A geothermal mirage

A geothermal mirage

RANCHO MIRAGE, CALIF. — In the heated griddle of Rancho Mirage, Calif., is Sunnylands, a modern estate with luscious greenery, architecture and works of art, contrasting uniquely with the surrounding desert landscape.  

RANCHO MIRAGE, CALIF. — In the heated griddle of Rancho Mirage, Calif., is Sunnylands, a modern estate with luscious greenery, architecture and works of art, contrasting uniquely with the surrounding desert landscape.

The estate’s crown jewel is a 25,000-sq.ft. home, which was designed by famed architect A. Quincy Jones. Part museum, part retreat and part conference center, the home was built by ambassador and media mogul Walter Annenberg and his wife in 1966. During their years in the home, they hosted U.S. presidents and international royalty. To share the Sunnylands experience with the public, the resort has a separate visitor center on the property. 

Known as the Sunnylands Center & Gardens, the visitor center celebrated its grand opening in February, with public tours that began in March. The tour features art and landscape with explanations of the estate’s sustainability, Annenberg family history and Midcentury Modern architecture.

Surrounded by nine acres of desert garden, the new 17,000-sq.ft. visitor center includes a shop, café and numerous interactive learning stations.  The project’s lofty goal to meet LEED Gold status was accomplished, even before its opening. With a state-of-the-art geothermal system and solar farm, it truly is a green oasis in the midst of a desert.

Green comfort

With the area’s ambient temperatures fluctuating from below freezing to well over 110°F, the constant 76°F deep-earth temperature provides the ideal opportunity to utilize a water-source geothermal heat pump system.

“The system was selected to achieve the high levels of energy efficiency typically associated with the most efficient water-cooled equipment, while as a closed loop geothermal system we don't need to evaporate or consume water,” said Doug Lemons, project manager at ACCO Engineered Systems of Glendale, Calif., the project’s mechanical contractor. “This is a key sustainability factor in the desert location of the visitor center. The project had 96 geothermal wells each drilled to a depth of 350 feet.”

With the assistance of ClimateMaster’s representative, Kaiser Sales Corp. of Los Angeles, MB&A Engineers specified 78 tons of geothermal heating and cooling capacity.  The ClimateMaster Tranquility Series geothermal water-source heat pumps are incorporated into a demand-based, variable flow system.

The 13 TLV and TSV units include the Climadry modulating reheat system for dehumidification capability. Though the arid region has only a very short monsoon season, managers say that the priceless artwork in the visitor center can’t be exposed to high humidity for any length of time. 

Buried under the sand about 100 feet from the main building is a vault, concealing various mechanical system components.  The concrete structure is 10 feet deep, just as wide, and 24 feet long.  Inside is the building’s water treatment equipment, circulators for the geo-exchange system and a bank of distribution manifolds.  Also housed in the subterranean vault are pumps and filters for two large garden fountains. 

“Hiding the pump room underground was the simplest way to retain the tranquility of the property,” said Bart Shively, vice president of Matt Construction.  “With the exterior of the visitor center being made up almost entirely of glass, it would have been tough to hide all that equipment inside without disrupting the ‘quasi-museum’ appeal.”  The building’s floor plan does allow for two mechanical rooms on ground level inside the building to house the 13 water-source heat pumps.

“A buried pump room brings up another challenge,” said Lemons. “We needed to trench between the vault and visitor center in order to run piping, ductwork and electrical wires.  The deep desert sand made that a real challenge.”

Installing the ground-source units, piping the horizontal portion of the exchange field, and running ductwork made up the lion’s share of the mechanical contractor’s work. 

“The project featured a unique cast-in-place underfloor air distribution system supplied by Airfloor, the electrical rooms are served by an R410 split system, otherwise the building is served by the GSHP's furnished by ClimateMaster,” said Lemons.

 “We had anywhere from six to 12 guys at the jobsite for the duration of the project,” added Lemons. The mechanical systems took approximately one year to install within an overall construction schedule of approximately22 months.

Desert Drilling

Gregg Drilling and Testing Inc., Signal Hill, Calif., was the drilling subcontractor for the job. The 150-person firm serves the entire state of California out of two offices. Since 1985, their focus has been geo-technical, environmental, ground source and water well drilling.  The company’s broad range of experience helped the project move along at a steady pace.

The well field, designed by Meline Engineering Corp. of Sacramento, consists of 96 closed-loop bore holes.  The 355 foot holes are spaced 25 feet on center in eight rows of 12. 

“When you show up at 5 a.m. and the mercury already reads 89°F, you know it’s going to be a full-time job just trying to stay hydrated,” said Mike Meyer, rotary operations manager for Gregg’s Southern California office.

The six workers took breaks often to avoid heat stroke in the 117°F temperatures. The sweltering desert air wasn’t the only challenge though. The sandy terrain proved nearly impassable, even for the all-wheel-drive trucks.

“We had to keep a bulldozer on site,” said Meyer. “Thankfully, the bore holes were in rows, because we had to tow the rigs from one position to the next.”  Despite the challenges, the crew made good time installing the exchange field. Averaging three holes per day, the six-man drilling crew kept the grout team busy installing the one-inch U-bend loops and backfilling the bore holes with a bentonite grout slurry.

The exchange field is roughly three acres in size, and like all other mechanical components on the property, is now invisible.  What was once sand and well caps is now green lawn, acting as a general outdoor activity area.

Solar farm

Shrouded by a thick row of Texas ebony trees, a remote corner of the estate’s massive garden holds a solar farm with 545 3-ft. x 5-ft. photovoltaic panels producing 125 kW powers the visitor center. 

“The system is ten feet off the ground, so that the land beneath the array could be utilized later,” said David Potovsky, senior project developer at Borrego Solar.  “It’s dual purposed, rather than the panels being low to the ground rendering that land only usable for PV.”

In the future, the Annenberg Foundation may find use for the shady area underneath.  The ebony trees were planted specifically to hide the three, 250 foot rows of solar modules. 

LEED construction

The geothermal and solar systems are just a portion of the total LEED-winning recipe. All the energy efficiency in the world doesn’t matter if the building envelope isn’t up to par.  From the white heat-shedding PVC roof to the eight-inch R-21 walls insulated with recycled shredded denim, the Annenberg Center is perfectly adapted to its harsh environment. 

“We started the design process with Mrs. Annenberg in 2006,” said John Berley, associate at Frederick Fisher and Partners, the architect firm for the project. 

“From the very beginning, ‘green’ was the goal,” he added.  The single-story, slab-on-grade building is steel-framed, with both steel and wood studs. The building’s R-38 roof keeps the desert heat outside.

 “One of the biggest challenges for us was the enormous garden,” continued Berley.  “Between the landscape architect and the installer, the garden came together, but it was a feat.” 

Careful planning was needed to place the 50,000 plants in accordance with the measured-volume sprinkler system. To make sure all landscape components were perfectly placed, the project was tracked by aerial photography. Amazingly, through careful selection of arid-climate vegetation and judicious placement of sprinkler heads, the massive garden and building use only 20% of the permissible water under Coachella Valley Water District regulations.  

 

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