About 12,000 pounds of oyster shells are heading back to the Virginia waters from where they came. More than 150 bushels of shells will be collected in Richmond on Friday and delivered to the Chesapeake Bay Foundation’s Oyster Restoration Center in Gloucester Point. They’ll be used to build oyster reefs and other restoration projects. Oyster shells have become scarce because of the bay’s much-diminished oyster population. They are critically needed to create platforms to restore one of the bay’s signature catches. The shells were collected by area restaurants, volunteer groups, the state and the Rice Center, VCU’s environmental life sciences field station on the James River.