PHILADELPHIA — The old Veterans Stadium here had some of the most notorious Astroturf of any football stadium in America. This season, however, the Philadelphia Eagles and their grateful NFL opponents are playing on natural grass in the new Lincoln Financial Field.

A turf-warming system keeps the grass growing through the end of the NFL post-season in January. Grass would ordinarily go dormant and groundskeepers have tried a number of methods over the years, including over-seeding, if weather permitted, or plugging in sod to cover bare spots. Some have painted the dirt green to make it look better on TV.

A groundskeeper would have more success with a turf-warming system, said Patrick Sauer, vice president/sales and marketing for Zurn Industries, which supplied a large part of the turf warming system at Lincoln Financial Field.

A turf-warming system creates an optimal root temperature. Groundskeepers can also cover the grass and blow warm air under the tarp, interspersed with periods of exposure to sunlight on bright days.

A turf-warming system does not melt snow, Sauer noted. It’s better to plow the snow off the field. In fact, if the system melted snow, it would suck up so much energy that the turf temperature would drop, he said.

The design of the Lincoln Financial Field was created by Avon, Colo., specifier ME Engineering and tweaked by West Virginia turf-warming specialist Subsurface Technologies. The Philadelphia stadium warms 100,000 sq. ft. of turf.

The playing surface is constructed with a top canopy of the turf itself, then 10 in. of root zone, a sand layer, a peat layer, diatomaceous (silica-based) earth mix designed to hold moisture and then below that is the PEX tubing. Below that is 12 in. to 18 in. of pea gravel for drainage and the tubing for the pop-up irrigation system.

A crew from mechanical Williard Inc., Jenkintown, Pa., under the direction of Project Executive Jim Quinn installed two natural gas Cleaver Brooks FLX 600 hot water boilers, 6 million Btuh each. Williard installed 6-in. black pipe headers underground until the pipe reached the field.

The pipe then transitioned into 3-in. HDPE headers. The field is broken into six zones, covered by nearly 40 miles of 34-in. ZurnPEX tubing spaced 9 in on center. Each circuit is about 400 ft.

Two circulator pumps feed the circuits, said Frank Mazzarese, project engineer for Zurn, each moving 300 gpm at 100 ft. of head. The circuits contain ball valves for isolation and zone valves in the boiler room for control, Mazzarese said. The system is piped reverse return.

The field system is DDC controlled via laptops that fire the boilers in sequence and control the zone pumps. Johnson Controls held the controls contract. There are eight field sensors in each zone, placed high strata and low strata and in four different locations. The sensors then average the temperatures and tell what zones to start up. The engineers did a shade study on what parts of field will have sun at what times.

Williard also handled the plumbing, heating and cooling contracts on the stadium. The job was challenging, Quinn said, in terms of logistics and dealing with the atypical elevations of the stadium.

The stadium has six levels: a service level, main concourse, lower suite level, club level, upper suite level and upper concourse level.

Heating is all electric. The facility contains 24 McQuay air-handling units and 235 fan-powered boxes with electric heat. The facility also contains electric fan coil units, unit heaters, cabinet heaters and electric baseboard that was installed by the electrical contractor.

Cooling comes from three McQuay R-123 chillers, two of them 700 tons and one 300 tons. A 30% ethylene glycol and chilled water mix flows through an Alfa Laval plate and frame heat exchanger. Baltimore Air Coil supplied three cooling towers.

Chilled water is pumped through primary-secondary loops by skid-mounted Taco pumps assembled by Flo-Pak. There are three primary pumps, two of them 1,130 gpm and one 520-gpm pump, two secondary pumps, each 1,390 gpm, and three condenser water pumps, each moving 1,580 gpm. The secondary pumps and one condenser water pump are controlled by variable frequency drives from ABB.

During cold weather, the chillers can be bypassed and cold condenser water can provide free cooling through the plate and frame heat exchanger.

Quinn’s crew installed a blend of welded and grooved joint black iron chilled water pipe. The Victaulic fittings worked well, Quinn said, “because we had no power on the site for electric welding machines.” The Victaulic fittings saved Williard the trouble of trying to use gas-powered welding equipment.

On the plumbing side, domestic water feeds through two skid-mounted domestic water booster pumps, assembled by Alyan Pump Co. with Armstrong pumps. Each skid, containing five pumps, serves half the stadium. The skids contain three 40-hp pumps moving 600 gpm each and two 20-hp pumps moving 200 gpm each.

Four gas-fired, vertical water heaters, containing 2,500-gal. of storage each, supply hot water through a circulating hot water system.

Water is supplied to 78 concessions stands and 132 suites. The bulk of concessions are on the main concourse and upper concourse levels. The club level and suite level contain pantries that feed the suites, but no concessions.

The stadium contains 4,000 American Standard fixtures, including the lavatories. All the suites have a bathroom. Some of the women’s gang toilet rooms contain 45 water closets, a fact that Quinn said has been noted by female journalists in the Philadelphia area.

In addition, Williard plumbed the four locker rooms, one for the Eagles and one for the visitor, and two college locker rooms. Temple University also plays its games there.

Storm water is a major issue. Williard installed a couple hundred Jay R. Smith drains just for the seating area. Four J-Line storm water pumps, two 8,000 gpm, one 5,500 gpm and a submersible 1,200 gpm, can all be staged depending on load going into the sump. They pump to a 36-in. main.

Williard also installed had 10 Flygt duplex sump pumps down on the service level, some for sewage and some for storm drainage.