The Health and Safety at Work Act (2015) requires companies to provide safe working environments for its staff. In response to this, our client sought to identify effective mitigation solutions for a rockfall hazard above an operational access road. The slope consists of a near vertical, 15 m high, cutting into a steep (~35°) natural slope. Below the cut face there is a single lane access road, with the natural slope continuing below. Groundwater seepage near the top of the cut face has resulted in ongoing rockfall, presenting a hazard to staff using the access road. Previous geotechnical assessments had recommended large scale earthworks to reshape the cutting to remove the hazard. This paper presents an alternative risk management approach developed by Opus, identifying the most appropriate mitigation solution. The current level of risk was evaluated (using the AGS Landslide Risk Management Guidelines), and compared with industry standards to determine an acceptable level of life safety risk. By evaluating the relative cost and risk reduction achieved for feasible mitigation solutions, a proportional cost and acceptable risk based solution was identified. This paper focuses on how the rockfall risk was effectively assessed, managed and communicated with our client.
Opus International Consultants Ltd (Opus) were engaged to undertake a site inspection, risk assessment and recommend mitigation options for an active rockfall site on an operational access road near Waipara in North Canterbury (refer to Figure 1).