 The North Carolina Institute for Transportation Research and Education presents pavement structure repair techniques, shoulder maintenance. In a roadway each part of the road, the pavement, the shoulder, and also the ditch has a specific function. The shoulder may be defined as the portion of the road between the edge of the travel way and the front slope of the ditch. What are the functions of a shoulder? The shoulder protects and gives lateral support to the pavement edge, base, and sub-grade on each side of the road. The shoulder provides emergency stopping area for the traveling motorist. It also provides a recovery area for vehicles that may leave the road surface accidentally. And probably the most important function of the shoulder is to provide a surface to drain water from the pavement surface into the roadside ditches. Proper drainage is vital to a good roadway. This shoulder will allow drainage away from the edge of the pavement. The shoulder elevation is the same or slightly lower than the edge of the pavement. The shoulder is sloped toward the ditch. This slope should be approximately three-quarters inch per foot or as originally designed. It should be greater than that of the pavement. Shoulder widths may vary depending upon geographical location. The width is measured from the edge of the pavement to the foreslope of the ditch. A minimum width of 6 to 8 feet would be desirable. It is also desirable to have established turf composed of grass or other vegetation on the shoulder. This will reduce damage due to erosion and blowing away of shoulder material. There are three types of operations that may be performed in maintaining a shoulder. These are reshaping of the shoulder, low shoulder repair, and high shoulder repair. Reshaping of the shoulders is performed where no material needs to be added or removed from the shoulder. This operation restores the typical cross section and slope of the shoulder. The steps to be taken in this operation are number one, place proper traffic control. Number two, blade shoulder with motor grater and windrow material at the edge of pavement. Number three, spread material back across shoulder at the proper slope. Number four, compact shoulder with the motor grater. Number five, remove traffic control. The second shoulder maintenance operation is the repair of a low shoulder. A low shoulder condition exists where the shoulder is considerably lower than the edge of the pavement. Generally one and a half to two inches or more. This situation generally requires the addition of material to the shoulder area. The steps to be taken in this operation are number one, place proper traffic control. Number two, till or scarify existing shoulder material. Number three, place material in low areas of shoulder. Number four, spread material with grater to rough grade. Number five, fine-grade shoulder with motor grater. Number six, compact shoulder material. Number seven, remove traffic control. The third shoulder maintenance operation is the repair of a high shoulder. Repair high shoulders when material has built up higher than the edge of the pavement. Generally this buildup is an inch or more. In many cases, excess material is hauled away from the work area. The steps to be taken in this operation are number one, place proper traffic control. Number two, cut away high spots on shoulders with motor grater. Number three, pick up excess material and dispose of it properly. Number four, remove traffic control. In any maintenance operation, it is extremely important that proper traffic control procedures be followed to ensure safety of the motoring public as well as the maintenance personnel. For more information on traffic control, refer to the videotape basic traffic control for pavement structure repair techniques. Once proper traffic control is in place, the shoulder maintenance operation can begin. The first type of shoulder maintenance is reshaping of the shoulder. No additional shoulder material is added and no excess shoulder material is removed. Reshaping restores the desired cross section and slope of the shoulder. The end result is a smooth shoulder with a smooth transition from the edge of pavement sloping down to the front slope of the ditch. Reshaping is required on an unpaved shoulder that has deep ruts in it. Reshaping is also needed to repair corrugations, ridges, buildups, and areas that have eroded. In general, the shoulder is not smooth and water cannot properly drain. A motor grater is the primary piece of equipment used in this operation. The motor grater can do an efficient job of reshaping the shoulder and eliminates the above problems. To begin, the operator positions the grater on the shoulder, angled the blade at approximately 45 degrees. The toe of the blade rests at the outside edge of the shoulder while the heel is set at the edge of the pavement. The blade pitch is upright or slightly back. Use a 10 to 15 degree wheel lean with the wheels leaning in the direction that material is being moved. The operator proceeds at a slow speed of three to five miles per hour. Cut just enough material on the first pass to remove unevenness, ruts, and depressions that exist. Pull the material from the outside of the shoulder at the front slope of the ditch. The material is neatly windrowed at the edge of the pavement. Note that the windrow is placed outside the rear wheels of the grater. All ruts, unevenness, and depressions have been cut smooth during this first pass. On the second pass, pick up the windrowed material and spread it back across the shoulder. Again, a 45 degree angle is used for the blade. The toe of the blade rests at the edge of the pavement. The heel is at the edge of the shoulder. Set the blade height at the desired slope for the shoulder, typically three-quarters inch per foot. The heel of the blade is loose so that material will be spread at the shoulder evenly and not create another windrow. If the heel is not loose, a windrow will be formed, creating a berm. This will interfere with the drainage of surface water across the shoulder into the ditch. Use a front wheel lean of 10 to 15 degrees in the direction that material is being moved. Operating speed is relatively slow, about three to five miles per hour. This prevents the blade from bouncing and creating an unevenness in the finished shoulder. The reshaped shoulder is flush with the edge of the pavement. Take care not to cut into the pavement with the edge of the blade. Depending upon the width of the unpaved shoulder, additional passes may be needed to reshape the unpaved shoulder area. As a final step, the motor grater rides over the shoulder area to compact the material with the wheels. This reduces the potential for material being blown or washed away. In some cases, it may be necessary to seed, fertilize and moch the material to restore vegetation. Vegetation is desirable to stabilize the shoulder material and prevent erosion caused by water or wind. The reshaped unpaved shoulder has a smooth transition. It is properly sloped toward the front slope of the ditch. The shoulder is now smooth with no unevenness, ruts, corrugations