DESCRIPTION
This project studied the feasibility of several options to provide flood control and/or habitat benefits on the White River in the area near 24th Street East, between RM 2.3 and 3.7 (left bank). The City of Sumner currently owns over 100 acres of the project site; several isolated parcels are not owned by the City. A Feasibility Study evaluated four options against numerous criteria related to habitat and flood mitigation and scored each in a matrix format. From the options a preferred option was selected: Conservation Option 2. This option would create a new 1.0 mile, 10 ac side channel. This option had the greatest amount of flood storage (220 ac-ft) and creation of new wetland/riparian (51 ac); it retains 33 acres of existing riparian area and doesn't excavate within the Channel Migration Zone. ELJs and cottonwood fences would be strategically placed in order to deter channel migration and protect an existing bridge and utilities. Preliminary cost estimate: $16.8M ($3.2M for design/permitting/administration). A preliminary design (30%) for the 5,280', 10 ac side channel was also funded by this project. In the 2008 Pierce County WRIA 10/12 Levee Setback Evauation the 9.2 acre project ranked third out of the study's six proposed setback levees.
Next steps: Property acquisition and final design/permitting.
The study area is located on the left bank of the White River from approximately RM 2.4 to 3.6. The City has expanded the proposed “Study Area”, which is identified in exhibit A. The project will considered a wide range of alternatives within the study area and a final recommendations is included in the design report. The river is currently only able to occupy the land within the proposed setback study area, which does not allow for the natural creation of salmon habitat. Once the setback has been constructed and material is removed from the river side of the setback natural riparian processes will begin to create habitat. This particular site has been identified by the Pierce County Levee Setback Evaluation done in 2008 for WRIA 10/12, this location was identified as site number 28 of the 32 listed in the evaluation. This project ranked 3rd out of the six proposed setback levees in the study our proposed analysis will go beyond the 9.2 acres from the levee evaluation to over 100 acres as shown in exhibit A. A design for the alternative selected by City Council has been taken to the 30% level along with associated reports.
