PIPELINE EMERGENCY LEAK PROCEDURES

1. Types of Leaks:

a) Small Leaks:

A small leak will not usually present a significant hazard in an open area where liquid is either vaporizing or flowing onto the ground and vapours are dispersing in the air as formed. A small leak may cause a hazardous condition if the vapours collect in a confined space sufficiently to form a flammable mixture.
Detection of a small leak is usually by some person reporting a condensate odour, discoloured or dying vegetation, visible product on the ground or an indication of frost forming at some point along the pipeline.
Detection of a small leak may be difficult and a combustible gas detector should be used in any suspicious area.

b) Medium Leaks:

A medium sized leak will be detected by a pool of product forming on the ground, killed vegetation or frost forming at the leak location. In the case of LPG leaks, vapours may also be visible. A medium-sized leak may be indicated by a large enough difference in the pipeline volume balance to initiate investigation for leakage.
Any leaks of a size to form pools or vapour forming from escaping liquid, which forms within a small area, creates a very hazardous condition. Vapours that are heavier than air (LPG) will tend to flow downwind and into low areas and form flammable mixtures.
The area of a leak, or adjacent lower areas, should be approached only with a combustible gas detector to avoid flammable concentrations of vapour mixtures.
If a quantity of liquid has escaped and vaporized, all sources of ignition, such as car and truck engines, must be kept well away from the probable hazardous area.

c) Large Leaks:

A large sized leak, probably caused by damage to the pipe by external sources, may show at the control center by changes in the operating pressure and throughput volumes. Shutdown time after the occurrence of the failure is critical to limit the duration of the hazard.
There will be an immediate outflow of liquid at the failure followed by intermittent slugs of liquid and/or vapour. On LPG lines, some of the liquid will flash into vapour. The remainder will form a pool of supercooled liquid and vaporize as rapidly as the heat flow from the surrounding air and ground will permit.
If the vapour - air plume from LPG and natural gas leaks ignites immediately, all efforts should be directed to minimizing fire damage and keeping the public out of danger until the line fill that can flow to the leak is exhausted and the fire dies from lack of fuel.
If the flammable vapour - air plume formed at the leak has not ignited, it will have reached its greatest size within the first half hour from the time the leak occurred. Every effort should be made to prevent an uncontrolled ignition of the vapour - air plume while the line fill available to the leak is depleted and the plume becomes diluted below the lower flammability limit.
The danger exists of detonation of the flammable part of the vapour - air plume from any source of ignition and all persons should be kept away from the area.
Studies indicate the extent of the flammable plume will vary from approximately 2,000 feet downwind of the failure site, under stable atmospheric conditions (as at night with less than 2 mph wind), to less than 1,000 feet under neutral conditions (as during the day with 6 mph winds or better.) Unstable conditions (as in daytime with light winds) will produce a lesser plume length. Due to the wind variation in conditions governing plume length and size, a downwind flammability length of approximately one-half mile should be assumed until the actual limits can be determined for crude oil and retired products and one mile for propane, butane, and natural gas liquids.
The whole area around the leak may contain flammable vapour - air mixture. This area should be evacuated as much as possible without men entering any area indicating any gas content approaching the lower flammability limits on a combustible gas detector.
The area around the leak must not be re-entered until the leak is under control and combustible gas detector readings show there is no gas concentration approaching the lower flammability limit.
For those products (such as gas, distillates, condensates, crude oils) vapour - air plumes will not form, however, the vapours given off by the flowing product and subsequent pools could produce explosion meter readings approaching the lower flammability limit.
The same approach should be taken as for LPG or natural gas - air plumes, however, the distances will not be as great for evacuation.

2. Control of Leaks:

a) Vapour-Air Plumes:
An intentional ignition of a vapour plume to reduce the hazard, must only be done after careful evaluation of the situation and only by qualified personnel.
The flammable plume formed from an LPG or natural gas leak will probably reach its greatest extent within the first half hour.
The beneficial effect of ignition limited to eliminating the potential hazard due to changing conditions, such as:
- Shifting wind direction, which would tend to drift the vapour plume over houses or other buildings.
- Change of atmospheric conditions to a stable state, which would enlarge the area covered by plume and endanger persons.

The decision to ignite an LPG or natural gas vapour- air plume must only be considered after:
- The area of flammable plume has been determined.
- All persons are at least 1,000 feet beyond the periphery of the plume.
- There is no apparent danger with the detonation of the flammable plume when ignited.
- Ignition would definitely reduce the potential hazard.

b) Flammable Liquid Leaks:
- Containment - Flammable liquids flowing from the leak should be contained as quickly as possible to prevent migration of the liquid and consequent danger to the public as well as damage to the environment. Flammable liquid should be contained taking advantage of natural terrain such as damming of hollows or swales, storm channels, drainage ditches, etc. All sewers in the immediate area must be covered as well.
- Burning - As a last resort, and after approval from public authorities, quantities of flammable liquid may be burned if safe to do so. Conditions relative to personnel, wind, equipment, etc. must be carefully analyzed before ignition.

3. Receipt of Reported Pipeline Leak:

a) Information to be Requested from Caller:

b) Instructions to Caller:

c) Instructions to Responsible Pipeline Company: