CHARLESTON, S.C. (AP) — After the longest cable-stayed bridge on the continent opens next month comes the massive job of demolishing the two bridges that will be replaced by the $632 million Ravenel Bridge.

The new bridge is scheduled to open on July 16. In August, crews will start a $57 million project to take down the existing Grace and Pearman bridges which link Charleston and Mount Pleasant. On Monday, highway officials held a public meeting on the demolition plans.

Residents heard from officials with the state Department of Transportation and the demolition contractor, The J. Cashman/Testa Corp. Joint Venture.

Mount Pleasant resident George Smyth had concerns about trucks hauling debris clogging local roadways. More than 321,000 tons of concrete will be trucked from the bridge sites.

‘‘There’s going to be a lot of truck traffic on both sides of the bridge,’’ he said.

George I. Boniface, 73, also of Mount Pleasant, disagrees with removing the old bridges before the new span has proven itself.

‘‘It has not been exposed to traffic. Why rush with the demolition of both bridges?’’ he asked. He said the Transportation Department should keep one of the existing bridges standing.

Charles Dwyer, the bridge project manager, said while the comments may not change the overall plans for the demolition, concerns from the public may help the department fine tune some aspects of the process.

‘‘If they never tell us, we never know,’’ he said.