Leak classification and action criteria—Grade—Definition—Priority of leak repair.
(1) A "Grade 1 leak" is a leak that represents an existing or probable hazard to persons or property and requiring prompt action, immediate repair, or continuous action until the conditions are no longer hazardous.
(a) Prompt action in response to a Grade 1 leak may require one or more of the following:
(i) Implementation of the gas pipeline company's emergency plan pursuant 49 C.F.R. § 192.615;
(ii) Evacuating the premises;
(iii) Blocking off an area;
(iv) Rerouting traffic;
(v) Eliminating sources of ignition;
(vi) Venting the area;
(vii) Stopping the flow of gas by closing valves or other means; or
(viii) Notifying police and fire departments.
(b) Examples. Grade 1 leaks requiring prompt action include, but are not limited to:
(i) Any leak, which in the judgment of gas pipeline company personnel at the scene, is regarded as an immediate hazard;
(ii) Escaping gas that has ignited unintentionally;
(iii) Any indication of gas that has migrated into or under a building or tunnel;
(iv) Any reading at the outside wall of a building or where the gas could potentially migrate to the outside wall of a building;
(v) Any reading of eighty percent LEL or greater in an enclosed space;
(vi) Any reading of eighty percent LEL, or greater in small substructures not associated with gas facilities where the gas could potentially migrate to the outside wall of a building; or
(vii) Any leak that can be seen, heard, or felt and which is in a location that may endanger the general public or property.
(2) A "Grade 2 leak" is a leak that is recognized as being not hazardous at the time of detection but justifies scheduled repair based on the potential for creating a future hazard.
(a) Each gas pipeline company must repair or clear Grade 2 leaks within fifteen months from the date the leak is reported. If a Grade 2 leak occurs in a segment of pipeline that is under consideration for replacement, an additional six months may be added to the fifteen months maximum time for repair provided above. In determining the repair priority, each gas pipeline company should consider the following criteria:
(i) Amount and migration of gas;
(ii) Proximity of gas to buildings and subsurface structures;
(iii) Extent of pavement; and
(iv) Soil type and conditions, such as frost cap, moisture and natural venting.
(b) Each gas pipeline company must reevaluate Grade 2 leaks at least once every six months until cleared. The frequency of reevaluation should be determined by the location and magnitude of the leakage condition.
(c) Grade 2 leaks vary greatly in degree of potential hazard. Some Grade 2 leaks, when evaluated by the criteria, will require prompt scheduled repair within the next five working days. Other Grade 2 leaks may require repair within thirty days. The gas pipeline company must bring these situations to the attention of the individual responsible for scheduling leakage repair at the end of the working day. Many Grade 2 leaks, because of their location and magnitude, can be scheduled for repair on a normal routine basis with periodic reevaluation as necessary.
(d) When evaluating Grade 2 leaks, each gas pipeline company should consider leaks requiring action ahead of ground freezing or other adverse changes in venting conditions, and any leak that could potentially migrate to the outside wall of a building, under frozen or other adverse soil conditions.
(e) Examples. Grade 2 leaks requiring action within six months include, but are not limited to:
(i) Any reading of forty percent LEL or greater under a sidewalk in a wall-to-wall paved area that does not qualify as a Grade 1 leak and where gas could potentially migrate to the outside wall of a building;
(ii) Any reading of one hundred percent LEL or greater under a street in a wall-to-wall paved area that does not qualify as a Grade 1 leak and where gas could potentially migrate to the outside wall of a building;
(iii) Any reading less than eighty percent LEL in small substructures not associated with gas facilities and where gas could potentially migrate creating a probable future hazard;
(iv) Any reading between twenty percent LEL and eighty percent LEL in an enclosed space;
(v) Any reading on a pipeline operating at thirty percent of the specified minimum yield strength or greater in Class 3 or 4 locations that does not qualify as a Grade 1 leak; or
(vi) Any leak that in the judgment of gas pipeline company personnel at the scene is of sufficient magnitude to justify scheduled repair.
(3) A "Grade 3 leak" is a leak that is not hazardous at the time of detection and can reasonably be expected to remain not hazardous.
(a) Each gas pipeline company should reevaluate Grade 3 leaks during the next scheduled survey, or within fifteen months of the reporting date, whichever occurs first, until the leak is regraded or no longer results in a reading.
(b) Examples. Grade 3 leaks requiring reevaluation at periodic intervals include, but are not limited to:
(i) Any reading of less than eighty percent LEL in small gas associated substructures, such as small meter boxes or gas valve boxes; or
(ii) Any reading 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.
[Statutory Authority: RCW 80.01.040
. WSR 08-12-046 (Docket PG-070975, General Order R-549), § 480-93-18601, filed 5/30/08, effective 6/30/08. Statutory Authority: RCW 80.04.160
, and 80.01.040
. WSR 05-10-055 (Docket No. UG-011073, General Order No. R-520), § 480-93-18601, filed 5/2/05, effective 6/2/05. Statutory Authority: RCW 80.01.040
. WSR 92-16-100 (Order R-375, Docket No. UG-911261), § 480-93-18601, filed 8/5/92, effective 9/5/92; Order R-103, Table 1 (codified as WAC 480-93-18601), filed 5/18/77.]