A TMDL allocation involves distributing allowable loads among sources within a watershed. It includes which types?

• A. Only point sources
• B. Only non-point sources
• C. Both point and non-point sources
• D. Only groundwater sources

Answer: (C)

A TMDL sets the maximum amount of pollutant that a watershed can receive without violating water quality standards and then distributes that allowed load among the sources within the watershed. The allocation must account for both types of sources that contribute to the pollutant entering surface waters: point sources, which are discrete and regulated discharges like wastewater treatment plants; and non-point sources, which are diffuse and harder to control, such as agricultural runoff, urban stormwater, and other landscape-based inputs. Groundwater can influence surface water quality, but a TMDL for surface water typically allocates loads to point and non-point sources rather than treating groundwater as a separate category. This combination is why the correct understanding is that allocations apply to both point and non-point sources.