 40 CFR § (d)(1)(v) “(W)hen the permitting authority determines, using the procedures in paragraph (d)(1)(ii) of this section, toxicity testing data... that a discharge causes, has the reasonable potential to cause... an in-stream excursion above a narrative criterion within an applicable State water quality standard, the permit must contain limits for (WET).”

Number of failures  Zero  One or two  Three or more

 Originally, RP was not determined for WET during the application process  WET was a monitoring requirement  A TRE was required for persistent significant lethality  At the end of a TRE a WET limit could be included in the permit

 In 2007 EPA began to objecting to permits being issued with no additional requirements for permittees that had a history of sublethal failures  Added a “trigger” for a sublethal TRE  Eventually lead to SL WET limits

 A single sample approaching or in excess of the calculated limit does not automatically require a limit  Samples may be averaged  Different than federal methodology

On December 28, 2015, EPA and TCEQ concurrently signed letters agreeing to a new procedure for making RP determinations. This agreement will allow the avoidance of the interim objection letters for draft permits that didn’t include WET limits after one or two failures.

 Zero failures, standard 5 year permit  One or two failures, 3 year permit, monthly testing after a failure  Three or more failures, 5 year permit with a WET limit, optional compliance period

With an agreement on RP in place, TCEQ will now draft a new WET section of the IPs apart from the rest of the document, since the WET section of the 2010 IPs were never approved.

Some of the other WET issues we are looking to address in the revised WET section of the IPs are:  Eliminating formal Toxicity Reduction Evaluations (TREs)  Switching to IC25 statistical methodology for test results  Other miscellaneous items

With an RP agreement now formally in place with EPA, we are looking at drafting a new WET IP section that will be approved separately from the rest of the IPs. Stakeholders will be allowed input during this development process just as they always have had for the IPs.  Michael Pfeil  (512)