The term 'DRAINAGE SPOT' can be broken down into two crossword solutions: 'SEWER' and 'BASIN'. A SEWER is an underground pipe or conduit that carries wastewater and surface runoff to a treatment plant. A BASIN is a depression in the Earth's surface, usually filled with water, that collects and drains water from a larger area. Together, these two terms refer to a location where water is collected and drained away.