I applied milorganite at the proper bag rate on my 13000sq ft lawn... In the sane timeframe I leveled out and fixed some parts of my drainage ditch in the front yard. (The ditch was graded improperly and held water for up to a week after rain) I used soil from the woods behind my house, the top layer was 1 ft of good black soil, then about a foot of sand, and then another foot of clay/sand mix. I mixed it up pretty well, and didn't notice any oil in the soil when I put it down.

After getting almost 5 inches of rain in two weeks, the drainage is much better, but can't be fixed until my neighbor fixes a high spot in his... But the ditch is now a rusty color and also had quite a bit of oily residue, like if you washed oil off concrete. I can see how the milorganite could cause some rust but not the oil... Any ideas? New to this