Lake Lou Yaeger - City of Litchfield

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
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Concerns
 Loss of lake depth due to
sedimentation – especially in the
northern area
 Shoreline erosion occurring on the
eastern shore
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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
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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
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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
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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.
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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
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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*
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1966 Topography vs. 2011 Bathymetry
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Historic
Depth
Change
Map
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Depth
Change
Projections
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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.
Location (by station – in
feet above the dam)
28500 and Upstream
23000 and Upstream
11750 and Upstream
Entire Lake
Surface
Area (acres)
31
191
694
1099
Avg Depth Avg Depth at
2011 (feet) Year 50 (feet)
3.3
0.9
4.9
2.8
8.4
6.8
11.7
10.6
Years to Zero
Avg Depth
70
125
297
794
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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.
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Wetlands
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Potential Paths Forward
 Option 1 – Continue Study with Wetlands Investigation
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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
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