Extra steps being taken to protect water quality

Steps are being taken to reduce the risk of bird droppings getting into Christchurch’s drinking water supply.

The Council is applying protective membranes to the roofs of its storage reservoirs to stop bird poop, which contains high concentrations of E.coli, from seeping through any cracks in the concrete into reservoirs when it rains.

A protective membrane is being sprayed on the roof of Christchurch's water reservoirs.

Even a very small amount of poop can pollute a reservoir and make the water potentially unsafe to drink.

“If there are any cracks in the roof of the reservoir then there is a risk when it rains that bird poop will get into the water supply and contaminate it,’’ said Council Reticulation and Maintenance Manager Rob Meek.

“We know that rain water is leaking into some of our reservoirs and we confirmed it by putting a miniature remote controlled submarine fitted with a camera into them and poured some water over those roofs to simulate rain and look for leaks. We believe if we can stop those leaks we can further reduce the incidence of E.coli contamination.

“Research has shown that it only takes one fortieth of a duck dropping to contaminate a 400,000 litre reservoir. If that happens the Council has to chlorinate the water to kill the resulting bacteria,’’ Mr Meek said.

“To avoid that we’re putting an impervious membrane over the tops of the reservoirs to cover all of the construction joints and micro-cracks that could potentially let contaminated water in.’’

Mr Meek said so far protective membranes had been applied to six reservoirs and crews were working on another three. After that there were 11 reservoirs to do; eight in Christchurch, two in Lyttelton and one in Diamond Harbour.

“It’s quite a time-consuming process of cleaning, prepping and appying and you can only do the work in certain weather, for instance wind can put it on hold and we get lots of wind in Canterbury, but the membrane, once applied, has a guaranteed life of 20 years so it is worth the effort.’’

The reservoir work is part of an ongoing programme of work the Council is doing to ensure the safety of Christchurch’s unchlorinated drinking water supply, including the Northwest well drilling work.