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HomeMy WebLinkAboutERC_Report_Docket_17A_D-208_Surface_Water_Design_Manual_UpdateDEPARTMENT OF COMMUNITY AND ECONOMIC DEVELOPMENT ERC Report 2022 Docket #17, Group A, #D-208 Surface Water Design Manual Update ENVIRONMENTAL REVIEW COMMITTEE REPORT ERC MEETING DATE: May 16, 2022 Project Name: 2022 Docket #17, Group A, #D-208 Surface Water Manual Update Project Number: LUA22-000146, ECF Project Manager: Angie Mathias, Long Range Planning Manager Owner: City of Renton Applicant: City of Renton Contact: Angie Mathias, 425-430-6576 Project Location: All docket items are citywide. Project Summary: The applicant is requesting Environmental (SEPA) Review to review for the following non-project item: #D-208 Surface Water Manual Update: The purpose of the proposed code amendment is to update the City of Renton’s Surface Water Design Manual (RSWDM) for consistency with the 2019 Ecology Stormwater Management Manual for Western Washington (SMMWM), and revise RMC 4-6-030, Drainage (Surface Water) Standards, and RMC 4-11-190, Definitions S, for consistency with the RSWDM update. Exist. Bldg. Area SF: N/A Proposed New Bldg. Area (footprint): Proposed New Bldg. Area (gross): N/A N/A Site Area: N/A Total Building Area GSF: N/A STAFF RECOMMENDATION: Staff Recommends that the Environmental Review Committee issue a Determination of Non-Significance (DNS). PART ONE: PROJECT DESCRIPTION / BACKGROUND The Surface Water Utility is updating the City’s Surface Water Design Manual (RSWDM). This manual is used by private developers and the City when designing new storm systems, upgrading existing stormwater infrastructure, or performing drainage review on projects. For example, Transportation, Parks, Development, and Utilities projects that add at least 2,000 square feet of impervious area or disturb 7,000 square feet or more of land are subject to drainage review. This update is primarily driven by the City’s current (2019-2024) Municipal Stormwater Permit issued by the Department of Ecology, which requires the adoption of a manual equivalent to the 2019 Ecology Stormwater Management Manual for Western Washington (SWMMWW). In the last update that took place in 2016, the City adopted the 2016 King County Surface Water Design Manual (KCSWDM) with amendments, resulting in the current 2017 RSWDM. Compared to the 2016 update, the current updates proposed are significantly less substantial. Therefore, rather than adopting the 2021 KCSWDM and amending it, updates are being proposed directly to the 2017 RSWDM to produce the 2022 RSWDM. City of Renton Department of Community & Economic Development Environmental Review Committee Report DOCKET #17, GROUP A, #D-208, SURFACE WATER DESIGN MANUAL UPDATE LUA22-000146, ECF Report of Monday, May 16, 2022 Page 2 of 3 ERC Report Docket 17A D-208E The updates are split into three (3) categories: 1. Changes required by Ecology for all municipal permittees and mirrored from the 2021 KCSWDM. These changes are mandatory for compliance with the Permit. An example in this category is the requirement to analyze the length of time and portion of the year wetlands hold water (called the wetland hydroperiod) for projects discharging to wetlands. 2. Changes mirrored from the 2021 KCSWDM that are not driven by Ecology requirements. Despite not being required by the Municipal Stormwater Permit, these updates are needed to maintain commonality with the King County manual, which was approved by Ecology. Because the City is not developing its own manual and submitting it to Ecology for review, such changes must also be incorporated into the revised City manual. An example of a change in this category includes the elimination of on-site BMP (best management practices) sizing credits for all privately maintained on-site BMPs, except for full dispersion and full infiltration. This is because King County has found it difficult and costly to regularly inspect private BMPs to ensure they are maintained and functioning as intended to protect downstream systems and comply with their National Pollutant Discharge Elimination System (NPDES) municipal stormwater permit. 3. Changes based on comments gathered from staff in the Surface Water Engineering, Development Engineering and Construction Inspection sections over the last 5 years that clarify existing language, update old references, improve workflows and eliminate facilities and materials no longer preferred by the City. These changes are not required by the Permit, but are proposed for clarity, consistency, and improved stormwater management practices. Examples of such changes include defining duplex units as single-family residences and clarifying which types of stormwater facilities are prohibited within aquifer protection areas. PART TWO: 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 with a 14-day Appeal Period. B. Mitigation Measures 1. None C. Exhibits None D. Environmental Impacts There are no environmental impacts that are anticipated to occur in conjunction with the proposal. E. Comments of Reviewing Departments City of Renton Department of Community & Economic Development Environmental Review Committee Report DOCKET #17, GROUP A, #D-208, SURFACE WATER DESIGN MANUAL UPDATE LUA22-000146, ECF Report of Monday, May 16, 2022 Page 3 of 3 ERC Report Docket 17A D-208E 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 30, 2022. Due to the ongoing state of emergency enacted by Governor’s Proclamation 20-28.14 (and as amended), the City Clerk’s Office is working remotely. For that reason, 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. 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.