Esshup, I do believe the roofing does have the anti moss stuff. I hadn't thought of that, could be.
BGK, I agree if pipes are too shallow it can kill the grass above but these pipes are plenty deep. The area where the grass died is where the water runs off the roof onto the surface of the grassed area and flows down a lowered shallow grassed channel to the pond.
On the color I was just guessing based on my experience with the glass window on my wood stove. After burning several hours it can get a brownish coating that when cleaned off with fireplace glass cleaner and paper towels leaves the paper towels brown. Also in hindsight now I remember seeing a lot of wood burning chimneys can stain the roof and surrounding areas brown over time.
Thanks for the ideas.
