9. POSSESSION AND CONDITION OF PREMISE - Full possession of said premises free of all tenants and occupants, except as herein provided, is to be delivered at the time of the delivery of the deed, said premises to be then (a) in the same condition as they now are, reasonable use and wear thereof excepted.
So the bank is most likely OBLIGATED to either fix the damages or give you the money to fix the damages.
The "as is" part of the agreement is as is as of the date the agreement was signed. If you need help with this get in touch with me ... I have 2 great attornies on my team.
While "generally" banks will not make repairs - it looks like they may be more willing to do so in your particular situation (especially since they incurred additional damage to the property, and agreed to install a new septic system). It definitely wouldn't hurt to ask them to simply repair the damage they caused as a result of the install - however there is no guarantee that they will agree to it. You definitely want to have these concerns addressed ASAP - and get a definitive answer either way to what they plan to do to remedy the damage. They "may" be planning on fixing/cleaning everything, and just might not be finished with the work. I wouldn't, however, "assume" everything you see damaged will be fixed, and blow past your attorney/inspection contingency date only to realize it hasn't been.
I would bring up your concerns and get an answer either way from the bank/bank's attorney ASAP. Depending on the specifics and dates outlined in your contract, your options may be limited the longer you wait. Hope that helps!