What killed fish in Agnes and Henry?
It's a mystery that may never be solved: What killed the fish in lakes Agnes and Henry?
The "suspects" include treated water from Alexandria Lakes Area Sanitary District (ALASD), chlorine from water used to battle a blaze at the SunOpta plant, chemicals from the plant that burned in the fire, or a combination of factors that depleted oxygen levels.
This is a sensitive story to tell because there are no clear-cut answers and there may never be any. Here's what is known: Several hundred fish, including walleyes and northerns, were found dead on the open areas of lakes Agnes and Henry in the last few weeks.
Agnes was the site of the Ice Fishing Challenge on February 12 - a tournament where no one caught anything.
Three weeks earlier, on January 21-22, firefighters used 1.1 million gallons of water to fight the stubborn blaze at the nearby SunOpta plant.
Dean Beck at the Department of Natural Resources Fisheries Office in Glenwood said it "would be a stretch" to blame chlorinated water for killing the fish. He acknowledged, however, that chlorine is toxic for fish, even in low doses.
"The water and chemicals from the fire could have washed into a middle pond that goes into Agnes and Henry," Beck said.
He added, however, it's also possible that soy-based products that were burned in the fire or treated water from ALASD may have contributed.
Beck was quick to note that he was not pointing fingers at anyone - especially firefighters who were just doing their job. In fact, he was impressed with the way they handled the fire, such as moving potentially hazardous materials to a separate building and calling in state biohazard experts to help at the scene.
If chlorine was a factor, how did it get into the lakes? That question, too, has no definite answer.
An old wooden culvert, built in the 1930s, is behind SunOpta and drains into a pond that flows into Lake Agnes. It's open and foam was collecting in front of it, Beck said.
Firefighting foam may have flowed through the culvert and into the lake, and might have been eaten by microorganisms, which may have lowered the oxygen levels. But as Beck admitted, that's a lot of mights and maybes.
Oxygen levels were tested after the fishing tournament and came back OK but the fish kill could have happened weeks earlier, he noted.
The extent of the fish kill isn't known because the lakes are still mostly covered in ice, Beck said. The incident has been reported to the Department of Agriculture, he added.
Beck said there is no evidence that whatever killed the fish has impacted any other lakes in the chain.
Samples from some of the dead fish were collected for laboratory testing but the fish had been dead too long to get any results.
Rain and snow have diluted any chemicals, which also complicates the process of getting a definitive answer to the fish kill, Beck said.
Alexandria Fire Chief Jeff Karrow said the department uses a foam that's 100 percent biodegradable and contains no pollutants listed under the Clean Water Act.
The water the firefighters use is city water that contains chlorine as a disinfectant, Karrow said. During the SunOpta fire, the water froze during the sub-zero temperatures but would have thawed the next week. If there was runoff, the department believed it would have gone into a holding pond and not into any lakes, Karrow said.
Bruce Nelson, ALASD director, doubts the treatment plant played a role in the fish kill. Lake Winona, the first lake the plant's discharge flows into, has not shown any signs of a fish kill, at least for now.
Nelson said that the plant conducts daily tests of its discharge and there have been no abnormal readings. If there were toxic chemicals present, it would immediately affect the plant's microorganisms and that hasn't happened.
Nelson speculated that a combination of thick ice and snow on the lake, which is shallow, triggered a lack of oxygen.
Fish kills on Lake Agnes were common decades ago, Beck said, but one hasn't occurred for quite some time.
He noted that shortly after the sewer treatment plant was moved years ago, Agnes and Henry were able to develop a good fish population. The bass numbers on Agnes were so promising, the DNR enacted special regulations on the lake to protect the fish. In light of what's happened, Beck said, "The good fishing development on the lake may be set back."
If the evidence indicates chlorine or some other chemical problem, Beck said the DNR would get involved in a containment operation. But again, that kind of action would be premature. "Right now, our perspective on this is to try and track down what may have happened and prevent any future incidents," he said.