Duluth agrees to $202,000 package after 1.7 million‑gallon potable water release kills trout in Tischer Creek

DULUTH — City staff on Monday walked the Duluth City Council through an investigation into an August 2024 release that drained roughly 1.7 million gallons of potable water from an underground Woodland neighborhood reservoir into Tischer Creek and caused a substantial fish kill.

Ryan Granlund, a utility program coordinator in the public works utilities division, told the council the reservoir’s bottom drain is physically connected to the storm sewer network that discharges untreated to Tischer Creek. On the day of the release the stream was at base flow — about 0.19 cubic feet per second — while the release flowed at roughly 10.7 CFS. Granlund said the disinfectant concentration in the distributed water was about 1.6 parts per million, a normal level for drinking water but far above thresholds toxic to brook trout: “Chlorine toxicity levels are 0.038 parts per million for trout,” he said, explaining how the mismatch in flow and concentration produced lethal conditions for fish.

The city’s review, conducted with the Minnesota Pollution Control Agency (MPCA) and the Minnesota Department of Natural Resources (DNR), concluded the discharge produced substantial ecological harm. Granlund said agency sampling and assessments documented more than 1,500 brook trout of multiple size classes affected, along with impacts to macroinvertebrates and the local food web used by trout.

Why it happened and the regulatory outcome

Granlund said the reservoir was drained to gain inspection access. Because the buried reservoir’s bottom drain connects to the storm sewer rather than the sanitary system, the potable water went directly to receiving waters without treatment or dilution.

Two parallel regulatory tracks followed: MPCA enforcement under the city’s MS4 stormwater program produced a stipulation agreement and a $12,000 civil penalty; the trustees’ Natural Resource Damage Assessment (NRDA) process — led by MPCA and DNR as co‑trustees — calculated injuries to fish and recreational use and produced a separate restoration and compensation package totaling about $190,000. The council voted unanimously to authorize both the stipulation agreement and the NRDA agreement.

Planned restoration projects and local use of funds

Granlund and staff described three restoration priorities the trustees and partners have identified for Tischer Creek: removing a low‑head dam upstream of West Lewis Street to improve fish passage, installing water‑quality treatment and sediment controls near the Hartley Nature Center where Tributary 7 enters the creek, and supporting a youth and adult brook trout angling and stewardship program in partnership with Hartley Nature Center. The presentation said roughly $50,000 of the NRDA package is expected to support programming and equipment for the fishing and stewardship component; other monies will go to restoration work identified by the trustees.

Granlund emphasized that MPCA and DNR, as co‑trustees, determine the projects to be funded through NRDA and that the city will partner on implementation where appropriate.

Steps to prevent future releases

City staff told the council they implemented immediate operational changes after the event, including tagging and lock‑out procedures for reservoir drains and large valves, integrating dechlorinating diffusers into hydrant‑draining operations, flagging critical valves in GIS utility maps, expanding reporting of unplanned releases, and developing a formal standard operating procedure for potable water releases. Granlund said those measures were integrated into the city’s stormwater pollution prevention program and reviewed with MPCA.

Council questions and agency input

Councilors pressed staff on recovery timelines and long‑term ecological impacts. Granlund said DNR’s injury assessment estimated the loss of full recreational value could persist for roughly eight years, though some fish and portions of the system were unaffected and restoration actions aim to accelerate recovery. Granlund said the DNR advised it does not plan to restock brook trout in Tischer Creek because of concerns about preserving the stream’s existing, locally adapted genetics.

What the council approved

The council approved two formal actions linked to the incident: Resolution 120, the MPCA stipulation agreement (civil penalty $12,000), and Resolution 121, the NRDA agreement (approximately $190,000 for restoration and programming). Both measures passed by unanimous votes following staff presentations and council discussion.

Granlund closed by urging that preventing future incidents was the primary takeaway and that the new operating procedures and interagency cooperation should reduce the risk of chlorine discharges to trout streams going forward.

— Ryan Benner contributed reporting from the Duluth council chambers.