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Sedro-Woolley, a small quaint logging town in Washington State has recently begun increasing their trenchless pipe installation program due its proven success. Trenchless pipe installation minimizes disruptions and costs, while proving to be an effective way to install pipe.

Trenchless Construction Services L.L.C. a trenchless pipe installation and replacement construction company was the general contractor for the $3.5 million dollar Sedro-Wooley SR9 Township trenchless sanitary sewer improvement project. Trenchless was responsible for installing 14 manholes and 3,400 lineal feet of 15 inch diameter and 24 inch diameter gravity sewer pipes at a .16% grade. Trenchless methods were required for this project because the pipe was to be placed under and adjacent to State Highway Route 20 and State Highway Route 9.

"These methods were used because of a lack of detour options to maintain traffic flow," says John Gustafson, Owner/ Manager of Trenchless Construction Services L.L.C. "The soil conditions, as well as the accuracy of pilot tube micro-tunneling, also made it the preferred method for the 15 inch and 24 inch portions of the project."

Pilot tube micro-tunneling, also referred to as guided auger boring, was introduced in the 1990s for the installation of small diameter sewer pipes and water lines. Guided auger boring systems are similar to micro-tunneling systems with the addition of a guidance system. This accurate guidance system consists of a camera-mounted theodolite to ensure a high accuracy of the line and grade.  "We choose the Bohrtec guided auger machine because we knew it would give us bullet like accuracy," says Gustafson.

Prior to construction, Trenchless sponsored a meeting with engineers, sub-contractors and Trenchless employees in order to get everyone on the same page. ICON, the New Jersey-based slide rail system manufacturer and Bohrtec pilot tube distributor and Mission Clay, the No Dig clay pipe manufacturer both made presentations of their products. "Our goal was to make sure all parties had a clear view of the project scope as well as the products we were going to use," says Gustafson. "This was very beneficial as everyone was able to ask questions and get direct answers from the manufacturers."