HYDRO25533

• Permit No: C1981022
• IBM Index Class Name: Hydrology
• Doc Date: 5/9/1994
• Doc Name: RATIONALE FOR PUBLIC NOTICE
• Permit Index Doc Type: NPDES
• Media Type: D
• Archive: No

PART I
Page lg of 19
Permit No. CO-0000132
B. MONITORING REQUIREMENTS
4. Acute WET Testing-Outfall 011 (continued)
(b) Failure of Test and Division Notification
An acute WET test is failed whenever the LCyo, which represents an estimate of
the effluent concentration which is lethal to SOY of the test organisms in the
time period prescribed by the test, is found to be less than or equal to 100Y
effluent. The permittee must provide written notification of the failure of a
WET test to the Division, along with a statement as to whether the Preliminary
Toxicity Incident ("PTI")/Toxicity Identification Evaluation ("TIE")
investigation or accelerated testing is being performed (see next section).
Notification must be received by the Division within 14 calendar days of the
demonstration of acute WET in the routine required test. "Demonstration" for
the purposes of Parts I.B.4(b),(c),(d) and (f) means no later than the last day
of the laboratory test.
(c) Automatic Compliance Schedule Uvon Failure of Test
If a routine acute WET test is failed, regardless of whether the limit is in
effect, the following automatic compliance schedule shall apply. As part of
this the permittee shall either:
(i) proceed to conduct the PTI/TIE investigation as described in Part
I.8.4.(d), or
(11) conduct accelerated testing using the single species found to be more
sensitive.
If accelerated testing is 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.
(d) PTI TIE
The results of the PTI/TIE investieation are to be received by the Division
within 120 days of the demonstration of acute WET in the routine test, as
defined above, or if accelerated testine is verformed, the date the vattern of
toxicity is demonstrated. A status report is to be vrovided to the Division at
the 30. 60 and 90 day points of the PT JTIE investigation.
Amendment 2 Issued Effective