Garden hose. Sweep the dirty water into the sump pit.

I second what glennsfc said about no plywood. I would even be leary of using laminate. We used vinyl tiles on our floor (self-stick) 26 years ago. Then put an inexpensive area rug where the kids played (in front of the tv). That was so easy and bullet-proof with whatever the kids spilled. Arts, crafts, glue, it took so much abuse. Easy to change out the area rug every so often. When we laid the tile, we used a waterproofing film over the cement floor first before laying the tiles. Ours is a walkout basement. No water issues and I have only occasionally had to run a dehumidifier. (i.e. this summer only once) 26 yrs later the tiles are still down and I'm looking to replace them only because I'm tired of them but they are still stuck tight and will require some work to get them up. Tile is in the laundry room and bathroom down there also. We do have carpeting in a bedroom down there - just regular padding and carpeting. We have never had a mold or mildew issue. Never. You don't say if your HVAC system runs thru the basement? And do you ever need to use a dehumidifier down there?

No it is not ruined. The concrete contractor will be able to prepare your slab for finishing. There are machines which will do the job.

Not sure if you have solved your cat urine issue yet? I wanted to give you a recipe that will eliminate the urine and the odor. It may have already been posted but here it is anyway. 1 (16) ounce bottle of Hydrogen Peroxide 1 (tsp) baking soda a couple of drops of dishwashing liquid like Dawn or Palmolive pour the peroxide into a clean container, add the baking soda and the dishwashing liquid, stir very gently to dissolve the baking soda. Pour onto stained area and leave it alone for 24 hours. This solution is the Best and most effective I have ever seen or used. If you can get ahold of a black light, you can turn it on and the urine areas will glow. After you use the above recipe and leave it for 24 hours, if you turn the black light on, the stains are gone and so is the odor. Give it a try, I think you'll be pleasantly surprised at the results. Thats it. You can double tripple or quadruple this recipe for very large areas.