Samaritan Medical Center will enter a new era Monday.

The Watertown hospital signed an amended 99-year lease with Rothschild/Breuer Associates, Syracuse, on Thursday afternoon that was the final holdup for the hospital's $61 million expansion and renovation project.

SMC spokeswoman Krista A. Kittle said the lease, which has been in place since about 1990, had to be reworked because the current parking area for clients using Watertown Medical Center, the building adjacent to the hospital, will be taken up by the project's three-story parking garage.

Rothschild/Breuer owns the medical building.

HBE Corp., St. Louis, Mo., the project's developer, will begin preliminary construction work Monday, surveying the area, putting up construction fences and starting the foundation for the 350-space parking garage.

Ms. Kittle said Thursday that the Watertown Medical Center parking lot would be closed Friday, and when clients seek services after the weekend, they will be directed to park in the 192-space Woodruff Street parking lot.

"The employees who park in there will find parking elsewhere, either by parking at Samaritan Medical Plaza and riding the shuttle, or at an off-site location," she said.

Patient and visitor parking won't be affected by this, she said.

Employees, however, will be required to park in employee-designated spots. Ms. Kittle said managers from the hospital and Samaritan Keep Home also will be required to use the shuttle service to and from Samaritan Medical Plaza.

"We strongly encourage them, out of respect for neighbors on the side streets around us, for safety and convenience purposes, to not park on city side streets," Ms. Kittle said.

In August, when HBE Corp. starts preliminary work on the second phase of the project, a 130,000-square-feet patient pavilion, more changes will be announced.

When that work is completed, the project's third phase, the renovation of 71,500 square feet of existing hospital space, will begin.