The Okeechobee Inland Waterway connects the Atlantic Ocean with the Gulf of Mexico, allowing boats to pass through Florida from the city of Stuart on the east coast through Lake Okeechobee to Fort Myers on the west. Along this 152-mile waterway are five locks, which allow the vessels traveling through to ascend as much as 13 feet at a single lift. Along with navigation, the waterway has been built to provide Florida citizens with multiple benefits of reduced flood damage, environmental protection, and recreation.
Management of the locks and parks on the waterway is the responsibility of the United States Army Corps of Engineers. Because of the Corps’ diverse responsibilities, maintenance on the locks is scheduled during the early summer months. During that time, the waterway is used less, and the shutdown is not likely to coincide with a hurricane.
PROBLEM
While summer is the best time to schedule maintenance, the weather brings the disadvantages of soaring temperatures and high humidity. Both conditions have a negative impact on the proper application of the vinyl coatings, which are applied to the lock gates for the prevention of corrosion in the harsh, saltwater environment.
In the case of two recently refurbished locks, St. Lucie Lock and Ortona Lock, other environmental concerns also arose. The coatings that had previously been used on the gates were found by environmental inspectors to contain lead. As a result, removal of the coatings required containment of the blasted material and control and filtration of the air leaving the containment area.
Holding complex coating requirements and dealing with environmental problems were critical on both projects, and the contractors were under a tight timeline.
SOLUTION
Previously, once a lock was dammed and drained, the gates were painted in the open air, but this method had proven ineffective. Coating specs required that relative humidity be a maximum of 80%. During the Florida summer, weather conditions make this nearly impossible. As a result, painting without environmental control on previous projects had led to premature coating failures. Polygon was asked to hold the spec because these failures required more frequent maintenance.
“On this job, we wanted to work fast and we needed to hold the blast,” said Carmen Spensieri, vice president of Spensieri Inc. in Syracuse, NY, the general and painting contractor for the Ortona Locks project.
“We told Polygon what our situation was and what we wanted to accomplish. They consulted with us, did the calculations, built the air-handling system and were there when we needed them.”
To control the work area environment, Spensieri built temporary containment structures. Constructed from a framework of scaffolding with translucent vinyl sheeting stretched to form the walls, they served several purposes. Initially, they provided a means to hold the specified humidity and temperature. Second, they prevented lead particulate from entering the surrounding air and water. Lastly, they had the advantage of a quick “tear-down” should a hurricane threaten to flood.
“Outside relative humidity was high, and temperatures were 90 to 100 degrees,” said Spensieri. “We wanted to keep the containment area floor about 80 degrees and control the humidity, as well. Polygon had no trouble delivering those conditions.”
After discussing the project, technical advisors suggested that meeting the painting spec of 80% RH should not be the final objective. Instead, conditions be kept at 50% RH. Not only would the lower humidity level meet the coating spec, but it would preclude all condensation on the steel surfaces. Without any condensation, corrosion could not occur before coating. This would promote an excellent bond between the coating and the metal and give the job the longest possible life.
To address the problem of lead abatement, Spensieri asked that the system provide a negative pressure inside the containment structure of 0.3 inches or greater. Negative pressure in the containment structure prevented leakage. Thus, the danger of lead particulate entering the outside environment was eliminated.
Polygon provided 25,000 scfm of dehumidified and cooled air to the containment area while exhausting 30,000 scfm through filters to remove all particulate. To do this, Polygon used desiccant and refrigerant dehumidifiers with a dust collection system that provided ten air changes per hour.
“I don’t think this job could have been done without Polygon,” said Spensieri. “Summer weather is so unpredictable in that part of Florida. You could start blasting with good conditions, and then have a change of weather that would cause you to lose your blast.”
RESULTS
Substantial Cost Reductions
By avoiding work interruptions, contractor Spensieri Inc. avoided costly work delays common when humidity is out of control.
Ensured Coating Performance
Humidity control allowed blasting and coating to be done without corrosion. This ensured the best possible adherence and cure of the coating and the longest possible life.
No Problems with Regulations
Project workers and the general public were shielded from hazardous lead particles, and working conditions were improved.
