Sonoma County Water Agency
Service Center

SCWA Service Center

Santa Rosa, CA

Project Start: Novermber 2011

Project End: June 2014

Owner: SCWA

Ground Loops: 20 slinky pond loops x 676 ft. long

A new building was constructed at the SCWA waste water treatment plant in Santa Rose in support of their fleet and service operations. Due to the proximity of the retention pond of treated waste water, a plan was devised to take advantage of this feature as a heat exchange medium. Because the level of the water in the retention pond fluctuates, a minimum depth of 4 feet was established for effective heat transfer. A hybrid design using the convection of the water and the small amount of conduction with the pond floor was utilized. Twenty 1-inch HDPE tubes 676 ft. each, configured into a 135 ft. long supported slinky design were floated out into the middle of the pond and sunk to lie directly on the pond floor. Pre-insulated HPDE pipe, for UV protection only, was used to connect the sunken heat exchanger with the building mains which were required by the Division of Safety of Dams (DSOD) to be routed over the top of the dike walls rather than through them. Challenges of keeping the circuit piping organized as pond levels rise and fall were addressed by creating weighted guides along the interior dike wall..

The surface water ground loop heat exchanger supports 17.5 tons of installed heat pump capacity through (4) ceiling mounted heat pumps in the Service Center building. System control is simple, thermostatic, engaging fractional horsepower pumps ‘on’ with each heat pump as space thermostats call for heating or cooling.