Concerns regarding highway stormwater runoff quality have increased as more roads are built or widened, and impervious surface areas grow throughout watersheds. To mitigate effects of highway runoff on receiving waters, low-impact development (LID) stormwater-management systems are being used as a method of decentralized, hydraulic and nonpoint  source control instead of centralized best management practices.

This study will develop and implement a comprehensive plan to determine the effectiveness and costs of multiple LID systems for mitigating adverse impacts of highway stormwater runoff. The Lorton Road widening project provides an ideal opportunity to evaluate a variety of LID systems that receive nearly identical rainfall, climate, daily traffic and maintenance. LID performance has been difficult to quantify due to the large variability observed in previous studies. Factors such as rainfall amount and intensity and LID inflow quality have a major effect on how LID systems perform.