University of Minnesota and transit officials who thought they could stop worrying about the Green Line's potential disruptions to lab experiments are having to think again.

Water, debris and in some cases animals are creeping their way into the light rail tracks through rail access boxes, causing interference with sensitive and costly University of Minnesota research equipment.

Researchers have not reported actual impact on current experiments, U officials said. But tests done over the Green Line's first year of operation on Washington Avenue revealed higher than desired electromagnetic interference (EMI). If it continues, the interference could affect how several nuclear magnetic resonance machines work. Those devices are used in drug research.

About 100 labs and more than 300 pieces of equipment are housed along the light rail tracks.

When leaves or litter accumulate around the access boxes, officials explain, they can provide a path for the flow of electricity. Metro Transit found one small dead bird in one of the boxes and officials there are working on an engineering solution to block outside material from collecting near the rails. The U has asked the Met Council present a permanent solution by the fall.

"We weren't just concerned about the existing laboratories but really concerned about how research was going to evolve in the future," said Leslie Krueger, chief of staff at University Services. "We wanted to make sure the train operations would not negatively impact our ability to do research in year one as well as 50 years from now."

Krueger used an analogy to explain how light rail could affect nuclear magnetic resonance machines.

"If you put a magnet up to a compass, the compass goes haywire and you're not able to get a good reading," she said. "Now imagine the train, or LRT, as that magnet, and our sensitive research equipment is that compass."

In 2010, the university and Met Council signed an agreement to conduct quarterly vibration and EMI testing during the Green Line's first year of service, which began in mid-June 2014. The agreement required the Met Council to test semi-annually after that.

The Nuclear Magnetic Resonance Center at the University of Minnesota campus. Riham Feshir | MPR News

Tests revealed acceptable vibration levels and no impact on sensitive research equipment so far. They confirmed that the floating slab track and rubber pads that were installed for vibration mitigation were doing their jobs, Krueger said.

Initial quarterly testing showed EMI levels, too, were well within performance standards. But as the year went on, and especially over the winter months, monitors at the labs started showing spikes in electromagnetic interference coming from the wiring under the rails.

Because EMI levels turned out higher than the standard, the agreement requires the Met Council to continue doing quarterly testing at least for another year.

Several rail access boxes are located right on the tracks. They're small, about two feet in height and length, and allow transit workers to inspect rail connections and sometimes to reset signals. Foreign objects provide a path for the electric current to flow away from the rail.

"We believe that because some leaves and trash and water collected in there, it was interfering with the ability for the system to balance itself," said Brian Funk, director of light rail operations for Metro Transit.

Certification testing done months before the line opened didn't detect the EMI problem. Metro Transit was getting data that suggested the line met the performance standards.

Funk said Metro Transit cleaned out rail access boxes before doing more tests this spring and found the readings were more in line with initial startup levels.

Metro Transit is still exploring options to keep rail access boxes permanently clean. Funk described one solution as a bladder system that can be filled with something to catch debris, water and leaves and then drained.

"We're looking at a number of solutions," Funk said. "It's still yet to be defined."

It's unclear how much a permanent solution will cost.

The University of Minnesota already has spent millions to move labs whose work it knew would be disrupted by light rail during the planning stages.

Among them was Gianluigi Veglia's Nuclear Magnetic Resonance Center, which serves 200 researchers around campus. It was housed just 75 feet away from the Green Line's tracks at Washington Avenue and Church Street.

The U spent about $25 million to move Veglia's equipment to the Mayo building, east of the old location.

"The original laboratory was very, very close to the street level and both the electromagnetic fields as well as the vibration would affect the measurements that we were taking," he said. "In fact, the laboratory was shut down for almost a year and a half."

Gianluigi Veglia, director of the U's Nuclear Magnetic Resonance Center, explained how light rail electromagnetic interference could affect how the technology works. Riham Feshir | MPR News

Now that he's working much farther away, the center director says his equipment is working as it should.

While Veglia's lab is safe, U officials say electromagnetic interference levels are noticeable at other NMR machines scattered throughout campus, including at the Center for Drug Design.

Removing his watch, cell phone and wallet full of credit cards before entering the NMR restricted zone, Veglia explained how the machines work. The technology is so sensitive that it can absorb anything remotely magnetic and throw the readings off.

"You need to have a very high homogeneous field; that's why they're very contained," Veglia said. "You need to get very, very sharp lines in order to interpret the atomic resolution of all these proteins."

The university's Board of Regents approved a resolution last month that requires the Met Council to provide a detailed plan for the engineering solution by Sept. 1 and implement it by June of next year.

According to the U, the average Green Line daily ridership when classes are in session is 9,300.

The Green Line also runs along Minnesota Public Radio's broadcast center in downtown St. Paul. An MPR spokesperson said the two parties are still working to find a solution to lessen vibrations generated by vehicles crossing the tracks next to MPR.

"We've had ongoing discussions with the Met Council regarding the continuing noise and vibrations resulting from light rail tracks outside of and impacting our broadcast center," Angie Andresen said. "We continue to investigate options and hope that we can reach a solution that is acceptable to both parties."