Helena, EPA say no impact to city water after mine waste spills into Tenmile Creek

Tenmile Spill
Tenmile Spill
Posted at 8:21 AM, Jul 14, 2021
and last updated 2021-07-14 10:21:18-04

HELENA — The U.S. Environmental Protection Agency says only about 100 feet of Tenmile Creek were affected by the release of sludge from a mine in Rimini.

Chris Wardell, community involvement section chief for the EPA, said in a statement that a small amount of sludge – about 20 to 40 gallons – was released Monday from the Susie Mine. He said crews had been using a hose to suck up water from inside the mine tunnel, when the hose accidentally picked up excess sediment and sludge.

“The sludge exited the Susie Adit draining to Tenmile Creek in a manner similar to many previous discharge events or ‘burps’ over the past century in this heavily mined and mineralized area,” Wardell said.

The EPA and Montana Department of Environmental Quality determined this “dewatering” operation was needed because of a collapse that occurred in the mine months ago.

“This collapse caused a blockage of mine-impacted water within the tunnel, which without action to remove mine-impacted water and prevent further degradation of the mine entrance, increases the risk of an uncontrolled release to Tenmile Creek,” said Wardell.

EPA leaders plan to resume dewatering in the next few days, and to install additional control measures to try to keep sludge releases like this from happening.

This story has been updated. Original post below:

The city of Helena and the U.S. Environmental Protection Agency say there will be no impact to the city’s drinking water supply, after material from an abandoned mine spilled into Tenmile Creek near Rimini.

Ryan Leland, Helena’s public works director, says city water operators received a report Monday about mine waste in the creek. They determined it came from the Susie Mine, a previously treated mine in the area.

The city of Helena takes much of its drinking water from the Tenmile Creek watershed. However, that water is removed from the creek upstream from the Susie Mine, and carried down to the water treatment plant through a pipe system.

“It’s never actually going to get into our drinking water, but it is in the watershed, and we’re concerned just with regular water quality and for other water users in the area,” said Leland.

An EPA spokesperson confirmed the event should not impact Helena’s water supply, and noted it happened in a section of the creek that has been receiving contaminated material for more than a century and is targeted for future remediation.

Tenmile Spill
Tenmile Creek near Rimini, July 12, 2021, after material from an abandoned mine reportedly spilled into the creek.

The area around Rimini is managed by the EPA as the Upper Tenmile Creek Mining Area, a Superfund site. It covers 53 square miles and includes about 150 active or abandoned mines. Mining for gold, lead, copper and zinc extended from the 1870s to the 1930s.

Over the last 20 years, authorities have removed contaminated soils from many nearby properties, set up new water systems for residents, and installed systems to limit outflows from area mines.

According to government reports, the Susie Mine had originally been one of the main sources of arsenic and other contaminants in the watershed.

Photos taken by city staff show a section of the creek turned orange after the spill. However, city leaders say they have no confirmation yet of what type of substances may have been in the spilled material.