Explain how replacing asphalt with gravel or other permeable material can improve water quality.

Answer:

Impervious surfaces like asphalt and concrete channel water across their tops until the water finds a point where it can infiltrate the ground. As it passes across these impervious surface the water gathers chemicals and debris that have collected and concentrates them at the point of infiltration. By using more permeable materials the water infiltrates more generally and does not flow along and collect additional pollutants.