Low flow no cause for concern
July 19, 2002
As the Roaring Fork River and other rivers around the state continue to drop to historic lows, concerns are rising about water quality.
“There isn’t a water source in the state that isn’t at risk from the drought,” said Christopher Dann, a public information officer with the water quality division of the Colorado Department of Public Health and Environment.
In the Front Range town of Morrison, state health officials advised residents this week to drink bottled water because the creek that supplies their drinking water is so low that contaminants coming from upstream may not be flushed from the water.
Bear Creek, which supplies the town’s water, is running at about 0.5 cubic feet per second, down from its normal flow of 16 cfs. Higher flow rates in a stream or river can mean there is a lower level of dilution of microorganisms and contaminants.
“There is a greater potential for a high level of effluent,” said Dann. Neither Aspen nor Snowmass Village need to worry too much about upstream users when it comes to their fresh water supplies, as the municipal water system in Aspen is fed mainly by high-mountain water from Castle Creek, and Snowmass’ water comes from Snowmass Creek and Brush Creek.
But what of the water quality in the Roaring Fork River below the town’s water treatment plants? As the river levels drop are more pollutants being concentrated in less water?
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The operators of the upper valley’s treatments plants say no.
“It is essentially clean water,” said Tracy Dillingham about the water coming out of Aspen’s sewage plant. Dillingham is the wastewater facility superintendent for the Aspen Consolidated Sanitation District, which manages Aspen’s treatment plant along the banks of the Roaring Fork River below the Airport Business Center.
On Thursday, the Aspen plant processed 1.7 million gallons of water and poured it into the Roaring Fork River. The outflow from the plant was higher than the flow of the river going by the plant, Dillingham estimated.
“We got more sewage flow than river flow,” Dillingham said, but stressed that the water leaving the plant is clean. “You could probably drink it and have no ill effects whatsoever.”
Dillingham’s counterpart in Snowmass Village, Robert Garcia, also stood behind the quality of the water coming out of his plant.
“Under our permit, we have to remove 85 percent of the strength of raw sewage before we can discharge it, and we are up in the 99 percent percent range,” said Garcia, who manages the treatment plant for the Snowmass Water and Sanitation District. “So we are doing better than we have to.”
The efficiency of local sewage treatment plants along the Roaring Fork River may be more important than ever this summer. The Roaring Fork River in Aspen was running only 40 cubic feet per second on Thursday, just 7 cfs above the 37-year low of 33 cfs.
And the Roaring Fork at its confluence with the Colorado River in Glenwood Springs was running at 454 cfs on Thursday, which is 34 percent of its normal flow for this time of year.
“Every water system in the state is under a certain amount of stress, and how severe that is is going to vary depending on the design specs of the water treatment plants,” said Dann.
Not all of the treatment plants that pour treated wastewater into the Roaring Fork River are as sophisticated as the plants in Aspen and Snowmass Village. There are many smaller plants in locations such as Woody Creek, Aspen Village, Lazy Glen and on down the valley.
But if the treatment plants are functioning as they are supposed to, and the state has no evidence that they are not, then it shouldn’t matter how low the river is. That’s because the river’s historic low flow, which usually occurs in the winter, has been taken into account when developing the requirements for a given treatment plant.
“The wastewater requirements are based on a presumption that there is a bottom low flow, and those are based on historical data,” Dann said. “But functionally, that’s not going to have any impact as long as the treatment plant is meeting its permitted requirement. The flow conditions don’t affect the permit that is in place.”
However, another concern is that pollutants may make their way into the river through individual septic tanks or from runoff, which can bring pesticides from lawns and golf courses or oil from local roadways into the river.
“All kinds of concerns start bubbling out when you have these low flows,” said Jeanne Beaudry, the executive director of the Roaring Fork Conservancy, which is now in its third year of gathering data about the health of the Roaring Fork River.
The Conservancy has been taking water samples from 24 sites along the river in an effort to establish a water quality baseline, but the group’s efforts are not focused on testing the water for specific manmade pollutants so much as monitoring the overall quality of the aquatic environment.
“We are still within the range of the state’s water quality standards, but we are starting to see numbers close to their recommended levels,” Beaudry said.