The low level submersible bridge is ideal for sites where it is not viable for a bridge to be above the required flood level. These slim profile concrete bridges are built for HNHO-72 loading and withstand being over-topped regularly. They have the advantage of keeping the stream bed clear allowing fish passage which is seen favourably from an environmental perspective.

Low level concrete - Submersible


  • Simple installation
  • Robust units
  • Low profile
  • Adaptable to different crossing widths and alignments
  • Designed to allow for debris and hydraulic loads
  • Can be relocatable in some cases
  • Can be installed at low levels to avoid need for building consent
  • Can be used (site dependent) in replace of a larger span bridge, which requires to clear flood heights, making it a more cost-effective solution
  • Seen as a favourable solution by local Councils as the bridge is designed to maintain flow and fish passage and considered a relatively low risk from a flood hazard perspective.
  • Can be designed to full highway HN HO 72 loading providing access to heavier, more frequent traffic.
  • Suitable for heavy vehicles 0.85 HN with a maximum axle loading: up to 7.5 tonne single axle and 15 tonne dual axle loading


  • Generally over top multiple times per year
  • Appropriate for sites with good rock layer (not erodible soil type)
  • Appropriate for low catchment areas
  • If high catchment area – is there appropriate area for spillway
  • Approaches are likely to wash out in flood event

Contact us to discuss your bridge requirements

0.85 HN

HO HN 72

Overweight Loading



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