E.Leak Classification and Repair The purpose of the leak grading system is to determine the degree or extent of the potential hazard resulting from gas leakage and to prescribe remedial actions. Operators must promptly respond to any notification of a gas leak or gas odor or any notification of damage to facilities by excavators or other outside sources.
Operators must ensure that leak grading is made only by those individuals who possess training, experience, and knowledge in the field of leak classification and investigation. The judgment of these individuals, based upon all pertinent information and a complete leakage investigation at the scene, must form the basis for the leak grade determination.
1.Leak Responsea. Operators must establish a leak repair priority based on their evaluation of the location and the magnitude of a leak.b. Operators must assign a classification of leaks in accordance with this subsection;c. Operators must immediately notify the fire department of the community involved of each Grade 1 leak found to exist in their pipeline systems.2.Grade 1 Leaksa. A Grade 1 leak is a leak that represents an existing or probable hazard to persons or property and requires prompt action, immediate repair, or continuous action until the conditions are no longer hazardous. A Grade 1 leak includes but is not limited to: 1. Any leak which, in the judgment of operating personnel at the scene, is regarded as an immediate hazard;2. Escaping gas that has ignited;3. Any indication of gas, which has migrated into or under a building, or into a conduit or tunnel;4. Any reading at the outside wall of a building, or where gas would likely migrate to an outside wall of a building;5. Any reading of 70% lower explosive limit (LEL) or greater in a confined space;6. Any reading of 70% LEL or greater in small substructures, other than gas associated substructures, from which gas would likely migrate to the outside wall of a building; or7. Any leak that can be seen, heard, or felt, and which is in a location that may endanger the general public or property.b. A Grade 1 Leak requires an operator to take action immediately to eliminate the hazard and make repairs. The action may require one or more of the following: 1. Implementing an emergency plan;5. Eliminating sources of ignition;6. Venting the area by removing manhole covers, barholing, installing vent holes, or other means;7. Stopping the flow of gas by closing valves or other means; or8. Notifying emergency responders.3.Grade 2 Leaksa. A Grade 2 leak means a leak that is recognized as being non-hazardous at the time of detection but justifies scheduled repair or removal within six months or less of detection due to the probability of its future hazard.b. Grade 2 leaks vary greatly in degree of potential hazard. Operators must establish a repair priority for all Grade 2 leaks. In determining the repair priority, Operators must consider criteria such as the following:1. The amount and migration of gas;2. The proximity of gas to buildings and subsurface structures;3. The extent of pavement; and4. Soil type and conditions, such as frost cap, moisture, and natural venting.c. Operators must complete Priority 1 repairs within 30 days of detection of any leak: 1. With a sustained reading of 40% LEL, or greater, under a sidewalk in a wall-to-wall paved area that does not qualify as a Grade 1 leak;2. With a sustained reading of 100% LEL, or greater, under a street in a wall-to-wall paved area that has significant gas migration and does not qualify as a Grade 1 Leak;3. With a sustained reading less than 70% LEL in small substructures (other than gas associated substructures) from which gas would likely migrate creating a probable future hazard;4. With a sustained reading between 20% LEL and 70% LEL in a confined space;5. With a reading on a pipeline operating at 30 percent SMYS, or greater, in a class 3 or 4 location, which does not qualify as a Grade 1 leak;6. With a reading of 70% LEL, or greater, in gas associated substructures; and7. Which, in the judgment of operating personnel at the scene, is of sufficient magnitude to justify scheduled repair.d. Operators must re-evaluate all active Grade 2 leaks at a minimum of every 30 days until the leak is repaired and cleared.e. Operators must take action ahead of ground freezing or other adverse changes in venting conditions with respect to any leak which, under frozen or other adverse soil conditions, would likely allow gas to migrate to the outside wall of a building.4.Grade 3 Leaksa. A Grade 3 leak is a leak that is non-hazardous at the time of detection and can be reasonably expected to remain non-hazardous.b. Operators must survey and re-evaluate each Grade 3 leak at least once every 180 days from the date of discovery, until the leak is repaired. A leak requiring re-evaluation at periodic intervals includes any reading:1. Of less than 70% LEL in small, gas-associated substructures;2. Under a street in areas without wall-to-wall paving where it is unlikely the gas could migrate to the outside wall of a building; and3. Of less than 20% LEL in a confined space.c. Operators must repair each Grade 3 leak within 24 months of its detection unless the leak is located within an approved main replacement program area in which case the operator may extend the time for repair to the scheduled replacement.5.Bare Steel Service Line LeaksOperators finding a leak on a bare steel service line must replace the entire service line.
6.Post-Repair Inspectionsa. In the case of leak repairs other than Grade 1, the need for a follow-up inspection must be determined by qualified personnel of the operator.b. Operators must conduct a follow-up inspection as follows: 1. The adequacy of leak repairs must be checked before backfilling;2. The perimeter of the leak area must be checked with a combustible gas indicator (CGI) or equivalent gas detection equipment; and3. Where there is residual gas in the ground after the repair of a Grade 1 leak, the operator must conduct a follow-up inspection as soon as practical after allowing the soil atmosphere to vent and stabilize, but in no case later than one month following the repair.c. A leak is considered to be effectively repaired when an operator's operating personnel obtains a gas concentration reading of 0%.d. For a repaired leak with a gas concentration reading greater than 0% at the time of repair, operators must conduct a post-repair leak inspection within 30 days after the repair to determine whether the leak has been effectively repaired. If the second post-repair inspection shows a gas concentration reading greater than 0%, operators must continue conducting post-repair leak inspections every 30 days until there is a gas concentration reading of 0%. If on cathodically protected steel or plastic pipe, three post-repair inspections have been performed and the operator is unable to obtain a gas concentration reading of 0%, then the operator must initiate a new repair. For cast iron or unprotected steel pipe, which is included in an MPUC-approved pipe replacement program, and the operator is unable to obtain gas concentration readings of 0% after the third recheck, then these leaks must be regraded and moved to active status. Additional repairs will be required utilizing the requirements established for the new leak grading. If, after the third post-repair leak inspection, an operator regrades a leak and moves it to active status, the new leak classification will be based on the highest gas reading, or other conditions found during the third inspection, that results in the most conservative leak grade, prior to venting or other activity.e. Post-repair inspections are not required for leak repairs completed by the replacement or insertion of an entire length of pipe or service line, or for the repair of leakage caused by excavator or third-party damage, provided a complete re-evaluation of the leak area after completion of repairs verifies that no further indications of leakage exist.f. Remedial measures such as lubrication of valves or tightening of packing nuts on valves which seal leaks are considered to be routine maintenance work and do not require a post-repair inspection.7.Upgrading. When operators upgrade a leak to a higher grade, the time period for repair is the remaining time based on its original classification or the time allowed for repair under its new grade, whichever is less. This requirement does not apply to leaks that, at the time of discovery, the operator classified at a lower grade pending a further, more complete investigation of the leak hazard area.8.Downgrading. Operators must not downgrade a leak unless it is repaired.