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General Minimal Discharge Permit Rationale Perini! No. COG600000 Page 17 V. TERMS AND CONDTITONS OF PERMIT F. Whole Effluent Toxicity IR'E7) Testier: (cont.) Species Toxicity: As a condition of certain applications of this permit, the permittee may be required to conduct routine monitoring for acute toxicity using two species, Ceriodaphnia sp. (water flea) and fathead minnows. An acute WET test is failed whenever the LCD which represents an estimate of the egluent concentration which is lethal to 50'90 of the test organisms in the time period prescribed by the test, is found to be less than or equal to 100% e~7uent. The permittee must provide written notification of the failure of a WET test to the Division, along with a sratemem as to whether the Preliminary Toxicity Incidem ("PTT")/Ioxiciry Identification Evaluation ("TIE") investigation or accelerated testing is being performed (see next section). Nohfrcation 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 this permit means no later than the last day of the laboratory test. The permittee should read the WET testing sections of Parr I.B and I.C of the permit carefully, and should note that the test methods for the toxicity rests are described in detail in the Division guidance document, Colorado Water Oualiry Control Division Biomonitorinr Guidance Dontment (July 1993). This documtnr should be read thoroughly prior to commertcirtg the required WET testing, to ensure that the permittee is aware of the various test conditions that could affect the test results (e.g., sample holding time). The permittee should be aware that eligibility for coverage under the general permit may change if the facility experiences a change in discharge, as outlined in Pan II.A.2 of the permit Such changes shall be reported to the Division immediately. G. Antideeradation Review: An aruidegradation review was performed by the Division for this genera! permit. Since these facility discharges are either temporary or minimal flows, they are considered to have a minimal effect on the receiving water quality, and thus no further review is necessary. However, permit limitations for total residual chlorine (IRC) are based upon antidegradation considerations for some receiving waters. See the TRC discussion in V.B.1. of this rationale. K Monitorint!: The monitoring frequency and sample type for each type of discharge is listed in 1. C.1. of the permit. See the particular type of discharge listed under I. C. 1. of the permit for this information. I. Rgportinx: The pernrittee mast submit a Discharge Monitoring Report (DMIl) on a quarterly basis [o the Divrsion. This report should contain the required summarization of the test results for parameters shown in I. C.1 of the permit. See the permit, Para I.E.1. for details on such submission.