rented storage flooding

I asked this about 2 weeks ago. I rented a storage sine 6/2005. There are furnitures and appliance in it worth about $10000. It was flooded 4/16/2007. There were total 50 units damaged and we are one of them. A public high school next to the storage building has a construction project. The construction company blocked the drain during the heavy rain. We do not have insurance (homeowner insurance won't cover flooding anyway). I asked a lawyer and he said storage company is responsible. But he will charge $4000 for this case. I want to write a 30 day demand letter to the storage company myself. Is there anybody can help me find the detailed law code on this? Many many thanks!