Skip to Main Content View Text-Only

Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Avenue, Room 1000, Portland, OR 97204

More Contact Info

Determining Impervious Area

industrial impervious areaImpervious area is the area of a property that does not allow rainwater to percolate naturally into the ground. The city classifies the following as impervious areas for billing purposes:

  • Roofs

  • Paved areas such as driveways, parking lots, or walkways

  • Areas of property that are covered by porous pavement. 

Areas comprised of compacted soils and gravels are excluded from our measurements.