I am not sure there is anything I can do at this point but I'm sharing anyway. If you have ideas, I'll hear them. If you have "sorry's' ... you can stuff those sorry's in a sack!
I've had this 10L oak barrel for a few years. First I used it to make an oaked imperial stout (very good results). Then, a few gravity cask ales (OK results).
I had been storing it for a long time with some cheap whiskey in it to keep it as sterile as possible. A few months ago I drained the whiskey, rinsed it, and added a half bottle of red wine. It had been stored that way for a few months.
Brewed 5 galllons of flanders red and put half of it in this barrel after 2 months. The thing showed no sign of leaking with the other fluids in it, but of course, they didn't fill the barrel. So, it started leaking. And now, it's growing mold!
I have not yet tasted the beer inside but most likely I'll just keg it and drink it in one shot during football season.
This barrel is a goner though, isn't it?