Places with many hundreds of houses are always changing and very different from place to place, and all the time people put bad stuff in the land and water. They did not do this before all the houses were there, and the land and water used to be cleaner. We should be able to find out what bad stuff people have put into land or water if we take bits of the land or water and find out what is in them, and look hard at what we find. We took bits of the dry land and wet land along some lines in a park near many hundreds of houses, close to where we live. We looked for all the bad stuff and some other things in these bits of land and water. We found that some of the bits of land had too much bad stuff and people could get sick. But the land was in a park, so we thought that people would not touch the bad stuff so much and they would be safe. How much bad stuff there was in the land was very different from place to place, so we should take care where we get the bits of land and water from so we don't miss any bad stuff or get too much. Different bad stuff was found in different places because people used to put different things on the land a long time ago, and now they put other stuff on the land. So we should try to find lots of different bad stuff just in case. We think this way of working might be good for other people to try because our way of doing it is good for land with bad stuff in it.