Memo on concrete curb protection at 7 WTC, Sep 1998

NYC 9/11 Public Portal Document

JAN 28/99 12:10 PR AMBASSADOR CONSTR. CO212 949 97^2 TO 6693640 P.05Z08 14 :‘3O FAX 2122190256 SWANKE H.\YDEN CONNELL @002/005

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Via Fax (212) 219-0059 & Regular Mail

September 12,1998

Mr. Juan M. Mejia, AlA ; Swanke Hayden Connell & Partners LLP 295 Lafayette Street New York, NY 10012

Re: OEM Radio Equipment Room 7 World Trade Center, NY. NY

Dear Jaun

As discussed, the new concrete curbs for the above project may be poured directly on the existing Kemperol membrane. Before pouring the new concrete, the existing membrane must be protected from alkalinity in the cement by applying two (2) coats of Primer 0 (@ 0.8-1.0 gal/100 SF) and broadcasting kiln-dried silica sand into second wet coat of primer. The above protective measures are mandatory in all areas where concrete is to be placed over Kemperol waterproofing membrane. In addition, care should be taken to clean adjacent areas of Kemperol with continuous water and brush (high-pressure water if necessary) to eliminate settlement of concrete residues on membrane.

Once installed, the new concrete curbs may be flashed with one of the attached details. Detail "D-1" shows a metal/Kemperol membrane composite flashing used to flash the new concrete curbs while the concrete is still green. Detail "D-2" would be used to flash the curbs after the concrete has coir^letely cured. As discussed, detoil “0'2* would require a bead of polyurethane sealant applied between the bottom edge of the concrete curb and existing Kemperol membrane to form a temporary water seat. Then, after the new concrete cures (with a maximum 5% moisture content), the Kemperol membrane flashing osuid ba installed.

Both flashino details require a tie-in of the ne^ Kemperol mombrane onto the existing Kempsrol field membrane. To accomplish this, the sand aggregate surfacing must be completely removed From the surface of the existing in-place membrane. The area of sand aggregate removed should be approximately 6" wide (o accommodate the new flashing. After removing th© aggregate, the top surface of the membrane must be thoroughly cleaned with toluene or acetone. After the solvent has been allowed lime to

KEMPER SVSI^MS, INC., East Coast Ofliee. 1182 Teaneck Road. Suite Tkanauk, NJ Q786S TEL; (soil 833-8898 FAX; (2Q1) 839-8422 E-MAIL: kerrpersV91Caol.com

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