SAN FRANCISCO (CBS SF) - The walking path atop the Transbay Transit Center in San Francisco already needs to be replaced, and the cost could top $1 million.

The center itself has been closed for several months after cracks were found in steel support beams last September.

READ MORE: Engineers Making 'Satisfactory Progress' On Salesforce Transit Center

The $2.2 billion four-story Salesforce Transit Center -- stretching four city blocks and equipped with access to bus service, a 5.4-acre rooftop public park and space for retail shops, art displays and restaurants -- first opened in August. Just weeks later, however, the discovery of the cracked steel beams forced the center's closure.

A date for the reopening of the transit center and the rooftop park has not been determined.