The ICC-ES AC358 standard mandates specific soil classification and installation protocols to ensure the structural integrity and durability of helical foundation systems.

### Soil and Corrosivity Requirements

AC358 classifies soil into three corrosivity categories, which dictate the necessary Corrosion Protection and material thickness:

• Non-aggressive: Requires a minimum steel thickness of 0.25 inches. Standard paint is acceptable, and no galvanizing is required.
• Aggressive: Soils with high chloride or acidic conditions require a minimum steel thickness of 0.375 inches and mandatory hot-dip galvanizing per ASTM A123.
• Extremely aggressive: Requires a minimum steel thickness of 0.5 inches, hot-dip galvanizing plus an additional protective layer, and recommended cathodic protection.

### Installation and Verification Requirements

To ensure code compliance during installation, the following protocols are required:

• Installation Torque Correlation: Installers must use a torque-to-capacity relationship (per section 5.3) to verify axial capacity in real-time. This involves recording the rotational torque required to advance the helix plates and applying a correlation factor derived from load tests.
• Design Capacity Verification: The system must use test piles or empirical methods (per section 4.2) to match load-bearing capacity with project-specific design loads.
• Load Testing Protocols: Standardized procedures include selecting representative test piles, incremental loading to observe settlement, and creep monitoring. A pile passes if net settlement and creep rates remain within allowable bounds defined by AC358.
• Documentation: A complete compliance package must include sealed design calculations, mill certificates for steel (ASTM A500/F1554), torque logs, and signed installation reports.