From October to December 2016, DTD installed a series of horizontal injection wells as part of a groundwater re-circulation study in East Palo Alto, CA. The ~13 acre construction site was once home to a hazardous waste management facility that closed in 2007. The soil and ground water beneath the 50-year-old industrial site is contaminated, primarily with chemical solvents such as trichloroethylene (TCE) and tetrachloroethylene (PCE). In an effort to clean up the site, which currently sits on prime redevelopment real estate in the middle of the Bay Area, DTD was contracted to drill and install 10 horizontal wells in three different groundwater zones ranging from 15 to 66 feet below ground surface (bgs).
For this project DTD mobilized one of our Vermeer 24×40 drill rigs and a mud recycling system. Borehole navigation was challenging due to overhead power lines and thick, steel reinforced concrete. For wells with screen depths shallower than 40 feet bgs navigation was accomplished using a walkover locating system. However, when we started drilling the deeper wells (screen intervals greater than 40 feet bgs), a combination of high interference and low signal strength led us to use a Short Steering Tool (SST). The SST is a wireline guidance system that allows for precision steering along a predetermined azimuth; it is not limited by depth or hindered by above-ground interference.
Using these two borehole navigation systems, all wells were completed in either a continuous or blind borehole with screen lengths ranging from 210 to 240 feet. In total, 4,234 feet of well material was installed during this project.
In 2017 the horizontal injection wells are scheduled to be connected to a series of vertical extraction wells and conveyance lines. Once connected, the re-circulation system will be operational and the decontamination process will begin.