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 water body 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 water body can receive and still meet water quality standards. It is the sum of the individual wasteload allocations (WLAs) for point sources, load allocations (LAs) for nonpoint sources and natural background, plus a margin of safety (MOS). The Minnesota Pollution Control Agency (MPCA) listed three stream reaches in the Pipestone Creek watershed as impaired for both excess fecal coliform bacteria (a human health concern that limits recreational use of the water) and excess turbidity (a measure of cloudiness of water that affects aquatic life). Both categories of impairment are addressed in this study because it is believed that they share some common sources and, therefore, it will be more efficient to plan implementation efforts. It also requires less administration by the State if the impairments are combined into one study. The primary contributing sources to fecal coliform bacteria are believed to be livestock on overgrazed riparian pasture, surface-applied manure on cropland and feedlots lacking adequate runoff controls. The primary contributing sources to the turbidity impairments appear to be soil erosion in the riparian zone from livestock, streambank erosion/slumping from livestock and increased flow related to land use, upland soil loss from row cropland and possibly nutrient additions leading to algae growth.
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Minnesota Pollution Control Agency (St. Paul, Minnesota)
Body of Water
Minnesota Pollution Control Agency