Glove Bags vs. Crawlspace Containment for 300 Feet of Steam Line
You are the project designer for removal of 300 linear feet of 10-inch steam pipe insulation in a 1920s county courthouse in Minot. The pipe runs through a crawlspace that is 36 inches high, 4 feet wide, and 300 feet long; the only access is a 24-inch by 24-inch hatch in a public hallway. The insulation is 20% amosite and is friable. The courthouse remains open during the project. The contractor proposes glove bags because the crawlspace is tight and has 10 glove bags on site. The mechanical engineer says the steam line cannot be shut down for more than 8 hours at a time.
1. Evaluate the contractor's glove-bag proposal and recommend a work method.
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Glove bags are useful for small, localized pipe work, but 300 linear feet of 10-inch friable amosite insulation is not a glove-bag-scale job. The work would require many bags, frequent bag changes, and repeated handling in a 36-inch crawlspace with a single 24-inch hatch. The 8-hour shutdown limit means the work must be sectioned, but that does not make glove bags the right choice. A better design is to treat the crawlspace as a negative-pressure containment with critical barriers at the hatch and at section boundaries, and to use mini-enclosures or wet removal methods at each pipe section. The designer should specify worker access, emergency egress, lighting, and a remote decontamination setup because the public hallway cannot become a dirty decon area. The method must match the friability, the amosite content, and the occupied building.
2. Calculate a reasonable negative-pressure requirement and describe the decontamination design.
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The crawlspace volume is roughly 300 feet by 4 feet by 3 feet, or 3,600 cubic feet. At four air changes per hour, the HEPA unit must move about 240 cfm (3,600 times 4 divided by 60). Select a HEPA unit rated above that flow at the actual static pressure of the long crawlspace, and provide a backup unit because a single failure would compromise the containment. Maintain a pressure differential of about -0.02 inches of water across the critical barrier and monitor it continuously. The decontamination design should keep the public hallway clean: build a three-stage worker decon in an adjacent room, with clean, shower, and dirty sides, and a separate equipment decon or bag-out route. Workers enter through the hatch in suits, and removed insulation is bagged and transferred out without crossing clean areas. The designer should also specify air monitoring and emergency rescue procedures for the crawlspace.
3. What notification and scheduling requirements apply before the first pipe section is opened?
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The project involves 300 linear feet of pipe insulation, which exceeds the NESHAP threshold of 260 linear feet on pipes. The owner or operator must notify NDDEQ before renovation begins and observe the required advance notification period. The notification must describe the facility, the amount and type of asbestos, the work practices, and the waste disposal plan. The designer should also account for the courthouse being occupied: the schedule must allow for containment construction, negative-pressure verification, and clearance before the space is returned to normal use. The 8-hour steam shutdown limit should be reflected in the sequencing, but it does not waive notification. No pipe section should be opened until notification is filed and the containment is operational.