Fischer’s Forest Park Septic System Update

Clackamas Water Environment Services (WES) owns and operates the Fischer’s Forest Park large onsite septic system (LOSS). The LOSS serves an area consisting of 26 homes on three cul-de-sac streets.

Process Area

The original LOSS was installed in the early 1970s and like any system that is 50 years old, even with routine maintenance, performance can deteriorate over time. In 2019, we hired consultants to complete an evaluation of the collection system (manholes, pipes, septic tanks, recirculation tanks, filtration units, etc.) and the drain fields.

The evaluations identified many deficiencies in the system:

  • Some of the pipes have developed sags and there are areas where pipe connections have separated.
  • Several of the concrete structures have developed cracks and while these cracks are not structural concerns, they let groundwater into the system, which can cause the system to exceed its treatment capacity.
  • Some locations where pipes enter the concrete structures have degraded, which allows groundwater into the system and can cause the system to exceed its treatment capacity.
  • Some of the concrete structures and cast iron pipes show signs of corrosion that could lead to structural failures if left unattended.
  • Damage caused by tree roots has left the central drain field severely damaged, and repairing the system in its current location is not a realistic option.
  • Evidence indicates the east and west drain fields are struggling and need to be rehabilitated or replaced.
  • The system’s operation and distribution controls are inefficient and should be modernized to improve the performance and life expectancy of the facility.


Treatment pods

The LOSS was initially built in the 1970s, consisting of three separate collection areas (East, Central and West), each with a septic tank and drain field. In the early 1980s, the drain field that serviced the West collection area began to fail. This unexpected system breakdown prompted a 1983 renovation of the system. The 1983 project made two major changes to the system.

First, instead of having separate drain fields for each collection area, the effluent from all three septic tanks was re-directed to a central recirculating tank. By combining the flows into one system, it would allow the updated facility to provide even dosing of the drain fields and help avoid overloading any one part of the system.

The second major change was the addition of a recirculating gravel filter. The filter served to further treat the wastewater, which in turn would limit the amount of solids being delivered to the drain fields. It was expected that wastewater with lower solids content would extend the life of the drain fields and decrease the likelihood of system issues in the future.

The system operated in that manner until 2006. In 2006, the recirculating gravel filter was replaced with a more modern filtration system and a more sophisticated drain field dosing control system was installed. Outside of regular maintenance and equipment replacement, no upgrades or modification have been done since 2006.

Virtual neighborhood meeting on the Fischer's Forest Park large onsite septic system (LOSS).

Moving Forward

The plan:

  • Replace the entire gravity collection system, including manholes, mainlines, and when possible, residential service laterals.
  • Make improvements to and move the treatment system to an area north of Merry Meadow court.
  • Create a new drain field over the area of the field that failed in the early 1980s.

Every effort will be made to make the construction activity as minimally disruptive as possible.

Department Staff
Nathan Seaver
Any questions or concerns can be sent to project lead


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