Septic Decommissioning Permits in Multnomah County

Learn about septic decommissioning permits and inspections for septic tanks, cesspools and seepage pits that were abandoned or are no longer in use. You need these permits when connecting to a public sanitary sewer from an active septic system, and often for demolition permits or building permits.
On this Page

You need to have a decommissioning permit whenever a septic tank, cesspool or seepage pits are no longer in use. This will be the official record of the location, material and decommissioning of the system.  A decommissioning permit is also required if a septic system has been decommissioned without a permit and future development (review the list below).  

Decommissioning will require excavation of the existing yard.   

Decommissioning permit application and important information   

When you need a septic decommissioning permit

Please note, septic decommissioning is not required for a real estate transaction. Septic decommissioning permits are required upon connection to a public sanitary sewer from a live septic system, and may be required as part of building demolitions, building permits, land divisions, property line adjustments, and abate a property nuisance due to a collapsed or open septic feature. 

You must have a septic decommissioning permit for any septic system, cesspool or seepage pit (septic system) when:

  • A property connects to public sanitary sewer and the active septic system is removed from service.  
  • The source of the sewage is permanently eliminated. For example, demolishing the structure served by a septic system.  
  • New construction is proposed within 10 feet of an abandoned septic system.  
  • Prior to the approval of a land division of a property with an abandoned septic system. 
  • Prior to the approval of a property line adjustment that will result in an abandoned septic system being located on a different lot than the structure it served or located within five feet of a proposed property line.  
  • To fill a sink hole resulting from an septic system.  
  • Final inspection approval of a City of Portland septic decommissioning permit is required to have a septic decommissioning on record in Multnomah County. 

Apply for a septic decommissioning permit  

Please complete the information in the left-hand column of the Septic Evaluation Application: 

  • Job Site Information and Location 
  • Property Owner Information 
  • Project/System Description 
  • Applicant Information 
  • Check Decommissioning box on top right 

You don't have to include a building permit or engineered drawings with the application. You can email us your completed application. The decommissioning permit will be set up within 1-2 business days. We'll contact the applicant with information about how to make fee payment using credit card. The decommissioning permit will be issued upon payment. 

Who can do the work 

Many types of contractors can perform septic decommissioning work including excavation companies, sanitary sewer contractors, specialty companies for home sales, and septic professionals. Homeowners and others may also perform the decommissioning work. You do not need a trade license to get a decommissioning permit. 

Get ready for septic decommissioning permit inspections

Locate the main plumbing vent stack (usually 4-inch) coming through the roof and visualize a straight line extending from the stack through the exterior foundation. Then follow the 4-6 inch diameter sanitary pipe exiting the building by digging to the end of the pipe either at the cesspool/septic tank or at the property line.   

Search historic plumbing records for septic system locations

You might find records showing septic system locations on Portland Maps. Enter an address to begin your search. Then, select Permits under the "Permits and Zoning" section. You can find any available historic plumbing records here. 


Step 1 Locate  

  • Original: Most original cesspools have been constructed directly in line with the main plumbing vent stack visible at the roof and 10-15 feet away from the building foundation.  
  • Replacement: Most replacement cesspools are usually located 10 feet straight out from the original cesspool or offset at a 45 degree angle (see diagram).  

Step 2 Excavate and remove the top of the cesspool    

In the approximate location of the cesspool, the top of the cesspool should be approximately 2-3 feet below the depth of the sanitary sewer pipe existing the building. Carefully remove the top and expose the cesspool. If the building has basement level plumbing, the top of the cesspool may be 10-12 feet below the ground surface.  

Step 3 Pump out any sewage 

If any residual solid or liquid sanitary waste is in the cesspool it must be pumped by a licensed DEQ pumper. If a cesspool has been abandoned for several years, it will likely be dry. If a cesspool is dry, pumping and a pump receipt are not required.  

If pumping is necessary, a copy of the pump receipt will be required for inspection approval.  

Step 4 Backfill  

Backfill the cesspool using clean ¾-inch minus crushed rock, gravel, masonry or playground sand, or concrete slurry. Native silty or clay soils, debris, and/or garbage cannot be used.  

Leave the upper 12-18 inches of the cesspool lining and the piping entering the cesspool exposed. The inspector will be documenting the piping and cesspool construction as brick, concrete ring, or unlined soil.  

You may be required to remove fill if these elements are not visible during inspection.  For fill using sand or gravel, it is recommended to fill in lifts of 6-12 inches thick and water down and/or tamp for proper compaction.  

If a new foundation will be constructed within 10 feet of the onsite septic system, the fill may need to be placed as structural fill with compaction testing by an engineer or testing agency. Please consult with your engineer or building inspector.  

Septic tanks 

Step 1 Locate  

Locate the septic tank by uncovering the sanitary pipe exiting the building to the end of the pipe either at the septic tank or the property line. The sanitary pipes are typically 4-6 inches in diameter. Occasionally septic tanks may have a riser to ground surface. Most original septic tanks have been installed directly in line with the main plumbing vent stack on the roof and 5-20 feet away from the side of the building foundation.  

Step 2 Pump out any sewage if applicable  

If any residual solid or liquid waste is in the tank it must be pumped by a licensed DEQ pumper. DEQ Link. Septic tanks typically must be pumped and are infrequently dry.  

Please keep a copy of the pump receipt. It is required prior for inspection approval.  

Step 3 Remove or decommission in-place  

To decommission a septic tank in place, it may be possible to fill the septic tank through an existing riser opening. In other situations, the top may need to be broken open to fill the septic tank. To ensure drainage, break up, punch, or drill holes in the bottom of the tank. Backfill the tank with ¾-inch minus or slurry. The top of the tank must be visible at the time of inspection so the tank construction and depth below grade can be documented.  

You can remove tanks if desired and backfill the excavation with sand, gravel, slurry, or according to an engineer’s recommendation. If you pull a septic tank before inspection, please make sure the tank remains on-site for inspection or photos are available showing the empty septic tank prior to removal.   

If a new foundation will be constructed within 10 feet of the onsite septic system, the fill may need to be placed as structural fill with compaction testing by an engineer or testing agency. Please consult with your engineer or building inspector.  

Schedule a septic decommissioning permit inspection, get inspection results and make corrections 

To schedule a septic decommissioning inspection, call the automated Requests for Inspection phone number. You need your IVR number and the three-digit code for the inspection. The IVR code for septic decommissioning is 842.  

Our inspection staff will call between 7 a.m. and 9 a.m the morning of the inspection. We'll confirm the site is accessible and the work is ready for inspection. We'll also provide an inspection window for arrival.  

The inspector will come to the property prepared with historic septic and plumbing records for the property. They will inspect the uncovered septic feature location(s), pipe type(s), and dimensions and compare to the available permit records. The inspector will sketch an as-built of the septic system feature(s) and document septic feature dimensions and backfill material. If a septic feature was not located, excavation efforts will be inspected and similarly documented. Keep all excavation efforts open for inspection. The inspector will collect the pump receipt to confirm the removal of septage.  Also:

  • If a pump receipt is unavailable at the time of the inspection, or other corrections are required, a list of the corrections will be documented on the inspection report.  
  • Get the results of the inspection on Portland Maps permit/case search the next day. Read more about why work does not get approved and how to schedule a reinspection
  • A reinspection fee may be charge if the inspector needs to perform three or more inspections on site. The fee must be paid prior to inspection approval.  
  • When the inspection has been approved, you may cover the cesspool or septic tank. 

Contact septic inspectors 

If you have questions about septic inspections, you can talk to an inspector between 7 a.m. to 9 a.m. on business days by calling Onsite Septic Permits & Inspections.