The District sought input from agencies, affected tribes and members of the public concerning three proposed alternatives for the Plan. Comments were solicited on alternatives, probable significant adverse impacts, mitigation measures, and required permits or other approvals. Each of the alternatives includes continued maintenance of existing flood facilities. Alternatives 2 and 3 would also include some drainage improvements to agricultural lands and flood-proofing of agricultural structures. Additional details on each of the alternatives are provided below.
Alternative 1: No Action Alternative
Alternative 1 proposes no action. This alternative is required under SEPA. While the term is no action, it assumes implementation of the currently adopted 2018-2023 six-year capital improvement program (CIP). This includes 2.1 miles of new facilities designed to contain a flow of 18,800 cubic feet per second, plus three feet of freeboard, a 500-year level of protection, as well as maintenance of existing levees and revetments.
Alternative 2: Moderate Geographic Extent of Increased Level of Protection Alternative
Alternative 2 proposes a limited increase in the geographic extent of level of protection. Under this alternative the District would build approximately 20 miles of new or improved facilities to meet the 500-year level of protection designed to contain a flow of 18,800 cubic feet per second, plus three feet of freeboard.
Alternative 3: Greater Geographic Extent with Increased Level of Protection, Integrated Habitat and Recreation, Agricultural Protection Facilities, and Habitat Restoration Project Partnerships Alternative
Alternative 3 proposes a greater increase in the geographic extent of level of protection, integrated habitat and recreation, agricultural protection facilities, and habitat restoration project partnerships. Under this alternative, the District would build approximately 30 miles of new or improved facilities to meet the 500-year level of protection designed to contain a flow of 18,800 cubic feet per second, plus three feet of freeboard. The District would also provide physical non-structural flood measures to reduce the consequence of flooding for approximately 2 miles.
Additional Project Information
Purpose and Need
The Lower Green River is susceptible to flooding and flood damage because of its relatively flat geography and the concentration of people and commercial, industrial, and agricultural properties along its banks.
The King County Flood Control District is preparing a Lower Green River Corridor Flood Hazard Management Plan (Plan) for approximately 21 river miles of the Lower Green River that travel through the cities of Auburn, Kent, Tukwila, Renton, and unincorporated King County.
The goal of the Plan is to provide a long-term approach to reduce flooding and improve fish habitat while supporting the economic prosperity of the region.
A consultant team is developing the Programmatic Environmental Impact Statement (PEIS) to provide neutral third-party evaluation of the alternatives proposed by the King County Flood Control District.