DEQ presents overhaul of septic rules: setbacks revised, installer bonds increased, guidance to be codified

The Department of Environmental Quality (DEQ) presented a comprehensive rewrite of IDAPA 58.01.03 — the state rules governing on-site decentralized wastewater disposal — and the committee approved the rulemaking after presentation and questions.

Mary Ann (Maryann) Nelson, Surface and Wastewater Division Administrator for DEQ, summarized the rewrite (docket 5801032301) as a “critical and comprehensive review” aimed at reducing regulatory burden, increasing clarity and streamlining the chapter. DEQ said it removed archaic language (for example, replacing “shall” in many places), cut over 1,000 words from the chapter, revised definitions, simplified permitting and approval processes, and identified technical guidance manual (TGM) provisions that should be moved into rule.

Major substantive changes Nelson highlighted include: - Definitions: Several new or revised terms were added (for example: alternative system, standard system, extended treatment package system, proprietary wastewater treatment product). - Tank and product submittals: The rule requires product and tank submittals to be stamped by a licensed professional engineer for certain items. - Installer/service-provider bonding: DEQ proposed increasing bond requirements for installers and service providers from $5,000 to $10,000, and higher bonds for complex systems (noted as a larger amount for complex installations). - Minimum tank size: The rule raises the minimum septic tank capacity from 750 gallons to 1,000 gallons, reflecting current industry practice. - Riser requirement: Risers to the surface will be required for all new tanks installed going forward. - Setbacks: DEQ removed a prior 300-foot uniform setback to surface water (a carryover from a 1990 rule) and replaced it with smaller setback values applied based on updated research and site-specific review; the TGM and Technical Guidance Committee (TGC) will allow case-by-case adjustments using local site conditions. - As-built and inspections: A system is not approved for use until the health district provides a final as-built drawing and inspection report. The rules moved several as-built plan requirements into the approval sections and added a requirement that written notice be provided 35 days before revocation of an installation permit. - Licensing and exams: DEQ streamlined service-provider licensing and exam requirements and moved operator-licensing references for large soil absorption systems to DEQ’s wastewater rules.

Nelson told the committee the revision followed negotiated rulemaking with health districts, the attorney general’s office, cities, sewer districts, septic installers and others; DEQ presented the draft to the division of financial management and published the proposed rule in Idaho’s administrative bulletin. The Department reported that the Board of Environmental Quality approved the revised rule on Nov. 14, 2024.

Committee members asked questions about several items. Senator Taylor, referencing concrete tanks, asked whether the committee had considered moving away from concrete given cracking concerns; Nelson acknowledged plastic tanks are approved in the TGM and that committee discussion touches on materials. On setback reductions, Nelson said the previous 300-foot setback chosen in 1990 lacked documented scientific sourcing, and DEQ’s current review of recent research on nutrient movement (noting that phosphorus can move in some soils about one meter per year) informed more nuanced, site-specific setbacks. Nelson emphasized that the TGM and the TGC will guide case-by-case decisions.

Senator Burton Shaw asked about the reason for raising bond amounts; Nelson said the increase reflects inflation and higher replacement costs if an installation must be corrected — not necessarily a spike in improper installations.

Following Nelson’s presentation, a motion to approve rule docket 5801032301 was made and seconded. The committee approved the rule by voice vote.

What this means: The rewrite consolidates and modernizes the septic rules, shifts some technical guidance into enforceable rule text, raises certain financial assurance requirements for installers and alters setback policy to allow site-specific determinations. Several technical clarifications (for example, exact new setback distances) will be implemented via the TGM and TGC process or are specified in the adopted rule text; the committee transcript records the changes DEQ summarized but does not print the full rule text.