Dam Safety and Security

Oroville Dam auxiliary spillway suffers erosion, area evacuated

In mid-February, the auxiliary spillway at Oroville Dam suffered erosion during high flows, leading to the evacuation of a reported 188,000 nearby residents.

According to the California Department of Water Resources, evacuation orders were delivered to residents surrounding Lake Oroville at about 4:30 pm on Sunday, Feb. 12. The concern was that erosion at the head of the auxiliary spillway threatened to undermine the concrete weir and allow large, uncontrolled releases of water from Lake Oroville that potentially could exceed the capacity of downstream channels.

Lake Oroville is the largest reservoir in the State Water Project, with a capacity of 3.5 million acre-feet. The auxiliary (emergency) spillway has not been used since the dam was finished in 1968.

DWR said it was monitoring conditions at the main and auxiliary spillways around the clock for signs of erosion that could threaten the integrity of the emergency spillway and allow large, uncontrolled flows to the Feather River.

Water from the auxiliary spillway eroded the roadway below the spillway.

To lower the lake level, thus reducing flows and the potential for erosion at the top of the emergency spillway, DWR increased flows down the main spillway to 100,000 cubic feet per second from 55,000 cfs. This was damaged Feb. 10, when a cavity opened on the concrete due to erosion. DWR said releases remained within the capacity of downstream channels.

For comparison, DWR said the morning of Feb. 11 that inflow to the lake was about 95,000 cfs. However, on Feb. 9, DWR reported inflow to the reservoir was about 192,000 cfs, thanks to “a storm that stalled over the watershed.”

Hampered by the erosion to the main spillway, Lake Oroville exceeded the elevation of 901 feet above sea level shortly after 8 am on Saturday, Feb. 11, at which point water began to flow over the concrete weir of the auxiliary spillway.

Also on Feb. 11, DWR reported it was focusing on ways to get its 645-MW Hyatt Power Plant, at Oroville Dam, back in operation because 140,000 cfs can be discharged from the plant when it is operating. Power generation was halted when the water levels in the channel that leads from the power plant became high enough to compromise operation.

Oroville Dam is a separate structure from the emergency spillway, and DWR says it remains sound. Oroville is the tallest dam in the U.S. at 770 feet and is a zoned earthfill embankment.

Ameren announces Bagnell Dam safety upgrade program

Ameren Missouri has announced that a major construction project will begin at Bagnell Dam and its associated Osage Energy Center this spring, to install a series of new anchors and concrete on the downstream side of the dam.

This work is anticipated to cost $52 million and take about 18 months.

“This project is about keeping this vital asset providing clean energy in the long term, using the best possible engineering available today,” says Warren Witt, director of hydro operations at Ameren Missouri.

The 242.59-MW Osage Energy Center, on the Osage River, has operated for 85 years.

The last major structural upgrade at Bagnell Dam was completed in the early 1980s with the installation of 277 post-tensioned anchors to hold the dam into the bedrock, Ameren Missouri reports.

This latest upgrade will be conducted in three parts: installing 68 new post-tensioned anchors to hold the dam to the underlying bedrock, placing concrete between the highway piers to add weight to the dam, and installing a new concrete overlay to replace worn and cracked concrete on the east and west sections.

In total more than 66 million pounds of new concrete will be added to the structure, Witt said.

Documents hint at federal dam safety measures

The Trump Administration has been tight-lipped about specific infrastructure projects it sees as being federal priorities, but a document distributed to the National Governors Association might provide some clues.

The report, titled “Emergency & National Security Projects,” was compiled while President Donald Trump was still President-elect Trump.

Among other measures, the document describes an $850 million federal allocation to be made to the U.S. Army Corps of Engineers that would be used for repair and safety improvement work at more than 600 dams in South Carolina.

These dams, identified as either high or significant hazards, are amongst those damaged during a thousand-year rainfall event in 2015 and again in 2016 during Hurricane Matthew.

According to the report, the undertaking could create up to 2,200 direct jobs.

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Dam Safety and Security

$1.3 million released for rehab activities at Buckeye Lake Dam

Ohio’s Controlling Board, a panel that oversees state spending, recently approved a $1.3 million release for design work and other pre-construction activities for the Buckeye Lake Dam rehabilitation project.

