Saskatchewan’s Water Security Agency (WSA) is monitoring conditions after a Canadian Pacific Kansas City (CPKC) engine spilled about 800 litres of fuel into the South Saskatchewan River late last week.

The WSA says it was made aware of the spill around 11 p.m. on Thursday through Alberta Environment and Protected Areas.

Saskatoon is downstream from the spill, and the community of Leader, Sask. has already indicated it would stop drawing water from the South Saskatchewan River as it expected the arrival of the fuel plume on Sunday.

In an emailed statement, WSA told CTV News that CPKC rail and the province of Alberta have environmental response teams working to assess and mitigate the situation.

The agency says it currently considers the risk to provincial water supplies “extremely low.”

“Communities that rely on the South Saskatchewan River as a drinking water source have been contacted, and can use water currently stored, or are already using wells that are removed from surface flows,” the WSA said in a statement.

“WSA is monitoring the situation and there is no indication of concern at this time.”

According to WSA spokesperson Leah Clark, given the size of the spill and the distance to Saskatoon — the most populous community in the path of the spill — it’s not believed to pose a threat to human health.

The WSA says the predicted travel time from the spill site to the Saskatchewan border is about five days.

By the agency’s estimate, what remains of the plume could reach Saskatoon by Thursday, Clark said.

The City of Saskatoon said it doesn’t expect the spill will pose a risk to the community’s drinking water.

“Diesel is a volatile substance and lighter than water and it is expected to dissipate long before any of the spilled fuel could reach Saskatoon,” the city said in an advisory Monday afternoon.

“Even if any spilled fuel were to reach Saskatoon after Lake Diefenbaker, the concentration would be far below any level of concern for public consumption. If that were to happen, an expected concentration would be one ten-millionth of a milligram per litre after Lake Diefenbaker — or one part per 10 million litres.

As an added layer of safety, Saskatoon’s raw water intake pumps in water below the surface, “which helps avoid intake of floating substances such as diesel fuel,” the city said.

The Water Security Agency says it’s working with officials in the Ministry of Environment, the Saskatchewan Public Safety Agency (SPSA), and Alberta Environment to stay up to date on conditions.