All concrete or cement activities should be done wholly within private property boundaries. This includes the mixing of cement or washing down of chutes/mixers. Any spilt or washdown materials should be fully contained within a designated area on site, away from drains or streams.
Water needs to be removed from footings, piles and foundations prior to pouring as concrete can severely impact the pH of water and silt fences and other erosion and sediment controls cannot prevent this.
If there is a spill, do not wash it to the drain.