NOTICE Interested parties are hereby notified that Dallas Fort Worth International Airport (DFW) proposes to implement the Inverted Siphon Project located within DFW Airport property in Tarrant County, Texas. The Federal Aviation Administration (FAA) has determined that portions of the proposed project are located within the 100-year floodplain, as mapped by the Federal Emergency Management Agency (FEMA). The purpose of this notice is to: (1) provide information regarding the proposed project and associated floodplain; (2) provide the public an opportunity to comment: and (3) comply with Executive Order 11988, Floodplain Management, FAA Order 1050.1G, Environmental Impacts: Policies and Procedures, FAA Order 1050.1F Desk Reference, and FAA Order 5050.4B, National Environmental Policy Act (NEPA) Implementing Instructions for Airport Actions. The proposed Inverted Siphon Project would include rehabilitation of two existing sanitary sewer inverted siphon junction boxes, construction of a permanent gravel maintenance access road, and installation of a low water drainage crossing to improve long-term operational reliability and maintenance access to critical wastewater infrastructure at DFW Airport. The project area is generally located north of Airport Freeway (TX-183), west of TX-360, and south of Trigg-Euless Road within the northern portion of DFW Airport property near Big Bear Creek. The inverted siphon conveys sanitary sewer flows from the DFW Pretreatment Plant downstream into the Trinity River Authority (TRA) wastewater system. The existing siphon infrastructure, originally constructed in 1970, includes one 24-inch and one 18-inch pipe beneath Big Bear Creek, with sanitary sewer junction structures at each end of the siphon. The proposed project would rehabilitate both junction boxes by installing protective surface lining systems and associated structural improvements to extend the operational life of the facilities. Project improvements would also include reconstructing and stabilizing an existing gravel access road that extends from the site's western section to the southern siphon structure. This will include replacing the current low water crossing with a new one, designed to handle the 1-year storm event while preserving the channel system's hydraulic function. The proposed project is located within portions of FEMA-designated Special Flood Hazard Area Zone AE and adjacent floodway areas associated with Big Bear Creek. Applicable FEMA Flood Insurance Rate Map (FIRM) Panel for the project area is Panel no. 48439C0235L, effective March 21, 2019. Hydraulic analysis determined that the proposed culvert would convey approximately 975 cubic feet per second (cfs) during the 1-year storm event compared to approximately 1,024 cfs under existing conditions. The proposed design results in flow velocities substantially consistent with existing conditions, with existing velocities estimated at approximately 3.39 feet per second (fps) and proposed velocities estimated at approximately 3.38 fps. Stone riprap and channel protection measures would be installed at the culvert to reduce erosion potential and maintain channel stability. The proposed action is not anticipated to significantly alter floodplain storage capacity, increase base flood elevations, or adversely impact the hydraulic function of the Big Bear Creek floodplain. Construction staging and employee parking areas would be located outside of the FEMA-designated floodway and 100-year floodplain. No materials would be staged within the floodway, 100-year floodplain, or 500-year floodplain during construction activities. Although no adverse floodplain impacts are anticipated, DFW Airport would monitor the channel area before and after construction to confirm that erosion does not occur near the low water crossing and culvert improvements. An inundation map for the crossing area would be developed during future updates to the Bear Creek hydrologic and hydraulic model. The environmental review, consultation, and other actions required by applicable federal environmental laws for this project are being, or have been, carried out by FAA Order 1050.1G and other applicable federal, state, and local regulations. If requested, an opportunity for a Public Meeting to review the project and provide comments will be granted in conjunction with FAA policy and floodplain review. Meeting requests may be submitted by contacting Cristian Sigala, DFW NEPA Project Manager, at 972-973-5564 or by email at csigala@dfwairport.com. Written comments will be accepted until June 21, 2026, or within 30 days of the Notice Publication date. Comments may be submitted by via email or by physical mail to: DFW International Airport, Environmental Affairs Attn: Cristian Sigala P.O. Box 619428 DFW Airport, TX 75261-9428 Please note that names and contact information provided with comments will become part of the public record and may be disclosed under the Freedom of Information Act. IPL0342677 May 22,29,Jun 5,12 2026