 Or look at porous pavement, it is a little more expensive. Or maybe look at pavers. Whether or not you can personally help out, this principle of letting rainwater soak into the ground instead of going into sewers can be applied in all sorts of contexts. Incorporating this green infrastructure into cities and towns is one way to help keep the water clean. Boston has all kinds of examples around the city, from rain gardens to sidewalks made to let the water through.