Policy should seek to eliminate phosphorus risk to lakes: consultant

Those are the conclusions from a report by Hutchinson Environmental Sciences, the consult behind a study seen as a key element of new waterfront development policies the city is working on to address the growing blue algae problem plaguing city lakes.

Dr. Neil Hutchinson told members of the planning committee Monday that the current model the province uses puts a limit of 50 per cent increase in phosphorus levels in lakes. It assumes the main source is from shoreline septic systems, and caps development on the lake when the limit is reached.

But Hutchinson said the model has proven a poor way to predict phosphorus levels, because of a number of variables that the model fails to take into account. For example, some lakes that have no residential development are seeing increases in phosphorus levels.

“It's not nearly accurate enough in predicting phosphorus levels,” he said. “And that's not unique to Sudbury. The province is looking at alternative ways of doing lakeshore guidance as a result.”

Stephen Monet, the city's manager of environmental planning, said while concern about toxic algae blooms is relatively recent, studies of water quality in area lakes has been going on since 1978. And more intensive monitoring of 66 lakes in Sudbury has been going on since 2001, giving them a baseline for the current work.

“The mounting community concern is relatively recent,” Monet said, but it has been a priority for the city for years.

The current study focused only on lakes with homes not serviced by the city, and therefore at greater risk of leaching from septic systems, as well as from lawns fertilized with phosphorus, that later leaches into the lake.

The Hutchinson report looked at lakes of 10 hectares in size – 354 in total, including 44 outside the city limits. It found no lakes are trending upward in phosphorus levels, and 12 are actually trending downward. However, the report also found the model used to determine whether a lake has reached its development capacity was poor, and did a bad job in predicting the impact the homes would have on phosphorus levels.

“There are better ways to manage your lakes,” Hutchinson said.

He recommended a new model introduced to regulate development in the Muskokas, which emphasizes adopting policies that aim to eliminate threat of phosphorus leaching into water, rather than setting a maximum capacity.

Water levels are monitored and three triggers would be considered key: if phosphorus levels start trending upward, if algae blooms begin to appear, and if measured phosphorus levels suddenly spike. If any of those issues arise, a study into the cause would be done.

In response to a question from the committee, Hutchinson said there are ways to combat algae blooms directly.

“There are ways to treat blooms, but they are not effective for every lake, however.”

Monet said the report was the first step in the city's process to come up with new policies to protect water quality.

“Policy recommendations on water quality won't just be based on this report, but is … part of a comprehensive community consultation process,” Monet said.

Planner Mark Simeoni said staff will continue work for another month coming up with draft plans, then come back to the committee. Public consultations will follow before proposals are finalized, he said.

Ward 9 Coun. Doug Craig asked if, down the road, adopting better policies could mean lakes that are now closed to development could be opened again.

Monet said the goal is to reduce the stress on waterbodies, and lower phosphorus levels.

“So that is a possibility,” he said. “It's too early for me to say.”