5900 36TH AVE W SEPA 015 - 034 - SOUNDVIEW BUSINESS CAMPUS - VERITAS Land Use Decision Documents 2025-04-22

B. A 401 certification determination is based on the project or activity meeting established turbidity levels. The EPA will be using as guidance the state of Washington's water quality standards [WAC 173- ' 201 a] and sediment quality standards [WAC 173-204]. Projects or activities that are expected to exceed these levels or that do exceed these levels will require an individual 401 certification. ' The water quality standards allow for short-term turbidity exceedances after all necessary Best Management Practices have been implemented (e.g., properly placed and maintained filter fences, hay bales and/or other erosion control devices, adequate detention of runoff to prevent turbid water from flowing off -site, providing a vegetated buffer between the activity and open water, etc.), and only up to the following limits: C' Wetted Stream Width at Discharge Point Approximate Downstream Point for Determining Compliance Up to 30 feet 50 feet >30 to 100 feet 100 feet >100 feet to 200 feet 200 feet >200 feet 300 feet LAKE, POND, RESERVOIR Lesser of 100 feet or maximum surface dimension C. 401 certification of projects and activities under NWPs will use Washington State Department of Ecology's most recent stormwater manual or an EPA approved equivalent manual as guidance in meeting water quality standards. D. For projects and activities requiring coverage under an NPDES permit, certification is based on compliance with the requirements of that permit. Projects and activities not in compliance with NPDES requirements will require individual 401 certification. E. Individual 4 01 certification is required for projects or activities authorized under NWPs if the ' project will discharge to a waterbody on the list of impaired waterbodies (the 303(d) List) and the discharge may result in further exceedance of a specific parameter the waterbody is listed for. The EPA shall make this determination on a case -by -case basis. For projects or activities that will discharge to a 303(d)-listed waterbody that does not have an approved Total Maximum Daily Load (TMDL) or an approved water quality management plan, the applicant must provide documentation for EPA approval showing that the discharge will not result in further exceedance of the listed contaminant or impairment. For projects or activities that will discharge to a 303(d)-listed waterbody that does not have an ' approved TMDL, the applicant must provide documentation for EPA approval showing that the discharge is within the limits established in the TMDL. The current list of 303(d)4isted waterbodies in Washington State will be consulted in making this determination and is available on Ecology's web site at: www.ecy.wa.gov/programs/wq/303d/2012/index.liti-al The EPA may issue 401 certification for projects or activities that would result in further exceedance ' or impairment if mitigation is provided that would result in a net decrease in listed contaminants or less impairment in the waterbody. This determination would be made during individual 401 certification review. 1 18