Stormwater I/I: Could It Be Making Your Flows Toxic?

Toxic stormwater?

One of the things that keeps CCTV pipeline inspectors busiest is identifying sources of inflow and infiltration (I/I) into stormwater conveyance systems, whether they be the old-fashioned combined storm/sanitary systems, or today’s separate pipelines.

Stormwater drainage systems are designed to move rainwater away from areas where they could cause backups and flooding. The system may include underground pipes, ditches, streams and creeks. Flows enter the system from a variety of inputs, including roof drains, foundation drains, lawn drains, and street drains/catch basins. The flows are discharged into nearby waterways, lakes and/or the ocean, depending on location.

Ideally, this runoff is simply rainwater moving from one place to another, but the reality is that it frequently (maybe even usually) picks up other liquids and even small solid materials as it flows along. What it picks up will depend on how much rain falls and how fast the resultant runoff is flowing: Longer and higher intensity rainfalls will generate faster runoffs, which produce more hydraulic power to lift and carry heavier objects.

Sources of toxic stormwater

As discussed in our previous post, some of the places where runoff can pick up toxic materials include:

  • industrial and manufacturing facilities –gas, oil and other petroleum products and processing byproducts
  • municipal and other government facilities – chemicals, petroleum products and any number of toxic substances
  • agricultural facilities –animal waste and fertilizer chemicals
  • commercial locations – cleaning solutions, lubricants and other chemicals

And these don’t cover plain old roadways and parking lots, which can accumulate many of the same nasty stuff, plus pesticides and herbicides.

Aside from the obvious dangers to the environment from polluted water, toxic I/I could also be causing chemical wear and damage to stormwater pipelines. Of course, there are BMPs that can be used on the other end, such as filtration basins to capture non-point-source pollution, but they’re not always wholly effective and don’t solve the problem of what it might be doing to your pipes. And it’s clear this problem will only get worse as more development happens and there are more vehicles on the road.

  • What do you think is going to happen with this issue—will regulators begin addressing it?
  • Are you concerned about toxic stormwater?
  • Are you monitoring the health of your stormwater flows?
  • If so, how are you identifying and measuring pollutants, and what are you doing about capturing and eliminating them?

We’d love to hear from you.