15 April 2016

Kerryn Pollock

Engineering Insight: How engineering improved our health

Late 19th Century urban New Zealanders lived in waste-lined streets and often drank contaminated water. In Christchurch, typhoid was considered as normal as colds are today. Public health was a serious problem – and engineers had the solution.

New Zealanders in the 19th Century had an intimate and often hazardous relationship with their own waste. In the days before flushing toilets whisked it away down sewer pipes, everyone made do with buckets or chamber pots emptied into cesspits in the back garden. Town and city streets were littered not only with animal excrement, but also the human variety.

Running down the middle of Auckland’s Queen Street until the 1870s was the notorious Ligar Canal. Once the Waihorotiu Stream, the canal was a large open drain full of sewage, dead animals and other stinking waste. To cross the street, pedestrians had to clamber over rickety bridges made of thin planks of timber. Scientist James Hector worked out that Dunedin, with a population of 15,000-odd in the 1860s, excreted 20,000 tonnes of waste per year. In Wellington, raw sewage running down the streets greeted politicians when Parliament opened there in 1865.

Flat, boggy Christchurch had an unfortunate (but deserved) reputation as the country’s unhealthiest city. Historian Geoff Rice paints a gruesome picture of the infant city as “a damp, fever-ridden swamp…. [with] many buildings…being put on top of its filth-soaked sub-soil to give the impression of a thriving town”. As the settlement grew, the Avon River – a major source of drinking water – was fouled with human and industrial waste. Artesian water supplies were discovered under the city in 1862, but householders’ cesspits often leaked into the wells sunk to tap it. It’s hardly surprising that by the mid-1870s, one third of all deaths in the city were caused by so-called “filth” diseases like typhoid and diarrhoea.

Christchurch wasn’t alone. Disease caused by contact with human waste was a nationwide problem. Though New Zealand’s overall death rates were comparable with Britain’s, death rates from filth diseases were worse. Though typhoid and diarrhoea were seen as “normal” illnesses – the way colds are today – migrants hoping to escape the ills of the old world must have been disappointed to find them firmly established in the new.

A national first

Christchurch’s swampy, flood-prone location meant drainage and sewerage assumed more urgency than in other centres. The city was the first place in the country to build a modern sewerage system, which was part of a wider drainage scheme. Construction of the system, designed initially by engineer John Carruthers and refined by William Clark, began in 1878, overseen by Charles Napier Bell of the Christchurch Drainage Board. These men were among New Zealand’s best engineering talent at the time.

“Christchurch’s swampy, flood-prone location meant drainage and sewerage assumed more urgency than in other centres. The city was the first place in the country to build a modern sewerage system.”

Egg-shaped sewers placed throughout the central city were connected to a steam-driven pumping station in Linwood. This building, one of the few visible features of the original sewerage system, is still standing, though is no longer used as a pumping station. From here, the waste was transported to a sewage farm in Bromley, which was operational from 1882. The other main centres were much slower to build their systems. Wellington’s was completed in 1899, Dunedin in 1908 and Auckland in 1914.

The most important medical development

How effective were the new sewerage systems in reducing the incidence of infectious diseases and improving public health? To what extent can engineering claim a role in this? At the time, sanitary reformers linked sewers to plummeting rates of typhoid and the like. In 2007, readers of the prestigious British Medical Journal judged the “sanitary revolution” – the development of effective sewerage systems and safe drinking water supplies – to be the most important medical development of the previous 150 years, followed by the discovery of antibiotics and the development of anesthesia.

“In Christchurch, which has the most comprehensive archival records of all New Zealand cities, filth disease death rates halved between 1875 and 1885, coinciding with the construction of the city’s sewerage system.”

In Christchurch, which has the most comprehensive archival records of all New Zealand cities, filth disease death rates halved between 1875 and 1885, coinciding with the construction of the city’s sewerage system. Closer inspection of the records shows the correlation is not so clear-cut. Disease rates not only fell, but fell significantly, before sewer construction commenced, and again fell rapidly while it was being built. This fall continued after the system was completed, but was slower.

A more low-tech solution to Christchurch’s sewage problem can take the credit for kicking off the reduction in disease. Cesspits were abolished in 1878 and a euphemistically-named “night soil” waste collection system was instituted. The city’s medical officer of health, Courtney Nedwill, was a sanitary crusader who personally inspected houses and threatened recalcitrant householders with prosecution. In this he was supported by Christchurch Drainage Board engineer Edwin Cuthbert. By 1881, no cesspits were in use in central Christchurch and typhoid was no longer a significant cause of death.

Water levels dropped in the wake of the sewerage system’s construction, reducing dampness in houses and contributing to lower respiratory disease rates. Even though public health had already started to improve, the system’s introduction undoubtedly made the city a healthier place, sustaining the benefits accrued by the abolition of cesspits. The Christchurch of the late 19th Century set the example when it came to combining engineering and medical knowledge to significantly improve New Zealanders’ health.