4 The record articles

Cooling Water Intake Structures and NPDES – No One is Exempt!

Posted: December 8th, 2021

Authors: Paul H. 

If you have a facility that uses cooling water and you are pursuing a National Pollutant Discharge Elimination System (NPDES) industrial wastewater permit renewal, you know the typical questions applicable to cooling water, specifically:

1) Does the Facility use at least 25% of the water it withdraws for cooling purposes and

2) Does the Facility have an intake flow greater than 2 million gallons per day (MGD)?

If you answer NO to either of these questions and think you’re done with the Clean Water Act (CWA) §316(b) component of the NPDES application process, you might be mistaken.  We have seen an increase in scrutiny about cooling water intake structures (CWIS) during the permit application and review process despite being exempt from the above threshold criteria.  The additional scrutiny has included information requests about the physical aspects of the CWISs and evidence that adverse environmental impacts are being minimized, including performance of biological monitoring.  Read on…

In accordance with 40 CFR §125.81(a) (New Facilities) and §125.91(a) (Existing Facilities), to be subject to the CWIS requirements of CWA §316(b), both the 25% and the 2 MGD must be exceeded, and if not, the presumption has been that nothing further is required.  However, for existing facilities, 40 §CFR 125.90(b) states:

Cooling water intake structures not subject to [the threshold] requirements…must meet requirements under section 316(b) of the CWA established by the Director on a case-by-case, best professional judgment (BPJ) basis.”  Parallel regulations for new facilities (40 CFR 125.80(c)) follow the same discretionary BPJ theme.

So, who decides which cases get the additional BPJ scrutiny and the rationale and frequency of this additional scrutiny?  The additional information is being requested to evaluate if the Best Technology Available (BTA) is being implemented to minimize adverse environmental impacts.  The ultimate driver for the additional inquiries is likely the participation of the “Services” (National Marine Fisheries Service and the U.S. Fish and Wildlife Service) during the permit review process.  It is unclear, however, whether the Services are participating under their authority to evaluate if “take” of threatened and endangered species (Endangered Species Act, 16 U.S.C. 1532(19)) is occurring, or if they are taking a broader review of all species regardless of status, taxa or associated critical habitat.  Keep in mind that the CWA §316(b) regulation only became effective October 14, 2014, and generally only applies to permits that expire after July 14, 2018.  Therefore, this timeline, compounded by the normal five-year NPDES renewal cycle, is perhaps the real reason for why we are just now starting to see the ripple of CWA §316(b) on the regulated community.

Takeaway: If you have a CWIS and are embarking on an NPDES industrial wastewater renewal, be prepared to provide additional physical and biological details during the application and draft permit review process, regardless of your status relative to the threshold criteria in 40 CFR §125.91(a).

ALL4 will continue to monitor this regulatory item and will report back periodically regarding frequency and impact on NPDES industrial wastewater permittees. If you have any questions in the interim, please reach out to Paul A. Hagerty, P.G., P.E. at (610) 422-1168 or phagerty@all4inc.com.


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