29 August 2024
DULUTH — The city has reported a second spill of clean drinking water into Tischer Creek this month after an earlier spill likely caused more than 1,000 fish to die.
City officials filed a report with the state Aug. 14 saying the second accidental spill happened for several hours Aug. 13 as water mysteriously flowed out of the large, underground reservoir the city operates for storage near the intersection of Minneapolis Avenue and East Mankato Street.
“Water is releasing from the Woodland Reservoir via an unknown means,” the city noted in its report to the state. “The water is reaching the storm sewer which is emptying into Tischer Creek. Cause is under evaluation. They are performing an emergency dig to divert that water into the sanitary sewer for reclamation by the water treatment process. No impact on water deliverability to the public. No cause of concern for water quality.”
Ryan Granlund of the Public Works Department said in the city’s report that an emergency diversion eventually stopped water from entering the storm sewage system that flows into Tischer Creek in that area. The diversion instead diverted the water into the sanitary sewage system, which is sent to the Western Lake Superior Sanitary District sewage treatment plant.
According to the city’s estimate at the time, the spill was about 36 gallons per minute, which would have amounted to more than 17,000 gallons by the time it was diverted.
On Aug. 1, a major dump of around 500,000 gallons of clean city water flowed for the same reservoir into Tischer Creek and is considered the likely cause of a major die-off of fish, crayfish and leeches. More than 1,000 fish died downstream of the spill, many of them brook trout.
Unlike the Aug. 1 spill, there have been no reports of a major fish die-off after the Aug. 13 spill, possibly because it was considerably smaller than the first spill and because so few fish remained in the creek in that area.
The Aug. 13 spill and report were made public by Fond du lac Band tribal officials at a city Natural Resources Commission meeting Wednesday and have not yet been announced by the city in any public manner.
Neither the city nor Minnesota Pollution Control Agency has released results of water and fish tissue samples taken after the initial spill reported by the News Tribune on Aug. 2. Neither the city nor state responded immediately to News Tribune requests to comment on the Aug. 13 spill.
In many similar cases in the recent past, the MPCA investigates and negotiates with the responsible party for a spill, often reaching a consent decree and/or stipulation agreement that often includes a penalty as well as a detailed report of how the responsible party is going to prevent the same thing from happening in the future.
Several biologists have said it’s likely the small amounts of chemicals added to make the lake water safe for people to drink are what made it unsafe for fish.
According to reports filed with the state, Duluth drinking water contains chlorine (as high as 1.72 parts per million) and fluoride (about 0.74 ppm) as the only chemicals intentionally added to the Lake Superior water. (The reports also show very tiny amounts of trihalomethanes and haloacetic acids, in parts per billion, both unintentional byproducts of the chlorine disinfection process.)
Chlorine can kill fish in two ways, said professor Allen Mensinger, a fish physiology expert in the biology department at the University of Minnesota Duluth. It can burn their gill tissue, damaging it enough to be fatal. More profoundly, chlorine disrupts how a fish’s red blood cells carry oxygen to the body.
“The chlorine changes the hemoglobin. … The fish essentially suffocates,’’ Mensinger told the News Tribune earlier this month. Chloramine, when present, does the same, he noted. Neither fluorides nor the other trace chemicals reported in Duluth water would have such fatal results.
City officials have for years sought funding to upgrade the city’s drinking water delivery system, noting much of the infrastructure is a century old. In November, the city received a stern letter from the federal Environmental Protection Agency after agency officials inspected the city system in August 2023.
“Based on the inspection, EPA has found evidence that your system has significant deficiencies,” the federal warning noted.
In all, the agency identified 55 “areas of concern” that included leaking tanks, valves and pipes; corrosion; failing roofs; and a lack of backup redundancy in the system to ensure continued operation in the event of a failure.
Duluth’s vast water system includes about 400 miles of pipe, the Lakewood pumping and treatment center, 15 ground reservoirs, five elevated tanks and 11 pumping and booster stations. In addition to Duluth residents and businesses, the city also supplies clean water to several of its surrounding neighbors, including Hermantown, Proctor and Rice Lake.
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