Building a bridge over a creek does take some technical knowledge but if you know how to run a backhoe and have access to a dump truck then you can easily build a bridge. Follow these tips and you can build a bridge in one day.
Before you begin building your bridge, check with your local planning and zoning department. You may have to get permits to build your bridge and you should have those permits before you begin building. A dump truck will also be needed to transport rock to the job site for your bridge. It is possible to rent a dump truck and haul your own rock but it will be faster to hire a company to bring in rock for you with its dump truck.
Buy a culvert pipe to place into your creek. The pipe should be wide enough to allow water to flow freely during the highest water flow. If you are not sure what size pipe you need then contact your local planning and zoning department for information. The length of the pipe is important, as well. Choose a pipe that is at least 4 feet longer than the length you require and make sure that if it is not exactly level that the end the water flows into is higher than the end the water flows out of.
After the pipe has been set into the creek, fill the sides with at least 3 inches of rock. This will stabilize the pipe so that you can pour more rock on it and keep it from rocking out of position.
Fill the sides of the pipe with rock and begin to cover the top of the pipe. Some of the rock will slide down into the creek in front of the pipe.
To hold back the small rock, use the backhoe to lower larger rocks down next to either side of the mouth of the pipe. These larger rocks will help keep the smaller rock in place and will help make the pipe and bridge more stable.
Use the backhoe to push rock over the top of the pipe. Try to get at least a foot of rock over the top of the pipe. Once the rock is settled where you like then cover the top with another layer of 1/4-inch rock to make it easier to drive on.
Once the rock is in place it would be best to add rails to the sides of the bridge. This rail could be concrete or wood and will help keep the rock in place so that it does not erode off of the bridge.