Interpretation Response #PI-85-001 ([INCA] [Lawrence Ogden])
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Response Publish Date:
Company Name: INCA
Individual Name: Lawrence Ogden
Location State: DC Country: US
View the Interpretation Document
Response text:
Mr. Lawrence Ogden
Vice President, Construction and Operations
INCA
1660 L. Street, N.W.
Suite 601
Washington, D.C. 20036
During the latter part of 1984, we established an enforcement policy on IR drop in which we deviated from our prior position. This policy has now been in effect sufficiently long for us to have collected data from the regulated public which is adequate to evaluate the policy. Our conclusion is that a revision to the policy is proper, and the purpose of this letter is to advise you of that revision.
The analysis of the data shows that most operators are considering IR drop in their voltage reading taken for impressed current systems within the original intent of the wording in Appendix D, Title 49 CFR, Part 192. They are assuming that there is a margin of safety built into the criteria, and thus knowledge of the exact amount of IR drop thru the soil is not necessary. For this reason they are not taking "instant off" readings, or using an extrapolation method to determine the polarized potential of the structure for impressed current systems.
We have decided to accept this type of consideration as meeting the criteria I A(1) and (2) of Appendix D with one reservation. If a galvanic corrosion leak occurs, the operator must measure the level of cathodic protection (polarized potential) at the soil to metallic structure interface. If the level is less than that required by the regulations, it is clear that the consideration was inadequate. This evidence could constitute the basis of a possible enforcement action on the operator.
We will continue with this revised policy until such time as new or changed regulations, improved measurement instruments or processes, or other events dictate a change.
Your response to this revision is requested should you care to do so.
Sincerely,
Robert L. Paullis
Associate Director for
Operations and Endorsement
Materials Transportation Bureau