Editor’s note: The following is the third 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.

ASPEN – The city of Aspen has never conducted and then made public a detailed and comprehensive feasibility study of either the potential Maroon Creek Reservoir or the Castle Creek Reservoir.

But in 1971, the Bureau of Reclamation drilled three out of five planned test holes at the Castle Creek dam site, two miles below Ashcroft. What they found in the first few test borings — 142 feet of loose rock and sand — prompted officials at Reclamation to abandon the last two planned bores.

The findings caused the federal agency to write a letter to Aspen’s city manager, telling him that to keep drilling would not be a “wise investment.”

The 1971 drill tests by Reclamation appear to be the high-water mark of investigation into the physical feasibility of either reservoir.

The city filed maps with the state in December 1965 for the two potential reservoirs, but it did very little work on the projects between 1965 and 1970, disregarding suggestions from its consulting engineer, Dale Rea, to conduct feasibility studies on the reservoirs.

But on May 11, 1970, according to city council minutes, the members of the council met with the head of the Colorado River Water Conservation District to discuss the Castle Creek Reservoir.

The minutes note that Rollie Fischer, the “secretary engineer” of the River District, was in Aspen “to discuss with council their cooperation on the reservoir for Castle Creek or the Ashcroft area.”

“Mr. Fischer gave the background and responsibilities of the Water Conservation District and discussed those items that the city and board co-operate on, i.e., proposed dam on Castle Creek,” the Aspen City Council minutes state. “The status of which the Bureau of Reclamation is presently doing preliminary studies as [to] the proposed location of the dam.”

It’s not yet clear just how serious officials at the Colorado River District and the U.S. Bureau of Reclamation were about constructing the Castle Creek Reservoir in cooperation with the city of Aspen, but in the fall of 1970, the Bureau decided to drill some test bores into the ground that would serve as the foundation of the proposed dam. Fischer went up to take a look at the work on Oct. 5, 1970.

“The Bureau of Reclamation has been taking cores at Aspen’s proposed Castle Creek Reservoir site,” Fischer wrote in a quarterly report to the River District Board on Oct. 10. “I visited the site of the coring work with a Bureau of Reclamation geologist. The first cores indicate that valley alluvium is approximately 142 feet deep and the dam site is in a fault zone.”

Word of Reclamation’s findings apparently soon reached Aspen officials.

A topographic map showing the location of the potential Castle Creek Reservoir, downstream of Ashcroft. The map was submitted by the city of Aspen as part of its Oct. 31, 2016, diligence filing. Credit: City of Aspen/Div. 5 Water Court

“Aspen’s proposed dam”

On Oct. 28, 1970, Rea sent a letter to J.W. Robins, a project manager at Reclamation’s office in Grand Junction.

“On several occasions I have had discussions with Mr. Leon A. Wurl, city manager, Aspen, Colorado, concerning any progress you have made with respect to Aspen’s proposed dam on Castle Creek,” Rea wrote to Robins. “We understand you did test drill our proposed dam site but have no further information. If you have made any progress at all in this matter, I would appreciate hearing from you, along with a copy to Mr. Wurl.”

On Nov 4, Rea heard back.

“This letter is in response to your inquiry of Oct. 28, 1970, regarding the status of our work at the Castle Creek dam site,” Robins wrote. “The dam axis we are considering is located about 1,400 feet upstream from the one originally contemplated. The purpose of this change is to place the dam embankment so as to reduce seepage loss through the alluvial fan on the right embankment.

“Our drill crew is presently working on a program of five test holes; to date two holes have been completed. The first hole was located adjacent to the creek channel and found 142 feet of pervious sand and gravel over bedrock of aplite, an igneous intrusive rock. The second hole was drilled on the alluvial fan on the east side of the creek and found 115 feet of overburden over aplite.

“Work is now beginning on a test hole on the right (east) abutment. Other items of work which we have completed at the site include plane table surveys of topography of the damsite and the digging of five test pits to explore for earth materials for dam embankment.

“The rather deep deposit of pervious sand and gravel at this site will present a special design problem to minimize seepage loss,” Robins wrote. “If we can provide further information, please let us know.”

The November 1970 letter was cc’d to Wurl at the city of Aspen.

The “rather deep deposits of pervious sand and gravel” at the Castle Creek dam site were, at a minimum, going to make the Castle Creek Reservoir more expensive.

The following spring, on May 8, 1971, Wurl wrote a letter to Rea.

“It was suggested by the Bureau of Reclamation that perhaps we obtain a cost estimate from a private concern to determine the estimated amount of seepage that would be lost in the bottom of the dam,” Wurl wrote.

A view of the Castle Creek valley near the proposed dam site for the Castle Creek Reservoir. Credit: Brent Gardner-Smith/Aspen Journalism

A deeper report

And on May 11, 1971 Wurl got a more formal report from Robins at Reclamation about the agency’s drill tests. The report was copied to Fischer at the River District, and it referenced a recent meeting where Wurl had asked Reclamation officials about the Castle Creek drilling tests.

“As explained at this meeting the Bureau drilled three deep holes at the Castle Creek site during the fall and early winter of last year,” Robins wrote.

