Revised On: Feb. 13, 2024 - 2:37 p.m.

The following is an overview of the process for establishing a TMDL for pollutant parameters on an impaired water. This process, depending on complexity, watershed size, the number of pollutants contributing to the impairment, etc., typically takes three to five years.

Step 1 — Project Prioritization

Arizona’s list of TMDLs on impaired waters is prioritized every two years as part of the Clean Water Act 305(b) & 303(d) Assessment | Learn More >

Step 2 — Data Review

Compilation of supporting information and existing data

Step 3 — Sampling and Analysis Plan

Includes site selection, sampling design, frequency, project duration, methods, budget, a health and safety plan, and other relevant information

Step 4 — Data Collection

Implementation of the sampling and analysis plan

Step 5 — Data Analysis

Analysis of all available data to identify sources of pollutants and recommend implementation activities to restore the water quality

Step 6 — Draft Report

Draft TMDL report incorporating data analysis findings and conclusions

Step 7 — Public Comment

Publish notice to receive public comment on the draft report in the Arizona Administrative Register per Arizona Revised Statutes §49-234(D)

Step 8 — Finalize Report

Review and respond to public comments, incorporate input into the report, if appropriate, and publish the final report in the Arizona Administrative Register per Arizona Revised Statutes §49-234(E)

Step 9 — TMDL Final Report Approval

Submit to EPA for approval

Access Current TMDLs

Find Arizona TMDL documents using the EPA's How’s My Waterway Application | View/Download How-To > | Visit EPA Application >

Opportunities for Public Input

In addition to the required public comment period in Arizona Revised Statutes §49-234, ADEQ will accept informal input throughout the development of a TMDL.

Receive TMDL updates, including notifications to provide input, by email or text | Subscribe >

In Progress TMDLs

Queen Creek TMDL | Current Step: Data Collection
Queen Creek and associated tributaries are impaired for copper and lead. ADEQ is working with a contractor to collect water quality data. Data collection activities will continue through the summer of 2025.

Statewide Mercury TMDL | Current Step: Data Analysis
31 waterbodies in Arizona are impaired for mercury. ADEQ is working with a contractor to gather and analyze all available data to determine the best path forward. ADEQ will work with contractor on next steps, including data analysis and modeling.

Oak Creek | Current Step: Preparing Draft for Public Comment
Oak Creek and associated tributaries are impaired for E.coli. ADEQ has worked with a contractor to complete data collection and analysis efforts. The TMDL draft is being prepared for public review and comment in late spring 2024.

Oak Creek TMDL Fact Sheet | View/Download >

Upper Agua Fria TMDL | Current Step: Data Review
Reaches of the Upper Agua Fria, Lynx Creek, and Big Bug Creek are impaired by multiple metals — Arsenic, Cadmium, Copper, Lead, Selenium, and Zinc. ADEQ is working with a contractor to compile and review available data on the region. 

Little Ash Creek TMDL | Current Step: Data Collection
Little Ash Creek is impaired for Dissolved Oxygen (DO). ADEQ is sampling the area to account for data gaps.

Salt River TMDL | Current Step: Data Collection
Salt River is impaired for Arsenic, E.coli and Phosphorus. ADEQ is samping the area to account for data gaps.