Now that is quite a conundrum. Kitty cat pee and poo and chemical fertilizer is best avoided. One possibility would be to excavate all that dirt down to about six inches then refill it with fresh dirt. Of course the kitty cats might thank you for cleaning their litter box and they’ll be back. Another option would be to plant that small area with grass. Or maybe clover. Or dandelions. Of course when the dandelions are blooming you’ll get yellow feet. Also, I suppose you could cover that area with burlap which wouldn’t cut the electromagnetic actions hardly at all. Maybe you could rent a jackhammer and get rid of some of that concrete. Sorry I’m not much help. I guess a little kitty pee and fertilizer is still better than never being able to ground. Good luck.