How do you remove lower right 1/2" bolt on supercharged 1998 Buick riviera water pump. It seems to hit the rear of a pulley.

SOURCE: 1999 Buick Park Avenue water pump removal

The bolt holding you up is on the bottom by the compressor, right? You Will have to have an inverted torx socket to remove the studs. Also there is a spacer behind the mount bracket, remember where it goes. You will have to pull the pully bolts and get it out of the way too. Some of those cars have plastic elbows going from the intake to the water pump, be carefull with it. Your motor may not have this but be ready to replace it if it does because it will most likley break. Good Luck.

SOURCE: 1999 Buick Park Avenue Water Pump Removal

Hi once you have all the bolts off for the mount raise the front of the motor up till you can remove the center part of the mount
I use a floor jack and a 2x4 across the oil pan then remove the studs for the motor mount bracket now remove the bracket and now you can get the water pump out
hope this helps

SOURCE: water pump

Too complicated to explain here...buy a Chiltons Manual at Auto Zone or NAPA $25...not too bad of a job but you should have a thorough knowledge of tools.
Good Luck

SOURCE: Water pump removal on a 1996 Buick Riviera (supercharged)

there are two bolts that hold the power steering pump in place that are accesable through the holes in the pulley. If you use a 6" extension and a 1/2" socket you can reach them. this will allow the pump to be removed and hang by the hoses and be out of the way. I was told also to inspect the cam sensor while it is apart because you have to remove the water pump in order to get to it.