The vehicle leaks antifreeze near the rear of the engine on the driver's side?

The leak does not occur until the vehicle has cooled down about forty-five to sixty minutes later. I go outside to look under the car and the leak is there on the cardboard which I replace regularly after driving. The leak saturates the cardboard and leaks onto the concrete. I normally must put one to two twelve ounces water bottles of antifreeze back in the antifreeze reservoir after the leak appears. A new water pump was placed on the vehicle with no success. There were no leaks once I replaced the antifreeze. The car does not overheat. A pressure test was conducted by the garage - twice. The mechanics are baffled. The engine temperature normally gets to about 213 degrees while driving around in the FT. Stewart, Ga area of 90 degrees running errands. There are no leaks when I stop at this store or that store to make purchases. I have been out as long as an hour at a time the last three weeks. The car drives beautifully. This car is well maintained. Can anyone help me or steer me in the right direction? Notr: How do I remove antifreeze stains from my driveway?