For as long as people have lived near rivers, the problem of how to get to the other side has existed.

I was asked to write this article to share my experiences and plans for a private bridge, as a number of us in the non-industrial forest owner community are interested in and share information about bridge building. I was asked to keep the article fairly basic and non-technical. The usual disclaimers would apply to the information contained herein. Ten miles east of Salem the Pudding River forms a small canyon and crosses our tree farm dividing it in two. A legal easement over surrounding property allows us access to the back portion of our property which is fine in good weather, but not during the rainy season. It became clear to us that a river crossing would greatly facilitate and improve year round access to our property.

The Pudding River in our area is classified as a large fish-bearing stream. In the summer the flow decreases to a shallow creek 15- 20' across. But during high flow events like February 1996, it becomes a raging torrent 5-6' deep and 40' across. For the last several years I have thought about and talked to many people about bridge design and construction. Last summer with the assistance of a professional forester, John Hatch of Macleay, Oregon, plans for a bridge began to take shape. John had experience building a variety of different types of bridges. More recently he had completed projects using old concrete road dividers and pre-fabricated pre-stressed concrete slabs on a smaller stream crossing.

We applied for a permit through the forestry department as our property is zoned for forestry and John completed and submitted the plan and notice of operations. The forestry department then sent out a team including a forest practices forester, a geo-technical engineer, and a fish biologist to inspect the site. They stressed the importance of not disturbing the stream and not spilling any wet concrete into the river. A short time later, we received approval to proceed with the project. In this case I believe that the fact that a professional forester was involved helped secure the approval. Many different methods of bridge construction were considered. We looked at prefab concrete slabs, railroad flatcar, steel I-beam with pressure-treated wood cross-members and steel I beam/concrete slab bridge designs. All of the above designs had their advantages. I finally decided on the last option. In my case I wanted the bridge to be strong enough to pass a concrete truck and/or loaded log truck. This translates into 105,000 to 80,000 pounds. (The question of how strong you want your bridge to be is one of the most important questions to answer, another being how much you want to spend!)

We then went out to speak with Gary Hamilton at Schnitzer Steel in Portland. Gary was extremely helpful and knowledgeable about bridge construction. He mentioned that about half his customers bought used or surplus steel from him for the purpose of building bridges. After explaining the strength of the bridge we wanted, he helped put together the list of materials. I, then, hired a trucking company to haul the material to my farm.

I spoke with civil engineers in Portland who quoted me engineering/plan fees of $11,000. Dennis McGee, out of Corvallis, was much more reasonable quoting $4,500, and is considered one of the best by commercial forestry companies. OSU's forestry engineering department was also recommended to me, specifically Brian Kramer, as a good source of information.

In our situation, the first step was to construct a road. John and I laid out the road using a clinometer and flagging. Then John contacted Ed Collver, of McMinnville, who with his D-6 cat, did an excellent job of cutting in the new road. The grade of the road is a bit steep in places, but this couldn't be helped. I installed cross drain culverts, laid down geotextile cloth and brought in crushed rock, ranging from 3"minus to 3/4"minus. With the road in place, I then built forms for concrete footings on either side of the river. The footings measure 3' wide, 2' deep and 17' long. I placed 4 layers of 5/8"rebar to reinforce the concrete footings leaving 2' rebar sections sticking out of the footings vertically to tie in the walls. The walls when done, will be 18"thick, 16' long and 7' high. Five 40' x 27"high steel I-beams will be mounted atop the concrete walls. The five I-beams placed parallel to each other will allow for 16' wide bridge surface. 3/16"sheet steel will be welded on top of the I-beams. The ends and sides of the bridge surface will be formed by 6"channel steel. The final bridge deck will then be formed by pumped concrete with 1/2"rebar reinforcement spaced 12"on center longwise and cross-wise. With this design, when all is said and done, the lowest portion of the bridge will be at least three feet above the 50 year flood level. This should allow the passage of large woody debris during flood/high river flow events.

In our particular setting, which is very damp and moist the majority of the year, I am choosing to use concrete for it's strength, low maintenance, and durability over pressure-treated wood decking, which is also more expensive. Since I am doing most of the work myself, I hope to hold down the costs to the $15,000 range.

Editor's Note: Mike Matthews graduated with the Clackamas County Master Woodland Manager class of 2000.