Portable Bridge Project for Temporary Water Crossings
Bayfield County Forestry Department
Basin Program Funds:
The soils in approximately one third of Bayfield County are characterized as
highly erodible calcareous red clay. Nearly all of those soils are located in
the Lake Superior watershed, along with a range of soils from deep glacial outwash
composed of sands to silt loams. Timber harvesting, a major part of the county's
economy, has a significant impact on these soils. Poor forestry practices, including
poor forest road construction and poorly designed or inadequate stream crossings,
are a major source of silt eroding into area streams.
Slightly less than 800 square miles of Bayfield County drains into Lake Superior,
with forested lands making up the majority of that land area. Timber harvesting
is a major part of the county's economy. Currently, there are 159.7 miles of
Outstanding Resource Waters (ORW), 91.6 miles of Exceptional Resource Waters
(ERW), and 181 miles of other perennial streams in the county. Logging practices
often impact these water resources, and poor practices have historically been
a significant contributor to nonpoint source pollution problems and water quality
degradation in the Lake Superior basin.
The goal of this project was to demonstrate the feasibility of using portable
timber bridges for temporary stream crossings for timber harvesting equipment
in order to reduce nonpoint source pollution in the Lake Superior watershed.
Portable bridges have not been widely used in the region, therefore this is
an opportunity to provide information about the cost and sources of portable
bridges as well as to encourage their use. The advantages of this type of crossing
are that it requires no in-stream construction or fill material placed in the
channel, there is a low potential for introduction of sediment into the waterways,
fish movement is not restricted, and there is minimal resistance to flood waters.
Portable bridges may also assist logging contractors or other forest users that
require temporary water crossings to access woodlands in an efficient, cost-effective,
and less damaging manner.
The bridge was designed, ordered, and delivered. Project personnel applied for
and received a navigable stream crossing permit. The bridge was then moved to
a site, but could not be installed due to poor weather and road conditions.
Another site was then selected and the bridge was installed. Demonstration materials
and related information were gathered and prepared, and notices about the first
demonstration day were sent to forestry staffs and other interested parties.
The first demonstration day was held and information was disseminated to a large
number of people in the forestry industry about the costs and benefits of temporary
After the first demonstration, a draft contract outlining bridge use by other
organizations was produced and approved by the Bayfield County Corporation Council.
The bridge was then made available for mechanical operations with stream crossings
within the Lake Superior watershed. A suitable project with permits from the
Department of Natural Resources was approved and the bridge was installed across
a Class 1 trout stream. Once installed, the bridge was available for other agency
personnel and loggers to view. When harvesting operations across the stream
were completed, analysis of the bridge was conducted which concluded that it
reduced the amount of nonpoint source pollution entering the stream. Customized
designs for different types of harvesting operations and equipment have been
Overall, the project has been quite successful, and has stimulated considerable
interest and discussion in the region about the use of portable bridges for
temporary stream crossings.
Contact: Paul G. Stone, (715) 373-6114