The single-family home annual utility charge is $122. Owners of single-family residences pay a flat utility charge, whereas owners of apartments, businesses, and commercial structures are charged a rate per quarter acre according to the percentage of impervious surfaces* on their properties. For a complete list of rate categories and charges, see Snohomish County Code 25.20.020. * Impervious surfaces are hard surfaced areas that prevent or retard the entry of water into the soil, or cause water to run off faster than under natural conditions. Common impervious surfaces include rooftops, sidewalks, pavement, patios, driveways, parking lots, gravel, and other surfaces that impede the natural infiltration or runoff of surface water.