Sunday, March 8, 2009

Turbidity Effluent Limits For Industrial - MS4 Stormwater Permits

US EPA has recently proposed effluent limits on turbidity for stormwater discharges from larger construction sites.

[Read more about Construction Stormwater Discharge Effluent Limits].

This has prompted many industrial and municipal stormwater permitees to speculate on whether or not similar effluent limits will be proposed under Multi-sector General Permits (MSGP) or Municipal Separate Storm Sewer System ("MS4") permits.

The simple answer is that almost anything is possible.

However, the establishment of construction site effluent limits has some important differences that may not be easily transferred to effluent limits for industrial or MS4 permits. Some of these differences include:

  1. Effluent limits proposed for larger construction sites are based on a specific stormwater treatment method that is added to the stormwater treatment pond already required for smaller sites. Without the requirement to install a pond, the additional treatment may not be economically-feasible. Unless specific structural BMPs, like ponds, are required for industrial or MS4 dischargers, it would be difficult to translate the construction site effluent limits. Because of the nature of industrial and MS4 discharges, requiring treatment ponds would be difficult.

  2. In general, the types of activities and stormwater handling practices associated with industrial and MS4 discharges will be significantly broader compared to construction sites. Therefore, again, translating the proposed effluent limits to industrial and MS4 dischargers would be difficult.

Given these factors, it may be difficult to demonstrate that similar Best Available Technology used to calculate effluent limits for construction site discharges could be equally applied to other types of discharges.

Caltha LLP provides expert consulting services to public and private sector clients nationwide to address water quality standards, wastewater permitting and assessing potential impacts of chemicals in the aquatic environment.

For more information on Stormwater Permitting & Compliance Services, go to:
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