Stop chipping away
A high-profile, $25 million rehabilitation project is under way in New Orleans, as the Crescent City Connection Bridge is being sandblasted and repainted. Built in 1958, this mile-long metal structure carries 80,000 cars southbound to the West Bank every day, and it’s the first major bridge rehabilitation to occur in Louisiana.
With high humidity and extreme temperatures common during New Orleans summers, it is no wonder the original lead paint on the metal bridge has peeled and lost its rust-protecting capability. The Louisiana Department of Transportation waited 42 years to repaint the bridge, but could not afford to wait much longer. Due to the deterioration of the bridge’s protective paint, oxidation began to significantly increase, along with the resulting potential for structural defects.
The sandblasting and repainting project is expected to last three years, extending from November 2000 to November 2003. Certified Coating Inc. was awarded the primary contract to sandblast and repaint the bridge, and Kazanas Industrial Maintenance, Tarpon Spring, Fla., was hired as the subcontractor. With an entire traffic lane blocked off for equipment storage and usage purposes, approximately 60 individuals from the two crews sandblast and repaint the bridge six days a week, 10 hours a day—completing the work regardless of adverse, extreme temperatures.
Doing their part
The Kazanas family is in its second generation of bridge work; the company’s founder started the business 25 years ago as a Greek immigrant to this country. With his two sons now running the business, the company has sandblasted and repainted steelwork bridges all over the U.S. Past projects have involved bridge work across the Willamette River in Oregon, the Milwaukee River in downtown Milwaukee and the Mississippi River. The company’s most recent assignment involved the rehabilitation of the 5,760-ft Julien Dubuque Bridge in Dubuque, Iowa.
Sandblasting the bridge with Ingersoll-Rand HP1300WCU compressors, the Kazanas Industrial Maintenance project duties are being directed by Project Superintendent George Gialousis. "We started our part of the project in April 2001 and expect to be here about a year-and-a-half," he said. "Our crewmembers have to carefully sandblast the metal and completely expose the old lead paint before the paint crews can begin their work. There is generally a three-day delay between sandblasting and painting. We like to have 5,000 to 6,000 ft completed before the painting process begins, but first we do a quick air sweep with compressed air to make sure no oxidization has occurred during this time."
An important part of the sandblasting project is environmental monitoring. Following federal standards, Consoer-Townsend Envirodyne Inc. (CTE), an environmental engineering firm from New Orleans, was contracted to monitor the entire project to prevent the sandblasting crew from polluting the ground, the Mississippi River or the air with lead paint or metal grit.
"Our primary goal is to monitor the sandblasting crew’s work. We are here to make sure the work fulfills a certain set of special conditions and does not deviate outside the specified parameters of the provisions," explained Greg Carter, engineer for CTE. "We have air pumps that sample the air 24 hours a day, and we take water samples from the river at two different intakes for the water treatment plant. Soil samples are drawn from below the bridge and at the equipment storage site for the project. All blastings also are inspected in order to guarantee they reach the minimum level of SSPC (Structural Steel Painting Council) specified for paint removal. Finally, the three coats of paint the bridge will receive will be inspected for the proper degree of sealing."
To prevent any environmental contamination from blasting, the crew constructs and maneuvers, as necessary, a huge containment tarp that holds blasted lead paint and metal shavings. "We create negative pressure inside the containment tarp by using 65,000 cfm and 45,000 cfm compressors to collect the dust inside and ensure nothing escapes," stated Gialousis. "Five, 20-in. ports collect the dust in the containment. At the end of each day, the floors of the containment are vacuumed to remove all debris."
The sandblasting is completed by six men protected inside the tarp by air conditioners, face shields, helmets, capes, gloves and protective clothing. Nozzles, less than a 1Ú2 in. in diam., are used to methodically remove the paint, with close to a ton of metal shavings used every hour. These metal filings are mixed in abrasive blasting pots with 150 psi compressed air and then piped through 300-ft lines.
At times, the rigging on the bridge has the crew standing on suspended scaffolding up to 235 ft above traffic lanes. To determine their compressed air needs, Gialousis calculated each nozzle requires 330 cfm to produce up to 110 lb of nozzle pressure. With three blasters per compressor, the crew will use roughly 1,100 cfm with 200 cfm to spare.
The biggest inhibitor to successfully completing a large project is lack of sufficient equipment. Gialousis explained why I-R compressors are important to the operation.
"One of our HP1300WCU units is two years old, and the second unit was purchased four months ago at the beginning of this job. We selected the HP1300WCU because we always have favorable experiences with I-R compressors. On long jobs, maintenance issues are inevitable; however, the long-term maintenance of I-R compressors is a lot easier."
Due to the humid air of New Orleans, one of the compressors’ main jobs has been to remove moisture and use the driest air possible. The sandblasters want to remove old paint without placing additional moisture onto the steel. As steel is sandblasted down to base metal, any moisture that forms begins the oxidation process immediately.
One of Gialousis’ I-R compressors is the Instrument Quality (IQ) version, which sends the hot compressed air to an aftercooler to drop the temperature. After being cooled, moisture is formed and separated out by a water separator unit. The air is then sent through two large filters that collect and remove additional moisture. After this stage, 78% of the moisture has been removed. The air is then channeled through regenerative desiccant dryers before leaving the compressor in order to remove even more moisture. The two dryers alternate cycles every 10 minutes—one dries while the other works. Gialousis’ older unit was purchased without the IQ option, so he added a separate desiccant drier to remove moisture from the compressed air.
As 80,000 drivers view the containment tarps, compressors and crew on the bridge every day, it is no wonder this project is a high-profile undertaking for the Louisiana DOT. Although bridge rehabilitation is much more common in large metropolitan areas like New York City and Chicago, it is becoming a necessary task for aging infrastructures located in the South. After completion of this project, the Louisiana DOT will begin negotiations regarding the rehabilitation of a bridge over the Mississippi River near Vicksburg.