A joint venture of three companies operated carefully to protect the environment in laying the St. Clair pipeline across the St. Clair River between the U.S. and Canada last year.
The companies-Union Gas Ltd., St. Clair Pipelines Ltd., and Michigan Consolidated Gas Co. -began planning the project to lay a 24 in. gas transmission line beneath the river in 1987. They employed horizontal directional drilling.
Company officials say the line, designed for bidirectional flow, ensures security of supply, allows inexpensive spot gas purchases, and makes storage on both sides of the river more useful.
The crossing runs 750 m from entry to exit, with water depth about 17 m at crossing point.
ENVIRONMENTAL SAFEGUARDS
Because the line crosses an international border, approvals were required from Ontario Energy Board, Canada's National Energy Board, Michigan Public Service Review, and the Federal Energy Regulatory Commission. The venture also had to obtain river crossing permits from the U.S. Army Corps of Engineers, Canadian Coast Guard, and Ontario Ministry of Natural Resources.
On Sept. 15, 1989, it secured the last of the required permits.
Crews first dug large sump pits on both sides of the river to contain all excess drilling slurry produced by directional drilling. Permits required that slurry not be discharged into the St. Clair River.
To ensure that drilling did not harm water quality downstream, the joint venture set up visual and chemical monitoring systems. It used helicopters and boats during drilling to identify any disruption to the riverbed, plumes, or discoloration of the water.
Water samples taken upstream, downstream, and at the crossing three times a day were sent to labs to check for deterioration in water quality as a result of drilling. Analyses revealed no damage to water quality during the course of the project.
DRILLING BEGINS
Directional drilling contractor Harcro Inc., Tulsa, moved a rig to the site on the U.S. side last Oct. 12. Sharewell Inc. began drilling a 2 7/8 in. pilot hole at the site Oct. 14, which took about 1 week.
An electric sensing device inserted at the end of the pilot hole pipe transmitted signals through a wire inside the pipe to a computer in the rig control room. A steering tool technician could then determine the pipeline's underground location.
Crews later inserted a 5 in. washover pipe over the pilot pipe to reduce soil friction on the pilot. On Oct. 21, the pilot pipe broke through Canadian soil.
In the next phase, the pilot hole was reamed by attaching a 36 in. cutter to the washover pipe on the Canadian side and pulling it through to the U.S. side.
The next phase, pull-in, was completed in 14 hr starting Oct. 27. After hydrostatic testing and a caliper pig survey revealed no defects, the line was deemed safe and ready to operate.
Facilities were also built to link the line with existing pipeline networks. Union Gas laid 11.4 km of line with measurement facilities to tie the river crossing in to Union's Bickford compressor station.
On the U.S. side, Michigan Consolidated laid 4.8 km of line and rebuilt parts of the Belle River Mills compressor station. Total project cost for all phases was about $15 million (Canadian).
Copyright 1990 Oil & Gas Journal. All Rights Reserved.
