As reopening nears, Memorial Stadium rolls out the green carpet

See the new turf being installed. (Cal Athletics video)

An enormous green welcome mat is being installed at Memorial Stadium — 100,000 square feet of state-of-the-art synthetic turf.

While it will take about 10 days to lay the turf, preparing the field for this final step began several months ago — one of many projects to ready the stadium to reopen for the Golden Bears’ first home game on Sept. 1. The stadium closed in December 2010 to undergo a massive $321 million overhaul, the core of which was a seismic retrofit of the historic site.

This past spring, the field was dug up and excavated an additional four feet. The lowering of the field was done to improve sightlines for fans in the lower seating areas and to make room for installation of an extensive infrastructure for game operations — including a network of water pipes (for drinking water and turf irrigation), broadcast cable, coaching and replay communications and storm-drain pipes.

“In these major sports venues, the field, in essence, is the stage for the event, and it takes a lot of support to make the event run properly,” said Bob Milano Jr., UC Berkeley’s assistant athletic director for capital planning and management.

As for why artificial turf needs irrigation, Milano explained that large overhead sprinkers on the perimeter of the field, fed by the irrigation system underground, will provide short-term, evaporative cooling to keep the turf cool on hot days and during heavy training sessions; it will also serve to help routinely clean the turf.

Above the game-operations infrastructure, crushed stone was placed to provide a smooth playing surface, then a shock pad or “e-layer.” The latter is a blend of crumb rubber and pea gravel with a polyurethane binder mixed together with a heavy paste and then leveled over the entire field. This layer under the turf provides additional shock absorption and safety for the athletes, Milano said.

“This elastic layer shock pad is not typically used (on college football fields),” said Milano. “But it has long-term benefits, mostly to provide additional shock absorption and make the surface safer for training and competition.”

After that, the turf is laid in place. The long, shag rug-like fibers — 2 1/4 inches long — on backing go in first, in five-yard panels with the white yard lines stitched in. The other field markings, such as hash marks, yard-line numbers and logos, are hand cut into the turf. Over this installation is spread a blend of rubber and sand, a soil substitute that stands the fiber up, Milano said, and provides cushioning for the players and traction for their cleats.

The new synthetic turf will be more durable than grass in Memorial Stadium, which multiple teams, headquartered in the Simpson Center for Student-Athlete High Performance, must share for practices and competition.

Seeing the green carpet as it’s being rolled out is generating excitement among those waiting for the stadium renovation to be completed. “The installation is one of the visual symbols that we’re getting close to being ready for the game on Sept. 1,” said Milano. “The turf is an element that the fans and the team really associate with the stadium being done and ready for football.”

The field contractor for the stadium is ValleyCrest Landscape Development of Pleasanton. The turf is being installed by Hellas Sports Construction of Austin, Texas.