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HomeMy WebLinkAbout10292019 City Council Work Session Laydown - Reduce Flood Risk ) c ! c29 viS End jt± ' `' Seward/Bear Creek 302 Railway Avenue, Suite 123 Seward, Alaska 99664 Flood Service Area (907)224-3340 • 224-5197 Fax Ui? 0v1G MEMORANDUM To: City Councilor Members Christy Terry, Mayor Thru: Scott Meszaros, City Manager�� Mark Ganser, SBCFSA Board Chair From: Stephanie Presley, SBCFSA Program Lead ItZ) (3) 0� Date: October 7, zolg Subject: Partnership Projects to Reduce Flood Risk from Japanese Creek Japanese Creek drains a large watershed to the northwest of Seward. The catchment, approximately 7.5 square kilometers, contains the remnants of cirque glaciers and debris laden grounded ice in the valley. The outlet for the stream is confined to one pinch point between Mount Benson to the north and Mount Marathon to the south. The stream then veers sharply to the north due to a levee system which was constructed to protect infrastructure and the Gateway, Afognak and Forest Acres neighborhoods, which were built upon the alluvial fan the stream has made over many thousands of years. The existing Japanese Creek levee, owned and maintained by the City of Seward, protects the neighborhood including the Seward Schools, Providence Mountain Haven, Seward Military Resort, Seward Electric Warehouse and an estimated $143 million in assessed property value. The floodplain is transected by Dieckgraeff Road,the community's only access to the KPB Solid Waste Transfer facility, and crosses State, City, Borough, University and private property before entering the Resurrection River. In 2010, the City of Seward, Kenai Peninsula Borough (KPB), and Seward/ Bear Creek Flood Service Area (SBCFSA) requested the U.S. Army Corps of Engineers (USACE) assistance for flood control management on five area creeks. The USACE under the Continuing Authorities Program (CAP) Section 205 of the 1948 Flood Control Act, as amended, allows the USACE to study, plan, and construct small flood risk management projects without specific authorization by congress. A project is accepted for construction after a detailed study shows engineering feasibility, economic justification, and environmental acceptability. The USACE Alaska District completed initial studies on Japanese Creek and Salmon Creek in 2013 with federal interest to continue to the feasibility study phase on both projects. The USACE and KPB/SBCFSA entered into a feasibility cost share agreement for Salmon Creek in 2014 and began construction on the Salmon Creek revetment in 2016. The 1,675 foot-long armored revetment was completed under budget in 2018 and protects the Bear Lake neighborhood from debris laden flooding. With the close out of the Salmon Creek project, the City of Seward, KPB, and SBCFSA requested the USACE Alaska District develop a feasibility cost share agreement to begin work on a flood risk management project for Japanese Creek. The USACE has determined the feasibility study will cost up to $goo,000, with a 5o% match from the local sponsors. The SBCFSA Board of Directors has committed the remaining funds of $175,000 from the Salmon Creek project for the Japanese Creek feasibility study. It is recommended that the City of Seward provide an additional $275,00o for the local match in the FY2o2o budget. A cooperative partnership agreement with the USACE, City of Seward and KPB/ SBCFSA for a three year feasibilty study of the Japanese Creek watershed will determine the preferred alternative for a small flood control project with up to $10 million in construction costs. The initial study from 2013 determined the project will likely include reconstruction of the existing levee which, at the time, was expected to capture no larger than a 10-year flood event. The USACE will design a levee to protect the neighborhood from a too-year flood event and may design a debris catch basin for future sediment management. Construction of the preferred alternative will have a 35% local match required.