Lake Lou Yaeger Section 206 Study Aquatic Ecosystem Restoration

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1 Lake Lou Yaeger Section 206 Study Aquatic Ecosystem Restoration Ashley Rasnic Michelle Kniep St. Louis District U.S. Army Corps of Engineers July 2, 2015 US Army Corps of Engineers

2 Concerns Loss of lake depth due to sedimentation especially in the northern area Shoreline erosion occurring on the eastern shore

3 Study Authority and Purpose Section 206 of WRDA 1996 Purpose: Determine if there is a Federal interest in participating in aquatic ecosystem restoration opportunities. 3

4 Restoration Objectives Increase fish overwintering habitat Improve water quality for aquatic organisms Increase dissolved oxygen through increase in lake depths Reduce water temperatures through increase in lake depths Increase wetland habitat supporting invertebrates and young fishes Restore shallow water habitat Increase habitat supporting migratory and shore birds

5 Study Milestones Federal Interest Determination (FID) Completed and Approved in January 2013 Sign Feasibility Cost Sharing Agreement Completed May 2014 Alternatives Formulation Briefing Draft Report Public Review of Report and Environmental Assessment Final Report

6 BUILDING STRONG

7 FID Plan Rock Berm: This berm would be placed at a strategic location in the northern end of the lake to trap a portion of the incoming sediments and restore wetland habitat, function, and processes in the area upstream of the berm. It would allow for shallow water fisheries habitat (spawning and rearing) and control of some pollutants such as suspended solids. The FID concept included a notch in the structure that would allow fish populations ingress/egress to the wetland area, as well as limited boat access.

8 Possible Measures Dredging In-Lake and Tributary Detention Structures Lake draw-down Artificial underwater reefs Lake Destratifiers Off-shore revetment On-shore revetment Breakwaters Island Restoration Riparian plantings

9 Activities Completed Sediment sampling and analysis Assessment of species utilizing the lake Consultation with NRCS regarding potential location(s) and design of sediment retention basins Sediment yield calculations for two primary tribs Lake bottom depth-change analysis*

10 1966 Topography vs Bathymetry

11 Historic Depth Change Map

12 Depth Change Projections

13 Depth Change Projections Calculations assume: Sediment transportation rates from the past will continue at the same rate into the future. Future sediment deposition will occur in the same general locations at the same rates as in the past. Surface Area (acres) Avg Depth 2011 (feet) Avg Depth at Year 50 (feet) and Upstream and Upstream and Upstream Entire Lake Location (by station in feet above the dam) Years to Zero Avg Depth

14 Initial Conclusions The most significant sediment deposition is occurring in a relatively small portion of the lake. Fish have sufficient overwintering habitat, cold water, and dissolved oxygen for their life needs Fish currently inhabiting the lake do not need access to the tributary watersheds for their life needs The eastern shoreline erosion is not making a significant contribution to the problem of lake depth and is not significantly reducing the amount of shallow water habitat and wetlands in the lake The potential wetland restoration identified in the 2013 FID could only be created by essentially eliminating motorized boat access to the northernmost portion of the lake.

15 Wetlands

16 Potential Paths Forward Option 1 Continue Study with Wetlands Investigation Investigate up to three possible locations for rock berm(s) Roughly calculate costs and ecosystem benefits to determine viability Present results to the City prior to proceeding further Option 2 Terminate Study and Return Funds Assemble all information gathered and calculated during the study and deliver it to the City Return any unused sponsor funds