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'Static Liquefaction' to Blame for MI Dam Failure

Thursday, September 16, 2021

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According to an interim report released by the federally commissioned independent forensic team tasked with the investigation the failure of the Edenville Dam near Midland, Michigan last spring, “static liquefaction” is to blame.

The five-member team further described static liquefaction as a rare type of failure more commonly associated with tailings dams that store mining wastewater than water storage dams, much like the Edenville Dam.

Infrastructure Failure Saga

Last spring, Michigan Gov. Gretchen Whitmer declared a state of emergency for Midland County, Michigan, after floodwaters caused two dam failures, risking water contamination from a nearby Dow Chemical Co. Superfund site and forcing the evacuation of roughly 10,000 people.

The affected dams included the area’s 96-year-old Edenville (about 20 miles northwest of Midland) and 95-year-old Sanford dams (about eight miles downriver).

On May 19, as a result of experiencing record rainfall, emergency responders reportedly went door-to-door to warn residents living along the Tittabawassee River and connected lakes in Midland County about rising flood waters and associated risks it posed to the nearby dam infrastructures.

However, just hours after the first evaluation and clearance to return home, residents were asked to leave a second time once the Edenville Dam officially breached. According to City of Midland spokesperson, Selina Tisdale, evacuations included the towns of Edenville, and parts of Midland and Sanford—where Dow Chemical Co.’s main plant sits on the city’s riverbank.

By Tuesday evening, the Tittabawassee River was reported to be at 30.5 feet high—the area’s flood stage is only 24 feet—and was predicted to crest Wednesday morning at a record high of roughly 38 feet, although, if the Sanford Dam were to fail, Kaye added that the water surge would be much higher.

While the Sanford Dam seemed to be holding up, state officials feared that floodwaters could be mixing with containment ponds at the nearby Dow Chemical Co. plant, displacing sediment from a Superfund site—an area contaminated with dioxins. However, Dow reported that the ponds only hold water, adding that the company hadn’t detected any chemical releases.

Regardless, the U.S. Environmental Protection Agency said state officials would evaluate the plant when conditions were favorable. Dow was also required to assess the Superfund site to determine if any contamination was released.

Following the infrastructure breaches, Whitmer announced that an investigation into the operators of the dams would be launched and that legal recourse would be pursued. According to reports, the 500-year-sized flood caused more than $200 million in estimated damages and forced the temporary evacuation of about 10,000 people.

The Federal Energy Regulatory Commission also directed that dam owner Boyce Hydro Power LLC establish an independent investigation team to determine the cause of the damage to Sanford Dam, and that it would reach out to state officials regarding the Edenville Dam. The FERC planned to send an engineer to help with the investigation once the area was safe.

In June, Michigan Attorney General Dana Nessel announced that a new state lawsuit had been filed against dam owners Boyce Hydro LLC and related companies regarding the infrastructure breach.

Filed by the Department of Attorney General on behalf of the Department of Environment, Great Lakes, and Energy and the Department of Natural Resources, in the 30th District Circuit Court in Ingham County, Michigan, state officials accused Boyce Hydro and its affiliates for the mismanagement of the structures and disregard for public safety.

The listed defendants include Lee Mueller; Boyce Michigan, LLC; Edenville Hydro Property, LLC; Boyce Hydro Power LLC; Boyce Hydro LLC; WD Boyce Trust 2350; WD Boyce Trust 3649; WD Boyce Trust 3650; Stephen B. Hultberg; and Michele G. Mueller.

According to WWMT-TV News Channel 3, the state sought compensation, civil fines and the cleanup and restoration of damages caused by the dam failures and subsequent flooding.

That same month, a group of Michigan engineers from consulting firm TRC Engineers Michigan Inc. presented its 46-page visual inspection report on the failure of the Edenville Dam. The report was filed in the Western U.S. District Court of Michigan as part of a court action between the Michigan Department of Environment, Great Lakes and Energy, the Michigan Department of Natural Resources and Boyce Hydro representatives.

The six-person independent forensic investigation team was made up of experts in geotechnical engineering, hydraulics, dam safety and dam design, and was approved by the FERC.

As a result of the inspection, officials gave the remains of the structure a “high” potential hazard classification. In its report, TRC also included a list of recommended remedial efforts to be made by Boyce Hydro ranking from recommended action to critical and non-critical action/maintenance.

Some of these efforts included the critical removal of debris within the left embankment of the dam's Tittabawassee section, in addition to establishing a new drainage/river channel.

Since the report’s publication, officials with the FERC announced that they had revoked Boyce Hydro’s hydropower generating license in an effort to “shock” the owners into compliance with recommended maintenance and repairs.

Previous Dam Reports

Back in 2017, the FERC began the process to revoke Boyce Hydro’s license to operate the Edenville Dam due to non-compliance issues that included spillway capacity and the inability to pass the most severe flood reasonably possible.

However, The Detroit News reported that the FERC notified the dam’s previous owner as far back as 1999 that that infrastructure required a larger spillway capacity, and informed Boyce Hydro when the license was transferred to them in 2004.

