Montana Dischargers Work Toward Predictable, Affordable, and Technically Feasible Numeric Nutrient Criteria Implementation

As part of a USEPA initiative for states to develop numeric nutrient criteria nationally, the State of Montana began work on developing criteria for its ecoregions in 2003. In developing the criteria the Montana Department of Environmental Quality (MDEQ) used an extensive dataset of high mountain streams with minimal anthropogenic influence. The proposed numeric criteria for wadeable streams in the western ecoregions of the state are very low; 0.3 mg/L total nitrogen (TN) and 0.03 mg/L total phosphorus (TP). Criteria are slightly higher in the eastern ecoregions; 0.5 mg/l TN and 0.08 mg/L TP. Ambient water quality in most of the receiving waters that the cities and towns of Montana discharge into exceeds these concentrations upstream of their wastewater discharges. This results in circumstances where it is difficult to reconcile technically achievable and affordable discharge permit limits with in-stream standards.