or depressions. Now, let us review the steps required for reshaping of shoulders. Number one, place proper traffic control. Number two, blade shoulder with motor grater and windrow material at the edge of pavement. Number three, spread material back across shoulder at the proper slope. Number four, compact shoulder with the motor grater. Number five, remove traffic control. Now, let us look at low shoulder repair. A low shoulder condition is generally caused by erosion or traffic riding on the shoulder of the road. On a narrow road, the outer wheels of a vehicle may ride at the edge of the pavement or possibly off the edge. This is especially true where there is a lot of truck traffic. One thing to be considered prior to this operation is the location of additional material. Possibly, material can be recovered from ditch maintenance performed in conjunction with the shoulder repair. Ditch maintenance or high shoulder repair performed on a nearby roadway can provide excess material. Borrow material or stock piled material can be hauled from the nearest available source. The quality of the material and the hauled distance are important factors to be considered when obtaining this material. Regardless of where this material comes from, the procedure to be followed in repairing the low shoulder is the same. The pieces of equipment needed for this operation are a motor grater, dump trucks for hauling, and a loader to load shoulder material into the trucks. Till or scarify the shoulder to a depth of approximately four inches. This permits the old and new soil material to be mixed and allows it to bond together better. Also, it allows oxygen to be mixed into the soil, which will enhance the ability for vegetation to grow on the shoulder. Place the additional material on the low shoulder areas from the tailgate of a dump truck. Place the material near the edge of pavement. Once the material has been dumped on the shoulder, spread it using the motor grater. Position the grater blade so as to rough grade the shoulder material. Spread from the edge of the pavement out toward the foreslope of the ditch. Take care not to windrow material along the edge of the shoulder with the heel of the blade. Additional passes may be needed depending on the width of the shoulder. Perform another pass with the motor grater to fine-grade the shoulder material. Angled the blade at approximately 45 degrees. The toe of the blade is flush with the edge of the pavement with the heel of the blade resting at the edge of the shoulder. Set the blade height to obtain the desired slope for the shoulder. Again, more passes may be needed depending on shoulder width. The last step is to roll the shoulder material. This can be done with the motor grater compacting the material with the tires. It is important that the shoulder material be rolled and compacted to prevent it from being easily washed or blown away. The finished product is a smooth uniform shoulder. It has the proper shape and slope. There are no low spots or drop-offs remaining. Place seed and mulch as needed to establish vegetation on the new shoulder material. Now, let us review the steps required for low shoulder repair. Number one, place proper traffic control. Number two, till or scarify existing shoulder material. Number three, place material in low areas of shoulder. Number four, spread material with grater to rough grade. Number five, fine grade shoulder with motor grater. Number six, compact shoulder. Number seven, remove traffic control. The last of the shoulder maintenance operations is high shoulder repair. On this roadway, the shoulders are approximately two to three inches higher than the edge of the pavement. This condition can be created by several things. High shoulders can be caused by soil material being washed away from driveways or other intersecting roads and collecting on the adjacent shoulders. High shoulders create a problem because water will pond at the edge of the pavement. It is trapped there and not able to drain across the shoulder and into the adjacent ditches. Water standing on the edge of the pavement may filter through the roadway and down into the base and subgrade below. Vehicles running through the standing water can suffer a loss of traction because of hydroplaning. High shoulders may be a problem for a driver trying to make a smooth emergency stop on the shoulder or perhaps trying to recover control of a vehicle in an emergency situation. Now, let's discuss how to repair a high shoulder. The equipment required to perform high shoulder repair includes a motor grater, dump trucks, and a loader. If the shoulder is very hard and densely compacted, loosen the material with a scarifier attached to the motor grater. Position the grater on the shoulder. Angle the blade at approximately 45 degrees. The blade pitch is upright or tilted back slightly. Place the toe of the blade at the edge of the shoulder. The heel of the blade is flush with the edge of the pavement surface. Use a front wheel lean of 10 to 15 degrees in the direction that the material is to be moved. The motor grater proceeds at no more than three to five miles per hour. This prevents the blade from bouncing and creating an unevenness in the shoulder. As the motor grater moves along, the blade cuts away the high spots of material and wind rows it along the edge of the pavement. Cut the shoulder to the desired slope. Behind the motor grater, a front-end loader picks up the wind-road material on the edge of the pavement. Load the material into dump trucks and haul it away to a waste area. If necessary, broom excess material off the pavement with a power broom. The repaired shoulder is flush with the edge of pavement. No build-up remains. Place seed and mulch as needed to reestablish vegetation on the unpaved shoulder. When high shoulder repair is performed on a fill section, it may be possible to waste the excess material over the edge of the fill. This eliminates the need to haul the material away from the work area. The cost of loading and hauling the excess material would be saved. Set the blade with the toe of the blade flush with the edge of pavement. The heel of the blade rests at the edge of the fill area. Cut off the high material and wind row it over the edge of the fill slope. This should only be done in areas that are approved by the maintenance engineer. Be sure that the proper slope is established and the shoulder is smooth and even. Let us review the steps required for the repair of high shoulders. Number one, place proper traffic control. Number two, cut away high spots on shoulders. Number three, pick up excess material and dispose of it properly. Number four, remove traffic control. Certainly proper shoulder maintenance is important to the performance of a roadway. This roadway has properly maintained shoulders allowing for lateral support of the pavement and proper drainage of surface water into the adjacent ditches. These shoulders are able to perform their intended function on the roadway. Shoulder maintenance is a necessary maintenance operation and when done the proper techniques should be used.