HYDRO22157 - Laserfiche WebLink

Home Browse Search

COLORADO DEPARTMENT OF HEALTH, Water Quality Control Division Rationale - Page 7. Permit No. CO-0042161 DISCUSSION: (Cont.) H. Whole Effluent Toxicity (WET) Testing (Con[.) These selected permits are limited to those facilities that have no known toxicity problem or potential"for toxicity. A mandatory reopener clause will be placed in this permit which calls for the imposition of limits in three years in those cases where areal or potential WET problem has been established. Occurrence of toxicity during the fourth and fifth years calls for the immediate introduction of limits. This approach is in conformance with the objective of the Region VIII NPDES WET Control Program in that, under both approaches, limits will be in effect in three years where there is a toxicity problem. The reference in the reopener clause to federal regulations directs that such limits must conform to applicable federal regulations in effect at that time. The determination as to whether or not an individual facility must conduct chronic WET testing is dependent upon the ratio of the chronic stream low flow (30E3) to the design flow of the wastewater treatment plant. If the ratio is less than 19:1, chronic WET testing is included as a permit requirement. In this case the ratio was determined to be 0.3:1. Therefore, chronic WET • testing is required. Such testing shall be semi-annually, with two species for the first year, and with only the most sensitive species during years two and three. After the third year of monitoring, the chronic testing requirement ends unless applicable regulations are adopted. Industrial facilities having simple effluents of consistent quality, which can be totally chazacterized chemically, may request a full or partial waiver of WET testing for the remainder of the life of the permit, subject to Division approval, if the first four quarters of testing show no pattern of toxicity. The permittee should read the WET testing sections of Part I.A. and I.B. of the permit carefully, and should note that the test methods for the toxicity tests are described in detail in the Division guidance document, Guidelines for Conducting Whole Effluent Toxicity Tests. This document should be read thoroughly prior to commencing 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 some of the conditions outlined above may be subject to change if the facility experiences a change in discharge, as outlined in Part II.A.1 of the permit. Such changes shall be reported to the Division immediately. I. Additional Monitoring As outlined in the facility description, the discharge is from the same • ore body as is currently being dewatered under permit number CO-0027154.