The study looked at ways to reduce pollution in stormwater runoff by analyzing the "first flush" effect, where the highest levels of contaminants are seen at the start of a storm. They focused on how different retention-detention systems can help with this. By studying runoff from an asphalt highway in Ohio, they found that these systems can significantly reduce the amount of pollutants like metals, solids, and chemicals in the water. On average, they saw a 38% decrease in pollution during the first flush of stormwater runoff.