Summary

EPA is issuing a notice of proposed action under the Clean Water Act. EPA is proposing to issue a National Pollutant Discharge Elimination System (NPDES) permit (No. NN0030344) to Navajo Tribal Utility Authority (NTUA) for the Twin Arrows Navajo Casino and Resort wastewater treatment facility located on 22181 Resort Boulevard, approximately 1.0 mile north of I-40 and 22.5 miles east of Flagstaff, Coconino County, Arizona, in the Southwestern portion of the Navajo Nation.

The facility serves the Twin Arrows casino and resort population of about 14,800 per day, receiving only domestic sewage with a design flow of 0.125 million gallons per day. Wastewater generated from the casino and resort complex is conveyed by gravity to a lift station located south of the treatment plant. Influent entering the plant is sent to a flow equalization basin and combined with returned activated sludge before undergoing screening, aeration and sedimentation. Secondary effluent is then filtered prior to ultraviolet (UV) disinfection and discharge. Treated effluent that is not discharged is stored in a small irrigation pond on-site. The proposed permit regulates the discharge of treated effluent from the facility to an unnamed wash which is a tributary to Padre Canyon, a tributary to Canyon Diablo, a tributary to the Little Colorado River.

***Please bring the foregoing notice to the attention of all persons who would be interested in this matter. ***