Source: http://omahanewsstand.com, July 28, 2011
By: Rachael Ruybalid
A groundwater contaminant at the former Nebraska Ordnance Plant wandered where it wasn’t wanted this spring.
During quarterly sampling in January and April at the perimeter monitoring well 116, trichloroethene (TCE), a solvent, was discovered in amounts exceeding the federal drinking water standards.
“We suspect an irrigation well pulled it that way,” Corps of Engineers Project Manager Kristine Stein said.
Because monitoring well 116, near the intersection of Johnson Creek and Clear Creek, is only located about 400 feet outside of the main contaminant plume, there is no reason to panic, Stein said. Once the drift was discovered, extraction well one was set to increase its pumping to its maximum rate of 191 gallons per minute in an attempt to bring the contaminated groundwater out of the perimeter monitoring well area.
So far, it seems to be working.
The level of contaminant in the monitoring well is already down from what it was.
“The extraction well is doing its job and the plume is in containment,” Stein said.
Stein added that none of the residential wells in the area were impacted by the escaped TCE.
The U.S. Army Corps of Engineers conducted its annual site tour and open house at the former NOP near Mead on July 20. The guided bus tour went around to several locations at the NOP site with representatives from the Corps and the Corps’ contractor, ECC, available for questioning.
The first stop on the tour was the main treatment plant. Plant operator Vince Stallbaumer explained how the contaminated water is pumped in, treated and then pumped back out to Clear Creek and Wahoo Creek. During irrigation season, two area farmers and the University of Nebraska, have permission from the Lower Platte North Natural Resources District to tap into the lines and use the treated water to irrigate their fields, Stallbaumer said.
The next stop in the tour was the load line four treatment plant and the advanced oxidation process (AOP) treatment plant.
The load line four treatment plant treats contaminated water by pumping it through an air stripper that removes the TCE from the water.
The AOP treatment plant uses an advanced oxidation process where the water is injected with ozone gas.
The water and gas then get mixed together and hydrogen peroxide is injected into it. The process turns the TCE into carbon dioxide, water and a little bit of chlorine, Stallbaumer said.
“It’s the heavy lifter in mass reduction,” Stein said.
The oxidation process also treats the royal demolition explosive (RDX) that is mixed in the groundwater with TCE but it only reduces it by half. The rest of it must be removed by pumping the water to the main treatment plant.
The third stop on the tour was the Accelerated Remediation Technologies well that is funded by Dow/General Dynamics. At the well, compressed air is pumped to the bottom of the well and then bubbled up, said Environmental Protection Agency representative Ken Rapplean.
“It’s basically an underground air stripper,” he added.
The TCE gases that bubble up are then captured and removed.
The tour drove by the two areas where pilot treatment studies are being planned.
The two studies will look at different ways of treating the contaminated groundwater in-situ, or in the ground.
“It’s an effort to shorten remedial time frames,” said ECC Hydro Geologist and Task Manager Dave Dander.
The two pilot treatment areas will hopefully be up and running by the fall of 2012, he added.
A special drive through the former atlas missile area was next on the tour. There are three above ground missile silos and a launch control building at the location. Currently the area is licensed to the Nebraska National Guard to use as a training site.
The last stop on the tour was focused extraction well 15. The well is close to the center of the TCE plume and extracts groundwater with high concentrations of TCE. The groundwater is then pumped to the load line four groundwater treatment plant and treated.
All of the contaminants are the results of NOP operations in the 1940s and 1950s.