General Permit 4

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Discharge from Private Sewage Disposal (Onsite) Systems

Any private sewage disposal system (PSDS, also known as an onsite wastewater treatment system or septic system) that discharges treated wastewater to a designated water of the state or a subsurface drainage tile must be monitored to ensure that it meets secondary treatment standards. To achieve these standards, all surface-discharging private sewage disposal systems must obtain coverage under NPDES General Permit #4 (GP #4) by submitting a Notice of Intent and must meet all the monitoring requirements of the permit.

NPDES General Permit #4 for Private Sewage Disposal Systems

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GP #4 Renewal

The Iowa Department of Natural Resources (DNR) is hosting an informal stakeholder meeting regarding the proposed changes to NPDES General Permit #4 (GP #4) for discharges from private sewage disposal systems. The purpose of this meeting is to accept comments and answer questions on changes to GP #4. The DNR is specifically seeking comments on the clarity, feasibility, and potential impact of the proposed changes.

The current general permit expires on February 28, 2028. Formal rulemaking to renew GP #4 is expected to begin in mid 2026.

The meeting will be held on Wednesday, February 4, 2026 at 11:00 AM. The meeting is open to the public and will be held virtually via Google Meet. 

Video call link: https://meet.google.com/hrr-qeje-nzc

Questions regarding the meeting may be directed to Cory Frank at cory.frank@dnr.iowa.gov.

Redline-strikeout version of the draft renewal of GP #4 (2025-11-12)

Submit all comments and any questions regarding the draft renewal or the rulemaking process to npdes.mail@dnr.iowa.gov

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GP #4 Notice of Intent (NOI)

NOI Requirements:

  • A GP #4 Notice of Intent (NOI) form signed by the system owner must be filed with the NPDES Section of the Iowa DNR prior a discharge from a private sewage disposal system (PSDS).
  • An NOI must be submitted when a construction permit for a new discharging PSDS is issued by the local administrative authority, or when a facility (e.g., home, business, etc.) with an existing discharging PSDS is purchased.
  • An NOI form may be obtained from a county sanitarian or downloaded below.
  • By signing the NOI, the system owner agrees to abide by the conditions of the permit. 

There is no fee associated with GP #4 permit coverage. Once a signed NOI form is received, the Iowa DNR will issue an authorization for coverage under GP #4 to the system owner.

NOI Form and Submission:

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GP #4 Sampling Requirements

The owner of a discharging private sewage disposal system is required by GP #4 to sample the discharge from the system at least twice per year, and to maintain sampling records. These requirements are in addition to any county construction or operating permit requirements for the system. 

Sample Testing and Submission:

  • The owner is required to make arrangements for the test samples from the system to be analyzed by a certified laboratory. To find a certified laboratory, please use the Iowa DNR Laboratory Certification database.
  • Submit all sample results to npdes.mail@dnr.iowa.gov

GP #4 Qualified Sampler Training:

  • A Qualified Sampler, for the purposes of collecting compliance effluent samples required under GP #4, means a city or county environmental health staff person, an Iowa-certified wastewater treatment operator, or an individual who has received training approved by the DNR to conduct effluent sampling.

  • Only a Qualified Sampler can conduct effluent sampling for compliance monitoring under GP #4. Becoming a Qualified Sampler involves receiving training directly from the DNR or a local county environmental health office.

  • Qualified Sampler training is provided on demand by your local county environmental health office or directly from the DNR. Formal training is essential for mastering the specific techniques and protocols required. After the training is completed, the Qualified Sampler will receive a Certificate of Completion from the DNR. 

  • Please contact the DNR by emailing npdes.mail@dnr.iowa.gov or contact your local County Environmental Heath department for more information on scheduling training to become a Qualified Sampler.

No Evidence of Discharge:

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GP #4 Notice of Discontinuation (NOD)

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