Directional Drilling Limits Excavation

September 28, 2010

In the 47 years the company has been in business, Selge Construction, of Niles, MI, has built a reputation as one of the most respected utility contractors in the Southwest Michigan-South Bend, IN, area.

Selge Construction is a multifaceted company specializing in municipal sewer and water systems, low-pressure sewer systems, concrete paving, and flatwork. President Marv Selge Jr. grew up in the business, purchasing the company from his father in 1992. “It is the only work I've ever done,” Selge said.

Selge has seen significant changes in water and sewer construction, and has made sure his crews are equipped with the latest technologies to keep pace with the needs of water and sewer utility owners and operators.

In addition to conventional open-cut construction, Selge crews use bore and jacking, and horizontal directional drilling (HDD) for underground infrastructure projects.

“We are capable of handling many of the difficult challenges often experienced in underground construction,” Selge said. “In conjunction with installing pipe in the ground, we install a variety of lift stations ranging in size from 6 to 10 feet in diameter.”

Selge always has been alert to market changes and conditions. Currently Selge Construction is actively involved in installing low-pressure sewer and grinder pump systems to serve rural homes near the area's many lakes. In response to initiatives to improve water quality standards in rural lakes, streams and rivers, these systems are being installed to solve several problems, Selge said.

“Often,” he explains, “homes and cottages around these lakes are in very close proximity to each other and have old, deteriorated septic tanks buried at or below the groundwater table. Sewage from these tanks finds its way into the lakes, causing contamination and increased weed and algae growth.”

Because many lakes are outside the boundaries of towns and cities, Selge said that regional sewer districts are formed to oversee the design, construction, operation, and maintenance of these low-pressure grinder pump systems.

A typical project consists of installing a small grinder station and control panel at every residence, service lines from the tank to the main line, main lines to collect the influent from each tank, large lift stations, and force mains to take the sewage to a treatment plant or tie into an existing municipal system if one is nearby.

“We have installed systems with as few as 68 grinder tanks and large systems with more than 500 tanks,” Selge said. “The first step in a project is to install HDPE service lines – usually 1-1/4 to 2 inches in diameter – from the proposed main line locations to the proposed locations of the grinder stations. Once all of the service lines are in the ground, a crew then installs the main sewer line, usually located within road right-of-way. After the main lines are installed, a crew then sets the grinder station at the predetermined location. A curb stop and a redundant check valve are usually installed on the outside of the grinder station.” Site conditions often present a challenge.

“With lake projects,” Selge explained, “homes often are within close proximity to each other, so we often deal with narrow easements to work in, landscaping, and sometimes grinder stations on the lake side of the house where it is difficult to reach with equipment. We have seen a wide variety of soil conditions from sand, gravel, clay, and silt to peat, marl and muck, often on a single project. In addition to different soil conditions, we often deal with areas that have high groundwater tables, especially close to lakes.”

For these and other reasons, Selge says that horizontal directional drilling plays a critical role in the company's low-pressure grinder system construction projects.

“Directional drilling limits the amount of excavation necessary to the tie-in points' and grinder stations' locations,” Selge said. “HDD lets us install both service lines and mains under landscaping, between houses, and in tight locations where typical open-cut operations would not be possible. HDD limits the damage to surface features, thus minimizing the restoration needed after the pipe has been installed. In high groundwater situations, HDD eliminates the need for extensive dewatering that open-cut operations would require.”

HDD equipment often used by Selge crews on these projects includes Ditch Witch JT2020 and JT2720 drilling units.

The compact size of the JT2020 suits it well to job conditions found on many low-pressure sewer projects. It is only 51-1/2 inches wide and 207 inches long. Mounted on rubber tracks, it moves easily over landscaped areas and paved surfaces. The JT2020 develops 20,000 pounds of pullback, 2,200 foot pounds of rotary torque, and spindle speeds to 150 rpm.

The larger 125-horsepower JT2720 produces 27,000 pounds of pullback, 2,700 foot pounds of torque, and spindle speeds to 195 rpm, providing plenty of power to make longer installations of main line pipe. For its production capabilities, the JT2720 also is a relatively compact unit. Subsite 750 and 752 electronic tracking systems are used. Other Ditch Witch equipment includes a skid-mounted fluid mixing system; two FX60 vacuum excavators, one mounted on a trailer, the other on a truck; and a SK500 compact skid-steer loader.

After all pipe is in place, Selge crews complete a low-pressure grinder system by connecting services to the grinder stations and to the main line by fusing a branch saddle to the side wall of the main. The main is tapped, and finally the service lines are electrofused to the branch saddles.

“A control panel is set within close proximity to the grinder station,” Selge continues.

“Wires are buried from the tank to the control panel using the SK500 skid steer, which is equipped with a trencher and vibratory plow attachments. Incoming power wires are trenched in from the service drop to the control panel. Once all of the tanks have been installed and the tie-ins made, the system is pressure tested and each grinder station is started to ensure that everything is running as designed.”

Selge points out that the use of directional drilling technology is not new to Selge Construction – the company was one of the first water and sewer contractors in the area to recognize its potential for water and sewer work, and the benefits of HDD construction are not limited to low-pressure sewer construction.

“We recently installed 28,000 feet of 8- and 12-inch water main for Niles Township, Michigan,” Selge said. “The job was originally bid to be open-cut, but the entire project was installed by HDD. By using this method, it minimized disruption to the heavily traveled commercial corridor, and kept restoration and drive closure to a bare minimum.

“We also utilize HDD to perform river crossings for municipal water and sewer mains, and we have used HDD in gravity sewer operations to install sewer mains and laterals. This causes the least amount of disturbance to heavily traveled streets and busy highways.”

With the growing need to replace and rehabilitate the nation's aging water and sewer infrastructure, Selge expects his company to remain busy on a variety of projects and expects demand for low-pressure sewer systems to continue to grow.

And as if utility construction doesn't keep Selge busy enough, the company continues to carry out a variety of local paving projects and has earned many awards of excellence in that industry.