Williams Canyon Maintenance

Overview

We have placed a great deal of importance on flood mitigation and resiliency in Manitou Springs. Part of this preparation is in regards to Williams Canyon Maintenance that takes place periodically throughout every year. Williams Canyon was the waterway that allowed for flooding in 2013, and the City understands the importance of maintenance in this area.

Maintenance

Tighten and Clear Debris Nets

Debris nets are located at three locations along the channel. These nets capture sediment and debris washed down from the upper watershed. Clearing them regularly will allow them to capture new debris without overtopping and passing the debris further down the channel where it is more difficult to remove. Tightening the anchors of the nets will prevent them from sagging over time.

Frequency: 2x per year (April & November)

Clearing the Sedimentation Basin

The sedimentation basin is located at the top of Canon Avenue just south of the Highway 24 overpass. Its purpose is to provide an area where stormwater flow can slow and drop sediment. In doing so, the basin bottom fills with sediment. This sediment must be removed periodically to allow for continued functionality. In addition to the flows entering the basin from the channel, a culvert also discharges into the basin on the north‐east side. The inlet for this culvert is located across the parking lot at the toe of the Highway 24 fill slope. This inlet should also be cleared as part of this work.

Frequency: 2x per year (April & November)

Clearing the Trickle Channels

Trickle channels are located along the outside edge of the main channel walls on both the upper and lower portions of the main channel. These trickle channels convey minor flows off the roadways and into inlets which discharge into the main channel. Maintenance of both the trickle channels and the inlets are included in this work.

Frequency: As appropriate following storm events.

Clearing Infiltration Block Areas

Infiltration block areas exist at five locations along the channel. These areas allow surface water to pass through the channel bottom into the ground. They periodically become covered with sediment which should be removed to allow water to pass through.

Frequency: 2x per year (April & November)

Inspection of Drop Structure Underdrains

Drop structures are located at four locations along the channel as noted on Figure 1. These drop structures have PVC underdrains below them which allow water pressure to be released through them and allow water to flow through them into the ground. These underdrains must be clear of debris to function.

Frequency: 2x per year (April & November)

Clearing Channel Bottom

A grouted boulder channel bottom runs the entire length of the improvements. This channel bottom collects sediment and debris. This sediment and debris must be removed periodically to allow for continued functionality.

Frequency: Annually

Inspection of Shotcrete Walls

Shotcrete walls are located west of the sedimentation basin. These walls prevent the natural soil slopes from spilling into the basin.

Frequency: 2x per year (April & November)

Clearing Trash Rack

A trash rack is located and the bottom of the improvements where the channel meets Canon Avenue. The trash rack covers the opening to a box culvert which carries flows beneath Canon Avenue which eventually discharges into Fountain Creek. The trash rack must be clear for the culvert to receive flows unobstructed.

Frequency: 2x per year (April & November)