The project to expand the high-pressure Medicine Bow Lateral natural gas pipeline in Colorado and Wyoming has been credited not only with providing energy for the region’s homeowners, but also with incorporating innovations in pipeline commissioning and welding technology.
Colorado Interstate Gas Co. (CIG) and Illinois-based contractor Murphy Brothers Inc. completed construction of a 155-mi. (248 km), 36-in. (91.4 cm) expansion loop late last year, with site restoration activities scheduled to continue in more recent months.
The $160-million expansion loop was designed to add natural gas capacity and to parallel the original 24-in. (61 cm) pipeline across Converse, Platte and Laramie counties in Wyoming and Weld County, CO.
Murphy Brothers used 165 pieces of its own Caterpillar equipment on the job. Welding systems used by various contractors on the project came from suppliers including CRC-Evans Automatic Welding of Houston, and Miller Electric Manufacturing Co. of Appleton, WI.
Pipelines such as the Medicine Bow Lateral Loop are built in an assembly line process involving 10 key steps. The key phases include clearing and grading; ditching; stringing (laying the pipe pieces alongside the ditch); bending (bending the pipe so it conforms to the ditch); pipe gang (an assembly line process where the individual pieces of pipe are lined up to be welded together); lowering in the pipe; backfill; hydrostatic testing (using water to fill the pipe and check tie-ins and welds); cleanup and restoration; and finally reseeding of vegetation. Crews worked on all of these phases simultaneously.
One unique aspect of this loop was the way CIG commissioned the pipeline. It’s called progressive commissioning and involved finishing the pipeline in segments so it can flow gas as soon as each of the nine segments were completed.
“There are a lot of people wanting to use this gas. Progressive commissioning allows us to get gas to our market quicker,” said John Jermyn, CIG project manager, early in the process.
The project was regulated by the Federal Energy Regulatory Commission (FERC), which has required CIG and its counterparts to demonstrate that each particular segment has been completely restored and reseeded before approval to operate the line is granted. Testing has been done by filling the pipes with water and performing ultrasonic testing to determine if the welds meet pre-determined acceptance specifications.
The water used in these tests has been drawn from local streams and pumped back into the streams after testing. BioResources of Logan, UT, was brought in to oversee environmental monitoring on the pipeline loop due to some potential problems with the stream waters. The pipeline crosses trout streams in the work corridor and some fish have been found to have whirling disease, a parasitic infection that attacks the nerves and cartilage of small trout. Because the fisheries department has been trying to prevent the disease from spreading into new areas, crews have been careful to return the hydrostatic test water to the places where it was pulled from originally.
FERC, the U.S. Fish and Wildlife Service and the Medicine Bow Lateral Pipeline Commission also worked together to assess the potential impact of the project on the Preble’s Meadow Jumping Mouse, which has been listed as a threatened species.
A large portion of the project crosses privately owned land, which has presented the challenge of keeping landowners happy.
“In ranching country you have to make sure fences are put back so cattle don’t escape, and that you keep the dust down and don’t alter their property roads,” said Jermyn. “We need to make sure we build the project in a responsible manner and impact the landowners as little as possible.”
Overall, the project went smoothly, Jermyn added. Because several other pipelines and cables were placed within the same corridor, crews havetaken care by closely monitoring where their equipment was working at all times. With an estimated 17 million cu. ft. of dirt removed for the pipe placement, there was a potential for problems.
The pipeline was placed at a minimum of 36 in. (91.4 cm) from the top of the pipe to the ground above. When you add in the 36-in. pipe, each ditch is at least 6 ft. (1.8 m) deep. Some of the pipe was placed as much as 10 ft. (3 m) below the lowest point in the road and at least 5 ft. (1.5 m) below streams.
The privately-funded, expansion also was designed to add 7,000 hp (5,218 kW) at the Douglas Compressor Station in Converse County, bringing the total to 21,000 hp (15,653 kW) at the pressure station to allow transport of more gas through the system. To increase the pressure of the natural gas stream flowing through the station, each compressor station houses large, natural gas-powered engines.
“In this case we had to extend an existing building and put one additional compressor in. We put in a Solar Taurus 60 package, rated at 7,200 hp,” said Jermyn.
With the added speed of mechanized welding, crews were able to top the typical progress of placing about a mile of pipe per day to somewhere between two and three miles per day. Murphy Brothers purchased the Double Bug Pulse Arc automated welding system to reduce manpower needs and produce a better quality weld.
According to Pipeline News, construction of the Medicine Bow loop represented the first use of mechanized welding in an entirely American project.
“Mechanized welding is somewhat new in the United States, but we’ve been using it in Canada for about the past 10 years,” said Steve Rooney, project superintendent for Murphy Brothers. CRC Pipeline of Tulsa, OK, provided technical support for the loop project.
Medicine Bow provided the opportunity for technologically advanced systems from two manufacturers to be used in tandem: the CRC-Evans P-600 double-headed welding system with distributed control technology was paired with Miller Electric’s Invision 456MP inverter-based power source with built-in pulsing controls.
CIG and contractor Murphy Brothers Inc. had several subcontractors on this project. Key subcontractors for CIG include Houston-based Microalloying (developing specifications, welding procedures and acceptance criteria for automatic ultrasonic testing), Canada-based Shaw/Edwards Pipeline Services (AUT), Oklahoma-based Gulf Interstate Field Services (field inspections), Wyoming-based Inberg Miller (surveying), and Colorado-based Metcalf (archeology).
Subcontractors for Murphy Brothers included Key Enterprise Ditching, Wyoming-based Redi Insulation Inc. (painting of above-ground piping), Indianhead Pipeline Services of Minnesota (concrete coating of pipeline), Western States Bagging of Wyoming, and Minnesota-based Midwest Seeding (specialized seeding mix).
Murphy Brothers Inc. specializes in mainline pipeline construction and is one of the largest pipeline contractors in the United States. At this project’s peak, 545 workers from Murphy Brothers were at work on the loop.
Founded in 1927, CIG provides natural gas production, transportation and storage to customers in the Rockies and other markets throughout the United States. Together with its affiliate pipeline, Wyoming Interstate Co., Ltd., CIG is the largest natural gas pipeline operating in Wyoming. CIG and its affiliates own and operate more than 4,850 mi. (7371 km) of natural gas pipeline, 65 compressor stations, nine processing plants and five vast underground storage fields. The system was designed to deliver more than 2 billion cu. ft. of natural gas on a peak day, enough to heat more than two million homes.
