Groundkeepers mow the course during the practice round at the 2011 U.S. Open at Congressional Country Club in Bethesda, Md. on Wednesday, June 15, 2011. (Copyright USGA/Joel Kowsky)

USGA Agronomist Darin Bevard uses a TruFirm to check the firmness of the putting surface during the practice round at the 2011 U.S. Open at Congressional Country Club in Bethesda, Md. on Wednesday, June 15, 2011. (Copyright USGA/Joel Kowsky)

USGA Agronomist Darin Bevard calculates green speed during the practice round at the 2011 U.S. Open at Congressional Country Club in Bethesda, Md. on Wednesday, June 15, 2011. (Copyright USGA/Joel Kowsky)

USGA Agronomist Darin Bevard uses a Stimpmeter to determine green speed during the practice round at the 2011 U.S. Open at Congressional Country Club in Bethesda, Md. on Wednesday, June 15, 2011. (Copyright USGA/Joel Kowsky)

A groundkeeper syringes the putting surface during the practice round at the 2011 U.S. Open at Congressional Country Club in Bethesda, Md. on Wednesday, June 15, 2011. (Copyright USGA/Joel Kowsky)

USGA Agronomist Darin Bevard, left, and Director of Grounds Mike Giuffre inspect the course during the practice round at the 2011 U.S. Open at Congressional Country Club in Bethesda, Md. on Wednesday, June 15, 2011. (Copyright USGA/Joel Kowsky)