 There's only one way to fix a pothole, and that's to patch it. Seal coating won't do it. Lane leveling won't do it. Even an overlay won't do it. That's because where there's a pothole, there's a problem under the road. And if you just go over it, the problem will reappear. So whether or not more material will be added, potholes have to be patched. This program covers the procedures to follow. From loading the truck to final compaction. But before we get to all the details, let's take a brief look at what causes potholes. For the most part, potholes are caused either by oxidation, as the pavement wears out, or by water under the road. Most often, water seeps in through the shoulders, or through cracks in the surface. That's why good drainage is so important. And why crack sealing is so important. Because any moisture that gets under the road expands and contracts as it freezes and thaws. And before long, cracks and potholes. So water is the major cause of potholes. Try to keep that in mind in any road maintenance activity. It's just as important to prevent these problems as it is to fix them. Okay, now let's look at the procedures to follow in making a permanent patch. Pothole patching has one thing in common with all other maintenance activities. And that is that it has to be done safely. So be sure to discuss traffic control with your foreman before you head out to the job. Keep in mind that no matter what signs and devices are called for, you should always wear the proper clothing, an orange U-dot hat, and an orange shirt, jacket, or safety vest. The procedures you'll see here are based on the department's maintenance handbook. Of course, potholes come in all shapes and sizes, and the handbook can't cover everything. So the more you know about patching, the better the job will be. Basically, you need to know which materials to use, the equipment you'll need, and the procedure to follow. So let's start with materials and equipment. The first thing you need is a good grade of asphalt mix, or mulch, as many people call it. The mulch can come from a stockpile of blade-mixed asphalt, or from a plant. Again, as long as it's a good grade. Obviously, it's best to load the mulch before you load your tools and signs. Just be sure to note the quantity before and after you patch, so you can tell your supervisor how much material was used. The only other material you need is tack oil. Here again, any good grade of tack oil will work. The important thing is that you use it. There is no way the patch will last without a good tack. As for equipment, you'll need an ordinary pick, shovel, and two brooms. One for cleaning and one for applying the tack oil. But you need a special rake known as a derby rake. As you can see here, one side of the rake is flat, and the other side is perforated. I'll explain the purpose of the perforations later. For now, just remember that this is the best type of rake to use. And that's it for equipment. Now the procedure, beginning with traffic control. As you know, there are many factors that determine the number and type of traffic control devices you'll need. But in patching, you'll always need at least this. Road work ahead signs to be placed at both ends of the work area. And traffic cones to be placed around the damaged pavement. And remember, when you're at the work site, proper clothing is always required. Okay, all the traffic control devices are in place. Now before you do anything else, look over the damaged pavement. It's a good idea to decide where you want to end up before you get started. There are two things to keep in mind. First, you want to remove all the damaged material to the extent that that's possible. And second, the patch can have as many sides as you want, as long as the angle between the sides is at least 90 degrees. Here are a couple of examples. As you can see, this is a fairly small pothole that looks easy enough to fix. But notice the small cracks surrounding the hole. Remember, that's how the water get in to cause the damage in the first place. So in this case, you should dig out to where the cracks end. That way you're sure to get all the damaged pavement. Here's another example. In this case, the cracks extend much farther away from the hole. You'd be digging all day if you tried to go to where the cracks end. In fact, the damage here is so extensive that it would be best to tack the entire area and cover it with sand after patching. Otherwise, you'll be back to fix the same hole or a new one before you know it. Remember, this job calls for a lot of judgment on your part. And if you're not sure, don't hesitate to discuss the alternatives with your supervisor. One more example. Here, there are two small potholes that are pretty close together. And because they're so close, you can fix them both with one patch. Notice how he's tracing the area. The patch won't be a square or a rectangle, but all the damaged pavement will be removed and the angle between the sides will be at least 90 degrees. And that brings us to digging out the hole. No matter how much material you're going to remove, you should always start at the hole and work away from it. Remember, you want to remove only the damaged material. So pull the material toward the hole. If you pull the material away from the hole, you'll end up extending