FEMA correspondence regarding historic building cleaning treatments, March 2002

NYC 9/11 Public Portal Document

MAR. 15. 2002 1 1:22AM NO. 792 P. 23.

APPENDIX B: PERFORIINCE STANDARDS

Requirements and Performance Standards CIeaning Masonry Exteriors

• Requirements

General; All work related to historic buildings shall comply with the Secretary of the ,Interior's Standards for the Treatment of Hrstoeic Properties, Treatment "gentlest means possible; 'and all methods 'should be material and approaches will be in the building specific. Programs for the cleaning of historic building facades shall be developed on a case-by-case basis with regard to eaeb building and all associated building materials.' Harsh treatments and inappropriate cleaning methods, . including abrasive cleaning and certain chemical significant historic building fabric and character-defining , applications, can damage features. Traditional abrasive applications such as "sand-blasting" and high-pressure water cleaning shall not de used. II. Performance standards

Qualified Contrictor(s)/Consultant(s): A qualified professional such as a historic preservation or building conservation expert shall be consulted to develop an appropriate cleaning program for each building, and to direct the work. A qualified contractor experienced in the cleaning of' historic buildings shall perform the work.

Testing; Prior to cleaning building, the source and type of soiling, a

dust, dirt, or debris shall be professionally tested. Identification of the type of soiling material, the type (e.g. stone, cast stone, brick, terra cotta) combined with of building material professional interpretation of test results will aid in the determination of the most appropriate cleaning method for a cleaning program is selected, the method shall be tested and evaluated by a building. After a widespread application. professional prior to ' WTC Site Specific Considerations:

o It 'should be noted that po'e, disaster cleaning of particulate soil and dust event should not be confused with cleaning of more persistent long generated by the term soiling that would require more aggressive methods,

o It is possible, based upon composition of the particulates generated by the 'event, that'the dust and/or debris on the facade may chemically react with applications and masonry substrate during the cleaning process, creating deposits that will cause problems to the building over time and .that will be difficult to remove from building fabric. Dust and debris deposited.on buildings should be tested rfor composition. If it is determined that a chemical reaction is possible, steps shall be taken to properly remove debris (from the • projecting ledges or elements, sills, fire escapes) and dust from the horizontal and vertical surfaces of the building prior to the application of water or liquid cleating agents. This may include vacuuming and/or gently brushing away dust fora all horizontal and vertical

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