Solves the environmental problems associated with the establishment of vegetation within roadside and attenuation swales.

Used to provide a growing medium within roadside and other attenuation swales, promoting rapid growth of vegetation in zero soil situations.

Our Swale package reduces the mobilisation of pollutants into the vegetation, stopping them from entering watercourses.

It can be used in combination with a proprietary hydroseeding material and TerraRhizae to successfully establish vegetation and prevent soil contamination on attenuation swales where standing water is likely.

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TerrAffix applied on roadside

TerrAffix special system freshly applied on roadside swale

The Swale package solves the environmental problems associated with establishing vegetation within roadside and attenuation swales:

  • Roadsides with poor soil, including high silt, clay or compacted aggregate content which need soil improvement
  • Low porosity of soil due to compaction exacerbating standing water and poor drainage
  • Historical difficulty in establishing vegetation on saturated soil or where there is temporary flowing water
  • Attenuation swales with high levels of soil contamination due to runoff from roads, road building and construction sites
  • Highway drainage discharges with hydrocarbons, salt and other road pollutants reaching soakaways and settling ponds which pollute the water
  • Areas requiring heavy metal remediation


  • Boosts depleted soils with nutrients, minerals and trace elements
  • British Biochar Foundation Accredited
  • Easy to handle and mix
  • Environmentally sustainable
  • Improves conditions for biological activity
  • Improves drainage and soil aeration
  • Promotes good structure by creating spaces within the soil
  • Provides opportunities for thriving microbial populations

In Depth

Our use of sustainably produced biochar ensures that hydroseeding with this product leads to a high surface, water retentive layer of rapidly established vegetation.

It is very effective at immobilising contaminants and remediating land pollution, in turn improving water quality and preventing water pollution from attenuation swales.

Other benefits for industry include:

  • Affordability
    • The sustainable biochar used to produce this system is low cost and as a whole is substantially cheaper than traditionally expensive friable topsoil replacement or geocell products.
  • Efficacy
    • When it is used as a hydroseeding additive, it is demonstrably more effective than standard hydroseeding. Independent large-scale slope testing has shown it to be 99.6% effective in soil erosion prevention and to have faster vegetation establishment.
    • Drainage and soil oxygenation are drastically improved.
    • Conditions for soil microbiota are improved.
    • The mix used can be specifically tailored to the ground conditions subject to detailed soil investigation.
  • Environmental sustainability
    • It improves the resilience of plants to pests and diseases, provides opportunities for thriving microbial populations and boosts depleted soils with nutrients, minerals and trace elements.
    • The natural environment is enhanced with the establishment of a “healthy, functioning ecosystem”.
    • Grass lined attenuation swales are a long-term, sustainable alternative to concrete lined channels and continue to control pollution from highways more effectively the more established they are.
    • Biochar is produced specifically for remediating polluted soil and has been described as a “win-win-win solution to energy, carbon storage, and ecosystem function” (Biederman and Harpole).
    • There is a genuine and measurable carbon sequestration value, contributing to any calculated offset, which assists construction companies’ to meet their Corporate Social Responsibility (CSR) goals.

The Swale package is made from amended biochar produced from sustainable biomass.

It works in the following ways:

  • It is used as a hydroseeding additive and can be applied directly onto compacted Type-1 crushed aggregate to quickly promote plant growth.
  • It is an amended matrix of biochar with naturally occurring nutrients and minerals bonded to the surface.
  • It provides long-term access to minerals and plant nutrients during the establishment, early stages of growth and maturity of vegetation.
  • Soil structure is promoted leading to improved soil aeration.
  • It has been specifically engineered to ensure its stability within flowing water in order to slow the flow, filter and immobilise a variety of salts, suspended solids, heavy metals and other harmful pollutants.
  • The biochar locks in pollutants, preventing them from leaching into watercourses, meaning it is a highly effective and sustainable way to control water pollution.
  • As biochar can help soil to store carbon for thousands of years, its use in this system leads to carbon sequestration and climate benefits.

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