CHARLESTON, S.C. (WCIV) -- The Charleston District of the U.S. Army Corps of Engineers is trying out a new, cost-effective way to stop erosion on the Isle of Palms.They're called oyster castles and they help protect the shoreline from erosion and create an oyster habitat.Officials say it's a cost-effective alternative to traditional rock structures which is also good for the environment. "Shoreline protection is very important to the public from the standpoint of protecting their high ground property," said Project Manager David Warren. "For us, it's protecting the dredge disposal area behind us and prevents the wave action from the boats that pass by from damaging what we spent millions of dollars to build."Dredging is the process of moving sediment to help keep water navigable.The people working this particular project say these oysters are not for harvesting which could actually damage the structure and negatively effect the project.The project began in May of 2012 and at the last inspection, was showing a growth of 97 percent from 15 millimeters in height to 29 millimeters. Contractors also not a growth in grass and sediment behind the castles.In June, District employees noted several species making the castles a home including crabs, fish and snails. Those new residents brought in birds that feed on the oysters."We used volunteers to build human chains for loading and unloading the blocks, stacking the blocks, and ultimately building a reef about 60 feet long by 3 feet wide," Joy Brown of The Nature Conservancy said in a statement. "This promotes oyster substrate growth and animal species population growth."TNC is now looking at the possibility of installing another system of oyster castles at James Island County Park.