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The City of Portland, Oregon

Development Services

From Concept to Construction

Phone: 503-823-7300


1900 SW 4th Ave, Portland, OR 97201

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Land Feasibility Study

A Land Feasibility Study is conducted to evaluate and determine the suitability of the soils relative to a parcel of land where an on-site sewage system would be used.

The following items should be taken into account when considering site location or installation of a septic tank/drainfield on-site system:

  • Septic tank and drainfield systems function as a gravity flow system. The location of a drainfield should be downgrade from the building site.
  • Maximum allowable slope is thirty (30%) percent (30 feet per 100 feet lineal)
  • Drainfields must be:
    • 100 feet from any wells or springs (domestic water supply) or any year round stream
    • 100 feet from any body of water or 50 feet from any intermittent stream
    • Fifty (50) feet from any roadways or steep slopes formed by erosion

5 Steps process to complete a Land Feasibility Study:

  1. Complete the Septic Evaluation Application
  2. A small section map or title insurance map for property identification
  3. Complete all sections of the Land Feasibility Study (perk test) form entitled, “Land Development Using an On-Site Sewage Disposal System Information.” Sections include:
    • Having the local water district complete the "water availability statement" of the form
    • Having the appropriate zoning jurisdiction complete the "intended use and zoning approval" statement form.
      City of Portland residents can visit Planning and Zoning staff at the Development Services Center.
      Unincorporated Multnomah County residents visit Planning and Zoning staff at the Development Services Center or call (503) 823-7526 to determine the appropriate zoning jurisdiction.
    • Dig two (2) test pits dug three (3) feet square by five (5) feet deep, spaced a minimum of seventy-five (75) feet apart, in the area to be used for the drainfield and complete the "test plat location map" of the form
    • For subdivisions only, include a copy of the preliminary plat as proposed by the subdivider
  4. Once the forms are completed, there are two ways to submit the application and pay the fees:
    1. In person - to the Development Services Center
    2. By mail - send the application and check to:
      City of Portland, Bureau of Development Services
      Attn: Environmental Soils Section
      1900 SW 4th Avenue, Suite 5000
      Portland, OR 97201
    If you have any questions please call (503) 823-6892.

  5. Once your application has been submitted, it will be reviewed and the test pits inspected by environmental soils staff.

    To have test pits inspected, please call (503) 823-7000 and follow the prompts. You will need your IVR number located on your fee statement, and the code for test pit inspections is #848.

    More information on Septic Inspections, call (503) 823-6892.

    Once the study is complete, the applicant will be informed of the suitability of the site for a standard or alternative sewage disposal system by letter.