Good practical observations and advice on how to stay in compliance with environmental SWPPP requirements in Texas:

As I walk across the property with one of my clients, I point to a patch of exposed soil and say, “That may be a problem.”  In most cases, the client comes back with a look of disbelief, scoffs, or utters some form of profanity prior to yelling, “It’s just dirt!!”  Does this sound familiar?

One of the most common and confusing issues in storm water compliance is the regulation of exposed soil or earth.  In fact, an entire section of regulation—Construction Storm Water Permitting—is devoted to ensuring that disturbed soils and earth from construction sites do not cause storm water pollution.  However, I digress…I will leave construction storm water to be discussed on another day.  Instead, I will focus on sites that have no construction occurring yet still have areas of exposed soil.  This information applies to businesses that fall under standard industrial classification codes (SICs) specified in the Texas Multi Sector General Permit (see pages 17-24).

The most common pollutant released into storm water is called total suspended solids (TSS), also known as dirt, soil, silt, sediment, particulate matter, murkiness, mud, turbidity, chocolate milk, etc.  Although we will focus on dirt here, it is important to note that TSS may also be caused by dusts, debris, trash, leaves, and grass clippings originating from grounds or production processes.  TSS is released into storm water runoff anywhere exposed earth and storm water is present.  A large portion of TSS is caused when moving water splashes on or scours an exposed soil surface.  This process, often referred to as erosion, increases with larger flows, higher velocities, and steeper slopes.  A good example is shown below:

Photo by: www.maine.gov

Erosion and subsequent TSS generation may be attenuated by use of structural controls such as velocity dissipation devices (silt fences, tombstones, splash blocks, hay bales, filter socks, terraced slopes), detention and filtration basins, stabilizing surfaces (vegetation, gravel) and reduction in storm water flow (rainwater collection, diversion, enhanced permeation e.g. porous pavement).  It may also be reduced through best management practices (BMPs) such as covering areas of exposed soil with a tarp, disposing of or stabilizing excess soil, and minimizing disturbances to vegetation.

Unfortunately, many businesses are unaware of the need for “dirt” management (let alone storm water regulations) and have assembled their operations without regard for it.  One recent example is that most of one of my client’s property is either dirt or graveled, which may give way to TSS during storm events.  When questioned about the issue of erosion/TSS, the client became concerned that his business would have to pave all of these surfaces, which would be very expensive.  After doing some research, I determined that the following observations should be made:

  • During a qualifying storm water event (where there is discharge to the outfalls), examine the site storm water flows and outfalls during rainfall events for visible TSS.
  • After rainfall events and water has had time to drain, examine low-lying areas for buildup of silt/sediment.

If the storm water is not relatively clear (substantial TSS is present) or silt and sediment are deposited in low-lying areas, it is likely that a business is not in compliance and would receive a violation during a regulatory inspection.  This of course, implies that the inspector would be there during or shortly after a rainfall event, which in Texas, are odds that many businesses are willing to bet against.  However, if you are concerned about compliance and the quality of receiving streams, the follow actions should be taken to achieve compliance:

  • Implement inexpensive BMPs to minimize TSS generated during storm events.
  • Install inexpensive velocity dissipation/filtration devices such as silt fencing, hay bales, or filter socks that will slow down and catch TSS before it is discharged to outfalls.
  • Set up preventive maintenance (PM) to periodically clean out the accumulated TSS from these areas and to replace or repair any control devices that are broken or malfunctioning.
  • Keep records of these efforts in the Storm Water Pollution Prevention Plan, so potential investigators/auditors can see that the business is aware of the problem and taking action to resolve it.

Prevention, collection, and disposition of storm water “dirt” may be a trial and error process, so it literally pays to be patient and persistent, especially when you get an investigator that likes to give out multiple-thousand dollar parking tickets for lesser storm water offenses.

As for my client, fortunately the site is located on flat terrain, so generation of TSS is not an issue.  How’s that for solid compliance?

Mike Frisch, PhD, PE, CEM

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