{"operation":"document","citation":"PI-77-025","title":"Florida Public Service Commission — Pipeline Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"1977-11-10","effective_on":null,"summary":"PI-77-025 response to Florida Public Service Commission concerning 192.457.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-77-025.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-77-025.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-77-025","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1977/PI77025.pdf","body":"<<<PAGE 1>>>\n\nNovember 10, 1977\nMr. Harold E. Janes\nDirector - Engineering Department\nFlorida Public Service Commission\n700 South Adams Street\nTallahassee, FL 32304\nDear Mr. Janes:\nYour letter dated May 20, 1977, to Mr. J. C. Thomas concerning Information Bulletins GS-26\nand GS-26A sent to all gas system operators under jurisdiction to the Florida Pubic Service\nCommission (PSC) has been sent to this Office for response.\nBased on our review, we find that the guidelines for electrical survey contained in the bulletins are\ninconsistent with the Office of Pipeline Safety Operations' (OPSO) interpretations of 49 CFR\nSection 192.457 concerning electrical surveys (copy enclosed). Under Section 192.457(b), an\noperator must use an electrical survey method which identifies all areas of continuing corrosion\nalong a pipeline with enough detail so that the operator can determine whether a condition\ndetrimental to public safety could result.\nAlthough we have no objection to the intent of the bulletin, we recommend that you consider the\nfollowing:\n* With regard to soil resistivity surveys, the intervals specified in the\nguidelines are misleading and are not adequate for some pipelines.\nIt would be difficult to meet compliance with 49 CFR Section\n192.457 using these guidelines.\n* With regard to the Florida PSC recommendation that \"P/S potential\nmeasurements need not be made in soils of resistivity above 50,000\nohm-cm, unless the operator has knowledge of environments or\ncorrosion leak histories which warrant investigation in high\nresistivity environments,\" this encourages noncompliance with the\nelectrical survey requirement. Furthermore, pipelines do corrode at\nresistivities higher than 50,000 ohm-cm.\ndal\\192\\457\\77-11-10\n1\n\n<<<PAGE 2>>>\n\n* With regard to the Florida PSC recommendation that \"Corrosion control is only\nrecommended on underground pipelines which lay [sic] in soils of resistivity of\n50,000 ohm-cm or less when the combination electrical survey indicates that active\ncorrosion does exist,\" OPSO has not received any information or evidence to show\nthat active corrosion does not exist on pipeline buried in resistivities higher than\n50,000 ohm-cm.\nMr. George Mocharko of my staff has discussed this matter with your Mr. Lamar Cockrell. If\nyou have any additional question, please advise.\nSincerely,\nCesar DeLeon\nActing Director\nOffice of Pipeline\nSafety Operations\nEnclosure\ndal\\192\\457\\77-11-10\n2\n\n<<<PAGE 3>>>\n\nMEMORANDUM\n5/23/77\nSUBJ: Interpretation of Section 192.457(b)\nFROM: Chief, Southern Region\nTO: Acting Director, OPSO\nMTP-1\nAttached is correspondence arising from a guideline published by the Florida\nPublic Service Commission. I have discussed this guideline with George\nMocharko and find it, in part, to be incompatible with current OPSO\ninterpretation.\nI notified the Commission of this conflict and by their letter of May 20, 1977 I\nhave not received assurance that corrective action will be taken. Further, Mr.\nJanes has raised additional questions. Therefore, in the interest of all concerned,\nwould you please comment directly to Mr. Janes so that this conflict can be\nresolved at the earliest possible date.\nJames C. Thomas\nAttachments:\n1. FPSC Informational Bulletin GS-26, 26A\n2. MTP-50-SO letter of May 13, 1977\n3. FPSC letter of May 20, 1977\n4. MTP-50-SO letter of May 23, 1977\ndal\\192\\457\\77-11-10\n3\n\n<<<PAGE 4>>>\n\nMay 23, 1977\nMr. Harold E. Janes\nDirector of Engineering Department\nFlorida Public Service Commission\n700 South Adams Street\nTallahassee, Florida 32304\nDear Mr. Janes:\nWith reference to your letter of May 20, 1977 concerning Informational Bulletin GS-26 and as I\ndiscussed this further with Mr. Charley White; the interpretation I quoted in my letter of May 13,\n1977 remains the guidance for this office.\nFurther, since you continue to question this interpretation and have raised additional questions, I\nam forwarding this information to the Acting Director, Office of Pipeline Safety Operations for\nhis comments direct to you.\nSincerely,\nJames C. Thomas\nChief, Southern Region\ndal\\192\\457\\77-11-10\n4\n\n<<<PAGE 5>>>\n\nPUBLIC SERVICE COMMISSION\nMay 20, 1977\nMr. James C. Thomas\nChief, Southern Region\nDepartment of Transportation\nMaterials Transportation Bureau\nOffice of Pipeline Safety Operations\n1568 Willingham Drive--Suite 2078\nAtlanta, Georgia 30337\nDear Mr. Thomas:\nThis is in reference to your letter of May 13, 1977 concerning our Informational Bulletin GS-26.\nThis reference bulletin has been amended by GS-26A due to an omission in the original bulletin\n(see attachment).\nWe are somewhat in a quandary over your letter. This informational bulletin was published after\nvarious meetings with consultants working in Florida and Florida operators because of\nmisunderstandings, misinterpretations, and requirements for conducting an appropriate electrical\nsurvey.