Damaged mortar casing caused break to 120

By Jeff Hogan | on February 10, 2023

LAPEER COUNTY — The Great Lakes Water Authority (GLWA) today issued a report that said the Aug. 13, 2022 break to a 120-inch water transmission main that distributes water from Lake Huron to communities in Lapeer County and elsewhere in its drinking water service area was caused by damage to the mortar casing covering the concrete pipe. The break occurred in Fort Gratiot Township in St. Clair County.

The water main break resulted in boil-water advisories in Almont and Imlay City for nearly a week, and also impacted water service in the City of Lapeer as well. Water distribution sites were established in the impacted Lapeer County communities, including the use of GLWA tanker trucks that brought water to Imlay City water customers at the Eastern Michigan State Fairgrounds. Bottled water was also made available to water customers in Almont, Imlay City and Lapeer.

The cities of Lapeer and Imlay City, and the Village of Almont each began use of their independent emergency connection to provide water to their distribution systems on Aug. 13.

The largest diameter water transmission main in the GLWA system extends approximately 26 miles from the Lake Huron Water Treatment Plant to the Imlay City Booster Pump Station. The 120-inch diameter main was installed in the early 1970s and has a normal operating pressure of up to 200 psi.

The morning of Sunday, Aug. 14, Gov. Gretchen Whitmer declared a state of emergency for Lapeer, Macomb, Oakland, and St. Clair counties. By declaring the state of emergency, the Michigan State Police Emergency Management and Homeland Security Division was authorized to provide resources and coordinate and maximize State efforts to assist. The Lapeer County Emergency Management Office directed by Jeff Satkowski helped coordinate local water relief efforts in Lapeer County during the water emergency.

GLWA declared the water emergency over on Oct. 3.

A key finding of the after-action report was that the regional system was operating under normal conditions before the break, and therefore pressure spikes do not appear to have played any role in the failure.

GLWA's engineering and inspection consultants have determined that the cause of the break was damage to the mortar casing covering the Prestressed Concrete Pressure Pipe (PCCP), which resulted in corrosion and hydrogen embrittlement of the pipe's interior wires. Cause of the mortar damage is unknown, however a ditch between fields located directly above the break location could have created an environment that was detrimental to the mortar casing.

Inspection of 4.5 miles of pipe adjacent to the break, which was completed while the main was out of service for repair, determined that no additional pieces of pipe were at risk for immediate failure, and should be managed proactively through periodic condition assessment, pressure management, and periodic focused repairs of any deteriorated pipe as it is identified. GLWA is developing plans for assessment of the remaining 21.5 miles of transmission main as a part of its Linear System Integrity Program, which will begin this year.

Cost of the transmission main repair was approximately $3 million.