Protecting Water Courses During Logging Operations
Portable Skidder Bridge Loan Program

Planning a water crossing is an important aspect of any logging operation. It is all about keeping abreast of the latest techniques, doing some preplanning and ensuring you take the appropriate steps to mitigate any environmental damage that may occur as a result of logging. When done properly, a good water crossing can provide access to isolated stands of timber, and your operations will have minimal impact on the watercourse.

If your management operations call for a water crossing as part of your harvesting activities, you should be aware of a unique program available to woodlot owners and loggers, in southwestern Ontario, called the Portable Skidder Bridge Loan Program. Sponsored by the Wellington County Stewardship Council, the program is designed to loan a portable bridge to assist landowners who have to deal with a stream crossing.

Portable bridges have become one of the latest techniques used by the forest industry to traverse small watercourses. As outlined in Table #1, the advantages of using such a simple technique is that it is both economically and environmentally friendly.
Table #1: Advantages and Disadvantages of Using a Portable Skidder Bridge
Advantages
Disadvantages
  • Less expensive than permanent structures. Little site preparation is required for bridge placement. And, there are no liability issues concerning access to the area after harvesting operations are completed.
  • Skidder bridges can be a safety hazard if the design and material to be used in its construction have not been assessed and evaluated by a professional engineer.
  • Minimal impact on the waterway. Provides protection to the steam banks and reduces the opportunity of sediment entering the watercourse. Water regulators favour their use (i.e., Fisheries and Oceans Canada).
  • The bridge may freeze into the ground if abutments are not used, and the surface may wear quickly from skidding operations.
  • Reduced skidding time because operator doesn’t have to slow down, drop and raise a hitch or negotiate the steeper banks of a drainage ditch.
  • Rot, decay, knot and the grain of the wood used in the bridge construction can greatly affect the bridge’s strength. Regular inspections are needed.
  • Reduced wear on skidding equipment (e.g., lower maintenance cost and less downtime) and cleaner wood products reduce chainsaw maintenance.



The portable bridge can be used to cross small creeks (or as demonstrated in this photograph) a small ravine
Bridge Specifications

Two different-sized bridges have been constructed. One measuring 19 ft. in length (weighing 2,000 lb.) – designed to accommodate a span of 17 ft. with a load rating of 24,000 lb. The second bridge is 25 ft. in length (weighing 2,630 lb.) – designed to accommodate a span of 23 ft. with a load rating of 19,000 lb.

Each bridge consists of two panels measuring 4.5 ft. wide. They are constructed with alternating 6- x 8-in. white oak and 6- x 6-in. western red cedar timbers. The larger hardwood timbers are on the edges to provide strength and to prevent the hitch from sliding off the bridge.

Installation Practices

It is recommended, before undertaking any water crossing, that you check with the local conservation authority, Ministry of Natural Resources, and/or Department of Fisheries and Oceans to determine if a permit is required. The following installation practices are provided as a guide:
  • Bridges should only be used to cross small streams or drains that have firm, stable banks;

  • The bridge should be placed on abutments that are placed on either bank, parallel to the stream flow. This will minimize disturbance to the bank and will make it easier for removal;

  • To install the bridge panels, the skidder should cross the stream, attach the cable to the panel and winch into place. Alternatively, a backhoe or grapple skidder may be used to set the panels in place;

  • The two panels should be butted together to ensure debris doesn’t fall between the two sections. One end of each panel should be anchored to a nearby object (i.e., a tree) upstream from the crossing;

  • Guardrails or curbs should be added if you plan to skid material across the bridge; and

  • After the bridge has been removed, you should seed, mulch or use erosion control blankets to stabilize disturbed areas to prevent sediment from entering the waterway.
Remember – the crossing must not cause excessive flooding or erosion, and the structure must not impede the flow of the watercourse.

For More Information

These portable bridges are available to woodlot owners and loggers in southwestern Ontario. Maintenance and transportation costs are borne by the individual borrowing the bridge. For more information regarding the design of these bridges, or about the loan program, contact either Terry Schwan at (519) 826-4933 or Peter Williams at (519) 856-1286.

This article appeared in the Fall/Winter 2003 (Volume 33) edition of the S&W Report the newsletter of the Ontario Woodlot Association.
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