Nutrient Assessment Reduction Plans

The Illinois EPA has required that major municipal facilities that discharge to a receiving waterbody that has been assessed to be impaired or at risk of eutrophication produce a Nutrient Assessment Reduction Plan (NARP) through the Natrional Pollutant Discharge Elimination System (NPDES) program.. The purpose of the NARP is to identify phosphorus input reductions and other measures that can be implemented by a major municipal facility or group of major municipal facilities via a watershed workgroup, to ensure that dissolved oxygen and offensive aquatic algae and aquatic plant criteria are met throughout a watershed.

A phosphorus-related impairment means that the downstream waterbody or segment is listed by Illinois EPA as impaired due to low dissolved oxygen and/or offensive conditions (algae and/or aquatic plant growth) that is related to elevated phosphorus levels. Illinois EPA will determine if the permittee’s treatment plant effluent is located upstream of a waterbody or stream segment that has been determined to have a phosphorus-related impairment. This determination is made upon reviewing available information concerning the characteristics of the relevant waterbody/segment and the relevant facility (e.g., quantity of discharge flow and nutrient load relative to the stream flow).

A waterbody or segment is at risk of eutrophication if there is plant, algal or cyanobacterial growth that may cause a violation of a water quality standard, or if there is pH and dissolved oxygen data that implies excessive plant growth. Illinois EPA will determine if the permittee’s treatment plant effluent is located upstream of a waterbody or stream segment that has been determined to be at risk of eutrophication. This determination is made upon reviewing relevant information concerning the characteristics of the relevant waterbody/segment and the relevant facility (e.g., quantity of discharge flow and nutrient load relative to the stream flow).

The following NARPs have been submitted to the Illinois EPA in response to NPDES permit requirements.