Typically any sort of boring operation will use certain specific sets of equipment, not just anything that can dig through the ground. For rock and dirt directional drilling these sets are often combined or work together to do the boring through layers as it gets deeper underground. Any kind of surface strata does not truly reflect what is underneath.
In this sense, you may start off with a soft soil surface and find a rock layer underneath. It may be costlier to dig through with the equipment you have or your outfit may have the necessary ones to do the directional dig. Manufactured items are available for this kind of work, but may cost some money.
Contractors often offer things like additional services for those digs that need them. Not that there is not a study made of soil structure first and the strata that are found beneath. Even so, you still have to dig into the ground to find out precisely what is there, and sometimes you simply start the project first without preliminaries.
The preliminaries of course can consist of things like some smaller bore to take out samples. When meeting with rock, chances are this smaller bore is not able to penetrate through this layer and find out what lies below. So most companies can start the drilling in earnest using rock breaking equipment and the normal ones for digging into soil.
Most stuff that is taken out is carted out of the sight so as not to add to the mess on the ground. In any case when you have them lying on the side of hole, it might run off and into the hole again when it rains or when it is impacted by machines. Directional digs are often some of the best kinds processes for all surfaces.
No matter what kind of rock strata is down there, you get to have options about the horizontal drill. That is with some added directions that is made by specialized equipment. The outfit which does this work is often related to firms that construct any number of public works, or do the building of utility lines underground.
In the busiest streets, there not only are rocks underneath, but any number of lines used for utilities. This means that these are usually working to improve the quality of the works that are found beneath the earth. Most times you see them working on street level with all sorts of stuff, tools and electronic control gears.
These work with the most advanced equipment in this trade. And while drilling is an optional thing, most times there may be need to break up rock and asphalt in combination after which dirt drilling and a special kind of process is used for the utility lines. The combination effort is tasked for this more complex method.
The effect or any drilling operation should be something ideally studied first before the work is started. In any case, all sorts of environmental compliance and regulations are at work here. And that means that some of the best outfits often are very much aware of environmental impact here.