Water and Sewer Improvements in Raleigh’s Historic Downtown

Raleigh, North Carolina has seen an explosion of growth and investment in the last decade. As a hub of commerce and government, downtown Raleigh is also home to well-preserved history in the area’s City Market, including major tourist attractions, open-air shopping and well-preserved cobblestone streets and architectural landmarks. As such, the city aims to protect and preserve its integrity while keeping up with all the maintenance and infrastructure updates that are required of a growing urban area. 

With the help of CDM Smith’s complete corridors team, the city embarked on a multi-phased utility project that combined stormwater, sewer and water upgrades with minimal disruption to the community. 

Raleigh Water, formerly known as the Raleigh Public Utilities Department, is recognized as a leader in the water utility industry for green­light­ing future-focused initiatives that boost the reliability of existing infra­struc­ture to ultimately provide a safer, more vibrant, and healthier community. The city had previously completed a holistic condition assessment of sanitary sewer mains in the area’s drainage basin and determined much of the water and sewer infra­struc­ture categorized as “highly critical” based on the probability of failure and subsequent conse­quences of those failures. 

Working with CDM Smith, Raleigh Water developed a phased reha­bil­i­ta­tion and replacement (R&R) plan which included condition assessments of the city’s 160,000 feet of gravity sewer, 690 manholes and 60,000 linear feet of raw water mains in the State Street area. The R&R plan worked to reduce the risk of sanitary sewer overflows and pipe failures, and ultimately provide a more reliable water system for the community.

The team encountered several unique stormwater conflicts in the project area. Existing water and sewer pipes that were identified for replacement were installed through a large, buried concrete storm structure on Tipton Street. The water main was re-routed to avoid the buried storm structure, but the area’s existing sewer was undersized and had a large sag in the center of the reach. The team collected and reviewed additional field information including CCTV inspection of the storm system and vacuum excavated test holes to determine the most feasible sewer replacement approach. On Davie Street, the existing water and sewer pipes passed through an old stone stormwater box culvert. The water main was re-routed to eliminate the conflict with the box culvert. The team worked with City Stormwater to obtain CCTV inspection of the storm box culvert to identify the preferred sewer replacement approach that would prevent disruption to the stone structure. 

The project posed a number of challenges associated with work in large, densely developed downtown areas maintained by both the North Carolina Department of Trans­porta­tion (NCDOT) and the city. These included historic residential homes, churches, schools and businesses located close to the right-of-way (ROW), which resulted in a limited construc­tion area with extremely congested underground conditions from existing water, sewer, gas, power, stormwater, telephone and fiber optic utilities. 

As a result of these conditions—and thanks to a wealth of experience with utility construc­tion in congested areas—the CDM Smith complete corridors team understood that extensive utility coor­di­na­tion services were necessary throughout the length of the project. Working with Raleigh Water, CDM Smith managed project phasing based on results from a prior condition assessment project to reduce construc­tion fatigue and minimize pedestrian and traffic impacts that could be associated with performing this much utility reha­bil­i­ta­tion/replacement work in a high-traffic urban area. 

“One of the major concerns with a project of this scale was the public commu­ni­ca­tion and coor­di­na­tion,” said Jim Perotti, project manager. Because the work area included a busy downtown area and needed to address impacts to major thor­ough­fares into and out of downtown, Perotti and his team distributed noti­fi­ca­tions to the area throughout the design and construc­tion phases. “In addition to noti­fi­ca­tion letters to the directly impacted areas, the city put up traffic boards warning of the upcoming work and produced a detailed video explaining the work and road closure which was available on the project website and issued with the press release. As a result, there were minimal issues or complaints received related to this closer despite the large number of commuters that were impacted,” he said. 

Thanks to steady growth in new single-family and multi-use development projects in the downtown Raleigh area, CDM Smith’s project team must continue to coordinate their design and construc­tion with the city’s expanding demands.