HYDRO20248

• Permit No: M1980244
• IBM Index Class Name: Hydrology
• Doc Date: 10/11/1994
• Doc Name: RATIONALE FOR PUBLIC NOTICE
• Media Type: D
• Archive: No

PART I
Page xv
Permit No. CO-0043648
(iii) During the period of the toxicity incident it has properly maintained and operated all facilities and systems
of treatment and control; and
(iv) Despite the circumstances described in paragraphs (i) and (iii) above, the source and/or cause of toxicity
could not be located or rrsolved.
If deemed appropriate by the Division, the permit or the compliance schedule may be modified to revise the
ongoing monitoring and toxicity investigation requirements to avoid eo unproductive expenditure of the
permittee's resources, provided that the underlying obligation to eliminate any continuing exceedance of the
tonicity limit shall remain.
(g) Spontaneous Disappearance
If toxicity spontaneously disappears at any time after a test failure, the permittee shell notify the Division in
writing within 14 days of a demonstration of disappearance of the toxicity. The Division may require the
permittee to develop and submit additional information which may include, but is not limited to, the results of
additional testing. If no pat[em of toxicity is identified or recurring tonicity is no[ identified, the toxicity
incident response is considered closed and normal WET testing shall resume.
(h) Toxicity Reooener
This permit may be reopened and modified (following proper administrative procedures) to include new
compliance dates, additional or modified numerical permit limitations, a new or different compliance schedule, a
change in the whole efFluent toxicity testing protocol, or any other conditions related to the control of toxicants
if one or more of the following events occur:
(i) Toxicity has been demonstrated in the efFluent and the permit does not contain a toxicity limitation.
(ii) The PTI/TIE results indicate that the toxicant (s) represent pollutant(s) that may be controlled with specific
numerical limits, and the Division agrees that the numerical controls are [he most appropriate course of
action.
(iii) The PTI/T[E reveals other unique conditions or characteristics which, in the opinion of the Division,
justify the incorporation of unanticipated special conditions in [he permit.
(iv) The Division may reopen this permit and impose chronic toxicity limits where chronic toxicity is
identified.
C. DEFINITIONS OF TERMS
1. "Acute Whole Effluent Toxicity" exists whenever the LCe, which represents an estimate 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.
2. "Composite" sample is a minimum of four (4) grab samples collected at equally spaced two (2) hour intervals and
proportioned according to flow.
3. "Continuous" measurement, is a measurement obtained from an automatic recording device which continually
measures provides measurements.
4. "Chronic lethality" occurs when a statistically significant difference, at the 95% confidence level, occurs in the
chronic test benveen the mortality of the test species in XYo efFluent (the chronic IWC = X~Y) and [he control.
INppP aNN)