This layer is dissolved and queried from PWD's internal sewer shed feature class named modelsheds. The polygons in this layer are catchments for sanitary, storm and/or combined sewer flows. These catchments are used in the hydraulic models. Data DevelopmentBase Modelsheds are maintained regularly and delineate waste water and stormwater and combined sewer catchments in Philadelphia. Storm water and waste water pipe flow are analyzed to delineate the shed boundaries.

This data layer identifies the locations of Combined sewer overflow outfalls. Combined sewer systems are sewers that are designed to collect rainwater runoff, domestic sewage, and industrial wastewater in the same pipe. Most of the time, combined sewer systems transport all of their wastewater to a sewage treatment plant, where it is treated and then discharged to a water body. During periods of heavy rainfall or snowmelt, however, the wastewater volume in a combined sewer system can exceed the capacity of the sewer system or treatment plant. For this reason, combined sewer systems are designed to overflow occasionally and discharge excess untreated wastewater directly to nearby streams, rivers, or other water bodies. For further information visit: http://cfpub1.epa.gov/npdes/home.cfm?program_id=5

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