Excavation soil tests and storm sewer confined spaces

June 15, 1992
Mr. George S. Kennedy
Director of Safety
National Utility Contractors Association
[Recipient address omitted]
Dear Mr. Kennedy:
This is in response to your May 5 letters requesting interpretations of Occupational Safety and Health Administration (OSHA) requirements addressing soil testing and confined spaces.
In regard to whether a thumb penetration test as described in Appendix A to Subpart P can be used to determine type "B" soil, please be advised that the thumb penetration test can be used as a test to determine type "B" soil. While the discussion of the thumb penetration test in Appendix A addresses only the characteristics of types "A" and "C" soils, type "B" soil would fall in between the characteristics given for types "A" and "C" soils. Type "A" soils can be readily indented by the thumb, but they can only be penetrated with great effort. Type "C" soils can be easily penetrated by the thumb. Extrapolation of these characteristics results in a finding that type "B" soils can be penetrated with moderate effort.
In regard to whether a manhole that is part of a storm sewer, not connected to a raw sewage line, is considered to be a confined space, please be advised that many manholes have limited means of egress and are subject to the accumulation of toxic or flammable contaminants or oxygen deficiency. Therefore, they must be considered confined spaces. Even though the manhole in your example is part of a storm sewer and not connected to a raw sewage line, it would still have the potential to accumulate toxic or flammable contaminants that might be washed in during rain storms; and, therefore, the atmosphere in any such space must be tested before an employee enters it.
In regard to whether OSHA would consider an enclosed area that is subject only to having a limited means of access to be a confined space, please be advised that it would be dependent on each situation. For example, a trench could be considered an enclosed area; but, since it would usually be subject to natural ventilation, it would not be considered a confined space unless other factors, such as those addressed in 29 CFR 1926.651(g), are present. On the other hand, because limited means of access implies a potential for an oxygen deficient atmosphere, other types of enclosed areas would be considered confined spaces.
If we can be of any further assistance, please contact [the Office of Construction Standards and Guidance at (202) 693-2020].
Sincerely,
Patricia K. Clark, Director
[Directorate of Enforcement Programs]
[Corrected 05/28/04]

[Requester letter reproduced on OSHA page; omitted here.]