BeneTerra was engaged to repair the damage, design integrated erosion and water-flow control and establish a stable surface capable of withstanding intense rainfall for years to come.

A 100-metre section of gas pipeline right of way—known onsite as the “Hill of Horrors”—had experienced repeated erosion failures under previous contractors.

Steep gradients, dispersive soils and the absence of effective water controls had caused deep gullies to form, exposing the pipeline to future risk.

Client Context

The client is a major international gas producer operating in central Queensland’s coal seam gas region—an environment dominated by shallow topsoils, dispersive clays and naturally erosion-prone sandstone ridges.

Despite two previous attempts using different consulting firms and contractors, each solution had failed during high-intensity storm events (50mm+ in one hour). The resulting erosion presented a safety and compliance concern, with the potential to undermine the buried gas pipeline.

The client needed a partner who could design and deliver a robust, science-backed solution—not just a surface repair.

The Challenge

The site combined several high-risk factors:

  • Extreme slope: Average gradient of 1:3, with sections at 1:1.
  • No topsoil layer: The right of way sat directly on weathered sandstone.
  • Highly dispersive soils: Fine, low-nutrient clays easily mobilised by stormwater.
  • Previous failures: Existing erosion gullies up to 1.5 metres deep.
  • Safety constraints: Working safely on such steep terrain required meticulous planning and specialist operators.

A system of engineered water bars was required to slow and divert stormwater without eroding themselves. These structures needed to be built from local materials—despite those materials being chemically unsuitable in their natural state. BeneTerra needed to design a soil amelioration mix that could both meet engineering performance requirements and support vegetation cover.

Beneterra’s Solution

  • SCIENCE-LED DESIGN AND MATERIAL PREPARATION

    Our soil scientists developed a tailored ameliorant mix using site-won clays, gypsum, composted organics and targeted fertilisers. This transformed the dispersive material into a stable, workable soil capable of compaction and vegetation growth.

    • Approximate application rates included:
    • 25 t/ha gypsum
    • 10 t/ha composted manure
    • 200 kg/ha fertiliser
  • CAREFUL CONSTRUCTION ON STEEP TERRAIN

    Under an approved design, our senior excavator operator methodically repaired erosion features, backfilled voids and compacted material while maintaining machine stability at all times. Safety was managed through strict procedures and on-ground supervision.

  • ENGINEERED WATER-FLOW CONTROLS

    Water bars were positioned at precise intervals and angles to control stormwater velocity and direct flows safely off the right of way—reducing the risk of future gully formation.

  • ESTABLISHING A RESILIENT VEGETATIVE LAYER

    To protect the slope during establishment, the right of way was hydromulched with a high-shear mix designed for areas subject to heavy rainfall. Because works occurred outside the typical growing season, BeneTerra installed temporary irrigation for four weeks, monitoring moisture levels to ensure optimal conditions for early root development.

Results & Impact

Vegetation established successfully outside the normal growing season, supported by targeted irrigation and soil chemistry design.

Within two months, the site withstood a 120mm rainfall event in just 90 minutes with zero visible erosion—a marked contrast to previous failures.

Five years later, despite drought, the soil structure remained stable. Once rains returned, grass cover re-established naturally.

The right of way remains intact and compliant, protecting the pipeline and reducing the client’s long-term maintenance burden.