May 24, 2007

Contractor Ingenuity

Contractor used a directional drill to pull and install six 3,000-foot sections of pipe

Some sections of pipe were floated a quarter-mile into a lake

STEVE GREENFIELD

correspondent

White Bear Lake, Minn.

Directional drilling for sewer construction work is fairly common. But it’s quite rare when that work needs to stretch 3-1/2 miles.

It becomes even more challenging when a project that length also requires pipes to be floated more than a quarter-mile into a lake before they’re pulled underground

The Metropolitan Council in Minnesota learned the answer in 2006 when it hired the Somerset, Wisconsin-based Frontier Pipeline, LLC for major sewer construction work in White Bear Township and the city of White Bear Lake, a northeast suburb of the Twin Cities.

Happily, the Met Council not only learned that pipe floating was a rare and difficult undertaking, but also learned it could be done quite successfully.

“Clients know what their needs and timelines are, but sometimes there are unusual challenges, and it’s our job to determine the best way to meet them,” said Frontier Pipeline project manager Mel Olson.

“When we were presented with various scenarios, for example, preferring to keep access open to homeowners during construction, we would respond with various potential solutions.

“In this particular case, we needed to come up with quite a few creative solutions.”

Frontier Pipeline’s assignment was to install six 3,000-foot sections of 28-inch-diameter sewer pipe in a directional drill that required a 42-inch-diameter bore hole.

The new pipe was needed to handle occasional peak wastewater overflows now, and also to provide capacity for anticipated growth in the future. Installation work began in April 2006.

Street configuration required one 3,000-foot, 150-ton pipeline to be placed in a straight line prior to being pulled into the ground. Yet there were only 1,500 feet of land until the staging area reached the shore of Bald Eagle Lake.

Frontier Pipeline, working in conjunction with the two municipalities, staged half of the pipe section on a street centerline and the other half in the lake; or rather on the lake as the new pipe floated quite nicely.

Adding another challenge was the need to “thread the needle” with the pipe just a few feet from neighboring docks. Buoys and light sticks marked the pipe, and the local sheriff’s department water patrol warned nighttime boaters of the one-night obstruction.

Great care was needed to coordinate staging of the drill rig, the mud recyclers and other heavy equipment to ensure minimal impact on the environment, residents and municipal services. Frontier used an American Auger 440 directional drill capable of 500,000 pounds of pull and thrust, two mud systems, MP500 and Tulsa Rig, and large excavators, including a Hitachi 550, Hitachi 450, and two Caterpillar 320.

To complete the project, a Caterpillar 950 loader and two Caterpillar 277 ASV loaders helped carry and support cradles for the floating pipes.

This particular drill shot for the project took approximately 40 days from start to finish.

Access was maintained to all driveways and docks throughout the process giving many residents a close-up view of the unique activities. Cross traffic at three intersections had to be detoured for only two days. The entire 3.5-mile project is expected to be completed in May.

“If we weren’t able to install this pipe the way we did, our next option would have been to do tiny sections of open-trench installation, tearing up parts of busy streets and taking far longer to complete,” said Olson.

“Working near bodies of water is a specialty we’ve developed out of necessity, because when you’re in the Land of 10,000 Lakes, there’s a pretty good chance you’re going to bump up against a few of them.”

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