Airport Runway Stabilization with Natural Enzyme Treatment: A Case Study

When a regional airport in the American Southwest identified progressive base failure beneath a 2,400-meter primary runway, the facility faced a difficult decision: close for a full-depth cement stabilization program, or find a treatment that could be applied during scheduled overnight maintenance windows.

TerraRoads™ natural enzyme soil stabilizer was specified after independent geotechnical review confirmed the existing base soils — a mix of sandy clay (SC) and low-plasticity clay (CL) — were well-suited to enzyme treatment. The project was completed over 14 consecutive nights with no daytime runway closures.

Project Overview

The Challenge

The airport's geotechnical report identified two compounding problems: base CBR values had degraded to an average of 4.1% across the runway centreline — well below the FAA advisory circular minimum for light aircraft operations — and optimum moisture content was running 3–4 percentage points above design specification, indicating progressive clay saturation.

The conventional solution — full-depth cement stabilization — was estimated at $1.24 million and required a 21-day runway closure. The airport authority needed an alternative that could be applied in stages during overnight maintenance windows, with no impact on daytime operations.

The Solution: TerraRoads™ Enzyme Stabilization

TerraRoads™ was applied at the standard rate of 1 litre per 15 m³ of compacted material, mixed into the construction water and applied through the airport's existing water bowser. No specialist plant was required beyond the grader and compactor already on site.

Application protocol:

• Existing base material scarified to 250 mm depth
• TerraRoads™ solution mixed at 1:200 dilution (product:water)
• Material re-graded and compacted to 98% modified Proctor density
• Treatment applied in 180-meter sections per night shift
• Final surface sealed with diluted TerraRoads™ spray application

Before and After: Performance Metrics

Post-treatment CBR of 19.8% exceeds the FAA advisory circular AC 150/5370-10 requirement for light aircraft base course by a factor of 2.5×.

Regulatory Compliance

TerraRoads™ is approved by the U.S. Army Corps of Engineers — the federal agency responsible for setting engineering standards for military and civil airfield construction in the United States. The product's approval covers soil stabilization applications including airfield base course treatment.

The treatment methodology followed USACE Engineering Manual EM 1110-3-137 (Soil Stabilization for Pavements) and was reviewed and accepted by the airport's independent geotechnical engineer of record.

> "We specified TerraRoads™ because it was the only USACE-approved enzyme product with independent lab data across the exact soil classifications we were dealing with. The results exceeded our design targets, and we completed the entire program without a single daytime closure. That was the outcome the airport authority needed."

>

> — Geotechnical Engineer of Record, project documentation

Cost Comparison

The $340,000 saving does not include the indirect cost of runway closure — lost landing fees, diverted traffic, and reputational impact — which the airport authority estimated at an additional $180,000–$220,000 for a 21-day closure.

12-Month Performance Review

A follow-up inspection at 12 months confirmed:

• No measurable rutting or surface deformation under normal aircraft loads
• Base CBR maintained at 18.6% (within 6% of post-treatment value)
• No evidence of moisture re-infiltration or clay re-saturation
• Dust suppression maintained across unsealed apron areas adjacent to the runway

The airport authority has since specified TerraRoads™ for two additional taxiway rehabilitation projects.

Why Enzyme Stabilization Works for Airfield Applications

Airfield base courses face a specific combination of stresses: high point loads from aircraft undercarriage, vibration from jet blast, and the need for a surface that sheds water rapidly to prevent hydroplaning. Cement stabilization addresses strength but creates a brittle layer prone to reflective cracking. Enzyme stabilization produces a flexible, dense base that distributes load without the brittleness of cementitious treatment.

TerraRoads™ enzyme formulation catalyses a permanent ion exchange reaction between soil particles, reducing the affinity of clay minerals for water molecules. The result is a base that becomes stronger — not weaker — when exposed to moisture cycles.

Key Takeaways for Airport Engineers

• TerraRoads™ is the only natural enzyme soil stabilizer with U.S. Army Corps of Engineers approval
• Enzyme stabilization can be applied in stages during overnight maintenance windows — no runway closure required
• CBR improvements of 300–400% are achievable in SC and CL soils, the most common base failure types at regional airports
• Product is non-toxic, biodegradable, and requires no specialist handling or PPE beyond standard site precautions
• Application rate: 1 litre per 15 m³ of compacted material

For site-specific soil analysis and application recommendations, contact the TerraRoads™ technical team at [terraroads.com/contact](/contact).

TerraRoads™ is a natural multi-enzyme soil stabilizer approved by the U.S. Army Corps of Engineers, Caltrans (California Department of Transportation), and 28+ regulatory bodies across 6 continents. In continuous commercial use since 1997. [View technical data →](/technical-data)