Dead or discoloured vegetation can be one of the signs of an underground gas leak. When natural gas escapes from a buried pipeline and migrates through the surrounding soil, the effects may become visible in grass, shrubs or trees.
This is known as vegetative leak detection. During a gas network inspection, unusual changes in vegetation can draw attention to an area that should be investigated more closely with suitable gas detection equipment.
Practical examples of leak detection using vegetation
Two examples from gas network inspections show how these visible changes can provide an important clue.
Example 1: A dead shrub indicates a gas leak
During the inspection of a low-pressure gas network in an urban area, a buried gas pipeline beneath a paved pedestrian walkway was being checked. Houses with small front gardens were located alongside the walkway, including one property bordered by a hedge of conifers.
A small gas concentration was detected during the inspection. At the same location, one brown and dried-out plant stood out clearly from the otherwise green hedge.
The sandy soil beneath the affected plant was examined more closely and significantly higher gas concentrations were detected. The condition of the plant was therefore not caused by a lack of water. Escaping natural gas had affected the soil around its roots.
Example 2: Dead grass along an underground gas pipeline
A similar situation occurred during the inspection of a medium-pressure gas network in a rural area.
A farm was connected to the gas network by a long underground HDPE service line running several hundred metres across meadows. The approximate route of the pipeline was known and was being systematically inspected.
Around ten metres away from the expected route, however, a relatively large area of dried grass attracted attention. The area was checked with a gas detector, which immediately indicated a significant gas concentration.
The change in vegetation led the inspection team to investigate an area outside the assumed pipeline route and ultimately helped locate the gas leak.
Does dead grass always mean there is a gas leak?
No, drought, plant disease and local soil conditions can all cause grass or other vegetation to turn brown. However, an isolated patch of dead grass in an otherwise healthy area can indicate an underground gas leak, particularly when it is located near the route of a gas pipeline.
Escaping natural gas can spread through the soil and displace the air around plant roots. This can affect the vegetation above or close to the leak and cause grass, shrubs or other plants to dry out or grow poorly.
What are the signs of an underground gas leak?
Visible changes in vegetation are one possible indication. During the inspection of underground gas pipelines, inspectors should therefore pay attention to unusual patterns such as dead grass, dried shrubs or poorly growing trees along or near the pipeline route. Such abnormalities can help determine where further measurements are required.
Vegetative leak detection should not be considered a replacement for professional gas leak detection. It does, however, provide an important additional visual indicator when inspecting underground gas networks.