Following the 22 February 2011 earthquake in Christchurch significant rockfall, cliff collapse and landslides occurred around the Port Hills. Rocks from numerous bluff systems and individual outcrops above Evans Pass Road fell and collapsed ending up on or impacting the road. Evans Pass Road is the only route out of Sumner if Main Road, below the 60 to 70 m high cliffs at Peacocks Gallop, is damaged or impacted by events such as rockfall and cliff collapse.
This report focuses on the processes undertaken to reopen Evans Pass Road to the public. The main stages of reopening the road were rockfall and source rock mapping, determining risk assessment criteria and assigning risk ratings, determining remedial options, undertaking the remediation, and reviewing and reassessing completed works. Remediation methods employed above Evans Pass Road included scaling, rock rolling, low and high energy blasting, and mechanical restraint; the reasons for using these methods at specific locations are discussed.
