Onsite Sewage

Notice: We have moved back to the Public Services Building, 155 N First Ave in Hillsboro. We are now in Suite 170.

The Washington County Environmental Health Program issues septic system permits for households that are not served by public sewer. These households usually depend on septic systems to treat and dispose of wastewater. A septic system has three main parts: the septic tank, the drainfield and the soil. A septic tank separates solids from wastewater and stores and decomposes the solid matter. The resulting liquid discharged from the septic tank seeps into a drainfield. The bacteria present in the soil below the drainfiled complete the final treatment of the wastewater. The soil also determines which type of septic system is suitable for a property.

A malfunctioning septic system is a health hazard; properly functioning septic systems treat sewage to prevent ground and surface water pollution. 

Fees, Forms and Applications

Site Evaluation- tests soils to determine septic system requirements


  • New Construction- brand new systems
  • Repair- repair an existing system or if existing system is failing
  • Alteration- make changes to a current system

Authorization- add bedrooms, replace home/dwelling, and health hardships

File Review- additional structures or additions to structures on the property other than additional bedrooms or structures of health hardship

Existing System Evaluation- environmental health specialist evaluates existing septic system

Tank Decommission- abandon/decommission tank
Final Request Notice- request inspection after septic system is installed