The National Weather Service estimates that Sandy dropped somewhere in the range of 6 to 8 inches of rain on the flood-prone Bloomingdale neighborhood since Sunday. And yet there was no significant flooding to be found. Streets were passable, basements were dry and politicians were happy.
The reasons are fairly straightforward: It simply did not rain fast enough to overwhelm Bloomingdale’s antiquated sewers, said D.C. Water General Manger George Hawkins at a news conference this afternoon. It had less to do, he said, with the utility’s efforts to clear storm drains and make sure other above-ground drainage matters were in order.
Anything falling less than 2 inches per hour, the system can handle, Hawkins said. So neighborhood residents have less to fear from drenching tropical/quasi-tropical megastorms like Sandy than they do from intense, fast-moving thunderstorms like June’s derecho or the two other summer storms that deluged the neighborhood.
That’s still bad news for Bloomingdale residents, because those storms come with much less warning than Sandy did. And it means the politicians they’re pressing for a quick fix shouldn’t take too much comfort in having dodged the worst-case scenario here.
In 10 to 15 years, D.C. Water expects to complete new stormwater storage tunnels that will solve the problem for good. It remains to be seen whether any medium-term fixes — such as impounding stormwater at the nearby McMillan Sand Filtration Site — are workable.