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Minrec, Incorporated Water Quality Assessment CO- 0048233 <br />needs to occur. If either the new concentration or loading is greater than the September 2000 <br />concentration or loading, then a new or increased impact is determined. If this is a new facility <br />(commencement of discharge after September 30, 2000) it is automatically considered a new or increased <br />impact. <br />Note that the AD Guidance document includes a step in the New or Increased Impact Test that calculates <br />the Non - Impact Limit (NIL). The permittee may choose to retain a NIL if certain conditions are met, and <br />therefore the AD evaluation for that parameter would be complete. The NIL is typically preferred by the <br />permittee as it is usually the least stringent limitation. For this WQA, the Division will also calculate the <br />AD limitations for use in the reasonable potential analysis contained in the fact sheet. <br />The non impact limit (NIL) is defined as the limit which results in no increased water quality impact (no <br />increase in load or limit over the September 2000 load or limit). If the design flow has increased (or <br />decreased), the NIL is calculated as the September 2000 loading, divided by the new design flow, and <br />divided by a conversion factor of 8.34. If there is no change in design flow or the current design flow has <br />decreased, then the NIL is equal to the September 2000 permit limitation. <br />The design flow of this facility has decreased from the September 2000 design flow. <br />If the facility was in place, but did not have a limitation for a particular parameter in the September 2000 <br />permit, the Division may substitute an implicit limitation. An implicit limitation is defined as the maximum <br />effluent concentration during the two years prior to September 2000. If the facility did not have a <br />limitation for a particular parameter in the September 2000 permit, the Division may substitute an implicit <br />limitation. For parameters that are undisclosed by the permittee, and unknown to the Division to be <br />present, an implicit limitation may not be recognized. Note that if there is a change in design flow, the <br />implicit limit /loading is subject to recalculation. <br />If a parameter is being evaluated in this WQA, where the September 2000 permit did not contain a <br />limitation for that parameter, then an implicit limitation may be substituted. Consistent with the First <br />Update to the AD Guidance of April 2002, an implicit limit is determined based on the approach that <br />specifies that the implicit limit is the maximum concentration of the effluent from October 1998 to <br />September 2000, if such data is available. If this data is unavailable, the Division may substitute more <br />recent representative data, if appropriate, on a case by case basis. <br />This facility was in place as a discharger prior to September 30, 2000, and was permitted under CO- <br />0029599. Therefore, the new or increased impacts test must be conducted. <br />For dissolved cadmium, the limitation as of September 2000 was used in the evaluation of new or <br />increased impacts. For total recoverable iron, implicit limits were determined based on the maximum <br />concentration (120 ug /1) during the period September 30, 2001 to December 31, 2005, as data from <br />October 1998 to September 2000 was not available. These limitations were used in the evaluation of new <br />or increased impacts. <br />For dissolved arsenic, total recoverable arsenic, dissolved copper, total recoverable trivalent chromium, <br />dissolved manganese, total mercury, dissolved lead, dissolved silver, dissolved nickel, dissolved selenium, <br />Appendix A (WQA v 7.0) Page 17 of 25 Last Revised Sept 14, 2009 /ES <br />