Building Code Guide 17-10: Drywell Location

Building Code Guides (BCGs) and Building Official Determinations (BODs) provide answers about the application of building codes and outline optional alternates. BODs are typically smaller in scope and address simpler questions. Code Guides provide a comprehensive alternative to a complicated set of code requirements.

BCG 17-10: Drywell Location  

QUESTION: When a drywell is an approved method of stormwater management, can the drywell be located closer than 5’ to a property line and/or closer than 10’ from a building without a plumbing code appeal?

RESPONSE: City of Portland Title 25.10 and the Oregon Plumbing Specialty Code (OPSC) 1101.6.3 requires that drywells be located no closer than 5’ from a property line and no closer than 10’ from a building.  The City of Portland has determined that drywells can be located closer than 5’ from a property line and/or closer than 10’ from a building without a plumbing code appeal if ALL of the following conditions are met.  This includes situations where the drywell is located underneath a building.

1. The drywell must be allowed as a method of stormwater management as approved by the Bureau of Environmental Services (BES).
2. Location adjacent to property lines: If the drywell is located closer than 5’ from a property line:
   1. The subject property line must be adjacent to a right of way including streets, alleys and public or private pedestrian tracts. 
   2. In situations where the City of Portland Stormwater Management Manual applies, an operations and maintenance agreement is required and must be recorded with the appropriate county recorder.  The agreement must include a description of the operation and maintenance, log sheets of proposed operation and maintenance, and infiltration testing results.  The operations and maintenance agreement must be reviewed and approved by BES prior to recording. 
   3. The drywell must be located and constructed in a way that it is accessible for maintenance.
3. Location adjacent to buildings: If the drywell is located either closer than 10’ from a building (measured from the exterior of the building foundation) on the subject or adjacent property or underneath a building:
   1. Infiltration testing and system sizing calculations must be reviewed and approved by BES.
   2. In situations where the City of Portland Stormwater Management Manual applies, an operations and maintenance agreement is required and must be recorded with the appropriate county recorder.  The agreement must include a description of the operation and maintenance, log sheets of proposed operation and maintenance, and infiltration testing results. The operations and maintenance agreement must be reviewed and approved by BES prior to recording. 
   3. The drywell must be in a located and constructed in a way that it is accessible for maintenance.
   4. The permit application must include plans that clearly show the building foundations and their relationship to the drywell.
   5. The permit application must include a report or reports, signed and stamped by a geotechnical engineer licensed in Oregon and a signed and stamped by a structural engineer licensed in Oregon that either:
      1. States location of the drywell does not impact the building foundations; or
      2. States location of the drywell does impact the building foundations, but includes design requirements for foundation design to address those impacts.

Alternative proposals not meeting the standards of this code guide may be approved on a case-by-case basis through the building code administrative appeals process.

HISTORY: Implemented June 1, 2017. Revised May 29, 2024.

DOWNLOAD a copy of this Code Guide:

QUESTIONS? Free 15-Minute Appointments for Permit, Code, and Zoning Questions