Tuesday, January 20, 2009

What Are Non Stormwater Discharges and Illicit Discharges?

Stormwater discharge permits include sections discussing the prohibition on non stormwater discharges. Municipal stormwater permits (MS4 permits) also refer to “illicit discharges”; illicit discharges are equivalent to non stormwater discharges. The municipality must develop programs to detect illicit discharges and to eliminate them from being discharged to their system.

Non stormwater discharges are any waste or wastewater discharge through a stormwater outfall that is not stormwater. Non stormwater discharges are not limited to piped discharge of wastewater; discharges could be infrequent or even one-time discharges. Examples of periodic or infrequent discharges include washing of equipment or pavement, blowdown from cooling towers, condensation from chillers or compressors. Non stormwater discharges can be small discharges of water, such as dumping floor scrubber water in a parking lot.

The Clean Water Act does not recognize a “deminimis” discharge – all non stormwater discharge is prohibited, regardless of how small. [Read more about connection between non stormwater discharge prohibition and the Clean Water Act]

The obligation on the discharger under most State stormwater permits is to 1) conduct and document an assessment of potential non stormwater discharges at the permitted facility, and 2) either eliminate the discharge, or to obtain a separate discharge permit that allows the discharge. Permits will also contain a list of allowable non stormwater discharges, which is a small subset of non stormwater discharges that can be discharged without a separate permit, if certain conditions are met.

Caltha LLP assists permitted facilities in conducting non stormwater discharge assessments and determining preferred options for the alternate disposal of non stormwater discharges. Click here to request further information on Stormwater and SWPPP Services.

For further information contact Caltha LLP at
Caltha LLP Website

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