PaintSquare.com
      | Connect Follow us on Twitter Like us on Facebook
About | Subscribe | Advertise
  

 

Download our Free Top Contractors e-Resource Guide.

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.

SAFE Systems, Inc.
Portable Dust Collectors for Tough Environments

Trailer and skid-mounted models in numerous sizes, powered by electric and/or diesel. Sloped roofs, multiple dust inlets, high static, dampered fans. Lockable power & drive compartments.


Industrial Vacuum Equipment Corp.
Hurricane Vacuums
& Dust Collectors

Vacuum and dust collector hose, filters and related accessories.
IndustrialVacuum.com


Fischer Technology Inc.
NEW Protective Coating Inspection Website

Click Here!


Hempel (USA) Inc.
Trusted worldwide for advanced protective coatings

Trusted worldwide
for advanced
protective, coatings
–Full range of 
  advanced coatings
–Optimised application
–Fast, reliable service  worldwide. Contact us at oilandgas@hempel.com


Axxiom Manufacturing
The Undisputed
Industry Leader.

Proven Innovation. Job Performance. Industry Training. Workplace Safety. Only Schmidt® abrasive blast equipment by Axxiom Manufacturing delivers it all!


Sherwin-Williams
Sherwin-Williams General Polymers Resinous Flooring App

Our coatings and linings expertise available 24/7, allowing you to explore the Sherwin-Williams systems best suited for your flooring needs. Android Users Click here to Download the app today!


NLB Corporation
NLB Sure Shroud: Greater Protection and Flexibility

NLB’s Sure Shroud’s lighter weight and flexibility reduces operator fatigue and offers unmatched protection against high pressure hose ruptures. 10k to 40k psi rated.


Polygon
POLYGON - Temporary Humidity Control

We specialize in innovative climate control solutions for industrial painting, utilizing alternative energy sources and combining desiccants with heating or cooling.


PSS Industrial Group
AirTech - World Leader in Custom Spray Solutions

AirTech is the solution
for any custom spray application. We have painting & finishing equipment, blast equipment, painting accessories, booth filter and many more items in inventory.


Dehumidifiers, Sales and Consulting
The pass-through or "daisy-chain" system by CamLok SAVES YOU MONEY!

Don Bechtol has over 40 years of experience utilizing climate control for blasting/painting projects. Call today!
1-713-249-1615
¡SE HABLA ESPAÑOL!

 
 
 

Technology Publishing Co., 2100 Wharton Street, Suite 310, Pittsburgh PA 15203-1951

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