Novel Use of Horizontally Directionally Drilled (HDD) Drainage Technology for Landslide Remediation

The La Nina weather pattern of 2020–2022 caused many natural disasters including floods and landslides in Australia, and the effects were particularly felt on the eastern coast of Queensland, NSW, and Victoria. Landslides caused impacts to many sites including houses, railway lines, council roads and state government roads. Case studies of two separate landslide remediations using new HDD (Horizontal Directional Drilling) drainage technology are presented. These sites are presented as traditional remediation solutions that would not have been as effective. The issues, unique HDD solutions implemented, and performance of these study sites south of Sydney remediated in 2020 and 2023 are discussed. We believe that these two sites are the first two sites in NSW and perhaps Australia where the use of a HDD drainage system has been implemented for landslide remediation. We believe that this novel HDD system can dramatically increase resilience of infrastructure against landslides for a relatively low cost (both construction cost and maintenance cost). This paper discusses the criteria used to arrive at the use of HDD drains over traditional measures, considerations for their implementation and provides preliminary results of monitoring to support the findings presented.