The U.S. Forest Service has begun draining Lion Lake near Hungry Horse in order to repair two dams that are more than 70 years old. Recent surveys found one of the earthfill dams is leaking and at risk of failure, which could affect wildlife habitat along the South Fork of the Flathead River.

Lion Lake is a popular recreation area about a mile south of U.S. 2 near Hungry Horse and Martin City. The U.S. Bureau of Reclamation dammed the lake around 1947 or 1948 to supply water for a government work camp during construction of the larger Hungry Horse Dam.

The main dam at the south end of Lion Lake, as well as a smaller structure at the northwest end, were transferred to the Forest Service sometime after 1950, according to a project memo from Rob Davies, chief of the Hungry Horse-Glacier View Ranger District.

The Forest Service announced Wednesday it would begin draining the reservoir immediately, with repairs expected to take place from August through October. Both dams will be closed to the public due to safety concerns, but visitors will still be able to access the lake via a recreation area on the north side as well as pullouts along Montana 895.

Davies approved a plan that involves draining the lake to the level of an outlet pipe on the main dam; slip-lining and replacing portions of the pipe; removing saturated earthfill; installing a chimney and a toe drain to collect water seepage; rebuilding the dam embankment and placing riprap on the shore to prevent erosion.

Additionally, crews will add about 2 feet to the height of the primary dam and about 3 feet to the height of the secondary dam, using material cut from slopes along a Forest Service road about half a mile from the lake.

The main dam is built over Whelp Creek, a tributary to the South Fork. Davies wrote that the project is not expected to impact grizzly bears, Canada lynx, or bull trout, which do not swim in Lion Lake.

"The short-term lowering of the reservoir creates short-term effects to the lake habitat but increases the long-term protection of wetlands, floodplains of the Whelp Creek watershed, including downstream segments of Whelp Creek and the South Fork of the Flathead River," he wrote.

In a news release, the Forest Service said it will begin refilling the lake as soon as the repairs are completed. The agency said it doesn't know how long it will take for the water to return to its current depth, but the water level and access points should be "back to normal for the 2022 summer season."

The Forest Service said it received only one comment on the proposed project during a 30-day public comment period that ended April 7.

Assistant editor Chad Sokol may be reached at 406-758-4439 or csokol@dailyinterlake.com.