20221523 Ver 1_281 Red Bird Circle Cr - Updated PCN Impact Table and Information_20230104

D. Proposed Impacts Inventory
4. Open Water Impacts
4a. Site #
4a1. Impact
4b. Impact
4c. Name of
4d. Activity
4e. Waterbody
4f. Impact
Reason
Type
Waterbody
Type
T e
Area
Bulkhead I
Shore
T
Lake
Permanent
Lake
0.01
Stabilization
Toxaway
Bulkhead
E. Impact Justification and Mitigation
1. Avoidance and Minimization
Ia. Specifically describe measures taken to avoid or minimize the proposed impacts in designing the
project: *
This project is to replace a failing sea wall. The existing wall has begun to settle and separate and looks to
be leaning under the pressure of the soils retained. If this wall is not repaired/replaced, it will eventually
collapse into the lake and release the soils retained behind it. The new permanent bulkhead will be placed
on an adequate stone foundation and will use a 60" broad concrete base layer to better distribute the
weight of the bulkhead to the earth. #57 stone backfill is being used to allow ground water to slowly pass
thru the bulkhead and enter the lake. A filter fabric is being used to separate the retained earth from the
#57 drainage stone and minimize passage of sediment.
lb. Specifically describe measures taken to avoid or minimize the proposed impacts through
construction techniques: *
A temporary cofferdam is being utilized to allow the work to be accomplished 'in the dry'. The temporary
cofferdam will utilize 0.027 acres of temporary fill material, that will be removed from the site once the
project is completed. A skimmer (Faircloth style) is being used to allow sediment to drop to the bottom of
the work basin. This draws cleanest water from the surface. In addition, a precast concrete wall design is
being used to accelerate the project schedule and minimize the time during which the construction site is
exposed severe weather.
Comments:
- The new bulkhead will be a permanent structure.
- The temporary Cofferdam will utilize 0.027 acres of temporary fill material.
- The length of the sea wall that will be replaced is 66 ft. This is the same length as the
existing failing sea wall that we are replacing.
- The cofferdam will not have a foundation, as to prevent any additional disturbance
to the lakebed. The cofferdam will ultimately sit on the bottom of the lake.
- The Dimensions of the foundation fill for the new permanent bulkhead, will be the
same as the existing sea wall which is approximately 66' long x 5' wide.