The Underlying Reasons Behind Sanitary Sewer Overflows

When a sanitary sewer overflow (SSO) occurs, the natural reaction is to repair it as quickly as possible and stop untreated wastewater from being discharged into rivers, lakes, streams and streets. But once the immediate problem is fixed, it's important to dig a little deeper into the reasons it happened.

Why was the pipe blocked?  Why did the equipment fail?  Did this happen before – and is there a chance it will happen again? Are you ready to mitigate the damage if another SSO occurs?

To answer these questions, it helps to have some basic facts at your fingertips so you know where and how to start your SSO investigation. Here are a few key pieces of information from our Fact Sheet that can help you quit chasing one quick fix after another and, instead, address the root causes to avoid SSOs altogether.

The Top Three Reasons SSOs Happen:

  • 50 percent are caused by pipe blockages. The most common cause of blockages is non-compostable wipes, cloths, or fat, oil and grease substances introduced into the piping system by users. Mother Nature isn't any better. If there are any cracks in your pipes caused by settling, freeze/thaw cycles or other similar movement, she'll make sure roots and dirt creep in to create blockages.

  • 25 percent are caused by weather infiltration and inflow. During heavy rainfall, large snowmelts and ground saturation, your system is at risk of being infiltrated by an earth-and-water mix coming in through cracks and breaks in the pipes. Also, if there is any improper routing of downspouts into the sewage system, it can cause weather-related overflows.
     
  • 25 percent are caused by mechanical/electrical failures. The culprit here can be aging equipment or lightning strikes and power outages that put the pump station out of commission.

Fortunately, routine cleaning and maintenance can help prevent many SSOs. Cleaning will remove unwanted materials and uncover problem areas that indicate cracked or broken sections of your piping system in need of repair. Regular maintenance will help ensure your equipment is part of the solution – not part of the problem.

However, no system is fail-proof. Even the best-designed and maintained system can expect five spills a year for every 100 miles of piping. The best way to protect your community is by planning ahead. Creating a Contingency Plan with your pumping provider allows you to rest easy knowing that you are taking action to mitigate damage from those SSOs that can't be prevented. 

by Michael J. Delzingaro
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