Sewer lines pose difficult challenges for HDD techniques. They require extremely tight tolerance in gradient, plus they are generally large in diameter and have to be connected to existing lines which cannot be moved.

Longbore installed a sewer line from an airport terminal building to a main sewer line, crossing beneath an active airport taxiway— without causing delays in airport operations. Gradients were held within tolerance and the end-points secured to existing locations, precision installation specifications called for placement within ±3 inches.