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Archive for August 17th, 2011

17
Aug
Antelope Valley channel in 2010.

What’s ailing Antelope Valley bridges?

A state investigation into problems with the new Antelope Valley Project bridges found poor workmanship and inspection of the bridges and called into question whether they would last 75 years, as intended.

Regarding the fact that pieces of concrete have broken away and even fallen from the bottom of the bridges, the authors of an state report into the problems wrote, “This shouldn’t have made it to the walk-through inspection, let alone through it and the work accepted under normal contract/construction procedures.”

The bridges are brand new; they just opened in the past few years as part of the city’s largest public works project to date.

“In our opinion the structural integrity of the bridge is not impacted due to above mentioned findings, but the service life for the next 75 years is definitely impacted,” the report said.

While a team of inspectors determined the structural integrity of the bridges is not compromised by the problems, they said if the bridges aren’t repaired the life of the structures could be “significantly reduced.”

The bridges are part of a $246 million downtown project designed to control flooding, improve transportation near the University of Nebraska-Lincoln and revitalize core neighborhoods.

The report made it clear that problems plague more than the four Antelope Valley bridges previously cited by this blog; they also extend to the three additional Antelope Valley bridges, on Vine, Military and Y streets.

The city and Joint Antelope Valley Authority (a board overseeing the project) were told to respond to the inspectors’ findings within 60 days.

The most serious problem is pieces of the bridges that have broken off the underside: A piece of concrete about 18 inches in diameter fell off the bottom of the O Street bridge in January, prompting the city to close Antelope Valley trails from N to Q street due to safety concerns and setting in motion an investigation of the bridges by the state.

The Federal Highway Administration contacted the state to determine the “level of risk and exposure to both agencies” as a result of Mayor Chris Beutler’s decision to go public about the bridge problem. The city, state and feds then got together and decided the state Department of Roads would lead an independent investigation into the cause of the concrete breakup.

Portions under the bridges where the concrete was breaking away were removed so the trails could be reopened in late January. However, the DOR investigation was only beginning.

Among the problems detailed in the final Department of Roads report:

• “Contamination” on the underside of the bridges inspected – including nails, wire and other debris hanging or embedded in the bottom of the bridges.

• Marks on the bottom of the bridges from the teeth of heavy equipment used to move the bridges – some of which were built on the ground and then moved over the channel. One bridge had “significant breaking away of the concrete along the bottom edge for 15 to 20 feet.”

• Numerous areas where the concrete separated along the bottom edges of the decks on nearly all the bridges from N to Q streets. Inspectors said the rebar and conduit was exposed at nearly all of those areas and the coupling for the conduit was visible.

• Other delaminated areas away from the edge of the deck – the coarse aggregate fractured. Small to large areas of poor consolidation of the concrete.

• In some areas, exposed rebar was painted right over.

• On the bridge piers, white material has “oozed out of cracks beginning at the top of the piers” for two to four feet in some cases.

• On top of the bridges, there were grout stains “all over the place left on the sidewalk.”

• At least one or more expansion joints already failed on both sides of one bridge, the report said, and there was an obvious dip in the road by the concrete rail on the O Street bridge.

• No electrical conduit drainage was installed even though it was supposed to be.

• Abnormal amounts of water were found inside the electrical conduits, indicating water infiltrated during construction or seeped into the broken seal around the light fixture.

“The city of Lincoln needs to review all upcoming projects to ensure that these problems with the conduit are not repeated again,” the report said.

• In all the areas where the underside of bridges was breaking away, it was underneath the electrical conduit and near conduit couplings.

In one part of the report, the authors were so adamant they used an exclamation mark to say, “Normal practice is not to let the popcorn holes go! (poor workmanship and poor inspection).”

The report says a combination of poorly vibrated/consolidated concrete and placing the electrical conduit very near the edge of the bridge deck without proper drainage – combined with backhoe impact and the method of construction – contributed to the breaking off of the concrete. The authors recommended the bridge be tested for the next couple years with infrared thermography and impact echo testing.

The authors recommended that:

• The surface be finished according to specifications.

• Additional sounding of the underside of bridges be done to determine if there are additional areas where concrete should be removed and repaired.

• Patch, repair and re-stain the bridge deck where the concrete was stained over exposed rebar and contaminated concrete.

• Re-install material in the roadway expansion joints at approach slabs.

• Determine the magnitude of water ponding on the P Street bridge deck by the concrete railing and the impact on traffic, particularly when it’s icy, and determine whether it can be corrected cost-effectively.

The bridges were designed and inspected by Parsons Brinckerhoff, one of the world’s largest transportation engineering companies, based out of New York. The company was hired to manage both design and construction – an construction arrangement that has been criticized because it is easier to cover up design flaws.

After a piece of the O Street bridge fell, the city hired PB to inspect the undersides of the bridges, according to the DOR report.

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