Dams, or bulkheads, seal off the two mines where they connect to Stobie at the 2,400 level.
All three mines receive large volumes of run-off and groundwater that collects in them.
In the spring, said Ward Warren, Inco's energy coordinator for Stobie Mine, it's not unusual for the mine to pump out five million gallons of water per day.
"The need to drain out Little Stobie and Frood is a liability to us and it costs a lot of money. We looked at that and found a way to minimize the impact and even use it to our advantage," said Warren
The idea was to use the two adjacent mines to collect water and store it so it could be pumped out on evenings, weekends and holidays to take advantage of off-peak electricity prices. It also serves as a buffer to the pump system during times of high water in-flow.
Drainage lines from the two dams to Stobie Mine's pumping infrastructure were badly corroded due to the acidic content of the water and had to be replaced anyway, so mine crews went one step further and installed flow and pressure monitoring instrumentation and automated valves.
"It was an effort requiring support and input from a huge group of people including Engineering, Operating, and Maintenance personnel," said Warren.
"The project was supported by everyone from the Divisional Energy Committee, to local mine management and department heads."
"We tied it all into an existing PLC infrastructure and automated it, so the control valves stay closed during peak hours and open up during off-peak periods," said Warren.
"Previously, most pumping was done on day shifts, Monday to Friday, simply because the people to maintain the system were here. Now, it's exactly the opposite."
The fact that the pumps are idle during the day creates "an excellent opportunity" to do maintenance, added Warren.
"I'd worked on pumps with guys where the water was coming over the sump wall and running through the pump room. We don't find ourselves in that situation anymore. It's a better way to work."
Once the water is pumped to surface, booster pumps send it on its way to Copper Cliff, several kilometres away, where it's pumped several more kilometres to a tailings area.
"They're also dealing with it off-peak, so it's a cascading benefit," said Warren.
Off-peak pumping at Stobie Mine began in May and saves approximately $25,000 per month. In July, when hot, dry weather and a stressed provincial electrical system caused Ontario's Independent Electricity System Operator to request reductions in electricity consumption, Stobie Mine shut off its pumps altogether and only resumed pumping in October. Total savings from May to October were more than $200,000.