Bluff Creek Watershed Total Maximum Daily Load Report: Turbidity and Fish Bioassessment Impairments

The Clean Water Act, Section 303(d), requires that every two years states publish a list of waters that do not meet water quality standards and do not support their designated uses. These waters are then considered to be "impaired". Once a waterbody is placed on the impaired waters list, a Total Maximum Daily Load (TMDL) must be developed. The TMDL provides a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet water quality standards. It is the sum of the individual wasteload allocations (WLAs) for point or permitted sources, load allocations (LAs) for nonpoint or nonpermitted sources and natural background, plus a margin of safety (MOS). Bluff creek is listed by the Minnesota Pollution Control Agency (MPCA) as impaired for aquatic life use due to excess turbidity levels and low fish biota scores. The Bluff Creek TMDL Biological Stressor Identification Report identified sediment, metals, habitat fragmentation, and flow as stressors to fish biota. Although this TMDL Report discusses all of these stressors, the TMDL equation is only written for total suspended solids (TSS) which represents a surrogate for both turbidity and fish biota