“Many were admitted in to hospital and this disease outbreak contributed to the loss of three lives. A subsequent inquiry identified the cause of the disease outbreak as being the failure to properly ‘flush and disinfect’ the new pipeline with chlorine prior to releasing water to consumers.”
The problem in 1964 was the failure to follow established standard procedure of sterilising the 100mm asbestos cement (AC) pipes by flushing and “super-do
zing” with chlorine before commissioning the final 4km section of AC ringmain reticulation.
The AC pipes in storage back in the 1960s were contaminated by the kiore-toka mimi (rat urine) and tutae (faeces) because there were no end-caps on the pipes to prevent contamination.
The new Te Mato Vai polyethylene pipes arrive with a significant number with no pipe end-caps on, and liable to be contaminated by dirt in the trench and handling or te kiore-toka. Pipe end-caps are removed when joining pipes in the trench during installation.
The total new pipe network – ring-mains, trunk-main, sub-mains, branch-mains and branch-sub-main – is close to 300km of pipeline plus the 10 new water treatment plants (settling tanks, filters and storage reservoirs) which by public health standard need flushing and disinfection prior to commissioning.
The problem we had in 1964 with no pipe end-cap to prevent contamination may repeat if no disinfection.
The 1964 incident had a significant health impact to survivors in that affected 4km piped water zone; there isno one in the area pasts the age of 70 years living today. Compare the life span to countries with disinfected water supply, well over 85 years.
I have several years’ record of bacterial count of surface water, rainwater and groundwater from 1930, 1958, 1960, 1980 and 2007 to 2014 provided by Public Health for the islands of Rarotonga, Aitutaki and Atiu. Deep groundwater source isnormally of high quality.
Surface water sources – those exposed to air on the surface of the earth – comprise waters of widely-varying quality.
Surface water sources are more prone to contamination than groundwater and so more often need pretreatment such as the “Ramos filters” that are used on all Rarotonga water intakes.
This system is now being upgraded by the Te Mato Vai water supply project to meet World Health Organization potable water standards.
Sam Napa snr