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Pipeline staging area includes land and water

Northeast sewer project minimizes disruption to local residents

The most recent phase of the Metropolitan Council's sewer construction project in White Bear Township and White Bear Lake was completed successfully in September.

Under plans approved by local officials, a 2,000-foot-long, 90-ton pipeline had to be placed in a straight line before it could be pulled into a hole drilled beneath a long stretch of Bald Eagle Avenue. Because of the pipe's length, half of the pipe's staging area was a local street, and the other half was the surface of Bald Eagle Lake.

The construction method saved many residents the disruption of having a long stretch of street torn up for several weeks.

The Council is installing six segments of new regional sewer pipe, totaling a little over three miles. The pipe will add capacity to handle the occasional peak wastewater flows, as well as increased daily flows that will come from anticipated growth in the northeast metro area.

A tractor-backhoe tandem makes quick work of pulling the pipe along the street. But that was only half the job.

A Frontier Pipeline worker watches the pipe being moved onto Bald Eagle Lake.

Construction method reduces disruption to neighborhood

"This project would have been very disruptive if completed by traditional open-trench pipe installation," explained Adam Gordon, a Council engineer and project manager. "Because this pipe is going through a predominantly developed area, we decided to use horizontal directional drilling methods to install the pipeline."

The traditional method would have meant excavating lengthy stretches of streets and boulevards, which would greatly inconvenience many homeowners and businesses, and result in extensive restoration work. Using horizontal directional drilling methods, most of the excavations and construction activity were limited to the beginning and end of a long hole that was drilled beneath the ground to contain the pipe.

Most people have seen horizontal directional drilling on a much smaller scale — to cross under roads, driveways and sidewalks to install small utility lines without disturbing the surface. The Council's use of horizontal directional drilling involves holes that are 42 inches in diameter and up to 3,000 feet long. The Council's contractor, Frontier Pipeline, believes it is among the largest horizontal directional drilling projects in the country.

Pipe floats on lake during installation

The 2,000-foot, 90-ton pipeline, along with a second 45-ton, 1,000-foot length of pipe, were connected and pulled into the hole over a half mile long and about 30 feet beneath Bald Eagle Avenue. Each stretch of pipe consisted of 53-foot segments — a suitable length for hauling to the jobsite on semi-trailers. The segments were heat welded together — forming joints stronger than the pipe itself — and the 1,000- and 2,000-foot stretches were stored along a nearby railroad track until the hole was ready.

In one day during the first week in September, the longer pipe was slowly and gently pulled in a wide sweep around the corner from the rail corridor to Bald Eagle Avenue, which runs roughly perpendicular to the tracks. With only 1,000 feet of Bald Eagle Avenue left stretching in a straight line beyond the end of the hole, half the pipe rested overnight on the street and half floated on Bald Eagle Lake. Buoys and light sticks marked the pipe, and the Ramsey County Sheriff's Department Water Patrol warned any nighttime boaters of the temporary obstruction.

The actual pipe installation began on the second day. The pipe is elevated with a crane to match the downward grade of the first part of the hole. Here, workers finish connecting the new sewer pipe to a metal rod that is coming up out of the hole. This rod extends 3,000 feet back through the hole and connects to the horizontal directional drilling machine. This machine - the same one that bored the hole - also pulls the pipe into place.

The next day the longer pipe was pulled into the hole, the shorter pipe was moved to the staging area and connected to the end, and the entire 3,000 feet were in place in about 15 hours. Even with the pipe sitting on the centerline of the street and floating on the lake, access was maintained to driveways on both sides of the street — and to the docks, too. Cross traffic at three intersections on Bald Eagle Avenue had to be detoured for only two days.

Residents watch in amazement

Some two dozen area residents watched the operation. Many of them were awestruck over the size and power of the machinery, and welcomed the short-lived excitement in their quiet neighborhood, observed Tim O'Donnell, a Council community relations staff member assisting the project. Others looked in similar amazement at a half mile of stretch of city street with a new sewer below and very little disturbance above. "I'd hate to think of the alternative," one resident said. "I like this way better."

Installation of all pipes associated with the White Bear Area Diversion Interceptor Sewer project is expected to be completed in 2007.