14-020 - City of Kent - Briscoe-Desimone Levee Repair

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EXHIBIT A Sheet 1 of 4 Description of Briscoe - Desimone Levee Improvements The Briscoe - Desimone Levee is located along the right bank (easterly side) of the Green River between S. 200th Street and S. 180th Street, (see Figure 1, Exhibit A Sheet 2 of 4). The Briscoe levee is located along the right bank of the Green River between S. 200th Street and S. 189th Street within the City of Kent. The Desimone levee is located along the right bank of the Green River between S. 189th Street and S 180th Street in the City of Tukwila. Together these levee segments are approximately 2.7 miles in length and protect properties within the cities of Kent, Tukwila and Renton. Tilt -up style buildings (manufacturing and industrial) are located adjacent to the entire stretch of levee. Four sections (reaches) of the levee, approximately 4,450 linear feet, don't meet slope and stability requirements and need repair to meet FEMA accreditation requirements. Reach 1 is located between RM 14.47 and 14.63 and totals 1,050 if. Reach 2 is located between RM 15.45 and 15.57 and totals 850 lf. Reach 3 is between RM 15.98 and 16.36, totaling 2,350 if, and Reach 4 is between RM 16.95 and 17.00 and totals 2001f. Reaches 1, 2 and 3 are on the outside of sharp bends in the river and Reach 4 is just north of the S. 200th Street Bridge. Structural steel sheet pile walls are proposed to be installed at the back of the existing levee slope to act as a secondary levee to reduce flood risk to the cities of Kent, Tukwila and Renton and protect the large number of warehouses, manufacturing facilities and some retail establishments behind these levees. These areas are shown on Figure 2, Reach Location Map (see Exhibit A Sheet 3 of 4). In addition, large stumps and roots will be removed in areas between the four reaches along the levee where they could compromise levee stability and/or are in the construction project area. The walls will provide a minimum of 3 feet of freeboard above the predicted 100 -year flood event, (see artist rendering Exhibit A Sheet 4 of 4). This proposal allows for some re- vegetation and habitat restoration work along the river between the ordinary high water line and the trail in areas where the wall is constructed. In areas where walls are installed, benches will be constructed where feasible and native vegetation will be planted above the ordinary high water line. 10 EC approved (RB -RK)