To address the above permit requirements, the County selected sediment, bacteria, and nutrients as the three high-priority water quality issues on which to focus its Public Education and Outreach Program.
Sediment and bacteria were selected because the County has been assigned a Total Maximum Daily Load (TMDL) for these impairments, which means the County has been put on a "Pollution Diet" to limit these two pollutants from entering its waterways. Nutrients (phosphorus and nitrogen, in particular) were selected as the third water quality issue on which to focus, because they have such negative impacts on receiving waters when in large quantities. Excess nutrients wash off from lawns, other managed turf areas, and farm fields and are transported via stormwater runoff to the area's local creeks, streams, and the Roanoke River. In these water bodies, they cause algae overgrowth, which in turn decreases the oxygen that marine life need to survive. This often results in fish kills, fish illnesses, and the tainting of human food.
Groundwater supplies may also be affected by nutrient pollution, thus making it an important topic on which to focus education efforts.