By: Hughes Simpson, BMP Forester, Texas Forest Service
Q: I am harvesting a tract of timber in Sabine County near Milam, in which a major stream bisects the property. The landowner wants to gain permanent access throughout the entire tract. This perennial stream carries a lot of water, has very steep banks, and is about 30 feet wide. Do you think it would be possible to accomplish this without impacting water quality? If so, how would you recommend crossing it?
A: Yes, it is certainly possible to cross this stream and minimize the impacts to water quality. However, given the stream conditions, the task of doing this can become quite expensive.
The best and most economical way to achieve this is to not cross this stream at all. Spending several hundred dollars buying an easement from an adjacent landowner will usually be cheaper than building a bridge or putting in a culvert. This method also provides the greatest protection to water quality.
Many times, gaining backside access is not possible and the stream must be crossed directly. Careful consideration must be given to a stream of this size. It is imperative that all stream crossings be installed at right angles and in straight sections to the stream channel. This reduces the potential impact to water quality.
Tank cars can be installed securely in the streambed and will function as large culverts, which may last between 30 and 50 years. The walls of these cars usually range anywhere from ½” - 1” thick, depending on the weight they must be able to withstand. Federal law mandates that tank cars go through steam cleaning before being used as a stream crossing, to prevent any impacts to water quality.
Flat cars and box car beds are also another method that is commonly used to cross streams of this nature. These tools function more as bridges that are appropriate for spanning larger streams. The major factor in determining what product to use is the actual width of the steam (distance that must be crossed). Flat cars are generally 89 feet long and about 8-9 feet wide. Box car beds are 50-60 feet long and 10 feet wide. When installing either one of these “bridges” it is important to anchor them into the bank with at least 8 or 10 feet of overhang on both sides of the stream.
Timber Creosote bridges are also used to gain permanent access across large streams. They can handle heavy traffic, minimize the amount of sedimentation and erosion, and also function under high water conditions. The major drawback to these devices is the high cost. When installing these bridges, choose approaches that have a constant grade. Build abutments parallel to the stream and imbed them into good foundation material.
To find out more information about suppliers and prices of these products, please consult the TFS Product and Vendor Guide. The Texas Forest Service does not endorse the use of specific products or vendors listed in this guide. You can view this on the Internet at http://txforestservice.tamu.edu/water. If you have a question regarding BMPs, please call me at (936) 639-8180.
* This article was published in the June 2001 issue of the Texas Logger