The New York Times says that's up from the 2006 estimate of just over $6 billion.
Metropolitan Transportation Authority officials also reiterated Monday that the new completion date for the project is August 2019.
MTA Chairman Joseph Lhota had revealed the delay earlier this month at a meeting of business leaders on Long Island.
The MTA is building a new tunnel under the East River to allow LIRR trains access to Grand Central Terminal. Now, all LIRR trains go to Penn Station, on Manhattan's west side.
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