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HomeMy WebLinkAboutSR_ERC_Report_LUA24-000367_CUP_and_Variance_250428_FinalDEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT Project Location Map SR_ERC_Report_LUA24-000367_CUP and Variance_250428_Final ENVIRONMENTAL REVIEW COMMITTEE REPORT ERC Meeting Date: May 5, 2025 Project File Number: PR24-000074 Bull Conditional Use Permit and Critical Areas Variance for Accessory Dwelling Unit Development Land Use File Number: LUA24-000367, ECF, CU-A, V-A Project Manager: Nichole Perry, Associate Planner Owner/Applicant/Contact: Leah and Tristan Bull, 5424 NE 10th St, Renton, WA 98059 Project Location: 5424 NE 10th St, Renton, WA 98059 (APN 1023059365) Project Summary: The applicant is requesting Environmental (SEPA) Review, a Conditional Use Permit (CUP), and a Reasonable Use Variance to construct a 968 square foot detached Accessory Dwelling Unit (ADU) over a garage at 5424 NE 10th St, Renton, WA 98059 (APN 1023059365). The 1.26-acre parcel is located in the Residential-4 (R-4) zoning district and is designated Residential Low Density (RLD) in the Comprehensive Plan. The site currently contains an existing single-family dwelling unit. According to City of Renton (COR) Maps, the site includes high erosion hazards, regulated slopes (>15% & <=40%), a Category II Wetland, and a Type F stream (Honey Creek) that flows through the western portion of the site. The applicant submitted a Geotechnical Engineering Investigation, Wetland and Stream Delineation Report, and Standard Stream Study with the application. Exist. Bldg. Area SF: Single Family Residence Proposed New Bldg. Area (footprint): Proposed New Bldg. Area (gross): 968 sq. ft. 968 sq. ft. Site Area: 1.26 acres Total Building Area GSF: 4,208 sq. ft. STAFF RECOMMENDATION: Staff Recommends that the Environmental Review Committee issue a Determination of Non-Significance with Mitigation DNS-M. Docusign Envelope ID: CF4F89F1-1EB5-4C12-B6C9-56F8F437FF55 City of Renton Department of Community & Economic Development Bull Conditional Use Permit and Critical Areas Variance for Accessory Dwelling Unit Development Staff Report to the Environmental Review Committee LUA 24-000367, ECF, CU-A, V-A Report on May 5, 2025 Page 2 of 6 SR_ERC_Report_LUA24-000367_CUP and Variance_250428_Final ENVIRONMENTAL REVIEW In compliance with RCW 43.21C.240, the following environmental (SEPA) review addresses only those project impacts that are not adequately addressed under existing development standards and environmental regulations. A. Environmental Threshold Recommendation Based on analysis of probable impacts from the proposal, staff recommends that the Responsible Officials: Issue a DNS-M with a 14-day appeal period. B. Mitigation Measures 1. The applicant shall comply with the recommendations outlined in the Geotechnical Evaluation Report, prepared by GEO Group Northwest, Inc., dated July 27, 2022 (Exhibit 5), as well as any future addenda. 2. The applicant shall prepare and submit an Inadvertent Discovery Plan (IDP) prior to the start of any ground-disturbing activities. In addition, the applicant shall provide notification to Tribes’ cultural committee prior to the start of construction per the Duwamish Tribe Comments. C. Exhibits Exhibit 1: Environmental Review Committee (ERC) Report Exhibit 2: Site Plans, Pacific Home Source LLC, dated September 4, 2024 Exhibit 3: Boundary and Topographic Survey, prepared by Plog Engineering Surveyors and Civil Engineers, dated February 21, 2024 Exhibit 4: Tree Retention and Credit Worksheet, received October 8, 2024 Exhibit 5: Geotechnical Engineering Investigation, prepared by GEO Group Northwest, Inc., dated July 27, 2022 Exhibit 6: Wetland and Stream Delineation Report, prepared by DCG/Watershed, dated November 21, 2023 Exhibit 7: Standard Stream Study, prepared by Cascade Ecology LLC, dated February 3, 2023 Exhibit 8: Project Narrative, dated September 19, 2024 Exhibit 9: Conditional Use Permit and Variance Justification, dated October 7, 2024 Exhibit 10: SEPA Environmental Checklist, prepared by Tristan Bull, dated April 8, 2025 Exhibit 11: Duwamish Tribe Comments Comment Letter, prepared by Duwamish Tribal Historic Preservation, dated April 9, 2025 Exhibit 12: Staff Response Email to the Duwamish Tribe’s Comment Letter, dated April 9, 2025 Exhibit 13: King County Wastewater Treatment Division Comments, dated April 17, 2025 Exhibit 14: Staff Response Email to the King County Wastewater Treatment Division, dated April 17, 2025 Docusign Envelope ID: