< Tideland EMC Completes 3,800 LF Pantego Creek Crossing of 25 kV Power Lines using 4-inch Fusible PVC<sup>®</sup> Conduit Bundle

Tideland EMC Completes 3,800 LF Pantego Creek Crossing of 25 kV Power Lines using 4-inch Fusible PVC® Conduit Bundle

Tideland EMC is an electric membership corporation formed in 1971 through the merger of four electric utilities. Headquartered in Pantego, NC, Tideland EMC currently serves more than 22,000 customers in six counties in northeastern North Carolina.

Part of Tideland EMC’s recent system improvement initiative included replacing electric power cables originally laid under Pantego Creek in 1989. At the time, power cables were installed from a barge directly into a shallow trench excavated in the bed of the waterway. In 1994, lightning struck the underground cables, damaging one cable such that it had to be replaced immediately. The only power cable available for emergency replacement at the time was smaller than the other two existing cables, and could not handle the full capacity of the circuit. As the electrical power load on the system increased over time it eventually became necessary to replace all of the power cables.

In 2011, bids were requested for a directional bore project to install four 4-inch conduits to house new power cables under the Creek. Due to the 3,800-foot length of the project only a few contractors chose to bid. Bid prices were deemed unacceptably high compared to the available project budget. The concern with the project as originally designed was that standard conduit materials (HDPE pipe and solvent welded PVC pipe) were determined by HDD contractors to be unsuitable for an uncased, 3,800-foot bore. Another option to install a 12-inch steel casing to house the conduits was considered, but this approach proved even more costly.

Tideland EMC’s engineering consultant, Utility Electrical Consultants, evaluated another option to install the new power cables in conduits suspended from a nearby bridge which was under construction at the time. Further investigation revealed that construction of the bridge had progressed to the point where adding a suspended cable installation would have required significant engineering modifications to the structure.

Finally, Lee Electrical Construction, Inc. suggested value engineering the project by using 4-inch Fusible PVC® conduits in a “slick bore” to be pulled uncased directly through the borehole. Ultimately, Tideland EMC accepted the proposal which produced a total project savings of over $300,000.

Ben Beagle, Tideland’s Manager of Operations, summarized the project approach: “Tideland EMC had a very specific requirement for conduit sizing and length to cross under Pantego Creek. Lee Electrical Construction brought Underground Solutions into the project and the two of them, along with Tideland’s construction team, were able to take the project from concept to successful completion in a year’s time. We commend all the parties for their efforts and recommend other utilities consider this approach for similar projects.”

Looking North across Pantego Creek from Pipe Staging Side to Drill Rig Site 3,800’ in the Distance

Pipeline Details and Project Summary
Project: Pantego Creek Crossing
Location: Belhaven, North Carolina
Length: 3,800 LF HDD; 4,400 LF total fused length
Conduit Size: 4” DR14 x 4 Fusible PVC® conduit bundle
Installation: Horizontal Directional Drilling
Owner: Tideland EMC
Contractor: Lee Electrical Construction, Inc.

One challenge was finding adequate space to string the 4,400-foot lengths of 4-inch conduit along the highway. A lack of usable road shoulder ultimately resulted in floating the conduit in an adjacent shallow canal. Each conduit was capped and pulled forward at 45-foot intervals as pipe fusion and de-beading operations proceeded. Once pullback was ready to commence, each conduit was filled with water to achieve neutral buoyancy, with the bundle pulled through the canal into the bore entrance pit (see below).

The bundle of four 4-inch conduits enters the bore pit to begin the 3,800-foot journey under Pantego Creek. Four independent pull heads were connected by swivels to a master pull head, which was connected by another swivel to the HDD drill rod. This tooling approach minimized torsion transfer to the conduit bundle.