Bridge #4 is the third of three bridges that feature two spans. A large
sandbar on the south side of the bridge allows for easy access to photograph
the side of the bridge. Going off the trail is generally not recommended
due to the swampy nature of the area and the presence of two species of
pit vipers in the area, the Timber Rattler and the Massasauga. Leaving
Bridge #4, the trail becomes more like a tunnel as the tree canopy covers
the space above the trail.
A key feature of the Bowstring Arch Truss Bridge is the fasteners used to
assemble the bridge. This includes pins, clips, and eyebars. These items
can all be mass-produced in a factory, then rapidly assembled on location.
This eliminates the need to custom fit parts and to do extensive riveting.
The cross-beams connect to the main arch using clips that hang over the
top end of the arch. The cross-beams then connect to the clips using pins.
This works for beams in both tension and compression modes. All of these
parts are accessible for inspection, and can be replaced in the field when
the bridge requires maintenance.
The main channel bridge was deemed to be unsafe in 1948. Despite local
efforts to preserve the bridge, it was demolished in 1954. A new bridge
across the Black River was built for highway WI-93, so McGilvray Road was
no longer needed for through traffic. The road did remain open for local
landowners. A large flood in 1970 washed out the road in several places
and damaged some of the bridges. The local township again attempted to
maintain the road, but was again hampered by limited funds. The township
deeded the land, road, and bridges to the State of Wisconsin Department of
Natural Resources in 1975. The DNR wanted to keep the road open for
pedestrians, but found that the damage was far too expensive to fix. Not
only was the road impassible, but in 1986 a consultant deemed it both unsafe
and a potential hazard. Funds were allocated to remove all but the first
bridge, with the demolition planned for the summer of 1989.
The photo above is a view of Bridge #4 as one would approach the bridge while
heading west on McGilvray Road. The road dips below the level of the bridge
deck on each side of the bridge, likely due to past flood damage. As a
result, the bridge appears to sit higher than the roadbed. A bench seat
is located at the southeast corner of the bridge, a welcome place to rest
for those who have hiked the three-fourths of a mile path to this bridge.
The photo above is looking west from the southeast corner of the structure.
The photo below is looking east down the length of the bridge deck.
The photo above is looking north towards the eastern of the two spans that
make up Bridge #4. The photo below is looking north towards the western of
the two bridge spans. The side channel that flows under the bridges makes
a sweeping turn to the south at this location, resulting in a large sandbar
on the east side of the channel south of the bridges. This sandbar provides
a nice profile view of Bridge #4.
The photo above is a detail view of the mid-channel pier of Bridge #4.
This pier is built using a steel piling and reinforced concrete. These
modern piers replaced the original 1907 wooden pilings. The photo below
is the east bridge abutment. While wood is used to build the bridge
abutment, the bridge actually sits on concrete piers.
The photo above is the view looking south from the deck of Bridge #4. The
photo below is looking north from the deck of Bridge #4. This bridge
crosses the largest of the side channels that flows through the river bottom
The photo above is a detail view of the end of the truss structure at the
northwest corner of the bridge. The bridge would have originally rested
on the wooden pilings that form the abutment. During the restoration,
concrete bridge piers were installed just to the inside of the abutment.
A vertical steel column was attached to the main truss member to support
the truss on this pier. Smaller horizontal braces were welded between the
new vertical support and the end of the main truss member. This shifts
the weight of the structure off of the wooden abutment and onto a more
stable set of piers.
The photo below is looking west down McGilvray Road towards Bridge #5,
located 2,000 feet west of Bridge #4.