Fast trenchless gas service lines with GRUNDOMAT: Contractor AGI Construction reaches high levels of productivity
Contractor AGI Construction, Smithfield from Rhode Island is one of the premier underground utility contractors in the northeastern United States. For over 25 years the construction company has provided a comprehensive range of contracting services for natural gas, telecommunications, and electric underground utility installations. With almost 200 skilled employees, the Rhode Island-based company’s service area includes all of New England.
AGI Vice President of Operations, Brian Minnis has over 35 years of natural gas pipeline experience and oversees all field operations for the company. Minnis began his career in the industry as a second-generation pipeline welder and originally started as a welder for AGI. That was almost 20 years ago. Today, Minnis manages a work force of 25 crews and 195 employees. As part of AGI’s leadership group, he has been a major contributor to the significant innovations that the company has developed, including the proprietary approach the company takes toward pipeline installation.
Minnis said, “The approach to project work in pipeline installation operations has improved efficiency and productivity in the field. We have moved to a very specialized approach. For example, we have crews that specialize in main installation. Then we have crews that focus solely on services and crews that just do tie-ins. Basically it’s a moving assembly line. We see major efficiencies with that approach.”
With a wide range of challenging soil conditions to contend with, along with established, older neighborhoods, Minnis said his crews are utilizing soil displacement hammers to facilitate a significant service line replacement programme for a local gas utility provider.
Minnis explained, “We’re currently replacing a large number of old cast iron mains and bare steel gas service lines. Residents are very particular on how you take care of their property. The soil displacement hammers allow us to limit the amount of disruption for the homeowner. We use them as much as possible. I’d say ninety percent of our service line work is done with ‘moles’.”
While soil displacement hammers range in size from 45 mm diameter up to 180 mm in diameter, AGI uses primarily 75 and 85 mm diameter tools. Throughout Rhode Island, crews are using GRUNDOMATs from TT Technologies, Aurora, IL., for service line installations.
TT Technologies soil displacement hammer specialist Ric Micelotta said, “Brian has developed an impressive service line replacement programme at AGI. It’s really a model of efficiency. They get a lot of productivity from their crews as well as the soil displacement hammers.”
Using a staple of trenchless technology combined with the company’s production-based project approach has helped in the establishment of a successful gas service line replacement programme.
Versatile soil displacement hammers
Soil displacement hammers are known for versatility. According to Micelotta, several techniques can be used with soil dispalcement hammers to install services. He said, “Soil displacement hammers offer many options for installing the actual product pipe. That’s one of the reasons they are so effective in service line installation situations. For pulling PVC or ridged plastic pipe directly behind the hammer, a specially designed pipe-pulling tailpiece is available. Several other tailpieces are also available for pulling PE and steel pipe.
“In certain situations, after the bore is complete, the tool is removed from the pit. Then the pipe is attached to the air hose and pulled into place when the hose is pulled out. Because of the poor, dry soil conditions in the area they are working in now, AGI crews are attaching the new service line and a tracer wire to the front of the tool, and backing the tool out through the bore hole, pulling in the new service simultaneously in severse mode. That method can be accomplished in several ways including a pulling eye adapter that slips over the tip of the tool head and is secured by roll pins.”
On the Job
In Rhode Island, AGI is getting significant productivity from its GRUNDOMAT crews, replacing approximately 3,000 gas service lines annually. Soil conditions vary from sandy in one part of the state to rocky gravel soils in the other.
The design of the GRUNDOMAT has a lot to do with its accuracy and overcoming difficult soil conditions. Micelotta said, “The chisel-head assembly is the key to accuracy. The assembly is spring-loaded and pushes forward from the casing creating a pilot bore for the tool to follow. The reciprocating action and stepped-cone design of the tool head allows it to overcome difficult soils and obstructions without being pushed off course.”
Minnis has 12 four-person crews working on service line replacement throughout the state, dividing tasks between pit preparations, installing the service and tie in. He said, “Most of the installations we’re doing are for replacement as opposed to new service. We’re installing 12,5 mm, 25 mm and 50 mm High Density Poly-ethylene (HDPE) gas service lines, depending on service requirements. Our crews are typically able to replace three services per day. And home-owners are only taken off for a short time, usually put back in service within 2 or 3 hours.”
Often, the service line replacements are taking place in well-established neighbourhoods, in tight working conditions, with landscaping, driveways and sidewalks to avoid. The setting is well suited for trenchless horizontal boring with soil displacement hammers. Launch and exit pits average in size 1,5 m long, 1,2 m wide and 1,2 m deep. Crews launch the soil dispalcement hammers by hand with a smart sighting mast.
Near side service installations range between 10 and 15 m in length while long side installations are typically around 20 m. Minnis estimates that boring rates average approximately 30 cm per minute depending on soil conditions. Once crews have completed the installation, the new service is tied into the main using mechanical or electro-fusion fittings.
Micelotta said, “With all the people they have performing service line installations, they’re running Grundomats all day long. Basic tool up-keep and maintenance is performed at their shop, but crews also service them when needed in the field. The tools are very easy to maintain. The programme that Brian has established at AGI for gas service installations is really something. Their crews are well trained and extremely efficient. They really know what they’re doing. Definitely top quality.”