Project Profiles: Government

PHOTO: Air Connection

Project Profiles

Sonoma County Water Agency, Santa Rosa, Calif.


Mechanical Engineer: Meline Engineering, Sacramento, Calif.,
Geothermal Drilling Contractor: Air Connection, Santa Rosa,
Geothermal Heat-pump Systems and Controls Installer: Bell Products, Napa, Calif.,


A 60-ton geothermal ground-source heat-pump system was installed at the site, including the following components:

  • Nine Tranquility Rooftop Series units with modulating economizers
  • One Tranquility 27 Two-Stage Series horizontal unit
  • One Tranquility 20 Single-Stage Series horizontal unit

Manufacturer: ClimateMaster,

The geothermal system is installed in a field of 32 400-foot-deep boreholes next to the agency’s building under a parking lot. In addition, exhaust fans were incorporated for warehouse ventilation, along with a building-management control system to monitor and optimize HVAC system performance.


In March 2011, the water agency’s board of directors approved an official energy policy, which outlines the pursuit of a net-carbon neutral power supply by 2015. Extending this mission into its internal operations, the water agency sought an efficient and renewable energy HVAC solution as part of a renovation project at its 1315 Airport Boulevard office building.

The 20,578-square-foot building, originally constructed in 1990, was modified in 2010 to house the agency’s maintenance and operations facilities. A section of the building that had previously been used for warehousing was remodeled into office space, which required extension of the HVAC system into that area. The building’s existing 51-ton HVAC system, which included nine packaged gas-electric rooftop units of various sizes, would have required additional equipment to support the renovations.

With assistance from Meline Engineering, the water agency designed a retrofit geothermal heat-pump system that supplies 100 percent of the building’s heating and cooling load, eliminating need for natural gas. The system, which was overseen and partially executed by the water agency, officially went online in September 2011.

“We’re expecting to save approximately 173,000 kilowatt hours annually in heating and cooling energy with the geothermal heat-pump system,” says Cordel Stillman, Sonoma County Water Agency’s deputy chief engineer. “This would result in offsetting approximately 75,000 pounds of greenhouse-gas emissions per year. We’re definitely interested in seeing how we can execute similar projects for the future.”

PHOTOS: Top, Air Connection; bottom, Art & Clarity

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