I am looking to group polygons together that are upstream of a trunk sewer line (Main Pipeline). Basically, the trunk sewers all have other (regular) sewers branching off of them. All of these sewers are currently contained in the same feature class (Sanitary_Pipes). The polygons that I want to group are in their own feature class (Sanitary_Catchments) and overlap with Sanitary_Pipes. The goal is to group together the polygons that overlap with the string any given string of connected regular pipes that branch off of a trunk pipe.
In the screenshot above, the thick green lines are trunk sewers, red lines are regular sewers, the points are manholes along the sewers and the green polygons are catchment areas that are a part of Sanitary_Catchments. The highlighted area is an example what I'm trying to do; all of the polygons that overlap with the set of connected pipes that are upstream of the trunk become grouped.
Is there any sort of tool/collection of tools that can do this?