Soil Classification Guide
USDA, AASHTO & Canadian Classification Systems
Understanding Soil Types for Fill Material
Proper soil classification is essential for selecting the right fill material for your project. This comprehensive guide covers classification systems used in both the United States and Canada, including federal and provincial regulations.
US Soil Classification Systems
USDA Soil Texture Classes
The USDA soil texture classification system is based on the proportions of sand, silt, and clay particles in the soil.
| Soil Type | Particle Size | Drainage | Compaction | Common Uses |
|---|---|---|---|---|
| Sand | 0.05-2.0mm | Excellent | Poor | Drainage, base material, concrete mix |
| Loamy Sand | Sand + some silt/clay | Good | Fair | Landscaping, gardens |
| Sandy Loam | Balanced with more sand | Good | Fair | General fill, landscaping |
| Loam | Balanced mix | Moderate | Good | Topsoil, gardens, lawns |
| Silt Loam | Fine particles | Moderate | Good | Agriculture, topsoil |
| Silt | 0.002-0.05mm | Poor | Fair | Limited construction use |
| Sandy Clay Loam | Sand + clay | Moderate | Good | Embankments, fill |
| Clay Loam | Clay dominant | Poor | Excellent | Pond liners, dams |
| Silty Clay Loam | Silt + clay | Poor | Excellent | Structural fill |
| Sandy Clay | Sand + high clay | Poor | Excellent | Dams, barriers |
| Silty Clay | Silt + high clay | Very Poor | Excellent | Landfill caps |
| Clay | <0.002mm | Very Poor | Excellent | Liners, caps, barriers |
AASHTO Engineering Classification
The AASHTO system classifies soils based on their suitability for highway construction. Lower group numbers indicate better engineering properties. This system is also used in Canada for road construction projects.
| Group | Description | Group Index | Subgrade Rating | Recommended Use |
|---|---|---|---|---|
| A-1-a | Stone fragments, gravel, sand | 0 | Excellent | Base courses, subbase |
| A-1-b | Fine sand | 0 | Excellent | Base courses |
| A-2-4 | Silty or clayey gravel/sand | 0-4 | Good to Excellent | Subbase material |
| A-2-5 | Silty gravel/sand | 0-8 | Fair to Good | Subbase material |
| A-2-6 | Clayey gravel/sand | 0-12 | Fair to Good | Limited use |
| A-2-7 | Clayey gravel/sand | 0-20 | Fair | Limited use |
| A-3 | Fine sand | 0 | Excellent | Drainage, backfill |
| A-4 | Silty soils | 0-8 | Fair to Poor | Subgrade only |
| A-5 | Silty soils (high LL) | 0-12 | Poor | Not recommended |
| A-6 | Clayey soils | 0-16 | Poor | Subgrade only |
| A-7-5 | Clayey soils (moderate PI) | 0-20 | Poor | Not recommended |
| A-7-6 | Clayey soils (high PI) | 0-20+ | Very Poor | Avoid |
What Qualifies as Clean Fill? (General Guidelines)
✓ Acceptable
Materials: Rock, stone, gravel, sand, soil, brick, block, concrete (no rebar)
Contaminants: None detected
⚠ Restricted
Materials: Asphalt (in some jurisdictions), minimal organic content
Contaminants: Below regulatory limits
✕ Not Clean Fill
Materials: Wood, metal, plastic, glass, hazardous materials, contaminated soil
Contaminants: Any detectable levels
Note: Clean fill requirements vary by jurisdiction. Always verify with local regulations before accepting or placing fill material.
Canadian Soil Classification & Regulations
Canada uses the Canadian System of Soil Classification (CSSC) developed by Agriculture and Agri-Food Canada, along with CCME guidelines and province-specific regulations for soil quality and clean fill management.
Canadian System of Soil Classification (CSSC)
The CSSC, developed by Agriculture and Agri-Food Canada, organizes soils into 9 orders based on observable and measurable properties reflecting soil genesis and environmental factors. This hierarchical system includes Orders → Great Groups → Subgroups → Families → Series.
