World Trade Center

Site of Former World Trade Center Towers
Services: Demolition and Erection Plans, Permanent Splice Design, Temporary Platforms​
Location: New York, New York
Owner: The Port Authority of New York and New Jersey
Contractors: Various

Siefert Associates, LLC has been engaged with numerous projects since 2007 at the locations of the former World Trade Center towers in Lower Manhattan. Siefert Associates, LLC has provided a variety of construction design support for multiple contractors including American Architectural, Atlantic Hoisting & Scaffolding, DCM Erectors, EE Cruz, Gramercy Group, Granite Construction, Navillus Contracting, O’Kane Electrical, Peri Formwork Systems, Phoenix Construction, Skanska, Tutor Perini Corporation, and Yonkers Contracting Company. Typical scope of work completed at this location includes demolition and erection plans, slurry wall analysis, temporary support, crane platforms, protective shields, analysis of existing structure under construction equipment loading, temporary retaining wall design and dunnage analysis. This momentous project has presented numerous organizational and scheduling challenges due to the mandates for existing PATH and NYCTA train schedules and the coordination between the numerous contractors working on site. Notably, Siefert Associates, LLC designed the trestle bridge, locally dubbed “The Siefert Bridge”, which created crane access for the installation of the memorial slab.



East Box Girder Concrete Duct Design

World Trade Center PATH Hall

Services: Reinforced Concrete Design

Contractor: Skanska/Granite/Skanska

Owner: Port Authority of New York and New Jersey

Status: Completed


As part of a Value Engineering initiative, Siefert Associates, LLC dedicated a team of engineers and CAD operators to successfully design and detail a very large (20’ x 12’) reinforced concrete duct.

In case of emergency, ventilation of superheated air (exhaust) and fresh air (intake) will be provided for the World Trade Center’s PATH Hall through the duct conveniently located within a large steel box girder. The Value Engineering Alternative was enacted to change the material from steel to reinforced concrete to lower costs, improve completion time, and eliminate the need for expensive fire-resistant paints. It was decided that “shotcrete” would be the most efficient and cost-effective method for applying the wet concrete due to the site constraints and the limited access to the girder to erect formwork.

Siefert provided construction engineering drawings and calculations to the client for the East Box Girder and its internal Concrete Duct Design. The concrete duct design has contributed to making the PATH commuters safer and more protected than ever before.








Connecticut Office: 180 Church Street, Naugatuck, CT 06770                                                                                                   

New York Office: 188 East Post Road, White Plains, NY 10601                                                                                                                                            © 2017 by Siefert Associates, LLC ​