I fish the Gallatin Steam Plant several times every winter. It is generally good for Largemouth Bass, White Bass, Skipjack and Striper. I plan on fishing it the weekend of 1/22. If you go before then, please post your results.
The closest ramp is about 1/4 mile up stream on Coles Ferry Pike. To get there take 109 out of Gallatin and once you cross the lake, go about 1 mile. Turn left on Academy Rd and go roughly another mile. Take a hard left onto Coles Ferry Pike and follow it to the ramp. As I recall, Coles Ferry dead ends at the ramp.
There is another ramp about 2 miles down stream at Flippers Bait and Tackle. This is a much nicer ramp and Flippers is a great shop. To get there, take 109 out of Gallatin and just before the lake turn left on Odems Bend Rd. go 1/4 mile at the most and Flippers will be on your right. As I said, this is a much better ramp, but it is a cold ride up the lake.
If you don't know this lake, keep a sharp eye out for the channel markers. This lake can go from 60ft to 3 ft in seconds. Good luck!