Approved Best Practices

NEW PRACTICES APPROVED

This wording was voted on and APPROVED by the Best Practices Committee during their meeting on March 4.  The approved practices will be included in Best Practices Version 18.0.

Approved Wording

TR 2019-02: Electronic RFID Markers 

New Practice 2-19: Underground Electronic Utility Markers

Practice Statement:  Underground electronic utility markers are an effective way to enable accurate locating and verification of underground facilities. [Reference TR 2019-02_Proposal 4 - Appendix B update if approved.]

Practice Description:  Facility owners/operators can consider several characteristics in the selection and installation of underground electronic utility markers for locating to ensure consistency among stakeholders’ future identification.  Various characteristics are included in Appendix B, Guideline for Underground Electronic Utility Marker Technology.  Underground utility markers such as electronic markers (EMs), RFID markers, ball markers and magnetic markers are devices that emit a signal to assist in the location of an underground facility. Underground electronic utility markers can be used to locate and identify an underground facility in two ways:  1) the underground utility markers can emit a signal that is a match to a predefined utility type and 2) the underground utility marker signal can carry identifying data associated with the underground utility/asset type. Underground utility marker selection and examples of frequency ranges by utility and marker type are included in Appendix B, Guideline for Underground Electronic Utility Marker Technology.

References:
  • VDOT Electronic RFID Marking and GPS Based Utility As-Built Mapping System
  • See Related Practices 2-5 “Markers for Underground Facilities”
  • See Related Practices 2-17 “Electronically Locatable Lines”
  • Publication No. FHWA-HRT-16-019 “Feasibility of Mapping and Marking Underground Utilities by State Transportation Departments”
  • Washington Gas, Engineering and Operating Standards, “Underground Plastic Pipe Location Identification”
  • Consolidated Edison – Installation of electronic markers on gas mains and services.
  • UGI

New Practice 6-17: As-Built Mapping of Underground Electronic Utility Markers

Practice Statement: The location of underground electronic utility markers is identified on as-built mapping, GIS mapping, and/or other underground facility mapping documents.

Practice Description: Appropriate asset data collection and data management procedures are in place after completion of the underground facility installation. Primary among these is the practice to note in all as-built mapping where path and point markers are installed to increase the awareness of the existence of underground facility markers during the locate process.

References:

  • ASCE 38-02 “Standard Guideline for the Collection and Depiction of Existing Subsurface Utility Data”
  • Add additional references from 2-18 as applicable.
  • Consolidated Edison – Installation of electronic markers on gas mains and services.

Addition to Appendix B Marking Guidelines

Guideline for Underground Electronic Utility Marker Technology

Underground electronic utility markers incorporate one or both capabilities to identify an underground asset (see below).  In general, radio frequency identification (RFID) has been in use for a few decades and incorporates unique frequencies for each type of utility; this allows for locators and operators to identify specific types of underground utilities. Data transfer RFID allows users to write to and read information from the marker.    Advantages of utility specific frequency RFID markers include greater depth of detection, no need to read data to identify a utility type, and tradition of use.   Advantages of data transfer RFID markers include utility agnostic (does not need different frequencies to communicate utility type) and ability to write and read specific underground utility information from the marker.

Underground electronic utility markers fall into two primary use case categories: point marking and path marking. Both device types generate an electromagnetic radio frequency to provide accurate location information. Point markers are installed along the vertical axis to identify the specific location of an underground facility feature, component, or utility type.  Path markers are installed along the horizontal axis along a buried underground facility and provides a running line direction and location of an underground utility.  Examples of point markers include: ultra-high frequency (UHF) RFID subsurface tags, high frequency (HF) subsurface markers, UHF RFID magnets, active UHF RFID subsurface tags, marker balls, disk markers, near surface markers, full range markers, mini markers, box markers, tap tee markers, duct markers, RFID tags. Path markers include intrinsically locatable plastic pipe, UHF RFID tape and rope, and HF RFID tape and rope.

Several factors require consideration with the installation, location, and data integration of electronic markers such as:

Installation Factors

  • Signal drift, burial depth, and power loss over time due to changing environmental conditions.
  • Signal loss that occurs with distance traveled.
  • Electronic Markers operating specifications to maximize underground facility and marker lifetime.
  • Ease of integration with other systems

According to VDOT Electronic RFID Marking and GPS Based Utility As-Built Mapping System, additional potential spacing protocols for electronic point maker placement for new construction are:

  • Every 25 ft along the utility path.
  • At significant horizontal and vertical changes in direction.
  • At critical utility crossings, tees, and service connection.
  • On appurtenances that are important to the utility owner.

Location Factors

During underground utility marker operation, it is possible to deteriorate the quality of the locating frequency if the underground utility marker is adjacent to a plurality of underground facilities with underground utility markers operating at a similar frequency. The following potentially applicable point marker locating frequencies, according to the VDOT Electronic RFID Marking and GPS Based Utility As-Built Mapping System, can be used to avoid signal interference and identify and locate a specific utility type. The verification frequency associated with the RFID tag can vary.

 

Commonly Used Frequencies for Various Electronic Underground Utility Markers

  Underground Facility

Point Frequencies

Path Frequencies

US UHF RFID

Power

169.8 kHz

34.9kHz

902-928 MHz

Water

145.7 kHz

73.5kHz

902-928 MHz

Wastewater

121.6 kHz

41.4kHz

902-928 MHz

Telecommunication

101.4 kHz

48.8kHz

902-928 MHz

Gas

83 kHz

53.9kHz

902-928 MHz

Cable TV and Communications

77 kHz

48.8 kHz

902-928 MHz

General Purpose/reclaimed water

66.35 kHz

44.9 kHz

902-928 MHz

 

Data Integration Factors

Additional factors are related to the storage and labeling of data tagged to a underground utility marker via RFID technology, including:

  • Information to be stored with the unique identifier.
  • Metadata template definition and creation to promote data collection consistency and underground utility marker operation across varying technology solutions. Sample data elements to collect may include: Asset type, Asset material, Asset class, Asset owner, Burial depth, Latitude/longitude, EM manufacturer, and Emergency Contact information.
  • Underground utility marker with RFID tagging integration into routine QLA investigations (subsurface utility engineering quality level) to label the location and burial distance of the exposed pipe.