I have noticed that the grass over my septic system yellows and dries
in a perfect outline of the tank itself. Google searches have
explained why this usually happens. I was wondering if it is possible
to dig the soil out from over the tank, cover the top with an
insulation, say polystyrene tiles or something, then replace the
soil?

Would this be detrimental to the tank in any way? I have about 6
inches of soil over the tank and the ky. blue grass fares worst, per
expectations. The p. rye and fine fescue seem to do better. I suppose
the other alternative is to over seed with this seed exclusively.

Thanks in advance for any advice.

Gary