HYDRO25301

• Permit No: C1981071
• IBM Index Class Name: Hydrology
• Doc Name: COLO DISCHARGE PERMIT SYSTEM CDPS AMENDMENT 4 RATIONALE
• Permit Index Doc Type: NPDES Permit 0027154 eff 9/1/94
• Media Type: D
• Archive: No

PART I
Page In of 14
Permit No. CO-0027154
B. MONITORING REQUIREMENTS
4. Chronic WET Testing-Outf ells 001, 005, 007 and 020 (continued)
If accelerated testing ie being performed, the permittee shall provide written
notification of the results within 14 calendar days of completion of the "Pattern of
Toxicity"/"NO Toxicity" demonstration. Testing will be at least once every two
weeks for up to five tests until; 1) two consecutive tests fail or three of five
tests fail, in which case a pattern of toxicity has been demonstrated or 2) two
consecutive tests pass or three of five tests pass, in which case no pattern of
toxicity has been found. If no pattern of toxicity is found the toxicity episode is
considered to be ended and routine testing is to resume. If a pattern of toxicity
is found, a PTI/TIE investigation is to be performed. If a pattern of toxicity is
not demonstrated but a significant level of erratic toxicity is found, the Division
may require an increased frequency of routine monitoring or some other modified
approach.
(e) PTI TIE
The results of the PTI/TIE investigation are to be received by the Division within
120 days of the demonstration of chronic WET in the routine test, ae defined above,
or if accelerated testing is performed, the date the pattern of toxicity ie
demonstrated. A statue report ie to be provided to the Division at the 30, 60 and
90 day points of the PTI/TIE investigation. The Division may extend the time frame
for investigation where reasonable justification exists. A request for an extension
must be made in writing and received prior to the 120 day deadline. Such request
must include a justification and supporting data for such an extension.
The permittee may use the time for investigation to conduct a PTI or move directly
into the TIE. A PTI consists of a brief search for possible sources of WET, which
might reveal causes of such toxicity and appropriate corrective actions more simply
and cost effectively than a formal TIE. If the PTI allows resolution of the WET
incident, the TIE need not necessarily be conducted. If, however, WET is not
identified or resolved during the PTI, the TIE must be conducted within the allowed
120 day time frame.
Any permittee that is required to conduct a PTI/TIE investigation shall do so in
conformance with procedures identified in the following documents, or as
subsequently updated: 1) Toxicity Identification Evaluation: Characterization of
Chronically Toxic Effluents, Phase I, EPA/600/6-91/OO5F May 92, 2) Methods for
Arc uatic Toxicity Identification Evaluations Phase I Toxicity Characterization
Procedures, EPA/600/6-91/003 Feb. 91 and 3) Methods for Aquatic Toxicity
Identification Evaluations. Phase II Toxicity Identification Procedures, EPA/600/3-
88/035 Feb. 1989.
A fourth document in this series is Methods for Aquatic Toxicity Identification
Evaluations, Phase III Toxicity Confirmation Procedures, EPA/600/3-68/036 Feb. 1989.
As indicated by the title, this procedure is intended to confirm that the suspected
toxicant is truly the toxicant. This investigation is optional.
Amendment No. 2 Issued Effective
Amendment No. 4 Issued Effective