20160804 Ver 1 _PCN 401 3e Answer _20160816

3e. Describe the overall project in detail, including the type of equipment to be used:
The most feasible alternative for providing future disposal capacity is to increase the capacity of
Cells 1-3 at Eagle Island by raising the dikes to elevation 50 feet NAVD 88. To ensure dike
stability, this additional raise will require the construction of a "toe berm" around portions of the
outer footprint of each cell. The toe berm will serve as a buttressing -type support for the dike,
allowing additional dike raises in increments of 3 to 5 feet, eventually reaching a maximum
elevation of 50 feet NAVD 88. The toe berms and dike raises will be constructed utilizing
existing material in the cells. Doing so will also increase the capacity of each cell providing
additional storage space for future disposal.
Although the USACE would prefer to construct the toe berm for all three cells at the same time,
this may not be possible based upon funding limitations. Therefore, construction of the toe
berm would be accomplished in a phased approach that may occur over a period of up to 5-6
years beginning in 2018, as funding becomes available. The proposed dike raise to elevation 50
feet NAVD 88 would provide disposal capacity for an additional 10-12 years (until year 2032).
Construction of the dike raises and toe berms will impact approximately 39 acres of coastal
Marsh. Excavators, backhoes, dump trucks, etc. will be used to lift, scrape and push material
from inside the cells to the outside of the existing dikes to construct the toe berm.
Ileight
200
160
120
80
40
0
-40
-80
-120
TYPICAL CROSS SECTION
60 120 180 240 300 WO 420 480 Length
Figure 1. Typical Cross Section of Proposed Dike Raise and Toe Berm