| Order | Description | Location in Canada | Great Groups | Fill Suitability |
|---|---|---|---|---|
| Brunisolic | Soils with genetic horizons but lacking diagnostic horizons of other orders | Subhumid to humid forested regions | Melanic Brunisol, Eutric Brunisol, Sombric Brunisol, Dystric Brunisol | Good |
| Chernozemic | Grassland soils with well-developed, base-rich, mineral-organic surface horizon (Ah) | Prairie provinces (AB, SK, MB) | Brown, Dark Brown, Black, Dark Gray Chernozem | Fair |
| Cryosolic | Permafrost soils with permanently frozen ground within 1-2m of surface | Northern Canada (~1/3 of country) | Turbic Cryosol, Static Cryosol, Organic Cryosol | Poor |
| Gleysolic | Soils with features from periodic or permanent high water tables and reduction | Depressions, level areas, poorly drained sites | Humic Gleysol, Gleysol, Luvic Gleysol | Poor |
| Luvisolic | Forest soils with clay translocation from A to B horizon (Bt) | Forested regions across Canada | Gray Luvisol, Gray Brown Luvisol | Good |
| Organic | Soils composed primarily of organic materials (>40cm organic layer) | Wetlands, bogs, fens across Canada | Fibrisol, Mesisol, Humisol, Folisol | Very Poor |
| Podzolic | Forest soils with iron, aluminum oxides and organic matter accumulated in B horizon | Boreal and coastal forests | Humic Podzol, Ferro-Humic Podzol, Humo-Ferric Podzol | Fair |
| Regosolic | Soils with minimal horizon development | Areas with recent deposition or erosion | Regosol, Humic Regosol | Excellent |
| Solonetzic | Soils with hard, compact B horizon high in sodium | Semi-arid prairie regions | Solonetz, Solodized Solonetz, Solod | Poor |
Source: Agriculture and Agri-Food Canada - Canadian System of Soil Classification, 3rd Edition (1998)
CCME Soil Quality Guidelines for Protection of Environmental and Human Health
The Canadian Council of Ministers of the Environment (CCME) provides federal soil quality guidelines used as reference standards across provinces. Values represent maximum acceptable concentrations in mg/kg (dry weight).
| Contaminant | Agricultural (mg/kg) | Residential/Parkland (mg/kg) | Commercial (mg/kg) | Industrial (mg/kg) |
|---|---|---|---|---|
| Arsenic | 12 | 12 | 12 | 12 |
| Barium | 750 | 500 | 2000 | 2000 |
| Cadmium | 1.4 | 10 | 22 | 22 |
| Chromium (Total) | 64 | 64 | 87 | 87 |
| Copper | 63 | 63 | 91 | 91 |
| Lead | 70 | 140 | 260 | 600 |
| Mercury | 6.6 | 6.6 | 24 | 50 |
| Nickel | 45 | 45 | 89 | 89 |
| Zinc | 200 | 200 | 360 | 360 |
| Benzene | 0.03 | 0.03 | 0.03 | 0.03 |
| Toluene | 0.8 | 0.8 | 0.8 | 0.8 |
| Ethylbenzene | 0.1 | 0.1 | 20 | 20 |
| Xylenes | 1 | 1 | 1 | 1 |
Petroleum Hydrocarbon (PHC) Fractions
| PHC Fraction | Agricultural | Residential | Commercial | Industrial | Notes |
|---|---|---|---|---|---|
| F1 (C6-C10) | 30 | 30 | 320 | 320 | Gasoline range |
| F2 (C10-C16) | 150 | 150 | 250 | 250 | Diesel/kerosene range |
| F3 (C16-C34) | 300 | 1300 | 2500 | 2500 | Heavy oils |
| F4 (C34-C50+) | 2800 | 5600 | 6600 | 6600 | Heavy oils/waxes |
Source: Canadian Council of Ministers of the Environment (CCME) - Soil Quality Guidelines Summary Tables. Values may be updated; verify with ccme.ca for current standards.
Ontario Excess Soil Standards (O.Reg 406/19 - Table 2)
Ontario Regulation 406/19 governs the management and reuse of excess soil. Table 2 provides full-depth excess soil quality standards for various property uses under potable groundwater conditions.
| Contaminant | Residential (mg/kg) | Commercial (mg/kg) | Industrial (mg/kg) |
|---|---|---|---|
| Arsenic | 18 | 18 | 18 |
| Barium | 390 | 670 | 670 |
| Cadmium | 1.2 | 1.9 | 12 |
| Chromium (Total) | 160 | 160 | 160 |
| Copper | 140 | 230 | 230 |
| Lead | 120 | 120 | 120 |
| Mercury | 0.27 | 0.27 | 0.27 |
| Nickel | 100 | 100 | 270 |
| Zinc | 340 | 340 | 340 |
| Benzene | 0.02 | 0.02 | 0.02 |
| PHC F1 (C6-C10) | 55 | 55 | 55 |
| PHC F2 (C10-C16) | 150 | 150 | 150 |
| PHC F3 (C16-C34) | 250 | 1300 | 1300 |
| PHC F4 (C34-C50) | 280 | 280 | 280 |
Key Ontario Requirements:
- • Soil characterization required for movement of excess soil >100m³
- • Registry tracking required for projects generating >2,000m³
- • Table 1 standards apply to sensitive areas (wetlands, agricultural lands, significant woodlands)
- • Qualified Person (QP) assessment may be required depending on site history
- • Effective January 1, 2021 with phased implementation
Source: Ontario Ministry of Environment, Conservation and Parks - Rules for Soil Management and Excess Soil Quality Standards (O.Reg 406/19)
Provincial Soil Regulations Summary
In Canada, soil and clean fill regulations are primarily governed at the provincial level. Each province has its own standards and requirements.