CF4F89F1-1EB5-4C12-B6C9-56F8F437FF55 City of Renton Department of Community & Economic Development Bull Conditional Use Permit and Critical Areas Variance for Accessory Dwelling Unit Development Staff Report to the Environmental Review Committee LUA 24-000367, ECF, CU-A, V-A Report on May 5, 2025 Page 3 of 6 SR_ERC_Report_LUA24-000367_CUP and Variance_250428_Final Exhibit 15: Advisory Notes D. Environmental Impacts The proposal was circulated and reviewed by various city departments and divisions to determine whether the applicant has adequately identified and addressed environmental impacts anticipated to occur in conjunction with the proposed development. Staff reviewers have identified that the proposal is likely to have the following probable impacts: 1. Earth Impacts: The 1.26-acre parcel located at 5424 NE 10th St is currently developed with an existing single-family residence. The applicant is proposing to construct a 968 square-foot detached Accessory Dwelling Unit (ADU) over a garage within a mapped wetland buffer area (Exhibit 2). According to the Geotechnical Engineering Investigation, prepared by GEO Group Northwest, Inc., dated July 27, 2022 (Exhibit 5), the site is underlain by a small peat deposit (Qlp) overlaying glacial till (Qgt). The peat layer, which varies in thickness from approximately three feet (3’) to 23 feet (23’), is noted to be very soft and may exhibit lateral flow when under load. This material is compressible and has a low shear strength, which poses challenges for conventional foundation support. The underlying glacial till is dense and more suitable for structural support but lies beneath the soft organic soils. Subsurface exploration consisted of one (1) boring (BH-1). The soils encountered were loose to a depth of 15 feet (15’) where they became dense throughout the rest of the 25-foot (25’) boring. The borehole revealed saturated conditions and a relatively high groundwater table, approximately seven and one-half feet (7.5’) below ground surface, in proximity to a north-south oriented creek located near the proposed structure. These site conditions suggest a potential for settlement, especially if construction occurs directly over the peat layer without adequate mitigation measures. Lateral spreading may also be a concern if significant loads are imposed without specialized engineering solutions. The report includes comprehensive recommendations for foundations, grading and earthwork, and slab-on-grade floors. The geotechnical report recommends the use of deep foundation systems or other engineered structural supports (e.g., 2-inch [2”] to 4-inch [4”] diameter galvanized pipe piles) to transfer building loads through the peat and into the more competent glacial till below. Site grading and earthwork activities will need to be carefully managed to avoid differential settlement and to maintain slope stability along the adjacent creek corridor. Erosion control measures will also be necessary during construction to prevent sediment transport into the nearby wetland buffer and associated critical areas. As such, staff recommends as a mitigation measure, that the applicant comply with the recommendations found in the submitted Geotechnical Engineering Investigation, prepared by GEO Group Northwest, Inc., dated July 27, 2022, and any future addenda. The Boundary and Topographic Survey, prepared by Plog Engineering Surveyors and Civil Engineers, dated February 21, 2024 (Exhibit 3) indicates that there is a deciduous tree, multi-trunk deciduous trees and a conifer tree near the proposed site. Mitigation Measures: The applicant shall comply with the recommendations outlined in the Geotechnical Engineering Investigation, prepared by GEO Group Northwest, Inc., dated July 27, 2022 (Exhibit 5), and any future addenda. Docusign Envelope ID: CF4F89F1-1EB5-4C12-B6C9-56F8F437FF55 City of Renton Department of Community & Economic Development Bull Conditional Use Permit and Critical Areas Variance for Accessory Dwelling Unit Development Staff Report to the Environmental Review Committee LUA 24-000367, ECF, CU-A, V-A Report on May 5, 2025 Page 4 of 6 SR_ERC_Report_LUA24-000367_CUP and Variance_250428_Final Nexus: State Environmental Policy Act (SEPA) Environmental Review; City of Renton Comprehensive Plan Policy L-35; RMC 4-3-050 Critical Areas Regulations; and RMC 4-4-060 Grading, Excavation, and Mining Regulations. 