WASHINGTON — Storage tanks and a tunnel that could hold millions of gallons of water are being proposed to provide flood relief to two Washington neighborhoods.

District officials unveiled the plan Thursday for the Bloomingdale and LeDroit Park neighborhoods of Northwest Washington. The two communities were particularly hard hit by flash flooding last summer.

The plan calls for converting the former McMillan sand filtration site into storage tanks that could hold 3 million gallons each. And a six-block long tunnel under First Street would be able to hold 6 million gallons.

Sewer authority officials say the plan would cost $40 million more than previous flood relief plans. And it would be finished by 2022, three years earlier than the previous plan.

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