The annual month-long effort to clean the town’s 114 kilometres of water lines begins on June 4.
That’s when Amherst Water Utility crews will place a swab – a 24-inch sponge that looks like a bullet – into the water main at the wellfield. Using the pressure from the wells, the swab is then pushed through the 15 kilometres of pipe that takes the water from the wellfield to the reservoir.
As the swab travels through the line, it picks up any silt or sand that may be in the pipe. The swab and silt are ejected from the line before they can enter the two water towers.
“This usually takes us about three hours, though it can take longer,” Ben Pitman, the town’s engineer, said. “We flush the water until it comes out of the line clean.”
Once the transmission line from the wellfield to the reservoir is cleaned, the crews begin concentrating on the remaining 99 kilometres of water mains that spread out over the town from the reservoir on Willow Street.
To clean these, the crew uses what is known as unidirectional flushing - the strategic manipulation of water valves and opening of hydrants to flush the lines that the crew refers to as a sequence.
“We manipulate the valves and open a hydrant in an area so the water is moving at the highest possible velocity to scour the inside of the pipes,” Pitman said. “We always draw water from previously cleaned areas so that we do not dirty up more than one area at a time.
“We have 100-plus sequences to go through.”
The crews begin at the top of the hill on Willow Street and work their way down towards the marsh and the industrial park before cleaning the section of line that takes water to the Village of Maccan.
Because the crews need to jump from one area of the town to another as they go through the sequences, it is difficult to let residents know in advance when and where crews will be working, Pitman said.
He advises people to check their water before using it during the next month and if it appears cloudy, residents should run the water until it is clear.
The particles that make the water cloudy are silt and sand, which are picked up each time a pump in the wellfield starts and accumulate on the bottom of the water mains. The water mains are tested weekly and the sediment poses no health risk, Pitman added.