The Slims River Bridge, Alaska Highway
Northern Highways - Alaska, Yukon & Northern BC
An Explorer's Guide to the Alaska Highway
The Slims River, which flows into Kluane Lake, was named after a pack horse that drowned while trying to cross it during the 1903 Kluane gold rush. The first bridge across it was built by U.S. Army Engineers in 1942, about a kilometer upstream from the current bridge position. The following year, the road was re-routed and another wooden bridge built at the current position.
The first steel Slims River Bridge was built by the Canadian Army in 1955, at what was by then Mile 1060 of the Alaska Highway (measured from Dawson Creek, B.C.). It later became Km 1704, and with highway straightening, it is now Km 1647. The 1955 bridge consisted of two steel through truss spans of 61 meters each on reinforced concrete piers and abutments.
The latest bridge, bult in 2009-2010, is an 80-meter single span with steel girders and concrete deck. The abutments are on steel piles filled with concrete. The finished bridge deck is 11 meters wide traveled way with a 2 meter wide sidewalk which ties into a trail system. The design life of the new bridge is 75 years. It has been designed to meet the seismic requirements for a lifeline bridge.
Construction of the new bridge:
- Fall 2008: Relocation and demolition by Surespan Construction Ltd. involved moving the south span of the existing bridge to the detour, and the demolition of the north span of the existing bridge.
- Fall and early winter 2008: installation of stone columns using the vibro-replacement technique, by Surespan Construction Ltd.
- Late fall 2009 and early 2010: Construction of the new bridge and approximately 900 meters of road work, by Ruskin Construction Ltd.
- Spring 2010: Remove detour and construct guide banks, by P. S. Sidhu Trucking
- Early summer 2010: BST (Bituminous Surface Treatment) of the roadway portion of the project.
Challenges in planning the new bridge:
- The bridge is located in a zone of high seismic activity with a high probability of soil liquefaction in the foundation areas. To overcome the detrimental effects of liquefaction, costly ground improvement techniques like soil densification near the abutments and pier foundations are normally required. Many factors had to be considered in the new bridge designs, however, it was preferable to limit the new structures to a single span and thereby limit the need for ground improvements.
- The harsh cold climate restricted the in-situ concrete work. Alternatives included pre-cast concrete or steel structural members, but very high transportation costs were a consideration, so a balance had to be struck between casting concrete in place and using steel or pre-cast concrete structural members.
- A shortage of experienced construction work forces in this remote location was also a issue.
Before and after photos from the Yukon Government Web site. Both views are to the west, to Sheep Mountain.
The 1955 bridge as it looked in July 1991. This view is to the east.
When the Google Streetview car photographed this area in July 2009, the south span of the old bridge was in place on the detour. This view is to the west, to Sheep Mountain.
The bridge on June 30, 2017. This view is also to the west, to Sheep Mountain.
This illustration by Tanya Handley is on an interpretive panel along the Soldier's Summit Trail on Sheep Mountain. It shows the 1942 route of the military road, the current position where bridges were built in 1943, 1955, 1956, and 2010, and the extent of the silt that forms Slims River Flats as it was in 2016.