Dillon Reservoir water-monitoring program changing, scaling back

CU researcher closes lab after university review

By Tom Lotshaw
Aspen Journalism
Upper Blue Sanitation District Chief of Plant Operations Earl Picard walks past advanced tertiary wastewater treatment equipment in the Farmers Korner plant on Dillon Reservoir. Improved wastewater treatment and extension of plant service lines have helped protect the reservoir’s water quality from additional phosphorus pollution even as wastewater loads from surrounding communities have grown significantly.
Tom Lotshaw / Aspen Journalism

SUMMIT COUNTY — A long-running collaborative program that protects the Dillon Reservoir from the excessive phosphorus levels and algae growth associated with wastewater and stormwater discharge is undergoing some changes and scaling back its monitoring.

The Summit Water Quality Committee’s monitoring program is losing the lab services of a longtime partner, University of Colorado Boulder professor William Lewis. Lewis, who is also the director of the Center for Limnology, said he doubted he could reorganize and modernize his lab as needed to keep up with university requirements for such programs, given his age and the lab’s budget. Limnology is the study of freshwater bodies.

CU officials said a review of the Center for Limnology’s administrative practices identified aspects that needed improvement and developed options for continued operations with improved practices.

“The university continually works to develop and maintain best practices to ensure proper stewardship of equipment, personnel and resources,” CU spokesperson Deborah Mendez Wilson said. “Subsequent to that review, Professor Lewis decided to close the service center and lab that performed analyses for various entities.”

According to an April 24, 2018 memo obtained through a Colorado Open Records Act request, the Campus Controller’s Office reviewed the Center for Limnology’s financial activities after a whistleblower complaint about the relationship between the center and Western Environmental Analysts, a private consulting company Lewis owns, which was using university employees and equipment to fulfill its contracts.

In the memo, the Campus Controller’s Office recommended an investigation to determine if financial misconduct occurred, as well as improved controls and oversight.

Lewis has helped the committee analyze water quality in Dillon Reservoir and its tributaries for four decades. He also helped lead a major two-year study, published in 1983, of Dillon Reservoir and the threats facing it.

As a result of the 1983 study, local governments and wastewater treatment plant operators in the watershed formed the Summit Water Quality Committee in 1984 to work together to monitor and reduce their phosphorus loads into the reservoir and its tributaries. Committee partners include Summit County; the towns of Breckenridge, Dillon, Frisco, Montezuma and Silverthorne; Copper Mountain Consolidated Metro District; Dillon/Silverthorne Joint Sewer Authority; the Snake River Wastewater Treatment Plant; and the Frisco and Upper Blue sanitation districts.

The program has succeeded in preserving Dillon Reservoir’s water quality, Lewis and committee partners said.

Summit County Commissioner Karn Stiegelmeier said the closure of Lewis’ lab is an immense loss for the committee and the end of an era at Dillon Reservoir.

“I would love to see some documentary done of all those years,” Stiegelmeier said. “Just the fact that we have maintained this clean lake here because of this committee’s work and Bill Lewis’ work.”

A snow-covered arm of Dillon Reservoir as seen from Sapphire Point overlook. Measures to prevent phosphorus pollution have protected the reservoir’s water quality for drinking and recreation, despite extensive development in the watershed over the past 50 years, according to the Summit Water Quality Committee.
Tom Lotshaw / Aspen Journalism

Phosphorus and algae concerns

At the time of the 1983 study, communities around Dillon Reservoir were growing rapidly and discharging more phosphorus-laden wastewater and stormwater into the watershed. A long list of towns and utility districts discharge wastewater and stormwater into Dillon Reservoir, which is Denver Water’s largest storage site for drinking water and a major recreation site in Summit County.

The concern was that the additional pollution would cause harmful algae growth that impaired the reservoir’s water quality for drinking and recreation.

The study jumpstarted coordinated measures to protect Dillon Reservoir from growing phosphorus pollution, which would trigger excessive algae growth in its waters.

After the study, state regulators limited the amount of phosphorus allowed to be discharged into Dillon Reservoir’s water and set a 7.4 microgram-per-liter phosphorus standard for the reservoir from June through October, the season for algae growth.

Denver Water owns Dillon Reservoir, which the agency built in 1963 with a dam on the Blue River. The reservoir, which can hold up to 257,304 acre-feet of water, provides 40% of the storage capacity for Denver Water’s 1.4 million customers, sending water to the Front Range through the 23.3-mile Roberts Tunnel under the Continental Divide.

The reservoir — with its sparkling-blue water, marinas, beaches, hiking trails, campgrounds and bike paths — is also a major summer-recreation site for the towns of Frisco, Dillon and Silverthorne.

Lewis said he plans to stay active with the Summit Water Quality Committee, which remains focused on limiting phosphorus pollution and the excessive algae growth caused by eutrophication, when the nutrient accumulates in a body of water.

