Hurricane Katrina was one of the most destructive storms to hit the Gulf Coast in decades. Most Americans, and indeed, many people around the world, spent the first part of September glued to their television sets, watching the never-ending scenes of devastation and destruction. These images showed stranded people on rooftops and houses and office buildings that were submerged under many feet of water.

Once the storm passed and the levees were patched, dewatering and cleanup began immediately. Areas of Louisiana, Mississippi, and southern Alabama were so devastated that it resulted in one of the largest disaster response mobilizations in the United States. Then, of course, came Hurricane Rita, which flooded parts of New Orleans all over again.

Dewatering a city the size of New Orleans was a Herculean task, but the bigger question will be: How many buildings can be restored? In the hot and sticky climate of the Southeastern United States, mold is always an issue anyway. Buildings that were submerged under water for two or more weeks will not only have mold issues, they will also potentially be contaminated from all the pollutants that were in the water. Even buildings that weren't flooded will have problems, since many were without power for days or weeks, giving mold and mildew an ample opportunity to flourish in the non-air conditioned environment.

It has yet to be determined how long the cleanup will take, or how many buildings will be inhabitable again. In the short term, building owners, restoration crews, and government officials were removing wet items such as carpet and sheetrock as quickly as possible and using dehumidification equipment to dry out the buildings. Where water is concerned, time is of the essence, and those working frantically to restore the buildings along the Gulf Coast are hoping they haven't missed their window of opportunity.

At a business in the French Quarter a commercial vacuum truck cleans out the waters left behind by Hurricane Katrina. Many buildings flooded by the storm are now being cleaned and sanitized and will soon be back up and running. (Photo courtesy of Win Henderson/FEMA.)

Thinking Ahead

Many of the commercial buildings in New Orleans and surrounding areas sustained relatively minor damage compared to the residential areas. John Bevington, president of ChillCo, Inc. in Mandeville, LA, rode out Katrina in his home, noting with a tad of understatement that it did get "a little breezy." His company, which services and rents chillers, is located 24 miles across Lake Pontchartrain from New Orleans. Once the storm abated, Bevington leaped into action, moving his rental equipment around the city in order to start drying out the buildings.

"I've been working in the downtown area, and the damage isn't that bad, relatively speaking. The high-rise office buildings and hotels really only got two feet of water or less in their lobbies. Some of them didn't even get that. Many of the houses, though, have been sitting in eight feet of water for almost three weeks, and they're destroyed. Proportionately speaking, the commercial buildings did pretty well," said Bevington.

There are three reasons why commercial buildings might have fared better than residential structures during the hurricane and subsequent floods, according to Dr. Michael Pinto, CEO of Wonder Makers Environmental, Kalamazoo, MI, and a member of the Association of Specialists in Cleaning and Restoration. "First, they are usually built more substantially, so they lose windows and drywall, but they're built out of concrete and steel, so they're sturdier. Second, because they're commercial buildings, people put more importance on them in terms of trying to get them back up and running."

The third reason is that commercial buildings usually have more resources available to them, in terms of insurance and awareness. For example, many have contingency plans drawn up and contracts already in place, so they are ready for most emergencies that could come their way. Nick Sickmen, marketing manager for Carrier Rental Systems in Houston, agreed, noting that his company had rental equipment in place at many locations two to three days before the storm.

"The companies that have plans in place beforehand know that generators, air conditioners, and drying equipment go fast. There's only so much of this equipment in the rental market," said Sickmen. "In times like these, where the devastation is so massive and with Hurricane Rita coming in right after Katrina, the amount of rental equipment available is limited."

Proper Procedure

Nonetheless, cleanup in the New Orleans area has been moving rapidly, and many are worried that it may be moving just a little too fast. Bevington noted that FEMA initially was so desperate for hotel rooms for its workers, that the organization was signing one-year leases with anybody who could give them a number of rooms immediately.

"The urge was to get the hotels up and running, so they could house these people," said Bevington. "The problem is if the supporting structure of a building is wood as opposed to metal, then the wood takes on the moisture. You've got to get that moisture out of the studs and replace the sheetrock before you can put anything back together or it will be an unsightly mess in no time."

