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Home / News / Newsfeed / Enforceable Storm Water Effluent Standards

Prepared for Enforceable Storm Water Effluent Standards?

January 1, 2021
orange sign in front of water body that reads "Caution end of storm drain"
California’s “Industrial General Permit” (IGP), which regulates pollutants in storm water discharges from many industrial facilities statewide, was amended effective July 1, 2020. The changes have particular implications for dischargers – mainly in Southern California – that discharge to “impaired” water bodies or watersheds. For a number of these watersheds, new regulatory levels were established that significantly increase the risk of being found in violation of the IGP.

Because these new levels were put in place only for a minority of California water bodies/watersheds, it is critical to first understand whether you will be affected by them. This requires reviewing the list of affected watersheds in Attachment E of the amended IGP. Attachment E establishes for the first time (and again, only for specified water bodies/watersheds) Numeric Effluent Limits (NELs). Unlike the Numeric Action Levels (NALs) established in the IGP, the new NELs institute pollutant concentration limits that, when exceeded, constitute a permit violation. Facilities will face potential fines for such violations and will be required to take actions as necessary to prevent future exceedances. This presents a real risk to facilities operating in watersheds where NELs are, or will be, established.

To avoid an avalanche of effluent violations, the State Water Resources Control Board (SWRCB) did two things. First, Attachment I of the amended IGP describes a process by which dischargers can become exempt from the NELs by implementing an on-site or off-site water management program that diverts storm water to one of several alternative uses. These “compliance options” can include infiltration, on-site storm water use, or even discharge to a sanitary sewer. The challenge, however, is that the design storm standard for these options is quite high. Not only is diversion of the 85th percentile 24-hour precipitation event required, but a 24-hour drawdown time is also specified.

Knowing that these compliance options may require significant time and money to design and construct, the State has promoted the use of Time Schedule Orders (TSOs). In this context, a TSO establishes an enforceable agreement between the discharger and Regional Water Quality Control Board to implement one of the compliance options in IGP Attachment I within a specified schedule, in exchange for the Regional Board agreeing not to take enforcement action for NEL exceedances during the design and construction period.

There is a time challenge, however. As a legally enforceable document, a TSO must be crafted carefully by both parties. Recent experience is showing that TSOs requested in mid-2020 are only now being finalized, owing to Regional Board resource availability, pandemic effects, and the need for each TSO to receive formal approval by the Regional Board executive. With the 2020-2021 winter rain season already upon us, there may be no time to lose if a discharger is hoping to use a TSO to address NEL exceedances occurring this winter.


Yorke Engineering has assisted over 1,800 industrial and government facilities with air, waste, and water regulatory compliance and permitting throughout California. Our staff are very experienced and specialized in assisting customers with their specific EH&S needs related to the local air districts, CARB, DTSC, Water Boards, CUPAs, U.S. EPA, and other regulatory agencies. Learn More about how we can help you here: Water | Yorke Engineering, LLC (yorkeengr.com).

Main Office:

31726 Rancho Viejo Rd. Suite 218
San Juan Capistrano, CA 92675

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