By Tom Robertson, PE
Tom has more than forty years experience with Cranston Engineering and as a consultant for a wide variety of civil engineering, planning, urban design, land surveying, and historic engineering projects throughout the southeast. In his engineering practice, he has a sound background in flood plain studies and in the design of dams, canals, and levees. Additionally, his experience includes safety inspections under Federal Emergency Management Agency (FEMA) and Federal Energy Regulatory Commission (FERC) guidelines.
I grew up fishing at the New Savannah Buff Lock and Dam and have spent nearly a lifetime engineering and planning for things that are dependent on its upstream pool.
I have reviewed the your posting of alleged “Misconceptions on Fish Passage Corrected,” and find that most of what you call “misconceptions” are actually official information taken straight from the Corps’ own documents, including the estimated costs. Other “assumptions or misinformation circulating within the community” are not that at all; rather, they are the Corps’ mischaracterizations of those assumptions. I have helped the “Save the Middle Savannah River” group formulate thoughtful comments on the currently-open scoping notice. That group’s official comments, to be sent to the Corps later this month, will address these issues in detail, which are too complicated to recount here.
Rising above those details, let’s look at the overall picture of the Middle Savannah River situation in its simplest terms:
We currently have an aged Lock and Dam with five adjustable spillway gates and a navigation lock. When we get a flood event, the gates are opened as needed to let the water out. Thus, they are used to regulate the pool level upstream. When the gates are fully open, the river doesn’t even know the dam is there.
If we had a stone weir or ramp across the river instead of the gates, it would be impossible to move them out of the way and open up the channel in times of flood, as is routinely done now with the dam. Therefore, if we got a similar flood event with the weir, the waters would have to go somewhere. Of course, they will go over the top and the water levels will rise upstream. Or, an excavated flood runaround pathway would be needed to carry the water at the same levels.
For the extreme event of the 100-year flood, Federal Emergency Management Agency (FEMA) regulations provide that any change in river channel or floodplain must cause no-rise in that flood. The FEMA computer model for the Savannah River assumes that the Lock and Dam gates are wide open when a flood of that magnitude happens. My experience with FEMA is that “no-rise” means “NO-RISE.” Zero. So, we can assume that the project cannot raise the 100 – year flood level.
Nor can the project lower the normal pool level. The WIIN law requires the project to maintain the current pool “as in existence on the date of enactment of this Act.”
Therefore, the WIIN Act alternatives, as drafted, are entirely unworkable – since the pool cannot be lowered and the flood levels cannot be raised. Physically you cannot have it both ways. It doesn’t take an engineer to figure that out.
Fortunately there is a common-sense solution that addresses all risks for the greater Augusta area and serves the goals of the Savannah Harbor Expansion Project. A modest-sized fish bypass, similar to the already-approved 2012 Fish Passage, would work quite well when the Lock and Dam is simultaneously repaired to support it. Moreover, this plan would appear to cost the least of all the alternatives heretofore proffered. It is already environmentally vetted, and is virtually shovel-ready -- the quickest to implement.
Why would we not do that?