Wellington Region's Reservoir Seismic Upgrade Standards

This paper outlines the technical basis to reservoir seismic resilience work in the Wellington region. Following an earthquake the Wellington region will rely on reservoirs to initially provide safe drinking water. For this reason reservoirs need to be seismically resilient. As part of region’s ongoing seismic resilience work Wellington Water manages the capex upgrade work to provide seismic resilience reservoir systems. That system includes the elements of: reservoir structure, geotechnical considerations, pipework, control huts, and control equipment.

Wellington Water manages the water assets for five Councils: Wellington, Hutt, Porirua, Upper Hutt, and Greater Wellington Regional. Within the water supply system there are currently some 140 reservoirs servicing a population of around 390,000 people. The reservoir age range is from new to over hundred years old. Nominally three to four reservoirs are upgraded across the region each year and a new reservoir constructed every three to five years.

This paper covers retrofit elements that are assessed and upgraded to provide a seismic resilient reservoir system including walls – hoop strength, roof uplift, floor slab capacity, overturning, roof capacity, and high level geotechnical considerations.

Existing reservoirs may not have been designed to current standards. Consideration is given to the retrofit seismic resilience classes that have been developed. Also considered are the adopted standards for new reservoirs.