The Army Corps of Engineers says it could take years to remove unexploded ordnance from Plum Tree Island National Wildlife Refuge.

George Follett, the corps' project manager, says the cleanup's cost and length won't be known until a baseline study of the area is completed.

The 3,276-acre refuge served as a bombing and gunnery range for the U.S. military for more than 40 years.

The corps awarded a two-year contract to Shaw Environmental Inc. to conduct the study, which will determine how much ordnance remains and where it is. Shaw also will determine whether soil or surface water has been contaminated.

Mike Clemens with Shaw says any exposed ordnance found during the study will be detonated on site.