Dealing with water drainage

[Joe Mazur]

After YEARS of looking for a "deal" we finally took the plunge and bought a SF house off of Roofstock, which comes with tenants and its own set of other problems.  One of them being no chance to step inside or really on the property until close.  Fast forward to closing and now we find out that heavy rains in the area can cause the "basement" of the split level to flood.  The current tenants had to deal with flooding during a bad storm the first weekend they moved in Aug 1st while we were under contract.  There is a creek that runs behind the house and it is in a flood plane for which we purchased flood insurance.  Now we are concerned about the drainage.  I have no desire to be moping or dealing with water even every so often and certainly would not want to disrupt the tenants every time it rains.  The previous owner installed a couple of pumps and put up a retaining wall.  I'm told the pumps didn't work during that Aug 1 storm because the power went out.  I have no idea what the best way to deal with this is.  So my question is.. what type of expert can I hire to help find some solutions?  We have a flood survey that was done and all that and it's really not in a bad spot in regards to elevation but the standing water is a problem.  A generator would certainly eat into years of cashflow and the margin is thin as it is for even hiring an expert.  Feeling kind of stuck less than a week after closing.  Any guidance would be greatly appreciated!