A steerable impact mole device. Like conventional piercing tools, the Grundosteer is pneumatically powered and driven by a piston in a casing. It features Teflon seals and tapes, as well as all modular construction for durability and long life. The tool can be surface launched or launched from a cradle in a pit. The tool is 3 inches in diameter, weighs 85 pounds and is 87 inches long. In all respects it operates and functions like a regular piercing with the big exception of its steering capabilities. The Grundosteer can bore up to 200 feet. Sensors on the tool provide pitch and roll information to the operator and an above ground locator is used to track the tool's position and movement. Depending on soil conditions, the tool can be steered at a maximum 85-foot radius. The operator can make adjustments to the tool's course by rotating the air hose with a hydraulic tensioning unit called a torquer. The wire reinforced air hose is placed in a specially developed torque frame where rotation takes place. The hydraulic torquer clamps down on the hose and allows the operator to turn it. A specially designed tapered steering head rotates accordingly then sets the tool's course.