Q: The Blue Book mentions rutting on roads but not so much about rutting in the harvest area. Are there BMP guidelines for rutting that apply across the harvest area as well? What are the concerns for rutting in the harvest area and how would you evaluate a site if you were conducting a voluntary site evaluation?
A: Great question, and one that could really use some clarification, especially as we move into the wet season!
Rutting is one of those situations where everybody loses. A skidder slogging through the mud certainly does not increase the efficiency of a logger’s operation, and landowners know that extensive rutting can lead to erosion and soil compaction, which can have a substantial impact on future tree growth. Rutting can also lead to environmental and water quality issues, especially if it occurs on steep slopes.
Rutting generally results from the tires of vehicles such as skidders, log trucks, pickups, ATVs, etc., operating under wet conditions. Most of the rutting occurring in the harvest area (i.e., off the established roads) will be caused by skidder traffic and to a lesser degree the shear. The BMP guidelines do not specifically mention the shear, but it would be considered part of the skidding operation since it travels over essentially the same area.
So, are there guidelines that cover rutting in the harvest area? I think that question can be answered by mentioning one point; skidding operations occur on skid trails. Skid trails are defined as a route over which logs are moved to a landing or road. So if a skidder passes over an area, any rutting that it causes would be considered occurring on a skid trail, and therefore be addressed by BMPs for skid trails. Make sense?
Rutting on skid trails is covered under the recommended specifications for skid trails in Part II of the Blue Book. The guidelines recommend that when soils are saturated, skidding should be restricted to prevent excessive soil compaction and channelized erosion. The general rule of thumb for determining excessive rutting is no deeper than six inches for no more than 50 feet (or about two skidder lengths). That comes from number 18 under the recommended specifications for haul roads in your BMP Blue Book. Certainly there are things you can do to minimize rutting during your operation. Using high flotation tires, keeping skidder loads light, or shovel logging extremely wet sites are all possible options.
But, don’t get the impression that when we do a site evaluation we come with ruler and tape measure in hand ready to measure every rut we see. Remember that BMP guidelines are for reducing impacts to water quality. When determining if rutting is too extensive, there are several factors to consider. Look to see if the ruts will change the direction of water flow, or cause it to puddle the next time it rains. Soil type and slope are both very important factors to consider. Look to see if the ruts will in some way channel rainwater so that it may deliver sediment to a stream. If you notice these things happening, then it may be time to head to drier ground. Our evaluations take the entire site into consideration, so if it is obvious to us that you pulled off when you noticed rutting started to occur, our evaluation will certainly reflect that.
For more information on BMPs visit the Texas Forest Service webpage at http://txforestservice.tamu.edu/water, contact me at (936) 639-8180.
* This article was published in the November 2010 issue of the Texas Logger