Crossing the Fraser River between Surrey and New Westminster, British Columbia, the South Surrey Interceptor is a vital link in the region’s sanitary network. A very deep scour hole has developed downstream of the crossing due to complex hydraulic interactions between the upstream Alex Fraser Bridge and an existing rock apron over the sewer line. Recent river surveys showed the scour hole migrating towards the crossing and threatening to undermine the pipe within a few years. NHC developed a scour protection design to arrest the progression of the scour hole and protect the pipe, subcontracted and supported environmental permitting, undertook quality assurance field reviews during construction, and provided record drawings and reporting. The use of novel approaches to analyse the scour hole development and design the scour protection allowed for a robust design that will extend the service life of the interceptor and ensure uninterrupted service for residents of BC’s Lower Mainland.