Sewage Floods
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Suggested Guidelines for Remediation of Sewage
Damage from Sewage Backflow into Buildings

Michael A. Berry, Ph.D.; Jeff Bishop; Claude Blackburn; Eugene C. Cole, Dr.P.H.; William G. Ewald; Terry Smith; Nathan Suazo; and Steve Swan. Mr. William G. Ewald Health Scientist Environmental Criteria and Assessment Office, U.S. Environmental Protection Agency (MD-52) Research Triangle Park, NC 27711



Sewage poses a very significant threat to human health. However, the severity of the health threat depends on the content of the sewage and the degree and extent of penetration into the building environment. The degree of penetration is dependent on the porosity of contaminated materials, the quantity of sewage, and the amount of time the sewage remains in contact with materials. Consider three examples of sewage spilling into an indoor environment; the restoration response may be different in each situation.

Situation 1. A very limited quantity of waste that originates in the built environment is deposited or flows slightly beyond the confines of the sewage system. In this situation, the waste is found in one specific location, is contained, and does not penetrate the building structure. A limited amount of contact time has occurred. An example of this situation might be waste that overflows in a bathroom and is deposited on and confined to a tile floor. In this situation, there is a limited quantity of waste, which is contained and does not contact absorbent materials. Decontamination, which includes water extraction, cleaning, and disinfection, can be effective in reducing this particular potential health risk.

Situation 2. Waste that originates in the built environment is deposited or flows beyond the confines of the building's disposal system. In this case, there is limited or confined flooding, but water and waste penetrate the structure and furnishings of the building. For example, flooding occurs in a men's room of an office building, water flows under a wall and into the carpet of an adjacent hallway. In this case, there is a limited amount of waste that is confined to a relatively small area of the building, but it penetrates regions of the environment that have complex surfaces and are difficult to restore. Effective restoration involves decontamination (as in Situation 1) as above and drying all surfaces that have been in contact with the sewage. In the case of stretch-in carpet, lifting and cleaning the contaminated carpet, disposing of the cushion, and treating both sides of the carpet thoroughly with a disinfectant are all necessary. Affected porous wall materials need to be treated with a disinfectant and evaluated for replacement. Because of the confinement of the sewage spill, aggressive, comprehensive treatment can be effective.

Situation 3. Waste that originates in the built environment, along with other wastes from the main line of the sewage system, is backed up into the immediate environment, where the waste is widely dispersed and penetrates both the structure and its furnishings. In this situation, there is extensive risk because humans can be exposed to pathogenic raw wastes that have penetrated and become contained by the building and its furnishings. If flooding is from this kind of primary outside sewage system, occupants should be evacuated, and restoration should begin immediately. In this situation, cleaning and restoration professionals should be protected by using respirators with high-efficiency particulate air (HEPA) cartridges, rubber boots, gloves, splash goggles, and protective garments. Extreme care should be taken to avoid puncture wounds during the restoration process. Restoration staff who have cuts or open sores should not be allowed to work on this kind of restoration project. The principles of restoration of this situation are outlined in the last section of this paper, which contains specific recommendations for techniques. The main discussion of this paper focuses on the potential health risks posed by a sewage backup similar to Situation 3.

Description of the Primary Problem

When a building is contaminated with sewage backing up from the septic lines, or flooding of a
building occurs that involves sewage or a heavy load or organic matter, as in the case of river
flooding, a serious threat to human health exists. Without appropriate action, extensive damage to materials will occur immediately or in time. Several days may elapse before the cause of the backup is determined, the problem is corrected, and flooding subsides. This allows extensive permeation and contamination of absorbent (hygroscopic) materials such as wood, gypsum, paper, and concrete to occur. This penetration with water and organic matter leads to the growth of potentially disease-causing (or opportunistic) microorganisms. These Organisms may pose a serious health risk to occupants of the building. Organic matter and water-saturated materials can be used as substrate for growth of microorganisms (such as gram-negative bacteria and toxigenic fungi) that can produce substances toxic to humans and damaging to materials. A large amount of water inside a building will cause high humidity, which can also contribute to microbial growth on structural materials and contents. -----."

CERL can provide pre- and post remediation inspection and testing using sampling methods consistent with standard industry protocols. Sampling is conducted to determine the level and locations of contamination before remediation; and, after remediation testing to show the effectivness of the clean-up.