Building sites are a special problem because builders produce a lot of waste. The local council is responsible for making the builders dispose of their waste correctly. Builders hire contractors who do a lot of the work. Many contractors arrive at the site, do their work and leave. Many contractors take no responsibility for their waste. On large building sites people are employed to make sure the site remains clean and all the waste is collected and disposed of correctly. But many house building sites become very messy. The most common form of litter in addition to waste building materials and wrapping material is food and drink packaging from the people working on the site. It is from these building sites that many plastic shopping bags escape. Even though every building site must have a container to collect rubbish, a lot of rubbish is thrown around and not collected for weeks.