Shallow HDD bores typically are started from the surface at an acute angle, and are guided to a subsurface or remote surface target using sophisticated electronics packages that enable the driller to navigate and steer the drill along a desired path. Unlike the deep directional bores used in oil exploration and production, which can extend thousands of feet deep, shallow HDD is performed from just a few feet to a few hundred feet beneath the ground surface. Meanwhile, a relatively new technology, shallow horizontal directional drilling (HDD) for utility and pipeline installation, has evolved rapidly over the past three decades. Even the venerable cable tool rig is still used for this purpose in some locales. Despite mechanic?al advancements in advancing a borehole, however, the extraction technology has remained the same: drilling and casing a vertical bore that intercepts a water table. Shovels gave way to cable tool rigs in the early 1800s and mechanical improvements incrementally led to current well-drilling technology, typically rotary drive rigs with automated casing drivers. Horizontal boring is an option, not the only option, sometimes it is the most cost effective, sometimes it is not.The technology for extracting groundwater from subsurface resources hasn?t advanced appreciably since drillers abandoned shovels and buckets for mechanized well drilling rigs. I hope this helps explain things a little clearer. If your lot size is too small vertical drilling is normally the only option due to the space requirements. Drilling in rocky ground is also not cost effective. A 300 foot loop (600' pipe) normally yields 1 1/2 tons of heat. The most cost effective bore is 300' in length. The disadvantage to horizontal boring is you need a large area for the heat field, an acre or more. If the machine can be set up close enough to the building then we manifold inside the building which is the best case possible, eliminating many fusion joints being buried underground. This requires a backhoe to expose the pipes to about the 5' depth the pipes are manifolded there to header pipes which go to the building. We normally manifold in the area where the drill was set up. The only ground scars left are where the boring machine was set up and a small 3" hole where the drill exited the ground. The pipes are then hooked to the drill head and pulled back to the machine. Horizontal directional boring machines have been used for years placing underground utilities (gas,power,telephone,sewer, etc.) The drill enters the ground at about a 25 degree down angle, upon reaching the desired bore depth the drill can be turned to travel horizontally, upon reaching the desired bore length the drill can be turned to go back up and exit the ground. I'd plan on the directional boring depth to be an average of 10-15'. All my installs so far have been good using vertical holes and I don't want to get a bad rep if we have another serious drought and I lose heat conductivity. I have never dug a horizontal field because the soil here is mostly black-land clay and during droughts the ground has dried out to a depth of >6ft. Additionally I realize I will need to grout the hole and plan on pulling the tremie pipe along with the HX piping to make sure there are no voids. The company is willing to send a machine to a job and demo it but I'd like to get some feedback before I waste time and money. Does anyone have experience using this type of technology for geo and did it work satisfactorily? I'm leaning toward the DitchWitch JT1220 if it seems that it will work. The soils here are conducive to using a directional drill and I will be able to schedule the work better and hopefully control costs and cleanup. I am unwilling to spend two years as an apprentice driller (not that anyone would hire a worn-out HVAC business owner) just to become licensed to drill a vertical hole and thought about using a directional horizontal rig. My problem is three-fold 1) The geo drillers prices have shot up in my area, 2) None have been very reliable, 3) The rigs and crews leave a big mess for us to clean up after. I'm hoping another geo professional or informed homeowner will be able to give me some insight on their experience/success/problems/performance concerning using a directional horizontal boring rig to install the HX field.
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