WQD | TMDL Process & Progress

Watershed Improvement & Protection

TMDL Process, Prioritization & Progress

Revised On: Nov. 5th, 2024 - 02:07 pm

The following is an overview of the process for establishing a Total Maximum Daily Load (TMDL) for pollutant parameters in impaired water. Depending on the complexity, watershed size, the number of pollutants contributing to the impairment, etc., this process typically takes three to five years.

TMDL Process

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 | See Prioritization Criteria >
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

Review Current TMDLs

Arizona TMDL documents can be reviewed with EPA's "How’s My Waterway" portal:

How-to Guide | View >

EPA's How’s My Waterway Portal | Visit Portal >

TMDLs In-Progress

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.
Lower Sonoita Creek Watershed TMDL | Current Step: Data Review
Thirteen reaches in the Patagonia Mountains are impaired for heavy metals and pH. These reaches are located in the sub-watersheds of 3R Canyon, Alum Gulch, and Harshaw Creek that all flow into Sonoita Creek. ADEQ will work with a contractor on next steps to update 45 TMDLs developed in 2003 and create TMDLs for six new impairments that were not originally covered.
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 | View Fact Sheet >
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, which will continue through the summer of 2025.
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.
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 a contractor on the next steps, including data analysis and modeling.
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.

Revised On: Nov. 5th, 2024 - 02:07 pm

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.

For future ADEQ communications and outreach regarding TMDLs, sign up for email notifications. When selecting subscription topics, select Water Quality, proceed to the next page(s), and then select Surface Water Quality where listed | Subscribe >