*'''Surface Sweeping''': Sweeping should occur once or twice a year with a commercial vacuum sweeping unit to mitigate sediment accumulation and ensure continued porosity. Permeable pavement should not be washed with high pressure water systems or compressed air units, because they will push particles deeper into the pavement.<ref name=manchester2002>Philadelphia Water Department (PWD). 2007. Philadelphia Stormwater Management Guidance Manual. Philadelphia </ref> | *'''Surface Sweeping''': Sweeping should occur once or twice a year with a commercial vacuum sweeping unit to mitigate sediment accumulation and ensure continued porosity. Permeable pavement should not be washed with high pressure water systems or compressed air units, because they will push particles deeper into the pavement.<ref name=manchester2002>Philadelphia Water Department (PWD). 2007. Philadelphia Stormwater Management Guidance Manual. Philadelphia </ref> |