when I set my 18' metal frame pool up, (along with the grading to level of the 2.5 degree pitch) I loosened the soil, pulled as much of the old grass, roots, what ever else I could find that wasn't grains of dirt/sand out, sprayed 5 gal of round up, turned the soil over about 6 inches, then I disolved about 25 lb of salt *block form, from my brine tank for my house water conditioner** and poored that onto the soil, turned it over again. I overlapped about 1 to 2 feet past the pool edge, where I put some drain field gravel down around the pool to prevent errosion. After all of that (this is week 2 now) I put down about 1/2 inch of builders sand (expensive), then I layed down 3 layers of 8 mil plastic, and then the big blue tarp (mistake, it detiorated over one year), then some more rock, almost to the edge of the pool where it meets the ground over the plastic. Bordered and it looks good, and the pool isn't going anywhere, plus, there is nada growing under, or around the pool!!

I did this because we are not planning to take it down each year, and I hope to upgrade, like yourself in the future to a solid wall pool.. so when I do, the ground will already be prepared.

Hope this helps, it is a lot of work, but I have found from this forum, and in life, if it is worth something to you, do it right the first time... and it will be a lot easier to take care of. I treat my water like its gold, I didn't want to have to drain it out just because I didn't do something write in the build.

"if you don't have time to do it right the first time, when are you going to have time to do it over ??" author unknown