2. Water a. Wetland, Streams, Lakes Impacts: Due to the presence of a wetland and stream on the property, the applicant submitted a Wetland and Stream Delineation Report, prepared by DCG/Watershed, dated November 21, 2023 (Exhibit 6), and a Standard Stream Study, prepared by Cascade Ecology LLC, dated February 3, 2023 (Exhibit 7). These studies included an analysis of existing conditions and the potential impacts of the proposed development on the wetland, stream, and their associated buffers. The wetland, Wetland A, is classified as a Category II wetland, consistent with the Washington State Wetland Rating System. Wetland A scored a six (6) for habitat, reflecting its moderate ecological value. The wetland’s total area covers approximately one-quarter (0.25) acre on-site. A standard 150-foot (150’) buffer is required for Wetland A, as stipulated by the City of Renton regulations. This buffer is essential in protecting water quality, wildlife habitat, and hydrological processes within the wetland and its surrounding environment. The stream on the property, Stream A (Honey Creek), is classified as a Type F (fish-bearing) stream as per the City of Renton’s classification system. Stream A flows through the western portion of the site, entering the property from the south edge and losing channel definition shortly after entering the parcel (approximately 30 feet (30’) northwest of the culvert). Stream A is associated with a 115-foot (115’) buffer in compliance with the city’s regulations for Type F streams. The buffer serves to protect the stream from potential impacts due to construction activities, ensuring that water quality, sedimentation, and habitat functions are maintained. The proposed development includes the construction of a detached garage and accessory dwelling unit (ADU) located approximately 29 feet, 7 inches from the edge of the wetland. This represents an encroachment of approximately 120 feet, 5 inches into the required 150-foot buffer. It’s important to note that the wetland buffer extends beyond the property lines and is therefore not fully shown on the site map. The existing single-family residence is already located within the wetland buffer. The current layout provides a 29-foot, 7-inch buffer from the wetland edge to the new development. Due to the wetland, stream, and topographical constraints on the property, the proposed building location is in one of the only flat and accessible portions of the lot, making it one of the only feasible area for the property owners to construct an ADU without significant grading or earthwork. Construction activities would result in impacts to the buffer areas, particularly due to minor grading and erosion control activities during construction. According to the Standard Stream Study, the applicant is currently planting the east-bank of the stream, closest to the project site and main residence, with native plants including Sword Fern (Polystichum munitum), Deer Fern (Struthiopteris spicant), and Bog Kalmia (Kalmia microphylla). In addition, the stream study indicated that the homeowners have previously restored the stream banks and the upland areas through removal of invasive Himalayan Blackberry shrubs (Rubus armeniacus) and replacement with a variety of native shrubs and trees. All proposed wetland buffer impacts would be subject to current code requirements. For example, compensation for wetland buffer impacts shall occur at a minimum one to one (1:1) ratio and compensatory mitigation for buffer impacts shall include enhancement of degraded buffers by planting native species, removing structures and impervious surfaces within buffers, and other measures. The 1:1 ratio refers to the practice of replanting one square foot of native vegetation for every square foot of wetland buffer that is Docusign Envelope ID: CF4F89F1-1EB5-4C12-B6C9-56F8F437FF55 City of Renton Department of Community & Economic Development Bull Conditional Use Permit and Critical Areas Variance for Accessory Dwelling Unit Development Staff Report to the Environmental Review Committee LUA 24-000367, ECF, CU-A, V-A Report on May 5, 2025 Page 5 of 6 SR_ERC_Report_LUA24-000367_CUP and Variance_250428_Final disturbed during development. This requirement comes from the City of Renton’s Critical Areas Regulations (RMC 4-3-050J.4.d). It is a common standard used in environmental mitigation to ensure that the ecological functions and values of wetlands are maintained or restored. In contrast, the 3:1 ratio applies specifically to direct wetland impacts, such as filling or altering the wetland itself, and requires three square feet of mitigation for every one square foot impacted. However, because the proposed