TMDL and NPDES Support for a Municipality

The City of Sheridan, Arkansas, asked FTN to develop a dissolved oxygen (DO) total maximum daily load (TMDL) to quantify the impact of the City’s intermittent discharge of treated wastewater in the receiving stream. FTN analyzed historical water quality data and showed that most DO violations were not occurring during the same months that the City was discharging.

We then collected field data and used those data to set up and calibrate a water quality model to develop recommended permit limits for the City’s discharge. The modeling included simulations for different flow conditions and different seasons to justify a hydrograph-controlled release that varies with seasons to provide operational flexibility for the City.

The Arkansas Department of Environmental Quality and EPA approved the TMDL and accepted the recommended limits for biochemical oxygen demand, ammonia nitrogen, and DO.

FTN also assisted the City with various NPDES issues, including permit limits for total suspended solids and total recoverable lead.