Although unseen or unnoticed by most drivers, utilities that travel along, across and under the pavement network are often among the most challenging aspects of any roadway upgrade and widening project. In Guilford County, North Carolina, conflicts with natural gas, power, water, sewer and communication lines that lie beneath, above and around Skeet Club Road could have caused massive delays and skyrocketing costs for a proposed three-mile widening. KCI worked with the North Carolina Department of Transportation (NCDOT) to coordinate with utility owners and develop innovative relocation and protection solutions that could move the project forward.
“Although initially the project had the appearance of being fairly straightforward from a utility coordination standpoint, further investigation found that there were no fewer than eight separate utilities present including two electric companies, both with transmission and distribution lines, three communications companies, a local municipality that owned several water and sewer systems, and two natural gas pipeline companies with major transmission lines crossing the alignment,” said Vice President and Utilities Discipline Head Scott Riddle. “This section of Skeet Club Road, which is very rural in nature, carried as many utilities as would be expected in an extremely urban area.”
Coordination to Facilitate Constructability
Engineers routinely manipulate a proposed roadway alignment to accommodate required relocations at a reasonable cost. Depending on easement agreements, state and local transportation agencies may have to fund all or part of the cost to move a utility, including purchasing additional property. The goal is to identify the most efficient mix of utility relocations, protection and avoidance to result in a constructible and cost-effective project. For Skeet Club Road, the team focused on helping the utility owners work together to make sure the project remained cohesive and workable.
“Utility coordination is a cradle-to-grave component of most highway projects,” said NCDOT Utility Coordinator Amy Dupree. “We are proactive on the front end to determine areas with conflicts, help with design to avoid potential showstoppers, and oversee relocations before and during construction.”
Several months into the project, utility engineers identified right-of-way associated with a 36-inch gas transmission line. The easement predated that of the roadway, meaning any costs associated with protection or relocation of the gas line would be the responsibility of the state. In the area of impact, where the pipeline crosses under the existing roadway, proposed plans called for additional fill needed to widen Skeet Club Road. Detailed analyses completed by the owner of the gas line indicated that even minor changes in soil depth above their steel transmission main could result in a potential future failure. Relocation would affect 1.5 miles of underground pipe, requiring acquisition of new easements and new permitting for an environmentally sensitive lake crossing. In total, moving the pipeline would cost an additional $14 million and add two to four years to the project schedule.
An Innovative Solution
Teamwork and brainstorming led the group to a unique solution. Instead of relocating the gas pipeline or significantly moving the roadway alignment, engineers recommended a land bridge to protect the transmission line. This compromise called for a 152-foot-long structure to span both the 36” and nearby 40” pipelines, allowing fill depths above both to match at existing conditions.
With a solution in place, KCI then took on the role of working with each stakeholder to keep the process moving, ask critical questions when obstacles arose, and push through issues that threatened the success of the project. Development of the pipeline preservation concept affected many other aspects of the proposed widening, including storm drainage in the area, hydrology coordination in the basin, design of a new retaining wall, and revisions to grading. The adjusted alignment encroached on an existing electric transmission line, which then had to be relocated. Engineers also had to meet strict guidelines to ensure the integrity and protection of the gas line at the crossing. Specifically, the foundation type of the bridge was selected in order to reduce vibrations during construction, and the design had to ensure that the utility owner had access beneath the structure for future pipeline maintenance.
By following the utility coordination principals of communicating, coordinating, and cooperating with all the different parties, we were able to turn a complex challenge with major financial and schedule repercussions into an innovative success for NCDOT.
D. Scott RiddleSenior Vice President, Utilities Market Leader
Innovation and partnering helped the design and utility coordination team avoid the astronomical cost associated with relocation of a major gas transmission line and meet the needs of all parties for long-term function and maintenance of their facilities. Skeet Club Road was successfully widened from two to four lanes, providing capacity improvements to the residents of Guilford County.