I would start with an environmental engineering company to see what their thoughts are.  

Even on small projects you could have to deal with the Army Corp of Engineers, and various environmental agencies.

But to ease your conscious call your water utility and ask the pH of the water (they are required to test this regularly so its no additional work for them.

Make sure you go down to building and planning, and whoever oversees environmental health and pull the files before you sign anything.

@Ben Leybovich   I looked at it very hard about mid to late 90's  ... there are environmental issues .. and the technology is very advanced..

Start with a title search, perform environmentals, review all current leases and perform a meet and greet with tenants, while always being sure to check with the Army Corps of Engineers when dealing with waterfront property.

If not I wouldn't be concerned.Best to call your state environmental department and ask knowing the size and what's in it and if such is common in the area, rural or in the city.I had a tank sink in the ground on one side, it tipped over and spilled, a filler wasn't tight.

The guy knew that I was price conscious and was able to make recommendations accordingly. 

With all the various environmental laws, etc. if it's an actual named creek or stream moving any dirt around would probably not be allowed.

While I could easily be picking up housing in Monessen, New Kensington, or Penn Hills I personally have made the conscious decision to look further out of the city.