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. NN0020621) to Navajo Tribal Utility Authority (NTUA) for the Shiprock wastewater treatment facility located approximately a mile northwest of US Highway 491 and ½ mile north of Highway 64 in San Juan County, New Mexico, within the northeastern portion of the Navajo Nation.

The facility serves approximately 5,780 customers, receiving only domestic sewage with a design flow rate of 1.0 million gallons per day. Treatment includes primary clarification, trickling filtration, secondary sedimentation, and disinfection. Primary clarification is achieved when wastewater flows by gravity to the primary clarifier where solids are separated and pumped to a digester and the liquid portion flows to a wet well. Secondary treatment is provided with wastewater flowing to a splitter box that directs to either of two (2) trickling filters then to a collection box before entering the aeration basin and secondary clarifier. Two anaerobic digesters with fixed and floating covers, mixing units and heating system are currently coding the digester. Once digested, the remaining material is placed into six sludge drying beds. Ultraviolet (UV) disinfection is accomplished with UV lamps that produce radiation to destroy bacteria, viruses and other microorganisms within the wastewater. Chlorination and dechlorination would be employed as a backup disinfection system. The proposed permit will regulate the discharge of treated effluent from the facility to San Juan River, in Segment 2401 of the San Juan River basin in the Navajo Nation.

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