Design Standards & Guidance

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Iowa Wastewater Facilities Design Standards (IWFDS)

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Ten States Standards

The "Recommended Standards for Wastewater Facilities" by the Great Lakes - Upper Mississippi River Board of State and Provincial Public Health and Environmental Managers, commonly referred to as the Ten States Standards, is referenced in state rules and used by the Iowa DNR to supplement Iowa's Wastewater Facilities Design Standards. This wastewater facilities design document is an update prepared jointly by a board including Iowa, nine other Midwestern states, and the Province of Ontario. The 2014 Edition is available on the Ten States Standards website. 

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IWFDS Update

The IIWFDS were adopted in the late 1970's and early 1980's. The Iowa DNR initiated a review of selected Chapters (11, 12, 13, 14, and 18C) in 2018, and revisions were proposed. As part of the required rule review for Executive Order 10 (EO10), all of the chapters in the IWFDS are being reviewed and revised. Copies of the proposed revisions can be downloaded using the links below. See the Water Quality Bureau Rulemaking page for more information on EO10 and the proposed rule revisions associated with EO10.

Proposed Changes November 2024

Proposed Changes August 2024

Responses to Previous Comments

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Alternative Wastewater Treatment Design Guidance Manuals

The DNR has developed design guidance manuals in an effort to provide uniform design guidelines and broaden the number of treatment options considered for managing wastewater within Iowa's communities with populations ranging from 25 to 250. Understanding the alternative design guidance is important for consulting engineers and planners involved in the planning, funding, and design, and construction of wastewater treatment improvement projects since they are not addressed in the current IWFDS. The guidance manuals will enable professionals to evaluate these alternatives and work through the state approval process with confidence.

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Alternative Wastewater Treatment Design Guidance Documents - Technology Assessments

Due to revisions to Iowa’s Water Quality Standards, many communities have been faced with more stringent NPDES permit limits for bacteria and ammonia. Communities may experience significant costs associated with upgrading existing or building new wastewater infrastructure to meet effluent limits. These conditions created a need to broaden the treatment options considered for managing wastewater in Iowa communities.

The DNR has evaluated several new technologies for wastewater treatment that are not addressed by detailed design criteria in the IWFDS. After research and data analysis, DNR staff developed the following technical design guidance for alternative wastewater treatment technologies. These treatment technologies were evaluated for technical capability when treating primarily domestic wastewater from small municipal systems without industrial or significant commercial loads. These assessments, in addition to the applicable IWFDS, are intended to provide guidance to designers for project submittals to DNR for review and approval based on current empirical information relative to the capabilities of the treatment technology in various applications. The assessments are not design standards, but when used in conjunction with the IWFDS, should serve as the DNR's expectations for permit approval. 

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Additional Design Guidance Documents

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