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This election day voters will decide on a multi-billion dollar bond measure that BART says will help pay for upgrades and repairs.
However opponents of Measure RR question whether all that taxpayer money will actually be spent on fixing the aging system.
To make its case BART gave KTVU a rare look at one of the agency's most critical maintenance problems. KTVU's Alex Savidge toured a leaking BART tunnel underneath San Francisco that workers refer to as the "rainforest."
It's a spot underneath San Francisco where thousands of gallons of ground water are constantly leaking through the BART tunnel - and all that water can lead to equipment problems and sometimes delays.
To get to there, our KTVU crew hopped on a maintenance truck at the Civic Center Station and drove through the darkness toward the 16th Street Station.
Our crew had to take the tour during the overnight hours when the trains aren't running.
After getting out of the truck, BART facilities superintendent Tom Delaney showed our crew where water, from an underground aquifer, seeps through the walls of the tunnel.
The problem is the water seeping into the tunnel is highly acidic. It eats away at the rails and fasteners and even damages train control boxes.
Crews are constantly replacing those parts. Last May the leaking tunnel caused a piece of rail to crack, which led to massive delays for BART riders across the system.
BART says the aging transit system has many maintenance problems, but this one is a top priority.
BART Facilities Superintendent Taylor Huckaby says a permanent solution would cost "millions and millions of dollars."
If voters approve measure RR on Election Day, BART says some of that $3.5 billion in bond money could be used to repair this problem.
That bond measure would raise property taxes on homeowners in San Francisco, Alameda and Contra Costa counties.
But opponents of RR say there's no guarantee all that tax money will go toward repairs. State Senator Steve Glazer says RR is a blank check.
He says about a third of the bond money from measure RR can be used to pay for employee salaries and benefits.
Whether or not the measure passes, BART says it will begin working on a permanent fix for the so called "rainforest" later this year.