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.
 |
| Flat cars can be used to establish sturdy bridge crossings |
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.
 |
| Timber Creosote bridges are a common approach to establishing permanent stream crossings |
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
