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Envirosock is a sediment and erosion control measure primarily used for containment during construction activities and slope interruption, particularly on hillside gradients prior to vegetation establishment and natural stabilization in conjunction with the Enviroblanket.
Easily installed and flexible, Envirosock is a preventative tool that slows runoff velocity and reduces soil erosion by dissipating the energy of overland water sheet flow. Designed with sediment and pollutant trapping materials, the Envirosock filters sediment and soluble pollutants on site before they enter the surrounding environment. Water temporarily ponds behind the sock, allowing enough time for filtration and deposition of suspended solids. 

Design Parameters and Specifications

Envirosock is locally manufactured of high strength UV stabilised polypropylene that can be delivered or extruded on-site and subsequently secured in place. The filling is a compost blend engineered to maximize filtration, reduce sheet flow and trap sediment. Composition specifications can be adjusted to enhance these functions for specific site requirements. 

By decreasing runoff velocity, trapping sediment and filtering soluble pollutants, Envirosock reduces the risk of potential riling erosion, post-construction remediation, and violations associated with environmental degradation.  Envirosock can be direct seeded at the time of installation to provide greater stability and filtration capacity once vegetation is established.

Application

Envirosock is to be installed perpendicular to the gradient and across the contour of the slope. Slope interruption is most effective
when used in conjunction with the Enviroblanket. This product combination allows sheet flow to be evenly dispersed by means of blanket filtration. Applied to long slopes prone to riling erosion, Envirosock can be installed to divert runoff away from hill faces and directed instead to storm water or assisted catchment systems. Envirosock must not be designed for application to slopes with a gradient greater than 1:1 unless engineered otherwise.

Advantages

  • Slows runoff velocity
  • Disperses water runoff on sloping ground
  •  Slope length is bisected and therefore reduced
  • Can be used on slopes up to 1:1 gradient
  • Better trapping and removal of sediment and pollutants
  •  More intimate contact with ground surface
  • No trenching
  • Can be installed on high country frozen ground
  • Useful in environmentally sensitive areas
  • Can be inoculated with mycorrhizal fungi beneficial to plant establishment
  • Binds and absorbs nutrients, heavy metals and hydrocarbon

Guidelines

Maintenance and removal

Envirosock withstands normal punishment on work sites, i.e being driven over with a ute; however, if moved or disturbed from its original position, the correct layout must be set back in place. Effectiveness of the installation will be reduced if heavy activity destroys the fabric or causes compaction reduction to the tubular dimensions. Envirosocks can be used for temporary erosion control measures, removed from site after use, or planted as a permanent functional or aesthetic component to the landscape design. Envirosock can be used as a soil amendment to improve existing soil structure if spread after site-works are complete.

Environmental Uses

The contents of Envirosock include organic matter and humus colloids that have the ability to bind and absorb nitrates, phosphorus, heavy metals, and hydrocarbons that may be present in surface water runoff. Microorganisms in organic compost also have the ability to degrade many of these inorganic and organic pollutants. The use of Envirosock is particularly useful in sensitive environmental areas where specific protections are required. For example, the movement of re-establishing lizard and invertebrate colonies are not impeded by the use of an Envirosock as opposed to a silt fence. Envirosock may also be inoculated with mycorrhizal fungi-specific to species or bioregional soil conditions and used in conjunction with the Enviroblanket to increase natural biodiversity nutrient cycling and biological activity within soil profiles.

Riparian and marginal edge treatment

Envirosocks can also be used as a bio engineering tool to form vegetated banks for water courses. Riparian and wetland seed readily available and Red Tree Environmental are planning trials to evaluate different seed rates and species ratios for these applications. Being able to grow a dense crop of plants would also prevent Pukekos from being able to pull out individual plants. The Envirosock is an ideal option, for reducing erosion impacts from temporary overland flow channels. Envirosocks can either be filled with a pre-seeded compost mix or applied to the surface after install via a hydroseed application. The socks are pinned back into the slope and can be installed without heavy machinery and bend around existing trees, rocks and other features. Socks can be filled on site or pre filled and lifted into position.

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