EROSION CONTROL/Retaining walls keep canal clear in Greeley, Colo.

In January, Greeley, Colo., completed a $20,200 erosion-control project on a portion of an irrigation canal in the city’s downtown. The city’s Streets Division constructed 400-foot-long retaining walls of concrete rip rap on each side of the canal.

The city needed to build the walls because erosion was diminishing the size of the residential and commercial lots that abut the canal, says Jerry Pickett, superintendent of the Streets Division, which also oversees drainage efforts in the city. The recently completed project is part of an ongoing city effort, launched in 1994, to improve the flow of the creek and to mitigate the erosion caused by it.

Approximately six miles of the 13-mile-long channel are located within the city limits of Greeley. Both the city and Greeley Irrigation, a locally based company, own the more-than-130-year-old canal. In the early 1960s, Greeley began diverting stormwater run-off into the canal, so it took responsibility for maintaining the channel within city limits.

For years, the city haphazardly lined portions of the canal’s bank with irregularly shaped concrete pieces to contain the creek and to stall erosion. However, that technique did not prove suitably effective, Pickett says. In 1994, concerned about the upkeep of the canal, the city initiated a more intensive maintenance program aimed at corralling erosion and creating better water flow.

Each year, the city identifies stretches of the canal that need erosion control and builds retaining walls. All of the work is done in the winter months, because the canal is empty from November until April 15. Since the program’s inception, the city has installed more than 7,400 linear feet of rip rap retaining walls.

During each project, the city follows the same process. First, old concrete along the shoreline is removed and, if necessary, the channel is widened to a minimum of 12 feet. Then, excess silt is removed from the channel’s bottom to improve water flow. After the silt is removed, the retaining walls are built. The rip rap used for the walls is recycled concrete that was removed during construction projects in the city. Once the retaining walls are in place, native grasses are planted on top of them.

Besides controlling erosion, the retaining walls make the refurbished canal more aesthetically pleasing than before, Pickett says. “You would be amazed at how many people call and say, ‘That really looks nice,’” he says.

While Pickett is proud of the job done so far, he acknowledges that it will take a long time for the city to build walls along the six miles of the canal in Greeley. “We’re not ever going to see it done in our lifetime. I mean, I won’t,” he says. “But, hopefully, the city will continue the program, and sooner or later, it will be done all the way through the city.”