- Cast-in-place Vortechs® System
In 1996, scientists from the National Oceanic and Atmospheric Association (NOAA) conducted a sediment toxicity survey of 22 estuaries in the United States. Newark Bay topped the list. The bay’s proximity to hubs of industry and transportation – including Newark Liberty International Airport – had long made it a receptacle of industrial waste and high doses of non-point source pollution.
When Continental Airlines opened its Global Gateway at Newark Liberty International Airport, airline passengers reveled in the improved traffic flow, easier check-in and arrival procedures, increased gate capacity, and award-winning concessions. But Terminal C, the centerpiece of the $1.4 billion expansion, also included cutting edge stormwater treatment technologies that help remove pollutants from the runoff of the airport’s roadways, runways and airplane taxiways prior to discharge into Newark Bay. While few will ever see the technology now buried beneath the tarmac of the airport’s taxiways, the system demonstrates the effectiveness of applying stormwater treatment technology to an already congested area where competition for space is fierce.
Airports generate enormous amounts of polluted stormwater runoff. In addition to hydrocarbons such as oil and fuel from cars, trucks and planes, winter weather brings added sand and salt to the roadways. The terminal area expansion for Continental’s new Global Gateway increased the paved areas around the terminal to accommodate the new taxiways and a new roadway, causing increased stormwater runoff and the resultant non-point source pollution.
The expansion triggered the need for stormwater permits under Phase I of NPDES, requiring that runoff be treated to ensure that oil and hydrocarbon concentrations did not exceed 15 parts per million (ppm), and that solids be reduced through treatment down to the 50 micron particle level. Prior to the expansion, stormwater was directed to a peripheral ditch that led to a pump station and discharged into Newark Bay.
Due to the size of the treatment area, the storm flows from the paved areas around the terminal will be conveyed via a 66-inch pipe that can handle flows up to 80 cubic feet per second (cfs). The water hits a flow splitting device which directs stormwater runoff from the paved areas of Terminal C first to a pair of cast-in-place Vortechs systems. Each system is 18-ft wide, 30-ft long, and 9-ft 3-in deep, and capable of handling the large flows from the site. Because the units are buried under taxiways for the terminal, they had to be constructed to meet B-747- 400 Aircraft loading requirements.
It is somewhat uncommon for treatment equipment like this to be buried under pavement requiring the kind of load bearings necessary for a 747. Because of that the roof slabs of the units were designed with a steel cross beam to help meet the loading specifications. And there are steel reinforced concrete columns in the baffle walls of the units for additional structural strength.
After treatment in the Vortechs Systems, the stormwater enters one of four oil and water separators to further remove oily contaminants from the stormwater. The combination of the Vortechs Systems and the oil and water separators reduces oil concentrations to 10 ppm, which is five ppm less than dictated by the permit. The result is that water discharged into the perimeter ditch is now free of most of the solids and debris and oil and grease is reduced to 10 ppm. From the ditch, the treated water is pumped into Newark Bay.
According to Henry Meyers, general contractor for the job, and president of Anselmi and DeCicco, Inc., the underground installation of the units happened while the airport was operational. Consequently, work had to stop any time a plane traveled near the excavation.
“We had to install these huge units into a hole that was 22 feet deep…it wasn’t feasible to just dig a big hole in the ground,” he said. “The wheel loading for a Boeing 747 is very large, so we wanted to make sure that the taxiway was far away from any soil that could give way. Plus, we didn’t want to have a big exposed hole in the ground and have the jet engines sucking debris from the hole.” They used sheeted excavation to help maintain the integrity of the taxiways.
Once installed, the stormwater treatment systems were covered by tarmac and are now accessible for inspection and maintenance from grade. Quarterly inspections during the first year were recommended, followed by annual inspections and cleanout with a vacuum truck to remove sediment and debris as needed. The oil and water separators include a corrugated plate to trap solids and oil coalescing material to trap oil, both of which should be inspected every six months and power washed as needed.
The stormwater treatment systems in place at Continental’s new Global Gateway at Newark Liberty Airport demonstrate how new stormwater treatment technologies can help control non-point source pollution and ensure cleaner water, even in highly industrialized areas.
- Cast-in-place Vortechs® System