TONS OF SEDIMENT REMOVED
NASA Langley Finishes Tabbs Creek Cleanup
NASA Langley Research Center in
Hampton, Va., has completed the cleanup of a creek singled out as
contaminated by the U.S. Environmental Protection Agency
Workers have dug up
and disposed of more than 11,000 tons of sediment from Tabbs Creek
since last November.
The creek, which is a tributary of
the Back River, had been contaminated by the release of PCBs
(Polychlorinated Biphenyls) and PCTs (Polychlorinated Terphenyls)
from the 1950s to the 1970s.
Before the cleanup technicians
measured contamination levels in parts of Tabbs Creek as high as
2,260 parts per million. Now those levels register at less than
five parts per million, well below what the EPA requires for the
protection of human health and the environment.
"We worked hard to plan and
execute this cleanup," said Greg Sullivan, Remedial Project Manager
for the Office of Security and Environmental Management at NASA
Langley. "We finished the project on time and substantially under
budget." Originally estimated to cost nearly $8 million, the Tabbs
Creek project was completed at a cost of $5.5 million.
NASA worked with the EPA and the
Virginia Department of Environmental Quality to formulate the
cleanup plan. "NASA has demonstrated its commitment to cleaning up
Tabbs Creek, adhering to a carefully developed plan. From what we
have seen, the results are excellent," said Stacie Driscoll,
Hazardous Site Cleanup Division Project Manager for EPA Region
NASA hired Foster Wheeler
Environmental Corporation, a nationwide environmental and remedial
cleanup company that has worked with NASA Langley for nearly a
decade, to do the dirty work.
The project presented some unique
challenges. Crews had to remove contaminated mud while protecting
existing wetlands. During excavation the wetlands were protected by
a "silt curtain," a screened fabric that allowed water to pass
through, but stopped sediment and suspended particles from flowing
from one cell to another.
Excavated sediment was taken to a
soil handling area, where it was dried and, when necessary,
stabilized with quick lime. Approximately 9300 tons of sediment,
with PCB/PCT contaminant levels below 50 parts per million, were
taken to the Southeastern Public Service Authority Public Landfill
in Suffolk, Va., and the Bethel Landfill in Hampton, Va. Another
2000 tons of sediment, with levels above 50 parts per million, were
taken to the Chemical Waste Management Landfill in Model City,
After the cleanup workers restored
the wetlands. "We did more than remediation - we enhanced the
site," said NASAs Sullivan. "The area is now completely
green. The wetlands look better than ever."
Crews removed piles of concrete
rubble and "undesirable vegetation" called phragmite, a tall swamp
grass-like plant that has grown unchecked in many areas of the
country. In addition, workers lowered the elevation in a
three-and-a-half acre area of the wetlands to encourage the
movement of more salt water, which discourages phragmite growth.
They also planted shrubs and seeded uplands.
Since 1992, hundreds of samples of
sediment, surface water and animal tissue have been taken from
Tabbs Creek. During the cleanup process, technicians removed 190
"pre-remedial" samples of sediment to further refine the excavation
limits. Another 200 "confirmatory samples" were also taken to
ensure that the contaminants had been reduced to required cleanup
levels. Now that the cleanup is over, the creek and wetlands will
be monitored on a regular basis. Samples from fish, crabs and other
indigenous animals will be taken every six months.
Foster Wheeler has issued a draft
final report documenting the work done and has sent it to NASA
Langley for review. Langley expects the EPA will okay the
cleanups completion by early September.
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