Ground Penetrating Radar Systems (GPRS) was recently called upon to investigate and perform emergency leak detection services in Buffalo, New York. The client indicated that they had a previous severe main break on their fire loop. This pipe leak erupted in what the client indicated as a “volcano”. It was apparent that it happened on a lateral which fed a riser for the sprinkler system along the eastern side of their main building. When excavated, it was found that there was a 6-foot-long lateral split in the main pipe. This was repaired, however when the fire loop was reactivated, the system would not hold at 150 psi, which is the static pressure that their jockey pump must hold at. This created an emergency leak issue as municipalities have specific requirements for fire loop pressures.
GPRS Water Loss Specialist, George Williams, was mobilized to the site in order to assess and locate the suspected water pipe leak. This fire loop is fed from the local municipal water system to a holding tank, and then from the holding tank through the jockey pump, to the system. In place there is a bypass to allow municipal water to be utilized if necessary. Upon initial assessment of the pump house, it was found that the jockey pump was cycling every 11 seconds. Observation of the jockey pump indicated a 10 psi drop from 150 psi to 140 psi in approximately 11 seconds. This indicated a potential leak as a fire loop is a static environment. Through isolation work, pressure observations and acoustic leak detection testing, it was found that the check valves in the building, as well as in the meter pit near the municipal side, were holding fine. The jockey pumps were then turned off and municipal water allowed to let the pressure continue to drop. Once the pressure dropped to the municipal pressure of 70 psi, the system appeared to hold, indicating a small pipe leak. The system was then brought up to 150 psi and water drained from a spigot in the pump room displaying volume loss. The 10-psi drop equated to 4 ounces of water in the 11-second cycle or approximately 250 gallons per day of actual water loss. This is a very small leak to detect utilizing non-invasive, surface acoustic leak detection testing. However, all contact points: hydrants, valves, post indicator vales and risers within the building were scanned acoustically for a leak signal utilizing the S-30 Surveyor, which is an acoustic leak detection device. Due to severe mechanical interference caused by facility operations, it was difficult to ascertain a suspect area for leak investigation. The fire loop was then systematically isolated, section by section, as each isolation of the jockey pump was activated while the pressure gauge was checked to assess if the main was holding. After several isolations it was found that the section between the meter pit and the pump house contained the suspected leak area. The jockey pumps were then reactivated, allowing the system to continually cycle at 150 psi. Correlations were performed with the LC2500 Leak Noise Correlator between contact points in this area. This device utilizes two transducers and a receiver, so based upon the distance between contact points and the water main pipe material, the LC2500 is able to evaluate and delineate a potential location of a suspect pipe leak. By utilizing this methodology a suspect area was determined and marked for excavation.
Post diagnostic information, on top of the initial pipeline assessment, confirmed this area as the source and allowed water loss specialists to locate the pipe leak. It was found to be an old repair sleeve that was leaking minimally. Due to the nature and severity of the original “volcano” leak, the overall main hammered, and slightly shifted, affecting the old repair. This was repaired and per the client the system was able to be maintained and corrected.
GPRS proudly provides an assortment of subsurface inspection services. These include but are not limited to: Single system to full municipal water loss assessment surveys, pipeline video inspections, utility mark out and mapping services, and data logging, as well as hydrostatic testing. To schedule a subsurface inspection of any type in the Buffalo area, please contact GPRS at 303-945-5415 to discuss how we may better assist your specific needs.
Note: GPRS does not provide geophysical, geological, land surveying or engineering services. If you need such services, please contact an appropriate professional.