Utility Manhole Rebuild / Underground Design

Challenge

This manhole project was located in a large metropolitan area in the Northeast region of the United States. It is a key power transit point, encompassing five critical circuits for federal and state government buildings, as well as multiple commercial buildings.

Deteriorating structural conditions, non-standard cable configuration and general inaccessibility compromised the critical circuits and hindered required maintenance, prompting the utility to contact TRC to investigate and develop a distribution design to rebuild the manhole structure and reconfigure and rack all cables while avoiding outages to the associated customers.

Solution

TRC led the coordination, fielding and distribution design to install a new system of manholes and conduits, providing alternate pathways for all related circuits. TRC worked with the client to address their needs and find the optimal solution. Our team leveraged its extensive underground design expertise to inspect and assess the surrounding manholes to determine the optimal solution to improve reliability.

It was integral that the new design considered the utility’s future infrastructure demands because the manholes’ location within a critical traffic corridor. If the manhole were to collapse, the electrical circuits in the surrounding area would be affected and the cable pathways would have to be restored in addition to a lengthy rebuilding of the manhole.

Given the complex access issues and existing utility conflicts, we employed specialty subcontractors to complete a DOT level B survey, test pitting and site-specific traffic control plans. The design included 3 new and 5 existing manholes in the surrounding area to ensure the critical circuits configuration were brought up to standards while also allowing for future development. In addition, we delivered a construction and cutover sequence to avoid any outages to the critical circuits.

Results

TRC provided inspection data, including 360˚ imagery, plan and profile civil drawings, electrical distribution design, material lists, construction phasing schedule and public space permitting for the proposed re-structure of the manhole network. The completed design considered the existing and future demands of the utility by adding in alternate routes and switching capabilities to allow switching to different feeds to improve reliability.