Urban rivers keep cities cool, but many are too dirty for swimming

BOULDER, Colo. — Michael Lawlor circled the lot at Eben G. Fine Park searching for a place to park. It was lunchtime on a Tuesday, but the summer’s first blast of 90-degree heat had drawn hordes of swimmers, sunbathers and call-out-sick-ers to the banks of Boulder Creek.

Come spring, snowmelt rolls off the Indian Peaks and races down Boulder Canyon. When the water tumbles through town, kayakers and tubers launch themselves into its current. On hot days, the creek is an elixir, shocking swimmers from their heat-induced stupor.

“It's one of the last free opportunities to cool down during these longer, hotter summers,” said Lawlor, who works as the urban water quality program coordinator for the City of Boulder.

Statewide, economists estimate that river recreation contributes $2-3 billion dollars into the economy every year, but many rivers are too dirty for safe swimming. The South Platte River, for example, continues to struggle with high E. coli levels, despite upgrades to Denver’s wastewater utilities along the river.

In addition to tubing and swimming, the river is a popular spot for anglers.

Michael Maestas (left) and his friends tube Boulder Creek in early-June.

Patrick Mulholland and Quinn Farrell pilot their inflatable packraft down Boulder Creek in early-June.

During spring runoff, high water levels can make Boulder Creek dangerous for swimming and tubing.

Since 2004, the Colorado Department of Public Health and Environment has listed Boulder Creek as impaired for E. coli bacteria. That means concentrations of E. coli bacteria periodically exceed state standards. Although most strains of E. coli are harmless, certain types can lead to gastrointestinal symptoms, such as nausea, vomiting, stomachache, diarrhea, headache and fever.

Despite the city’s robust monitoring program, which collects monthly water quality samples at six locations along the creek, and more frequently during late summer and early fall, addressing sources of E. coli contamination is difficult. Bacteria are highly dispersed and concentrations fluctuate frequently.

E. coli bacteria can enter the stream through runoff or stormwater outfalls. Major sources of contamination include scat from wildlife, pet waste and human poop. Improper trash and sanitation practices, over-watering and chemical spills can worsen the problem. For example, grease that enters waterways can attract wildlife and increase bacterial growth.

The City of Boulder has collected water quality data for more than 30 years. Long term trends indicate that E. coli concentrations remain relatively stable. Bacteria levels tend to increase as you move downstream through the city and peak in late-summer and fall when lower flows and warmer water temperatures are favorable for E. coli.

“We don't see we don't see a direct correlation in our data of increased camping along the creek and increased E.coli in Boulder Creek,” said Lawlor.

Michael Lawlor, urban water quality program coordinator with the City of Boulder, readies his equipment to test Boulder Creek bacteria levels.

Lawlor wears fishing waders to test the water. Right: Lawlor uses an aquatic probe to test the creek near Eben G. Fine Park. In addition to collecting water samples, he collects data on the river temperature, pH and conductivity.

The City of Boulder collects monthly E. coli samples at various points along Boulder Creek.

Once at the lab, researchers manipulate each sample’s chemistry, allow it to incubate, then use fluorescent light to evaluate E. coli levels.

Because the city has more than three decades of monitoring data, Lawlor said that scientists are now focusing their efforts on source identification.

They hope to identify hotspots by, “looking at our stormwater outfalls and sampling our stormwater pipe networks.”

Dog waste can contribute to elevated E. coli levels in the creek. The City of Boulder hopes to reduce human-related sources of E. coli through education and awareness.

For those who plan to dip in Boulder Creek this summer, the city recommends:

- Don’t get water in your mouth, eyes or open wounds.

- Stay out of the water if you are sick or have a weakened immune system.

- Wash your hands and shower after being in the creek

- Don’t swim within 48 hours of a rainstorm or if the water looks cloudy or discolored.

- Be aware that small children and older adults may have more risk of contracting serious illness from waterborne pathogens.

A swimmer clings to his tube after getting pummeled by a rapid on Boulder Creek.

Type of story: News
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