Methodology for Iowa’s 2018 Water Quality Assessment, Listing, and Reporting Pursuant to Sections 305(b) and 303(d) of the Federal Clean Water Act

(2020) Methodology for Iowa’s 2018 Water Quality Assessment, Listing, and Reporting Pursuant to Sections 305(b) and 303(d) of the Federal Clean Water Act. Natural Resources, Department of

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Abstract

Iowa’s 2018 assessment and listing methodology attempts to incorporate recommendations in U.S. EPA’s historical [305(b)/303(d)/Integrated Reporting] guidance as well as the current guidance for the 2018 assessment, listing, and reporting requirements pursuant to Sections 303(d) and 305(b) of the federal Clean Water Act (U.S. EPA 2015). EPA guidance establishes the formats for an “integrated report” (IR) that satisfies the listing requirements of Section 303(d) and the reporting requirements of Sections 305(b) and 314 of the Clean Water Act (CWA). The current EPA 2015 guidance replaces all previous guidance pertaining to Sections 305(b) and 303(d) except EPA’s Consolidated Assessment and Listing Methodology (CALM) (U.S. EPA 2002). Due to the continued lack of details regarding the mechanics of CWArelated water quality assessment in more recent EPA guidance (e.g., U.S. EPA 2002), Iowa Department of Natural Resources (Iowa DNR) continues to use assessment methods described and recommended in previous EPA guidance for Section 305(b) reporting (U.S. EPA 1997). Iowa DNR uses the 1997 guidance only in cases where EPA’s more recent guidance is inadequate. Iowa DNR’s 2018 methodology generally meets the requirements of CWA, Section 303(d)(1)(a) and 40 CFR Section 130.24 and incorporates requirements of Iowa’s credible data law (2001 Iowa Code, Section 455B.194, subsection 1). The changes in methodology between the 2016 and 2018 listing cycles are summarized in Table 1 and are explained throughout this document.