This is a derived feature class from data stored in TLDD. TLDD is the single source of record for all transmission asset layers (structures, spans, and lines). This layer is derived independently from the structure layer. Generated by getting a serial number from the database, retrieving the structure location, finding the ahead on line serial number, finding the AOL structure location, and connecting the two points with a line representing the span. Structure locations are maintained by the Survey Group in the eGIS SDE database, but are stored and updated in the TLDD structure table. All attribute data coming from other systems such as TLM, TLDD, and TRED are also updated in TLDD. The BPA_TLDD_Span feature class is created using four TLDD view tables:

• TranLineDesign.stgr.v_Span (pk: Strc_Serial_Nbr)

• TranLineDesign.dbo.Strc (pk: Strc_Serial_Nbr) - used for structure locations until TLDD updates the stgr.v_Structure table with these values)

• TranLineDesign.stgr.v_Structure (pk: Strc_Serial_Nbr)

• TranLineDesign.stgr.v_Line (pk: XRef_Cd, Maint_District_Nm)