Editor’s note: The following is the second part in a series exploring the city of Aspen’s historic intent in filing for and maintaining conditional water rights for storage reservoirs on Castle and Maroon creeks. The series, which began Monday, continues tomorrow.

ASPEN – In December 1965, an engineer working for the city of Aspen filed maps of two dams and reservoirs with the state engineer’s office, indicating the city intended to build a 170-foot-tall dam on upper Castle Creek and a 155-foot-tall dam on upper Maroon Creek.

And by June 16, 1966, Aspen’s claim for storage was formalized in a proposed water-rights decree labeled as Civil Action 5884, which indicates the city of Aspen was serious about building both reservoirs.

Under the heading of “Maroon Creek Reservoir,” for example, the court document says, “The claimant of said reservoir is the city of Aspen.”

“The purposes for which the water stored in said reservoir will be used are industrial, irrigation, domestic, municipal and other beneficial uses, both consumptive and non-consumptive,” the decree application states. “The capacity of said reservoir is 4,567 acre-feet.”

“The appropriation date hereby awarded said structure is the 19th day of July 1965,” the court document continues.

That’s the date on which Aspen City Council directed its consulting engineer, Darrell “Dale” Rea, to prepare maps of both reservoirs.

The court document closes by noting that the conditional water right was “granted on condition that the dam and other structures necessary to store water in said reservoir shall be completed and that the water stored in said reservoir shall be applied to beneficial use with due diligence and within a reasonable length of time.”

In other words, Aspen could have its conditional rights to store water, as long as the city actually built the dams at the center of their claim “within a reasonable length of time.”

That was half a century ago.

A detail from the water right decree for Maroon Creek Reservoir. Credit: Source: State of Colorado

On to water court

After the city filed to have its water rights approved, a hearing in water court was held on Nov. 29, 1966, so a water court judge could make a decision about the city’s proposed rights. Rea, the city’s consulting engineer who originally surveyed the Castle Creek and Maroon Creek reservoirs, testified.

An attorney representing Aspen, Janet Gaylord, walked Rea through a series of questions meant to inform the court of Aspen’s intent to store water from the creeks.

Rea said in court that he started working for Aspen as a consulting engineer in July 1956, when the city was trying to acquire and develop a municipal water system.

“At that time we made a feasibility report for the development of surface rights for the city … which included proposed rights on Hunter Creek, Castle Creek and Maroon Creek,” Rea said. “We made the estimated cost for construction of a filter plant and diversion structure necessary to deliver and bring this water to the city of Aspen.”

One key component of the city’s new water system was to rebuild a diversion dam on lower Castle Creek, not far below Midnight Mine Road, and another was to install a 30-inch pipe that could bring 25 cubic feet per second (cfs) of water from the diversion dam to a new water-treatment plant on a knoll above Aspen Valley Hospital between Castle and Maroon creeks.

According to the archives of the Aspen Historical Society, this is a photo of the Aspen water plant under construction in 1966. The plant was a significant step forward for Aspen’s municipal water supply system. Credit: Aspen Historical Society
According to the archives of the Aspen Historical Society, this is a photo of the Aspen water plant under construction in 1966. The plant was a significant step forward for Aspen’s municipal water supply system. Credit: Aspen Historical Society

Water for Aspen

Rea said during these projects he also looked into the supply of, and projected demand for, water in Aspen.

“Our studies of projection show that Castle Creek and Maroon Creek had low flows in the summer that would not be sufficient to sustain the city more than a few years,” Rea testified. “This meant that they would have to store water in either or both of these creeks.”

And so Rea had surveyed two dams that were to sit astride upper Castle and Maroon creeks. Stored water was then to be released to run several miles down the streams to the city’s diversion dams, which would direct the water into pipelines to the city’s water-treatment plant.

Rea identified for the court the November 1964 water plan he prepared for the city, which included charts of flow levels on the creeks, as recorded by the state engineer from 1913 to 1917.

Based on those four years of records, Rea projected that low flows in some dry years could drop to 24 cfs in Castle Creek and 16 cfs in Maroon Creek.

He said such low flows “would not yield enough water unless storage supplemented the flow in the dry years,” and that “these flows would not suffice the city at the presently projected growth for more than, I think, five years.”

“Somewhere between ’70 and ’75,” Rea said, “the city would need supplemental flows either from Maroon Creek, which it is not now presently using, or the construction of storage on Castle Creek.”

Then, reviewing his “proposed steps of development,” Rea said that within “the next five or 10 years” Aspen would need to build a reservoir on Castle Creek and later a reservoir on Maroon Creek.

He added, “That will take care of the city of Aspen for the foreseeable future.”

A young skier on Buttermilk Mountain about 1965. Aspen was starting to grow as a result of its ski areas, but it wasn’t clear how big the community would get by 2000. Credit: Source: Aspen Historical Society
A young skier on Buttermilk Mountain about 1965. Aspen was starting to grow as a result of its ski areas, but it wasn’t clear how big the community would get by 2000. Credit: Source: Aspen Historical Society

Locals and visitors

Gaylord, the attorney for the city, asked Rea about his population projections.

Rea said his estimates took into account “transit population,” referring to the growing number of visitors coming to Aspen in both winter and summer, as well as “permanent residents.”

He estimated that the combination of visitors and locals equaled 7,000 people in 1965, and the combination would rise to 30,000 people in 1990.

“We have found that it is necessary for Aspen to have storage on these streams in order to meet this population,” he told the court.

In his 1964 plan, Rea at one point had estimated that as many as 66,000 people might someday live in the greater Aspen area, but in his court testimony, he spoke of a more modest population estimate.