According to Detroit News, Boyce Hydro claimed to have lacked millions funding to repair the infrastructure, regardless of having inked a contract with Consumers Energy to sell electricity generated by the dam.

After taking jurisdiction, the state reported in a September 2018 inspection report that the dam and its spillways were in "fair structural condition" and posed no imminent threat.

In January 2020, the Four Lakes Task Force announced a $9.4 million deal to buy the Edenville Dam and three others owned by Boyce Hydro by 2022. The task force is owned by Midland and Gladwin counties, and was tasked with repairing and restoring power generation at the dams.

Four months prior to the failure of Edenville Dam, Dam Safety Engineer Luke Trumble with the Michigan Department of Environment, Great Lakes and Energy told consultants that the structure failed to meet state standards and wouldn’t accommodate flood predictions.

Although a final analysis was expected in March, Trumble reported that the dam was deficient even without considering the impact of waves on Wixom Lake.

While both structures were scheduled to undergo an investigation, Detroit Free Press pointed out that issues with the state’s dam infrastructure run deeper than lack of maintenance and repair. According to their report, the state of Michigan only has two officials—Trumble and Dan DeVan—to inspect and review dams, in addition to unit supervisor, Mario Fusco.

In 2018, the EGLE was given a budget of only $397,215. The state is reported to have more than 2,500 dams which are inspected on three-, four- or five-year cycles.

New Safety Regulations

Most recently, in February, the Michigan Dam Safety Task Force announced that it would be delayed in submitting new safety measures to Gov. Gretchen Whitmer. According to The Associated Press, some members of the 19-person task force were concerned about sharp or dramatic language written within the recommendations and have decided that the document requires minor revisions before delivering a quick turnaround to Whitmer.

While the recommendations were still going through final revisions, among the 86 recommendations slated to be included was one requiring that owners of all high and significant hazard dams be required to provide surveillance and monitoring plans to the Michigan Department of Environment, Great Lakes and Energy.

In addition, owners would also have to have independent reviews of their structures completed every 10 years. However, inspections for high-hazard dams would require yearly inspections, while significant-hazard dams call for inspections to be conducted every other year.

Another recommendation crafted by the task force is the formation of a volunteer Safety at Dams Initiative Teams to further develop outreach, education and coordination efforts. Ideally, the teams would be made up of stakeholders, public safety officers, conservation officers and others involved with outdoor recreation.

Regarding funds for infrastructure maintenance and repair, the task force requested an annual $20 million revolving fund for the next 20 years. As for hazard cleanup in the event of a dam failure due to owner neglect, the task force is also requesting the establishment of a dam safety emergency fund.

Evan Pratt, a task force chairman, noted that while the recommendations won’t stop dams from failing, the task force is dedicated to reducing the severity and frequency of said failures. While the need for change is urgent—a “ticking time bomb”—and the recommendations include pressing language, Pratt predicts that it will take time to be implemented, as information on over 1,000 dams must be collected and put into a usable system.

Failure Investigation Findings

In an interim report published on Sept. 13, the independent forensic team (IFT) announced that it had essentially completed its evaluation of the physical mechanisms of the dam failures, but the evaluation of the human factors was still in progress.

Although the IFT’s final report isn’t slated to be issued for several months, the IFT reports that in examining three potential primary failure mechanisms for Edenville Dam (overtopping, internal erosion and instability), the failure could best be attributed to static liquefaction.

The team went on to explain that the Edenville collapse could have been triggered by increased groundwater pressure within loose embankment sands combined with shear stress while the dam was holding back historic water volume following several days of heavy rainfall.

While high water levels were reported to have contributed to the infrastructure’s instability, the water never overtopped the embankments. However, internal erosion could have accounted for the witnessed embankment depression observed before the collapse.

In their report, authors also noted that the failure occurred at a location along the earthen embankment where clay tile drains (a type of plumbing typically used on farms to drain excess water from subsurface soil) were noted as missing in a 2012 survey report.

The conclusions are drawn from imagery of the failure, data from past inspections and other analyses and testing performed by the expert team.

“Based on (a) the likelihood of loose, uniform fine sand in the embankment, (b) the dramatic collapse behavior exhibited in laboratory tests on loose specimens of uniform sand collected from the breach remnant, and (c) the reasonably close match of a simplified kinetic analysis with the characteristics of the failure shown in the dam failure video, the (Independent Forensic Team) believes that static liquefaction failure of the downstream section of the Edenville left embankment is the most plausible explanation for the physics of the failure,” the team wrote.

The interim conclusions follow more than 15 months after the dam collapse.

The team was led by John W. France, president of JWF Consulting. Other members include dam engineering expert Irfan Alvi, hydraulics structural engineer Steve Higinbotham, water resources expert Arthur Miller and geotechnical engineer Jennifer Williams.

The full IFT interim report can be viewed here.

   

Tagged categories: Accidents; Failure analysis; Health & Safety; Health and safety; Infrastructure; Locks and dams; NA; North America; Program/Project Management; Project Management; Safety

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