Divers are set to jump into the reservoirs of Prince Albert, Sask., as part of a plan to clean the city's contaminated water supply and end a weeks old boil water directive.

It has been 19 days since harmful microorganisms were detected in the water supply and some 40,000 residents of the city and nearby rural areas have had to boil water for consumption.

The water was contaminated when a valve failed, allowing water that was not ready for distribution into the supply.

On Wednesday, the city said divers would be deployed to clean reservoirs — a move designed to speed up the restoration process.

"The cleaning of these reservoirs represent step three of the system cleaning plan," the city said. "It was originally expected that these reservoirs could be drained and cleaned individually, but due to the length of time it will take to replenish the reservoirs, it is considered more timely to utilize the divers."

The reservoirs are located on Marquis Drive and 2nd Avenue West.

The city is also waiting for provincial water officials to approve, or amend, their plans.

"Progress continues to be made in the plan to restore the water system back to normal," the city said.

The city was also expecting to shut down the water treatment for 12 hours on Thursday, although supplies will still flow from existing reservoirs.

Officials said they are nearing a crucial time — spring runoff — and want to be ready for a change in the condition of the raw water supply.

"Spring is an important deadline for us because the ice melt has an impact on the quality of the river water," Robert Cotterill, the city manager, said Wednesday. "We want the plant operating at the fullest capacity possible before this occurs."

According to the city, health officials have not detected any giardia or cryptosporidium in people, based upon samples sent in by medical clinics for Prince Albert and area residents.

Despite that, the emergency boil water order remains in effect, which especially applies to the use of water for drinking, brushing teeth or washing dishes.