Twin Falls, Idaho (KMVT-TV) As of the first of August, The City of Twin Falls started working underwater to fill holes in lower blue lakes.

"We've been filing the crack and putting pone line over to seal it and there was one big boulder kind of in the middle where the crack is. The boulder splits it right in between” said Mike Trabert Environmental Engineer, City of Twin Falls.

Divers began filling and sealing cracks underwater at upper blue lakes two weeks ago.

It needs to be completed to meet an agreement with the blue lakes country club to manage the lake level.

During the process, workers noticed a bolder that became more exposed during construction.

"Really what happened was when we started to seal the other areas that didn't have the velocity and all of a sudden the water was able to go in those areas and so new areas opened up” said Mike Trabert Environmental Engineer, City of Twin Falls.

City workers are expected to have the project completed by Friday as 95% is done.

The challenge will be filling the areas around the bolder.

"Trying to finish up, going around the boulder and sealing it down with the bigger rock and more liner” said Mike Trabert Environmental Engineer, City of Twin Falls.

The project is costing the city less than $20,000.

Diving this water is very rare experience for scuba divers, but it's not for pleasure, it’s to fix cracks that are leading to major water loss.