Work is scheduled to begin in March 2017, with a 2019 completion date, and includes replacing the current structure with a new dam.

Lawmakers proposed $61.5 million be directed to the Buckeye Lake Dam rehabilitation project as part of a $2.6 billion capital budget introduced in late April 2015, according to the Ohio Department of Natural Resources.

The dam is a 4.1-miles-long earthen embankment structure completed in 1832 that is located in portions of Licking and Fairfield counties. The dam impounds more than 4.5 billion gallons of water at its principal spillway level, potentially threatening about 3,000 people and 2,100 homes in the projected failure inundation zone that stretches more than 2 miles downstream.

In March 2015, the U.S. Army Corps of Engineers released a report that identified “serious problems” and a “significant risk to the public.”

State sets deadline for interim repairs to Woodlake Dam

North Carolina’s Department of Environmental Quality has given the Woodlake Resort and Country Club a March 1 deadline to complete interim emergency repairs at Woodlake Dam.

Portions of the dam’s spillway collapsed in October 2016, forcing an evacuation of residents living below the structure and a drawdown of Lake Surf, which was, at one time, the largest manmade lake in the state.

In the immediate future, state officials said, the owners must remove Woodlake Dam’s spillway gates and reduce the elevation of risers along its two emergency spillways. A toe drain will also be installed.

The fixes will give the owners more time to perform permanent repairs, which, according to state officials, could take several years to complete.

Woodlake Dam was constructed in the early 1970s but has changed hands a number of times in the ensuing decades. The state deemed it a “high hazard” structure in August 2014, when it was held by a previous ownership group. Several safety orders were sent to the other owners citing deficiencies in the dam’s spillway, according to state records, although those repairs were never made.

South Carolina legislators ask for $5 million to improve dam safety

South Carolina’s Department of Health and Environmental Control is asking the state for $5 million in the 2017 budget to help address dam safety issues.

The state’s infrastructure has been hit hard in back-to-back years — first in October 2015 during a thousand-year rainfall event and again in October 2016 during Hurricane Matthew — both of which caused more than 70 state-regulated dams to burst and damaged hundreds more.

DHEC said South Carolina now needs to allocate $2.3 million to stabilize or remove more than 20 dams, with the remainder to be used for inspections and safety improvements.

The proposal for the 2017-18 budget would exceed the $3 million granted the previous year but would be a one-time, non-recurring increase, lawmakers said. The money would be primarily used to address dams that owners cannot or will not repair or remove dams on their own.

The funding would also allow all of the state’s dams to be inspected at a price of about $1,500 each.

A state House panel recommended in 2016 that South Carolina improve its dam safety laws by requiring all infrastructure owners to register their dams with DHEC.

Association of State Dam Safety Officials inducts new officers

The Association of State Dam Safety Officials (ASDSO) has named new officers for 2016-2017. They are:

  • President: Dusty Myers, chief of the Dam Safety Division of the Mississippi Department of Environmental Quality
  • President-Elect: Jonathan Garton, dam safety engineer with the Iowa Dam Safety Program
  • Treasurer: Roger P. Adams, chief of the Pennsylvania Division of Dam Safety
  • Secretary: Hal Van Aller, geotechnical engineer with the Maryland Dam Safety Division

Immediate Past President is Jim Pawloski, dam safety engineer with the Michigan Department of Environmental Quality.

ASDSO is a non-profit organization dedicated to helping its members learn more about dam safety through engineering, operation, maintenance and emergency response.

Updatedbook now available

A second edition of the book Design of Hydraulic Gates is now available from CRC Press.

The updated version builds on the legacy of the first edition, presenting the main aspects of the design, manufacture, installation and operation of hydraulic gates, while also introducing new products, technologies and calculation procedures.

The second edition also includes new chapters on intake gates, trashrack design, and safety, operational and maintenance procedures. The author, engineer Paulo Erbisti, said the book ombines theoretical and practical approaches to hydraulic gates, making the book applicable as both a reference and textbook.

Erbisti is an internationally recognized leader in his field, having worked on a number of significant hydro projects, including Itaipu, Belo Monte, Tucurui, Gotvand, Tarbela, Capanda, Kariba, Guri and Tacoma.

The book is available at https://www.crcpress.com.