The United States Environmental Protection Agency (EPA) is issuing a notice of proposed action under the Clean Water Act to reopen a National Pollutant Discharge Elimination System (NPDES) permit AZ0020524 issued to: the City of Phoenix 91st Avenue Wastewater Treatment Plant located in Tolleson, Maricopa County, Arizona.
Following the issuance of the permit for the above referenced facility in October 2016, in a letter dated December 9, 2019, the City of Phoenix requested to change the ammonia impact ration (AIR) maximum daily limit. This request was based on a review of the recent AZPDES permits issued by the Arizona Department of Environmental Quality (ADEQ), which indicated that a technical error may have occurred when the AIR limit was established in the current permit. ADEQ has been including an AIR maximum daily limit of 2.0 instead of 1.0 which is the limit in the current permit. EPA reviewed the basis for the AIR maximum daily limit established by ADEQ and agrees that this is the correct limit that should apply. Therefore, EPA is re-opening Part I. Section B. Table 1. to make this change and is soliciting comments on just this specific section of the permit.