City of Seattle – Seattle City Light Sourdough Creek Vented Ford Maintenance Determination of Non-Significance (DNS) Seattle City Light (SCL) has prepared an environmental checklist under provisions of the State Environmental Policy Act for routine maintenance of the Sourdough Creek vented ford at Diablo Dam Road. Description of the proposed Project: During periods of high flow, including atmospheric rivers, significant volumes of small boulders, cobbles, gravel, and some large woody debris (LWD) are moved and deposited at the vented ford on Sourdough Creek along the Diablo Dam Road, within the Federal Energy Regulatory Commission (FERC) Project No. 553 Project Boundary. Sediment and large woody debris can partially fill the vented ford and cause water to flow over the roadway and pose a public safety concern for visitors to the Skagit Hydroelectric Project and employees and visitors to the North Cascade Institute's Environmental Learning Center (ELC). Catastrophic flooding and erosion may occur if sediments are not removed in a timely manner. Seattle City Light proposes to remove deposited material at the vented ford on an as-needed basis for the next five years. To the extent possible, work should be performed after Sourdough Creek, an intermittent stream, goes dry. However, this may not always be possible, such as in emergency situations to restore safe access to the ELC. When working in the dry, debris removal and redistribution work may extend up to 150 feet upstream and downstream of the vented ford. When emergency work in the wet is required, debris removal will be limited to 100 feet upstream and downstream of the ford, and the removed debris will be placed in an upland location outside of the OHWM of Sourdough Creek. When working in the dry, most material from upstream of the ford will be relocated to the downstream side to replenish erosion and mimic natural deposition; some material may be distributed on the bank above the OHWM of Sourdough Creek. Large material (e.g. boulders) would be left in place. All work will remain upstream of the confluence with Diablo Lake, and at no point will any work be done below its OHWM. Debris removal and sediment distribution work will be done to maintain the integrity and functionality of the permitted channel realignment project (USACE NWS-2022-589) constructed in 2022. Proponent: Seattle City Light Location of proposal including street address, if any: The proposed project is located at 48.7195046, -121.1196901 and is within the NW 1/4 of SE 1/4 of Section 4, Township 37 North, Range 13 East. Lead Agency: Seattle City Light, the lead agency for this proposal, has determined that it does not have a probable significant adverse impact on the environment. Therefore, an environmental impact statement (EIS) is not required under RCW 43.21C.030(2)(c). This decision was made after review of a completed environmental checklist and other information on file with the lead agency. This DNS is issued under WAC 197-11-340(2). The lead agency will not act on this proposal for 14 days from the publication date. A copy of the DNS and checklist can be obtained at no charge from SCL by calling 206-677-6368 or by visiting the office of SCL's Environmental Affairs and Real estate Division at Suite 3200, 700 Fifth Ave., Seattle. The public is invited to comment on the DNS. The comment period closes on 8/24/2026 – allow 14 days. Appeals to this determination must be received by the Office of the Hearing Examiner, 700 Fifth Ave., Seattle, WA 98104 no later than 5 pm on 8/31/2026 –there is a 7 day appeal period. The mailing address is PO Box 94729, Seattle, WA 98124-4729. The appeal should be based on specific factual objections. There is an $85 filing fee for the appeal (check payable to City of Seattle). Contact the Hearing Examiner at 206.684.0521 or visit www.seattle.gov/examiner to ask about or read procedures for SEPA appeals, including electronic filing and credit/debit card payments. IPL0364767 Aug 11 2026