IDAPA 58.01.03: An Environmental Law

Understanding Idaho's Septic System Regulations

In the State of Idaho, the Idaho Administrative Procedure Act (IDAPA) 58.01.03 governs Individual/Subsurface Sewage Disposal and Rules for Cleaning of Septic Tanks.

This rule applies to individual landowners and homeowners who wish to install or operate septic systems to treat and dispose of sewage through a subsurface sewage disposal system.

The purpose of this rule is to establish limitations on the construction and use of individual and subsurface sewage disposal systems. It also outlines the requirements for obtaining installation permits and installer registration permits.

These regulations are designed to protect public health and ground and surface water by establishing minimum standards for the design, construction, and operation of subsurface sewage disposal systems.

Inadequately treated sewage can lead to:

• Surface water eutrophication

• Groundwater contamination

• Reduced environmental quality

• Public health risks

The rules are managed by the Idaho Department of Environmental Quality (IDEQ) and enforced locally through Idaho's seven health districts.

Disclaimer: This blog provides a condensed overview of IDAPA 58.01.03. It is intended for informational purposes only and should not be used as a legal document or substitute for official regulatory guidance.

Official Resources:

• IDAPA 58.01.03 – Individual/Subsurface Sewage Disposal Rules

• Technical Guidance Manual for Individual/Subsurface Sewage Disposal (TGM)

IDAPA 58.01.03: Rules and Requirements

Section 000: Legal Authority

This rule implements the following statutes passed by the Idaho Legislature:

Health and Safety:

• Chapter 1, Title 39, Idaho Code – Environmental Quality

• Chapter 36, Title 39, Idaho Code – Water Quality

Section 001: Scope, Conflict, and Responsibilities

This section identifies the scope, conflicts, and responsibilities of those involved in treating, storing, and disposing of wastewater.

Section 002: Reference Materials

This section references the Technical Guidance Manual for Individual/Subsurface Sewage Disposal (TGM) and applicable NSF International standards related to nitrogen reduction and residential onsite systems.

The TGM provides guidance to clarify areas of the rule that may require additional interpretation. Although the TGM is not itself a set of administrative rules, it is used to guide regulatory decisions and implementation.

View the Technical Guidance Manual

Section 003: Definitions

This section provides definitions of important terms and vocabulary used throughout IDAPA 58.01.03 and the Technical Guidance Manual.

Section 004: General Requirements

The Idaho Board of Environmental Quality established these rules to protect the health, safety, and environment of Idaho residents.

This section includes references to:

• The Technical Guidance Manual (TGM)

• The Technical Guidance Committee (TGC)

• Septic system limitations and requirements

Section 005: Permits and Permit Applications

This section outlines the permitting process and application requirements for individual and subsurface sewage disposal systems.

Topics include:

• Installation permit applications

• Permit issuance and renewal

• Permit fees

• Septic system abandonment

• Operation and maintenance requirements

Section 006: Registration Permits for Installers and Service Providers

Septic system installers, whether basic or complex, must obtain the appropriate installer registration permit.

Registration requirements include:

• Submitting an application

• Paying applicable fees

• Providing the required bond

• Passing a standardized examination

This section also addresses exemptions for homeowners installing qualifying basic onsite sewage disposal systems.

Section 007: Septic Tanks and Construction Standards

Septic tanks serve as the first line of treatment in an onsite wastewater system.

A septic tank is an underground container designed to collect wastewater, separate solids, and allow naturally occurring bacteria to break down organic matter.

Wastewater from toilets, sinks, showers, and washing machines flows through household plumbing and into the septic tank.

This section covers:

• Septic tank design and approval

• Minimum tank capacities

• Wastewater flow requirements

• Minimum separation distances from wells, surface water, water lines, foundations, and other features of concern

• Septic tank construction standards

• Septic tank abandonment procedures

Section 008: Standard Subsurface Disposal Facility Design and Construction (Drainfields)

A drainfield disperses and treats wastewater effluent after it leaves the septic tank.

As the effluent moves through the native soil beneath the drainfield trenches, naturally occurring microorganisms and aerobic bacteria help remove or reduce remaining harmful bacteria, viruses, and nutrients.

Site Suitability Requirements

Before a standard drainfield can be constructed, the proposed site must meet specific conditions.

These include:

• Soil texture classification and design soil groups

• Effective soil depth

• Depth to groundwater, bedrock, and impermeable layers

• Land slope

• Required separation distances from wells, surface water, property lines, and other features of concern

Drainfield Design Requirements

Once a site is approved, the subsurface disposal system must meet specific design and construction standards.

