By Selena Hill (staff@latinospost.com) | First Posted: Aug 08, 2013 02:36 PM EDT

The idea that BART and its union workers will reach a new contract deal by Sunday is, at best, "optimistic"—on Wednesday opposing sides were $100 million apart on basic math calculations for negotiations.

Considering the divide, the threat of another BART strike could come as soon as Monday if Gov. Jerry Brown doesn't intervene and implement a 60-day "cooling down" period to prevent workers from shutting down the rail system through at least mid-October.

The original contract was extended for a 30-day period in early July after unions went on a 4½ day strike, inconveniencing the 400,000 daily commuters that depend on the rail system to get around. To prevent the unions from striking again last Monday, Gov. Brown appointed a three-member board to investigate the stalled negotiations. The board must now provide the governor with a written public report on the contract talks by next Sunday. Until then, unions are not allowed to walk off the job, nor can they be locked out by BART.

At a public meeting hosted by Brown's board committee Wednesday, it was apparent the two sides are still far from reaching an agreement on issues like wage hikes and contributions toward health and pension benefits, reports Mecury News. The governor's committee heard both sides and noted that they have not agreed on even basic math issues. BART says the gap between its proposal and what its unions want is $100 million over four years, while the unions say the difference is closer to $56 million.

The two sides also disagree on average employee pay. The average compensation for BART workers is $79,500, according to BART, but unions say it's closer to $66,000.

"It's disappointing that they can't even agree on math," said Jacob Appelsmith, one of the advisers Brown appointed to sit on his special three-member board, according to the San Francisco Examiner.

Workers note that they relinquished $100 million in compensation in 2009, and say that BART's proposal will leave wages flat since a requirement for employees to contribute more toward their pensions will offset a wage increase.

These huge differences indicate that hoping for an agreement by Sunday is "very optimistic," said committee member Robert Balgenorth, a member of the State Building and Construction Trades Council of California.

BART and the unions are expected to continue negotiations Thursday through Saturday.

BART has warned that passenger fares will rise by double digits if management acquiesces to union demands. However, unions note that BART uses more than $100 million in passenger fares and regional sales taxes every year to fund capital projects like debt on the Oakland airport connector - money that could easily cover the difference between the two sides.