Cesspool Decommissioning Common Questions

What is a cesspool?

In the most basic terms a cesspool is a constructed underground vault for the disposal of liquid waste and sewage. Cesspools are made of loose-fitting brick or concrete rings, which allows the liquids to seep through the brick gaps or perforations within the concrete rings, leaving the solids behind.

Original cesspools are typically 3- to 4-feet in diameter and usually located 10 feet away from the exterior foundation of the home, in line with the main 4” sewer-vent pipe. Homes with crawlspaces or slab on grade construction have cesspools typically located about 3- to 5-feet below ground surface, while homes with a basement will commonly be 8- to 10-feet below the ground surface.

Cesspool Decommissioning

Cesspool Decommissioning – Technician performing an onsite cesspool evaluation

Why should I worry about a cesspool?

Abandoned cesspools can become unstable and collapse, causing a sinkhole or completely collapse within the yard. Falling into a collapsed or collapsing cesspool, that may contain liquids and sludge, can cause serious injury or death.

If you suspect that a sinkhole is forming within your yard, the area should be roped off immediately to prevent anyone from falling into the opening and a qualified expert should be contacted for assistance.

How do you find a cesspool(s)?

The likely location(s) of the cesspool(s) would need to be determined by sending out a technician to the property and conducting research through public records, if available.  The on-site technician locates the main 4” main sewer-vent pipe that extends through the roof and matches it up to information gained through public records.  From the foundation, original cesspools are usually 10’ from the home. If multiple cesspools are located on the property, they can generally be found through diagrams within public records. Following the original plumbing, gaining information through public records and physically probing to them is the most reliable way to find the cesspool(s).


Cesspool Decommissioning

Cesspool Decommissioning – Cesspool marked out for excavation

Decommissioning of a cesspool

How do you decommission a cesspool?

EcoTech uses excavation equipment to dig to the top of the structure to expose and open the cesspool. Once the cesspool lid is removed, our technicians will then inspect the interior of the cesspool, pump any liquid or sludge that may be present, and completely fill the cesspool with gravel or sand. After the decommissioning has taken place, the technicians replace the soil overburden, bringing the area back to surface grade

The proper cesspool decommissioning permit will need to be obtained for the city and/or the county the cesspool is located in.  An inspection may also need to take place, after the system has been filled, depending on the county. Multnomah County will always require an inspection of the filled cesspool, prior to the decommissioning permit being finalized and the overburden replaced. If an inspection is required by the city/county, and a permit pulled for the cesspool decommissioning, once approved, the permit will be closed with the city.


Cesspool Decommissioning

Cesspool Decommissioning – Cesspool found, constructed out of loose fitting bricks

Cesspool Decommissioning

Cesspool Decommissioning – Cesspool found, constructed of concrete rings

Cesspool Decommissioning

Cesspool Decommissioning – Cesspool filled with sand, excavation fenced off and ready for inspection

For more information on local cities requirements on cesspool decommissioning within the Portland Metro area, please click on the following links:

Please note: although most of these links will reference septic tanks, the decommissioning processes is relatively similar.