\nIt is our view that if operators follow our bulletin, electrical surveys made in Florida are more\ncomprehensive, are more meaningful and use more good engineering practices than are probably\nfollowed in many other parts of the country. The interpretation of section 192.457(b) contained\nin your letter requires a more definitive interpretation as to what an electrical survey is and how a\nproper electrical survey should be made. It is one that this Commission was unaware of and leads\nus to question as to whether or not this is an official opinion of OPSO and whether or not it is\npublished and required nationally.\nThis interpretation does present some problems to us not only due to its lack of specifics but also\nthe first sentence of the interpretation. Should a gas operator decide to use the 300 milovolt [sic]\nshift criteria then in our opinion original pipe/soil potential measurements would be needed.\ndal\\192\\457\\77-11-10\n5\n\n<<<PAGE 6>>>\n\nWe would appreciate receiving your response to this inquiry before this Commission decides what\nfurther action, if any, should be taken.\nYours very truly,\nHAROLD E. JANES\nDirector\nEngineering Department\nAttachment\ndal\\192\\457\\77-11-10\n6\n\n<<<PAGE 7>>>\n\nINFORMATIONAL BULLETIN GS-26\nMarch 25, 1977\nTO: ALL GAS SYSTEMS UNDER SAFETY JURISDICTION OF THE FLORIDA\nPUBLIC SERVICE COMMISSION\nFROM: ENGINEERING DEPARTMENT SAFETY SECTION\nRE: CORROSION CONTROL GUIDELINES FOR ELECTRICAL SURVEY\n_\nThe following guidelines are intended to supplement Commission Rule 25-12.53:\n1. An electrical survey must include both soil resistivity and P/S potential\nmeasurements as a minimum. These guidelines are primarily applicable to surveys\nof system gas mains to determine where galvanic corrosion may exist.\n2. Soil Resistivity Tests\na. 4-Pin Method\nIn urban and suburban areas soil resistivity measurements should be taken\nat least one/city block or approximately every 500 ft. where city blocks do\nnot exist. In areas of variable soils or fill areas measurements should be\nmore closely spaced or a minimum of 200 ft.\nIn rural areas readings may be taken at a maximum spacing of 800 ft. in\nstable soils and closer spacing should be used in variable soils and fill areas.\nIn application of the 4-pin method a minimum of two measurements should\nbe made, one at 2-1/2 ft. and one at 5 ft. depth.\nb. Single-Probe Soil Resistivity Instrument\nFor corrosion control personnel who choose to use a single-probe soil\nresistivity bar, it should penetrate the soil at least 40 (forty) inches; and\neven deeper if the pipe is at greater depth.\ndal\\192\\457\\77-11-10\n7\n\n<<<PAGE 8>>>\n\nThe spacing of test measurements should be a minimum of 50 (fifty) to 100\n(one hundred) ft. apart depending upon the soil stability.\n3. Pipe/Soil Potential Measurements\n4. 5. a. In conjunction with the Wenner 4-pin survey, a P/S potential measurement\nshould be taken in the immediate vicinity of each soil resistivity\nmeasurement.\nb. When the single-probe soil resistivity rod is being used, P/S measurements\nshould be taken at same location as soil resistivity readings or on a\nminimum spacing of 200 ft.\nP/S potential measurements need not be made in soils of resistivity above 50,000\nohm-cm, unless the operator has knowledge of environments or corrosion leak\nhistories which warrant investigation in high resistivity environments.\nWherever soil resistivities of 50,000 ohm-cm or less are recorded, make sure that\nP/S potentials are taken directly above the pipeline for a minimum of 500 ft.\nupstream and 500 ft. downstream from the pertinent soil resistivity reading.\nWhenever these measurements reveal potential peak profiles it is recommended\nthat P/S measurements be made at 20 ft. spacing directly above the pipeline plus\nthe related 20 ft. remote reading in order to determine the anodic or cathodic\nstatus of the pipeline. It may be feasible to expose pipelines at indicated \"hot\nspots\" of active corrosion to determine if cathodic protection is warranted in the\nnear future or at a later date. For record purposes, some gas operators may desire\nto photograph the pipeline corrosion and record pipe wall thicknesses plus depths\nof corrosion pits.\nThe intent of these guidelines is to eliminate an expensive electrical survey in\nenvironments that ar not normally corrosive. Corrosion control is only\nrecommended on underground pipelines which lay in soils of resistivity of 50,000\nohm-cm or less when the combination electrical survey indicates that active\ncorrosion does exist.\nWhen a gas system operator intends to cathodically protect all underground\npipelines in environments below a specific soil resistivity such as 15K, 20K, 25K\nohm-cm, etc., (appears there was more to be added here, but the information\nwas not available).\ndal\\192\\457\\77-11-10\n8\n\n<<<PAGE 9>>>\n\nINFORMATIONAL BULLETIN GS-26A\nApril 28, 1977\nTO: ALL GAS SYSTEMS UNDER SAFETY JURISDICTION OF THE FLORIDA\nPUBLIC SERVICE COMMISSION\nFROM: SAFETY SECTION, ENGINEERING DEPARTMENT\nRE: CORROSION CONTROL GUIDELINES FOR ELECTRICAL SURVEY\n-------------------------------------------------------------------\nInformational Bulletin GS-26 dated March 25, 1977 inadvertently omitted a phrase in the\nfirst sentence of the second paragraph of section 4.\nThe following will replace the first sentence of the second paragraph of Section 4:\nWhenever soil resistivities of 50,000 ohm-cm or less are encountered, proceed to take P/S\npotential measurements at 100 feet intervals directly above the pipeline for a minimum of\n500 feet upstream and 500 feet downstream from the pertinent soil resistivity reading.\ndal\\192\\457\\77-11-10\n9","truncated":false,"body_characters":10430}