Rea’s estimate of a population of 30,000 people was fairly accurate, although time would prove that Aspen’s municipal water system would be able to serve 30,000 people without having to build a reservoir.

By 2008, for example, Aspen’s year-round resident population was about 6,400. And data from the Aspen Consolidated Sanitation District showed that another 8,000 people or so were also in town each day, bringing the town’s average daily population to about 15,000.

But peak days such as the Fourth of July and Christmas could attract about 30,000 people to Aspen.

“In 2007, the average daily flow of sewage to the treatment plant, which is next to the river below the Aspen Business Center, was about 1.5 million gallons, which means there were an average of 14,362 people in town each day,” the Aspen Daily News reported in 2008. “The plant can handle 3 million gallons a day, which is enough capacity for about 31,000 people.”

Sheep being driven across the Castle Creek bridge from their summer range in the mountains in 1967. Sheep were grazed on the ski areas in Aspen and Snowmass until the early 1980s. Credit: Aspen Historical Society

Timing and feasibility

During his 1966 appearance in water court, the judge asked Rea when the city proposed to complete the two dams for which it held water rights.

“Well, they have three alternatives,” Rea replied of the city. “I would say between ’70 and ’75 one of these will need to be constructed in order to [supplement] the direct flow.”

He also said that while the city might build both dams at once, “from the actual demand they would build this one first and the other one later.”

“It is proposed that they drill the two reservoir sites for the geological surveys, and depending upon that result they will select either the Maroon Creek Reservoir or Castle Creek Reservoir, and it will be constructed and there is no time schedule for the second reservoir,” Rea said, speaking in November 1966. “I would assume that all of these facilities would be needed within the next 35 years.”

A detail of a letter sent by Dale Rea to the Aspen city manager in 1967 about studying the Maroon and Castle creek reservoirs. Credit: Source: City of Aspen

Feasibility study?

On May 5, 1967, Rea sent a letter to Leon Wurl, Aspen’s city manager, proposing to conduct a feasibility study for the two reservoirs.

“We would recommend the preparation of an interim report during the 1967-68 winter season,” Rea said. “The purpose of this report would be to form the basis of a continuance with the district court on the reservoir and pipeline decrees.”

The reference to “the basis of a continuance” is to the expected diligence review that would be required for the proposed reservoirs.

“A final report could be performed only after geological studies and field surveys have been completed along with investigations for financing the project,” Rea wrote. “Geological studies could start in 1968 or 1969. The engineering cost of such a report should await discussions with the council on the actual scope of such a report.

“The interim report would set forth problems that would have to be evaluated before construction could start on the dams,” Rea also wrote.

He provided an outline of information that today still seems relevant. And much of the information he proposed the city investigate has apparently never been done. Or if it has, the city has yet to make it public following a request under the Colorado Open Records Act.

Rea’s outline included investigating and compiling information about water rights, hydrologic data, and geologic data.

It also included producing surveys, maps and “data” on the proposed dams, including “choice of materials for constructing dam” and “final location of dam.”

A 2016 rendering from Wilderness Workshop of a potential Maroon Creek Reservoir, which would hold 4,567 acre-feet of water behind a 155-foot-tall dam. The rendering was prepared by a professional hydrologist and is based on plans submitted to the state by the city 1965. Credit: Source: Wilderness Workshop


The city was slow to respond to Rea’s suggestion of an investigation into the dams, so Rea sent a follow-up letter.

In the Jan. 12, 1968, missive to Aspen’s Wurl, Rea presented costs for “engineering, aerial [photography] and geological in the eight items of our letter and outline of May 5, 1967.

“The report as presented should firm up the location, capacity and cost of the two reservoirs,” Rea said. “It will also show how much water is needed, where it will be used, and the cost of treating and transmitting the water to the areas of use. Methods of financing the total construction costs will be also presented.”

In November 1968, Rea checked one of the items off his list for additional study when he submitted a preliminary report to the city on “stream gauging, hydrology and water supply.”

“The purpose of this preliminary report is to collect data that will supplement the water filings made with the state engineer in December 1965 for reservoirs on Castle and Maroon creeks,” he wrote. “This report is limited to stream gauging, hydrology and water supply because they offer a good beginning that is highly desirable and lays the foundation for collection of further needed data in order to adequately design the two dams.”

On March 3, 1969, Rea wrote yet another proposal letter to the city, which included a detailed budget for an investigation into the reservoirs.

“We would recommend the entire preliminary report be started in 1969 and completed in 1969 or 1970,” Rea wrote.

Under the heading “Final Report – Phase II” he wrote, “This final report may be completed on both dams at the same time or at separate times. There will be some savings in field investigations if the two dams are investigated at the same time.”

He went on to write that for “the purpose of a capital improvement program, we would recommend that $22,500 be set up for 1971 and $22,500 in 1972 to cover pre-design information on the two dams. This can always be deferred if financially necessary, provided the attorney feels that the criteria of ‘due diligence’ has been met.”

As 1969 drew to a close, it appears the city had yet to act on Rea’s suggestion to conduct a detailed feasibility study of the dams. But while the city was apparently sitting on its hands, the Bureau of Reclamation conducted its own investigation, which did not bode well for the Castle Creek dam site.

Next in our series: The Bureau of Reclamation finds serious flaws at the Castle Creek Reservoir site.

Editor’s note: Aspen Journalism and the Aspen Daily News are collaborating on the coverage of rivers and water. The Daily News published this story on Tuesday, Dec. 27, 2016.

Brent Gardner-Smith

Brent Gardner-Smith, the founder of Aspen Journalism, and who served as AJ’s executive director until August 2021 and as editor from 2011-2020, is the news director at Aspen Public Radio. He's also been...