What Lies beneath

We needed to replace a retaining wall which had collapsed over the winter, and while we were at it replaced some underground pipes to improve drainage. Big surprise to everyone when the workmen uncovered this tank for water/grease emanating from the kitchen sink. One of the grossest things I've ever seen! It's been there for at least 40-50 years unbeknownst to us or the previous owner would lived there for 25 years. All pumped out now, and tank removed. Waste water now flowing to the proper place.