A rendering of what the hybrid parking/stormwater management facility would look like.

Parking down by the National Mall has always been a challenge, but the National Coalition to Save Our Mall has a relatively simple solution—a parking lot underneath the mall itself able to fit up to 1,000 cars and tour buses.

In a proposal presented last week, the coalition argued that a parking lot could be built alongside a network of cisterns that would serve to store stormwater runoff and provide improved irrigation for the parched section of grass on the mall. The underground facility would be located between Ninth and 12th Streets and Jefferson and Madison Drives NW.

To head off any claims that the idea sounds crazy, the coalition’s proposal points out that underground parking was envisioned as far back as 1966 and that a 2011 study proposed the construction of the large underground stormwater cisterns to protect the mall against flooding. The coalition also notes that this has been done before, in the Netherlands:

One model is this hybrid parking garage/rainwater reservoir in Rotterdam, The Netherlands. The multi-story garage holds 1,200 cars and approximately 2.65 million gallons of water. Several million euros were saved by combining parking and reservoir functions.

Of course, a big obstacle would be cost: the stormwater cisterns were estimated to cost $400 million, and parking facilities could only add to that cost. Still, the coalition says that people paying to park underneath the mall would help offset the significant capital costs.

Over the weekend, though, the proposal got the support of the Post’s editorial board, which called it a “pretty sensible idea.”

2013 Hybrid Parking Flood Reservoir Mall