WHAT DOES THE DNR DO WITH RECEIVING WATER DATA (collected during WET tests)?
The WDNR requires most permittees to use the receiving water upstream of the discharge as the diluent in WET tests (i.e., effluent is mixed with receiving water to make up test concentrations). In order to insure that only effluent effects are measured in these tests and that receiving water effects do not interfere with test results, certain criteria have been established to keep track of receiving water performance. These criteria are very stringent (e.g., acute receiving water controls are only allowed 10% mortality, as opposed to the 50% mortality an effluent is allowed to “pass”) and therefore a receiving water that does not meet one of these criteria is not necessarily “toxic”. In most cases, natural factors can be found which explain why a receiving water did not perform perfectly in a WET test. However, in order to insure that receiving water samples that have shown repeated control problems are not indicative of potential toxicity problems in the receiving water, the Biomonito
