Environment Property

I bought seven acres of land. I didn't know when I bought the property that their was and oil field company that had left the property in bad shap. The first three acres was clean and cut down but the four acres in the back was wooded area. I walked into the woods and there were pipes running a cross the woods and a big pit that was not coved all the way. This took place around twenty years age. So there are big trees all around the pipes and pit. It seems like the company just up and left with out cleaning up. The company that did the drilling is know longer in buisness. Need advice