Underground Service Company provides utility location services, independent line testing, leak location surveys, and turn-key repairs. We serve energy companies, water districts, environmental engineers, and pipeline contractors.

We have included limitations, advantages, and requirements for each survey method and the parameters required for a successful on site test. This information is intended to be used as a guide. For a site-specific proposal, please contact us.

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Leak Survey - Acoustic Testing

Impact noise created by a leak on an underground pipeline travels along the pipe wall and through the fluid column inside the pipe. Significantly sized leaks also create a vibration that travels outward through the soil and to the ground surface. This leak noise can be identified with the help of an acoustic listening system at available contact points to pipeline appurtenances and ground surface over the top of pipe. The distance to which the noise travels from the leak outward along the pipeline and through the soil changes with different factors, the most important being the leak rate, the pipe size and type, and the dynamics of the surrounding soil.

Applications: The acoustic method can be beneficial on larger leaks (1/2 gallon per minute plus) because it is a relatively fast procedure that usually does not require the set up that a tracer gas survey does.

The following table shows the amount of leakage in terms of gallons per minute that is able to be detected by the equipment on the given pipeline from a distance of 200 feet from contact points in ideal conditions. This table is intended as a guideline, figures used are approximate, and results can vary with site conditions.

Dia.	Iron	PVC	CLMC	Steel	A/C
2"	1/2 gpm	1 gpm	n/a	< 1/2 gpm	n/a
6"	3/4 gpm	1.5 gpm	1 gpm	1/2 gpm	1 gpm
18"	1.5 gpm	2.5 gpm	2 gpm	1 gpm	2.5 gpm
36"	2 gpm	3.5 gpm	2.5 gpm	1.5 gpm	n/a

(200 psi test pressure)

If the rate of the leak is unknown, then a pressure test should be performed if able to aid in calculation of the rate of the leak. If a pressure test cannot be preformed, a cursory acoustic survey should be administered.

• Provide all known information on the site conditions to Underground Service Company.
• Ensure that contact points are accessible.
• Any valves or appurtenances that are known to be faulty should be repaired prior to the test if possible.
• If able, tests should be scheduled at a time when any demand, usage, pumping, and ambient noise is at its lowest levels.
• The client is responsible for any required notifications.

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Leak Survey - Tracer Gas Test

A mixture of 96% helium and 4% hydrogen is combined with compressed air as it is introduced into the piping test segment. The gas is purged through the system allowing a full column of gas to be present within the pipeline. A varying soak time is required to allow the gas to escape through the leak to permeate the soil and reach the surface where a gas analyzer is used by an operator to record concentrations. Some conditions may required that 1/2 inch diameter holes be drilled through the surface area to expedite the process such as cases of thick concrete or asphalt surfaces acting as a "cap" to the permeating tracer gas. The operator is able to observe readings as slight as 25 parts per million.