THE COHEN GROUP
  Environmental Health & Safety Consulting Services

The Cohen Group Newsletter - Volume 6  Issue 2, Article 5,  April, 2004

Mark Golembiewski, CIH, CPEA

The Cohen Group recently had a request from a client who needed help in assessing the extent of damage from a sewer system backup at a tenant’s facility. A blockage occurred in the sewer line somewhere downstream of the tenant’s building, causing sewer system effluent to suddenly back up through floor drains and toilets. The resulting flooding affected a significant portion of the tenant’s research laboratory operations, including a Class 10,000 clean area.

Requests for help with sewage contamination issues are a relatively infrequent occurrence at The Cohen Group, particularly when compared to the number of requests we receive for mold, asbestos and lead-based paint assessments. For each of those common evaluations, there are multiple guidance documents and published studies to enable one to develop an assessment strategy based on scientific and generally accepted practices. Comparable information for assessing sewage contamination in buildings is limited and very little on this subject has been published. The purpose of this article is to briefly summarize what is known and to provide you with some tips on properly identifying sewage contamination and cleaning up after the damage.

Sanitary sewer backups into buildings not only present unpleasant odor problems, they may cause property damage, and can result in potentially serious threats to human health. Untreated sewage contains a variety of microorganisms, such as bacteria, viruses, and parasites, capable of causing human disease and illness. Contact with contaminated water and/or surfaces may cause skin infections and rashes, and if ingested accidentally via improperly cleaned hands or surfaces, these contaminants can cause nausea, abdominal pain, vomiting and diarrhea. Respiratory infections and allergic reactions may also result from inhaling associated airborne microorganisms.

The severity of the health threat, however, depends on several factors including the volume of the release, the content of the sewage, the timeframe the sewage is left untreated, the environmental conditions, and the degree and extent of penetration into the building environment. The degree of penetration is dependent upon the porosity of the contaminated materials, the quantity of the sewage, and the amount of time the sewage remains in contact with the building materials.

Once a sewage backup incident occurs inside a building, time is a critical factor in executing a successful cleanup effort. The damaged area must be thoroughly cleaned, dried and disinfected to reduce the risk of disease and restore the building to its original condition. When small areas are affected and cleanup is relatively simple, individuals may complete the cleanup process on their own. But when significant areas and permeable surfaces are impacted, which make the remediation effort more complex, professional restoration companies with the proper equipment and expertise should be employed to perform the cleanup.

Standing waste water must be removed as quickly as possible and affected surfaces washed down with clean water. The humidity in the damaged area should be lowered by opening windows, circulating air (using portable fans, not ventilation systems) and using dehumidifiers as needed. Contents impacted by the sewage should be sorted to separate those that are salvageable (i.e., can be successfully disinfected or steam cleaned) from those that must be discarded. Generally, wall-to-wall carpeting and carpet padding cannot be effectively cleaned and should be removed and replaced.

After the initial sewage removal and wash-down, non-porous affected surfaces should be thoroughly cleaned and disinfected. In most cases, common household cleaning products and disinfectants, such as chlorine bleach will do the job if used correctly. It is important to ensure that plenty of fresh air is provided when using cleaners and disinfectants on large surface areas. Also, handling these cleaners will likely require the use of personal protective equipment such as eye and skin protection. If semi-porous materials, such as painted drywall, have been affected, especially if they have not been dried quickly, it may be necessary to remove and replace the affected sections of drywall. Often, removing the first one to two feet of drywall at the base of the wall is sufficient to ensure that the remaining drywall areas are unaffected. If questions arise about the adequacy of this approach or if it appears that the wall cavity (framing materials) have been affected, a professional consultant who can perform moisture and surface contamination testing should be contacted for assistance.

Once the cleanup has been completed, or if areas suspected to be contaminated must be confirmed to allow for cleanup, it is then necessary to test the affected surfaces for residual microbial contamination. Some laboratories recommend testing for total coliforms, fecal coliforms and fecal Streptococcus as indicator organisms of sewage contamination. However, the presence of many of these organisms is not indicative of fecal contamination, per se, and therefore do not provide definitive evidence of sewage contamination. The microbial laboratory used by The Cohen Group instead recommends testing for the specific indicator organisms E. coli and species within the genus Enterococci as indicators of fecal contamination, thereby providing the best available data on possible contamination.

Proper sampling procedures (i.e., sterile sampling equipment, use of gloves, etc.) must be followed or contamination of the samples may produce false positives and result in needless anxiety, re-testing and remediation. Surfaces should be sampled in multiple locations using a swab or similar sampling method. Each sample should be collected from a defined area for accuracy, consistency and reproducibility. Samples must be promptly submitted to the lab (within 24 hours) using cold packs, since bacterial sampling is time and heat sensitive.

Sampling results are evaluated for the presence of bacteria such as E. coli and the Enterococcus group (E. faecalis, E. faecium, E gallinarum, and E. avium) that specifically indicate contamination with sewage. The presence of the Enterococcus group in a sample confirms that the sample is contaminated with fecal material and the surface where the sample was collected must be cleaned (or re-cleaned). Coliform bacteria occur naturally in soil and in the intestines of humans and animals. Since E. coli is one type of fecal coliform that is indigenous to the intestines of humans and animals, their presence in a sample is also indicative of fecal contamination. It should be noted, however, that the majority of E. coli types do not cause human illness.

For more information or assistance with sampling for sewage contamination, please contact The Cohen Group.