In the previous article about roads and driveways we discussed how to determine the pathway for your new driveway. In this post we’ll cover issues of drainage, the anatomy of a road and the cost.
Dealing with Drainage
Drainage is a huge consideration, especially with gravel or dirt roads. In the worst case, your road could wash out, but the prospect of constantly repairing an improperly build driveway is not a good one. You’ll first want to observe how water currently flows around the area. Notice where it pools during rain. Look for ruts or gulleys. These will be indicators of the volume of water you’ll be dealing with, and how it’s currently routed.
The most common approach in our area is to raise the bed of the road with chert fill, and then install ditches on either side to handle the wash.
A culvert is then installed in areas where the water builds up to allow it to pass down grade. A culvert is a metal or plastic pipe of varying diameter that is installed under the road. With the right placement and capacity, the volume of water collected during a heavy rain will be dispersed at a higher rate than it is accumulated. This prevents water from rising over the road. Once the road becomes submerged under moving water, it is only a matter of time before it will wash out completely.
The key to managing water is to keep it moving slowly. Fast moving water has an enormous amount of power and can quickly erode soil. Slower moving water tends to just spill over without creating damage.
During heavy rains the volume of water that flows across the Ant Farm is quite impressive. Our driveway travels down a long hill and then back up toward the home site. At the bottom of the hill there is a wet-weather creek bed. The road had to be built up about three feet with a large culvert installed to carry the creek water across. The property is generally higher on the south side, so all of the water flow tends to move from South to North.
That being the case, ditches were installed on the South side of the road to collect water and direct it toward the culvert in the creek bed. An additional culvert was needed near the main road to dispose of the water that was being deposited by a large culvert installed by the county under the main road.
I’m pretty sure we’re going to have some issues with drainage on the part of the driveway near the home site. The grade is pretty steep, and the excavator chose to route the water across the drive instead of having it join in the creek bed. He was concerned that the volume of water collected from both directions would be far too much for the culvert to handle. His plan was to slow the water down by widening out the flow. He left a very wide depression in the road to act as a swale. I don’t believe it’s going to solve the problem, and my expectation is that in three or four months, we’ll be installing ditches and a new culvert to handle the runoff. He definitely has more experience than I do, but we’ll see…
Anatomy of a Rural Driveway
The first step for the driveway is to clear the land and roughly grade it. The machines will clear an area about twenty feet across. The excavator will then drive over the area repeatedly, packing it and smoothing large mounds and filling voids.
In Ashville, Alabama, driveways are typically built with chert. Chert is a type of dirt that is gravelly and includes a high amount of quartz. When it’s packed into place, it’s almost like concrete, which is why it’s used in road building. After the bed is ready, dump truck loads of chert are spread to raise the overall level of the road. In some places this may only be six inches, in others it can be significantly more. The edge of the chert will form a natural ditch that will prevent water from flowing over the road and carry water down-grade.
In order to prevent water from pooling, the surface of the road is graded higher in the center and lower on the outer edges. Adding a crown to the road is very important for maintaining its longevity.
With cost being a significant factor, not all roads include a top layer covering. Asphalt is an expensive option, but it can last up to 12 years. Chip and tar drives are the next best option, costing 40% less. They can last up to eight years. Gravel is the cheapest option, but it requires maintenance on an ongoing basis.
Due to cost, we chose to cover our driveway with gravel. I’m hoping that we can recover it with chip and tar in the future, but we couldn’t justify the expense with everything else going on.
It’s kind of impossible to estimate the cost of a driveway without a lot of specifics. However, I can give the details of my own project.
For my road, it took 10 hours of clearing at $70/hr. My road used 20 loads of chert at $135/load and 2 loads of gravel at about $300/load. In addition, I had 20ft. of 24″ double wall culvert and 40ft. of 12″ double wall culvert. The final road was about 700ft. long, and the total for this work was about $5,400.