 If you've ever closely examined an asphalt pavement, you know that cracks come in all shapes and sizes. Anything from long, wide and straight to short, narrow and jagged. Fortunately, we don't have to come up with new repair procedures for each type of crack. Nearly all of them can be corrected by sealing, except these. We call this condition alligator cracking because the cracks are so close together. Sealing simply won't correct this problem. That's because both the cohesion and strength of the pavement are lost. So for alligator cracking, the best solution is to remove and replace the damaged pavement, or as title in the Foreman's Handbook, but tumenous surface replacement. Basically, this procedure involves closing one lane of traffic, excavating the damaged pavement, leveling and compacting the base material, tacking the surrounding pavement, placing premixed material in the repair area, leveling the material to the original line and grade, and compacting the reconstructed pavement. Okay, that's the basic procedure. Now let's go back and look at each step of the operation in detail. As with any other maintenance activity, the first step is to set up all the necessary traffic control devices. Because of the nature of this operation, you always have to close at least one lane of traffic. So you'll need a lane drop symbol sign if two or more lanes will remain open to traffic. Or a one lane road ahead sign if traffic will have to alternate through the work area. And of course cones are needed for all lane closures. After all the devices are in place, closely examine the damaged pavement. The major thing to look for at this point is settlement of the roadway. If you find anything like this, surface replacement won't be enough to solve the problem. This situation calls for base repair because the base itself can no longer support the pavement. So discuss the matter with your supervisor before continuing. If you've gotten to the problem early enough, though, settlement won't be a problem and you can continue with excavation. Be careful not to undercut the remaining pavement. The sides of the repair area should be as vertical as possible. Also, take care not to disturb any of the material under the pavement because that could weaken the base and sub-base. And the strength of the foundation is critical to the success of the repair. After excavation, level the underlying material and compact it as much as possible. Again, don't disturb the material any more than you have to. The whole purpose of this step is to simply make the foundation uniform and stable. Now before the pavement is reconstructed, apply a thin coating of tack material for a few inches along the existing pavement and to the sides and bottom of the repair area. This procedure will help bond the new pavement to the existing pavement. In order to get the most compaction for the new pavement, you'll normally have to place it in two lifts. So if the reconstructed pavement will be about eight inches thick, place two four-inch lifts. Here again, the thickness of each lift has to be uniform and compact it as much as possible. The top lift, however, has to be fine-graded first. Pay special attention to all the transition areas. The new pavement has to match the existing pavement all around. You'll find that it's a good idea to compact the material after each grading pass. That way you can better determine how smooth the transitions are. After fine-grading, the steel wheel roller can be used. This, of course, provides the final compaction, but it also smooths the transitions as much as possible. And here's the completed job, a reconstructed pavement over a firm foundation. Try to keep the points you've seen here in mind. And remember, these procedures are intended to repair alligator cracking. If you notice any settlement in the roadway, or if you uncover another problem such as water or spongy material under the roadway, discuss the situation with your supervisor. It's entirely possible that the activity will have to be reclassified as base repair.