City crews have been working this week on the lake shore at the west end of the dog walk, installing an emergency water treatment system.
They are installing pipes and valves to hook to a portable, modular treatment system that would be rented when needed.
“You can get treatment systems that are mounted on a truck or in a shipping container,” says the city’s Chris Gainham. “It would not make sense for us to buy that. You can rent them during an earthquake or other emergency.”
The most likely emergency in Nelson would be a drought. The system would treat and pump lake water to the lower parts of the city in the event of a shortage such as the one the city narrowly avoided in the summer of 2015.
Gainham said the new pipes from the lake will run to the nearby city public works yard, where the rented disinfection system would be stationed. It would filter and chlorinate the water and also apply ultra-violet treatment.
Then the treated water would enter the lower end of the city water system.
For the past year, in conjunction with the Interior Health Authority, the city has carried out continuous testing of the lake water in that location and found it clean, Gainham said, adding that the swift flow in the lake at that point helps to keep the water uncontaminated.
He said they have tested for “a full range of microbiological, chemical and physical parameters.”
Gainham said the system is designed to provide 45 litres per second or four megalitres a day, the equivalent volume of about 1.6 Olympic-sized swimming pools.
The idea for an emergency lake water treatment plant has been around since the city wrote its original water master plan in 2006.
The west entrance to the dog walk will be closed for another three weeks.