development is entirely within the wetland buffer and does not disturb the wetland itself, only the 1:1 buffer mitigation ratio applies. Therefore, the construction of the 968-square-foot ADU requires 968 square feet of replanting with native vegetation. If the project had directly impacted the wetland, the mitigation requirement would have been 2,904 square feet (3:1 ratio), reflecting the greater ecological impact. By complying with the 1:1 buffer mitigation requirement, the development ensures that water quality is protected, wildlife has adequate habitat, and the buffer’s protective function is preserved. This is essential for maintaining the long-term health and sustainability of the wetland and its surrounding ecosystem. Finally, all compensatory mitigation projects shall be monitored for a period necessary to establish that performance standards have been met, but generally not for a period less than five (5) years to ensure that the proposal would not result in a net loss of functions or values. It is anticipated that the requirements set forth by RMC 4-3-050 would be sufficient to mitigate wetland buffer impacts generated by the proposed development and no specific mitigation measures are recommended. Mitigation Measures: No further mitigation is recommended. Nexus: Not applicable. 3. Vegetation Impacts: According to the Tree Retention and Credit Worksheet, received October 8, 2024 (Exhibit 4), the site contains a total of 60 significant trees, as defined by RMC 4-11-200. After applicable deductions (including trees located within wetlands, streams, and associated buffers, as well as those within existing or proposed public right-of-way), 46 trees are proposed to remain. Per the SEPA checklist prepared by the applicant (Exhibit 10), no vegetation other than invasive species would be removed within the critical area buffers to accommodate the construction of the ADU and associated grading activities. The area of work is currently used as a second driveway which will be removed and a single driveway will be used for both the ADU and primary residence. There is a variety of deciduous trees, evergreen trees, shrubs, grass, and wet soil plants on-site. This vegetation is within the critical area buffer and would not disturb the wetland/stream itself. Removal and replanting portions of the second driveway would support more long-term ecological health. Therefore, no further mitigation is being proposed. Mitigation Measures: No further mitigation is recommended. Nexus: Not applicable. 4. Historic and Cultural Preservation Impacts: The project site is located within the ancestral lands of the Duwamish people. According to the SEPA Environmental Checklist, prepared by the applicant (Exhibit 10), no known cultural or archaeological resources are currently documented on the property. However, the Duwamish Tribal Historic Preservation Office submitted comments, dated April 9, 2025 (Exhibit 11), identifying the site as an area of cultural significance with the potential for unknown archaeological deposits. The Tribe requires the applicant to receive notice and prepare and submit an Inadvertent Discovery Plan (IDP) prior to the start of ground-disturbing activities. City Docusign Envelope ID: CF4F89F1-1EB5-4C12-B6C9-56F8F437FF55 City of Renton Department of Community & Economic Development Bull Conditional Use Permit and Critical Areas Variance for Accessory Dwelling Unit Development Staff Report to the Environmental Review Committee LUA 24-000367, ECF, CU-A, V-A Report on May 5, 2025 Page 6 of 6 SR_ERC_Report_LUA24-000367_CUP and Variance_250428_Final staff responded to the comments and is recommending that the applicant prepare and submit an Inadvertent Discovery Plan (IDP) prior to the start of any ground-disturbing activities. In addition, the applicant shall provide notification to Tribes’ cultural committee prior to the start of construction per the Duwamish Tribe Comments. Mitigation Measures: The applicant shall prepare and submit an Inadvertent Discovery Plan (IDP) prior to the start of any ground-disturbing activities. In addition, the applicant shall provide notification to Tribes’ cultural committee prior to the start of construction per the Duwamish Tribe Comments. Nexus: State Environmental Policy Act (SEPA) Environmental Review; RCW 27.53 Archaeological Sites and Resources; RCW 27.44 Indian Graves and Records; and City of Renton Comprehensive Goals and Policies, L-AA, L-44, and L-45; and Duwamish Tribe Comment, dated April 9, 2025. 