MICHIGAN CITY, Ind. -- A popular 126-foot high sand dune at Indiana Dunes National Lakeshore will remain closed indefinitely while scientists continue to investigate what caused an Illinois boy to become buried under 11 feet of sand last summer, officials said Thursday.
The decision to keep Mount Baldy and its Lake Michigan beachfront closed was made because two more holes have been found on the dune in addition to the one then-6-year-old Nathan Woessner of Sterling, Ill., fell into July 12, acting park Superintendent Garry Traynham said.
"Mount Baldy is one of the most visited sites in the national lakeshore, attracting thousands of visitors each year, but the continued development of these holes in the dune surface poses a serious risk to the public," Traynham said.
Scientists report the holes are short-lived, remaining open for less than 24 hours before collapsing and filling in naturally with surrounding sand.
Scientists are trying to determine why part of the dune collapsed, burying the boy for more than three hours. The boy spent weeks undergoing rehabilitation after the accident. The dune has remained closed to the public since.
Park officials say ground-penetrating radar studies by the Environmental Protection Agency have identified a large number of anomalies below the surface of Mount Baldy, but scientists from the National Park Service, Indiana University and the Indiana Geological Survey have not been able to determine what causes the holes to form.
Scientists plan to map openings, depressions and anomalous features on the dune and use more advanced ground-penetrating radar to try to determine the cause of the holes. Park employees also plan to continue planting Marram grass on portions of Mount Baldy where the native dune grass used to grow hoping that could help prevent holes from opening.
Park officials say the investigation could last until this fall.