On average it only rains about seven inches a year. There are two completely separate sewer systems in Gilbert and in most of the surrounding municipalities.
- There is a sanitary sewer that collects waste from homes and businesses from the sinks, toilets, showers, and baths. From there the waste water goes through pipes to a waste water treatment plant.
- Then there is the storm sewer that includes the gutters, streets, retention basins, drywells, and other storm sewer structures. The water and other things that enter the storm sewer aren't treated for contaminants, it goes right into the ground via infiltration into the soil or through a drywell.