(Ben Bloker / S&S)

(Ben Bloker / S&S)

Workers put down the lava rock type top layer on a portion of the Kaiserslautern Military Community Center’s green roof. Seven types of sedum plant, like the plants in the top photo, will be grown to prevent water runoff on the 10-acre roof. (Ben Bloker / S&S)

RAMSTEIN AIR BASE, Germany — As customers graze in the food court or catch a movie in the new four-screen movie theater complex, work on the Kaiserslautern Military Community Center continues above their heads.

The KMCC’s roof is the final piece of a yearslong beleaguered project. And to the disappointment of Air Force officials, it won’t be done before the Sept. 21 scheduled opening of the facility’s military exchange.

But compared to 18 months ago, things are looking up.

"We’re going to leave the project this time with a working green roof, and a green roof that doesn’t leak," said Col. David Reynolds, U.S. Air Forces in Europe’s engineering programs division chief.

So far, there are no leaks, something officials couldn’t say last year.

In April 2008 workers had to rip up the roof — in many places scraping it all the way back down to the concrete — after numerous leaks were discovered. Soil was already spread across the 35,000 square meters covering the mall section, awaiting only the planting of seeds. It all had to be removed.

Reynolds said the idea to make the 10-acre KMCC roof green was agreed to by the Air Force and German government in order to meet environmental and energy savings requirements.

A green roof cuts energy costs by moderating temperature extremes, thereby reducing interior heating and air-conditioning requirements, Reynolds said.

It also reduces storm runoff, since rainwater is filtered through the soil and captured for use by the plants. On a typical black tar and asphalt rooftop, the water splashes off the building, requiring the addition of extensive drainage such as ditches or a pond, especially for larger roofs, so as not to inundate ground runoff systems.

At the KMCC, where space is tight, there was no such room, Air Force officials said.

Sprouting atop the KMCC will be a mix of seven different desert sedums. According to the online botanical dictionary Gardenguides.com, sedums are mostly low-growing, hardy plants that do well in poor soil and in hot, sunny conditions, requiring little water.

For the Air Force, that means little maintenance. Workers won’t have to mow the roof, though they will have to weed on occasion, Reynolds said. The roof also holds an irrigation system in the event of a drought.

The dirt is more than a foot thick, equal parts’ mixture of volcanic rock and organic soil. Multiple filtering, insulation and adhesive layers are stacked under the soil. A waterproof membrane locks moisture out of the building. Egg crates retain water that the plants don’t immediately absorb. A felt-like material, dubbed the "coffee filter," collects fine dirt.

Though a green roof costs more than a conventional one, it’s expected to last 40 years or more, twice the life expectancy of an artificial roof. The KMCC’s green roof cost $7 million — the first time around. Repairs could cost $10 million or more, according to some estimates, and it’s still not certain who will pick up the tab.

The faulty roof was a big reason the opening of the 844,000-square-foot KMCC was delayed by years. The project was originally supposed to open in late 2005. The KMCC finally opened in phases this summer, starting with the 350-room hotel, Outdoor Recreation, Macaroni Grill restaurant, Ramstein Tickets and Tours, and a few shops on July 2.

Reynolds blamed the roof troubles on "poor workmanship, improper materials in some locations," but said the problems were not driven by green roof technology.

"It was the failure of a contractor to build a basic, built-up roof, which are the layers below the green roof," he said.

That contractor went bankrupt, and German state construction agency Landesbetrieb Liegenschafts und Baubetreuung, or LBB, which is coordinating the mall-hotel project with additional oversight by USAFE, hired three new contractors to repair the roof, according to USAFE officials.

LBB spokesman Markus Ramp said Friday the work will likely continue on past October, offering no estimated completion date.

The roof repairs are being financed by a loan provided by the German government. The U.S. and German governments still have to work out the details of who will ultimately pay those costs, though Reynolds says the Air Force doesn’t expect to have to pay for its roof twice.

LBB officials said earlier this year they have asked a German court to start an independent review of what caused the problems with the KMCC construction and who should be held responsible for repair costs. Those issues likely won’t be resolved until after construction on the KMCC finishes completely and final costs are known.

Marcus Klöckner contributed to this story.