Forwarding WTC air monitoring scope for final review, Aug 2002

NYC 9/11 Public Portal Document

Environmental Protection Agency Pf. 763, Subpt. E. App. B 3. The removed asbestos material from the work Is to be performed. Such enclosures pipe or other surface that has fallen into the should be constructed of 6-mll-thlck poly­ enclosed bag must be thoroughly wetted ethylene plastic sheeting and can be small with a wetting agent (applied with an airless enough to restrict entry to the asbestos sprayer through the precut port provided In work area to one worker. most gloves bags or applied through a small For example, a minienclosure can be built hole In the bag). in a small utility closet when asbestos-con­ 4. Once the asbestos material has been taining duct covering is to be removed. The thoroughly wetted. It can be removed from enclosure is constructed by: the pipe, beam, or other surface. The choice 1. Affixing plastic sheeting to the walls of tool to use to remove the asbestos-con­ with spray adhesive and tape. taining material depends on the type of ma­ 2. Covering the floor with plastic and seal­ terial to be removed. Asbestos-containing ing the plastic covering the floor to the plas­ materials are generally covered with painted tic on the walls. canvas and/or wire mesh. Painted canvas can 3. Sealing any penetrations such as pipes be cut with a razor knife and peeled away or electrical conducts with tape. from the asbestos-containing material un­ 4. Constructing a small change room (ap­ derneath. Once the canvas has been peeled proximately 3 feet square) made of 6-mll- away, the asbestos-containing material un­ thlck polyethylene plastic supported by 2- derneath may be dry, in which case It should inch by 4-inch lumber (the plastic should be be resprayed with a wetting agent to ensure attached to the lumber supports with staples that it generates as little dust as possible or spray adhesive and tape). when removed. If the asbestos-containing The change room should be contiguous to material Is covered with wire mesh, the the minienclosure, and Is necessary to allow mesh should be cut with nips, tin snips, or the worker to vacuum off his protective cov­ other appropriate tool and removed. eralls and remove them before leaving the A wetting agent must then be used to spray work area. While inside minienclosure, the any layer of dry material that Is exposed be­ worker should wear Tyvek ‘ disposable cover­ neath the mesh, the surface of the stripped alls and use the appropriate HEPA-filtered underlying structure, and the Inside of the dual-cartridge or more protective res­ glove bag. piratory protection. 5. After removal of the layer of asbestos­ The advantages of minienclosures are that containing material, the pipe or surface from they limit the spread of asbestos contamina­ which asbestos has been removed must be tion. reduce the potential exposure of by­ thoroughly cleaned with a wire brush and standers and other workers who may be wet-wiped with a wetting agent until no working in adjacent areeis, and are quick and traces of the asbestos-containing material easy to Install. The disadvantage of can be seen. minienclosures is that they may be too small 6. Any asbestos-containing insulation to contain the equipment necessary to create edges that have been exposed as a result of a negative pressure within the enclosure; the removal or maintenance activity must however the double layer of plastic sheeting be encapsulated with bridging encapsulant to will serve to restrict the release of asbestos ensure that the edges do not release asbestos fibers to the area outside the enclosure. fibers to the atmosphere after the glove bag Removal of entire structures. When pipes are has been removed. insulated with asbestos-containing mate­ 7. When the asbestos removal and encap­ rials, removal of the entire pipe may be more sulation have been completed, a vacuum protective, easier, and more cost-effective hose from a HEPA filtered vacuum must be than stripping the asbestos Insulation from inserted into the glove bag through the port the pipe, ^fore such a pipe is cut. the asbes­ to remove any air In the bag that may con­ tos-containing insulation must be wrapped tain asbestos fibers. When the air has been with 6-mll polyethylene plastic and securely removed from the bag. the bag should be sealed with duct tape or equivalent. This squeezed tightly (as close to the top as pos­ plastic covering will prevent asbestos fibers sible), twisted, and sealed with tape, to keep from becoming airborne as a result of the vi­ the asbestos materials safely In the bottom bration created by the power saws used to of the bag. The HEPA vacuum can then be cut the pipe. If possible, the pipes should be removed from the bag and the glove bag cut at locations that are not insulated to itself can be removed from the work area to avoid disturbing the asbestos. If a pipe Is be disposed of properly. completely Insulated with asbestos-con­ Minlenclosures. In some instances, such as taining materials, small sections should be removal of asbestos from a small ventilation stripped using the glove-bag method de­ system or from a short length of duct, a scribed above before the pipe is cut at the glove bag may not be either large enough or stripped sections. of the proper shape to enclose the work area. Enclosure. The decision to enclose rather In such cases, a minienclosure can be built than remove asbestos-containing material around the area where small-scale, short-du­ from an area depends on the building owner’s ration asbestos maintenance or renovation preference, l.e., for removal or containment.

707

NYC-WTC_000139322