Description: This line file represents the different types of storm drain pipe associated with ACHD Storm Drain infrastructure. SD Pipes, carry storm water ,Combo pipes carry a mix of storm water and irrigation, Seepage Bed pipes are those pipes associate with a Pre-Treatment structure that is represented in SD Structure point file. Siphon pipes are pipes that have no outlet, they are associated with a Siphon inlet that is represented in SD Structure point file.