State agencies are investigating dead fish and an unusual green color in the Salt Fork River first noticed by residents last week.

The intense green color of the river, which is low after weeks with no significant rainfall and with hot summer temperatures, was first noticed Wednesday and Thursday by nearby residents who reported it to local agencies, including the Illinois Environmental Protection Agency.

Since then, the bright green color has been observed as far upstream as Flatville in Champaign County, and downstream, east of Homer into Vermilion County. Dead floating fish and dying fish have also been observed within the green zone. 

By Saturday, some residents at various points along the river were reporting a lot of dead fish, including carp, suckers, small darters and minnows.

Initial samples taken Friday by IEPA were inconclusive, Briggs said. Additional samples were collected and sent to the agency’s laboratory for further analysis.

“The individual that reported the possible bloom was notified that we are investigating, and it was noted that it is best to avoid contact with the water until it returns to normal,” Biggs said.

According to the U.S. EPA, harmful algal blooms are “overgrowths of algae in water” that can produce dangerous toxins that can sicken people and animals, create dead zones in water, and increase drinking water treatment costs, but even nontoxic blooms can hurt the environment. To occur, blooms need sunlight, slow-moving water and nutrients (nitrogen and phosphorus), and nutrient pollution makes the problem worse, leading to more severe blooms that occur more often, according to the EPA.

Oakwood’s water treatment plant is downstream from where the green color has been observed in the Salt Fork.

Biggs said IEPA has been in contact with a conservation officer with the Illinois Department of Natural Resources regarding the fish kill on the Salt Fork. She said IEPA informed their staff of the sampling being done, adding that IEPA will remain in contact with their office as results are made available.

Biggs said their additional testing results should be done soon, and if there’s confirmation of an algae bloom, IEPA typically issues a news release alerting people in the area to avoid contact, including recreational activities.

Primary sources of nitrogen and phosphorus are agriculture from animal manure and chemical fertilizers; stormwater when rain falls in cities and towns and carries pollutants, including nitrogen and phosphorus, into local waterways; wastewater from sewer and septic systems that don’t always operate properly or remove enough nitrogen and phosphorus before discharging into waterways; fossil fuels like electric power generation, industry, transportation and agriculture that have increased the amount of nitrogen in the air through use of fossil fuels; and homes where fertilizers, yard and pet waste and certain soaps and detergents contain nitrogen and phosphorus that contribute to nutrient pollution if not properly used or disposed.