Geology

Water Main Break Repair Effect on Building Foundation (2010 Spring/Summer Newsletter)

Case Synopsis: A water main adjacent to a medical plaza cracked and caused a water leak. The Water Authority’s subcontractor repaired the leak by installing a repair clamp over a piece of water main that had cracked and resulted in the initial leak. After the repaired section of the pipe failed again, the subcontractor was blamed for washing out the foundation of an adjacent building.

Expert Analysis: Defendant’s safety expert provided geological documentation that the area was known to have sinkholes due to naturally acidic rain, over the years. This led to chemical erosion of the limestone deposits. The geology of the area has a high incident rate of sinkholes due to acid rain dissolving the thick layers of dolomitic limestone. Rainwater is naturally acidic, even without the burning of fossil fuel sulfur and nitrous oxides, due to carbonic acid from carbon dioxide. Geology has “lots of time” compared to a human lifetime. Areas with thick layers of carbonate rock such as limestone (dolomite is a carbonate mineral with a high amount of magnesium) are notorious for caverns and often sinkholes, especially if the rock formations are looser in nature. Natural sinkholes are somewhat analogous to underground mine subsidence.

Result: Defendant’s safety expert opined that the pipe did not cause the erosion under the building because the eroded soil went down into the earth and there was a huge hole. Had the water main caused the erosion the soil would have been deposited where the water velocity slowed. The eroded soil just couldn’t “disappear” and had to go somewhere which was into a series of underground caves. Case settled.

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