ACHRNEWS

Contractor dehumidifies FL inland waterway

April 20, 2000
Not many maintenance projects require a hurricane watch, but a contractor assigned to refurbish a lock on Florida’s Okeechobee Inland Waterway must worry about the weather in both extreme and subtle regards.

“When you work outside, weather is always a factor,” said Carmen Spensieri, vice president of Spensieri, Inc., Syracuse, NY.

“We’ve done other lock projects in Upstate New York in the winter. There you work in temperatures below zero with snow every day, but as the project goes along at least you know spring is coming. In Florida, you could be face-to-face with a hurricane if you don’t meet your deadline.”

Spensieri, Inc., recently served as the general maintenance and painting contractor for the Army Corps of Engineers on the Ortona Lock project. The project included damming off the lock, draining it, cleaning away debris, sand blasting the walls and resurfacing them with concrete, installing a dewatering system, and protecting the lock gates with a vinyl coating system.

“You get a small window — maybe six or eight weeks — to complete the project,” said Spensieri. “Projects are scheduled for summer because use of the Okeechobee Waterway is down and hurricanes aren’t likely until August. That keeps the pressure on.

“If we are in the middle of the project and a hurricane threatens, we have to pull out our men and equipment,” Spensieri explained. “Then we must quickly tear down the bulkheads that temporarily dam off the flow, so that the flood water can run through the lock.

“Because there is no way to know how much rain the storm will pour on the state, the waterway must be returned to full operating capacity to control water levels.”

The job's humidity requirements

But weather also can threaten the job in more subtle ways. For example, high humidity, which is common during the Florida summer, can interfere with the cure of coatings used to protect the surfaces of the lock gates.

“Using the vinyl coating specified for the job,” said Spensieri, “required that the relative humidity be 80% or lower. In Florida during the summer, that can be almost impossible to achieve over an extended work period.”

Seeking help with humidity control, Spensieri turned to Munters Corp. (Amesbury, MA). The company specializes in building rental systems that control humidity in work environments for a variety of purposes.

“We’ve built temporary systems to accomplish hundreds of different objectives,” said Ken Gernenz, Munters southern regional manager.

“But much of the time our services are used by tank-coating contractors to prevent corrosion that could jeopardize the integrity of the coating they are applying.”

On a prior project on the same waterway, St. Lucie Lock, the company encountered similar concerns — meeting the original paint spec and the discovery of lead in the coating that would be blasted off the lock gates.

Containment areas

“Because of the lead content in the existing coating, an abatement program was needed,” said Gernenz.

“To keep the lead from entering the surrounding air and water during blasting, Spensieri would have to build a containment structure around the work areas. This structure would have the added advantage of making it possible to control humidity and temperature.”

The containment areas, which were approximately 45 ft long by 40 ft wide by 40 ft high, enclosed the gates. They were sized so that workers and equipment could move about without damaging the walls during the project.

Constructed from a framework of tubular scaffolding, the containment areas had translucent vinyl sheeting stretched to form the walls.

Once erected, the containment area served several purposes. First, it provided a controlled environment to hold the specified humidity and temperature conditions. Second, it prevented blasted lead particulate from entering the surrounding air and water. Third, it had the advantage of a quick tear down should an out-of-season hurricane threaten southern Florida with flooding.

In the past, the gates had been painted in the open atmosphere. But this practice had proven unproductive, as without environmental control, changeable weather made holding the spec nearly impossible.

As a result, earlier projects had experienced premature coating failures. These failures, in turn, required more frequent maintenance. To stop this unproductive cycle, Munters was asked — first for the St. Lucie project and later for the Ortona project — to supply an environmental control system that could hold the spec.

After discussing the project, the company’s technical advisors suggested that meeting the painting spec of 80% rh should not be the final objective. Instead, it was proposed that 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, no corrosion could occur on the surfaces before coating,” said Gernenz. “This would promote an excellent bond between the coating and the metal, giving the job the longest possible life.”

Lead abatement

To address the problem of lead abatement, Spensieri requested that the system provide negative pressure inside the containment structure of 0.3 in. or greater. Negative pressure in the containment area prevented leakage. Thus, the danger of lead particulate entering the outside environment was precluded.

“We needed to work fast and we needed to hold the blast,” said Spensieri. “We told [the equipment manufacturer] about our situation and what we wanted to accomplish. They did the calculations, built the air-handling system, and were there whenever we needed them.”

The system provided 25,000 cfm of dehumidified and cooled air to the containment area while exhausting 30,000 cfm through HEPA filters to remove all particulate. Inside, the dewpoint temperature was held to the mid-70s. To do this, desiccant dehumidifiers were combined with refrigeration equipment including DX units, chillers, cooling coils, and a dust-collection system.

The system provided 10 air changes per hour inside the containment area.

“Outside relative humidity was high and temperatures were 90° to 100°F,” said Spensieri. “We wanted to keep the containment area floor about 80° and control the humidity as well. [The equipment] had no trouble delivering those conditions.”

Sidebar: Worksite details

The Okeechobee Inland Waterway, which links the Atlantic Ocean on the east coast near Stuart, FL, with the Gulf of Mexico on the west in Fort Myers, is 152 miles long. Boaters traveling across Florida must pass through Lake Okeechobee in the center of the state.

Okeechobee is one of the largest fresh-water lakes in the United States and at the heart of Florida bass fishing country. Making the journey, vessels use five locks where they ascend as much as 13 ft at a single lift.

But transportation and recreation is only a part of the reason the waterway exists. It originally was built to drain Everglade swamps to create farmland. Today, it helps preserve nature areas for wildlife and controls flooding after major storms.