In 1996 a group of scientists from the National Oceanic and
Atmospheric Association (NOAA) conducted a sediment toxicity survey of 22
estuaries in the United States. Newark Bay in New Jersey topped that list for
concentrations of toxicity. The bay's proximity to high hubs of industry and transportation
(including Newark Liberty International Airport) has meant that is has long
been the receptacle of industrial waste as well as high doses of non-point
source pollution.
When Continental Airlines opened its much awaited Global
Gateway at Newark Liberty International Airport in late 2001, airline
passengers reveled in the improved traffic flow, easier check-in and arrival
procedures, increased gate capacity (by nearly 50 percent) and award-winning
concessions featuring mall-style retailers and an international food court.
Terminal C, the centerpiece of the $1.4 billion expansion of Newark Liberty
also included some cutting edge stormwater treatment technologies to 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 potentially can 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. Expanding the terminal area for Continental's new Global Gateway
included increasing the paved areas around the terminal to accommodate the new
taxiways and roadways. Stormwater runoff volumes increase as a result of the
additional impervious surfaces, and so does the resultant non-point source
pollution.
Expansion
The expansion of the terminal triggered the need for
stormwater permits. The Phase I rules of NPDES required that runoff be treated
to ensure that oil/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 from the paved
terminal and parking areas was directed to a nearly 60' wide peripheral ditch
that led to a pump station that discharged the water directly into Newark Bay.
Now, stormwater from the site is directed first to a stormwater treatment train
that will remove solids such as sediment, debris and hydrocarbons such as oil
and fuel, before being released into the ditch.
Due to the size of the treatment area, the storm flows from
the paved areas around the terminal will be quite large. Therefore, runoff is
conveyed via a 66" pipe that can handle flows of up to 80 cubic feet per
second (cfs). The water hits a flow-splitting device that routes the runoff to
two separate treatment systems. Project engineers designed the treatment train
to incorporate two cast-in-place hydrodynamic separators from Vortechnics,
Inc., Scarborough, Maine, combined with four oil and water separators from
Highland Tank, Stoystown, Pa.
Stormwater runoff from the paved areas of Terminal C is
directed first to the pair of hydrodynamic separators that have been shown in
field tests to remove 80 percent of total suspended solids (TSS) on a net
annual basis. These systems use a combination of vortex motion, flow controls
and a series of baffle walls to help trap floatable oil and gas while also
capturing sediment that has been shown to carry other pollutants such as lead,
zinc, cadmium and copper. Full-scale laboratory tests of the system have
consistently demonstrated that the unit is capable of removing particles down
to 50 microns. Because the system can be cast in place, it was the most
practical system to install to handle the large flows from the site. Each of
the Vortechs systems is 18' wide by 30' long, and 9'3" deep. 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," said Francis Tighe, vice president of Vortechnics. "We
designed each of the roof slabs for the cast-in-place units 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 these systems, the stormwater enters one
of four oil and water separators to further remove oily contaminants from the
stormwater. The tanks for the oil and water separators were specially
constructed of 3/8" steel with 1/2" by 6" reinforcement rings to
ensure the tanks could withstand pressure from the burial depth and surface
loading. This combination of systems is designed to reduce oil concentrations
to 10 ppm.
The two systems complement each other, with the hydrodynamic
separators helping to optimize the coalescing capacity of the oil and water
separators. The result is that water discharged from the units into the
perimeter ditch is now free of most of the solids and debris carried from the
roadway in stormwater and the oil is reduced to 10 parts per million. From the
ditch, the cleaner treated water is pumped into Newark Bay.
Installation
Installation of the huge stormwater treatment systems at
Terminal C was complicated by heightened airport security. The large Vortechs
Systems, made of concrete that had to be cast in place at the job site, were installed
in the fall of 2001.
"Getting the trucks and workers onto the job site
became much more difficult because security was so tight," said Henry
Meyers, president of Anselmi and DeCicco, Inc., the general contractor for the
job. "Every truck had to be escorted to the site by security
personnel."
In addition, Meyers said that the underground installation
of the units happened while the airport was operational. This meant 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' deep. The aircraft's wing came within 20' of the excavation site, and
it wasn't feasible to just dig a big hole in the ground," he said.
The wheel loading for a Boeing 747 is quite large, so care
was taken to keep the taxiway far away from any soil that could give way. In
addition, a big exposed hole in the ground could result in the jet engines
sucking debris from the hole.
"So we ended up using sheeted excavation to help
maintain the integrity of the taxiways and keep the construction zone compact.
By driving steel sheeting for excavation with internal bracing, we could keep
the hole as small as possible," Meyers said.
Once installed, the stormwater treatment systems were
covered by tarmac and are accessible for inspection and maintenance from grade.
Quarterly inspections are recommended during the first year, followed by annual
inspections and cleanout with a vacuum truck to remove accumulated 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.
Airport sites in general pose a variety of environmental
challenges in terms of air and water pollution. The stormwater treatment
systems in place at Continental's 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.
