The Kaikōura M7.8 Earthquake caused widespread damage to the road and rail corridor 20 km North and South of the Kaikoura town ship. Over 40 major slips inundated the road and rail with over 750,000 m³ of material form source zones up to 500 m above sea level. The highly fractured Grey Wacke meant frequent future rockfalls were expected. The rockfall frequency and wide run out area at SR8 and 9 created the requirement for a system that attenuated the rockfall energy to a manageable level, was quick to install and required minimal future maintenance. The Slope on average is approximately 50 degrees but in some parts is near vertical.
A 110 m wide rockfall attanuator (ATT - 60) with a 35-40 m tail was specified due to its high puncturing resistant yet light weight high tensile (1770 MPa) TECCO 65/4 tail which enables the attenuated material to pass down through to the lower section for clearing if required. The 65 mm aperture is small enough that no secondary mesh is required and the Ultracoating ensures design life in the coastal environment. The attenuator system utilises a 3 m high hinged post with a 16 m spacing and a support rope separation half way. A double top rope was installed for increased safety in design and Type III flex heads were installed to transfer the load to the Gewi 32 anchor bar. Overall the benefits of an attenuator creating a quick and cost effective solution.