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Item Number: I.1. CITY COUNCIL REPORT SUBJECT: Ordinance No. 619 N.S. - Tolleson Wastewater Treatment Plant Local Limits Adoption MEETING DATE: April 22, 2025 TO: Mayor and Council FROM: Aaron Dougherty, Environmental Manager REVIEWED: Reyes Medrano Jr., City Manager PURPOSE: The purpose of this report is to request City Council approval of the final proposed local limits as presented in the Final Tolleson Local Limits Evaluation (LLE) Report dated April 29, 2024. These revised limits are intended to update and strengthen the City's industrial pretreatment program, ensuring continued compliance with applicable regulatory standards and protection of public health, infrastructure, and the environment. BACKGROUND: The City of Tolleson operates a permitted wastewater treatment plant (WWTP) that must comply with the U.S. Environmental Protection Agency’s (EPA) pretreatment regulations and the Arizona Department of Environmental Quality (ADEQ) requirements. The last Local Limits Evaluation was conducted in 2010, based on data from 2009. Subsequently, Tolleson received a revised Arizona Pollutant Discharge Elimination System (AZPDES) permit (effective December 11, 2020), necessitating a comprehensive reassessment of the city’s industrial pretreatment local limits. This current LLE was conducted to update these limits using recent site-specific data and regulatory criteria. DISCUSSION: The updated LLE employed EPA- and ADEQ-sanctioned methodologies to: • Identify pollutants of concern (POCs) through data screening, sampling, and regulatory comparison. • Calculate Allowable Headworks Loadings (AHLs) using several criteria, including: o Water quality standards o AZPDES and APP permit limits o Treatment inhibition thresholds (trickling filters, nitrification, anaerobic digestion) o Sludge disposal regulations o Design criteria • Determine Maximum Allowable Headworks Loadings (MAHLs) and apply safety factors. • Subtract domestic/commercial background loads to compute Maximum Allowable Industrial Loadings (MAILs). Significant findings include: • Revised or new MAILs for 18 pollutants such as ammonia, BOD, TSS, copper, arsenic, lead, and selenium. • Updated limits for traditionally monitored pollutants like pH, oil and grease, and sulfides will remain unchanged. • Specific pollutants with elevated toxicity or unclear regulatory thresholds (e.g., PCBs, chlordane, DDT, toxaphene) continue to be prohibited. These MAILs will now enable site-specific allocation of industrial discharge permits, supporting both flexibility and environmental protection. BUDGET IMPACT: There is no direct financial cost associated with adopting the updated local limits. However, benefits include: • Avoidance of future non-compliance penalties. • Reduced risk of treatment system disruptions due to interference. • Improved long-term planning for infrastructure and service area growth. • Enhanced regulatory readiness and credibility in compliance audits. Any downstream operational or administrative costs related to enforcement or monitoring will be covered under existing program budgets. RECOMMENDATION: Staff recommends that the City Council: 1. Approve the Final Proposed Local Limits as detailed in the attached LLE report. 2. Authorize implementation of these limits into the Industrial Pretreatment Program. This approval ensures the WWTP’s continued operational integrity, environmental stewardship, and regulatory compliance. ATTACHMENTS: 1. Ord 619 N.S. Adopting the April 29, 2024 City of Tolleson Wastewater Treatment Plant Local Limits 04 22 25