Hi jkyocom, the pic shows a setup similiar to a site where my old company is currently remediating the ground water. The only thing different is they have a shed instead of a trailer. The cuts in the concrete leading to the island and tank field indicate lines that are feeding the seperator pump ground water and seperating the contaminates from the water. The water is returned to the ground(maybe not if near river, stream, lakes,or water plant) and the contamniates collected. I guess the contaminates(gas, diesel, waste oil) would need to vent in hot weather. My co. doesn't have the vent system but then again the shed is rather open. Contaminates are collected in a unsealed 55gal drum and siphoned off regularly by a waste hauler. Since we are located in Illinois the system only functions in the warm weather months. Have to shut down in early December. But Georgia would operate year round which may explain the trailer and larger collection system with venting. It appears the trailer is on the property line. This position would make sure they could monitor contaminates that may migrate offsite.