My husband spilt about 1/4 of a 1 lb bag of 63% Cal-Hypo on the cement deck. (We won't even go in to why there was a bag of open Cal-Hypo on the deck, except to say that only 2 ppl live here and I didn't put it there. ). So, I swept up all I could and put it in the pool, but there was a fair amount of it in the cracks of the deck. My husband, being of the "nothing bad ever happens" school of life said to let the rain take care of it. Me, being of the "the chances of bad stuff happening is significantly reduced if you're careful" school had visions of the neighborhood being chlorine poisoned. So, I washed it out with a hose. Now I'm wondering if that was the right thing.