From Michael's Sketchy and Sci-Fi Book Covers, via scribblingwoman. I'm not sure how well you can read the top blurb, but it says

TONY COSTAINE and BURT McCALL are flooded with trouble from an unfinished dam - and a whisky mine.

"Whisky mine"? I vividly remember walking up a road one freezing, blustery day in Scotland. The wind carried the smell of the whisky distillery, and we hiked straight there to, um, warm up. We somehow managed to miss all those whisky mines, though. Better go back and check.