16" clay storm sewer running UNDER home

My wife and I are under contract on our first home, but considering walking away (we are in the due diligence period) because of a recently discovered storm drain on the property. The storm drain originates on the street, about 20 feet over the lot line, and is a pretty typical arrangement with inlets on both sides of the road. The pipe exits near the opposite corner of the property, into a small creek. The pipe appears to run at an angle directly under the house.

There are no recorded easements on the property, and the city (a major metro area) has no records for a majority of the storm sewer system. The house dates to 1948. It is still active, as I've stuffed a hose down there at street level, and observed flowing water 2 minutes later. The agent/builder who just finished renovating the home claims he knew nothing about it, since there are no easements, and it didn't show up on a survey. But, it's there.

This concerns us greatly. Isn't this essentially begging for a sinkhole to eat up part of, or all of, the house? It seems like rerouting the storm drain to the driveway or lining the pipe are the only real viable solutions. I'm guessing either would easily be in the tens of thousands of dollar range.

We love this house. It has every feature we were looking for, and then some, but we have serious misgivings about the storm drain. So . . . walk away immediately, or get additional information?

Just because it is a clay pipe does not automatically mean you will have a sink hole. Before doing anything have a pipe locator trace the path of the pipe to see if it actually does go under the house.