Prior to mobilizing onto the site, several days of multiple training days were completed andon site orientation were a must to make sure all involved parties were aware of the tasks DTD was going to complete. Also, in accord with the facility policy a large scale utility finding procedure was completed to ensure the entry location and projected bore path would pass clear of any potential utilities.
Drilling began with the horizontal remediation well. We used our 100,000 lb – CMS9030 drill rig and American Augers MP400 mud recycling unit for this bore. The well targeted a depth of 39.0′ below ground surface and once at the start of the well screen, the bore pitched upward at a slight slope. Also, the orientation of the plume meant the bore needed a horizontal bend to keep the screen within the contaminant zone. DTD carefully planned the bore profile and used walkover locating technology to steer the bore under site infrastructure, and under a intersection of two state roads. Multiple survey marks were placed along the bore path to ensure the drilling could be navigated correctly. Once drilled to the end target, we installed 4″ SCH80 PVC well materials through rod using our patent Knock Off Technology to disconnect the sacrificial drill bit. Installation was a success leaving the horizontal remediation well in place, as designed.
While the one crew began the well development and vault construction tasks, a second DTD crew began drilling the extraction water conveyance line. We utilized a second, smaller drill rig (Vermeer 24×40) to complete this HDD. Similar to the horizontal well installation, an in-depth utility locating process was completed prior to entering the ground. Once complete, the team began drilling. Minor deviations to the bore path were completed to exit the bore in the vault/wellhead area for final construction tasks. The installation was completed with the pullback of a 3″ and 2″ diameter HDPE line.
Horizontal groundwater recovery wells have a large amount of screen when compared to most vertical wells, and hence require extensive development. This ensures the drilling mud and fine-grained formation materials are removed from the well bore and that the pumped groundwater was low enough turbidity to pass through the treatment system. This involved flushing, jetting, and purging multiple thousands of gallons of groundwater through the well. Lastly, a large pre-cast, concrete vault (weighing almost 15,000 lbs) with protective bollards, was installed to secure the wellhead and complete the project.