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Scurrying to get in as much work as possible during the few short months of no snow.

Moving The Mountain

California’s premier ski resort has earned its name. Mammoth Mountain dominates the eastern Sierra skyline, with the central peak towering out at 11,053 feet. Framed by the Sierra’s rugged beauty and tucked deep into the Inyo National Forest, the town of Mammoth Lakes, home of Mammoth Mountain ski resort, is the perfect base camp from which to explore California’s wild side.

And explore they do! Each year, the summer season attracts more than 1.2 million visitors for camping, climbing, hiking, biking and fishing. And when the snow flies, an equal number of visitors follow. Winter enthusiasts flock to Mammoth Lakes at the first sign of snow. World-class Mammoth Mountain averages one of the longest seasons anywhere, opening in early November and often running well beyond Memorial Day.

Yet, when winter makes its move the crestline location of Mammoth Mountain becomes a beacon for snowstorms. They come fast as temperatures drop to near zero and frequently leave behind two or three feet of fresh powder, enough to challenge any infrastructure. By the end of each ski season, an average of 32 feet of snow collects on the slopes of the mountain, and in the community of Mammoth Lakes where skiers live, gather and shop.

During the last couple of years, Excel Mechanical Systems, Inc., has won continuing mechanical contracts at Mammoth through developer Howard CDM. Each year mechanical system work is eagerly accomplished during the four or five months that snow does not fall...though, work at the jobsite never comes to a standstill. Recently, an $800 million master plan was put in place to move the resort into “world class” status and enhance its reputation as a full-service ski destination.

During the project’s first phase, general contracting firm, Howard CDM, hired Xcel to design and install all mechanical, plumbing and snowmelt systems for the gondola lift stations and commercial facilities within Mammoth Village. As part of this project, McCoy Station, the mid-mountain day lodge at the base of the ski area, received its share of the work. “The job entailed building a large concrete dining deck with extensive use of snowmelt technology,” explained Rick Demshki, Howard DCM project manager. The snowmelt system would also serve walkways, sidewalks, loading docks, stairs, bridges, equipment platforms, bus stops, and loading areas of the new, high-speed gondola running from Village Gondola Station to Canyon Station.

Smartly automated controls would permit the zones, high-temp for paver areas and low-temp for concrete, to start by phone calls for nights when they knew snow was coming and they wanted to pre-heat slab surfaces. Xcel set us primary-secondary pumping with injection and zone pumps for the snowmelt. Each zone had a zone pump to eliminate field water balancing at the individual manifolds. “Each snowmelt zone is controlled by a dedicated pump zone,” says Kevin Michel, P.E., Xcel Mechanical Services. “These were a huge benefit because of time saved when piping the mechanical rooms, and for space considerations; they’re very compact and sensibly laid out.”

Snowmelt is seen as a valuable investment. There are so many advantages to the placement and use of this technology, including public safety, operating issues (the lifts must be open and accessible), and workforce impact. There are fewer employee and maintenance issues, and much less use of volcanic cinder, preventing damage to buildings and paved surfaces, and much less need for snowplowing.”

“Typically, Pacific storms roll in every 5 to 15 days,” says Bob Bradley, manager of facilities and energy management at Mammoth Mountain. “And because of the irregularity of the storms and the length of time between them, we tend not to idle our snowmelt systems. We use sophisticated building control systems connected by Ethernet to help us activate all snowmelt systems, permitting the buildings, deck and walkway systems to “talk to each other.”

Essentially, the operation of the snowmelt system and connectivity of all the various snowmelt locations spread throughout Mammoth Mountain’s vast facilities has been automated.

Interestingly, the system is programmed to recognize the characteristics of a small storm - with melt temperatures set at a modest, normal 34ºF -and a large storm system, when the computer ratchets-up the temperature to a more aggressive 39ºF for faster action. For the uppermost location, Mountain Lodge, the system detects precipitation and activates the snowmelt. Then information is passed down the line to alert other systems, activating them.

“We also take into consideration the sun’s warmth and how we can use it to our best advantage,” says Bradbury. “This is especially important because we typically don’t idle our snowmelt systems. In fact, this is something we consider before the walkways, decks and other snowmelted surfaces are even planned; we orient them to take best advantage of southern exposure. Very often the sun will warm the surfaces faster than we could mechanically melt them.”

Gondola decks are quite a challenge. One side of the structure is always in the shadow; the other, frequently in the sun. So they always design these places with at least two zones. Driftng snow is another big challenge. “So what we do to counteract it is to place precipitation sensors strategically in shaded areas or those prone to drifting where snow can accumulate very quickly,” added Bradbury. “These sensors also play a valuable role in helping us know when to deactivate snowmelt operations.”

