General Permit 4

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Discharge from Private Sewage Disposal (Onsite) Systems

Any private sewage disposal system (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) and must meet all the monitoring requirements of the permit.

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GP #4 Notice of Intent (NOI)

NOI Requirements:

  • A 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).
  • A 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 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:

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.
  • Sample results must be submitted to the Iowa DNR at npdes.mail@dnr.iowa.gov.

No Evidence of Discharge:

  • If there is no evidence of a discharge from the system within the previous six months, the discharge area must be physically inspected for any signs of surfacing effluent.
  • If no sample can be collected, the  GP #4: Notice of Non-Discharge Form (NND) (542-0696) must be completed and submitted.
  • Submit NDDs to the Iowa DNR at npdes.mail@dnr.iowa.gov and to the local County Environmental Health department.
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