Construction of Water Bars and Turn-Outs

1. Construction of Water Bars and Turn-Outs 2005, Mid Star Timber Harvesting, Inc.

2. Purpose This course has been designed to ensure all equipment operators who work in forestry operations have the knowledge and skills necessary to properly and consistently construct, maintain, and repair water bars and turn-outs in accordance with Best Management Practices for Forestry.

3. Course Objectives • Demonstrate correct size, distances between, and angle of construction for water bars • Demonstrate correct size, distances between, angle of construction, and outfall design for turn-outs • Learn step-by-step procedures for constructing a water bar/turn-out system. • Consider alternative construction techniques for water bars and turn-outs when faced with non-routine situations

4. The Erosive Effects of Moving Water The purpose of water bars and turn-outs is to prevent erosion of the road surface and ditches by forcing water to leave the road bed and enter the forest floor. As water moves down-grade, it picks up soil and carries it away, resulting in erosion. The farther the water is allowed to travel down the road bed, the more velocity it will gain. If the distance the water is allowed to travel is not somehow shortened, the increasing velocity of the water can result in increased erosion of the road bed and an undesirable amount of silt being carried to the forest floor when the water finally reaches a point of discharge from the road bed.

5. Water Bar Design Considerations Water bars must be designed so that water is not allowed to travel great distances down the road bed before being discharged and should in most cases be constructed so that the road bed may still be used by light truck traffic. By constructing water bars of a sufficient height, width, angle from the road edge, and distance between them, erosion control objectives can be met while maintaining aesthetic qualities that are pleasing to forest road owners and users.

6. Water Bar Construction Time To properly construct water bars takes time. A good rule of thumb to use when constructing water bars is to allow thirty minutes for each water bar constructed on an average road bed twenty-four feet wide. Patience during construction will ensure the water bar will continue to function properly for years to come.

7. Water Bar Size Water bars should reach all the way across the road, be approximately 12 feet wide at the base, and 2 feet high from the uphill trough to the crest. 12’ 2’

8. Distance Between Water Bars The table below shows recommended distances between adjacent water bars depending on the slope of the road. SlopeDistance 3% 200’ 5% 135’ 10% 80’ 15% 20’ 20% 45’ 30% 35’

9. Distance Between Water Bars Instead of having to remember the slope to distance relationship shown in the previous table, a good rule of thumb is to use the method shown below. Standing at the crest (or trough)of the lower water bar, the crest (or trough) of the next water bar uphill should be at approximately eye level.

10. Angle of Construction for Water Bars Water bars should be constructed at approximately 30 degrees to the direction of travel on the road. This angle will allow the water to flow off the surface of the road with little or no obstruction in flow. Although ideally there will be minimal silt carried in the water diverted by a properly constructed water bar, during heavy rainfall, as water reaches a water bar built directly across the road, it tends to resist an abrupt change in direction of flow and will either jump the water bar or deposit excess silt in the trough during the change in direction and velocity…..

11. Angle of Construction for Water Bars Over time, excess silt deposited in the trough can reduce the working height of the water bar and render it ineffective. By building the water bar at an angle, the water retains enough of it’s initial velocity to keep the trough cleaned out and the water bar will remain effective over a longer period of time.

12. Angle of Construction for Water Bars A rule of thumb for achieving the correct angle of a water bar is shown below. Step off the distance from the beginning of where you want the water bar on one side of the road straight across to the other side. Divide that distance by three and step the resulting distance downhill to find the ending point of the water bar.

13. Turn-Outs It goes without saying that water bars would be completely ineffective without a means for water to exit the road. Turn-outs are used at every water bar and as needed along the road to allow water an escape to the forest floor. The proper construction of turn-outs is as important as water bars to prevent erosion and excessive siltation of the forest floor.

14. The size of turn-outs should be at least as wide at the entrance to the turn-out as the width of the water bar or ditch that feeds water into it. This prevents any bottleneck in the flow of water from the water bar or ditch to the turn-out. The turn-out should then broaden and flatten out as it continues onto the forest floor. Turn-Out Size

15. Distance Between Turn-Outs Turn-outs should be placed at the exit side of every water bar and at every opportunity along the road. The bottom line is this: You really can’t have too much road drainage. Install turn-outs as often as possible along the road on each side to carry water off the traveling surface of the road.

16. The following table shows some guidelines for distances between turn-out installations based on the slope of the road. SlopeDistance 3% 235’ 5% 180’ 10% 140’ 15% 125’ Remember, in most cases, you can’t have too much drainage! Distance Between Turn-Outs

17. Angle of Construction for Turn-Outs Turn-outs should be built at the same angle as the water bar that feeds it. In the case of a stand-alone turn-out, it should gradually curve away from the road toward the forest floor, but in no case should the outfall be greater than 90 degrees from the direction of travel on the road.

18. Angle of Construction for Turn-Outs Right Wrong

19. Outfall Design for Turn-Outs The outfall section of a turn-out should be flat andabout a dozer blade wide, if possible. There should be no obstruction to prevent water from flowing freely out of the outfall. Standing water in a turn-out after a rain is an indication of an improperly constructed one.

20. Water Bar/Turn-Out ConstructionStep 1 Determine the landowner/customer’s objectives. Some want a more thorough job than others based on financial or time constraints. Some may want water bars built not only to prevent erosion, but also to prevent access. In this case, the water bars should be built higher and steeper than normal. A clear understanding beforehand can prevent most dissatisfaction with jobs after completion.

21. Water Bar/Turn-Out ConstructionStep 2 Assess the terrain and soil type and develop a plan. Based on terrain and soil type observations, decisions can be made on water bar and turn-out placement and frequency. Sandy soils need more frequent water bars and turn-outs than rocky ones. Make a note of any stream crossings or streamside management zones in your planned work zone. These require special treatment in order to avoid water quality violations.

22. Water Bar/Turn-Out ConstructionStep 3 Remove any organic debris (leaves, straw, grass, sticks) from the surface of the road in the areas around where water bars are to be constructed. This debris, if mixed in with the soil used to construct a water bar, will not allow the soil to become cohesive and stabilize. Also, remove any organic debris from the area where the turn-out leading out of a water bar is to be constructed. If at all possible, soil from the turn-out area should be brought back into the road and used in the construction of the water bar.

23. Water Bar/Turn-Out ConstructionStep 4 Step off or visualize the correct angle and size of construction. Gather the soil into a pile shaped slightly larger than you think you will need for the finished water bar. The lowest part of the trough should be cut out of natural ground, if possible. Pack the entire pile by walking back and forth over it with your machine (dozer, skidder, etc.).

24. Water Bar/Turn-Out ConstructionStep 5 Finish shaping the pile with the blade of your machine. If the road is to be used while the water bars are in place, this step is crucial to the aesthetic quality of the job. Any excess material bladed off the uphill side of the water bar should be placed on the downhill side. Using a dozer, you should be able to blade all the way over the water bar, keeping the blade in contact with the ground. If not, the crest of the water bar is probably too sharp.

25. Water Bar/Turn-Out ConstructionStep 6 If you were able to use dirt for the water bar from the turn-out area, complete construction of the system by finish grading the turn-out at the exit side of the water bar. The turn-out should slope downhill from the water bar at about the same rate of slope as the water bar that feeds it.

26. Non-Routine Situations Inevitably situations will arise where these guidelines for water bars and turn-outs will not be practicable. When faced with those situations, you should study carefully any possibilities and options available. The most important thing to remember is the reason you are building water bars and turn-outs on the road to begin with: ELIMINATE OR REDUCE THE POSSIBILTY OF EROSION!