Fax forwarding DEP briefing materials for Mayor's meeting, March 2002

NYC 9/11 Public Portal Document ...--

Friday 15 of Mar 2002, Mayor Office ->718 595 4544 Page 19 of 29

APPENDIX PFJEFORMANCE STANDARDS

Requirements and Performance Standards Cleaning Masonry Exteriors

I. Reqiiiienicnts

General: All work related to historic buildings shall comply with the Secretary of the. Intenor's Standards for the Treattnent of Historic Properties. Treatment approaches wil! be in the "gentlest means possible," and all methods''should be materia! and building specific. Programs for the cleaning of historic building fo^ades shall be developed on a case-by-case basi.s with regard to each building and all associated building materials. Harsh treatments and inappropriate cleaning methods, including abrasixe cleaning and certain chemical applications, can damage significant historic building fabric and character-defining features. Traditional abrasive applications such as "sand-blasting" and high-pressure water cleaning shall not de used.

II. Pei'forinaiu'e Stiindards

Qualified Contractor(s)/Consultant(s): .A qualified professional such as a historic preservation or building conserx’ation e.vpert shall be consulted to develop an appropriate cleaning program for each building and to direct the work. .A qualified contractor e.xperienced in the cleaning of historic buildings shall perform the work.

Testing: Prior to cleaning a building, the source and type of soiling, dust, dirt, or debris shall be professionally tested. Identification of the type of soiling material, the type of building materia! (e.g. stone, cast stone, brick, terra cotta) combined with professional interpretation of test results will aid in the determination of the most appropriate cleaning method for a building. .After a cleaning program is selected, the method shall be tested and ewiluated by a professional prior to widespread a pp 1 i ca t i on.

WTC Site Spevitk Considerations:

It should be noted that post disaster cleaning o.t'particulate soil and dust generated by the event should not be confused with cleaning of more persistent long 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 masomx- substrate during the cleaning process, creating deposits that will cause problems to the building over time and that wil! be difficult to remove from building fabric. Dust and debri.s deposited on buildings should be tested for composition. If it is detennined that a chemical reaction is pos.sible. S[ep.s shall be taken to properly remove debris (from the projecting ledges or elements, sills, fire escapes) and dust from the horizontal and vertical SLirface.s of the building prior to the application of water or liquid cleaning agents. Thi.s may include vacuuming and or gently brushing away dust from al! horizontal and vertical

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