 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

 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

 EPA and TCEQ signed letters on December 28, 2015, agreeing to an RP policy  One or two failures will lead to 3-year permits that will require increased testing for any additional failures.  A WET limit will be included in the next permit if three or more failures occur during the 3-year permit term.  Michael Pfeil  (512)