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Understanding Stormwater Discharge Compliance

Understanding Stormwater Discharge Compliance

Section 402 (p) of the Federal Clean Water Act requires certain industries to obtain a National Pollutant Discharge Elimination System (NPDES) permit. Specifically, industries that are categorized under Standard Industrial Classification (SIC) codes and those whose stormwater is discharged into surface water or a storm drain system are required to have a permit. In California, these industrial facilities can achieve compliance by applying for coverage under California’s General Permit for Stormwater Discharges Associated with Industrial Activities (Industrial General Permit), or by applying for an individual NPDES Permit.

With the upcoming rainy season, all SoCal Industrial Storm Water General Permit Dischargers should understand the requirements for compliance during upcoming storms. The following are criteria that you should consider to ensure you stay in compliance:

Remember to note your facility operating hours in your Stormwater Pollution Prevention Plan – you may be required to collect a sample during these hours regardless if the discharge started during your facility’s scheduled operating hours or not.

Be sure to maintain your best management practices to reduce/prevent exposure of stormwater discharge to industrial areas. These sampling events are intended to represent all industrial stormwater discharge that occurs from your facility. You can prepare your facility by either covering or moving any objects indoors that could expose stormwater to pollutants or industrial substances.

If there is rain predicted to occur within your scheduled facility operating hours, make sure to calibrate any tools needed for sampling (ex. pH pens). Acceptable field pH levels are those between 6 to 9, and the pH MUST be taken within 15 minutes of collecting the stormwater sample. Samples from each discharge location MUST also be collected within 4 hours of the start of the facility’s stormwater discharge OR at the start of facility operations if the storm occurred within a previous 12-hour period (ex. if the storm occurred the night before and your facility opens during the day).

Please regularly check your local forecast or rain gauge before sampling to ensure the start of the discharge began within the 4-hour or 12-hour window. If it rains but the discharge stops at any time, then the Qualifying Storm Event is over. The next Qualifying Storm Event can be sampled after 48 hours.

If you have any questions or require assistance regarding this matter, please contact us for EHS compliance support.

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