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Highlight 8-16 of the HRS Guidance Manual

Highlight 8-16 : Defining a Single Watershed with Multiple Probable Points of Entry

  • In this example, two sources are located along a topographic high.
  • Establish all PPEs for each source.
  • Determine the TDLs from each PPE:
    • The TDL from PPE1 ends farthest downstream, past the confluence of the East and West Branches (TDL1).
    • The TDL from PPE2 ends just past the confluence of the East and West Branches (TDL2).
    • TDL from PPE3 ends on the East Branch (TDL3).
  • Since the hazardous substance migration paths for both souces overlap within the TDL, evaluate the in­water segments of North Run, East Branch, and West Branch as a single watershed, using TDL1 as the TDL for the site.


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