Why is Flat Branch Creek Green?

Flat Branch Creek dyed green.  Photo courtesy of Benjamin Zach with Missourian

It's NOT anti-freeze.  The City uses dye testing to investigate sanitary sewers.  

So why is green dye in our creek?  

One of the biggest problems with our sanitary sewer system is too much stormwater finds it's way in.  This is a problem because the sanitary sewer system and wastewater treatment plant are not designed to handle stormwater - they are separate systems.  (See  Separate vs. Combined)  When too much stormwater gets into the sanitary sewer system, it can cause the lids of manholes to come off and stormwater mixed with raw sewage can flow onto the ground and into our creeks.  This is a health hazard. 

The City of Columbia has developed an extensive I&I Program.  I&I= Inflow and Infiltration.  The purpose of the I&I Program is to investigate how stormwater is entering the sanitary sewer system and prevent it from happening.  Some of the investigation methods include camera inspection of sewer pipes, visual inspection, smoke testing and dye testing.

Smoke testing fills the sanitary sewer line with a harmless, non-toxic smoke (think theater productions) and looks for places where the smoke comes out.  The smoke should come out of the vent stack for houses.  Smoke should not come out of the ground, downspouts and gutters, or storm drainage structures.  When it does, we do further investigations.

The next step when smoke comes out of storm drainage structures is dye flood testing.  We attempt to flood the storm drainage structure in question with water,  and then dye the water with a non-toxic coloring.  We do a camera inspection of the sanitary sewer line to see where the dyed water is getting into the sanitary system.  From this information we can determine what kind of fix the sanitary sewer system needs. 

Technician dying water going into a storm inlet.

Dyed water coming out of a storm inlet

 Once the camera inspection is complete, the dyed water in the storm system is released and goes downstream.  All of our current dye flood testing is taking place in the Flat Branch watershed.  So the Flat Branch may be bright green for a few days.  This will eventually make it's way to Hinkson Creek and Perche Creek, but will become diluted along the way.

By investigating stormwater leaks into the sanitary sewer system, we can prioritize improvements.  Improvements to our sanitary sewer system will reduce the occurrence of wastewater in our streams.

So next time you see a little of bit of green in the stream, it might be anti-freeze - report it!  But if it is a lot, the City is dye testing to figure out how to make our streams cleaner!

Photos from the Missourian

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.

Separate vs. Combined

On a recent site visit to a storm drainage system, I was met by a property owner. While we were talking, I looked down into the curb inlet and noticed multiple piles of dog waste. About that time, I noticed the property owner had a large dog. I asked the property owner if they knew that storm water going into that curb inlet went directly to the water way across the street and into Bear Creek about ½ mile away. “Really? I had no idea.”

Columbia has SEPARATE storm water and sanitary sewer systems.

All storm water runoff that flows into curb inlets travels through a few pipes, long or short, and discharges to the closest water way. All water ways in Columbia end up in the Missouri River by way of one of our creeks such as Hinkson, Flat Branch, Bear Creek, Grindstone, Bonne Femme. Therefore, the pet waste was going directly to the creek without treatment!

All waste water from the sanitary sewer system goes to the waste water treatment plant (WWTP). Therefore all toilets, sinks and baths from your home and any drains inside a building travel through miles of pipe to go to the WWTP. Processes at the WWTP remove all solid waste and pollutants from the sewage. The WWTP further filters the treated wastewater through an extensive wetland system and then discharges to Perche Creek right by the Missouri River. The removed waste products and pollutants are recycled and disposed properly.

Some towns and cities like Kansas City and a part of downtown St. Louis have a COMBINED storm water and sanitary sewer system. These systems are typically under a consent decree by the EPA to separate their system or eliminate raw sewage from discharging to creeks and rivers during storm water runoff events.

Columbia officials in the early half of the 1900’s saw the benefits of having SEPARATE storm water and sanitary sewer systems. Outhouses used to dump directly to the Flat Branch (photo above), now Columbia has an extensive sanitary sewer system throughout the City that takes our raw sewage to the WWTP.

Since we do have a SEPARATE system, everything that goes into the storm drain goes right to our creeks and waterways. If you need ideas on how to dispose of various items, check out the City website and search “Go Stormwater”.

SO PLEASE KEEP PET WASTE, PAINT, OIL, LEAVES, BRANCHES, GRASS CUTTINGS AND ALL OTHER TRASH OUT OF OUR STORM DRAINS AND WATERWAYS!

Check it out!  Proper Pet Waste Disposal Video

Help to keep our local waterways clean and healthy!