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Small streams often crisscross rural land, and even those that remain dry for most of the year may have steep banks that prevent vehicles from crossing. The simplest way to safely drive across such an obstacle, while protecting the stream, is to install a culvert and earth bridge.
Culverts can be purchased at farm or building supply stores. Sometimes, highway departments, the Forest Service or Bureau of Land Management have old culverts in usable condition that can be bought for less than a new one.
You will need a backhoe or excavator and a soil compactor when installing all but the smallest culverts.