By James F. Lowe
REPUBLICAN CITY, Neb. – The Kansas City District and the Harlan County Lake team hosted a ribbon cutting event at the recently repaired Harlan County Dam May 11, 2018.
When dam safety inspections in 2010 and 2011 revealed tainter gate defects similar to those associated with the gate failure at Folsom Dam, the Kansas City District team restricted seven tainter gates from operation and the dam was placed under an interim operating plan that reduced the flood control pool by one-half.
On July 17, 1995, the Folsom Dam, a hydropower generation plant, about 25 miles northeast of Sacramento, Calif., while at full capacity, an operator began to open a gate to maintain the flow of the river during a scheduled power plant shutdown. While minimally open, the operator felt an "unusual vibration" and harsh grinding noises. Within five seconds the radial gate swung completely open releasing approximately 40,000 cubic feet per second. Nearly 40 percent of the storage in Folsom Lake was released to the American River causing confused fish down river near San Francisco to misread the season and migrate early but thankfully no injuries or deaths to people.
Harlan County Lake is located on the Republican River in Nebraska, just north of Kansas. The discharge travels through Milford Lake, and enters the Kansas River near Junction City. If the dam had breached at lower levels of being filled, the impacts would be projected limited to the river reach above Milford Dam. Because of the very large outflow volumes for the higher fill scenarios, a failure of the gates would likely have had catastrophic effects downstream particularly to the local residents along the Republican River within Harlan, Franklin, Webster, and Nuckolls Counties, local irrigation districts, ultimately reaching Milford Lake, and potentially threatening levee systems in Kansas City.
The many changes needed to the tainter gates, sluicegates, and irrigation lines required a multi-disciplined project delivery team to focus on execution, quality, and schedule. This allowed for efficient accomplishment of the work on this complex dam project. The Harlan County Dam was the District’s top dam safety concern and received immediate and sustained attention to reduce the risk early and find the right repairs to greatly enhance the long-term safety of the dam.
Investigators determined that long-term corrosion of bearings and load-bearing parts, could cause the tainter gates to fail while being opened to release water, similar to what had happened at the Folsom Dam. By reducing the flood pool to one-half, this risk was mitigated while engineers, hydrologists, contracting specialist and others developed a plan to address the repairs needed to reduce the risk.
The initiating team project manager, Ken Stark, Kansas City District, Corps of Engineers said, "The gates were designed for no friction but there was a lot of friction in the gate bearings, so the project was very necessary to prevent failure of the gates."
The team’s efforts and successful management of three separate contracts have led to the completion of eighteen fully operational tainter gates, nine sluiceways, and irrigation line repairs. The team collaborated closely between engineering, operations and construction to ensure smooth resolution of challenges. The team faced many challenges including a lack of an existing dewatering system, limited funding, the need for multiple dive operations, and the need to ensure safety during construction.
"Repairing a 60-year old dam while it’s still in operation has many challenges. The team did a great job of handling situations such as a severe wind and wave storm caused by a nearby tornado. The team responded with emergency dive operations to remove a damaged temporary construction platform in front of the dam in order to restore the operations of the sluice gates," said Stark.
The project delivery team and on-site construction representatives coordinated closely with the contractor to resolve technical issues, maintain schedule and produce a high quality product. The team prioritized and promoted dam safety through design and construction, regularly briefing the Dam Safety Officer and Dam Safety Committee.
The project repaired all 18 tainter gates, including all seven gates that were restricted from operation. The teamwork, technical expertise, and mission focus in planning, design and construction execution has reduced dam safety risks of the project and greatly improved flood risk management.
"The project was totally complete two months ahead of schedule in February 2018, below budget for a total project cost of $31 million, no small feat," said Col. Douglas Guttormsen, commander of the Kansas City District, at the ribbon cutting.
"With the magnitude of the project I would have never guessed it would have been completed in the time period allocated and within budget," said Larry Janicek, operations project manager, Harlan County Lake and Dam.
The team of the Harlan County Dam Project significantly reduced the dam safety risk of the project to the downstream population and restored the project to full performance of its authorized purposes, whereas it had been at one half its flood pool – limiting its utility when high waters presented. The purposes of flood risk reduction, water supply, irrigation and recreation are now fully restored. The team has modeled execution of the Corps of Engineers vision by implementing a successful solution to this extremely tough challenge.