Citigroup (NYSE: C) and Goldman Sachs (NYSE: GS) are reportedly closing some of their New York offices ahead of Hurricane Sandy, set to come on shore in the next 24 hours. The banks have offices in some of the riskiest areas of the city, so will need to leverage alternate plans to maintain normal business operations.

The firms occupy multiple office spaces in the low lying areas of New York, known as ‘Zone A’, which coincidentally are in the evacuation zone due to flooding concerns.  The firms are among Wall Street firms planning to shift operations to other cities and have staff work from home as Hurricane Sandy’s arrival in New York forces evacuations.

Employees at Citigroup, the third-biggest U.S. bank by assets, won’t be able to enter Lower Manhattan offices on Greenwich Street and Wall Street, which include the main trading floor, according to a memo sent to workers and confirmed by spokeswoman Shannon Bell. Goldman Sachs, whose corporate headquarters at 200 West St. is also located in an evacuation zone, told the staff in an internal memo that most of them will work from home.

With multiple reports predicting Hurricane Sandy will flood parts of the city, the Banks turned to emergency plans. Floods in Manhattan pose a particular risk due to the usage of subways, and as such, the MTA began shutting down the mass transit system at 7 pm Sunday. The New York Stock Exchange will close its trading floor starting today and conduct business on NYSE Arca, its electronic market.

With office closures in New York, the banks will seek to leverage their international operations, a good test for their continuity of business plans. Goldman Sachs, the fifth-biggest U.S. bank by assets and the largest equity trader by revenue, said in its memo that some activities will be shifted to London and other locations around the world, and that some employees will work from offices in Greenwich, Connecticut, and Princeton, New Jersey. Staff deemed critical may be called upon to report to offices in Lower Manhattan and Jersey City, New Jersey, according to the memo.

 The slow approach of the storm over the past four days has offered the banks plenty of time to plan accordingly. Many of the European Banks with offices in the city (including UBS (NYSE: UBS), and Deutsche Bank (NYSE: DB) have similarly made arrangements to move personnell out of the evacuation zones, and into alternate spaces or work from home arrangements.