Official State of Iowa Website Here is how you know

NPDES General Permit #8 for Hydrostatic Testing, Tank Ballasting, and Water Lines

On July 1, 2018, the Iowa DNR issued a new general permit to authorize discharges from the following activities:

  • Hydrostatic testing of pipes, lines, tanks, and associated equipment.
  • Ballasting of underground storage tanks during installation.
  • Disinfection, flushing, and testing of potable water lines.

General Permit #8 (GP8) was reissued on July 1, 2023.

GP8 covers discharges to surface waters of the state and to the ground surface. Certain discharges from potable water lines in MS4 cities may already be authorized under the city’s MS4 permit.

Permit and Helpful Documents

Please use the links below to view General Permit 8 and documents intended to assist you in navigating the general permit requirements.

General Permit 8 - effective July 1, 2023

Several documents have been developed to help people determine what permit requirements are applicable in a given situation.

  • GP8 Decision Matrix  The GP8 Matrix is a series of yes/no questions. As you answer each question, you will be directed to the next applicable question. You may prefer this if you are a linear thinker or like flow charts.
  • GP8 Requirements Summary The GP8 Requirements Summary has all the permit requirements laid out in one document, so you can easily find the requirements for your situation. You may prefer this if you are a visual thinker, or if you wish to compare requirements among different situations.

Coverage Under General Permit 8:

Most permittees will be automatically covered under GP8. However, some permittees will need to submit an electronic Notice of Intent for Coverage (eNOI). To determine if you need to submit an eNOI, please refer to the documents linked above. If you need to submit an eNOI, please proceed to the NPDES Databases page.

A few permittees will need to complete an Antidegradation Document as part of the the electronic Notice of Intent. For more information on the antidegradation requirements, please see the Water Quality Standards Antidegradation page.

Effect of GP8:

What GP8 does:

  • Authorize temporary and limited discharges that can meet water quality standards.
  • Authorize certain discharges that are not temporary and limited but that are approvable under Iowa’s Antidegradation Implementation Procedure.
  • Provide a permit shield to authorized discharges.
  • Establish eligibility requirements and best management practices to ensure protection of water quality.
  • Reduce the number of permittees required to pursue individual permits.
  • Greatly reduce the amount of time needed to obtain permit coverage for most permittees.
What GP8 does NOT do:
  • Authorize discharges that will cause violations of water quality standards.
  • Authorize discharges to Outstanding Iowa Waters or state-owned lakes.
  • Establish burdensome notification requirements.
  • Require fees.
  • Eliminate the department’s ability to require a discharger to apply for an individual permit.
  • Eliminate a discharger’s ability to apply for an individual permit.

More information:

For more information on this permit, contact Wendy Hieb at or 515-808-3039.