DULUTH - About 1.7 million gallons of chloramine-treated water drained from a reservoir into the city's Tischer Creek over 15 hours in July, killing hundreds of brook trout and other fish.

The Minnesota Pollution Control Agency (MPCA) said Monday the city revised the number it had initially reported, which was 500,000 gallons. The Woodland neighborhood reservoir leaked again in mid-August, but an emergency excavation routed the water into a sanitary sewer.

The MPCA said in a statement that while the release wasn't dangerous for humans, "it created conditions that were potentially toxic to fish and other aquatic life."

Chloramine is made up of chlorine and ammonia. The water was released during a maintenance operation.

Last month, MPCA crews collected invertebrate samples at five locations along the creek to determine the impact of the fish kill and the rate of recovery. Don Schreiner, a fisheries biologist with the University of Minnesota Sea Grant program, has said he expects recovery to take at least three years.

Test results will take several months, the MPCA said.

The eastern Duluth creek empties into Lake Superior through the grounds of Glensheen Mansion, and is one of the city's designated trout streams. The dead fish were found along nearly 2 miles of the creek.

Brook trout are critical to a stream's ecosystem, and the only native stream-trout species in the area. Some of the city's trout streams have undergone extensive restoration efforts to combat warming and habitat and water access loss.

Annika Hansen was the first to report the kill after she noticed several dead fish belly up in the creek. She had brought her dog there to swim.

"It's a beautiful little stream and it's so nice to see fish swimming locally," she said of Tischer Creek. "Hopefully it can come back quickly."