Air Quality

Water Quality

INCOG's Role
Regional Water Quality Programs
Pollution and Impairment
Total Maximum Daily Loads (TMDLs)
Resources and Links

Energy Management

Metropolitan Environmental Trust (M.e.t.)



Point Source vs. Nonpoint Source
In the past 10 years, wasteload allocation studies have become more complex by adding nonpoint source load assessments. Nonpoint sources are different from the discrete single pipe discharges of point sources that come from a treatment facility. Nonpoint sources have no discrete discharge pipe, and they are from pollutant sources that do not undergo any type of waste treatment. Nonpoint sources are usually associated only with rainfall runoff, so under dry conditions, nonpoint sources are usually minimal or non-existent.

Characterizing and calculating nonpoint source loads is very difficult, and the scientific investigations and modeling of nonpoint sources is still actively evolving. Also, most nonpoint sources do not have permit limits and are not regulated. Exceptions are discharges from Concentrated Animal Feeding Operations (CAFOs) and stormwater discharges from designated Phase I and II municipal stormwater systems, both of which are regulated as point sources in TMDLs.

A study that incorporates point source wasteloads, nonpoint source loads and includes a margin of safety calculation is called a Total Maximum Daily Load (TMDL). TMDLs set daily maximum limits on all point source and nonpoint source load discharges. A TMDL can address bacteria, dissolved oxygen, turbidity, metals, pesticides or any other type of pollutant. Hundreds of TMDLs have been prepared across Oklahoma for bacteria (pathogens), turbidity, dissolved solids, dissolved oxygen and nutrients.

It is difficult to implement reduction strategies for some TMDL pollutants, particularly in urban areas. Turbidity in streams is frequently caused by stream bank erosion which is often related to too much impervious surface (e.g. from parking lots, streets and rooftops). Pesticides in urban areas frequently come from individual home use. Control of home chemicals is largely accomplished through public education programs and individuals taking personal responsibility for how they apply and dispose of chemicals.
Rural agricultural nonpoint sources are addressed in a TMDL by deploying voluntary measures. A TMDL implementation strategy identifies the pollutant sources, and state agencies can bring resources into the watershed to encourage voluntary pollution reduction projects.

Treatment plants must meet numerical effluent limits. Their discharge permits have mandatory compliance requirements with penalty provisions for failure to comply. Stormwater permitted cities and counties within TMDL watersheds must implement Best Management Practices (BMPs) to control pollution in runoff.