1997 sunfire belt

Hi,

i am trying to replace the alternator on my wifes sunfire.  it is a 1997 with the 2.2 engine.i can not find the belt tensioner to save my life.  there is only one idler pully in the engine and it is a thru bolt not a spring loaded tensioner.  the othe pulleys all do something, water, ac, crank steering, alt.  when i remove the idler pulley, it has an allen bolt that appears to attach to the block, is this the tensioner, and if so how do you get a tool in there, because when installed, the pulley is almost flush with the block.  thanks in advance. a cupla pics