A score of homes near a small stream in northwestern Arlington should be better protected against flooding after the county board authorized spending just more than $1 million on a new culvert.

The Arlington county board on Tuesday voted to spend the funds to increase the size of the culvert, or pipe, that directs the stream under Old Dominion Drive between N. George Mason Drive and N. Dickerson St.

During the June 2006 flooding, many of the homes surrounding the stream flooded, some with as much as 4 feet of water, said Michael Collins, chief of engineering for Arlington’s environmental services department.

The culvert that directs Little Pimmit Run stream under Old Dominion Drive was too narrow to handle the amount of rain that fell last June. Instead of directing the water down stream, the pipe acted as a dam, Collins said. A pond as much as 15 feet deep formed, causing the flooding.

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Building the larger culvert should reduce the depth of any pond formed by as much as seven feet, Collins said. The current culvert is about 8 feet across, Collins said, while the new arched culvert will be 16 feet wide and 9 feet high.

This will protect 12 of the 29 affected homes from a flood of such magnitude it should only occur once per century, according to county documents. An additional 11 homes should be better protected.

Collins said it isn't possible to protect all the homes by building a bigger culvert. This would likely cause more backups downstream, he said.

“This development occurred in a way not permitted with today’s knowledge of watersheds,” Collins said.

The homes Little Pimmit has flooded over the past 40 years were built in the 1950s and ‘60s, before developers and planners were aware of watershed and runoff issues. Parks surround most of the county’s streams, so the flooding doesn't go into Arlingtonians' homes, Collins said. Sagres Construction should begin work on the new culvert in late May.