📘 DEQ Technical Manual
350-Page Authoritative Reference
The most comprehensive technical guidance for:
- Complex system designs
- Alternative treatment technologies
- Site-specific engineering solutions
- Performance-based designs
Engineer & Designer Resources
Engineer & Designer Resources
Section titled “Engineer & Designer Resources”Technical Guidance for Professional System Design
Section titled “Technical Guidance for Professional System Design”This page provides comprehensive resources for engineers, soil scientists, designers, and environmental consultants designing septic systems across Idaho's diverse terrain and regulations.
🎯 Essential Technical Resources
Section titled “🎯 Essential Technical Resources”📏 Separation Distances
Complete Setback Requirements
District-specific distance tables for:
- Wells and water sources
- Property boundaries
- Surface water bodies
- Soil absorption systems
⚙️ Alternative Systems
27+ System Types Documented
Technical specifications for:
- Aerobic treatment units
- Pressure distribution
- At-grade systems
- Mound systems
- Advanced treatment
🧪 Soil Evaluation
Site Assessment Standards
Guidance on:
- Percolation testing
- Soil profile analysis
- Groundwater evaluation
- Site constraints
📐 System Design Workflow
Section titled “📐 System Design Workflow”Phase 1: Site Assessment
Section titled “Phase 1: Site Assessment”-
Preliminary evaluation
- Property boundaries and easements
- Topographic survey
- Utility locations
- Access considerations
-
Soil investigation
- Test pit excavation (minimum 2 pits)
- Soil profile description
- Seasonal high water table determination
- Percolation or infiltration testing
-
Site constraints analysis
- Separation distance compliance
- Slope limitations
- Bedrock or impervious layers
- Seasonal flooding potential
Phase 2: System Selection
Section titled “Phase 2: System Selection”-
Design flow calculation
- Bedroom count method (standard)
- Fixture unit method (commercial)
- Actual use data (if available)
- Peak flow considerations
-
Treatment level determination
- Standard soil treatment adequate?
- Enhanced treatment required?
- Discharge limitations?
- Sensitive area considerations?
-
System type selection
- Conventional gravity system (if suitable)
- Pressure distribution (uniform dosing)
- At-grade or mound (poor soils)
- Alternative treatment (site constraints)
Phase 3: Design Documentation
Section titled “Phase 3: Design Documentation”-
Site plan requirements
- Scale drawing (1"=20' or better)
- All existing and proposed structures
- Septic system components and locations
- Separation distances clearly marked
- Easements and property lines
-
System design details
- Component sizing calculations
- Hydraulic profile
- Construction specifications
- Materials list
- Installation sequence
-
Supporting documentation
- Soil investigation report
- Percolation test results
- Design flow calculations
- Professional seal (if required)
📋 Permit Submittal Requirements
Section titled “📋 Permit Submittal Requirements”Standard Submissions (Most Districts)
Section titled “Standard Submissions (Most Districts)”- Completed application form (district-specific)
- Site plan meeting district standards
- Soil investigation report
- Design calculations
- Construction details
- Applicable fees
Enhanced Requirements (Complex Systems)
Section titled “Enhanced Requirements (Complex Systems)”Central District (Boise Metro) may require:
- Professional engineer seal on designs
- O&M (Operations & Maintenance) manual
- Monitoring plan
- As-built drawings after installation
Check with your district for specific requirements.
