Document Yje51G9GwOE5Nz0DYBa8667gK

Region 6 Compliance Assurance and Enforcement Division INSPECTION REPORT Inspection Date(s): Media: Regulatory Program(s) Company Name: Facility Names: Facility Physical Locations: (city, state, zip code) Mailing address: (city, state, zip code) County/Parish: Facility Contact: 1/29/2026 Water Clean Water Act City of Rio Grande City of Rio Grande 1501 Mile 8 N Rio Grande, Texas, 78582 5332 E. Highway 83 Rio Grande City, TX 78582 Hidalgo County Gilberto Falcon (956) 487-0672 FRS Number: Identification/Permit Number: Media Number: NAICS: SIC: TX0068764/TXR05FH33 4952 Personnel participating in inspection: Michael Williams EPA/ 6EN-WMH Ruben Salinas City of Rio Grande Mayor Inspector Public Utilities Director 281-983-2150 956-487-2702 EPA Lead Inspector Signature/Date Supervisor Signature/Date MICHAEL WILLIAMS 2026.04.03 11:08:37 -05'00' MICHAEL WILLIAMS Michael D. Williams Date ROBERTO BERNIER Roberto Bernier Digitally signed by ROBERTO BERNIER Date: 2026.04.06 12:26:01 -05'00' Date City of Rio Grande TX0068764/TXR05FH33 Inspection Date 1/29/2026 Section I - Introduction PURPOSE OF THE INSPECTION EPA Region 6 inspector, Michael Williams, arrived at the City of Rio Grande Wastewater Treatment Plant (WWTP) at 9:45 am on January 29, 2026, for an announced National Pollutant Discharge Elimination System (NPDES) inspection. During the opening conference, I met Rubin Salinas, the Public Utilities Director. Mr. Salinas was informed that this was an EPA lead compliance evaluation inspection to determine compliance with the facility's NPDES permit TX0068764 and Stormwater permit TXR05GH33, facility operations and maintenance requirements under the Clean Water Act (CWA). The inspection was conducted under the authority of the NPDES and Stormwater General permit programs, in accordance with the Federal CWA. The information presented in this report is based on the materials and information supplied by the City of Rio Grande representatives, observations made during the inspection, and records or reports maintained by the permittee, permittee contract laboratory, the State of Texas and EPA. FACILITY DESCRIPTIONS (TX0068764) The City of Rio Grande wastewater treatment plant is designed to treat an average daily flow of 1.5 million gallons per day (MGD). The city plans to expand the plant to 1.9 MGD. Influent enters the facility at the headworks, where preliminary treatment is provided through both mechanical and manual bar screens to remove large debris and protect downstream equipment. Following screening, the influent is conveyed to two parallel racetrack-style oxidation ditches, which serve as the biological treatment process. Within the oxidation ditches, wastewater is aerated and mixed to promote the growth of microorganisms that biologically degrade organic matter and reduce biochemical oxygen demand (BOD) and suspended solids. The mixed liquor from the oxidation ditches then flows to one of two secondary clarifiers, where solids separation occurs. In the clarifiers, biological solids settle to the bottom, forming sludge, while clarified effluent rises to the surface for further treatment. A portion of the settled sludge is returned to the headworks or process stream as needed, while excess sludge (waste activated sludge) is discharged directly to the six drying beds for dewatering and final solids handling. The clarified effluent is then routed to a chlorine contact chamber, where disinfection is achieved through chlorination to inactivate pathogenic organisms. The treated and disinfected effluent is discharged to Outfall 001. Dewatered biosolids generated at the facility are transported off-site for disposal. 2 City of Rio Grande TX0068764/TXR05FH33 Inspection Date 1/29/2026 Section II- Observations This inspection revealed the following observations for TX0021547: Mechanical Bar Screen Out of Service At the time of the inspection, the mechanical bar screen was not operational. Facility personnel indicated that the unit has been out of service since August 2025. Oxidation Ditches Both oxidation ditches were in operation at the time of the inspection; however, each basin exhibited a noticeable accumulation of surface foam. The characteristics and persistence of the foam were indicative of elevated oil and grease concentrations in the influent as stated by facility personnel, which appeared to be contributing to the observed conditions within the treatment process. No Holding Tank or Digester The existing facility design limits operational flexibility for managing solids inventory within the treatment system. The sludge wasting is constrained