the damaged area. So again, pull the material toward the hole. There's one more thing to keep in mind as you dig out the hole. And that is to keep all the sides as vertical as possible. Here's why. If the sides of the patch are undercut, you won't be able to compact the mulch at the edges. And that would increase the chances of the patch failing. And if the sides slope outward, the mulch will get pushed right out of the patch. With vertical sides, all parts of the patch get properly compacted and the new material gets the lateral support it needs to stay in place. The next step is to take out the old material. There are two important points to remember in this step. One, dig down to a firm, stable base. It can't be spongy or the patch will collapse. And two, don't damage the edges. Keep them as vertical as you can. Not only will that help in compaction, but it also helps make the patch more stable. Then clean out all the loose material and dispose of it properly. Do as good a job as possible when you sweep out the hole, too. Because the next step is to tack the patch. The whole purpose of the tack is to bond the mulch to the pavement. And if the area is dirty, the tack will bond to the dirt, not the pavement. The tack should be applied in a light, even coat along the vertical edges and all around the hole about the same width as the width of the broom. That way any hairline cracks around the hole will be sealed. If the tack is too light, you'll get a bad bond. And if it's too heavy, it'll seep into the new material and work its way to the surface. That can make the patch both weak and slippery. So again, a light uniform coverage works best. Notice how he shakes the brush to tack the bottom of the hole. A lot of times that's the only way to do it. Because no matter how well you sweep the bottom of the hole, it'll still be mostly dirt. So a little tack around the bottom is better than none at all. The important point is to try to get as uniform a coverage as you can. And that's it for the tack. The next step is to place the mulch and compact it. Because this patch is so shallow, it can be completely filled in one lift. Notice how they're working the material toward the edges of the patch. That's the way to do it because it's difficult for the truck tires to reach the material at the edges. And the more compaction you get, the better the patch. One more thing about filling the hole. Be careful not to add too much material. The mulch should just slightly overfill the hole so it can be compacted for a smooth surface. The next step is to spread the material evenly over the patch area. Obviously the main purpose of this step is to make the patch smooth. But there is one more thing to be careful of. You have to be sure to use the perforated side of the derby. That way only the finest parts of the mulch will be spread onto the pavement around the patch. And that makes sense. The finer parts of the mulch can bond more easily with the tack than the larger parts. Now the patch can be compacted. As I said earlier, the more compaction, the better the patch. Most stations have to make do by rolling the patch with truck tires. But if you have a mechanical tamper, by all means use it. After you've compacted the patch from one side to the other, check it. Make sure it's reasonably smooth. Most of the time you'll have to add a little more material, rake it, and compact it again. Now I said that this hole was shallow enough to fill it in a single lift. Deeper holes are different. This drawing is a side view of a pothole that goes down to the sub-base. The procedure here would be to place the mulch in separate 4-inch lifts, compacting each lift. The top lift should slightly overfill the hole so you can compact it for a smooth surface. And that's the procedure for making permanent pothole repairs. But there's one more thing you can do that will extend the life of the patch. A day or so after you've made the patch, tack the entire area. Then spread just enough sand to cover the tack. Tacking and sanding seal the patch so that no moisture can set in and the repair will last a lot longer. So to review, set up all the required traffic control devices. Look over the damaged pavement and decide how much material to remove and how to shape the patch. Dig out the material by pulling it toward the hole. Clean the hole as well as you can. Pack the hole and the surrounding pavement to about the width of the broom. Fill the hole with material but not more than 4 inches at a time. Smooth the patch with the derby. Drive over the patch to compact it or use a mechanical tamper if you have one. Check the patch to see that it's smooth. And add more mulch, rake, and compact the patch as necessary. Finally, estimate the amount of mulch that was used and the beginning and ending milepost markers. Your foreman needs that information for reporting. Well, as you've seen, there's a whole lot more to patching than just throwing mulch in a hole. And each step of the procedure is as important as the next, beginning with your judgment as to the size and shape of the repair. So try to keep the points you've seen here in mind. Remember, these repairs not only solve an immediate problem, but they serve as an important first step in doing any additional work, such as seal coating or lane leveling.