Memories of last season’s drought-busting, reservoir-filling snow and rainfall, along with the well-known Lake Oroville spillway incident are ever-present reminders of what nature is capable of throwing at us. But in general, most Californians probably don’t give maintenance of their local dams a second thought – until there is a near catastrophe.
For the U.S. Army Corps of Engineers Sacramento District (Corps), dam safety is always on the minds of teams of experts who regularly monitor area dams to make sure you are safe and don’t have to think about them.
So just what does the Sacramento District Corps do to ensure their inventory of 17 California dams are always as ready as possible? Inspect, inspect, inspect.
On Nov. 30, members of the Corps’ Sacramento District Operations and Dam Safety Sections traveled to Black Butte Lake, eight miles west of Orland, California, where they conducted one of their regularly scheduled annual inspections.
“The annual inspections, also called ‘pre-flood’ inspections, are focused on ensuring that the dam will be functionally ready for the upcoming winter storms. We look at the critical systems and components at the dam and identify any deficiencies or maintenance issues that need to be addressed,” said Charles Jeung, Engineer for Dam Safety.
A checklist of items at Black Butte Dam included a close look at the control tower’s outlet works, scrutiny of the dam itself, checking for proper functioning of the bulkhead gate and gate hoist, along with visual inspections of the embankment, dikes, spillway and more.
During the day-long assessment, the group split into two smaller teams with David Simpson, Civil Engineer for Operations, joining Jeung in giving the nearly eight-story high control Tower a thorough assessment.
From verifying function of an industrial-size generator that will power the infrastructure of the dam in an emergency, to raising the bulkhead gate and ensuring proper operating condition, the team looked for anything that could signal a potential problem.
“We raise the bulkhead to make sure everything is good operating, check the condition of the coating system, the seals, guide wheels and welds,” said Jeung.
Ken Pattermann, a Geotechnical Engineer, held a small notebook in his hands, making notes on observations of his own. He checked the condition of the spillway, noted the water level in a borehole, then mindfully walked the length of the paved road atop the 140 foot-high, 2,970 foot long zone embankment dam.
“I’m doing a visual inspection to make sure there is no slope instability; looking for any signs of erosion, seepage or cracking,” said Pattermann.
Should any deficiencies be found, they are noted and written up in a report following the assessment. Levels of actions to take then fall into three categories:
Corrective: A deficiency with an existing component or feature of the dam that required repair, replacement, or maintenance. This can be handled with in-house staff or contracted out if necessary.
Recommended: A recommendation that will improve the performance of the project.
Maintenance: Tasks for the in-house maintenance staff to perform to ensure functional readiness of the dam.
On top of these annual inspections, Sacramento District gives each dam an even more thorough scrutinizing with a detailed periodic inspection every five years, and an in-depth periodic assessment every 10 years – which reevaluates risk level, seismic information, and potential failure mode analysis.
While it is impossible to know what nature will throw at us as we head into the winter of 2017-18, either way the Corps of Engineers continues to work toward safeguarding communities.