Chlorination of Christchurch water supply after the earthquake : the planning and the reality

Following the magnitude 6.3 earthquake in Christchurch on Tuesday the 22nd of February City Council requested that GHD review the reticulated water network in Christchurch.

GHD staff were in Christchurch on the 2nd and 3rd of March 2011 to review the situation and gather the information to prepare a report in regards to disinfection requirements.

The main objectives of the report were to:

• Confirm the requirement for disinfection,
• Review the implications of introduction of chlorination, and
• Provide a process, and guidelines for, the eventual lifting of the boiled water notice.

Franz Resl, working for City Care Ltd, led the team that managed the chlorination regime.

Commissioning, optimization and maintenance happened in parallel while the stations had to operate at the required dosing rate. A smart control strategy was developed to allow for a fast (less than 1 hour) response for required repairs. Well understood routines about plant start-up and operation had to be left behind. Success under the amazing time pressure was relying on engineering intuition and novel strategies for maintaining dosing equipment.

This paper compares and contrasts the theory behind the chlorination exercise with the practicalities of implementing a chlorination strategy.