City Sewer System Backlogged Into My House And Several Others

So to make a long story short we had a a storm the other day I woke up in the basement and stepped into about 2 inches at the time sewage water because the city system got clogged up. 7 other houses on our street also had sewage damage. The basement was essentially my home, all my furniture, clothes, artwork, ect has either been directly contaminated or indirectly damaged. Home insurance will only cover 5000$ but we have to pay 2500, so really just 2500. The city water sanitation has already stated they will cover some damages but haven't disclosed the level of coverage offered. It's all just happened so its really just getting out ducks in a row so to speak.

Location is upper Illinois.

Edit to add: looking for advice and recommendations. Haven't had to deal with something like this before, and the amount in damages is going to exceed our personal capabilities.