By John A. Kupersmith, Alexandria
(File Photo)

To the editor:

“Why would the city build a $5 million floodwall that will be repeatedly overtopped?” my engineering mind keeps asking.

The cynical answer is that City Hall cannot afford to build the 13-foot barrier that will meet the Federal Emergency Management Agency’s 100-year floodplain protection requirements. So in its effort to eradicate nuisance flooding (up to four feet), officials decide to build a seawall with an elevation of six feet.

Never mind that the records show only six instances in the last six and a half years where floodwaters elevations exceeded 4.25 feet or that the FEMA statistics predict that the six-foot seawall will be overtopped every 10 years. What’s another $5 million in tax dollars when one fifth of that expenditure will eliminate all nuisance flooding?

Well, for one thing, a six-foot seawall gives the city an opportunity to build and man a couple of Colonial-style pump houses, one along The Strand and the other by Thompson’s Alley. It seems that the seawall will trap storm water runoff on the landside and require about 1,800 gallons per second of pumping capacity to keep up with the runoff from the 100-year rain event. So rather than having the rainwater just flow down the streets directly into the Potomac, the city gets to be a New Orleans-on-the-Potomac.

And a New Orleans it will become when we have our own mini Katrina every 10 years or so.

The planning department’s estimated cost for two pump stations to accommodate the undersized seawall: $2.3 million. Not to worry, says City Hall, once the storm surge subsides those same pumps will discharge the 2.3 million gallons (this is a city estimate) of polluted water pooled behind the seawall back into the Potomac (in violation of the Clean Water Act). It fails to mention that the pump houses will be flooded and inaccessible, except by boat, or that the overtopping event itself can create a wall of water drowning anyone in its path, or the tons of polluted flotsam left trapped in the basin to clog the pumps.

“This is a complicated question,” I’m thinking, “so perhaps I’ll discuss the issue with the planning commission.” The commission’s chairman, Eric Wagner, took his rose-colored glasses off just long enough to ask the city engineer for her opinion of my presentation. She replied that I am substantially accurate but city staff do not believe the dire situation I predict will occur.

Let’s hope she is correct, because city council could quite possibly be throwing $4 million down the sewer.