HYDRO28507

• Permit No: C1981010
• IBM Index Class Name: Hydrology
• Doc Date: 7/1/1991
• Doc Name: CDPS RATIONALE- AMENDMENT 1
• Permit Index Doc Type: NPDES
• Media Type: D
• Archive: No

PART I
Page No. 7
Permit No. CO-00321 IS
.. DEFINTTION OF EFFLUENT LIMITATIONS
2. Acute WET Testine - Outfalls 00(.002. 005. 009. 011. 013. 015. 016. 017 and 019 (continued)
The results shall be submitted on the Acute Toxicity Test report form, available from the Division. Copies of these
reports are to be submitted to both the Division and EPA along with the DMR.
The permittee shall conduct an acute 48-hour WET test using Ceriodanhnia sp., and an acute 96-hour WET test
using fathead minnows'. Acute tests will be replacement static tests of a single effluent grab sample. The permittee
shall conduct each acute WET test in general accordance with methods described in Methods for Measuring the
Acute Toxicity of Effluents and Receivine Waters to Freshwater and Marine Oreanistns, EPA/600/4-90/027 or the
most current edition, except az modified by the most current Division guidance document entitled Guidelines for
Conductine Whole Effluent Toxicity Tests.
(b) Failure of Test and Division Notification
An acute WET test is failed whenever the LCD, which represents an cstimate of the effluent concentration which is
lethal to 50'% of the test organisms in the time period prescribed by the test, is found to be less than or equal to
100% 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 ("PTl")/Toxicity Identification Evaluation ('T1E')
investigation or accelerated testing is being performed (see next section). Notilcation 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.A.2.(b),(c),(d) and (t) means no later than the last day of the
laboratory test.
(c) Automatic Compliance Schedule Unon Failure of Test
If a routine acute WET test is failed, the following automatic cotnpliaace schedule shall apply. As part of this the
pennittee shall either:
(i) proceed to conduct the PTI/TIE investigation as described in Part I.A.2.(d), or
(ii) conduct accelerated testing using the single species found to be more sensitive.
[f accelerated testing fs being performed, the petmittee shall provide written notifiratioo 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 fait or three of five tests fail, in which
case a pattern of toxicity Itas been demonstrated or, 2) two consecutive tests pats or three of five tests pass, in
which case no pattem of toxicity has been found. If no pattem of toxicity is found the toxicity episode is considered
to be ended and routine testing is to resume. If a pattem of tonicity is found, a PT[/TIE investigation is to be
performed. If a pattern of tonicity is not demonstrated but a significant level of erratic toxicity is found, the
Division may require an increazed frequency of routine monitoring or some other modified approach.
(d) PTIIT~
and 90 day points of the PTi/'rIE investigation. The Division may extend the time Crame 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 permit[ee may use the time for investigation to conduct a PT- or move directly into the TIE. A PTL 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
T[E need not necessarily be conducted. If, however, WET is not identified or resolved during the I'T[, the TIE
must be conducted within the allowed 120 day time frame..
Except outfall 1X12 -see Part I.B.I.b). Amendment No. 1 Issued MAY 3 ~ IqQ~ Effective ~U~ ~ - ~97
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