Iowa Department of Natural Resources
Nov. 15, 2007
For immediate release
GREEN STREAM COLOR
AND FISH KILL NEAR CRESTON IS TIED TO INDUSTRIAL
DISCHARGE
MEDIA CONTACT: Kirk Mathis at (712) 250-8643 (cell) or (712) 243-1934 (office).
CRESTON - Preliminary laboratory results indicate that the fluorescent green dye that discolored more than eight miles of stream below Creston Nov. 1 and 2 is also the cause of the fish kill that occurred.
Results from samples collected as the material entered and left the Creston Wastewater Treatment Plant, along with water samples collected by the DNR both upstream and downstream, indicate that the dye has a very high oxygen demand.
"This means that as the dye decomposes in the stream it can deplete the stream of oxygen, killing fish in the process," said Dan Stipe, supervisor of the DNR Atlantic field office.
"However there may also be a component in the dye that is toxic," he added. "The University of Iowa Hygienic Laboratory is testing for toxicity of the dye, Zyglo. Although they haven't completed the tests, results show that the dye is toxic to fish at fairly low concentrations - when it's diluted by 32,000 parts of water per one part of Zyglo."
The UHL is also testing the dye for metal levels and other substances to determine the specific cause of the fish kill. Testing is expected to be completed within a week.
"We can conclude that the fluorescent green dye killed the fish," said Dan Stipe, supervisor of the DNR Atlantic field office. "However, we don't yet know the mechanism that killed them."
The green dye was traced to Fansteel/Wellman Dynamics located on the east side of Creston where 280 gallons of the fluorescent dye was pumped into the sanitary sewer last week.
Company representatives told Stipe that the responsible employee was on a new job assignment and disposed of the dye to the sanitary sewer because the product label said the dye was biodegradable.
"Lots of products are biodegradable, but that doesn't mean that they are safe for disposal in the sanitary sewer, landfill or the nearest stream," Stipe said. "We've had fish kills caused by products like milk which people don't think of as dangerous.
"But milk has a high oxygen demand which pulls oxygen out of the water as it decomposes and it can cause fish kills in large enough amounts," he said. "Ammonia is another biodegradable product that can be toxic to inhale or in water."
DNR fisheries biologists counted 2,583 dead fish on the Platte River and the tributary leading to the river. Both small and large fish were killed, including mostly minnows, shiners, chub and dace. Fish killed also included carpsuckers, carp, bullhead, channel catfish, sunfish and largemouth bass.
Writer: Karen Grimes
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