Like the rest of the region, the rain started soaking into the ground at Rocky Flats on Monday, Sept. 9. By the following Wednesday night, the ground was fully saturated and the flooding began in earnest, with runoff from the hills, gullies and holding ponds at the site, filling North and South Walnut Creeks as well as Woman Creek beyond their capacities.
As the water finally began to recede, the debris caught in the fences above the usual creek banks bore witness to the unprecedented water levels that had swept through the area between Wednesday night and Saturday morning.
The water washing across the four square miles of land at Rocky Flats had raced down the creeks and dry washes and off the property towards the lakes and housing additions to the east, closing Indiana Avenue and raising concerns and more than a few questions.
Was there contamination in the floodwater and, if so, what kind and at what levels? And is the threat of contamination spreading due to the rains now over?
At least some of the answers to these questions will likely come sometime around Oct. 11, when the Colorado Department of Public Health and Environment (CDPHE) estimates that it will get back test results from two labs that examined samples from the 10 surface-water monitoring stations at the Flats, most of which are located along the Walnut and Woman creeks. But will these test results answer all the questions being raised? Considering the long history of Rocky Flats and the ongoing, 30-plus years of controversy surrounding its contamination and cleanup, it seems unlikely.
Rocky Flats is a former nuclear weapons production facility just south of Boulder that operated from 1952 to 1992.
At one time, prior to its closure and remediation, the former plant and the lands surrounding it were considered one of the most contaminated places in the world. The area’s ground and surface waters are still being monitored today for radiation, and there are measurable levels of plutonium, Americium and uranium in some locations at the site that exceed Environmental Protection Agency (EPA) standards.
Other contaminants at the Flats include PCBs and carcinogenic BTEX contaminants, named for benzene, toluene, ethylbenzene and xylene.
In addition, groundwater recovery systems designed to capture uranium and nitrate contamination that has leaked into groundwater are in place to strip out the contamination before allowing the groundwater to be released into the area’s creeks and lakes.
And finally, critics of the government’s remediation of Rocky Flats, including the Rocky Mountain Peace and Justice Center, claim that plutonium contamination well above normal background levels can still be found in the surface soils at Rocky Flats in widespread locations across the area, including, according to tests commissioned by RMPJ in 2012, outside the site’s eastern boundary along Indiana Avenue, where a privately funded toll road, the Jefferson Parkway, has been proposed for construction.
The following is an overview of what is known to have occurred at Rocky Flats due to the flooding, concerns about what may have occurred, and possible future problems that could arise as a result of the September floods.
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Shortly after the flood, several news outlets, including Denver television station Fox 31, reported that a cap covering a landfill at Rocky Flats had cracked due to the flooding and that emergency repairs were under way even as the rain was falling. No further details were offered.
Rocky Flats in 2007, after cleanup. | Photo courtesy of the EPA
The station, aided by Dr. Jeffrey King of the Colorado School of Mines, later tested for radiation along the creeks where the water coming from the Flats had passed and reported that nothing alarming was found.
As for the cracked landfill cap, there are two former landfills at Rocky Flats. One is known as the original landfill (OLF) and the other is referred to as the present landfill (PLF).
According to Carl Spreng, Rocky Flats coordinator for the CDPHE, both of the landfills are capped, but with differing types of caps for different purposes.
The PLF cap is a combination of clay and waterproofing materials designed to prevent rainwater from infiltrating the landfill beneath the cap, an outcome that would likely cause groundwater contamination that could spread from the PLF, eventually making its way into area surface waters.
The primary contaminant of concern in the PLF, according to Spreng, is benzene, one of the BTEX compounds. As a result, a waterproof cap is needed because BTEX contaminants are easily transported long distances in groundwater. Spreng says that no plutonium or other radioactive contaminants are in the PLF, and that the cap on the PLF was not the one breached during the flood.
The top of the OLF is what actually cracked. Although news reports referred to a “cap on a landfill,” what actually cracked was not a cap but the cover over the OLF, which is made of earth. According to the Department of Energy’s Rocky Flats Site Manager Scott Surouchak, “cap” is a term describing a federally required waterproof covering under the RCRA laws such as the one over the PLF. He says that the dirt top over the OLF predates the Resources Conservation and Recovery Act (RCRA) and can only be referred to as a “cover.”
Spreng says the OLF cover is made of dirt and was not designed to be waterproof. The primary contaminants of concern in the OLF are polychlorinated biphenyls (PCBs). PCBs are not easily soluble in water and tend to cling to soil. They can migrate, however, in water along with soil that is being swept away. They are also easily re-emitted to the air and can travel long distances before settling or being driven down by rain, according to the EPA and the Oregon Department of Environmental Quality.
This explains the need to quickly repair the OLF cover following the flood. Spreng says that the OLF cover will likely be re-engineered in coming weeks because it was already sagging in some spots.
Surouchak says that the Department of Energy has no plans to test for potential PCB releases because the levels in the OLF years ago were already very low and looking for PCBs would be pointless.
