DTD has completed the installation of four ETEC
The horizontal injection wells will be used to allow in-situ oxidation of contaminants found in the soils and groundwater beneath the building. Specifically the horizontal wells provide a pathway for groundwater with elevated dissolved oxygen (DO) to be injected below the building slab. The elevated DO allows the degradation of the site contaminants without either massive intrusion into or removal of the building.
Although the HDD project was reasonably straightforward (wells 75 – 100 ft long screened 6 ft below the building floor) this site came with its share of challenges. Contamination was also present in the soils surrounding the building, and those soils were excavated and hauled offsite. This required integration with the site works contractor to bring our drill rig in while the excavation was open. The drill rig was tracked into the excavation and set at a near horizontal pitch, to enter the ground through the shoring, and under the footer.
Geologically speaking, the site is near the terminus of the glacial advances of the Wisconsin Ice Age, and the ground conditions include glacial till with abundant boulder, cobble and gravel. Construction debris backfill including concrete added to the difficult drilling conditions. This required multiple passes and a variety of drill tooling to successfully install the injection wells. The cohesiveness provided by the small amount of fine sediment in this formation helped to keep the borehole stable after drilling through the cobbles and boulders, and each of these wells were completed as a blind installation. All project activities were completed during one week on site.