DTD installed two conveyance lines under the Shenandoah River in Front Royal, Virginia. The lines will be used to transfer water from the west side of the river to a newly built treatment facility on the eastern side of the river. Each bore totaled 750 ft in length and crossed at a depth of 37 ft beneath the river bed.
We mobilized our Vermeer D36x50 DR dual rod drill rig to the Superfund site based on the hard bedrock overlain by sediments and cobbles. The dual rod technology and low pumping rates of this system are ideal for the conditions and minimize the risk of inadvertent return of drilling fluid to the river.
Drilling progressed quickly through the upper sediment layers as care was taken to maintain an open borehole and to successfully enter the bedrock at an oblique angle. The borepaths were sub parallel to the folded and layered bedrock, and the bedding planes are plainly visible on the river bottom (see photo above). Walkover locating was successfully employed by wading in the river, until rains raised the river level and required the use of a boat. In the end, careful and patient locating, and good communication between the driller and locator ensured the safe and successful bore completions.
The 4-inch HDPE pulled into the bores serve as secondary containment for the smaller and primary 2-inch HDPE conduit. The primary 2-inch pipe was pulled inside the 4″ containment pipe with our smaller 10,000 lb drill rig.