Although utilities strive to use existing rights-of-way (ROW), and are often successful, extensive alternate route analyses are typically required prior to gaining approval. Environmental analysis of new routes or multiple routes can add significant time to the permitting process. Once routing and permitting have been approved, utilities and their consultants and contractors are faced with the challenge of constructing the alignment within the limitations set forth in each of the permits.
A portion of the new Susquehanna to Roseland Electric Reliability Project (SRERP) crosses Troy Meadows, a 3,100-acre (12,505-hectare) freshwater marsh located in Morris County, New Jersey, U.S. The area has been designated a priority wetland by the U.S. Environmental Protection Agency as well as a national natural landmark by the U.S. National Park Service. Within the protected area, the project scope included replacement of seven 230-kV lattice towers with seven new double-circuit 500-kV monopoles. Public Service Electric & Gas (PSE&G) coordinated closely with regulatory agencies and employed unique construction methods to ensure all construction was completed with minimal impacts to the wetland.
Detailed studies were completed for three potential alignment routes as a portion of the project siting application. The New Jersey Board of Public Utilities concurred with PSE&G that use of the existing ROW was the preferred route for the new 500-kV SRERP. This route included traversing the Troy Meadows wetland. The contractor preferred to use conventional foundations, but road building for transportation of the necessary equipment and materials would have required extensive temporary fill or timber matting. Temporary fill was rejected immediately for a variety of reasons. Timber mat roads were considered, but their impact, though temporary in nature, would have been significant. With conventional construction ruled out, the project team explored helicopter-supported construction as an alternative.
The first challenge associated with this option was the feasibility of using a helicopter to set the monopoles, which had already been selected as tl1e structure type for this portion of the project. Fortunately, the route through Troy Meadows did not include angle structures and allowed for lighter-weight, tangent monopole suspension towers to be used. However, at 190 ft (58 m) tall and weighing 150,000 lb (68,039 kg), the towers were still substantial. Burns & McDonnell, PSE&G's program manager for the project, worked with the monopole supplier and engineer to incorporate helicopter installation means into the design of the monopoles. This was accomplished by further segmenting the poles and incorporating innovative guide details into the flange-connected pole sections.
The second challenge was tO select a foundation tO meet the needs of the project. A comparative study was completed to determine the foundation type that would impose the least environmental impact and could also be constructed entirely by helicopter.
Ultimately, micropile foundations were selected, and Burns & McDonnell worked with the T-line construction contractor Kh&m (a joint venture between Kiewit and Henkels & McCoy) to select a micropile foundation contractor. Micropile foundations have been employed for numerous projects requiring helicopter construction techniques. They can be constructed with lighter-weight equipment and materials, making them conducive to Light- and medium-lift helicopter transportation. Another benefit of micropile foundations over conventional foundation equipment is the compact nature of the smaller drilling equipment and the ability to minimize the total area of temporary and permanent disturbance.
With the unique capabilities to meet project schedule and other requirements, Kh&m selected Crux Subsurface to design and install the micropile foundations. The selection of a single specialty foundation contractor with numerous projects of similar design-build experience created the highest level of assurance of on-time completion for this project with an aggressive schedule. Once it was determined helicopter support and micropile foundations would be employed, individual activities needed to be scheduled within a condensed project time frame. A bald eagle siting in close proximity to the ROW limited construction within Troy Meadows to a 106-daywindow, with just60 of those days allotted for foundation work. This necessitated efficient collaboration among all parties involved.