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Microplastics found in multiple Front Range watersheds

The headgate that diverts some of Boulder Creek after it flows under Broadway in downtown Boulder, Colorado.
Sam Fuqua
The headgate that diverts some of Boulder Creek after it flows under Broadway in downtown Boulder, Colorado.

Plastic is almost everywhere through its presence in packaging and all kinds of products.

Little bits of it end up in our natural environment, including in the water. 

Scientists call them microplastics, and they're showing up in many places, including the Boulder Creek Watershed.

Rob Runkel is sitting next to Boulder Creek describing what sees in waterway where it flows under Broadway in the heart of downtown Boulder.

He’s a research hydrologist with the US Geological Survey.

“There’s a full gallon milk jug, for example, sitting there, and some smaller pieces of plastic and other debris,” he says.

“And, the basic thing with microplastics is that most of them start out as macroplastics. We buy things at the store and just over time, they break, and they become smaller and smaller.“

This is an important spot in the creek’s journey down from the Rocky Mountains out to the eastern plains.

The creek splits here. On one side is the pond, where the milk jug and some other trash is floating—part of the creek flows on from there.

On the other side is a big metal plate and that opens to let water into another channel.

“So we have what’s called a head gate,” says Runkel’s colleague Sheila Murphy.

She’s also a research hydrologist with the Geological Survey.

“A colleague of mine said it looked like a guillotine, so I laugh when I see it now that it makes me think of that. When (the gate) is open, water moves out and is used for other agricultural, urban water supply, etc.”

They’re both co-authors of a study published in May that examined the movement of microplastics through Boulder Creek and South Boulder Creek.

The hydrologists teamed up with microplastics researchers at the University of Birmingham in England.

They sampled at multiple points along both waterways.

They found higher concentrations of microplastics in Boulder Creek once it flowed into the city—about four times as much as in South Boulder Creek.

It’s less urbanized—it flows through more rural parts of southwestern Boulder County before meeting up with Boulder Creek on the east edge of town.

Runkel says this study adds new information on the important role manmade diversions play in the movement of microplastics in waterways.

“All the kind of the thinking about microplastics globally is that everything gets flushed into the ocean,” he said.

“Through this paper and this work we’re showing very clearly that some of the microplastics that get in the surface water is just there for a short time and then it gets diverted for agricultural or human use.“

If the water is diverted for agriculture, that’s likely to disperse the microplastics even further.

They end up in the topsoil that gets blown around or in the water that runs off the fields during irrigation, sometimes into a different waterway.

But if the water is diverted for drinking, the microplastics will be filtered out at a facility like the City of Boulder’s Betasso Water Treatment Plant, in the foothills a few miles west of town.

Up to 40 million gallons of water can be treated here everyday.

The water goes through a series of rectangular pools.

Some of it’s pretty murky, with brown foam floating on top.

In other pools, the water is clear.

Kate Dunlop, who works on source water protection for the City of Boulder, explains the process:

“Coagulant polymer is added to the raw water which settles out larger suspended sediments or solids. Then the cleaner water is brought through filters where it filters through layers of sand and anthracite that further removes any solids. And all of those solids are then pressed so that they’re more like a wet mud. And they are shipped out on a dumpster to Western Disposal and they go to a landfill,” she said.

That soggy mud that goes to the landfill contains a lot stuff we don’t want in drinking water, including microplastics.

Water treatment manager John Stoddard says it’s not clear where in the filtration process the microplastics are being removed.

“We don’t have data to demonstrate the degree to which microplastics are being removed through any of our treatment processes,” he said.

“I think all we know is that microplastics have been detected in our source water, but they are not detected in our finished water. So they are being removed via the treatment processes. We’re not exactly sure which process is providing the removal to what degree.”

Plenty of contaminants are subject to legal limits in drinking water—heavy metals, bacteria, various chemicals—but not microplastics or their even tinier cousin, nanoplastics.

But the City of Boulder is part of a consortium of water utilities on the Front Range that monitor microplastics and other unregulated substances that they call Contaminants of Emerging Concern.

“And through that, we monitor every year, three or four times a year, for about 150 plus emerging contaminants such as pharmaceuticals, pesticides, herbicides, hormones. and personal care products,” said Dunlap.

Scientists aren’t the only ones sampling Boulder Creek for microplastics.

They teamed up with Environment Colorado and high school students to collect water samples from Boulder Creek and other rivers and streams earlier this year.

Their study looked at 16 waterways along the Front Range, some of them more pristine creeks, others urban.

They found microplastics in all of them.

Danny Katz is Executive Director of the Colorado Public Interest Research Group or COPIRG.

Katz says he was not surprised that they found microplastics in every waterway.

“Almost anything that’s plastic can break into these microplastics eventually,” he said.

“So it could be a single-use plastic bag, it could be those foamy cups and containers, some of our clothing have bits and pieces of plastics in it, so those plastic microfibers, all the packaging that comes wrapped around basically anything we order nowadays.”

Even a hiker or camper trying to observe the outdoor ethic of “leave no trace” could be depositing microplastics in the wilderness.

That synthetic fleece jacket sheds microfibers.

So does that plastic tarp you lay on the forest floor under your tent.

Some of those fibers end up washing into the closest stream with the rain or the melting snow.

They can also end up in the stomach of a bird or animal.

So while we can filter microplastics out of our drinking water by the current detectable standards, we can’t remove them from the environment once they’ve ended up there.

Katz says a big part of the solution lies in government and corporate policies that reduce our use of plastic.

“There are different ways, either through funding or setting guidelines that states and local governments can act,” said Katz.

“And there’s also ways that companies can make sure they’re looking at their own products and figuring out ways to reduce the amount of plastic they’re wrapping things with, or just the kind of microfiber plastics that are in clothing.”

Katz points to legislation that will come into effect January 1, 2024, prohibiting most retail businesses from using styrofoam containers and single use plastic bags, with some exceptions.

This story was shared via Rocky Mountain Community Radio, a network of public media stations in Colorado, Wyoming, Utah and New Mexico including KDNK.

Sam Fuqua