NORFOLK, Va. (AP) - About 600 concrete balls will be placed into the Lafayette River this summer to help restore the oyster population.

The Chesapeake Bay Foundation said in statement that it used a crane last week to lower 100 of the balls into the water in Norfolk.

The Lafayette is a tributary of the Elizabeth River, which flows into the Chesapeake Bay. The nearly 5-acre (2-hectare) reef is being constructed at the mouth of the Lafayette.

The foundation said it will install the most reef balls ever placed on a single site in Virginia. The hollow balls weight up to 300 pounds (136 kilograms) each. They provide habitat for oysters, fish, crabs and other sea life.