CDOT says the Glenwood Hot Springs Pool aquifer will be fine
Post Independent Staff
Glenwood Springs, CO Colorado
GLENWOOD SPRINGS ” There is no such thing as a “geothermal mantle” just below the ground that could be easily damaged and draw down flows at the Hot Springs Lodge and Pool, according to the Colorado Department of Transportation.
That was a key point in CDOT’s presentation to the City Council Thursday. CDOT shared its estimation of geothermal flows with the city after the Hot Springs Lodge and Pool asked the city in November to draft an ordinance restricting excavation in
Glenwood for fear it could harm flows to hot springs.
Pool officials began a letter to the city about the ordinance by mentioning that the former Mid-Continent property is under contract for sale and saying CDOT plans to build an office building near there, also close to CDOT’s current facility.
“In some letters in 2007, they talked about nicking the geothermal mantle, which
seems like it could be misleading or confusing,” said Mark Levorsen, a
hydrogeologist for the URS Corporation. “What I believe they’re referring to is
Levorsen worked on the CDOT team to study geothermal flows. He said travertine is
formed at the surface from discharge of mineralized groundwater from hot springs. It
is a hard layer with very low permeability, he said.
But Levorsen said travertine deposits are spotty and aren’t very good confining layers
“Travertine is not the primary confining layer,” he said. “It’s not a geothermal mantle,
either. I hope you all don’t use that term when you leave here tonight. The Belden
formation is the confining layer.”
Mike Galloway, a hydrogeologist with ERO Resources Corporation, also worked on
CDOT’s team. He said permeable Leadville limestone is the primary conduit of hot
water from underground to the surface. Pressure to drive hot water upwards is
maintained by a confining layer of Belden shale, he said.
The CDOT team displayed an image showing the Leadville limestone layer coming
to the surface near the Yampa Hot Springs that feeds the Hot Springs Lodge and
Pool. The layer dives down farther underground and continues to drop lower to the
south and to the west.
Citing a Bureau of Reclamation salinity study, Levorsen said eight or nine boreholes
were drilled 70 to 80 feet before they hit the Belden shale layer near the former
CDOT project engineer Joe Elsen said CDOT is considering constructing a four-story,
40,000 square-foot building near its current facility. The building would utilize
geothermal exchange, meaning a liquid like antifreeze would be piped into the
ground, heated by the earth, and returned to the surface, Elsen said.
He said the excavation would reach 20 feet deep or less.
Levorsen said that as long as excavation doesn’t impact the Leadville limestone
formation ” generally far below the travertine deposits ” flows to the Yampa Spring
feeding the Hot Springs Lodge and Pool shouldn’t be affected.
The pool has maintained that the aquifer could be easily damaged by excavation.
Mayor Bruce Christensen said, “We’ve been asked to assess two different
descriptions of what’s happening.”
The pool expressed fears the aquifer could be damaged by construction of a
whitewater park near downtown. Christensen said he heard at that time that there
was a continuous layer or mantle holding back the hot water. The other description,
he said, is “no it’s not these spotty pieces of travertine, it’s the Belden shale which is
much, much lower beneath the surface.”
Christensen joked that CDOT’s planned construction would prove which version is
true. Formal action wasn’t required in Thursday’s work session.
Contact Pete Fowler: 384-9121
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