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This feature class contains features mapped to represent sanitary sewer manholes which are manhole access points in the sanitary sewer system. The GIS data herein have been incorporated by SGS during Phase I as derived from plans (see process steps) or surveyed by SGS during Phase II. All data herein are identified as to their source (Scanned Hardcopy Plan, AutoCAD data, NCAGR Redline Drawing, Mapping Grade GPS Survey, and Survey Grade GPS Survey).For diameter, material, and invert elevation attributes for inlet and outlet pipes, the protocol utilized herein for identifying pipe # is to number them ascending in a clockwise fashion from the outlet pipe. For example, the outlet pipe is the outlet pipe and the inlet pipe that is first in a clockwise fashion from a plan view perspective is pipe #1, the next is pipe #2, and so on. This protocol is designed to identify which pipe is being referred to for inverts, pipe sizes, and pipe materials via attribute fields.The aforementioned data may be recorded from AutoCAD or hardcopy plans in which case the available data was entered. This will only be the case for City of Raleigh owned manholes. In this case, certain information may be absent due to the addition of infrastructure subsequent to the plan date or due to incomplete plans. If invert attributes are derived from plans and the plans do not specify the difference between 2 pipes of the same dimension they will be entered without verifying that they follow the clockwise protocol for City of Raleigh owned manholes.For NCAGR owned manholes, every inlet pipe and the outlet pipe in the manhole structure was documented via this project with respect to pipe material, pipe size, and the invert elevation data. The manhole attribute data may present information for more inlet pipes than are currently documented in the GIS as line features because an undocumented pipe or pipes may exist that will be inventoried in Phase III.For invert elevations, depth to invert was recorded in the field with the calculation of invert elevation values made in the office by subtracting the depth as recorded for a specific invert from the rim elevation value. The rim elevation data field is identical to and calculated based off of the elevation data field. The elevation data field was derived via direct GPS observation where the desired accuracy was achievable via GPS. Alternatively, where GPS observations were not sufficient for vertical positional accuracy (e.g. under canopy), differential leveling was used from SGS surveyed horizontal reference points to the manholes to achieve rim elevations. |