The cost of building a water-play area at Hawrelak Park has ballooned to $5.1 million.
Three years ago, council approved construction of a wading pool, splash pad and change rooms adjacent to the lake at a cost of $3.3 million.
But since 2013, the project has undergone significant redesign due to a change in location from the lake edge to an area near the playground, said a city report.
The lake has also grown in size to accommodate more visitors, so the filtration system is now inadequate, the report said.
"A combination of scope clarification, utility requirements, environmental reviews and associated design cost have resulted in the $1.8 million shortfall," it said.
On Monday, council will have to decide whether to spend the money, scrap the project or scale it back to just a splash pad.
The city has already spent $800,000 on the project, with construction scheduled to start this year.
Money for the full cost of the park is available in a fund set aside for trail and park renewal, city staff said.