question about ferals pooping in garage where they sleep

hi, i have 3 feral cats who have access to a garage through a window. however, they are pooping in there. i am going after work to buy a litter box and cat litter, as well as a scooper. how often does it need to be cleaned? is there a certain litter i should use? i was thinking of using the scoop away litter from costco. i will try to put the box where they have been going to the bathroom. any other ideas? is it safe for everyone who comes into contact with the garage as it is used for storage of equipment for a landscaping company. the men do go in daily. are there any health hazards i should be worried about?

thank you in advance to anyone can give me information.

Hi Jenny 2786,
First, one box is not enough for 3 cats. Second, they may not like kitty litter because if they are used to pooping on bare ground or natural sand, they might not use the kitty litter. For 3 cats, cleaning or scooping will be at least 2-3 times a day for each cat. It's not just scooping poo but also scooping pee. And let's say if it's only one box, it'll be full,in no time and when it's full and dirty, they'll not want to use the litter box and will do it on the ground.
It's pretty safe if they use the litter box and if they cover up their business. That way will be less or no smell at all rather than on the bare ground and not covered up at all and the smell of poop will be in the air and so will the smell of pee.
So it's a little tricky for you regarding the litter box and kitty litter.

You probably do need more than one box.  You can get a large storage tote to use - advantages are it is equal to two or more regular boxes and the high sides help keep them from over spraying.  I would get a good enzyme cleaner (like Nature's Miracle) and spray down the area where they've already peed.  It will help kill the smell, so they aren't tempted to use that area again.

Also, sprinkle some dirt or dried leaves on top of the litter.  This is what they are used to using and It will help them understand what litter is for.  Within a week or so, they should get the idea.

The presence of a litter box won't hurt anyone, although if not scooped enough, it might be a little offensive.