by the capacity and availability of the drying beds, which serve as the primary solids handling method. During periods when the drying beds are at capacity, as well as during extended rainfall events or colder months when drying efficiency is reduced, the facility's ability to waste solids is significantly restricted, resulting in intermittent or delayed sludge removal. Not documenting time of sampling and analysis During the inspection, it was observed that the facility did not document the actual collection times for grab samples or the corresponding analysis of pH, dissolved oxygen (DO), and chlorine. Instead, the facility relies on a pre-stamped sampling log indicating 8:00 AM, 12:00 PM, and 3:00 PM. Operators reported that samples are not consistently collected or analyzed at these exact times. As a result, the accuracy of recorded data cannot be verified, and the required holding times for sample integrity are uncertain. Section III- Areas of Concern This inspection revealed the following areas of concern for TX0021547: During the inspection, it was noted that the pH, dissolved oxygen (DO), and chlorine grab samples collected for the months of September, October, and November 2025 could not be validated to confirm compliance with required holding times. Accurate documentation of sample collection times is necessary to ensure adherence to holding time requirements as specified in 40 CFR Part 136 - Guidelines Establishing Test Procedures for the Analysis of Pollutants. Without recorded times, there is no verification that samples were analyzed within the regulatory holding periods, 3 City of Rio Grande TX0068764/TXR05FH33 Inspection Date 1/29/2026 potentially compromising data integrity and compliance with permit monitoring requirements. Section IV - Stormwater TXR05FH33 Observations & Areas of Concern The City of Rio Grande obtained coverage under the Texas Pollutant Discharge Elimination System (TPDES) Multi-Sector General Permit for Industrial Stormwater, which became effective on November 12, 2021. At the time of the inspection, the facility maintained a Stormwater Pollution Prevention Plan (SWP3) on-site. The plan was available for review and appeared to be complete and properly maintained. Key elements of the SWP3 were documented and implemented, including the facility's organizational structure and responsible personnel, employee training program, routine monthly facility inspections, quarterly visual monitoring of stormwater discharges, rainfall monitoring, and benchmark monitoring data. Records reviewed during the inspection indicated that these compliance activities were current and maintained in accordance with permit requirements. Additionally, the Best Management Practices (BMPs) outlined in the SWP3 appeared to be implemented effectively and were functioning as intended to minimize potential pollutant discharges in stormwater runoff from the facility. Section V - LIST OF APPENDICES Appendix A - Photos 4 City of Rio Grande TX0068764/TXR05FH33 Inspection Date 1/29/2026 Appendix A Photograph Log UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Photograph Log Location: City of Rio Grande City: Rio Grande Photo No. 1 County/Parish: Hidalgo State: Texas Bar Screen UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Photograph Log Location: City of Rio Grande City: Rio Grande Photo No. 2 County/Parish: Hidalgo State: Texas Oxidation Ditch UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Photograph Log Location: City of Rio Grande City: Rio Grande Photo No. 3 County/Parish: Hidalgo State: Texas Oxidation Ditch UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Photograph Log Location: City of Rio Grande City: Rio Grande Photo No. 4 County/Parish: Hidalgo State: Texas Clarifier UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Photograph Log Location: City of Rio Grande City: Rio Grande Photo No. 5 County/Parish: Hidalgo State: Texas Clarifier #2 UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Photograph Log Location: City of Rio Grande City: Rio Grande Photo No. 6 County/Parish: Hidalgo State: Texas Drying Beds UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Photograph Log Location: City of Rio Grande City: Rio Grande Photo No. 7 County/Parish: Hidalgo State: Texas Drying Beds UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Photograph Log Location: City of Rio Grande City: Rio Grande Photo No. 8 County/Parish: Hidalgo State: Texas Chlorine Chamber UNITED STATES ENVIRONMENTAL PROTECTION AGENCY Photograph Log Location: City of Rio Grande City: Rio Grande Photo No. 9 County/Parish: Hidalgo State: Texas Chlorine Chamber