Ontario
O.Reg 406/19: On-Site and Excess Soil Management
Authority: Ministry of Environment, Conservation and Parks (MECP)
- •Table 1: Background standards for sensitive areas (wetlands, woodlands, agricultural)
- •Table 2: Standards by land use (residential, commercial, industrial)
- •Soil characterization required for movement of excess soil >100m³
- •Registry tracking for large projects (>2000m³)
- •Qualified Person (QP) assessment may be required
British Columbia
Contaminated Sites Regulation (CSR)
Authority: Ministry of Environment and Climate Change Strategy
- •Schedule 3.1: Matrix soil standards by land use
- •Part 1: Matrix standards considering site-specific factors
- •Part 2: Generic standards for human health protection
- •Part 3: Generic standards for ecological health protection
- •Site Profile required for land use changes
Alberta
Tier 1 & Tier 2 Soil and Groundwater Remediation Guidelines
Authority: Alberta Environment and Protected Areas
- •Tier 1: Generic standards for agricultural, residential, commercial, industrial
- •Tier 2: Site-specific risk-based standards
- •Subsoil Salinity Tool (SST) for sodium chloride contamination
- •Updated June 2024 with revised values for dioxins, furans, xylenes
- •Environmental Site Assessment (ESA) requirements
Quebec
Protection and Rehabilitation of Contaminated Lands Regulation
Authority: MELCCFP (Ministère de l'Environnement)
- •Criteria A: Background levels (natural soil)
- •Criteria B: Residential land use limits
- •Criteria C: Commercial/industrial land use limits
- •Matières Résiduelles Fertilisantes (MRF) Code for soil amendments
- •PFAS limits introduced (13 compounds, total cap 120 ppb)
New Brunswick
Clean Fill Guidelines
Authority: Department of Environment and Local Government
- •Clean fill: Unimpacted rock, soil, concrete, asphalt, brick
- •Material generator responsible for verification
- •Watercourse Alteration Regulation applies within 30m of water
- •Brush and grubbing materials acceptable
- •No direct regulation of clean fill placement
Canadian Clean Fill & Excess Soil Definitions
| Category | Definition | Acceptable Materials | Testing Requirements |
|---|---|---|---|
| Clean Fill / Inert Fill | Uncontaminated, non-water-soluble, non-decomposable, inert solids | Rock, soil, gravel, sand, concrete (unreinforced), brick, block, glass, ceramic | May require verification testing depending on source and volume |
| Excess Soil | Soil excavated from a project site that is not reused on-site | All soil types, may include fill from previous development | Characterization required for volumes >100m³ (Ontario) or as per provincial rules |
| Table 1 Soil (Ontario) | Soil meeting background/natural quality standards | Native soil with no evidence of contamination | Full analytical testing to Table 1 standards |
| Table 2 Soil (Ontario) | Soil meeting land-use-based quality standards | Soil meeting residential, commercial, or industrial standards | Full analytical testing to Table 2 standards for land use |
| Contaminated Soil | Soil exceeding applicable quality standards | Soil with contaminant concentrations above provincial limits | Full characterization required, waste classification |
Important Regulatory Notes
- •Verify Current Standards: Soil quality guidelines are updated periodically. Always verify current values with the relevant regulatory authority.
- •Site-Specific Conditions: Guidelines provide general standards. Site-specific factors (groundwater, sensitive receptors) may require more stringent limits.
- •Provincial Authority: In Canada, provinces have primary jurisdiction over soil management. Municipal bylaws may add additional requirements.
- •Documentation Required: Most provinces require documentation for excess soil movement, including source site assessments and receiving site agreements.
- •Qualified Professionals: Soil characterization and site assessments should be conducted by qualified professionals (QPs, P.Eng, P.Geo) as required by regulation.
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