Viterbo currently has four parking lots that are made of pervious asphalt paving. These parking lots were constructed in a manner that allows rainwater to filter through them rather than drain to the City storm water system. This type of lot is preferred, as they reduce demand on the storm water system and help prevent debris from getting into nearby water ways. Viterbo receives a city tax credit for each of these parking lots due to the reduced demand on the City storm system. One interesting fact it that in order to keep the asphalt pervious and from filling up with sand and leaves, they must be vacuumed twice per year.