Remediation wells, whether vertical or directional, generally need to be connected to a treatment system, and sometimes to power, control systems, or data lines. With increased interest in horizontal treatment wells, DTD has not only been busy in the past year installing environmental remediation systems, but has completed a variety of these connections from the wells we install – and even from vertical wells – to central treatment systems. Connections have included conveyance for sparge air, chemical reagents, or biological amendments, vacuum lines for soil vapor, pressure lines for extracted water, and power and control circuits for pumps and other wellhead instrumentation.
Depending on the site conditions, well layout, power availability, and other factors, treatment systems may need to be placed a marked distance from the entry locations of the horizontal wells or drains. There may be obstacles (roadways, water bodies, or sensitive “no dig” areas) that prevent conventional trenching activities. Further, situating the treatment building/system at a distance from the wells may permit more options in design.
Our most recent conveyance line – measuring over 1200 feet in length – was installed in California to supply two air sparge wells situated remotely from the blower system. At a refinery in Louisiana, DTD installed a short run of conveyance piping and power from a treatment system to a cluster of vertical wells, which could not be reached through trenching due to high pressure piping and a busy road crossing the intervening distance.
In other recent projects multiple conveyance lines were completed on a government installment in Puerto Rico. DTD was contracted to install a network of small diameter wells to assist in meeting the remediation goals of the facility. Once the wells were successfully completed, conveyance lines were necessary to connect a manifold design to the treatment facility. The same drill rig and tooling that completed the environmental wells was able to complete the conveyance via directional drilling.
Another example again defines a conveyance line, this time at a southern air base. With sparge wells designed to attack a groundwater plume that spans across a busy airplane taxi way, a single conveyance line was necessary to connect the wells. Drilling under this taxiway was the only option to connect the wells to the treatment area.
Consideration of horizontal drilling to complete a network of horizontal wells is well worthwhile. Since the horizontal rig is already on site, no additional mobilization is required, and the client is assured that the same crew that installed the wells will maintain high quality standards in making those crucial connections. Horizontal drilling can be shallow or deep – often impractical with trenching – to avoid disruption of site traffic patterns, exposure of employees to open trenches or potentially contaminated soils, or potential collision with buried utilities or piping that may cross the access lines. Installation of conveyance lines is also completed at a less expensive footage rate than are wells, since non-biodegradable mud is used and the installation is less complex.