Anchoring a Floating Sewer

Project Overview

Jensen Drilling Company was contracted to drill and install more than 400 anchors in the bottom of a lake to permanently submerge a sewer line. The anchors were installed on 25-foot centers for approximately two miles in a sinusoidal pattern that followed the alignment of the buried pipe.

The project required working in 50 feet of water while drilling down to 200 feet below the lake bottom — all while maintaining a placement tolerance of just 6 inches. Achieving that level of precision in an open water environment demanded specialized equipment and a highly experienced crew.

JDC mounted two Longyear BD 102 drills on a purpose-built barge with a 150-foot open middle section, allowing the drill rigs to straddle the sewer alignment and work in tandem. This custom setup allowed JDC to maintain production rates while keeping precise positional control.

In addition to the main anchor installation, JDC also installed 12 manholes with 6 anchors each — another layer of precision work requiring careful coordination with the overall project schedule.

The project was voted Project of the Year by the Associated General Contractors (AGC) in 2010, recognizing the complexity, innovation, and flawless execution JDC brought to this one-of-a-kind challenge.