These include:

• Trench length

• Trench width

• Trench depth

• Distance between trenches

• Absorption bed requirements

• Aggregate specifications

• Wastewater distribution methods

This section also addresses procedures involving failing sewage disposal systems.

Section 009: Other Components

When a standard septic system cannot be approved, alternative wastewater treatment systems may be considered.

These systems may provide additional treatment or accommodate sites with reduced effective soil depths and other limitations.

Examples include:

Extended Treatment Package Systems

• AdvanTex treatment systems

Proprietary Wastewater Treatment Products

• Eljen Geotextile Sand Filter (GSF) systems

Non-Discharging Systems

• Incinerating toilets

• Composting toilets

• Vault toilets

All alternative systems must meet applicable regulatory approval and design requirements.

Section 010: Variances

Technical allowances, also called variances, may be granted for certain dimensional or construction requirements.

A minor technical allowance may be considered when it:

• Does not negatively affect adjacent properties

• Does not violate the intent of the rules

• Does not conflict with another applicable rule or standard

Changes to dimensional requirements generally cannot exceed 10%, unless otherwise provided in the Technical Guidance Manual.

Section 011: Inspections

Inspections are required to verify compliance with applicable septic system regulations.

Inspections should be coordinated with the regulatory authority at least 48 hours in advance.

A final inspection is required to document:

• The components installed

• The location of the septic system

• Information showing the actual installation

If portions of the septic system have been buried and cannot be inspected, the installer may be required to uncover those components.

Section 012: Violations and Penalties

All individual and subsurface sewage disposal systems must be constructed and installed according to applicable regulations.

If information regarding a septic system is presented falsely or misleadingly, the regulatory authority may revoke an installation or registration permit.

Section 013: Large Soil Absorption Systems (LSAS)

A subsurface sewage disposal system designed to receive 2,500 gallons or more of wastewater per day is considered a Large Soil Absorption System (LSAS).

All LSAS systems must be designed by a professional engineer licensed in Idaho.

These systems have additional requirements, including:

• Greater effective soil depths

• Increased setback requirements

• Additional site evaluations

• Potential nutrient-pathogen testing performed by IDEQ

Monitoring and Reporting Requirements

Before a permit can be issued, the regulatory authority must approve a monitoring and reporting plan.

The plan may include:

• Wastewater flow data

• Physical observations for signs of system failure

• Groundwater monitoring

Operation and Maintenance Requirements

A detailed operation and maintenance plan must also be submitted.

This plan must include:

• Physical monitoring protocols

• Maintenance procedures

• Identification of a system operator as outlined under IDAPA 58.01.16

Sections 014–049: Reserved

These sections are reserved.

Section 050: Septic Tank Cleaning

All individuals, firms, and corporations operating trucks or equipment used to pump, clean, or transport human waste must comply with the applicable regulations.

Requirements include:

• Watertight pumping and hauling equipment

• Equipment that can be properly cleaned

• Regulatory approval of septage disposal methods

• Annual permit applications and applicable fees for pumpers, haulers, and transport equipment

Sections 051–995: Reserved

These sections are reserved.

Section 996: Administrative Provisions

Individuals may be entitled to appeal certain agency actions authorized under these rules.

Appeal procedures are addressed under applicable administrative provisions, including the referenced contested-case rules.

Sections 997–999: Reserved

These sections are reserved.

Who Do I Contact for More Information About IDAPA 58.01.03?

For additional information regarding Idaho's individual and subsurface sewage disposal regulations, contact the Idaho Department of Environmental Quality.

Jayson Foley
Idaho Department of Environmental Quality
1410 N. Hilton
Boise, ID 83706

Phone: (208) 373-0347
Email: jayson.foley@deq.idaho.gov
Website: www.deq.idaho.gov

Final Thoughts

Understanding Idaho's septic system regulations is important for homeowners, contractors, septic installers, and property developers.

IDAPA 58.01.03 establishes standards that help protect public health, preserve groundwater quality, and ensure that onsite wastewater treatment systems are properly designed, installed, and maintained.

Whether you're planning a new septic installation, replacing an existing system, or exploring alternative wastewater treatment options, reviewing the applicable regulations and working with your local health district can help ensure compliance.

For information about wastewater pumps, septic pumping equipment, lift stations, and related components, visit R.C. Worst & Company.

This article is a general educational summary, not legal or regulatory advice. Always consult the current official rules, IDEQ, and your local health district for applicable requirements.