Wastewater Treatment Plant

Watch our video introduction to the water cycle at Sanford Lab.

Video by Nick Hubbard and Erin Broberg.

The journey begins with a single drop

It appears seemingly out of nowhere: a gently flowing waterfall just to the left as you drive from Deadwood to Lead. It’s a lovely sight, really, and people stop to admire it, pose for photos and even shower (seriously). But it isn’t a waterfall. It’s the effluent from the Sanford Underground Research Facility’s Wastewater Treatment Plant. The waterfall begins with a single drop of precipitation that makes its way deep underground, a fascinating journey that brings it full circle.

Where does the water come from?

When it rains, the Open Cut acts like a big funnel, bringing a lot of water underground—every inch of precipitation is equal to roughly 3 million gallons of water coming into the underground. It is also likely that there is some infiltration from ground water.

“We don’t know how much water actually comes into the underground,” said Ken Noren, foreman of the Wastewater Treatment Plant. “We can’t track every inch, but we monitor what comes in on the 2000 Level—right now, it's about 155 gallons per minute. At that rate, we can estimate that 650 gallons per minute comes in throughout the whole facility.”

But that amount can change depending on the amount of precipitation. As water enters the facility, it collects in a deep pool and must be pumped out.

Pumping the water out

The water level underground is at about the 5900 feet; however, a recently completed water inflow project allows some of the water to be collected at higher levels. The pumping system includes a deep well pump (6200 feet), and pumping stations on four levels—the 5000, 3650, 2450 and 1250.

“Having several pumps throughout the underground allows us to reduce pressure and gives us more control over the amount of water pumped,” said Tim Baumgartner, infrastructure director.

As water comes in, it is collected, stored and eventually pumped up to the surface. Approximately 700 gallons of water per minute are pumped from underground to a surface reservoir where it awaits the treatment process.

5.7 billion

Gallons of water pumped from the underground between 2008 and 2024.

9.7 Billion

Gallons of water treated between 2008 and 2024.

The reservoir

"The water that comes out of the underground is about 98 degrees Fahrenheit—too warm to be released into Gold Run creek," said Doug Coolley, an operator at the WWTP. But the bacteria love the warm water. “It needs to be no lower than 46 degrees to keep the bacteria happy and no higher than 75 degrees to be released into the creek.”

Once in the reservoir, the water is mixed with water from Grizzly Gulch, Barrick Gold Corporation’s holding pond for the tailings left over from mining operations. That water is as low 32 degrees in winter months.

Coolley and other operators use a formula to ensure the temperature falls where it should, then constantly monitor everything. “It’s a matter of balancing the flow from Grizzly Gulch and the flow from underground. We adjust that formula as needed.”

Treating the water

The water that comes from underground isn’t toxic, but it does contain dirt and some suspended solids, like iron. "We want to make sure all of that is removed before we release the water into the creek,” Noren said.

Sanford Lab samples the treated water daily to ensure it meets EPA standards, but it’s also a predictive test, Baumgartner said. “If we see variances in the water samples, it allows us to diagnose and correct any problems.”

The Lab also regularly monitors the health of the creeks, counting fish and macro invertebrate populations. In 2023, the WWTP was recognized for the fifteenth consecutive year by the South Dakota Department of Agriculture and Natural Resources (DANR) for its “outstanding operation of the wastewater system and environmental compliance” with DANR’s Surface Water Discharge Permit Award.

Water treatment step-by-step

1. Filters

From the reservoir, the water goes into the Yardney multi-media filters, where it runs through four layers starting at the top with anthracite coal, fine garnet, coarse garnet and, finally, clean gravel. As it filters through to the bottom, more and more impurities are removed. Once a day, the filters are backwashed to prevent blockage.

2. Sludge Tank

From the storage tanks, the water is moved to the sludge tank where it is mixed with a coagulant that neutralizes the charge of the iron particles and a flocculant, or clarifying agent, that causes the iron to form into clumps that settle to the bottom of the tank. The sludge layer is pumped out and the water goes to the next step in its journey.

Three people next to RBCs at the water treatment plant

3. Rotating Biological Contactors

Once the iron is removed, the water runs through 18 rotating biological contactors to remove ammonia and any remaining heavy metals (ammonia comes from the tailings from Grizzly Gulch). Each RBC houses millions of tiny, very hungry bacteria that thrive on these impurities.

“The bacteria need the same things we do—they just eat different things. They eat ammonia like you’d eat a cheeseburger,” Noren said.

In 2024, the RBCs will be replaced with a new Moving Bed Biofilm Reactor, or MBBR. The ammonia nitrification process by bacteria will be nearly similar to the RBC process. However, instead of growing on rotating discs, the bacteria will grow on specialized MBBR bio media and float around in an aerated water treatment tank.

Pumps used to move water to the polishing filters

4. More Filters

These pumps move the water to the polishing filters.

From the RBCs, the water goes to the Baker Filters where it “polished” to move any remaining impurities. These pumps are now only used four minutes a day to provide the extra water pressure needed to back wash the Baker Filters. A new bypass water line allows a gravity flow system to move about 1,200 gallons per minute.

Finally, the water is ready to be released into Gold Run Creek.

The start and end of the effluent waterfall.

5. Effluent

For decades, the creeks in this neck of the woods were gray and lifeless. But the WWTP changed all that. Today, they are teeming with trout, mayflies and microbial life.

“Cleaning the water is part of our permit, but we would do it regardless because we want to be responsible stewards of the environment,” Baumgartner said.

So, when you see that waterfall, by all means stop and admire it, take a photo. It is a testament to SURF’s commitment to the environment. And it really is pretty.

But maybe leave the shower for the hotel room.