Brambilla's have had problems but it was many years ago. I think they may have changed some of their lot policies.
Most of the boat storage places could accommodate you. I live 5 miles North of Chaska so you could give me a call and I may have a spot for you in mind. Send me a PM and tell me some more details of what you're looking for regarding storage, i.e. duration, use, location.
BTW, welcome to the Land of 10,000 Lakes. There are some very nice recreational choices in and around Chaska.
Also, the Community Center has one of the best pool/whirlpool/sauna/steam rooms around. Lifetime Fitness's flagship fitness resort is also in Chaska.