“It’s easy to see why Xcel is our preferred plumbing and mechanical contractor,” said Rick Demshki. “They routinely meet the unique challenges posed by the mountain’s location and extreme weather.”

“The manpower issue is critical,” added Demshki. “Union Hall is five hours away. Yet, Howard CDM mans the projects as fully as possible so that when weather does permit work, the manpower is there to continue operations. Xcel has crews on hand year-round. They’ve also educated me about snowmelt, and so have Watts Radiant and Laars,” continued Demshki. “We’ve had great connections with the two companies regarding the types of tubing for different operations, heat transfer of pipe, header balancing devices, and boiler installation and function.”

“I was especially interested in how Xcel did extensive stairway snowmelt systems with the synthetic rubber hose, Onix, which permitted the tubing to easily follow the exact contour of the stairs, extremely important because the tubing is nearer to the stair nose, permitting fast, efficient snowmelt operation.”

“The following winter, we built the mechanical room and all exterior snowmelt systems at Canyon Station, another gondola/lift center with about 10,000 square feet of snowmelt and six zones,” said Michel. Part of the 10,000 square feet of snowmelt at Canyon Station, which provides access to 150 ski runs, included a snowmelt refreshment bar, now one of the hottest spots in the Mammoth Mountain complex. “This was also the very first commercial use of the boiler we now rely on heavily at Mammoth - Laars’ ‘Rheos’ boiler, a full-condensing commercial system with modulating burner technology that’s proved itself several times over.”

Rheos condensing boilers by Laars are the ultimate tool for low, and super-low liquid temperatures at start-up. “The boiler’s secondary heat exchanger transfers exhaust heat to warm liquids before they reach the primary HX. At peak efficiency, water vapor produced in the combustion process condenses back into liquid form to release latent heat,” Michel explained.

Also, its sealed combustion, positive-pressure design assures that the boiler can be installed in many different environments, even outdoors. Without the need of room air for combustion, the boiler is not affected by limited air from within the building, or by negative pressures created by other equipment.

A function stipulated by Mammoth Mountain led to Xcel’s choice of the Rheos boilers: that they must be fully modulating systems. “It was a great fit because the Rheos provides not just one or two stages of firing capacity, but an infinite variability of modulation between 100% and 50% of the input rate.”

Other benefits, adds Michel, include the boiler’s stainless steel secondary heat exchanger. these systems are built for direct contact with a 50-50 glycol mix. No need for an external heat exchanger. It’s also one of the “greenest” and most environmentally sound heating systems on the marketplace with NOx levels of less than 10ppm and low CO greenhouse gas emissions - a big plus in California. And the systems offer up to 96% combustion efficiency.

“And there’s no risk of thermal shock,” added Michel. “The boiler’s heat exchangers go with the flow, at any temperature. While the boiler requires a minimum of 70ºF return water temperature on an ongoing basis, initial start-up temperatures can be far lower. Peak operating efficiency occurs when the return water temperature reaches 70º, and a fully automatic internal mixing system protects the primary heat exchanger from condensation. As system temperatures begin to rise, the boiler’s control system responds accordingly, maintaining the desired output temperatures and obtaining maximum efficiency from the boiler.”

Further proof that the Rheos boilers were the best fit lies in the fact that two, 2.4 million BTU boilers, located in one mechanical room, serve both the Village Gondola Station and the Mountain Center. Although connected by a bridge, these two separate buildings are served by one single mechanical room, ultimately servicing 12 zones of snowmelt conditions and 8 hydronically heating fan coil units. Underground hot water piping from the mechanical room in Mountain Center conveys hot water to the HydroControl panels in the Village Gondola Station. Each panel is designed to minimize wall space requirements for piping and controls in tight mechanical room layouts and to greatly reduce field installation time.

The systems are sized to operate all zones simultaneously, though the two boilers allow for partial redundancy: one boiler can handle 65% of the current total load. Over-sizing boilers allows for future expansion. Controls allow for operation of all zones or for one zone to efficiently operate if all zones don’t require snow melting.

Much has been done to help “move the mountain” at Mammoth Lakes. And each year as the 1.2 million visitors to this world-class ski resort return, they will give little thought to the areas within the village without snow, looking only for the “best powder” to begin their day. But rest assured that the staff of Xcel Mechanical Services and Mammoth Mountain ski resort will be on top of where the snow should and shouldn’t be.

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