In This Issue

High Consequence Area Identification Methods Advisory Bulletin (ADB-2016-07)

[Docket No. PHMSA-2016-0065]

In response to NTSB Recommendation P-15-06, PHMSA has issued advisory bulletin ADB-2016-07 to inform owners and operators of gas transmission pipelines that PHMSA has developed guidance on the identification and periodic verification of HCAs, including the application of a buffer zone to the PIR, and information regarding the accuracy of class locations. PHMSA recommends operators frequently and consistently review their data, including class location data, for potential inaccuracies or limitations, and add a buffer zone to the calculated PIR to help ensure proper HCA identification. The purpose and usage of buildings, open structures, and outside areas can shift over time, changing the number of “identified sites” in a PIR, and therefore, whether an area is an HCA. PHMSA believes that if operators review class location and PIR data on an annual basis as a part of their IM programs, the accuracy of HCA determinations will be greatly improved.

A review of early PHMSA inspections has shown that many operators (28%) did not have procedures to adequately describe how to identify HCAs, using Method 1 or Method 2. To effectively use Method 2, operators should have a detailed and documented process in place to monitor the conditions surrounding their pipelines, including the existence of “identified sites.”

A list of PHMSA-provided frequently asked questions on HCA identification can be found on the gas IM site at: Gas IM Frequently Asked Question Number 174 reminds operators that they should consider the uncertainties in the distances they measure or infer when evaluating PICs and consider geographic information system accuracy in locating HCAs: “… Operators may use a combination of techniques in order to account for these inaccuracies. For instance, aerial photography may be used as an initial screen. Field measurements (such as pipeline locators along with chainage measurements or survey quality range finders) may be used to verify if structures near the edge of the PIC (i.e., within the range of mapping/geographic information system inaccuracies) are actually inside or outside the PIC. PHMSA will inspect each operator’s approach to assure that the operator’s process is adequate to identify all covered segments.”

Therefore, PHMSA is reminding operators of the existing guidance for making those determinations and is providing additional recommendations on how to improve the accuracy of HCA identification. Specifically:

  • PHMSA expects that most large operators will use a geographic information system or similar mapping software for segment identification. Operators should be able to demonstrate the usability of their system and show a graphical overlay of HCAs with their pipeline system.
  • An operator not using geographic information system or similar mapping software should describe or demonstrate how it performed its HCA segment identifications.
  • For both geographic information system-based and non-geographic information system based HCA identification processes, the operator should address how it will deal with tolerances (or buffers) on top of the calculated PIR regarding the accuracy of measured distances to structures and the location of the pipeline centerline.

For a copy of ADB-2016-07 HCA Identification Methods, contact Jessica Foley.