Reconstruction plan approved for historic Yellowstone bridge

Yellowstone National Park officials plan to reconstruct the historic bridge at Isa Lake atop Craig Pass, between West Thumb and Old Faithful. (Ruffin Prevost/Yellowstone Gate)

Yellowstone National Park officials plan to reconstruct the historic bridge at Isa Lake atop Craig Pass, between West Thumb and Old Faithful. (Ruffin Prevost/Yellowstone Gate)

By Ruffin Prevost

A two-year project to reconstruct a historic bridge in Yellowstone National Park will move forward after a planning review concluded last month that the work would have no significant environmental impact.

Reconstruction of the Isa Lake bridge, which spans a section of the road connecting West Thumb and Old Faithful, will proceed when funding becomes available through the Federal Lands Highway Program, according to a statement released by the park’s public affairs office.

Park officials said the work is needed to bring the bridge up to current design standards, improve safety, increase vehicle load capacity and preserve the historic integrity of the bridge.  Improvements will also be made to adjacent parking and pullout areas.

The 70-year-old Isa Lake bridge is located atop Craig Pass at an elevation of 8,262 feet. A September 2010 inspection report from the Federal Highway Administration found the bridge in poor condition and recommended replacing it.

Isa Lake, which actually is more pond than lake, sits within Craig Pass, and is famous because it drains to two different oceans, but does so “backwards,” according to the National Park Service. Isa Lake has been described as “the silver ribbon that connects two oceans.”

Early visitors to Yellowstone Park pause alongside Isa Lake at Craig Pass, atop the continental divide. (NPS photo - click to enlarge)

Early visitors to Yellowstone Park pause alongside Isa Lake at Craig Pass, atop the continental divide. (NPS photo – click to enlarge)

“At one time, it was probably the only lake on Earth that drained naturally backwards to two oceans, the east side draining to the Pacific and the west side to the Atlantic,” states the 2012 edition of Yellowstone Resources and Issues Handbook, a Park Service reference guide.

Isa Lake’s water levels typically don’t fluctuate much during most of the year. But during the peak of spring runoff after a snowy winter, it will drain from the east into Shoshone Lake and the Lewis River in Yellowstone, then into the Snake River and the Columbia River, emptying in the Pacific. From the west, it feeds the park’s Firehole River, which flows into the Missouri River, feeding the Mississippi River on its way to the Gulf of Mexico.

An environmental assessment of the bridge reconstruction project resulted in a Finding of No Significant Impact, allowing the existing Isa Lake Bridge to be removed and a bridge of similar appearance on the existing alignment to be built.

Among the highlights of the approved reconstruction plan:

  • During bridge reconstruction, the road will remain open via a temporary bridge spanning Isa Lake to the north of the existing bridge.
  • The existing parking area and pullouts will be repaired. One handicapped accessible parking space will be created.
  • New curb logs will be installed.
  • The existing kiosk structure will be rehabilitated.

Planning documents are available on the National Park Service Planning, Environment and Public Comment website at http://parkplanning.nps.gov/Isa.

Contact Ruffin Prevost at 307-213-9818 or [email protected].

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