A few years ago, we had our old lawn removed, and a new sod installed.
Looked great, but over time, crabgrass returned to a corner of the new lawn,
where it once existed in the old lawn. What I can't figure out is why the
height of the dirt in that area has increased. It is like the dirt is
multiplying! Maybe crabgrass roots are "swelling" the soil? Still, this is
happening, to a lesser degree, along other parts of the lawn, all on the
lowest part, which is against a sidewalk. This is evident when the lawn is
edged, as the soil must be 2-1/2" high or more. The soil used to be even
with the sidewalk. I have to be really careful not to scalp the lawn when
mowing, whereas this was not a problem before. It is like my entire lawn is
slowly sliding to the street, and building up in size at the sidewalk edge.
Also, the pop-up sprinklers can no longer clear the sod/lawn. The slope to
the sidewalk is slight (18" over 30 feet maybe). What is happening, and how
do I stop it? And correct it.

Thanks,

- Phil