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KITTI AS COUNTY <br />DEPARTMENT OF PUBLIC WORKS <br />PUBLIC WORKS — BOARD OF COUNTY COMMISSIONERS <br />STUDY SESSION STAFF REPORT <br />STUDY SESSION DATE: December 8, 2025 <br />TOPIC: Interlocal Agreement for Flood Insurance Rate Map <br />Updates for Whiskey and Mercer Creeks <br />ACTION REQUESTED: Approve a Resolution Authorizing Chair Signature on <br />Interlocal Agreement with the City of Ellensburg <br />LEAD STAFF: <br />Arden Thomas <br />RECOMMENDATION: <br />Authorize the Chair's Signature on an Interlocal Agreement with the City of Ellensburg. <br />BRIEFING SUMMARY: <br />• Kittitas County and the City of Ellensburg propose to jointly request that FEMA <br />update the Flood Insurance Rate Maps (FIRMS) for Whiskey and Mercer Creeks. <br />• Updated flood modeling funded by state, federal, and local Flood Control Zone <br />District sources provides improved technical informahon to support map <br />revisions. <br />• The County will lead flood -risk modeling, prepare draft FIRMS, develop and <br />submit the LIDMI package to FEMI, coordinate FEMA responses, and manage <br />required public notices. <br />• Both parties will jointly review modeling and draft map products , coordinate on <br />the LOMR submittal, conduct public outreach, and hold a public meeting. <br />BACKGROUND: <br />Whiskey and Mercer Creeks traverse both unincorporated Kittitas County and the City of <br />Ellensburg. The current FEMA Flood Insurance Rate Maps (FIRMS) for these creeks are <br />based on studies conducted I*n the 1970s and no longer reflect present-day conditions. <br />Both jurisdictions participate in the National Flood Insurance Program and rely on <br />FIRMS for floodplal*n development regulation. Updated, accurate mapping is therefore <br />necessary to ensure proper floodplain management and regulatory compliance. <br />Significant investments have been made to improve the understanding of flood risks <br />along these creeks. FEMA and the County"s Flood Control Zone District funded the <br />development of a two-di'mensional hydraulic model suitable for assessing flood risk and <br />supporting regulatory map updates. The City of Ellensburg led a detailed urban flood <br />modeling and analysis effort supported by the Department of Ecology's Flood Control <br />Assistance Account Program, coordinated with the County -led floo ain modeling <br />Page 1 of 4 <br />Public Works "Work Session Staff Report", 2025 <br />