303(d)-Listing-Methodology

303(d) Listing Methodology

Section 303(d) of the Federal Clean Water Act requires states to identify waters where effluent limitations are not stringent enough to attain water quality standards. To support this requirement, Colorado develops the 303(d) List of Impaired Waters that identifies water bodies that do not attain water quality standards or designated uses. The 303(d) Listing Methodology provides a framework for determining attainment or non-attainment of assigned water quality standards and designated uses. Generally, the Water Quality Control Division’s (division) recommendation to include or not include a water body in the 303(d) List is based upon the strict application of the listing methodology criteria.

The 303(d) Listing Methodology workgroup reviews and updates this document on a biennial basis in anticipation of 303(d) List and Monitoring & Evaluation List development. The listing methodology is revised with the intent of clarifying the division’s procedures for determining the attainment of the uses and standards assigned to Colorado waterbodies. Frequently, revisions or additions come from issues raised during the previous 303(d) listing cycle.