Monday, February 27, 2012

319 Grant - Step Pools Under Construction

Time lapse video of step pool construction. Note:  inactive days are non-work days (weekends).

The City of Columbia Water Department has been "stepping" up their work.  Since mid-January, the Water Department has had a crew of two or three operators working on construction of over 18 "steps" and "pools" to replace an incised channel.

Looking upstream, incised and eroding channel is approximately three feet deep.
The channel behind the Columbia Water & Light Pole Yard on Ashley Street carries runoff from the City Power Plant, the Public Works Maintenance Operations facility (Grissum), parts of Ashley Street, adjacent private businesses and the pole yard.  Approximately 300 feet of channel will be retrofit with a system of steps and pools that will filter, infiltrate and slow down runoff through the channel.  The final system of steps and pools will filter out pollution and reduce runoff from the sites.  These measures help improve the health and water quality of Bear Creek.

Work begins with clearing underbrush to access the downstream part of the channel.

Looking downstream, the Forestry Division of the Parks & Recreation Department clears the underbrush and Water Department  prepares access to the site.

Looking upstream, access is complete and step pool construction can begin.

Once the site has been cleared (including the invasive Honeysuckle), an access was installed so equipment could reach the downstream end of the project.  Flow has been temporarily diverted to an existing roadside channel along Interstate 70.  Erosion and sediment control measures are installed.  Construction of the step pools can begin.

Looking downstream, various sizes of rock are used to install the step pools.
Pools are constructed to hold water to allow the runoff to infiltrate to the constructed sand layer below the rock pools.  The layers of rock and sand along with future plants will remove pollutants from the runoff.

Looking downstream, pools are stepping down to the right.
The "step" between the pools reduces the erosive potential of the water.  The "step" is constructed of large rock shaped like a check dam to slow the flow of water and direct it toward the center of the channel.  Although the pools look stark now, restoration of the stream channel will be complete when native plants are installed to keep the banks stable, help remove pollutants from runoff and provide a natural aesthetic.

Many steps and pools are yet to be constructed over the next month or so.  Meanwhile, shredded mulch is placed to prevent surface erosion.  Planting will take place this spring.

US Environmental Protection Agency Region 7, through the Missouri Department of Natural Resources, has provided partial funding for this project under Section 319 of the Clean Water Act. (G11-NPS-12).