Progress Energy awarded the $42 million duct bank project to Kiewit Southern Co., a subsidiary of Kiewit Corporation. The project included procuring and installing four miles of a 16-duct utility in the corridor from the Bartow power plant to its northeast substation. The duct bank includes sixteen 8-inch-diameter PVC ducts, installed in an existing 100-foot-wide right-of-way, paralleling two existing high-voltage lines and a hot-oil line. The duct bank, which will carry a high-voltage power line, is encased in concrete.
Trench boxes were used during the duct bank’s construction to prevent the earth from caving into the 9-foot deep trench and to act as a forming system for the 6.5-foot-tall duct bank construction. Sixty pre-cast manholes 7 feet deep and 14 feet long were installed in sheeted excavations every 2,000 feet for cable pulling and splicing.
Part of the project entailed pulling two 42-inch steel casings pre-loaded with eight 8-inch high-density polyethylene conduits under a major intersection. The pipe casing was pulled through a predrilled hole that utilized a directional drill process. Six additional bores were performed utilizing micro-tunneling and conventional jack and bore technology. These procedures allowed the duct bank to be constructed without demolishing the intersection and roadways, or interrupting traffic and to minimize environmental impacts.