Sources of excessive clear water in a collection system include

• A. A problem at the wastewater treatment plant
• B. A water distribution main construction project
• C. Evaporation
• D. Infiltration from a high water table

Answer: (D)

Excessive clear water in a collection system mainly comes from infiltration of groundwater into the sewer pipes. When the groundwater table is high, water can seep through cracked joints, damaged pipes, and around manholes or service connections, adding clean, untreated water to the sewer flow. This increases the volume without adding pollutants and can overload pumping and treatment facilities. The scenario described by infiltration from a high water table fits this mechanism exactly, since it’s groundwater entering the sewer system and producing clear water. The other possibilities don’t describe this influx of clean groundwater: issues at the treatment plant affect downstream processes, a construction project on a distribution main isn’t the typical source of widespread clear-water inflow into the sewer, and evaporation reduces water rather than increases it.