“The first hole was located adjacent to the present channel of Castle Creek to determine the depth to bedrock and the character of the overburden. The hole found 142 feet of pervious sand and gravel over bedrock. The bedrock was also quite broken and believed to represent a possibly dangerous fault zone.

“The second hole was drilled on the alluvial fan near the base of the right abutment and found 125 feet of sand, gravel, and cobbles over bedrock,” Robins wrote. “Percolations tests showed this material to be unacceptably pervious.

“Although the exact quantity of water that would be lost through this material if a dam were to be constructed at this site without a cutoff trench would be impossible to estimate without detailed tests, the results of the percolation tests we performed indicate the seepage losses would be excessive to acceptable standards for Reclamation design as the resulting piping may dangerously weaken the foundation of the dam.”

This could not have been good news for Aspen city officials, especially the part about how “the seepage losses would be excessive to acceptable standards for Reclamation.”

“The third hole was located at about dam crest elevation on the right abutment,” Robins continued in his letter to the city. “Igneous rock was found but the rock was badly broken to a depth of 142 feet where drilling was stopped. Percolation tests in this hole also showed the rock to be very pervious and an expensive grouting program would be necessary to properly seal this foundation material.

“The fourth hole, planned on the left abutment, was not drilled because of the unsatisfactory geological conditions encountered at the other three holes.

“The results of this drilling indicate that an excessive amount of seepage loss could be expected through the sand and gravel in the canyon bottom unless a cutoff trench or some type of special treatment was performed. The great depth (as much as 142 feet) and the distance of about 900 feet across the bottom area would make such treatment unjustifiably expensive.

“Because of the poor conditions found at the three exploratory holes drilled by the Bureau, we do not believe this additional work would be a wise investment for the district or the city of Aspen,” Robins concluded.

In 1971, Reclamation was still in the business of funding and building large reservoirs in Colorado, but Robins had just dismissed the idea of building one on the city’s proposed site on Castle Creek.

One of the many wetlands in the area that would be covered by a Castle Creek Reservoir. Credit: Brent Gardner-Smith/Aspen Journalism

‘Costly mitigation’

In 2012, Aspen Journalism posed a number of questions in writing to city officials about the two reservoirs, including one about the Bureau’s 1971 report.

“Any construction at these sites would require extensive permitting as well as consideration of environmental values and community priorities at the time,” city officials replied at the time. “Construction is very expensive. The Castle Creek site, in particular, will likely require costly mitigation of soil conditions, such as grouting and lining.”

But it’s not clear how expensive such a “grouting and lining” effort would be.

In its Oct. 31 application for finding of reasonable diligence in Division 5 Water Court, the city made a reference to the “significant cost of permitting, design and construction” for the reservoirs, but it has yet to make public a detailed and updated estimate of those costs.

When asked recently if it had produced a recent estimate, David Hornbacher, the city’s director of utilities and environmental initiatives, said the city had “nothing to share at this time.”

A public record search has not provided any evidence of Aspen’s response to the Bureau’s advice that additional work on the Castle Creek dam site would be an unwise investment.

A detail of a map showing the location of a potential dam forming the Castle Creek Reservoir, with underlying property owners. The map was prepared with information based on a map the city filed with the state in 1965. Credit: Source: Aspen Journalism

Rights decreed, despite drill tests

But on Nov. 5, 1971, the slowly turning wheels of justice produced an official water court decree for Aspen’s conditional water rights for both reservoirs. The decree came as part of Civil Action W-5884 and gave Maroon Creek Reservoir a priority number of 806 and Castle Creek Reservoir a priority number of 805.

The priority numbers represent the water right’s place in the state’s prior appropriation system, which is predicated on the idea of “first in time, first in right.”

The 1971 date marks the adjudication for the conditional water rights, while the appropriation date, when the “first step” was taken on the water rights, is July 19, 1965, the date on which the Aspen City Council gave direction to Rea to survey the dams and prepare maps to file with the state.

In April 1971, city officials were apparently still discussing the Castle Creek Reservoir with officials at the Bureau of Reclamation and the Colorado River District.

Wurl sent a letter to Rea on April 15, 1971, inviting him to a meeting in Aspen.

“On April 27 at 11:00 there will be a meeting here with the Bureau of Reclamation and the Colorado River Conservation District people relating to the proposed dam site on Castle Creek,” Wurl wrote. “I thought perhaps you would like to attend this meeting.”

About a year later, on May 31, 1972 the city filed its first finding for reasonable diligence with the water court to extend the conditional water rights for the two reservoirs.

The diligence report was prepared by the law firm of Delaney and Balcomb in Glenwood Springs, a leading local water law firm.

In its effort to convince the court it was making progress on building the two dams, the city said it conducted “Geologic core drilling on Castle Creek dam site in November of 1970.”

It did not, however, tell the court of the results of that core drilling, which the city had learned about a year-and-a-half earlier, in November 1970.

Editor’s note: Aspen Journalism and the Aspen Daily News are collaborating on the coverage of rivers and water. The Daily News published a version of this story on Wednesday, Dec. 28, 2016. This version includes the correct year – 1971 – of a letter referenced in the last section.

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...