GEOGRAPHIC INFORMATION SYSTEM

GIS Protocols

Comprehensive GIS Mapping Requirements
Use of Existing Comprehensive GIS Mapping
Technical Requirements
GIS Attribute Data Requirements

The following standards are technical protocols for municipalities, engineers and GIS users for mapping and collecting data regarding sewer systems.


Comprehensive GIS Mapping Requirements

A. A Municipality shall create an updated, comprehensive sewer map of the sanitary sewers within the entire portion of its sewer system tributary to the ALCOSAN Sewer System.

 

B. A Municipality may build upon the base sewer map that has been created by the 3 Rivers Wet Weather Demonstration Program (3RWWDP), or an ESRI-compatible base sewer map. The base maps shall include streets, street names, municipal boundaries, and streams.

 

C. The comprehensive sewer map shall be submitted in Environmental Systems Research Institute (ESRI) compatible format, and shall indicate the following content:

  • Location of the sewer lines,
  • Direction of flow,
  • Size of the sewer lines,
  • Sewer line material,
  • Locations of interconnections with other municipal sewer systems and private collector systems,
  • Field-verified location of sanitary sewer manholes (identified by a comprehensive numbering or lettering system),
  • Location of pump stations, force mains, and siphons,
  • Location of streams or drainage ways tributary to the sewers,
  • Location of SSO structures,
  • Location of chronic sanitary overflow including chronic manhole overflows and chronic basement back-ups,
  • Location of known buried manholes, and
  • Identification of unsewered residential areas and associated populations.

D. The GIS mapping shall be capable of being converted to the specified attribute table data dictionary referenced in this protocol.

 

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Use of Existing Comprehensive GIS Mapping

Previous comprehensive sewer mapping may be used to satisfy this requirement if the following conditions are met:

  • Existing GIS mapping represents current "as-built" conditions and conforms to the content requirement under Section 2.C. of this protocol.
  • Existing GIS comprehensive sewer map is in Environmental Systems Research Institute (ESRI) format or convertible to ESRI format.
  • The GIS mapping shall be convertible to the specified attribute tables.
  • Mapping is maintained and readily available.

Technical Requirements


A. Location data records that document sewer system structures will additionally include spatial coordinates collected with a minimum horizontal accuracy of 1 meter. Horizontal coordinates will be recorded in the Pennsylvania South State Plane coordinate system using the NAD83 datum. A spatial data projection file will be included in ESRI format noting the projection and datum used. Vertical survey information shall reference the NAVD 88 datum.

 

B. Structure locations may be determined using one or a combination of the following alternative methods:

  • Existing "as-built" sewer system maps, as long as the maps have been field-verified, digitized, and spatially registered to the existing ACHD GIS (Geographic Information System) base maps, or
  • Using a Global Positioning System (GPS) where conditions allow, or
  • Using traditional land surveying methods.

C. In some geographic areas traditional surveying methods may be more productive than using GPS and, in some cases, a combination of above methods may be required.

 

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GIS Attribute Data Requirements


A. Formatting of the collected data in fields and data field values should follow the "GIS Sewer Data Dictionary" created and maintained by Allegheny County. Data to be populated is outlined in Part 2. C. above. The data shall be created in the format of the Sewer Data Dictionary or be convertible to that format. The primary aspects that are covered in the data dictionary relate to the physical description and location of the appurtenances and are not intended to cover all potential cases. If additional fields must be added, then those fields or values shall be described in the metadata, the documentation accompanying the GIS data.

 

B. Metadata documentation shall be compiled and maintained. Metadata documentation shall explain the accuracy, source, projection and datum, update schedule, etc. for the Comprehensive GIS mapping. Metadata shall conform to standards developed by PaMagic, an organization developing statewide standards, or comparable metadata standard based on the Federal Geographic Data Committee's (FGDC) metadata standard. The entire Metadata Workbook can be found at www.fgdc.gov/metadata.

 

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