Another potential, but by no means substantiated at this time, source of contamination resulting from the floods could be the release of sediments from the three remaining holding ponds at the Flats, which are located on North Walnut, South Walnut and Woman Creeks.
According to a 1996 technical report titled Characterization of Releases to Surface Water From the Rocky Flats Plant, in 1972-73 the three holding ponds were drained and reconstructed. During this draining process, the levels of radioactivity found in the creeks increased 80-fold as a result of sediment-heavy waters containing plutonium being released from the ponds to the creeks.
Plutonium is heavy and not particularly water-soluble, so it tends to collect in sediment at the bottoms of ponds and creeks, or in the sediment of the lakes where the creeks eventually deposit their waters.
This explains why there are still low levels of plutonium in the top 12 inches of sediment in both Stanley Lake, which receives water from Woman Creek, and Great Western Reservoir, which gets its water from the two Walnut Creeks. Neither reservoir has been used as a city water supply since the 1990s due to the discovery of contamination originating from Rocky Flats.
During the September floods, the water levels in the three current holding ponds rose extremely fast and approached overtopping the spillways but did not do so, according to Spreng.
“It reached up to the overflow but then drained off quickly without ever going over. But it doesn’t really matter, the water all goes to the same place anyway. It was drained off into the channels to the creeks where it is monitored,” he says.
The question of whether or not the rapid rise and equally quick draining of the holding ponds could have caused the release of sediments from the ponds and whether there was any contamination in that sediment could be answered by the upcoming release of the CDPHE’s creek monitoring results.
Surouchak says that while it’s certainly possible that plutonium in the pond sediments could have been released by floodwaters, he doesn’t believe that it is of much concern because the levels of plutonium in the sediment have been tested and are near or even below background levels. But the ponds are not the most likely area to have released plutonium into the watershed.
The easiest pathway for plutonium to have left the Rocky Flats site during the flood was simply by way of surface soils being washed away by the incredible amounts of rain that fell over the five-day period. That’s because, according to a recent test, plutonium levels on top of and in some of the soils at the Flats are just as prevalent today as they were decades ago.
In 2012, the Rocky Mountain Peace and Justice Center, which has been monitoring the operation and cleanup at Rocky Flats for the past 30 years (see related story, page 15), commissioned a study to determine how much plutonium was still in the soil at the site.
Because they were not allowed to sample on the site itself, the samples were actually taken outside of the fence line on the east side of the Flats, along Indiana Avenue. According to RMPJ, the plutonium levels were just as high in 2012 as they were 40 years earlier, before Rocky Flats had ever been cleaned up.
If true, this would mean that nearly all of the water leaving Rocky Flats during the flood was quite possibly contaminated with small quantities of plutonium.
Surouchak disputes the claims of the 2012 RMPJ study, saying that it was done with an optical rather than radiological analysis and was therefore inapropriate for determining the true levels of plutonium in surface soil.
He does say that the rains left “two inches of sheet water just flowing across the prairie” during the floods.
But when it comes to measuring any contaminant in moving water, the more water that’s flowing, the more diluted the contamination becomes, and the less likely it is to be measured as it passes by a monitor. For that reason, it is quite likely that the CDPHE monitoring stations along the creeks, which saw unprecedented water flows, will find no increase in contamination at the time of the flood, even if the amount of contamination leaving the site had actually increased during the flood.
In fact, it’s quite possible that even the lone monitoring station that, for some still unexplained reason, frequently shows spikes in both plutonium and Americium levels in surface water may well show a decrease in contaminant levels during the flood event itself.
Because of the obvious, temporary dilution from flood waters, the time for accurate testing to determine if contamination was released is actually now, after the flood, under more normal conditions. If plutonium was being transported in floodwaters, the evidence of such movement could likely be found today in the area’s creek and lake sediments or even the drainage ditches along Indiana Avenue.
Surouchack says the DOE has no plans for any additional testing because the levels since the completion of the Cleanup have been so low.
Uranium is another issue at Rocky Flats. While plutonium is heavy and not likely to travel far in groundwater, uranium is the opposite. Uranium is quite soluble and is already contaminating groundwater at Rocky Flats, groundwater that has to be captured and cleaned by way of an expensive, ongoing remediation process.
There is no question that the long, lingering rains of September and the subsequent floods have caused a flushing of sorts in our groundwater aquifers. For that reason it is imperative that the groundwater uranium capture system at Rocky Flats should be rechecked to determine that groundwater pathways weren’t temporarily shifted during the rains and floods, allowing contaminants to bypass the system.
And finally, any massive infiltration of rain such as what occurred in September has the potential to drive old contamination to groundwater, whether it is by getting under caps/covers over pits and landfills or simply by leaching through long-ago-contaminated soil on its way to the underlying aquifer.
Considering that such groundwater normally only moves towards its eventual connection to surface water at a rate of a few feet per year at Rocky Flats, according to the CDPHE, some contamination resulting from September’s rains and floods may not show up in the groundwater and surface water monitoring systems at the site for quite some time.
What happened at Rocky Flats has been called a 1,000-year event. So it’s not likely that we will know or understand all of the implications of such an event for quite some time.