Crews began work Monday to remove more than 18,000 cubic yards of sediment from the floodplain of Fourmile Canyon Creek in north Boulder where the creek flows north of Violet Avenue.

Boulder residents can expect to see heavy equipment in and along all 14 of the city's major drainageways over the next several months as the city tries to return those waterways to pre-flood conditions by the end of spring.

Boulder drainageways

Flood repair work began Monday on Fourmile Canyon Creek and is scheduled to begin next Monday in Eben G. Fine Park along Boulder Creek.

Other drainageways scheduled for flood remediation are South Boulder Creek, Dry Creek and Viele Channel, Goose Creek, Twomile Canyon Creek, Wonderland Creek, Skunk Creek, King's Gulch and Bluebell, Gregory Creek (culverts only), Sunshine Creek, Bear Canyon Creek and Elmer's Twomile Creek.

Info: BoulderFloodInfo.net

Fourmile Canyon Creek and Boulder Creek are the top priorities because of the sheer amount of sediment in those drainageways and the heavy use Boulder Creek gets from tubers during the spring run-off.

Crews will start to remove sediment and debris from Eben G. Fine Park at the mouth of Boulder Canyon next Monday.

Anne Noble, Boulder's flood and greenways engineering coordinator, said the amount of sediment along Fourmile Canyon Creek could reduce the conveyance capacity of the floodplain, meaning that if the sandy material is not removed, even much smaller rain events than September's floods could produce higher water levels than they otherwise would.

Fourmile Canyon Creek jumped its banks in September and sent water coursing through the neighborhoods to the south of its usual channel.

After the flood, public works crews repeatedly walked all the drainageways as the waters receded and made note of sediment, debris, damage to structures that help control flood waters, and high water levels, Noble said.

That information was laid over maps of the city's drainageways to guide the repair work.

Boulder's work is limited just to its property and easements because the Federal Emergency Management Agency will not reimburse the city for work on private property or for other jurisdictions, Noble said.

The city is coordinating with the Colorado Department of Transportation and the Urban Drainage and Flood Control District to remove sediment and clear culverts that are not on city property or city rights-of-way, including on University of Colorado property.

In some cases, such as Gregory Canyon Creek, the city will only be clearing culverts because most of the drainageway is private property.

Noble said the city hopes private property owners also remove sediment that could affect the conveyance zone in future floods.

On Monday afternoon, an excavator piled sand into enormous mounds on the undeveloped Violet Park site between the creek and the road, and a steady stream of dump trucks took the sand from the creek's flood plain to the Cemex plant in Lyons, where it will be used to fill in an old gravel pit.

Monitors at the creek site and at the gravel pit watch the sediment "from cradle to grave," Noble said. This ensures it is going where it is supposed to go and that the city will get as much FEMA reimbursement as possible.

Boulder flood. Derek Ornelas, left, and Jose Louis Campos, of Red Line Pipeline, work to remove flood debris from Fourmile Canyon Creek on Monday near the intersection of Broadway and Violet Avenue in Boulder.
Derek Ornelas, left, and Jose Louis Campos, of Red Line Pipeline, work to remove flood debris from Fourmile Canyon Creek on Monday near the intersection of Broadway and Violet Avenue in Boulder. For more photos of the cleanup, visit dailycamera.com, (Jeremy Papasso / Daily Camera)

Noble said sending the sediment where it is wanted will save the city money compared to dumping it into a landfill.

Next week, Boulder will start accepting bids to repair the bike path and flood control structures at Violet Crossing, where Fourmile Canyon Creek passes under Broadway.

These projects are only to return the drainageways to their pre-flood conditions and don't include any mitigation efforts to address future flooding, Noble said.

However, the city does have plans with the Urban Drainage and Flood Control to create a sediment pond along Fourmile, near Rosewood and Broadway, that should capture sediment in future large rain events, though it wouldn't protect residents from something at the magnitude of September's floods.

The total project cost will depend on the volume of sediment that is ultimately removed from the drainageways, Noble said.

Contact Camera Staff Writer Erica Meltzer at 303-473-1355, meltzere@dailycamera.com or twitter.com/meltzere.