Happy New Year: Cleaning Out Debris

No, we're not talking your closets or your basement.  It's time to clean out sediment and debris that is clogging culverts and bridges around town.

Part of the natural process for a stream is to "pick up" sediment from one location and "drop off" sediment in another location.  A favorite "drop off" spot is culverts and bridges where water slows down, allowing heavier particles (rock, pebbles, sand, soil) to settle out.

Grass growing on sediment clogging a culvert under Nifong.

When sediment fills up in front of culverts and bridges, it does not allow stormwater runoff from larger rainstorms to flow through as easily.  Sometimes, this can cause street flooding during very heavy rainfall events.

Sediment inside a culvert reducing capacity for stormwater runoff.

The Street and Stormwater Maintenance division of Public Works is responsible for maintenance of stormwater facilities.  A crew of four operators plus a supervisor is paid from the stormwater utility to be responsible for maintenance of ALL inlets, pipes and culverts in City right-of-way or drainage easements. 

The stormwater utility crew is currently removing sediment and debris from the larger culverts and bridges around town.

Culvert under Nifong, recently cleaned by stormwater utility crew.

Stormwater facilities are designed to keep our roadways safe and passable for emergency vehicles during most rainfall events.  The Public Works stormwater utility crew works year round to keep Columbia's stormwater facilities in good working order.  Much of Columbia's stormwater infrastructure is reaching the end of its life expectancy, so the stormwater utility crew is very busy repairing and replacing stormwater structures around town.  Meanwhile, as Columbia grows, there are more and more culverts and bridges to be kept clean.

Your safety is important to us!  If you know of a stormwater structure that is a hazard and needs some attention, please contact us at (573) 874-6289 or pubw@GoColumbiaMO.com.

Meanwhile, if you see the Public Works stormwater utility crew out cleaning a culvert near your home or fixing a broken storm inlet, thank them for keeping you and your neighbors safe!

Bear Creek Bank Stabilization Project

In an effort to protect existing sanitary sewer infrastructure, Public Works is stabilizing portions of the streambank on Bear Creek along the Bear Creek Trail.  When sewer lines are undermined by eroding banks, joints can sag causing waste to leak into the creek.  By maintaining and protecting the sewer lines, the City can prevent waste from entering our creeks and waterways.

The existing banks were six to ten feet tall, near vertical, continuing to erode and beginning to expose vital sanitary sewer infrastructure.  The City contracted with Plan B Development to construct a bank stabilization project. A product called A-Jacks was used to stabilize the toe (or bottom) of the slope.  These armour units are available in many sizes.  A smaller size was chosen for this project so that it could be installed by a person reducing the need for large machinery.  Most alternative solutions would require multiple concrete trucks or dump trucks full of rock to travel up and down the trail.  By using A-Jacks, the contractor could minimize the use of large construction equipment and minimize damage to the Bear Creek Trail.


A-Jacks fit together and interlock.

The A-Jacks interlock, creating a solid foundation for the streambank.  The streambank is then sloped away from the creek and will be re-vegetated.  The roots of vegetation will help to keep the soil from eroding.  A special fabric is installed as an interim erosion control measure until the vegetation is established.


Sloping banks with A-Jacks at the bottom. 
Erosion control fabric and vegetation will stablize the upper portion of the slope.

Extra A-Jacks were used at this pipe outlet.  They are easy to install and will slow the water and prevent erosion. 

A-Jacks at pipe outlet with erosion control fabric on the adjacent bank.

Not only will this bank stabilization project protect our sanitary sewer infrastructure, but it will stablize a portion of Bear Creek and prevent continued erosion.  All these measures keep our creeks and waterways clean.

Bourn Avenue: Infrastructure Failure

 About a month ago, a portion of Bourn Avenue failed.  Some would blame it on the heavy trucks working at the intersection of Broadway and Stadium, using Bourn as an access.  However, failure had already occurred, the trucks were merely a catalyst to make the failure evident.

As you can see from the above photo, there is a gap between two pipes.  When curb and gutter was placed on Bourn Avenue many, many years ago, the construction crew placed a concrete pipe at the end of a metal pipe.  The gap between the two pipes was not sealed.  During storm events, the gap allowed soil to be drawn from the outside of the pipe through the storm system and to a nearby drainage way.  After time, a large void developed outside the pipe and under the pavement.

In the photo above, you can still see a small part of the void under the pavement.

Eventually, the void became too great and the pavement could not bridge the gap and failed.  The Public Works Storm Water Operations crew has spent many hours replacing the failed system including pipe, inlets and street pavement.  The photo below shows some of the completed street repair.

Storm water pipes in Columbia are beginning to face a crisis.  Many pipes installed in the 1950’s and 1960’s are at the end of their life span.  The last two years have had record rainfalls, which can exacerbate pipe failures.   We will continue to see pipe failures across town.