Question
25 years ago local heating oil company sprung a leak in their hose while delivering oil to me. Have planted grass 6-10 times since. Nothing seems to take. Affected area has now spread out over 250 sq ft. Killed an 80 ft tall tree. Only weeds now grow in that area, if anything grows at all. Is there ANY thing that I can do besides laying a tarp over it and applying mulch and building a park-like area with planter boxes? Thanks very much.

Answer
Hi Ronn,  The best fix is to have the soil removed and replaced.  If you have documentation from the time, the oil company may still be responsible for clean up.  You'll probably need to have some soil tests done to establish the width and depth of soil that needs to be removed.
Short of removal, tilling the area in the spring and fall to expose as much to air and sunlight will speed decomposition and incorporating activated charcoal may help significantly.
Your suggestion is probably the cheapest, but cleanup may well be required if you ever sell the property, so I think I'd address it now.
YOu might also check with your local legislator.  They might be cleanup funds available if you can prove the spill was not of your doing.  Jim