Space is a commodity in the Bay Area.

In recent years, multimillion-dollar properties have squeezed into every corner of Peninsula cities, including next to the railroad tracks. However, dozens of those owners may be forced to give up small portions or all of their property as Caltrain moves forward on its much-anticipated electrification project.

SamTrans, which has the power of eminent domain, is eyeing some extra square-footage on 55 properties along the South Bay and Peninsula to assist with Caltrain's acquisition.

But it isn’t the lost value that concerned Justyna Cruz, the owner of a Belmont property about to be acquired by the transit system.

"The very small portion of the building that I own is going to be acquired by the electrification system," Cruz said. "I work near that wall 10 hours a day, every day. If I sign, I give away all my rights."

While SamTrans staff reports say its acquisition will not disrupt businesses or any current uses of the property, Cruz says its reports on the health effects from the electromagnetic fields have been inconclusive.

"I don’t want to be working there for 10 years, 20 years and then find out that I have cancer when I take very good care of myself," Cruz said. "I would like to know what can they do to protect my health."

No drugs, alcohol or meat, Cruz means business when it comes to healthy living.

His testimony spurred "no" votes from board supervisors Carole Groom, Karyl Matsumoto and Josh Powell, but the acquisition proposal ultimately passed 6-3 at the advising of Joan Cassman, an attorney with the San Mateo County Transit District.

"This has been a long, thoughtful process," Cassman said. "These property takes by and large are very, very small."

Most of the changes to the properties will be to place poles for the support structure, though several will require an electrical safety zone, which requires the removal of pools, ponds or foliage in the area.

Cassman said the agency would address Cruz's health concerns later with documents already provided to the property owner. However, if negotiations fail, it will seize the property through eminent domain.

"The documents that I’ve received do not specify if there’s any health issues that I should be concerned about," Cruz said.

It isn't the first time Caltrain has expanded into surrounding private property. The transit line has regularly acquired extra space over the course of its nearly 153-year history, with several properties most recently acquired for a Hillsdale Station and other projects on the Peninsula near Michaels Stores, Jersey’s Mike Subs and Big 5.

According to Caltrain, the need for more space to complete the electrification project is critical. Its ridership has nearly tripled in the past decade, with commuters making about 65,000 daily trips, roughly 25 percent over its capacity.

Caltrain argues that electrification is necessary to modernize the diesel-fueled system and provide more services to the growing population’s demand.