PaintSquare.com
Follow us on Twitter Follow us on LinkedIn Like us on Facebook Follow us on Instagram Visit the TPC Store
Search the site

 

Advertisement

PaintSquare


Coatings Industry News

Main News Page


Report: Bad Math Led to Crack in Dam

Friday, May 16, 2014

Comment | More

A 50-year-old math error made during the design of the Wanapum Dam is the chief suspect in a 65-foot-long crack that will now cost $61 million to repair, officials have found.

An 11-week investigation by a team of more than 100 engineers identified three likely causes of the massive underwater crack, the Grant County Public Utility District announced in an update Tuesday (May 13).

The primary culprit, officials said: an apparent miscalculation that understated the amount of concrete and/or reinforced steel needed for construction of the dam's monolith.

Drawdown Ordered

The fracture was discovered Feb. 27 at the central Washington State dam on the Columbia River.

Wanapum Dam
Photos: Grant County Utility District

The 65-foot-long crack occurred on the upstream side of the No. 4 spillway pier monolith below the water line. Investigators determined that a math error during design had led to insufficient support for the spillway.

The two-inch-wide horizontal crack ran below the water line on the upstream side, prompting district officials to draw down the reservoir elevation by 26 feet to reduce pressure on the structure.

The crack occurred in the fourth of 13 spillway pier monoliths that support the spillway gates. A follow-up inspection March 4 showed that the fracture had closed, the monolith was stable, and the rest of the upstream face showed no fractures, Grant County PUD reported.

The 8,637-foot-long dam was built from 1959 to 1963 at a cost of $93 million.

Doing the Math

The math error came to light when engineers recalculated the original design formulas of the structure from the late 1950s, said dam officials. They did not detail the precise miscalculation at issue.

"The original designers of the dam miscalculated that the weight of the spillway’s concrete provided enough strength to resist the force of the water pushing against it," the district reported.

"Over time, this weak point on the spillway pier No. 4 succumbed to the force of the water pushing against it until after approximately 50 years of operation, the fracture formed."

Had the utility known of the error earlier, it could have reinforced the structure, officials said. But the crack was the first sign of a problem.

The investigation showed the fracture "may have originated a number of years ago and spread gradually over time, ultimately allowing enough water into the fracture to push the upper portion of the structure visibly out of place," authorities said.

Wanapum Dam infographic

An infographic by the Grant County Public Utility District shows the highlights in the incident's timeline.

The utility's regular monitoring programs "never identified this section of the dam as being susceptible to this type of potential failure and did not identify the issue at the time the fracture began," the agency said.

Other Causes

Two other factors played a role in the fracture, the investigation found.

First, the dam's 800-foot-long spillway section is not anchored to bedrock with steel, a lapse that will be corrected during repairs this year.

Second, the concrete cube for the fractured section, poured on a hot July day in 1960, "might not have cured properly," utility district spokesman Thomas Stredwick told the NW News Network.

Making Repairs

Officials have said repairs to the dam will cost about $61 million—about two-thirds of the original construction cost. The project will include additional steel reinforcement through the concrete into bedrock below the dam.

Repairs are expected to begin this summer, and the utility hopes it can raise the reservoir by 19 feet to about 561 feet in the fourth quarter of the year.

Meanwhile, public access to the shoreline and boat launches will remain off limits, and the area is being patrolled seven days a week.

The dam is currently operating at between 50 and 60 percent of capacity.

Regular updates on the project are available at www.grantpud.org.

   

Tagged categories: Concrete repair; Cracks; Design; Locks and dams; Structural steel

Comment Join the Conversation:

Sign in to our community to add your comments.

Advertisements
 
SAFE Systems, Inc.
 
SAFE Systems'
Blast Lights &
Deadman Switches
 
Halogen or LED blast lights available with our NEW urethane bumper. Switches available in many colors for color coding your hoses.
 

 
Safway Services
 
Safeguard Assets. Ensure Productivity. HAKI®
 
Protect assets and equipment. Keep facilities open and operational. Maintain schedules regardless of weather. Ensure smooth and continuous production. Easy to erect. Safway is the primary distributor of HAKI® products including HAKISPAN and HAKITEC® 750 – in North America.
 

 
SEMicro Division, M.E. Taylor Engineering, Inc.
 
Coatings Adhesion Testers
 
The PATTI® accurately measures the bond strength between coating & substrate. Outfitted properly, the surface can be rough, porous, or curved & >10K psi strong!
 

 
Strategic Materials Inc.
 
www.truabrasives.com
 
TruAbrasives™, a clean crushed glass abrasive superior to other abrasives for performance, health, and environmental benefits.
 

 
Advanced Recycling Systems
 
ARS Blast Vacuum Recycling System
 
• Closed loop vacuuming eliminates multi-handling of blasting media and wastes.
• Abrasive waste reduced by 98%
• Process between one and fifteen tons of media per hour.
 

 
SSPC: The Society for Protective Coatings
 
http://www.sspc.org/
 
Join SSPC and Enhance
Your Career !
 

 
Blastox/The TDJ Group, Inc.
 
Blastox® - One Step Lead Abatement
 
Sandblast additive delivered to jobsite pre-blended to eliminate hazardous abrasive wastes. Why mix, meter or apply at the job-site? Blast with ease and
Let your painters paint!
1(800)-252-7869
 

 
Termarust Technologies
 
Termarust (HR CSA) Chemically Stops
Active Corrosion
 
Arch truss treated with Termarust's (HR CSA) in 2003. This steel arch bridge is rust free on all surfaces including the crevice corroded joints and connections.
 

 
Fischer Technology Inc.
 
NEW PROBE FOR MEASURING TSA THICKNESS
 
Paired with the PHASCOPE PMP10, Fischer’s new probe is quick and accurate for measuring thermally sprayed aluminum on stainless steel. Click to learn more.
 

 
 
 

Technology Publishing Co., 1501 Reedsdale Street, Suite 2008, Pittsburgh, PA 15233

TEL 1-412-431-8300  • FAX  1-412-431-5428  •  EMAIL webmaster@paintsquare.com


The Technology Publishing Network

Durability + Design PaintSquare the Journal of Protective Coatings & Linings Paint BidTracker

 
EXPLORE:      JPCL   |   PaintSquare News   |   Interact   |   Buying Guides   |   Webinars   |   Resources   |   Classifieds
REGISTER AND SUBSCRIBE:      Free PaintSquare Registration   |   Subscribe to JPCL   |   Subscribe to PaintSquare News
MORE:      About PaintSquare.com   |   Privacy policy   |   Terms & conditions   |   Site Map   |   Search   |   Contact Us