An active retail gas station next to a wetland area has benzene and trimethylbenzene plumes in a water table aquifer containing sand, gravel and cobbles. Rock fragments and boulders several feet in diameter lie in the vadose zone, between the ground surface and the water table. Business at the gas station would slow down or stop for an extended period of time if a vertical air sparge and soil vapor extraction wells had to be drilled through the rock, because the wells would surround the pump island, block the driveways, and even interfere with access to the store itself. The vertical wells would have to be closely spaced because of their limited zone of influence.
As an experienced national directional driller based in New England, Directional Technologies, Inc. has the experience to complete projects that may confound other companies. New England is known for its tough subsurface conditions and the company has been installing conduits and horizontal wells in gravel, cobbles and rock since 1992. Directional Technologies installed three blind wells—two air sparge wells and one soil vapor extraction well under the pump island, driveways, and even under the retail store—within a week. Blind wells have only one wellhead, avoiding the need to exit through the wetland area, and limiting the amount of drilling through boulders in the vadose zone to three riser sections (one for each well). Cars pumped gas while the directional wellbore was advancing beneath the pump island and driveways. Customers roamed the store aisles and paid at the cash register even as the drillers were locating the advancing drill bit beneath 20 feet beneath the floor. The project was completed on time and without a change order request, despite the need to adjust well entry points, paths, screen depths, and completion details.