In 1971, the first concrete overlay of an existing asphalt runway was built. The project was performed at Storm Lake Airport in Buena Vista County, Iowa. The project consisted of 20,000 square yards of 5 inch concrete being placed on the existing asphalt. The project was opened 7 days after paving once the opening strength of 4,000 psi was achieved. The project had a joint spacing of 12.5 feet and did not use any reinforcement. The project is still in service today with some minor patching and joint resealing.