According to Pinto, if the buildings aren't completely dried out before being restored, then long-term safety may be sacrificed for short-term gain. "If they don't dehumidify and restore the buildings properly - and by that I mean dehumidify, physically remove all the porous material that has been impacted by the water including drywall, carpets, ceiling tiles, and then open up the wall cavities so they can properly clean and sanitize - then it's going to smell like a flooded building for decades."

Dehumidifying quickly (usually with desiccant dehumidifiers) is very important in these situations, since mold will grow in no time at all. Indeed, just three weeks after the first hurricane, a report in USA Today stated that "hot, humid New Orleans has become a giant mold factory," with mold growing on walls and furnishings throughout the city.

Desiccant equipment is preferred in these circumstances, because it can dry out the buildings in a more precision-controlled manner than other types of dehumidifiers. "Typically a refrigerant-based dehumidification system can only get to about 45% relative humidity. With desiccant equipment, you can go much lower than that," said Oliver Stulz, vice president of sales with Stulz Air Technology Systems Inc. "Once you get below that point, that's where the desiccant starts to shine."

The damage that results from water is progressive, so the longer the wet conditions exist, the more that is absorbed and the greater the recovery challenge. "The first step is to get power to the building, and in New Orleans, this usually required generators," said Pat Rucker, president of Entech in Dallas. "The standing water must be pumped out, and then drying equipment and air conditioning units working together must be put into operation. Fans must also be located in various locations to move air through the building."

Rucker said that it can take between one and three weeks to fully dehumidify a building, which brings up the question: How can an owner be sure the building is "dry enough" before beginning the restoration process?

"Anything can be dehumidified enough," said John Bergman, sales and marketing consultant for Des Champs Technologies. "The problem is that if mold has started, it will go into remission when the relative humidity is reduced below about 60%, but it will re-grow and give off spores if the humidity is allowed to rise again. It's the spores of mold that cause the respiratory problems and bring on the lawsuits." (Coincidentally, a study from National Institutes of Health was released shortly after Katrina hit, which stated that those who occupy previously water-damaged buildings are more likely to have respiratory problems, see sidebar).

According to Mickey Lee, vice president of Global Technology for Munters - MCS Division, Glendale Heights, IL, the drying contractor must first decide which building materials should be removed and replaced and which can be dried. For example, highly porous materials that have absorbed contaminated water are normally removed and replaced rather than dried.

After the restorative drying effort has started, the contractor will allow the building to "tell him" when it is dry enough and when to stop the drying process. "Beware the drying company that tells you they can dry the building in five days, but cannot define how they will know when the building is dry," said Lee. "A knowledgeable contractor should demonstrate a familiarity with moisture-measuring instruments, which he will use to test the affected materials for moisture content."

Lee added that the contractor should monitor how dry the building is by determining the pre-loss moisture contents of the gypsum board, wood floors, and other building materials; by frequently monitoring the moisture in the building materials to track their drying progress; and by monitoring daily the conditions of the air inside the water damaged areas, as well as the status of the building's HVAC system.

Drying is usually considered to be sufficient, said Lee, when the interior ambient conditions are at or better than normal room conditions (e.g., the building's HVAC will be able to maintain the proper ambient conditions), and the moisture on and in the building materials themselves will not support active microbial growth.

Employees of a professional cleaning service company carry wet/dry vacuum cleaners and drying fans into a flooded hotel in the French Quarter to begin needed renovations. (Photo courtesy of Win Henderson/FEMA.)

To Raze Or Restore

When water sits inside a building for a period of time, the walls, ceilings, and floors absorb the water, which can threaten the overall structural integrity of the building, creating an unsafe environment. Organizations such as FEMA or the insurance companies may then recommend that the building be razed rather than restored, particularly if more than half the building has been damaged or the structure has been in contact with toxic materials.

Not so fast, though, said Pinto. "If it's obvious that the damage is substantial, such as the building has been moved off its foundation and the whole roof is collapsed, then the economic feasibility of saving it is probably pretty quickly exceeded, unless you've got a historic facility or something special that might need to be accommodated. In general, if you've got a lot of structural damage, then it might make more sense to raze the building as compared to saving it."

