What percentage of impervious cover is used in the phosphorus load limit calculation?

The phosphorus load limit calculation is a critical component of stormwater management, especially in Virginia, where the impact of impervious surfaces on water quality is significant. In this context, the percentage of impervious cover that is used in the phosphorus load limit calculation is 10%. This figure is established to reflect the contribution of impervious surfaces—such as roads, rooftops, and parking lots—to phosphorus runoff, which can lead to nutrient pollution in water bodies.

By incorporating this 10% figure into the load calculation, regulators can better assess and manage the potential for phosphorus discharges from developed sites, enabling them to establish appropriate control measures to protect water quality. This focus on impervious cover supports the broader goals of the Virginia DEQ in maintaining the health of its waterways and ensuring compliance with water quality standards.