5. Utilities Impacts: The project proposal is resulting in an additional residential unit on the property. This change in use would result in a new connection to the public sanitary sewer system and an increase in plumbing fixtures. King County Wastewater Treatment Division (WTD) submitted comments on April 17, 2025 (Exhibit 13), indicating that the project is subject to a capacity charge in accordance with King County Code, which applies to all new connections to the regional wastewater treatment system. The capacity charge is a one-time fee that recovers the cost of system expansion necessary to accommodate growth, such as additional residential units. This creates a direct and proportionate impact on the public wastewater infrastructure operated by King County. The capacity charge serves as a legally established mitigation tool that ensures those who generate new demand contribute equitably to the cost of expanding the system to maintain capacity, reliability, and service standards. The requirement to submit the Sewer Use Certification form and pay the capacity charge is consistent with the State Environmental Policy Act (SEPA) and the King County Code WTD (Exhibit 13). The Residential Sewer Use Certification form will be forwarded to the city department responsible for Sewer Use Certification forms. No further site-specific mitigation is proposed. Mitigation Measures: No further mitigation is recommended. Nexus: Not applicable. The proposal has been circulated to city department and division reviewers. Where applicable, their comments have been incorporated into the text of this report and/or “Advisory Notes to Applicant.” ✓ Copies of all Review Comments are contained in the Official File and may be attached to this report. The Environmental Determination decision will become final if the decision is not appealed within the 14-day appeal period (RCW 43.21.C.075(3); WAC 197-11-680). Environmental Determination Appeal Process: Appeals of the environmental determination must be filed in writing on or before 5:00 p.m. on May 19, 2025. Appeals must be submitted electronically to the City Clerk at cityclerk@rentonwa.gov or delivered to City Hall 1st floor Lobby Hub Monday through Friday. The appeal fee, normally due at the time an appeal is submitted, will be collected at a future date if your appeal is submitted electronically. The appeal submitted in person may be paid on the first floor in our Finance Department. Appeals to the Hearing Examiner are governed by RMC 4-8-110 and additional information regarding the appeal process may be obtained from the City Clerk’s Office, cityclerk@rentonwa.gov. Docusign Envelope ID: CF4F89F1-1EB5-4C12-B6C9-56F8F437FF55 CITY OF RENTON DEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT STAFF REPORT TO THE ENVIRONMENTAL REVIEW COMMITTEE EXHIBITS Project Name: Bull Conditional Use Permit and Critical Areas Variance for Accessory Dwelling Unit Development Land Use File Number: LUA24-000367, ECF, CU-A, V-A Date of Meeting May 5, 2025 Staff Contact Nichole Perry Associate Planner Project Contact Leah and Tristan Bull, 5424 NE 10th St, Renton, WA 98059 Project Location 5424 NE 10th St, Renton, WA 98059 (APN 1023059365) The following exhibits are included with the ERC Report: Exhibit 1: Environmental Review Committee (ERC) Report Exhibit 2: Site Plans, Pacific Home Source LLC, dated September 4, 2024 Exhibit 3: Boundary and Topographic Survey, prepared by Plog Engineering Surveyors and Civil Engineers, dated February 21, 2024 Exhibit 4: Tree Retention and Tree Credit Worksheet, dated October 24, 2023 Exhibit 5: Geotechnical Engineering Investigation, prepared by GEO Group Northwest, Inc., dated July 27, 2022 Exhibit 6: Wetland and Stream Delineation Report, prepared by DCG/Watershed, dated November 21, 2023 Exhibit 7: Standard Stream Study, prepared by Cascade Ecology LLC, dated February 3, 2023 Exhibit 8: Project Narrative, dated September 19, 2024 Exhibit 9: Conditional Use and Variance Justification, dated October 7, 2024 Exhibit 10: SEPA Environmental Checklist, prepared by Tristan Bull, dated April 7, 2025 Exhibit 11: Duwamish Tribe Comments, prepared by Duwamish Tribal Historic Preservation, dated April 9, 2025 Exhibit 12: Staff Response Email to the Duwamish Tribe’s Comment Letter, dated April 9, 2025 Exhibit 13: King County Wastewater Treatment Division Comments, dated April 17, 2025 Exhibit 14: Staff Response Email to the King County Wastewater Treatment Division, dated April 17, 2025 Exhibit 15: Advisory Notes Docusign Envelope ID: CF4F89F1-1EB5-4C12-B6C9-56F8F437FF55