# Airborne Environmental Surveys — Pipeline Safety Interpretation

- **operation:** document
- **citation:** PI-93-039
- **title:** Airborne Environmental Surveys — Pipeline Safety Interpretation
- **source type:** guidance
- **agency:** Pipeline and Hazardous Materials Safety Administration
- **status:** guidance
- **official:** true
- **published on:** 1993-07-16
- **effective on:** Not available
- **summary:** PI-93-039 response to Airborne Environmental Surveys concerning 192.463.
- **machine formats:** - **json:** https://regulus.evalyn.ai/document/phmsa-interpretation-pi-93-039.json
- **markdown:** https://regulus.evalyn.ai/document/phmsa-interpretation-pi-93-039.md
- **app url:** https://regulus.evalyn.ai/document/phmsa-interpretation-pi-93-039
- **source url:** https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1993/PI93039.pdf
**body:**

<<<PAGE 1>>>

July 16, 1993 (?)
Mr. Dave Mitchel
Director
Airborne Environmental Surveys
Suite 108
3130 Skyway Drive
Santa Maria, CA 93455
Dear Mr. Mitchel:
This responds to your letter of April 12, 1993, to George W. Tenley, Jr. regarding the use
of airborne cathodic monitoring equipment to detect and measure the impressed cathodic
currents in pipelines. Your letter states that your technology involves the determination of
current and current density at any point on an impressed-current pipeline by direct
measurement of electromagnetics, specifically the magnetic field associated with the
impressed current. Your letter further states that these measurements may be made from
ground surface, or from airborne platforms.
Properly applied, electromagnetic can yield continuous measurements and plots of current
along a pipeline, including interference from foreign pipelines, bonds, taps, casing shorts,
coupling separations, coating conductivity changes and holidays. It is very important that
an existing baseline pipe-to-soil potential be established by conventional methods. The
electromagnetic techniques can be employed to establish baseline data that can be overlaid
on the original baseline pipe-to-soil to accurately portray the performance of the cathodic
protection system. This technique would provide an approach to assess the performance
of the cathodic protection system to determine compliance with the requirements of 49
CFR 192.463(a) and §192.465(b) and (c).
As set forth in my letter of November 7, 1991, an operator has the freedom to conduct its
inspections utilizing whatever appropriate technology or means it chooses, including your
airborne cathodic monitoring equipment, to comply with the inspections under 49 CFR
192.463(a) and §192.465(b) and (c) of rectifiers or other impressed current power source.
If the airborne cathodic monitoring equipment provides reliable data, your airborne remote
sensing technique is an acceptable means of inspection under the above rules.
Sincerely,
Cesar De Leon
Director, Regulatory Programs
Office of Pipeline Safety
dal\192.463\93-07-16
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