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Back in Good Standing Formerly a source of civic pride, the plaza at a county government building in Apple Valley, Minnesota, a southeast suburb of Minne- apolis/St. Paul, had lost that designation thanks to years of pedestrian wear, harsh weather, and the required maintenance by snow removal equipment and heavy salting. Dakota County officials decided to re- pair its reputation. As the entrance to the Western Service Center, which houses a library, courts, county engineering department and more, the 7,000-square-foot plaza was re-envisioned as a space that would not only enhance the building's character and serve as a public gathering place, but would require less maintenance. To address the third goal and to help provide pedestrian safety, an in-slab, glycol heating system became a component of the design: a highly collaborative effort between the Dakota County project manager Josh Kinney, PLA, and the project landscape architect, Ben Hartberg, PLA, of Calyx Design Group. Joel Dunning, AIA, and Pat Jansen, PE, of Wold Architects and Engineers, provided electrical & mechanical engineering as well as overall construction administra- tion. Besides a plaza made with bands of concrete with integral color, the design called for an amphitheater, seat walls, bicycle parking, LED lighting and raised plant beds. The construction team included general contractor and concrete finisher Morcon Construction Company with Jason Preusser serv- ing as project manager, and subcontractors Kamish Excavating Inc., Wenzel HVAC Inc., and A&J; Electric Company. Plant Pros Inc. was the landscape contractor. Demolition of the old plaza was done with a John Deere 225D excavator with a hydraulic hammer to break up the six-inch rein- forced concrete. Ground preparation included digging seven-foot- deep footings for the amphitheater and seat walls. A mini-excavator handled prep work for drain trenches. The subgrade was compacted and eight inches of aggregate was added to make the base ready for installation of the heating system. "The mechanical engineer designed a system that would utilize re- turn water from the building's central heating plant to pre-heat the glycol tank," states Hartberg. "Then a heat exchanger would boost Top, Left: Over 20 years of foot traffic, frigid winters, heavy use of snow removal equipment and salting had damaged the 7,000-square-foot plaza at the Dakota County Western Service Center in Apple Valley, Minn., a suburb of Minneapolis. Renovation plans included an in-slab, glycol heating system to help provide pedestrian safety and reduce maintenance time and costs. Top, Right: After the deteriorating pavement was removed, the sub-grade compacted and an 8" base of class 5 aggregate was laid down, 4' x 8' sheets of 2"-thick extruded polystyrene were placed end to end. On top of that went a layer of 10/10 woven wire mesh, which helps keep the tubing tight to the bottom of the slab even if the polystyrene separates from the concrete during curing. Left: Nearly 5 miles of radiant heat tubing was installed; secured to the mesh through the polystyrene with a foamboard stapler gun. The tubing was pressurized with an air compressor to prevent damage from the workers and to help identify any leaks that could then be repaired immediately. 26 LC DBM (Continued on page 28) PHOTOS: BEN HARTBERG, PLA, CALYX DESIGN GROUP