulated by RMC 4-3-090, of how the preferred alternative achieves the standard of no net loss of ecological functions under RMC 4-3-090D2; An increase in shoreline ecologist function will occur as part of this proposal. Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 11 (f) Evaluation of each of the mitigation plan criteria found in RMC 4-3-050L1, Mitigation Plan Required. Approximately 250 square feet of replacement of dock decking material is proposed on the north side of the property between the existing structure and the OHWM. No Net Loss of Shoreline Ecological Function The existing condition of the site is virtually entirely developed with an existing house and associated improvements similar to the parcels in its immediate vicinity. The proposed development activity is to expand the existing structure over the existing impervious surfaces, but within the 25-foot shoreline setback. The existing residential improvements, including the nearshore dock, limit its potential ecological value due to its developed and maintained condition. No additional impervious surfaces or impacts to shoreline ecological function will occur as part of this development activity. Given the lack of shoreline function currently provided on-site, the ecologically isolated location of the improvement, and the proposed re-decking of the dock, a net improvement of shoreline ecological function is expected for this proposal. 6.0 USE OF THIS REPORT This Shoreline Mitigation Plan is supplied to Northwest Architectural LLC as a means of determining the presence of critical habitat, as required by the City of Renton during the permitting process. This report is based largely on readily observable conditions and, to a lesser extent, on readily ascertainable conditions. No attempt has been made to determine hidden or concealed conditions. The laws applicable to salmonid habitat are subject to varying interpretations and may be changed at any time by the courts or legislative bodies. This report is intended to provide information deemed relevant in the applicant's attempt to comply with the laws now in effect. The work for this report has conformed to the standard of care employed by ecologists. No other representation or warranty is made concerning the work or this report and any implied representation or warranty is disclaimed. Wetland Resources, Inc. Scott Brainard, PWS Principal Ecologist Asdourian Remodel Shoreline Mitigation Plan WRI Project #20102 Northwest Architectural LLC Revision: May 31, 2022 12 7.0 REFERENCES Kerwin, J. 2001. Salmon and Steelhead Habitat Limiting Factors Report for the Cedar – Renton Basin (Water Resource Inventory Area 8). Washington Conservation Commission. Olympia, WA. http://www.pugetsoundnearshore.org/supporting_documents/WRIA_8_LFR_FINAL.pdf. Accessed December 2016. NOAA National Weather Service Forecast Office, Seattle, Washington. http://www.weather.gov/climate/index.php?wfo=sew. Accessed December 2016. Olson, P. and E. Stockdale. 2010. Determining the Ordinary High Water Mark on Streams in Washington State. Second Review Draft. Washington State Department of Ecology, Shorelands and Environmental Assistance Program. Lacey, WA. Ecology Publication # 08-06-001. StreamNet. 2016. StreamNet Mapper. http://www.streamnet.org/mapping_apps.cfm. Accessed December 2016. U.S. Fish and Wildlife Service. National Wetland Inventory (NWI). Wetlands Mapper. http://www.fws.gov/wetlands/. Accessed December 2016. Washington State Department of Fish and Wildlife (WDFW). 2016. Priority Habitats and Species: PHS on the Web. (http://wdfw.wa.gov/mapping/phs/). Accessed December 2016. Washington State Department of Fish and Wildlife (WDFW). 2016. SalmonScape. (http://wdfw.wa.gov/mapping/salmonscape/index.html). Accessed December 2016. Parametrix. 2010. Shoreline Master Program Revised Draft Shoreline Inventory and Analysis. Prepared by Parametrix, Bellevue, Washington. March 2010.