(Boulder County Colo.) After removing the water and wet building materials from a flooded structure, the next crucial step is to clean and sanitize the building as needed and to thoroughly dry both living and storage spaces. As with the previous stages of clean up, the relative cleanliness of the floodwater makes a difference for how drastically the affected space must be treated. The established scale for flood events is as follows: Category 1 is clean water such as tap water from a burst pipe other plumbing supply leak, or fresh rainwater or snowmelt leaking through a roof. Category 2 (gray water) is usually groundwater or other water flooding in from outside, but it could also come from the drain side of a dishwasher or clothes washer. Category 3 (black water) is sewage that typically backs up through soil pipes and spills out of toilets, shower and sink drains, and floor drains.

Cleaning and Sanitizing

Before a space is dried out, it needs to be cleaned well. A clean-up contractor I interviewed uses a pressure washer on walls and floors for any category 2 or 3 clean ups--it's a lot easier than trying to scrub every nook and cranny of furring strips, wall studs, radiators, etc.. The wash and rinse water is collected by a large truck-mounted water extractor similar to a carpet cleaning extractor. Strong broad-spectrum anti-microbial cleansers are used at this stage in a flood clean up. Besides cleaning any scum and contaminants left behind by floodwater, backed up sewage, or both; the proper cleaning products used for this work disinfect and sanitize surfaces. One major benefit of anti-microbial disinfectants over bleach is that they don't have to be rinsed and therefore can provide lasting bacteriostatic and fungistatic protection. After wet cleaning, a second application of disinfectant is usually applied to affected surfaces to sanitize them

There are many professional anti-microbial disinfecting cleansers available (with different kill levels for whatever you need to clean up), but according to commercial supply houses and disaster restoration contractors alike, the latest botanical formulations are revolutionizing the industry. Unlike traditional formulas, these products don't require any PPE for safe handling, making them safer and easier for workers to apply. (This PPE requirement relates to just the products themselves--of course protective suits, boots, gloves, and respirators may still be required to work in a contaminated area).
Unless mold is detected in a building, a separate treatment to prevent mold is usually not required.

Mold Remediation

If any mold is detected or even suspected, a trained and certified mold remediation contractor should be brought in. Unless you are aware of all of the advanced requirements and methods of treatment, you would be wise to sub out this step. You don't want to be liable if a flood-damaged building you worked on ever develops mold in the future—leave that to a specialist.

If you do tackle any mold clean-up and treatment, remember that the mold has to be chemically killed as well as physically removed. Any "dead" mold left in place still presents a hazard to the building and its occupants. Be sure to follow established remediation guidelines like those published by the Institute of Inspection, Cleaning, and Restoration Certification (IICRC). The IICRC is a non-profit organization that develops ANSI-approved standards for water damage restoration and mold remediation that professionals in the industry look to. www.iicrc.org

While working in an area where you suspect mold is present, the Center for Disease Control (CDC) and the EPA recommend using at least an N-95 NIOSH-approved particulate respirator mask to prevent breathing in airborne microorganisms. An N-100 rated respirator mask is a step above that and half- or full-face respirators with canister filters offer even better protection.

Regardless of your previous experience with seemingly harmless mold in shower stalls or under sink cabinets, any exposure should be treated with caution. A friend of mine recounted how spending just a few nights in an apartment with flooded walls and floors (caused by a plumbing leak) triggered adult onset asthma that she suffered from for two years.

Drying Out

Once everything is cleaned, you will need to set up equipment to dry out a space. If you are renting, keep in mind that the experts around here say they typically have to keep the machines running for three to five days. If you live in a more humid area or if it is cold out, it may take longer. The large tool rental chain in town said they brought in five semi trailers with over one thousand pieces of drying equipment right after the flood and that it all got put into service right away. The demand for machines was in the following order.

Dehumidifiers are the most effective tool for drying out a building because they actively condense moisture from the air. Large, high capacity mobile units dry air more quickly than household units to better help you stay ahead of mold. In regions with high ambient humidity, for spaces without ample ventilation like basements and crawlspaces, and during heating season, a dehumidifier is probably a necessity for drying a building.

Air Movers — also called carpet driers or carpet fans--blast a high volume of air along the floor to hasten evaporation. They are typically used in conjunction with dehumidifiers; the powerful stream of air pulls the moisture out of materials at the surface, and the dehumidifier draws the moisture out of the air. During times of warm weather in relatively dry areas like Boulder, air movers and other fans may be enough to dry out a space as long as there is good ventilation with fresh air at a lower humidity level

Air Scrubbers are recirculating fans that have a series of three or four filters to clean particulates out of the air. The third filter is a HEPA filter which can trap fine mold spores, and the optional fourth filter contains activated charcoal to absorb odors.

Moisture Content

While the building is drying out, spot moisture meters are used to monitor the moisture content of the wood that was wet. Sample readings should be taken all over, but it's especially important to check where the wood stayed wet the longest and dries the slowest such as stud wall plates sitting on concrete. Some clean-up contractors prefer using moisture meters with probe pins while others prefer the non-intrusive scanning type. There are also two methods for determining when a building is dry. One company I interviewed said they keep the machines going until every reading they take is at 9% or below. Another company said that their target number is within 4% of readings of known dry areas in the same building, which means drying to between 4% and 11%. Either way, materials in the building need to be brought way below the 17% moisture content that will harbor mold.

Keep checking back for more coverage. Links to guidelines and standards for clean up and restoration work are coming, followed by a look at some volunteer organizations that can help flood victims save valuable documents, photos, and artwork. And I am still compiling a veritable flood of information from local, state, and federal building officials regarding some standards that are being relaxed or modified during this state of disaster.

This is the fourth in a series of reports intended to help inform both the victims of natural disasters as well as the contractors they look to in these times of crisis.