I have water/moisture issues in my dirt crawlspace and recently hired
a company to get a liner put down and two sump pumps put in (among
other things; a whole home energy efficiency improvement procedure was
done).

The way they installed the liner (6 mil) was that they just put it
down without properly attaching it to all the walls. To me it makes
the impression that things like mold (developing underneath the liner)
can still have a negative impact on the air quality of my house if the
dirt is not properly sealed of.

Any opinion about this?