To the Editor:
“Why would the city build a $5M floodwall that will be repeatedly overtopped?” my engineering mind keeps saying. The cynical answer is that it cannot afford to build the 13-foot barrier that will meet FEMA 100-year floodplain protection requirements. So in its effort to eradicate nuisance flooding (up to 4 foot elevation), it decides to build a seawall to 6-foot elevation. Give it a little “headroom”, so to speak. Never mind that the records show only 6 instances in the last 6.5 years where floodwaters elevations exceeded 4.25 feet or that the FEMA statistics predict that the 6-foot seawall will be overtopped every 10 years. What’s another $5M in tax dollars when 1/5th of that expenditure will eliminate all nuisance flooding?
Well for one thing, the 6-foot seawall gives the city an opportunity to build and man a couple of colonial-style pump houses, one on the Strand and the other on Thompson’s Alley. It seems that the seawall itself will trap stormwater runoff on the land side and will 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. Planning’s estimated cost for two pump stations to accommodate the undersized seawall? $2.3M, check.
Not to worry, says the city, once the storm surge subsides those same pumps will discharge the 2.3M gallons (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. “Complicated question,” I’m thinking, so perhaps I’ll discuss the issue at the Planning Commission meeting. But, I forgot about its chairman who took his rose-colored glasses off just long enough to ask the city engineer for her opinion of my abbreviated presentation. To which she replied that Mr. Kupersmith is substantially accurate but staff does not believe the “dire situation” he predicts will occur. Let’s hope she is correct, because council could quite possibly be throwing $4M down the sewer.
John A. Kupersmith, Alexandria