Mike McKibbin

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August 8, 2012
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Flash flood speeds up culvert replacement

A flash flood on July 22 caused heavy damage to two culverts that run under West 12th Street near the Garfield County Fairgrounds in Rifle, leading to a quick response by the city.

A heavy thunderstorm up Hubbard Gulch washed a "significant" amount of water and debris down the channel, wrote City Engineer Rick Barth to the City Council on Aug. 1.

"This flood was powerful enough to pick up a substantial amount of natural and man-made debris, which slammed into and clogged the twin 48-inch corrugated metal pipe culverts at the 12th Street crossing," Barth wrote. "The flood and associated debris damaged the timber headwall and the entry into the pipes."

Much of the timber headwall was undercut, Barth continued, and the entry to the two pipes was severely dented and bent.

The damage and erosion is enough that there is very little holding up the remaining timbers, Barth said.

"Further, one of the [pipes] suffered a gash for several feet into the pipe as the powerful flows forced a rock into the pipe and essentially cut the flowline of the pipe like a razor," Barth said in his memo.

City crews cleared the culverts, but Barth said this drainage crossing "cannot take another hit" similar to this storm. Barth strongly recommended emergency action be taken to replace this crossing.

The twin metal pipes are undersized, he said, and the damaged headwall was already substandard for today's construction. Barth said the city has crews and equipment to quickly replace the pipes with a large concrete box culvert and associated headwalls, wingwalls, apron and rip rap protection. The alignment will stay essentially the same, he added. The box culvert will be as large as the local topography will allow, Barth said.

The improvement will greatly increase water flow capacity at this crossing, Barth said. Secondly, a large box culvert will allow the city's smaller equipment to clean it out quickly and safely, he added. The box will be long enough to allow a sidewalk crossing on the north side of the street. The guardrail will be reused and/or replaced to match the remaining guardrail, Barth added.

Should another flood occur and this culvert become clogged, Barth said, the overflow should help keep such floods relatively contained in the creek corridor.

Rifle City Council approved the use of $80,000 in street improvement contingency funds, along with other capital improvement funds, for the project. Barth said the timeline is to order materials in August, with construction in late September.

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The Post Independent Updated Aug 8, 2012 05:44PM Published Aug 8, 2012 05:42PM Copyright 2012 The Post Independent. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.