If you have that mold all around your yard you are not likely to ever get rid of it. New spores are being created all the time so there is a constant source. For it to grow it needs moisture and a food source. That food source could be anything organic, rotting leaves, grass, or chicken poop for example. Some molds are dangerous, some are beneficial, most are neutral. I don’t know if that mold is harmful to your chickens or you or not but I can understand you wanting to get rid of it or at least minimize it. And I certainly don’t like wet runs.
I share Aart’s concern about deep litter, if it stays wet it can get moldy and really stink. I don’t think sand is the right answer either. For sand to work the water has to have a place to drain to. I don’t think you have that.
I’m not sure how that water is getting in at ground level, it could flow in when it rains but I’m guessing your yard is just a general low spot that stays wet a lot. If water is flowing in maybe you could put a berm around the run to stop it from getting in.
If it were mine I’d probably fill the run in with dirt to a depth of a few inches. Not sand but some kind of clay dirt that will stop the water from flowing or soaking in. I did that to my coop when I built it, added some dirt to raise the floor above the surrounding area. And I put a swale/berm on the uphill side to divert running water. I don’t know if this would work for you or not. It’s hard to say.
I share Aart’s concern about deep litter, if it stays wet it can get moldy and really stink. I don’t think sand is the right answer either. For sand to work the water has to have a place to drain to. I don’t think you have that.
I’m not sure how that water is getting in at ground level, it could flow in when it rains but I’m guessing your yard is just a general low spot that stays wet a lot. If water is flowing in maybe you could put a berm around the run to stop it from getting in.
If it were mine I’d probably fill the run in with dirt to a depth of a few inches. Not sand but some kind of clay dirt that will stop the water from flowing or soaking in. I did that to my coop when I built it, added some dirt to raise the floor above the surrounding area. And I put a swale/berm on the uphill side to divert running water. I don’t know if this would work for you or not. It’s hard to say.