🗺️ District-Specific Engineering Resources
Section titled “🗺️ District-Specific Engineering Resources”Urban Districts (Higher Complexity)
Section titled “Urban Districts (Higher Complexity)”Central District Health (CDH)
- Most stringent review process
- Professional seal often required
- Alternative systems common due to lot constraints
- Higher permit fees
Rural Districts (Site-Specific Solutions)
Section titled “Rural Districts (Site-Specific Solutions)”North Central District
- Extensive DIY homeowner installer program
- Detailed training materials available
- Flexible approach for difficult sites
- Strong technical support
Panhandle District
- Lake and shoreline considerations
- Cold climate design factors
- Seasonal water table challenges
- Bedrock and steep slope solutions
🛠️ Common Design Challenges
Section titled “🛠️ Common Design Challenges”Challenge 1: Limited Separation Distances
Section titled “Challenge 1: Limited Separation Distances”Problem: Property boundaries, wells, or surface water too close
Solutions:
- Proprietary advanced treatment units
- Drip irrigation dispersal (smaller footprint)
- Engineered fill systems
- Shared systems (if permitted)
Key Resource: Alternative Systems Guide
Challenge 2: Poor Soil Conditions
Section titled “Challenge 2: Poor Soil Conditions”Problem: Tight soils (clay), shallow soils, or high water table
Solutions:
- At-grade or mound systems
- Pressure distribution for uniform loading
- Imported fill material (certified)
- Soil modification (limited conditions)
Key Resource: DEQ Technical Guidance Manual Chapter 5
Challenge 3: Steep Slopes
Section titled “Challenge 3: Steep Slopes”Problem: Terrain >25% grade, downslope seepage concerns
Solutions:
- Upslope tank placement
- Pressure distribution mandatory
- Curtain drains for groundwater control
- Terracing and retaining walls
Key Resource: DEQ Technical Guidance Manual Chapter 7
Challenge 4: Commercial or High-Flow Applications
Section titled “Challenge 4: Commercial or High-Flow Applications”Problem: Restaurants, offices, subdivisions with large flows
Solutions:
- Advanced treatment required
- Flow equalization tanks
- Redundant system components
- Professional O&M contracts
Key Resource: DEQ Pre-Treatment Requirements
📊 Design Standards by District
Section titled “📊 Design Standards by District”Conventional System Minimums (Typical)
Section titled “Conventional System Minimums (Typical)”| Component | Minimum Requirement | Notes |
|---|---|---|
| Septic Tank | 1,000 gallons (residential) | 1,500+ for garbage disposal |
| Soil Depth | 18-24" unsuitable material | Below drainfield bottom |
| Absorption Area | Varies by percolation rate | See district tables |
| Tank Access | 6" minimum risers to grade | Required for inspection |
Separation Distances (Most Restrictive)
Section titled “Separation Distances (Most Restrictive)”- Wells: 100 feet minimum (some districts 150')
- Property lines: 5-10 feet (varies by district)
- Surface water: 50-100 feet (varies)
- Buildings: 5-10 feet minimum
Always verify current requirements with local district.
💡 Professional Practice Tips
Section titled “💡 Professional Practice Tips”Best Practices for Smooth Approvals
Section titled “Best Practices for Smooth Approvals”-
Pre-application consultation
- Meet with district staff before design
- Discuss site constraints early
- Clarify documentation requirements
- Confirm fee schedules
-
Conservative design approach
- Use safety factors on critical dimensions
- Plan for future expansion if feasible
- Consider replacement area requirements
- Document design assumptions clearly
-
Clear communication
- Label all plan components clearly
- Provide calculation summaries
- Include construction notes
- Specify inspection requirements
-
Professional relationships
- Maintain good rapport with district staff
- Respond promptly to review comments
- Attend pre-construction meetings
- Ensure installer understands design intent
📚 Technical References
Section titled “📚 Technical References”Idaho State Resources
Section titled “Idaho State Resources”- IDAPA 58.01.03 - Idaho Individual/Subsurface Sewage Disposal Rules
- DEQ Technical Guidance Manual - Chapter-by-chapter system design guidance
- DEQ Guidance Memorandums - 20 policy interpretations (1993-2021)
Industry Standards
Section titled “Industry Standards”- NSF/ANSI Standards - Product certification requirements
- ASTM Standards - Materials and testing methods
- Soil Science Society of America - Soil classification guidance
Continuing Education
Section titled “Continuing Education”Many districts offer:
- Annual training workshops
- New technology seminars
- Regulatory update sessions
- Complex system design courses
🏘️ Subdivision & Large System Design
Section titled “🏘️ Subdivision & Large System Design”Multi-Unit Considerations
Section titled “Multi-Unit Considerations”-
Shared vs. individual systems
- District policies vary significantly
- Maintenance responsibility structure
- Easement and access requirements
- Long-term management plans
-
Capacity planning
- Conservative flow estimates
- Peak demand analysis
- Future expansion provisions
- Reserve areas required
-
Community system requirements
- Professional O&M mandatory
- Monitoring and reporting
- Financial assurance mechanisms
- Homeowner association covenants
🔍 Find Your District Resources
Section titled “🔍 Find Your District Resources”🗺️ Browse by District
Find forms, fee schedules, and technical requirements for your project location.
📋 Permit Applications
District-specific application forms and submittal checklists.
🎓 Training Resources
Access installer and professional training materials.
❓ Questions or Need Help?
Section titled “❓ Questions or Need Help?”For technical engineering questions:
- Contact your local health district directly
- Consult the DEQ Technical Guidance Manual
- Attend district training workshops
For product-specific questions:
- Refer to manufacturer's design manuals
- Verify NSF/ANSI certification status
- Check district approved products lists
Always verify current requirements and fees with your local health district before beginning design work.