Ground was broken for PNC Park on April 7, 1999,[34] after a ceremony to christen the newly renamed Roberto Clemente Bridge.[35] As part of original plans to create an enjoyable experience for fans, the bridge is closed to vehicular traffic on game days to allow spectators to park in Pittsburgh's Golden Triangle and walk across the bridge to the stadium.[36][37] PNC Park was built with Kasota limestone shipped from a Minnesota river valley, to contrast the brick bases of other modern stadiums.[38] The American-made raw steel for the ballpark was fabricated in Brownsville, Pennsylvania by Wilhelm and Krus.[39] The stadium was constructed over a 24-month span—at the time of construction, three months faster than any other modern major league ballpark—and the Pirates played their first game less than two years after groundbreaking.[40] The quick construction was accomplished with the use of special computers, which relayed building plans to builders 24 hours per day.[40] In addition, all 23 labor unions involved in the construction signed a pact that they would not strike during the building process.[40] As a result of union involvement and attention to safety regulations, the construction manager, the Dick Corporation, received a merit award for its safety practices from the Occupational Safety and Health Administration.[8]