Communication Technologies Inc. (CTI) is installing a 12-block-long duct system for MidAmerican Energy Co. in downtown Des Moines, Iowa, connecting to its substation that feeds much of the city's businesses and office buildings. The year-long relocation project, a joint-effort between MidAmerican and the City of Des Moines, was needed to make room for a major storm sewer project that overlaps the energy company's existing cable route.

Digging and trenching within an already crowded downtown utility corridor has been a challenge in itself, but the bigger challenge was the delicate task of installing the two 6-ft-deep connecting conduits inside MidAmerican's substation. Installing a duct system is typically a job for a back hoe or trencher, something CTI has been doing since the company began more than 15 years ago. But working inside the congested substation environment required a different set of equipment and experience.

Congested Work Area

The job included the tedious task of digging trenches, installing pipe, encasing the pipe in concrete and backfilling the encasement once the concrete had set in a 150-ft by 150-ft area. The majority of the conduit was 6 ft deep, but a combination of different-sized ducts was included in each of the two circuits: a 2-inch duct for grounding; a 4-inch duct for communications; and four 6-inch ducts for the phases of the circuit. Not only were there tight quarters in the switching area to maneuver around, the crew also had to contend with existing underground cables already in place, overhead clearance issues and height restrictions.

Equipment That Fits

Needless to say, selecting the right equipment became a key factor to ensure the successful completion of the duct system installation. Aside from the obvious safety concerns, a lot was at stake considering the fact that the live substation feeds power to a major section of downtown Des Moines. CTI owns and operates a fleet of trenchers, track equipment and large track hoes. In recent years, the company, which started out in phone, cable and fiber-optic installations, has also purchased several horizontal directional drilling (HDD) rigs. The HDD machines have been used for water and sewer installation, but are primarily used on MidAmerican jobs replacing aging primary cables running from transformer to transformer in neighborhoods.

Given the tight working conditions and the existing infrastructure, CTI did not feel comfortable with using its trenchers, hoes or HDD rigs inside the fence. In talking with a local equipment dealership, more compact equipment, such as a mini-excavator, appeared to be a safer and more efficient way to complete the work. CTI had bought its HDD rigs from Vermeer Sales & Service in Pella, Iowa, and had developed a long-standing relationship with the dealership. CTI crews tried out several pieces of compact equipment to determine which models would work the best.

There was also the debate about buying or renting the equipment. While CTI has worked inside the MidAmerican Energy substation before, the conditions have seldom required smaller compact equipment. CTI's current fleet of equipment works in 95% of the cases. Looking at the long-term picture, equipment that would be used for 5% or less of the company's jobs just didn't justify the cost of buying it. So, the decision was made to rent two compact units: a Vermeer S600TX mini skid steer and a CX219 compact excavator.

Extra Training

Another key to a successful installation on a substation job like this was having experienced crews that are well trained and safety conscious. Substation work includes working around high-voltage equipment, energized circuits and sensitive equipment and monitoring devices. On a periodic basis CTI voluntarily provides its crews with substation and other in-depth safety training. Employees are also trained to comply with MidAmerican's strict safety guidelines and substation prequalifications. The rules are stringent, but there is peace of mind that comes with having a qualified crew of professionals doing the work, especially in the substation environment.

The training has paid off. According to MidAmerican Field Service Representative Gene Shipley, the relationship between CTI and MidAmerican has evolved over time. The extra training that CTI provides employees has resulted in maintaining a higher-than-average safety record. It has also earned CTI additional repeat business. Small-bid jobs have led to bigger and more challenging jobs. Significant opportunities like the current substation project are prime examples.

The Job

To complete the job, CTI crews used the S600TX mini skid steer for several purposes within the substation: to remove the substation floor's top layer of gravel, to keep the spoils picked up and to haul excavated dirt away from the job site. The CX219 excavator was used to dig the trenches and other underground service pits. The mini-excavator features a zero tail swing, which allowed the operator to rotate the unit within the track's width. This eliminated the potential for accidental tail collisions with work site structures and other workers. Both compact units have proved to be very maneuverable, and their power and capabilities have exceeded the crew's expectations.

Late Summer Completion

With the right equipment and a well-trained crew, the duct installation progressed successfully for an on-time end-of-summer 2006 completion date. CTI crews have found the compact equipment to be a critical factor in tackling the challenging job conditions created by the confined boundaries of the maze of the substation's equipment and structures. Once the duct-work installation was complete, another MidAmerican Energy subcontractor installed the actual underground cabling. The downtown conduit run and the two circuits inside the substation began in November 2005 and were completed in less than 12 months.

---

Pat Carroll, a foreman for Communication Technologies Inc. (CTI), has been in utility construction for 18 years. He began working for CTI in 1997. His duties today include overseeing directional boring crews. CTI, a Des Moines, Iowa, utility contractor, was founded by Mike Heggen 16 years ago and employs 35 to 40 workers. pcarroll@iowatelecom.net