Falling Object Protection – Best Practices from the WTC
As a young man, I started in the construction industry during the NYC building boom of the mid-80’s. I entered the industry at an interesting time; there was a rash of incidents at construction sites, many involving falling objects.
After several serious incidents involving the public, legislation was proposed to attach netting to the existing perimeter cable guardrails to enhance existing falling object protection. Legislation soon became regulation and 42” perimeter rails with secured netting was as common a sight as hard hats.
Fast-forward a few decades. After being absent from the NYC construction scene for many years, I was offered an opportunity to participate in the rebuilding efforts of the World Trade Center. At this point in my career I was well versed in the rules of construction safety as spelled out in OSHA’s 1926 construction safety regulations, but things in NYC were a bit different. There was an additional layer of regulations mandated by the NYC Department of Buildings (DOB) which, as with OSHA’s regulations, are typically created as a result of significant mishaps.
One notable difference upon my return to NYC was that the perimeter cable guardrails now had a requirement of an additional cable at 60 inches with netting secured from the floor to the 60” cable, exceeding OSHA’s 42” requirement. This alone should certainly prevent tools and construction materials from hurtling down onto passersby or other construction workers below, or so you would think. Soon after starting at the WTC site, a high-rise under construction across the street had a number of high profile incidents involving falling objects. This finally led to an extended shut-down until a plan was developed indicating measures that would prevent recurrence. This plan was presented to the DOB and the local Community Board, and when both were content with the protective measures indicated in the plan, it was implemented and work resumed. The project was completed without further incident.
About the time the project across the street topped-out, Tower 1 of the WTC was rising above grade and rapidly going vertical. All parties involved with the rebuild of the WTC were keenly aware of the painful experiences “next-door”, and decided to adopt the protective measures as a lessons learned. These measures, considered best practices as they exceeded code, included;
- Installation of 60” perimeter netting upon completion of metal decking (previously it was installed after the casting of concrete slab).
- Netting extended full height to the underside of the floor above, once concrete was completed.
In addition to these measures, a state-of-the-art perimeter protection system, known as a “cocoon”, was installed around the uppermost floors, continually wrapping where the steel framework was being erected.
Consisting of four floors of netting-clad scaffold frame with an additional 16 floors of fire resistant protective netting trailing below, it was designed to keep workers – and anything else – from falling off. The frame attached to the outside of the building, rising at the same pace as the steel erection.
These measures were also used at WTC’s Tower 4 and Tower 3 (still under construction) and I’m pleased to say that these protective measures were very effective, and are now common practice on high-rise sites in NYC and elsewhere.