Preserving the past, powering the future: USACE brings geothermal technology to historic Hacienda Copy
Now, the historic Hacienda at Fort Hunter Liggett is preparing for a different kind of transformation, one that will take place largely out of sight.
The U.S. Army Corps of Engineers Sacramento District is overseeing an $8.7 million renovation that will replace the building's aging heating and cooling systems with geothermal technology, bringing modern comfort and improved energy efficiency to the landmark while preserving the architectural character that has defined it since 1930.
For the engineers and preservation specialists involved, the project presents an unusual opportunity: using modern technology not only to improve a historic building, but to help restore its original appearance.
"One of the things that makes this project so exciting from a historic preservation standpoint is that the technology is largely invisible," said Tatum Clinton-Selin, a Sacramento District historian. "We're able to introduce a modern heating and cooling system without significantly changing the building's exterior. In fact, removing the window air conditioners and other mechanical equipment will help return the Hacienda to something closer to its historic appearance."
Completed in 1930, the Hacienda was designed by Morgan, the celebrated California architect best known for designing Hearst Castle. Originally built to accommodate Hearst's ranch employees and guests, the building later became part of Fort Hunter Liggett when the Army acquired the property in 1940.
Its white stucco walls, red tile roof and distinctive architectural details have remained largely unchanged for nearly a century. The Hacienda was listed on the National Register of Historic Places in 1977 and continues to operate as a hotel and gathering place for military personnel and civilian visitors.
But maintaining a nearly 100-year-old building comes with challenges, particularly when modern mechanical systems must be accommodated within a structure never designed for them.
“Modernizing such an iconic structure is delicate, but essential in preserving the legacy of the installation’s Hearst linkage,” said Garrison Commander Col. Jason McKenzie. “We are honored to champion this cost savings effort as part of a broader beautification aligned with the goal of total energy independence.”
The renovation will replace a patchwork of equipment with a geothermal heating and cooling system designed to serve the building while minimizing alterations to its historic features.
Unlike conventional heating and cooling systems that rely on combustion for heating or exchange heat with outdoor air, geothermal heat pumps use the relatively stable temperatures underground to heat and cool buildings.
"Historic preservation isn't just about keeping a building exactly as it was," said Clinton-Selin. "It's about making sure these places remain useful and relevant so people continue to occupy them, appreciate them and care for them. This project accomplishes that while actually improving the building's historic appearance."
Geothermal systems have already been incorporated into the installation’s housing facilities and other buildings.
At the Hacienda, the proposed system will use boreholes extending approximately 500 feet below ground to allow water contained in pipe loops installed into the boreholes to exchange heat with the groundwater at depth. During colder months, heat pumps will transfer thermal energy from the water heated via the boreholes into the building. During warmer months, the process reverses, moving heat from the building back underground via the water contained in the pipe loops that extend down in the boreholes.
The renovation will also remove the existing propane-fired heating equipment and associated infrastructure, eliminating the need for propane to heat the building.
The project is part of a much larger effort at Fort Hunter Liggett to achieve net-zero energy consumption, producing enough renewable electricity over the course of a year to offset its annual electrical use.
In September 2024, the installation activated a renewable-energy microgrid designed to keep critical operations running during disruptions to the commercial electrical grid. Developed in partnership with USACE and other organizations, the system combines solar power generation, battery storage and automated controls to provide electricity independently of the local utility when needed.
The microgrid was designed to support critical installation operations for up to 14 days during a utility outage, a significant capability for a remote military training installation where reliable electricity is essential to maintaining readiness.
"This isn't a cookie-cutter HVAC replacement," said Jarrod Ross, Fort Hunter Liggett's resource efficiency manager. "We're taking an innovative approach that supports our energy goals while respecting a building with tremendous historical significance."
For Ross, the connection between geothermal technology and the installation's renewable electricity infrastructure is particularly important.
"Fort Hunter Liggett has already made significant investments in generating its own electricity and improving energy resilience," Ross said. "Moving heating and cooling to electric systems allows us to build on those investments and reduce our dependence on propane and other delivered fuels."
The renovation is funded through the Army's Resilient Energy Funding for Readiness and Modernization, or REFoRM, program, which allows qualifying energy savings from previous projects to be reinvested in additional energy improvements.
While geothermal technology is not new to Fort Hunter Liggett, installing it in a nationally-recognized historic building requires more considerate planning.
The Hacienda's age, construction materials and architectural significance limit where engineers can route piping, place equipment and modify existing systems.
Sacramento District's project delivery team has spent approximately nine months coordinating the design, working through a three-phase review process with engineers, contractors and historic preservation specialists to identify potential conflicts before construction begins to save time and costs during construction phase.
"The value USACE brings is our ability to manage all of those moving parts," said Bob Roy, an engineer at Fort Hunter Liggett Project Office under the Sacramento Resident Office. "We have engineers who understand the mechanical systems, historians who understand the preservation requirements and construction professionals who know how to execute a complex renovation. Bringing that expertise together early gives us a much better opportunity to deliver a successful project."
Construction is scheduled to begin in January 2027 and is expected to take approximately nine months, putting the building on track to receive its new mechanical systems well ahead of its 100th anniversary in 2030.
The Hacienda is expected to remain operational during construction, albeit with some temporary disruptions.
“This project is such an exciting and welcomed enhancement for our guests," said Kathy Escalera, Hacienda Business Operations Officer. "Having a modern, dependable geothermal system gives us a truly reliable energy source to keep our visitors comfortably warm through the winter and cool during the peak of summer.
For Sacramento District's construction team, the project represents more than another facility renovation.
"I've visited Hearst Castle several times, and I never realized this incredible piece of that history was just on the other side of the hills," said Greg Sokolis, Resident Engineer at the Sacramento Resident Office. "To be part of a project that improves the building for the people who use it, while helping restore its original appearance, is pretty special."
For a landmark that has served everyone from Hearst's guests to generations of Soldiers, the geothermal renovation promises to help ensure the Hacienda remains both functional and historically recognizable for decades to come.
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