The new lake adds $90 million to $150 million in costs
Alternatives D and E propose excavating and clearing the Pearl River between Lakeland Drive and Interstate 20 to increase the river's "hydraulic conveyance." Increasing hydraulic conveyance increases the river’s “efficiency,” meaning the river would be able to move more water at lower flood heights. The excavated material would then be used to fill in wetlands and create new developable properties. (See image below for a map.)
The cost and benefit-cost ratio of each plan is given in Table 3-8, page 135 of the DEIS and repeated here:
Calculating the cost difference between Alternatives D and E provides a cost estimate of the proposed lake. That's $91 million to $153 million.
What are the major physical elements of the Corps’s lake plan?
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clear and expand river channel (excavation in pink)
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Excavated material plan (fill-in wetlands in brown)
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construct a new weir (a type of dam); create a recreational lake (in blue)
The map also shows levees in the Jackson metropolitan area as dashed lines. The ring levee at the bottom left of the image represents the levees at the Savanna Waste Water Treatment Plant. This levee would be upgraded under Alternatives D and E.