 will focus on leveling and overlaying with a motor grader to repair depressions, rutting, and corrugations. These defects must be repaired promptly to prevent further deterioration to the road and to improve skid resistance for vehicles. We will now look at depressions. They form low spots in the pavement, creating a driving hazard. Frequently, depressions extend across roadways over drainage culverts that have settled because of improper backfilling during construction. Another surface defect we are concerned with is rutting. It is a narrow depression in the vehicle's tire path, which can cause serious steering problems. Rutting is usually caused by the weight of heavy truck tires, while in the same area, depressions are also the source for concern. They are small depressions, ridges, and ripples found across a roadway. Corrigations occur where brakes must be used frequently, such as curbs, downgrades, and areas where the upper layer of pavement is weaker. These defects can cause serious driving problems, as well as damage to the vehicle and its cargo. If these defects are not repaired promptly, or extensively repair these defects, you will need the proper equipment. You will need a mechanical sweeper to clean the work site. An asphalt distributor to apply the TAC coat. A motor grater to spread the asphalt mix. A sufficient number of dump trucks to haul materials to the work site. A rubber-tired roller to compact the leveling course and the overlaying course. This roller is preferred, but if not available, you can use a tandem steel-wheeled roller. You will need the appropriate hand tools to work the asphalt mix. These tools include shovels, a hand tamper, rakes, a straight-edge or sand block, and brooms. You will also need the proper materials to make a good repair. Use hot mix to level the low places and to overlay the entire area to be repaired. You can use cold mix if hot mix is not available. You will also need rapid-setting asphalt cutback or asphalt emulsion for the TAC coat. The basic steps for repair of depressions, rutting, and corrugations. Step 1. Place the traffic control devices. Step 2. Clean the surface area. Step 3. Mark the limits for leveling and overlaying. Step 4. Apply the TAC coat. Step 5. Spread the leveling layers and compact. Step 6. Place the overlay and compact. Step 7. Clean the work site. Step 8. Remove the traffic control devices. We will now look at each step more closely. Step 9. Place the traffic control devices. Safety for the drivers, workers, and equipment must be planned carefully. If the area to be repaired extends across the road, repair one side or lane at a time to allow room for traffic to get by. Extra fragment may be needed if the repair area is large or extends around a curve. For further instruction, refer to the IRF videotape, traffic control, during maintenance. Step 2. Clean the surface area. Sweep any debris away from the work site. You will use either a mechanical sweeper or a stiff broom. Step 3. Mark the limits for leveling and overlaying. For leveling the low places, you mark their contour with chalk. For identifying the area to be overlaid, place side markers along the limits. Step 4. Apply the TAC coat. Spray a light coat of asphalt emulsion or asphalt cutback over the marked area for the first leveling course. The application rate should be light. The proper TAC forms a bond between the pavement and the leveling course. Allow the TAC to cure until it is sticky to touch. Step 5. Spread the leveling layers and compact. The volume of the depressions determines the amount of mix to be used and where it should be placed. To spread the asphalt mix, use a rake for small areas or a motor grater for large areas. If the area being repaired is less than 8 centimeters deep, only a single leveling layer of asphalt mix is required. Be sure to feather the asphalt mix at the edges. Check the new surface to make sure it is smooth and slightly higher than the surrounding pavement. If the depression being repaired is deeper than 8 centimeters, more than one layer will be needed. Mark the limits for each needed layer. TAC for each additional layer is not required if each one is placed and compacted before the asphalt mix cures. The layers should be flat and the same thickness. Do not allow the layers to conform to the defect. Compact each layer thoroughly. Use a rubber-tired roller, a vibratory roller or a tandem steel wheel roller. Rolling must be done immediately after the mix is spread. Several passes across each layer are necessary for proper compaction and rolling should be in the same direction as the defect for good compaction where roughing and depressions were located. If the area being repaired has corrugations, the top layer must be even with the tops of the ridges after it is compacted. Step 6 Place the overlay and compact. Before starting this operation, determine the limits of the overlay. It must cover the repair, overlap the surrounding pavement, be of uniform thickness and be the width of one lane. You calculate the volume of the overlay by multiplying the overlay length, width and thickness. The volume of overlay will determine the number of dump trucks needed to bring the hot mix to the work site. Place the asphalt mix over the area, set the motor greater blade to spread the asphalt mix evenly across the lane. Spread the mix in a single pass. Taper the ends to make the surface as smooth as possible. Depind the motor greater to compact the overlay. This thin layer of asphalt concrete will cool very quickly. Start at the outside edge for the first pass. Then overlap each additional pass one-third the width of the roller, and the entire surface several times to assure full compaction. Remember to roll the overlay in the direction of traffic flow. When the surface is fully compacted, repeated applications of the roller will not leave any impressions in the overlay. Step 7 Clean the work site. Keep the area clean of any loose material. If there was striping, make a record of where it must be replaced so your maintenance supervisor can schedule it. Step 8 Remove the traffic control devices. If this repair is to be continued on the other side, remove the traffic control devices in the reverse order of their placement. Then put them in the correct order on the other side. Remember there are eight steps for repair of depressions, rutting, and corrugations. Step 1 Place the traffic control devices. Be sure the signs, cones, and barricades are placed correctly. Step 2 Clean the surface area. Sweep debris away from the area to be repaired. Step 3 Mark the limits for leveling and overlaying. Follow the contour of the depression and the limits of the overlay. Step 4 Apply the tack coat. Make a light application over the marked area. Step 5 Spread the leveling layers and compact. Make sure the layers are flat and are fully compacted. Step 6 Place the overlay and compact. Use the motor grater blade to evenly spread hot mix over the repair. Then compact it thoroughly. Step 7 Clean the work site. A clean road is a safer road for everyone. Step 8 Remove the traffic control devices. Pick them up in the reverse order of their placement. The procedure for repair of depressions, rutting, and corrugations improves the quality of the road surface and helps prevent serious accidents.