When you arrive at the site you should already know what the warden/landowner wishes you to do with any rubbish (you don't? Go and ask now). My knowledge of local, 'modern' sites is that they have specific areas for rubbish disposal, clearly placed bins, and an incinerator of their own. They also tend not to let people dig any pits/trenches for any use (campfire, rubbish disposal or latrines). Make sure you know what you can and cannot do on your site.