Trenchless Construction Services Goes Low Profile

October 2008 Vol. 63 No. 10

The Birch Bay Water and Sewer District provides water and wastewater service to approximately 7,500 people. The district is located in the city of Blaine, WA, and has been operating since 1968. The district features a three member elected board and a general manager who is responsible for day to day operations.

The area's water system is comprised of three reservoirs and approximately 70 miles of water mains. The district recently became a member of the Whatcom Water Alliance that includes member cities in the area as well as several other water and sewer districts. The group's aims include water conservation efforts and public information activities.

Realizing the issues with the water main along Drayton Harbor Road and an impending asphalt overlay project, the district needed to act quickly in order to facilitate the repair to the main before completion of the asphalt overlay project. According to Gustafson, Trenchless Construction Services was contracted on an emergency basis to pipeburst and replace over 6,300 feet of 2.5 inch water main.

The Birch Bay waterline replacement project consisted of replacing 6,300 feet of existing 2.5 inch PVC force water main with new 4 inch DR 11 HDPE. In order to accommodate a pipebursting application, Trenchless Construction Services needed to utilize a pipebursting unit with a low profile bursting rod to fit within the small diameter waterline. Moore said, "The nice thing about the compact Grundoburst 400 is that it has the smaller profile bursting rod capability, but doesn't sacrifice power. Plus, those smaller rods still incorporate the Quicklock system, the preferred method for connecting static bursting rods without the inconvenience of screwed together rod systems."

The project was further complicated because the original pipe was installed without bedding and on a radius in many areas. Additionally numerous bends complicated the insertion of the Quicklock rods. Moore explained that “because the existing pipe had so many turns and bends, we could not just pick places for launch and exit pits. We had to insert the rods into the existing pipe as far as the pressure and resistance would allow. This was the determining factor in the location of the pipe insertion pits."

Artifacts

One of the primary reasons pipebursting was specified for this project was because much of the project ran through the Lummi Indian Reservation, along the western edge of Whatcom County. This required special procedures for the excavation of launch and exit pits, in order to minimize the disturbance of any Lummi Nation artifacts encountered during excavation.