A large university described interconnected steam, chilled water, and hot water systems serving multiple buildings through in-ground utility vaults designated as permit-required confined spaces. The vaults contain piping, valves, and connections that pass through but do not terminate in the spaces. While the piping can be isolated and drained by closing valves, doing so for certain spaces would require draining millions of gallons of water and could render dormitories uninhabitable and disrupt research for days.
The first question was whether employers must isolate and drain all flowable utilities with valves and connections before entry when workers are not working on the piping, there is no known breach, and the hazard assessment shows no engulfment or atmospheric hazard. OSHA explained that the confined space standard is performance-oriented, requiring evaluation under 29 CFR 1910.146(c)(1). Under 29 CFR 1910.146(d)(3)(iii), isolation is required only when the employer's evaluation determines there is 'potential for the piping inside the space to rupture or leak' causing engulfment or another serious hazard. If the evaluation determines the piping presents no rupture or leakage risk, isolation is not mandated.
On whether piping with valves and flanges that passes through but does not terminate in a space presents a 'reasonable probability of a rupture or leak,' OSHA said that determination belongs to the employer, and listed factors to weigh: the age and condition of the piping; whether routine inspection and maintenance have been performed and how often; whether the planned work will involve the piping or occur close enough that piping systems could be damaged; the history of failures; and whether the maximum volume and flow would cause a serious safety or health hazard.
OSHA declined to answer the remaining questions, noting they require site-specific evaluation unsuitable for a written interpretation, and suggested pursuing a variance request if compliance appears infeasible.