Short of that extensive damage, Pinto stated that most times a structure can be restored. "You can strip a building down to its studs and rebuild it and still have a fairly substantial cost savings as compared to building new."

He noted that copper pipes and electrical wiring are usually not harmed if they have been submerged for awhile, and it's easy enough to change the outlets and switches, as well as sanitize the water pipes. "There's a lot of value in these buildings from the foundation to the chimney, skipping the interior finish. Even if you have to pull the exterior siding off, you can still generally do that cheaper than building new."

The catch is to start the cleanup and restoration process immediately after the water is pumped out, because a submerged building deteriorates much less quickly than a previously submerged building. That's why many of the restoration companies responded so rapidly after Hurricane Katrina passed. "There's a window of opportunity, and if they can get in there during the window, they can fix a lot of problems before they actually happen. In this case, they just couldn't get into many of the affected areas, so there's just no telling what they're going to be able to save," stated Sickmen.

Of course, Hurricane Rita threw a wrench in the works as well, because the second flood that occurred so quickly after Katrina increased the odds that some buildings may become unsalvageable. "You already have swollen wood, for example, and nutrients and contaminants that have been carried into the building and then have receded. Re-flooding just potentially drives the contaminants deeper into the building and structural materials," noted Pinto.

Which leads us to the question of contamination: That is, will the toxic elements in the floodwaters cause problems down the road in restored buildings? Unfortunately, there's no quick answer. Reporters have been fond of calling the floodwaters a "toxic soup," but the elements in the water can vary from block to block or building to building.

Pinto noted that basic questions should be asked, such as: Was the building located next door to a gas station? If so, what was the integrity of the underground tanks? What was the general direction of the floodwater? Each general area has to be looked at in terms of what the impact of the contaminant could be.

The initial testing of the water was only done from a health and disease prevention standpoint, as the Centers for Disease Control was looking for things that could cause disastrous disease outbreaks in the population. "But there are all sorts of bacteria associated with sewage that are not appropriate for surfaces inside a building afterwards. Then there are the petroleum distillates, as well as the amount of silt or dirt that becomes an organic or a nutrient source, let alone the other chemicals such as pesticides and lawn fertilizers, and all those sorts of things that get mixed with the floodwaters," stated Pinto.

For the moment, there are no answers to these questions. The only thing that's certain is that the cleanup and restoration of the affected Gulf Coast areas, including New Orleans, will be time-consuming and expensive. ES

NIH Study Looks At Occupants In Water-Damaged Buildings

The National Institutes of Health (NIH) recently released the results of a study entitled, "Respiratory Morbidity in Office Workers in a Water-Damaged Building." The study looked at occupants who returned to a previously water-damaged building to see if they were more likely to have respiratory problems.

As part of a program to study occupational respiratory disease in the nonindustrial environment, Centers for Disease Control and Prevention (CDC) and National Institute for Occupational Safety and Health (NIOSH) investigated building-related respiratory health in the employees of a 20-story office building in the northeastern United States. Since the mid-1990s, the building had leaked through the roof, around windows, and through sliding doors of terraces. The upper floors had suffered the most water damage and mold contamination.

During investigation of these problems, the building was found to be operating at a negative pressure with respect to the outdoors, which could exacerbate water incursion through the building envelope. Furthermore, there had been plumbing leaks on many floors, which had damaged interior walls. The first major construction activity related to water incursion began in 2000, with repair of roof copings and brick caulking. From 2000 to 2002, cubicle partitions and carpets were cleaned, wetted carpet and stained wallboard replaced, wallpaper and underlying mold removed from bathrooms, upgrades to the air-handling system made, and windows caulked. In 2002, permanent repairs on the building exterior, including roof replacement, began to prevent water incursion.

In the study, building occupants reported health conditions that they considered building-related. Symptom onset spanned several years. This article reports evidence of excesses of respiratory symptoms and physician diagnoses of asthma in the occupants of the water-damaged building as well as verification of self-reported respiratory illness with objective testing.

The study concluded that water-damaged buildings can be associated with work-related respiratory disease and that building-related respiratory disease warrants increased public health, medical research, and policy attention. To read the entire study, go to