At 2 p.m. Wednesday, the National Park Service (NPS) lifted the swimming
advisory for all beach areas at Indiana Dunes National Lakeshore.
The advisory had been issued on Monday when a possible hazardous material
spill was observed at Porter Beach, NPS said. “Laboratory tests conducted by
both the U.S. Geologic Survey and the Indiana Department of Environmental
Management determined that the substances found in the water did not pose a
health threat to swimmers.”
NPS rangers were dispatched to the beach area just after 12 p.m. on Monday,
when visitors reported an unidentified substance sticking to swimmers as
they exited the water. Working with the Porter Fire and Police departments
and the Indiana Department of Natural Resources, NPS made the decision to
remove visitors from the water until the substance could be identified.
In addition, the U.S. Coast Guard used a helicopter to observe the extent of
the material and estimated it to be approximately one-eighth of a mile in
length and being moved by lake currents to the east from Porter Beach
towards the Indiana Dunes State Park and the eastern portions of the
National Lakeshore, NPS said.
Water samples taken initially ruled out an oil spill and further laboratory
analysis indicated the presence of tricalcium orthophosphate, a food
additive. An increased amount of natural products, including algae and mica
particles, were also found to be in the water.
NPS continues to work with other agencies in investigating the source of