July 2, 2001
To: Tom Yelvington; Program Director
From: Jim Scott; McMurdo Area Mgr.
McMurdo Asbestos Issues
In response to recent asbestos issues at McMurdo, summarized below is an overview of the situation.
Building 165: This building has been undergoing room by room renovations. Most of this has involved "non evasive" work such as removal of drop ceilings, etc., with minimal disturbance to the building structure. Prior to initiating this work, FEMC reviewed the comprehensive AECOM Asbestos Survey Report (1992) in an effort to avoid disruption of asbestos containing building materials. This survey included analysis of sample building materials using phase contrast microscopy with polarized light and dispersion staining. This provides positive identification of asbestos through refractive index, morphology and color analyses.
During the performance of this survey thirty-seven (37) building interior samples were taken and analyzed. With the exception of vinyl flooring, asbestos was only found in joint compounds (1-5% asbestos by weight), not sheet rock.
Concern about the presence of asbestos occurred recently during renovation at two locations in the building:
--In room 207 after a piece of door trim/frame was removed and the underlying material looked suspect.
--In room 119/120 where glued corkboard was being removed from sheet rock on the walls near ceiling level.
As soon as the materials were deemed suspect, work was halted and samples were tested using a rudimentary field test kit for hazardous waste characterization. While one sample indicated the presence of asbestos, the test kit is subject to false positives from contamination of other materials mixed with the asbestos. It is possible some joint compound could have been mixed with the tested materials. All other field tests were negative. The more accurate AECOM tests indicated the other building materials to be asbestos free.
When it was determined the materials could contain asbestos; air sampling was conducted to assess the exposure hazard. Initial samples indicated levels inside and outside the rooms to be less than 1/2 the occupational standard. The rooms were isolated with poly. Subsequent samples indicated levels outside the rooms to be less than 1/10 the standard, and in several cases, non-detectable.
Building 203: This building has been 95% demo’ed, to date. Because it is relatively new in comparison to building 165, it was considered to be asbestos free at the start of the work. The AECOM survey was not referenced. This was an oversight. The survey does indicate the building to be asbestos free (12 samples) with the exception of approximately 100 square feet of vinyl flooring in the vestibule area. Although this was unknowingly removed, asbestos in embedded vinyl materials is usually tightly bound, minimizing airborne exposure during handling. In addition the vinyl was removed as a single sheet.
This building was sampled for airborne fibers and found to have levels less than 1/10 the occupational standard for asbestos. It should be noted this sampling method counts total fibers – it cannot differentiate the asbestos fibers from non-hazardous fibers consequently, it over estimates the results. A comparative sample taken on T-site, where no asbestos materials are present (new building) indicated total fiber levels 4 times those found in 203.
Current Situation
While some asbestos containing materials may have been disturbed in the renovation of these buildings, based on the quantities involved, time, and the conservative (over estimating) sampling methods, it appears the exposures were very low. In most cases, levels were well below the permissible limit. The isolation of the subject rooms in building 165 has resulted in levels in adjacent areas considered safe for public use. Building 203 also meets these criteria, though work was initially suspended in the building pending further evaluation due the sensitivity of the issues.
Additionally, 9 out of 10 very recent samples taken in both buildings using the field test, indicated negative results. This included dust residue, drywall, and ceiling tiles. The only positive sample was for vinyl flooring.
While there were oversights in our renovation management planning process, we feel we responded responsibly to minimize exposures after suspect material was identified.