From the NY Times:
The concrete pedestrian ramps at the brand-new $1.2 billion city-subsidized Yankee Stadium have been troubled by cracks, and the team is seeking to determine whether the problems were caused by the installation, the design, the concrete or other factors, according to several people briefed on the problems.
The ramps were built by a company accused of having links to the mob, and the concrete mix was designed and tested by a company under indictment on charges that it failed to perform some tests and falsified the results of others. But it is unclear whether work performed by either firm contributed to the deteriorating conditions of the ramps.
The Yankees have hired an engineering company to take samples from the ramps — they ascend from field level to the stadium’s upper tiers, carrying thousands of people each game — to determine the cause and the extent of the problems as the team finishes its first season in the new stadium and prepares for what could be its first World Series there.