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AUGUST 2021 | SRNS TODAY | 3

Key progress on nuclear legacy

groundwater cleanup at F and H Areas

RS has made significant progress in cleaning up contaminated “The groundwater under the basins is acidic from nitric acid present
groundwater left from legacy nuclear operations near the Site’s in the waste solutions,” said Jeffrey Thibault, SRNS Engineering
S now shuttered F Canyon and the still active H Canyon chemical and Remediation Support. “The acidic property of the water allows
separations facilities, affirming the Site’s continued commitment to some contaminants to remain dissolved and slowly migrate with the
environmental remediation. groundwater towards a nearby stream. Our system uses a wall to
direct the water into open spaces, called gates, where a base solution
For decades, low-level radioactive waste solutions were generated
from operations in F and H Canyons and were disposed in pond-like is injected into the water to increase the pH and slow down the
pools of water known as seepage basins, which was the accepted movement of the contaminants.”
method at the time. However, with advances in waste processing, The environmentally harmless base solution is made by mixing clean
this disposal method became outdated. The last of the basins was water, from the Site’s drinking water system, with a base concentrate
backfilled, capped and closed in 1991; however, 33 years of use and baking soda. A system of pumps, sensors and piping, mounted
had resulted in hazardous and radioactive contamination of the on a small metal skid platform, blends the concentrate with water
groundwater beneath each basin. in precise proportions prior to delivering the solution through
underground pipes to a network of 24 injection wells at F Area. The
After the basins were closed, post-closure care and groundwater wells are turned on when treatment is needed to neutralize the acidic
corrective actions were initiated in accordance with a permit issued by water. Once enough base has been injected, the wells are turned off
the South Carolina Department of Health and Environmental Control. and remain off for a period of 12 to 18 months, until sampling data
Initially, SRS constructed and used two water treatment units to clean shows treatment is required again.
the contaminated groundwater by extracting, treating and reinjecting
the water once clean. However, this method was costly to operate, Since SRNS became the SRS managing and operating contractor in
produced large volumes of radioactive waste sludge that was expensive 2008, 126.4 million gallons of base solution have been injected into
to dispose of, and became less effective as the groundwater cleanup the groundwater.
progressed. In 2004, SRS transitioned to a new, phased groundwater “We’ve seen great results from this method,” said Thibault. “It’s
clean-up approach employing new innovative remedial technologies. effectively a passive system, meaning we only run it when testing
These technologies include installing underground barrier walls, in a shows that the acidity is increasing in the soil again; it’s economically
funnel-and-gate configuration, that redirect and channel groundwater friendly; and, most importantly, it’s environmentally friendly, restores
flow toward base injection zones that make the groundwater less acidic the pH of the groundwater to more natural conditions, and lets
and reduce the migration of contaminants. The new system is a shift nature essentially take care of itself. Restoring the neutral pH of
towards a more passive system that provides for improved remedial groundwater at F and H Areas reduces the migration of hazardous
effectiveness, is more cost effective and does not create radioactive and radioactive metal contaminants in the groundwater and acts to
waste that has to be managed and disposed. protect a nearby stream.”

F Area Operator Thomas Harman and SRNS Scientist Kevin Boerstler check the pumps, sensors and piping that blend
a base concentrate to inject into acidic groundwater at SRS, part of the Site’s environmental remediation strategy.