The Arizona Department of Environmental Quality (ADEQ) is currently in the process of submitting the 2024 Clean Water Act Assessment to the Environmental Protection Agency (EPA). The purpose of the assessment is to conduct an analysis on the quality of Arizona’s surface waters and determine if surface water standards are being met. ADEQ and the EPA use the assessment to determine land use activities, discharge standards, program initiatives, and permit discharge limits. This article is intended to provide an overview of the assessment’s findings and potential impacts Arizona water regulations.
Background
Aa a part of the 1972 Clean Water Act (CWA), Arizona is subject to certain monitoring, assessment, and listing requirements for surface water quality. ADEQ assesses Arizona’s surface waters every two (2) years under EPA guidance and reports changes in water quality. Every three (3) years, ADEQ must adopt new water quality standards based on the biannual assessment findings. The next assessment will then use the previously approved standards as a basis. The EPA has not yet approved the 2019 standards which have been published in the Arizona Administrative Register. Arizona’s 2024 CWA Assessment is based on the 2016 standards.
Assessment Findings
The assessment classifies surface water quality under three (3) classifications: Attaining, Inconclusive, or Impaired. Attaining waterbodies have demonstrated sufficient, credible, and scientifically defensible data to assess a surface water or segment and the surface water or segment does not meet the definition of impaired or not attaining. Attaining waterbodies are approved for all uses. Inconclusive waterbodies lack sufficient data to justify an attainment or impairment decision. Impaired waters have at least one designated use which is not supported and at least one parameter is not meeting water quality standards. Of the total 537 waterbodies included in the assessment, 182 were impaired, 272 were inconclusive, and 83 were attained. The total count of 182 out of 537 (33.9%) can be misleading as the bodies of water vary from a few hundred feet or an acre, to miles and thousands of acres. When considering the area of the lakes in the assessment, 103,656 acres out of the 109,341 assessed (94.8%) were designated as impaired. For streams, just over 29% of the miles were determined to be impaired. Approximately 50% of the assessed streams were inconclusive. The high percentage of assessed streams being determined as inconclusive is primarily due to Arizona’s large number of ephemeral streams, which flow in response to precipitation and can be difficult to sample. Arizona has been trending upwards with the total number of impaired waters reported every two (2) years increasing since 2004. 136 impaired waters were reported in 2016, the last year a standard was published. That number is now 182.
Impairment was caused mainly by Selenium, Copper, Mercury, Zinc, and E. coli. There are two main causes of pollution identified by ADEQ: point sources and non-point sources. Non-point sources include long-lasting pesticides from agricultural uses, cattle grazing, road erosion near streams, and non-discrete discharges. Regulations cannot be used to control non-point sources; instead, pollutants from non-point sources are controlled using ADEQ grants to local organizations to help improve water quality.
Point sources are discrete discharges to a surface water and must be permitted under an ADEQ Arizona Pollutant Discharge Elimination System (AZPDES) permit. Point sources are subject to the Total Maximum Daily Load (TMDL) which ADEQ determines for each body of water based on the assessment findings. The TMDL is based on existing water quality, and nearby point and non-point sources.
As the TMDL lowers to help clean impaired waters, requirements for permits will become more stringent. When a body of water is designated as impaired, that body of water is not allowed to have any further degradation by the pollutant causing impairment; therefore, ADEQ would deny any AZPDES permit application for a facility which has the potential to discharge the pollutant.
Future Actions
The EPA is years behind schedule on the approval of water quality standards. Arizona’s 2024 CWA Assessment is based on the 2016 standards, as the 2019 standards are still under review. As the EPA catches up on issuing new standards, which will be more stringent given the increasing number of impaired bodies of water, acquiring water related permits such as AZPDES, Aquifer Protection Permits, Grazing Permits, will become more difficult. In the 2016 Assessment, 71.3% of lake acreage and 22.8% of stream mileage were assessed as impaired. In 2024, those numbers are now 91.9% and 21.3%. While the percentage of miles has decreased, the total number of miles has increased from 680 miles to 997 miles. This is possibly due to the change in the definition of Waters of the United States (WOTUS) which removed some stream and rivers from the most recent study.
Additionally, ADEQ’s TMDL program was audited in 2021 and it was found that ADEQ had failed to develop some required TMDLs and had failed to update certain TMDLs for the last 15 years. As ADEQ works to catch up on guidelines, drastic changes in water quality requirements may be issued. ADEQ currently has contractors working updating TMDL’s and is looking into programmatic changes to address TMDL development in the future.
More information regarding the findings can be found in the
full assessment. If you would like to see if there are any impaired waters nearby to your facility, ADEQ has an
online interactive map that shows water quality.