Lewis is also helping to investigate trout-fishery declines in a formerly Gold Medal stretch of the Blue River downstream of Dillon Reservoir. He recently published a study on climate change’s effects on the high-elevation reservoir, finding that its surface waters have warmed by 2.5 degrees Celsius over the past 35 years.

“I’ll probably be part of the evaluation process as long as the committee wants me to be part of it. I’m very interested in it,” Lewis said.

William Lewis, a professor at the University of Colorado Boulder and director of its Center for Limnology, has studied and helped monitor Dillon Reservoir’s water quality for four decades. Lewis closed his water quality lab at the university Dec. 31, prompting the Summit Water Quality Committee to change its watershed monitoring program.
Courtesy University of Colorado Boulder

Scaling back

Confronted with the closure of Lewis’ lab, the Summit Water Quality Committee’s watershed-monitoring program is continuing but scaling back, at least for now.

Partners are contracting with the U.S. Geological Survey to sample and analyze Dillon Reservoir six times a year from June through October, as well as contracting with High Sierra Water Laboratory in Tahoe City, Calif., to help analyze samples, according to Lane Wyatt, the Summit Water Quality Committee administrator and watershed-services director for Northwest Colorado Council of Governments.

That monitoring will show whether Dillon Reservoir’s phosphorus standard is being met, Wyatt said. But the program will no longer monitor the reservoir the rest of the year and no longer monitor Green Mountain Reservoir, which is downstream and not subject to the stringent phosphorus regulations.

About two dozen tributary sites will be monitored monthly for phosphorus, nitrogen, algae and other measures, down from 15-17 times a year, with samples sent to ACZ Laboratories in Steamboat Springs for analysis. The monitoring sites are on the Blue and Snake rivers, Tenmile Creek, Soda Creek and Straight Creek. Miners Creek will no longer be monitored as part of the program.

The changes will not result in additional costs for Summit Water Quality Committee partners, Wyatt said. The total annual cost will remain at $80,000-$90,000. Denver Water and Climax Mine also help pay for the monitoring program.

“When you have 30 years of data, we have a sense we don’t need to collect those samples at this time, a higher level of comfort,” Wyatt said of the committee’s decision to scale back the monitoring program for now. “So we’ll do this for one to three years and see how it goes.”

Dillon Reservoir’s phosphorus standard has been exceeded only twice, in 2002 and 2004. Both exceedances were in drought years with low water flows, and the committee’s monitoring data helped show state regulators that they were anomalies and not a sign that programs to limit phosphorus pollution in the watershed were not working, Wyatt said.

Lewis said there is less phosphorus pollution reaching Dillon Reservoir today than in the early 1980s and algae growth is less than half of what it was at its peak. He called the partnership to protect Colorado’s seventh-largest reservoir from eutrophication “a textbook example of the way things should be done in anticipating and preventing damage to an aquatic resource.”

“The monitoring will probably not be quite as comprehensive but sufficient to prove that the lake is complying with the standard and there isn’t any creep in algal populations,” Lewis said. “I think it’s in good hands.”

Committee partners have worked to protect Dillon Reservoir even as Summit County’s population and wastewater loads have continued to grow significantly.

The county grew from 2,700 residents in 1970 to 8,800 residents in 1980 and to an estimated 30,600 residents in 2017. The number of people in the county can top 150,000 during times of high visitation, said Dan Hendershott, Summit County’s environmental health manager.

“We actually decreased our (phosphorus) loading — despite the increased quantity of wastewater generated,” he said.

Improving wastewater-treatment plants helped reduce phosphorus loads early on, and extending their service lines has helped remove some of the oldest and most-polluting septic systems in the watershed, according to Hendershott.

Management of septic systems remains a concern, with an estimated 3,000 systems in the county, Hendershott said, adding that modern systems the county approves are more effective at treating wastewater and are set back from watershed conduits such as creeks, wetlands and groundwater.

Other measures aimed at reducing erosion and stormwater runoff from roadways and construction sites have also helped keep phosphorus pollution in check, Hendershott said, adding, “It’s really been a team effort from all the stakeholders and been a very cooperative process.”

Denver Water representatives say they agree the program has worked to limit phosphorus pollution and prevent excessive algae growth in Dillon Reservoir.

“We see the collaborative partnership as a resounding success, one that has been critical in nutrient control in the watershed,” utility spokesman Todd Hartman said. “The partnership has protected the reservoir not only for drinking but also for recreation and the general health of the water body.”

“The work of Dr. Lewis has been of tremendous value, and it’s unfortunate that the CU lab is closing,” Hartman said. “However, we’re confident the Summit Water Quality Committee will continue to conduct a high-quality monitoring program.”

Aspen Journalism collaborates with the Summit Daily News and other Swift Communications newspapers on coverage of water and rivers. For more, go to

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